SILABS C8051F39X 50 mips 16 kb flash, 512b eeprom mixed-signal mcu Datasheet

C8051F39x/37x
50 MIPS 16 kB Flash, 512B EEPROM Mixed-Signal MCU
Analog Peripherals (‘F390/2/4/6/8 and ‘F370/4)
- 10-Bit ADC
• Programmable throughput up to 500 ksps
• Up to 16 external inputs, programmable as single-
•
-
Two 10-Bit Current Output DACs
•
-
Supports output through resets for continuous
operation
-
Comparator
•
•
-
ended or differential
Reference from on-chip voltage reference, VDD or
external VREF pin
Internal or external start of conversion sources
Programmable hysteresis and response time
Configurable as interrupt or reset source
Precision Temperature Sensor
•
Accurate to ±2 °C across temperature range with no
user calibration
On-Chip Debug
- On-chip debug circuitry facilitates full speed, non-
intrusive in-system debug (no emulator required)
Provides breakpoints, single stepping,
inspect/modify memory and registers
Low Power
- 160 µA/MHz Active mode with 49 MHz internal
precision oscillator
- 200 nA Stop mode current
Temperature Range
- –40 to +85 °C (‘F37x)
- –40 to +105 °C (‘F39x)
Package
- 24-Pin QFN (‘F390/1/4/5 and ‘F37x)
- 20-Pin QFN (‘F392/3/6/7/8/9)
VREF
10-bit
10-bit
Current
Current
DAC
DAC
Temp Sensor
Precision
Temp Sensor
–
VOLTAGE
COMPARATOR
Digital Peripherals
- 21 or 17 Port I/O
- UART, 2 SMBus (I2C compatible), and SPI serial
-
ports
Six general purpose 16-bit counter/timers
16-Bit programmable counter array (PCA) with three
capture/compare modules and PWM functionality
Clock Sources
- 49 MHz ±2% precision internal oscillator
• Supports crystal-less UART operation
• Low-power suspend mode with fast wake time
- 80 kHz low-frequency, low-power oscillator
- External oscillator: Crystal, RC, C, or CMOS clock
- Can switch between clock sources on-the-fly; useful
in power saving modes
10-bit
500 ksps
ADC
+
byte Sectors
512 bytes of byte-programmable EEPROM; 1 million write/erase cycles (‘F37x)
Supply Voltage 1.8 to 3.6 V
- Built-in voltage supply monitor
ANALOG
PERIPHERALS
A
M
U
X
instructions in 1 or 2 system clocks
- Up to 50 MIPS throughput with 50 MHz clock
- Expanded interrupt handler
Memory
- Up to 1 kbytes internal data RAM (256 + 768)
- Up to 16 kB Flash; In-system programmable in 512-
‘F390/2/4/6/8 &
‘F370/4 Only
49 MHz PRECISION
INTERNAL OSCILLATOR
DIGITAL I/O
UART
SMBus0
SMBus1
SPI
PCA0
PCA1
PCA2
Timer 0
Timer 1
Timer 2
Timer 3
Timer 4
Timer 5
80 KHz LOW FREQUENCY
INTERNAL OSCILLATOR
Port 0
CROSSBAR
•
High-Speed 8051 µC Core
- Pipelined instruction architecture; executes 70% of
Port 1
P2.0
P2.1–
P2.4*
*P2.1–2.4 QFN24 Only
512 B
EEPROM
HIGH-SPEED CONTROLLER CORE
16/8 kB
8051 CPU
1024 B
ISP FLASH
(50 MIPS)
SRAM
FLEXIBLE
DEBUG
POR WDT
INTERRUPTS
CIRCUITRY
Preliminary Rev. 0.71 8/12
Copyright © 2012 by Silicon Laboratories
C8051F39x/37x
This information applies to a product under development. Its characteristics and specifications are subject to change without notice.
C8051F39x/37x
2
Preliminary Rev. 0.71
C8051F39x/37x
Table of Contents
1. System Overview ..................................................................................................... 17
2. Ordering Information ............................................................................................... 20
3. C8051F33x Compatibility ........................................................................................ 21
3.1. Hardware Incompatibilities ................................................................................ 21
4. Pin Definitions.......................................................................................................... 22
5. QFN-20 Package Specifications ............................................................................. 28
6. QFN-24 Package Specifications ............................................................................. 30
7. Electrical Characteristics ........................................................................................ 32
7.1. Absolute Maximum Specifications..................................................................... 32
7.2. Electrical Characteristics ................................................................................... 33
7.3. Typical Performance Curves ............................................................................. 44
8. Precision Temperature Sensor
(C8051F390/2/4/6/8 and C8051F370/4 Only)............................................................... 45
8.1. Temperature in Two’s Complement .................................................................. 45
9. 10-Bit ADC (ADC0, C8051F390/2/4/6/8 and C8051F370/4 Only) ........................... 48
9.1. Output Code Formatting .................................................................................... 49
9.2. Modes of Operation ........................................................................................... 50
9.2.1. Starting a Conversion................................................................................ 50
9.2.2. Tracking Modes......................................................................................... 51
9.2.3. Settling Time Requirements...................................................................... 52
9.3. Programmable Window Detector....................................................................... 56
9.3.1. Window Detector Example........................................................................ 58
9.4. ADC0 Analog Multiplexer (C8051F390/2/4/6/8 and C8051F370/4 Only) .......... 59
10. Temperature Sensor (C8051F390/2/4/6/8 and C8051F370/4 Only)..................... 62
10.1. Calibration ....................................................................................................... 63
11. 10-Bit Current Mode DACs
(IDA0, IDA1, C8051F390/2/4/6/8 and C8051F370/4 Only) .......................................... 64
11.1. IDAC Output Scheduling ................................................................................. 64
11.1.1. Update Output On-Demand .................................................................... 64
11.1.2. Update Output Based on Timer Overflow ............................................... 66
11.1.3. Update Output Based on CNVSTR Edge ............................................... 66
11.2. IDAC Reset Behavior ...................................................................................... 66
11.3. IDAC Output Mapping ..................................................................................... 66
12. Voltage Reference Options ................................................................................... 71
13. Voltage Regulator .................................................................................................. 73
13.1. Power Modes................................................................................................... 73
14. Comparator0........................................................................................................... 74
14.1. Comparator Multiplexer ................................................................................... 78
15. CIP-51 Microcontroller........................................................................................... 80
15.1. Instruction Set.................................................................................................. 81
15.1.1. Instruction and CPU Timing .................................................................... 81
15.2. CIP-51 Register Descriptions .......................................................................... 85
16. Prefetch Engine...................................................................................................... 90
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C8051F39x/37x
17. Memory Organization ............................................................................................ 91
17.1. Program Memory............................................................................................. 92
17.1.1. MOVX Instruction and Program Memory ................................................ 92
17.2. Data Memory ................................................................................................... 92
17.2.1. Internal RAM ........................................................................................... 92
17.2.1.1. General Purpose Registers ............................................................ 93
17.2.1.2. Bit Addressable Locations .............................................................. 93
17.2.1.3. Stack ............................................................................................ 93
17.2.2. External RAM .......................................................................................... 93
18. Device ID Registers ............................................................................................... 95
19. Special Function Registers................................................................................... 99
19.1. SFR Paging ..................................................................................................... 99
19.2. Interrupts and Automatic SFR Paging ............................................................. 99
19.3. SFR Page Stack Example ............................................................................. 101
20. Interrupts .............................................................................................................. 115
20.1. MCU Interrupt Sources and Vectors.............................................................. 116
20.1.1. Interrupt Priorities.................................................................................. 116
20.1.2. Interrupt Latency ................................................................................... 116
20.2. Interrupt Register Descriptions ...................................................................... 118
20.3. External Interrupts INT0 and INT1................................................................. 126
21. Flash Memory....................................................................................................... 129
21.1. Programming The Flash Memory .................................................................. 129
21.1.1. Flash Lock and Key Functions .............................................................. 129
21.1.2. Flash Erase Procedure ......................................................................... 129
21.1.3. Flash Write Procedure .......................................................................... 130
21.2. Non-volatile Data Storage ............................................................................. 130
21.3. Security Options ............................................................................................ 131
21.4. Flash Write and Erase Guidelines ................................................................. 133
21.4.1. VDD Maintenance and the VDD Monitor ................................................ 133
21.4.2. PSWE Maintenance .............................................................................. 133
21.4.3. System Clock ........................................................................................ 134
22. EEPROM (C8051F37x) ......................................................................................... 138
22.1. EEPROM Communication Protocol.............................................................. 138
22.1.1. Slave Address Byte............................................................................... 139
22.1.2. Acknowledgement (ACK) ...................................................................... 139
22.1.3. Not-Acknowledgement (NACK)............................................................. 139
22.1.4. Reset..................................................................................................... 139
22.2. Write Operation ............................................................................................. 140
22.3. Read Operation ............................................................................................. 141
22.3.1. Current Address Read .......................................................................... 141
22.3.2. Selective Address Read........................................................................ 143
23. Cyclic Redundancy Check Unit (CRC0)............................................................. 145
23.1. CRC Algorithm............................................................................................... 145
23.2. Preparing for a CRC Calculation ................................................................... 147
23.3. Performing a CRC Calculation ...................................................................... 147
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C8051F39x/37x
23.4. Accessing the CRC0 Result .......................................................................... 147
23.5. CRC0 Bit Reverse Feature............................................................................ 147
24. Reset Sources ...................................................................................................... 153
24.1. Power-On Reset ............................................................................................ 154
24.2. Power-Fail Reset / VDD Monitor ................................................................... 155
24.3. External Reset ............................................................................................... 157
24.4. Missing Clock Detector Reset ....................................................................... 157
24.5. Comparator0 Reset ....................................................................................... 157
24.6. PCA Watchdog Timer Reset ......................................................................... 157
24.7. Flash Error Reset .......................................................................................... 157
24.8. Software Reset .............................................................................................. 157
25. Power Management Modes................................................................................. 159
25.1. Idle Mode....................................................................................................... 159
25.2. Stop Mode ..................................................................................................... 160
