Mixed Signal ISP Flash MCU Family
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 12/05 Copyright © 2005 by Silicon Laboratories C8051F04x
Analog Peripherals
-10 or 12-Bit SAR ADC
•12-bit (C8051F040/1) or
10-bit (C8051F042/3/4/5/6/7) resolution
•± 1 LSB INL, guaranteed no missing codes
•Programmable throughput up to 100 ksps
•13 External Inputs; single-ended or differential
•SW programmable high voltage difference amplifier
•Programmable amplifier gain: 16, 8, 4, 2, 1, 0.5
•Data-dependent windowed interrupt generator
•Built-in temperature sensor
-8-bit SAR ADC (C8051F040/1/2/3 only)
•Programmable throughput up to 500 ksps
•8 External Inputs, single-ended or differential
•Programmable amplifier gain: 4, 2, 1, 0.5
-Two 12-bit DACs (C8051F040/1/2/3 only)
•Can synchronize outputs to timers for jitter-free wave-
form generation
-Three Analog Comparators
•Programmable hysteresis/response time
-Voltage Referenc e
-Precision VDD Monitor/Brown-Out Detector
On-Chip JTAG Debug & Boundary Scan
-On-chip debug circuitry facilitates full- speed, non-
intrusive in-circuit/in-system debugging
-Provides breakpoints, single-stepping, watchpoints,
stack monitor; inspect/modify memory and registers
-Superior performance to emulation systems using
ICE-chips, target pods, and sockets
-IEEE1149.1 compliant boundary scan
-Complete development kit
High-Speed 8051 µC Core
-Pipelined instruction architecture; executes 70% of
instruction set in 1 or 2 system clocks
-Up to 25 MIPS throughput with 25 MHz clock
-20 vectored interrupt sources
Memory
-4352 bytes internal data RAM (4 k + 256)
-64 kB (C8051F040/1/2/3/4/5)
or 32 kB (C8051F046/7) Flash; in-system program-
mable in 512-byte sectors
-External 64 kB data memory interface (programma-
ble multiplexed or non-multiplexed modes)
Digital Peripherals
-8 byte-wide port I/O (C8051F040/2/4/6); 5 V tolerant
-4 byte-wide port I/O (C8051F041/3/5/7); 5 V tolerant
-Bosch Controller Area Network (CAN 2.0B), hard-
ware SMBus™ (I2C™ Compatible), SPI™, and
two UART serial ports available concurrently
-Programmable 16-bit counter/timer array with
6 capture/compare modules
-5 general purpose 16-bit counter/timers
-Dedicated watch-dog timer; bi-directional reset pin
Clock Sources
-Internal calibrated programmable oscillator: 3 to
24.5 MHz
-External oscillator: crystal, RC, C, or clock
-Real-time clo ck mo de usi n g Timer 2, 3, 4, or PCA
Supply Voltage: 2.7 to 3.6 V
-Multiple power saving sleep and shutdown modes
100-Pin and 64-Pin TQFP Packages Available
-Temperature Range: –40 to +85 °C
JTAG
64 kB/32 kB
ISP FLASH 4352 B
SRAM SANITY
CONTROL
+
-
12/10-bit
100 ksps
ADC
CLOCK
CIRCUIT
PGA
VREF
12 - Bit
DAC
TEMP
SENSOR
VOLTAGE COMPARATORS
ANALOG PERIPHERALS
Port 0
Port 1
Port 2
Port 3
CROSSBAR
DIGITAL I/O
HIGH-SPEED CONTROLLER CORE
DEBUG
CIRCUITRY
20
INTERRUPTS
8051 CP U
(25 MIP S )
+
-
8-bit
500 ksps
ADC
Port 4
Port 5
Port 6
Port 7
External Memory Interface
100 pin64 pin
PGA
UART0
SMBus
SPI Bus
PCA
Timer 0
Timer 1
Timer 2
Timer 3
Timer 4
UART1
AMUX
AMUX
CAN
2.0B
+
-
HV
DIFF
AMP
12 - Bit
DAC
C8051F041/2/3
ONLY
C8051F040/1/2/3/4/5/6/7
2 Rev. 1.5
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 3
Table of Contents
1. System Overview.................................................................................................... 19
1.1. CIP-51™ Microcontroller Core.......................................................................... 25
1.1.1. Fully 8051 Compatible.............................................................................. 25
1.1.2. Improved Throughput............................................................................... 25
1.1.3. Additional Features .................................................................................. 26
1.2. On-Chip Memory............................................................................................... 27
1.3. JTAG Debug and Boundary Scan..................................................................... 28
1.4. Programmable Digital I/O and Crossbar........................................................... 29
1.5. Programmable Counter Array........................................................................... 30
1.6. Controller Area Network.................................................................................... 31
1.7. Serial Ports ....................................................................................................... 31
1.8. 12/10-Bit Analog to Digital Converter................................................................ 32
1.9. 8-Bit Analog to Digital Converter (C8051F040/1/2/3 Only)............................... 33
1.10.Comparators and DACs ................................................................................... 34
2. Absolute Maximum Ratings .................................................................................. 35
3. Global DC Electrical Characteristic...................................................................... 36
4. Pinout and Package Definitions............................................................................ 37
5. 12-Bit ADC (ADC0, C8051F040/1 Only)................................................................. 47
5.1. Analog Multiplexer and PGA............................................................................. 47
5.1.1. Analog Input Configuration....................................................................... 48
5.2. High-Voltage Difference Amplifier..................................................................... 52
5.3. ADC Modes of Operation.................................................................................. 54
5.3.1. Starting a Conversion............................................................................... 54
5.3.2. Tracking Modes........................................................................................ 54
5.3.3. Settling Time Requirements..................................................................... 56
5.4. ADC0 Programmable Window Detector ........................................................... 62
6. 10-Bit ADC (ADC0, C8051F042/3/4/5/6/7 Only)..................................................... 69
6.1. Analog Multiplexer and PGA............................................................................. 69
6.1.1. Analog Input Configuration....................................................................... 70
6.2. High-Voltage Difference Amplifier..................................................................... 74
6.3. ADC Modes of Operation.................................................................................. 76
6.3.1. Starting a Conversion............................................................................... 76
6.3.2. Tracking Modes........................................................................................ 76
6.3.3. Settling Time Requirements..................................................................... 78
6.4. ADC0 Programmable Window Detector ........................................................... 84
7. 8-Bit ADC (ADC2, C8051F040/1/2/3 Only)............................................................. 91
7.1. Analog Multiplexer and PGA............................................................................. 91
7.2. ADC2 Modes of Operation................................................................................ 92
7.2.1. Starting a Conversion............................................................................... 92
7.2.2. Tracking Modes........................................................................................ 92
7.2.3. Settling Time Requirements..................................................................... 94
7.3. ADC2 Programmable Window Detector ......................................................... 100
7.3.1. Window Detector in Single-Ended Mode ................................................ 100
C8051F040/1/2/3/4/5/6/7
4 Rev. 1.5
7.3.2. Window Detector in Differential Mode.................................................... 102
8. DACs, 12-Bit Voltage Mode (C8051F040/1/2/3 Only)......................................... 105
8.1. DAC Output Scheduling.................................................................................. 106
8.1.1. Update Output On-Demand ................................................................... 106
8.1.2. Update Output Based on Timer Overflow .............................................. 106
8.2. DAC Output Scaling/Justification.................................................................... 106
9. Voltage Reference (C8051F040/2/4/6)................................................................. 113
10.Voltage Reference (C8051F041/3/5/7)................................................................. 117
11.Comparators......................................................................................................... 121
11.1.Comparator Inputs.......................................................................................... 123
12.CIP-51 Microcontroller......................................................................................... 127
12.1.Instruction Set................................................................................................. 129
12.1.1.Instruction and CPU Timing................................................................... 129
12.1.2.MOVX Instruction and Program Memory............................................... 129
12.2.Memory Organization..................................................................................... 133
12.2.1.Program Memory ................................................................................... 133
12.2.2.Data Memory.......................................................................................... 134
12.2.3.General Purpose Registers.................................................................... 134
12.2.4.Bit Addressable Locations...................................................................... 134
12.2.5.Stack ..................................................................................................... 134
12.2.6.Special Function Registers .................................................................... 135
12.2.7.Register Descriptions............................................................................. 150
12.3.Interrupt Handler............................................................................................. 153
12.3.1.MCU Interrupt Sources and Vectors...................................................... 153
12.3.2.External Interrupts.................................................................................. 154
12.3.3.Interrupt Priorities................................................................................... 156
12.3.4.Interrupt Latency.................................................................................... 156
12.3.5.Interrupt Register Descriptions............................................................... 156
12.4.Power Management Modes............................................................................ 163
12.4.1.Idle Mode ............................................................................................... 163
12.4.2.Stop Mode.............................................................................................. 164
13.Reset Sources....................................................................................................... 165
13.1.Power-On Reset............................................................................................. 166
13.2.Power-Fail Reset............................................................................................ 166
13.3.External Reset................................................................................................ 166
13.4.Missing Clock Detector Reset ........................................................................ 167
13.5.Comparator0 Reset........................................................................................ 167
13.6.External CNVSTR0 Pin Reset........................................................................ 167
13.7.Watchdog Timer Reset................................................................................... 167
13.7.1.Enable/Reset WDT ................................................................................ 168
13.7.2.Disable WDT.......................................................................................... 168
13.7.3.Disable WDT Lockout ............................................................................ 168
13.7.4.Setting WDT Interval.............................................................................. 168
14.Oscillators............................................................................................................. 173
14.1.Programmable Internal Oscillator................................................................... 173
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 5
14.2.External Oscillator Drive Circuit...................................................................... 175
14.3.System Clock Selection.................................................................................. 175
14.4.External Crystal Example............................................................................... 177
14.5.External RC Example..................................................................................... 178
14.6.External Capacitor Example........................................................................... 178
15.Flash Memory ....................................................................................................... 179
15.1.Programming The Flash Memory................................................................... 179
15.2.Non-volatile Data Storage .............................................................................. 180
15.3.Security Options............................................................................................. 180
15.3.1.Summary of Flash Security Options....................................................... 183
16.External Data Memory Interface and On-Chip XRAM ........................................ 187
16.1.Accessing XRAM............................................................................................ 187
16.1.1.16-Bit MOVX Example........................................................................... 187
16.1.2.8-Bit MOVX Example............................................................................. 187
16.2.Configuring the External Memory Interface.................................................... 188
16.3.Port Selection and Configuration.................................................................... 188
16.4.Multiplexed and Non-multiplexed Selection.................................................... 191
16.4.1.Multiplexed Configuration....................................................................... 191
16.4.2.Non-multiplexed Configuration............................................................... 192
16.5.Memory Mode Selection................................................................................. 193
16.5.1.Internal XRAM Only ............................................................................... 193
16.5.2.Split Mode without Bank Select.............................................................. 193
16.5.3.Split Mode with Bank Select................................................................... 194
16.5.4.External Only.......................................................................................... 194
16.6.Timing .......................................................................................................... 194
16.6.1.Non-multiplexed Mode........................................................................... 196
16.6.2.Multiplexed Mode................................................................................... 199
17.Port Input/Output.................................................................................................. 203
17.1.Ports 0 through 3 and the Priority Crossbar Decoder..................................... 204
17.1.1.Crossbar Pin Assignment and Allocation............................................... 205
17.1.2.Configuring the Output Modes of the Port Pins...................................... 206
17.1.3.Configuring Port Pins as Digital Inputs................................................... 206
17.1.4.Weak Pullups......................................................................................... 207
17.1.5.Configuring Port 1, 2, and 3 Pins as Analog Inputs ............................... 207
17.1.6.External Memory Interface Pin Assignments......................................... 208
17.1.7.Crossbar Pin Assignment Example........................................................ 210
17.2.Ports 4 through 7............................................................................................ 220
17.2.1.Configuring Ports Which are Not Pinned Out......................................... 221
17.2.2.Configuring the Output Modes of the Port Pins...................................... 221
17.2.3.Configuring Port Pins as Digital Inputs................................................... 221
17.2.4.Weak Pullups......................................................................................... 221
17.2.5.External Memory Interface..................................................................... 221
18.Controller Area Network (CAN0)......................................................................... 227
18.1.Bosch CAN Controller Operation.................................................................... 228
18.1.1.CAN Controller Timing........................................................................... 229
C8051F040/1/2/3/4/5/6/7
6 Rev. 1.5
18.1.2.Example Timing Calculation for 1 Mbit/Sec Communication ................. 229
18.2.CAN Registers................................................................................................ 231
18.2.1.CAN Controller Protocol Registers......................................................... 231
18.2.2.Message Object Interface Registers...................................................... 231
18.2.3.Message Handler Registers................................................................... 232
18.2.4.CIP-51 MCU Special Function Registers............................................... 232
18.2.5.Using CAN0ADR, CAN0DATH, and CANDATL to Access CAN Registers.
232
18.2.6.CAN0ADR Autoin crement Feature ........................................................ 232
19.System Management BUS/I2C BUS (SMBUS0).................................................. 239
19.1.Supporting Documents................................................................................... 240
19.2.SMBus Protocol.............................................................................................. 241
19.2.1.Arbitration............................................................................................... 241
19.2.2.Clock Low Extension.............................................................................. 242
19.2.3.SCL Low Timeout................................................................................... 242
19.2.4.SCL High (SMBus Free) Timeout .......................................................... 242
19.3.SMBus Transfer Modes.................................................................................. 242
19.3.1.Master Transmitter Mode....................................................................... 242
19.3.2.Master Receiver Mode........................................................................... 243
19.3.3.Slave Transmitter Mode......................................................................... 243
19.3.4.Slave Receiver Mode............................................................................. 244
19.4.SMBus Special Function Registers................................................................ 245
19.4.1.Control Register..................................................................................... 245
19.4.2.Clock Rate Register............................................................................... 248
19.4.3.Data Register......................................................................................... 249
19.4.4.Address Register.................................................................................... 249
19.4.5.Status Register....................................................................................... 250
20.Enhanced Serial Peripheral Interface (SPI0)...................................................... 255
20.1.Signal Descriptions......................................................................................... 256
20.1.1.Master Out, Slave In (MOSI).................................................................. 256
20.1.2.Master In, Slave Out (MISO).................................................................. 256
20.1.3.Serial Clock (SCK)................................................................................. 256
20.1.4.Slave Select (NSS) ................................................................................ 256
20.2.SPI0 Master Mode Operation......................................................................... 257
20.3.SPI0 Slave Mode Operation........................................................................... 259
20.4.SPI0 Interrupt Sources................................................................................... 259
20.5.Serial Clock Timing......................................................................................... 260
20.6.SPI Special Function Registers...................................................................... 261
21.UART0.................................................................................................................... 265
21.1.UART0 Operational Modes ............................................................................ 266
21.1.1.Mode 0: Synchronous Mode.................................................................. 266
21.1.2.Mode 1: 8-Bit UART, Variable Baud Rate.............................................. 267
21.1.3.Mode 2: 9-Bit UART, Fixed Baud Rate.................................................. 269
21.1.4.Mode 3: 9-Bit UART, Variable Baud Rate.............................................. 270
21.2.Multiprocessor Communications .................................................................... 270
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 7
21.3.Configuration of a Masked Address ............................................................... 271
21.4.Broadcast Addressing .................................................................................... 271
21.5.Frame and Transmission Error Detection....................................................... 272
22.UART1.................................................................................................................... 277
22.1.Enhanced Baud Rate Generation................................................................... 278
22.2.Operational Modes......................................................................................... 279
22.2.1.8-Bit UART............................................................................................. 279
22.2.2.9-Bit UART............................................................................................. 280
22.3.Multiprocessor Communications .................................................................... 281
23.Timers.................................................................................................................... 287
23.1.Timer 0 and Timer 1....................................................................................... 287
23.1.1.Mode 0: 13-bit Counter/Timer................................................................ 287
23.1.2.Mode 1: 16-bit Counter/Timer................................................................ 288
23.1.3.Mode 2: 8-bit Counter/Timer with Auto-Reload...................................... 289
23.1.4.Mode 3: Two 8-bit Counter/Timers (Timer 0 Only)................................. 290
23.2.Timer 2, Timer 3, and Timer 4........................................................................ 295
23.2.1.Configuring Timer 2, 3, and 4 to Count Down........................................ 295
23.2.2.Capture Mode ........................................................................................ 296
23.2.3.Auto-Reload Mode................................................................................. 297
23.2.4.Toggle Output Mode .............................................................................. 298
24.Programmable Counter Array............................................................................. 303
24.1.PCA Counter/Timer........................................................................................ 304
24.2.Capture/Compare Modules ............................................................................ 305
24.2.1.Edge-triggered Capture Mode................................................................ 306
24.2.2.Software Timer (Compare) Mode........................................................... 307
24.2.3.High-Speed Output Mode ...................................................................... 308
24.2.4.Frequency Output Mode ........................................................................ 309
24.2.5.8-Bit Pulse Width Modulator Mode......................................................... 310
24.2.6.16-Bit Pulse Width Modulator Mode....................................................... 311
24.3.Register Descriptions for PCA0...................................................................... 312
25.JTAG (IEEE 1149.1) .............................................................................................. 317
25.1.Boundary Scan............................................................................................... 318
25.1.1.EXTEST Instruction................................................................................ 319
25.1.2.SAMPLE Instruction............................................................................... 319
25.1.3.BYPASS Instruction............................................................................... 319
25.1.4.IDCODE Instruction................................................................................ 319
25.2.Flash Programming Commands..................................................................... 321
25.3.Debug Support ............................................................................................... 324
Document Change List............................................................................................. 325
Contact Information.................................................................................................. 326
C8051F040/1/2/3/4/5/6/7
8 Rev. 1.5
NOTES:
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 9
List of Figures
1. System Overview
Figure 1.1. C8051F040/2 Block Diagram................................................................. 21
Figure 1.2. C8051F041/3 Block Diagram................................................................. 22
Figure 1.3. C8051F044/6 Block Diagram................................................................. 23
Figure 1.4. C8051F045/7 Block Diagram................................................................. 24
Figure 1.5. Comparison of Peak MCU Execution Speeds ....................................... 25
Figure 1.6. On-Board Clock and Reset.................................................................... 26
Figure 1.7. On-Chip Memory Map............................................................................ 27
Figure 1.8. Development/In-System Debug Diagram............................................... 28
Figure 1.9. Digital Crossbar Diagram....................................................................... 29
Figure 1.10. PCA Block Diagram.............................................................................. 30
Figure 1.11. CAN Controller Diagram....................................................................... 31
Figure 1.12. 10/12-Bit ADC Block Diagram.............................................................. 32
Figure 1.13. 8-Bit ADC Diagram............................................................................... 33
Figure 1.14. Comparator and DAC Diagram............................................................ 34
2. Absolute Maximum Ratings
3. Global DC Electrical Characteristic
4. Pinout and Package Definitions
Figure 4.1. TQFP-100 Pinout Diagram..................................................................... 43
Figure 4.2. TQFP-100 Package Drawing................................................................. 44
Figure 4.3. TQFP-64 Pinout Diagram....................................................................... 45
Figure 4.4. TQFP-64 Package Drawing................................................................... 46
5. 12-Bit ADC (ADC0, C8051F040/1 Only)
Figure 5.1. 12-Bit ADC0 Functional Block Diagram................................................. 47
Figure 5.2. Analog Input Diagram ............................................................................ 48
Figure 5.3. High Voltage Difference Amplifier Functional Diagram.......................... 52
Figure 5.4. 12-Bit ADC Track and Conversion Example Timing.............................. 55
Figure 5.5. ADC0 Equivalent Input Circuits.............................................................. 56
Figure 5.6. Temperature Sensor Transfer Function................................................. 57
Figure 5.7. ADC0 Data Word Example .................................................................... 61
Figure 5.8. 12-Bit ADC0 Window Interrupt Example:
Right Justified Single-Ended Data ........................................................ 63
Figure 5.9. 12-Bit ADC0 Window Interrupt Example:
Right Justified Differential Data............................................................. 64
Figure 5.10. 12-Bit ADC0 Window Interrupt Example:
Left Justified Single-Ended Data........................................................... 65
Figure 5.11. 12-Bit ADC0 Window Interrupt Example: Left Justified Differential Data.
66
6. 10-Bit ADC (ADC0, C8051F042/3/4/5/6/7 Only)
Figure 6.1. 10-Bit ADC0 Functional Block Diagram................................................. 69
Figure 6.2. Analog Input Diagram ............................................................................ 70
Figure 6.3. High Voltage Difference Amplifier Functional Diagram.......................... 74
Figure 6.4. 10-Bit ADC Track and Conversion Example Timing.............................. 77
C8051F040/1/2/3/4/5/6/7
10 Rev. 1.5
Figure 6.5. ADC0 Equivalent Input Circuits.............................................................. 78
Figure 6.6. Temperature Sensor Transfer Function................................................. 79
Figure 6.7. ADC0 Data Word Example .................................................................... 83
Figure 6.8. 10-Bit ADC0 Window Interrupt Example:
Right Justified Single-Ended Data ........................................................ 85
Figure 6.9. 10-Bit ADC0 Window Interrupt Example:
Right Justified Differential Data............................................................. 86
Figure 6.10. 10-Bit ADC0 Window Interrupt Example:
Left Justified Single-Ended Data........................................................... 87
Figure 6.11. 10-Bit ADC0 Window Interrupt Example: Left Justified Differential Data.
88
7. 8-Bit ADC (ADC2, C8051F040/1/2/3 Only)
Figure 7.1. ADC2 Functional Block Diagram............................................................ 91
Figure 7.2. ADC2 Track and Conversion Example Timing....................................... 93
Figure 7.3. ADC2 Equivalent Input Circuit................................................................ 94
Figure 7.4. ADC2 Data Word Example .................................................................... 99
Figure 7.5. ADC Window Compare Examples, Single-Ended Mode...................... 101
Figure 7.6. ADC Window Compare Examples, Differential Mode.......................... 102
8. DACs, 12-Bit Voltage Mode (C8051F040/1/2/3 Only)
Figure 8.1. DAC Functional Block Diagram............................................................ 105
9. Voltage Reference (C8051F040/2/4/6)
Figure 9.1. Voltage Reference Functional Block Diagram ..................................... 113
10.Voltage Reference (C8051F041/3/5/7)
Figure 10.1. Voltage Reference Functional Block Diagram.................................... 117
11.Comparators
Figure 11.1. Comparator Functional Block Diagram .............................................. 121
Figure 11.2. Comparator Hysteresis Plot ............................................................... 122
12.CIP-51 Microcontroller
Figure 12.1. CIP-51 Block Diagram........................................................................ 127
Figure 12.2. Memory Map ...................................................................................... 133
Figure 12.3. SFR Page Stack................................................................................. 136
Figure 12.4. SFR Page Stack While Using SFR Page 0x0F To Access Port 5...... 137
Figure 12.5. SFR Page Stack After ADC2 Window Comparator Interrupt Occurs. 138
Figure 12.6. SFR Page Stack Upon PCA Interrupt Occurring During an ADC2 ISR....
139
Figure 12.7. SFR Page Stack Upon Return From PCA Interrupt........................... 140
Figure 12.8. SFR Page Stack Upon Return From ADC2 Window Interrupt........... 141
13.Reset Sources
Figure 13.1. Reset Sources.................................................................................... 165
Figure 13.2. Reset Timing...................................................................................... 166
14.Oscillators
Figure 14.1. Oscillator Diagram.............................................................................. 173
Figure 14.2. 32.768 kHz External Crystal Example................................................ 177
15.Flash Memory
Figure 15.1. Flash Program Memory Map and Security Bytes............................... 181
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 11
16.External Data Memory Interface and On-Chip XRAM
Figure 16.1. Multiplexed Configuration Example.................................................... 191
Figure 16.2. Non-multiplexed Configuration Example............................................ 192
Figure 16.3. EMIF Operating Modes...................................................................... 193
Figure 16.4. Non-multiplexed 16-bit MOVX Timing................................................ 196
Figure 16.5. Non-multiplexed 8-bit MOVX without Bank Select Timing ................. 197
Figure 16.6. Non-multiplexed 8-bit MOVX with Bank Select Timing ...................... 198
Figure 16.7. Multiplexed 16-bit MOVX Timing........................................................ 199
Figure 16.8. Multiplexed 8-bit MOVX without Bank Select Timing......................... 200
Figure 16.9. Multiplexed 8-bit MOVX with Bank Select Timing.............................. 201
17.Port Input/Output
Figure 17.1. Port I/O Cell Block Diagram ............................................................... 203
Figure 17.2. Port I/O Functional Block Diagram..................................................... 204
Figure 17.3. Priority Crossbar Decode Table......................................................... 205
Figure 17.4. Priority Crossbar Decode Table......................................................... 208
Figure 17.5. Priority Crossbar Decode Table......................................................... 209
Figure 17.6. Crossbar Example:............................................................................. 211
18.Controller Area Network (CAN0)
Figure 18.1. Typical CAN Bus Configuration.......................................................... 227
Figure 18.2. CAN Controller Diagram..................................................................... 228
Figure 18.3. Four Segments of a CAN Bit Time..................................................... 229
Figure 18.4. CAN0DATH: CAN Data Access Register High Byte.......................... 234
19.System Management BUS/I2C BUS (SMBUS0)
Figure 19.1. SMBus0 Block Diagram ..................................................................... 239
Figure 19.2. Typical SMBus Configuration............................................................. 240
Figure 19.3. SMBus Transaction............................................................................ 241
Figure 19.4. Typical Master Transmitter Sequence................................................ 242
Figure 19.5. Typical Master Receiver Sequence.................................................... 243
Figure 19.6. Typical Slave Transmitter Sequence.................................................. 243
Figure 19.7. Typical Slave Receiver Sequence...................................................... 244
20.Enhanced Serial Peripheral Interface (SPI0)
Figure 20.1. SPI Block Diagram............................................................................. 255
Figure 20.2. Multiple-Master Mode Connection Diagram....................................... 258
Figure 20.3. 3-Wire Single Master and Slave Mode Connection Diagram............. 258
Figure 20.4. 4-Wire Single Master and Slave Mode Connection Diagram............. 258
Figure 20.5. Data/Clock Timing Diagram ............................................................... 260
21.UART0
Figure 21.1. UART0 Block Diagram....................................................................... 265
Figure 21.2. UART0 Mode 0 Timing Diagram........................................................ 266
Figure 21.3. UART0 Mode 0 Interconnect.............................................................. 267
Figure 21.4. UART0 Mode 1 Timing Diagram........................................................ 267
Figure 21.5. UART0 Modes 2 and 3 Timing Diagram ............................................ 269
Figure 21.6. UART0 Modes 1, 2, and 3 Interconnect Diagram .............................. 269
Figure 21.7. UART Multi-Processor Mode Interconnect Diagram.......................... 272
C8051F040/1/2/3/4/5/6/7
12 Rev. 1.5
22.UART1
Figure 22.1. UART1 Block Diagram....................................................................... 277
Figure 22.2. UART1 Baud Rate Logic.................................................................... 278
Figure 22.3. UART Interconnect Diagram.............................................................. 279
Figure 22.4. 8-Bit UART Timing Diagram............................................................... 279
Figure 22.5. 9-Bit UART Timing Diagram............................................................... 280
Figure 22.6. UART Multi-Processor Mode Interconnect Diagram.......................... 281
23.Timers
Figure 23.1. T0 Mode 0 Block Diagram.................................................................. 288
Figure 23.2. T0 Mode 2 Block Diagram.................................................................. 289
Figure 23.3. T0 Mode 3 Block Diagram.................................................................. 290
Figure 23.4. Tn Capture Mode Block Diagram....................................................... 296
Figure 23.5. Tn Auto-reload Mode and Toggle Mode Block Diagram.................... 297
24.Programmable Counter Array
Figure 24.1. PCA Block Diagram............................................................................ 303
Figure 24.2. PCA Counter/Timer Block Diagram.................................................... 304
Figure 24.3. PCA Interrupt Block Diagram............................................................. 305
Figure 24.4. PCA Capture Mode Diagram.............................................................. 306
Figure 24.5. PCA Software Timer Mode Diagram.................................................. 307
Figure 24.6. PCA High-Speed Output Mode Diagram............................................ 308
Figure 24.7. PCA Frequency Output Mode............................................................ 309
Figure 24.8. PCA 8-Bit PWM Mode Diagram......................................................... 310
Figure 24.9. PCA 16-Bit PWM Mode...................................................................... 311
25.JTAG (IEEE 1149.1)
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 13
List of Tables
1. System Overview
Table 1.1. Product Selection Guide ......................................................................... 20
2. Absolute Maximum Ratings
Table 2.1. Absolute Maximum Ratings* .................................................................. 35
3. Global DC Electrical Characteristic
Table 3.1. Global DC Electrical Characteristics ....................................................... 36
4. Pinout and Package Definitions
Table 4.1. Pin Definitions ......................................................................................... 37
5. 12-Bit ADC (ADC0, C8051F040/1 Only)
Table 5.1. AMUX Selection Chart (AMX0AD3–0 and AMX0CF3–0 bits) ................ 50
Table 5.2. 12-Bit ADC0 Electrical Characteristics ................................................... 67
Table 5.3. High-Voltage Difference Amplifier Electrical Characteristics .................. 68
6. 10-Bit ADC (ADC0, C8051F042/3/4/5/6/7 Only)
Table 6.1. AMUX Selection Chart (AMX0AD3-0 and AMX0CF3-0 bits) .................. 72
Table 6.2. 10-Bit ADC0 Electrical Characteristics ................................................... 89
Table 6.3. High-Voltage Difference Amplifier Electrical Characteristics .................. 90
7. 8-Bit ADC (ADC2, C8051F040/1/2/3 Only)
Table 7.1. AMUX Selection Chart (AMX2AD2-0 and AMX2CF3-0 bits) .................. 96
Table 7.2. ADC2 Electrical Characteristics ............................................................ 103
8. DACs, 12-Bit Voltage Mode (C8051F040/1/2/3 Only)
Table 8.1. DAC Electrical Characteristics .............................................................. 111
9. Voltage Reference (C8051F040/2/4/6)
Table 9.1. Voltage Reference Electrical Characteristics ....................................... 115
10.Voltage Reference (C8051F041/3/5/7)
Table 10.1. Voltage Reference Electrical Characteristics ..................................... 119
11.Comparators
Table 11.1. Comparator Electrical Characteristics ................................................ 126
12.CIP-51 Microcontroller
Table 12.1. CIP-51 Instruction Set Summary ........................................................ 129
Table 12.2. Special Function Register (SFR) Memory Map .................................. 144
Table 12.3. Special Function Registers ................................................................. 146
Table 12.4. Interrupt Summary .............................................................................. 154
13.Reset Sources
Table 13.1. Reset Electrical Characteristics .......................................................... 171
14.Oscillators
Table 14.1. Internal Oscillator Electrical Characteristics ....................................... 175
15.Flash Memory
Table 15.1. Flash Electrical Characteristics .......................................................... 180
16.External Data Memory Interface and On-Chip XRAM
Table 16.1. AC Parameters for External Memory Interface ................................... 202
17.Port Input/Output
Table 17.1. Port I/O DC Electrical Characteristics ................................................. 203
C8051F040/1/2/3/4/5/6/7
14 Rev. 1.5
18.Controller Area Network (CAN0)
Table 18.1. Background System Information ........................................................ 229
Table 18.2. CAN Register Index and Reset Values .............................................. 233
19.System Management BUS/I2C BUS (SMBUS0)
Table 19.1. SMB0STA Status Codes and States .................................................. 252
20.Enhanced Serial Peripheral Interface (SPI0)
21.UART0
Table 21.1. UART0 Modes .................................................................................... 266
Table 21.2. Oscillator Frequencies for Standard Baud Rates ............................... 273
22.UART1
Table 22.1. Timer Settings for Standard Baud Rates Using the Internal 24.5 MHz Os-
cillator ................................................................................................. 284
Table 22.2. Timer Settings for Standard Baud Rates Using an External 25.0 MHz Os-
cillator ................................................................................................. 284
Table 22.3. Timer Settings for Standard Baud Rates Using an External 22.1184 MHz
Oscillator ............................................................................................. 285
Table 22.4. Timer Settings for Standard Baud Rates Using an External 18.432 MHz
Oscillator ............................................................................................. 285
Table 22.5. Timer Settings for Standard Baud Rates Using an External 11.0592 MHz
Oscillator ............................................................................................. 286
Table 22.6. Timer Settings for Standard Baud Rates Using an External 3.6864 MHz
Oscillator ............................................................................................. 286
23.Timers
24.Programmable Counter Array
Table 24.1. PCA Timebase Input Options ............................................................. 304
Table 24.2. PCA0CPM Register Settings for PCA Capture/Compare Modules .... 305
25.JTAG (IEEE 1149.1)
Table 25.1. Boundary Data Register Bit Definitions .............................................. 318
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 15
List of Registers
SFR Definition 5.1. AMX0CF: AMUX0 Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . 49
SFR Definition 5.2. AMX0SL: AMUX0 Channel Select . . . . . . . . . . . . . . . . . . . . . . . . . 49
SFR Definition 5.3. AMX0PRT: Port 3 Pin Selection . . . . . . . . . . . . . . . . . . . . . . . . . . 51
SFR Definition 5.4. HVA0CN: High Voltage Difference Amplifier Control . . . . . . . . . . . 53
SFR Definition 5.5. ADC0CF: ADC0 Configuration Register . . . . . . . . . . . . . . . . . . . . 58
SFR Definition 5.6. ADC0CN: ADC0 Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
SFR Definition 5.7. ADC0H: ADC0 Data Word MSB . . . . . . . . . . . . . . . . . . . . . . . . . . 60
SFR Definition 5.8. ADC0L: ADC0 Data Word LSB . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
SFR Definition 5.9. ADC0GTH: ADC0 Greater-Than Data High Byte . . . . . . . . . . . . . 62
SFR Definition 5.10. ADC0GTL: ADC0 Greater-Than Data Low Byte . . . . . . . . . . . . . 62
SFR Definition 5.11. ADC0LTH: ADC0 Less-Than Data High Byte . . . . . . . . . . . . . . . 62
SFR Definition 5.12. ADC0LTL: ADC0 Less-Than Data Low Byte . . . . . . . . . . . . . . . . 63
SFR Definition 6.1. AMX0CF: AMUX0 Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . 71
SFR Definition 6.2. AMX0SL: AMUX0 Channel Select . . . . . . . . . . . . . . . . . . . . . . . . 71
SFR Definition 6.3. AMX0PRT: Port 3 Pin Selection . . . . . . . . . . . . . . . . . . . . . . . . . . 73
SFR Definition 6.4. HVA0CN: High Voltage Difference Amplifier Control . . . . . . . . . . . 75
SFR Definition 6.5. ADC0CF: ADC0 Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
SFR Definition 6.6. ADC0CN: ADC0 Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
SFR Definition 6.7. ADC0H: ADC0 Data Word MSB . . . . . . . . . . . . . . . . . . . . . . . . . . 82
SFR Definition 6.8. ADC0L: ADC0 Data Word LSB . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
SFR Definition 6.9. ADC0GTH: ADC0 Greater-Than Data High Byte . . . . . . . . . . . . . 84
SFR Definition 6.10. ADC0GTL: ADC0 Greater-Than Data Low Byte . . . . . . . . . . . . . 84
SFR Definition 6.11. ADC0LTH: ADC0 Less-Than Data High Byte . . . . . . . . . . . . . . . 84
SFR Definition 6.12. ADC0LTL: ADC0 Less-Than Data Low Byte . . . . . . . . . . . . . . . . 85
SFR Definition 7.1. AMX2CF: AMUX2 Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . 95
SFR Definition 7.2. AMX2SL: AMUX2 Channel Select . . . . . . . . . . . . . . . . . . . . . . . . . 95
SFR Definition 7.3. ADC2CF: ADC2 Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
SFR Definition 7.4. ADC2CN: ADC2 Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
SFR Definition 7.5. ADC2: ADC2 Data Word . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
SFR Definition 7.6. ADC2GT: ADC2 Greater-Than Data . . . . . . . . . . . . . . . . . . . . . . 100
SFR Definition 7.7. ADC2LT: ADC2 Less-Than Data . . . . . . . . . . . . . . . . . . . . . . . . . 100
SFR Definition 8.1. DAC0H: DAC0 High Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
SFR Definition 8.2. DAC0L: DAC0 Low Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
SFR Definition 8.3. DAC0CN: DAC0 Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
SFR Definition 8.4. DAC1H: DAC1 High Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
SFR Definition 8.5. DAC1L: DAC1 Low Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
SFR Definition 8.6. DAC1CN: DAC1 Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
SFR Definition 9.1. REF0CN: Reference Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
SFR Definition 10.1. REF0CN: Reference Control . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
SFR Definition 11.1. CPTnCN: Comparator 0, 1, and 2 Control . . . . . . . . . . . . . . . . . 124
SFR Definition 11.2. CPTnMD: Comparator Mode Selection . . . . . . . . . . . . . . . . . . . 125
SFR Definition 12.1. SFR Page Control Register: SFRPGCN . . . . . . . . . . . . . . . . . . 142
SFR Definition 12.2. SFR Page Register: SFRPAGE . . . . . . . . . . . . . . . . . . . . . . . . . 142
C8051F040/1/2/3/4/5/6/7
16 Rev. 1.5
SFR Definition 12.3. SFR Next Register: SFRNEXT . . . . . . . . . . . . . . . . . . . . . . . . . 143
SFR Definition 12.4. SFR Last Register: SFRLAST . . . . . . . . . . . . . . . . . . . . . . . . . . 143
SFR Definition 12.5. SP: Stack Pointer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
SFR Definition 12.6. DPL: Data Pointer Low Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
SFR Definition 12.7. DPH: Data Pointer High Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
SFR Definition 12.8. PSW: Program Status Word . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
SFR Definition 12.9. ACC: Accumulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
SFR Definition 12.10. B: B Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
SFR Definition 12.11. IE: Interrupt Enable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
SFR Definition 12.12. IP: Interrupt Priority . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158
SFR Definition 12.13. EIE1: Extended Interrupt Enable 1 . . . . . . . . . . . . . . . . . . . . . 159
SFR Definition 12.14. EIE2: Extended Interrupt Enable 2 . . . . . . . . . . . . . . . . . . . . . 160
SFR Definition 12.15. EIP1: Extended Interrupt Priority 1 . . . . . . . . . . . . . . . . . . . . . 161
SFR Definition 12.16. EIP2: Extended Interrupt Priority 2 . . . . . . . . . . . . . . . . . . . . . 162
SFR Definition 12.18. PCON: Power Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
SFR Definition 13.1. WDTCN: Watchdog Timer Control . . . . . . . . . . . . . . . . . . . . . . 169
SFR Definition 13.2. RSTSRC: Reset Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170
SFR Definition 14.1. OSCICL: Internal Oscillator Calibration . . . . . . . . . . . . . . . . . . . 174
SFR Definition 14.2. OSCICN: Internal Oscillator Control . . . . . . . . . . . . . . . . . . . . . 174
SFR Definition 14.3. CLKSEL: Oscillator Clock Selection . . . . . . . . . . . . . . . . . . . . . 175
SFR Definition 14.4. OSCXCN: External Oscillator Control . . . . . . . . . . . . . . . . . . . . 176
SFR Definition 15.1. FLACL: Flash Access Limit . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184
SFR Definition 15.2. FLSCL: Flash Memory Control . . . . . . . . . . . . . . . . . . . . . . . . . 184
SFR Definition 15.3. PSCTL: Program Store Read/Write Control . . . . . . . . . . . . . . . 185
SFR Definition 16.1. EMI0CN: External Memory Interface Control . . . . . . . . . . . . . . 189
SFR Definition 16.2. EMI0CF: External Memory Configuration . . . . . . . . . . . . . . . . . 190
SFR Definition 16.3. EMI0TC: External Memory Timing Control . . . . . . . . . . . . . . . . 195
SFR Definition 17.1. XBR0: Port I/O Crossbar Register 0 . . . . . . . . . . . . . . . . . . . . . 212
SFR Definition 17.2. XBR1: Port I/O Crossbar Register 1 . . . . . . . . . . . . . . . . . . . . . 213
SFR Definition 17.3. XBR2: Port I/O Crossbar Register 2 . . . . . . . . . . . . . . . . . . . . . 214
SFR Definition 17.4. XBR3: Port I/O Crossbar Register 3 . . . . . . . . . . . . . . . . . . . . . 215
SFR Definition 17.5. P0: Port0 Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
SFR Definition 17.6. P0MDOUT: Port0 Output Mode . . . . . . . . . . . . . . . . . . . . . . . . . 216
SFR Definition 17.7. P1: Port1 Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216
SFR Definition 17.8. P1MDIN: Port1 Input Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217
SFR Definition 17.9. P1MDOUT: Port1 Output Mode . . . . . . . . . . . . . . . . . . . . . . . . . 217
SFR Definition 17.10. P2: Port2 Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218
SFR Definition 17.11. P2MDIN: Port2 Input Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . 218
SFR Definition 17.12. P2MDOUT: Port2 Output Mode . . . . . . . . . . . . . . . . . . . . . . . . 219
SFR Definition 17.13. P3: Port3 Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219
SFR Definition 17.14. P3MDIN: Port3 Input Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . 220
SFR Definition 17.15. P3MDOUT: Port3 Output Mode . . . . . . . . . . . . . . . . . . . . . . . . 220
SFR Definition 17.16. P4: Port4 Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222
SFR Definition 17.17. P4MDOUT: Port4 Output Mode . . . . . . . . . . . . . . . . . . . . . . . . 222
SFR Definition 17.18. P5: Port5 Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 17
SFR Definition 17.19. P5MDOUT: Port5 Output Mode . . . . . . . . . . . . . . . . . . . . . . . . 223
SFR Definition 17.20. P6: Port6 Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224
SFR Definition 17.21. P6MDOUT: Port6 Output Mode . . . . . . . . . . . . . . . . . . . . . . . . 224
SFR Definition 17.22. P7: Port7 Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
SFR Definition 17.23. P7MDOUT: Port7 Output Mode . . . . . . . . . . . . . . . . . . . . . . . . 225
SFR Definition 18.1. CAN0DATL: CAN Data Access Register Low Byte . . . . . . . . . . 235
SFR Definition 18.2. CAN0ADR: CAN Address Index . . . . . . . . . . . . . . . . . . . . . . . . 235
SFR Definition 18.3. CAN0CN: CAN Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236
SFR Definition 18.4. CAN0TST: CAN Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236
SFR Definition 18.5. CAN0STA: CAN Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237
SFR Definition 19.1. SMB0CN: SMBus0 Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247
SFR Definition 19.2. SMB0CR: SMBus0 Clock Rate . . . . . . . . . . . . . . . . . . . . . . . . . 248
SFR Definition 19.3. SMB0DAT: SMBus0 Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249
SFR Definition 19.4. SMB0ADR: SMBus0 Address . . . . . . . . . . . . . . . . . . . . . . . . . . 250
SFR Definition 19.5. SMB0STA: SMBus0 Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251
SFR Definition 20.1. SPI0CFG: SPI0 Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . 261
SFR Definition 20.2. SPI0CN: SPI0 Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262
SFR Definition 20.3. SPI0CKR: SPI0 Clock Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263
SFR Definition 20.4. SPI0DAT: SPI0 Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264
SFR Definition 21.1. SCON0: UART0 Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274
SFR Definition 21.2. SSTA0: UART0 Status and Clock Selection . . . . . . . . . . . . . . . 275
SFR Definition 21.3. SBUF0: UART0 Data Buffer . . . . . . . . . . . . . . . . . . . . . . . . . . . 276
SFR Definition 21.4. SADDR0: UART0 Slave Address . . . . . . . . . . . . . . . . . . . . . . . 276
SFR Definition 21.5. SADEN0: UART0 Slave Address Enable . . . . . . . . . . . . . . . . . 276
SFR Definition 22.1. SCON1: Serial Port 1 Control . . . . . . . . . . . . . . . . . . . . . . . . . . 282
SFR Definition 22.2. SBUF1: Serial (UART1) Port Data Buffer . . . . . . . . . . . . . . . . . 283
SFR Definition 23.1. TCON: Timer Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291
SFR Definition 23.2. TMOD: Timer Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292
SFR Definition 23.3. CKCON: Clock Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293
SFR Definition 23.4. TL0: Timer 0 Low Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293
SFR Definition 23.5. TL1: Timer 1 Low Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294
SFR Definition 23.6. TH0: Timer 0 High Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294
SFR Definition 23.7. TH1: Timer 1 High Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294
SFR Definition 23.8. TMRnCN: Timer n Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299
SFR Definition 23.9. TMRnCF: Timer n Configuration . . . . . . . . . . . . . . . . . . . . . . . . 300
SFR Definition 23.10. RCAPnL: Timer n Capture Register Low Byte . . . . . . . . . . . . . 301
SFR Definition 23.11. RCAPnH: Timer n Capture Register High Byte . . . . . . . . . . . . 301
SFR Definition 23.12. TMRnL: Timer n Low Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301
SFR Definition 23.13. TMRnH Timer n High Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302
SFR Definition 24.1. PCA0CN: PCA Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312
SFR Definition 24.2. PCA0MD: PCA0 Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313
SFR Definition 24.3. PCA0CPMn: PCA0 Capture/Compare Mode . . . . . . . . . . . . . . 314
SFR Definition 24.4. PCA0L: PCA0 Counter/Timer Low Byte . . . . . . . . . . . . . . . . . . 315
SFR Definition 24.5. PCA0H: PCA0 Counter/Timer High Byte . . . . . . . . . . . . . . . . . . 315
SFR Definition 24.6. PCA0CPLn: PCA0 Capture Module Low Byte . . . . . . . . . . . . . . 316
C8051F040/1/2/3/4/5/6/7
18 Rev. 1.5
SFR Definition 24.7. PCA0CPHn: PCA0 Capture Module High Byte . . . . . . . . . . . . . 316
JTAG Register Definition 25.1. IR: JTAG Instruction Register . . . . . . . . . . . . . . . . . . 317
JTAG Register Definition 25.2. DEVICEID: JTAG Device ID Register . . . . . . . . . . . . 320
JTAG Register Definition 25.3. FLASHCON: JTAG Flash Control Register . . . . . . . . 322
JTAG Register Definition 25.4. FLASHDAT: JTAG Flash Data . . . . . . . . . . . . . . . . . 323
JTAG Register Definition 25.5. FLASHADR: JTAG Flash Address . . . . . . . . . . . . . . 323
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 19
1. System Overview
The C8051F04x fa mily of de vices ar e fully in te grated mixed-signal System-on-a-Chip MCUs with 64 digit al
I/O pins (C8051F040/2/4/6) or 32 digital I/O pins (C8051F041/3/5/7), and an integrated CAN 2.0B control-
ler. Highlighted features are listed below; refer to Table 1.1 for specific product feature selection.
• High-Speed pipelined 8051-compatible CIP-51 microcontroller core (up to 25 MIPS)
• Controller Area Network (CAN 2.0B) Controller with 32 message objects, each with its own indentifier
mask.
• In-system, full-speed, non-intrusive debug interface (on-chip)
• True 12-bit (C8051F040/1) or 10-bit (C8051F042/3/4/5/6/7) 100 ksps 8-channel ADC with PGA and
analog multiplexer
• High Voltage Difference Amplifier input to the 12/10-bit ADC (60 V Peak-to-Peak) with programmable
gain.
• True 8-bit 500 ksps 8-channel ADC with PGA and analog multiplexer (C8051F040/1/2/3)
• Two 12-bit DACs with programmable update scheduling (C8051F040/1/2/3)
•64 kB (C8051F040/1/2/3/4/5) or 32 kB (C8051F046/7) of in-system programmable Flash memory
• 4352 (4096 + 256) bytes of on-chip RAM
• External Data Memory Interface with 64 kB address space
• SPI, SMBus/I2C, and (2) UART serial interfaces imple men te d in ha rd wa re
• Five general purpose 16-bit Timers
• Programmable Counter/Timer Array with six capture/compare modules
• On-chip Watchdog Timer, VDD Monitor, and Temperature Sensor
With on-chip VDD monitor, Watchdog Timer, and clock oscillator, the C8051F04x family of devices are truly
stand-alone System-on-a-Chip solutions. All analog and digital peripherals are enabled/disabled and con-
figured by user firmware. The Flash memory can be reprogrammed even in-circuit, providing non-volatile
data storage, and also allowing field upgrades of the 8051 firmware.
On-board JTAG debug circuitry allows non-intrusive (uses no on-chip resources), full speed, in-circuit pro-
gramming and debugging using the production MCU installed in the final application. This debug system
supports inspection and modification of memory and registers, setting breakpoints, watchpoints, single
stepping, Run, and Halt commands. All analog and digital peripherals are fully functional while debugging
using JTAG.
Each MCU is specified for 2.7 V to 3.6 V operation over the industrial temperature range (–45 to +85 °C).
The Port I/Os, /RST, and JTAG pins are tolerant for input signals up to 5 V. The C8051F040/2/4/6 are avail-
able in a 100-pin TQFP and the C8051F041/3/5/7 are available in a 64-pin TQFP.
C8051F040/1/2/3/4/5/6/7
20 Rev. 1.5
Table 1.1. Product Selection Guide
Ordering Part Number
MIPS (Peak)
Flash Mem or y
RAM
External Memory Interface
SMBus/I2C and SPI
CAN
UARTS
Timers (16-bit)
Programmab le Co un te r Arr ay
Digital Port I/O’s
12-bit 100ksps ADC
10-bit 100ksps ADC
8-bit 500 ksps ADC Inputs
High Voltage Diff Amp
Voltage Refere nce
Temperature Sensor
DAC Resolution (bits)
DAC Outputs
Analog Comparators
Lead-free (RoHS Compliant)
Package
C8051F040 25 64 kB 4352
2 5
64
- 8
12 2 3 - 100TQFP
C8051F040-GQ 25 64 kB 4352
2 5
64
- 8
12 2 3
100TQFP
C8051F041 25 64 kB 4352
2 5
32
- 8
12 2 3 - 64TQFP
C8051F041-GQ 25 64 kB 4352
2 5
32
- 8
12 2 3
64TQFP
C8051F042 25 64 kB 4352
2 5
64 -
8
12 2 3 - 100TQFP
C8051F042-GQ 25 64 kB 4352
2 5
64 -
8
12 2 3
100TQFP
C8051F043 25 64 kB 4352
2 5
32 -
8
12 2 3 - 64TQFP
C8051F043-GQ 25 64 kB 4352
2 5
32 -
8
12 2 3
64TQFP
C8051F044 25 64 kB 4352
2 5
64 -
3 - 100TQFP
C8051F044-GQ 25 64 kB 4352
2 5
64 -
3
100TQFP
C8051F045 25 64 kB 4352
2 5
32 -
3 - 64TQFP
C8051F045-GQ 25 64 kB 4352
2 5
32 -
3
64TQFP
C8051F046 25 32 kB 4352
2 5
64 -
3 - 100TQFP
C8051F046-GQ 25 32 kB 4352
2 5
64 -
3
100TQFP
C8051F047 25 32 kB 4352
2 5
32 -
3 - 64TQFP
C8051F047-GQ 25 32 kB 4352
2 5
32 -
3
64TQFP
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 21
Figure 1.1. C8051F040/2 Block Diagram
UART1
SMBus
SPI Bus
PCA
Timers
0,1,2,3,4
VDD
VDD
VDD
DGND
DGND
DGND
/RST
XTAL1
XTAL2
P2.0
P2.7
P0.0
P0.7
DAC1 DAC1
(12-Bit)
VREF
DAC0
(12-Bit)
AIN0.0
DAC0
VREF
UART0
8:1
MONEN WDT
VREFD
VREF0
P7 Latch
P5 Latch
P6 Latch
P5.0/A8
P5.7/A51
P5
DRV
P6.0/A0
P6.7/A7
P6
DRV
P4
DRV P4.5/ALE
P4.6/RD
P4.7/WR
P4.4
Addr [7:0]
Addr [15:8]
Ctrl Latch
Data L a t c h
A
M
U
X
8:2
HVAIN+
HVAIN-
HVREF
HVCAP
HVAMP
TEMP
SENSOR
P0
Drv
P1
Drv
P2
Drv
P3
Drv
Port
0,1,2,3
&4
Latches
CAN
2.0B CANTX
8
0
5
1
C
o
r
e
Reset
A
M
U
X
Prog
Gain
ADC
100 ksps
(12 or 10-
Bit)
32x136
CANRAM
256 byte
RAM
4 kB
RAM
P3.0
P3.7
P1.0
P1.7
64 kB
Flash
System
Clock
Internal
Oscillator
External
Oscillator
Circuit
VDD
Monitor
C
R
O
S
S
B
A
R
Data [7:0]
Address [15:0]
Bus Control
Digital Power
Memories
Port 4 <from crossbar>
A
M
U
X
Prog
Gain
ADC
500 ksps
(8-Bit)
VREF2
P4.0
SFR Bus
P7
DRV
P7.0/D0
P7.7/D7
AV+
Debug HW
Boundary Scan
JTAG
Logic
TCK
TMS
TDI
TDO
AGND
AGND
AGND
AV+
AV+ Analog Power
P2.7
P2.6
+
-
CP0
P2.3
P2.2
+
-
CP1
P2.5
P2.4
+
-
CP2
AIN0.3
AIN0.2
AIN0.1
CANRX
External Memory Data
Bus
C8051F040/1/2/3/4/5/6/7
22 Rev. 1.5
Figure 1.2. C8051F041/3 Block Diagram
UART1
SMBus
SPI Bus
PCA
Timers
0,1,2,3,4
VDD
VDD
VDD
DGND
DGND
DGND
/RST
XTAL1
XTAL2
P2.0
P2.7
P0.0
P0.7
DAC1 DAC1
(12-Bit)
VREF
DAC0
(12-Bit)
AIN0.0
DAC0
VREF
UART0
8:1
MONEN WDT
VREFA
P7 Latch
P5 Latch
P6 Latch
P5
DRV
P6
DRV
P4
DRV
Addr [7:0]
Addr [ 15 :8]
Ctrl La tc h
Data Latch
A
M
U
X
8:2
HVAIN+
HVAIN-
HVREF
HVCAP
HVAMP
TEMP
SENSOR
P0
Drv
P1
Drv
P2
Drv
P3
Drv
Port
0,1,2,3
&4
Latches
CAN
2.0B CANTX
8
0
5
1
C
o
r
e
Reset
A
M
U
X
Prog
Gain
ADC
100 ksps
(12 or 10-
Bit)
32x136
CANRAM
256 byte
RAM
4 kB
RAM
P3.0
P3.7
P1.0
P1.7
64 kB
Flash
System
Clock
Internal
Oscillator
External
Oscillator
Circuit
VDD
Monitor
C
R
O
S
S
B
A
R
Data [7:0]
Address [15: 0]
Bus Control
Digital Power
Memories
Port 4 <from crossbar>
A
M
U
X
Prog
Gain
ADC
500 ksps
(8-Bit)
VREFA
SFR Bus
P7
DRV
Debug HW
Boundary Scan
JTAG
Logic
TCK
TMS
TDI
TDO
P2.7
P2.6
+
-
CP0
P2.3
P2.2
+
-
CP1
P2.5
P2.4
+
-
CP2
AIN0.3
AIN0.2
AIN0.1
CANRX
External Mem ory Data
Bus
AGND
AGND
AV+
AV+ Analog Power
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 23
Figure 1.3. C8051F044/6 Block Diagram
UART1
SMBus
SPI Bus
PCA
Timers
0,1,2,3,4
VDD
VDD
VDD
DGND
DGND
DGND
/RST
XTAL1
XTAL2
P2.0
P2.7
P0.0
P0.7
VREF
AIN0.0
VREF
UART0
MONEN WDT
VREF0
P7 Latch
P5 Latch
P6 Latch
P5.0/A8
P5.7/A51
P5
DRV
P6.0/A0
P6.7/A7
P6
DRV
P4
DRV P4.5/ALE
P4.6/RD
P4.7/WR
P4.4
Addr [7:0]
Add r [1 5: 8 ]
Ctrl Latch
Data Latch
A
M
U
X
8:2
HVAIN+
HVAIN-
HVREF
HVCAP
HVAMP
TEMP
SENSOR
P0
Drv
P1
Drv
P2
Drv
P3
Drv
Port
0,1,2,3
&4
Latches
CAN
2.0B CANTX
8
0
5
1
C
o
r
e
Reset
A
M
U
X
Prog
Gain
ADC
100 ksps
(10-Bit)
32x136
CANRAM
256 byte
RAM
4 kB
RAM
P3.0
P3.7
P1.0
P1.7
64/32 kB
Flash
System
Clock
Internal
Oscillator
External
Oscillator
Circuit
VDD
Monitor
C
R
O
S
S
B
A
R
Data [7:0]
Address [15: 0 ]
Bus Control
Digital Power
Memories
Port 4 <from crossbar>
P4.0
SFR Bus
P7
DRV
P7.0/D0
P7.7/D7
AV+
Debug HW
Boundary Sca n
JTAG
Logic
TCK
TMS
TDI
TDO
AGND
AGND
AGND
AV+
AV+ Analog Power
P2.7
P2.6
+
-
CP0
P2.3
P2.2
+
-
CP1
P2.5
P2.4
+
-
CP2
AIN0.3
AIN0.2
AIN0.1
CANRX
Exter n a l M e mory D a ta
Bus
C8051F040/1/2/3/4/5/6/7
24 Rev. 1.5
Figure 1.4. C8051F045/7 Block Diagram
UART1
SMBus
SPI Bus
PCA
Timers
0,1,2,3,4
VDD
VDD
VDD
DGND
DGND
DGND
/RST
XTAL1
XTAL2
P2.0
P2.7
P0.0
P0.7
VREF
AIN0.0
VREF
UART0
MONEN WDT
VREFA
P7 Latch
P5 La tc h
P6 La tc h
P5
DRV
P6
DRV
P4
DRV
Addr [7:0]
Addr [15:8]
Ctrl Latch
Data Latch
A
M
U
X
8:2
HVAIN+
HVAIN-
HVREF
HVCAP
HVAMP
TEMP
SENSOR
P0
Drv
P1
Drv
P2
Drv
P3
Drv
Port
0,1,2,3
&4
Latches
CAN
2.0B CANTX
8
0
5
1
C
o
r
e
Reset
A
M
U
X
Prog
Gain
ADC
100 ksps
(10-Bit)
32x136
CANRAM
256 byte
RAM
4 kB
RAM
P3.0
P3.7
P1.0
P1.7
64/32 kB
Flash
System
Clock
Internal
Oscillator
External
Oscillator
Circuit
VDD
Monitor
C
R
O
S
S
B
A
R
Data [7:0]
Address [15:0]
Bus Control
Digital Power
Memories
Port 4 <from crossbar>
SFR Bus
P7
DRV
Debug HW
Boundary Scan
JTAG
Logic
TCK
TMS
TDI
TDO
P2.7
P2.6
+
-
CP0
P2.3
P2.2
+
-
CP1
P2.5
P2.4
+
-
CP2
AIN0.3
AIN0.2
AIN0.1
CANRX
External Mem ory D ata
Bus
AGND
AGND
AV+
AV+ Analog Power
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 25
1.1. CIP-51™ Microcontroller Core
1.1.1. Fully 8051 Compatible
The C8051F04x family of devices utilizes Silicon Labs' proprietary CIP-51 microcontroller core. The CIP-
51 is fully compatible with the MCS-51™ instruction set; standard 803x/805x assemblers and compilers
can be used to develop software. The core has all the peripherals included with a standard 8052, inclu din g
five 16-bit counter/timers, two full-duplex UARTs, 256 bytes of internal RAM, 128 byte Special Function
Register (SFR) address space, and up to 8 byte-wide I/O Ports.
1.1.2. Improved Throughput
The CIP-51 employ s a p ipelined architectu re that grea tly increases it s instr uction throughpu t over the st an-
dard 8051 architecture. In a standard 8051, all instructions except for MUL and DIV take 12 or 24 system
clock cycles to execute with a maximum system clock of 12-to-24 MHz. By contrast, the CIP-51 core exe-
cutes 70% of its instr uctions in one or two syste m cloc k cycles, with only four instructions taking more than
four system clock cycles.
The CIP-51 has a total of 109 instructions. The table below shows the total number of instructions that
require each execution time.
With the CIP-51's maximum system clock at 25 MHz, it has a peak throughput of 25 MIPS. Figure 1.5
shows a comparison of peak throughputs of various 8-bit microcontroller cores with their maximum system
clocks.
Figure 1.5. Comparison of Peak MCU Execution Speeds
Clocks to Execute 1 2 2/3 33/4 44/5 5 8
Number of Instructions 26 50 514 73121
5
10
15
20
ADuC812
8051
(16 MHz clk)
Philips
80C51
(33 MHz clk)
Microchip
PIC17C75x
(33 MHz clk)
Silicon Labs
CIP-51
(25 MHz clk)
MIPS
25
C8051F040/1/2/3/4/5/6/7
26 Rev. 1.5
1.1.3. Additional Features
The C8051F04x MCU family includes several key enhancements to the CIP-51 core and peripherals to
improve overall performance and ease of use in end applications.
The extended interrup t handler provides 20 interrupt sources into the CIP-51 ( as opposed to 7 for the st an-
dard 8051), allowing the numerous analog and digital peripherals to interrupt the controller. An interrupt
driven system requires less intervention by the MCU, giving it more effective throughput. The extra inter-
rupt sources are very useful when building multi-tasking, real-time systems.
There are up to seven reset sources for the MCU: an on-board VDD monitor, a Watchdog Timer, a missing
clock detector, a voltage level detection from Comparator0, a forced software reset, the CNVSTR0 input
pin, and the /RST pin. The /RST pin is bi-directional, accommodating an external reset, or allowing the
internally generated POR to be output on the /RST pin. Each reset source ex cept for t he V DD monitor and
Reset Input pin may be disabled by the user in software; the VDD monitor is enabled/disabled via the
MONEN pin. The Watchdog Timer may be permanently enabled in software after a power-on reset during
MCU initialization.
The MCU has an internal, stand alone clock generator which is used by default as the system clock after
any reset. If desired, the clock source may be switched on the fly to the external oscillator, which can use a
crystal, ceramic resonator, capacitor, RC, or external clock source to generate the system clock. This can
be extremely useful in low power applications, allowing the MCU to run from a slow (power saving) exter-
nal crystal source, while periodically switching to the fast (up to 25 MHz) internal oscillator as needed.
Figure 1.6. On-Board Clock and Reset
WDT
XTAL1
XTAL2 OSC
Internal
Clock
Generator System
Clock CIP-51
Microcontroller
Core
Missing
Clock
Detector
(one-
shot)
WDT
Strobe
Software Reset
Extended In terrupt
Handler
Clock Select
RST
+
-
VDD
Supply
Reset
Timeout (wired-OR)
System Reset
Supply
Monitor
PRE
Reset
Funnel
+
-
CP0+ Comparator0
CP0-
(Port I/O) Crossbar CNVSTR
(CNVSTR
reset
enable)
(CP0
reset
enable)
EN
WDT
Enable
EN
MCD
Enable
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 27
1.2. On-Chip Memory
The CIP-51 has a standard 8051 program and data address configuration. It includes 256 bytes of data
RAM, with the upper 128 bytes dual-mapped. Indir ect addressing accesse s the upper 128 bytes of general
purpose RAM, and direct addressing accesses the 128 byte SFR address space. The CIP-51 SFR
address space contains up to 256 SFR Pages. In this way, the CIP-51 MCU can accommodate the many
SFRs required to control and configure the various peripherals featured on the device. The lower
128 bytes of RAM are acce ssible via direct an d indirect addressing. The first 32 bytes are addressable as
four banks of gene ral purpose registers, a nd the next 16 bytes can be byte addressable or bit addressab le.
The CIP-51 in the C8051F04x MCUs additionally has an on-chip 4 kB RAM block and an external memory
interface (EMIF) for accessing off-chip data memory or memory-mapped peripherals. The on-chip 4 byte
block can be addressed over the entire 64 kB external data memory address range (overlapping 4 kB
boundaries). External data memory address space can be mapped to on-chip memory only, off-chip mem-
ory only, or a combination of the two (addresses up to 4 kB directed to on-chip, above 4 kB directed to
EMIF). The EMIF is also configurable for multiplexed or non-multiplexed address/data lines.
The MCU's program memory consists of 64 kB (C8051F040/1/2/3/4/5) or 32 kB (C8051F046/7) of Flash.
This memory may be reprogrammed in-system in 512 byte sectors, and requires no special off-chip pro-
gramming voltage. The 512 bytes from addresses 0xFE00 to 0xFFFF are reserved for the 64 kB devices.
There is also a single 128 byte sector at address 0x10000 to 0x1007F, which may be useful as a small
table for software constants. See Figure 1.7 for the MCU system memory map.
Figure 1.7. On-Chip Memory Map
PROGRAM/DATA MEMORY
(FLASH)
(Direct and Indirect
Addressing)
0x00
0x7F
Upper 128 RAM
(Indirect Addressing
Only)
0x80
0xFF Special Function
Registers
(Direct Addressing Only)
DATA MEMORY (RAM)
General Purpose
Registers
0x1F
0x20
0x2F Bit Addressable Lower 128 RAM
(Direct and Indirect
Addressing)
0x30
INTERNAL DATA ADDRESS SPACE
EXTERNAL DATA ADDRESS SPACE
XRAM - 4096 Bytes
(accessable using MOVX
instruction)
0x0000
0x0FFF
Off-chip XRAM space
0x1000
0xFFFF
64 kB
Flash
(In-System
Programmable in 512
Byte Sectors)
0x0000
RESERVED
0xFE00
0xFDFF
Scrachpad Memory
(DATA only)
0x1007F
0x10000
Up To
256 SFR Pages
13
0
2F
C8051F040/1/2/3/4/5
32 kB
Flash
(In-System
Programmable in 512
Byte Sectors)
0x0000
RESERVED
0x8000
0x7FFF
Scrachpad Memory
(DATA only)
0x1007F
0x10000
C8051F046/7
C8051F040/1/2/3/4/5/6/7
28 Rev. 1.5
1.3. JTAG Debug and Boundary Scan
The C8051F04x family has on-chip JTAG boundary scan and debug circuitry that provides non-intrusive,
full speed, in-circuit debugging using the production part installed in the end application, via the four-pin
JTAG interface. The JTAG port is fully compliant to IEEE 1149.1, providing full boundary scan for test and
manufacturing purposes.
Silicon Labs' debugging system supports inspection and modification of memory and registers, break-
points, watchpoints, a stack monitor, and single stepping. No additional t ar get RAM, prog ram mem ory, tim-
ers, or communications channels are required. All the digital and analog peripherals are functional and
work correctly while debugging. All the peripherals (except for the ADC and SMBus) are stalled when the
MCU is halted, during single stepping, or at a breakpoint in order to keep them synchronized with instruc-
tion execution.
The C8051F040DK development kit provides all the hardware and software necessary to develop applica-
tion code and perform in-circuit debugging with the C8051F04x MCUs. The development kit includes two
target boards and a cable to facilitate evaluating a simple CAN communication network. The kit also
includes software with a developer's studio and debugger, a target application board with the associated
MCU installed, and the required cables and wall-mount power supply. The Serial Adapter takes its power
from the application board; it requires roughly 20 mA at 2.7-3.6 V. For applications where there is not suffi-
cient power available from the target system, the provided power supply can be connected directly to the
Serial Adapter.
Silicon Labs’ debug environment is a vastly superior configuration for developing and debugging embed-
ded applications comp a red to st andard MCU emulators, which use on-board "ICE Chip s" and t arget cables
and require the MCU in the application board to be socketed. Silicon Labs' debug environment both
increases ease of use and preserves the performance of the precision, on-chip analog peripheral s.
Figure 1.8. Development/In-System Debug Diagram
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 29
1.4. Programmable Digital I/O and Crossbar
The standard 8051 Ports (0, 1, 2, and 3) are available on the MCUs. The C8051F040/2/4/6 have 4 addi-
tional 8-bit ports (4, 5, 6, and 7) fo r a total of 64 general-purpose I/O Ports. The Ports behave like th e stan-
dard 8051 with a few enhancements.
Each port pin can be c onfigur ed as eit her a push -pull or open -drain ou tpu t. Also, the "w eak pullups" which
are normally fixed on an 8051 can be globally disabled, providing additional power s aving capabilities for
low-power applications.
Perhaps the most unique enhancement is the Digital Crossbar. This is essentially a large digital switching
network that allows mapping of internal digital system resources to Port I/O pins on P0, P1, P2, and P3
(See Figure 1.9). Unlike microcontrollers with standard multiplexed digital I/O ports, all combinations of
functions are supported with all package options offered.
The on-chip counter/timers, serial buses, HW interrupts, ADC Start of Conversion input, comparator out-
puts, and othe r digi tal signals in the controller can be configured to appear on the Port I/O pins specified in
the Crossbar Control registers. Th is allows the user to select the exact mix of ge neral purpose Port I/O an d
digital resources needed for the particular application.
Figure 1.9. Digital Crossbar Diagram
External
Pins
Digital
Crossbar
Priority
Decoder
SMBus
2
SPI 4
UART0
2
PCA
2
T0, T1,
T2, T2EX,
T3, T3EX,
T4,T4EX,
/INT0,
/INT1
P1.0
P1.7
P2.0
P2.7
P0.0
P0.7
Highest
Priority
Lowest
Priority
8
8
Comptr.
Outputs
(Internal Dig ital Signals )
Highest
Priority
Lowest
Priority
UART1
6
2
P3.0
P3.7
8
8
P0MDOUT, P1MDOUT,
P2MDOUT, P3MDOUT
Registers
XBR0, XBR1, XBR2,
XBR3 P1MDIN,
P2MDIN, P3MDIN
Registers
P1
I/O
Cells
P3
I/O
Cells
P0
I/O
Cells
P2
I/O
Cells
8
Port
Latches
P0
P1
P2
8
8
8
P3
8
(P2.0-P2.7)
(P1.0-P1.7)
(P0.0-P0.7)
(P3.0-P3.7)
To
ADC2
Input
To External
Memory
Interface
(EMIF) To
ADC0
Input
To
Comparators
/SYSCLK
CNVSTR0
CNVSTR2
C8051F040/1/2/3/4/5/6/7
30 Rev. 1.5
1.5. Programmable Counter Array
The C8051F04x MCU family includes an on-board Programmable Counter/Timer Array (PCA) in add ition
to the five 16-bit general purpose counter/timers. The PCA consists of a dedicated 16-bit counter/timer
time base with six programmable capture/compare modules. The timebase is clocked from one of six
sources: the system clock divided by 12, the system clock divided by 4, Timer 0 overflow, an External
Clock Input (ECI pin), the system clock, or the external oscillator source divided by 8.
Each capture/compare module can be configured to operate in one of six modes: Edge-Triggered Capture,
Software Timer, High Speed Output, Frequency Output, 8-Bit Pulse Wid th Modulato r, or 16-Bit Pulse Width
Modulator. The PCA Capt ure/ Compare M odule I /O an d Exte rnal Clo ck Inpu t are route d to the MCU Po rt I/
O via the Digital Crossbar.
Figure 1.10. PCA Block Diagram
Capture/Compare
Module 1
Capture/Compare
Module 0 Capture/Compare
Module 2 Capture/Compare
Module 3
CEX1
ECI
Crossbar
CEX2
CEX3
CEX0
Port I/O
16-Bit Counter/T ime r
PCA
CLOCK
MUX
SYSCLK/12
SYSCLK/4
Timer 0 Overflow
ECI
SYSCLK
External Clock/8
Capture/Compare
Module 4
CEX4
Capture/Compare
Module 5
CEX5
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 31
1.6. Controller Area Network
The C8051F04x family of devices feature a Controller Area Network (CAN) controller that implements
serial communication using the CAN protocol. The CAN controller facilitates communication on a CAN net-
work in accordance with the Bosch specification 2.0A (basic CAN) and 2.0B (full CAN). The CAN controller
consists of a CAN Core, Message RAM (separate from the C8051 RAM), a message handler state
machine, and control registers.
The CAN controller can operate at bit rates up to 1 Mbit/second. Silicon Labs CAN has 32 message
objects each having its own identifier mask used for acceptance filtering of received messages. Incoming
data, message o bject s and identifier masks are stor ed in the CAN me ssage RAM . All protocol functions for
transmission of data and acceptance filtering is performed by the CAN controller and not by the C8051
MCU. In this way, minimal CPU bandwidth is used for CAN communication. The C8051 configures the
CAN controller, accesses received data, and passes data for transmissio n via Special F unction Registers
(SFR) in the C8051.
Figure 1.11. CAN Controller Diagram
1.7. Serial Ports
The C8051F04x MCU Family includes two Enhanced Full-Duplex UARTs, an enhanced SPI Bus, and
SMBus/I2C. Each of the serial buses is fully implemented in hardware and makes extensive use of the
CIP-51's interrupts, thus requiring very little intervention by the CPU. The serial buses do not "share"
resources such as timers, interr upts, or Por t I/O, so any or all of th e serial buses may be used tog ether with
any other.
Message Handler
REGISTERS
Message RAM
(32 Message Objects)
CAN
Core
TX RX
CAN Controller
CIP-51
MCU
Interrupt
S
F
R
's
CANTX CANRX C8051F04x
S
Y
S
C
L
K
CAN_CLK
(fsys)
BRP
Prescaler
C8051F040/1/2/3/4/5/6/7
32 Rev. 1.5
1.8. 12/10-Bit Analog to Digital Converter
The C8051F040/1 devices have an on-chip 12-bit SAR ADC (ADC0) with a 9-channel input multiplexer
and programmable g ain a mplifier. With a maximum throughput of 100 ksp s , the ADC offers true 12-bit per-
formance with an INL of ±1LSB. C8051F042/3/4/5/6/7 devices include a 10-bit SAR ADC with similar spec-
ifications and configuration options. The ADC0 voltage reference is selected between the DAC0 output
and an external VREF pin. On C8051F040/2/4/6 devices, ADC0 has its own dedicated VREF0 input pin;
on C8051F041/3/5/7 devices, the ADC0 uses the VREFA input pin and, on the C8051F041/3, shares it
with the 8-bit ADC2. The on-chip 15 ppm/°C voltage reference may generate the voltage reference for the
on-chip ADCs or other system components via the VREF output pin.
The ADC is under full control of the CIP-51 microcontroller via its associated Special Function Registers.
One input channel is tied to an internal temperature sensor, while the other eight channels are available
externally. Each pair of the eight external input channels can be configured as either two single-ended
inputs or a single differential input. The system controller can also put the ADC into shutdown mode to
save power.
A programmable gain amplifier follows the analog multiplexer. The gain can be set to 0.5, 1, 2, 4, 8, or 16
and is sof tware progr ammable. The gain st age can be espe cially useful wh en dif fere nt ADC input channels
have widely varied input voltage signals, or when it is necessary to "zoom in" on a signal with a large dc
offset (in differential mode, a DAC could be used to provide the dc offset).
Conversions can be started in four ways; a software command, an overflow of Timer 2, an overflow of
Timer 3, or an external signal input. This flexibility allows the start of conversion to be tri ggered by software
events, external HW signals, or a periodic timer overflow signal. Conversion completions are indicated by a
status bit and an interrupt (if enabled). The resulting 10- or 12-bit data word is latched into two SFRs up on
completion of a conversion. The data can be right or left justified in these registers under software control.
Window Compare registers for the ADC data can be configured to interrupt the controller when ADC data
is within or outside of a specified range. The ADC can monitor a key voltage continuously in background
mode, but not interrupt the controller unless the converted data is within the specified window.
Figure 1.12. 10/12-Bit ADC Block Diagram
12 /1 0 -Bit
SAR
ADC 12
+
-
TEMP
SENSOR
+
-
+
-9-to-1
AMUX
(SE or
DIFF)
+
-
X
AIN0.0
AIN0.1
AIN0.2
AIN0.3 AV+
Pr o gramm ab le G ain
Amplifier
Analog Multiplexer Window Com pare
Logic
ADC Data
Registers
Window
Compare
Interrupt
Conversion
Complete
Interrupt
Configuration, Control, and Data
Registers
Start
Conversion Timer 3 Overflow
Timer 2 Overflow
Write to AD0B US Y
CNVSTR0
External VREF
Pin
DAC0 Output
(C8051F040/1/2/3 Only)
VREF
AGND
HVDA
HVAIN +
HVAIN -
Port 3
Pins
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 33
1.9. 8-Bit Analog to Digital Converter (C8051F040/1/2/3 Only)
The C8051F040/1/2/3 devices have an on-board 8-bit SAR ADC (ADC2) with an 8-channel input multi-
plexer and programmable gain amplifier. This ADC features a 500 ksps maximum throughput and true 8-
bit performance with an INL of ±1LSB. Eight input pins are available for measurement and can be pro-
grammed as single-ended or diff erential inputs. The ADC is under full control of the CIP-51 microcontroller
via the Special Function Registers. The ADC2 voltage reference is selected between the analog power
supply (AV+) and an external VREF pin. On C8051F040/2 devices, ADC2 has its own dedicated VREF2
input pin; on C8051F04 1/3 device s, ADC2 sh ares th e VREFA input pin with the 12/10-bit ADC0. User soft-
ware may put ADC2 into shutdown mode to save power.
A programmable gain amplifier follows the analog multiplexer. The gain stage can be especially useful
when different ADC input channels have widely varied input voltage signals, or when it is necessary to
"zoom in" on a signal with a lar ge dc o f fset (in d ifferential mode, a DAC cou ld be used to provide the dc off-
set). The PGA gain ca n be set in software to 0.5, 1, 2, or 4.
A flexible conversion scheduling system allows ADC2 conversion s to be initiated by software comman ds,
timer overflo ws, or an ex ternal inpu t signal. ADC 2 conver sions may also be synch ronized with ADC0 soft-
ware-commanded conversions. Conversion completions are indicated by a status bit and an interrupt (if
enabled), and the resulting 8-bit data word is latched into an SFR upon completion.
Figure 1.13. 8-Bit ADC Diagram
+
-
AV+
8
8-to-1
AMUX
X
AIN2.0
AIN2.1
AIN2.2
AIN2.3
AIN2.4
AIN2.5
AIN2.6
AIN2.7
Configuration, Control, and Data Registers
Programmable Gai n
Amplifier
Analog Multiplexer
8-Bit
SAR
ADC
Start Conversion Timer 3 Overflow
Timer 2 Overflow
Write to AD2BUSY
CNVSTR2 Input
Write to AD0BUSY
(synchronized with
ADC0)
ADC Data
Register
Conversion
Complete
Interrupt
External VREF
Pin
AV+
VREF
Single-ended or
Differential Measurement
+
-
+
-
+
-
+
-
Window
Compare Logic Window
Compare
Interrupt
C8051F040/1/2/3/4/5/6/7
34 Rev. 1.5
1.10. Comparators and DACs
Each C8051F040/1/2/3 MCU has two 12 -bit DACs, and all C8051 F04x devices ha ve three comp arators on
chip. The MCU data and control interface to each comparator and DAC is via the Special Function Regis-
ters. The MCU can place any DAC or comparator in low power shutdown mode.
The comparators have software programmable hysteresis and response time. Each comparator can gen-
erate an interrupt on its rising edge, falling edge, or both; these interrupts are capable of waking up the
MCU from sleep mode. The comparators' output state can also be polled in software. The comparator out-
puts can be programmed to appear on the Port I/O pins via the Crossbar.
The DACs are voltage output mode and include a flexible output scheduling mechanism. This scheduling
mechanism allows DAC output updates to be forced by a software write or a Timer 2, 3, or 4 overflow. The
DAC voltage reference is supplied via the dedicated VREFD input pin on C8051F040/2 devices or via the
internal voltage reference on C8051F041/3 devices. The DACs are especially us eful as re ferenc es for the
comparators or offsets for the differential inputs of the ADC.
Figure 1.14. Comparator and DAC Diagram
+
-
CPn+
CPn-
DAC0
DAC1
VREF
VREF
CIP-51
and
In te rru p t
Handler
CPn
D A C0
D A C1
CP n Output
(Po rt I/O)
SFR's
(Data
and
Cntrl)
CROSSBAR
3 C om parators
Com p arator inputs
P ort 2 .[7:2]
(C 8051F040/1/2/3 only)
(C 8051F040/1/2/3 only)
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 35
2. Absolute Maximum Ratings
Table 2.1. Absolute Maximum Ratings*
Parameter Conditions Min Typ Max Units
Ambient temperature under bias –55 — 125 °C
Storage Temperature –65 — 150 °C
Voltage on any Pin (except VDD, Port I/O, and JTAG
pins) with respect to DGND –0.3 — VDD +
0.3 V
Voltage on any Port I/O Pin, /RST, and JTAG pins with
respect to DGND –0.3 — 5.8 V
Voltage on VDD with respect to DGND –0.3 — 4.2 V
Maximum Total current through VDD, AV+, DGND,
and AGND ——800mA
Maximum output current sunk by any Port pin — — 100 mA
Maximum output current sunk by any other I/O pin — — 50 mA
Maximum output current sourced by any Port pin — — 100 mA
Maximum output current sourced by any other I/O pin — — 50 mA
*Note: Stresses above those listed under “Absolute Maximum Ratings” may cause permanent damage to the device.
This is a stress rating only and functional operation of the devices at those or any other conditions above those
indicated in the operation listings of this specification is not implied. Exposure to maximum rating conditions for
extended periods may affect device reliability.
Due to special I/O design requirements of the High Voltage Difference Amplifier, undue electrical over-voltage
stress (i.e., ESD) experienced by these pads may result in impedan ce degradation of these inputs (HVAIN+
and HVAIN–). For this reason, care should be taken to ensure proper handling and use as typically required to
prevent ESD damage to electrostatically sensitive CMOS devices (e.g., static-free workstations, use of
grounding straps, over-voltage protection in end-applications, etc.)
C8051F040/1/2/3/4/5/6/7
36 Rev. 1.5
3. Global DC Electrical Characteristic
Table 3.1. Global DC Electrical Characteristics
–40 to +85 °C , 25 MHz System Clock unless otherwise specified.
Parameter Conditions Min Typ Max Units
Analog Supply Voltage12.7 3.0 3.6 V
Analog Supply Current Internal REF, ADC, DAC, Com-
parators all active —1.7—mA
Analog Supply Current with
analog sub-systems inactive Internal REF, ADC, DAC, Com-
parators all disabled, oscillator
disabled
—0.2—µA
Analog-to-Digital Supply
Delta (|VDD - AV+|) ——0.5V
Digital Supply Voltage 2.7 3.0 3 .6 V
Digital Supply Current with
CPU active
(Normal Mode)
VDD = 2.7 V, Clock = 25 MHz
VDD = 2.7 V, Clock = 1 MHz
VDD = 2.7 V, Clock = 32 kHz
—
—
—
10
0.5
20
—
—
—
mA
mA
µA
Digital Supply Current with
CPU inactive (not accessing
Flash) (Idle Mode)
VDD = 2.7 V, Clock = 25 MHz
VDD = 2.7 V, Clock = 1 MHz
VDD = 2.7 V, Clock = 32 kHz
—
—
—
5
0.2
10
—
—
—
mA
mA
µA
Digital Supply Current
(shutdown) (Stop Mode) Oscillator not running — 0.2 — µA
Digital Supply RAM Data
Retention Voltage —1.5— V
Specified Operating
Temperature Range –40 — +85 °C
SYSCLK (system clock
frequency)20—25MHz
Tsysl (SYSCLK low time) 18 — — ns
Tsysh (SYSCLK high time) 18 — — ns
Notes:
1. Analog Supply AV+ must be greater than 1 V for VDD monitor to operate.
2. SYSCLK must be at least 32 kHz to enable debugging.
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 37
4. Pinout and Package Definitions
Table 4.1. Pin Definitions
Name Pin Numbers Type Description
F040/2/4/6 F041/3/5/7
VDD 37, 64, 90 24, 41, 57 Digital Supply Voltage. Must be tied to +2.7 to +3.6 V.
DGND 38, 63, 89 25, 40, 56 Digital Ground. Must be tied to Ground.
AV+ 8, 11, 14 3, 6 Analog Supply Voltage. Must be tied to +2.7 to +3.6 V.
AGND 9, 10, 13 4, 5 Analog Ground. Must be tied to Ground.
TMS 158 D In JTAG Test Mode Select with internal pullup.
TCK 259 D In JTAG Test Clock with internal pullup.
TDI 360 D In JTAG Test Data Input with internal pullup. TDI is latched
on the rising edge of TCK.
TDO 461 D Out JTAG Test Data Output with internal pullup. Data is
shifted out on TDO on the falling edge of TCK. TDO out-
put is a tri-state driver.
/RST 562 D I/O Device Reset. Open-drain output of internal VDD monitor.
Is driven low when VDD is < 2.7 V and MONEN is hig h. An
external source can initiate a system reset by driving this
pin low.
XTAL1 26 17 A In Crystal Input. This pin is the return for the internal oscilla-
tor circuit for a crystal or ceramic resonator. For a preci-
sion internal clock, connect a crystal or ceramic re sonator
from XTAL1 to XTAL2. If overdrive n by an external CMOS
clock, this becomes the system clock.
XTAL2 27 18 A Out Crystal Output. This pin is the excitation driver for a crystal
or ceramic resonator.
MONEN 28 19 D In VDD Monitor Enable. When tied high, this pin ena bles the
internal VDD monitor, which forces a system reset when
VDD is < 2.7 V. When tied low, the internal VDD monitor is
disabled.
In most applications, MONEN should be connected
directly to VDD.
VREF 12 7A I/O Bandgap Voltage Reference Output (all devices).
DAC Voltage Reference Input (C8051F041/3 only).
VREFA 8A In ADC0 (C8051F041/3/5/7) and ADC2 (C8051F041/3 only)
Voltage Reference Input.
VREF0 16 A In ADC0 Voltage Reference Input.
VREF2 17 A In ADC2 Voltage Reference Input (C8051F040/2 only).
VREF 15 A In DAC Voltage Reference Input (C8051F040/2 only).
AIN0.0 18 9A In ADC0 Input Channel 0 (See ADC0 Specification for com-
plete description).
C8051F040/1/2/3/4/5/6/7
38 Rev. 1.5
AIN0.1 19 10 A In ADC0 Input Channel 1 (See ADC0 Specification for com-
plete description).
AIN0.2 20 11 A In ADC0 Input Channel 2 (See ADC0 Specification for com-
plete description).
AIN0.3 21 12 A In ADC0 Input Channel 3 (See ADC0 Specification for com-
plete description).
HVCAP 22 13 A I/O High Voltage Difference Amplifier Capacitor.
HVREF 23 14 A In High Voltage Difference Amplifier Bias Reference.
HVAIN+ 24 15 A In High Voltage Difference Amplifier Positive Signal Input.
HVAIN- 25 16 A In High Voltage Difference Amplifier Negative Signal Inpu t.
CANTX 7 2 D Out Controller Area Network Transmit Output.
CANRX 6 1 D In Controller Area Network Receive Input.
DAC0 100 64 A Out Digital to Analog Converter 0 Voltage Output. (See DAC
Specification for complete description). (C8051F040/1/2/3
only)
DAC1 99 63 A Out Digital to Analog Converter 1 Voltage Output. (See DAC
Specification for complete description). (C8051F040/1/2/3
only)
P0.0 62 55 D I/O Port 0.0. See Port Input/Output section for complete
description.
P0.1 61 54 D I/O Port 0.1. See Port Input/Output section for complete
description.
P0.2 60 53 D I/O Port 0.2. See Port Input/Output section for complete
description.
P0.3 59 52 D I/O Port 0.3. See Port Input/Output section for complete
description.
P0.4 58 51 D I/O Port 0.4. See Port Input/Output section for complete
description.
P0.5/ALE 57 50 D I/O ALE Strobe for External Memory Address bus (multi-
plexed mode) Port 0.5
See Port Input/Output section for complete description.
P0.6/RD 56 49 D I/O /RD Strobe for External Memory Address bus
Port 0.6
See Port Input/Output section for complete description.
P0.7/WR 55 48 D I/O /WR Strobe for External Memory Address bus
Port 0.7
See Port Input/Output section for complete description.
Table 4.1. Pin Definitions (Continued)
Name Pin Numbers Type Description
F040/2/4/6 F041/3/5/7
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 39
P1.0/AIN2.0/A8 36 29 A In
D I/O ADC1 Input Channel 0 (See ADC1 Specification for com-
plete description).
Bit 8 External Memory Address bus (Non-multiplexed
mode)
Port 1.0
See Port Input/Output section for complete description.
P1.1/AIN2.1/A9 35 28 A In
D I/O Port 1.1. See Port Input/Output section for complete
description.
P1.2/AIN2.2/
A10 34 27 A In
D I/O Port 1.2. See Port Input/Output section for complete
description.
P1.3/AIN2.3/
A1133 26 A In
D I/O Port 1.3. See Port Input/Output section for complete
description.
P1.4/AIN2.4/
A12 32 23 A In
D I/O Port 1.4. See Port Input/Output section for complete
description.
P1.5/AIN2.5/
A13 31 22 A In
D I/O Port 1.5. See Port Input/Output section for complete
description.
P1.6/AIN2.6/
A14 30 21 A In
D I/O Port 1.6. See Port Input/Output section for complete
description.
P1.7/AIN2.7/
A15 29 20 A In
D I/O Port 1.7. See Port Input/Output section for complete
description.
P2.0/A8m/A0 46 37 D I/O Bit 8 External Memory Address bus (Multiplexed mode)
Bit 0 External Memory Address bus (Non-multiplexed
mode) Port 2.0
See Port Input/Output section for complete description.
P2.1/A9m/A1 45 36 D I/O Port 2.1. See Port Input/ Output section for complete
description.
P2.2/A10m/A2 44 35 D I/O Port 2.2. See Port Input/Output section for complete
description.
P2.3/A11m/A3 43 34 D I/O Port 2.3. See Port Input/Output section for complete
description.
P2.4/A12m/A4 42 33 D I/O Port 2.4. See Port Input/Output section for complete
description.
P2.5/A13m/A5 41 32 D I/O Port 2.5. See Port Input/Output section for complete
description.
P2.6/A14m/A6 40 31 D I/O Port 2.6. See Port Input/Output section for complete
description.
P2.7/A15m/A7 39 30 D I/O Port 2.7. See Port Input/Output section for complete
description.
Table 4.1. Pin Definitions (Continued)
Name Pin Numbers Type Description
F040/2/4/6 F041/3/5/7
C8051F040/1/2/3/4/5/6/7
40 Rev. 1.5
P3.0/AD0/D0 54 47 A In
D I/O Bit 0 External Memo ry Add re ss/Data bus (Multiplexe d
mode)
Bit 0 External Memory Data bus (Non-multiplexed mode)
Port 3.0
See Port Input/Output section for complete description.
ADC0 Input. (See ADC0 Specification for complete
description.)
P3.1/AD1/D1 53 46 A In
D I/O Port 3.1. See Port Input/Output section for complete
description.
ADC0 Input. (See ADC0 Specification for complete
description.)
P3.2/AD2/D2 52 45 A In
D I/O Port 3.2. See Port Input/Output section for complete
description.
ADC0 Input. (See ADC0 Specification for complete
description.)
P3.3/AD3/D3 51 44 A In
D I/O Port 3.3. See Port Input/Output section for complete
description.
ADC0 Input. (See ADC0 Specification for complete
description.)
P3.4/AD4/D4 50 43 A In
D I/O Port 3.4. See Port Input/Output section for complete
description.
ADC0 Input. (See ADC0 Specification for complete
description.)
P3.5/AD5/D5 49 42 A In
D I/O Port 3.5. See Port Input/Output section for complete
description.
ADC0 Input. (See ADC0 Specification for complete
description.)
P3.6/AD6/D6 48 39 A In
D I/O Port 3.6. See Port Input/Output section for complete
description.
ADC0 Input. (See ADC0 Specification for complete
description.)
P3.7/AD7/D7 47 38 A In
D I/O Port 3.7. See Port Input/Output section for complete
description.
ADC0 Input. (See ADC0 Specification for complete
description.)
P4.0 98 D I/O Port 4.0. See Port Input/Output section for complete
description.
P4.1 97 D I/O Port 4.1. See Port Input/Output section for complete
description.
P4.2 96 D I/O Port 4.2. See Port Input/Output section for complete
description.
P4.3 95 D I/O Port 4.3. See Port Input/Output section for complete
description.
Table 4.1. Pin Definitions (Continued)
Name Pin Numbers Type Description
F040/2/4/6 F041/3/5/7
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 41
P4.4 94 D I/O Port 4.4. See Port Input/Output section for complete
description.
P4.5/ALE 93 D I/O ALE Strobe for External Memory Address bus (multi-
plexed mode)
Port 4.5
See Port Input/Output section for complete description.
P4.6/RD 92 D I/O /RD Strobe for External Memory Address bus
Port 4.6
See Port Input/Output section for complete description.
P4.7/WR 91 D I/O /WR Strobe for External Memory Address bus
Port 4.7
See Port Input/Output section for complete description.
P5.0/A8 88 D I/O Bit 8 External Memory Address bus (Non-multiplexed
mode)
Port 5.0
See Port Input/Output section for complete description.
P5.1/A9 87 D I/O Port 5.1. See Port Input/Output section for complete
description.
P5.2/A10 86 D I/O Port 5.2. See Port Input/Output section for complete
description.
P5.3/A11 85 D I/O Port 5.3. See Port Inpu t/Output section for complete
description.
P5.4/A12 84 D I/O Port 5.4. See Port Input/Output section for complete
description.
P5.5/A13 83 D I/O Port 5.5. See Port Input/Output section for complete
description.
P5.6/A14 82 D I/O Port 5.6. See Port Input/Output section for complete
description.
P5.7/A15 81 D I/O Port 5.7. See Port Input/Output section for complete
description.
P6.0/A8m/A0 80 D I/O Bit 8 External Memory Address bus (Multiplexed mode)
Bit 0 External Memory Address bus (Non-multiplexed
mode)
Port 6.0
See Port Input/Output section for complete description.
P6.1/A9m/A1 79 D I/O Port 6.1. See Port Input/ Output section for complete
description.
P6.2/A10m/A2 78 D I/O Port 6.2. See Port Input/Output section for complete
description.
P6.3/A11m/A3 77 D I/O Port 6.3. See Port Input/Output section for complete
description.
Table 4.1. Pin Definitions (Continued)
Name Pin Numbers Type Description
F040/2/4/6 F041/3/5/7
C8051F040/1/2/3/4/5/6/7
42 Rev. 1.5
P6.4/A12m/A4 76 D I/O Port 6.4. See Port Input/Output section for complete
description.
P6.5/A13m/A5 75 D I/O Port 6.5. See Port Input/Output section for complete
description.
P6.6/A14m/A6 74 D I/O Port 6.6. See Port Input/Output section for complete
description.
P6.7/A15m/A7 73 D I/O Port 6.7. See Port Input/Output section for complete
description.
P7.0/AD0/D0 72 D I/O Bit 0 Ex te rn al Mem o ry Add re ss /Da ta bus (Mult iple xe d
mode)
Bit 0 External Memory Data bus (Non-multiplexed mode)
Port 7.0
See Port Input/Output section for complete description.
P7.1/AD1/D1 71 D I/O Port 7.1. See Port Input/Output section for complete
description.
P7.2/AD2/D2 70 D I/O Port 7.2. See Port Input/Output section for complete
description.
P7.3/AD3/D3 69 D I/O Port 7.3. See Port Input/Output section for complete
description.
P7.4/AD4/D4 68 D I/O Port 7.4. See Port Input/Output section for complete
description.
P7.5/AD5/D5 67 D I/O Port 7.5. See Port Input/Output section for complete
description.
P7.6/AD6/D6 66 D I/O Port 7.6. See Port Input/Output section for complete
description.
P7.7/AD7/D7 65 D I/O Port 7.7. See Port Input/Output section for complete
description.
Table 4.1. Pin Definitions (Continued)
Name Pin Numbers Type Description
F040/2/4/6 F041/3/5/7
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 43
Figure 4.1. TQFP-100 Pinout Diagram
C8051F040/2/4/6
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
42
43
44
45
46
47
48
49
50
1
2
3
4
5
6
7
8
9
100
99
98
97
96
95
94
93
92
91
90
89
88
87
86
85
84
83
82
81
80
79
78
77
76
66
65
64
63
62
61
60
59
58
57
56
55
54
53
52
51
75
74
73
72
71
70
69
68
67 P7.6/AD6/D6
P7.7/AD7/D7
VDD
DGND
P0.0
P0.1
P0.2
P0.3
P0.4
P0.5/ALE
P0.6/RD
P0.7/WR
P3.0/AD0/D0
P3.1/AD1/D1
P3.2/AD2/D2
P3.3/AD3/D3
P6.5/A13m/A5
P6.6/A14m/A6
P6.7/A15m/A7
P7.0/AD0/D0
P7.1/AD1/D1
P7.2/AD2/D2
P7.3/AD3/D3
P7.4/AD4/D4
P7.5/AD5/D5
DAC0
DAC1
P4.0
P4.1
P4.2
P4.3
P4.4
P4.5/ALE
P4.6/RD
P4.7/WR
VDD
DGND
P5.0/A8
P5.1/A9
P5.2/A10
P5.3/A11
P5.4/A12
P5.5/A13
P5.6/A14
P5.7/A15
P6.0/A8m/A0
P6.1/A9m/A1
P6.2/A10m/A2
P6.3/A11m/A3
P6.4/A12m/A4
AGND
AV+
VREF
AGND
AV+
VREFD
VREF0
VREF2
AIN0.0
AIN0.1
AIN0.2
AIN0.3
HVCAP
HVREF
HVAIN+
HVAIN-
TMS
TCK
TDI
TDO
/RST
CANRX
CANTX
AV+
AGND
XTAL1
XTAL2
MONEN
P1.7/AIN2.7/A15
P1.6/AIN2.6/A14
P1.5/AIN2.5/A13
P1.4/AIN2.4/A12
VDD
DGND
P1.3/AIN2.3/A11
P1.2/AIN2.2/A10
P1.1/AIN2.1/A9
P1.0/AIN2.0/A8
P2.7/A15m/A7
P2.6/A14m/A6
P2.5/A13m/A5
P2.4/A12m/A4
P2.3/A11m/A3
P2.2/A10m/A2
P2.1/A9m/A1
P2.0/A8m/A0
P3.7/AD7/D7
P3.6/AD6/D6
P3.5/AD5/D5
P3.4/AD4/D4
C8051F040/1/2/3/4/5/6/7
44 Rev. 1.5
Figure 4.2. TQFP-100 Package Drawing
A
A1
A2
b
D
D1
e
E
E1
L
-
0.05
0.95
0.17
-
-
-
-
-
0.45
-
-
1.00
0.22
16.00
14.00
0.50
16.00
14.00
0.60
1.20
0.15
1.05
0.27
-
-
-
-
-
0.75
MIN
(mm) NOM
(mm) MAX
(mm)
100
e
A1
b
A2
A
PIN 1
DESIGNATOR 1
E1 E
D1
D
L
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 45
Figure 4.3. TQFP-64 Pinout Diagram
C8051F041/3/5/7
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
64
63
62
61
60
59
58
57
56
55
54
53
52
51
50
49
DAC0
DAC1
/RST
TDO
TDI
TCK
TMS
VDD
DGND
P0.0
P0.1
P0.2
P0.3
P0.4
P0.5/ALE
P0.6/RD
P0.7/WR
P3.0/AD0/D0
P3.1/AD1/D1
P3.2/AD2/D2
P3.3/AD3/D3
P3.4/AD4/D4
P3.5/AD5/D5
VDD
DGND
P3.6/AD6/D6
P3.7/AD7/D7
P2.0/A8m/A0
P2.1/A9m/A1
P2.2/A10m/A2
P2.3/A11m/A3
P2.4/A12m/A4
CANRX
CANTX
AV+
AGND
AGND
AV+
VREF
VREFA
AIN0.0
AIN0.1
AIN0.2
AIN0.3
HVCAP
HVREF
HVAIN+
HVAIN-
XTAL1
XTAL2
MONEN
P1.7/AIN2.7/A15
P1.6/AIN2.6/A14
P1.5/AIN2.5/A13
P1.4/AIN2.4/A12
VDD
DGND
P1.3/AIN2.3/A11
P1.2/AIN2.2/A10
P1.1/AIN2.1/A9
P1.0/AIN2.0/A8
P2.7/A15m/A7
P2.6/A14m/A6
P2.5/A13m/A5
C8051F040/1/2/3/4/5/6/7
46 Rev. 1.5
Figure 4.4. TQFP-64 Package Drawing
A
A1
A2
b
D
D1
e
E
E1
L
-
0.05
0.95
0.17
-
-
-
-
-
0.45
-
-
-
0.22
12.00
10.00
0.50
12.00
10.00
0.6
1.20
0.15
1.05
0.27
-
-
-
-
-
0.75
MIN
(mm) NOM
(mm) MAX
(mm)
1
64
E
E1
e
A1
b
D
D1
PIN 1
DESIGNATOR
A2
A
L
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 47
5. 12-Bit ADC (ADC0, C8051F040/1 Only)
The ADC0 subsystem for the C8051F040/1 consists of a 9-channel, configurable analog multiplexer
(AMUX0), a programmable gain amplifier (PGA0), and a 100 ksps, 12-bit successive-approximation-regis-
ter ADC with integrated track-and-hold and Programmable Window Detector (see block diagram in
Figure 5.1). The AMUX0, PGA0, Data Conversion Modes, and Win dow Detector are all con figurable under
software control via the Special Function Registers shown in Figure 5.1. The voltage reference used by
ADC0 is selected as described in Section “9. Voltage Reference (C8051F040/2/4/6)” on page 113 for
C8051F040 devices, or Section “10. Voltage Reference (C8051F041/3/5/7)” on page 117 for
C8051F041 devices. The ADC0 subsystem (ADC0, track-and-hold and PGA0) is enabled only when the
AD0EN bit in the ADC0 Control regis ter (ADC0CN) is set to logic 1. The ADC0 subsystem is in low power
shutdown when this bit is logic 0.
Figure 5.1. 12-Bit ADC0 Functional Block Diagram
5.1. Analog Multiplexer and PGA
The analog multiplexer can input analog signals to the ADC from four external analog input pins (AIN0.0 -
AIN0.3), Port 3 port pins (optionally configured as analog input pins), High Voltage Difference Amplifier, or
an internally connected on-chip temperature sensor (temperature transfer function is shown in Figure 5.6).
AMUX input pairs can be programmed to operate in either differential or single-ended mode. This allows
the user to select the best measurement te chnique fo r ea ch input chann el, and eve n acco mmodates mode
changes "on-the-fly". The AMUX defaults to all single-ended inputs upon reset. There are three registers
associated with the AMUX: the Ch annel Selection re gister AMX0SL (SFR Definition 5.2), the Co nfiguration
register AMX0CF (SFR Definition 5.1), and the Port Pin Selection register AMX0PRT (SFR Definition 5.3).
Table 5.1 shows AMUX functionality by channel for each possible configuration. The PGA amplifies the
AMUX output signal by an amount determined by the states of the AMP0GN2-0 bits in the ADC0 Configu-
ration register, ADC0CF (SFR Defin ition 5.5). Th e PGA can be software-programm ed for gains o f 0.5, 2, 4,
8 or 16. Gain defaults to unity on reset.
12-Bit
SAR
ADC
REF
+
-
AV+
TEMP
SENSOR
12
9-to-1
AMUX
(SE or
DIFF)
AV+
24
12
AD0EN
SYSCLK
X
Start Conversion
AGND
AMX0CF
ADC0L ADC0H
ADC0LTLADC0LTHADC0GTLADC0GTH
AMX0SL
AMX0AD0
AMX0AD1
AMX0AD2
AMX0AD3
AIN01IC
AIN23IC
HVDAIC
PORT3IC
ADC0CF
AMP0GN0
AMP0GN1
AMP0GN2
AD0SC0
AD0SC1
AD0SC2
AD0SC3
AD0SC4
ADC0CN
AD0LJST
AD0WINT
AD0CM0
AD0CM1
AD0BUSY
AD0INT
AD0TM
AD0EN
Timer 3 Overflow
00
01
10
11
AD0BUSY (W)
CNVSTR0
AD0WINT
Comb.
Logic
HV
Input
Port 3
I/O Pins
Analog
Input
Pins
AGND Timer 2 Overflow
C8051F040/1/2/3/4/5/6/7
48 Rev. 1.5
5.1.1. Analog Input Configuration
The analog multiplexer routes signals from external analog input pins, Port 3 I/O pins (See Section
“17.1.5. Configuring Port 1, 2, and 3 Pins as Analog Inputs” on page 207), a High Voltage Difference
Amplifier, and an on-chip temperature sensor as shown in Figure 5.2.
Figure 5.2. Analog Input Diagram
Analog signals may be input from four external analog input pins (AIN0.0 through AIN0.3) as differential or
single-ended measurements. Additionally, Port 3 I/O Port Pins may be configured to input analog signals.
Port 3 pins config ured as analog input s are sele cted using the Port Pin Selection register (AMX0PR T). Any
number of Port 3 pins may be selected simultaneously as inputs to the AMUX. Even numbered Port 3 pins
and odd numbered Port 3 pins are routed to separate AMUX inputs. (Note: Even port pins and odd port
pins that are simultaneously selected will be shorted together as “wired-OR”.) In this way, differential mea-
surements may be made when using the Port 3 pins (voltage difference between selected even and odd
Port 3 pins) as shown in Figure 5.2.
The High Voltage Difference Amplifier (HVDA) will accept analog input signals and reject up to 60 volts
common-mode for differential measurement of up to the reference voltage to the ADC (0 to VREF volts).
The output of the HVDA can be selected as an input to the ADC using the AMUX as any other channel is
selected for input. (See Section “5.2. High-Voltage Difference Amplifier” on page 52).
+
-
+
-
+
-
9-to-1
AMUX
(SE or
DIFF)
AMX0CF
AIN01IC
AIN23IC
HVDAIC
PORT3IC
12-Bit
SAR
ADC
X
TEMP SENSOR
AGND
AIN0.0
AIN0.1
AIN0.2
AIN0.3
AMX0SL
AMX0AD0
AMX0AD1
AMX0AD2
AMX0AD3
0
7
6
5
4
3
2
1
8
HV
AMP
HVCAP
HVREF
HVAIN -
HVAIN +
P3.6
P3.4
P3.2
P3.0
P3.7
P3.5
P3.3
P3.1
(WIRED-OR)
(WIRED-OR)
AMX0PRT
PAIN0EN
PAIN2EN
PAIN4EN
PAIN6EN
PAIN7EN
PAIN5EN
PAIN3EN
PAIN1EN P3EVEN
P3ODD
+
-
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 49
SFR Definition 5.1. AMX0CF: AMUX0 Configuration
SFR Definition 5.2. AMX0SL: AMUX0 Channel Select
Bits7-4: UNUSED. Read = 0000b; Write = don’t care
Bit3: PORT3IC: Port 3 even/odd Pin Input Pair Configuration Bit
0: Port 3 even and odd input channels are independent single-ended inputs
1: Port 3 even and odd input channels are (respectively) +, - difference input pair
Bit2: HVDA2C: HVDA 2’s Compliment Bit
0: HVDA output measured as an independent single-ended input
1: HVDA result for 2’s compliment value
Bit1: AIN23IC: AIN0.2, AIN0.3 Input Pair Configuration Bit
0: AIN0.2 and AIN0.3 are independent single-ended inputs
1: AIN0.2, AIN0.3 are (respectively) +, - differ ence input pair
Bit0: AIN01IC: AIN0.0, AIN0.1 Input Pair Configuration Bit
0: AIN0.0 and AIN0.1 are independent single-ended inputs
1: AIN0.0, AIN0.1 are (respectively) +, - differ ence input pair
NOTE: The ADC0 Data Word is in 2’s complement format for channels configured as difference.
R R R R R/W R/W R/W R/W Reset Value
- - - - PORT3IC HVDA2C AIN23IC AIN01IC 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR
Address:
SFR Address:
SFR Page: 0xBA
0
Bits7-4: UNUSED. Read = 0000b; Write = don’t care
Bits3-0: AMX0AD3-0: AMX0 Address Bits
0000-1111b: ADC Inputs selected per Table 5.1.
R R R R R/W R/W R/W R/W Reset Value
- - - - AMX0AD3 AMX0AD2 AMX0AD1 AMX0AD0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xBB
0
C8051F040/1/2/3/4/5/6/7
50 Rev. 1.5
Note: “P3EVEN” denotes even numbered and “P3ODD” odd numbered Port 3 pins selected in the AMX0PRT
register.
Table 5.1. AMUX Selection Chart (AMX0AD3–0 and AMX0CF3–0 bits)
AMX0AD3-0
0000 0001 0010 0011 0100 0101 0110 0111 1xxx
AMX0CF Bits 3-0
0000 AIN0.0 AIN0.1 AIN0.2 AIN0.3 HVDA AGND P3EVEN P3ODD TEMP
SENSOR
0001 +(AIN0.0)
-(AIN0.1) AIN0.2 AIN0.3 HVDA AGND P3EVEN P3ODD TEMP
SENSOR
0010 AIN0.0 AIN0.1 +(AIN0.2)
-(AIN0.3) HVDA AGND P3EVEN P3ODD TEMP
SENSOR
0011 +(AIN0.0)
-(AIN0.1) +(AIN0.2)
-(AIN0.3) HVDA AGND P3EVEN P3ODD TEMP
SENSOR
0100 AIN0.0 AIN0.1 AIN0.2 AIN0.3 +(HVDA)
-(HVREF) P3EVEN P3ODD TEMP
SENSOR
0101 +(AIN0.0)
-(AIN0.1) AIN0.2 AIN0.3 +(HVDA)
-(HVREF) P3EVEN P3ODD TEMP
SENSOR
0110 AIN0.0 AIN0.1 +(AIN0.2)
-(AIN0.3) +(HVDA)
-(HVREF) P3EVEN P3ODD TEMP
SENSOR
0111 +(AIN0.0)
-(AIN0.1) +(AIN0.2)
-(AIN0.3) +(HVDA)
-(HVREF) P3EVEN P3ODD TEMP
SENSOR
1000 AIN0.0 AIN0.1 AIN0.2 AIN0.3 HVDA AGND +P3EVEN
-P3ODD TEMP
SENSOR
1001 +(AIN0.0)
-(AIN0.1) AIN0.2 AIN0.3 HVDA AGND +P3EVEN
-P3ODD TEMP
SENSOR
1010 AIN0.0 AIN0.1 +(AIN0.2)
-(AIN0.3) HVDA AGND +P3EVEN
-P3ODD TEMP
SENSOR
1011 +(AIN0.0)
-(AIN0.1) +(AIN0.2)
-(AIN0.3) HVDA AGND +P3EVEN
-P3ODD TEMP
SENSOR
1100 AIN0.0 AIN0.1 AIN0.2 AIN0.3 +(HVDA)
-(HVREF) +P3EVEN
-P3ODD) TEMP
SENSOR
1101 +(AIN0.0)
-(AIN0.1) AIN0.2 AIN0.3 +(HVDA)
-(HVREF) +P3EVEN
-P3ODD TEMP
SENSOR
1110 AIN0.0 AIN0.1 +(AIN0.2)
-(AIN0.3) +(HVDA)
-(HVREF) +P3EVEN
-P3ODD TEMP
SENSOR
1111 +(AIN0.0)
-(AIN0.1) +(AIN0.2)
-(AIN0.3) +(HVDA)
-(HVREF) +P3EVEN
-P3ODD TEMP
SENSOR
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 51
SFR Definition 5.3. AMX0PRT: Port 3 Pin Selection
Bit7: PAIN7EN: Pin 7 Analog Input Enable Bit
0: P3.7 is not selected as an analog input to the AMUX.
1: P3.7 is selected as an analog input to the AMUX.
Bit6: PAIN6EN: Pin 6 Analog Input Enable Bit
0: P3.6 is not selected as an analog input to the AMUX.
1: P3.6 is selected as an analog input to the AMUX.
Bit5: PAIN5EN: Pin 5 Analog Input Enable Bit
0: P3.5 is not selected as an analog input to the AMUX.
1: P3.5 is selected as an analog input to the AMUX.
Bit4: PAIN4EN: Pin 4 Analog Input Enable Bit
0: P3.4 is not selected as an analog input to the AMUX.
1: P3.4 is selected as an analog input to the AMUX.
Bit3: PAIN3EN: Pin 3 Analog Input Enable Bit
0: P3.3 is not selected as an analog input to the AMUX.
1: P3.3 is enabled as an analog input to the AMUX.
Bit2: PAIN2EN: Pin 2 Analog Input Enable Bit
0: P3.2 is not selected as an analog input to the AMUX.
1: P3.2 is enabled as an analog input to the AMUX.
Bit1: PAIN1EN: Pin 1 Analog Input Enable Bit
0: P3.1 is not selected as an analog input to the AMUX.
1: P3.1 is enabled as an analog input to the AMUX.
Bit0: PAIN0EN: Pin 0 Analog Input Enable Bit
0: P3.0 is not selected as an analog input to the AMUX.
1: P3.0 is enabled as an analog input to the AMUX.
Note:Any number of Port 3 pins may be selected simultaneously inputs to the AMUX. Odd numbered and even
numbered pins that are selected simultaneously are shorted together as “wired-OR”.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
PAIN7EN PAIN6EN PAIN5EN PAIN4EN PAIN3EN PAIN2EN PAIN1EN PAIN0EN 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xBD
0
C8051F040/1/2/3/4/5/6/7
52 Rev. 1.5
5.2. High-Voltage Difference Amplifier
The High Voltage Dif fere nce Amplifier (HVDA) can be used to m easure high dif feren tial voltages up to 60 V
peak-to-peak, reject h igh common-mode volt ages up to ±60 V, and condition the signal volt age r ange to be
suitable for input to ADC0. The input signal to the HVDA may be below AGND to –60 volts, and as high as
+60 volts, making the device suitable for both single and dual supply applications. The HVDA provides a
common-mode signal for the ADC via the High Voltage Reference Input (HVREF), allowing measurement
of signals outside the specified ADC input range using on-chip circuitry. The HVDA has a gain of 0.05 V/V
to 14 V/V. The first stage 20:1 difference amplifier has a gain of 0.05 V/V when the output amplifier is used
as a unity gain buffer. When the output amplifier is set to a gain of 280 (selected using the HVGAIN bits in
the High Voltage Control Register), an over all gain of 14 can be attained.
The HVDA uses four available external pins: +HVAIN, –HVAIN, HVCAP, and HVREF. HVAIN+ and HVAIN-
serve as the d ifferential inputs to the HVDA. HVREF should be used to pro vide a com mon mode refe ren ce
for input to ADC0, and to prevent the output of the HVDA circuit from saturating. The output from the
HVDA circuit as calculated by Equation 5.1 must remain within the “Output Voltage Range” specification
listed in Table 5.3. The ideal value for HVREF in most applications is e qual to 1/2 the su pply volt age for the
device. When the ADC is configured for differential measurement, the HVREF signal is applied to the AIN-
input of the ADC, thereby removing HVREF from the measurement. HVCAP facilitates the use of a capac-
itor for noise filtering in conjunction with R7 (see Figure 5.3 for R7 and other appro ximat e resisto r va lues) .
Alternatively, the HVCAP could also be used to access amplification of the first stage of the HVDA at an
external pin. (See Table 5.3 on page 68 for electrical specifications of the HVDA.)
Equation 5.1. Calculating HVDA Output Voltage to AIN+
Figure 5.3. High Voltage Difference Amplifier Functional Diagram
VOUT HVAIN+HVAIN-–Gain HVREF+=
Note: The output voltage of the HVDA is selected as an input to the AIN+ input of ADC0 via its analog multiplexer
(AMUX0). HVDA output voltages outside the ADC’s input range will result in saturation of the ADC input. Allow
for adequate settle/tracking time for proper voltage measurements.

k
5k
100k
5k
HVA0CN
Gain Setting
HVAIN-
HVAIN+
HVREF
HVCAP
Vout
(To AMUX0)
5k
Resistor values are
approximate
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 53
SFR Definition 5.4. HVA0CN: High Voltage Difference Amplifier Control
Bit7: HVDAEN: High Voltage Difference Amplifier (HVDA) Enable Bit.
0: The HVDA is disabled.
1: The HVDA is enabled.
Bits6-3: Reserved.
Bits2-0: HVGAIN3-HVGAIN0: HVDA Gain Control Bits.
HVDA Gain Control Bits set the amplification gain if the difference signal input to the HVDA
as defined in the table below:
R/W R R R R/W R/W R/W R/W Reset Value
HVDAEN - - - HVGAIN3 HVGAIN2 HVGAIN1 HVGAIN0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xD6
0
HVGAIN3:HVGAIN0 HVDA Gain
0000 0.05
0001 0.1
0010 0.125
0011 0.2
0100 0.25
0101 0.4
0110 0.5
0111 0.8
1000 1.0
1001 1.6
1010 2.0
1011 3.2
1100 4.0
1101 6.2
1110 7.6
1111 14
C8051F040/1/2/3/4/5/6/7
54 Rev. 1.5
5.3. ADC Modes of Operation
ADC0 has a maximum conversion speed of 100 ksps. The ADC0 conversion clock is derived from the sys-
tem clock divided by the value held in the ADC0SC bits of register ADC0CF.
5.3.1. Starting a Conversion
A conversion can be initiated in one of four ways, depending on the programmed states of the ADC0 Start
of Conversion Mode bits (AD0CM1, AD0CM0) in ADC0CN. Conversions may be initiated by the following:
• Writing a ‘1’ to the AD0BUSY bit of ADC0CN;
• A Timer 3 overflow (i.e., timed continuous conversions);
• A rising edge detected on the external ADC convert start signal, CNVSTR0;
• A Timer 2 overflow (i.e., timed continuous conversions).
The AD0BUSY bit is set to logic 1 during conversion and restored to logic 0 when conversion is complete.
The falling edge of AD0BUSY triggers an interrupt (when enabled) and sets the AD0INT interrupt flag
(ADC0CN.5). Converted dat a is availabl e in the ADC0 dat a word MSB an d LSB registers, ADC0H, ADC0L.
Converted data can be either left or right justified in the ADC0H:ADC0L register pair (see example in
Figure 5.7) depending on the programmed state of the AD0LJST bit in the ADC0CN register.
When initiating conversions by writing a ‘1’ to AD0BUSY, the AD0INT bit should be polled to determine
when a conversion has completed (ADC0 interrupts may also be used). The recommended polling proce-
dure is shown below.
Step 1. Write a ‘0’ to AD0INT;
Step 2. Write a ‘1’ to AD0BUSY;
Step 3. Poll AD0INT for ‘1’;
Step 4. Process ADC0 data.
5.3.2. Tracking Modes
According to Table 5.2, each ADC0 conversion must be preceded by a minimum tracking time for the con-
verted result to be accurate. The AD0TM bit in register ADC0CN controls the ADC0 track-and-hold mode.
In its default state, the ADC0 input is continuously tracked when a conversion is not in progress. When the
AD0TM bit is logic 1, ADC0 operates in low-power tracking mode. In this mode, each conversion is pre-
ceded by a tracking period of 3 SAR clocks afte r the st art-of-con version signal. When the CNVSTR0 signal
is used to initiate conversions in low-power tracking mode, ADC0 tracks only when CNVSTR0 is low; con-
version begins on the rising edge of CNVSTR0 (see Figure 5.4). Tracking can also be disabled when the
entire chip is in low power s tandby or sleep modes. Low-power tracking mode is also useful when AMUX
or PGA settings are frequently changed, to ensure that settling time requirements are met (see Section
“5.3.3. Settling Time Requirements” on page 56).
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 55
Figure 5.4. 12-Bit ADC Track and Conversion Example Timing
1234567891
01
11
21
31
41
51
6
CNVSTR
(AD0CM[1:0]=10)
ADC0TM=1
ADC0TM=0
Timer 2, Timer 3 Overflow;
W rit e '1 ' to A D0 B US Y
(AD0C M [1 :0]=00 , 01, 11)
ADC0TM=1
ADC0TM=0
A. ADC Timing for External Trigger Source
B. ADC Timing for Internal Trigger Sources
SAR
Clocks
SAR
Clocks
1234567891
01
11
21
31
41
51
61
71
81
9
1234567891
01
11
21
31
41
51
6
SAR
Clocks
Track Convert Low Power Mode
Low Power
or Convert
Track Or C onv ert Convert Track
Track Convert Low Power Mode
Low Power
or Convert
Track or
Convert Convert Track
C8051F040/1/2/3/4/5/6/7
56 Rev. 1.5
5.3.3. Settling Time Requirements
A minimum tracking time is requir ed before an accu rate conver sion can be pe rformed. This tracking time is
determined by the ADC0 MUX resistance, the ADC0 sampling capacitance, any external source resis-
tance, and the accuracy required for the conversion. Figure 5.5 shows the equivalent ADC0 input circuits
for both dif ferential and Single-ended mo des. Notice that the equivalen t time constant for both input circuit s
is the same. The required settling time for a given settling accuracy (SA) may be approximated by
Equation 5.2. When measuring the Temperature Sensor output, RTOTAL reduces to RMUX. Note that in
Low-Power tracking mode, three SAR clocks are used for tracking at the start of every conversion. For
most applications, these three SAR clocks will meet the tracking requirements. See Table 5.2 for absolute
minimum settling/tracking time requirements.
Equation 5.2. ADC0 Settling Time Requirements
Where:
SA is the settling accuracy, given as a fraction of an LSB (for example, 0.25 to settle within 1/4 LSB)
t is the required settling time in seconds
RTOTAL is the sum of the ADC0 MUX resistance and any external source resistance.
n is the ADC resolution in bits (12).
Figure 5.5. ADC0 Equivalent Input Circuits
t2n
SA
-------

RTOTALCSAMPLE
ln=
R
MUX
= 5k
RC
Input
= R
MUX
* C
SAMPLE
R
MUX
= 5k
C
SAMPLE
= 10pF
C
SAMPLE
= 10pF
MUX Select
MUX Select
Differe ntial Mode
AIN0.x
AIN0.y
R
MUX
= 5k
C
SAMPLE
= 10pF
RC
Input
= R
MUX
* C
SAMPLE
MUX Select
Single -Ended Mode
AIN0.x
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 57
Figure 5.6. Temperature Sensor Transfer Function
0-50 50 100
(Celsius)
0.500
0.600
0.700
0.800
0.900
(Volts)
V
TEMP
= 0.00286(TEMP
C
) + 0.776
for PGA Gain = 1
1.000
C8051F040/1/2/3/4/5/6/7
58 Rev. 1.5
SFR Definition 5.5. ADC0CF: ADC0 Configuration Register
Bits7-3: AD0SC4-0: ADC0 SAR Conversion Clock Period Bits
SAR Conversion clock is der ived from system clock by the following equation, where
AD0SC refers to the 5-b it value held in AD0SC4-0, and CLKSAR0 refers to the desired ADC0
SAR clock. See Table 5.2 for SAR clock configuration requirements.
* or
*Note: AD0SC is the rounded-up result.
Bits2-0: AMP0GN2-0: ADC0 Internal Amplifier Gain (PGA)
000: Gain = 1
001: Gain = 2
010: Gain = 4
011: Gain = 8
10x: Gain = 16
11 x: Gain = 0.5
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
AD0SC4 AD0SC3 AD0SC2 AD0SC1 AD0SC0 AMP0GN2 AMP0GN1 AMP0GN0 11111000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xBC
0
AD0SC SYSCLK
CLKSAR0
-----------------------1–
CLKSAR0SYSCLK
AD0SC 1+
----------------------------
=
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 59
SFR Definition 5.6. ADC0CN: ADC0 Control
Bit7: AD0EN: ADC0 Enable Bit.
0: ADC0 Disabled. ADC0 is in low-power shutdown.
1: ADC0 Enabled. ADC0 is active and ready for data conversions.
Bit6: AD0TM: ADC Track Mode Bit
0: When the ADC is enabled, tracking is continuous unless a conversion is in process
1: Tracking Defined by AD0CM1-0 bit s
Bit5: AD0INT: ADC0 Conversion Complete Interrupt Flag.
This flag must be cleared by software.
0: ADC0 has not completed a data conversion since the last time this flag was cleared.
1: ADC0 has completed a data conversion.
Bit4: AD0BUSY: ADC0 Busy Bit.
Read:
0: ADC0 Conversion is complete or a conversion is not currently in progress. AD0INT is set
to logic 1 on the falling edge of AD0BUSY.
1: ADC0 Conversion is in progress.
Write:
0: No Effect.
1: Initiates ADC0 Conversion if AD0CM1-0 = 00b
Bit3-2: A D0 CM 1-0 : AD C0 Start of Conversio n Mo de Sele ct.
If AD0TM = 0:
00: ADC0 conversion initiated on every write of ‘1’ to AD0BUSY.
01: ADC0 conversion initiated on overflow of Timer 3.
10: ADC0 conversion initiated on rising edge of external CNVSTR0.
11: ADC0 conversion initiated on overflow of Timer 2.
If AD0TM = 1:
00: Tracking starts with the write of ‘1’ to AD0BUSY and lasts for 3 SAR clocks, followed by
conversion.
01: Tracking started by the overflow of T imer 3 and last for 3 SAR clocks, followed by con-
version.
10: ADC0 tracks only when CNVSTR0 input is logic low; conversion starts on rising
CNVSTR0 edge.
11: Tracking started by the overflow of Timer 2 and last for 3 SAR clocks, followed by con-
version.
Bit1: AD0WINT: ADC0 Window Compare In te rr up t Fla g.
This bit must be cleared by software.
0: ADC0 Window Comparison Data match has not occurred since this flag was last cleared.
1: ADC0 Window Comparison Data match has occurred.
Bit0: AD0LJST: ADC0 Left Justify Select.
0: Data in ADC0H:ADC0L registers are right-justified.
1: Data in ADC0H:ADC0L registers are left-justified.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
AD0EN AD0TM AD0INT AD0BUSY AD0CM1 AD0CM0 AD0WINT AD0LJST 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 Bit
Addressable
SFR Address:
SFR Page: 0xE8
0
C8051F040/1/2/3/4/5/6/7
60 Rev. 1.5
SFR Definition 5.7. ADC0H: ADC0 Data Word MSB
SFR Definition 5.8. ADC0L: ADC0 Data Word LSB
Bits7-0: ADC0 Data Word High-Order Bits.
For AD0LJST = 0: Bits 7-4 are the sign exten sion of Bit3. Bits 3-0 are the upp er 4 bits of the
12-bit ADC0 Data Word.
For AD0LJST = 1: Bits 7-0 are the most-significant bits of the 12-bit ADC0 Data Word.
R/W R/W R/W R/W R / W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
SFR Address:
SFR Page: 0xBF
0
Bits7-0: ADC0 Data Word Low-Order Bits.
For AD0LJST = 0: Bits 7-0 are the lower 8 bits of the 12-bit ADC0 Data Word.
For AD0LJST = 1: Bits 7-4 are the lower 4 bits of the 12-bit ADC0 Data Word. Bits3-0 will
always read ‘0’.
R/W R/W R/W R/W R / W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
SFR Address:
SFR Page: 0xBE
0
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 61
Figure 5.7. ADC0 Data Word Example
12-bit ADC0 Data Word appears in the ADC0 Dat a Word Registers as follows:
ADC0H[3:0]:ADC0L[7:0], if AD0LJST = 0
(ADC0H[7:4] will be sign-extension of ADC0H.3 for a differential reading,
otherwise = 0000b).
ADC0H[7:0]:ADC0L[7:4], if AD0LJST = 1
(ADC0L[3:0] = 0000b).
Example: ADC0 Data Word Conversion Map, AIN0 Input in Single-Ended Mode
(AMX0CF = 0x00, AMX0SL = 0x00)
Example: ADC0 Data Word Conversion Map, AIN0-AIN1 Differential Input Pair
(AMX0CF = 0x01, AMX0SL = 0x00)
For AD0LJST = 0:
; ‘n’ = 12 for Single-Ended; ‘n’= 11 for Differential.
AIN0-AGND (Volts) ADC0H:ADC0L
(AD0LJST = 0) ADC0H:ADC0L
(AD0LJST = 1)
VREF * (4095/4096) 0x0FFF 0xFFF0
VREF / 2 0x0800 0x8000
VREF * (2047/4096) 0x07FF 0x7FF0
0 0x0000 0x0000
AIN0-AGND (Volts) ADC0H:ADC0L
(AD0LJST = 0) ADC0H:ADC0L
(AD0LJST = 1)
VREF * (2047/2048) 0x07FF 0x7FF0
VREF / 2 0x0400 0x4000
VREF * (1/2048) 0x0001 0x0010
0 0x0000 0x0000
-VREF * (1/2048) 0xFFFF (-1d) 0xFFF0
-VREF / 2 0xFC00 (-1024d) 0xC000
-VREF 0xF800 (-2048d) 0x8000
Code Vin Gain
VREF
---------------
2n
=
C8051F040/1/2/3/4/5/6/7
62 Rev. 1.5
5.4. ADC0 Programmable Window Detector
The ADC0 Programmabl e Windo w Detector contin uously compares the ADC0 output to user-prog ramme d
limits, and no tifies th e system whe n an out-of-b ound co ndition is detected. This is especially effective in an
interrupt-driven system, saving code space and CPU bandwidth while delivering faster system response
times. The window detector interrupt flag (AD0WINT in ADC0CN) can also be used in polled mode. The
high and low bytes of the reference words are loaded into the ADC0 Greater-Than and ADC0 Less-Than
registers (ADC0GTH, ADC0GTL, ADC0LTH, and ADC0LTL). Reference comparisons are shown starting
on page 63. No tice th at the window de tecto r flag can be asser ted when the measur ed da t a is inside or out-
side the user-programmed limits, depending on the programming of the ADC0GTx and ADC0LTx regis-
ters.
SFR Definition 5.9. ADC0GTH: ADC0 Greater-Than Data High Byte
SFR Definition 5.10. ADC0GTL: ADC0 Greater-Than Data Low Byte
SFR Definition 5.11. ADC0LTH: ADC0 Less-Than Data High Byte
Bits7-0: High byte of ADC0 Grea te r- T ha n Da ta Word.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
11111111
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xC5
0
Bits7-0: Low byte of ADC0 Gr ea te r- T han Da ta Word.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
11111111
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xC4
0
Bits7-0: High byte of ADC0 Less-T han Da ta Word.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xC7
0
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 63
SFR Definition 5.12. ADC0LTL: ADC0 Less-Than Data Low Byte
Figure 5.8. 12-Bit ADC0 Window Interrupt Example:
Right Justified Single-Ended Data
Bits7-0: Low byte of ADC0 Le ss- Tha n Data Word.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xC6
0
Given:
AMX0SL = 0x00, AMX0CF = 0x00
AD0LJST = ‘0’,
ADC0LTH:ADC0LTL = 0x0200,
ADC0GTH:ADC0GTL = 0x0100.
An ADC0 End of Conversion will cause an
ADC0 Window Compare Interrupt (AD0WINT
= ‘1’) if the resulting ADC0 Data Word is
< 0x0200 and > 0x0100.
Given:
AMX0SL = 0x00, AMX0CF = 0x00,
AD0LJST = ‘0’,
ADC0LTH:ADC0LTL = 0x0100,
ADC0GTH:ADC0GTL = 0x0200.
An ADC0 End of Conversion will cause an
ADC0 Window Compare Interrupt (AD0WINT
= ‘1’) if the resulting ADC0 Data Word is
> 0x0200 or < 0x0100.
0x0FFF
0x0201
0x0200
0x01FF
0x0101
0x0100
0x00FF
0x0000
AD0WINT=1
AD0WINT
not affected
AD0WINT
not affected
ADC Data
Word
0x0FFF
0x0201
0x0200
0x01FF
0x0101
0x0100
0x00FF
0x0000
AD0WINT=1
AD0WINT
not affected
AD0WINT=1
ADC0LTH:ADC0LTL
ADC0GTH:ADC0GTL
ADC Data
Word
ADC0GTH:ADC0GTL
ADC0LTH:ADC0LTL
0
Input Voltage
(AD0 - AGND)
REF x (4095/4096)
REF x (256/4096)
REF x (512/4096)
0
Input Voltage
(AD0 - AGND)
REF x (4095/4096)
REF x (256/4096)
REF x (512/4096)
C8051F040/1/2/3/4/5/6/7
64 Rev. 1.5
Figure 5.9. 12-Bit ADC0 Window Interrupt Example:
Right Justified Differential Data
0x07FF
0x0101
0x0100
0x00FF
0x0000
0xFFFF
0xFFFE
0xF800
AD0WINT=1
AD0WINT
not af fected
AD0WINT
not af fected
0x07FF
0x0101
0x0100
0x00FF
0x0000
0xFFFF
0xFFFE
0xF800
AD0WINT=1
AD0WINT
not affected
-REF
Input Voltage
(AD0 - AD1)
AD0WINT=1
REF x (2047/2048)
ADC0LTH:ADC0LTL
ADC0GTH:ADC0GTL
ADC Data
Word
ADC Data
Word
ADC0LTH:ADC0LTL
ADC0GTH:ADC0GTL
REF x (256/2048)
REF x (-1/2048)
-REF
Input Voltag e
(AD0 - AD1)
REF x (2047/2048)
REF x (256/2048)
REF x (-1/2048)
Given:
AMX0SL = 0x00, AMX0CF = 0x01,
AD0LJST = ‘0’,
ADC0LTH:ADC0LTL = 0x0100,
ADC0GTH:ADC0GTL = 0xFFFF.
An ADC0 End of Conversion will cause an
ADC0 Window Compare Interrupt (AD0WINT
= ‘1’) if the resulting ADC0 Data Word is
< 0x0100 and > 0xFFFF. (In two’s-complement
math, 0xFFFF = -1.)
Given:
AMX0SL = 0x00, AMX0CF = 0x01,
AD0LJST = ‘0’,
ADC0LTH:ADC0LTL = 0xFFFF,
ADC0GTH:ADC0GTL = 0x0100.
An ADC0 End of Conversion will cause an
ADC0 Window Compare Interrupt (AD0WINT
= ‘1’) if the resulting ADC0 Data Word is
< 0xFFFF or > 0x0100. (In two’s-complement
math, 0xFFFF = -1.)
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 65
Figure 5.10. 12-Bit ADC0 Window Interrupt Example:
Left Justified Single-Ended Data
0xFFF0
0x2010
0x2000
0x1FF0
0x1010
0x1000
0x0FF0
0x0000
AD0WINT=1
AD0WINT
not af fected
AD0WINT
not af fected
ADC Data
Word
0xFFF0
0x2010
0x2000
0x1FF0
0x1010
0x1000
0x0FF0
0x0000
AD0WINT=1
AD0WINT
not affected
AD0WINT=1
ADC0LTH:ADC0LTL
ADC0GTH:ADC0GTL
ADC Data
Word
ADC0GTH:ADC0GTL
ADC0LTH:ADC0LTL
0
Input Voltage
(AD0 - AGND)
REF x (4095/4096)
REF x (256/4096)
REF x (512/4096)
0
Input Voltage
(AD0 - AGND)
REF x (4095/4096)
REF x (256/4096)
REF x (512/4096)
Given:
AMX0SL = 0x00, AMX0CF = 0x00,
AD0LJST = ‘1’,
ADC0LTH:ADC0LTL = 0x2000,
ADC0GTH:ADC0GTL = 0x1000.
An ADC0 End of Conversion will cause an
ADC0 Window Compare Interrupt (AD0WINT
= ‘1’) if the resulting ADC0 Data Word is
< 0x2000 and > 0x1000.
Given:
AMX0SL = 0x00, AMX0CF = 0x00,
AD0LJST = ‘1’
ADC0LTH:ADC0LTL = 0x1000,
ADC0GTH:ADC0GTL = 0x2000.
An ADC0 End of Conversion will cause an
ADC0 Window Compare Interrupt (AD0WINT
= ‘1’) if the resulting ADC0 Data Word is
< 0x1000 or > 0x2000.
C8051F040/1/2/3/4/5/6/7
66 Rev. 1.5
Figure 5.11. 12-Bit ADC0 Window Interrupt Example: Lef t Justified Differential Data
0x7FF0
0x1010
0x1000
0x0FF0
0x0000
0xFFF0
0xFFE0
0x8000
AD0WINT=1
AD0WINT
not af fec ted
AD0WINT
not af fec ted
0x7FF0
0x1010
0x1000
0x0FF0
0x0000
0xFFF0
0xFFE0
0x8000
AD0WINT=1
AD0WINT
no t affec ted
-REF
Input Voltage
(AD0 - AD1)
AD0WINT=1
REF x (2047/2048)
ADC0LTH:ADC0LTL
ADC0GTH:ADC0GTL
ADC Data
Word
ADC Data
Word
ADC0LTH:ADC0LTL
ADC0GTH:ADC0GTL
REF x (256/2048)
REF x (-1/2048)
-REF
Input Voltage
(AD0 - AD1)
REF x (2047/2048)
REF x (256/2048)
REF x (-1/2048)
Given:
AMX0SL = 0x00, AMX0CF = 0x01,
AD0LJST = ‘1’,
ADC0LTH:ADC0LTL = 0x1000,
ADC0GTH:ADC0GTL = 0xFFF0.
An ADC0 End of Conversion will cause an
ADC0 Window Compare Interrupt (AD0WINT
= ‘1’) if the resulting ADC0 Data Word is
< 0x1000 and > 0xFFF0. (Two’s-complement
math.)
Given:
AMX0SL = 0x00, AMX0CF = 0x01,
AD0LJST = ‘1’,
ADC0LTH:ADC0LTL = 0xFFF0,
ADC0GTH:ADC0GTL = 0x1000.
An ADC0 End of Conversion will cause an
ADC0 Window Compare Interrupt (AD0WINT
= ‘1’) if the resulting ADC0 Data Word is
< 0xFFF0 or > 0x1000. (Two’s-complement
math.)
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 67
Table 5.2. 12-Bit ADC0 Electrical Characteristics
VDD = 3.0 V, AV+ = 3.0 V, VREF = 2.40 V (REFBE = 0), PGA Gain = 1, –40 to +85 °C unless otherwise specified.
Parameter Conditions Min Typ Max Units
DC Accuracy
Resolution 12 bits
Integral Nonlinearity — — ±1 LSB
Differential Nonlinearity Guaranteed Monotonic — — ±1 LSB
Offset Error Note 1 —0.5±3 —LSB
Full Scale Error Differential mode; See Note 1 —0.4±3 —LSB
Offset Temperature Coefficient —±0.25 —ppm/°C
Dynamic Performance (10 kHz sine-wave input, 0 to 1 dB below Full Scale, 100 ksps)
Signal-to-Noise Plus Distortion 66 — — dB
Total Harmonic Distortion Up to the 5th harmonic —–75 —dB
Spurious-Free Dynamic Range —80 —dB
Conversion Rate
Maximum SAR Clock Frequency — — 2.5 MHz
Conversion Time in SAR Clocks 16 — — clocks
Track/Hold Acquisition Time 1.5 — — µs
Throughput Rate — — 100 ksps
Analog Inputs
Input Voltage Range Single-ended operation 0 — VREF V
Common-mode Voltage Range Differential operation AGND —AV+ V
Input Capacitance —10 —pF
Temperature Sens or
Nonlinearity Notes 1, 2 —±1 —°C
Absolute Accuracy Notes 1, 2 —±3 —°C
Gain Notes 1, 2 —2.86
±0.034 — mV/°C
Offset Notes 1, 2 (Temp = 0 °C) —0.776
±0.009 — V
Power Specifications
Power Supply Current (AV+ sup -
plied to ADC) Operating Mode, 100 ksps —450 900 µA
Power Supply Rejection —±0.3 —mV/V
Notes:
1. Represents one standard deviation from the mean.
2. Includes ADC offset, gain, and linearity variations.
C8051F040/1/2/3/4/5/6/7
68 Rev. 1.5
Table 5.3. High-Voltage Difference Amplifier Electrical Characteristics
VDD = 3.0 V, AV+ = 3.0 V, VREF = 3.0 V, –40 to +85 °C unless otherwise specified.
Parameter Conditions Min Typ Max Units
Analog Inputs
Differential range peak-to-peak ——60 V
Common Mode Range (HVAIN+) – (HVAIN–) = 0 V –60 — +60 V
Analog Output
Output Voltage Range 0.1 — 2.9 V
DC Performance
Common Mode Rejection Ratio Vcm= –10 V to +10 V, Rs=0 44 52 — dB
Offset Voltage —±3— mV
Noise HVCAP floating —500—nV/rtHz
Nonlinearity G = 1 —72— dB
Dynamic Performance
Small Signal Bandwidth G = 0.05 —3—MHz
Small Signal Bandwidth G = 1 —150— kHz
Slew Rate —2—V/µs
Settling Time 0.01%, G = 0.05, 10 V step —10— µs
Input/Output Impedance
Differential (HVAIN+) input —105— k
Differential (HVAIN-) input —98— k
Common Mode input —51— k
HVCAP —5— k
Power Specification
Quiescent Current — 450 1000 µA
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 69
6. 10-Bit ADC (ADC0, C8051F042/3/4/5/6/7 Only)
The ADC0 subsystem for the C8051F042/3/4/5/6/7 consists of a 9-channel, configurable analog multi-
plexer (AMUX0), a programmable gain amplifier (PGA0), and a 100 ksps, 10-bit successive-approxima-
tion-register ADC with integrated track-and-hold and Programmable Window Detector (see block diagram
in Figure 6.1). The AMUX0, PGA0, Data Conversion Modes, and Window Detector are all configurable
under soft ware con trol via th e Special Function Registers shown in Fig ure 6.1. The volt a ge refe rence use d
by ADC0 is selected as described in Section “9. Voltage Refere nce (C80 51F040/2 /4/6)” on page 113 for
C8051F042/4/6 devices, or Section “10. Voltage Reference (C8051F041/3/5/7)” on page 117 for
C8051F043/5/7 devices. The ADC0 subsystem (ADC0, track-and-hold and PGA0) is enabled only when
the AD0EN bit in the ADC0 Control register (ADC0CN) is set to logic 1. The ADC0 subsystem is in low
power shutdown when this bit is logic 0.
Figure 6.1. 10-Bit ADC0 Functional Block Diagram
6.1. Analog Multiplexer and PGA
The analog multiplexer can input analog signals to the ADC from four external analog input pins, Port 3
port pins (o ptionally configured a s analog input pins), High Voltage Difference Amplifier, and an internally
connected on-chip temperature sensor (temperature transfer function is shown in Figure 6.6). AMUX input
pairs can be programmed to operate in either differential or single-ended mode. This allows the user to
select the best measurement technique for each input channel, and even accommodates mode changes
"on-the-fly". The AMUX defau lt s to a ll sin gle-ende d input s u pon reset. There are three registers a ssociated
with the AMUX: the Channel Selection register AMX0SL (SFR Definition 6.2), the Configuration register
AMX0CF (SFR Definition 6.1), and the Port Pin Selection register AMX0PRT (SFR Definition 6.3).
Table 6.1 shows AMUX functionality by channel for each possible configuration. The PGA amplifies the
AMUX output signal by an amount determined by the states of the AMP0GN2-0 bits in the ADC0 Configu-
ration register, ADC0CF (SFR Defin ition 6.5). Th e PGA can be software-programm ed for gains o f 0.5, 2, 4,
8 or 16. Gain defaults to unity on reset.
10-Bit
SAR
ADC
REF
+
-
AV+
TEMP
SENSOR
10
9-to-1
AMUX
(SE or
DIFF)
AV+
20
10
AD0EN
SYSCLK
X
Start Conver s ion
AGND
AMX0CF
ADC0L ADC0H
ADC0LTLADC0LTHADC0GTLADC0GTH
AMX0SL
AMX0AD0
AMX0AD1
AMX0AD2
AMX0AD3
AIN01IC
AIN23IC
HVDA2IC
PORT3IC
ADC0CF
AMP0GN0
AMP0GN1
AMP0GN2
AD0SC0
AD0SC1
AD0SC2
AD0SC3
AD0SC4
ADC0CN
AD0LJST
AD0WINT
AD0CM0
AD0CM1
AD0BUSY
AD0INT
AD0TM
AD0EN
Timer 3 Overflow
00
01
10
11
AD0BUSY (W)
CNVSTR0
AD0WINT
Comb.
Logic
HV
Input
Port 3
I/O Pins
Analog
Input
Pins
AGND Timer 2 Overflow
C8051F040/1/2/3/4/5/6/7
70 Rev. 1.5
6.1.1. Analog Input Configuration
The analog multiplexer routes signals from external analog input pins, Port 3 I/O pins (programmed to be
analog inputs), a High Voltage Difference Amplifier, and an on-chip temperature sensor as shown in
Figure 6.2.
Figure 6.2. Analog Input Diagram
Analog signals may be input from four external analog input pins (AIN0.0 through AIN0.3) as differential or
single-ended measurements. Additionally, Port 3 I/O Port Pins may be configured to input analog signals.
Port 3 pins config ured as analog input s are sele cted using the Port Pin Selection register (AMX0PR T). Any
number of Port 3 pins may be selected simultaneously as inputs to the AMUX. Even numbered Port 3 pins
and odd numbered Port 3 pins are routed to separate AMUX inputs. (Note: Even port pins and odd port
pins that are simultaneously selected will be shorted together as “wired-OR”.) In this way, differential mea-
surements may be made when using the Port 3 pins (voltage difference between selected even and odd
Port 3 pins) as shown in Figure 6.2.
The High-Voltage Difference Amplifier (HVDA) will accept analog input signals and reject up to 60 volts
common-mode for differential measurement of up to the reference voltage to the ADC (0 to VREF volts).
The output of the HVDA can be selected as an input to the ADC using the AMUX as any other channel is
selected for measurement.
+
-
+
-
+
-
9-to-1
AMUX
(SE or
DIFF)
AMX0CF
AIN01IC
AIN23IC
HVDAIC
PORT3IC
10-Bit
SAR
ADC
X
TEMP SENSOR
AGND
AIN0.0
AIN0.1
AIN0.2
AIN0.3
AMX0SL
AMX0AD0
AMX0AD1
AMX0AD2
AMX0AD3
0
7
6
5
4
3
2
1
8
HV
AMP
HVCAP
HVREF
HVAIN -
HVAIN +
P3.6
P3.4
P3.2
P3.0
P3.7
P3.5
P3.3
P3.1
(WIRED-OR)
(WIRED-OR)
AMX0PRT
PAIN0EN
PAIN2EN
PAIN4EN
PAIN6EN
PAIN7EN
PAIN5EN
PAIN3EN
PAIN1EN P3EVEN
P3ODD
+
-
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 71
SFR Definition 6.1. AMX0CF: AMUX0 Configuration
SFR Definition 6.2. AMX0SL: AMUX0 Channel Select
Bits7-4: UNUSED. Read = 0000b; Write = don’t care
Bit3: PORT3IC: Port 3 even/odd Pin Input Pair Configuration Bit
0: Port 3 even and odd input channels are independent single-ended inputs
1: Port 3 even and odd input channels are (respectively) +, - differential input pair
Bit2: HVDA2C: HVDA 2’s Compliment Bit
0: HVDA output measured as an independent single-ended input
1: 2’s compliment value Result from HVDA
Bit1: AIN23IC: AIN2, AIN3 Input Pair Configuration Bit
0: AIN2 and AIN3 are independent single-ended input s
1: AIN2, AIN3 are (respectively) +, - differential input pair
Bit0: AIN01IC: AIN0, AIN1 Input Pair Configuration Bit
0: AIN0 and AIN1 are independent single-ended input s
1: AIN0, AIN1 are (respectively) +, - differential input pair
NOTE: The ADC0 Data Word is in 2’s complement format for channels configured as differential.
R R R R R/W R/W R/W R/W Reset Value
- - - - PORT3IC HVDA2C AIN23IC AIN01IC 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
SFR Address:
SFR Page: 0xBA
0
Bits7-4: UNUSED. Read = 0000b; Write = don’t care
Bits3-0: AMX0AD3-0: AMX0 Address Bits
0000-1111b: ADC Inputs selected per Table 6.1.
R R R R R/W R/W R/W R/W Reset Value
- - - - AMX0AD3 AMX0AD2 AMX0AD1 AMX0AD0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xBB
0
C8051F040/1/2/3/4/5/6/7
72 Rev. 1.5
Note: “P3EVEN” denotes even numbered and “P3ODD” odd numbered Port 3 pins selected in the AMX0PRT
register.
Table 6.1. AMUX Selection Chart (AMX0AD3-0 and AMX0CF3-0 bits)
AMX0AD3-0
0000 0001 0010 0011 0100 0101 0110 0111 1xxx
AMX0CF Bits 3-0
0000 AIN0.0 AIN0.1 AIN0.2 AIN0.3 HVDA AGND P3EVEN P3ODD TEMP
SENSOR
0001 +(AIN0.0)
-(AIN0.1) AIN0.2 AIN0.3 HVDA AGND P3EVEN P3ODD TEMP
SENSOR
0010 AIN0.0 AIN0.1 +(AIN0.2)
-(AIN0.3) HVDA AGND P3EVEN P3ODD TEMP
SENSOR
0011 +(AIN0.0)
-(AIN0.1) +(AIN0.2)
-(AIN0.3) HVDA AGND P3EVEN P3ODD TEMP
SENSOR
0100 AIN0.0 AIN0.1 AIN0.2 AIN0.3 +(HVDA)
-(HVREF) P3EVEN P3ODD TEMP
SENSOR
0101 +(AIN0.0)
-(AIN0.1) AIN0.2 AIN0.3 +(HVDA)
-(HVREF) P3EVEN P3ODD TEMP
SENSOR
0110 AIN0.0 AIN0.1 +(AIN0.2)
-(AIN0.3) +(HVDA)
-(HVREF) P3EVEN P3ODD TEMP
SENSOR
0111 +(AIN0.0)
-(AIN0.1) +(AIN0.2)
-(AIN0.3) +(HVDA)
-(HVREF) P3EVEN P3ODD TEMP
SENSOR
1000 AIN0.0 AIN0.1 AIN0.2 AIN0.3 HVDA AGND +P3EVEN
-P3ODD TEMP
SENSOR
1001 +(AIN0.0)
-(AIN0.1) AIN0.2 AIN0.3 HVDA AGND +P3EVEN
-P3ODD TEMP
SENSOR
1010 AIN0.0 AIN0.1 +(AIN0.2)
-(AIN0.3) HVDA AGND +P3EVEN
-P3ODD TEMP
SENSOR
1011 +(AIN0.0)
-(AIN0.1) +(AIN0.2)
-(AIN0.3) HVDA AGND +P3EVEN
-P3ODD TEMP
SENSOR
1100 AIN0.0 AIN0.1 AIN0.2 AIN0.3 +(HVDA)
-(HVREF) +P3EVEN
-P3ODD) TEMP
SENSOR
1101 +(AIN0.0)
-(AIN0.1) AIN0.2 AIN0.3 +(HVDA)
-(HVREF) +P3EVEN
-P3ODD TEMP
SENSOR
1110 AIN0.0 AIN0.1 +(AIN0.2)
-(AIN0.3) +(HVDA)
-(HVREF) +P3EVEN
-P3ODD TEMP
SENSOR
1111 +(AIN0.0)
-(AIN0.1) +(AIN0.2)
-(AIN0.3) +(HVDA)
-(HVREF) +P3EVEN
-P3ODD TEMP
SENSOR
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 73
SFR Definition 6.3. AMX0PRT: Port 3 Pin Selection
Bit7: PAIN7EN: Pin 7 Analog Input Enable Bit
0: P3.7 is not selected as an analog input to the AMUX.
1: P3.7 is selected as an analog input to the AMUX.
Bit6: PAIN6EN: Pin 6 Analog Input Enable Bit
0: P3.6 is not selected as an analog input to the AMUX.
1: P3.6 is selected as an analog input to the AMUX.
Bit5: PAIN5EN: Pin 5 Analog Input Enable Bit
0: P3.5 is not selected as an analog input to the AMUX.
1: P3.5 is selected as an analog input to the AMUX.
Bit4: PAIN4EN: Pin 4 Analog Input Enable Bit
0: P3.4 is not selected as an analog input to the AMUX.
1: P3.4 is selected as an analog input to the AMUX.
Bit3: PAIN3EN: Pin 3 Analog Input Enable Bit
0: P3.3 is not selected as an analog input to the AMUX.
1: P3.3 is enabled as an analog input to the AMUX.
Bit2: PAIN2EN: Pin 2 Analog Input Enable Bit
0: P3.2 is not selected as an analog input to the AMUX.
1: P3.2 is enabled as an analog input to the AMUX.
Bit1: PAIN1EN: Pin 1 Analog Input Enable Bit
0: P3.1 is not selected as an analog input to the AMUX.
1: P3.1 is enabled as an analog input to the AMUX.
Bit0: PAIN0EN: Pin 0 Analog Input Enable Bit
0: P3.0 is not selected as an analog input to the AMUX.
1: P3.0 is enabled as an analog input to the AMUX.
NOTE: Any numbe r of Port 3 pins ma y be selecte d sim ultaneously inputs to the AMUX. Odd nu m -
bered and even numbered pins that are selected simultaneously are shorted together as
“wired-OR”.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
PAIN7EN PAIN6EN PAIN5EN PAIN4EN PAIN3EN PAIN2EN PAIN1EN PAIN0EN 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xBA
0
C8051F040/1/2/3/4/5/6/7
74 Rev. 1.5
6.2. High-Voltage Difference Amplifier
The High-Voltage Difference Amplifier (HVDA) can be used to measure high differential voltages up to
60 V peak-to-peak, reject h igh co mmon- mod e voltages up to ±60 V, and condition the sign al voltage range
to be suitable for input to ADC0. The input signal to the HVDA may be below AGND to –60 volts, and as
high as +60 volts, making the device suitable for both single and dual supply applications. The HVDA pro-
vides a common-mode signal for the ADC via the High Voltage Reference Input (HVREF), allowing mea-
surement of signals outside th e specified ADC input r ang e using on-chi p circuitry. The HVDA has a gain of
0.05 V/V to 14 V/V. The first stage 20:1 difference amplifier has a gain of 0.05 V/V when the output ampli-
fier is used as a unity gain buffer. When the output amplifier is set to a gain of 280 (selected using the
HVGAIN bits in the High Voltage Control Register), an overall gain of 14 can be attained.