25.3. Suspend Mode .............................................................................................. 160
26. Oscillators and Clock Selection ......................................................................... 162
26.1. System Clock Selection................................................................................. 163
26.2. Programmable Internal High-Frequency (H-F) Oscillator .............................. 164
26.2.1. Internal Oscillator Suspend Mode ......................................................... 164
26.3. Programmable Internal Low-Frequency (L-F) Oscillator ............................... 166
26.3.1. Calibrating the Internal L-F Oscillator.................................................... 166
26.4. Internal Low-Power Oscillator........................................................................ 167
26.5. External Oscillator Drive Circuit..................................................................... 167
26.5.1. External Crystal Mode........................................................................... 167
26.5.2. External RC Example............................................................................ 169
26.5.3. External Capacitor Example.................................................................. 169
27. Port Input/Output ................................................................................................. 171
27.1. Port I/O Modes of Operation.......................................................................... 172
27.1.1. Port Pins Configured for Analog I/O...................................................... 172
27.1.2. Port Pins Configured For Digital I/O...................................................... 172
27.2. Assigning Port I/O Pins to Analog and Digital Functions............................... 173
27.2.1. Assigning Port I/O Pins to Analog Functions ........................................ 173
27.2.2. Assigning Port I/O Pins to Digital Functions.......................................... 174
27.2.3. Assigning Port I/O Pins to External Event Trigger Functions................ 175
27.3. Priority Crossbar Decoder ............................................................................. 176
27.4. Port I/O Initialization ...................................................................................... 178
27.5. Port Match ..................................................................................................... 181
27.6. Special Function Registers for Accessing and Configuring Port I/O ............. 183
28. SMBus0 and SMBus1 (I2C Compatible)............................................................. 190
28.1. Supporting Documents .................................................................................. 191
28.2. SMBus Configuration..................................................................................... 191
28.3. SMBus Operation .......................................................................................... 191
28.3.1. Transmitter vs. Receiver ....................................................................... 192
28.3.2. Arbitration.............................................................................................. 192
28.3.3. Clock Low Extension............................................................................. 192
Preliminary Rev. 0.71
5
C8051F39x/37x
28.3.4. SCL Low Timeout.................................................................................. 192
28.3.5. SCL High (SMBus Free) Timeout ......................................................... 193
28.4. Using the SMBus........................................................................................... 193
28.4.1. SMBus Configuration Register.............................................................. 193
28.4.2. SMBus Pin Swap .................................................................................. 195
28.4.3. SMBus Timing Control .......................................................................... 195
28.4.4. SMBnCN Control Register .................................................................... 199
28.4.4.1. Software ACK Generation ............................................................ 199
28.4.4.2. Hardware ACK Generation ........................................................... 199
28.4.5. Hardware Slave Address Recognition .................................................. 202
28.4.6. Data Register ........................................................................................ 207
28.5. SMBus Transfer Modes................................................................................. 209
28.5.1. Write Sequence (Master) ...................................................................... 209
28.5.2. Read Sequence (Master) ...................................................................... 210
28.5.3. Write Sequence (Slave) ........................................................................ 211
28.5.4. Read Sequence (Slave) ........................................................................ 212
28.6. SMBus Status Decoding................................................................................ 212
29. UART0 ................................................................................................................... 218
29.1. Enhanced Baud Rate Generation.................................................................. 219
29.2. Operational Modes ........................................................................................ 220
29.2.1. 8-Bit UART ............................................................................................ 220
29.2.2. 9-Bit UART ............................................................................................ 221
29.3. Multiprocessor Communications ................................................................... 222
30. Enhanced Serial Peripheral Interface (SPI0) ..................................................... 226
30.1. Signal Descriptions........................................................................................ 227
30.1.1. Master Out, Slave In (MOSI)................................................................. 227
30.1.2. Master In, Slave Out (MISO)................................................................. 227
30.1.3. Serial Clock (SCK) ................................................................................ 227
30.1.4. Slave Select (NSS) ............................................................................... 227
30.2. SPI0 Master Mode Operation ........................................................................ 228
30.3. SPI0 Slave Mode Operation .......................................................................... 229
30.4. SPI0 Interrupt Sources .................................................................................. 230
30.5. Serial Clock Phase and Polarity .................................................................... 230
30.6. SPI Special Function Registers ..................................................................... 232
31. Timers ................................................................................................................... 240
31.1. Timer 0 and Timer 1 ...................................................................................... 243
31.1.1. Mode 0: 13-bit Counter/Timer ............................................................... 243
31.1.2. Mode 1: 16-bit Counter/Timer ............................................................... 244
31.1.3. Mode 2: 8-bit Counter/Timer with Auto-Reload..................................... 245
31.1.4. Mode 3: Two 8-bit Counter/Timers (Timer 0 Only)................................ 246
31.2. Timer 2 .......................................................................................................... 251
31.2.1. 16-bit Timer with Auto-Reload............................................................... 251
31.2.2. 8-bit Timers with Auto-Reload............................................................... 252
31.2.3. Low-Frequency Oscillator (LFO) Capture Mode ................................... 253
31.3. Timer 3 .......................................................................................................... 257
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Preliminary Rev. 0.71
C8051F39x/37x
31.3.1. 16-bit Timer with Auto-Reload............................................................... 257
31.3.2. 8-bit Timers with Auto-Reload............................................................... 258
31.3.3. Low-Frequency Oscillator (LFO) Capture Mode ................................... 259
31.4. Timer 4 .......................................................................................................... 263
31.4.1. 16-bit Timer with Auto-Reload............................................................... 263
31.4.2. 8-bit Timers with Auto-Reload............................................................... 264
31.5. Timer 5 .......................................................................................................... 268
31.5.1. 16-bit Timer with Auto-Reload............................................................... 268
31.5.2. 8-bit Timers with Auto-Reload............................................................... 269
32. Programmable Counter Array............................................................................. 273
32.1. PCA Counter/Timer ....................................................................................... 274
32.2. PCA0 Interrupt Sources................................................................................. 275
32.3. Capture/Compare Modules ........................................................................... 276
32.3.1. Edge-triggered Capture Mode............................................................... 277
32.3.2. Software Timer (Compare) Mode.......................................................... 278
32.3.3. High-Speed Output Mode ..................................................................... 279
32.3.4. Frequency Output Mode ....................................................................... 280
32.3.5. 8-bit, 9-bit, 10-bit and 11-bit Pulse Width Modulator Modes ................ 280
32.3.5.1. 8-bit Pulse Width Modulator Mode............................................... 281
32.3.5.2. 9/10/11-bit Pulse Width Modulator Mode..................................... 282
32.3.6. 16-Bit Pulse Width Modulator Mode..................................................... 283
32.4. Watchdog Timer Mode .................................................................................. 284
32.4.1. Watchdog Timer Operation ................................................................... 284
32.4.2. Watchdog Timer Usage ........................................................................ 285
32.5. Comparator Clear Function ........................................................................... 286
32.6. Register Descriptions for PCA0..................................................................... 288
33. C2 Interface .......................................................................................................... 295
33.1. C2 Interface Registers................................................................................... 295
33.2. C2 Pin Sharing .............................................................................................. 298
Document Change List.............................................................................................. 299
Contact Information................................................................................................... 300
Preliminary Rev. 0.71
7
C8051F39x/37x
List of Figures
Figure 1.1. C8051F392/3/6/7/8/9 Block Diagram .................................................... 18
Figure 1.2. C8051F390/1/4/5 Block Diagram .......................................................... 18
Figure 1.3. C8051F370/1/4/5 Block Diagram .......................................................... 19
Figure 4.1. C8051F392/3/6/7/8/9 QFN-20 Pinout Diagram (Top View) ................... 25
Figure 4.2. C8051F390/1/4/5 Pinout Diagram (Top View) ...................................... 26
Figure 4.3. C8051F370/1/4/5 Pinout Diagram (Top View) ...................................... 27
Figure 5.1. QFN-20 Package Drawing .................................................................... 28
Figure 5.2. QFN-20 Recommended PCB Land Pattern .......................................... 29
Figure 6.1. QFN-24 Package Drawing .................................................................... 30
Figure 6.2. QFN-24 Recommended PCB Land Pattern .......................................... 31
Figure 7.1. Normal Mode Digital Supply Current vs. Frequency ............................. 44
Figure 7.2. Idle Mode Digital Supply Current vs. Frequency ................................... 44
Figure 9.1. ADC0 Functional Block Diagram ........................................................... 48
Figure 9.2. 10-Bit ADC Track and Conversion Example Timing ............................. 51
Figure 9.3. ADC0 Equivalent Input Circuits ............................................................. 52
Figure 9.4. ADC Window Compare Example: Right-Justified, Single-Ended Data . 58
Figure 9.5. ADC Window Compare Example: Left-Justified, Single-Ended Data .... 58
Figure 9.6. ADC0 Multiplexer Block Diagram .......................................................... 59
Figure 10.1. Temperature Sensor Transfer Function .............................................. 62
Figure 10.2. Temperature Sensor Error with 1-Point Calibration at 0 °C ................ 63
Figure 11.1. IDA0 Functional Block Diagram .......................................................... 64
Figure 11.2. IDA1 Functional Block Diagram .......................................................... 65
Figure 11.3. IDA0 Data Word Mapping ................................................................... 66
Figure 12.1. Voltage Reference Functional Block Diagram ..................................... 71
Figure 14.1. Comparator0 Functional Block Diagram ............................................. 74
Figure 14.2. Comparator Hysteresis Plot ................................................................ 75
Figure 14.3. Comparator Input Multiplexer Block Diagram ...................................... 78