The HVDA uses four available external pins: +HVAIN, –HVAIN, HVCAP, and HVREF. HVAIN+ and HVAIN-
serve as the d ifferential inputs to the HVDA. HVREF should be used to pro vide a com mon mode refe ren ce
for input to ADC0, and to prevent the output of the HVDA circuit from saturating. The output from the
HVDA circuit as calculated by Equation 6.1 must remain within the “Output Voltage Range” specification
listed in Table 6.3. The ideal value for HVREF in most applications is e qual to 1/2 the su pply volt age for the
device. When the ADC is configured for differential measurement, the HVREF signal is applied to the AIN-
input of the ADC, thereby removing HVREF from the measurement. HVCAP facilitates the use of a capac-
itor for noise filtering in conjunction with R7 (see Figure 6.3 for R7 and other appro ximat e resisto r va lues) .
Alternatively, the HVCAP could also be used to access amplification of the first stage of the HVDA at an
external pin. (See Table 6.3 on page 90 for electrical specifications of the HVDA.)
Equation 6.1. Calculating HVDA Output Voltage to AIN+
Figure 6.3. High Voltage Difference Amplifier Functional Diagram
VOUT HVAIN+HVAIN-–Gain HVREF+=
Note: The output voltage of the HVDA is selected as an input to the AIN+ input of ADC0 via its analog multiplexer
(AMUX0). HVDA output voltages outside the ADC’s input range will result in saturation of the ADC input. Allow
for adequate settle/tracking time for proper voltage measurements.

k
5k
100k
5k
HVA0CN
Gain Setting
HVAIN-
HVAIN+
HVREF
HVCAP
Vout
(To AMUX0)
5k
Resistor values are
approximate
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 75
SFR Definition 6.4. HVA0CN: High Voltage Difference Amplifier Control
Bit7: HVDAEN: High Voltage Difference Amplifier (HVDA) Enable Bit.
0: The HVDA is disabled.
1: The HVDA is enabled.
Bits6-3: Reserved.
Bits2-0: HVGAIN3-HVGAIN0: HVDA Gain Control Bits.
HVDA Gain Control Bits set the amplification gain if the difference signal input to the HVDA
as defined in the table below:
R/W R R R R/W R/W R/W R/W Reset Value
HVDAEN - - - HVGAIN3 HVGAIN2 HVGAIN1 HVGAIN0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xD6
0
HVGAIN3:HVGAIN0 HVDA Gain
0000 0.05
0001 0.1
0010 0.125
0011 0.2
0100 0.25
0101 0.4
0110 0.5
0111 0.8
1000 1.0
1001 1.6
1010 2.0
1011 3.2
1100 4.0
1101 6.2
1110 7.6
1111 14
C8051F040/1/2/3/4/5/6/7
76 Rev. 1.5
6.3. ADC Modes of Operation
ADC0 has a maximum conversion speed of 100 ksps. The ADC0 conversion clock is derived from the sys-
tem clock divided by the value held in the ADC0SC bits of register ADC0CF.
6.3.1. Starting a Conversion
A conversion can be initiated in one of four ways, depending on the programmed states of the ADC0 Start
of Conversion Mode bits (AD0CM1, AD0CM0) in ADC0CN. Conversions may be initiated by the following:
• Writing a ‘1’ to the AD0BUSY bit of ADC0CN;
• A Timer 3 overflow (i.e., timed continuous conversions);
• A rising edge detected on the external ADC convert start signal, CNVSTR0;
• A Timer 2 overflow (i.e., timed continuous conversions).
The AD0BUSY bit is set to logic 1 during conversion and restored to logic 0 when conversion is complete.
The falling edge of AD0BUSY triggers an interrupt (when enabled) and sets the AD0INT interrupt flag
(ADC0CN.5). Converted dat a is availabl e in the ADC0 dat a word MSB an d LSB registers, ADC0H, ADC0L.
Converted data can be either left or right justified in the ADC0H:ADC0L register pair (see example in
Figure 6.7) depending on the programmed state of the AD0LJST bit in the ADC0CN register.
When initiating conversions by writing a ‘1’ to AD0BUSY, the AD0INT bit should be polled to determine
when a conversion has completed (ADC0 interrupts may also be used). The recommended polling proce-
dure is shown below.
Step 1. Write a ‘0’ to AD0INT;
Step 2. Write a ‘1’ to AD0BUSY;
Step 3. Poll AD0INT for ‘1’;
Step 4. Process ADC0 data.
6.3.2. Tracking Modes
According to Table 6.2, each ADC0 conversion must be preceded by a minimum tracking time for the con-
verted result to be accurate. The AD0TM bit in register ADC0CN controls the ADC0 track-and-hold mode.
In its default state, the ADC0 input is continuously tracked when a conversion is not in progress. When the
AD0TM bit is logic 1, ADC0 operates in low-power tracking mode. In this mode, each conversion is pre-
ceded by a tracking period of 3 SAR clocks afte r the st art-of-con version signal. When the CNVSTR0 signal
is used to initiate conversions in low-power tracking mode, ADC0 tracks only when CNVSTR0 is low; con-
version begins on the rising edge of CNVSTR0 (see Figure 6.4). Tracking can also be disabled when the
entire chip is in low power s tandby or sleep modes. Low-power tracking mode is also useful when AMUX
or PGA settings are frequently changed, to ensure that settling time requirements are met (see Section
“6.3.3. Settling Time Requirements” on page 78).
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 77
Figure 6.4. 10-Bit ADC Track and Conversion Example Timing
1234567891
01
11
21
31
41
51
6
CNVSTR
(AD0CM[1:0]=10)
ADC0TM=1
ADC0TM=0
Timer 2, Timer 3 Overflow;
W rit e '1 ' to A D0 B US Y
(AD0C M [1 :0]=00 , 01, 11)
ADC0TM=1
ADC0TM=0
A. ADC Timing for External Trigger Source
B. ADC Timing for Internal Trigger Sources
SAR
Clocks
SAR
Clocks
1234567891
01
11
21
31
41
51
61
71
81
9
1234567891
01
11
21
31
41
51
6
SAR
Clocks
Track Convert Low Power Mode
Low Power
or Convert
Track Or C onv ert Convert Track
Track Convert Low Power Mode
Low Power
or Convert
Track or
Convert Convert Track
C8051F040/1/2/3/4/5/6/7
78 Rev. 1.5
6.3.3. Settling Time Requirements
A minimum tracking time is requir ed before an accu rate conver sion can be pe rformed. This tracking time is
determined by the ADC0 MUX resistance, the ADC0 sampling capacitance, any external source resis-
tance, and the accuracy required for the conversion. Figure 6.5 shows the equivalent ADC0 input circuits
for both Differential and Single-ended modes. Notice that the equivalent time constant for both input cir-
cuits is the same. The required settling time for a given settling accuracy (SA) may be approximated by
Equation 6.2. When measuring the Temperature Sensor output, RTOTAL reduces to RMUX. Note that in low-
power tracking mode, three SAR clocks are used for tracking at the start of every conversion. For most
applications, these three SAR clocks will meet the tracking requ irements. See Table 6.2 for absolute mini-
mum settling/tracking time requirements.
Equation 6.2. ADC0 Settling Time Requirements
Where:
SA is the settling accuracy, given as a fraction of an LSB (for example, 0.25 to settle within 1/4 LSB)
t is the required settling time in seconds
RTOTAL is the sum of the ADC0 MUX resistance and any external source resistance.
n is the ADC resolution in bits (10).
Figure 6.5. ADC0 Equivalent Input Circuits
t2n
SA
-------

RTOTALCSAMPLE
ln=
R
MUX
= 5k
RC
Input
= R
MUX
* C
SAMPLE
R
MUX
= 5k
C
SAMPLE
= 10pF
C
SAMPLE
= 10pF
MUX Select
MUX Select
Differe ntial Mode
AIN0.x
AIN0.y
R
MUX
= 5k
C
SAMPLE
= 10pF
RC
Input
= R
MUX
* C
SAMPLE
MUX Select
Single -Ended Mode
AIN0.x
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 79
Figure 6.6. Temperature Sensor Transfer Function
0-50 50 100
(Celsius)
0.500
0.600
0.700
0.800
0.900
(Volts)
V
TEMP
= 0.00286(TEMP
C
) + 0.776
for PGA Gain = 1
1.000
C8051F040/1/2/3/4/5/6/7
80 Rev. 1.5
SFR Definition 6.5. ADC0CF: ADC0 Configuration
Bits7-3: AD0SC4-0: ADC0 SAR Conversion Clock Period Bits
SAR Conversion clock is der ived from system clock by the following equation, where
AD0SC refers to the 5-b it value held in AD0SC4-0, and CLKSAR0 refers to the desired ADC0
SAR clock. See Table 6.2 on page 89 for SAR clock setting requirements.
* or
*Note: AD0SC is the rounded-up result.
Bits2-0: AMP0GN2-0: ADC0 Internal Amplifier Gain (PGA)
000: Gain = 1
001: Gain = 2
010: Gain = 4
011: Gain = 8
10x: Gain = 16
11 x: Gain = 0.5
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
AD0SC4 AD0SC3 AD0SC2 AD0SC1 AD0SC0 AMP0GN2 AMP0GN1 AMP0GN0 11111000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xBC
0
AD0SC SYSCLK
CLKSAR0
-----------------------1–
CLKSAR0SYSCLK
AD0SC 1+
----------------------------
=
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 81
SFR Definition 6.6. ADC0CN: ADC0 Control
Bit7: AD0EN: ADC0 Enable Bit.
0: ADC0 Disabled. ADC0 is in low-power shutdown.
1: ADC0 Enabled. ADC0 is active and ready for data conversions.
Bit6: AD0TM: ADC Track Mode Bit
0: When the ADC is enabled, tracking is continuous unless a conversion is in process
1: Tracking Defined by AD0CM1-0 bit s
Bit5: AD0INT: ADC0 Conversion Complete Interrupt Flag.
This flag must be cleared by software.
0: ADC0 has not completed a data conversion since the last time this flag was cleared.
1: ADC0 has completed a data conversion.
Bit4: AD0BUSY: ADC0 Busy Bit.
Read:
0: ADC0 Conversion is complete or a conversion is not currently in progress. AD0INT is set
to logic 1 on the falling edge of AD0BUSY.
1: ADC0 Conversion is in progress.
Write:
0: No Effect.
1: Initiates ADC0 Conversion if AD0CM1-0 = 00b
Bit3-2: A D0 CM 1-0 : AD C0 Start of Conversio n Mo de Sele ct.
If AD0TM = 0:
00: ADC0 conversion initiated on every write of ‘1’ to AD0BUSY.
01: ADC0 conversion initiated on overflow of Timer 3.
10: ADC0 conversion initiated on rising edge of external CNVSTR0.
11: ADC0 conversion initiated on overflow of Timer 2.
If AD0TM = 1:
00: Tracking starts with the write of ‘1’ to AD0BUSY and lasts for 3 SAR clocks, followed by
conversion.
01: Tracking started by the overflow of T imer 3 and last for 3 SAR clocks, followed by con-
version.
10: ADC0 tracks only when CNVSTR0 input is logic low; conversion starts on rising
CNVSTR0 edge.
11: Tracking started by the overflow of Timer 2 and last for 3 SAR clocks, followed by con-
version.
Bit1: AD0WINT: ADC0 Window Compare In te rr up t Fla g.
This bit must be cleared by software.
0: ADC0 Window Comparison Data match has not occurred since this flag was last cleared.
1: ADC0 Window Comparison Data match has occurred.
Bit0: AD0LJST: ADC0 Left Justify Select.
0: Data in ADC0H:ADC0L registers are right-justified.
1: Data in ADC0H:ADC0L registers are left-justified.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
AD0EN AD0TM AD0INT AD0BUSY AD0CM1 AD0CM0 AD0WINT AD0LJST 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 Bit
Addressable
SFR Address:
SFR Page: 0xE8
0
C8051F040/1/2/3/4/5/6/7
82 Rev. 1.5
SFR Definition 6.7. ADC0H: ADC0 Data Word MSB
SFR Definition 6.8. ADC0L: ADC0 Data Word LSB
Bits7-0: ADC0 Data Word High-Order Bits.
For AD0LJST = 0: Bits 7 -2 are the sign extension of Bit 1. Bit s 0 and 1 are the upp er 2 bits of
the 10-bit ADC0 Data Word.
For AD0LJST = 1: Bits 7-0 are the most-significant bits of the 10-bit ADC0 Data Word.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR
Address:
SFR Address:
SFR Page: 0xBF
0
Bits7-0: ADC0 Data Word Low-Order Bits.
For AD0LJST = 0: Bits 7-0 are the lower 8 bits of the 10-bit ADC0 Data Word.
For AD0LJST = 1: Bits 6 and 7 are the lower 2 bits of the 10-bit ADC0 Data Word. Bits 5-0
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR
Address:
SFR Address:
SFR Page: 0xBE
0
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 83
Figure 6.7. ADC0 Data Word Example
10-bit ADC Data Word appears in the ADC Data Word Registers as follows:
ADC0H[1:0]:ADC0L[7:0], if ADLJST = 0
(ADC0H[7:2] will be sign-extension of ADC0H.1 for a differential reading,
otherwise = 000000b).
ADC0H[7:0]:ADC0L[7:6], if ADLJST = 1
(ADC0L[5:0] = 000000b).
Example: ADC Data Word Conversion Map, AIN0 Input in Single-Ended Mode
(AMX0CF = 0x00, AMX0SL = 0x00)
Example: ADC Data Word Conversion Map, AIN0-AIN1 Differential Input Pair
(AMX0CF = 0x01, AMX0SL = 0x00)
ADLJST = 0:
; ‘n’ = 10 for Single-Ended; ‘n’=9 for Differential.
AIN0-AGND (Volts) ADC0H:ADC0L
(ADLJST = 0) ADC0H:ADC0L
(ADLJST = 1)
VREF * (1023/1024) 0x03FF 0xFFC0
VREF / 2 0x0200 0x8000
VREF * (511/1024) 0x01FF 0x7FC0
0 0x0000 0x0000
AIN0-AGND (Volts) ADC0H:ADC0L
(ADLJST = 0) ADC0H:ADC0L
(ADLJST = 1)
VREF * (511/512) 0x01FF 0x7FC0
VREF / 2 0x0100 0x4000
VREF * (1/512) 0x0001 0x0040
0 0x0000 0x0000
-VREF * (1/512) 0xFFFF (-1) 0xFFC0
-VREF / 2 0xFF00 (-256) 0xC000
-VREF 0xFE00 (-512) 0x8000
Code Vin Gain
VREF
---------------
2n
=
C8051F040/1/2/3/4/5/6/7
84 Rev. 1.5
6.4. ADC0 Programmable Window Detector
The ADC0 Programmabl e Windo w Detector contin uously compares the ADC0 output to user-prog ramme d
limits, and no tifies th e system whe n an out-of-b ound co ndition is detected. This is especially effective in an
interrupt-driven system, saving code space and CPU bandwidth while delivering faster system response
times. The window detector interrupt flag (AD0WINT in ADC0CN) can also be used in polled mode. The
high and low bytes of the reference words are loaded into the ADC0 Greater-Than and ADC0 Less-Than
registers (ADC0GTH, ADC0GTL, ADC0LTH, and ADC0LTL). Reference comparisons are shown starting
on page 85. No tice th at the window de tecto r flag can be asser ted when the measur ed da t a is inside or out-
side the user-programmed limits, depending on the programming of the ADC0GTx and ADC0LTx regis-
ters.
SFR Definition 6.9. ADC0GTH: ADC0 Greater-Than Data High Byte
SFR Definition 6.10. ADC0GTL: ADC0 Greater-Than Data Low Byte
SFR Definition 6.11. ADC0LTH: ADC0 Less-Than Data High Byte
Bits7-0: High byte of ADC0 Grea te r- T ha n Da ta Word.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
11111111
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xC5
0
Bits7-0: Low byte of ADC0 Gr ea te r- T han Da ta Word.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
11111111
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xC4
0
Bits7-0: High byte of ADC0 Less-T han Da ta Word.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xC7
0
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 85
SFR Definition 6.12. ADC0LTL: ADC0 Less-Than Data Low Byte
Figure 6.8. 10-Bit ADC0 Window Interrupt Example:
Right Justified Single-Ended Data
Bits7-0: Low byte of ADC0 Le ss- Tha n Data Word.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xC6
0
Given:
AMX0SL = 0x00, AMX0CF = 0x00, ADLJST = 0,
ADC0LTH:ADC0LTL = 0x0200,
ADC0GTH:ADC0GTL = 0x0100.
An ADC End of Conversion will cause an ADC
Window Compare Interrupt (ADWINT=1) if the
resulting ADC Data Word is < 0x0200 and
> 0x0100.
Given:
AMX0SL = 0x00, AMX0CF = 0x00, ADLJST = 0,
ADC0LTH:ADC0LTL = 0x0100,
ADC0GTH:ADC0GTL = 0x0200.
An ADC End of Conversion will cause an ADC
Window Compare Interrupt (ADWINT=1) if the
resulting ADC Data Word is > 0x0200 or
< 0x0100.
0x03FF
0x0201
0x0200
0x01FF
0x0101
0x0100
0x00FF
0x0000
AD0WINT=1
AD0WINT
not affected
AD0WINT
not affected
ADC Data
Word 0x03FF
0x0201
0x0200
0x01FF
0x0101
0x0100
0x00FF
0x0000
AD0WINT=1
AD0WINT
not affected
AD0WINT=1
ADC0LTH:ADC0LTL
ADC0GTH:ADC0GTL
ADC Data
Word
ADC0GTH:ADC0GTL
ADC0LTH:ADC0LTL
0
Input Voltage
(AD0 - AGND)
REF x (1023/1024)
REF x (256/1024)
REF x (512/1024)
0
Input Voltage
(AD0 - AGND)
REF x (1023/1024)
REF x (256/1024)
REF x (512/1024)
C8051F040/1/2/3/4/5/6/7
86 Rev. 1.5
Figure 6.9. 10-Bit ADC0 Window Interrupt Example:
Right Justified Differential Data
Given:
AMX0SL = 0x00, AMX0CF = 0x01, ADLJST = 0,
ADC0LTH:ADC0LTL = 0x0100,
ADC0GTH:ADC0GTL = 0xFFFF.
An ADC End of Conversion will cause an ADC
Window Compare Interrupt (ADWINT=1) if the
resulting ADC Data Word is < 0x0100 and
> 0xFFFF. (In two’s-complement math,
0xFFFF = -1.)
Given:
AMX0SL = 0x00, AMX0CF = 0x01, ADLJST = 0,
ADC0LTH:ADC0LTL = 0xFFFF,
ADC0GTH:ADC0GTL = 0x0100.
An ADC End of Conversion will cause an ADC
Window Compare Interrupt (ADWINT=1) if the
resulting ADC Data Word is < 0xFFFF or
> 0x0100. (In two’s-complement math,
0xFFFF = -1.)
0x01FF
0x0101
0x0100
0x00FF
0x0000
0xFFFF
0xFFFE
0xFE00
AD0WINT=1
AD0WINT
not a ffe cted
AD0WINT
not a ffe cted
0x01FF
0x0101
0x0100
0x00FF
0x0000
0xFFFF
0xFFFE
0xFE00
AD0WINT=1
AD0WINT
not a ffe cted
-REF
Input Voltage
(AD 0 - AD 1 )
AD0WINT=1
REF x (511/512)
ADC0LTH:ADC0LTL
ADC0GTH:ADC0GTL
ADC Data
Word
ADC Data
Word
ADC0LTH:ADC0LTL
ADC0GTH:ADC0GTL
REF x (256/512)
REF x (-1/512)
-REF
Input Voltage
(AD 0 - AD 1 )
REF x (511/512)
REF x (256/512)
REF x (-1/512)
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 87
Figure 6.10. 10-Bit ADC0 Window Interrupt Example:
Left Justified Single-Ended Data
Given:
AMX0SL = 0x00, AMX0CF = 0x00 , ADLJST = 1,
ADC0LTH:ADC0LTL = 0x8000,
ADC0GTH:ADC0GTL = 0x4000.
An ADC End of Conversion will cause an ADC
Window Compare Interrupt (ADWINT=1) if the
resulting ADC Data Word is < 0x8000 and
> 0x4000.
Given:
AMX0SL = 0x00, AMX0CF = 0x00, ADLJST = 1,
ADC0LTH:ADC0LTL = 0x4000,
ADC0GTH:ADC0GTL = 0x8000.
An ADC End of Conversion will cause an ADC
Window Compare Interrupt (ADWINT=1) if the
resulting ADC Data Word is < 0x4000 or
> 0x8000.
0xFFC0
0x8040
0x8000
0x7FC0
0x4040
0x4000
0x3FC0
0x0000
AD0WINT=1
AD0WINT
not affected
AD0WINT
not affected
ADC Data
Word 0xFFC0
0x8040
0x8000
0x7FC0
0x4040
0x4000
0x3FC0
0x0000
AD0WINT=1
AD0WINT
not affected
AD0WINT=1
ADC0LTH:ADC0LTL
ADC0GTH:ADC0GTL
ADC Data
Word
ADC0GTH:ADC0GTL
ADC0LTH:ADC0LTL
0
Input Voltage
(AD 0 - AG N D )
REF x (1023/1024)
REF x (256/1024)
REF x (512/1024)
0
Input Voltage
(AD 0 - AG N D )
REF x (1023/1024)
REF x (256/1024)
REF x (512/1024)
C8051F040/1/2/3/4/5/6/7
88 Rev. 1.5
Figure 6.11. 10-Bit ADC0 Window Interrupt Example: Lef t Justified Differential Data
Given:
AMX0SL = 0x00, AMX0CF = 0x01, ADLJST = 1,
ADC0LTH:ADC0LTL = 0x4000,
ADC0GTH:ADC0GTL = 0xFFC0.
An ADC End of Conversion will cause an ADC
Window Compare Interrupt (ADWINT=1) if the
resulting ADC Data Word is < 0x4000 and
> 0xFFC0. (Two’s-complement math.)
Given:
AMX0SL = 0x00, AMX0CF = 0x01, ADLJST = 1,
ADC0LTH:ADC0LTL = 0xFFC0,
ADC0GTH:ADC0GTL = 0x4000.
An ADC End of Conversion will cause an ADC
Window Compare Interrupt (ADWINT=1) if the
resulting ADC Data Word is < 0xFFC0 or
> 0x4000. (Two’s-complement math.)
0x7FC0
0x4040
0x4000
0x3FC0
0x0000
0xFFC0
0xFF80
0x8000
AD0WINT=1
AD0WINT
not affected
AD0WINT
not affected
0x7FC0
0x4040
0x4000
0x3FC0
0x0000
0xFFC0
0xFF80
0x8000
AD0WINT=1
AD0WINT
not affected
-REF
Input Voltage
(AD 0 - A D 1 )
AD0WINT=1
REF x (511/512)
ADC0LTH:ADC0LTL
ADC0GTH:ADC0GTL
ADC Data
Word
ADC Data
Word
ADC0LTH:ADC0LTL
ADC0GTH:ADC0GTL
REF x (256/512)
REF x (-1/512)
-REF
Input Voltage
(AD 0 - AD 1)
REF x (511/512)
REF x (256/512)
REF x (-1/512)
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 89
Table 6.2. 10-Bit ADC0 Electrical Characteristics
VDD = 3.0 V, AV+ = 3.0 V, VREF = 2.40 V (REFBE = 0), PGA Gain = 1, –40 to +85 °C unless otherwise specified.
Parameter Conditions Min Typ Max Units
DC Accuracy
Resolution 10 bits
Integral Nonlinearity ——±1 LSB
Differential Nonlinearity Guaranteed Monotonic ——±1 LSB
Offset Error —0.2±1— LSB
Full Scale Error Differential mode —0.1±1— LSB
Offset Temperature Coefficient — ±0.25 — ppm/°C
Dynamic Performance (10 kHz sine-wave input, 0 to 1 dB below Full Scale, 100 ksps)
Signal-to-Noise Plus Distortion 59 — — dB
Total Harmonic Distortion Up to the 5th harmonic —–70— dB
Spurious-Free Dynamic Range —80— dB
Conversion Rate
SAR Clock Frequency ——2.5MHz
Conversion Time in SAR Clocks 16 — — clocks
Track/Hold Acquisition Time 1.5 — — µs
Throughput Rate ——100ksps
Analog Inputs
Input Voltage Range Single-ended operation 0 — VREF V
Common-mode Voltage Range Differential operation AGND — AV+ V
Input Capacitance —10— pF
Temperature Sens or
Nonlinearity1,2 —±1— °C
Absolute Accuracy1,2 —±3— °C
Gain1,2 —2.86
±0.034 —mV/°C
Offset1,2 Temp = 0 °C —0.776
±0.009 —V
Power Specifications
Power Supply Current
(AV+ supplied to ADC) Operating Mode, 100 ksps —450900 µA
Power Supply Rejection —±0.3— mV/V
Notes:
1. Represents one standard deviation from the mean.
2. Includes ADC offset, gain, and linearity variations.
C8051F040/1/2/3/4/5/6/7
90 Rev. 1.5
Table 6.3. High-Voltage Difference Amplifier Electrical Characteristics
VDD = 3.0 V, AV+ = 3.0 V, VREF = 3.0 V, –40 to +85 °C unless otherwise specified.
Parameter Conditions Min Typ Max Units
Analog Inputs
Differential range peak-to-peak ——60 V
Common Mode Range (HVAIN+) – (HVAIN–) = 0 V –60 — +60 V
Analog Output
Output Voltage Range 0.1 — 2.9 V
DC Performance
Common Mode Rejection Ratio Vcm= –10 V to +10 V, Rs=0 44 52 — dB
Offset Voltage —±3— mV
Noise HVCAP floating —500—nV/rtHz
Nonlinearity G = 1 —72— dB
Dynamic Performance
Small Signal Bandwidth G = 0.05 —3—MHz
Small Signal Bandwidth G = 1 —150— kHz
Slew Rate —2—V/µs
Settling Time 0.01%, G = 0.05, 10 V step —10— µs
Input/Output Impedance
Differential (HVAIN+) input —105— k
Differential (HVAIN–) input —98— k
Common Mode input —51— k
HVCAP —5—k
Power Specification
Quiescent Current — 450 1000 µA
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 91
7. 8-Bit ADC (ADC2, C8051F040/1/2/3 Only)
The ADC2 subsystem for the C8051F040/1/2/3 consists of an 8-channel, configurable analog multiplexer,
a programmable gain amplifier, and a 500 ksps, 8-bit successive-approximation-register ADC with inte-
grated track-and- hold (see block diagram in Figure 7.1). The AMUX2, PGA2, and Dat a Con version Modes,
are all configurable under software control via the Special Function Registers shown in Figure 7.1. The
ADC2 subsystem (8-bit ADC, track-and-hold and PGA) is enabled only when the AD2EN bit in the ADC2
Control register (ADC2CN) is set to logic 1. The ADC2 subsystem is in low power shutdown when this bit is
logic 0. The voltage reference used by ADC2 is selected as described in Section “9. Voltage Reference
(C8051F040/2/4/6)” on page 113 for C8051F040/2 devices, or Section “10. Voltage Reference
(C8051F041/3/5/7)” on page 117 for C8051F041/3 devices.
Figure 7.1. ADC2 Functional Block Diagram
7.1. Analog Multiplexer and PGA
Eight ADC2 channels are available for measurement, as selected by the AMX2SL register (see SFR Defi-
nition 7.2). The PGA amplifies the ADC2 output signal by an amount determined by the states of the
AMP2GN2-0 bits in the AD C2 Con fig ur at ion r e gist er, ADC2CF ( S FR Definit i on 7. 1) . T h e PG A c an be s oft-
ware-programmed for gains of 0.5, 1, 2, or 4. Gain defaults to 0.5 on reset.
Import ant Not e: AIN2 pi ns also function a s Port 1 I/O pins, and must be configur ed as a nalog inpu t s whe n
used as ADC2 inputs. To configure an AIN2 pin for analog input, set to ‘0’ the corresponding bit in register
P1MDIN. Port 1 pins selected as analog inputs are skipped by the Digital I/O Crossbar. See Section
“17.1.5. Configuring Port 1, 2, and 3 Pins a s Ana log Inputs” on page 207 for more infor mation on con-
figuring the AIN2 pins.
8-Bit
SAR
ADC
REF
+
-
AV+
8
AV+
AD2EN
SYSCLK
X
AGND
ADC2
ADC2CF
AMP2GN0
AMP2GN1
AD2SC0
AD2SC1
AD2SC2
AD2SC3
AD2SC4
AMX2SL ADC2CN
AD2CM0
AD2CM1
AD2CM2
AD2BUSY
AD2INT
AD2TM
AD2EN
Start Conversion
Timer 3 Overflow
Timer 2 Overflow
000
001
010
011
Write to AD2BUSY
CNVSTR
1xx Write to AD0BUSY
(synchronized with
ADC0)
AMX2AD0
AMX2AD1
AMX2AD2
8-to-1
AMUX
AIN2.0 (P1.0)
AIN2.1 (P1.1)
AIN2.2 (P1.2)
AIN2.3 (P1.3)
AIN2.4 (P1.4)
AIN2.5 (P1.5)
AIN2.6 (P1.6)
AIN2.7 (P1.7)
+
-
+
-
+
-
+
-
AMX2CF
AIN01IC
AIN23IC
AIN45IC
AIN67IC
ADC2LTHADC2GTH
16 Dig
Comp
ADC Window
Interrupt
C8051F040/1/2/3/4/5/6/7
92 Rev. 1.5
7.2. ADC2 Modes of Operation
ADC2 has a maximum conversion speed of 500 ksps. The ADC2 conversion clock (SAR2 clock) is a
divided version of the system clock, determined by the AD2SC bits in the ADC2CF register (system clock
divided by (AD2SC + 1) for 0 AD2SC 31). The maximum ADC2 conversion clock is 7.5 MHz.
7.2.1. Starting a Conversion
A conversion ca n be in itiated in one of five w ays, de pending on the programmed states of the ADC2 Start
of Conversion Mode bits (AD2CM2–0) in ADC2CN. Conversions may be initiated by the following:
•Writing a ‘1’ to the AD2BUSY bit of ADC2CN;
•A Timer 3 overflow (i.e., timed continuous conversions);
•A rising edge detected on the external ADC convert start signal, CNVSTR2 or CNVSTR0 (see
important note below);
•A Timer 2 overflow (i.e., timed continuous conversions);
•Writing a ‘1’ to the AD0BUSY of register ADC0CN (initiate conversion of ADC2 and ADC0 with a
single software command).
An important note about external convert start (CNVSTR0 and CNVSTR2): If CNVSTR2 is enabled in the
digital crossbar (Section “17.1. Ports 0 through 3 and the Priority Crossbar Decoder” on page 204),
CNVSTR2 will be the external convert start signal for ADC2. However, if only CNVSTR0 is enabled in the
digital crossbar and CNVSTR2 is not enabled, then CNVSTR0 may serve as the start of conversion for
both ADC0 and ADC2. This permits synchronous sampling of both ADC0 and ADC2.
During conversion, the AD2BUSY bit is set to logic 1 and restored to 0 when conversion is complete. The
falling edge of AD2BUSY triggers an interrupt (when enabled) and sets the interrupt flag in ADC2CN. Con-
verted data is available in the ADC2 data word, ADC2.
When a conversion is initiated by writing a ‘1’ to AD2BUSY, it is recommended to poll AD2INT to determine
when the conversion is complete. The recommended procedure is:
Step 1. Write a ‘0’ to AD2INT;
Step 2. Write a ‘1’ to AD2BUSY;
Step 3. Poll AD2INT for ‘1’;
Step 4. Process ADC2 data.
7.2.2. Tracking Modes
According to Table 7.2, each ADC2 conversion must be preceded by a minimum tracking time for the con-
verted result to be accurate. The AD2TM bit in register ADC2CN controls the ADC2 track-and-hold mode.
In its default state, the ADC2 input is continuously tr acked, except when a conversion is in progress. When
the AD2TM bit is logic 1, ADC2 operates in low-power tracking mode. In this mode, each conversion is pre-
ceded by a tracking period of 3 SAR clocks (after the start-of-conversion signal). When the CNVSTR2 (or
CNVSTR0, See Section 7.2.1 above) signal is used to initiate conversions in low-power tracking mode,
ADC2 tracks only when CNVSTR2 is low; conversion begins on the rising edge of CNVSTR2 (see
Figure 7.2). Tracking can also be disabled (shutdown) when the entire chip is in low power standby or
sleep modes. Low-power Track-and-Hold mode is also useful when AMUX or PGA settings are frequently
changed, due to the settling time requirements described in Section “7.2.3. Settling Time Require-
ments” on page 94.
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 93
Figure 7.2. ADC2 Track and Conversion Example Timing
Write '1' to AD2BUSY,
Timer 3 Overf low,
Timer 2 Overfl ow,
Write '1' to AD0BUSY
(AD2CM[2:0]=000, 001, 011, 0xx)
AD2TM=1
AD2TM=0
SAR2 Clocks
123456789101112
123456789
SAR2 Clocks
Track Convert Low Power Mode
Lo w Power
or Convert
Track or
Convert Convert Track
B. ADC Timing for Internal Trigger Source
123456789
CNVSTR2/CNVSTR0
(AD2CM[2:0]=010)
AD2TM=1
A. ADC Timing for External Trigger Source
SAR2 Clocks
Track or Convert Convert TrackAD2TM=0
Track Convert Low Power Mode
Lo w Power
or Convert
C8051F040/1/2/3/4/5/6/7
94 Rev. 1.5
7.2.3. Settling Time Requirements
A minimum tracking time is requir ed before an accu rate conver sion can be pe rformed. This tracking time is
determined by the ADC2 MUX resistance, the ADC2 sampling capacitance, any external source resis-
tance, and the accuracy required for the conversion. Figure 7.3 shows the equivalent ADC2 input circuit.
The required ADC2 settling time for a given settling accuracy (SA) may be approximated by Equation 7.1.
Note: An absolute minimum settling time of 0.8 µs required after any MUX selection. Note that in low-
power tracking mode, three SAR2 clocks are used for tracking at the start of every conversion. For most
applications, these three SAR2 clocks will meet the tracking requirements.
Equation 7.1. ADC2 Settling Time Requirements
Where:
SA is the settling accuracy, given as a fraction of an LSB (for example, 0.25 to settle within 1/4 LSB)
t is the required settling time in seconds
RTOTAL is the sum of the ADC2 MUX resistance and any external source resistance.
n is the ADC resolution in bits (8).
Figure 7.3. ADC2 Equivalent Input Circuit
t2n
SA
-------

RTOTALCSAMPLE
ln=
R
MUX
= 5k
C
SAMPLE
= 10pF
RC
Input
= R
MUX
* C
SAMPLE
MUX Select
AIN2.x
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 95
SFR Definition 7.1. AMX2CF: AMUX2 Configuration
SFR Definition 7.2. AMX2SL: AMUX2 Channel Select
Bits7-4: UNUSED. Read = 0000b; Write = don’t care
Bit3: PIN67IC: P1.6, P1.7 Input Pair Configuration Bit
0: P1.6 and P1.7 are independent single-ended inputs
1: P1.6, P1.7 are (respectively) +, - differential input pair
Bit2: PIN45IC: P1.4, P1.5 Input Pair Configuration Bit
0: P1.4 and P1.5 are independent single-ended inputs
1: P1.4, P1.5 are (respectively) +, - differential input pair
Bit1: PIN23IC: P1.2, P1.3 Input Pair Configuration Bit
0: P1.2 and P1.3 are independent single-ended inputs
1: P1.2, P1.3 are (respectively) +, - differential input pair
Bit0: PIN01IC: P1.0, P1.1 Input Pair Configuration Bit
0: P1.0 and P1.1 are independent single-ended inputs
1: P1.0, P1.1 are (respectively) +, - differential input pair
NOTE: The ADC2 Data Word is in 2’s complement format for channels configured as differential.
RRRRR/WR/WR/WR/WReset Value
- - - - PIN67IC PIN45IC PIN23IC PIN01IC 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xBA
2
Bits7-3: UNUSED. Read = 00000b; Write = don’t care
Bits2-0: AMX2AD2-0: AMX2 Address Bits
000-111b: ADC Inputs selected per Table 7.1.
RRRRRR/WR/WR/WReset Value
- - - - - AMX2AD2 AMX2AD1 AMX2AD0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xBB
2
C8051F040/1/2/3/4/5/6/7
96 Rev. 1.5
Table 7.1. AMUX Selection Chart (AMX2AD2-0 and AMX2CF3-0 bits)
AMX2AD2-0
000 001 010 011 100 101 110 111
AMX2CF Bits 3-0
0000 P1.0 P1.1 P1.2 P1.3 P1.4 P1.5 P1.6 P1.7
0001 +(P1.0)
-(P1.1) -(P1.0)
+(P1.1) P1.2 P1.3 P1.4 P1.5 P1.6 P1.7
0010 P1.0 P1.1 +(P1.2)
-(P1.3) -(P1.2)
+(P1.3) P1.4 P1.5 P1.6 P1.7
0011 +(P1.0)
-(P1.1) -(P1.0)
+(P1.1) +(P1.2)
-(P1.3) -(P1.2)
+(P1.3) P1.4 P1.5 P1.6 P1.7
0100 P1.0 P1.1 P1.2 P1.3 +(P1.4)
-(P1.5) -(P1.4)
+(P1.5) P1.6 P1.7
0101 +(P1.0)
-(P1.1) -(P1.0)
+(P1.1) P1.2 P1.3 +(P1.4)
-(P1.5) -(P1.4)
+(P1.5) P1.6 P1.7
0110 P1.0 P1.1 +(P1.2)
-(P1.3) -(P1.2)
+(P1.3) +(P1.4)
-(P1.5) -(P1.4)
+(P1.5) P1.6 P1.7
0111 +(P1.0)
-(P1.1) -(P1.0)
+(P1.1) +(P1.2)
-(P1.3) -(P1.2)
+(P1.3) +(P1.4)
-(P1.5) -(P1.4)
+(P1.5) P1.6 P1.7
1000 P1.0 P1.1 P1.2 P1.3 P1.4 P1.5 +(P1.6)
-(P1.7) -(P1.6)
+(P1.7)
1001 +(P1.0)
-(P1.1) -(P1.0)
+(P1.1) P1.2 P1.3 P1.4 P1.5 +(P1.6)
-(P1.7) -(P1.6)
+(P1.7)
1010 P1.0 P1.1 +(P1.2)
-(P1.3) -(P1.2)
+(P1.3) P1.4 P1.5 +(P1.6)
-(P1.7) -(P1.6)
+(P1.7)
1011 +(P1.0)
-(P1.1) -(P1.0)
+(P1.1) +(P1.2)
-(P1.3) -(P1.2)
+(P1.3) P1.4 P1.5 +(P1.6)
-(P1.7) -(P1.6)
+(P1.7)
1100 P1.0 P1.1 P1.2 P1.3 +(P1.4)
-(P1.5) -(P1.4)
+(P1.5) +(P1.6)
-(P1.7) -(P1.6)
+(P1.7)
1101 +(P1.0)
-(P1.1) -(P1.0)
+(P1.1) P1.2 P1.3 +(P1.4)
-(P1.5) -(P1.4)
+(P1.5) +(P1.6)
-(P1.7) -(P1.6)
+(P1.7)
1110 P1.0 P1.1 +(P1.2)
-(P1.3) -(P1.2)
+(P1.3) +(P1.4)
-(P1.5) -(P1.4)
+(P1.5) +(P1.6)
-(P1.7) -(P1.6)
+(P1.7)
1111 +(P1.0)
-(P1.1) -(P1.0)
+(P1.1) +(P1.2)
-(P1.3) -(P1.2)
+(P1.3) +(P1.4)
-(P1.5) -(P1.4)
+(P1.5) +(P1.6)
-(P1.7) -(P1.6)
+(P1.7)
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 97
SFR Definition 7.3. ADC2CF: ADC2 Configuration
Bits7-3: AD2SC4-0: ADC2 SAR Conversion Clock Period Bits
SAR Conversion clock is der ived from system clock by the following equation, where
AD2SC refers to the 5-bit value held in AD2SC4-0. SAR conversion clock requirements are
given in Table 7.2.
* or
*Note: AD2SC is the rounded-up result.
Bit2: UNUSED. Read = 0b. Write = don’t care.
Bits1-0: AMP2GN1-0: ADC2 Internal Amplifier Gain (PGA)
00: Gain = 0.5
01: Gain = 1
10: Gain = 2
11: Gain = 4
R/W R/W R/W R/W R / W R R/W R/W Reset Value
AD2SC4 AD2SC3 AD2SC2 AD2SC1 AD2SC0 - AMP2GN1 AMP2GN0 11111000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xBC
2
AD2SC SYSCLK
CLKSAR2
-----------------------1–
CLKSAR2SYSCLK
AD2SC 1+
---------------------------- –=
C8051F040/1/2/3/4/5/6/7
98 Rev. 1.5
SFR Definition 7.4. ADC2CN: ADC2 Control
Bit7: AD2EN: ADC2 Enable Bit.
0: ADC2 Disabled. ADC2 is in low-power shutdown.
1: ADC2 Enabled. ADC2 is active and ready for data conversions.
Bit6: AD2TM: ADC2 Track Mode Bit.
0: Normal Track Mode: When ADC2 is enabled, tracking is continuous unless a conversion is in
process.
1: Low-power Track Mode: Tracking defined by AD2CM2-0 bits (see below).
Bit5: AD2INT: ADC2 Conversion Complete Interrupt Flag.
This flag must be cleared by software.
0: ADC2 has not completed a data conversion since the last time this flag was cleared.
1: ADC2 has completed a data conversion.
Bit4: AD2BUSY: ADC2 Busy Bit.
Read:
0: ADC2 Conversion is complete or a conversion is not currently in progress. AD2INT is set to
logic 1 on the falling edge of AD2BUSY.
1: ADC2 Conversion is in progress.
Write:
0: No Effect.
1: Initiates ADC2 Conversion if AD2CM2-0 = 000b
Bits3-1: AD2CM2-0: ADC2 Start of Conversion Mode Select.
AD2TM = 0:
000: ADC2 conversion initiated on every write of ‘1’ to AD2BUSY.
001: ADC2 conversion initiated on overflow of Timer 3.
010: ADC2 conversion initiated on rising edge of external CNVSTR2 or CNVSTR0.
011: ADC2 conversion initiated on overflow of Timer 2.
1xx: ADC2 conversion initiated on write of ‘1’ to AD0BUSY (synchronized with ADC0 software-
commanded conversions).
AD2TM = 1:
000: Tracking initiated on write of ‘1’ to AD2BUSY and lasts 3 SAR2 clocks, followed by conver-
sion.
001: Tracking initiated on overflow of Timer 3 and lasts 3 SAR2 clocks, followed by conversion.
010: ADC2 tracks only when CNVSTR2 (or CNVSTR0, See Section 7.2.1) input is logic low; con-
version starts on rising CNVSTR2 edge.
011: Tracking initiated on overflow of Timer 2 and lasts 3 SAR2 clocks, followed by conversion.
1xx: Tracking initiated on write of ‘1’ to AD0BUSY and lasts 3 SAR2 clocks, followed by conver-
sion.
Bit0: AD2WINT: ADC2 Window Compare Interrupt Flag.
0: ADC2 window comparison data match has not occurred since this flag was last cleared.
1: ADC2 window comparison data match has occurred. This flag must be cleared in software.
An important note about external convert start (CNVSTR0 and CNVSTR2): If CNVSTR2 is enabled in
the digital crossbar (Section “17.1. Port s 0 through 3 and the Priority Crossbar Decoder”
on page 204), CNVSTR2 will be the external convert start signal for ADC2. However, if only
CNVSTR0 is enabled in the digital crossbar and CNVSTR2 is not enabled, then CNVSTR0 may
serve as the start of conversion for both ADC0 and ADC2.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
AD2EN AD2TM AD2INT AD2BUSY AD2CM2 AD2CM1 AD2CM0 AD2WINT 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xE8
2
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 99
SFR Definition 7.5. ADC2: ADC2 Data Word
Figure 7.4. ADC2 Data Word Example
Bits7-0: ADC2 Data Word.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xBE
2
8-bit ADC Data Word appears in the ADC2 Data Word Register as follows:
Example: ADC2 Data Word Conversion Map, AIN1.0 Input
(AMX2SL = 0x00)
AIN1.0-AGND
(Volts) ADC2
VREF * (255/256) 0xFF
VREF / 2 0x80
VREF * (127/256) 0x7F
0 0x00
Code Vin Gain
VREF
---------------
256=
C8051F040/1/2/3/4/5/6/7
100 Rev. 1.5
7.3. ADC2 Programmable Window Detector
The ADC2 Programmabl e Windo w Detector contin uously compares the ADC2 output to user-prog ramme d
limits, and no tifies th e system whe n an out-of-b ound co ndition is detected. This is especially effective in an
interrupt-driven system, saving code space and CPU bandwidth while delivering faster system response
times. The window detector interrupt flag (AD2WINT in ADC2CN) can also be used in polled mode. The
reference words are loaded into the ADC2 Greater-Than and ADC2 Less-Than registers (ADC2GT and
ADC2LT). Notice that the window detector flag can be asserted whe n the measured data is inside or out -
side the user-programmed limits, depending on the programming of the ADC2GT and ADC2LT registers.
SFR Definition 7.6. ADC2GT: ADC2 Greater-Than Data
SFR Definition 7.7. ADC2LT: ADC2 Less-Than Dat a
7.3.1. Window Detector in Single-Ended Mode
Figure 7.5 shows two example window comparisons for Single-ended mode, with ADC2LT = 0x20 and
ADC2GT = 0x10. In Single-ended mode, the codes vary from 0 to VREF x (255/256) and are represented
as 8-bit unsigned integers. In the left example, an AD2WINT interrupt will be generated if the ADC2 con-
version word (ADC2) is within the range defined by ADC2GT and ADC2LT (if 0x10 ADC2 0x20). In the
right example, and AD2WINT interrupt will be generated if ADC2 is outside of the range defined by
ADC2GT and ADC2LT (if ADC2 0x10 or ADC2 0x20).
Bits7-0: High byte of ADC2 Grea te r- T ha n Da ta Word.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
11111111
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xC4
2
Bits7-0: Low byte of ADC2 Gr ea te r- T han Da ta Word.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xC6
2
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 101
Figure 7.5. ADC Window Compare Examples, Single-Ended Mode
0xFF
0x21
0x20
0x1F
0x11
0x10
0x0F
0x00
0
Input Voltage
(P1.x - GND)
REF x (255/256)
REF x (32/256)
REF x (16/256)
AD2WINT=1
AD2WINT
not affected
AD2WINT
not affected
ADC2LT
ADC2GT
0xFF
0x21
0x20
0x1F
0x11
0x10
0x0F
0x00
0
Input Voltage
(P1.x - G N D)
REF x (255/256)
REF x (32/256)
REF x (16/256)
AD2WINT
not affected
ADC2GT
ADC2LT
AD2WINT=1
AD2WINT=1
ADC2 ADC2
C8051F040/1/2/3/4/5/6/7
102 Rev. 1.5
7.3.2. Window Detector in Differential Mode
Figure 7.6 shows two example window comparisons for differential mode, with ADC2LT = 0x10 (+16d) and
ADC2GT = 0xFF (–1d). Notice that in Differential mode, the codes vary from –VREF to VREF x (127/128)
and are represented as 8-bit 2s complement signed integers. In the left example, an AD2WINT interrupt
will be generated if the ADC2 conversion word (ADC2L) is within the range defined by ADC2GT and
ADC2LT (if 0xFF (–1d) < ADC2 < 0x0F (16d)). In th e right example, an AD2WINT interrupt will be gener-
ated if ADC2 is outside of the range defined by ADC2GT and ADC2LT (if ADC2 < 0xFF (–1d) or ADC2 >
0x10 (+16d)).
Figure 7.6. ADC Window Compare Examples, Differential Mode
0x7F (127d)
0x11 (17d)
0x10 (16d)
0x0F (15d)
0x00 (0d)
0xFF (-1d)
0xFE (- 2d)
0x80 (-128d)
-REF
Input Voltage
(P1.x - P1.y )
REF x (127/128)
REF x (16/128)
REF x (-1/256)
0x7F (127d)
0x11 (17d)
0x10 (16d)
0x0F (15d)
0x00 (0d)
0xFF (-1d)
0xFE (- 2d)
0x80 (-128d)
-REF
Input Voltage
(P1.x - P1.y )
REF x (127/128)
REF x (16/128)
REF x (-1/256)
AD2WINT=1
AD2WINT
not affected
AD2WINT
not affected
ADC2LT
ADC2GT
AD2WINT
not affected
ADC2GT
ADC2LT
AD2WINT=1
AD2WINT=1
ADC2ADC2
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 103
Table 7.2. ADC2 Electrical Characteristics
VDD = 3.0 V, AV+ = 3.0 V, VREF2 = 2.40 V (REFBE = 0), PGA2 = 1, –40 to +85 °C unless otherwise specified.
Parameter Conditions Min Typ Max Units
DC Accuracy
Resolution 8bits
Integral Nonlinearity ——±1LSB
Differential Nonlinearity Guaranteed Monotonic ——±1LSB
Offset Error — 0.5±0.3 — LSB
Full Scale Error Differential mode — –1±0.2 — LSB
Dynamic Performance (10 kHz sine-wave input, 0 to 1 dB below Full Scale, 500 ksps)
Signal-to-Noise Plus Distortion 45 47 — dB
Total Harmonic Distortion Up to the 5th harmonic —–51— dB
Spurious-Free Dynamic Range —52— dB
Conversion Rate
SAR Conversion Clock
Frequency —— 6MHz
Conversion Time in SAR Clocks 8 — — clocks
Track/Hold Acquisition Time 300 — — ns
Throughput Rate ——500ksps
Analog Inputs
Input Voltage Range Single-ended 0 — VREF V
Common Mode Range 0—AV+V
Input Capacitance —5—pF
Power Specifications
Power Supply Current
(AV+ supplied to ADC2) Operating Mode, 500 ksps —420900 µA
Power Supply Rejection —±0.3—mV/V
C8051F040/1/2/3/4/5/6/7
104 Rev. 1.5
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 105
8. DACs, 12-Bit Voltage Mode (C8051F040/1/2/3 Only)
Each C8051F040/1/2/3 devices include two on-chip 12-bit voltage-mode Digital-to-Analog Converters
(DACs). Each DAC has an output swing of 0 V to (VREF – 1 LSB) for a corresponding input code range of
0x000 to 0xFFF. The DACs may be enabled/disabled via their corresponding control registers, DAC0CN
and DAC1CN. While disabled, the DAC output is maint ained in a high-impedance state, and the DAC sup-
ply current falls to 1 µA or less. The voltage reference for each DAC is supplied at the VREFD pin
(C8051F040/2 devices) or the VREF pin ( C8051F0 41/3 devices). Note that the VREF pin on C8051F041 /3
devices may be driven by the internal voltage reference or an external source. If the internal voltage refer-
ence is used it must be enabled in order for the DAC outputs to be valid. See Section “9. Voltage Refer-
ence (C8051F040/2/4/6)” on page 113 or Section “10. Voltage Reference (C8051F041/3/5/7)” on
page 117 for more information on configuring the voltage reference for the DACs.
Figure 8.1. DAC Functional Block Diagram
DAC0
AV+
12
AGND
8
8
REF
DAC0
DAC0CN
DAC0EN
DAC0MD1
DAC0MD0
DAC0DF2
DAC0DF1
DAC0DF0
DAC0HDAC0L
Dig. MUX
Latch Latch
8
8
DAC1
AV+
12
AGND
8
8
REF
DAC1
DAC1CN
DAC1EN
DAC1MD1
DAC1MD0
DAC1DF2
DAC1DF1
DAC1DF0
DAC1HDAC1L
Dig. MUX
Latch Latch
8
8
DAC0H
Timer 3
Timer 4
Timer 2
DAC1H
Timer 3
Timer 4
Timer 2
C8051F040/1/2/3/4/5/6/7
106 Rev. 1.5
8.1. DAC Output Scheduling
Each DAC features a flexible output update mechanism which allows for seamless full-scale changes and
supports jitter-free updates for waveform generation. The following examples are written in terms of DAC0,
but DAC1 operation is identical.
8.1.1. Update Output On-Demand
In its default mode (DAC0CN.[4:3] = ‘00’) the DAC0 output is updated “on-demand” on a write to the high-
byte of the DAC0 dat a registe r (DAC0H). It is important to note that writes to DAC0L are held, an d have no
effect on the DAC0 output until a write to DAC0H takes place. If writing a full 12-bit word to the DAC data
registers, the 12-bit data word is written to the low byte (DAC0L) and high byte (DAC0H) data registers.
Data is latched into DAC0 after a write to the corresponding DAC0H register, so the write sequence
should be DAC0L followed by DAC0H if the full 12-bit resolution is required. The DAC can be used in 8-
bit mode by initializing DAC0L to the desired value (typically 0x00), and writing data to only DAC0H (also
see Section 8.2 for information on formatting the 12-bit DAC data word within the 16-bit SFR space).
8.1.2. Update Output Based on Timer Overflow
Similar to the ADC operation, in which an ADC conversion can be initiated by a timer overflow indepen-
dently of the processor, the DAC outputs can use a Timer overflow to schedule an output update event.
This feature is useful in systems where the DAC is used to generate a waveform of a d efined sampling rate
by eliminating the effects of variable interrupt latency and instruction execution on the timing of the DAC
output. When the DAC0MD bits (DAC0CN.[4:3]) are set to ‘01’, ‘10’, or ‘11’, writes to both DAC data regis-
ters (DAC0L and DAC0H) are held until an associated Timer overflow event (Timer 3, Timer 4, or Timer 2,
respectively) occurs, at which time the DAC0H:DAC0L content s ar e copie d to the DAC input latches allow-
ing the DAC output to change to the new value.
8.2. DAC Output Scaling/Justification
In some instances, input data should be shifted prior to a DAC0 write operation to properly justify data
within the DAC input registers. This action would typically require one or more load and shift operations,
adding software overhead and slowing DAC throughput. To alleviate this problem, the data-formatting fea-
ture provides a means for the user to program the orientation of the DAC0 data word within data registers
DAC0H and DAC0L. The three DAC0DF bits (DAC0CN.[2:0]) allow the user to specify one of five data
word orientations as shown in the DAC0CN register definition.
DAC1 is functionally the same as DAC0 described above. The electrical specifications for both DAC0 and
DAC1 are given in Table 8.1.
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 107
SFR Definition 8.1. DAC0H: DAC0 High Byte
SFR Definition 8.2. DAC0L: DAC0 Low Byte
Bits7-0: DAC0 Data Word Most Significant Byte.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xD3
0
Bits7-0: DAC0 Data Word Least Significant Byte.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xD2
0
C8051F040/1/2/3/4/5/6/7
108 Rev. 1.5
SFR Definition 8.3. DAC0CN: DAC0 Control
Bit7: DAC0EN: DAC0 Enable Bit.
0: DAC0 Disabled. DAC0 Output pin is disabled; DAC0 is in low-power shutdown mode.
1: DAC0 Enabled. DAC0 Output pin is active; DAC0 is operational.
Bits6-5: UNUSED. Read = 00b; Write = don’t care.
Bits4-3: DAC0MD1-0: DAC0 Mode Bits.
00: DAC output updat es occur on a write to DAC0H.
01: DAC output updates occur on Timer 3 overflow.
10: DAC output updates occur on Timer 4 overflow.
11: DAC output updates occur on Timer 2 overflow.
Bits2-0: DAC0DF2-0: DAC0 Data Format Bits:
000: The most significant nibble of the DAC0 Dat a Word is in DAC0H[3:0], while the least
significant byte is in DAC0L.
001: The most significant 5-bits of the DAC0 Data Word is in DAC0H[4:0], while the least
significant 7-bits are in DAC0L[7:1].
010: The most significant 6-bits of the DAC0 Data Word is in DAC0H[5:0], while the least
significant 6-bits are in DAC0L[7:2].
011: The most significant 7-bits of the DAC0 Data Word is in DAC0H[6:0], while the least
significant 5-bits are in DAC0L[7:3].
1xx: The most significant 8-bits of the DAC0 Data Word is in DAC0H[7:0], while the least
significant 4-bits are in DAC0L[7:4].
R/W R R R/W R/W R/W R/W R/W Reset Value
DAC0EN - - DAC0MD1 DAC0MD0 DAC0DF2 DAC0DF1 DAC0DF0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xD4
0
DAC0H DAC0L
MSB LSB
DAC0H DAC0L
MSB LSB
DAC0H DAC0L
MSB LSB
DAC0H DAC0L
MSB LSB
DAC0H DAC0L
MSB LSB
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 109
SFR Definition 8.4. DAC1H: DAC1 High Byte
SFR Definition 8.5. DAC1L: DAC1 Low Byte
Bits7-0: DAC1 Data Word Most Significant Byte.
R/WR/WR/WR/WR/WR/WR/W R/WReset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xD3
1
Bits7-0: DAC1 Data Word Least Significant Byte.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xD2
1
C8051F040/1/2/3/4/5/6/7
110 Rev. 1.5
SFR Definition 8.6. DAC1CN: DAC1 Control
Bit7: DAC1EN: DAC1 Enable Bit.
0: DAC1 Disabled. DAC1 Output pin is disabled; DAC1 is in low-power shutdown mode.
1: DAC1 Enabled. DAC1 Output pin is active; DAC1 is operational.
Bits6-5: UNUSED. Read = 00b; Write = don’t care.
Bits4-3: DAC1MD1-0: DAC1 Mode Bits:
00: DAC output updat es occur on a write to DAC1H.
01: DAC output updates occur on Timer 3 overflow.
10: DAC output updates occur on Timer 4 overflow.
11: DAC output updates occur on Timer 2 overflow.
Bits2-0: DAC1DF2: DAC1 Data Format Bits:
000: The most significant nibble of the DAC1 Dat a Word is in DAC1H[3:0], while the least
significant byte is in DAC1L.
001: The most significant 5-bits of the DAC1 Data Word is in DAC1H[4:0], while the least
significant 7-bits are in DAC1L[7:1].
010: The most significant 6-bits of the DAC1 Data Word is in DAC1H[5:0], while the least
significant 6-bits are in DAC1L[7:2].
011: The most significant 7-bits of the DAC1 Data Word is in DAC1H[6:0], while the least
significant 5-bits are in DAC1L[7:3].
1xx: The most significant 8-bits of the DAC1 Data Word is in DAC1H[7:0], while the least
significant 4-bits are in DAC1L[7:4].
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
DAC1EN - - DAC1MD1 DAC1MD0 DAC1DF2 DAC1DF1 DAC1DF0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0SFR
Address:
SFR Page:
0xD4
1
DAC1H DAC1L
MSB LSB
DAC1H DAC1L
MSB LSB
DAC1H DAC1L
MSB LSB
DAC1H DAC1L
MSB LSB
DAC1H DAC1L
MSB LSB
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 111
.
Table 8.1. DAC Electrical Characteristics
VDD = 3.0 V, AV+ = 3.0 V, VREF = 2.40 V (REFBE = 0), No Output Load unless otherwise specified.
Parameter Conditions Min Typ Max Units
Static Performance
Resolution 12 bits
Integral Nonlinearity —±2— LSB
Differential Nonlinearity —±1LSB
Output Noise No Output Filter
100 kHz Output Filter
10 kHz Output Filter
—
—
—
250
128
41
—
—
—
µVrms
Offset Error Data Word = 0x014 —±3±30 mV
Offset Tempco — 6 — ppm/°C
Full-Scale Error —±20±60 mV
Full-Scale Error Tempco — 10 — ppm/°C
VDD Power Supply Rejection
Ratio —–60— dB
Output Impedance in Shutdown
ModeDACnEN = 0 —100— k
Output Sink Current —300— µA
Output Short-Circuit Current Data Wor d = 0xFFF —15— mA
Dynamic Performance
Voltage Output Slew Rate Load = 40 pF —0.44— V/µs
Output Settling Time to 1/2 LSB Load = 40 pF, Output swing from
code 0xFFF to 0x014 —10— µs
Output Voltage Swing 0—VREF
– LSB V
Startup Time —10— µs
Analog Outputs
Load Regulation IL = 0.01 mA to 0.3 mA at code
0xFFF —60— ppm
Power Consumption (each DAC)
Power Supply Current (AV+
supplied to DAC) Dat a Word = 0x7FF —110400 µA
C8051F040/1/2/3/4/5/6/7
112 Rev. 1.5
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 113
9. Voltage Reference (C8051F040/2/4/6)
The voltage reference circuit of fers full flexibility in operating the ADC and DAC modules. Three voltage ref-
erence input pins a llow each ADC and the two DACs (C8051F 040/2 o nly) to re ference a n extern al voltage
reference or the on-chip voltage reference output. ADC0 may also reference the DAC0 output internally,
and ADC2 may reference the analog power supply voltage, via the VREF multiplexers shown in Figure 9.1.
The internal voltage reference circuit consists of a 1.2 V, temperature stable bandgap voltage reference
generator and a gain-of-two output buffer amplifier. The internal reference may be r outed via the VREF pin
to external system components or to the voltage reference input pins shown in Figure 9.1. Bypass capaci-
tors of 0.1 µF and 4.7 µF are recommended from the VREF pin to AGND, as shown in Figure 9.1. See
Table 9.1 for voltage reference specifications.
The Reference Control Register, REF0CN (defined in SFR Definition 9.1) enables/disables the internal ref-
erence generator and selects the reference inputs for ADC0 and ADC2. The BIASE bit in REF0CN enables
the on-board reference generator while the REFBE bit enables the gain-of-two buffer amplifier which drives
the VREF pin. When disabled, the supply current drawn by the bandgap and buffer amplifier falls to less
than 1 µA (typical) and the output of the buffer amplifier enters a high impedance state. If the internal band-
gap is used as the reference voltage generator, BIASE and REFBE must both be set to logic 1. If the inter-
nal reference is not used, REFBE may be set to logic 0. Note that the BIASE bit must be set to logic 1 if
either DAC or ADC is used, regardless of the voltage reference used. If neith er the ADC nor the DAC are
being used, both of these bits can be set to log ic 0 to conserve power. Bits AD0VRS and AD2VRS select
the ADC0 and ADC2 voltage reference sources, respectively. The electrical specifications for the Voltage
Reference are given in Table 9.1.
The temperature sensor connects to the highest order input of the ADC0 input multiplexer (see
Section
“5.1. Analog Multiplexer and PGA” on p age 47
for C8051F040 devices, or
Section “6.1. Analog Multi-
plexer and PGA” on page 69
for C8051F042/4/6 devices). The TEM PE bit within REF0CN enables and
disables the temperature sensor. While disabled, the temperature sensor defaults to a high impedance
state and any A/D measurements performed on the sensor while disabled result in meaningless d ata.
Figure 9.1. Voltage Reference Functional Block Diagram
Recommen ded Bypass
Capacitors
x2
VREF
DAC0
DAC1
Ref
VREFD
AV+ ADC2
ADC0
VREF2
Ref
Ref
1
0
0
1
VREF0
4.7F0.1F
REF0CN
REFBE
BIASE
TEMPE
AD2VRS
AD0VRS
REFBE
BIASE
Bias to
ADCs,
DACs
1.2V
Band-Gap
EN
External
Voltage
Reference
Circuit
R1
VDD
(C8051F040/2 only)
(C8051F040/2 only)
C8051F040/1/2/3/4/5/6/7
114 Rev. 1.5
SFR Definition 9.1. REF0CN: Reference Control
Bits7-5: UNUSED. Read = 000b; Write = don’t care.
Bit4: AD0VRS: ADC0 Voltage Reference Select
0: ADC0 voltage reference from VREF0 pin.
1: ADC0 voltage reference from DAC0 output ( C8 051F040/2 only).
Bit3: AD2VRS: ADC2 Voltage Reference Select (C8051F040/2 only).
0: ADC2 voltage reference from VREF2 pin.
1: ADC2 voltage reference from AV+.
Bit2: TEMPE: Temperature Sensor Enable Bit.
0: Internal Temperature Sensor Off.
1: Internal Temperature Sensor On.
Bit1: BIASE: ADC/DAC Bias Generator Enable Bit. (Must be ‘1’ if using ADC or DAC).
0: Internal Bias Generator Off.
1: Internal Bias Generator On.
Bit0: REFBE: Internal Reference Buffer Enable Bit.
0: Internal Reference Buffer Off.
1: Internal Reference Buffer On. Internal voltage r eference is driven on the VREF pin.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
- - - AD0VRS AD2VRS TEMPE BIASE REFBE 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xD1
0
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 115
Table 9.1. Voltage Reference Electrical Characteristics
VDD = 3.0 V, AV+ = 3.0 V, –40 to +85°C unless otherwise specified.
Parameter Conditions Min Typ Max Units
Internal Referenc e (REF BE = 1)
Output Voltage 25 °C amb i en t 2.36 2.43 2.48 V
VREF Short-Circuit Current —— 30 mA
VREF Temperature Coefficient — 15 — ppm/°C
Load Regulation Load = 0 to 200 µA to AGND — 0.5 — ppm/µA
VREF Turn-on T ime 1 4.7 µF tantalum, 0.1 µF
ceramic bypass —2 — ms
VREF Turn-on T ime 2 0.1 µF ceramic bypass —20 — µs
VREF Turn-on T ime 3 no bypass cap —10 — µs
Reference Buffer Power Sup-
ply Current —40 — µA
Power Supply Rejection — 140 — ppm/V
External Reference (REFBE = 0)
Input Voltage Range 1.00 — (AV+) – 0.3 V
Input Current —0 1 µA
C8051F040/1/2/3/4/5/6/7
116 Rev. 1.5
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 117
10. Voltage Reference (C8051F041/3/5/7)
The internal voltage reference circuit consists of a 1.2 V, temperature stable bandgap voltage reference
generator and a gain -o f-t wo outp ut buffer amplifier. The internal reference ma y be r oute d via the VREF pi n
to external system components or to the VREFA input pin shown in Figure 10.1. Bypass capacitors of
0.1 µF and 4.7 µF are recommended from the VREF pin to AGND, as shown in Figure 10.1. See
Table 10.1 for voltage reference specifications.
The VREFA pin provides a voltage reference input for ADC0 and ADC2 (C8051F041/3 only). ADC0 may
also refere nce the DAC0 output intern ally (C8051F041 /3 only), and ADC2 may reference the analog power
supply voltage, via the VREF multiplexers shown in Figure 10.1.
The Reference Control Register, REF0CN (defined in SFR Definition 10.1) enables/disables the internal
reference generator and selects the reference inputs for ADC0 and ADC2. The BIASE bit in REF0CN
enables the on-board reference generator while the REFBE bit enables the gain-of-two buffer amplifier
which drives the VREF pin. When disabled, the supply current drawn by the bandgap and buffer amplifier
falls to less than 1 µA (typical) and the output of the buffer amplifier enters a high impedance state. If the
internal bandgap is used as the reference volt age generator, BIASE and REFBE must both be set to 1 (this
includes any time a DAC is used). If the internal reference is not used, REFBE may be set to logic 0. Note
that the BIASE bit must be set to logic 1 if either ADC is used, regardless of the voltage reference used. If
neither the ADC nor the DAC are being used, both of these bits can be set to logic 0 to conserve power.
Bits AD0VRS and AD2VRS select the ADC0 and ADC2 voltage reference sources, respectively. The elec-
trical specifications for the Voltage Reference are given in Table 10.1.
The temperature sensor connects to the highest order input of the ADC0 input multiplexer (see Section
“5.1. Analog Multiplexer and PGA” on page 47 for C8051F041 devices that feature a 12-bit ADC, or
Section “6.1. Analog Multiplexer and PGA” on page 69 for C8051F043/5/7 devices that feature a 10-bit
ADC). The TEMPE bit within REF0CN enables and disables the temperature sensor. While disabled, the
temperature sensor de fa ults to a high impedance state and any A/D measur ements performed on the sen-
sor while disabled result in meaningless da ta.
Figure 10.1. Voltage Reference Functional Block Diagram
Recomme nded Bypass
Capacitors
x2
VREF
DAC0
DAC1
Ref
AV+ ADC2
ADC0
Ref
Ref
1
0
0
1
VREFA
4.7F0.1F
REF0CN
REFBE
BIASE
TEMPE
AD2VRS
AD0VRS
REFBE
BIASE
Bias to
ADCs,
DACs
1.2V
Band-Gap
EN
External
Voltage
Reference
Circuit
R1
VDD
(C8051F041/3 only)
(C8051F041/3 only)
C8051F040/1/2/3/4/5/6/7
118 Rev. 1.5
SFR Definition 10.1. REF0CN: Reference Control
Bits7-5: UNUSED. Read = 000b; Write = don’t care.
Bit4: AD0VRS: ADC0 Voltage Reference Select
0: ADC0 voltage reference fro m VREFA pin.
1: ADC0 voltage reference fro m DAC 0 outp ut (C8051F041 /3 only ).
Bit3: AD2VRS: ADC2 Voltage Reference Select (C8051F041/3 only).
0: ADC2 voltage reference fro m VREFA pin.
1: ADC2 voltage reference fro m AV+.
Bit2: TEMPE: Temperat ur e Sen so r Ena b le Bit.
0: Internal Temperature Sensor Off.
1: Internal Temperature Sensor On.
Bit1: BIASE: ADC/DAC Bias Generator Enable Bit. (Must be ‘1’ if using ADC or DAC).
0: Internal Bias Generator Off.
1: Internal Bias Generator On.
Bit0: REFBE: Internal Reference Buffer Enable Bit.
0: Internal Reference Buffer Off.
1: Internal Reference Buffer On. Internal voltage reference is driven on the VREF pin.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
- - - AD0VRS AD1VRS TEMPE BIASE REFBE 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xD1
0
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 119
Table 10.1. Voltage Reference Electrical Characteristics
VDD = 3.0 V, AV+ = 3.0 V, –40 to +85 °C unless otherwise specified.
Parameter Conditions Min Typ Max Units
Internal Referenc e (REF BE = 1)
Output Voltage 25 °C amb i en t 2.36 2.43 2.48 V
VREF Short-Circuit Current —— 30 mA
VREF Temperature Coefficient — 15 — ppm/°C
Load Regulation Load = 0 to 200 µA to AGND — 0.5 — ppm/µA
VREF Turn-on T ime 1 4.7 µF tantalum, 0.1 µF
ceramic bypass —2 — ms
VREF Turn-on T ime 2 0.1 µF ceramic bypass —20 — µs
VREF Turn-on T ime 3 no bypass cap —10 — µs
Reference Buffer Power Sup-
ply Current —40 — µA
Power Supply Rejection — 140 — ppm/V
External Reference (REFBE = 0)
Input Voltage Range 1.00 — (AV+) – 0.3 V
Input Current —0 1 µA
C8051F040/1/2/3/4/5/6/7
120 Rev. 1.5
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 121
11. Comparators
C8051F04x family of devices include three on-chip programmable voltage comparators, shown in
Figure 11.1. Each comparator offers programmable response time and hysteresis. When assigned to a
Port pin, the Comparator output may be configured as open drain or push-pull, and Comparator inputs
should be con figured as a nalog inputs (see Section “17.1.5. Configuring Port 1, 2, and 3 Pins as Ana-
log Inputs” on page 207). The Comparator may also be used as a reset source (see Section
“13.5. Comparator0 Reset” on page 167).
The output of a Comparator can be polled by software, used as an interrupt source, used as a reset
source, and/or routed to a Port pin. Each comp ar ator can be individu ally enabled and disab led (shu t down).
When disabled, the Comparator output (if assigned to a Port I/O pin via the Crossbar) defaults to the logic
low state, and its supply current falls to less than 1 µA. See Section “17. 1.1. Crossbar Pin Assignment
and Allocation” on page 205 for details on configuring the Comparator output via the digital Crossbar.
The Comparator inputs can be externally driven from -0.25 V to (VDD) + 0.25 V without damage or upset.
The complete electrical specifications for the Comparator are given in Table 11.1.
The Comparator response time may be configured in software using the CPnMD1-0 bits in register CPT-
nMD (see SFR Definition 11.2). Selecting a longer response time reduces the amount of power consumed
by the comparator. See Table 11.1 for complete timing and current consumption specifications.
Figure 11.1. Comparator Functional Block Diagram
VDD
CPTnCN
Reset
Decision
Tree
+
-
Crossbar
Interrupt
Logic
Q
Q
SET
CLR
D
Q
Q
SET
CLR
D
(SYNCHRONIZER)
CPn +
CPn -
CPnEN
CPnOUT
CPnRIF
CPnFIF
CPnHYP1
CPnHYP0
CPnHYN1
CPnHYN0
CPTnMD
CPnRIEN
CPnFIEN
CPnMD1
CPnMD0
CPn
Rising-edge
Interrupt Flag
CPn
Falling-edge
Interrupt Flag
CPn
CP0 +
CP0 -
CP1 +
CP1 -
CP2 +
CP2 -
P2.6
P2.7
P2.2
P2.3
P2.4
P2.5
Comparator Pin Assignments
GND
CPn
Interrupt
C8051F040/1/2/3/4/5/6/7
122 Rev. 1.5
Figure 11.2. Comparator Hysteresis Plot
The hysteresis of the Comparator is software-programmable via its Comparator Control register (CPT-
nCN). The user can progr am both the amoun t of hyster esis vo ltage (referred to the input voltage) and the
positive and negative-going symmetry of this hysteresis around the threshold voltage.
The Comparator hysteresis is programmed using Bits3-0 in the Comparator Control Register CPTnCN
(shown in SFR Definition 11.1). The amount of negative hysteresis voltage is determined by the settings of
the CPnHYN bits. As shown in Table 11.1, settings of approximately 20, 10 or 5 mV of negative hysteresis
can be programmed, or negative hysteresis can be disabled. In a similar way, the amount of positive hys-
teresis is determined by the setting the CPnHYP bits.
Comparator interrupts can be generated on either rising-edge and falling-edge output transitions. (For
Interrupt enable and priority control, see Section “12.3. Interrupt Handler” on page 153). The risi ng and/
or falling -edge interrupts are enabled using the comparator’s Rising/Falling Edge Interrupt Enable Bits
(CPnRIE and CPnFIE) in their respective Comparator Mode Selection Register (CPTnMD), shown in SFR
Definition 11.2. These bits allow the user to control which edge (or both) will cause a comparator interrupt.
However, the comparator interrupt must also be enabled in the Extende d Interrupt Enable Register (EIE1).
The CPnFIF flag is set to logic 1 upon a Comparator falling-edge interrupt, and the CPnRIF flag is set to
logic 1 upon the Comparator rising-edge interrupt. Once set, these bits remain set until cleared by soft-
ware. The output state of a Comparator can be obtained at any time by reading the CPnOUT bit. A Com-
parator is enabled by setting its respective CPnEN bit to logic 1, and is disabled by clearing this bit to logic
0.Upon enabling a comparator, the output of the comparator is not immediately valid. Before using a com-
parator as an interrupt or reset source, software should wait for a minimum of the specified “Power-up
time” as specified in Table 11.1, “Comparator Electrical Characteristics,” on page 126.
Posit ive H ystere sis V olta ge
(Programmed with CPnHYP Bits)
Negative H yste resi s Volt age
(Programmed by CPnHYN Bits)
VIN-
VIN+
INPUTS
CIRCUI T CONFIGURATI ON
+
_
CPn+
CPn- CPn
VIN+
VIN- OUT
V
OH
Posit ive Hy stere sis
Disabled Maximum
Positiv e H ysteresis
Negative Hysteresis
Disabled Maximum
Negative Hysteresis
OUTPUT
V
OL
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 123
11.1. Comparator Inputs
The Port pins selected as comp arator inputs should be configured a s analog input s in the Por t 2 Input Con-
figuration Registe r (f or details on Port configu ration, see Se ct io n “17 .1.3 . Configuring Po rt Pins as Dig i-
tal Input s” on page 206). The inputs for Comparator are on Port 2 as follows:
Comparator Input Port PIN
CP0+ P2.6
CP0– P2.7
CP1+ P2.2
CP1– P2.3
CP2+ P2.4
CP2– P2.5
C8051F040/1/2/3/4/5/6/7
124 Rev. 1.5
SFR Definition 11.1. CPTnCN: Comparator 0, 1, and 2 Control
Bit7: CPnEN: Comparator Enable Bit. (Please see note below.)
0: Comparator Disabled.
1: Comparator Enabled.
Bit6: CPnOUT: Comparator Output State Flag.
0: Voltage on CPn+ < CPn–.
1: Voltage on CPn+ > CPn–.
Bit5: CPnRIF: Comparator Rising-Edge Interrupt Flag.
0: No Comparator Rising Edge Interrupt has occurred since this flag was last cleared.
1: Comparator Rising Edge Interrupt has occurred. Must be cleared by software.
Bit4: CPnFIF: Comparator Falling-Edge Interrupt Flag.
0: No Comparator Falling-Edge Interrupt has occurred since this flag was last cleared.
1: Comparator Falling-Edge Interrupt has occurred. Must be cleared by software.
Bits3-2: CPnHYP1-0: Comparator Positive Hysteresis Control Bits.
00: Positive Hysteresis Disabled.
01: Positive Hysteresis = 5 mV.
10: Positive Hysteresis = 10 mV.
11: Positive Hysteresis = 20 mV.
Bits1-0: CPnHYN1-0: Comparator Negative Hysteresis Control Bits.
00: Negative Hysteresis Disabled.
01: Negative Hyste r esis = 5 mV.
10: Negative Hysteresis = 10 mV.
11: Negative Hysteresis = 20 mV.
NOTE: Upon enabling a comparator, the output of the comparator is not immediately valid. Before
using a comparator as an interrupt or reset source, software should wait for a minimum of
the specified “Power-up time” as specified in Table 11.1, “Comparator Electrical Characteris-
tics,” on page 126.
R/W R R/W R/W R/W R/W R/W R/W Reset Value
CPnEN CPnOUT CPnRIF CPnFIF CPnHYP1 CPnHYP0 CPnHYN1 CPnHYN0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address: CPT0CN: 0x88; CPT1CN: 0x88; CPT2CN: 0x88
SFR Pages: CPT0CN:page 1;CPT1CN:page 2; CPT2CN:page 3
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 125
SFR Definition 11.2. CPTnMD: Comparator Mode Selection
Bits7-6: UNUSED. Read = 00b, Write = don’t care.
Bit 5: CPnRIE: Comparator Rising-Edge Interrupt Enable Bit.
0: Comparator rising-edge interrupt disabled.
1: Comparator rising-edge interrupt enabled.
Bit 4: CPnFIE: Comparator Falling-Edge In terrupt Enable Bit.
0: Comparator falling-edge interrupt disabled.
1: Comparator falling-edge interrupt enabled.
Bits3-2: UNUSED. Read = 00b, Write = don’t care.
Bits1-0: CPnMD1-CPnMD0: Comparator Mode Select
These bits select the response time for the Comparator.
R/W R/W R/W R/W R R R/W R/W Reset Value
- - CPnRIE CPnFIE - - CPnMD1 CPnMD0 00000010
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address: CPT0MD: 0x89; CPT1MD: 0x89;CPT2MD: 0x89
SFR Page: CPT0MD:page 1;CPT1MD:page 2; CPT2MD:page 3
Mode CPnMD1 CPnMD0 CPn Typical Response Time
0 0 0 Fastest Respon se Time
101 —
210 —
3 1 1 Lowest Power Consumption
C8051F040/1/2/3/4/5/6/7
126 Rev. 1.5
Table 11.1. Comparator Electrical Characteristics
VDD = 3.0 V, –40 to +85 °C unless otherwise specified.
Parameter Conditions Min Typ Max Units
Response Time,
Mode 0 CPn+ – CPn– = 100 mV —100 — ns
CPn+ – CPn– = 10 mV —250 — ns
Response Time,
Mode 1 CPn+ – CPn– = 100 mV —175 — ns
CPn+ – CPn– = 10 mV —500 — ns
Response Time,
Mode 2 CPn+ – CPn– = 100 mV —320 — ns
CPn+ – CPn– = 10 mV — 1100 — ns
Response Time,
Mode 3 CPn+ – CPn– = 100 mV —1050 — ns
CPn+ – CPn– = 10 mV —5200 — ns
Common-Mode Rejection
Ratio —1.5 4 mV/V
Positive Hysteresis 1 CPnHYP1-0 = 00 —0 1 mV
Positive Hysteresis 2 CPnHYP1-0 = 01 24.5 7 mV
Positive Hysteresis 3 CPnHYP1-0 = 10 49 13 mV
Positive Hysteresis 4 CPnHYP1-0 = 11 10 17 25 mV
Negative Hysteresis 1 CPnHYN 1-0 = 00 01mV
Negative Hysteresis 2 CPnHYN 1-0 = 01 24.5 7 mV
Negative Hysteresis 3 CPnHYN 1-0 = 10 49 13 mV
Negative Hysteresis 4 CPnHYN 1-0 = 11 10 17 25 mV
Inverting or Non-Inverting
Input Voltage Range –0.25 VDD + 0.25 V
Input Capacitance —7 — pF
Input Bias Curren t –5 0.001 +5 nA
Input Offset Voltage –5 +5 mV
Power Supply
Power Supply Rejection —0.1 1 mV/V
Power-up Time —10 — µs
Supply Current at DC
Mode 0 —7.6 — µA
Mode 1 —3.2 — µA
Mode 2 —1.3 — µA
Mode 3 —0.4 — µA
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 127
12. CIP-51 Microcontroller
The MCU system controller core is the CIP-51 microcontroller. The CIP-51 is fully compatible with the
MCS-51™ instruction set; standard 803x/805x assemblers and compilers can be used to develop soft-
ware. The MCU family has a superset of all the peripherals included with a standard 8051. Included are
five 16-bit counter/timers (see description in Section 23), two full-duplex UARTs (see description in Sec-
tion 21 and Section 22), 256 bytes of internal RAM, 128 byte Special Function Register (SFR) address
space (see Section 12.2.6), and 8/4 by te-wide I/O Po rts (see descrip tion in Section 17). The CIP-51 also
includes on-chip debug hardware (see description in Section 25), and interfaces directly with the MCUs'
analog and d igital subsystems pro viding a com plete data acquisition or control-system solution in a single
integrated circuit.
The CIP-51 Microcontroller core implements the standard 8051 organization and peripherals as well as
additional custom peripherals and functions to extend its capability (see Figure 12.1 for a block diagram).
The CIP-51 includes the following features:
Figure 12.1. CIP-51 Block Diagram
DATA BUS
TMP1 TMP2
PRGM. ADDRESS REG.
PC INCRE MEN TER
ALU
PSW
DATA BUS
DATA BUS
MEMORY
INTERFACE
MEM_ADDRESS
D8
PIPELINE
BUFFER
DATA P OINTER
INTERRUPT
INTERFACE
SYSTEM_IRQs
DEBUG_IRQ
MEM_CONTROL
CONTROL
LOGIC
A16
PROGRAM COUNTER (PC)
STOP
CLOCK
RESET
IDLE POWER CONTROL
REGISTER
DATA BUS
SFR
BUS
INTERFACE
SFR_ADDRESS
SFR_CONTROL
SFR_WRITE_DATA
SFR_READ_DATA
D8
D8
B REGISTER
D8
D8
ACCUMULATOR
D8
D8
D8
D8
D8
D8
D8
D8
MEM_WRITE_DATA
MEM_READ_DATA
D8
SRAM
ADDRESS
REGISTER
SRAM
(256 X 8)
D8
STAC K PO INTE R
D8
- Fully Compatible with MCS-51 Instruction Set
- 25 MIPS Peak Throughput with 25 MHz Clock
- 0 to 25 MHz Clock Frequency
- 256 Bytes of Internal RAM
- 8/4 Byte-W ide I/O Ports
- Extended Interrupt Handler
- Reset Input
- Power Management Modes
- On-chip Debug Logic
- Program and Data Memory Security
C8051F040/1/2/3/4/5/6/7
128 Rev. 1.5
Performance
The CIP-51 employ s a p ipelined architectu re that grea tly increases it s instr uction throughpu t over the st an-
dard 8051 architecture. In a standard 8051, all instructions except for MUL and DIV take 12 or 24 system
clock cycles to execute, and usually have a maximum system clock of 12 MHz. By contrast, the CIP-51
core executes 70% of its instructions in one or two system clock cycles, with no instructions taking more
than eight system clock cycles.
With the CIP-51's maximum system clock at 25 MHz, it has a peak throughput of 25 MIPS. The CIP-51 has
a total of 109 instructions. The table below shows the total number of instructions that require each execu-
tion time.
Programming and Debugging Support
A JTAG-based serial interface is provided for in-system programming of the Flash program memory and
communication with on-chip debug support logic. The re-programmable Flash can also be read and
changed a single byte at a time by the application software using the MOVC and MOVX instructions. This
feature allows program memory to be u sed for non-volatile data storage as well as updating program code
under software control.
The on-chip debug support logic facilitates full speed in-circuit debugging, allowing the setting of hardware
breakpoints and watch points, starting, stopping and single stepping through program execution (including
interrupt service routin es), e xaminatio n of th e progr am' s ca ll stack, and reading/writing the content s of reg-
isters and memory. This method of on-chip debug is completely non-intrusive and non-invasive, requiring
no RAM, Stack, timers, or other on-chip resources.
The CIP-51 is supported by development tools from Silicon Labs and third party vendors. Silicon Labs pro-
vides an integrated development environment (IDE) including editor, macro assembler, debugger and pro-
grammer. The IDE's debugger and programmer interface to the CIP-51 via its JTAG interface to provide
fast and efficient in-system device programming and debugging. Third party macro assemblers and C
compilers are als o ava ila ble.
Clocks to Execute 1 2 2/3 33/4 44/5 5 8
Number of Instructions 26 50 514 73121
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 129
12.1. Instruction Set
The instruction set of the CIP-51 System Controller is fully compatible with the st and ard MCS-51 ™ inst ruc-
tion set; standard 8051 development tools can be used to develop software for the CIP-51. All CIP-51
instructions are the binary and functional equivalent of their MCS-51™ counterparts, including opcodes,
addressing modes and effect on PSW flags. However, instruction timing is different than that of the stan-
dard 8051.
12.1.1. Instruction and CPU Timing
In many 8051 implementations, a distinction is made between machine cycles and clock cycles, with
machine cycles varying from 2 to 12 clock cycles in length. However, the CIP-51 implementation is based
solely on clock cycle timing. All instruction timings are specified in terms of clock cycles.
Due to the pipelined architecture of the CIP-51, most instructions execute in the same number of clock
cycles as there are program bytes in the instruction. Conditional branch instructions take one less clock
cycle to complete when the branch is not taken as opposed to when the branch is taken. Table 12.1 is the
CIP-51 Instruction Set Summary, which includes the mnemonic, number of bytes, and number of clock
cycles for each instruction.
12.1.2. MOVX Instruction and Program Memory
In the CIP-51, the M OVX instruction serves th ree purposes: accessing on-chip XRAM, accessing off-chip
XRAM, and accessing on-chip program Flash memory. The Flash access feature provides a mechanism
for user software to update program code and use the program memory space for non-volatile data stor-
age (see Section “15. Flash Memory” on page 179). The External Memory Interface provides a fast
access to off-chip XRAM (or memory-mapped peripherals) via the MOVX instruction. Refer to Section
“16. External Data Memory Interface and On-Chip XRAM” on page 187 for details.
Table 12.1. CIP-51 Instruction Set Summary
Mnemonic Description Bytes Clock
Cycles
Arithmetic Operations
ADD A, Rn Add register to A 1 1
ADD A, direct Add direct byte to A 2 2
ADD A, @Ri Add indirect RAM to A 1 2
ADD A, #data Add immediate to A 2 2
ADDC A, Rn Add register to A with carry 1 1
ADDC A, direct Add direct byte to A with carry 2 2
ADDC A, @Ri Add indirect RAM to A with carry 1 2
ADDC A, #data Add immediate to A with carry 2 2
SUBB A, Rn Subtract register from A with bo rr ow 1 1
SUBB A, direct Subtract direct byte from A with borrow 2 2
SUBB A, @Ri Subtract ind ire ct RAM from A with bo rr ow 1 2
SUBB A, #data Subtract imme dia te from A with bo rr ow 2 2
INC A Increment A 1 1
INC Rn Increment register 1 1
INC direct Increment direct byte 2 2
INC @Ri Increment indirect RAM 1 2
DEC A Decrement A 1 1
C8051F040/1/2/3/4/5/6/7
130 Rev. 1.5
DEC Rn Decrement register 1 1
DEC direct Decrement direc t byt e 2 2
DEC @Ri Decrement indirect RAM 1 2
INC DPTR Increment Data Pointer 1 1
MUL AB Multiply A and B 1 4
DIV AB Divide A by B 1 8
DA A Decimal adjust A 1 1
Logical Operations
ANL A, Rn AND Register to A 1 1
ANL A, direct AND direct byte to A 2 2
ANL A, @Ri AND indirect RAM to A 1 2
ANL A, #data AND immediate to A 2 2
ANL direct, A AND A to direct byte 2 2
ANL direct, #data AND immediate to direct byte 3 3
ORL A, Rn OR Register to A 1 1
ORL A, direct OR direct byte to A 2 2
ORL A, @Ri OR indirect RAM to A 1 2
ORL A, #data OR immediate to A 2 2
ORL direct, A OR A to direct byte 2 2
ORL direct, #data OR immediate to direct byte 3 3
XRL A, Rn Exclusive-OR Register to A 1 1
XRL A, direct Exclusive-OR direct byte to A 2 2
XRL A, @Ri Exclusive-OR indirect RAM to A 1 2
XRL A, #data Exclusive-OR immediate to A 2 2
XRL direct, A Exclusive-OR A to direct byte 2 2
XRL direct, #data Exclusive-OR immediate to direct byte 3 3
CLR A Clear A 1 1
CPL A Complement A 1 1
RL A Rotate A left 1 1
RLC A Rotate A left through Carry 1 1
RR A Rotate A right 1 1
RRC A Rotate A right through Carry 1 1
SWAP A Swap nibbles of A 1 1
Data Transfer
MOV A, Rn Move Register to A 1 1
MOV A, direct Move direct byte to A 2 2
MOV A, @Ri Move indirect RAM to A 1 2
MOV A, #data Move immediate to A 2 2
MOV Rn, A Move A to Register 1 1
MOV Rn, direct Move direct byte to Register 2 2
MOV Rn, #data Move immediate to Register 2 2
MOV direct, A Move A to direct byte 2 2
MOV direct, Rn Move Register to direct byte 2 2
MOV direct, direct Move direct byte to direct byte 3 3
MOV direct, @Ri Move indirect RAM to direct byte 2 2
Table 12.1. CIP-51 Instruction Set Summary (Continued)
Mnemonic Description Bytes Clock
Cycles
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 131
MOV direct, #data Move immediate to direct byte 3 3
MOV @Ri, A Move A to indirect RAM 1 2
MOV @Ri, direct Move direct byte to indirect RAM 2 2
MOV @Ri, #data Move immediate to indirect RAM 2 2
MOV DPTR, #data16 Load DPTR with 16-bit constant 3 3
MOVC A, @A+DPTR Move code byte relative DPTR to A 1 3
MOVC A, @A+PC Move code byte relative PC to A 1 3
MOVX A, @Ri Move external data (8-bit address) to A 1 3
MOVX @Ri, A Move A to external data (8-bit address) 1 3
MOVX A, @DPTR Move external data (16-bit address) to A 1 3
MOVX @DPTR, A Move A to external data (16-bit address) 1 3
PUSH direct Push direct byte onto stack 2 2
POP direct Pop direct byte from stack 2 2
XCH A, Rn Exchange Register with A 1 1
XCH A, direct Exchange direct byte with A 2 2
XCH A, @Ri Exchange indirect RAM with A 1 2
XCHD A, @Ri Exchange low nibble of indirect RAM with A 1 2
Boolean Manipulation
CLR C Clear Carry 1 1
CLR bit Clear direct bit 2 2
SETB C Set Carry 1 1
SETB bit Set direct bit 2 2
CPL C Complement Carry 1 1
CPL bit Complement direct bit 2 2
ANL C, bit AND direct bit to Carry 2 2
ANL C, /bit AND complement of direct bit to Carry 2 2
ORL C, bit OR direct bit to carry 2 2
ORL C, /bit OR complement of direct bit to Carry 2 2
MOV C, bit Move direct bit to Carry 2 2
MOV bit, C Move Carry to direct bit 2 2
JC rel Jump if Carry is set 22/3
JNC rel Jump if Carry is not set 22/3
JB bit, rel Jump if direct bit is set 33/4
JNB bit, rel Jump if direct bit is not set 33/4
JBC bit, rel Jump if direct bit is set and clear bit 33/4
Program Branch in g
ACALL addr11 Absolute subroutine call 2 3
LCALL addr16 Long subroutine call 3 4
RET Return from subroutine 1 5
RETI Return from interrupt 1 5
AJMP addr11 Absolute jump 2 3
LJMP addr16 Long jump 3 4
SJMP rel Short jump (relative address) 2 3
JMP @A+DPTR Jump indirect relative to DPTR 1 3
JZ rel Jump if A equals zero 22/3
Table 12.1. CIP-51 Instruction Set Summary (Continued)
Mnemonic Description Bytes Clock
Cycles
C8051F040/1/2/3/4/5/6/7
132 Rev. 1.5
JNZ rel Jump if A does not equal zero 22/3
CJNE A, direct, rel Compare direct byte to A and jump if not equal 33/4
CJNE A, #data, rel Compare imm ediate to A and jump if not equal 33/4
CJNE Rn, #data, rel Compare immediate to Register and jump if not
equal 33/4
CJNE @Ri, #data, rel Compare immediate to indirect and jump if not
equal 34/5
DJNZ Rn, rel Decrement Register and jump if not zero 22/3
DJNZ direct, rel Decrement direc t byte and jump if not zero 33/4
NOP No operation 1 1
Table 12.1. CIP-51 Instruction Set Summary (Continued)
Mnemonic Description Bytes Clock
Cycles
Notes on Registers, Operands and Addressing Modes:
Rn - Register R0-R7 of the currently selected register bank.
@Ri - Data RAM location addre ssed indirectly through R0 or R1.
rel - 8-bit, signed (two’s complement) of fset relative to the first byte of the following instruction. Used by
SJMP and all conditional jumps.
direct - 8-bit internal data location’s address. This could be a direct-access Data RAM location (0x00-
0x7F) or an SFR (0x80-0xFF).
#data - 8-bit constant
#data16 - 16-bit constant
bit - Direct-accessed bit in Data RAM or SFR
addr11 - 11-bit destination address used by ACALL and AJMP. The destination must be within the
same 2K-byte page of program memory as the first byte of the following instruction.
addr16 - 16-bit destination address used by L CALL and LJMP. The destination may be anywhere within
the 64 kB program memory space.
There is one unused opcode (0xA5) that performs the same function as NOP.
All mnemonics copyrighted © Intel Corporation 1980.
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 133
12.2. Memory Organization
The memory organization of the CIP-51 System Controller is similar to that of a standard 8051. There are
two separate memory spaces: program memory and data memory. Program and data memory share the
same address space but are accessed via different instruction types. There are 256 bytes of internal data
memory and 64k bytes of internal program memory address space implemented within the CIP-51. The
CIP-51 memory organization is shown in Figure 12.2.
Figure 12.2. Memory Map
12.2.1. Program Memory
The CIP-51 has a 64 kB program memory space. The MCU implements 64 kB (C8051F040/1/2/3/4/5 ) and
32 kB (C8051F046/7) of this program memory space as in-system re-programmed Flash memory, orga-
nized in a contiguous block from addresses 0x0000 to 0xFFFF (C8051F040/1/2/3/4/5) and 0x0000 to
0x7FFF (C8051F046/7). Note: 512 bytes from 0xFE0 0 to 0xFFFF (C8051F04 0/1/2/3/4/5 only) of this mem-
ory are reserved for factory use and are not available for user program storage.
Program memory is nor mally assumed to be re ad-on ly. However, the CIP-51 can wr ite to progr am memo ry
by setting the Program S tore Write Enable bit (PSCTL.0) and using the MOVX instruction. This feature pro-
vides a mechanism for the CIP-51 to update program code and use the program memory space for non-
volatile data storage. Refer to Section “15. Flash Memory” on page 179 for further details.
PROGRAM/DATA MEMORY
(FLASH)
(Direct and Indirect
Addressing)
0x00
0x7F
Upper 128 RAM
(Indirect Addressing
Only)
0x80
0xFF Special Function
Registers
(Direct Addressing Only)
DATA MEMORY (RAM)
General Purpose
Registers
0x1F
0x20
0x2F Bit Addressable Lower 128 RAM
(Direct and Indirect
Addressing)
0x30
INTERNAL DATA ADDRESS SPACE
EXTERNAL DATA ADDRESS SPACE
XRAM - 4096 Bytes
(accessable using MOVX
instruction)
0x0000
0x0FFF
Off-chip XRAM space
0x1000
0xFFFF
64 kB
Flash
(In-System
Programmable in 512
Byte Sectors)
0x0000
RESERVED
0xFE00
0xFDFF
Scrachpad Memory
(DATA only)
0x1007F
0x10000
Up To
256 SFR Pages
13
0
2F
C8051F040/1/2/3/4/5
32 kB
Flash
(In-System
Programmable in 512
Byte Sectors)
0x0000
RESERVED
0x8000
0x7FFF
Scrachpad Memory
(DATA only)
0x1007F
0x10000
C8051F046/7
C8051F040/1/2/3/4/5/6/7
134 Rev. 1.5
12.2.2. Data Memory
The CIP-51 implement s 256 bytes of internal RAM mapped into the dat a mem ory space from 0x00 through
0xFF. The lower 128 bytes of data memory are used for general purpose registers and scratch pad mem-
ory. Either direct or indirect addressing may be used to access the lower 128 bytes of data memory. Loca-
tions 0x00 through 0x1F are addr essable as four banks of general pur pose reg isters, each bank consisting
of eight byte-wide registers. The next 16 bytes, locations 0x20 through 0x2F, may either be addressed as
bytes or as 128 bit locations accessible with the direct addressing mode.
The upper 128 bytes of data memory are accessible only by indirect addressing. This region occupies the
same address space as the Special Function Registers (SFR) but is physically separate from the SFR
space. The addressing mode used by an instruction when accessing locations above 0x7F determines
whether the CP U acce sses the uppe r 12 8 bytes of d ata mem ory space o r the SFR ’s. Instruction s tha t use
direct addressing will access the SFR space. Instructions using indirect addressing above 0x7F access the
upper 128 bytes of data memory. Figure 12.2 illustrates the data memory organization of the CIP-51.
12.2.3. General Purpose Registers
The lower 32 bytes of dat a memory, locations 0x00 through 0x1F, may be addressed as four banks of gen-
eral-purpose registers. Each bank consists of eight byte-wide registers designated R0 through R7. Only
one of these banks may be ena bled at a time. Two bits in the program st atus word , RS0 (PSW.3) and RS1
(PSW.4), select the active register bank (see description of the PSW in SFR Definition 12.8). This allows
fast context switching when entering su brou tines and interr upt service ro utines. Indirect ad dressing mod es
use registers R0 and R1 as index registers.
12.2.4. Bit Addressable Locations
In addition to dir ect access to data memory organ ized as bytes, the sixtee n data memory locations at 0x20
through 0x2F are also accessible as 128 individually addressable bits. Each bit has a bit address from
0x00 to 0x7F. Bit 0 of the byte at 0x20 has bit address 0x00 while bit 7 of the byte at 0x20 has bit address
0x07. Bit 7 of the byte at 0x2F has bit address 0x7F. A bi t access is distinguished from a full byte access by
the type of instruction used (bit source or destination operands as opposed to a byte source or destina-
tion).
The MCS-51™ assembly language allows an alternate notation for bit addressing of the form XX.B where
XX is the byte address and B is the bit position within the byte. For example, the instruction:
MOV C, 22.3h
moves the Boolean value at 0x13 (bit 3 of the byte at location 0x22) into the Carry flag.
12.2.5. Stack
A programmer's st ack can be located anywhere in the 256 b yte data memo ry. The stack area is designated
using the Stack Pointer (SP, address 0x81) SFR. The SP will point to the last location used. The next value
pushed on the stack is placed at SP+1 and then SP is incremented. A reset initializes the stack pointer to
location 0x07; the first value pushed on the stack is placed at location 0x08, which is also the first register
(R0) of register ban k 1. Thu s, if m ore than one register bank is to be used, the SP should be initialized to a
location in the data memory not being used for data storage. The stack depth can extend up to 256 bytes.
The MCUs a lso h ave built-i n ha rdware for a stack re cord whic h is a ccess ed b y th e de bug logic . The stack
record is a 32-bit shift re gister, where each PUSH or increment SP pushes one record bit onto the register,
and each CALL pushes two record bits onto the register. (A POP or decrement SP pops one record bit,
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 135
and a RET pops two record bits, also.) The stack record circuitry can also detect an overflow or underflow
on the 32-bit shift register, and can notify the debug software even with the MCU running at speed.
12.2.6. Special Function Registers
The direct-access data memory locations from 0x80 to 0xFF constitute the special function registers
(SFR’s). The SFR’s provide control and data exchange with the CIP-51's resources and peripherals. The
CIP-51 duplicates the SFR’s found in a typical 8051 implementation as well as implementing additional
SFR’s used to configure and access the sub-systems unique to the MCU. This allows the addition of new
functionality while retaining compatibility with the MCS-51™ instruction set. Table 12.2 lists the SFR’s
implemented in the C IP- 51 Syste m Co nt ro ller.
The SFR registers are accessed whenever the direct addressing mode is used to access memory loca-
tions from 0x80 to 0xFF. SFR’s with addresses ending in 0x0 or 0x8 (e.g. P0, TCON, P1, SCON, I E, etc.)
are bit-addressable as well as byte-addressable. All other SFR’s are byte-addressable only. Unoccupied
addresses in the SFR space are reserved for future use. Accessing these areas will have an indeterminate
effect and should be avoided. Refer to the corresponding pages of the datasheet, as indicated in
Table 12.3, for a detailed description of each register.
12.2.6.1. SFR Paging
The CIP-51 features SFR paging, allowing the device to map many SFR’s into the 0x80 to 0xFF memory
address space. The SF R memory space has 256 pages. In this way, each memory location from 0x80 to
0xFF can access up to 256 SFR’s. The C8051F04x family of devices utilizes five SFR pages: 0, 1, 2, 3,
and F. SFR pages are selected using the Special Function Register Page Selection register, SFRPAGE
(see SFR Definition 12.2). The procedure for reading and wr iting an SFR is as follows:
1. Select the appropriate SFR page number using the SFRPAGE register.
2. Use direct accessing mode to read or write the special function register (MOV instruction).
12.2.6.2. Interrupts and SFR Paging
When an interrupt occurs, the SFR Page Register will automatically switch to the SFR page containing the
flag bit that caused the interrupt. The automatic SFR Page switch function conveniently removes the bur-
den of switching SFR pages from the interrupt service routine. Upon execution of the RETI instruction, the
SFR page is automatically restored to the SFR Page in use prior to the interrupt. This is accomplished via
a three-byte SFR Page Stack. The top byte of the stack is SFRPA GE, the curren t SFR Page. The se cond
byte of the S FR Page Stack is SFRNE XT. The third, or bottom byte of the SFR Page Stack is SFRLAST.
On interrupt, the current SFRPAGE value is pushed to the SFRNEXT byte, and the value of SFRNEXT is
pushed to SFRLAST. Hardware then loads SFRP AGE with the SFR Page containing the flag bit associated
with the interrupt. On a return from interrupt, the SFR Page Stack is popped re sulting in the value of SFRN-
EXT returning to the SFRPAGE register, thereby restoring the SFR page context without software interven-
tion. The value in SFRLAST (0x00 if there is no SFR Page value in the bottom of the stack) of the stack is
placed in SFRNEXT register. If desired, the values stored in SFRNEXT and SFRLAST may be modified
during an interrupt, enabling the CPU to return to a different SFR Page upon execution of the RETI instruc-
tion (on interrupt exit). Modifying registers in the SFR Page Stack does not cause a push or pop of the
stack. Only interrupt calls and returns will cause push/pop operations on the SFR Page Stack.
C8051F040/1/2/3/4/5/6/7
136 Rev. 1.5
Figure 12.3. SFR Page Stack
Automatic hardware switching of the SFR Page on interru pts may be enabled or disabled as desired using
the SFR Automatic Page Control Enable Bit located in the SFR Page Contro l Register (SFRPGCN). This
function defaults to ‘enabled’ upon reset. In this way, the autoswitching function will be enabled unless dis-
abled in software.
A summary of the SFR locations (address and SFR page) is provided in Table 12.2. in the form of an SFR
memory map. Each memory location in the map has an SFR page row, denoting the page in which that
SFR resides. Note that certain SFR’s are accessible from ALL SFR pages, and are denoted by the “(ALL
PAGES)” designation. For example, the Port I/O registers P0, P1, P2, and P3 all have the “(ALL PAGES)”
designation, indic ating the se SFR’s are acces sible from all SFR pages rega rdless of the SF RPAGE regis-
ter value.
12.2.6.3. SFR Page Stack Example
The following is an example of a C8051F040 device that shows the operation of the SFR Page Stack dur-
ing interrupts.
In this example, the SFR Page Control is left in the default enabled state (i.e., SFRPGEN = 1), and the
CIP-51 is executing in-line code that is writing values to Port 5 (SFR “P5”, located at address 0xD8 on SFR
Page 0x0F). The device is also using the Programmable Counter Array (PCA) and the 8-bit ADC (ADC2)
window compar ator to mo nitor a vo ltage. The PCA is timing a critical control function in its interrupt service
routine (ISR), so its interrupt is enabled and is set to high priority. The ADC2 is monitoring a voltage that is
less import ant, bu t to minimize the software overhead its window comparator is being used with an associ-
ated ISR that is set to low priority. At this point, the SFR page is set to access the Port 5 SFR (SFRPAGE =
0x0F). See Figure 12.4 below.
SFRNEXT
SFRPAGE
SFRLAST
Interrupt
Logic
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 137
Figure 12.4. SFR Page Stack While Using SFR Page 0x0F To Access Port 5
While CIP-51 executes in-line code (writing values to Port 5 in this example), an ADC2 Window Compara-
tor Interrupt occurs. The CIP-51 vectors to the ADC2 Window Comparator ISR and pushes the current
SFR Page value (SFR Page 0x0F) into SFRNEXT in the SFR Page Stack. The SFR page needed to
access ADC2’s SFR’s is then automatically placed in the SFRPAGE register (SFR Page 0x02). SFRPAGE
is considered the “top” of the SFR Pa ge Stack. Software can now access the AD C2 SFR’s. Software may
switch to any SFR Page by writing a new value to the SFRPAGE register at any time during the ADC2 ISR
to access SFR’s that are not on SFR Page 0x02 . See Fig ur e 12.5 .
0x0F
(Port 5) SFRPAGE
SFRLAST
SFRNEXT
SFR Page
Stack SFR's
C8051F040/1/2/3/4/5/6/7
138 Rev. 1.5
Figure 12.5. SFR Page Stack After ADC2 Window Comparator Interrupt Occurs
While in the ADC2 ISR, a PCA interrupt occurs. Recall the PCA interrupt is configured as a high priority
interrupt, while the ADC2 interrupt is configured as a low priority interrupt. Thus, the CIP-51 will now vector
to the high priority PCA ISR. Upon doing so, the CIP-51 will automatically place the SFR page needed to
access the PCA’s special function registers into the SFRPAGE register, SFR Page 0x00. The value that
was in the SFRPAGE register before the PCA interrupt (SFR Page 2 for ADC2) is pushed down the stack
into SFRNEXT. Likewise, the value that was in the SFRNEXT register before the PCA interrupt (in this
case SFR Page 0x0F for Port 5) is pushed down to the SFRLAST register, the “bottom” of the stack. Note
that a value stored in SFRLAST (via a previous software write to the SFRLAST register) will be overwritten.
See Figure 12.6 below.
0x02
(ADC2)
0x0F
(P ort 5 )
SFRPAGE
SFRLAST
SFRNEXT
SFRPAGE
pushed to
SFRNEXT
SFR Page 0x02
A u tomatic ally
pushed on stack in
SFRPAGE on ADC2
interrupt
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 139
Figure 12.6. SFR Page Stack Upon PCA Interrupt Occurring During an ADC2 ISR
On exit from the PCA interrupt service routine, the CIP-51 will return to the ADC2 Window Comparator
ISR. On execution of the RETI instruction, SFR Page 0x00 used to access the PCA registers will be auto-
matically popped off of the SFR Page Stack, and the contents of the SFRNEXT register w ill be moved to
the SFRPAGE register. Software in the ADC2 ISR can continue to access SFR’s as it did prior to the PCA
interrupt. Likewise, the contents of SFRLAST are moved to the SFRNEXT register. Recall this was the
SFR Page value 0x0F being used to access Port 5 before the ADC2 interrupt occurred. See Figure 12.7
below.
0x00
(PCA)
0x02
(ADC2)
0x0F
(Port 5)
SFRPAGE
SFRLAST
SFRNEXT
SFR Page 0x00
Automatically
pushed on stack in
SFRPAGE on PCA
interrupt
SFRPAGE
pushed to
SFRNEXT
SFRNEXT
pushed to
SFRLAST
C8051F040/1/2/3/4/5/6/7
140 Rev. 1.5
Figure 12.7. SFR Page Stack Upon Return From PCA Interrupt
On the execution of the RETI instruction in the ADC2 Window Comparator ISR, the value in SFRPAGE
register is overwritten with the contents of SFRNEXT. The CIP-51 may now access the Port 5 SFR bits as
it did prior to the interrupts occurring. See Figure 12.8 below.
0x02
(ADC2)
0x0F
(Port 5)
SFRPAGE
SFRLAST
SFRNEXT
SFR Page 0x00
Automatically
popped off of the
stack on return from
interrupt
SFRNEXT
popped to
SFRPAGE
SFRLAST
popped to
SFRNEXT
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 141
Figure 12.8. SFR Page Stack Upon Return From ADC2 Window Interrupt
Note that in the above example, all three bytes in the SFR Page Stack are accessible via the SFRPAGE,
SFRNEXT, and SFRLAST special function r eg ist er s. If th e s tack is a lter e d while s ervicing an interrupt, it is
possible to return to a different SFR Page upon interrupt exit than selected prior to the interrupt call. Direct
access to the SFR Page stack can be useful to enable real-time operating systems to control and manage
context switching between multiple tasks.
Push operations on the SFR Page Stack only occur on interrupt service, and pop op erations only occur on
interrupt exit (execution on the RETI instruction). The automatic switching of the SFRPAGE and operation
of the SFR Page Stack as described above can be disabled in software by clearing the SFR Automatic
Page Enable Bit (SFRPGEN) in the SFR Page Control Register (SFRPGCN). See SFR Definition 12.1.
0x0F
(Port 5) SFRPAGE
SFRLAST
SFRNEXT
SFR Page 0x02
Automatically
popped off of the
stack on return from
interrupt
SFRNEXT
popped to
SFRPAGE
C8051F040/1/2/3/4/5/6/7
142 Rev. 1.5
SFR Definition 12.1. SFR Page Control Register: SFRPGCN
SFR Definition 12.2. SFR Page Register: SFRPAGE
Bits7-1: Reserved.
Bit0: SFRPGEN: SFR Automatic Page Control Enable.
Upon interrupt the C8051 Core will vector to the specified interrupt service routine and auto-
matically switch the SFR page to the corresponding periphe ral or fu nction’s SFR page. This
bit is used to control this autopaging function.
0: SFR Automatic Paging disabled. C8051 core will not automatically change to the appro-
priate SFR page (i.e., the SFR page that contains the SFR’s for the peripheral/function that
was the source of the interrupt).
1: SFR Automatic Paging enabled. Upon interrupt, the CIP-51 will switch the SFR page to
the page that contains the SFR’s for the peripheral or function that is the source of the inter-
rupt.
R R R R R R R R/W Reset Value
-------SFRPGEN00000001
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0x81
All Pages
Bits7-0: SFRPAGE: SFR Page Register.
Byte represents the SFR page the CIP-51 uses when reading or modifying SFR’s.
SFR page context is retained upon interrup ts/retu rn from interr u pts in a 3 byte SFR Pag e
Stack: SFRPAGE is the first entry, SFRNEXT is the second, an d SFR LAS T is thir d en tr y.
The SFRPAGE, SFRSTACK, and SFRLAST bytes may be used alter the context in the SFR
Page Stack. Only interrupts and returns from interrupt service routines push and pop the
SFR Page Stack. (See Section 12.2.6.2 and Section 12.2.6.3 for further information.)
Write:
Sets the SFR Page
Read:
Byte is the SFR page the CIP-51 MCU is using.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0x84
All Pages
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 143
SFR Definition 12.3. SFR Next Register: SFRNEXT
SFR Definition 12.4. SFR Last Register: SFRLAST
Bits7-0: SFR page context is retained upon interrupts/return from interrupts in a 3 byte SFR Page
Stack: SFRPAGE is the first entry, SFRNEXT is the second, an d SFR LAS T is thir d en tr y.
The SFRPAGE, SFRSTACK, and SFRLAST bytes may be used alter the context in the SFR
Page Stack. Only interrupts and returns from interrupt service routines push and pop the
SFR Page Stack. (See Section 12.2.6.2 and Section 12.2.6.3 for further information.)
Write:
Sets the SFR Page contained in the second byte of the SFR Stack. This will cause the
SFRPAGE SFR to have this SFR page value upon a return from interrupt.
Read:
Returns the value of the SFR page contained in the second byte of the SFR stack. This is
the value that will go to the SFR Page register upon a return from interrupt.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0x85
All Pages
Bits7-0: SFR page context is retained upon interrupts/return from interrupts in a 3 byte SFR Page
Stack: SFRPAGE is the first entry, SFRNEXT is the second, and SFRLAST is the third
entry. The SFR stack bytes may be used alter the context in the SFR Page Stack, and will
not cause the stack to ‘push’ or ‘pop’. Only interrupts and returns from the interrupt service
routine push and pop the SFR Page Stack.
Write:
Sets the SFR Page in the last entry of the SFR Stack. This will cause the SFRNEXT SFR to
have this SFR page value upon a return from interrupt.
Read:
Returns the value of the SFR page contained in the last entry of the SFR stack.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0x86
All Pages
C8051F040/1/2/3/4/5/6/7
144 Rev. 1.5
Table 12.2. Special Function Register (SFR) Memory Map
A
D
D
R
E
S
S
0(8) 1(9) 2(A) 3(B) 4(C) 5(D) 6(E) 7(F)
SFR
P
A
G
E
F8
SPI0CN
CAN0CN
P7
PCA0L PCA0H PCA0CPL0 PCA0CPH0 PCA0CPL1 PCA0CPH1 WDTCN
(ALL PAGES)
0
1
2
3
F
F0 B
(ALL PAGES) EIP1
(ALL PAGES) EIP2
(ALL PAGES)
0
1
2
3
F
E8
ADC0CN
ADC2CN
P6
PCA0CPL2 PCA0CPH2 PCA0CPL3 PCA0CPH3 PCA0CPL4 PCA0CPH4 RSTSRC 0
1
2
3
F
E0 ACC
(ALL PAGES)
PCA0CPL5
XBR0
PCA0CPH5
XBR1 XBR2 XBR3
EIE1
(ALL PAGES) EIE2
(ALL PAGES)
0
1
2
3
F
D8
PCA0CN
CAN0DATL
P5
PCA0MD
CAN0DATH PCA0CPM0
CAN0ADR PCA0CPM1
CAN0TST PCA0CPM2 PCA0CPM3 PCA0CPM4 PCA0CPM5 0
1
2
3
F
D0 PSW
(ALL PAGES)
REF0CN DAC0L
DAC1L DAC0H
DAC1H DAC0CN
DAC1CN HVA0CN 0
1
2
3
F
C8
TMR2CN
TMR3CN
TMR4CN
P4
TMR2CF
TMR3CF
TMR4CF
RCAP2L
RCAP3L
RCAP4L
RCAP2H
RCAP3H
RCAP4H
TMR2L
TMR3L
TMR4L
TMR2H
TMR3H
TMR4H
SMB0CR 0
1
2
3
F
C0
SMB0CN
CAN0STA SMB0STA SMB0DAT SMB0ADR ADC0GTL
ADC2GT
ADC0GTH ADC0LTL
ADC2LT
ADC0LTH 0
1
2
3
F
B8 IP
(ALL PAGES)
SADEN0 AMX0CF
AMX2CF
AMX0SL
AMX2SL
ADC0CF
ADC2CF
AMX0PRT ADC0L
ADC2
ADC0H 0
1
2
3
F
0(8) 1(9) 2(A) 3(B) 4(C) 5(D) 6(E) 7(F)
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 145
B0 P3
(ALL PAGES)
FLSCL
FLACL
0
1
2
3
F
A8 IE
(ALL PAGES)
SADDR0
P1MDIN P2MDIN P3MDIN
0
1
2
3
F
A0 P2
(ALL PAGES)
EMI0TC EMI0CN EMI0CF
P0MDOUT P1MDOUT P2MDOUT P3MDOUT
0
1
2
3
F
98
SCON0
SCON1 SBUF0
SBUF1 SPI0CFG SPI0DAT
P4MDOUT
SPI0CKR
P5MDOUT P6MDOUT P7MDOUT
0
1
2
3
F
90 P1
(ALL PAGES)
SSTA0
SFRPGCN CLKSEL
0
1
2
3
F
88
TCON
CPT0CN
CPT1CN
CPT2CN
TMOD
CPT0MD
CPT1MD
CPT2MD
TL0
OSCICN
TL1
OSCICL
TH0
OSCXCN
TH1 CKCON PSCTL 0
1
2
3
F
80 P0
(ALL PAGES) SP
(ALL PAGES) DPL
(ALL PAGES) DPH
(ALL PAGES) SFRPAGE
(ALL PAGES) SFRNEXT
(ALL PAGES) SFRLAST
(ALL PAGES) PCON
(ALL PAGES)
0
1
2
3
F
Table 12.2. Special Function Register (SFR) Memory Map (Continued)
A
D
D
R
E
S
S
0(8) 1(9) 2(A) 3(B) 4(C) 5(D) 6(E) 7(F)
SFR
P
A
G
E
0(8) 1(9) 2(A) 3(B) 4(C) 5(D) 6(E) 7(F)
C8051F040/1/2/3/4/5/6/7
146 Rev. 1.5
Table 12.3. Special Function Registers
SFRs are listed in alphabetical order. All undefined SFR locations are reserved.
Register Address SFR Page Description Page No.
ACC 0xE0 All Pages Accumulator page 152
ADC0CF 0xBC 0ADC0 Configuration page 581, page 802
ADC0CN 0xE8 0ADC0 Control page 591, page 812
ADC0GTH 0xC5 0ADC0 Greater-Than High page 621, page 842
ADC0GTL 0xC4 0ADC0 Greater-Than Low page 621, page 842
ADC0H 0xBF 0ADC0 Data Word High page 601, page 822
ADC0L 0xBE 0ADC0 Data Word Low page 601, page 822
ADC0LTH 0xC7 0ADC0 Less-Than High page 621, page 842
ADC0LTL 0xC6 0ADC0 Less-Than Low page 631, page 852
ADC230xBE 2ADC2 Data Word page 99
ADC2CF30xBC 2ADC2 Analog Multiplexer Configuration page 95
ADC2CN30xE8 2ADC2 Control page 98
ADC2GT30xC4 2ADC2 Window Comparator Greater-Than page 100
ADC2LT30xC6 2ADC2 Window Comparator Less-Than page 100
AMX0CF 0xBA 0ADC0 Multiplexer Configuration page 491, page 712
AMX0PRT 0xBD 0ADC0 Port 3 I/O Pin Select page 51
AMX0SL 0xBB 0ADC0 Multiplexer Channel Select page 491, page 712
AMX2CF30xBA 2ADC2 Multiplexer Configuration page 97
AMX2SL30xBB 2ADC2 Multiplexer Channel Select page 95
B0xF0 All Pages B Register page 152
CAN0ADR 0xDA 1CAN0 Address page 213
CAN0CN 0xF8 1CAN0 Control page 213
CAN0DATH 0xD9 1CAN0 Data Register High page 212
CAN0DATL 0xD8 1CAN0 Data Register Low page 212
CAN0STA 0xC0 1CAN0 Status page 214
CAN0TST 0xDB 1CAN0 Test Register page 214
CKCON 0x8E 0Clock Control page 293
CLKSEL 0x97 FOscillator Clock Selection Register page 175
CPT0MD 0x89 1Comparator 0 Mode Selection page 125
CPT1MD 0x89 2Comparator 1 Mode Selection page 125
CPT2MD 0x89 3Comparator 2 Mode Selection page 125
CPT0CN 0x88 1Comparator 0 Control page 124
CPT1CN 0x88 2Comparator 1 Control page 124
CPT2CN 0x88 3Comparator 2 Control page 124
DAC0CN30xD4 0DAC0 Control page 108
DAC0H30xD3 0DAC0 High page 107
DAC0L30xD2 0DAC0 Low page 107
DAC1CN30xD4 1DAC1 Control page 110
DAC1H30xD3 1DAC1 High Byte page 109
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 147
DAC1L30xD2 1DAC1 Low Byte page 109
DPH 0x83 All Pages Data Pointer High page 150
DPL 0x82 All Pages Data Pointer Low page 150
EIE1 0xE6 All Pages Extended Interrupt Enable 1 page 159
EIE2 0xE7 All Pages Extended Interrupt Enable 2 page 160
EIP1 0xF6 All Pages Extended Interrupt Priority 1 page 161
EIP2 0xF7 All Pages Extended Interrupt Priority 2 page 162
EMI0CF 0xA3 0EMIF Configuration page 190
EMI0CN 0xA2 0External Memory Interface Control page 189
EMI0TC 0xA1 0EMIF Timing Control page 195
FLACL 0xB7 FFlash Access Limit page 184
FLSCL 0xB7 0Flash Scale page 184
HVA0CN 0xD6 0High Voltage Differential Amp Control page 531, page 752
IE 0xA8 All Pages Interrupt Enable page 157
IP 0xB8 All Pages Interrupt Priority page 158
OSCICL 0x8B FInternal Oscillator Calibration page 174
OSCICN 0x8A FInternal Oscillator Control page 174
OSCXCN 0x8C FExternal Oscillator Control page 176
P0 0x80 All Pages Port 0 Latch page 215
P0MDOUT 0xA4 FPort 0 Output Mode Configuration page 216
P1 0x90 All Pages Port 1 Latch page 216
P1MDIN 0xAD FPort 1 Input Mode Configuration page 217
P1MDOUT 0xA5 FPort 1 Output Mode Configuration page 217
P2 0xA0 All Pages Port 2 Latch page 218
P2MDIN 0xAE FPort 2 Input Mode Configuration page 218
P2MDOUT 0xA6 FPort 2 Output Mode Configuration page 219
P3 0xB0 All Pages Port 3 Latch page 219
P3MDIN 0xAF FPort 3 Input Mode Configuration page 220
P3MDOUT 0xA7 FPort 3 Output Mode Configuration page 220
P440xC8 FPort 4 Latch page 222
P4MDOUT40x9C FPort 4 Output Mode Configuration page 222
P540xD8 FPort 5 Latch page 223
P5MDOUT40x9D FPort 5 Output Mode Configuration page 223
P640xE8 FPort 6 Latch page 224
P6MDOUT40x9E FPort 6 Output Mode Configuration page 224
P740xF8 FPort 7 Latch page 225
P7MDOUT40x9F FPort 7 Output Mode Configuration page 225
PCA0CN 0xD8 0PCA Control page 312
PCA0CPH0 0xFC 0PCA Capture 0 High page 316
PCA0CPH1 0xFE 0PCA Capture 1 High page 316
PCA0CPH2 0xEA 0PCA Capture 2 High page 316
PCA0CPH3 0xEC 0PCA Capture 3 High page 316
Table 12.3. Special Function Registers (Continued)
SFRs are listed in alphabetical order. All undefined SFR locations are reserved.
Register Address SFR Page Description Page No.
C8051F040/1/2/3/4/5/6/7
148 Rev. 1.5
PCA0CPH4 0xEE 0PCA Capture 4 High page 316
PCA0CPH5 0xE2 0PCA Capture 5 High page 316
PCA0CPL0 0xFB 0PCA Capture 0 Low page 316
PCA0CPL1 0xFD 0PCA Capture 1 Low page 316
PCA0CPL2 0xE9 0PCA Capture 2 Low page 316
PCA0CPL3 0xEB 0PCA Capture 3 Low page 316
PCA0CPL4 0xED 0PCA Capture 4 Low page 316
PCA0CPL5 0xE1 0PCA Capture 5 Low page 316
PCA0CPM0 0xDA 0PCA Module 0 Mode Register page 314
PCA0CPM1 0xDB 0PCA Module 1 Mode Register page 314
PCA0CPM2 0xDC 0PCA Module 2 Mode Register page 314
PCA0CPM3 0xDD 0PCA Module 3 Mode Register page 314
PCA0CPM4 0xDE 0PCA Module 4 Mode Register page 314
PCA0CPM5 0xDF 0PCA Module 5 Mode Register page 314
PCA0H 0xFA 0PCA Counter High page 315
PCA0L 0xF9 0PCA Counter Low page 315
PCA0MD 0xD9 0PCA Mode page 313
PCON 0x87 All Pages Power Control page 164
PSCTL 0x8F 0Program Store R/W Control page 185
PSW 0xD0 All Pages Progra m Status Word page 151
RCAP2H 0xCB 0Timer/Counter 2 Capture/Reload High page 301
RCAP2L 0xCA 0Timer/Counter 2 Capture/Reload Low page 301
RCAP3H 0xCB 1Timer/Counter 3 Capture/Reload High page 301
RCAP3L 0xCA 1Timer/Counter 3 Capture/Reload Low page 301
RCAP4H 0xCB 2Timer/Counter 4 Capture/Reload High page 301
RCAP4L 0xCA 2Timer/Counter 4 Capture/Reload Low page 301
REF0CN 0xD1 0Programmable Voltage Reference Control page 1144, page 1185
RSTSRC 0xEF 0Reset Source Register page 170
SADDR0 0xA9 0UART 0 Slave Address page 276
SADEN0 0xB9 0UART 0 Slave Address Enable page 276
SBUF0 0x99 0UART 0 Data Buffer page 276
SBUF1 0x99 1UART 1 Data Buffer page 283
SCON0 0x98 0UART 0 Control page 274
SCON1 0x98 1UART 1 Control page 282
SFRPAGE 0x84 All Pages SFR Page Register page 142
SFRPGCN 0x96 FSFR Page Control Register page 142
SFRNEXT 0x85 All Pages SFR Next Page Stack Access Register page 143
SFRLAST 0x86 All Pages SFR Last Page Stack Access Register page 143
SMB0ADR 0xC3 0SMBus Slave Address page 250
SMB0CN 0xC0 0SMBus Control page 247
SMB0CR 0xCF 0SMBus Clock Rate page 248
SMB0DAT 0xC2 0SMBus Data page 249
SMB0STA 0xC1 0SMBus Status page 251
SP 0x81 All Pages Stack Pointer page 150
Table 12.3. Special Function Registers (Continued)
SFRs are listed in alphabetical order. All undefined SFR locations are reserved.
Register Address SFR Page Description Page No.
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 149
SPI0CFG 0x9A 0SPI Configuration page 261
SPI0CKR 0x9D 0SPI Clock Rate Control page 263
SPI0CN 0xF8 0SPI Control page 262
SPI0DAT 0x9B 0SPI Data page 264
SSTA0 0x91 0UART0 Status and Clock Selection page 275
TCON 0x88 0Timer/Counter Control page 291
TH0 0x8C 0Timer/Counter 0 High page 294
TH1 0x8D 0Timer/Counter 1 High page 294
TL0 0x8A 0Timer/Counter 0 Low page 293
TL1 0x8B 0Timer/Counter 1 Low page 294
TMOD 0x89 0Timer/Counter Mode page 292
TMR2CF 0xC9 0Timer/Counter 2 Configuration page 300
TMR2CN 0xC8 0Timer/Counter 2 Control page 299
TMR2H 0xCD 0Timer/Counter 2 High page 302
TMR2L 0xCC 0Timer/Counter 2 Low page 301
TMR3CF 0xC9 1Timer/Counter 3 Configuration page 300
TMR3CN 0xC8 1Timer 3 Control page 299
TMR3H 0xCD 1Timer/Counter 3 High page 302
TMR3L 0xCC 1Timer/Counter 3 Low page 301
TMR4CF 0xC9 2Timer/Counter 4 Configuration page 300
TMR4CN 0xC8 2Timer/Counter 4 Control page 299
TMR4H 0xCD 2Timer/Counter 4 High page 302
TMR4L 0xCC 2Timer/Counter 4 Low page 301
WDTCN 0xFF All Pages Watchdog Timer Control page 169
XBR0 0xE1 FPort I/O Crossbar Control 0 page 212
XBR1 0xE2 FPort I/O Crossbar Control 1 page 213
XBR2 0xE3 FPort I/O Crossbar Control 2 page 214
XBR3 0xE4 FPort I/O Crossbar Control 3 page 215
0x97, 0xA2, 0xB3, 0xB4,
0xCE, 0xDF Reserved
Notes:
1. Refers to a register in the C8051F0 40 only.
2. Refers to a register in the C8051F0 41 only.
3. Refers to a register in C8051F040/1/2/3 only.
4. Refers to a register in the C8051F040/2/4/6 onl y.
5. Refers to a register in the C8051F041/3/5/7 onl y.
Table 12.3. Special Function Registers (Continued)
SFRs are listed in alphabetical order. All undefined SFR locations are reserved.
Register Address SFR Page Description Page No.
C8051F040/1/2/3/4/5/6/7
150 Rev. 1.5
12.2.7. Register Descriptions
Following are descriptions of SFRs related to the operation of the CIP-51 System Controller. Reserved bits
should not be set to logic 1. Future product versions may use these bits to implement new features, in
which case the reset value of the bit will be logic 0, selecting the feature's default state. Detailed descrip-
tions of the remaining SFRs are included in the sections of the data sheet associated with their corre-
sponding system function.
SFR Definition 12.5. SP: St ack Pointer
SFR Definition 12.6. DPL: Data Pointer Low Byte
SFR Definition 12.7. DPH: Data Pointer High Byte
Bits7-0: SP: Stack Pointer.
The S tack Pointer holds the location of the top of the stack. The stack pointer is incremented
before every PUSH operation. The SP register defaults to 0x07 after reset.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000111
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0x81
All Pages
Bits7-0: DPL: Data Pointer Low.
The DPL register is the low byte of the 16-bit DPTR. DPTR is used to access indirectly
addressed XRAM and Flash memory.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0x82
All Pages
Bits7-0: DPH: Data Pointer High.
The DPH register is the high byte of the 16-bit DPTR. DPTR is used to access indirectly
addressed XRAM and Flash memory.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0x83
All Pages
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 151
SFR Definition 12.8. PSW: Program Status Word
Bit7: CY: Ca rry Flag.
This bit is set when the last arithmetic operation resulted in a carry (addition) or a borrow
(subtraction). It is cleared to 0 by all other arithmetic operations.
Bit6: AC: Auxiliary Carry Flag
This bit is set when the last a rithmetic operation resulte d in a carry into (addition) or a borrow
from (subtraction) the high order nibble. It is cleared to 0 by all othe r ar ith me tic ope ra tions.
Bit5: F0: User Flag 0.
This is a bit-addressable, general purpose flag for use under software control.
Bits4-3: RS1-RS0: Register Bank Select.
These bits select which register bank is used during register accesses.
Bit2: OV: Overflow Flag.
This bit is set to 1 under the following circumstances:
• An ADD, ADDC, or SUBB instruction causes a sign-change overflow.
• A MUL instruction results in an overflow (result is greater than 255).
• A DIV instr uctio n cau se s a divide -b y- zer o cond ition.
The OV bit is cleared to 0 by the ADD, ADDC, SUBB, MUL, and DIV instructions in all
other cases.
Bit1: F1: User Flag 1.
This is a bit-addressable, general purpose flag for use under software control.
Bit0: PARITY: Parity Flag.
This bit is set to 1 if the sum of the eight bits in the accumulator is odd and cleared if the sum
is even.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
CY AC F0 RS1 RS0 OV F1 PARITY 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 Bit
Addressable
SFR Address:
SFR Page: 0xD0
All Pages
RS1 RS0 Register Bank Address
0 0 0 0x00–0x07
0 1 1 0x08–0x0F
1 0 2 0x10–0x17
1 1 3 0x18–0x1F
C8051F040/1/2/3/4/5/6/7
152 Rev. 1.5
SFR Definition 12.9. ACC: Accumulator
SFR Definition 12.10. B: B Register
Bits7-0: ACC: Accumulator.
This register is the accumulator for arithmetic operations.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
ACC.7 ACC.6 ACC.5 ACC.4 ACC.3 ACC.2 ACC.1 ACC.0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 Bit
Addressable
SFR Address:
SFR Page: 0xE0
All Pages
Bits7-0: B: B Register.
This register serves as a second accumulator for certain arithmetic operations.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
B.7 B.6 B.5 B.4 B.3 B.2 B.1 B.0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 Bit
Addressable
SFR Address:
SFR Page: 0xF0
All Pages
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 153
12.3. Interrupt Handler
The CIP-51 includes an extended interrup t system supporting a total o f 20 interrupt sources with two prior-
ity levels. The allocation of interrupt sources between on-chip peripherals and external inputs pins varies
according to the specific version of th e device. Each in terrupt sou rce has one or mor e associated interrup t-
pending flag(s) located in an SFR. When a peripheral or external source meets a valid interrupt condition,
the associat ed interr up t- pe n din g fla g is set to logic 1.
If interrupt s are ena bled for the sour ce, an interrupt req uest is generated when the inter rupt-pend ing flag is
set. As soon as execution of the current instruction is complete, the CPU generates an LCALL to a prede-
termined address to begin execu tion of an interrupt service routine ( ISR). Each ISR must end with an RETI
instruction, which returns program execution to the next instruction that would have been executed if the
interrupt request h ad not occurred. If inter rupt s are not enabled, the inter rupt-pen ding flag is ignored by the
hardware and program execution continues as normal. The interrupt-pending flag is set to logic 1 regard-
less of the interrupt's enable/disable state.
Each interrupt source can be individually enabled or disabled through the use of an associated interrupt
enable bit in an SFR (IE-EIE2). However, interrupts must first be globally enabled by setting the EA bit
(IE.7) to logic 1 before the individual interrup t ena bles are recognized. Setting the EA bi t to logic 0 disab les
all interrupt sources regardless of the individual interrupt-enable settings.
Note: Any instruction that clears the EA bit should be immediately followed by an instruction that has two
or more opcode bytes. For example:
// in 'C':
EA = 0; // clear EA bit
EA = 0; // ... followed by another 2-byte opcode
; in assembly:
CLR EA ; clear EA bit
CLR EA ; ... followed by another 2-byte opcode
If an interrupt is posted during the execution phase of a "CLR EA" opcode (or any instruction which clears
the EA bit), and the instruction is followed by a single-cycle instruction, the interrupt may be taken. How-
ever, a read of the EA bit will return a '0' inside the interrupt service routine. When the "CLR EA" opcode is
followed by a multi-cycle instruction, the interrupt will not be taken.
Some interrupt-pending flags ar e au tomatically cleare d by the hardware when the CPU vectors to the ISR.
However, most are not cleared by the hardware and must be cleared by so f tware befo re returning from the
ISR. If an interrupt-pending flag remains set after the CPU completes the return-from-interrupt (RETI)
instruction, a new interrupt request will be generated immediately and the CPU will re-enter the ISR after
the completion of the next instruction.
12.3.1. MCU Interrupt Sources and Vectors
The MCUs support 20 interrupt sources. Software can simulate an interrupt event by setting any interrupt-
pending flag to logic 1. If interrupts are enabled for the flag, an interrupt request will be generated and the
CPU will vector to the ISR address associated with the interrupt-pending flag. MCU interrupt sources,
associated vector addresses, priority order and control bits are summarized in Table 12.4. Refer to the
datasheet section associated with a particular on-chip peripheral for information regarding valid interrupt
conditions for th e pe rip her al an d th e be ha vio r of its interrupt-p end ing flag (s) .
C8051F040/1/2/3/4/5/6/7
154 Rev. 1.5
12.3.2. External Interrupts
The external interrupt sources (/INT0 and /INT1) are configurable as active-low level-sensitive or active-
low edge-sensitive inputs depending on the setting of bits IT0 (TCON.0) and IT1 (TCON.2). IE0 (TCON.1)
and IE1 (TCON.3) serve as the interrupt-pending flag for the /INT0 and /INT1 external interrupts, respec-
tively. If an /INT0 or /INT1 external interrupt is configured as edge-sensitive, the corresponding interrupt-
pending flag is automatically cleared by the hardware when the CPU vectors to the ISR. When configured
as level sensitive, the interrupt-pending flag follows the state of the external interrupt's input p in. The exter-
nal interrupt source must hold the input active until the interrupt request is recognized. It must then deacti-
vate the interrupt request before execution of the ISR completes or another interrupt request will be
generated.
Table 12.4. Interrupt Summary
Interrupt Source Interrupt
Vector Priority
Order Pending Flag
Bit addressable?
Cleared by HW ?
SFRPAGE (SFRPGEN = 1)
Enable
Flag Priority
Control
Reset 0x0000 Top None N/A N/A 0 Always
Enabled Always
Highest
External Interrupt 0
(/INT0) 0x0003 0IE0 (TCON.1) Y Y 0 EX0 (IE.0) PX0 (IP.0)
Timer 0 Overflow 0x000B 1TF0 (TCON.5) Y Y 0 ET0 (IE.1) PT0 (IP.1)
External Interrupt 1
(/INT1) 0x0013 2IE1 (TCON.3) Y Y 0 EX1 (IE.2) PX1 (IP.2)
Timer 1 Overflow 0x001B 3TF1 (TCON.7) Y Y 0 ET1 (IE.3) PT1 (IP.3)
UART0 0x0023 4RI0 (SCON0.0)
TI0 (SCON0.1) Y 0 ES0 (IE.4) PS0 (IP.4)
Timer 2 0x002B 5TF2 (TMR2CN.7) Y 0 ET2 (IE.5) PT2 (IP.5)
Serial Peripheral
Interface 0x0033 6
SPIF (SPI0CN.7)
WCOL (SPI0CN.6)
MODF (SPI0CN.5)
RXOVRN
(SPI0CN.4)
Y 0 ESPI0
(EIE1.0) PSPI0
(EIP1.0)
SMBus Interface 0x003B 7SI (SMB0CN.3) Y 0 ESMB0
(EIE1.1) PSMB0
(EIP1.1)
ADC0 Window
Comparator 0x0043 8AD0WINT
(ADC0CN.2) Y 0 EWADC0
(EIE1.2) PWADC0
(EIP1.2)
Programmable
Counter Array 0x004B 9CF (PCA0CN.7)
CCFn (PCA0CN.n) Y 0 EPCA0
(EIE1.3) PPCA0
(EIP1.3)
Comparator 0 0x0053 10 CP0FIF/CP0RIF
(CPT0CN.4/.5) 1CP0IE
(EIE1.4) PCP0
(EIP1.4)
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 155
Comparator 1 0x005B 11 CP1FIF/CP1RIF
(CPT1CN.4/.5) 2CP1IE
(EIE1.5) PCP1
(EIP1.5)
Comparator 2 0x0063 12 CP2FIF/CP2RIF
(CPT2CN.4/.5) 3CP2IE
(EIE1.6) PCP2
(EIP1.6)
Timer 3 0x0073 14 TF3 (TMR3CN.7) 1ET3
(EIE2.0) PT3
(EIP2.0)
ADC0 End of
Conversion 0x007B 15 ADC0INT
(ADC0CN.5) Y 0 EADC0
(EIE2.1) PADC0
(EIP2.1)
Timer 4 0x0083 16 TF4 (TMR4CN.7) 2ET4
(EIE2.2) PT4
(EIP2.2)
ADC2 Window
Comparator 0x0093 17 AD2WINT
(ADC2CN.0) 2EWADC2
(EIE2.3) PWADC2
(EIP2.3)
ADC2 End of
Conversion 0x008B 18 ADC2INT
(ADC1CN.5) 2EADC1
(EIE2.4) PADC1
(EIP2.4)
CAN Interrupt 0x009B 19 CAN0CN.7 Y 1 ECAN0
(EIE2.5) PCAN0
(EIP2.5)
UART1 0x00A3 20 RI1 (SCON1.0)
TI1 (SCON1.1) 1ES1
(EIE2.6) PS1
(EIP2.6)
Table 12.4. Interrupt Summary (Continued)
Interrupt Source Interrupt
Vector Priority
Order Pending Flag
Bit addressable?
Cleared by HW?
SFRPAGE (SFRPGEN = 1)
Enable
Flag Priority
Control
C8051F040/1/2/3/4/5/6/7
156 Rev. 1.5
12.3.3. Interrupt Priorities
Each interrupt source can be in dividually pr og rammed to one of two priority levels: low or high. A low prior-
ity interrupt service routine can be pree mpted by a high priority interrupt. A high priority interrupt cannot be
preempted. Each interrupt has an associated interrupt priority bit in an SFR (IP-EIP2) used to configure its
priority level. Low priority is the default. If two interrupts are recognized simultaneously, the interrupt with
the higher priority is serviced first. If both interrupts have the same priority level, a fixed priority order is
used to arbitrate, given in Table 12.4.
12.3.4. Interrupt Latency
Interrupt response time dep en ds on the state of the CPU when the inte rr upt occurs. Pen ding inter rupts are
sampled and priority decoded each system clock cycle. The fastest possible response time is 5 system
clock cycles: 1 clock cycle to detect the interrupt and 4 clock cycles to complete the LCALL to t he ISR. If
an interrupt is pending whe n a RETI is executed, a single instruction is executed before an LCALL is made
to service the pending interrup t. There fore, the slowes t response time for an inter rupt (when no other inter-
rupt is currently being serviced or the new interrupt is of grea ter p rior ity) oc curs when the CPU is perform-
ing an RETI instruction followed by a DIV as the next instruction. In this case, the response time is
18 system clock cycles: 1 clock cycle to detect the interrupt, 5 clock cycles to execute the RETI, 8 clock
cycles to complete the DIV instruction and 4 c lock cycles to execute the LCALL to the ISR. If the CPU is
executing an ISR for an interrupt with equal or higher priority, the new interrupt will not be serviced until the
current ISR completes, including the RETI and following instruction.
12.3.5. Interrupt Register Descriptions
The SFRs used to enable th e inte rrupt sources an d set their priori ty level ar e descr ibed be low. Refer to the
datasheet section associated with a particular on-chip peripheral for information regarding valid interrupt
conditions for th e pe rip her al an d th e be ha vio r of its interrupt-p end ing flag (s) .
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 157
SFR Definition 12.11. IE: Interrupt Enable
Bit7: EA: Enable All Interrupts.
This bit globally enables/disables all interrupts. It overrides the individual interrupt mask set-
tings.
0: Disable all interrupt sources.
1: Enable each interrupt according to its individual mask setting.
Bit6: IEGF0: General Purpose Flag 0.
This is a general purpose flag for use under software control.
Bit5: ET2: Enabler Timer 2 Interrupt.
This bit sets the masking of the Timer 2 interrupt.
0: Disable Timer 2 interrupt.
1: Enable interrupt requests generated by the TF2 flag.
Bit4: ES0: Enable UART0 Interrupt.
This bit sets the masking of the UART0 interrupt.
0: Disable UART0 interrupt.
1: Enable UART0 interrupt.
Bit3: ET1: Enable Timer 1 Interrupt.
This bit sets the masking of the Timer 1 interrupt.
0: Disable all Timer 1 interrupt.
1: Enable interrupt requests generated by the TF1 flag.
Bit2: EX1: Enable External Interrupt 1.
This bit sets the masking of external interrupt 1.
0: Disable extern al inte r ru pt 1.
1: Enable interrupt requests generated by the /INT1 pin.
Bit1: ET0: Enable Timer 0 Interrupt.
This bit sets the masking of the Timer 0 interrupt.
0: Disable all Timer 0 interrupt.
1: Enable interrupt requests generated by the TF0 flag.
Bit0: EX0: Enable External Interrupt 0.
This bit sets the masking of external interrupt 0.
0: Disable extern al inte r ru pt 0.
1: Enable interrupt requests generated by the /INT0 pin.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
EA IEGF0 ET2 ES0 ET1 EX1 ET0 EX0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 Bit
Addressable
SFR Address:
SFR Page: 0xA8
All Pages
C8051F040/1/2/3/4/5/6/7
158 Rev. 1.5
SFR Definition 12.12. IP: Interrupt Priority
Bits7-6: UNUSED. Read = 11b, Write = don't care.
Bit5: PT2: Timer 2 Interrupt Priority Control.
This bit sets the priority of the Timer 2 interrupt.
0: Timer 2 inter rupt prio rit y set to low priority level.
1: Timer 2 interrupts set to high priority level.
Bit4: PS0: UART0 Interrupt Priority Control.
This bit sets the priority of the UART0 interrupt.
0: UART0 interrupt priority set to low priority level.
1: UART0 interrupts set to high priority level.
Bit3: PT1: Timer 1 Interrupt Priority Control.
This bit sets the priority of the Timer 1 interrupt.
0: Timer 1 inter rupt prio rit y set to low priority level.
1: Timer 1 interrupts set to high priority level.
Bit2: PX1: External Interrupt 1 Priority Control.
This bit sets the priority of the External Interrupt 1 interrupt.
0: External Interrupt 1 priority set to low priority level.
1: External Interrupt 1 set to high priority level.
Bit1: PT0: Timer 0 Interrupt Priority Control.
This bit sets the priority of the Timer 0 interrupt.
0: Timer 0 inter rupt prio rit y set to low priority level.
1: Timer 0 inter rupt set to high priority level.
Bit0: PX0: External Interrupt 0 Priority Control.
This bit sets the priority of the External Interrupt 0 interrupt.
0: External Interrupt 0 priority set to low priority level.
1: External Interrupt 0 set to high priority level.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
- - PT2 PS0 PT1 PX1 PT0 PX0 11000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 Bit
Addressable
SFR Address:
SFR Page: 0xB8
All Pages
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 159
SFR Definition 12.13. EIE1: Extended Interrupt Enable 1
Bit7: Reserved. Read = 0b, Write = don’t care.
Bit6: CP2IE: Enable Comparator (CP2) Interrupt.
This bit sets the masking of the CP2 interrupt.
0: Disable CP2 interrupts.
1: Enable interrupt requests generated by the CP2IF flag.
Bit6: CP1IE: Enable Comparator (CP1) Interrupt.
This bit sets the masking of the CP1 interrupt.
0: Disable CP1 interrupts.
1: Enable interrupt requests generated by the CP1IF flag.
Bit6: CP0IE: Enable Comparator (CP0) Interrupt.
This bit sets the masking of the CP0 interrupt.
0: Disable CP0 interrupts.
1: Enable interrupt requests generated by the CP0IF flag.
Bit3: EPCA0: Enable Programmable Counter Array (PCA0) Interrupt.
This bit sets the masking of the PCA0 interrupts.
0: Disable all PCA0 interrupts.
1: Enable interrupt requests generated by PCA0.
Bit2: EWADC0: Enable Window Comparison ADC0 Interrupt.
This bit sets the masking of ADC0 Window Comparison interrupt.
0: Disable ADC0 Window Comparison Interrupt.
1: Enable Interrupt requests generated by ADC0 Window Comparisons.
Bit1: ESMB0: Enable System Management Bus (SMBus0) Interrupt.
This bit sets the masking of the SMBus interrupt.
0: Disable all SMBus interrupts.
1: Enable interrupt requests generated by the SI flag.
Bit0: ESPI0: Enable Serial Peripheral Interface (SPI0) Interrupt.
This bit sets the masking of SPI0 interrupt.
0: Disable all SPI0 interrupts.
1: Enable Interrupt requests generated by the SPI0 flag.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
CP2IE CP1IE CP0IE EPCA0 EWADC0 ESMB0 ESPI0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xE6
All Pages
C8051F040/1/2/3/4/5/6/7
160 Rev. 1.5
SFR Definition 12.14. EIE2: Extended Interrupt Enable 2
Bit7: Reserved
Bit6: ES1: Enable UART1 Interrupt.
This bit sets the masking of the UART1 interrupt.
0: Disable UART1 interrupt.
1: Enable UART1 interrupt.
Bit5: ECAN0: Enable CAN Controller Interrupt.
This bit sets the masking of the CAN Controller Interrupt.
0: Disable CAN Controller Interrupt.
1: Enable interrupt requests generated by the CAN Controller.
Bit4: EADC2: Enable ADC2 End Of Conversion Interrupt (C8051F040/1/2/3 only).
This bit sets the masking of the ADC2 End of Conversion interrupt.
0: Disable ADC2 End of Conversion interrupt.
1: Enable interrupt requests generated by the ADC2 End of Conversion Interrupt.
Bit3: EWADC2: Enable Window Comparison ADC2 Interrupt (C8051F040/1/2/3 only).
This bit sets the masking of ADC2 Window Comparison interrupt.
0: Disable ADC2 Window Comparison Interrupt.
1: Enable Interrupt requests generated by ADC2 Window Comparisons.
Bit2: ET4: Enable Timer 4 Interrupt
This bit sets the masking of the Timer 4 interrupt.
0: Disable Timer 4 interrupt.
1: Enable interrupt requests generated by the TF4 flag.
Bit1: EADC0: Enable ADC0 End of Conversion Interrupt.
This bit sets the masking of the ADC0 End of Conversion Interrupt.
0: Disable ADC0 Conversion Interrupt.
1: Enable interrupt requests generated by the ADC0 Conversion Interrupt.
Bit0: ET3: Enable Timer 3 Interrupt.
This bit sets the masking of the Timer 3 interrupt.
0: Disable all Timer 3 interrupts.
1: Enable interrupt requests generated by the TF3 flag.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
- ES1 ECAN0 EADC2 EWADC2 ET4 EADC0 ET3 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xE7
All Pages
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 161
SFR Definition 12.15. EIP1: Extended Interrupt Priority 1
Bit7: Reserved.
Bit6: PCP2: Comparator2 (CP2) Interrupt Priority Control.
This bit sets the priority of the CP2 interrupt.
0: CP2 interrupt set to low priority level.
1: CP2 interrupt set to high priority level.
Bit5: PCP1: Comparator1 (CP1) Interrupt Priority Control.
This bit sets the priority of the CP1 interrupt.
0: CP1 interrupt set to low priority level.
1: CP1 interrupt set to high priority level.
Bit4: PCP0: Comparator0 (CP0) Interrupt Priority Control.
This bit sets the priority of the CP0 interrupt.
0: CP0 interrupt set to low priority level.
1: CP0 interrupt set to high priority level.
Bit3: PPCA0: Programmable Counter Array (PCA0) Interrupt Priority Control.
This bit sets the priority of the PCA0 interrupt.
0: PCA0 interrupt set to low priority lev el.
1: PCA0 interrupt set to high priority level.
Bit2: PWADC0: ADC0 Window Comp arator Interrupt Priority Control.
This bit sets the priority of the ADC0 Window interrupt.
0: ADC0 Window interrupt set to low priority level.
1: ADC0 Window interrupt set to high priority level.
Bit1: PSMB0: System Management Bus (SMBus0) Interrupt Priority Control.
This bit sets the priority of the SMBus0 interrupt.
0: SMBus interrupt set to low priority level.
1: SMBus interrupt set to high priority level.
Bit0: PSPI0: Serial Peripheral Interface (SPI0) Interrupt Priority Control.
This bit sets the priority of the SPI0 interrupt.
0: SPI0 interrupt set to low priority level.
1: SPI0 interrupt set to high priority level.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
- PCP2 PCP1 PCP0 PPCA0 PWADC0 PSMB0 PSPI0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xF6
All Pages
C8051F040/1/2/3/4/5/6/7
162 Rev. 1.5
SFR Definition 12.16. EIP2: Extended Interrupt Priority 2
Bit7: Reserved.
Bit6: EP1: UART1 Interrupt Priority Control.
This bit sets the priority of the UART1 interrupt.
0: UART1 interrupt set to low level.
1: UART1 interrupt set to high level.
Bit5: PCAN0: CAN Interrupt Priority Control.
This bit sets the priority of the CAN Interrupt.
0: CAN Interrupt set to low priority level.
1: CAN Interrupt set to high priority level.
Bit4: PADC2: ADC2 End Of Conversion Interrupt Priority Control (C8051F040/1/2/3 only).
This bit sets the priority of the ADC2 End of Conversion interrupt.
0: ADC2 End of Conversion interrupt set to low level.
1: ADC2 End of Conversion interrupt set to low level.
Bit3: PWADC2: ADC2 Window Comparator Interrupt Priority Control (C8051F040/1/2/3 only).
0: ADC2 Window interrupt set to low level.
1: ADC2 Window interrupt set to high level.
Bit2: PT4: Timer 4 Interrupt Priority Control.
This bit sets the priority of the Timer 4 interrupt.
0: Timer 4 interrupt set to low level.
1: Timer 4 interrupt set to low level.
Bit1: PADC0: ADC End of Conversion Interrupt Priority Control.
This bit sets the priority of the ADC0 End of Conversion Interrupt.
0: ADC0 End of Conversion interrupt set to low priority level.
1: ADC0 End of Conversion interrupt set to high priority level.
Bit0: PT3: Timer 3 Interrupt Priority Control.
This bit sets the priority of the Timer 3 interrupts.
0: Timer 3 inter rupt set to low priority level.
1: Timer 3 inter rupt set to high priority level.