Figure 15.1. CIP-51 Block Diagram ......................................................................... 80
Figure 17.1. C8051F39x/37x Memory Map ............................................................. 91
Figure 17.2. Flash Program Memory Map ............................................................... 92
Figure 19.1. SFR Page Stack ................................................................................ 100
Figure 19.2. SFR Page Stack While Using SFR Page 0x0F To Access TS0CN .. 101
Figure 19.3. SFR Page Stack After SPI0 Interrupt Occurs .................................... 102
Figure 19.4. SFR Page Stack Upon PCA Interrupt Occurring During a SPI0 ISR 103
Figure 19.5. SFR Page Stack Upon Return from PCA0 Interrupt ......................... 104
Figure 19.6. SFR Page Stack Upon Return From SPI0 Interrupt .......................... 105
Figure 21.1. Security Byte Decoding ..................................................................... 131
Figure 22.1. Slave Address Byte Definition ........................................................... 139
Figure 22.2. Write Operation (Single Byte) ............................................................ 140
Figure 22.3. Write Operation (Multiple Bytes) ....................................................... 140
Figure 22.4. Current Address Read Operation (Single Byte) ................................ 141
Figure 22.5. Current Address Read Operation (Multiple Bytes) ............................ 142
Figure 22.6. Selective Address Read (Single Byte) .............................................. 143
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C8051F39x/37x
Figure 22.7. Selective Address Read (Multiple Bytes) .......................................... 144
Figure 23.1. CRC0 Block Diagram ........................................................................ 145
Figure 23.2. Bit Reverse Register ......................................................................... 147
Figure 24.1. Reset Sources ................................................................................... 153
Figure 24.2. Power-On and VDD Monitor Reset Timing ....................................... 154
Figure 26.1. Oscillator Options .............................................................................. 162
Figure 26.2. External Crystal Example .................................................................. 168
Figure 27.1. Port I/O Functional Block Diagram .................................................... 171
Figure 27.2. Port I/O Cell Block Diagram .............................................................. 172
Figure 27.3. Crossbar Priority Decoder - Possible Pin Assignments .................... 176
Figure 27.4. Crossbar Priority Decoder Example .................................................. 177
Figure 28.1. SMBus0 Block Diagram .................................................................... 190
Figure 28.2. Typical SMBus Configuration ............................................................ 191
Figure 28.3. SMBus Transaction ........................................................................... 192
Figure 28.4. Typical SMBus SCL Generation ........................................................ 194
Figure 28.5. Typical Master Write Sequence ........................................................ 209
Figure 28.6. Typical Master Read Sequence ........................................................ 210
Figure 28.7. Typical Slave Write Sequence .......................................................... 211
Figure 28.8. Typical Slave Read Sequence .......................................................... 212
Figure 29.1. UART0 Block Diagram ...................................................................... 218
Figure 29.2. UART0 Baud Rate Logic ................................................................... 219
Figure 29.3. UART Interconnect Diagram ............................................................. 220
Figure 29.4. 8-Bit UART Timing Diagram .............................................................. 220
Figure 29.5. 9-Bit UART Timing Diagram .............................................................. 221
Figure 29.6. UART Multi-Processor Mode Interconnect Diagram ......................... 222
Figure 30.1. SPI Block Diagram ............................................................................ 226
Figure 30.2. Multiple-Master Mode Connection Diagram ...................................... 228
Figure 30.3. 3-Wire Single Master and 3-Wire Single Slave
Mode Connection Diagram .............................................................................. 229
Figure 30.4. 4-Wire Single Master Mode and 4-Wire Slave
Mode Connection Diagram .............................................................................. 229
Figure 30.5. Master Mode Data/Clock Timing ....................................................... 231
Figure 30.6. Slave Mode Data/Clock Timing (CKPHA = 0) ................................... 231
Figure 30.7. Slave Mode Data/Clock Timing (CKPHA = 1) ................................... 232
Figure 30.8. SPI Master Timing (CKPHA = 0) ....................................................... 236
Figure 30.9. SPI Master Timing (CKPHA = 1) ....................................................... 237
Figure 30.10. SPI Slave Timing (CKPHA = 0) ....................................................... 237
Figure 30.11. SPI Slave Timing (CKPHA = 1) ....................................................... 238
Figure 31.1. T0 Mode 0 Block Diagram ................................................................. 244
Figure 31.2. T0 Mode 2 Block Diagram ................................................................. 245
Figure 31.3. T0 Mode 3 Block Diagram ................................................................. 246
Figure 31.4. Timer 2 16-Bit Mode Block Diagram ................................................. 251
Figure 31.5. Timer 2 8-Bit Mode Block Diagram ................................................... 252
Figure 31.6. Timer 2 Low-Frequency Oscillation Capture Mode Block Diagram ... 253
Figure 31.7. Timer 3 16-Bit Mode Block Diagram ................................................. 257
Preliminary Rev. 0.71
9
C8051F39x/37x
Figure 31.8. Timer 3 8-Bit Mode Block Diagram ................................................... 258
Figure 31.9. Timer 3 Low-Frequency Oscillation Capture Mode Block Diagram ... 259
Figure 31.10. Timer 4 16-Bit Mode Block Diagram ............................................... 263
Figure 31.11. Timer 4 8-Bit Mode Block Diagram ................................................. 264
Figure 31.12. Timer 5 16-Bit Mode Block Diagram ............................................... 268
Figure 31.13. Timer 5 8-Bit Mode Block Diagram ................................................. 269
Figure 32.1. PCA Block Diagram ........................................................................... 273
Figure 32.2. PCA Counter/Timer Block Diagram ................................................... 274
Figure 32.3. PCA Interrupt Block Diagram ............................................................ 275
Figure 32.4. PCA Capture Mode Diagram ............................................................. 277
Figure 32.5. PCA Software Timer Mode Diagram ................................................. 278
Figure 32.6. PCA High-Speed Output Mode Diagram ........................................... 279
Figure 32.7. PCA Frequency Output Mode ........................................................... 280
Figure 32.8. PCA 8-Bit PWM Mode Diagram ........................................................ 281
Figure 32.9. PCA 9, 10 and 11-Bit PWM Mode Diagram ...................................... 282
Figure 32.10. PCA 16-Bit PWM Mode ................................................................... 283
Figure 32.11. PCA Module 2 with Watchdog Timer Enabled ................................ 284
Figure 32.12. Comparator Clear Function Diagram .............................................. 286
Figure 32.13. CEXn with CPCEn = 1, CPCPOL = 0 .............................................. 286
Figure 32.14. CEXn with CPCEn = 1, CPCPOL = 1 .............................................. 287
Figure 32.15. CEXn with CPCEn = 1, CPCPOL = 0 .............................................. 287
Figure 32.16. CEXn with CPCEn = 1, CPCPOL = 1 .............................................. 287
Figure 33.1. Typical C2 Pin Sharing ...................................................................... 298
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C8051F39x/37x
List of Tables
Table 2.1. Product Selection Guide ......................................................................... 20
Table 3.1. C8051F33x Replacement Part Numbers ................................................ 21
Table 4.1. Pin Definitions for the C8051F39x/37x ................................................... 22
Table 5.1. QFN-20 Package Dimensions ................................................................ 28
Table 5.2. QFN-20 PCB Land Pattern Dimensions ................................................. 29
Table 6.1. QFN-24 Package Dimensions ................................................................ 30
Table 6.2. QFN-24 PCB Land Pattern Dimensions ................................................. 31
Table 7.1. Absolute Maximum Ratings .................................................................... 32
Table 7.2. Global Electrical Characteristics ............................................................. 33
Table 7.3. Port I/O DC Electrical Characteristics ..................................................... 34
Table 7.4. Reset Electrical Characteristics .............................................................. 35
Table 7.5. Flash Electrical Characteristics .............................................................. 36
Table 7.6. EEPROM Electrical Characteristics ........................................................ 36
Table 7.7. Internal High-Frequency Oscillator Electrical Characteristics ................. 37
Table 7.8. Internal Low-Frequency Oscillator Electrical Characteristics ................. 37
Table 7.9. Internal Low-Power Oscillator Electrical Characteristics ........................ 37
Table 7.10. ADC0 Electrical Characteristics ............................................................ 38
Table 7.11. ADC Temperature Sensor Electrical Characteristics ............................ 39
Table 7.12. Precision Temperature Sensor Electrical Characteristics .................... 39
Table 7.13. Voltage Reference Electrical Characteristics ....................................... 40
Table 7.14. Voltage Regulator Electrical Characteristics ........................................ 40
Table 7.15. IDAC Electrical Characteristics ............................................................. 41
Table 7.16. Comparator Electrical Characteristics .................................................. 42
Table 8.1. Example Temperature Values in TS0DATH:TS0DATL .......................... 45
Table 15.1. CIP-51 Instruction Set Summary .......................................................... 82
Table 19.1. SFR Page Stack ................................................................................... 99
Table 19.2. Special Function Register (SFR) Memory Map .................................. 109
Table 19.3. Special Function Registers ................................................................. 110
Table 20.1. Configurable Interrupt Priority Decoding ............................................ 116
Table 20.2. Interrupt Summary .............................................................................. 117
Table 21.1. Flash Security Summary .................................................................... 131
Table 23.1. Example 16-bit CRC Outputs ............................................................. 146
Table 27.1. Port I/O Assignment for Analog Functions ......................................... 173
Table 27.2. Port I/O Assignment for Digital Functions ........................................... 174
Table 27.3. Port I/O Assignment for External Event Trigger Functions ................. 175
Table 28.1. SMBus Clock Source Selection .......................................................... 194
Table 28.2. Minimum SDA Setup and Hold Times ................................................ 195
Table 28.3. Sources for Hardware Changes to SMBnCN ..................................... 202
Table 28.4. Hardware Address Recognition Examples (EHACK = 1) ................... 203
Table 28.5. SMBus Status Decoding: Hardware ACK Disabled (EHACK = 0) ...... 213
Table 28.6. SMBus Status Decoding: Hardware ACK Enabled (EHACK = 1) ...... 215
Table 29.1. Timer Settings for Standard Baud Rates
Using The Internal 49 MHz Oscillator ................................................. 225
Preliminary Rev. 0.71
11
C8051F39x/37x
Table 29.2. Timer Settings for Standard Baud Rates
Using an External 22.1184 MHz Oscillator ......................................... 225
Table 30.1. SPI Slave Timing Parameters ............................................................ 239
Table 32.1. PCA Timebase Input Options ............................................................. 274
Table 32.2. PCA0CPM and PCA0PWM Bit Settings for PCA
Capture/Compare Modules ................................................................ 276
Table 32.3. Watchdog Timer Timeout Intervals1 ................................................... 285
12
Preliminary Rev. 0.71
C8051F39x/37x
List of Registers
SFR Definition 8.1. TS0CN: Temperature Sensor Control ........................................... 46
SFR Definition 8.2. TS0DATH: Temperature Sensor Output High Byte ....................... 47
SFR Definition 8.3. TS0DATL: Temperature Sensor Output Low Byte ........................ 47
SFR Definition 9.1. ADC0CF: ADC0 Configuration ...................................................... 53
SFR Definition 9.2. ADC0H: ADC0 Data Word MSB .................................................... 54
SFR Definition 9.3. ADC0L: ADC0 Data Word LSB ...................................................... 54
SFR Definition 9.4. ADC0CN: ADC0 Control ................................................................ 55
SFR Definition 9.5. ADC0GTH: ADC0 Greater Than Data High Byte .......................... 56
SFR Definition 9.6. ADC0GTL: ADC0 Greater-Than Data Low Byte ............................ 56
SFR Definition 9.7. ADC0LTH: ADC0 Less-Than Data High Byte ................................ 57
SFR Definition 9.8. ADC0LTL: ADC0 Less-Than Data Low Byte ................................. 57
SFR Definition 9.9. AMX0P: AMUX0 Positive Channel Select ..................................... 60
SFR Definition 9.10. AMX0N: AMUX0 Negative Channel Select ................................. 61
SFR Definition 11.1. IDA0CN: IDA0 Control ................................................................. 67
SFR Definition 11.2. IDA0H: IDA0 Data Word MSB ..................................................... 68
SFR Definition 11.3. IDA0L: IDA0 Data Word LSB ....................................................... 68
SFR Definition 11.4. IDA1CN: IDA1 Control ................................................................. 69
SFR Definition 11.5. IDA1H: IDA1 Data Word MSB ..................................................... 70
SFR Definition 11.6. IDA1L: IDA1 Data Word LSB ....................................................... 70
SFR Definition 12.1. REF0CN: Reference Control ....................................................... 72
SFR Definition 13.1. REG0CN: Voltage Regulator Control .......................................... 73
SFR Definition 14.1. CPT0CN: Comparator0 Control ................................................... 76
SFR Definition 14.2. CPT0MD: Comparator0 Mode Selection ..................................... 77
SFR Definition 14.3. CPT0MX: Comparator0 MUX Selection ...................................... 79
SFR Definition 15.1. DPL: Data Pointer Low Byte ........................................................ 86
SFR Definition 15.2. DPH: Data Pointer High Byte ....................................................... 86
SFR Definition 15.3. SP: Stack Pointer ......................................................................... 87
SFR Definition 15.4. ACC: Accumulator ....................................................................... 87
SFR Definition 15.5. B: B Register ................................................................................ 88
SFR Definition 15.6. PSW: Program Status Word ........................................................ 89
SFR Definition 16.1. PFE0CN: Prefetch Engine Control .............................................. 90
SFR Definition 17.1. EMI0CN: External Memory Interface Control .............................. 94
SFR Definition 18.1. DERIVID: Device Derivative ID .................................................... 95
SFR Definition 18.2. REVISION: Device Revision ID ................................................... 96
SFR Definition 18.3. SN3: Serial Number Byte 3 .......................................................... 96
SFR Definition 18.4. SN2: Serial Number Byte 2 .......................................................... 97
SFR Definition 18.5. SN1: Serial Number Byte 1 .......................................................... 97
SFR Definition 18.6. SN0: Serial Number Byte 0 .......................................................... 98
SFR Definition 19.1. SFRPAGE: SFR Page ............................................................... 106
SFR Definition 19.2. SFRPGCN: SFR Page Control .................................................. 107
SFR Definition 19.3. SFRSTACK: SFR Page Stack ................................................... 108
SFR Definition 20.1. IE: Interrupt Enable .................................................................... 118
SFR Definition 20.2. IP: Interrupt Priority .................................................................... 119
Preliminary Rev. 0.71
13
C8051F39x/37x
SFR Definition 20.3. IPH: Interrupt Priority High ......................................................... 120
SFR Definition 20.4. EIE1: Extended Interrupt Enable 1 ............................................ 121
SFR Definition 20.5. EIP1: Extended Interrupt Priority 1 ............................................ 122
SFR Definition 20.6. EIP1H: Extended Interrupt Priority 1 High ................................. 123
SFR Definition 20.7. EIE2: Extended Interrupt Enable 2 ............................................ 124
SFR Definition 20.8. EIP2: Extended Interrupt Priority 2 ............................................ 125
SFR Definition 20.9. EIP2H: Extended Interrupt Priority 2 High ................................. 125
SFR Definition 20.10. IT01CF: INT0/INT1 Configuration ............................................ 127
SFR Definition 21.1. PSCTL: Program Store R/W Control ......................................... 135
SFR Definition 21.2. FLKEY: Flash Lock and Key ...................................................... 136
SFR Definition 21.3. FLSCL: Flash Scale ................................................................... 137
SFR Definition 23.1. CRC0CN: CRC0 Control ........................................................... 148
SFR Definition 23.2. CRC0IN: CRC0 Data Input ........................................................ 149
SFR Definition 23.3. CRC0DAT: CRC0 Data Output .................................................. 149
SFR Definition 23.4. CRC0AUTO: CRC0 Automatic Control ...................................... 150
SFR Definition 23.5. CRC0CNT: CRC0 Automatic Flash Sector Count ..................... 151
SFR Definition 23.6. CRC0FLIP: CRC0 Bit Flip .......................................................... 152
SFR Definition 24.1. VDM0CN: VDD Monitor Control ................................................ 156
SFR Definition 24.2. RSTSRC: Reset Source ............................................................ 158
SFR Definition 25.1. PCON: Power Control ................................................................ 161
SFR Definition 26.1. CLKSEL: Clock Select ............................................................... 163
SFR Definition 26.2. OSCICL: Internal H-F Oscillator Calibration .............................. 164
SFR Definition 26.3. OSCICN: Internal H-F Oscillator Control ................................... 165
SFR Definition 26.4. OSCLCN: Internal L-F Oscillator Control ................................... 166
SFR Definition 26.5. OSCXCN: External Oscillator Control ........................................ 170
SFR Definition 27.1. XBR0: Port I/O Crossbar Register 0 .......................................... 179
SFR Definition 27.2. XBR1: Port I/O Crossbar Register 1 .......................................... 180
SFR Definition 27.3. P0MASK: Port 0 Mask Register ................................................. 181
SFR Definition 27.4. P0MAT: Port 0 Match Register .................................................. 182
SFR Definition 27.5. P1MASK: Port 1 Mask Register ................................................. 182
SFR Definition 27.6. P1MAT: Port 1 Match Register .................................................. 183
SFR Definition 27.7. P0: Port 0 ................................................................................... 184
SFR Definition 27.8. P0MDIN: Port 0 Input Mode ....................................................... 184
SFR Definition 27.9. P0MDOUT: Port 0 Output Mode ................................................ 185
SFR Definition 27.10. P0SKIP: Port 0 Skip ................................................................. 185
SFR Definition 27.11. P1: Port 1 ................................................................................. 186
SFR Definition 27.12. P1MDIN: Port 1 Input Mode ..................................................... 186
SFR Definition 27.13. P1MDOUT: Port 1 Output Mode .............................................. 187
SFR Definition 27.14. P1SKIP: Port 1 Skip ................................................................. 187
SFR Definition 27.15. P2: Port 2 ................................................................................. 188
SFR Definition 27.16. P2MDIN: Port 2 Input Mode ..................................................... 188
SFR Definition 27.17. P2MDOUT: Port 2 Output Mode .............................................. 189
SFR Definition 27.18. P2SKIP: Port 2 Skip ................................................................. 189
SFR Definition 28.1. SMB0CF: SMBus Clock/Configuration ...................................... 196
SFR Definition 28.2. SMB1CF: SMBus Clock/Configuration ...................................... 197
14
Preliminary Rev. 0.71
C8051F39x/37x
SFR Definition 28.3. SMBTC: SMBus Timing and Pin Control ................................... 198
SFR Definition 28.4. SMB0CN: SMBus Control .......................................................... 200
SFR Definition 28.5. SMB1CN: SMBus Control .......................................................... 201
SFR Definition 28.6. SMB0ADR: SMBus0 Slave Address .......................................... 203
SFR Definition 28.7. SMB0ADM: SMBus0 Slave Address Mask ................................ 204
SFR Definition 28.8. SMB1ADR: SMBus1 Slave Address .......................................... 205
SFR Definition 28.9. SMB1ADM: SMBus1 Slave Address Mask ................................ 206
SFR Definition 28.10. SMB0DAT: SMBus Data .......................................................... 207
SFR Definition 28.11. SMB1DAT: SMBus Data .......................................................... 208
SFR Definition 29.1. SCON0: Serial Port 0 Control .................................................... 223
SFR Definition 29.2. SBUF0: Serial (UART0) Port Data Buffer .................................. 224
SFR Definition 30.1. SPI0CFG: SPI0 Configuration ................................................... 233
SFR Definition 30.2. SPI0CN: SPI0 Control ............................................................... 234
SFR Definition 30.3. SPI0CKR: SPI0 Clock Rate ....................................................... 235
SFR Definition 30.4. SPI0DAT: SPI0 Data ................................................................. 236
SFR Definition 31.1. CKCON: Clock Control .............................................................. 241
SFR Definition 31.2. CKCON1: Clock Control 1 ......................................................... 242
SFR Definition 31.3. TCON: Timer Control ................................................................. 247
SFR Definition 31.4. TMOD: Timer Mode ................................................................... 248
SFR Definition 31.5. TL0: Timer 0 Low Byte ............................................................... 249
SFR Definition 31.6. TL1: Timer 1 Low Byte ............................................................... 249
SFR Definition 31.7. TH0: Timer 0 High Byte ............................................................. 250
SFR Definition 31.8. TH1: Timer 1 High Byte ............................................................. 250
SFR Definition 31.9. TMR2CN: Timer 2 Control ......................................................... 254
SFR Definition 31.10. TMR2RLL: Timer 2 Reload Register Low Byte ........................ 255
SFR Definition 31.11. TMR2RLH: Timer 2 Reload Register High Byte ...................... 255
SFR Definition 31.12. TMR2L: Timer 2 Low Byte ....................................................... 255
SFR Definition 31.13. TMR2H Timer 2 High Byte ....................................................... 256
SFR Definition 31.14. TMR3CN: Timer 3 Control ....................................................... 260
SFR Definition 31.15. TMR3RLL: Timer 3 Reload Register Low Byte ........................ 261
SFR Definition 31.16. TMR3RLH: Timer 3 Reload Register High Byte ...................... 261
SFR Definition 31.17. TMR3L: Timer 3 Low Byte ....................................................... 261
SFR Definition 31.18. TMR3H Timer 3 High Byte ....................................................... 262
SFR Definition 31.19. TMR4CN: Timer 4 Control ....................................................... 265
SFR Definition 31.20. TMR4RLL: Timer 4 Reload Register Low Byte ........................ 266
SFR Definition 31.21. TMR4RLH: Timer 4 Reload Register High Byte ...................... 266
SFR Definition 31.22. TMR4L: Timer 4 Low Byte ....................................................... 266
SFR Definition 31.23. TMR4H Timer 4 High Byte ....................................................... 267
SFR Definition 31.24. TMR5CN: Timer 5 Control ....................................................... 270
SFR Definition 31.25. TMR5RLL: Timer 5 Reload Register Low Byte ........................ 271
SFR Definition 31.26. TMR5RLH: Timer 5 Reload Register High Byte ...................... 271
SFR Definition 31.27. TMR5L: Timer 5 Low Byte ....................................................... 271
SFR Definition 31.28. TMR5H Timer 5 High Byte ....................................................... 272
SFR Definition 32.1. PCA0CN: PCA Control .............................................................. 288
SFR Definition 32.2. PCA0MD: PCA Mode ................................................................ 289
Preliminary Rev. 0.71
15
C8051F39x/37x
SFR Definition 32.3. PCA0PWM: PCA PWM Configuration ....................................... 290
SFR Definition 32.4. PCA0CLR: PCA Comparator Clear Control ............................... 291
SFR Definition 32.5. PCA0CPMn: PCA Capture/Compare Mode .............................. 292
SFR Definition 32.6. PCA0L: PCA Counter/Timer Low Byte ...................................... 293
SFR Definition 32.7. PCA0H: PCA Counter/Timer High Byte ..................................... 293
SFR Definition 32.8. PCA0CPLn: PCA Capture Module Low Byte ............................. 294
SFR Definition 32.9. PCA0CPHn: PCA Capture Module High Byte ........................... 294
C2 Register Definition 33.1. C2ADD: C2 Address ...................................................... 295
C2 Register Definition 33.2. DEVICEID: C2 Device ID ............................................... 296
C2 Register Definition 33.3. REVID: C2 Revision ID .................................................. 296
C2 Register Definition 33.4. FPCTL: C2 Flash Programming Control ........................ 297
C2 Register Definition 33.5. FPDAT: C2 Flash Programming Data ............................ 297
16
Preliminary Rev. 0.71
C8051F39x/37x
1. System Overview
C8051F39x/37x devices are fully integrated mixed-signal System-on-a-Chip MCUs. Highlighted features
are listed below. Refer to Section “2. Ordering Information” on page 20 for specific product feature selection and part ordering numbers.