R/W R/W R/W R/W R / W R/W R/W R/W Reset Value
- EP1 PX7 PADC2 PWADC2 PT4 PADC0 PT3 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xF7
All Pages
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 163
12.17. Power Management Modes
The CIP-51 core has two software programmable power management modes: Idle and Stop. Idle mode
halts the CPU while leaving the external peripherals and internal clocks active. In Stop mode, the CPU is
halted, all interrupts and timers (except the Missing Clock Detector) are in ac tive, and the internal oscillator
is stopped. Since clocks are running in Idle mode, p ower consumptio n is dependent u pon the system clock
frequency and the numb er of pe ripherals le f t in active mode befor e entering Idle. Stop mode consumes th e
least power. SFR Definition 12.18 describes the Power Control Register (PCON) used to control the CIP-
51's power management modes.
Although the CIP-51 has Idle and Stop modes built in (as with any standard 8051 architecture), power
management of the entire MCU is better accomplished by enabling/disabling individual peripherals as
needed. Each analog peripheral can be disabled when not in use and put into low power mode. Digital
peripherals, such as timers or serial buses, draw little power whenever they are not in use. Turning off the
oscillator saves even more power, but requires a reset to restart the MCU.
12.17.1.Idle Mode
Setting the Idle Mode Select bit (PCON.0) causes the CIP-51 to halt the CPU and enter Idle mode as soon
as the instruction that sets the bit completes. All internal registers and memory maintain their original
data. All analog and digital peripherals can remain active during Idle mode.
Idle mode is terminated when an enabled interrupt or /RST is asserted. The assertion of an enabled inter-
rupt will cause the Idle Mode Selection bit (PCON.0) to be cleared and the CPU to resume operation. The
pending interrupt will be serviced and the next instruction to be executed after the return from interrupt
(RETI) will be the instruction immediately following the one that set the Idle Mode Select bit. If Idle mode is
terminated by an internal or external reset, the CIP-51 performs a normal reset sequence and begins pro-
gram execution at address 0x0000.
If enabled, the WDT will eventually cause an internal watchdog reset and thereby terminate the Idle mode.
This feature protects the system from an unintended permanent shutdown in the event of an inadvertent
write to the PCON register. If this behavior is not desired, the WDT may be disabled by software prior to
entering the Idle mode if the WDT was initially configured to allow this operation. This provides the oppor-
tunity for additional power savings, allowing the system to remain in the Idle mode indefinitely, waiting for
an external stimulus to wake up the system. Refer to Section 13.7 for more information on the use and
configuration of the WDT.
Note: Any instruction that sets the IDLE bit should be immediately followed by an instruction that has 2 or
more opcode bytes. For example:
// in 'C':
PCON |= 0x01; // set IDLE bit
PCON = PCON; // ... followed by a 3-cycle dummy instruction
; in assembly:
ORL PCON, #01h ; set IDLE bit
MOV PCON, PCON ; ... followed by a 3-cycle dummy instruction
If the instruction following the write of the IDLE bit is a single -byte instruction and an interrupt occurs du ring
the execution phase of the instruction that sets the IDLE bit, the CPU may no t wake from IDLE mode when
a future interrupt occurs.
C8051F040/1/2/3/4/5/6/7
164 Rev. 1.5
12.17.2.Stop Mode
Setting the Stop Mode Select bit (PCON.1) causes the CIP-51 to e nter Stop m ode as soon as th e instr uc-
tion that sets the bit completes. In Stop mode, the CPU and internal oscillators are stopped, effectively
shutting down all digital peripherals. Each analog peripheral must be shut down individually prior to enter-
ing Stop Mode. Stop mode can only be terminated by an internal or external reset. On reset, the CIP-51
performs the normal reset sequence and begins program execution at address 0x0000.
If enabled, the Missing Clock Detector will cause an internal reset and thereby terminate the Stop mode.
The Missing Clock Detector should be disabled if the CPU is to be put to sleep for longer than the MCD
timeout of 100 µs.
SFR Definition 12.18. PCON: Power Control
Bits7-3: Reserved.
Bit1: STOP: STOP Mode Select.
Writing a ‘1’ to this bit will place the CIP-51 into STOP mode. This bit will always read ‘0’.
0: No effect.
1: CIP-51 forced into power-down mode. (Turns off internal oscillator).
Bit0: IDLE: IDLE Mode Select.
Writing a ‘1’ to this bit will place the CIP-51 into IDLE mode. This bit will always read ‘0’.
0: No effect.
1: CIP-51 forced into idle mode. (Shut s of f clock to CPU, but clock to Timers, Interrupts, and
all peripherals remain active.)
R/W R/W R/W R/W R / W R/W R/W R/W Reset Value
— — — — — — STOP IDLE 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0x87
All Pages
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 165
13. Reset Sources
Reset circuitry allows the controller to be easily placed in a predefined default condition. On entry to this
reset state, the following occur:
• CIP-51 halts program execution
• Special Function Registers (SFRs) are initialized to their defined reset values
• External port pins are forced to a known state
• Interrupts and timers are disabled.
All SFRs are reset to the predefined values noted in the SFR detailed descriptions. The contents of internal
data memory are unaffected during a reset; any previously stored data is preserved. However, since the
stack pointer SFR is reset, the stack is effectively lost even though the data on the sta ck are not altered.
The I/O port latches are reset to 0xFF (all logic 1s), activating internal weak pullups which t ake the external
I/O pins to a high state. For VDD Monitor resets, the /RST pin is driven low until the end of the VDD reset
timeout.
On exit from the reset state, the program counter (PC) is reset, and the system clock defaults to the inter-
nal oscillator running at its lowest frequency. Refer to Section “14. Oscillators” on page 173 for informa-
tion on selecting and configuring the system clock source. The Watchdog Timer is enabled using its
longest timeout interva l (see Section “13.7. Wa tchdog T imer Reset” on p age 167). Once the system clock
source is stable, program execution begins at location 0x0000.
There are seven sources for putting the MCU into the reset state: power-on, power-fail, external /RST pin,
external CNVSTR0 signal, software command, Comparator0, Missing Clock Detector, and Watchdog
Timer. Each reset source is described in the following sections.
Figure 13.1. Reset Sources
WDT
XTAL1
XTAL2 OSC
Internal
Clock
Generator System
Clock CIP-51
Microcontroller
Core
Missing
Clock
Detector
(one-
shot)
WDT
Strobe
Software Reset
Extended Interrupt
Handler
Clock Select
RST
+
-
VDD
Supply
Reset
Timeout (wired-OR)
System Reset
Supply
Monitor
PRE
Reset
Funnel
+
-
CP0+ Comparator0
CP0-
(Port I/O) Crossbar CNVSTR
(CNVSTR
reset
enable)
(CP0
reset
enable)
EN
WDT
Enable
EN
MCD
Enable
(wired-OR)
VDD Monitor
reset enable
C8051F040/1/2/3/4/5/6/7
166 Rev. 1.5
13.1. Power-On Reset
The C8051F04x family incorpora tes a powe r supply monitor tha t holds the MCU in the reset st ate until VDD
rises above the VRST level during power- up. See Figure 13.2 for timing diag ram, and refer to Table 13.1 for
the Electrical Characteristics of the power supply monitor circuit. The /RST pin is asserted low until the end
of the 100 ms VDD Monitor timeout in order to allow the VDD supply to stabilize. The VDD Monitor reset is
enabled and disabled using the external VDD monitor enable pin (MONEN).
On exit from a power-on reset, the PORSF flag (RSTSRC.1) is set by hardware to logic 1. All of the other
reset flags in the RSTSRC register are indeterminate. PORSF is cleared by all other resets. Since all
resets cause program execution to begin at the same location (0x0000), software can read the PORSF
flag to determine if a power-up was the cause of reset. The contents of internal data memory should be
assumed to be undefined after a power-on reset.
Figure 13.2. Reset Timing
13.2. Power-Fail Reset
When a power-down transition or power irregularity causes VDD to drop below VRST, the power supply
monitor will drive the /RST pin low and return the CIP-51 to the reset state. When VDD returns to a level
above VRST, the CIP-51 will leave the reset state in the same manner as that for the pow er-on reset (see
Figure 13.2). Note that even though internal data memory contents are not altered by the power-fail reset,
it is impossible to determine if VDD dropped below the level requir ed for d ata retention. If the PORSF flag is
set to logic 1, the data may no longer be valid.
13.3. External Reset
The external /RST p in provid es a means fo r exte rnal cir cuitry to force th e MCU into a reset st ate. Asserting
the /RST pin low will cause the MCU to enter the reset state. It may be desirable to provide an external pul-
VDD Monitor ResetPower-On Reset
/RST
t
volts
1.0
2.0
Logic HIGH
Logic LOW
Reset Time
Delay Reset Time
Delay
VDD
2.70
2.55 VRST
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 167
lup and/or decoupling of the /RST pin to avoid erroneous noise-induced resets. The MCU will remain in
reset until at least 12 clock cycles after the active-low /RST signal is removed. The PINRSF flag (RST-
SRC.0) is set on exit from an external reset.
13.4. Missing Clock Detector Reset
The Missing Clock Detector is essentially a one-shot circuit that is triggered by th e MCU system clock. If
the system clock goes away for more than 100 µs, the one-shot will time out and generate a reset. After a
Missing Clock Detector reset, the MCDRSF flag (RSTSRC.2) will be set, signifying the MCD as the reset
source; otherwise, this bit reads ‘0’. The state of the /RST pin is unaffected by this reset. Setting the
MCDRSF bit, RSTSRC.2 (see Section “14. Oscillators” on p age 173) enables the Missing Clock Detector .
13.5. Comparator0 Reset
Comparator0 can be configured as a reset input by writing a ‘1’ to the C0RSEF flag (RSTSRC.5).
Comparator0 should be enabled using CPT0CN.7 (see Section “11. Comparators” on page 121) prior to
writing to C0RSEF to prevent any turn-on chatter on the output from generating an unwanted reset. The
Comparator0 reset is active-low: if the non-inverting input voltage (CP0+ pin) is less than the inverting
input voltage (CP0- pin), the MCU is put into the reset state. After a Comparator0 Reset, the C0RSEF flag
(RSTSRC.5) will read ‘1’ signifying Comparator0 as the reset source; otherwise, this bit reads ‘0’. The state
of the /RST pin is unaffected by this reset.
13.6. External CNVSTR0 Pin Reset
The external CNVSTR0 signal can be configured as a reset input by writing a ‘1’ to the CNVRSEF flag
(RSTSRC.6). The CNVSTR0 signal can appear on any of the P0, P1, P2 or P3 I/O pins as described in
Section “17.1. Ports 0 through 3 and the Priority Crossbar Decoder” on p age 204. Note that the Cross-
bar must be configured for the CNVSTR0 signal to be routed to the appropriate Port I/O. The Crossbar
should be configured and enabled before the CNVRSEF is set. When configured as a reset, CNVSTR0 is
active-low and level sensitive. After a CNVSTR0 reset, the CNVRSEF flag (RSTSRC.6) will read ‘1’ signi-
fying CNVSTR0 as the reset sour ce; otherwise, this bi t re ads ‘0’. Th e st ate of the /RST pin is unaf fe cted by
this reset.
13.7. W a tchdog Timer Reset
The MCU includes a programmable Watchdog Timer (WDT) running off the system clock. A WDT overflow
will force the MCU into the reset state. To prevent the reset, the WDT must be restarted by application sof t-
ware before overflow. If the system experiences a software or hardware malfunction preventing the soft-
ware from restarting the WDT, the WDT will overflow and cause a reset. This should prevent the system
from running out of control.
Following a reset the WDT is automatically enabled and running with the default maximum time interval. If
desired the WDT can be disabled by system software or locked on to prevent accidental disabling. Once
locked, the WDT cannot be disabled until the next system reset. The state of the /RST pin is unaffected by
this reset.
The WDT consists of a 21-bit timer running from the programmed system clock. The timer measures the
period between specific writes to its control register. If this period exceeds the programmed limit, a WDT
reset is generated. The WDT can be enabled and disabled as needed in software, or can be permanently
enabled if desired. Watchdog features are controlled via the Watchdog Timer Control Register (WDTCN)
shown in SFR Definition 13.1.
C8051F040/1/2/3/4/5/6/7
168 Rev. 1.5
13.7.1. Enable/Reset WDT
The watchdog timer is both enabled and reset by writing 0xA5 to the WDTCN register. The user's applica-
tion software should include periodic writes of 0xA5 to WDTCN as needed to prevent a watchdog timer
overflow. The WDT is enabled and reset as a result of any system reset.
13.7.2. Disable WDT
Writing 0xDE followed by 0xAD to the WDTCN register disables the WDT. The following code segment
illustrates disabling the WDT:
CLR EA ; disable all interrupts
MOV WDTCN,#0DEh ; disable software watchdog timer
MOV WDTCN,#0ADh
SETB EA ; re-enable interrupts
The writes of 0xDE and 0xAD must occur within 4 clock cycles of each other, or the disable operation is
ignored. Interrupts should be disabled during this procedure to avoid delay between the two writes.
13.7.3. Disable WDT Lockout
Writing 0xFF to WDTCN locks out the disable feature. Once locked out, the disable operation is ignored
until the next system reset. Writing 0xFF does not enable or reset the watchdog timer. Applications always
intending to use the watchdog should write 0xFF to WDTCN in the initialization code.
13.7.4. Setting WDT Interval
WDTCN.[2:0] control the watchdog timeout interval. The interval is given by the following equation:
; where Tsysclk is the system clock period.
For a 3 MHz system clock, this provides an interval range of 0.021 ms to 349.5 ms. WDTCN.7 must be
logic 0 when setting this interval. Reading WDTCN returns the programmed interval. WDTCN.[2:0] reads
111b after a system reset.
43WDTCN 20–+Tsysclk
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 169
SFR Definition 13.1. WDTCN: Watchdog Timer Control
Bits7-0: WDT Control
Writing 0xA5 both enables and reloads the WDT.
Writing 0xDE followed within 4 system clocks by 0xAD disables the WDT.
Writing 0xFF locks out the disable feature.
Bit4: Watchdog Status Bit (when Read)
Reading the WDTCN.[4] bit indicates the Watchdog Timer Status.
0: WDT is inactive
1: WDT is active
Bits2-0: Watchdog Timeout Interval Bits
The WDTCN.[2:0] bits set the Watchdog Timeout Interval. When writing these bits,
WDTCN.7 must be set to 0.
R/WR/WR/WR/WR/WR/WR/W R/WReset Value
xxxxx111
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xFF
All Pages
C8051F040/1/2/3/4/5/6/7
170 Rev. 1.5
SFR Definition 13.2. RSTSRC: Reset Source
Bit7: Reserved.
Bit6: CNVRSEF: Convert Start Reset Source Enable and Flag
Write: 0: CNVSTR0 is not a reset source.
1: CNVSTR0 is a reset source (active low).
Read: 0: Source of prior reset was not CNVSTR0.
1: Source of prior reset was CNVSTR0.
Bit5: C0RSEF: Comparator0 Reset Enable and Flag.
Write: 0: Comparator0 is not a reset source.
1: Comparator0 is a reset source (active low).
Read: 0: Source of last reset was not Comparator0.
1: Source of last reset was Comparator0.
Bit4: SWRSF: Software Reset Force and Flag.
Write: 0: No effect.
1: Forces an internal reset. /RST pin is not effected.
Read: 0: Source of last reset was not a write to the SWRSF bit.
1: Source of last reset was a write to the SWRSF bit.
Bit3: WDTRSF: Watchdog Timer Reset Flag.
0: Source of last reset was not WDT timeout.
1: Source of last reset was WDT timeout.
Bit2: MCDRSF: Missing Clock Detector Flag.
Write: 0: Missing Clock Detector disabled.
1: Missing Clock Detector enabled; triggers a reset if a missing clock condition is
detected.
Read: 0: Source of last reset was not a Missing Clock Detector timeout.
1: Source of last reset was a Missing Clock Detector timeout.
Bit1: PORSF: Power-On Reset Flag.
Write: If the VDD monitor circuitry is enabled (by tying the MONEN pin to a logic high state), this
bit can be written to select or de-select the VDD monitor as a reset source.
0: De-select the VDD monitor as a reset source.
1: Select the VDD monitor as a reset source.
Important: At power-on, the VDD monitor is enabled/disabled using the external VDD moni-
tor enable pin (MONEN). The PORSF bit does not disable or enable the VDD monitor cir-
cuit. It simply selects the VDD monitor as a reset source.
Read: This bit is set whenever a power-on reset occurs. This may be due to a true power-on
reset or a VDD monitor reset. In either case, data memory should be considered indeterminate
following the reset.
0: Source of last reset was not a power-on or VDD monitor reset.
1: Source of last reset was a power-on or VDD monitor reset.
Note: When this flag is read as '1', all other reset flags are indeterminate.
Bit0: PINRSF: HW Pin Reset Flag.
Write: 0: No effect.
1: Forces a Power-On Reset. /RST is driven low.
Read: 0: Source of prior reset was not /RST pin.
1: Source of prior reset was /RST pin.
R R/W R/W R/W R R/W R R/W Reset Value
- CNVRSEF C0RSEF SWRSEF WDTRSF MCDRSF PORSF PINRSF 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xEF
0
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 171
Table 13.1. Reset Electrical Characteristics
–40 to +85 °C unless otherwise specified.
Parameter Conditions Min Typ Max Units
RST Output Low Voltage IOL = 8.5 mA, VDD = 2.7 V to 3.6 V ——0.6 V
RST Input High Voltage 0.7 x
VDD —— V
RST Input Low Voltage ——
0.3 x
VDD
RST Input Leakage Current RST = 0.0 V —50— µA
VDD for /RST Output Valid 1.0 — — V
AV+ for /RST Output Valid 1.0 — — V
VDD POR Threshold (VRST)2.40 2.55 2.70 V
Minimum /RST Low Time to
Generate a System Reset 10 — — ns
Reset Time Delay RST rising edge after VDD crosses
VRST threshold 80 100 120 ms
Missing Clock Detector
Timeout Time from last system clock to
reset initiation 100 220 500 µs
C8051F040/1/2/3/4/5/6/7
172 Rev. 1.5
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 173
14. Oscillators
Figure 14.1. Oscillator Diagram
14.1. Programmable Internal Oscillator
All C8051F04x devices include a programmable internal oscillator that defaults as the system clock after a
system reset. The internal oscillator period can be programmed via the OSCICL register as defined by
SFR Definition 14.1. OSCICL is factory calibrated to obt ain a 24.5 MHz frequency.
Electrical specifications for the precision internal oscillator are given in Table 14.1 on page 175. The pro-
grammed internal oscillator frequency must not exceed 25 MHz. The system clock may be derived from
the programmed internal oscillator divided by 1, 2, 4, or 8, as defined by the IFCN bits in register OSCICN.
OSC
Programmable
Internal Clock
Generator
Input
Circuit
EN
SYSCLK
n
OSCICL OSCICN
IOSCEN
IFRDY
IFCN1
IFCN0
XTAL1
XTAL2
Option 2
VDD
XTAL1
Option 1
Option 3
XTAL1
XTAL2
Option 4
XTAL1
OSCXCN
XTLVLD
XOSCMD2
XOSCMD1
XOSCMD0
XFCN2
XFCN1
XFCN0
CLKSEL
CLKSL
0
1
C8051F040/1/2/3/4/5/6/7
174 Rev. 1.5
SFR Definition 14.1. OSCICL: Internal Oscillator Calibration
SFR Definition 14.2. OSCICN: Internal Oscillator Control
Bits 7-0: OSCICL: Internal Oscillator Calibration Register
This register calibrates the internal oscillator period. The reset value for OSCICL defines the
internal oscillator base frequency. The reset value is factory calibrated to generate an inter-
nal oscillator freq ue n cy of 24 .5 MHz .
R/WR/WR/WR/WR/WR/WR/W R/WReset Value
Variable
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0x8B
F
Bit7: IOSCEN: Internal Oscillator Enable Bit.
0: Internal Oscillator Disabled
1: Internal Oscillator Enabled
Bit6: IFRDY: Internal Oscillator Frequency Ready Flag.
0: Internal Oscillator is not running at programmed frequency.
1: Internal Oscillator is running at programmed frequency.
Bits5-2: Reserved.
Bits1-0: IFCN1-0: Internal Oscillator Frequency Control Bits.
00: SYSCLK derived from Internal Oscillator divided by 8.
01: SYSCLK derived from Internal Oscillator divided by 4.
10: SYSCLK derived from Internal Oscillator divided by 2.
11: SYSCLK derived from Internal Oscillator divided by 1.
R/W R/W R/W R R/W R/W R/W R/W Reset Value
IOSCEN IFRDY - - - - IFCN1 IFCN0 11000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0x8A
F
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 175
14.2. External Oscillator Drive Circuit
The external oscillator circuit may drive an external crystal, ceramic resonator, capacitor, or RC network. A
CMOS clock m ay also provide a clock inp ut. For a crystal or ceramic resonator configuration, the crystal/
resonator must be wired across the XTAL1 and XTAL2 pins as shown in Option 1 of Figure 14.1. In RC,
capacitor, or CMOS clock configuration, the clock source should be wired to the XTAL2 and/or XTAL1
pin(s) as shown in Option 2, 3, or 4 of Figure 14.1. The type of external oscillator must be selected in the
OSCXCN register, and the frequency control bits (XFCN) must be selected appropriately (see SFR Defini-
tion 14.4).
14.3. System Clock Selection
The CLKSL bit in register CLKSEL selects which oscillator is used as the system clock. CLKSL must be
set to ‘1’ for the system clock to run from the external oscillator; however the external oscillator may still
clock peripherals (timers, PCA) when the internal oscillator is selected as the system clock. The system
clock may be switched on-the-fly between the internal and external oscillator, so long as the selected oscil-
lator is enabled and has settled. The internal oscillator requires little start-up time and may be enabled and
selected as the system clock in the same write to OSCICN. External crystals and ceramic resonators typi-
cally require a start-up time before they are settled and ready for use as the system clock. The Crystal
Valid Flag (XTLVLD in register OSCXCN) is set to ‘1’ by hardware when the external oscillator is settled. To
avoid reading a false XTLVLD in crystal mode, software should delay at least 1 ms between enabling the
external oscillator and checking XTLVLD. RC and C modes typically require no startup time.
SFR Definition 14.3. CLKSEL: Oscillator Clock Selection
Table 14.1. Internal Oscillator Electrical Characteristics
–40 to +85 °C unless otherw ise specified.
Parameter Conditions Min Typ Max Units
Calibrated Internal Oscillator
Frequency 24 24.5 25 MHz
Internal Oscillator Supply Current
(from VDD)OSCICN.7 = 1 —450— µA
External Clock Frequency 0—30MHz
TXCH (External Clock High Time) 15 — — ns
TXCL (External Clock Low Time) 15 — — ns
Bits7-1: Reserved.
Bit0: CLKSL: System Clock Source Select Bit.
0: SYSCLK derived from the Internal Oscillator, and scaled as per the IFCN bits in OSCICN.
1: SYSCLK derived from the External Oscillator circuit.
R R R R R R R R/W Reset Value
-------CLKSL00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0x97
F
C8051F040/1/2/3/4/5/6/7
176 Rev. 1.5
SFR Definition 14.4. OSCXCN: External Oscillator Control
Bit7: XTLVLD: Cry stal Oscillator Va lid Flag.
(Read only when XOSCMD = 11x.)
0: Crystal Oscillator is unused or not yet stable.
1: Crystal Oscillator is running and stable.
Bits6-4: XOSCMD2-0: External Oscillator Mode Bits.
00x: External Oscillator circuit off.
010: External CMOS Clock Mode (External CMOS Clock input on XTAL1 pin).
011: External CMOS Clock Mode with divide by 2 stage (External CMOS Clock input on
XTAL1 pin).
10x: RC/C Oscillator Mode with divide by 2 stage.
110: Crystal Oscillator Mode.
111: Crystal Oscillator Mode with divide by 2 stage.
Bit3: RESERVED. Read = 0, Write = don't care.
Bits2-0: XFCN2-0: External Oscillator Frequency Control Bits.
000-111: see table below:
CRYSTAL MODE (Circuit from Figure 14.1, Option 1; XOSCMD = 11x)
Choose XFCN value to match crystal frequency.
RC MODE (Circuit from Figure 14.1, Option 2; XOSCMD = 10x)
Choose XFCN value to match frequency range:
f = 1.23(103) / (R x C), where
f = frequency of oscillation in MHz
C = capacitor value in pF
R = Pullup resistor value in k
C MODE (Circuit from Figure 14.1, Option 3; XOSCMD = 10x)
Choose K Factor (KF) for the oscillation frequency desired:
f = KF / (C x VDD), where
f = frequency of oscillation in MHz
C = capacitor value on XTAL1, XTAL2 pins in pF
VDD = Power Supply on MCU in volts
R R/W R/W R/W R R/W R/W R/W Reset Value
XTLVLD XOSCMD2 XOSCMD1 XOSCMD0 - XFCN2 XFCN1 XFCN0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0x8C
F
XFCN Crystal (XOSCMD = 11x) RC (XOSCMD = 10x) C (XOSCMD = 10x)
000 f 32 kHz f 25 kHz K Factor = 0.87
001 32 kHz f 84 kHz 25 kHz f 50 kHz K Factor = 2.6
010 84 kHz f 225 kHz 50 kHz f 100 kHz K Factor = 7.7
011 225 kHz f 590 kHz 100 kHz f 200 kHz K Factor = 22
100 590 kHz f 1.5 MHz 200 kHz f 400 kHz K Factor = 65
101 1.5 MHz f 4 MHz 400 kH z f 800 kHz K Factor = 180
110 4 MHz f 10 MHz 800 kHz f 1.6 MHz K Factor = 664
111 10 MHz f 30 MHz 1.6 MHz f 3.2 MHz K Factor = 1590
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 177
14.4. External Crystal Example
If a crystal or ceramic resonator is used as an external oscillator source for the MCU, the circuit should be
configured as shown in Figure 14.1, Option 1. The External Oscillator Frequency Control value (XFCN)
should be chosen from the Crystal column of the table in SFR Definition 14.4 (OSCXCN register). For
example, an 11.0592 MHz crystal requires an XFCN setting of 111b.
When the crystal oscillator is enabled, the oscillator amplitude detection circuit requires a settle time to
achieve proper bias. Introducing a delay of at least 1 ms between enabling the oscillator and checking the
XTLVLD bit will prevent a premature switch to the external oscillator as the system clock. Switc hing to the
external oscillator before the crystal oscillator has stabilized can result in unpredictable behavior. The rec-
ommended procedure is:
Step 1. Enable the external oscillator in crystal oscillator mode.
Step 2. Wait at least 1 ms.
Step 3. Poll for XTLVLD => '1'.
Step 4. Switch the system clock to the external oscillator.
Note: Tuning-fork crystals may require additional settling time before XTLVLD returns a valid result.
The capacitors shown in the external crystal configuration provide the load capacitance required by the
crystal for correct oscillation. These capacitors are "in series" as seen by the crystal and "in parallel" with
the stray capacitance of the XTAL1 and XTAL2 pins .
Note: The load capacitance depends upon the crystal and the manufacturer. Please refer to the crystal
data sheet when completing these calculations.
For examp le, a tun ing-fo rk crystal of 32.7 68 kHz with a recommended load capacitance of 12.5 pF should
use the configuration shown in Figur e 14.1, Option 1. Th e tota l value of the cap acitors and the stray capac-
itance of the XTAL pins should equal 25 pF. With a stray capacitance of 3 pF per pin, the 22 pF capacitors
yield an equivalent capacitance of 12.5 pF across the crystal, as shown in Figure 14.2.
Figure 14.2. 32.768 kHz External Crystal Example
Important Note on External Crystals: Crystal oscillator circuits are quite sensitive to PCB layout. The
crystal should be placed as close as possible to the XTAL pins on the device. The traces should be as
short as possible and shielded with ground plane from any other traces which could introduce noise or
interference.
22 pF
22 pF
32.7 68 kH z
XTAL1
XTAL2
10 M
C8051F040/1/2/3/4/5/6/7
178 Rev. 1.5
14.5. External RC Example
If an RC network is used as an external oscillator source for the MCU, the circ uit should be configured as
shown in Figure 14.1, Option 2. The capacitor should be no greater than 100 pF; however, for very small
capacitors, the total capacitance may be dominated by parasitic capacitance in the PCB layout. To deter-
mine the required External Oscillator Frequency Control value (XFCN) in the OSCXCN Register, first
select the RC network value to produce the desired frequency of oscillation. If the frequency desired is
100 kHz, let R = 246 k and C = 50 pF:
f = 1.23( 103 ) / RC = 1.23 ( 103 ) / [ 246 x 50 ] = 0.1 MHz = 100 kHz
Referring to the table in SFR Definition 14.4, the required XFCN setting is 010b.
14.6. External Capacitor Example
If a capacitor is used as an external oscillator for the MCU, the circuit should be configured as shown in
Figure 14.1, Option 3. The capacitor should be no greater than 100 pF; however, for very small capacitors,
the total capacitance may be dominated by parasitic capacitance in the PCB layout. To determine the
required External Oscillator Frequency Control value (XFCN ) in the OSCXCN Register, select the desired
frequency of oscillation and find the capacitor to be used from the equations below. Assume VDD = 3.0 V
and f = 50 kHz:
f = KF / ( C x VDD ) = KF / ( C x 3 ) = 0.050 MHz
If a frequency of roughly 50 kHz is desired, select the K Factor from the table in SFR Definition 14.4 as
KF = 7.7:
0.050 MHz = 7.7 / (C x 3)
C x 3 = 7.7 / 0.050 = 154, so C = 154 / 3 pF = 51.3 pF
Therefore, the XFCN value to use in this example is 010b.
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 179
15. Flash Memory
The C8051F04x family includes 64 kB + 128 (C8051F040/1/2/3/4/5) or 32 kB + 128 (C8051F046/7) of on-
chip, reprogrammable Flash memory for program code and non-volatile data storage. The Flash memory
can be programmed in-system, a single byte at a time, through the JTAG interface or by software using the
MOVX write instructions. Once cleared to logic 0, a Flash bit must be erased to set it back to logic 1. The
bytes would typically be erased (set to 0xFF) before being reprogrammed. Flash write and erase opera-
tions are automatically timed by hardware for proper execution; data polling to determine the end of the
write/erase operation is not required. The CPU is stalled during write/erase operations while the device
peripherals remain active. Int errupts that occur du ring Flash writ e/erase oper ations are he ld, and are then
serviced in their priority order once the Flash operation has completed . Refer to Table 15.1 for the e lectri-
cal characteristics of the Flash memory.
15.1. Programming The Flash Memory
The simplest means of programming the Flash memory is through the JTAG interface using programming
tools provided by Silicon Labs or a third party vendor. This is the only means for programming a non-initial-
ized device. For det a ils on the JTAG commands to program Flash memory, see Section “25.2. Flash Pro-
gramming Commands” on page 321.
The Flash memory can b e programmed by so ftware using the MOVX write instruction with the address and
data byte to be programmed provided as normal operands. Before writing to Flash memory using MOVX,
Flash write operatio ns must b e enabled by setting the PSWE Program Store Write Enable bit (PSCTL.0) to
logic 1. This directs the MOVX writes to Flash memory instead of to XRAM, which is the default t arget. The
PSWE bit remains set until cleared by software. To avoid errant Flash writes, it is recommended that inter-
rupts be disabled while the PSWE bit is logic 1.
Flash memory is read using the MOVC instruction. MOVX reads are always directed to XRAM, regardless
of the state of PSWE.
Note: To ensure the integrity of Flash memory contents, it is strongly recommended that the on-chip VDD
monitor be enabled by connecting the VDD monitor enable pin (MONEN) to VDD in any system that exe-
cutes code that writes and/or erases Flash memory from software. See “Reset Sources” on page 165 for
more information.
A write to Flash memory can clear bits but cannot set them; only an erase operation can set bits in Flash.
A byte location to be programmed must be erased before a new value can be written. The Flash
memory is organized in 512-byte pages. The erase operation applies to an en tire page (s et tin g a ll byt es in
the page to 0xFF). The following steps illustrate the algorithm for programming Flash by user software.
Step 1. Disable interrupts.
Step 2. Set FLWE (FLSCL.0) to enable Flash wr ites/erases via user software.
Step 3. Set PSEE (PSCTL.1) to enable Flash erases.
Step 4. Set PSWE (PSCTL.0) to redirect MOVX command s to writ e to Flas h.
Step 5. Use the MOVX command to write a data byte to any location within the 512-byte page to
be erased.
Step 6. Clear PSEE to disable Flash erases
Step 7. Use the MOVX command to write a data byte to the desired byte location within the
erased 512-byte p age. Repeat this step u ntil all desired bytes are written (within the t arget
page).
Step 8. Clear the PSWE bit to redirect MOVX commands to the XRAM data spa ce.
Step 9. Re-enable interrupts.
Write/Erase timing is automatically controlled by hardware. Note that code execution in the 8051 is stalled
while the Flash is being programmed or erased. Note that 512 bytes at locations 0xFE00 (C8051F040/1/2/
C8051F040/1/2/3/4/5/6/7
180 Rev. 1.5
3/4/5) and all locations above 0x8000 (C8051F046/7) are reserved. Flash writes and erases targeting the
reserved area should be avoided.
15.2. Non-volatile Data Storage
The Flash memory can be used for non-volatile data storage as well as program code. This allows data
such as calibration coefficients to be calculated and stored at run time. Data is written using the MOVX
write instruction (as described in the previous section) and read using the MOVC instruction.
An additional 128-byte sector of Flash memory is included for non-volatile data storage. Its smaller sector
size makes it particularly well suited as general purpose, non-volatile scratchpad memory. Even though
Flash memory can be written a single byte at a time, an entire sector must be erased first. In order to
change a single byte of a multi-byte data set, the data must be moved to temporary storage. The 128-byte
sector-size facilitates updating data without wasting program memory or RAM space. The 128-byte sector
is double-mapped over the 64k byte Flash memory; its address ranges from 0x00 to 0x7F (see
Figure 15.1). To access this 128-byte sector, the SFLE bit in PSCTL must be set to logic 1. Code execution
from this 128-byte scratchpad sector is not permitted.
15.3. Security Options
The CIP-51 provides security options to protect the Flash memory from inadvertent modification by soft-
ware as well as prevent the viewing of proprietary program code and constants. The Program Store Write
Enable (PSCTL.0) and the Program Store Erase Enable (PSCTL.1) bits protect the Flash memory from
accidenta l modification by sof twa re. These bit s must be ex plicitly set to logic 1 before sof twa re can write or
erase the Flash memory. Additional security features prevent propriet ary program cod e and data consta nts
from being read or altered across the JTAG interface or by software running on the system controller.
A set of security lock bytes stored at 0xFDFE and 0xFDFF (C8051F040/1/2/3/4/5) and at 0x7FFE and
0x7FFF (C8051F046/7) protect the Flash program memory from being read or altered across the JTAG
interface. Each bit in a security lock-byte protects one 8k-byte block of memory. Clearing a bit to logic 0 in
a Read Lock Byte prevents the corresponding block of Flash memory from being read across the JTAG
interface. Clearing a bi t in the W rit e/Erase Lock Byte protects the block from JTAG erasures and/or writes.
The Read Lock Byte is at locations 0xFDFF (C8051F040/1/2/3/4/5) and 0x7FFF (C8051F046/7). The
Write/Erase Lock Byte is located at 0xFDFE (C8051F040/1/2/3/4/5) and 0x7FFE (C8051F046/7).
Figure 15.1 shows the location and bit definitions of the security bytes. The 512-byte sector containing
the lock bytes can be written to, but not erased by software. An attempte d read of a read- locked b yte
returns undefined data. Debugging code in a read-locked sector is not possible through the JTAG inter-
face.
Table 15.1. Flash Electrical Characteristics
VDD = 2.7 to 3.6 V; Ta = –40 to +85 °C
Parameter Conditions Min Typ Max Units
Flash Size1C8051F040/1/2/3/4/5
C8051F046/7 656642
32896 Bytes
Endurance 20 k 100 k — Erase/Write
Erase Cycle Time 10 12 14 ms
Write Cycle Time 40 50 60 µs
Notes:
1. Includes 128-byte scratchpad.
2. 512 bytes at locations 0xFE00 to 0xFFFF are reserved.
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 181
Figure 15.1. Flash Program Memory Map and Security Bytes
Flash Read Lock Byte
Bits7-0: Each bit locks a corresponding block of memory. (Bit7 is MSB).
0: Read oper ations ar e locke d (disabled ) fo r co rrespondin g block across the JTAG interface.
1: Read operati on s ar e un loc ke d (e na ble d ) for corresponding block across the JTAG inter-
face.
Flash Write/Erase Lock Byte
Bits7-0: Each bit locks a corresponding block of memory.
0: Write/Erase operations are locked (disabled) for correspondin g block across the JTAG
interface.
1: Write/Erase operations are unlocked (enabled) for corresponding block across the JTAG
interface.
NOTE: When the highest block is locked, the security bytes may be written but not erased.
Flash access Limit Register (FLACL)
The content of this register is used as the high byte of the 16-bit Software Read Limit
address. This 16-bi t read limit ad dress value is calculated a s 0xNN00 where NN is re placed
by content of this register on reset. Software running at or above this address is prohibited
from using the MOVX and MOVC instructions to read, write, or erase Flash locations below
this address. Any attempts to read locations below this limit will return the value 0x00.
0xFE00
0xFDFE
Program/Data
Memory Space
0x0000
0xFDFF
Read Lock B yte
Write/Erase Lock Byte
Software Read Limit
Reserved
0xFDFD
SFLE = 0
Bit Memory Block
C8051F0 40/1/2/3/4/5 C8 051F 046/7
7
6
5
4
0xC000 - 0xDFFF
0xE000 - 0xFDFD
0xA000 - 0xBFFF
0x8000 - 0x9FFF
3
2
1
0
0x4000 - 0x5FFF
0x6000 - 0x7FFF
0x2000 - 0x3FFF
0x0000 - 0x1FFF
Read and Write/Erase Se curity Bits.
(Bit 7 is MSB.) 0x007F
0x0000
Scratchpad Mem ory
(Data only)
SFLE = 1
0x8000
0x7FFE
Program/Data
Memory Space
0x0000
0x7FFF
Read Lock B yte
Write/Erase Lock Byte
Software Read Limit
Reserved
0x7FFD
C8051F040/1/2/3/4/5
C8051F046/7
No effe c t
No effe c t
No effe c t
No effe c t
0x4000 - 0x5FFF
0x6000 - 0x7FFD
0x2000 - 0x3FFF
0x0000 - 0x1FFF
C8051F040/1/2/3/4/5/6/7
182 Rev. 1.5
The lock bits can always be read and cleared to logic 0 regardless of the security setting applied to the
block containing the security bytes. This allows additional blocks to be protected after the block containing
the security bytes has been locked. Import ant Note: The only means of removing a lock once set is to
erase the entire program memory space by performing a JTAG erase operation (i.e., cannot be
done in user firmware). Addressing either security byte while performing a JTAG erase operation
will automatically initiate erasure of the entire program memory space (except for the reserved
area). This erasure can only be performed via JTAG. If a non-security byte in the 0xFBFF-0xFDFF
(C8051F040/1/2/3/4/5) or 0x7DFF-0x7FFF (C8051F046/7) page is addressed during the JTAG era-
sure, only that page (including the security bytes) will be erased.
The Flash Access Limit security feature (see Figure 15.1) protect s propriet ary pr ogram code and da ta fro m
being read by software running on the C8051F04x. This feature provides support for OEMs that wish to
program the MCU with proprietary value-added firmware before distribution. The value-added firmware
can be protected while allowing additional code to be programmed in remaining program memory space
later.
The Software Read Limit (SRL) is a 16-bit address that establishes two logical partitions in the program
memory space. The first is an upper partition consisting of all the program memory locations at or above
the SRL address, and the second is a lower partition consisting of all the program memory locations start-
ing at 0x0000 up to (but excluding) the SRL address. Software in the upper partition can execute code in
the lower partition, but is prohibited from reading lo cations in the lower partition using the MOVC instruc-
tion. (Executing a MOVC instruction from the upper partition with a source address in the lower partition
will always return a data value of 0x00.) Sof tware running in the lower partition can access locations in both
the upper and lower partition without restriction.
The Value-added firmware should be p laced in the lower partition. On reset, control is passed to the value-
added firmware via the reset vector. Once the value-added firmware completes its initial execution, it
branches to a predetermined location in the upper partition. If entry points are published, software running
in the upper partition may execute program code in the lower partition, but it cannot read the contents of
the lower partition. Parameters may be passed to the program code running in the lower partition either
through the typical method of placing them on the stack or in registers before the call or by placing them in
prescribed memory locations in the upper partition.
The SRL address is specified using the contents of the Flash Access Register. The 16-bit SRL address is
calculated as 0xNN00, where NN is the contents of the SRL Security Register. Thus, the SRL can be
located on 256-byte boundaries anywhere in program memory space. However, the 512-byte erase sector
size essentially requires that a 512 boundary be used. The contents of a non-initialized SRL security byte
is 0x00, thereby setting the SRL address to 0x0000 and allowing read access to all locations in program
memory space by default.
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 183
15.3.1. Summary of Flash Security Options
There are three Flash access methods supported on the C8051F04x devices; 1) Accessing Flash through
the JTAG debug interface, 2) Accessing Flash from firmwar e residing below the Flash Access Limit, and 3)
Accessing Flash from firmware residing at or above the Flash Access Limit.
Accessing Flash through the JTAG debug interface:
1. The Read and Write/Erase Lock bytes (security bytes) provide security for Flash access
through the JTAG interface.
2. Any unlocked page may be read from, written to, or erased.
3. Locked pages cannot be read from, written to, or erased.
4. Reading the security bytes is always permitted.
5. Locking additional pages by writing to the security bytes is always permitted.
6. If the page containing the security bytes is unlocked, it can be dir ectly er ased. Doing so wil l
reset the security bytes and unlock all pages of Flash.
7. If the page containing the securi ty bytes is locked, it cannot be directly erased. To unlock the
page containing the security bytes, a full JTAG device erase is required. A full JTAG
device erase will erase all Flash pages, including the page containing the security bytes and
the security bytes themselves.
8. The Reserved Area cannot be read from, written to, or erased at any time.
Accessing Flash from firmware residing below the Flash Access Limit:
1. The Read and Write/Erase Lock bytes (security bytes) do not restrict Flash access from user
firmware.
2. Any page of Flash except the page containing the security bytes may be read from, written to,
or erased .
3. The page containing the security bytes cannot be erased. Unlocking pages of Flash can
only be performed via the JTAG interface.
4. The page containing the security bytes may be read from or written to. Pages of Flash can be
locked from JTAG access by writing to the security bytes.
5. The Reserved Area cannot be read from, written to, or erased at any time.
Accessing Flash from firmware residing at o r above the Flash Access Limit:
1. The Read and Write/Erase Lock bytes (security bytes) do not restrict Flash access from user
firmware.
2. Any page of Flash at or above the Flash Access Limit except the page containing the security
bytes may be read from, written to, or erased.
3. Any page of Flash below the Flash Access Limit cannot be read from, written to, or erased.
4. Code branches to locat ion s be low the Flas h Acce ss Lim it ar e pe rm itt ed .
5. The page containing the security bytes cannot be erased. Unlocking pages of Flash can
only be performed via the JTAG interface.
6. The page containing the security bytes may be read from or written to. Pages of Flash can be
locked from JTAG access by writing to the security bytes.
7. The Reserved Area cannot be read from, written to, or erased at any time.
C8051F040/1/2/3/4/5/6/7
184 Rev. 1.5
SFR Definition 15.1. FLACL: Flash Access Limit
SFR Definition 15.2. FLSCL: Flash Memory Control
Bits 7-0: FLACL: Flash Access Limit.
This register holds the high byte of the 16-bit program memory read/write/erase limit
address. The entire 16-bit access limit address value is calculated as 0xNN00 where NN is
replaced by contents of FLACL. A write to this register sets the Flash Access Limit. This reg-
ister can only be written once after any reset. Any subsequent writes are ignored until the
next reset.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
SFR Address:
SFR Page: 0xB7
F
Bit7: FOSE: Flash One-Shot Timer Enable
This is the timer that turns off the sense amps after a Flash read.
0: Flash One-Shot Timer disabled.
1: Flash One-Sh ot Timer enabled (recom men d ed sett ing ).
Bit6: FRAE: Flash Read Always Enable
0: Flash reads occur as necessary (recommended setting).
1: Flash reads occur every system clock cycle.
Bits5-1: RESERVED. Read = 00000b. Must Write 00000b.
Bit0: FLWE: Flash Write/Erase Enable
This bit must be set to allow Flash writes/erases from user software.
0: Flash writes/erases disabled.
1: Flash writes/erases enabled.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
FOSE FRAE Reserved Reserved Reserved Reserved Reserved FLWE 10000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
SFR Address:
SFR Page: 0xB7
0
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 185
SFR Definition 15.3. PSCTL: Program Store Read/Write Control
Bits7-3: UNUSED. Read = 00000b, Write = don't care.
Bit2: SFLE: Scratchpad Flash Memory Access Enable
When this bit is set, Flash reads and writes from user software are directed to the 128-byte
Scratchpad Flash sector. When SFLE is set to logic 1, Flash accesses out of the address
range 0x00-0x7F should not be attempted. Reads/Writes out of this range will yield unde-
fined results.
0: Flash access from user software directed to the Program/Data Flash sector.
1: Flash access from user software directed to the 128 byte Scratchpad sector.
Bit1: PSEE: Program Store Erase Enable.
Setting this bit allows an entire page of the Flash program memory to be erased provided
the PSWE bit is also set. After setting this bit, a write to Flash memory using the MOVX
instruction will erase the entire page that contains the location addressed by the MOVX
instruction. The value of the data byte written does not matter. Note: The Flash page con-
taining the Read Lock Byte and Write/Erase Lock Bytes cannot be erased by soft-
ware.
0: Flash program memory erasure disabled.
1: Flash program memory erasure enabled.
Bit0: PSWE: Program Store Write Enable.
Setting this bit allows writing a byte of data to the Flash program memory using the MOVX
write instruction. The location must be erased prior to writing data.
0: Write to Flash program memory disabled. MOVX write operation s target External RAM.
1: Write to Flash program memory enabled. MOVX write operations target Flash memory.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
- - - - - SFLE PSEE PSWE 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
SFR Address:
SFR Page: 0x8F
0
C8051F040/1/2/3/4/5/6/7
186 Rev. 1.5
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 187
16. External Data Memory Interface and On-Chip XRAM
The C8051F04x MCUs include 4 kB of on-chip RAM mapped into the external data memory space
(XRAM), as well as an External Data Memory Interface which can be used to access off-chip memories
and memory-mapped d evices connected to the GPIO port s. The external memor y sp ace may be accesse d
using the external move instruction (MOVX) and the data pointer (DPTR), or using the MOVX indirect
addressing mode using R0 or R1. If the MOVX instruction is used with an 8-bit address operand (such as
@R1), then the high byte of the 16-bit address is provided by the External Memory Interface Control Reg-
ister (EMI0CN, shown in SFR Definition 16.1). Note: the MOVX instruction can also be used for writing to
the Flash memory. See Section “15. Flash Memory” on page 179 for details. The MOVX instruction
accesses XRAM by default. The EMIF can be configured to appear on the lower GPIO Ports (P0- P3) or the
upper GPIO Ports (P4-P7).
16.1. Accessing XRAM
The XRAM memory space is accessed using the MOVX instruction. The MOVX instruction has two forms,
both of which use an indirect addressing method. The first method uses the Data Pointer, DPTR, a 16-bit
register which contains the effective address of the XRAM location to be read from or written to. The sec-
ond method uses R0 or R1 in combination with the EMI0CN register to generate the effective XRAM
address. Examples of both of these methods are given below.
16.1.1. 16-Bit MOVX Example
The 16-bit form of the MOVX instruction accesses the memory location pointed to by the contents of the
DPTR register. The following series of instructions reads the value of the byte at address 0x1234 into the
accumulator A:
MOV DPTR, #1234h ; load DPTR with 16-bit address to read (0x1234)
MOVX A, @DPTR ; load contents of 0x1234 into accumulator A
The above example uses the 16-bit immediate MOV instruction to set the contents of DPTR. Alternately,
the DPTR can be accessed thro ugh the SFR reg ister s DPH, which contains the upper 8-bits of DPT R, and
DPL, which contains the lower 8-bits of DPTR.
16.1.2. 8-Bit MOVX Example
The 8-bit form of the MOVX instruction uses the content s of the EMI0CN SF R to dete rmine the u pper 8-bit s
of the effective address to be accessed and the contents of R0 or R1 to determine the lower 8-bits of the
effective address to be accessed. The following series of instructions read the contents of the byte at
address 0x1234 into the accumulator A.
MOV EMI0CN, #12h ; load high byte of address into EMI0CN
MOV R0, #34h ; load low byte of address into R0 (or R1)
MOVX a, @R0 ; load contents of 0x1234 into accumulator A
C8051F040/1/2/3/4/5/6/7
188 Rev. 1.5
16.2. Configuring the External Memory Interface
Configuring the External Memory Interface consists of five steps:
1. Select EMIF on Low Ports (P3, P2, P1, and P0) or High Ports (P7, P6, P5, and P4).
2. Configure the Output Modes of the port pins as either push-pull or open-drain.
3. Select Multiplexed mode or Non-multiplexed mode.
4. Select the memory mode (on-chip only, split mode without bank select, split mode with bank
select, or off-chip only).
5. Set up timing to interface with off-chip memory or peripherals.
Each of these five steps is explained in detail in the following sections. The Port selection, Multiplexed
mode selection, and Mode bits are located in the EMI0CF register shown in SFR Definition 16.2.
16.3. Port Selection and Configuration
The External Memory Interface can appear on Ports 3, 2, 1, and 0 (C8051F04x devices) or on Ports 7, 6,
5, and 4 (C8051F040/2/4/6 devices only), depending on the state of the PRTSEL bit (EMI0CF.5). If the
lower Ports are selected, the EMIFLE bit (XBR2.1) must be set to a ‘1’ so that the Crossbar will skip over
P0.7 (/WR), P0.6 (/RD), and, if multiplexed mode is selected, P0.5 (ALE). For more information about the
configuring the Crossb ar, see Section “17.1. Ports 0 through 3 and the Priority Cros sbar Decode r” on
page 204.
The External Memory Interface claims the associated Port pins for memory operations ONLY during the
execution of an off-chip MOVX instruction. Once the MOVX instruction has completed, control of the Port
pins reverts to the Port latches or to the Crossbar (on Ports 3, 2, 1, and 0). See Section “17. Port Input/
Output” on page 203 for more information about the Crossbar and Port operation and configuration. The
Port latches should be explicitly configured as push-pull to ‘park’ the External Memory Interface
pins in a dormant state, most commonly by setting them to a logic 1.
During the execution of the MOVX instruction, the External Memory Interface will explicitly disable the driv-
ers on all Port pins that are actin g as In puts (Data[7:0] dur ing a READ ope ra tion , for example). The Output
mode of the Port pins (whether the pin is configured as Open-Drain or Push-Pull) is unaffected by the
External Memory Interface operation, and remains controlled by the PnMDOUT registers. In most cases,
the output modes of all EMIF pins should be configured for push-pull mode. See Section
“17.1.2. Configuring the Output Modes of the Port Pins” on page 206.
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 189
SFR Definition 16.1. EMI0CN: External Memory Interface Control
Bits7-0: PGSEL[7:0]: XRAM Page Select Bits.
The XRAM Page Select Bits provide the high byte of the 16-b it ext er n al data memor y
address when using an 8-bit MOVX command, effectively selecting a 256-byte page of
RAM.
0x00: 0x0000 to 0x00FF
0x01: 0x0100 to 0x01FF
...
0xFE: 0xFE 0 0 to 0xFEFF
0xFF: 0xFF00 to 0xFFFF
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
PGSEL7 PGSEL6 PGSEL5 PGSEL4 PGSEL3 PGSEL2 PGSEL1 PGSEL0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xA2
0
C8051F040/1/2/3/4/5/6/7
190 Rev. 1.5
SFR Definition 16.2. EMI0CF: External Memory Configuration
Bits7-6: Unused. Read = 00b. Write = don’t care.
Bit5: PRTSEL: EMIF Port Select.
0: EMIF active on P0-P3.
1: EMIF active on P4-P7.
Bit4: EMD2: EMIF Multiplex Mode Select.
0: EMIF operates in multiplexed address/data mode.
1: EMIF operates in non-multiplexed mode (separate address and data pins) .
Bits3-2: EMD1-0: EMIF Operating Mode Select.
These bits control the operating mode of the External Memory Interface.
00: Internal Only: MOVX accesses on-chip XRAM only. All effective addresses alias to on-
chip memory space.
01: Split Mode without Bank Select: Accesses below the 4k boundary a re directed on-chip.
Accesses above the 4k boundary are directed off-chip. 8-bit off-chip MOVX oper ations
use the current content s of the Addre ss High port latche s to resolve upper ad dress byte.
Note that in orde r to acce ss off-chip space, EMI0CN must be set to a page that is not
contained in the on-chip address space.
10: Split Mode with Bank Select: Accesses below the 4k boundary are directe d on-chip.
Accesses above the 4k boundary are directed off-chip. 8-bit off-chip MOVX oper ations
use the contents of EMI0CN to determine the high-byte of the address.
11 : External Only: MOVX acces ses off-chip XRAM only. On-chip XRAM is not visible to the
CPU.
Bits1-0: EALE1-0: ALE Pulse-Width Select Bits (only has effect when EMD2 = 1).
00: ALE high and ALE low pulse width = 1 SYSCLK cycle.
01: ALE high and ALE low pulse width = 2 SYSCLK cycles.
10: ALE high and ALE low pulse width = 3 SYSCLK cycles.
11: ALE high and ALE low pulse width = 4 SYSCLK cycles.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
- - PRTSEL EMD2 EMD1 EMD0 EALE1 EALE0 00000011
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xA3
0
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 191
16.4. Multiplexed and Non-multiplexed Selection
The External Memory Interface is capable of acting in a Multiplexed mode or a Non-multiplexed mode,
depending on the state of the EMD2 (EMI0CF.4) bit.
16.4.1. Multiplexed Configuration
In Multiplexed mode, the Data Bus and the lower 8-bits of the Address Bus share the same Port pins:
AD[7:0]. In this mode, an external latch (74HC373 or equivalent logic gate) is used to hold the lower 8-bits
of the RAM address. The external latch is controlled by the ALE (Address Latch Enable) signal, which is
driven by the External Memory Interface logic. An example of a Multiplexed Configuration is shown in
Figure 16.1.
In Multiplexed m ode, th e exte rnal MOVX op eratio n can be broken into two phases delineated by the state
of the ALE signal. During the first phase, ALE is high and the lower 8-bits of the Address Bus are pre-
sented to AD[7:0]. During this phase, the address latch is configured such that the ‘Q’ outputs reflect the
states of the ‘D’ inputs. When ALE falls, signaling the beginning of the second phase, the address latch
outputs remain fixed and are no longer dependent on the latch inputs. Later in the second phase, the Data
Bus controls the state of the AD[7:0 ] po rt at the time /RD or /WR is asserted.
See Section “16.6.2. Multiplexed Mode” on page 199 for more information.
Figure 16.1. Multiplexed Configuration Example
ADDRESS/DATA BUS
ADDRESS BUS
E
M
I
F
A[15:8]
AD[7:0]
/WR
/RD
ALE
64K X 8
SRAM
OE
WE
I/O[7:0]
74HC373
G
DQ
A[15:8]
A[7:0]
CE
V
DD
8
(Optional)
C8051F040/1/2/3/4/5/6/7
192 Rev. 1.5
16.4.2. Non-multiplexed Configuration
In Non-multiplexed mode, the Data Bus and the Address Bus pins are not shared. An example of a Non-
multiplexed Configuration is shown in Figure 16.2. See Section “16.6.1. Non-multiplexed Mode” on
page 196 for more information about Non-multiplexed operation.
Figure 16.2. Non-multiplexed Configuration Example
ADDRESS BUS
E
M
I
F
A[15:0]
64K X 8
SRAM
A[15:0]
DATA BUSD[7:0] I/O[7:0]
V
DD
8
/WR
/RD OE
WE
CE
(Optional)
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 193
16.5. Memory Mode Selection
The external data memory space can be configured in one of four modes, shown in Figure 16.3, based on
the EMIF Mode bits in the EMI0CF register (SFR Definition 16.2). These modes are summarized below.
More information about the different modes can be found in Section “16.6. Timing” on page 194.
16.5.1. Internal XRAM Only
When EMI0CF.[3:2] are set to ‘00’, all MOVX instructions will target the internal XRAM space on the
device. Memory accesses to addresses beyond the populated space will wrap on 4k boundaries. As an
example, the addresses 0x1000 and 0x2000 both evaluate to address 0x0000 in on-chip XRAM space.
• 8-bit MOVX operations use the contents of EMI0CN to determine the high-byte of the ef fective address
and R0 or R1 to determine the low-byte of the effective address.
• 16-bit MOVX operations use the contents of the 16-bit DPTR to determine the effective address.
16.5.2. Split Mode without Bank Select
When EMI0CF.[3:2] are set to ‘01’, the XRAM memory map is split into two areas, on-chip space and off-
chip space.
• Effective addresses below the 4k boundary will access on-chip XRAM space.
• Effective addresses above the 4k boundary will access off-chip space.
• 8-bit MOVX operations use the contents of EMI0CN to determine whether the memory access is on-
chip or off-chip. However, in the “No Bank Select” mode, an 8-bit MOVX operation will not drive the
upper 8-bits A[15:8] of the Add re ss Bus du ring an off-chip acces s . This allo ws th e use r to ma nip ulate
the upper address bits at will by setting the Port state directly via the port latches. This behavior is in
contrast with “Split Mode with Bank Select” described below. The lower 8-bits of the Add ress Bus
A[7:0] are driven, determined by R0 or R1.
• 16-bit MOVX operations use the contents of DPTR to determine whether the memory access is on-
chip or off-chip, and unlike 8-bit MOVX operations, the full 16-bits of the Address Bus A[15:0] are
driven during the off-chip transaction.
Figure 16.3. EMIF Operating Modes
EMI0CF[3:2] = 00 0xFFFF
0x0000
EMI0CF[3:2] = 11 0xFFFF
0x0000
EMI0CF[3:2] = 01 0xFFFF
0x0000
EMI0CF[3:2] = 10
On-Chip XRAM
On-Chip XRAM
On-Chip XRAM
On-Chip XRAM
On-Chip XRAM
On-Chip XRAM
Off-Chip
Memory
(No Bank Select)
On-Chip XRAM
0xFFFF
0x0000
Off-Chip
Memory
(Bank Select)
On-Chip XRAM
Off-Chip
Memory
C8051F040/1/2/3/4/5/6/7
194 Rev. 1.5
16.5.3. S plit Mode with Bank Select
When EMI0CF.[3:2] are set to ‘10’, the XRAM memory map is split into two areas, on-chip space and off-
chip space.
• Effective addresses below the 4k boundary will access on-chip XRAM space.
• Effective addresses above the 4k boundary will access off-chip space.
• 8-bit MOVX operations use the contents of EMI0CN to determine whether the memory access is on-
chip or off- chip. The upper 8-bits of the Address Bus A[15:8 ] are determined by EMI0CN, and the lower
8-bit s of the Address Bus A[7:0] are determined by R0 or R1. All 16-bits of the Add ress Bus A[15:0] are
driven in “Bank Select” mode.
• 16-bit MOVX operations use the contents of DPTR to determine whether the memory access is on-
chip or off-chip, and the full 16-bits of the Address Bus A[15:0] are driven during the off-chip transac-
tion.
16.5.4. External Only
When EMI0CF[3:2] are set to ‘11’, all MOVX operations are directed to off-chip space. On-chip XRAM is
not visible to the CPU. This mode is useful for accessing off-chip memo ry located betwee n 0x0000 and th e
4k boundary.
• 8-bit MOVX operations ignore the contents of EMI0CN. The upper Address bits A[15:8] are not driven
(identical behavior to an off-chip access in “Split Mode without Bank Select” described above). This
allows the user to manipulate the upper address bits at will by setting the Port state directly. The lower
8-bits of the effective address A[7:0] are determined by the contents of R0 or R1.
• 16-bit MOVX operations use th e content s o f DPTR to determine the ef fective addre ss A[15:0]. T he fu ll
16-bits of the Address Bus A[15:0 ] ar e dr ive n du rin g the off-chip trans act ion .
16.6. Timing
The timing parameters of the External Memory Interface can be configured to enable connection to
devices having different setup and hold ti me requiremen ts. The Address Setup tim e, Address Hold time , /
RD and
/WR strobe widths, and in multiplexed mode, the width of the ALE pulse are all programmable in units of
SYSCLK periods through EMI0TC, shown in SFR Definition 16.3, and EMI0CF[1:0].
The timing for an off-chip MOVX instruction can be calculated by adding 4 SYSCLK cycles to the timing
parameters defined by the EMI0TC register. Assuming non-multiplexed operation, the minimum execution
time for an off-chip XRAM operation is 5 SYSCLK cycles (1 SYSCLK for /RD or /WR pulse + 4 SYSCLKs).
For multiplexed operations, the Address Latch Enable signal will require a minimum of 2 additional SYS-
CLK cycles. Therefore, the minimum execution time of an off-chip XRAM operation in multiplexed mode is
7 SYSCLK cycles (2 SYSCLKs for /ALE, 1 for /RD or /WR + 4 SYSCLKs). The programmable setup and
hold times default to the maximum delay settings after a reset.
Table 16.1 lists the AC p a ra meters fo r the Exte rn al Me mory In terface , and Figu re 16.4 through F igur e 16.9
show the timing diagrams for the different External Memory Interface modes and MOVX operations.
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 195
SFR Definition 16.3. EMI0TC: External Memory Timing Control
Bits7-6: EAS1-0: EMIF Address Setup Time Bits.
00: Address setup time = 0 SYSCLK cycles.
01: Address setup time = 1 SYSCLK cycle.
10: Address setup time = 2 SYSCLK cycles.
11: Address setup time = 3 SYSCLK cycles.
Bits5-2: EWR3-0: EMIF /WR and /RD Pulse-Width Control Bits.
0000: /WR and /RD pulse width = 1 SYSCLK cycle.
0001: /WR and /RD pulse width = 2 SYSCLK cycles.
0010: /WR and /RD pulse width = 3 SYSCLK cycles.
0011: /WR and /RD pulse width = 4 SYSCLK cycles.
0100: /WR and /RD pulse width = 5 SYSCLK cycles.
0101: /WR and /RD pulse width = 6 SYSCLK cycles.
0110: /WR and /RD pulse width = 7 SYSCLK cycles.
0111: /WR and /RD pulse width = 8 SYSCLK cycles.
1000: /WR and /RD pulse width = 9 SYSCLK cycles.
1001: /WR and /RD pulse width = 10 SYSCLK cycles.
1010: /WR and /RD pulse width = 11 SYSCLK cycles.
1011: /WR and /RD pulse width = 12 SYSCLK cycles.
1100: /WR and /RD pulse width = 13 SYSCLK cycles.
1101: /WR and /RD pulse width = 14 SYSCLK cycles.
1110: /WR and /RD pulse width = 15 SYSCLK cycles.
1111: /WR and /RD pulse width = 16 SYSCLK cycles.
Bits1-0: EAH1-0: EMIF Address Hold Time Bits.
00: Address hold time = 0 SYSCLK cycles.
01: Address hold time = 1 SYSCLK cycle.
10: Address hold time = 2 SYSCLK cycles.
11: Address hold time = 3 SYSCLK cycles.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
EAS1 EAS0 ERW3 EWR2 EWR1 EWR0 EAH1 EAH0 11111111
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xA1
0
C8051F040/1/2/3/4/5/6/7
196 Rev. 1.5
16.6.1. Non-multiplexed Mode
16.6.1.1.16-bit MOVX: EMI0CF[4:2] = ‘101’, ‘110’, or ‘111’.
Figure 16.4. Non-multiplexed 16-bit MOVX Timing
EMIF ADDRESS (8 MSBs) from DPH
EMIF ADDRESS (8 LSBs) from DPLP2/P6
P1/P5
P0.7/P4.7
P0.6/P4.6
P3/P7 EMIF WRITE DATA
P2/P6
P1/P5
P0.7/P4.7
P0.6/P4.6
P3/P7
T
ACH
T
WDH
T
ACW
T
ACS
T
WDS
ADDR[15:8]
ADDR[7:0]
DATA[7:0]
/WR
/RD
EMIF ADDRESS (8 MSBs) from DPH
EMIF ADDRESS (8 LSBs) from DPLP2/P6
P1/P5
P0.6/P4.6
P0.7/P4.7
P3/P7
P2/P6
P1/P5
P0.6/P4.6
P0.7/P4.7
P3/P7
T
ACH
T
RDH
T
ACW
T
ACS
T
RDS
ADDR[15:8]
ADDR[7:0]
DATA[7:0]
/RD
/WR
EMIF READ DATA
Nonmuxed 16-bit WRITE
Nonmuxed 16-bit READ
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 197
16.6.1.2.8-bit MOVX without Bank Select: EMI0CF[4:2] = ‘101’ or ‘111’.
Figure 16.5. Non-multiplexed 8-bit MOVX without Bank Select Timing
EMIF ADDRESS (8 LSBs) from R0 or R1P2/P6
P1/P5
P0.7/P4.7
P0.6/P4.6
P3/P7 EMIF WRITE DATA
P2/P6
P0.7/P4.7
P0.6/P4.6
P3/P7
T
ACH
T
WDH
T
ACW
T
ACS
T
WDS
ADDR[15:8]
ADDR[7:0]
DATA[7:0]
/WR
/RD
EMIF ADDRESS (8 LSBs) from R0 or R1P2/P6
P1/P5
P0.6/P4.6
P0.7/P4.7
P3/P7
P2/P6
P0.6/P4.6
P0.7/P4.7
P3/P7
T
ACH
T
RDH
T
ACW
T
ACS
T
RDS
ADDR[15:8]
ADDR[7:0]
DATA[7:0]
/RD
/WR
EMIF READ DATA
Nonmuxed 8-bit WRITE without Bank Select
Nonmuxed 8-bit READ without Bank Select
C8051F040/1/2/3/4/5/6/7
198 Rev. 1.5
16.6.1.3.8-bit MOVX with Bank Select: EMI0CF[4:2] = ‘110’.
Figure 16.6. Non-multiplexed 8-bit MOVX with Bank Select Timing
EMIF ADDRESS (8 MSBs) from EMI0CN
EMIF ADDRESS (8 LSBs) from R0 or R1P2/P6
P1/P5
P0.7/P4.7
P0.6/P4.6
P3/P7 EMIF WRITE DATA
P2/P6
P1/P5
P0.7/P4.7
P0.6/P4.6
P3/P7
T
ACH
T
WDH
T
ACW
T
ACS
T
WDS
ADDR[15:8]
ADDR[7:0]
DATA[7:0]
/WR
/RD
EMIF ADDRESS (8 MSBs) from EMI0CN
EMIF ADDRESS (8 LSBs) from R0 or R1P2/P6
P1/P5
P0.6/P4.6
P0.7/P4.7
P3/P7
P2/P6
P1/P5
P0.6/P4.6
P0.7/P4.7
P3/P7
T
ACH
T
RDH
T
ACW
T
ACS
T
RDS
ADDR[15:8]
ADDR[7:0]
DATA[7:0]
/RD
/WR
EMIF READ DATA
Nonmuxed 8-bit WRITE with Bank Select
Nonmuxed 8-bit READ with Bank Select
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 199
16.6.2. Multiplexed Mode
16.6.2.1.16-bit MOVX: EMI0CF[4:2] = ‘001’, ‘010’, or ‘011’.
Figure 16.7. Multiplexed 16-bit MOVX Timing
P3/P7
P2/P6
P3/P7
ADDR[15:8]
AD[7:0]
P2/P6
P0.7/P4.7
P0.6/P4.6
P0.5/P4.5
P0.7/P4.7
P0.6/P4.6
P0.5/P4.5
T
ACH
T
WDH
T
ACW
T
ACS
T
WDS
ALE
/WR
/RD
EMIF ADDRESS (8 MSBs) from DPH
EMIF WRITE DATA
EMIF ADDRESS (8 LSBs) from
DPL
T
ALEH
T
ALEL
P3/P7
P2/P6
P3/P7
ADDR[15:8]
AD[7:0]
P2/P6
P0.6/P4.6
P0.7/P4.7
P0.5/P4.5
P0.6/P4.6
P0.7/P4.7
P0.5/P4.5
T
ACH
T
ACW
T
ACS
ALE
/RD
/WR
EMIF ADDRESS (8 MSBs) from DPH
EMIF ADDRESS (8 LSBs) from
DPL
T
ALEH
T
ALEL
T
RDH
T
RDS
EMIF READ DATA
Muxed 16-bit WRITE
Muxed 16-bit READ
C8051F040/1/2/3/4/5/6/7
200 Rev. 1.5
16.6.2.2.8-bit MOVX without Bank Select: EMI0CF[4:2] = ‘001’ or ‘011’.
Figure 16.8. Multiplexed 8-bit MOVX without Bank Select Timing
P3/P7
P2/P6
P3/P7
ADDR[15:8]
AD[7:0]
P0.7/P4.7
P0.6/P4.6
P0.5/P4.5
P0.7/P4.7
P0.6/P4.6
P0.5/P4.5
T
ACH
T
WDH
T
ACW
T
ACS
T
WDS
ALE
/WR
/RD
EMIF WRITE DATA
EMIF ADDRESS (8 LSBs) from
R0 or R1
T
ALEH
T
ALEL
P3/P7
P2/P6
P3/P7
ADDR[15:8]
AD[7:0]
P0.6/P4.6
P0.7/P4.7
P0.5/P4.5
P0.6/P4.6
P0.7/P4.7
P0.5/P4.5
T
ACH
T
ACW
T
ACS
ALE
/RD
/WR
EMIF ADDRESS (8 LSBs) from
R0 or R1
T
ALEH
T
ALEL
T
RDH
T
RDS
EMIF READ DATA
Muxed 8-bit WRITE Without Bank Select
Muxed 8-bit READ Without Bank Select
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 201
16.6.2.3.8-bit MOVX with Bank Select: EMI0CF[4:2] = ‘010’.
Figure 16.9. Multiplexed 8-bit MOVX with Bank Select Timing
P3/P7
P2/P6
P3/P7
ADDR[15:8]
AD[7:0]
P2/P6
P0.7/P4.7
P0.6/P4.6
P0.5/P4.5
P0.7/P4.7
P0.6/P4.6
P0.5/P4.5
T
ACH
T
WDH
T
ACW
T
ACS
T
WDS
ALE
/WR
/RD
EMIF ADDRESS (8 MSBs) from EMI0CN
EMIF WRITE DATA
EMIF ADDRESS (8 LSBs) from
R0 or R1
T
ALEH
T
ALEL
P3/P7
P2/P6
P3/P7
ADDR[15:8]
AD[7:0]
P2/P6
P0.6/P4.6
P0.7/P4.7
P0.5/P4.5
P0.6/P4.6
P0.7/P4.7
P0.5/P4.5
T
ACH
T
ACW
T
ACS
ALE
/RD
/WR
EMIF ADDRESS (8 MSBs) from EMI0CN
EMIF ADDRESS (8 LSBs) from
R0 or R1
T
ALEH
T
ALEL
T
RDH
T
RDS
EMIF READ DATA
Muxed 8-bit WRITE with Bank Select
Muxed 8-bit READ with Bank Select
C8051F040/1/2/3/4/5/6/7
202 Rev. 1.5
Table 16.1. AC Parameters for External Memory Interface
Parameter Description Min Max Units
TSYSCLK System Clock Period 40 — ns
TACS Address/Control Setup Time 0 3 x TSYSCLK ns
TACW Address/Control Pulse Width 1 x TSYSCLK 16 x TSYSCLK ns
TACH Address/Control Hold Time 0 3 x TSYSCLK ns
TALEH Address Latch Enable High Time 1 x TSYSCLK 4 x TSYSCLK ns
TALEL Address Latch Enable Low Time 1 x TSYSCLK 4 x TSYSCLK ns
TWDS Write Data Setup Time 1 x TSYSCLK 19 x TSYSCLK ns
TWDH Write Data Hold Ti me 0 3 x TSYSCLK ns
TRDS Read Data Setup Time 20 — ns
TRDH Read Data Hold Time 0—ns
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 203
17. Port Input/Output
The C8051F04x family of devices are fully integrated mixed-signal System on a Chip MCUs with 64 digital
I/O pins (C8051F040/2/4/6) or 32 digital I/O pins (C8051F041/3/5/7), organized as 8-b it Por ts. All ports are
both bit- and byte-addressable through their corresponding Port Data registers. All Port pins are 5 V-toler-
ant, and all support configurable Open-Drain or Push-Pull output modes and weak pullups. A block dia-
gram of the Port I/O cell is shown in Figure 17.1. Complete Electrical Specifications for the Port I/O pins
are given in Table 17.1.
Figure 17.1. Port I/O Cell Block Diagram
Table 17.1. Port I/O DC Electrical Characteristics
VDD = 2.7 to 3.6 V, –40 to +85 °C unless otherwise specified.
Parameter Conditions Min Typ Max Units
Output High Voltage
(VOH)
IOH = –3 mA, Port I/O Push-Pull
IOH = –10 µA, Port I/O Push-Pull
IOH = –10 mA, Port I/O Push-Pull
VDD – 0.7
VDD – 0.1
—
—
—
VDD – 0.8
—
—
—V
Output Low Voltage
(VOL)
IOL = 8.5 mA
IOL = 10 µA
IOL = 25 mA
—
—
—
—
—
1.0
0.6
0.1
—V
Input High Voltage (VIH) 0.7 x VDD ——
Input Low Voltage (VIL) — — 0.3 x VDD
Input Leakage Current DGND < Port Pin < VDD, Pin Tri-state
Weak Pullup Off
Weak Pullup On
—
—
—
—
—
10
—
± 1
—µA
Input Capacitance —5—pF
DGND
/PORT-OUTENABLE
PORT-OUTPUT
PUSH-PULL VDD VDD
/WEAK-PULLUP
(WEAK)
PORT
PAD
ANALOG INPUT
Analog Select
(Ports 1, 2, and 3)
PORT-INPUT
C8051F040/1/2/3/4/5/6/7
204 Rev. 1.5
The C8051F04x family of devices have a wide array of digital resources which are available through the
four lower I/O Ports: P0, P1, P2, and P3. Each of the pins on P0, P1, P2, and P3, can be defined as a Gen-
eral-Purpose I/O (GPIO) pin or can be controlled by a digital peripheral or function (like UART0 or /INT1 for
example), as shown in Figure 17.2. The system designer controls which digital functions are assigned
pins, limited only by the number of pins available. This resource assignment flexibility is achieved through
the use of a Priority Crossbar Decoder. The state of a Port I/O pin can always be read from its associated
Data r egister r ega rd less of wheth er that pin has bee n assigned to a d igital peripheral or behaves a s GPIO.
The Port pins on Ports 1, 2, and 3 can be used as Analog Input s to ADC2 (C8051F040/1/2/3 only), Analog
Voltage Comparators, and ADC0, respectively.
Figure 17.2. Port I/O Functional Block Diagram
An External Memory Interface, which is active during the execution of an off-chip MOVX instruction, can be
active on either the lower Ports or the upper Ports. See Section “16. External Data Memory Interface
and On-Chip XRAM” on page 187 for more information about the External Memory Interface.
17.1. Ports 0 through 3 and the Priority Crossbar Decoder
The Priority Crossbar Decoder, or “Crossbar”, allocates and assigns Port pins on Port 0 through Port 3 to
the digital peripherals (UARTs, SMBus, PCA, Timers, etc.) on the device using a priority order. The Port
pins are allocated in order starting with P0.0 and continue through P3.7, if necessary. The digital peripher-
als are assigned Port pins in a priority order which is listed in Figure 17.3, with UART0 having the highest
priority and CNVSTR2 having the lowest priority.
External
Pins
Digital
Crossbar
Priority
Decoder
SMBus
2
SPI 4
UART0
2
PCA
2
T0, T1,
T2, T2EX,
T3, T3EX,
T4,T4EX,
/INT0,
/INT1
P1.0
P1.7
P2.0
P2.7
P0.0
P0.7
Highest
Priority
Lowest
Priority
8
8
Comptr.