High-speed pipelined 8051-compatible microcontroller core (up to 50 MIPS)
In-system, full-speed, non-intrusive debug interface (on-chip)
True 10-bit 500 ksps 20 or 16-channel single-ended/differential ADC with analog multiplexer
Two 10-bit Current Output DACs
Precision temperature sensor with ±2 °C absolute accuracy
Precision programmable 49 MHz internal oscillator
Low-power, low-frequency oscillator
16 kB of on-chip Flash memory
1024 bytes of on-chip RAM

Co-packaged with 512 bytes of EEPROM memory, accessible via I2C (C8051F37x)








Two SMBus/I2C, UART, and SPI serial interfaces implemented in hardware
 Six general-purpose 16-bit timers
 Programmable Counter/Timer Array (PCA) with three capture/compare modules and Watchdog Timer
function
 On-chip Power-On Reset, VDD Monitor, and Temperature Sensor

On-chip Voltage Comparator
21 or 17 Port I/O
 Low-power suspend mode with fast wake-up time
With on-chip Power-On Reset, VDD monitor, Watchdog Timer, and clock oscillator, the C8051F39x/37x
devices are truly stand-alone System-on-a-Chip solutions. The Flash memory can be reprogrammed even
in-circuit, providing non-volatile data storage, and also allowing field upgrades of the 8051 firmware. User
software has complete control of all peripherals, and may individually shut down any or all peripherals for
power savings.


The on-chip Silicon Labs 2-Wire (C2) Development Interface allows non-intrusive (uses no on-chip
resources), full speed, in-circuit debugging using the production MCU installed in the final application. This
debug logic supports inspection and modification of memory and registers, setting breakpoints, single
stepping, run and halt commands. All analog and digital peripherals are fully functional while debugging
using C2. The two C2 interface pins can be shared with user functions, allowing in-system debugging without occupying package pins.
The C8051F37x devices are specified for 1.8 to 3.6 V operation over the industrial temperature range (–40
to +85 °C), while the C8051F39x devices operate over an extended temperature range (-40 to +105 °C).
The C8051F392/3/6/7/8/9 are available in a 20-pin QFN package and the C8051F390/1/4/5 and
C8051F37x are available in a 24-pin QFN package. Both package options are lead-free and RoHS compliant. See Section “2. Ordering Information” on page 20 for ordering information. Block diagrams are
included in Figure 1.1, Figure 1.2 and Figure 1.3.
Preliminary Rev. 0.71
17
C8051F39x/37x
Power On
Reset
Reset
C2CK/RST
Port I/O Configuration
CIP-51 8051
Controller Core
Debug /
Programming
Hardware
UART
Timers 0
through 5
256 Byte SRAM
768 Byte XRAM
2xI2C /
SMBus
SPI
Internal
LDO
Crossbar Control
Power Net
SFR
Bus
GND
XTAL2
P2.0/C2D
IDA0
IDA1
Port 2
Drivers
Precision Temperature
Sensor
SYSCLK
A
M
U
X
10-bit
500 ksps
ADC
External
Oscillator
Circuit
XTAL1
Analog Peripherals
2 x 10-bit
IDACs
Precision
49 MHz
Oscillator
Low-Freq.
Oscillator
Port 1
Drivers
P1.0/IDA1
P1.1
P1.2
P1.3
P1.4
P1.5
P1.6
P1.7
Priority
Crossbar
Decoder
PCA/
WDT
C2D
VDD
Port 0
Drivers
P0.0/VREF
P0.1/IDA0
P0.2/XTAL1
P0.3/XTAL2
P0.4/TX
P0.5/RX
P0.6/CNVSTR
P0.7
Digital Peripherals
16/8/4 kB ISP Flash
Program Memory
C8051F392/6/8 Only
System Clock
Configuration
CP0, CP0A
+
-
Comparator
Figure 1.1. C8051F392/3/6/7/8/9 Block Diagram
Power On
Reset
Reset
C2CK/RST
Port I/O Configuration
CIP-51 8051
Controller Core
16/8 kB ISP Flash
Program Memory
Debug /
Programming
Hardware
UART
Timers 0
through 5
256 Byte SRAM
768 Byte XRAM
Crossbar Control
Power Net
SFR
Bus
GND
XTAL1
XTAL2
External
Oscillator
Circuit
System Clock
Configuration
IDA0
IDA1
SYSCLK
Precision Temperature
Sensor
A
M
U
X
10-bit
500 ksps
ADC
C8051F390/4 Only
CP0, CP0A
+
-
Comparator
Figure 1.2. C8051F390/1/4/5 Block Diagram
18
P2.0
P2.1
P2.2
P2.3
P2.4/C2D
Analog Peripherals
2 x 10-bit
IDACs
Precision
49 MHz
Oscillator
Low-Freq.
Oscillator
Port 2
Drivers
2xI2C /
SMBus
SPI
Internal
LDO
Port 1
Drivers
P1.0
P1.1
P1.2/IDA1
P1.3
P1.4
P1.5
P1.6
P1.7
Priority
Crossbar
Decoder
PCA/
WDT
C2D
VDD
Port 0
Drivers
P0.0/VREF
P0.1/IDA0
P0.2/XTAL1
P0.3/XTAL2
P0.4/TX
P0.5/RX
P0.6/CNVSTR
P0.7
Digital Peripherals
Preliminary Rev. 0.71
C8051F39x/37x
Power On
Reset
Reset
C2CK/RST
Port I/O Configuration
CIP-51 8051
Controller Core
16 kB ISP Flash
Program Memory
Debug /
Programming
Hardware
UART
Timers 0
through 5
256 Byte SRAM
768 Byte XRAM
EESCL
VDD
Internal
LDO
SPI
Crossbar Control
SFR
Bus
Power Net
XTAL2
System Clock
Configuration
IDA0
IDA1
2 x 10-bit
IDACs
Precision
49 MHz
Oscillator
External
Oscillator
Circuit
P2.0
P2.1
P2.2/EESCL
P2.3/EESDA
P2.4/C2D
Analog Peripherals
GND
XTAL1
Port 2
Drivers
2xI2C /
SMBus
512 Byte I2C EEPROM
Low-Freq.
Oscillator
Port 1
Drivers
P1.0
P1.1
P1.2/IDA1
P1.3
P1.4
P1.5
P1.6
P1.7
Priority
Crossbar
Decoder
PCA/
WDT
C2D
EESDA
Port 0
Drivers
P0.0/VREF
P0.1/IDA0
P0.2/XTAL1
P0.3/XTAL2
P0.4/TX
P0.5/RX
P0.6/CNVSTR
P0.7
Digital Peripherals
SYSCLK
Precision Temperature
Sensor
A
M
U
X
10-bit
500 ksps
ADC
C8051F370/4 Only
CP0, CP0A
+
-
Comparator
Figure 1.3. C8051F370/1/4/5 Block Diagram
Preliminary Rev. 0.71
19
C8051F39x/37x
2. Ordering Information
The following features are common to all device in this family:
50 MIPS throughput (peak)
 1 kB of RAM (256 internal bytes and 768 XRAM bytes)
 Calibrated internal 49 MHz oscillator
 Internal 80 kHz oscillator







Two SMBus/I2C
Enhanced SPI, Enhanced UART
Six Timers
Three Programmable Counter Array channels
Analog Comparator
Lead-free / RoHS Compliant
Table 2.1 shows the features that differentiate the devices in this family.
Table 2.1. Product Selection Guide
Ordering Part
Number
Flash EEPROM Digital
10-bit
10-bit
On-Chip
Precision
Package
Memory (Bytes) Port I/Os
ADC
DAC
Voltage Temperature 4x4 mm
(Bytes)
Channels Channels Reference
Sensor
C8051F370-A-GM
16k
512
21
20
2
Y
Y
QFN-24
C8051F371-A-GM
16k
512
21
—
—
—
—
QFN-24
C8051F374-A-GM
8k
512
21
20
2
Y
Y
QFN-24
C8051F375-A-GM
8k
512
21
—
—
—
—
QFN-24
C8051F390-A-GM
16k
—
21
20
2
Y
Y
QFN-24
C8051F391-A-GM
16k
—
21
—
—
—
—
QFN-24
C8051F392-A-GM
16k
—
17
16
2
Y
Y
QFN-20
C8051F393-A-GM
16k
—
17
—
—
—
—
QFN-20
C8051F394-A-GM
8k
—
21
20
2
Y
Y
QFN-24
C8051F395-A-GM
8k
—
21
—
—
—
—
QFN-24
C8051F396-A-GM
8k
—
17
16
2
Y
Y
QFN-20
C8051F397-A-GM
8k
—
17
—
—
—
—
QFN-20
C8051F398-A-GM
4k
—
17
16
2
Y
Y
QFN-20
C8051F399-A-GM
4k
—
17
—
—
—
—
QFN-20
20
Preliminary Rev. 0.71
C8051F39x/37x
3. C8051F33x Compatibility
The C8051F39x/37x family is designed to be a pin and code compatible replacement for the C8051F33x
device family, with an enhanced feature set. The C8051F39x/37x device should function as a drop-in
replacement for the C8051F33x devices in most applications. Table 3.1 lists recommended replacement
part numbers for C8051F33x devices. See “3.1. Hardware Incompatibilities” to determine if any changes
are necessary when upgrading an existing C8051F33x design to the C8051F39x/37x.