Outputs
(Internal Digital Signals)
Highest
Priority
Lowest
Priority
UART1
6
2
P3.0
P3.7
8
8
P0MDOUT, P1MDOUT,
P2MDOUT, P3MDOUT
Registers
XBR0, XBR1, XBR2,
XBR3 P1MDIN,
P2MDIN, P3MDIN
Registers
P1
I/O
Cells
P3
I/O
Cells
P0
I/O
Cells
P2
I/O
Cells
8
Port
Latches
P0
P1
P2
8
8
8
P3
8
(P2.0-P2.7)
(P1.0-P1.7)
(P0.0-P0.7)
(P3.0-P3.7)
To
ADC2
Input
To External
Memory
Interface
(EMIF) To
ADC0
Input
To
Comparators
/SYSCLK
CNVSTR0
CNVSTR2
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 205
Figure 17.3. Priority Crossbar Decode Table
(EMIFLE = 0; P1MDIN = 0xFF)
17.1.1. Crossbar Pin Assignment and Allocation
The Crossbar assigns Port pins to a peripheral if the corresponding enable bits of the peripheral are set to
a logic 1 in the Crossbar configuration registers XBR0, XBR1, XBR2, and XBR3, shown in SFR Definition
17.1, SFR Definition 17.2, SFR Definition 17.3, and SFR Definition 17.4. For example, if the UART0EN bit
(XBR0.2) is set to a logic 1, the TX0 and RX0 pins will be mapped to P0.0 and P0.1 respectively. Because
UART0 has the highest priority, its pins will always be mapped to P0.0 and P0.1 when UART0EN is set to
a logic 1. If a digital peripheral’s enable bits are not set to a logic 1, then its ports are not accessible at the
Port pins of the d evice. Also note tha t the Crossbar assign s pins to all associated fu nctions when a ser ial
communication peripheral is selected (i.e. SMBus, SPI, UART). It would be impossible, for example, to
assign TX0 to a Port pin without assigning RX0 as well. Each combination of enabled peripher als results in
a unique device pinout.
All Port pins on Ports 0 through 3 that are not allocated by the Crossbar can be accessed as General-Pur-
pose I/O (G PIO) pins by reading and writing the as sociated P ort Data registers (S ee SFR Defini tion 17.5,
PIN I/O 01234567012345670123456701234567
TX0
z
RX0
z
SCK
zz
MISO
zz
MOSI
zz
NSS
zz
NSS is not assigned to a port pin when the SPI is placed in 3-wire mode
SDA
z zzzzz
SCL
z zzzzz
TX1
z zzzzzzz
RX1
z zzzzzzz
CEX0
z zzzzzzzzz
CEX1
z zzzzzzzzz
CEX2
z zzzzzzzzz
CEX3
z zzzzzzzzz
CEX4
z zzzzzzzzz
CEX5
z zzzzzzzzz
ECI
zzzzzzzzzzzzzzzzz
ECI0E: XBR0.6
CP0
zzzzzzzzzzzzzzzzzz
CP0E: XBR0.7
CP1
zzzzzzzzzzzzzzzzzzz
CP1E: XBR1.0
CP2
zzzzzzzzzzzzzzzzzzzz
CP2E: XBR3.3
T0
zzzzzzzzzzzzzzzzzzzzz
T0E: XBR1.1
/INT0
zzzzzzzzzzzzzzzzzzzzzz
INT0E: XBR1.2
T1
zzzzzzzzzzzzzzzzzzzzzzz
T1E: XBR1.3
/INT1
zzzzzzzzzzzzzzzzzzzzzzzz
INT1E: XBR1.4
T2
zzzzzzzzzzzzzzzzzzzzzzzzz
T2E: XBR1.5
T2EX
zzzzzzzzzzzzzzzzzzzzzzzzzz
T2EXE: XBR1.6
T3
zzzzzzzzzzzzzzzzzzzzzzzzzzz
T3E: XBR3.0
T3EX
zzzzzzzzzzzzzzzzzzzzzzzzzzzz
T3EXE: XBR3.1
T4
zzzzzzzzzzzzzzzzzzzzzzzzzzzzz
T4E: XBR2.3
T4EX
zzzzzzzzzzzzzzzzzzzzzzzzzzzzzz
T4EXE: XBR2.4
/SYSCLK
zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz
SYSCKE: XBR1.7
CNVSTR0
zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz
CNVSTE0: XBR2.0
CNVSTR2
zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz
CNVSTE2: XBR3.2
ALE
/RD
/WR
AIN1.0/A8
AIN1.1/A9
AIN1.2/A10
AIN1.3/A11
AIN1.4/A12
AIN1.5/A13
AIN1.6/A14
AIN1.7/A15
A8m/A0
A9m/A1
A10m/A2
A11m/A3
A12m/A4
A13m/A5
A14m/A6
A15m/A7
AD0/D0
AD1/D1
AD2/D2
AD3/D3
AD4/D4
AD5/D5
AD6/D6
AD7/D7
XBR2.2
XBR0.[5:3]
UART0EN:
SPI0EN:
Crossbar Register Bits
XBR0.2
XBR0.1
XBR0.0SMB0EN:
AIN1 Inputs/Non-muxed Addr H Muxed Addr H/Non-muxed Addr L Muxed Data/Non-muxed Data
UART1EN:
PCA0ME:
P0 P1 P2 P3
C8051F040/1/2/3/4/5/6/7
206 Rev. 1.5
SFR Definition 17.7, SFR Definition 17.10, and SFR Definition 17.13), a set of SFRs which are both byte-
and bit-addressable. The ou tp ut states of Port pins tha t are allocated by the Crossbar are contro lled by the
digital peripheral that is mapped to those pins. Writes to the Port Data registers (or associated Port bits)
will have no effect on the states of these pins.
A Read of a Port Data register (or Port bit) will always return the logic state present at the pin itself, regard-
less of whether the Crossbar has allocated the pin for peripheral use or not. An exception to this occurs
during the execution of a read-modify-write instruction (ANL, ORL, XRL, CPL, INC, DEC, DJNZ, JBC,
CLR, SET, and the bitwise MOV operation). During the read cycle of the read-modify-write instruction, it is
the contents of the Port Data register, not the state of the Port pins themselves, which is read.
Because the Crossbar registers affect the pinout of the peripherals of the device, they are typically config-
ured in the initialization code of the syste m before th e periph erals themselves are con figured. Once config-
ured, the Crossbar registers are typically left alone.
Once the Crossbar registers have been properly configured, the Crossbar is enabled by setting XBARE
(XBR2.4) to a logic 1. Until XBARE is set to a logic 1, the output drivers on Ports 0 through 3 are
explicitly disabled in order to prevent possible contention on the Port pins while the Crossbar reg-
isters and other registers which can affect the device pinout are being written.
The output drivers on Crossbar-assigned input signals (like RX0, for example) are explicitly disabled; thus
the values of the Port Data registers and the PnMDOUT registers have no effect on the states of these
pins.
17.1.2. Configuring the Output Modes of the Port Pins
The output drivers on Ports 0 through 3 remain disabled until the Crossbar is enabled by setting XBARE
(XBR2.4) to a logic 1.
The output mode of each port pin can be configured to be either Open-Drain or Push-Pull. In the Push-Pull
configuration, writing a logic 0 to the associated bit in the Port Data register will cause the Port pin to be
driven to GND, and writing a logic 1 will cause the Port pin to be driven to VDD. In the Open-Drain configu-
ration, writing a logic 0 to the associated bit in the Port Data register will cause the Port pin to be driv en to
GND, and a logic 1 will cause the Port pin to assume a high-impedance state. The Open-Drain configura-
tion is useful to prevent contention between devices in systems where the Port pin participates in a sha red
interconnection in which multiple ou tputs are conn ected to the same p hysical wire (like the SDA signal on
an SMBus connection).
The output modes of the Port pins on Ports 0 through 3 are determined by the bits in the associated
PnMDOUT registers (See SFR Definition 17.6, SFR Definition 17.9, SFR Definition 17.12, and SFR Defini-
tion 17.15). For example, a logic 1 in P3MDOUT.7 will configure the output mode of P3.7 to Push-Pull; a
logic 0 in P3MDOUT.7 will configure the output mode of P3.7 to Open-Drain. A ll Port pins default to Open-
Drain output.
The PnMDOUT registers contro l th e o utput m ode s of the p or t pi ns rega rd less of wh ether the Cro ssbar h as
allocated the Port pin for a digital peripheral or not. The exceptions to this rule are: the Port pin s conne cted
to SDA, SCL, RX0 (if UART0 is in Mode 0), and RX1 (if UART1 is in Mode 0) are always configured as
Open-Drain outputs, regardless of the settings of the associated bits in the PnMDOUT registers.
17.1.3. Configuring Port Pins as Digital Inputs
A Port pin is configured as a digital input by setting its output mode to “Open-Drain” in the PnMDOUT reg-
ister and writing a logic 1 to the associated bit in the Port Data register. For example, P3.7 is configured as
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 207
a digital input by setting P3MDOUT.7 to a logic 0, which selects open-drain output mode, and P3.7 to a
logic 1, which disables the low-side output driver.
If the Port pin has been assigned to a digital peripheral by the Crossbar and that pin functions as an input
(for example RX0, the UART0 receive pin), then the output drivers on that pin are automatically disabled.
17.1.4. Weak Pullups
By default, each Port pin has an internal wea k pullup device ena bled which pro vides a resistive co nnection
(about 100 k) between the pin and VDD. The weak pullup devices can be globally disabled by writing a
logic 1 to the Weak Pullup Disable bit, (WEAKPUD, XBR2.7). The weak pullup is automatically deactivated
on any pin that is driving a logic 0; that is, an output pin will not contend with its own pullup device. The
weak pullup device can also be explicitly disabled on Ports 1, 2, and 3 pin by configuring the pin as an
Analog Input, as described below.
17.1.5. Configuring Port 1, 2, and 3 Pins as Analog Inputs
The pins on Port 1 can serve as analog inputs to the ADC2 analog MUX (C80 51 F040/1/2/3 only), the pins
on Port 2 can serve as analog inputs to the Comparators, and the pins on Port 3 can serve as inputs to
ADC0. A Port pin is con figur ed as an Ana log I nput by writing a logic 0 to the as sociat ed bit in t he PnM DIN
registers. All Port pins default to a Digital Input mode. Configuring a Port pin as an analog input:
1. Disables the digital input path from the pin. This prevents additional power supp ly cu rrent fro m
being drawn when the voltage at the pin is near VDD / 2. A read of the Port Data bit will return
a logic 0 regardless of the voltage at the Port pin .
2. Disables the weak pu llu p de vice on the pin .
3. Causes the Crossbar to “skip over” the pin when allocating Port pins for digital peripherals.
Note that the output drivers on a pin configured as an Analog Input are not explicitly disabled. Therefore,
the associated PnMDOUT bits of pins configured as Analog Inputs should explicitly be set to logic 0
(Open-Drain output mode), and the associated Port Data bits should be set to logic 1 (high-impedance).
Also note that it is not required to configure a Port pin as an Analog Input in order to use it as an input to
the ADC’s or Comparators; however, it is strongly recommended. See the analog peripheral’s correspond-
ing section in this datasheet for further information.
C8051F040/1/2/3/4/5/6/7
208 Rev. 1.5
17.1.6. External Memory Interface Pin Assignments
If the External Memory Interface (EMIF) is enabled on th e Low port s (Ports 0 through 3), EMIFLE (XBR2.5)
should be set to a logic 1 so that the Crossbar will not assign peripherals to P0.7 (/WR), P0.6 (/RD), and, if
the External Memory Interface is in Multiplexed mo de, P0.5 (ALE ). Figure 17.4 shows a n example Cro ss-
bar Decode Table with EMIFLE=1 and the EMIF in Multiplexed mode. Figure 17.5 shows an example
Crossbar Decode Table with EMIFLE=1 and the EMIF in Non-multiplexed mode.
If the External Memory Interface is enabled on the Low ports and an off-chip MOVX operation occurs, the
External Memory Interface will control the output states (logic 1 or logic 0) of the affected Port pins during
the execution phase of the MOVX instruction, regardless of the settings of the Crossbar registers or the
Port Data registers. The output configuration (push-pull or open-drain) of the Port pins is not affected by
the EMIF operation, except that Read operations will explicitly disable the output drivers on the Data Bus.
In most cases, GPIO pins used in EMIF operations (especially the /WR and /RD lines) should be
configured as push-pull and ‘parked’ at a logic 1 state. See Section “16. External Data Memory
Interface and On-Chip XRAM” on page 187 for more information about the External Memo ry In ter fa ce .
Figure 17.4. Priority Crossbar Decode Table
(EMIFLE = 1; EMIF in Multiplexed Mode; P1MDIN = 0xFF)
PIN I/O 01234567012345670123456701234567
TX0
z
RX0
z
SCK
zz
MISO
zz
MOSI
zz
NSS
zzNSS is not assigned to a port pin when the SPI is placed in 3-wire mode
SDA
z zzz zz
SCL
z zz zzz
TX1
z zzz zzzz
RX1
z zz zzzzz
CEX0
z zzz zzzzzz
CEX1
z zz zzzzzzz
CEX2
z z zzzzzzzz
CEX3
z zzzzzzzzz
CEX4
z zzzzzzzzz
CEX5
z zzzzzzzzz
ECI
zzzzz zzzzzzzzzzzz
ECI0E: XBR0.6
CP0
zzzzz zzzzzzzzzzzzz
CP0E: XBR0.7
CP1
zzzzz zzzzzzzzzzzzzz
CP1E: XBR1.0
CP2
zzzzz zzzzzzzzzzzzzzz
CP2E: XBR3.3
T0
zzzzz zzzzzzzzzzzzzzzz
T0E: XBR1.1
/INT0
zzzzz zzzzzzzzzzzzzzzzz
INT0E: XBR1.2
T1
zzzzz zzzzzzzzzzzzzzzzzz
T1E: XBR1.3
/INT1
zzzzz zzzzzzzzzzzzzzzzzzz
INT1E: XBR1.4
T2
zzzzz zzzzzzzzzzzzzzzzzzzz
T2E: XBR1.5
T2EX
zzzzz zzzzzzzzzzzzzzzzzzzzz
T2EXE: XBR1.6
T3
zzzzz zzzzzzzzzzzzzzzzzzzzzz
T3E: XBR3.0
T3EX
zzzzz zzzzzzzzzzzzzzzzzzzzzzz
T3EXE: XBR3.1
T4
zzzzz zzzzzzzzzzzzzzzzzzzzzzzz
T4E: XBR2.3
T4EX
zzzzz zzzzzzzzzzzzzzzzzzzzzzzz
T4EXE: XBR2.4
/SYSCLK
zzzzz zzzzzzzzzzzzzzzzzzzzzzzz
SYSCKE: XBR1.7
CNVSTR0
zzzzz zzzzzzzzzzzzzzzzzzzzzzzz
CNVSTE0: XBR2.0
CNVSTR2
zzzzz zzzzzzzzzzzzzzzzzzzzzzzz
CNVSTE2: XBR3.2
ALE
/RD
/WR
AIN1.0/A8
AIN1.1/A9
AIN1.2/A10
AIN1.3/A11
AIN1.4/A12
AIN1.5/A13
AIN1.6/A14
AIN1.7/A15
A8m/A0
A9m/A1
A10m/A2
A11m/A3
A12m/A4
A13m/A5
A14m/A6
A15m/A7
AD0/D0
AD1/D1
AD2/D2
AD3/D3
AD4/D4
AD5/D5
AD6/D6
AD7/D7
XBR2.2
XBR0.[5:3]
UART0EN:
SPI0EN:
Crossbar Register Bits
XBR0.2
XBR0.1
XBR0.0SMB0EN:
AIN1 Inputs/Non-muxed Addr H Muxed Addr H/Non-muxed Addr L Muxed Data/Non-muxed Data
UART1EN:
PCA0ME:
P0 P1 P2 P3
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 209
Figure 17.5. Priority Crossbar Decode Table
(EMIFLE = 1; EMIF in Non-multiplexed Mode; P1MDIN = 0xFF)
PIN I/O 01234567012345670123456701234567
TX0
z
RX0
z
SCK
zz
MISO
zz
MOSI
zz
NSS
zz NSS is not assigned to a port pin when the SPI is placed in 3-wire mode
SDA
z zzzz z
SCL
z zzz zz
TX1
z zzzz zzz
RX1
z zzz zzzz
CEX0
z zzzz zzzzz
CEX1
z zzz zzzzzz
CEX2
zzz zzzzzzz
CEX3
zz zzzzzzzz
CEX4
zzzzzzzzzz
CEX5
zzzzzzzzzz
ECI
zzzzzz zzzzzzzzzzz
ECI0E: XBR0.6
CP0
zzzzzz zzzzzzzzzzzz
CP0E: XBR0.7
CP1
zzzzzz zzzzzzzzzzzzz
CP1E: XBR1.0
CP2
zzzzzz zzzzzzzzzzzzzz
CP2E: XBR3.3
T0
zzzzzz zzzzzzzzzzzzzzz
T0E: XBR1.1
/INT0
zzzzzz zzzzzzzzzzzzzzzz
INT0E: XBR1.2
T1
zzzzzz zzzzzzzzzzzzzzzzz
T1E: XBR1.3
/INT1
zzzzzz zzzzzzzzzzzzzzzzzz
INT1E: XBR1.4
T2
zzzzzz zzzzzzzzzzzzzzzzzzz
T2E: XBR1.5
T2EX
zzzzzz zzzzzzzzzzzzzzzzzzzz
T2EXE: XBR1.6
T3
zzzzzz zzzzzzzzzzzzzzzzzzzzz
T3E: XBR3.0
T3EX
zzzzzz zzzzzzzzzzzzzzzzzzzzzz
T3EXE: XBR3.1
T4
zzzzzz zzzzzzzzzzzzzzzzzzzzzzz
T4E: XBR2.3
T4EX
zzzzzz zzzzzzzzzzzzzzzzzzzzzzzz
T4EXE: XBR2.4
/SYSCLK
zzzzzz zzzzzzzzzzzzzzzzzzzzzzzz
SYSCKE: XBR1.7
CNVSTR0
zzzzzz zzzzzzzzzzzzzzzzzzzzzzzz
CNVSTE0: XBR2.0
CNVSTR2
zzzzzz zzzzzzzzzzzzzzzzzzzzzzzz
CNVSTE2: XBR3.2
ALE
/RD
/WR
AIN1.0/A8
AIN1.1/A9
AIN1.2/A10
AIN1.3/A11
AIN1.4/A12
AIN1.5/A13
AIN1.6/A14
AIN1.7/A15
A8m/A0
A9m/A1
A10m/A2
A11m/A3
A12m/A4
A13m/A5
A14m/A6
A15m/A7
AD0/D0
AD1/D1
AD2/D2
AD3/D3
AD4/D4
AD5/D5
AD6/D6
AD7/D7
XBR2.2
XBR0.[5:3]
UART0EN:
SPI0EN:
Crossbar Register Bits
XBR0.2
XBR0.1
XBR0.0SMB0EN:
AIN1 Inputs/Non-muxed Addr H Muxed Addr H/Non-muxed Addr L Muxed Data/Non-muxed Data
UART1EN:
PCA0ME:
P0 P1 P2 P3
C8051F040/1/2/3/4/5/6/7
210 Rev. 1.5
17.1.7. Crossbar Pin Assignment Example
In this example (Figure 17.6), we configure the Crossbar to allocate Port pins for UART0, the SMBus,
UART1, /INT0, and /INT1 (8 pins total). Additionally, we configure the External Memory Interface to oper-
ate in Multiplexed mode and to appear on the Low ports. Further, we configure P1.2, P1.3, and P1.4 for
Analog Input mode so that the voltages at these pins can be measured by ADC2. The configuration steps
are as follows:
1. XBR0, XBR1, and XBR2 are set such that UART0EN = 1, SMB0EN = 1, INT0E = 1, INT1E =
1, and EMIFLE = 1. Thus: XBR0 = 0x05, XBR1 = 0x14, and XBR2 = 0x02.
2. We configure the External Memory Interface to use Multiplexed mode and to appear on the
Low ports. PRTSEL = 0, EMD2 = 0.
3. We configure the desired Port 1 pins to Analog Input mode by setting P1MDIN to 0xE3 (P1.4,
P1.3, and P1.2 are Analog Inputs, so their associated P1MDIN bits are set to logic 0).
4. We enable the Crossbar by setting XBARE = 1: XBR2 = 0x42.
- UART0 has the highest priority, so P0.0 is assigned to TX0, and P0.1 is assigned to RX0.
- The SMBus is next in priority order, so P0.2 is assigned to SDA, and P0.3 is assigned to
SCL.
- UART1 is next in priority order, so P0.4 is assigned to TX1. Because the External Memory
Interface is selected on the lower Ports, EMIFLE = 1, which causes the Crossbar to skip
P0.6 (/RD) and P0.7 (/WR). Because the External Memory Interface is con fig ured in Mu lti-
plexed mode, the Crossbar will also skip P0.5 (ALE). RX1 is assigned to the next non-
skipped pin, which in this case is P1.0.
- /INT0 is next in priority order, so it is assigned to P1.1.
- P1MDIN is set to 0xE3, which configures P1.2, P1.3, and P1.4 as Analog Inputs, causing
the Crossbar to skip these pins.
- /INT1 is next in priority order, so it is assigned to the next non-skipped pin, which is P1.5.
- The External Memory Interface will drive Ports 2 and 3 (denoted by red dots in
Figure 17.6) during the execution of an off-chip MOVX instruction.
5. We set the UART0 TX pin (TX0, P0.0) and UART1 TX pin (TX1, P0.4) outputs to Push-Pull by
setting P0MDOUT = 0x11.
6. We configure all EMIF-controlled p ins to push- pull output m ode by setting P0MDOUT |= 0xE0;
P2MDOUT = 0xFF; P3MDOUT = 0xFF.
7. We explicitly disable the output drivers on the 3 Analog Input pins by setting P1MDOUT =
0x00 (configure outputs to Open-Drain) and P1 = 0xFF (a logic 1 selects the high-impedance
state).
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 211
Figure 17.6. Crossbar Example:
(EMIFLE = 1; EMIF in Multiplexed Mode; P1MDIN = 0xE3;
XBR0 = 0x05; XBR1 = 0x14; XBR2 = 0x42)
PIN I/O 01234567012345670123456701234567
TX0
z
RX0
z
SCK
zz
MISO
zz
MOSI
zz
NSS
zz
SDA
zzzz zz
SCL
zzzzzz
TX1
zzzzzz zz
RX1
zzz zz zzz
CEX0
z zzz zz zzzz
CEX1
zzzzzzzzzz
CEX2
z z zz zzzzzz
CEX3
z zz zzzzzzz
CEX4
z z zzzzzzzz
CEX5
z zzzzzzzzz
ECI
zzzzz zz zzzzzzzzzz
ECI0E: XBR0.6
CP0
zzzzz zz zzzzzzzzzzz
CP0E: XBR0.7
CP1
zzzzz zz zzzzzzzzzzzz
CP1E: XBR1.0
CP2
zzzzz zz zzzzzzzzzzzzz
CP2E: XBR3.2
T0
zzzzz zz zzzzzzzzzzzzzz
T0E: XBR1.1
/INT0
zzzzz zzzzzzzzzzzzzzzzz
INT0E: XBR1.2
T1
zzzzz zz zzzzzzzzzzzzzzzz
T1E: XBR1.3
/INT1
zzzzz zz zzzzzzzzzzzzzzzzz
INT1E: XBR1.4
T2
zzzzz zz zzzzzzzzzzzzzzzzzz
T2E: XBR1.5
T2EX
zzzzz zz zzzzzzzzzzzzzzzzzzz
T2EXE: XBR1.6
T3
zzzzz zz zzzzzzzzzzzzzzzzzzz
T3E: XBR3.0
T3EX
zzzzz zz zzzzzzzzzzzzzzzzzzz
T3EXE: XBR3.1
T4
zzzzz zz zzzzzzzzzzzzzzzzzzz
T4E: XBR2.3
T4EX
zzzzz zz zzzzzzzzzzzzzzzzzzz
T4EXE: XBR2.4
/SYSCLK
zzzzz zz zzzzzzzzzzzzzzzzzzz
SYSCKE: XBR1.7
CNVSTR0
zzzzz zz zzzzzzzzzzzzzzzzzzz
CNVSTE0: XBR2.0
CNVSTR2
zzzzz zz zzzzzzzzzzzzzzzzzzz
CNVSTE2: XBR3.2
ALE
/RD
/WR
AIN1.0/A8
AIN1.1/A9
AIN1.2/A10
AIN1.3/A11
AIN1.4/A12
AIN1.5/A13
AIN1.6/A14
AIN1.7/A15
A8m/A0
A9m/A1
A10m/A2
A11m/A3
A12m/A4
A13m/A5
A14m/A6
A15m/A7
AD0/D0
AD1/D1
AD2/D2
AD3/D3
AD4/D4
AD5/D5
AD6/D6
AD7/D7
XBR2.2
XBR0.[5:3]
UART0EN:
SPI0EN:
Crossbar Register Bits
XBR0.2
XBR0.1
XBR0.0SMB0EN:
AIN1 Inputs/Non-muxed Addr H Muxed Addr H/Non-muxed Addr L Muxed Data/Non-muxed Data
UART1EN:
PCA0ME:
P0 P1 P2 P3
C8051F040/1/2/3/4/5/6/7
212 Rev. 1.5
SFR Definition 17.1. XBR0: Port I/O Crossbar Register 0
Bit7: CP0E: Comparator 0 Output Enable Bit.
0: CP0 unavailable at Port pin.
1: CP0 routed to Port pin.
Bit6: ECI0E: PCA0 External Counter Input Enable Bit.
0: PCA0 External Counter Input unavailable at Port pin.
1: PCA0 External Counter Input (ECI0) routed to Port pin.
Bits5-3: PCA0ME: PCA0 Module I/O Enable Bits.
000: All PCA0 I/O unavailable at port pins.
001: CEX0 routed to port pin.
010: CEX0, CEX1 routed to 2 port pins.
011: CEX0, CEX1, and CEX2 routed to 3 port pins.
100: CEX0, CEX1, CEX2, and CEX3 routed to 4 port pins.
101: CEX0, CEX1, CEX2, CEX3, and CEX4 routed to 5 port pins.
110: CEX0, CEX1, CEX2, CEX3, CEX4, and CEX5 routed to 6 port pins.
Bit2: UART0EN: UART0 I/O Enable Bit.
0: UART0 I/O unavailable at Port pins.
1: UART0 TX routed to P0.0, and RX routed to P0.1.
Bit1: SPI0EN: SPI0 Bus I/O Enable Bit.
0: SPI0 I/O unavailable at Port pins.
1: SPI0 SCK, MISO, MOSI, and NSS routed to 4 Port pins. Note that the NSS signal is not
assigned to a port pin if the SPI is in 3-wire mode. See Section “20. Enhanced Seri al
Peripheral Interface (SPI0)” on page 255 for more information.
Bit0: SMB0EN: SMBus0 Bus I/O Enable Bit.
0: SMBus0 I/O unavailable at Port pins.
1: SMBus0 SDA and SCL routed to 2 Port pins.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
CP0E ECI0E PCA0ME UART0EN SPI0EN SMB0EN 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xE1
F
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 213
SFR Definition 17.2. XBR1: Port I/O Crossbar Register 1
Bit7: SYSCKE: /SYSCLK Output Enable Bit.
0: /SYSCLK unavailable at Port pin.
1: /SYSCLK routed to Port pin.
Bit6: T2EXE: T2EX Input Enable Bit.
0: T2EX unavailable at Port pin.
1: T2EX routed to Port pin.
Bit5: T2E: T2 Input Enable Bit.
0: T2 unavailable at Port pin.
1: T2 routed to Port pin.
Bit4: INT1E: /INT1 Input Enable Bit.
0: /INT1 unavaila b le at Por t pin .
1: /INT1 routed to Port pin.
Bit3: T1E: T1 Input Enable Bit.
0: T1 unavailable at Port pin.
1: T1 routed to Port pin.
Bit2: INT0E: /INT0 Input Enable Bit.
0: /INT0 unavaila b le at Por t pin .
1: /INT0 routed to Port pin.
Bit1: T0E: T0 Input Enable Bit.
0: T0 unavailable at Port pin.
1: T0 routed to Port pin.
Bit0: CP1E: CP1 Output Enable Bit.
0: CP1 unavailable at Port pin.
1: CP1 routed to Port pin.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
SYSCKE T2EXE T2E INT1E T1E INT0E T0E CP1E 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xE2
F
C8051F040/1/2/3/4/5/6/7
214 Rev. 1.5
SFR Definition 17.3. XBR2: Port I/O Crossbar Register 2
Bit7: WEAKPUD: Weak PullUp Disable Bit.
0: Weak pullups globally enabled.
1: Weak pullups globally disabled.
Bit6: XBARE: Crossbar Enable Bit.
0: Crossbar disabled. All pins on Ports 0, 1, 2, and 3, are forced to Input mode.
1: Crossbar enabled.
Bit5: UNUSED. Read = 0, Write = don't care.
Bit4: T4EXE: T4EX Input Enable Bit.
0: T4EX unavailable at Port pin.
1: T4EX routed to Port pin.
Bit3: T4E: T4 Input Enable Bit.
0: T4 unavailable at Port pin.
1: T4 routed to Port pin.
Bit2: UART1E: UART1 I/O Enable Bit.
0: UART1 I/O unavailable at Port pins.
1: UART1 TX and RX routed to 2 Port pins.
Bit1: EMIFLE: External Memory Interface Low-Port Enable Bit.
0: P0.7, P0.6, and P0.5 fu nctions are determined by the Crossbar or the Port latches.
1: If EMI0CF.4 = ‘0’ (External Memory Interface is in Multiplexed mode)
P0.7 (/WR), P0.6 (/RD), and P0.5 (ALE) are ‘skippe d’ by the Cro ssbar a nd thei r out-
put states are determined by the Port latches and the External Memory Interface.
1: If EMI0CF.4 = ‘1’ (External Memory Interface is in Non-multiplexed mode)
P0.7 (/WR) and P0.6 (/RD) are ‘skipped’ by the Crossb ar and their output st ates are
determined by the Port latches and the External Memory Interface.
Bit0: CNVST0E: ADC0 External Convert Start Input Enable Bit.
0: CNVST0 for ADC0 unava ilab le at Port pin .
1: CNVST0 for ADC0 routed to Port pin.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
WEAKPUD XBARE — T4EXE T4E UART1E EMIFLE CNVST0E 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xE3
F
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 215
SFR Definition 17.4. XBR3: Port I/O Crossbar Register 3
SFR Definition 17.5. P0: Port0 Data
Bit7: CTXOUT: CAN Transmit Pin (CTX) Output Mode.
0: CTX pin output mode is configured as open-drain.
1: CTX pin output mode is configured as push-pull.
Bit6-4: Reserved
Bit3: CP2E: CP2 Output Enable Bit.
0: CP2 unavailable at Port pin.
1: CP2 routed to Port pin.
Bit2: CNVST2E: ADC2 External Convert Start Input Enable Bit (C8051F040/1/2/3 only).
0: CNVST2 for ADC2 unava ilab le at Port pin .
1: CNVST2 for ADC2 routed to Port pin.
Bit1: T3EXE: T3EX Input Enable Bit.
0: T3EX unavailable at Port pin.
1: T3EX routed to Port pin.
Bit0: T3E: T3 Input Enable Bit.
0: T3 unavailable at Port pin.
1: T3 routed to Port pin.
R/W R R R R /W R/W R/W R/W Reset Value
CTXOUT — — — CP2E CNVST2E T3EXE T3E 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xE4
F
Bits7-0: P0.[7:0]: Port0 Output Latch Bits.
(Write - Output appears on I/O pins per XBR0, XBR1, XBR2, and XBR3 Registers)
0: Logic Low Output.
1: Logic High Output (open if corresponding P0MDOUT.n bit = 0).
(Read - Regardless of XBR0, XBR1, XBR2, and XBR3 Register settings).
0: P0.n pin is logic low.
1: P0.n pin is logic high.
Note: P0.7 (/WR), P0.6 (/RD), and P0.5 (ALE) can be driven by the External Data Memory
Interface. See Section “16. External Data Memory Interface and On-Chip XRAM” on
page 187 for more information. See also SFR Definition 17.3 for information about configur-
ing the Crossbar for External Memory accesses.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
P0.7 P0.6 P0.5 P0.4 P0.3 P0.2 P0.1 P0.0 11111111
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 Bit
Addressable
SFR Address:
SFR Page: 0x80
All Pages
C8051F040/1/2/3/4/5/6/7
216 Rev. 1.5
SFR Definition 17.6. P0MDOUT: Port0 Output Mode
SFR Definition 17.7. P1: Port1 Data
Bits7-0: P0MDOUT.[7:0]: Port0 Output Mode Bits.
0: Port Pin output mode is configured as Open-Drain.
1: Port Pin output mode is configured as Push-Pull.
Note: SDA, SCL, and RX0 (when UART0 is in Mode 0) and RX1 (when UART1 is in Mode 0) are
always configured as Open-Drain when they appear on Port pins.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xA4
F
Bits7-0: P1.[7:0]: Port1 Output Latch Bits.
(Write - Output appears on I/O pins per XBR0, XBR1, XBR2, and XBR3 Registers)
0: Logic Low Output.
1: Logic High Output (open if corresponding P1MDOUT.n bit = 0).
(Read - Regardless of XBR0, XBR1, XBR2, and XBR3 Register settings).
0: P1.n pin is logic low.
1: P1.n pin is logic high.
Notes:
1. P1.[7:0] can be configured as input s to ADC1 as AIN1.[7:0], in which case they are ‘skip ped’
by the Crossbar assignmen t process and their digit al input paths are disabled , depending on
P1MDIN (See SFR Definition 17.8 ). Note that in analog mode, the output mode of the pin is
determined by the Port 1 latch and P1MDOUT (SFR Definition 17.9). See Section “7. 8-Bit
ADC (ADC2, C8051F040/1/2/3 Only)” on page 91 for more information about ADC2.
2. P1.[7:0] can be driven by the External Dat a Memo ry Interface (as Addre ss[15:8] in Non-mul-
tiplexed mode). See Section “16. External Data Memory Interface and On-Chip XRAM”
on page 187 for more information about the External Memory Interface.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
P1.7 P1.6 P1.5 P1.4 P1.3 P1.2 P1.1 P1.0 11111111
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 Bit
Addressable
SFR Address:
SFR Page: 0x90
All Pages
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 217
SFR Definition 17.8. P1MDIN: Port1 Input Mode
SFR Definition 17.9. P1MDOUT: Port1 Output Mode
Bits7-0: P1MDIN.[7:0]: Port 1 Input Mode Bits.
0: Port Pin is configured in Analog Input mo de. The digital input path is disabled (a read from
the Port bit will always return ‘0’). The weak pullup on the pin is disabled.
1: Port Pin is configured in Digital Input mode. A read from the Port bit will return the logic
level at the Pin. The state of the weak pullup is determined by the WEAKPUD bit (XBR2.7,
see SFR Definition 17.3).
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
11111111
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xAD
F
Bits7-0: P1MDOUT.[7:0]: Port1 Output Mode Bits.
0: Port Pin output mode is configured as Open-Drain.
1: Port Pin output mode is configured as Push-Pull.
Note: SDA, SCL, and RX0 (when UART0 is in Mode 0) and RX1 (when UART1 is in Mode 0) are
always configured as Open-Drain when they appear on Port pins.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xA5
F
C8051F040/1/2/3/4/5/6/7
218 Rev. 1.5
SFR Definition 17.10. P2: Port2 Data
SFR Definition 17.11. P2MDIN: Port2 Input Mode
Bits7-0: P2.[7:0]: Port2 Output Latch Bits.
(Write - Output appears on I/O pins per XBR0, XBR1, XBR2, and XBR3 Registers)
0: Logic Low Output.
1: Logic High Output (open if corresponding P2MDOUT.n bit = 0).
(Read - Regardless of XBR0, XBR1, XBR2, and XBR3 Register settings).
0: P2.n pin is logic low.
1: P2.n pin is logic high.
Note: P2.[7:0] can be driven by the External Data Memory Interface (as Address[15:8] in Multi-
plexed mode, or as Address[7:0] in Non-multiplexed mode). See Section “16. External
Dat a Memor y Inter face and On-Ch ip XRAM” on page 187 for more info rmatio n about the
External Memory Interface.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
P2.7 P2.6 P2.5 P2.4 P2.3 P2.2 P2.1 P2.0 11111111
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 Bit
Addessable
SFR Address:
SFR Page: 0xA0
All Pages
Bits7-0: P1MDIN.[7:0]: Port 2 Input Mode Bits.
0: Port Pin is configured in Analog Input mo de. The digital input path is disabled (a read from
the Port bit will always return ‘0’). The weak pullup on the pin is disabled.
1: Port Pin is configured in Digital Input mode. A read from the Port bit will return the logic
level at the Pin. The state of the weak pullup is determined by the WEAKPUD bit (XBR2.7,
see SFR Definition 17.3).
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
11111111
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xAE
F
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 219
SFR Definition 17.12. P2MDOUT: Port2 Output Mode
SFR Definition 17.13. P3: Port3 Data
Bits7-0: P2MDOUT.[7:0]: Port2 Output Mode Bits.
0: Port Pin output mode is configured as Open-Drain.
1: Port Pin output mode is configured as Push-Pull.
Note: SDA, SCL, and RX0 (when UART0 is in Mode 0) and RX1 (when UART1 is in Mode 0) are
always configured as Open-Drain when they appear on Port pins.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xA6
F
Bits7-0: P3.[7:0]: Port3 Output Latch Bits.
(Write - Output appears on I/O pins per XBR0, XBR1, XBR2, and XBR3 Registers)
0: Logic Low Output.
1: Logic High Output (open if corresponding P3MDOUT.n bit = 0).
(Read - Regardless of XBR0, XBR1, XBR2, and XBR3 Register settings).
0: P3.n pin is logic low.
1: P3.n pin is logic high.
Note: P3.[7:0] can be driven by the External Data Memory Interface (as AD[7:0] in Multiplexed
mode, or as D[7:0] in Non-multiplexed mode). See Section “16. External Data Memory
Interface and On-C hip XRAM” on page 187 for more information about the Extern al Mem-
ory Interface.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
P3.7 P3.6 P3.5 P3.4 P3.3 P3.2 P3.1 P3.0 11111111
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 Bit
Addressable
SFR Address:
SFR Page: 0xB0
All Pages
C8051F040/1/2/3/4/5/6/7
220 Rev. 1.5
SFR Definition 17.14. P3MDIN: Port3 Input Mode
SFR Definition 17.15. P3MDOUT: Port3 Output Mode
17.2. Ports 4 through 7
On C8051F040/2/4/6 devices, all Port pins on Ports 4 through 7 can be accessed as General-Purpose I/O
(GPIO) pins by reading and writing the associated Port Data registers (See SFR Definition 17.16, SFR
Definition 17.18, SFR Definition 17.20, and SFR Definition 17.22 located on SFR Page F), a set of SFRs
which are both bit and byte-addressable.
A Read of a Port Data register (or Port bit) will always return the logic state present at the pin itself, regard-
less of whether the Crossbar has allocated the pin for peripheral use or not. An exception to this occurs
during the execution of a read-modify-write instruction (ANL, ORL, XRL, CPL, INC, DEC, DJNZ, JBC,
CLR, SET, and the bitwise MOV operation). During the read cycle of the read-modify-write instruction, it is
the contents of the Port Data register, not the state of the Port pins themselves, which is read.
Bits7-0: P1MDIN.[7:0]: Port 3 Input Mode Bits.
0: Port Pin is configured in Analog Input mo de. The digital input path is disabled (a read from
the Port bit will always return ‘0’). The weak pullup on the pin is disabled.
1: Port Pin is configured in Digital Input mode. A read from the Port bit will return the logic
level at the Pin. The state of the weak pullup is determined by the WEAKPUD bit (XBR2.7,
see SFR Definition 17.3).
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
11111111
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xAF
F
Bits7-0: P2MDOUT.[7:0]: Port3 Output Mode Bits.
0: Port Pin output mode is configured as Open-Drain.
1: Port Pin output mode is configured as Push-Pull.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xA7
F
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 221
17.2.1. Configuring Ports Which are Not Pinned Out
Although P4, P5, P6, and P7 are not brought out to pins on the C8051F041/3/5/7 devices, the Port Data
registers are still present and can be used by software. Because the digital input paths also remain active,
it is recommended that these pins not be left in a ‘floating’ state in order to avoid unnecessary power dissi-
pation arising from the inputs floating to non-valid logic levels. This condition ca n be prevented by any of
the following:
1. Leave the weak pullup de vice s en a ble d by setting WEAKPUD (XBR2.7) to a logic 0.
2. Configure the output modes of P4, P5, P6, and P7 to “Push-Pull” by writing PnOUT = 0xFF.
3. Force the output states of P4, P5, P6, and P7 to logic 0 by writing zer os to the Por t Dat a regi s-
ters: P4 = 0x00, P5 = 0x00, P6= 0x00, and P7 = 0x00.
17.2.2. Configuring the Output Modes of the Port Pins
The output mode of each port pin can be configured to be either Open-Drain or Push-Pull. In the Push-Pull
configuration, a logic 0 in the associated bit in the Port Data register will cause the Port pin to be driven to
GND, and a logic 1 will cause the Port pin to be driven to VDD. In the Open-Drain configuration, a logic 0 in
the associated bit in the Port Data register will cause the Port pin to be driven to GND, and a logic 1 will
cause the Port pin to assume a high-impedance state. The Open-Drain configuration is useful to prevent
contention between devices in systems where the Port pin participates in a shared interconnection in
which multiple outputs are connected to the same physical wire.
The output modes of the Port pins on Ports 4 through 7 are determined by the bits in their respective
PnMDOUT Output Mode Registers. Each bit in PnMDOUT controls the output mode of its corresponding
port pin (see SFR De finition 17.17 , SFR Definition 17 .1 9, SFR Definition 17 .2 1, and SF R De fini tion 1 7.23 ).
For example, to place Port pin 4.3 in push-pull mode (digital output), set P4MDOUT.3 to logic 1. All port
pins default to open-drain mode upon device reset.
17.2.3. Configuring Port Pins as Digital Inputs
A Port pin is configured as a digital input by setting its output mode to "Open-Drain" in the PnMDOUT reg-
ister and writing a logic 1 to the associated bit in the Port Data register. For example, P7.7 is configured as
a digital input by setting P7MDOUT.7 to a logic 0, which selects open-drain output mode, and P3.7 to a
logic 1, which disables the low-side output driver.
17.2.4. Weak Pullups
By default, each Port pin has an internal wea k pullup device ena bled which pro vides a resistive co nnection
(about 100 k) between the pin and VDD. The weak pullup devices can be globally disabled by writing a
logic 1 to the Weak Pullup Disable bit, (WEAKPUD, XBR2.7). The weak pullup is automatically deactivated
on any pin that is driving a logic 0; that is, an output pin will not contend with its own pullup device.
17.2.5. External Memory Interface
If the External Memory Interface (EMIF) is enabled on the High ports (Ports 4 through 7), EMIFLE
(XBR2.5) should be set to a logic 0.
If the External Memory Interface is enabled on the High ports and an off-chip MOVX operation occurs, the
External Memory Interface will control the output states of the affected Port pins during the execution
phase of the MOVX instruction, regardless of the settings of the Po rt Da ta registers. The output configura-
tion of the Port pins is not affected by the EMIF operation, except that Read operations will explicitly dis-
able the output drivers on the Data Bus during the MOVX execution. See Section “16. External Data
Memory Interface and On-Chip XRAM” on page 187 for more information about the External Memory
Interface.
C8051F040/1/2/3/4/5/6/7
222 Rev. 1.5
SFR Definition 17.16. P4: Port4 Data
SFR Definition 17.17. P4MDOUT: Port4 Output Mode
Bits7-0: P4.[7:0]: Port4 Output Latch Bits.
Write - Output appears on I/O pins.
0: Logic Low Output.
1: Logic High Output (Open-Drain if cor responding P4MDOUT.n bit = 0). See SFR Definitio n
17.17.
Read - Returns states of I/O pins.
0: P4.n pin is logic low.
1: P4.n pin is logic high.
Note: P4.7 (/WR), P4.6 (/RD), and P4.5 (ALE) can be driven by the External Data Memory
Interface. See Section “16. External Data Memory Interface and On-Chip XRAM” on
page 187 for more information.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
P4.7 P4.6 P4.5 P4.4 P4.3 P4.2 P4.1 P4.0 11111111
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 Bit
Addressable
SFR Address:
SFR Page: 0xC8
F
Bits7-0: P4MDOUT.[7:0]: Port4 Output Mode Bits.
0: Port Pin output mode is configured as Open-Drain.
1: Port Pin output mode is configured as Push-Pull.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0x9C
F
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 223
SFR Definition 17.18. P5: Port5 Data
SFR Definition 17.19. P5MDOUT: Port5 Output Mode
Bits7-0: P5.[7:0]: Port5 Output Latch Bits.
Write - Output appears on I/O pins.
0: Logic Low Output.
1: Logic High Output (Open-Drain if corresponding P5MDOUT bit = 0). See SFR Definition
17.19.
Read - Returns states of I/O pins.
0: P5.n pin is logic low.
1: P5.n pin is logic high.
Note: P5.[7:0] can be driven by the External Data Memo ry Interface (as Addre ss[15:8] in Non-mul-
tiplexed mode). See Section “16. External Data Memory Interface and On-Chip XRAM”
on page 187 for more information about the External Memory Interface.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
P5.7 P5.6 P5.5 P5.4 P5.3 P5.2 P5.1 P5.0 11111111
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 Bit
Addressable
SFR Address:
SFR Page: 0xD8
F
Bits7-0: P5MDOUT.[7:0]: Port5 Output Mode Bits.
0: Port Pin output mode is configured as Open-Drain.
1: Port Pin output mode is configured as Push-Pull.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0x9D
F
C8051F040/1/2/3/4/5/6/7
224 Rev. 1.5
SFR Definition 17.20. P6: Port6 Data
SFR Definition 17.21. P6MDOUT: Port6 Output Mode
Bits7-0: P6.[7:0]: Port6 Output Latch Bits.
Write - Output appears on I/O pins.
0: Logic Low Output.
1: Logic High Output (Open-Drain if corresponding P6MDOUT bit = 0). See SFR Definition
17.21.
Read - Returns states of I/O pins.
0: P6.n pin is logic low.
1: P6.n pin is logic high.
Note: P6.[7:0] can be driven by the External Data Memory Interface (as Address[15:8] in Multi-
plexed mode, or as Address[7:0] in Non-multiplexed mode). See Section “16. External
Dat a Memor y Inter face and On-Ch ip XRAM” on page 187 for more info rmatio n about the
External Memory Interface.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
P6.7 P6.6 P6.5 P6.4 P6.3 P6.2 P6.1 P6.0 11111111
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 Bit
Addressable
SFR Address:
SFR Page: 0xE8
F
Bits7-0: P6MDOUT.[7:0]: Port6 Output Mode Bits.
0: Port Pin output mode is configured as Open-Drain.
1: Port Pin output mode is configured as Push-Pull.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0x9E
F
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 225
SFR Definition 17.22. P7: Port7 Data
SFR Definition 17.23. P7MDOUT: Port7 Output Mode
Bits7-0: P7.[7:0]: Port7 Output Latch Bits.
Write - Output appears on I/O pins.
0: Logic Low Output.
1: Logic High Output (Open-Drain if corresponding P7MDOUT bit = 0). See SFR Definition
17.23.
Read - Returns states of I/O pins.
0: P7.n pin is logic low.
1: P7.n pin is logic high.
Note: P7.[7:0] can be driven by the External Data Memory Interface (as AD[7:0] in Multiplexed
mode, or as D[7:0] in Non-multiplexed mode). See Section “16. External Data Memory
Interface and On-C hip XRAM” on page 187 for more information about the Extern al Mem-
ory Interface.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
P7.7 P7.6 P7.5 P7.4 P7.3 P7.2 P7.1 P7.0 11111111
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 Bit
Addressable
SFR Address:
SFR Page: 0xF8
F
Bits7-0: P7MDOUT.[7:0]: Port7 Output Mode Bits.
0: Port Pin output mode is configured as Open-Drain.
1: Port Pin output mode is configured as Push-Pull.
Note: SDA, SCL, and RX0 (when UART0 is in Mode 0) and RX1 (when UART1 is in Mode 0) are
always configured as Open-Drain when they appear on Port pins.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0x9F
F
C8051F040/1/2/3/4/5/6/7
226 Rev. 1.5
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 227
18. Controller Area Network (CAN0)
IMPORTANT DOCUMENTATION NOTE: The Bosch CAN Controller is integrated in the C8051F04x Fam-
ily of devices. This section of the data sheet gives a description of the CAN co ntroller as an over view and
offers a description of how the Silicon Labs CIP-51 MCU interfaces with the on-chip Bosch CAN controller.
In order to use the CAN controller, please refer to Bosch’s C_CAN User’s Manual (revision 1.2) as an
accompanying manual to Silicon Labs’ C8051F04x Data sheet.
The C8051F04x fa mily of devices feature a Contr ol Area Network ( CAN) controller tha t enables seria l com-
munication using the CAN protocol. Silicon Labs CAN facilitates communication on a CAN network in
accordance with the Bosch specification 2.0A (basic CAN) and 2.0B (full CAN). The CAN controller con-
sists of a CAN Core, M essage RAM (s eparate from the C IP-51 RAM), a me ssage han dler state machine,
and control registers. Silicon Labs CAN is a protocol controller and does not provide physical layer drivers
(i.e., transceivers). Figure 18.1 shows an example typical configuration on a CAN bus.
Silicon Labs CAN operates at bit rates of up to 1 Mbit/second, though this can be limited by the physical
layer chosen to transmit data on the CAN bus. The CAN processor has 32 Message Objects that can be
configured to transmit or receive data. Incoming data, message objects and their identifier masks are
stored in the CAN message RAM . All pr otocol function s for tr an smission of dat a and accept a nce filtering is
performed by the CAN controller and not by the CIP-51 MCU. In this way, minimal CPU bandwidth is
needed to use CAN communication. The CIP-51 configures the CAN controller, accesses received data,
and passes data for transmission via Special Function Registers (SFRs) in the CIP-51.
Figure 18.1. Typical CAN Bus Configuration
C8051F04x
CANTX CANRX
CAN_H
CAN_L
Isolation/Buffer (Optional)
CAN
Transceiver
Isolation/Buffer (Optional)
CAN
Transceiver
Isolation/Buffer (Optional)
CAN
Transceiver
RR
CAN Protocol Device CAN Protocol Device
C8051F040/1/2/3/4/5/6/7
228 Rev. 1.5
18.1. Bosch CAN Controller Operation
The CAN Controller featured in the C8051F04x family of devices is a full implementation of Bosch’s full
CAN module and fully complies with CAN specification 2.0B. A block diagram of the CAN controller is
shown in Fig ure 18.2. The CAN Core pr ovides s hifting (CANTX and CANRX), serial/parallel conversion of
messages, and other protocol related tasks such as transmission of data and acceptance filtering. The
message RAM stores 32 message objects which can be received or transmitted on a CAN network. The
CAN registers and message handler provide an interface for data transfer and notification between the
CAN controller and the CIP-51.
The function and use of the CAN Controller is detailed in the Bosch CAN User’s Guide. The User’s Guide
should be used as a reference to configure and use the CAN controller. This Silicon Labs data sheet
describes how to access the CAN controller.
The CAN Controller is typically initialized using the following steps:
Step 1. Set the SFRPAGE register to CAN0_PAGE.
S tep 2. Set the INIT the CCE bits to ‘1’ in the CAN0CN Register . See the CAN User’s Guide for bit
definitions.
Step 3. Set timing parameters in the Bit Timing Register and the BRP Extension Register.
Step 4. Initialize each message object or set it’s MsgVal bit to NOT VALID.
Step 5. Reset the INIT bit to ‘0’.
The CAN Control Register (CAN0CN), CAN Test Register (CAN0TST), and CAN Status Register
(CAN0STA) in the CAN controller can be accessed directly or indirectly via CIP-51 SFR’s. All other CAN
registers must be accessed via an indirect indexing method described in Section “18.2.5. Using
CAN0ADR, CAN0DATH, and CANDATL to Access CAN Registers” on page 232.
Figure 18.2. CAN Controller Diagram
Message H andler
REGISTERS
Message R AM
(32 Message Objects)
CAN
Core
TX RX
CAN C ontroller
CIP-51
MCU
Interrupt
S
F
R
's
CANTX CANRX C8051F04x
S
Y
S
C
L
K
CAN_CLK
(fsys)
BRP
Prescaler
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 229
18.1.1. CAN Controller Timing
The CAN controller’s system clock (f sys) is derived from the CIP-51 system clock (SYSCLK). Note that an
external oscillator (such as a quartz crystal) is typically required due to the high accuracy requirements for
CAN communication. Refer to Section “4.10.4 Oscillator Tolerance Range” in the Bosch CAN User’ s Guide
for further information regarding this topic.
18.1.2. Example Timing Calculation for 1 Mbit/Sec Communication
This example shows how to configure the CAN contoller timing parameters for a 1 Mbit/Sec bit rate.
Table 18.1 shows timing-related system parameters needed for the calculation.
Each bit transmitted on a CAN network has 4 segments (Sync_Seg, Prop_Seg, Phase_Seg1, and
Phase_Seg2), as shown in Figure 18.3. The sum of these segments determines the CAN bit time (1/bit
rate). In this example, the desired bit rate is 1 Mbit/sec; therefore, the desired bit time is 1000 ns.
Figure 18.3. Four Segments of a CAN Bit Time
Table 18.1. Background System Information
Parameter Value Description
CIP-51 system clock (SYSCLK) 22.1184 MHz External oscillator in ‘Crystal Oscillator Mode’. A
22.1184 MHz quartz cr ystal is connected between
XTAL1 and XTAL2.
CAN Controller system clock
(fsys)22.1184 MHz Derived from SYSCLK.
CAN clock period (tsys)45.211 ns Derived from 1/fsys.
CAN time quantum (tq)45.211 ns Derived from tsys x BRP1,2
CAN bus length 10 m 5 ns/m signal delay between CAN nodes.
Propagation delay time3400 ns 2 x (transceiver loop delay + bus line delay)
Notes:
1. The CAN time quantum (tq) is the smallest unit of time recognized by the CAN contoller . Bit timing parameters
are often specified in integer multiples of the time quantum.
2. The Baud Rate Prescaler (BRP) is defined as the value of the BRP Extension Register plus 1. The BRP
Extension Register has a reset value of 0x0000; the Baud Rate Prescaler has a reset value of 1.
3. Based on an ISO-11898 compliant transceiver. CAN does not specify a physical layer.
Prop_Seg Phase_Seg1 Phase_Seg2
CAN Bit Time (4 to 25 t
q
)
Sync_Seg
1t
q
1 to 8 t
q
1 to 8 t
q
1 to 8 t
q
1t
q
Sample Point
C8051F040/1/2/3/4/5/6/7
230 Rev. 1.5
We will adjust the length of the 4 bit segments so that their sum is as close as possible to the desired bit
time. Since each segment must be an integer multiple of the time quantum (tq), the closest achievable bit
time is 22 tq (994.642 ns), yielding a bit rate of 1.00539 Mbit/sec. The Sync_Seg is a constant 1 tq. The
Prop_Seg must be greater than or equal to the propagation delay of 400 ns; we choose 9 tq (406.899 ns) .
The remaining time quanta (tq) in the bit time are divided between Phase_Seg1 and Phase_Seg2 as
shown in Figure 18.1. We select Phase_Seg1 = 6 tq and Ph ase _ Seg 2 = 6 tq.
Equation 18.1. Assigning the Phase Segments
The Synchronization Jump Width ( SJW) timing p arameter is defined by Figure 18.2. It is used for determin-
ing the value written to the Bit Timing Register and for determining the required oscillator tolerance. Since
we are using a quartz crystal as the system clock source, an oscillator tolerance calculation is not needed.
Equation 18.2. Synchronization Jump Width (SJW)
The value written to the Bit Timing Register can be calculated using Equation 18.3. The BRP Extension
register is left at its reset value of 0x0000.
Equation 18.3. Calculating the Bit Timing Register Value
The following steps are performed to initialize the CAN timing registers:
Step 1. Set the SFRPAGE register to CAN0_PAGE.
Step 2. Set the INIT the CCE bits to ‘1’ in the CAN Control Register accessible through the
CAN0CN SFR.
Step 3. Set the CAN0ADR to 0x03 to point to the Bit Timing Register.
Phase_Seg1 Phase_Seg2+ Bit Time Sync_Seg Prop_Seg+–=
Note 1: If Phase_Seg1 + Phase_Seg2 is even, then Phase_Seg2 = Phase_Seg1.
Note 2: Phase_Seg2 should be at least 2 tq.
SJW = min ( 4, Phase_Seg1 )
BRPE = BRP - 1 = BRP Extension Register = 0x0000
SJWp = SJW - 1 = min ( 4, 6 ) – 1 = 3
TSEG1 = (Prop_Seg + Phase_Seg1 - 1) = 9 + 6 - 1 = 14
TSEG2 = (Phase_Seg2 - 1) = 5
Bit Timing Register = (TSEG2 * 0x1000) + (TSEG1 * 0x0100) + (SJWp * 0x0040) + BRPE = 0x5EC0
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 231
Step 4. Write the value 0x5EC0 to the [CAN0DATH:CAN0DATL] CIP-51 SFRs to set the Bit
T iming Register using the indirect indexing method described on Section 18.2.5 on page
232.
Step 5. Perform other CAN initializations.
18.2. CAN Registers
CAN registers are classified as follows:
1. CAN Controller Protocol Registers: CAN control, interrupt, error control, bus status, test
modes.
2. Message Object Interface Registers: Used to configure 32 Message Objects, send and
receive data to and from Message Objects. The CIP-51 MCU accesses the CAN mes-
sage RAM via the Message Object Interface Registers. Upon writing a message object
number to an IF1 or IF2 Command Request Register, the contents of the associated
Interface Registers (IF1 or IF2) will be transferred to or from the message object in CAN
RAM.
3. Message Handler Registers: These read only registers are used to provide information to
the CIP-51 MCU about the message objects (MSGVLD flags, Transmission Request
Pending, New Data Flags) and Interrupts Pending (which Message Objects have caused
an interrupt or status interrupt condition).
4. CIP-51 MCU Special Function Registers (SFR): Six registers located in the CIP-51 MCU
memory map that allow direct access to certain CAN Controller Protocol Registers, and
Indexed indirect access to all CAN registers.
18.2.1. CAN Controller Protocol Registers
The CAN Control Protocol Registers are used to configure the CAN controller, process interrupts, monitor
bus status, and place the controller in test modes. The CAN controller protocol registers are accessible
using CIP-51 MCU SFR’s by an indexed method, and some can be accessed directly by addressing the
SFR’s in the CIP-51 SFR map for convenience.
The registers are: CAN Control Register (CAN0CN), CAN Status Register (CAN0STA), CAN Test Register
(CAN0TST), Error Counter Register, Bit Timing Register, and the Baud Rate Prescaler (BRP) Extension
Register. CAN0STA, CAN0CN, and CAN0TST can be accessed via CIP-51 MCU SFR’s. All others are
accessed indire ct ly usin g th e CA N address indexed method via CAN0ADR, CAN0DATH, and CAN0DATL.
Please refer to the Bosch CAN User ’s Guide for information on the function and use of the CAN Control
Protocol Registers.
18.2.2. Message Object Interface Registers
There are two sets of Message Object Interface Registers used to config ure the 32 Me ssage Objects that
transmit and receive data to and from the CAN bus. Message objects can be configured for transmit or
receive, and are assigned arbitration message identifiers for acceptance filtering by all CAN nodes.
Message Objects are stored in Message RAM, and are accessed and configured using the Message
Object Interf ace Registers. These register s are accessed via the CIP-51’s CAN0ADR and CAN0DAT reg-
isters using the indirect indexed address method.
Please refer to the Bosch CAN User’s Guide for information on the function and use of the Message Object
Interface Registers.
C8051F040/1/2/3/4/5/6/7
232 Rev. 1.5
18.2.3. Message Handler Registers
The Message Handler Registers are read only registers. Their flags can be read via the indexed access
method with CAN0ADR, CAN0DATH, and CAN0DATL. The message handler registers provide interrupt,
error, transmit/receive requests, and new data information.
Please refer to the Bosch CAN User’s Guide for information on the function and use of the Message Han-
dler Registers.
18.2.4. CIP-51 MCU Special Function Reg isters
C8051F04x family peripherals are modified, monitored, and controlled using Special Function Registers
(SFR’s). Only three of the CAN Controller’s registers may be accessed directly with SFR’s. However, all
CAN Controller registers can be accessed indirectly using three CIP-51 MCU SFR’s: the CAN Data Regis-
ters (CAN0DATH and CAN0DATL) and CAN Address Register (CAN0ADR).
18.2.5. Using CAN0ADR, CAN0DATH, and CANDATL to Access CAN Registers
Each CAN Controller Register has an index number (see Table 18.2). The CAN register address space is
128 words (256 bytes). A CAN register is accessed via the CAN Data Registers (CAN0DATH and
CAN0DATL) when a CAN register ’s index number is placed into the CAN Address Register (CAN0ADR).
For example, if the Bit Timing Register is to be configured with a new value, CAN0ADR is loaded with
0x03. The low by te of the desired value is accessed us ing CAN0DATL and the high byte of the bit timing
register is accessed using CAN0DATH. CAN0DATL is bit addressable for convenience. To load the value
0x2304 into the Bit Timing Register:
CAN0ADR = 0x03; // Load Bit Timing Register’s index (Table 18.1)
CAN0DATH = 0x23; // Move the upper byte into data reg high byte
CAN0DATL = 0x04; // Move the lower byte into data reg low byte
Note: CAN0CN, CAN0STA, and CAN0TST may be accessed ei ther by using the index method, or by direct
access with the CIP-51 MCU SFR’s. CAN0CN is located at SFR location 0xF8/SFR page 1 (SFR Definition
18.3), CAN0TST at 0xDB/SFR page 1 (SFR Definition 18.4), and CAN0STA at 0xC0/SFR page 1 (SFR
Definition 18.5).
18.2.6. CAN0ADR Autoincrement Feature
For ease of programming message objects, CAN0ADR features autoincrementing for the index ranges
0x08 to 0x12 (Interface Registers 1) and 0x20 to 0x2A (Interface Registers 2). When the CAN0ADR regis-
ter has an index in these ranges, the CAN0ADR will autoin creme nt by 1 to poin t to the n ext CA N reg-
ister 16-bit word upon a read/write of CAN0DATL. This speeds programming of the frequently-
accessed interface registers when configuring message objects.
NOTE: Table 18.2 below supersedes Figure 5 in Section 3, “Programmer’s Model” of the Bosch CAN
User’s Guide.
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 233
Table 18.2. CAN Register Index and Reset Values
CAN Register
Index Register Name Reset
Value Notes
0x00 CAN Control Register 0x0001 Accessible in CIP-51 SFR Map
0x01 Status Register 0x0000 Accessible in CIP-51 SFR Map
0x02 Error Regist er 0x0000 Read Only
0x03 Bit Timing Register 0x2301 Write Enabled by CCE Bit in CAN0CN
0x04 Interrupt Register 0x0000 Read Only
0x05 Test Register 0x0000 Bit 7 (RX) is determined by CAN bus
0x06 BRP Extension Register 0x0000 Write Enabled by TEST bit in CAN0CN
0x08 IF1 Command Request 0x0001 CAN0ADR autoincrements in IF1 index space
(0x08 - 0x12) upon write to CAN0DATL
0x09 IF1 Command Mask 0x0000 CAN0ADR autoincrement upon write to
CAN0DATL
0x0A IF1 Mask 1 0xFFFF CAN0ADR autoincrement upon write to
CAN0DATL
0x0B IF1 Mask 2 0xFFFF CAN0ADR autoincrement upon write to
CAN0DATL
0x0C IF1 Arbitration 1 0x0000 CAN0ADR autoincrement upon write to
CAN0DATL
0x0D IF1 Arbitration 2 0x0000 CAN0ADR autoincrement upon write to
CAN0DATL
0x0E IF1 Message Control 0x0000 CAN0ADR autoincrement upon write to
CAN0DATL
0x0F IF1 Data A1 0x0000 CAN0ADR autoincrement upon write to
CAN0DATL
0x10 IF1 Data A2 0x0000 CAN0ADR autoincrement upon write to
CAN0DATL
0x11 IF1 Data B1 0x0000 CAN0ADR autoincrement upon write to
CAN0DATL
0x12 IF1 Data B2 0x0000 CAN0ADR autoincrement upon write to
CAN0DATL
0x20 IF2 Command Request 0x0001 CAN0ADR autoincrements in IF2 index space
(0x20 - 0x2A) upon write to CAN0DATL
0x21 IF2 Command Mask 0x0000 CAN0ADR autoincrement upon write to
CAN0DATL
0x22 IF2 Mask 1 0xFFFF CAN0ADR autoincrement upon write to
CAN0DATL
0x23 IF2 Mask 2 0xFFFF CAN0ADR autoincrement upon write to
CAN0DATL
0x24 IF2 Arbitration 1 0x0000 CAN0ADR autoincrement upon write to
CAN0DATL
0x25 IF2 Arbitration 2 0x0000 CAN0ADR autoincrement upon write to
CAN0DATL
C8051F040/1/2/3/4/5/6/7
234 Rev. 1.5
0x26 IF2 Message Control 0x0000 CAN0ADR autoincrement upon write to
CAN0DATL
0x27 IF2 Data A1 0x0000 CAN0ADR autoincrement upon write to
CAN0DATL
0x28 IF2 Data A2 0x0000 CAN0ADR autoincrement upon write to
CAN0DATL
0x29 IF2 Data B1 0x0000 CAN0ADR autoincrement upon write to
CAN0DATL
0x2A IF2 Data B2 0x0000 CAN0ADR autoincrement upon write to
CAN0DATL
0x40 Transmission Request 1 0x0000 T ransmissio n request flags for messag e objects
(read only)
0x41 Transmission Request 2 0x0000 T ransmissio n request flags for messag e objects
(read only)
0x48 New Data 1 0x0000 New Data flags for message objects (read only)
0x49 New Data 2 0x0000 New Data flags for message objects (read only)
0x50 Interrupt Pending 1 0x0000 Interrupt pending flags for message objects
(read only)
0x51 Interrupt Pending 2 0x0000 Interrupt pending flags for message objects
(read only)
0x58 Message Valid 1 0x0000 Message valid flags for message objects (read
only)
0x59 Message Valid 2 0x0000 Message valid flags for message objects (read
only)
Table 18.2. CAN Register Index and Reset Values (Continued)
CAN Register
Index Register Name Reset
Value Notes
Figure 18.4. CAN0DATH: CAN Data Access Register High Byte
Bit7-0: CAN0DATH: CAN Data Access Register High Byte.
The CAN0DAT Registers are used to read/write reg ister values and data to and from the
CAN Registers pointed to with the index number in the CAN0ADR Register.
The CAN0ADR Register is used to point the [CAN0DATH:CAN0DATL] to a desired CAN
Register. The desired CAN Register’s index number is moved into CAN0ADR. The
CAN0DAT Register can then read/write to and from the CAN Register.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xD9
1
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 235
SFR Definition 18.1. CAN0DATL: CAN Data Access Register Low Byte
SFR Definition 18.2. CAN0ADR: CAN Address Index
Bit7-0: CAN0DATL: CAN Data Access Register Low Byte.
The CAN0DAT Registers are used to read/write reg ister values and data to and from the
CAN Registers pointed to with the index number in the CAN0ADR Register.
The CAN0ADR Register is used to point the [CAN0DATH:CAN0DATL] to a desired CAN
Register. The desired CAN Register’s index number is moved into CAN0ADR. The
CAN0DAT Register can then read/write to and from the CAN Register.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000001
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xD8
1
Bit7-0: CAN0ADR: CAN Address Index Register.
The CAN0ADR Register is used to point the [CAN0DATH:CAN0DATL] to a desired CAN
Register. The desired CAN Register’s index number is moved into CAN0ADR. The
CAN0DAT Register can then read/write to and from the CAN Register.
Note: When the value of CAN0ADR is 0x08-0x12 and 0x20-0x2A (IF1 and IF2 registe rs),
this register will autoincrement by 1 upon a write to CAN0DATL. See Section
“18.2.6. CAN0ADR Autoincrement Feature” on page 232.
All CAN registers’ functions/definitions are listed and described in the Bosch CAN
User’s Guide.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xDA
1
C8051F040/1/2/3/4/5/6/7
236 Rev. 1.5
SFR Definition 18.3. CAN0CN: CAN Control
SFR Definition 18.4. CAN0TST: CAN Test
Bit 4: CANIF: CAN Interrupt Flag. Write = don’t care.
0: CAN interrupt has not occurred.
1: CAN interrupt has occurred and is active.
CANIF is controlled by the CAN controller and is cleared by hardware once all interrupt con-
ditions have been cleared in the CAN controller. See Section 3.4.1 in the Bosch C AN Us er’s
Guide (page 24) for more information concerning CAN controller interrupts.
*All CAN registers’ functions/definitions are listed and described in the Bosch CAN
User’s Guide with the exception of the CANIF bit.
This register may be accessed dire ctly in the CIP-51 SFR r egister sp ace, or th rough the indi-
rect, index method (See Section “18.2.5. Using CAN0ADR, CAN0DA TH, and CANDATL to
Access CAN Registers” on page 232).
R/W R/W R/W R R/W R/W R/W R/W Reset Value
***CANIF****
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xF8
1
All CAN registers’ functions/definitions are listed and described in the Bosch CAN
User’s Guide.
This register may be accessed dire ctly in the CIP-51 SFR r egister sp ace, or th rough the indi-
rect, index method (See Section “18.2.5. Using CAN0ADR, CAN0DA TH, and CANDATL to
Access CAN Registers” on page 232).
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
Please see the Bos ch CAN Use r’s Guide for a com p let e de fin itio n of this register
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xDB
1
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 237
SFR Definition 18.5. CAN0STA: CAN Status
All CAN registers’ functions/definitions are listed and described in the Bosch CAN
User’s Guide.
This register may be accessed dire ctly in the CIP-51 SFR r egister sp ace, or th rough the indi-
rect, index method (See Section “18.2.5. Using CAN0ADR, CAN0DA TH, and CANDATL to
Access CAN Registers” on page 232).
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
Please see the Bosch CAN User’s Guide for a complete definition of this register
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xC0
1
C8051F040/1/2/3/4/5/6/7
238 Rev. 1.5
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 239
19. System Management BUS/I2C BUS (SMBUS0)
The SMBus0 I/O interface is a two-wire, bi-directional serial bus. SMBus0 is compliant with the System
Management Bus Specification, version 2, and compatible with the I2C serial bus. Reads and writes to the
interface by the system controller are byte oriented with the SMBus0 interface autonomously controlling
the serial transfer of the data. A method of extending the clock-low duration is available to accommodate
devices with different speed capabilities on the same bus.
SMBus0 may operate as a master a nd/or slave, and may function on a b us with multiple ma sters. SMBus0
provides control of SDA (serial data), SCL (serial clock) generation and synchronization, arbitration lo gic,
and START/STOP control and gene ration. SMBus0 is contro lled by SFRs as described in Sect ion 19 .4 on
page 245.
Figure 19.1. SMBus0 Block Diagram
SFR Bus
Data Path
Control
SFR Bus
Write to
SMB0DAT
SMBUS CONTROL LOGIC
Read
SMB0DAT
SMB0ADR
S
L
V
6G
C
S
L
V
5
S
L
V
4
S
L
V
3
S
L
V
2
S
L
V
1
S
L
V
0
C
R
O
S
S
B
A
R
Clock Divide
Logic
SYSCLK
SMB0CR
C
R
7
C
R
6
C
R
5
C
R
4
C
R
3
C
R
2
C
R
1
C
R
0
SCL
FILTER
N
SDA
Control
0000000b
7 MSBs 8
AB
A=B
8
01234567 SMB0DAT
8
SMB0CN
S
T
A
S
IA
AF
T
E
T
O
E
E
N
S
M
B
B
U
S
Y
S
T
O
SMB0STA
S
T
A
4
S
T
A
3
S
T
A
2
S
T
A
1
S
T
A
0
SCL
Control
Status Generation
Arbitration
SCL Synchronization
SCL Generation (Master Mode)
IRQ Generation
S
T
A
5
S
T
A
6
S
T
A
7
AB
A=B
SMBUS
IRQ
Interrupt
Request
Port I/O
1
0
SDA
FILTER
N
7
C8051F040/1/2/3/4/5/6/7
240 Rev. 1.5
Figure 19.2 shows a typical SMBus configuration. The SMBus0 interface will work at any voltage between
3.0 V and 5.0 V and different devices on the bus may operate at different voltage levels. The bi-directional
SCL (serial clock) and SDA (serial data) lines must be connected to a positive power supply voltage
through a pullup resistor or similar circuit. Every device connected to the bus must have an open-drain or
open-collector output for both the SCL and SDA lines, so that both are pulled high when the bus is free.
The maximum number of devices on the bus is limited only by the requirement that the rise and fall times
on the bus will not exceed 300 ns and 1000 ns, respectively.
Figure 19.2. Typical SMBus Configuration
19.1. Supporting Documents
It is assumed the reader is familiar with or has access to the following supporting documents:
•I
2C Manual (AN10216-01) -- March 24, 2003, Philips Semiconductor.
• System Management Bus Specification -- Version 1.1, SBS Implementers Forum.
VDD = 5 V
Master
Device Slave
Device 1 Slave
Device 2
VDD = 3 V VDD = 5 V VDD = 3 V
SDA
SCL
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 241
19.2. SMBus Protocol
Two types of data transfers are possible: data transfers from a master transmitter to an addressed slave
receiver (WRITE), and data transfers from an addressed slave transmitter to a master receiver (READ).
The master device initiates both types of data transfers and provides the se ria l clock pulse s on SCL. Note:
multiple master devices on the same bus are supported. If two or more masters attempt to initiate a data
transfer simultan eously, an arbitration scheme is employed with a single master always winning the arbitra-
tion. Note that it is not necessary to specify one device as the master in a system; any device who trans-
mits a START and a slave address becomes the master for that transfer.
A typical SMBus transaction consists of a START condition followed by an address byte (Bits7-1: 7-bit
slave address; Bit0: R/W direction bit), one or more bytes of data, and a STOP condition. Each byte that is
received (by a master or slave) must be acknowledged (ACK) with a low SDA during a high SCL (see
Figure 19.3). If the receiving device does not ACK, the transmitting device will read a “not acknowledge”
(NACK), which is a high SDA during a high SCL.
The direction bit (R/W) occupies the least-significant bit position of the address. The direction b it is set to
logic 1 to indicate a "READ" operation and cleared to logic 0 to indi cate a "WRITE" operation.
All transactions are initiated by a master, with one or more addressed slave devices as the target. The
master generates the START condition and then transmits the slave address and direction bit. If the trans-
action is a WRITE operation from the master to the slave, the master transmits the data one byte at a time
and expects an A C K fr om th e slave at th e en d of each byte. For READ operations, the slave transmits the
data and expe ct s an ACK from the master at the end of each byte . At the end of the dat a transfer, the mas-
ter generates a STOP condition to terminate the transaction and free the bus. Figure 19.3 illustrates a typ-
ical SMBus transaction.
Figure 19.3. SMBus Transaction
19.2.1. Arbitration
A master may star t a transfer on ly if the bus is free. The b us is free af ter a STOP condition or after the SCL
and SDA lines remain high for a specified time (see Se ct io n 19 .2 .4). In the event that two or mo re devices
attempt to begin a transfer at the same time, an arbitration scheme is employed to force o ne master to gi ve
up the bus. The master d evices continue tr ansmitting until one a ttempt s a HIGH while the other tran smit s a
LOW. Since the bus is open-drain, the bus will be pulled LOW. The master attempting the HIGH will detect
a LOW SDA and give up the bus. The winning master continues its transmission without interruption; the
losing master becomes a slave and receives the rest of the transfer. This arbitration scheme is non-
destructive: one device always wins, and no data is lost.
SLA6
SDA SLA5-0 R/W D7 D6-0
SCL
Slave Add re ss + R /W Data By teSTART ACK NACK STOP
C8051F040/1/2/3/4/5/6/7
242 Rev. 1.5
19.2.2. Clock Low Extension
SMBus provides a clock synchronization mechanism, similar to I2C, which allows devices with different
speed capabilities to coexist on the bus. A clock-low extension is used during a transfer in order to allow
slower slave devices to communicate with faster masters. The slave may temporarily hold the SCL line
LOW to extend the clock low period, effectively decreasing the serial clock frequency.
19.2.3. SCL Low Timeout
If the SCL line is held low b y a slave device on the bus, no fur ther communication i s possible. Fur thermore,
the master cann ot force the SCL lin e high to corr ect th e error condition. To solve this problem, the SMBus
protocol specifies that devices participating in a transfer must detect any clock cycle held low longer than
25 ms as a “timeout” condition. Devices that have detected the timeout condition must reset the communi-
cation no later than 10 ms after detecting the timeout condition.
19.2.4. SCL High (SMBus Free) Timeout
The SMBus specification stipulates that if the SCL and SDA lines remain high for more that 50 µs, the bus
is designated as free. If an SMBus device is waiting to generate a Master START, the START will be gen-
erated following th e bu s fre e tim eou t.
19.3. SMBus Transfer Modes
The SMBus0 interfa ce may be configure d to op erate as a master a nd/or a slave. At a ny p articul ar time, the
interface will be operating in one of the following modes: Master Transmitter, Master Receiver, Slave
Transmitter, or Slave Receiver. See Table 19.1 for transfer mode status decoding using the SMB0STA sta-
tus register. The following mode descriptions illustrate an interrupt-driven SMBus0 application; SMBus0
may alternatively be operated in polled mode.