Table 3.1. C8051F33x Replacement Part Numbers
C8051F33x Part Number
C8051F39x/37x Part Number
C8051F330-GM
C8051F396-A-GM
C8051F331-GM
C8051F397-A-GM
C8051F332-GM
C8051F398-A-GM
C8051F333-GM
C8051F399-A-GM
C8051F334-GM
C8051F398-A-GM
C8051F335-GM
C8051F399-A-GM
C8051F336-GM
C8051F392-A-GM
C8051F337-GM
C8051F393-A-GM
C8051F338-GM
C8051F390-A-GM
C8051F339-GM
C8051F391-A-GM
3.1. Hardware Incompatibilities
While the C8051F39x/37x family includes a number of new features not found on the C8051F33x family,
there are some differences that should be considered for any design port.
Internal High-Frequency Oscillator: The undivided high-frequency oscillator on the C8051F39x/37x
is 49 MHz, whereas the undivided high-frequency oscillator on the C8051F33x is 24.5 MHz.
Correspondingly, the internal high frequency divide ratios (IFCN) have doubled. Thus, firmware written
for the C8051F33x where the CLKSL[1:0] = 00b will result in the same SYSCLK frequency on the
C8051F39x/37x.
 Fabrication Technology: The C8051F39x/37x is manufactured using a different technology process
than the C8051F33x. As a result, many of the electrical performance parameters will have subtle
differences. These differences should not affect most systems but it is nonetheless important to review
the electrical parameters for any blocks that are used in the design, and ensure they are compatible
with the existing hardware.
 5 V Tolerance: The port I/O pins on the C8501F39x/37x are not 5 V tolerant, whereas the port I/O pins
on the C8051F33x are 5 V tolerant.
 Lock Byte Address: The lock byte for C8051F39x/7x devices with 16 kB of Flash resides at address
0x3FFF, whereas the lock byte for C8051F33x devices with 16 kB of Flash resides at address 0x3DFF.
The lock byte for C8051F39x/7x devices with 8 kB of Flash resides at address 0x1FFF, whereas the
lock byte for C8051F33x devices with 8 kB of Flash resides at address 0x1DFF.

Preliminary Rev. 0.71
21
C8051F39x/37x
4. Pin Definitions
Table 4.1. Pin Definitions for the C8051F39x/37x
Name
Pin
‘F392/3/6/
7/8/9
Pin
’F390/1/
4/5
Pin
’F370/1/
4/5
VDD
3
4
4
Power Supply Voltage.
GND
2
3
3
Ground.
This ground connection is required. The center
pad may optionally be connected to ground also.
RST/
4
5
5
C2CK
C2D
5
6
6
P0.0/
1
2
2
VREF
P0.1
20
1
1
24
24
XTAL1
P0.3/
D I/O
Clock signal for the C2 Debug Interface.
D I/O
Bi-directional data signal for the C2 Debug Interface. Shared with P2.0 on 20-pin packaging and
P2.4 on 24-pin packaging.
D I/O or Port 0.0.
A In
18
23
23
External VREF input.
D I/O or Port 0.1.
A In
IDA0 Output.
D I/O or Port 0.2.
A In
A In
XTAL2
22
Device Reset. Open-drain output of internal
POR or VDD monitor. An external source can initiate a system reset by driving this pin low for at
least 10 µs.
A Out
19
Description
D I/O
A In
IDA0
P0.2/
Type
External Clock Input. This pin is the external
oscillator return for a crystal or resonator.
D I/O or Port 0.3.
A In
A I/O or External Clock Output. For an external crystal or
resonator, this pin is the excitation driver. This
D In
pin is the external clock input for CMOS, capacitor, or RC oscillator configurations.
P0.4
17
22
22
D I/O or Port 0.4.
A In
P0.5
16
21
21
D I/O or Port 0.5.
A In
Preliminary Rev. 0.71
C8051F39x/37x
Table 4.1. Pin Definitions for the C8051F39x/37x (Continued)
Name
Pin
‘F392/3/6/
7/8/9
Pin
’F390/1/
4/5
Pin
’F370/1/
4/5
P0.6/
15
20
20
CNVSTR
Type
Description
D I/O or Port 0.6.
A In
D In
ADC0 External Convert Start or IDA0 Update
Source Input.
P0.7
14
19
19
D I/O or Port 0.7.
A In
P1.0
13
—
—
D I/O or Port 1.0.
A In
IDA1
A Out
P1.0
IDA1 Output.
18
18
D I/O or Port 1.0.
A In
P1.1
12
17
17
D I/O or Port 1.1.
A In
P1.2
-
16
16
D I/O or Port 1.2.
A In
IDA1
A Out
IDA1 Output.
P1.2
11
—
—
D I/O or Port 1.2.
A In
P1.3
10
15
15
D I/O or Port 1.3.
A In
P1.4
9
14
14
D I/O or Port 1.4.
A In
P1.5
8
13
13
D I/O or Port 1.5.
A In
P1.6
7
12
12
D I/O or Port 1.6.
A In
P1.7
6
11
11
D I/O or Port 1.7.
A In
P2.0
5
10
10
D I/O or Port 2.0. (Also C2D on 20-pin Packaging)
A In
P2.1
—
9
9
D I/O or Port 2.1.
A In
Preliminary Rev. 0.71
23
C8051F39x/37x
Table 4.1. Pin Definitions for the C8051F39x/37x (Continued)
Name
Pin
‘F392/3/6/
7/8/9
Pin
’F390/1/
4/5
Pin
’F370/1/
4/5
P2.2
—
8
—
D I/O or Port 2.2.
A In
P2.2
-
—
8
D I/O or Port 2.2.
A In
EESCL
D I/O
Description
EEPROM SCL Connection.
P2.3
—
7
—
D I/O or Port 2.3.
A In
P2.3
-
—
7
D I/O or Port 2.3.
A In
EESDA
P2.4
24
Type
—
6
6
D I/O
EEPROM SDA Connection.
D I/O
Port 2.4. (Also C2D on 24-pin Packaging)
Preliminary Rev. 0.71
P0.1
P0.2
P0.3
P0.4
P0.5
20
19
18
17
16
C8051F39x/37x
P0.0
1
15
P0.6
GND
2
14
P0.7
VDD
3
13
P1.0
/RST/C2CK
4
12
P1.1
P2.0/C2D
5
11
P1.2
QFN-20
Top View
7
8
9
10
P1.6
P1.5
P1.4
P1.3
P1.7
6
GND (optional)
Figure 4.1. C8051F392/3/6/7/8/9 QFN-20 Pinout Diagram (Top View)
Preliminary Rev. 0.71
25
P0.2
P0.3
P0.4
P0.5
P0.6
P0.7
24
23
22
21
20
19
C8051F39x/37x
P0.1
1
18
P1.0
P0.0
2
17
P1.1
GND
3
16
P1.2
VDD
4
15
P1.3
/RST/C2CK
5
14
P1.4
P2.4/C2D
6
13
P1.5
QFN-24
Top View
7
8
9
10
11
12
P2.3
P2.2
P2.1
P2.0
P1.7
P1.6
GND (optional)
Figure 4.2. C8051F390/1/4/5 Pinout Diagram (Top View)
26
Preliminary Rev. 0.71
P0.2
P0.3
P0.4
P0.5
P0.6
P0.7
24
23
22
21
20
19
C8051F39x/37x
P0.1
1
18
P1.0
P0.0
2
17
P1.1
GND
3
16
P1.2
VDD
4
15
P1.3
/RST/C2CK
5
14
P1.4
13
P1.5
QFN-24
Top View
GND (optional)
7
8
9
10
11
12
P2.2/EESCL
P2.1
P2.0
P1.7
P1.6
6
P2.3/EESDA
P2.4/C2D
Figure 4.3. C8051F370/1/4/5 Pinout Diagram (Top View)
Preliminary Rev. 0.71
27
C8051F39x/37x
5. QFN-20 Package Specifications
Figure 5.1. QFN-20 Package Drawing
Table 5.1. QFN-20 Package Dimensions
Dimension
Min
Typ
Max
Dimension
Min
Typ
Max
A
A1
b
D
D2
e
E
E2
0.80
0.00
0.20
0.85
0.035
0.25
4.00 BSC.
2.10
0.50 BSC.
4.00 BSC.
2.10
0.90
0.05
0.30
L
aaa
bbb
ccc
ddd
eee
ggg
0.50
—
—
—
—
—
0.55
—
—
—
—
—
0.60
0.10
0.10
0.08
0.10
0.10
0.05
2.00
2.00
2.20
2.20
Notes:
1. All dimensions shown are in millimeters (mm) unless otherwise noted.
2. Dimensioning and Tolerancing per ANSI Y14.5M-1994.
3. This drawing conforms to the JEDEC Solid State Outline MO-220, variation VGGD except for
custom features D2, E2, Z, Y, and L which are toleranced per supplier designation.
4. Recommended card reflow profile is per the JEDEC/IPC J-STD-020C specification for Small
Body Components.
28
Preliminary Rev. 0.71
C8051F39x/37x
Figure 5.2. QFN-20 Recommended PCB Land Pattern
Table 5.2. QFN-20 PCB Land Pattern Dimensions
Dimension
Max
Dimension
Max
C1
C2
E
X1
3.80
3.80
0.50
0.30
X2
Y1
Y2
2.20
1.00
2.20
Notes:
General
1. All dimensions shown are in millimeters (mm) unless otherwise noted.
2. Dimensioning and Tolerancing is per the ANSI Y14.5M-1994 specification.
3. This Land Pattern Design is based on the IPC-7351 guidelines.
Solder Mask Design
4. All metal pads are to be non-solder mask defined (NSMD). Clearance between the solder
mask and the metal pad is to be 60 µm minimum, all the way around the pad.
Stencil Design
5. A stainless steel, laser-cut and electro-polished stencil with trapezoidal walls should be used
to assure good solder paste release.
6. The stencil thickness should be 0.125 mm (5 mils).
7. The ratio of stencil aperture to land pad size should be 1:1 for all perimeter pins.
8. A 2x2 array of 0.95mm openings on a 1.1 mm pitch should be used for the center pad to
assure the proper paste volume (71% Paste Coverage).
Card Assembly
9. A No-Clean, Type-3 solder paste is recommended.
10. The recommended card reflow profile is per the JEDEC/IPC J-STD-020C specification for
Small Body Components.