19.3.1. Master Transmitter Mode
Serial data is transmitted on SDA while the serial clock is output on SCL. SMBus0 generates a START
condition and then transmits the first byte containing the address of the target slave device and the data
direction bit. In this case the data direction bit (R/W) will be logic 0 to indicate a "WRITE" operation. The
SMBus0 interface transmits one or more bytes of serial data, waiting for an acknowledge (ACK) from the
slave after each byte. To indicate the end of the serial transfer, SMBus0 generates a STOP condition.
Figure 19.4. Typical Master Tr ansmitter Sequence
A AAS W PData Byte Data ByteSLA
S = START
P = STOP
A = ACK
W = WRITE
SLA = Slave Address
Received by SMBus
Interface
Transmitted by
SMBus Interface
Interrupt Interrupt InterruptInterrupt
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 243
19.3.2. Master Receiver Mode
Serial data is received on SDA while the serial clock is ou tp ut o n S CL. T h e SM Bu s0 in te rf ac e generates a
START followed by the first data byte containing the address of the target slave and the data direction bit.
In this case the data direction bit (R/W) will be logic 1 to indicate a "READ" operation. The SMBus0 inter-
face receives serial data from the slave and generates the clock on SCL. After each byte is received,
SMBus0 generates an ACK or NACK depending on the state of the AA bit in register SMB0CN. SMBus0
generates a STOP condition to indicate the end of the serial transfer.
Figure 19.5. Typical Master Receiver Sequence
19.3.3. Slave Transmitter Mode
Serial dat a is transm itted on SDA while the serial clock is received on SCL. The SMBus0 interface receives
a START followed by data byte contain ing the slave address and direction bit. If the received slave address
matches the address held in register SMB0ADR, the SMBus0 interface generates an ACK. SMBus0 will
also ACK if the general call address (0x00) is received and the General Call Address Enable bit
(SMB0ADR.0) is set to logic 1. In this case the data direction bit (R/W) will be logic 1 to indicate a "READ"
operation. The SMBus0 interface receives the clock on SCL and transmits one or more bytes of serial
data, waiting for an ACK from the master after each byte. SMBus0 exits slave mode after receiving a
STOP condition from the master.
Figure 19.6. Typical Slave Transmitter Sequence
Data B yteData Byte A NAS R PSLA
S = START
P = STOP
A = ACK
N = NACK
R = READ
SLA = Slave Address
Received by SMBus
Interface
Transm itt ed by
SMBus Interface
Interrupt Interrupt InterruptInterrupt
PRSLASData ByteData Byte A NA
S = START
P = STOP
N = NACK
W = WRITE
SLA = Slave Address
Received by SMBus
Interface
Transmitted by
SMBus Interface
Interrupt Interrupt Interrupt
Interrupt
C8051F040/1/2/3/4/5/6/7
244 Rev. 1.5
19.3.4. Slave Receiver Mode
Serial data is received on SDA while the serial clock is received on SCL. The SMBus0 interface re ce ives a
START followed by data byte containing the slave address and direction bit. If the received slave address
matches the address held in register SMB0ADR, the interface generates an ACK. SMBus0 will also ACK if
the general call addre ss (0x00) is received and the G eneral Call Address Enable bit (SMB0ADR.0) is set to
logic 1. In this case the data direction bit (R/W) will be logic 0 to indicate a "WRITE" operation. The
SMBus0 interface receives one or more bytes of serial data; after each byte is received, the interface
transmits an ACK or NACK depending on the state of the AA bit in SMB0CN. SMBus0 exits Slave Receiver
Mode after receiving a STOP condition from the master.
Figure 19.7. Typical Slave Receiver Sequence
PWSLASData ByteData Byte A AA
S = START
P = STOP
A = ACK
R = READ
SLA = Slave Address
Receiv ed by S MBus
Interface
Transmitted by
SMBus Interface
Interrupt Interrupt Interrupt
Interrupt
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 245
19.4. SMBus Special Function Registers
The SMBus0 serial interface is accessed and controlled through five SFRs: SMB0CN Control Register,
SMB0CR Clock Rate Register, SMB0ADR Address Register, SMB0DAT Data Register and SMB0STA Sta-
tus Register. The five special function registers related to the operation of the SMBus0 interface are
described in the following sections.
19.4.1. Control Register
The SMBus0 Control register SMB0CN is used to configure and control the SMBus0 interface. All of the
bits in the register can be read or written by software. Two of the control bits are also affected by the
SMBus0 hardware. The Serial Interrupt flag (SI, SMB0CN.3) is set to logic 1 by the hardware when a valid
serial interrupt condition occurs. It can only be cleared by sof tware. The Stop flag (STO, SMB0CN.4) is set
to logic 1 by software. It is cleared to logic 0 by hardware when a STOP condition is detected on the bus.
Setting the EN SMB flag to lo gic 1 enables the SMBus0 inte rface. Clearin g the ENSMB f lag to logic 0 dis-
ables the SMBus0 interface and removes it from the bus. Momentarily clearing the ENSMB flag and then
resetting it to logic 1 will reset SMBus0 communication. However, ENSMB should not be used to tempo-
rarily remove a device from the bus since the bus state information will be lost. Instead, the Assert
Acknowledge (AA) flag should be used to temporarily remove the device from the bus (see description of
AA flag below).
Setting the Start flag (STA, SMB0CN.5) to logic 1 will put SMBus0 in a master mode. If the bus is free,
SMBus0 will generate a START condition. If the bus is not free, SMBus0 wait s for a ST OP condition to free
the bus and then generates a START condition after a 5 µs delay per the SMB0CR value (In accordance
with the SMBus prot ocol, the SM Bus0 interfa ce also cons iders the bus fr ee if the bus is idle for 50 µs and
no STOP condition was recognized). If STA is set to logic 1 while SMBus0 is in master mode and one or
more bytes have been transferred, a repeated START condition will be generated.
When the Stop flag (STO, SMB0CN.4) is set to logic 1 while the SMBus0 interface is in master mode, the
interface generates a ST OP condition. In a slave m ode, the ST O flag may be use d to recover from an error
condition. In this case, a STOP condition is not generated on the bus, but the SMBus hardware behaves
as if a STOP condition has been received and enters the "not addressed" slave receiver mode. Note that
this simulated STOP will not cause the bus to appear free to SMBus0. The bus will remain occupied until a
STOP appears on the bus or a Bus Free Timeout occurs. Hardware automatically clears the STO flag to
logic 0 when a STOP condition is detected on the bus.
The Serial Interrupt flag (SI, SMB0CN.3) is set to logic 1 by hardware when the SMBus0 interface enters
any one of the 28 possible states except the Idle state. If interrupts are enabled for the SMBus0 interface,
an interrupt request is generated when the SI flag is set. The SI flag must be cleared by software.
Important Note: If SI is set to logic 1 while the SCL line is low, the clock-low period of the serial clock will
be stretched and the serial transfer is suspended until SI is cleared to logic 0. A high level on SCL is not
affected by the setting of the SI flag.
The Assert Acknowledge flag (AA, SMB0CN.2) is used to set the level of the SDA line during the acknowl-
edge clock cycle on the SCL line. Setting the AA flag to logic 1 will cause an ACK (low level on SDA) to be
sent during the acknowledge cycle if the device has been addressed. Setting the AA flag to logic 0 will
cause a NACK (high level on SDA) to be sent during acknowledge cycle. After the transmission of a byte in
slave mode, the slave can be temporarily removed from the bus by clearing the AA flag. The slave's own
address and general call address will be ignored. To resume operation on the bus, the AA flag must be
reset to logic 1 to allow the slave's address to be recognized.
C8051F040/1/2/3/4/5/6/7
246 Rev. 1.5
Setting the SMBus0 Free Timer Enable bit (FTE, SMB0CN.1) to logic 1 enables the timer in SMB0CR.
When SCL goes high, the timer in SMB0CR counts up. A timer overflow indicates a free bus timeout: if
SMBus0 is waiting to generate a START, it will do so after this timeout. The bus free period should be less
than 50 µs (see SFR Definition 19.2, SMBus0 Clock Rate Register).
When the TOE bit in SMB0CN is set to logic 1, Timer 4 is used to detect SCL low timeouts. If Timer 4 is
enabled (see Section “23.2. Timer 2, Timer 3, and Timer 4” on page 295), Timer 4 is forced to reload
when SCL is high, and forced to count when SCL is low. With Timer 4 enabled and configured to overflow
after 25 ms (and TOE set), a Timer 4 overflow indicates a SCL low timeout; the Timer 4 interrupt service
routine can then be used to reset SMBus0 communication in the event of an SCL low timeout.
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 247
SFR Definition 19.1. SMB0CN: SMBus0 Control
Bit7: BUSY: Busy S tatus Flag.
0: SMBus0 is free
1: SMBus0 is busy
Bit6: ENSMB: SMBus Enable.
This bit enables/disables the SMBus serial interface.
0: SMBus0 disabled.
1: SMBus0 enabled.
Bit5: STA: SMBus Start Flag.
0: No START condition is transmitted.
1: When operating as a master, a START condition is transmitted if the bus is free. (If the
bus is not free, the START is transmitted after a STOP is r eceived.) If STA is set after one or
more bytes have been transmitted or received and b efore a STOP is received, a repe ated
START condition is transmitted.
Bit4: STO: SMBus Stop Flag.
0: No STOP condition is transmitted.
1: Setting STO to logic 1 causes a STOP condition to be transmitted. When a STOP condi-
tion is received, hardware clears STO to logic 0. If both STA and STO are set, a STOP con-
dition is transmitted followed by a START condition. In slave mode, setting the STO flag
causes SMBus to behave as if a STOP condition was received.
Bit3: SI: SMBus Serial Interrupt Flag.
This bit is set by hardware when one of 27 possib le SMBus0 st ates is entered. (Status code
0xF8 does not cause SI to be set.) When the SI interrupt is enabled, setting this bit causes
the CPU to vector to the SMBus interrupt service routine. This bit is not automatically
cleared by hardware and must be cleared by software.
Bit2: AA: SMBus Assert Acknowledge Flag.
This bit defines the type of acknowledg e returned during the acknowledge cycle on the SCL
line.
0: A "not acknowledge" (high level on SDA) is returned during the acknowledge cycle.
1: An "acknowledge" (low level on SDA) is returned during the acknowledge cycle.
Bit1: FTE: SMBus Free Timer Enable Bit
0: No timeout when SCL is high
1: Timeout when SCL high time exceeds limit specified by the SMB0CR value.
Bit0: TOE: SMBus Timeout Enable Bit
0: No timeout when SCL is low.
1: Timeout when SCL low time exceeds limit specified by Timer 4, if enabled.
R R/W R/W R/W R/W R/W R/W R/W Reset Value
BUSY ENSMB STA STO SI AA FTE TOE 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 Bit
Addressable
SFR Address:
SFR Page: 0xC0
0
C8051F040/1/2/3/4/5/6/7
248 Rev. 1.5
19.4.2. Clock Rate Register
SFR Definition 19.2. SMB0CR: SMBus0 Clock Rate
Bits7-0: SMB0CR.[7:0]: SMBus0 Clock Rate Preset
The SMB0CR Clock Rate register controls the frequency of the serial clock SCL in master
mode. The 8-bit word stored in the SMB0CR Register preloads a dedicated 8-bit timer. The
timer counts up, and when it rolls over to 0x00, the SCL logic state toggles.
The SMB0CR setting should be bounded by the following equation, where SMB0CR is the
unsigned 8-bit value in register SMB0 CR, and SYSCLK is the system clock frequency in Hz:
The resulting SCL signal high and low times are given by the following equations:
Using the same value of SMB0CR from above, the Bus Free Timeout period is given in the
following equation:
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xCF
0
SMB0CR 288 0.85–SYSCLK1.124 6E
TLOW 256 SMB0CR–SYSCLK=
THIGH 258 SMB0CR–SYSCLK625ns+
TBFT 10 256 SMB0CR–1+
SYSCLK
-----------------------------------------------------
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 249
19.4.3. Data Register
The SMBus0 Data register SMB0DAT holds a byte of serial data to be transmitted or one that has just
been received. Software can read or write to this register while the SI flag is set to logic 1; software should
not attempt to access the SMB0DAT register when the SMBus is enabled and the SI flag reads logic 0
since the hardware may be in the process of shifting a byte of data in or out of the register.
Data in SMB0DAT is always shifted out MSB first. After a byte has been received, the first bit of received
data is located at the MSB of SMB0DAT. While data is being shifted out, data on the bus is simultaneously
being shifted in. Therefore, SMB0DAT always contains the last data byte present on the bus. In the event
of lost arbitration, the transition from master transm itter to slave receiver is made with the correct data in
SMB0DAT.
SFR Definition 19.3. SMB0DAT: SMBus0 Data
19.4.4. Address Register
The SMB0ADR Address register holds the slave address for the SMBus0 interface. In slave mode, the
seven most-significant bits hold the 7-bit slave address. The least significant bit (Bit0) is used to enabl e the
recognition of the general call address (0x00). If Bit0 is set to logic 1, the general call address will be recog-
nized. Otherwise, the general call address is ignored. The contents of this register are ignored when
SMBus0 is operating in master mode.
Bits7-0: SMB0DAT: SMBus0 Data.
The SMB0DAT register contain s a byte of da ta to be transmitted on th e SMBus0 ser ial in ter-
face or a byte that has just been received on the SMBus0 serial interf ace. The CPU can
read from or write to this register whenever the SI serial interrupt flag (SMB0CN.3) is set to
logic 1. When the SI flag is not set, the system may be in the process of shif ting dat a and the
CPU should not attempt to access this register.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xC2
0
C8051F040/1/2/3/4/5/6/7
250 Rev. 1.5
SFR Definition 19.4. SMB0ADR: SMBus0 Address
19.4.5. Status Register
The SMB0STA Status register holds an 8-bit status code indicating the current state of the SMBus0 inter-
face. There are 28 possible SMBus0 states, each with a corresponding unique status code. The five most
significant bits of the st atu s code vary while the three le ast-significant bit s of a valid st atus code are fixed at
zero when SI = ‘1’. Therefore, all possible status codes are multiples of eight. This facilitates the use of st a-
tus codes in software as an index used to branch to appropriate service routines (allowing 8 bytes of code
to service the state or jump to a more extensive service routine).
For the purposes of user soft ware, the content s of the SMB0STA register is only defined when the SI flag is
logic 1. Software should never write to the SMB0STA register; doing so will yield indeterminate results. The
28 SMBus0 states, along with their corresponding status codes, are given in Ta b le 19 .1 .
Bits7-1: SLV6-SLV0: SMBus0 Slave Address.
These bits are loaded with the 7-bit slave address to which SMBus0 will respond when oper-
ating as a slave transmitter or slave receiver. SLV6 is the most significant bit of the address
and corresponds to the first bit of the address byte received.
Bit0: GC: General Call Address Enable.
This bit is used to enable general call address (0x00) recognition.
0: General call address is ignored.
1: General call address is recognized.
R/WR/WR/WR/WR/WR/WR/W R/WReset Value
SLV6 SLV5 SLV4 SLV3 SLV2 SLV1 SLV0 GC 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xC3
0
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 251
SFR Definition 19.5. SMB0STA: SMBus0 Status
Bits7-3: STA7-STA3: SMBus0 Status Code.
These bits contain the SMBus0 Status Code. Ther e are 28 possible stat us codes; each sta-
tus code corresponds to a single SMBus state. A valid status code is present in SMB0STA
when the SI flag (SMB0CN.3) is set to logic 1. The content of SMB0STA is not defined when
the SI flag is logic 0. Writing to the SMB0STA register at any time will yield indeterminate
results.
Bits2-0: STA2-STA0: The three least significant bits of SMB0STA are always read as logic 0 when
the SI flag is logic 1.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
STA7 STA6 STA5 STA4 STA3 STA2 STA1 STA0 11111000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xC1
0
C8051F040/1/2/3/4/5/6/7
252 Rev. 1.5
Table 19.1. SMB0STA Status Codes and States
Mode Status
Code SMBus State Typical Action
MT/
MR
0x08 START condition transmitted. Load SMB0DAT with Slave Address +
R/W. Cle ar STA.
0x10 Repeated START condition transmitted. Load SMB0DAT with Slave Address +
R/W. Cle ar STA.
Master Transmitter
0x18 Slave Address + W transmitted. ACK
received. Load SMB0DAT with data to be transmit-
ted.
0x20 Slave Address + W transmitted. NACK
received. Acknowledge poll to retry. Set STO +
STA.
0x28 Data byte transmitted. ACK received. 1) Load SMB0DAT with next byte, OR
2) Set STO, OR
3) Clear STO then set STA for repeated
START.
0x30 Data byte transmitted. NA CK received. 1) Retry transfer OR
2) Set STO.
0x38 Arbitration Lost. Save current data.
Master Receiver
0x40 Slave Address + R transmitted. ACK received. If only receiving one byte, clear AA (send
NACK after received byte). Wait for
received data.
0x48 Slave Address + R transmitted. NACK
received. Acknowledge poll to retry. Set STO +
STA.
0x50 Data byte received. ACK transmitted. Read SMB0DAT. Wait for next byte. If
next byte is last byte, clear AA.
0x58 Data byte received. NACK transmitted. Set STO.
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 253
Slave Receiver
0x60 Own slave address + W received. ACK trans-
mitted. Wait for data.
0x68 Arbitration lost in sending SLA + R/W as mas-
ter. Own address + W received . ACK transmit-
ted.
Save current data for retry when bus is
free. Wait for data.
0x70 General call address received. ACK transmit-
ted. Wait for data.
0x78 Arbitration lost in sending SLA + R/W as mas-
ter. General call address received. ACK trans-
mitted.
Save current data for retry when bus is
free.
0x80 Data byte received. ACK transmitted. Read SMB0DAT. Wait for next byte or
STOP.
0x88 Data byte received. NACK transmitted. Set STO to reset SMBus.
0x90 Data byte received after general call address.
ACK transmitted. Read SMB0DAT. Wait for next byte or
STOP.
0x98 Data byte received after general call address.
NACK transmitted. Set STO to reset SMBus.
0xA0 STOP or repeated START received. No action necessary.
Slave Transmitter
0xA8 Own address + R received. ACK transmitted. Load SMB0DAT with data to transmit.
0xB0 Arbitr at io n lost in transmitti ng SLA + R/W as
master. Own address + R received. ACK
transmitted.
Save current data for retry when bus is
free. Load SMB0DAT with data to trans-
mit.
0xB8 Data byte transmitted. ACK received. Load SMB0DAT with data to transmit.
0xC0 Data byte transmitted. NACK received. Wait for STOP.
0xC8 Last data byte transmitted (AA=0). ACK
received. Set STO to reset SMBus.
Slave
0xD0 SCL Clock High Timer per SMB0CR timed out Set STO to reset SMBus.
All
0x00 Bus Error (illegal START or STOP) Set STO to reset SMBus.
0xF8 Idle State does not set SI.
Table 19.1. SMB0STA Status Codes and States (Continued)
Mode Status
Code SMBus State Typical Action
C8051F040/1/2/3/4/5/6/7
254 Rev. 1.5
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 255
20. Enhanced Serial Peripheral Interface (SPI0)
The Enhanced Serial Peripheral Interface (SPI0) provides access to a flexible, full-duplex synchronous
serial bus. SPI0 can operate as a master or slave device in both 3-wire or 4-wire modes, and supports mul-
tiple masters and slaves on a single SPI bus. The slave-select (NSS) signal can be configured as an input
to select SPI0 in slave mode, or to disable Master Mode operation in a multi-master environment, avoidin g
contention on the SPI bus when more than one master attempts simultaneous data transfers. NSS can
also be configur ed as a ch ip-select ou tput in master mode, or disable d for 3-wire operatio n. Additional gen-
eral purpose port I/O pins can be used to select multiple slave devices in master mode.
Figure 20.1. SPI Block Diagram
SFR Bus
Data Path
Control
SFR Bus
Write
SPI0DAT
Receive Data Buffer
SPI0DAT
01234567
Shift Register
SPI CONTROL LOGIC
SPI0CKR
SCR7
SCR6
SCR5
SCR4
SCR3
SCR2
SCR1
SCR0
SPI0CFG SPI0CN
Pin Interface
Control
Pin
Control
Logic
C
R
O
S
S
B
A
R
Port I/O
Read
SPI0DAT
SPI IRQ
Tx Data
Rx Data
SCK
MOSI
MISO
NSS
Transmit Data Buffer
Clock Divide
Logic
SYSCLK
CKPHA
CKPOL
SLVSEL
NSSMD1
NSSMD0
SPIBSY
MSTEN
NSSIN
SRMT
RXBMT
SPIF
WCOL
MODF
RXOVRN
TXBMT
SPIEN
C8051F040/1/2/3/4/5/6/7
256 Rev. 1.5
20.1. Signal Descriptions
The four signals used by SPI0 (MOSI, MISO, SCK, NSS) are described below.
20.1.1. Master Out, Slave In (MOSI)
The master-out, slave-in (MOSI) signal is an output from a master device and an input t o slave d evices. I t
is used to serially trans fer data from the ma ster to th e slave. This signal is an output when SPI0 is operat-
ing as a master and an input when SPI0 is operating as a slave. Data is transferred most-significant bit
first. When configured as a master, MOSI is driven by the MSB of the shift register in both 3- and 4-wire
mode.
20.1.2. Master In, Slave Out (MISO)
The master-in, slave-out (MISO) signal is an output from a slave device and an input to the master device.
It is used to serially transfer data from the slave to the master. This signal is an input when SPI0 is operat-
ing as a master and an output when SPI0 is operating as a slave. Data is transferred most-significant b it
first. The MISO pin is placed in a high-impeda nce sta te when the SPI module is di sabled and when the SPI
operates in 4-wire mode as a slave that is not selected. When acting as a slave in 3-wire mode, MISO is
always driven by the MSB of the shift register.
20.1.3. Serial Clock (SCK)
The serial c lock (SCK) signal is an ou tput from the m aster device and an input to slave devices. It is used
to synchronize the transfer of data between the master and slave on the MOSI and MISO lines. SPI0 gen-
erates this signal when operating as a master. The SCK signal is ignored by a SPI slave when the slave is
not selected (NSS = 1) in 4-wire slave mode.
20.1.4. Slave Select (NSS)
The function of the slave-select (NSS) signal is dependent on the setting of the NSSMD1 and NSSMD0
bits in the SPI0CN register. There are three possible modes that can be selected with these bits:
1. NSSMD[1:0] = 00: 3-Wire Master or 3-Wire Slave Mode: SPI0 operates in 3-wire mode, and
NSS is disabled. When operating as a slave device, SPI0 is always selected in 3-wire mode.
Since no select signal is present, SPI0 can be the only slave on the bus in 3-wire mode. This is
intended for point-to-point communication between a master and one slave.
2. NSSMD[1:0] = 01: 4-Wire Slave or Multi-Master Mode: SPI0 operates in 4-wire mode, and
NSS is enabled as an input. When operating as a slave, NSS selects the SPI0 device. When
operating as a master, a 1-to-0 transition of the NSS signal disables the master function of
SPI0 so that multiple master devices can be used on the same SPI bus.
3. NSSMD[1:0] = 1x: 4-Wire Master Mode: SPI0 operates in 4-wire mode , and NSS is ena bled as
an output. The setting of NSSMD0 determines what logic level the NSS pin will output. This
configuration should only be used when operating SPI0 as a master device.
See Figure 20.2, Figure 20.3, and Figure 20.4 for typical connection diagrams of the various operational
modes. Note that the setting of NSSMD bits affects the pinou t of the device. Wh en in 3- wire maste r or
3-wire slave mode, the NSS pin will not be mapped by the crossbar. In all other modes, the NSS signal will
be mapped to a pin on the device. See Section “17.1. Ports 0 through 3 and the Priority Crossbar
Decoder” on page 204 for general purpose port I/O and crossbar information.
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 257
20.2. SPI0 Master Mode Operation
A SPI master device initiates all data transfe r s o n a SPI bu s. SPI0 is pl ac ed in m ast er m ode by se ttin g the
Master Enable flag (MSTEN, SPI0CN.6). Writing a byte of data to the SPI0 data register (SPI0DAT) when
in master mode writes to the transmit buffer. If the SPI shift register is empty, the byte in the transmit buffer
is moved to the shift registe r, an d a data transf er begins. The SPI0 master immediately shifts out the data
serially on the MOSI line while providing the serial clock on SCK. The SPIF (SPI0CN.7) flag is set to logic
1 at the end of the transfer. If interrupts are enabled, an interrupt request is generated when the SPIF flag
is set. While the SPI0 master transfers data to a slave on the MOSI line, the addressed SPI slave device
simultaneously transfers the contents of its shif t register to the SPI master on the MISO line in a full-duplex
operation. Therefore, the SPIF flag serves as both a transmit-complete and receive-data-ready flag. The
data byte received from the slave is transferred MSB-first into the master's shift register. When a byte is
fully shifted into the register, it is moved to the receive buffer where it can be read by the processor by
reading SPI0DAT.
When configured as a master, SPI0 can operate in one of three dif feren t modes: multi-master mode , 3-wire
single-master mode, and 4-wire single-master mode. The default, multi-master mode is active when
NSSMD1 (SPI0CN.3) = 0 and NSSMD0 (SPI0CN.2) = 1. In this mode, NSS is an input to the device, and
is used to disable the master SPI0 when another master is accessing the bus. When NSS is pulled low in
this mode, MSTEN (SPI0CN.6) and SPIEN (SPI0CN.0) are set to 0 to disable the SPI master device, and
a Mode Fault is generated (MODF, SPI0CN.5 = 1). Mode Fault will generate an interrupt if enabled. SPI0
must be manually re-enabled in software under these circumstances. In multi-master systems, devices will
typically default to being sla ve devices wh ile they are not a cting as th e system master device . In multi -mas-
ter mode, slave devices can be addressed individually (if needed) using general-purpose I/O pins.
Figure 20.2 shows a connection diagram between two master devices in multiple-master mode.
3-wire single-m aster m ode is active wh en NSSMD1 (S PI0CN.3) = 0 and NSSMD0 (SPI0CN.2) = 0. In this
mode, NSS is not used , and do es not ge t mapped to an external port pin through the crossbar. Any slave
devices that must be addressed in this mode should be selected using general-purpose I/O pins.
Figure 20.3 shows a connection diagram between a master device in 3-wire master mode and a slave
device.
4-wire single-master mode is active when NSSMD1 (SPI0CN.3) = 1. In this mode, NSS is configured as an
output pin, and can be used as a slave-select signal for a single SPI device. In this mode, the output value
of NSS is controlled (in software) with the bit NSSMD0 (SPI0CN.2). Additional slave devices can be
addressed using gene ral-p urpose I/O pi ns. Figur e 20.4 shows a con nection diag ram for a ma ster de vice in
4-wire master mode and two slave devices.
C8051F040/1/2/3/4/5/6/7
258 Rev. 1.5
Figure 20.2. Multiple-Master Mode Connection Diagram
Figure 20.3. 3-Wire Single Master and Slave Mode Connection Diagram
Figure 20.4. 4-Wire Single Master and Slave Mode Connection Diagram
Master
Device 2
Master
Device 1
MOSI
MISO
SCK
MISO
MOSI
SCK
NSS
GPIO NSS
GPIO
Slave
Device
Master
Device
MOSI
MISO
SCK
MISO
MOSI
SCK
Slave
Device
Master
Device
MOSI
MISO
SCK
MISO
MOSI
SCK
NSS NSS
GPIO
Slave
Device
MOSI
MISO
SCK
NSS
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 259
20.3. SPI0 Slave Mode Operation
When SPI0 is enabled and not configured as a master, it will operate as a SPI slave. As a slave, bytes are
shifted in through the MOSI pin and out through the MISO pin by a master device controlling the SCK sig-
nal. A bit coun te r in the SPI0 lo gic cou nts SCK edges. When 8 bits have been sh if ted thro ugh the shif t reg-
ister, the SPIF flag is set to logic 1, and the byte is copied into the receive buffer. Data is read from the
receive buffer by reading SPI0DAT. A slave device cannot initiate transfers. Data to be transferred to the
master device is pre-loaded into the shift register by writing to SPI0DAT. Writes to SPI0DAT are double-
buf fered, and a re placed in the tra nsmit buf fer first. If the shif t re gister is e mpty, the contents o f the tra nsmit
buffer will immediately be transferred into the shift register. When the shift register already contains data,
the SPI will wait until the byte is transferred before loading it with the transmit buffer’s contents.
When configured as a slave, SPI0 can be configured for 4-wire or 3-wire operation. The default, 4-wire
slave mode, is active when NSSMD1 (SPI0CN.3) = 0 and NSSMD0 (SPI0CN.2) = 1. In 4- wire mode, the
NSS signal is routed to a port pin and configured as a digital input. SPI0 is enabled when NSS is logic 0,
and disabled when NSS is logic 1. The bit counter is reset on a falling edge of NSS. Note that the NSS sig-
nal must be driven low at least 2 system clocks before the first active edge of SCK for each byte transfer.
Figure 20.4 shows a connection diagram between two slave devices in 4-wire slave mode and a master
device.
3-wire slave mode is active when NSSMD1 (SPI0CN.3) = 0 and NSSMD0 (SPI0CN.2) = 0. NSS is not
used in this mode, and does not get map ped to an e xternal por t pin throug h the crossb ar. Since there is no
way of uniquely addressing the device in 3-wire slave mode, SPI0 must be the only slave device present
on the bus. It is important to note that in 3-wire slave mode there is no external means of resetting the bit
counter that determines when a full byte has been received. The bit counter can only be reset by disabling
and re-enabling SPI0 with the SPIEN bit. Figure 20.3 shows a connection diagr am betwee n a slave d evice
in 3-wire slave mod e an d a ma st er dev ice.
20.4. SPI0 Interrupt Sources
When SPI0 interrupts are enabled, the following four flags will generate an interrupt when they are set to
logic 1:
Note: All of the following interrupt bits must be cleared by software.
1. The SPI Interrupt Flag, SPIF (SPI0CN.7) is set to logic 1 at the end of each byte transfer. This
flag can occur in all SPI0 modes.
2. The Write Collision Flag, WCOL (SPI0CN.6) is set to logic 1 if a write to SPI0DAT is attempted
when the transmit buffer has not been emptied to the SPI shift register. When this occurs, the
write to SPI0DAT will be ignored, and the transmit buffer will not be written.This flag can occur
in all SPI0 modes.
3. The Mode Fault Flag MODF (SPI0CN.5) is set to logic 1 when SPI0 is configured as a master,
and for multi-master mode and the NSS pin is pulled low. When a Mode Fault occurs, the
MSTEN and SPIEN bits in SPI0CN are set to logi c 0 to di sable SPI0 and allow another master
device to access the bus.
4. The Receive Overrun Flag RXOVRN (SPI0CN.4) is set to logic 1 when configured as a slave,
and a transfer is completed and the receive buffer still holds an unread byte from a previous
transfer. The new byt e is not tr an sf er re d to th e r ece ive bu ffer, allo win g the p re vio usly received
data byte to be read. The data byte which caused the overrun is lost.
C8051F040/1/2/3/4/5/6/7
260 Rev. 1.5
20.5. Serial Clock Timing
As shown in Figure 20.5, four combinations of serial clock phase and polarity can be selected using the
clock control bits in the SPI0 Configuration Register (SPI0CFG). The CKPHA bit (SPI0CFG.5) selects one
of two clock pha se s (edg e u sed to latch the d ata). The CKPOL bit (SPI0 CFG.4) select s betwee n an a ctive-
high or active -low clock. Both m aster and slave de vices must be configured to use the same clock phase
and polarity. Note: SPI0 should be disabled (by clearing the SPIEN bit, SPI0CN.0) when changing the
clock phase or polarity.
Note that in master mode, the SPI samples MISO one system clock before the inactive edge of SCK (the
edge where MOSI changes state) to provide maximum settling time for the slave device.
The SPI0 Clock Rate Register (SPI0CKR) as shown in SFR Definition 20.3 controls the master mode
serial clock frequency. This register is ignored when operating in slave mode. When the SPI is configured
as a master, the maximum data transfer rate (bits/sec) is one-half the system clock frequency. When the
SPI is configured as a slave, the maximum data transfer rate (bits/sec) for full-duplex operation is 1/10 the
system clock frequency, provided that the master issues SCK, NSS (in 4-wire slave mode), and the serial
input data synchronously with the system clock. If the master issues SCK, NSS, and the serial input data
asynchronously, the maximum data transfer rate (bits/sec) must be less than 1/10 the system clock fre-
quency. In the special case where the ma ster only want s to transmit dat a to the sla ve and does n ot need to
receive data from the slave (i.e. half-duplex operation), the SPI slave can receive data at a maximum data
transfer rate (bits/sec) of 1/4 the system clock frequency. This is provided that the master issues SCK,
NSS, and the serial input data synchronously with the system clock.
Figure 20.5. Data/Clock Timing Diagram
SCK
(CKPOL=0, CKPHA=0)
SCK
(CKPOL=0, CKPHA=1)
SCK
(CKPOL=1, CKPHA=0)
SCK
(CKPOL=1, CKPHA=1)
MSB Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0MISO/MOSI
NSS
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 261
20.6. SPI Special Function Registers
SPI0 is accessed and controlled through four special function registers in the system controller: SPI0CN
Control Register, SPI0DAT Data Register, SPI0CFG Configuration Register, and SPI0CKR Clock Rate
Register. The four special function registers related to the operation of the SPI0 Bus are described in the
following definitions.
SFR Definition 20.1. SPI0CFG: SPI0 Configuration
Bit 7: SPIBSY: SPI Busy.
This bit is set to logic 1 when a SPI transfer is in progress (Master or slave Mode).
Bit 6: MSTEN: Master Mode Enable.
0: Disable master mode. Operate in slave mode.
1: Enable master mode. Operate as a master.
Bit 5: CKPHA: SPI0 Clock Phase.
This bit controls the SPI0 clock phase.
0: Data sampled on first edge of SCK period.
1: Data sampled on second edge of SCK period.
Bit 4: CKPOL: SPI0 Clock Polarity.
This bit controls the SPI0 clock polarity.
0: SCK line low in idle state.
1: SCK line high in idle state.
Bit 3: SLVSEL: Slave Selected Flag.
This bit is set to logic 1 whenever the NSS pin is low indicating SPI0 is the selected slave. It
is cleared to logic 0 when NSS is high (slave not selected). This bit does not indicate the
instantaneous value at the NSS pin, but rather a de-glitched version of the pin input.
Bit 2: NSSIN: NSS Instantaneous Pin Input.
This bit mimics the instantaneous value that is present on the NSS port pin at the time that
the register is read. This input is not de-glitched.
Bit 1: SRMT: Shift Register Empty (Valid in Slave Mode).
This bit will be set to logic 1 when all data has been transferred in/out of the shift register,
and there is no new information available to read from the transmit buffer or write to the
receive buffer. It returns to logic 0 when a data byte is transferr ed to the shift register from
the transmit buffer or by a transition on SCK.
NOTE: SRMT = 1 when in Master Mode.
Bit 0: RXBMT: Receive Buffer Empty (Valid in Slave Mode).
This bit will be set to logic 1 when the receive buffer has been read and contains no new
information. If there is new information availa ble in the receive buf fer that ha s not been read,
this bit will return to logic 0.
NOTE: RXBMT = 1 when in Master Mode.
R R/W R/W R/W R R R R Reset Value
SPIBSY MSTEN CKPHA CKPOL SLVSEL NSSIN SRMT RXBMT 00000111
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0x9A
0
C8051F040/1/2/3/4/5/6/7
262 Rev. 1.5
SFR Definition 20.2. SPI0CN: SPI0 Control
Bit 7: SPIF: SPI0 Interrupt Flag.
This bit is set to logic 1 by hardware at the end of a data transfer. If interrupts are enabled,
setting this bit causes the CPU to vector to the SPI0 interrupt service routine. This bit is not
automatically cleared by hardware. It must be cleared by software.
Bit 6: WCOL: Write Collision Flag.
This bit is set to logic 1 by hardware (and generates a SPI0 interrupt) to indicate a write to
the SPI0 data register was attempted while a data transfer was in progress. It must be
cleared by software.
Bit 5: MODF: Mode Fault Flag.
This bit is set to logic 1 by hardware (and generates a SPI0 interrupt) when a master mode
collision is detected (NSS is low, MSTEN = 1, and NSSMD[1:0] = 01). This bit is not auto-
matically cleared by hardware. It must be cleared by sof tware.
Bit 4: RXOVRN: Receive Overrun Flag (Slave Mode only).
This bit is set to logic 1 by hardware (and generates a SPI0 interrupt) when the receive
buffer still holds unread data from a previous transfer and the last bit of the current transfer
is shifted into the SPI0 shift register. This bit is not automatically cleared by hardware. It
must be cleared by software.
Bits 3-2: NSSMD1-NSSMD0: Slave Select Mode.
Selects between the following NSS operation modes:
(See Section “20.2. SPI0 Master Mode Operation” on p age 257 and Section “20.3. SPI0
Slave Mode Operation” on page 259).
00: 3-Wire Slave or 3-wire Master Mode. NSS signal is not routed to a port pin.
01: 4-Wire Slave or Multi-Master Mode (Default). NSS is always an input to the device.
1x: 4-Wire Single-Master Mode. NSS signal is mapped as an output from the device and will
assume the value of NSSMD0.
Bit 1: TXBMT: Transmit Buffer Empty.
This bit will be set to logic 0 when new data has been written to the transmit buffer. When
data in the transmit buffer is transferred to the SPI shift register, this bit will be set to logic 1,
indicating that it is safe to write a new byte to the transmit buffer.
Bit 0: SPIEN: SPI0 Enable.
This bit enables/disables the SPI.
0: SPI disabled.
1: SPI enabled.
R/W R/W R/W R/W R/W R/W R R/W Reset Value
SPIF WCOL MODF RXOVRN NSSMD1 NSSMD0 TXBMT SPIEN 00000110
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 Bit
Addressable
SFR Address:
SFR Page: 0xF8
0
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 263
SFR Definition 20.3. SPI0CKR: SPI0 Clock Rate
Bits 7-0: SCR7-SCR0: SPI0 Clock Rate
These bits determine the frequency of the SCK output when the SPI0 module is configured
for master mode operation. The SCK clock frequency is a divided version of the system
clock, and is give n in th e follo win g equat i on , whe re SYSCLK is the system clock frequency
and SPI0CKR is the 8-bit value held in the SPI0CKR register.
for 0 <= SPI0CKR <= 255
Example: If SYSCLK = 2 MHz and SPI0CKR = 0x04,
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
SCR7 SCR6 SCR5 SCR4 SCR3 SCR2 SCR1 SCR0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0x9D
0
fSCK 2000000
241+
--------------------------
=
fSCK 200kHz=
fSCK SYSCLK
2SPI0CKR 1+
-------------------------------------------------
=
C8051F040/1/2/3/4/5/6/7
264 Rev. 1.5
SFR Definition 20.4. SPI0DAT: SPI0 Data
Bits 7-0: SPI0DAT: SPI0 Transmit and Receive Data.
The SPI0DAT register is used to transmit and receive SPI0 data. Writing data to SPI0DAT
places the data into the transmit buffer and initiates a transfer when in Master Mode. A read
of SPI0DAT returns the contents of the receive buffer.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0x9B
0
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 265
21. UART0
UART0 is an enhanced serial port with frame error detection and address recognition hardware. UART0
may operate in full-duplex asynchronous or half-duplex sync hrono us modes, an d muti procces sor comm u-
nication is fully supported. Receive data is buffered in a holding register, allowing UART0 to start reception
of a second incoming data byte before software has finished reading the previous data byte. A Receive
Overrun bit indicates when new received data is latched into the receive buffer before the previously
received byte ha s be en read .
UART0 is accessed via its associated SFRs, Serial Control (SCON0) and Serial Dat a Buffer (SBUF0). The
single SBUF0 locat ion provides a ccess to both transmit and receive registers. Reading SCON0 accesses
the Receive regis te r an d writ ing SCON0 acce ss es the Transmit register.
UART0 may be operated in polled or interrupt mode. UART0 has two sources of interrupts: a Transmit
Interrupt flag, TI0 (SCON0.1) set when transmission of a data byte is complete, and a Receive Interrupt
flag, RI0 (SCON0.0) set when reception of a data byte is complete. UART0 interrupt flags are not cleared
by hardware when the CPU vectors to the interrupt service rou tin e; they must be cleared manually by soft-
ware. This allows software to determine the cause of the UART0 interrupt (transmit complete or receive
complete).
Figure 21.1. UART0 Block Diagram
Tx Control
Tx Clock Tx IRQ
Zero Detector
Send
Shift
SET
QD
CLR
Stop Bit
Gen.
TB80
Start
Data
Wr ite to
SBUF0
Crossbar
TX0
Port I/O
Serial Port
(UART0) Interrupt
Rx Control
Start
Rx Clock Load
SBUF
0x1FFShift
EN Rx IRQ
UART0
Baud Rate Generation
Logic
SFR Bus
Input Shi ft Register
(9 bits)
Frame Error
Detection
SBUF0
Read
SBUF0
SFR Bus
SADDR0
SADEN0
Match Detect
RB80
Load
SBUF0
Crossbar
RX0
SBUF0
Address
Match
SCON0
S
M
2
0
T
B
8
0
R
B
8
0
T
I
0
R
I
0
S
M
1
0
S
M
0
0
R
E
N
0
SSTA0
T
X
C
O
L
0
S
0
T
C
L
K
1
S
0
T
C
L
K
1
S
0
R
C
L
K
1
S
0
R
C
L
K
1
R
X
O
V
0
F
E
0
S
M
O
D
0
TI0
RI0
C8051F040/1/2/3/4/5/6/7
266 Rev. 1.5
21.1. UART0 Operational Modes
UART0 provides four operating modes (one synchronous and three asynchronous) selected by setting
configuration bits in the SCON0 register. These four modes offer different baud rates and communication
protocols. The four modes are summarized in Table 21.1.
21.1.1. Mode 0: Synchronous Mode
Mode 0 provide s synchronous, half-duplex comm unication. Serial data is transmitted and received on the
RX0 pin. The TX0 pin provides the shift clock for both transmit and receive. The MCU must be the master
since it generates the shift clock for transmission in both directions (see the interconnect diagram in
Figure 21.3).
Data transmission begins when an instruction writes a data byte to the SBUF0 register. Eight data bits are
transferred LSB first (see the timing diagram in Figure 21.2), and the TI0 Transmit Interrupt Flag
(SCON0.1) is set at the end of the eighth bit time. Data reception begins when the REN0 Receive Enable
bit (SCON0.4) is set to logic 1 and the RI0 Receive Interrupt Flag (SCON0.0) is cleared. One cycle after
the eighth bit is shifted in, the RI0 flag is set and reception stops until software clears the RI0 bit. An inter-
rupt will occur if enabled when either TI0 or RI0 are set.
The Mode 0 baud rate is SYSCLK/12. RX0 is forced to open-drain in Mode 0, and an external pullup will
typically be required.
Figure 21.2. UART0 Mode 0 Timing Diagram
Table 21.1. UART0 Modes
Mode Synchronization Baud Clock Data Bits Start/Stop Bits
0 Synchronous SYSCLK / 12 8 None
1 Asynchron o us Timer 1, 2, 3, or 4 Ov er flo w 8 1 Start, 1 Stop
2 Asynchronous SYSCLK / 32 or SYSCLK / 64 9 1 Start, 1 Stop
3 Asynchron o us Timer 1, 2, 3, or 4 Ov er flo w 9 1 Start, 1 Stop
D1D0 D2 D3 D4 D5 D6 D7
RX (data out) MODE 0 TRANSMIT
D0
MODE 0 RECEIVE
RX (data in)
D1 D2 D3 D4 D5 D6 D7
TX (clk out)
TX (clk out)
Shift
Reg.
CLK
C8051Fxxx
RX
TX
DATA
8 Extra Outputs
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 267
Figure 21.3. UART0 Mode 0 Interconnect
21.1.2. Mode 1: 8-Bit UART, Variable Baud Rate
Mode 1 provides standard asynchronous, full-duplex communication using a total of 10 bits per data byte:
one start bit, eight data bits (LSB first), and one stop bit. Data are transmitted from the TX0 pin and
received at the RX0 pin. On receive, the eight data bits are stored in SBUF0 and the stop bit goes into
RB80 (SCON0.2).
Data transmission begins when an instruction writes a data byte to the SBUF0 register. The TI0 Transmit
Interrupt Flag (SCON0.1) is set at the end of the transmission (the beginning of the stop-bit time). Data
reception can begin any time after the REN0 Receive Enable bit (SCON0.4) is set to logic 1. After the stop
bit is received, the data byte will be loaded into the SBUF0 receive register if the following conditions are
met: RI0 must be logic 0, and if SM20 is logic 1, the stop bit must be logic 1.
If these condition s ar e me t, the eig h t bits of data is stored in SBUF0, the stop bit is stored in RB80 and the
RI0 flag is set. If these conditions are not met, SBUF0 and RB80 will not be loaded and the RI0 flag will not
be set. An interrupt will occur if enabled when either TI0 or RI0 are set.
Figure 21.4. UART0 Mode 1 Timing Diagram
The baud rate generated in Mode 1 is a function of timer overflow, shown in Equation 21.1 and
Equation 21.3. UART0 can use Timer 1 operating in 8-Bit Auto-Reload Mode, or Timer 2, 3, or 4 operating
in Auto-reload Mode to generate the baud rate (note that the TX and RX clocks are selected separately).
On each timer overflow event (a rollover from all ones—0xFF for Timer 1, 0xFFFF for Timers 2, 3 and 4—
to zero) a clock is sent to the baud rate logic.
Timers 1, 2, 3, and 4 are selected as the baud rate source with bits in the SSTA0 register (see SFR Defini-
tion 21.2). The transmit baud rate clock is selected using the S0TCLK1 and S0TCLK0 bits, a nd the rece ive
baud rate clock is selected using the S0RCLK1 and S0RCLK0 bits.
The Mode 1 baud rate equations are shown below, where T1M is bit4 of register CKCON, TH1 is the 8-bit
reload register for Timer 1, and [RCAPnH, RCAPnL] is the 16-bit reload register for Timer 2, 3, or 4.
Equation 21.1. Mode 1 Baud Rate using Timer 1
The Timer 1 overflow rate is determine d by the Timer 1 clock source (T1CLK) and reload value (TH1). The
frequency of T 1CLK is selected as described in Section “23.1. Timer 0 and Timer 1” on page 287. The
Timer 1 overflow rate is calculated as shown in Equation 21.2.
D1D0 D2 D3 D4 D5 D6 D7
START
BIT
MARK STOP
BIT
BIT TIMES
BIT SAMPLING
SPACE
Mode1_BaudRate 1 32Timer1_OverflowRate=
When SMOD0 = 0:
Mode1_BaudRate 1 16Timer1_OverflowRate=
When SMOD0 = 1:
C8051F040/1/2/3/4/5/6/7
268 Rev. 1.5
Equation 21.2. Timer 1 Overflow Rate
When Timers 2, 3, or 4 are selected as a baud rate source, the baud rate is generated as shown in
Equation 21.3.
Equation 21.3. Mode 1 Baud Rate using Timer 2, 3, or 4
The overflow rate for Timer 2, 3, or 4 is determined by the clock source for the timer (TnCLK) and the 16-
bit reload value stored in the RCAPn register (n = 2, 3, or 4), as shown in Equation 21.4.
Equation 21.4. Timer 2, 3, or 4 Overflow Rate
Timer1_OverflowRate T1CLK 256 TH1–=
Mode1_BaudRate 1 16Timer234_OverflowRate=
Timer234_OverflowRate TnCLK 65536 RCAPn–=
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 269
21.1.3. Mode 2: 9-Bit UART, Fixed Baud Rate
Mode 2 provides asyn chronous, full-du plex communicatio n using a tot al of eleven bits per data b yte: a start
bit, 8 data bits (LSB first), a programmable ninth data bit, and a stop bit. Mode 2 supports multiprocessor
communications and hardware address recognition (see Section 21.2). On transmit, the ninth data bit is
determined by the valu e in TB80 (SCON0.3). It can be assigned the value of the p arity flag P in th e PSW or
used in multiprocessor communications. On receive, the ninth data bit goes into RB80 (SCON0.2) and the
stop bit is ignored.
Data transmission begins when an instruction writes a data byte to the SBUF0 register. The TI0 Transmit
Interrupt Flag (SCON0.1) is set at the end of the transmission (the beginning of the stop-bit time). Data
reception can begin any time after the REN0 Receive Enable bit (SCON0.4) is set to logic 1. After the stop
bit is received, the data byte will be loaded into the SBUF0 receive register if RI0 is logic 0 and one of the
following requirements are met:
• SM20 is logic 0
• SM20 is logic 1, the received 9th bit is logic 1, and the re ce ived ad dre ss matches th e UART0 address
as described in Section 21.2.
If the above conditions are satisfied, the eight bits of data are stored in SBUF0, the ninth bit is stored in
RB80 and the RI0 flag is set. If these conditions are not met, SBUF0 and RB80 will not be loaded and the
RI0 flag will not be set. An interrupt will occur if enabled when either TI0 or RI0 are set.
The baud rate in Mode 2 is either SYSCLK / 32 or SYSCLK / 64, according to the value of the SMOD0 bit
in register SSTA0.
Equation 21.5. Mode 2 Baud Rate
Figure 21.5. UART0 Modes 2 and 3 Timing Diagram
Figure 21.6. UART0 Modes 1, 2, and 3 Interconnect Diagram
BaudRate 2SMOD0SYSCLK
64
----------------------


=
D1D0 D2 D3 D4 D5 D6 D7
START
BIT
MARK STOP
BIT
BIT TIMES
BIT SAMPLING
SPACE D8
OR
RS-232
C8051Fxxx
RS-232
LEVEL
XLTR
TX
RX
C8051Fxxx
RX
TX
MCU
RX
TX
C8051F040/1/2/3/4/5/6/7
270 Rev. 1.5
21.1.4. Mode 3: 9-Bit UART, Variable Baud Rate
Mode 3 uses the Mode 2 transmission protocol with the Mode 1 baud rate generation. Mode 3 operation
transmits 11 bits: a start bit, 8 data bits (LSB first), a programmable ninth data bit, and a stop bit. The baud
rate is derived from Timer 1 or Timer 2, 3, or 4 overflows, as defined by Equation 21.1 and Equa tion 21.3.
Multiprocessor communications an d hardware address recog nition are suppor ted, as descri bed in Section
21.2.
21.2. Multiprocessor Communications
Modes 2 and 3 suppo rt multipro cessor communica tion betwe en a master processor and on e or more slave
processors by special use of the ninth data bit and the built-in UART0 address recognition hardware. When
a master processor wants to transmit to one or more sl a ves, it first sends an addr ess byte to select the tar-
get(s). An address byte differs from a data byte in that its ninth bit is logic 1; in a data byte, the ninth bit is
always set to logic 0. UART0 will recognize as “valid” (i.e., capable of causing an interrupt) two types of
addresses: (1) a masked address and (2) a broadcast address at any given time. Both are described
below.
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 271
21.3. Configuration of a Masked Address
The UART0 address is configured via two SFRs: SADDR0 (Serial Address) and SADEN0 (Serial Address
Enable). SADEN0 sets the bit mask for the address held in SADDR0: bits set to logic 1 in SADEN0 corre-
spond to bits in SADDR0 that are checked against the received address byte; bit s set to logic 0 in SADEN0
correspond to “don’t care” bits in SADDR0.
Setting the SM20 bit (SCON0.5) configures UART0 such that when a stop bit is received, UART0 will gen-
erate an interrupt on ly if the n inth b it is logic 1 (RB80 = ‘1’) and th e r eceived data byte matches the UART 0
slave address. Following the received address interrupt, the slave will clear its SM20 bit to enable inter-
rupts on the reception of the following data byte(s). Once the entire message is received, the addressed
slave resets its SM20 bit to ignore all transmissions until it receives the next address byte. While SM20 is
logic 1, UART0 ignores all bytes that do not match the UART0 address and include a ninth bit that is logic
1.
21.4. Broadcast Addressing
Multiple address es can be assigned to a sin gle slave and/or a single address can be assigned to multiple
slaves, thereby enabling "broadcast" transmissions to more than one slave simultaneously. The broadcast
address is the logical OR of registers SADDR0 and SADEN0, and ‘0’s of the result are treated as “don’t
cares”. Typically a broadcast address of 0xFF (hexadecimal) is acknowledged by all slaves, assuming
“don’t care” bi ts as ‘1’s. The master processo r can be co nfigured to receive all tr ansmiss ions or a prot ocol
can be implemented such that the master/slave role is temporarily reversed to enable half-duplex trans-
mission between th e or igin al ma st er and slave ( s).
Note in the above examples 4, 5, and 6, each slave would recognize as “valid” an address of 0xFF as a
broadcast address. Also note that examples 4, 5, and 6 uses the same SADDR0 and SADEN0 register
values as shown in the examples 1, 2, and 3 respectively (slaves #1, 2, and 3). Thus, a master could
address each slave device individually using a masked address, and also broadcast to all three slave
devices. For example, if a Master were to send an address “11110101”, only slave #1 would recognize the
address as valid. If a master were to then send an address of “11111111”, all three slave devices would rec-
ognize the add ress as a va lid br oa dcast addres s.
Example 1, SLAVE #1 Example 2, SLAVE #2 Example 3, SLAVE #3
SADDR0 = 00110101 SADDR0 =
00110101 SADDR0 = 00110101
SADEN0 = 00001111 SADEN0 =
11110011 SADEN0 = 11000000
UART0 Address = xxxx0101 UART0 Address = 0011xx01 UART0 Address = 00xxxxxx
Example 4, SLAVE #1 Example 5, SLAVE #2 Example 6, SLAVE #3
SADDR0 = 00110101 SADDR0 = 00110101 SAD DR0 = 00110101
SADEN0 = 00001111 SADEN0 = 11110011 SADEN0 = 11000000
Broadcast Address = 00111111 Broadcast Address = 11110111 Broadcast Address = 11110101
Where all ZEROES in the Broadcast address are don’t cares.
C8051F040/1/2/3/4/5/6/7
272 Rev. 1.5
Figure 21.7. UART Multi-Processor Mode Interconnect Diagram
21.5. Frame and Transmission Error Detection
All Modes:
The Transmit Collision bit (TXCOL0 bit in register SSTA0) reads '1' if user software writes data to the
SBUF0 register while a transmit is in progress.
Modes 1, 2, and 3:
The Receive Overrun bit (RXOV0 in register SSTA0) reads '1' if a new data byte is latched into the receive
buffer before software has read the previous byte. The Frame Error bit (FE0 in register SSTA0) reads '1' if
an invalid (low) STOP bit is detected.
Master
Device Slave
Device
TXRX RX TX
Slave
Device
RX TX
Slave
Device
RX TX
+5V
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 273
Table 21.2. Oscillator Frequencies for Standard Baud Rates
Oscillator frequency
(MHz) Divide Factor Timer 1 Reload
Value1Timer 2, 3, or 4
Reload Value Resulting Baud Rate (Hz)2
24.0 208 0xF3 0xFFF3 115200 (115384)
22.1184 192 0xF4 0xFFF4 115200
18.432 160 0xF6 0xFFF6 115200
11.0592 96 0xFA 0xFFFA 115200
3.6864 32 0xFE 0xFFFE 115200
1.8432 16 0xFF 0xFFFF 115200
24.0 832 0xCC 0xFFCC 28800 (28846)
22.1184 768 0xD0 0xFFD0 28800
18.432 640 0xD8 0xFFD8 28800
11.0592 348 0xE8 0xFFE8 28800
3.6864 128 0xF8 0xFFF8 28800
1.8432 64 0xFC 0xFFFC 28800
24.0 2496 0x64 0xFF64 9600 (9615)
22.1184 2304 0x70 0xFF70 9600
18.432 1920 0x88 0xFF88 9600
11.0592 1152 0xB8 0xFFB8 9600
3.6864 384 0xE8 0xFFE8 9600
1.8432 192 0xF4 0xFFF4 9600
Notes:
1. Assumes SMOD0=1 and T1M=1.
2. Numbers in parenthesis show the actual baud rate.
C8051F040/1/2/3/4/5/6/7
274 Rev. 1.5
SFR Definition 21.1. SCON0: UART0 Control
Bits7-6: SM00-SM10: Serial Port Operation Mode:
Write:
When written, these bits select the Serial Port Operation Mode as follows:
Reading these bits returns the current UAR T0 mode as defined above.
Bit5: SM20: Multiprocessor Communication Enable.
The function of this bit is dependent on the Serial Port Operation Mode.
Mode 0: No effect
Mode 1: Checks for valid stop bit.
0: Logic level of stop bit is ignored.
1: RI0 will only be activated if stop bit is logic level 1.
Mode 2 and 3: Multiprocessor Communications Enable.
0: Logic level of ninth bit is ignored.
1: RI0 is set and an interrupt is generated only when the ninth bit is logic 1 and the
received address matches the UART0 address or the broadcast address.
Bit4: REN0: Receive Enable.
This bit enables/disables the UART0 receiver.
0: UART0 reception disabled.
1: UART0 reception enabled.
Bit3: TB80: Ninth Transmission Bit.
The logic level of this bit will be assigned to the ninth transmission bit in Modes 2 and 3. It is
not used in Modes 0 and 1. Set or cleared by software as required.
Bit2: RB80: Ninth Receive Bit.
The bit is assigned the logic level of the ninth bit received in Modes 2 and 3. In Mode 1, if
SM20 is logic 0, RB80 is assigned the logic level of the received stop bit. RB8 is not used in
Mode 0.
Bit1: TI0: Transmit Interrupt Flag.
Set by hardware when a byte of data has been transmitted by UART0 (after the 8th bit in
Mode 0, or at the beginning of the stop bit in other modes). When the UART0 interrupt is
enabled, setting this bit causes the CPU to vector to the UART0 interrupt se rvic e ro utine.
This bit must be cleared manually by software.
Bit0: RI0: Receive Interrupt Flag.
Set by hardware when a byte of data has been received by UART0 (as selected by the
SM20 bit). When the UART0 interr upt is enabled, setting this bit causes the CPU to vector to
the UART0 interrupt service routine. This bit must be cleared manually by software.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
SM00 SM10 SM20 REN0 TB80 RB80 TI0 RI0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0x98
0
SM00 SM10 Mode
0 0 Mode 0: Synchronous Mode
0 1 Mode 1: 8-Bit UART, Variable Baud Rate
1 0 Mode 2: 9-Bit UART, Fixed Baud Rate
1 1 Mode 3: 9-Bit UART, Variable Baud Rate
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 275
SFR Definition 21.2. SSTA0: UART0 Status and Clock Selection
Bit7: FE0: Frame Error Flag.
This flag indicates if an invalid (low) STOP bit is detected.
0: Frame Error has not been detected
1: Frame Error has been detected.
Bit6: RXOV0: Receive Overrun Flag.
This flag indicates new data has been latched into the receive buffer before software has
read the previous byte.
0: Receive overrun has not been detected.
1: Receive Overrun has been detected.
Bit5: TXCOL0: Transmit Collision Flag.
This flag indicates user software has written to the SBUF0 r egister while a transmission is in
progress.
0: Transmission Collision has not been detected.
1: Transmission Collision has been detected.
Bit4: SMOD0: UART0 Baud Rate Doubler Enable.
This bit enables/disables the divide-by-two function of the UART0 baud rate logic for config-
urations descr ib ed in the UART0 section.
0: UART0 baud rate divide-by-two enabled.
1: UART0 baud rate divide-by-two disabled.
Bits3-2: UART0 Transmit Baud Rate Clock Selection Bits.
Bits1-0: UART0 Receive Baud Rate Clock Selection Bits
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
FE0 RXOV0 TXCOL0 SMOD0 S0TCLK1 S0TCLK0 S0RCLK1 S0RCLK0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0x91
0
S0TCLK1 S0TCLK0 Serial Transmit Baud Rate Clock Source
0 0 Timer 1 generates UART0 TX Baud Rate
0 1 Timer 2 Overflow gener ates UART0 TX baud rate
1 0 Timer 3 Overflow gener ates UART0 TX baud rate
1 1 Timer 4 Overflow gener ates UART0 TX baud rate
S0RCLK1 S0RCLK0 Serial Receive Baud Rate Clock Source
0 0 Timer 1 genera te s UART0 RX Baud Rate
0 1 Timer 2 Overflow generates UART0 RX baud rate
1 0 Timer 3 Overflow generates UART0 RX baud rate
1 1 Timer 4 Overflow generates UART0 RX baud rate
C8051F040/1/2/3/4/5/6/7
276 Rev. 1.5
SFR Definition 21.3. SBUF0: UART0 Data Buffer
SFR Definition 21.4. SADDR0: UART0 Slave Address
SFR Definition 21.5. SADEN0: UART0 Slave Address Enable
Bits7-0: SBUF0.[7:0]: UART0 Buffer Bits 7-0 (MSB-LSB)
This is actually two registers; a transmit and a receive buffer register . When data is moved to
SBUF0, it goes to the transmit buffer and is held for serial tr ansmission. Moving a byte to
SBUF0 is what initiates the transmission. When data is moved from SBUF0, it comes from
the receive buffer.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0x99
0
Bits7-0: SADDR0.[7:0]: UART0 Slave Address
The contents of this r egister are used to define the UAR T0 slave address. Register SADEN0
is a bit mask to determine which bits of SADDR0 are checked against a received address:
corresponding bits set to logic 1 in SADEN0 are checked; corresponding bits set to logic 0
are “don’t cares”.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xA9
0
Bits7-0: SADEN0.[7:0]: UART0 Slave Address Enable
Bits in this register enable corresponding bits in register SADDR0 to determine the UART0
slave address.
0: Corresponding bit in SADDR0 is a “don’t care”.
1: Corresponding bit in SADDR0 is checked against a received address.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xB9
0
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 277
22. UART1
UART1 is an asynchronous, full duplex serial port offering modes 1 and 3 of the standard 8051 UART.
Enhanced baud rate su pport allows a wide r ange o f clock sources to genera te st an dard baud r ates (details
in Section “22.1. Enhanced Baud Rate Generation” on page 278). Received data buffering allows
UART1 to st art rece ption of a second incoming dat a byte before sof tware has finished reading the previous
data byte.
UART1 has two associated SFRs: Serial Control Register 1 (SCON1) and Serial Data Buffer 1 (SBUF1).
The single SBUF1 location provides access to both transmit and receive registers. Reading SBUF1
accesses the buffered Receive register; writing SBUF1 accesses the Transmit register.
With UART1 interrupts enabled, an interrupt is generated each time a transmit is completed (TI1 is set in
SCON1), or a data byte has been received (RI1 is set in SCON1). The UART1 interrupt flags are not
cleared by hardwa re when the CPU vectors to th e interrupt ser vice routine. They must be cle ared manually
by software, allowing software to determine the cause of the UART1 interrupt ( transmit complete or re ceive
complete).
Figure 22.1. UART1 Block Diagram
UART1 Baud
Rate Generator
RI1
SCON1
RI1
TI1
RB81
TB81
REN1
MCE1
S1MODE
Tx Control
Tx Clock Send
SBUF1
(TX Shift)
Start
Data
Write to
SBUF1
Crossbar
TX1
Shift
Zero Detector
Tx IRQ
SET
QD
CLR
Stop Bit
TB81
SFR Bus
Serial
Port
Interrupt
TI1
Port I/O
Rx Control
Start
Rx Clock
Load
SBUF1
Shift 0x1FF RB81
Rx IRQ
Input Shift Register
(9 bits)
Load SBUF1
Read
SBUF1
SFR Bus
Crossbar
RX1
SBUF1
(RX Latch)
C8051F040/1/2/3/4/5/6/7
278 Rev. 1.5
22.1. Enhanced Baud Rate Generation
The UART1 baud rate is generated by Timer 1 in 8-bit auto-reload mode. The TX clock is generated by
TL1; the RX clock is generated by a copy of TL1 (shown as RX Timer in Figure 22.2), which is not user-
accessible. Both TX and RX Timer overflows are divided by two to generate the TX and RX baud rates.
The RX Timer runs when Timer 1 is enabled, and uses the same reload value (TH1). However, an
RX Timer reload is forced when a START condition is detected on the RX pin. This allows a receive to
begin any time a START is detected, independent of the TX Timer state.
Figure 22.2. UART1 Baud Rate Logic
Timer 1 should be configured for Mode 2, 8-bit auto-reload (see Section “23.1.3. Mode 2: 8-bit Counter/
Timer with Auto-Reload” on page 289). The Timer 1 reload value should be set so that overflows will
occur at two times the desired baud rate. Note that Timer 1 may be clocked by one of five sources: SYS-
CLK, SYSCLK / 4, SYSCLK / 12, SYSCLK / 48, or the external oscillator clock / 8. For any given Timer 1
clock source, the UART1 baud rate is determined by Equation 22.1, where T1CLK is the frequency of the
clock supplied to Timer 1, and TH1 is the high byte of Timer 1 (reload value).
Equation 22.1. UART1 Baud Rate
Timer 1 clock frequency is selected as described in Section “23.1. Timer 0 and Timer 1” on page 287. A
quick reference for typical baud rates and system clock frequencies is given in Table 22.1 through
Table 22.6. Note that the internal oscillator may still generate the system clock when the external oscillator
is driving Timer 1 (see Section “23.1. Time r 0 and Timer 1” on page 287 for more details).
RX Timer
Start
Detected
Overflow
Overflow
TH1
TL1
TX Clock
2
RX Cl ock
2
Timer 1 UART1
UartBaudRate T1CLK
256 TH1–
-------------------------------1
2
---
=
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 279
22.2. Operational Modes
UART1 provides standard asynchronous, full duplex communication. The UART mode (8-bit or 9-bit) is
selected by the S1MODE bit (SCON1.7). Typical UART connection options are shown below.
Figure 22.3. UART Interconnect Diagram
22.2.1. 8-Bit UART
8-Bit UART mode uses a total of 10 bits per data byte: one start bit, eight data bits (LSB first), and one stop
bit. Data are transmitted LSB first from the TX1 pin and received at the RX1 pin. On receive, the eight data
bits are stored in SBUF1 and the stop bit goes into RB81 (SCON1.2).
Data transmission begins when software writes a data byte to the SBUF1 register. The TI1 Transmit Inter-
rupt Flag ( SCON1.1) is set at th e end of the transm ission (the beginning of the stop-bit time). Data recep-
tion can begin any time after the REN1 Receive Enable bit (SCON1.4) is set to logic 1. After the stop bit is
received, the data byte will be loaded into the SBUF1 receive register if the following conditions are met:
RI1 must be logic 0, a nd if MCE1 is logic 1, the stop bi t must be logic 1. In the event of a receive data over-
run, the first received 8 bits are latched into the SBUF1 receive register and the following overrun data bits
are lost.
If these condition s ar e me t, the eig h t bits of data is stored in SBUF1, the stop bit is stored in RB81 and the
RI1 flag is set. If these conditions are not met, SBUF1 and RB81 will not be loaded and the RI1 flag will not
be set. An interrupt will occur if enabled when either TI1 or RI1 is set.
Figure 22.4. 8-Bit UART Timing Diagram
OR
RS-232
C8051Fxxx
RS-232
LEVEL
XLTR
TX
RX
C8051Fxxx
RX
TX
MCU RX
TX
D1D0 D2 D3 D4 D5 D6 D7
START
BIT
MARK
STOP
BIT
BIT TIMES
BIT SAMPLING
SPACE
C8051F040/1/2/3/4/5/6/7
280 Rev. 1.5
22.2.2. 9-Bit UART
9-bit UART mode uses a total of eleven bits per data byte: a start bit, 8 data bits (LSB first), a programma-
ble ninth data bit, and a stop bit. The state of the ninth transmit data bit is determined by the value in TB81
(SCON1.3), which is assigned by user so f twa re. It ca n be assigned the value of the p arity fla g (bit P in reg-
ister PSW) for error detection, or used in multiprocessor communications. On receive, the ninth data bit
goes into RB81 (SCON1.2) and the stop bit is ignored.
Data transmission begins when an instruction writes a data byte to the SBUF1 register. The TI1 Transmit
Interrupt Flag (SCON1.1) is set at the end of the transmission (the beginning of the stop-bit time). Data
reception ca n begin any time after the REN1 Receive Enable bit (SCON1.4) is set to ‘1’. After the stop bit
is received, the data byte will be loaded into the SBUF1 receive register if the following conditions are met:
(1) RI1 must be logic 0, and (2) if MCE1 is logic 1, the 9th bit must be logic 1 (when MCE1 is logic 0, the
state of the ninth data bit is unimportant). If these conditions are met, the eight bits of data are stored in
SBUF1, the ninth bit is stored in RB81, and the RI1 flag is set to ‘1’. If the above conditions are not met,
SBUF1 and RB81 will not be loaded and the RI1 flag will not be set to ‘1’. A UART1 interrupt will occur if
enabled when either TI1 or RI1 is set to ‘1’.
Figure 22.5. 9-Bit UART Timing Diagram
D1D0 D2 D3 D4 D5 D6 D7
START
BIT
MARK
STOP
BIT
BIT TIMES
BIT SAMPLING
SPACE
D8
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 281
22.3. Multiprocessor Communications
9-Bit UART mode supports multiprocessor communication between a master processor and one or more
slave processors by special use of the ninth dat a bit. When a master proce ssor wa nts to transmit to one or
more slaves, it first sends an address byte to select the target(s). An address byte differs from a data byte
in that its ninth bit is logic 1; in a data byte, the ninth bit is always set to logic 0.
Setting the MCE1 bit (SCON1.5) of a slave processor configures its UART such that when a stop bit is
received, the UART will generate an interrupt only if the ninth bit is logic one (RB81 = 1) signifying an
address byte has been received. In the UART interrupt handler, software should compare the received
address with the slave's own assigned 8-bit address. If the addresses match, the slave should clear its
MCE1 bit to enable interrupts on the reception of the following data byte(s). Slaves that weren't addressed
leave their MCE1 bits set and do not generate interrupts on the reception of the following data bytes,
thereby ignoring the data. Once the entire message is received, the addressed slave should reset its
MCE1 bit to ignore all transmissions until it receives the next address byte.
Multiple address es can be assigned to a sin gle slave and/or a single address can be assigned to multiple
slaves, thereby enabling "broadcast" transmissions to more than one slave simultaneously. The master
processor can be configured to receive all transmissions or a protocol can be implemented such that the
master/slave role is temporarily reversed to enable half-duplex transmission between the original master
and slave(s).
Figure 22.6. UART Multi-Processor Mode Interconnect Diagram
Master
Device Slave
Device
TXRX RX TX
Slave
Device
RX TX
Slave
Device
RX TX
+5V
C8051F040/1/2/3/4/5/6/7
282 Rev. 1.5
SFR Definition 22.1. SCON1: Serial Port 1 Control
Bit7: S1MODE: Serial Port 1 Operation Mode.
This bit selects the UART1 Operation Mode.
0: Mode 0: 8-bit UART with Variable Baud Rate
1: Mode 1: 9-bit UART with Variable Baud Rate
Bit6: UNUSED. Read = 1b. Write = don’t care.
Bit5: MCE1: Multiprocessor Communication Enable.
The function of this bit is dependent on the Serial Port 0 Operation Mode.
Mode 0: Checks for valid stop bit.
0: Logic level of stop bit is ignored.
1: RI1 will only be activated if stop bit is logic level 1.
Mode 1: Multiprocessor Communications Enable.
0: Logic level of ninth bit is ignored.
1: RI1 is set and an interrupt is generated only when the ninth bit is logic 1.
Bit4: REN1: Receive Enable.
This bit enables/disables the UART receiver.
0: UART1 reception disabled.
1: UART1 reception enabled.
Bit3: TB81: Ninth Transmission Bit.
The logic level of this bit will be assigned to the ninth transmission bit in 9-bit UART Mode. It
is not used in 8-bit UART Mode. Set or cleared by software as required.
Bit2: RB81: Ninth Receive Bit.
RB81 is assigned the value of the STOP bit in Mode 0; it is assigned the value of the 9th
data bit in Mode 1.
Bit1: TI1: Transmit Interrupt Flag.
Set by hardware when a byte of data has been transmitted by UART1 (after the 8th bit in 8-
bit UAR T Mode, or at the beginni ng of th e ST OP bit in 9-bit UART Mode). When the UAR T1
interrupt is enable d, setting this bit causes the CPU to vector to the UAR T1 interrupt service
routine. This bit must be cleared manually by software.
Bit0: RI1: Receive Interrupt Flag.
Set to ‘1’ by hardware when a byte of data has been received by UART1 (set at th e STOP
bit sampling time). When the UART1 interrupt is enabled, setting this bit to ‘1’ causes the
CPU to vector to the UART1 interrupt service routine. This bit must be cleared manually b y
software.
R/WR/WR/WR/WR/WR/WR/W R/WReset Value
S1MODE - MCE1 REN1 TB81 RB81 TI1 RI1 01000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 Bit
Addressable
SFR Address:
SFR Page: 0x98
1
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 283
SFR Definition 22.2. SBUF1: Serial (UART1) Port Data Buffer
Bits7-0: SBUF1[7:0]: Serial Data Buffer Bits 7-0 (MSB-LSB)
This SFR accesses two registers; a transmit shift register and a receive latch register. When
data is written to SBUF1, it goes to the transmit shift register and is held for serial transmis-
sion. Writing a byte to SBUF1 is what initiates the transmission. A read of SBUF 1 returns the
contents of the receive latc h .
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0x99
1
C8051F040/1/2/3/4/5/6/7
284 Rev. 1.5
Table 22.1. Timer Settings for Standard Baud Rates Using the Internal 24.5 MHz
Oscillator
Frequency: 24.5 MHz
Target
Baud Rate
(bps)
Baud Rate
% Error Oscillator
Divide
Factor
Timer Clock
Source SCA1-SCA0
(pre-scale
select)*
T1M*Ti mer 1
Reload
Value
(hex)
SYSCLK from
Internal Osc.
230400 -0.32% 106 SYSCLK XX 1 0xCB
115200 -0.32% 212 SYSCLK XX 1 0x96
57600 0.15% 426 SYSCLK XX 1 0x2B
28800 -0.32% 848 SYSCLK / 4 01 0 0x96
14400 0.15% 1704 SYSCLK / 12 00 0 0xB9
9600 -0.32% 2544 SYSCLK / 12 00 0 0x96
2400 -0.32% 10176 SYSCLK / 48 10 0 0x96
1200 0.15% 20448 SYSCLK / 48 10 0 0x2B
X = Don’t care
*Note: SCA1-SCA0 and T1M bit definitions can be found in Section 23.1.
Table 22.2. Timer Settings for Standard Baud Rates Using an External 25.0 MHz
Oscillator
Frequency: 25.0 MHz
Target
Baud Rate
(bps)
Baud Rate
% Error Oscillator
Divide
Factor
Timer Clock
Source SCA1-SCA0
(pre-scale
select)*
T1M*Timer 1
Reload
Value (hex)
SYSCLK from
External Osc.
230400 -0.47% 108 SYSCLK XX 1 0xCA
115200 0.45% 218 SYSCLK XX 1 0x93
57600 -0.01% 434 SYSCLK XX 1 0x27
28800 0.45% 872 SYSCLK / 4 01 0 0x93
14400 -0.01% 1736 SYSCLK / 4 01 0 0x27
9600 0.15% 2608 EXTCLK / 8 11 0 0x5D
2400 0.45% 10464 SYSCLK / 48 10 0 0x93
1200 -0.01% 20832 SYSCLK / 48 10 0 0x27
SYSCLK from
Internal Osc.
57600 -0.47% 432 EXTCLK / 8 11 0 0xE5
28800 -0.47% 864 EXTCLK / 8 11 0 0xCA
14400 0.45% 1744 EXTCLK / 8 11 0 0x93
9600 0.15% 2608 EXTCLK / 8 11 0 0x5D
X = Don’t care
*Note: SCA1-SCA0 and T1M bit definitions can be found in Section 23.1.
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 285
Table 22.3. Timer Settings for Standard Baud Rates Using an External
22.1184 MHz Oscillator
Frequency: 22.1184 MHz
Target
Baud Rate
(bps)
Baud Rate
% Error Oscillator
Divide
Factor
Timer Clock
Source SCA1-SCA0
(pre-scale
select)*
T1M*Timer 1
Reload
Value (hex)
SYSCLK from
External Osc.
230400 0.00% 96 SYSCLK XX 1 0xD0
115200 0.00% 192 SYSCLK XX 1 0xA0
57600 0.00% 384 SYSCLK XX 1 0x40
28800 0.00% 768 SYSCLK / 12 00 0 0xE0
14400 0.00% 1536 SYSCLK / 12 00 0 0xC0
9600 0.00% 2304 SYSCLK / 12 00 0 0xA0
2400 0.00% 9216 SYSCLK / 48 10 0 0xA0
1200 0.00% 18432 SYSCLK / 48 10 0 0x40
SYSCLK from
Internal Osc.
230400 0.00% 96 EXTCLK / 8 11 0 0xFA
115200 0.00% 192 EXTCLK / 8 11 0 0xF4
57600 0.00% 384 EXTCLK / 8 11 0 0xE8
28800 0.00% 768 EXTCLK / 8 11 0 0xD0
14400 0.00% 1536 EXTCLK / 8 11 0 0xA0
9600 0.00% 2304 EXTCLK / 8 11 0 0x70
X = Don’t care
*Note: SCA1-SCA0 and T1M bit definitions can be found in Section 23.1.
Table 22.4. Timer Settings for S tandard Baud Rates Using an External 18.432 MHz
Oscillator
Frequency: 18.432 MHz
Target
Baud Rate
(bps)
Baud Rate
% Error Oscillator
Divide
Factor
Timer Clock
Source SCA1-SCA0
(pre-scale
select)*
T1M*Timer 1
Reload
Value
(hex)
SYSCLK from
External Osc.
230400 0.00% 80 SYSCLK XX 1 0xD8
115200 0.00% 160 SYSCLK XX 1 0xB0
57600 0.00% 320 SYSCLK XX 1 0x60
28800 0.00% 640 SYSCLK / 4 01 0 0xB0
14400 0.00% 1280 SYSCLK / 4 01 0 0x60
9600 0.00% 1920 SYSCLK / 12 00 0 0xB0
2400 0.00% 7680 SYSCLK / 48 10 0 0xB0
1200 0.00% 15360 SYSCLK / 48 10 0 0x60
SYSCLK from
Internal Osc.
230400 0.00% 80 EXTCLK / 8 11 0 0xFB
115200 0.00% 160 EXTCLK / 8 11 0 0xF6
57600 0.00% 320 EXTCLK / 8 11 0 0xEC
28800 0.00% 640 EXTCLK / 8 11 0 0xD8
14400 0.00% 1280 EXTCLK / 8 11 0 0xB0
9600 0.00% 1920 EXTCLK / 8 11 0 0x88
C8051F040/1/2/3/4/5/6/7
286 Rev. 1.5
X = Don’t care
*Note: SCA1-SCA0 and T1M bit definitions can be found in Section 23.1.
Table 22.4. Timer Settings for St andard Baud Rates Using an External 18.432 MHz
Oscillator
Frequency: 18.432 MHz
Target
Baud Rate
(bps)
Baud Rate
% Error Oscillator
Divide
Factor
Timer Clock
Source SCA1-SCA0
(pre-scale
select)*
T1M*Timer 1
Reload
Value
(hex)
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 287
Table 22.5. Timer Settings for Standard Baud Rates Using an External
11.0592 MHz Oscillator
Frequency: 11.0592 MHz
Target
Baud Rate
(bps)
Baud Rate
% Error Oscillator
Divide
Factor
Timer Clock
Source SCA1-SCA0
(pre-scale
select)*
T1M*Timer 1
Reload
Value
(hex)
SYSCLK from
External Osc.
230400 0.00% 48 SYSCLK XX 1 0xE8
115200 0.00% 96 SYSCLK XX 1 0xD0
57600 0.00% 192 SYSCLK XX 1 0xA0
28800 0.00% 384 SYSCLK XX 1 0x40
14400 0.00% 768 SYSCLK / 12 00 0 0xE0
9600 0.00% 1152 SYSCLK / 12 00 0 0xD0
2400 0.00% 4608 SYSCLK / 12 00 0 0x40
1200 0.00% 9216 SYSCLK / 48 10 0 0xA0
SYSCLK from
Internal Osc.
230400 0.00% 48 EXTCLK / 8 11 0 0xFD
115200 0.00% 96 EXTCLK / 8 11 0 0xFA
57600 0.00% 192 EXTCLK / 8 11 0 0xF4
28800 0.00% 384 EXTCLK / 8 11 0 0xE8
14400 0.00% 768 EXTCLK / 8 11 0 0xD0
9600 0.00% 1152 EXTCLK / 8 11 0 0xB8
X = Don’t care
*Note: SCA1-SCA0 and T1M bit definitions can be found in Section 23.1.
Table 22.6. Timer Settings for S tandard Baud Rates Using an External 3.6864 MHz
Oscillator
Frequency: 3.6864 MHz
Target
Baud Rate
(bps)
Baud Rate
% Error Oscillator
Divide
Factor
Timer Clock
Source SCA1-SCA0
(pre-scale
select)*
T1M*Tim er 1
Reload
Value (hex)
SYSCLK from
External Osc.
230400 0.00% 16 SYSCLK XX 1 0xF8
115200 0.00% 32 SYSCLK XX 1 0xF0
57600 0.00% 64 SYSCLK XX 1 0xE0
28800 0.00% 128 SYSCLK XX 1 0xC0
14400 0.00% 256 SYSCLK XX 1 0x80
9600 0.00% 384 SYSCLK XX 1 0x40
2400 0.00% 1536 SYSCLK / 12 00 0 0xC0
1200 0.00% 3072 SYSCLK / 12 00 0 0x80
SYSCLK from
Internal Osc.
230400 0.00% 16 EXTCLK / 8 11 0 0xFF
115200 0.00% 32 EXTCLK / 8 11 0 0xFE
57600 0.00% 64 EXTCLK / 8 11 0 0xFC
28800 0.00% 128 EXTCLK / 8 11 0 0xF8
14400 0.00% 256 EXTCLK / 8 11 0 0xF0
9600 0.00% 384 EXTCLK / 8 11 0 0xE8
C8051F040/1/2/3/4/5/6/7
288 Rev. 1.5
X = Don’t care
*Note: SCA1-SCA0 and T1M bit definitions can be found in Section 23.1.
Table 22.6. Timer Settings for S tandard Baud Rates Using an External 3.6864 MHz
Oscillator
Frequency: 3.6864 MHz
Target
Baud Rate
(bps)
Baud Rate
% Error Oscillator
Divide
Factor
Timer Clock
Source SCA1-SCA0
(pre-scale
select)*
T1M*Tim er 1
Reload
Value (hex)
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 287
23. Timers
Each MCU includes 5 counter/timers: Timer 0 and Timer 1 are 16-bit counter/timers compatible with those
found in the standard 8051. Timer 2, Timer 3, and Timer 4 are 16-bit auto-reload and capture counter/tim-
ers for use with the ADC, DAC’s, square-wave generation, or for general-purpose use. These timers can
be used to measure time intervals, count external events and ge ner ate period i c interru pt requ ests. Timer 0
and Timer 1 are nearly identical and have four primary modes of operation. Timers 2, 3, and 4 are identi-
cal, and offer not only 16-bit auto-reload and capture, but have the ability to produce a 50% duty-cycle
square-wave (toggle output) at an external port pin.
Timers 0 and 1 may be clocked by one of five sources, determined by the Timer Mode Select bits (T1M-
T0M) and the Clock Scale bits (SCA1-SCA0). The Clock Scale bits define a pre-scaled clock by which
Timer 0 and/or Timer 1 may be clocked (See SFR Definition 23.3 for pre-scaled clock selection). Timer 0/1
may then be configured to use this pre-scaled clock signal or the system clock. Timers 2, 3, and 4 may be
clocked by the system clock, the system clock divided by 12, or the external oscillator clock source divided
by 8.
Timer 0 and Timer 1 may also be operated as counters. When functioning as a counter, a counter/timer
register is incremented on each high-to-low transition at the selected input pin. Events with a frequency of
up to one-fourth the system clock's frequency can be counted. The input signal need not be periodic, but it
should be held at a given logic level for at least two full system clock cycles t o ensure the level is properly
sampled.
23.1. Timer 0 and Timer 1
Each timer is implemented as 16-bit register accessed as two separate bytes: a low byte (TL0 or TL1) and
a high byte (TH0 or TH1 ). The Counte r/Timer Control register (TCON) is used to enable Timer 0 and T i mer
1 as well as indicate their status. Timer 0 interrupts can be enab le d by s et ting th e ET 0 bit in th e IE re gis te r
(Section “12.3.5. Interrupt Register Descriptions” on page 156); Timer 1 inter rupts can be enabled by
setting the ET1 bit in the IE register (Section 12.3.5). Both counter/timers operate in one of four primary
modes selected by setting the Mode Select bits T1M1-T0M0 in the Counter/Timer Mode register (TMOD).
Each timer can be configured independently.
23.1.1. Mode 0: 13-bit Counter/Timer
Timer 0 and Timer 1 operate as 13-bit counter/timers in Mode 0. The following describes the configuration
and operation of Timer 0. However, both timers operate identically, and Timer 1 is configured in the same
manner as described for Timer 0.
The TH0 register holds the eight MSBs of the 13-bit counter/timer. TL0 holds the five LSBs in bit positions
TL0.4-TL0.0. The three upper bits of TL0 (TL0.7-TL0.5) are indeterminate and should be masked out or
ignored when reading. As the 13-bit timer register increments and overflows from 0x1FFF (all ones) to
0x0000, the timer overflow flag TF0 (TCON.5) is set and an interrupt will occur if Timer 0 interrupts are
enabled.
Timer 0 and Timer 1 Modes: Timer 2, 3, and 4 Modes:
13-bit counter/timer 16-bit counter/timer with auto-reload
16-bit counter/timer 16-bit counter/timer with capture
8-bit counter/timer with auto-reload Toggle Output
Two 8-bit counter/timers (Timer 0 only)
C8051F040/1/2/3/4/5/6/7
288 Rev. 1.5
The C/T0 bit (TMOD.2) selects the counter/timer's clock source. When C/T0 is set to logic 1, high-to-low
transitions at the selected Timer 0 input pin (T0) increment the timer register (Refer to Section
“17.1. Ports 0 through 3 and the Priority Crossbar Decoder” on page 204 for information on selecting
and configuring external I/O pins). Clearing C/T0 selects the clock defined by the T0M bit (CKCON.3).
When T0M is se t, Timer 0 is cloc ke d by t he s ystem clock. When T0M is cleared, Timer 0 is clocked by the
source selected by the Clock Scale bits in CKCON (see SFR Definition 23.3).
Setting the TR0 bit (TCON.4) enables the timer when either GATE0 (TMOD.3) is logic 0 or the input signal
/INT0 is logic-level 1. Setting GATE0 to ‘1’ allows the timer to be controlled by the external input signal /
INT0 (see Section “12.3.5. Int erru pt Regi st er De sc rip ti ons ” o n page 156), facilit ating pulse width mea-
surements.
Setting TR0 does not force the timer to reset. The timer registers should be loaded with the desired initial
value before the timer is enabled.
TL1 and TH1 form the 13-bit re gister for Timer 1 in the same manner as d escribe d above for TL0 a nd TH0.
Timer 1 is configured and controlled using the relevant TCON and TMOD bits just as with Timer 0. The
input signal /INT1 is used with Timer 1.
Figure 23.1. T0 Mode 0 Block Diagram
23.1.2. Mode 1: 16-bit Counter/Timer
Mode 1 operation is the same as Mode 0, except that the counter/timer registers use all 16 bits. The coun-
ter/timers are enabled and configured in Mode 1 in the same manner as for Mode 0.
TR0 GATE0 /INT0 Counter/Timer
0 X X Disabled
1 0 X Enabled
110Disabled
111Enabled
Note: X = Don't Care
TCLK
TL0
(5 bi ts) TH0
(8 bi ts)
TCON
TF0
TR0
TR1
TF1
IE1
IT1
IE0
IT0
Interrupt
TR0
0
1
0
1
SYSCLK
Pre-scaled Clock
CKCON
S
C
A
0
S
C
A
1
T
1
M
T
0
M
TMOD
T
1
M
1
T
1
M
0
C
/
T
1
G
A
T
E
1
G
A
T
E
0
C
/
T
0
T
0
M
1
T
0
M
0
GATE0
/INT0
T0
Crossbar
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 289
23.1.3. Mode 2: 8-bit Counter/Timer with Auto-Reload
Mode 2 configures Timer 0 and Timer 1 to operate as 8-bit cou nter/timers with automa tic reload of the st art
value. TL0 holds the count and TH0 holds the reload value. When the counte r in TL0 overflows fro m 0x FF
to 0x00, the timer overflow flag TF0 (TCON.5) is set and the counter in TL0 is reloaded from TH0. If Timer
0 interrupts are enabled, an interrupt will occur when the TF0 flag is set. The reload value in TH0 is not
changed. TL0 must be initialized to the desired value before enabling the timer for the first count to be cor-
rect. When in Mode 2, Timer 1 operates identically to Timer 0.
Both counter/timers are enabled and configured in Mode 2 in the same manner as Mode 0. Setting the
TR0 bit (TCON.4) enables th e timer when ei ther GATE0 (TMOD.3) is logic 0 or when the inp ut signal /INT0
is low.
Figure 23.2. T0 Mode 2 Block Diagram
TCLK
TMOD
T
1
M
1
T
1
M
0
C
/
T
1
G
A
T
E
1
G
A
T
E
0
C
/
T
0
T
0
M
1
T
0
M
0
TCON
TF0
TR0
TR1
TF1
IE1
IT1
IE0
IT0
Interrupt
TL0
(8 bits)
Reload
TH0
(8 bits)
0
1
0
1
SYSCLK
Pre-scaled Clock
CKCON
S
C
A
0
S
C
A
1
T
1
M
T
0
M
TR0
GATE0
/INT0
T0
Crossbar
C8051F040/1/2/3/4/5/6/7
290 Rev. 1.5
23.1.4. Mode 3: Two 8-bit Counter/Timers (Timer 0 Only)
In Mode 3, Timer 0 is configu red as two separate 8-bit counter/timers held in TL0 and TH0. T he counter/
timer in TL0 is controlled using the T imer 0 control/status bits in TCON and TMOD: TR0, C/T0, GATE0 and
TF0. TL0 can use either the system clock or an external input signal as its timebase. The TH0 register is
restricted to a timer function sourced by the system clock or prescaled clock. TH0 is enabled using the
Timer 1 run control bit TR1. TH0 sets the Timer 1 overflow flag TF1 on overflow and thus controls the
Timer 1 interru pt .
Timer 1 is inactive in Mode 3. When Timer 0 is operating in Mode 3, Timer 1 can be operated in Modes 0,
1 or 2, but cannot be clocked by external signals nor set the TF1 flag and generate an interrupt. However,
the Timer 1 overflow can be used to generate baud rates for the SMBus and/or UART, and/or initiate A DC
conversions. While Timer 0 is operating in Mode 3, Timer 1 run control is handled through its mode set-
tings. To run Timer 1 while Timer 0 is in Mode 3, set the Timer 1 Mode as 0, 1, or 2. To disable Timer 1,
configure it for Mode 3.
Figure 23.3. T0 Mode 3 Block Diagram
TL0
(8 bits)
TMOD
0
1
TCON
TF0
TR0
TR1
TF1
IE1
IT1
IE0
IT0
Interrupt
Interrupt
0
1
SYSCLK
Pre-scaled Clock TR1 TH0
(8 bits)
CKCON
S
C
A
0
S
C
A
1
T
1
M
T
0
M
T
1
M
1
T
1
M
0
C
/
T
1
G
A
T
E
1
G
A
T
E
0
C
/
T
0
T
0
M
1
T
0
M
0
TR0
GATE0
/INT0
T0
Crossbar
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 291
SFR Definition 23.1. TCON: Timer Control
Bit7: TF1: Timer 1 Overflow Flag.
Set by hardware when Timer 1 overflows. This flag can be cleared by software but is auto-
matically cleared when the CPU vectors to the Time r 1 interr u pt se rvic e ro utine.
0: No Timer 1 over flo w det ec te d.
1: Timer 1 has overflowed.
Bit6: TR1: Timer 1 Run Control.
0: Timer 1 disabled.
1: Timer 1 enabled.
Bit5: TF0: Timer 0 Overflow Flag.
Set by hardware when Timer 0 overflows. This flag can be cleared by software but is auto-
matically cleared when the CPU vectors to the Time r 0 interr u pt se rvic e ro utine.
0: No Timer 0 over flo w det ec te d.
1: Timer 0 has overflowed.
Bit4: TR0: Timer 0 Run Control.
0: Timer 0 disabled.
1: Timer 0 enabled.
Bit3: IE1: External Interrupt 1.
This flag is set by hardware when an edge/le vel of type defined by IT1 is de tected. It can be
cleared by soft ware but is automatica lly cleared when the CPU vectors to the Exter nal Inter-
rupt 1 service routine if IT1 = 1. This flag is the inverse of the /INT1 signal.
Bit2: IT1: Interrupt 1 Type Select.
This bit selects whether the configured /INT1 interrupt will be falling-edge sensitive or
active-low.
0: /INT1 is level triggered, active-low.
1: /INT1 is edge triggered, falling-edge.
Bit1: IE0: External Interrupt 0.
This flag is set by hardware when an edge/le vel of type defined by IT0 is de tected. It can be
cleared by soft ware but is automatica lly cleared when the CPU vectors to the Exter nal Inter-
rupt 0 service routine if IT0 = 1. This flag is the inverse of the /INT0 signal.
Bit0: IT0: Interrupt 0 Type Select.
This bit selects whether the configured /INT0 interrupt will be falling-edge sensitive or
active-low.
0: /INT0 is level triggered, ac tive logic -low.
1: /INT0 is edge triggered, falling-edge.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
TF1 TR1 TF0 TR0 IE1 IT1 IE0 IT0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 Bit
Addressable
SFR Address:
SFR Page: 0x88
0
C8051F040/1/2/3/4/5/6/7
292 Rev. 1.5
SFR Definition 23.2. TMOD: Timer Mode
Bit7: GATE1: Timer 1 Gate Control.
0: Timer 1 enable d wh en TR1 = 1 irres pec tiv e of /IN T1 log ic leve l.
1: Timer 1 enabled only when TR1 = 1 AND /INT1 = logic 1.
Bit6: C/T1: Counter/Timer 1 Select.
0: Timer Function: Timer 1 incremented by clock defined by T1M bit (CKCON.4).
1: Counter Function: Timer 1 incremented by high-to-low transitions on external input pin
(T1).
Bits5-4: T1M1-T1M0: Timer 1 Mode Select.
These bits select the Timer 1 operation mode.
Bit3: GATE0: Timer 0 Gate Control.
0: Timer 0 enable d wh en TR0 = 1 irres pec tiv e of /IN T0 log ic leve l.
1: Timer 0 enabled only when TR0 = 1 AND /INT0 = logic 1.
Bit2: C/T0: Counter/Timer Select.
0: Timer Function: Timer 0 incremented by clock defined by T0M bit (CKCON.3).
1: Counter Function: Timer 0 incremented by high-to-low transitions on external input pin
(T0).
Bits1-0: T0M1-T0M0: Timer 0 Mode Select.
These bits select the Timer 0 operation mode.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
GATE1 C/T1 T1M1 T1M0 GATE0 C/T0 T0M1 T0M0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0x89
0
T1M1 T1M0 Mode
0 0 Mode 0: 13-bit coun te r/ tim er
0 1 Mode 1: 16-bit coun te r/ tim er
1 0 Mode 2: 8-bit counter/timer with auto-reload
1 1 Mode 3: Timer 1 inactive
T0M1 T0M0 Mode
0 0 Mode 0: 13-bit counter/timer
0 1 Mode 1: 16-bit counter/timer
1 0 Mode 2: 8-bit counter/timer with auto-reload
1 1 Mode 3: Two 8-bit counter/timers
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 293
SFR Definition 23.3. CKCON: Clock Control
SFR Definition 23.4. TL0: Timer 0 Low Byte
Bits7-5: UNUSED. Read = 000b, Write = don’t care.
Bit4: T1M: Timer 1 Clock Select.
This select the clock source supplied to Timer 1. T1M is igno re d when C/T1 is set to logic 1.
0: Timer 1 uses the clock defined by the prescale bit s, SCA1-SCA0.
1: Timer 1 uses the system clock.
Bit3: T0M: Timer 0 Clock Select.
This bit selects the clock source supplied to Timer 0. T0M is ignored when C/T0 is set to
logic 1.
0: Counter/Timer 0 uses the clock defined by the prescale bits, SCA1-SCA0.
1: Counter/Timer 0 uses the system clock.
Bit2: UNUSED. Read = 0b, Write = don’t care.
Bits1-0: SCA1-SCA0: Timer 0/1 Prescale Bits
These bits control the division of the clock supplied to Timer 0 and/or Timer 1 if configured
to use prescaled clock inputs.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
- - - T1M T0M - SCA1 SCA0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0x8E
0
SCA1 SCA0 Prescaled Clock
0 0 System clock divided by 12
0 1 System clock divided by 4
1 0 System clock divided by 48
1 1 External clock divided by 8
Bits 7-0: TL0: Timer 0 Low Byte.
The TL0 register is the low byte of the 16-bit Timer 0.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0x8A
0
C8051F040/1/2/3/4/5/6/7
294 Rev. 1.5
SFR Definition 23.5. TL1: Timer 1 Low Byte
SFR Definition 23.6. TH0: Timer 0 High Byte
SFR Definition 23.7. TH1: Timer 1 High Byte
Bits 7-0: TL1: Timer 1 Low Byte.
The TL1 register is the low byte of the 16-bit Timer 1.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0x8B
0
Bits 7-0: TH0: Timer 0 High Byte.
The TH0 register is the high byte of the 16-bit Timer 0.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0x8C
0
Bits 7-0: TH1: Timer 1 High Byte.
The TH1 register is the high byte of the 16-bit Timer 1.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0x8D
0
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 295
23.2. Timer 2, Timer 3, and Timer 4
Timers n are 16-bit counter/timers, each formed by two 8-bit SFRs: TMRnL (low byte) and TMRnH (high
byte) where n = 2, 3, and 4 for timers 2, 3, and 4 respectively. These timers feature auto-reload, capture,
and toggle output modes with the ability to count up or down. Capture Mode and Auto-reload mode are
selected using bits in the Timer n Control registers (TMRnCN). Toggle output mode is selected using the
T imer 2, 3, and 4 Configuration registers (TMRnCF). These timers may also be used to generate a square-
wave at an external pin. As with Timers 0 and 1, T i mers n can use eithe r the system clock (divided b y one,
two, or twelve), external clock (divided by eight) or transitions on an external input pin as its clock source.
The Counter/Timer Select bit C/Tn (TMRnCN.1) configures the peripheral as a counter or timer. Clearing
C/Tn configures the Timer to be in a timer mode (i.e., the system clock or external clock as input for the
timer). When C/Tn is set to 1, the timer is configured as a counter (i.e., high-to-low transitions at the Tn
input pin increment (or decrement) the counter/timer register). Refer to Section “17.1. Port s 0 through 3
and the Priority Crossbar Decoder” on page 204 for information on selecting and configuring external I/
O pins for digital peripherals, such as the Tn pin. Timer 2 and 3 can be used to start an ADC Data Conver-
sion and Timers 2, 3, and 4 can schedule DAC outputs. Only Timer 1 can be used to generate baud rates
for UART 1, and Timers 1, 2, 3, or 4 may be used to generate baud rates for UART 0.
Timer n can use either SYSCLK, SYSCLK divided by 2, SYSCLK divided by 12, an external clock divided
by 8, or high-to-low transitions on the Tn input pin as its clock source when operating in Counter/Timer with
Capture mode . Clearing the C/Tn bit (TMRnCN.1) sele cts the system clock/externa l clock as the input fo r
the timer. The Timer Clock Select bits TnM0 and TnM1 in TMRnCF can be used to select the system clock
undivided, system clock divided by two, system clock divided by 12, or an external clock provided at the
XTAL1/XTAL2 pins divided by 8 (see SFR Definition 23.9). When C/Tn is set to logic 1, a high-to-low tran-
sition at the Tn input pin increments the counter/timer register (i.e., configured as a counte r) .
23.2.1. Configuring Timer 2, 3, and 4 to Count Down
Timers 2, 3, and 4 have the ability to count down. When the timer’s respective Decrement Enable Bit
(DCEN) in the T imer Configuration Register (See SFR Definition 23.9) is set to ‘1’, the timer can then count
up or down. When DCEN = 1, the direction of the timer ’s count is controlled by the TnEX pin’s logic level.
When TnEX = 1, the counter/timer will count up; when TnEX = 0, the counter/timer will count down. To use
this feature, TnEX must be enabled in the digital crossbar and configured as a digital input.
Note: When DCEN = 1, other functions of the TnEX input (i.e., capture and auto-reload) are not available.
TnEX will only control the direction of the timer when DCEN = 1.
C8051F040/1/2/3/4/5/6/7
296 Rev. 1.5
23.2.2. Capture Mode
In Capture Mode, T ime r n will operate as a 16-bit counter/timer with capture facility. When the Timer Exter-
nal Enable bit (found in the TMRnCN register) is set to ‘1’, a high-to-low transition on the TnEX input pin
causes the 16-bit value in the associated timer (TMRnH, TMRnL) to be loaded into the capture registers
(RCAPnH, RCAPnL). If a capture is triggered in the counter/timer, the Timer External Flag (TMRnCN.6)
will be set to ‘1’ and an interrupt will occur if the interrupt is enabled. See Section “12.3. Interrupt Han-
dler” on page 153 for further information concerning the configuration of interrupt sources.
As the 16-bit timer register increments and overflows TMRnH:TMRnL, the TFn Timer Overflow/Underflow
Flag (TMRnCN.7) is set to ‘1’ and an interrupt will occur if the interrupt is enabled. The timer can be config-
ured to count down by setting the Decrement Enable Bit (TMRnCF.0) to ‘1’. This will cause the timer to
decrement with every timer clock/count event and underflow when the timer transitions from 0x0000 to
0xFFFF. Just as in overflows, the Overflow/Underflow Flag (TFn) will be set to ‘1’, and an interrupt will
occur if enabled.
Counter/Timer with Capture mode is selected by setting the Capture/Reload Select bit CP/RLn
(TMRnCN.0) and the Timer n Run Control bit TRn (TMRnCN.2) to logic 1. The Timer n respective External
Enable EXENn (TMRnCN.3) must also be set to logic 1 to enable captures. If EXENn is cleared, transi-
tions on TnEX will be ignored.
Figure 23.4. Tn Capture Mode Block Diagram
TMRnL TMRnH
TRn
TCLK
Interrupt
TMRnCN
EXFn
EXENn
TRn
C/Tn
CP/RLn
TFn
SYSCLK 12
2
TMRnCF
D
C
E
N
T
n
O
E
T
O
G
n
T
n
M
1
T
n
M
0
Toggle Logic
Tn
(Port Pin)
0
1
1
0
EXENn
Crossbar
TnE
X
RCAPnL RCAPnH
0xFF 0xFF
8
External Clock
(XTAL1)
Tn Crossbar
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 297
23.2.3. Auto-Reload Mode
In Auto-Reload Mode, the counter/timer can be configured to count up or down and cause an interrupt/flag
to occur upon an overflow/underflow event. When counting up, the counter/timer will set its overflow/under-
flow flag (TFn) and cause an interrupt (if enabled) upon overflow/underflow, the values in the Reload/Cap-
ture Registers (RCAPnH and RCAPnL) are loaded into the timer, and the timer is restarted. When the
Timer External Enable Bit (EXENn) bit is set to ‘1’ and the Decrement Enable Bit (DCEN) is ‘0’, a ‘1’-to-‘0’
transition on the TnEX pin (configured as an input in the digital crossbar) will cause a timer reload (in addi-
tion to timer overflows causing auto-reloads). When DCEN is set to ‘1’, the state of the TnEX pin controls
whether the counter/timer counts up (increment s) or down (decrements), and will not cause an auto-reload
or interrupt event. See Section 23.2.1 for information concerning configuration of a timer to count down.
When counting down, the counter/timer will set its overflow/underflow flag (TFn) and cause an interrupt (if
enabled) when the value in the timer (TMRnH and TMRnL registers) matches the 16-bit value in the
Reload/Capture Registers (RCAPnH and RCAPnL). This is considered an underflow event, and will cause
the timer to load the value 0xFFFF. The timer is automatically restarted when an underflow occurs.
Counter/Timer with Auto-Reload mode is selected by clearing the CP/RLn bit. Setting TRn to logic 1
enables and starts the timer.
In Auto-Reload Mode, the External Flag (EXFn) toggles upon every overflow or underflow and does not
cause an interrupt. The EXFn flag can be thought of as the most significant bit (MSB) of a 17-bit counter.
Figure 23.5. Tn Auto-reload Mode and Toggle Mode Block Diagram
TMRnL TMRnH
TRn
TCLK
Reload Interrupt
EXENn
Crossbar
TnE
X
TMRnCN
EXFn
EXENn
TRn
C/Tn
CP/RLn
TFn
SYSCLK 12
2
TMRnCF D
E
C
E
N
T
n
O
E
T
O
G
n
T
n
M
1
T
n
M
0
Toggle Logic Tn
(Port Pin)
0
1
1
0
RCAPnL RCAPnH
0xFF 0xFF
OVF
8
External Clock
(XTAL1)
Tn Crossbar
C8051F040/1/2/3/4/5/6/7
298 Rev. 1.5
23.2.4. Toggle Output Mode
T imer n have the capability to toggle the state of their respective output port pins (T2, T3, or T4) to produce
a 50% duty cycle waveform output. The port pin state will change upon the overflow or underflow of the
respective timer (depending on whether the timer is counting up or down). The toggle frequency is deter-
mined by the clock source of the timer an d the values loaded into RCAPnH and RCAPnL. When counting
DOWN, the auto-reload value for the timer is 0xFFFF, and underflow will occur when the value in the timer
matches the value stored in RCAPnH:RCAPnL. When counting UP, the auto-reload value for the timer is
RCAPnH:RCAPnL, and overflow will occur when the value in the timer transitions from 0xFFFF to the
reload value.
To output a square wave, the timer is placed in reload mode (the Capture/Reload Select Bit in TMRnCN
and the Timer/Counter Select Bit in TMRnCN are cleared to ‘0’). The timer output is enabled by setting the
Timer Output Enable Bit in TMRnCF to ‘1’. The timer should be configured via the timer clock source and
reload/underflow values such that the timer overflow/underflows at 1/2 the desired output frequency. The
port pin assigned by the crossbar as the timer’s output pin should be configured as a digital output (see
Section “17. Port Input/Output” on page 203). Setting the timer’s Run Bit (TRn) to ‘1’ will start the toggle
of the pin. A Read/Write of the Timer’s Toggle Output State Bit (TMRnCF.2) is used to read the state of the
toggle output, or to fo rce a value of the ou tput. T his is useful wh en it is d esired to st art the toggle of a pin in
a known state, or to force the pin into a desired state when the toggle mode is halted.
Equation 23.1. Square Wave Frequency
Equation 23.1 applies regardless of whether the timer is configured to count up or down.
Fsq
FTCLK
265536RCAPn–
------------------------------------------------------
=
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 299
SFR Definition 23.8. TMRnCN: Timer n Control
Bit7: TFn: Timer n Overflow/Underflow Flag.
Set by hardware when either the Timer overflows from 0xFFFF to 0x0000, underflows from
the value placed in RCAPnH:RCAPnL to 0xFFFF (in Auto-reload Mode), or underflows from
0x0000 to 0xFFFF (in Capture Mode). When the Timer interrupt is enabled, setting this bit
causes the CPU to vecto r to the Timer interrupt service routine. This bit is not automatically
cleared by hardware and must be cleared by software.
Bit6: EXFn: Timer 2, 3, or 4 External Flag.
Set by hardware when either a capture or reload is caused by a high-to-low tra nsition on the
TnEX input pin and EXENn is logic 1. When the Timer interrupt is enabled, setting this bit
causes the CPU to vector to the Timer Interrupt service routine. This bit is not automatically
cleared by hardware and must be cleared by software.
Bit5-4: Reserved.
Bit3: EXENn: Timer n External Enable.
Enables high-to-low transitions on TnEX to trigger captures, reloads, and control the direc-
tion of the timer/counter (up or down count). If DECEN = 1, TnEX will determine if the timer
counts up or down when in Auto-reload Mode. If EXENn = 1, TnEX should be configured as
a digital input.
0: Transitions on the TnEX pin are ignored.
1: Transitions on the TnEX pin cause capture, reload, or control the direction of timer count
(up or down) as follows:
Capture Mod e: ‘1’-to-’0’ Transition on TnEX pin causes RCAPnH:RCAPnL to capture timer
value.
Auto-Reload Mode:
DCEN = 0: ‘1’-to-’0’ transition causes reload of timer and sets the EXFn Flag.
DCEN = 1: TnEX logic level controls direction of timer (up or down).
Bit2: TRn: Timer n Run Control.
This bit enables/disables the respective Timer.
0: Timer disabled.
1: Timer enabled and running/counting.
Bit1: C/Tn: Counter/Timer Select.
0: Timer Function: Timer incremented by clock defined by TnM1:TnM0
(TMRnCF.4:TMRnCF.3).
1: Counter Function: Timer incremented by high-to-low transitions on external input pin.
Bit0: CP/RLn: Capture/Reload Select.
This bit selects whether the Timer functions in capture or auto-reload mode.
0: Timer is in Auto-Reload Mode.
1: Timer is in Capture Mode.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
TFn EXFn - - EXENn TRn C/Tn CP/RLn 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 Bit
Addressable
SFR Address: TMR2CN:0xC8;TMR3CN:0xC8;TMR4CN:0xC8
SFR Page: TMR2CN: page 0;TMR3CN: page 1;TMR4CN: page 2
C8051F040/1/2/3/4/5/6/7
300 Rev. 1.5
SFR Definition 23.9. TMRnCF: Timer n Configuration
Bit7-5: Reserved.
Bit4-3: TnM1 and TnM0: Timer Clock Mode Select Bits.
Bits used to select the Timer clock source. The sources can be the System Clock
(SYSCLK), SYSCLK divided by 2 or 12, or an external clock signal routed to Tn (port pin)
divided by 8. Clock source is selected as follows:
00: SYSCLK/12
01: SYSCLK
10: EXTERNAL CLOCK/8
11: SYSCLK/2
Bit2: TOGn: Toggle output state bit.
When timer is used to toggle a port pin, this bit can be used to read the state o f the output, or
can be written to in order to force the state of the output.
Bit1: TnOE: Timer output enable bit.
This bit enables the timer to output a 50% duty cycle output to th e timer’s assigned extern al
port pin.
NOTE: A timer is configured for Square Wave Output as follows:
CP/RLn= 0
C/Tn = 0
TnOE = 1
Load RCAPnH:RCAPnL (See Section “Equation 23.1. Square Wave Frequency” on
page 298).
Configure Port Pin for output (See Section “17. Port Input/Output” on page 203).
0: Output of toggle mode not available at Timers’ assigned port pin.
1: Output of toggle mo d e av aila ble at Timers’ assigned port pin.
Bit0: DCEN: Decrement Enable Bit.
This bit enables the timer to count up or down as determined by the state of TnEX.
0: Timer will count up, regardless of the state of TnEX.
1: Timer will count up or down depending on the state of TnEX as follows:
if TnEX = 0, the timer counts DOWN
if TnEX = 1, the timer counts UP.
R/W R/W R/W R/W R/W Reset Value
- - - TnM1 TnM0 TOGn TnOE DCEN 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 Bit
Addressable
SFR Address: TMR2CF:0xC9;TMR3CF:0xC9;TMR4CF:0xC9
SFR Page TMR2CF: page 0;TMR3CF: page 1;TMR4CF: page 2
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 301
SFR Definition 23.10. RCAPnL: Timer n Capture Register Low Byte
SFR Definition 23.11. RCAPnH: Timer n Capture Register High Byte
SFR Definition 23.12. TMRnL: Timer n Low Byte
Bits 7-0: RCAPnL: Timer n Capture Register Low Byte.
The RCAPnL register captur es the low byte of T ime r n when T imer n is configured in ca pture
mode. When Timer n is configured in auto-reload mode, it holds the low byte of the reload
value.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address: RCAP2L: 0xCA; RCAP3L: 0xCA; RCAP4L: 0xCA
SFR Page: RCAP2L: page 0; RCAP3L: page 1; RCAP4L: page 2
Bits 7-0: RCAPnH: Timer n Capture Register High Byte.
The RCAPnH register captures the high byte of Timer n when Timer n is configured in cap-
ture mode. When Timer n is configured in auto-reload mode, it holds the high byte of the
reload value.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address: RCAP2H: 0xCB; RCAP3H: 0xCB; RCAP4H: 0xCB
SFR Page: RCAP2H: page 0; RCAP3H: page 1; RCAP4H: page 2
Bits 7-0: TMRnL: Timer n Low Byte.
The TMRnL register contains the low byte of the 16-bit Timer n
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address: TMR2L: 0xCC; TMR3L: 0xCC; TMR4L: 0xCC
SFR Page: TMR2L: page 0; TMR3L: page 1; TMR4L: page 2
C8051F040/1/2/3/4/5/6/7
302 Rev. 1.5
SFR Definition 23.13. TMRnH Timer n High Byte
Bits 7-0: TMRnH: Timer n High Byte.
The TMRnH register contains the high byte of the 16-bit Timer n
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address: TMR2H: 0xCD; TMR3H: 0xCD; TMR4H: 0xCD
SFR Page: TMR2H: page 0; TMR3H: page 1; TMR4H: page 2
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 303
24. Programmable Counter Array
The Programmable Counter Array (PCA0) provides enhanced timer functionality while requiring less CPU
intervention than the standard 8051 counter/timers. PCA0 consists of a dedicated 16-bit counter/timer and
six 16-bit capture/compare modules. Each capture/compare module has its own associated I/O line
(CEXn) which is routed through the Crossbar to Port I/O when enabled (See Section “17.1. Ports 0
through 3 and the Prio rity Cros sbar Decoder” on page 204). The counter/timer is driven by a progr am-
mable timebase that can select between six inputs as its source: system clock, system clock divided by
four, system clock divided by twelve, the ex ternal oscillator clock source divided by 8, Timer 0 overflow, or
an external clock signal on the ECI line. Each capture/compare module may be configured to operate inde-
pendently in one of six modes: Edge-Triggered Capture, Software Timer, High-Speed Output, Frequency
Output, 8-Bit PWM, or 16-Bit PWM (each is described in Section 24.2). The PCA is configured and con-
trolled through the system controller's Special Function Registers. The basic PCA block diagram is shown
in Figure 24.1.
Figure 24.1. PCA Block Diagram
Capture/Compare
Module 1
Capture/Compare
Module 0 Capture/Compare
Module 2 Capture/Compare
Module 3
CEX1
ECI
Crossbar
CEX2
CEX3
CEX0
Port I/O
16-Bit Counter/Timer
PCA
CLOCK
MUX
SYSCLK/12
SYSCLK/4
Timer 0 Overflow
ECI
SYSCLK
External Clock/8
Capture/Compare
Module 4
CEX4
Capture/Compare
Module 5
CEX5
C8051F040/1/2/3/4/5/6/7
304 Rev. 1.5
24.1. PCA Counter/Timer
The 16-bit PCA counter/timer consists of two 8-bit SFRs: PCA0L and PCA0H. PCA0H is the high byte
(MSB) of the 16-bit counter/timer and PCA0L is the low byte (LSB). Reading PCA0L automatically latches
the value of PCA0H into a “snapshot” register; the following PCA0H read accesses this “snapshot” register.
Reading the PCA0L Regist er first gu arantees an a ccurate r eading of t he entire 16 -bit PCA0 counte r.
Reading PCA0H or PC A0L does not disturb the counte r operation. The CPS2-CPS0 bits in the PCA0MD
register select the timebase for the counter/timer as shown in Table 24.1. Note that in ‘External oscillator
source divided by 8’ mode, the external oscillator source is synchronized with the system clock,
and must have a frequency less than or equal to the system clock.
When the counter/timer overflows from 0xFFFF to 0x0000, the Counter Overflow Flag (CF) in PCA0MD is
set to logic 1 and an interrupt request is generated if CF interrupts are enabled. Setting the ECF bit in
PCA0MD to logic 1 enables the CF flag to generate an interrupt request. The CF bit is not automatically
cleared by hardware when the CPU vectors to the interrupt service routine, and must be cleared by soft-
ware (Note: PCA0 interrupts must be globally enabled before CF interrupts are recognized. PCA0 inter-
rupts are globally enabled by setting the EA bit (IE.7) and the EPCA0 bit in EIE1 to logic 1). Clearing the
CIDL bit in the PCA0MD register allows the PCA to continue normal operation while the CPU is in Idle
mode.
Figure 24.2. PCA Counter/Timer Block Diagram
Table 24.1. PCA Timebase Input Options
CPS2 CPS1 CPS0 Timebase
0 0 0 System clock divided by 12
0 0 1 System clock divided by 4
0 1 0 Timer 0 overflow
011
High-to-low transition s on ECI 1 (max rate = system clock divided by 4)
100System clock
101
External clock divided by 82
Notes:
1. The minimum high or low time for the ECI input signal is at least 2 system clock cycles.
2. External oscillator source divided by 8 is synchronized with the system clock.
PCA0MD
C
I
D
L
W
D
T
E
E
C
F
C
P
S
1
C
P
S
0
W
D
L
C
K
C
P
S
2
IDLE
0
1
PCA0H PCA0L
Snapshot
Register
To SFR Bus
Overflow To PCA Interrupt System
CF
PCA0L
read
To PCA Modules
SYSCLK/12
SYSCLK/4
Timer 0 Overflow
ECI
000
001
010
011
100
101
SYSCLK
External C lock/8
PCA0CN
C
FC
RC
C
F
0
C
C
F
2
C
C
F
1
C
C
F
5
C
C
F
4
C
C
F
3
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 305
24.2. Capture/Compare Modules
Each module can be configured to operate independently in one of six operation modes: Edge-triggered
Capture, Software Timer, High Speed Output, Frequency Output, 8-Bit Pulse Width Modulator, or 16-Bit
Pulse Width Modulator. Each module has Special Function Registers (SFRs) associated with it in the CIP-
51 system controller. These registers are used to exchange dat a with a module an d configure the mo dule's
mode of operation.
Table 24.2 summarizes the bit settings in the PCA0CPMn registers used to select the PCA0 capture/com-
pare module’s operating modes. Setting the ECCFn bit in a PCA0CPMn register enables the module's
CCFn interrupt. Note: PCA0 interrupts must be globally enabled before individual CCFn interrupts are rec-
ognized. PCA0 interrupts are globally enabled by setting the EA bit (IE.7) and the EPCA0 bit (EIE1.3) to
logic 1. See Figure 24.3 for details on the PCA interrupt configuration.
Figure 24.3. PCA Interrupt Block Diagram
Table 24.2. PCA0CPM Register Settings for PCA Capture/Compare Modules
PWM16 ECOM CAPP CAPN MAT TOG PWM ECCF Operation Mode
X X 10000X
Capture triggered by positive edge on
CEXn
X X 01000X
Capture trigg ere d by ne g ativ e ed ge on
CEXn
X X 11000XCapture triggered by transition on CEXn
X 1 00100X Software Timer
X 1 00110X High-Speed Output
X 1 00011X Frequency Output
0 1 000010 8-Bit Pulse Width Modulator
1 1 000010 16-Bit Pulse Width Modulator
X = Don’t Care
PCA0CN
C
FC
RC
C
F
0
C
C
F
2
C
C
F
1
C
C
F
5
C
C
F
4
C
C
F
3
PCA0MD
C
I
D
L
E
C
F
C
P
S
1
C
P
S
0
C
P
S
2
0
1
PCA Module 0
CCF0
PCA Module 1
CCF1
ECCF1
0
1
ECCF0
0
1
PCA Module 2
CCF2
ECCF2
0
1
PCA Module 3
CCF3
ECCF3
ECCF4
PCA Counter/
Timer Overflow 0
1
Inter ru p t
Priority
Decoder
EPCA0
(EIE1.3)
PCA0CPMn
(for n = 0 to 5)
P
W
M
1
6
n
E
C
O
M
n
E
C
C
F
n
T
O
G
n
P
W
M
n
C
A
P
P
n
C
A
P
N
n
M
A
T
n
0
1
PCA Module 4
CCF4
0
1
PCA Module 5
CCF5
0
1
EA
(IE.7)
0
1
ECCF5
C8051F040/1/2/3/4/5/6/7
306 Rev. 1.5
24.2.1. Edge-triggered Capture Mode
In this mode, a valid transition on the CEXn pin causes PCA0 to capture the value of the PCA0 counter/
timer and load it into the corresponding module's 16-bit capture/compare register (PCA0CPLn and
PCA0CPHn). The CAPPn and CAPNn bits in the PCA0CPMn re gister ar e u sed to select th e type of tr ansi-
tion that triggers the capture: low-to-high transition (positive edge), high-to-low transition (negative edge),
or either transition (positive or negative edge). When a capture occurs, the Capture/Compare Flag (CCFn)
in PCA0CN is set to logic 1 and an interrup t requ est is generated if CCF interrup ts are enabled. The CCFn
bit is not automatically cleared by hardware when the CPU vectors to the interrupt service routine, and
must be cleared by software.
Note: The signal at the CEXn pin mu st be logic high or low for at least two system clock cycles in order for
it to be recognized as valid by the hardware.
Figure 24.4. PCA Capture Mode Diagram
PCA0L
PCA0CPLn
PCA
Timebase
CEXn
CrossbarPort I/O
PCA0H
Capture
PCA0CPHn
0
1
0
1
(to CCFn)
PCA Interrupt
PCA0CPMn
P
W
M
1
6
n
E
C
O
M
n
E
C
C
F
n
T
O
G
n
P
W
M
n
C
A
P
P
n
C
A
P
N
n
M
A
T
n
PCA0CN
C
FC
RC
C
F
0
C
C
F
2
C
C
F
1
C
C
F
5
C
C
F
4
C
C
F
3
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 307
24.2.2. Software Timer (Compare) Mode
In Software Timer mode, the PCA0 counter/timer is comp a red to the mod ule's 16 -bit captur e/compare reg-
ister (PCA0CPHn and PCA0CPLn). When a match occurs, the Capture/Compare Flag ( CCFn) in PCA0CN
is set to logic 1 and an interrupt request is generated if CCF interrupts are enabled. The CCFn bit is not
automatically cleared by hardware when the CPU vectors to the interrupt service routine, and must be
cleared by software. Setting the ECOMn and MATn bits in the PCA0CPMn register enables Software
Timer mod e.
Important Note About Capture/Compare Registers: When writing a 16-bit value to the PCA0 Capture/
Compare register s, the low byte should always be written first. Writing to PCA0CPLn clears the ECOMn bit
to '0'; writing to PCA0CPHn sets ECOMn to '1'.
Figure 24.5. PCA Software Timer Mode Diagram
Match
16-bit Comparator
PCA0H
PCA0CPHn
Enable
PCA0L
PCA
Timebase
PCA0CPLn
00 00
PCA
Interrupt
0
1
x
ENB
ENB
0
1
Write to
PCA0CPLn
Write to
PCA0CPHn
Reset
PCA0CPMn
P
W
M
1
6
n
E
C
O
M
n
E
C
C
F
n
T
O
G
n
P
W
M
n
C
A
P
P
n
C
A
P
N
n
M
A
T
n
x
PCA0CN
C
FC
RC
C
F
0
C
C
F
2
C
C
F
1
C
C
F
5
C
C
F
4
C
C
F
3
C8051F040/1/2/3/4/5/6/7
308 Rev. 1.5
24.2.3. High-Speed Output Mode
In High-Speed Output mode, a module’s associated CEXn pin is toggled each time a match occurs
between the PCA Counter and the module's 16-bit capture/compare register (PCA0CPHn and
PCA0CPLn). Setting the TOGn, MATn, and ECOMn bits in the PCA0CPMn register enables the High-
Sp ee d Ou tp ut mod e .
Important Note About Capture/Compare Registers: When writing a 16-bit value to the PCA0 Capture/
Compare register s, the low byte should always be written first. Writing to PCA0CPLn clears the ECOMn bit
to '0'; writing to PCA0CPHn sets ECOMn to '1'.
Figure 24.6. PCA High-Speed Output Mode Diagram
Match
16-bit Comparator
PCA0H
PCA0CPHn
Enable
PCA0L
PCA
Timebase
PCA0CPLn
PCA
Interrupt
0
1
00 0x
ENB
ENB
0
1
Write to
PCA0CPLn
Write to
PCA0CPHn
Reset
PCA0CPMn
P
W
M
1
6
n
E
C
O
M
n
E
C
C
F
n
T
O
G
n
P
W
M
n
C
A
P
P
n
C
A
P
N
n
M
A
T
n
x
CEXn
Crossbar Port I/O
Toggle
0
1
TOGn
PCA0CN
C
FC
RC
C
F
0
C
C
F
2
C
C
F
1
C
C
F
5
C
C
F
4
C
C
F
3
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 309
24.2.4. Frequency Output Mode
Frequency Output Mode produces a programmable-frequency square wave on the module’s associated
CEXn pin. The capture/compare module high byte holds the number of PCA clocks to count before the out-
put is toggled. The frequency of the square wave is then defined by Equation 24.1, where FPCA is the fre-
quency of the clock selected by the CPS2-0 bits in the PCA mode register, PCA0MD.
Note: A value of 0x00 in the PCA0CPHn register is equal to 256 for this equation.
The lower byte of the capture/compare module is compared to the PCA0 counter low byte; on a match,
CEXn is toggled and the offset held in the high byte is added to the matched value in PCA0CPLn. Fre-
quency Output Mode is enable d by setting the ECOMn, TOGn, and PWMn bits in the PCA0CPMn reg iste r.
Figure 24.7. PCA Frequency Output Mode
Equation 24.1. Square Wave Frequency Output
Fsqr FPCA
2PCA0CPHn
-----------------------------------------
=
8-bit
Comparator
PCA0L
Enable
PCA Timebase
000 0
match
PCA0CPMn
P
W
M
1
6
n
E
C
O
M
n
E
C
C
F
n
T
O
G
n
P
W
M
n
C
A
P
P
n
C
A
P
N
n
M
A
T
n
0
PCA0CPHn8-bit AdderPCA0CPLn
Adder
Enable
CEXn
Crossbar Port I/O
Toggle
0
1
TOGn
1
C8051F040/1/2/3/4/5/6/7
310 Rev. 1.5
24.2.5. 8-Bit Pulse Width Modulator Mode
Each module can be used independently to generate pulse width modulated (PWM) outputs on its associ-
ated CEXn pin. The frequency of the output is dependent on the timebase fo r the PCA0 coun te r/timer. The
duty cycle of the PWM output signal is varied using the module's PCA0CPLn capture/compare register.
When the value in the low byte of the PCA0 counter/timer (PCA0L) is eq ual to the value in PCA0CPLn, the
output on the CEXn pin will be high. When the count value in PCA0L overflows, the CEXn output will be
low (see Figure 24.8). Also, when the counter/timer low byte (PCA0L) overflows from 0xFF to 0x00,
PCA0CPLn is reloaded automatically with the value stored in the counter/timer's high byte (PCA0H) with-
out software intervention. Setting the ECOMn and PWMn bits in the PCA0CPMn register enables 8-Bit
Pulse Width Modulator mode. The duty cycle for 8-Bit PWM Mode is given by Equation 24.2.
Important Note About Capture/Compare Registers: When writing a 16-bit value to the PCA0 Capture/
Compare register s, the low byte should always be written first. Writing to PCA0CPLn clears the ECOMn bit
to '0'; writing to PCA0CPHn sets ECOMn to '1'.
Equation 24.2. 8-Bit PWM Duty Cycle
Figure 24.8. PCA 8-Bit PWM Mode Diagram
DutyCycle 256 PCA0CPHn–
256
---------------------------------------------------
=
8-bit
Comparator
PCA0L
PCA0CPLn
PCA0CPHn
CEXn
Crossbar Port I/O
Enable
Overflow
PCA Timebase
0000 0
Q
Q
SET
CLR
S
R
match
PCA0CPMn
P
W
M
1
6
n
E
C
O
M
n
E
C
C
F
n
T
O
G
n
P
W
M
n
C
A
P
P
n
C
A
P
N
n
M
A
T
n
0
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 311
24.2.6. 16-Bit Pulse Width Modulator Mode
Each PCA0 module may also be operated in 16-Bit PWM mode. In this mode, the 16-bit capture/compare
module defines the number of PCA0 clocks for the low time of the PWM signal. When the PCA0 counter
matches the module contents, the output on CEXn is asserted high; when the counter overflows, CEXn is
asserted low. To output a varying duty cycle, new value writes should be synchronized with PCA0 CCFn
match interrupts. 16-Bit PWM Mode is enabled by setting the ECOMn, PWMn, and PWM16n bits in the
PCA0CPMn register. For a varying duty cycle, CCFn should also be set to logic 1 to enable match inter-
rupts. The duty cycle for 16-Bit PWM Mode is given by Equation 24.3.
Important Note About Capture/Compare Registers: When writing a 16-bit value to the PCA0 Capture/
Compare register s, the low byte should always be written first. Writing to PCA0CPLn clears the ECOMn bit
to '0'; writing to PCA0CPHn sets ECOMn to '1'.
Equation 24.3. 16-Bit PWM Duty Cycle
Figure 24.9. PCA 16-Bit PWM Mode
DutyCycle 65536 PCA0CPn–
65536
-----------------------------------------------------
=
PCA0CPLnPCA0CPHn
Enable
PCA Timebase
0000 0
PCA0CPMn
P
W
M
1
6
n
E
C
O
M
n
E
C
C
F
n
T
O
G
n
P
W
M
n
C
A
P
P
n
C
A
P
N
n
M
A
T
n
1
16-bit Comparator
CEXn
Crossbar Port I/O
Overflow
Q
Q
SET
CLR
S
R
match
PCA0H PCA0L
C8051F040/1/2/3/4/5/6/7
312 Rev. 1.5
24.3. Register Descriptions for PCA0
Following are detailed descriptions of the special function registers related to the op eration of PCA0.
SFR Definition 24.1. PCA0CN: PCA Control
Bit7: CF: PCA Counter/Timer Overflow Flag.
Set by hardware when the PCA0 Counter/Timer overflows from 0xFFFF to 0x0000. When
the Counter/T imer Overflow (CF) interr upt is ena bled, setting this bit causes the CPU to vec-
tor to the CF interrupt service routine. This bit is not automatically cleared by hardware and
must be cleared by software.
Bit6: CR: PCA0 Counter/Timer Run Control.
This bit enables/disables the PCA0 Counter/Timer.
0: PCA0 Counter/Timer disabled.
1: PCA0 Counter/Timer enabled.
Bit5: CCF5: PCA0 Module 5 Capture/Compare Flag.
This bit is set by hardware when a match or capture occurs. When the CCF interrupt is
enabled, setting this bit causes the CPU to vector to the CCF interrupt service routine. This
bit is not automatically cleared by hardware and must be cleared by software.
Bit4: CCF4: PCA0 Module 4 Capture/Compare Flag.
This bit is set by hardware when a match or capture occurs. When the CCF interrupt is
enabled, setting this bit causes the CPU to vector to the CCF interrupt service routine. This
bit is not automatically cleared by hardware and must be cleared by software.
Bit3: CCF3: PCA0 Module 3 Capture/Compare Flag.
This bit is set by hardware when a match or capture occurs. When the CCF interrupt is
enabled, setting this bit causes the CPU to vector to the CCF interrupt service routine. This
bit is not automatically cleared by hardware and must be cleared by software.
Bit2: CCF2: PCA0 Module 2 Capture/Compare Flag.
This bit is set by hardware when a match or capture occurs. When the CCF interrupt is
enabled, setting this bit causes the CPU to vector to the CCF interrupt service routine. This
bit is not automatically cleared by hardware and must be cleared by software.
Bit1: CCF1: PCA0 Module 1 Capture/Compare Flag.
This bit is set by hardware when a match or capture occurs. When the CCF interrupt is
enabled, setting this bit causes the CPU to vector to the CCF interrupt service routine. This
bit is not automatically cleared by hardware and must be cleared by software.
Bit0: CCF0: PCA0 Module 0 Capture/Compare Flag.
This bit is set by hardware when a match or capture occurs. When the CCF interrupt is
enabled, setting this bit causes the CPU to vector to the CCF interrupt service routine. This
bit is not automatically cleared by hardware and must be cleared by software.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
CF CR CCF5 CCF4 CCF3 CCF2 CCF1 CCF0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xD8
0
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 313
SFR Definition 24.2. PCA0MD: PCA0 Mode
Bit7: CIDL: PCA0 Counter/Timer Idle Control.
Specifies PCA0 behavior when CPU is in Idle Mode.
0: PCA0 continues to function normally while the system controller is in Idle Mode.
1: PCA0 operation is suspended while the system controller is in Idle Mode.
Bits6-4: UNUSED. Read = 000b, Write = don't care.
Bits3-1: CPS2-CPS0: PCA0 Counter/Timer Pulse Select.
These bits select the timebase source for the PCA0 counter
Bit0: ECF: PCA Counter/Timer Overflow Interrupt Enable.
This bit sets the masking of the PCA0 Counter/Timer Overflow (CF) interrupt.
0: Disable the CF interrupt.
1: Enable a PCA0 Counter/Timer Overflow interrupt request when CF (PCA0CN.7) is set.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
CIDL — — — CPS2 CPS1 CPS0 ECF 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xD9
0
CPS2 CPS1 CPS0 Timebase
0 0 0 System clock divided by 12
0 0 1 System clock divided by 4
0 1 0 Timer 0 overflow
011
High-to-low transitions on ECI1 (max rate = system clock
divided by 4)
1 0 0 System clock
101
External clock divided by 82
1 1 0 Reserved
1 1 1 Reserved
Notes:
1. The minimum high or low time for the ECI input signal is at least 2 system clock cycles.
2. External oscillator source divided by 8 is synchronized with the system clock.
C8051F040/1/2/3/4/5/6/7
314 Rev. 1.5
SFR Definition 24.3. PCA0CPMn: PCA0 Capture/Compare Mode
Bit7: PWM16n: 16-bit Pulse Width Modulation Enable
This bit selects 16-bit mode when Pulse Width Modulation mode is enabled (PWMn = 1).
0: 8-bit PWM selected.
1: 16-bit PWM selected.
Bit6: ECOMn: Comparator Function Enable.
This bit enables/disables the comparator function for PCA0 module n.
0: Disabled.
1: Enabled.
Bit5: CAPPn: Capture Positive Function Enable.
This bit enables/disables the positive edge capture for PCA0 module n.
0: Disabled.
1: Enabled.
Bit4: CAPNn: Capture Negative Function Enable.
This bit enables/disables the negative edge capture for PCA0 module n.
0: Disabled.
1: Enabled.
Bit3: MATn: Match Function Enable.
This bit enables/disa bles the match function for PCA0 module n. When enabled , matches of
the PCA0 counter with a module's captur e/compare register cause the CCFn bit in PCA0MD
register to be set to logic 1.
0: Disabled.
1: Enabled.
Bit2: TOGn: Toggle Function Enable.
This bit enables/disa bles the toggle function for PCA0 module n. When enabled, matches of
the PCA0 counter with a module's capture/compare register cause the logic level on the
CEXn pin to togg le. If the PWMn b it is a lso set to lo gic 1, the m odu le op era tes in Fr eq uency
Output Mode.
0: Disabled.
1: Enabled.
Bit1: PWMn: Pulse Width Modulation Mode Enable.
This bit enables/disables the PWM function for PCA0 module n. When enabled, a pulse
width modulated signal is output on the CEXn pin. 8-bit PWM is used if PWM16n is logic 0;
16-bit mode is used if PWM16n logic 1. If the TOGn bit is also set, the module operates in
Frequency Output Mode.
0: Disabled.
1: Enabled.
Bit0: ECCFn: Capture/Compare Flag Interrupt Enable.
This bit sets the masking of the Capture/Compare Flag (CCFn) interrupt.
0: Disable CCFn interrupts.
1: Enable a Capture/Compare Flag interrupt request when CCFn is set.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
PWM16n ECOMn CAPPn CAPNn MATn TOGn PWMn ECCFn 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address: PCA0CPM0: 0xDA, PCA0CPM1: 0xDB, PCA0CPM2: 0xDC, PCA0CPM3: 0xDD, PCA0CPM4: 0xDE, PCA0CPM5:
0xDF
SFR Page: PCA0CPM0: page 0, PCA0CPM1: page 0, PCA0CPM2: page 0, PCA0CPM3: page 0, PCA0CPM4: page 0,
PCA0CPM5: page 0
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 315
SFR Definition 24.4. PCA0L: PCA0 Counter/Timer Low Byte
SFR Definition 24.5. PCA0H: PCA0 Counter/Timer High Byte
Bits 7-0: PCA0L: PCA0 Counter/Timer Low Byte.
The PCA0L register holds the low byte (LSB) of the 16-bit PCA0 Counter/Timer.
R/WR/WR/WR/WR/WR/WR/W R/WReset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xF9
0
Bits 7-0: PCA0H: PCA0 Counter/Timer High Byte.
The PCA0H register holds the high byte (MSB) of the 16-bit PCA0 Counter/Timer.
R/WR/WR/WR/WR/WR/WR/W R/WReset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address:
SFR Page: 0xFA
0
C8051F040/1/2/3/4/5/6/7
316 Rev. 1.5
SFR Definition 24.6. PCA0CPLn: PCA0 Capture Module Low Byte
SFR Definition 24.7. PCA0CPHn: PCA0 Capture Module High Byte
Bits7-0: PCA0CPLn: PCA0 Capture Module Low Byte.
The PCA0CPLn register holds the low byte (LSB) of the 16-bit capture module n.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address: PCA0CPL0: 0xFB, PCA0CPL1: 0xFD, PCA0CPL2: 0xE9, PCA0CPL3: 0xEB, PCA0CPL4: 0xED, PCA0CPL5:
0xE1
SFR Page: PCA0CPL0: page 0, PCA0CPL1: page 0, PCA0CPL2: page 0, PCA0CPL3: page 0, PCA0CPL4: page 0,
PCA0CPL5: page 0
Bits7-0: PCA0CPHn: PCA0 Capture Module High Byte.
The PCA0CPHn register holds the high byte (MSB) of the 16-bit capture module n.
R/W R/W R/W R/W R/W R/W R/W R/W Reset Value
00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
SFR Address: PCA0CPH0: 0xFC, PCA0CPH1: 0xFE, PCA0CPH2: 0xEA, PCA0CPH3: 0xEC, PCA0CPH4: 0xEE, PCA0CPH5:
0xE2
SFR Page: PCA0CPH0: page 0, PCA0CPH1: page 0, PCA0CPH2: page 0, PCA0CPH3: page 0, PCA0CPH4: page 0,
PCA0CPH5: page 0
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 317
25. JTAG (IEEE 1149.1)
Each MCU has an on-chip JTAG interface and logic to support boundary scan for production and in-sys-
tem testing, Flash read/write operations, and non-intrusive in-circuit debug. The JTAG interface is fully
compliant with the IEEE 1149.1 specification. Refer to this specification for det ailed descriptions of the Test
Interface and Boundary-Scan Architecture. Access of the JTAG Instruc tion Register (IR) and Data Regis-
ters (DR) are as described in the Test Access Port and Operation of the IEEE 1149.1 specification.
The JTAG interface is accessed via four dedicated pins on the MCU: TCK, TMS, TDI, and TDO.
Through the 16 -bit JTAG Instruction Re gister (IR), any of the seven instructions shown in Figure 25.1 can
be commanded. There are three DRs associated with JTAG Boundary-Scan, and four associated with
Flash read/write operations on the MCU.
JTAG Register Definition 25.1. IR: JTAG Instruction Register
Reset Value
0x0000
Bit15 Bit0
IR
Value Instruction Description
0x0000 EXTEST Selects the Boundary Data Register for control and observability of all
device pins
0x0002 SAMPLE/
PRELOAD Selects the Boundary Data Register for observability and presetting the
scan-path latches
0x0004 IDCODE Selects device ID Register (DEVICEID)
0xFFFF BYPASS Selects Bypass Data Register
0x0082 Flash Control Selects FLASHCON Register to control how the interface logic responds
to reads and writes to the FLASHDAT Register
0x0083 Flash Data Selects FLASHDAT Register for reads and writes to the Flash mem ory
0x0084 Flash Address Selects FLASHADR Register which holds the address of all Flash read,
write, and erase operations
C8051F040/1/2/3/4/5/6/7
318 Rev. 1.5
25.1. Boundary Scan
The DR in the Boundary Scan path is an 134-bit shift register. The Boundary DR provides control and
observability of all the device pins as well as the SFR bus and Weak Pullup feature via the EXTEST and
SAMPLE commands.
Table 25.1. Boundary Data Register Bit Definitions
EXTEST provides access to both capture and update actions, while Sample only performs a capture.
Bit Action Target
0Capture Reset Enable from MCU
Update Reset Enable to /RST pin
1 Capture Reset input from /RST pin
Update Reset output to /RST pin
2 Capture Reset Enable from MCU
Update Reset Enable to /RST pin
3 Capture Reset input from /RST pin
Update Reset output to /RST pin
4 Capture CANRX output enable to pin
Update CANRX output enable to pin
5 Capture CANRX input from pin
Update CANRX output to pin
6 Capture CANTX output enable to pin
Update CANTX output enable to pin
7 Capture CANTX input from pin
Update CANTX output to pin
8 Capture External Clock from XTAL1 pin
Update Not used
9 Capture Weak pullup enable from MCU
Update Weak pullup enable to Port Pins
10, 12, 14, 16, 18,
20, 22, 24 Capture P0.n output enable from MCU (e.g. Bit6=P0.0, Bit8=P0.1, etc.)
Update P0.n output enable to pin (e.g. Bit6=P0.0oe, Bit8=P0.1oe, etc.)
11, 13, 15, 17, 19,
21, 23, 25 Capture P0.n input from pin (e.g. Bit7=P0.0, Bit9=P0.1, etc.)
Update P0.n output to pin (e.g. Bit7=P0.0, Bit9=P0.1, etc.)
26, 28, 30, 32, 34,
36, 38, 40 Capture P1.n output enable from MCU
Update P1.n output enable to pin
27, 29, 31, 33, 35,
37, 39, 41 Capture P1.n input from pin
Update P1.n output to pin
42, 44, 46, 48, 50,
52, 54, 56 Capture P2.n output enable from MCU
Update P2.n output enable to pin
43, 45, 47, 49, 51,
53, 55, 57 Capture P2.n input from pin
Update P2.n output to pin
58, 60, 62, 64, 66,
68, 70, 72 Capture P3.n output enable from MCU
Update P3.n output enable to pin
59, 61, 63, 65, 67,
69, 71, 73 Capture P3.n input from pin
Update P3.n output to pin
74, 76, 78, 80, 82,
84, 86, 88 Capture P4.n output enable from MCU
Update P4.n output enable to pin
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 319
25.1.1. EXTEST Instruction
The EXTEST instruction is accessed via the IR. The Boundary DR provides control and observability of all
the device pins as well as the Weak Pullup feature. All inputs to on-chip logic are set to logic 1.
25.1.2. SAMPLE Instruction
The SAMPLE instruction is accessed via the IR. The Boundary DR provides observability and presetting of
the scan-path latches.
25.1.3. BYPASS Instruction
The BYPASS instruction is accessed via the IR. It provides access to the standard JTAG Bypass data reg-
ister.
25.1.4. IDCODE Instruction
The IDCODE instruction is accessed via the IR. It provides access to the 32-bit Device ID register.
75, 77, 79, 81, 83,
85, 87, 89 Capture P4.n input from pin
Update P4.n output to pin
90, 92, 94, 96, 98,
100, 102, 104 Capture P5.n output enable from MCU
Update P5.n output enable to pin
91, 93, 95, 97, 99,
101, 103, 105 Capture P5.n input from pin
Update P5.n output to pin
106, 108, 110, 112,
114, 116, 118, 120 Capture P6.n output enable from MCU
Update P6.n output enable to pin
107, 109, 111, 113,
115, 117, 119, 121 Capture P6.n input from pin
Update P6.n output to pin
122, 124, 126, 128,
130, 132, 134, 136 Capture P7.n output enable from MCU
Update P7.n output enable to pin
123, 125, 127, 129,
131, 133, 135, 137 Capture P7.n input from pin
Update P7.n output to pin
Table 25.1. Boundary Data Register Bit Definitions (Continued)
EXTEST provides access to both capture and update actions, while Sample only performs a capture.
Bit Action Target
C8051F040/1/2/3/4/5/6/7
320 Rev. 1.5
JTAG Register Definition 25.2. DEVICEID: JTAG Device ID Register
Version = 0000b
Part Number = 0000 0000 0000 0101b (C8051F040/1/2/3/4/5/6/7)
Manufacturer ID = 0010 0100 001b (Silicon Labs)
Reset Value
Version Part Number Manufacturer ID 1 0xn0005243
Bit31 Bit28 Bit27 Bit12 Bit11 Bit1 Bit0
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 321
25.2. Flash Programming Commands
The Flash memory can be programmed directly over the JTAG interface using the Flash Control, Flash
Data, Flash Address, and Flash Scale reg isters. These Indirect Data Registers are accessed via the JTAG
Instruction Register. Read and write operations on indirect data registers are performed by first setting the
appropriate DR address in the IR register. Each read or write is then initiated by writing the appropriate
Indirect Operation Code (IndOpCode) to the selected data register. Incoming commands to this register
have the following format:
IndOpCode: These bit set the operation to perform according to the following tabl e:
The Poll operation is used to check the Busy bit as described below. Although a Capture-DR is performed,
no Update-DR is allowed for the Poll operation. Since updates are disabled, polling can be accomplished
by shifting in/out a single bit.
The Read operation initia te s a read from th e reg ister addressed by the DRAddress. Re ad s can be initiate d
by shifting only 2 bits into the indirect register. After the read operation is initiated, polling of the Busy bit
must be performed to determine when the operation is complete.
The write operation initiates a write of WriteData to the registe r addres sed by DRAddress. Registers of any
width up to 18 bits can be written. If the register to be written contains fewer than 18 bits, the data in Write-
Data should be left-justified, i.e. its MSB should occupy bit 17 above. This allows shorter registers to be
written in fewer JTAG clock cycle s. For example, an 8-bit register could be written by shifting only 10 bits.
After a Write is initiated, the Busy bit should be polled to determine when the next operation can be initi-
ated. The content s of the Instr uction Re gister should not be altered while ei ther a read o r write o per ation is
busy.
Outgoing data from the indirect Data Register has the following format:
The Busy bit indicates that the curr ent operation is not complete. It goes high when an operatio n is initiated
and returns low when complete. Read and Write commands are ignored while Busy is high. In fact, if poll-
ing for Busy to be low will be followed by another read or write operation, JTAG writes of the next operation
can be made while checking for Busy to be low. They will be ignored until Busy is read low, at which time
the new operation will initiate. This bit is placed ate bit 0 to allow polling by single-bit shifts. When waiting
for a Read to complete and Busy is 0, the following 18 bits can be shifted out to obtain the resulting data.
ReadData is always right-justified. This allows registers shorter than 18 bits to be read using a reduced
number of shifts. For example, the result s from a byte-read requires 9 bit shifts (Busy + 8 bits).
19:18 17:0
IndOpCode WriteData
IndOpCode Operation
0x Poll
10 Read
11 Write
19 18:1 0
0 ReadData Busy
C8051F040/1/2/3/4/5/6/7
322 Rev. 1.5
JTAG Register Definition 25.3. FLASHCON: JTAG Flash Control Register
This register determines how the Flash interface logic will respond to reads and writes to the
FLASHDAT Register.
Bit 7: SFLE: Scratchpad Flash Memory Access Enable
When this bit is set, Flash reads and writes from user software are directed to the 128-byte
scratchpad Flash sector. When accessing the scratchpad, Flash accesses ou t of th e
address range 0x00-0x7F should not be attempted. Reads/Wr ites outside of this range will
yield undefine d resu lts.
0: Flash access is directed to the Program/Data Flash sector.
1: Flash access is directed to the 128-byte scratchpad sector.
Bits6-4: WRMD2-0: Write Mode Select Bits.
The Write Mode Select Bits control how the interface logic responds to writes to the FLASH-
DAT Register per the following values:
000: A FLASHDAT write replaces the data in the FLASHDAT register, but is otherwise
ignored.
001: A FLASHDAT write initiates a write of FLASHDAT into the memory address by the
FLASHADR register. FLASHADR is incremented by one when complete.
010: A FLASHDAT write initiates an erasure (sets all bytes to 0xFF) of the Flash page
containing the address in FLASHADR. The data written must be 0xA5 for the erase
to occur. FLASHADR is not affected. If FLASHADR targets the Read Lock Byte or
the Write/Erase Lock Byte, the entire user space will be erased (i.e. entire Flash
memory except for the Reserved area (See Section “15. Flash Memory” on
page 179).
(All other value s for WRMD 2- 0 ar e re se rve d .)
Bits3-0: RDMD3-0: Read Mode Select Bits.
The Read Mode Select Bits control how the interface logic responds to reads to the FLASH-
DAT Register per the following values:
0000: A FLASHDAT read pro vid es th e da ta in the FLASHDAT re gis ter, but is otherw ise
ignored.
0001: A FLASHDAT read initiates a read of the byte addressed by the FLASHADR regis-
ter if no operation is currently active. This mode is used for block reads.
0010: A FLASHDAT read initiates a read of the byte addressed by FLASHADR only if no
operation is active and any data from a previous read has already been read from
FLASHDAT. This mode allows single bytes to be read (or the last byte of a block)
without initiating an extra read.
(All other value s for RDMD 3- 0 ar e re se rve d .)
Reset Value
SFLE WRMD2 WRMD1 WRMD0 RDMD3 RDMD2 RDMD1 RDMD0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 323
JTAG Register Definition 25.4. FLASHDAT: JTAG Flash Data
JTAG Register Definition 25.5. FLASHADR: JTAG Flash Address
This register is used to read or write data to the Flash memory across the JTAG interface.
Bits9-2: DATA7-0: Flash Data Byte.
Bit1: FAIL: Flash Fail Bit.
0: Previous Flash memory operation was successful.
1: Previous Flash memory operation failed. Usually indicates the associated memory loca-
tion was locked.
Bit0: BUSY: Flash Busy Bit.
0: Flash interfa ce log i c is not bus y.
1: Flash interface logic is processing a request. Reads or writes while BUSY = 1 will not
initiate another operation.
Reset Value
0000000000
Bit9 Bit0
This register holds the address for all JTAG Flash read, write, and erase operations. This register auto-
increments after each read or write, regardless of whether the operation succeeded or failed.
Bits15-0: Flash Operation 16-bit Address.
Reset Value
0x0000
Bit15 Bit0
C8051F040/1/2/3/4/5/6/7
324 Rev. 1.5
25.3. Debug Support
Each MCU has on-chip JTAG and debug logic that provides non-intrusive, full speed, in-circuit debug sup-
port using the production part inst alled in the end application, via the four pin JTAG I/F. Silicon Labs' debug
system supports inspection and modification of memory and registers, breakpoints, and single stepping.
No additional target RAM, program memory, or communications channels are required. All the digital and
analog peripherals are functional and work correctly (remain synchronized) while debugging. The Watch-
dog Timer (WDT) is disabled when the MCU is halted during single stepping or at a breakpo int.
The C8051F040DK is a development kit with all the hardware and software necessary to develop applica-
tion code and perform in-circuit debug with each MCU in the C8051F04x family. Each kit includes an Inte-
grated Development Environment (IDE) which has a debugger and integrated 8051 assembler. The kit
also includes a JTAG interface module referred to as the Serial Adapter. There is also a target application
board with a C8051F040 installed. The required cables and wall-mount power supply are also included.
C8051F040/1/2/3/4/5/6/7
Rev. 1.5 325
DOCUMENT CHANGE LIST
Revision 1.4 to Revision 1.5
• High Voltage Difference Amplifier Electrical Characteristics Tables: Corrected Common Mode Rejec-
tion Ratio MIN and TYP specifications.
• Flash Memory Chapter: Corrected text reference to “C8051F12x and C8051F13x”; Changed to
“C8051F04x”.
• 10 and 12-bit ADC0 Track and Conversion Example Timing Figures: Corrected bit name text from
“AD0STM” to “AD0C M”.
• ADC0 Chapters (10 and 12-bit): Updated analog multiplexer figure to represent correct connection of
HVREF to AIN- in differential HVDA configuration.
• ADC0 Chapters (10 and 12-bit): Updated HVDA section text to clarify usage of HVREF pin.
• ADC0 Chapters (10 and 12-bit): Added differential HVDA options to AMUX Selection Chart Table.
• Product Selection Guide Table: Added RoHS-compliant ordering information.
• Global DC Electrical Characteristics Table: Corrected units for “Analog Supply Current with Analog
Subsystems Inactive” to “µA”.
• Pin Definitions Table: Corrected HVAIN- pin description to “High Voltage Difference Amplifier Negative
Signal Input.”
• Interrupt Summary Table: Added “SFRPAGE” column and SFRPAGE value for each interrupt source.
• Interrupt Summary Table: Corrected “T4CON” to “TM R4 CN” .
• Interrupt Summary Table: Corrected “T2CON” to “TM R2 CN” .
• Interrupt Summary Table: Corrected “ADWINT” to “AD0WINT”.
• SFR Memory Map Table: Corrected SFR Page for ADC2CN from page 1 to page 2.
• Oscillators Chapter: Corrected steps for enabling external crystal oscillator.
• PCA0CPHn SFR Definition: Corrected SFR address of PCA0CPH1 from “0xFD” to “0xFE”.
C8051F040/1/2/3/4/5/6/7
326 Rev. 1.5
CONTACT INFORMATION
Silicon Laboratories Inc.
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Austin, TX 78735
Email: MCUinfo@silabs.com
Internet: www.silabs.com
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