Preliminary Rev. 0.71
29
C8051F39x/37x
6. QFN-24 Package Specifications
Figure 6.1. QFN-24 Package Drawing
Table 6.1. QFN-24 Package Dimensions
Dimension
Min
Typ
Max
Dimension
Min
Typ
Max
A
A1
b
D
D2
e
E
E2
0.70
0.00
0.18
0.75
0.02
0.25
4.00 BSC.
2.70
0.50 BSC.
4.00 BSC.
2.70
0.80
0.05
0.30
L
L1
aaa
bbb
ddd
eee
Z
Y
0.30
0.00
—
—
—
—
—
—
0.40
—
—
—
—
—
0.24
0.18
0.50
0.15
0.15
0.10
0.05
0.08
—
—
2.55
2.55
2.80
2.80
Notes:
1. All dimensions shown are in millimeters (mm) unless otherwise noted.
2. Dimensioning and Tolerancing per ANSI Y14.5M-1994.
3. This drawing conforms to JEDEC Solid State Outline MO-220, variation WGGD except for
custom features D2, E2, Z, Y, and L which are toleranced per supplier designation.
4. Recommended card reflow profile is per the JEDEC/IPC J-STD-020C specification for Small
Body Components.
30
Preliminary Rev. 0.71
C8051F39x/37x
Figure 6.2. QFN-24 Recommended PCB Land Pattern
Table 6.2. QFN-24 PCB Land Pattern Dimensions
Dimension
Min
Max
Dimension
Min
Max
C1
C2
E
X1
3.90
3.90
4.00
4.00
X2
Y1
Y2
2.70
0.65
2.70
2.80
0.75
2.80
0.50 BSC
0.20
0.30
Notes:
General
1. All dimensions shown are in millimeters (mm) unless otherwise noted.
2. This Land Pattern Design is based on the IPC-7351 guidelines.
Solder Mask Design
3. All metal pads are to be non-solder mask defined (NSMD). Clearance between the solder
mask and the metal pad is to be 60 µm minimum, all the way around the pad.
Stencil Design
4. A stainless steel, laser-cut and electro-polished stencil with trapezoidal walls should be used
to assure good solder paste release.
5. The stencil thickness should be 0.125 mm (5 mils).
6. The ratio of stencil aperture to land pad size should be 1:1 for all perimeter pads.
7. A 2 x 2 array of 1.10 mm x 1.10 mm openings on a 1.30 mm pitch should be used for the
center pad.
Card Assembly
8. A No-Clean, Type-3 solder paste is recommended.
9. The recommended card reflow profile is per the JEDEC/IPC J-STD-020C specification for
Small Body Components.
Preliminary Rev. 0.71
31
C8051F39x/37x
7. Electrical Characteristics
7.1. Absolute Maximum Specifications
Table 7.1. Absolute Maximum Ratings
Parameter
Condition
Min
Typ
Max
Unit
Ambient Temperature under Bias
–55
—
125
°C
Storage Temperature
–65
—
150
°C
Voltage on any Port I/O Pin or RST with
respect to GND
–0.3
—
VDD + 0.3
V
Voltage on VDD with Respect to GND
–0.3
—
4.2
V
Maximum Total Current through VDD or GND
—
—
100
mA
Maximum Output Current Sunk by RST or
any Port Pin
—
—
100
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.
32
Preliminary Rev. 0.71
C8051F39x/37x
7.2. Electrical Characteristics
Table 7.2. Global Electrical Characteristics
–40 to +105 °C (C8051F39x), –40 to +85 °C (C8051F37x), 50 MHz system clock, unless otherwise specified.
Parameter
Typ
Max
Unit
3.0
3.6
V
1.8
3.0
3.6
V
Digital Supply RAM Data
Retention Voltage
—
1.5
—
V
SYSCLK (System Clock) 2
0
—
50
MHz
TSYSH (SYSCLK High Time)
9.5
—
—
ns
TSYSL (SYSCLK Low Time)
9.5
—
—
ns
Supply Voltage (VDD)
Condition
Normal Operation
Writing or Erasing Flash Memory
Specified Operating
Temperature Range
Min
VRST
1
C8051F39x
–40
—
+105
°C
C8051F37x
–40
—
+85
°C
Digital Supply Current—CPU Active (Normal Mode, Fetching Instructions from Flash)
IDD 3
VDD = 3.6 V, F = 50 MHz
—
7.1
10.5
mA
VDD = 3.0 V, F = 50 MHz
—
7.0
10.4
mA
VDD = 3.6 V, F = 25 MHz
—
4.6
6.5
mA
VDD = 3.0 V, F = 25 MHz
—
4.5
6.4
mA
VDD = 3.6 V, F = 1 MHz
—
0.35
—
mA
VDD = 3.0 V, F = 1 MHz
—
0.35
—
mA
VDD = 3.0 V, F = 80 kHz
—
0.25
—
mA
Digital Supply Current—CPU Inactive (Idle Mode, Not Fetching Instructions from Flash)
IDD 3
VDD = 3.6 V, F = 50 MHz
—
3.9
4.5
mA
VDD = 3.0 V, F = 50 MHz
—
3.8
4.4
mA
VDD = 3.6 V, F = 25 MHz
—
2.1
2.5
mA
VDD = 3.0 V, F = 25 MHz
—
2.0
2.4
mA
VDD = 3.6 V, F = 1 MHz
—
0.15
—
mA
VDD = 3.0 V, F = 1 MHz
—
0.15
—
mA
VDD = 3.0 V, F = 80 kHz
—
0.1
—
mA
Digital Supply Current
(Suspend Mode)
Oscillator not running,
VDD Monitor Disabled,
Regulator running (STOPCF = 0)
—
77
—
µA
Digital Supply Current
(Stop Mode)
Oscillator not running,
VDD Monitor Disabled,
Regulator running (STOPCF = 0)
—
81
—
µA
Digital Supply Current
(Stop Mode, regulator shutdown)
Oscillator not running,
VDD Monitor Disabled,
Regulator Shutdown (STOPCF = 1)
—
0.2
—
µA
Notes:
1. Given in Table 7.4 on page 35.
2. SYSCLK must be at least 32 kHz to enable debugging.
3. Based on device characterization data; Not production tested.
Preliminary Rev. 0.71
33
C8051F39x/37x
Table 7.3. Port I/O DC Electrical Characteristics
VDD = 1.8 to 3.6 V, –40 to +105 °C (C8051F39x), –40 to +85 °C (C8051F37x), unless otherwise specified.
Parameters
Condition
Min
Typ
Max
Unit
VDD – 0.7
—
—
V
IOH = –10 µA, Port I/O push-pull
VDD – 0.1
—
—
V
IOH = –10 mA, Port I/O push-pull
—
VDD – 0.8
—
V
IOL = 8.5 mA
—
—
0.6
V
IOL = 10 µA
—
—
0.1
V
IOL = 10 mA, 1.8 V ≤ VDD < 2.7 V
—
0.8
—
V
IOL = 25 mA, 2.7 V ≤ VDD ≤ 3.6 V
—
1.0
—
V
1.8 V ≤ VDD < 2.7 V
VDD – 0.4
—
—
V
2.7 V ≤ VDD ≤ 3.6 V
VDD – 0.5
—
—
V
1.8 V ≤ VDD < 2.7 V
—
—
0.5
V
2.7 V ≤ VDD ≤ 3.6 V
—
—
0.6
V
Weak Pullup Off
—
—
±1
µA
Weak Pullup On, VIN = 0 V
—
20
100
µA
Standard Port I/O
Output High Voltage IOH = –3 mA, Port I/O push-pull
Output Low Voltage
Input High Voltage
Input Low Voltage
Input Leakage
Current
EESDA and EESCL (C8051F37x Only)*
Output Low Voltage
(EESDA)
IOL = 0.15 mA, VDD = 1.8 V
—
—
0.2
V
Output Low Voltage
(EESDA)
IOL = 2.1 mA, VDD = 3 V
—
—
0.4
V
Output Leakage
Current
(EESDA)
EEPUE = 0, VDD = 3.6 V,
0 V ≤ VOUT ≤ VDD
—
—
2
µA
Input High Voltage
VDD x 0.7
—
—
V
Input Low Voltage
—
—
VDD x 0.3
V
—
—
±3
µA
Input Leakage
Current
EEPUE = 0, Standby, VDD = 3.6 V,
0 V ≤ VIN ≤ VDD
Note: Applicable when interfacing to the C8051F37x EEPROM. Otherwise, standard port I/O characteristics apply.
34
Preliminary Rev. 0.71
C8051F39x/37x
Table 7.4. Reset Electrical Characteristics
–40 to +105 °C (C8051F39x), –40 to +85 °C (C8051F37x), unless otherwise specified.
Parameter
RST Output Low Voltage
Condition
IOL = 4 mA,
VDD = 1.8 V to 3.6 V
RST Input Low Voltage
Min
Typ
Max
Unit
—
—
0.6
V
—
—
0.6
V
RST Input Pullup Current
RST = 0.0 V
—
20
100
µA
VDD POR Threshold (VRST)
VRST_LOW
1.7
1.75
1.8
V
VRST_HIGH
2.4
2.55
2.7
V
Missing Clock Detector Timeout
Time from last system clock
rising edge to reset initiation
80
580
800
µs
Reset Time Delay
Delay between release of any
reset source and code
execution at location 0x0000
—
—
40
µs
Minimum RST Low Time to
Generate a System Reset
15
—
—
µs
VDD Monitor Turn-on Time
100
—
—
µs
—
20
50
µA
VDD Monitor Supply Current
Preliminary Rev. 0.71
35
C8051F39x/37x
Table 7.5. Flash Electrical Characteristics
VDD = 1.8 to 3.6 V, –40 to +105 °C (C8051F39x), –40 to +85 °C (C8051F37x), unless otherwise specified.
Parameter
Flash Size
Condition
Min
Typ
Max
Unit
C8051F390/1/2/3, C8051F370/1
16384
Bytes
C8051F394/5/6/7, C8051F374/5
8192
Bytes
C8051F398/9
4096
Bytes
Endurance
20000
100000
—
Erase/Write
Erase Cycle Time
23
25
27
ms
Write Cycle Time
58
61
64
µs
Max
Unit
Table 7.6. EEPROM Electrical Characteristics
VDD = 1.8 to 3.6 V, –40 to +85 °C (C8051F37x), unless otherwise specified.
Parameter
EEPROM Size
Condition
Min
C8051F37x
Endurance
Typ
512
Bytes
1000000
—
—
Write Cycles
Write Cycle Time
—
—
3.5
ms
EESCL Clock Frequency
—
—
400
kHz
VDD = 3.6 V, Standby
—
—
3
µA
VDD = 3.6 V, Read
—
—
2
mA
VDD = 3.6 V, Write
—
—
3
mA
Supply Current
36
Preliminary Rev. 0.71
C8051F39x/37x
Table 7.7. Internal High-Frequency Oscillator Electrical Characteristics
VDD = 1.8 to 3.6 V, –40 to +105 °C (C8051F39x), –40 to +85 °C (C8051F37x), using factory-calibrated settings,
unless otherwise specified.
Parameter
Condition
Min
Typ
Max
Unit
Oscillator Frequency
IFCN = 11b
48
49
50
MHz
Oscillator Supply Current
(from VDD)
25 °C, VDD = 3.0 V,
OSCICN.7 = 1,
OCSICN.5 = 0
—
840
880
µA
Power Supply Sensitivity
Constant Temperature
—
0.12
—
%/V
Temperature Sensitivity
Constant Supply
—
90
—
ppm/°C
Table 7.8. Internal Low-Frequency Oscillator Electrical Characteristics
VDD = 1.8 to 3.6 V, –40 to +105 °C (C8051F39x), –40 to +85 °C (C8051F37x), using factory-calibrated settings,
unless otherwise specified.
Parameter
Condition
Min
Typ
Max
Unit
Oscillator Frequency
OSCLD = 11b
75
80
85
kHz
Oscillator Supply Current
(from VDD)
25 °C, VDD = 3.0 V,
OSCLCN.7 = 1
—
5.5
12
µA
Power Supply Sensitivity
Constant Temperature
—
0.05
—
%/V
Temperature Sensitivity
Constant Supply
—
160
—
ppm/°C
Table 7.9. Internal Low-Power Oscillator Electrical Characteristics
VDD = 1.8 to 3.6 V, –40 to +105 °C (C8051F39x), –40 to +85 °C (C8051F37x), using factory-calibrated settings,
unless otherwise specified.
Parameter
Condition
Oscillator Frequency
Min
Typ
Max
Unit
18.5
20
21.5
MHz
Power Supply Sensitivity
Constant Temperature
—
0.1
—
%/V
Temperature Sensitivity
Constant Supply
—
60
—
ppm/°C
Preliminary Rev. 0.71
37
C8051F39x/37x
Table 7.10. ADC0 Electrical Characteristics
VDD = 3.0 V, VREF = 2.40 V (REFSL = 0), –40 to +105 °C (C8051F39x), –40 to +85 °C (C8051F37x), unless
otherwise specified.
Parameter
Condition
Min
Typ
Max
Unit
DC Accuracy
Resolution
10
Integral Nonlinearity
bits
—
<±0.5
±2.0
LSB
—
<±0.5
±1
LSB
Offset Error
–2
0
2
LSB
Full Scale Error
–5
–2
1
LSB
Offset Temperature Coefficient
—
0.005
—
LSB/°C
Differential Nonlinearity
Guaranteed Monotonic
Dynamic performance (10 kHz sine-wave single-ended input, 1 dB below Full Scale, 500 ksps)
Signal-to-Noise Plus Distortion
55
58
—
dB
—
–73
—
dB
—
68
—
dB
SAR Conversion Clock
—
—
8.33
MHz
Conversion Time in SAR Clocks
13
—
—
clocks
Track/Hold Acquisition Time
300
—
—
ns
—
—
500
ksps
0
—
VREF
V
–VREF
—
VREF
V
0
—
VDD
V
Sampling Capacitance (CSAMPLE)
—
5
—
pF
Input Multiplexer Impedance
(RMUX)
—
1.6
—
k
Total Harmonic Distortion
Up to the 5th harmonic
Spurious-Free Dynamic Range
Conversion Rate
Throughput Rate
Analog Inputs
ADC Input Voltage Range
Single Ended (AIN+ – GND)
Differential (AIN+ – AIN–)
Absolute Pin Voltage with
respect to GND
Single Ended or Differential
Power Specifications
Power Supply Current
(VDD supplied to ADC0)
Operating Mode, 500 ksps
—
860
1010
µA
Power Supply Rejection
Single Ended (AIN+ – GND)
—
1.15
—
mV/V
Differential (AIN+ – AIN–)
—
2.45
—
mV/V
38
Preliminary Rev. 0.71
C8051F39x/37x
Table 7.11. ADC Temperature Sensor Electrical Characteristics
VDD = 3.0 V, –40 to +105 °C (C8051F39x), –40 to +85 °C (C8051F37x), unless otherwise specified.
Parameter
Condition
Min
Typ
Max
Unit
Linearity
—
0.75
—
°C
Slope
—
2.92
—
mV/°C
Slope Error*
—
70
—
µV/°C
Offset
Temp = 0 °C
—
785
—
mV
Offset Error*
Temp = 0 °C
—
13
—
mV
—
90
120
µA
Supply Current
Note: Represents one standard deviation from the mean.
Table 7.12. Precision Temperature Sensor Electrical Characteristics
VDD = 1.8 to 3.6 V, –40 to +105 °C (C8051F39x), –40 to +85 °C (C8051F37x), unless otherwise specified.
Parameter
Condition
Min
Typ
Max
Unit
Range
–40
—
105
°C
Absolute Error
–2
0
+2
°C
Integral Nonlinearity
—
0
±0.8
°C
Resolution
0.0078125
°C
Power Supply Rejection
—
0.05
0.2
°C/V
Supply Current
—
230
280
µA
320
520
730
kHz
Clock Frequency (FTS0)
Preliminary Rev. 0.71
39
C8051F39x/37x
Table 7.13. Voltage Reference Electrical Characteristics
VDD = 3.0 V, –40 to +105 °C (C8051F39x), –40 to +85 °C (C8051F37x), unless otherwise specified.
Parameter
Condition
Min
Typ
Max
Unit
2.4 V Setting
2.37
2.4
2.43
V
1.2 V Setting
1.18
1.2
1.22
V
VREF Short-Circuit Current
—
—
8
mA
VREF Temperature
Coefficient
—
33
—
ppm/°C
Internal Reference (REFBE = 1)
Output Voltage
Load Regulation
Load = 0 to 200 µA to AGND
—
6
—
µV/µA
VREF Turn-on Time 1
4.7 µF tantalum, 0.1 µF ceramic bypass
—
1.5
—
ms
VREF Turn-on Time 2
0.1 µF ceramic bypass
—
110
—
µs
Power Supply Rejection
2.4 V Setting
—
3.5
—
mV/V
1.2 V Setting
—
1.1
—
mV/V
1.0
—
VDD
V
Sample Rate = 200 ksps; VREF = 3.0 V
—
3
—
µA
REFBE = “1” or TEMPE = “1”
—
70
100
µA
External Reference (REFBE = 0)
Input Voltage Range
Input Current
Power Specifications
Supply Current
Table 7.14. Voltage Regulator Electrical Characteristics
VDD = 3.0 V, –40 to +105 °C (C8051F39x), –40 to +85 °C (C8051F37x), unless otherwise specified.
Parameter
Condition
Output Voltage
Min
Typ
Max
Unit
1.73
1.78
1.83
V
Power Supply Sensitivity
Constant Temperature
—
0.5
—
%/V
Temperature Sensitivity
Constant Supply
—
55
—
ppm/°C
40
Preliminary Rev. 0.71
C8051F39x/37x
Table 7.15. IDAC Electrical Characteristics
VDD = 3.0 V, –40 to +105 °C (C8051F39x), –40 to +85 °C (C8051F37x), full-scale output current set to 2 mA,
unless otherwise specified.
Parameter
Condition
Min
Typ
Max
Unit
Static Performance
Resolution
10
Integral Nonlinearity
bits
—
<±1
±3
LSB
0 to +105 °C,
Guaranteed Monotonic
—
<±0.5
±1
LSB
–40 to 0°C
—
<±0.5
±1.3
LSB
Output Compliance Range
0
—
VDD – 1.0
V
Offset Error
—
0
—
µA
2 mA Full Scale Output Current
TBD
0
TBD
µA
1 mA Full Scale Output Current
TBD
0
TBD
µA
0.5 mA Full Scale Output Current
TBD
0
TBD
µA
Full Scale Error Tempco
—
80
—
ppm/°C
VDD Power Supply
Rejection Ratio
—
1.05
—
µA/V
Output Settling Time to 1/2 IDA0H:L = 0x3FF to 0x000
LSB
—
7
—
µs
Startup Time
—
6.5
—
µs
1 mA Full Scale Output Current
—
TBD
—
%
0.5 mA Full Scale Output Current
—
TBD
—
%
2 mA Full Scale Output Current
—
2065
—
µA
1 mA Full Scale Output Current
—
1065
—
µA
0.5 mA Full Scale Output Current
—
565
—
µA
Differential Nonlinearity
Full Scale Error
Dynamic Performance
Gain Variation
Power Consumption
Power Supply Current
(VDD supplied to IDAC)
Preliminary Rev. 0.71
41
C8051F39x/37x
Table 7.16. Comparator Electrical Characteristics
VDD = 3.0 V, –40 to +105 °C (C8051F39x), –40 to +85 °C (C8051F37x), unless otherwise specified.
Parameter
Condition
Min
Typ
Max
Unit
Response Time
Mode 0, Vcm* = 1.5 V
CP0+ – CP0– = 100 mV
—
370
—
ns
CP0+ – CP0– = –100 mV
—
135
—
ns
Response Time
Mode 3, Vcm* = 1.5 V
CP0+ – CP0– = 100 mV
—
1575
—
ns
CP0+ – CP0– = –100 mV
—
3705
—
ns
—
0.6
5
mV/V
CP0HYP1–0 = 00
—
0.5
—
mV
CP0HYP1–0 = 01
—
8
—
mV
CP0HYP1–0 = 10
—
16
—
mV
CP0HYP1–0 = 11
—
32
—
mV
CP0HYN1–0 = 00
—
0.5
—
mV
CP0HYN1–0 = 01
—
–8
—
mV
CP0HYN1–0 = 10
—
–16
—
mV
CP0HYN1–0 = 11
—
–32
—
mV
CP0HYP1–0 = 00
—
0.5
—
mV
CP0HYP1–0 = 01
—
6
—
mV
CP0HYP1–0 = 10
—
12
—
mV
CP0HYP1–0 = 11
—
24.5
—
mV
CP0HYN1–0 = 00
—
0.5
—
mV
CP0HYN1–0 = 01
—
–6
—
mV
CP0HYN1–0 = 10
—
–12
—
mV
CP0HYN1–0 = 11
—
–24.5
—
mV
CP0HYP1–0 = 00
—
0.7
—
mV
CP0HYP1–0 = 01
—
4.5
—
mV
CP0HYP1–0 = 10
—
10
—
mV
CP0HYP1–0 = 11
—
19
—
mV
CP0HYN1–0 = 00
—
0.7
—
mV
CP0HYN1–0 = 01
—
–4.5
—
mV
CP0HYN1–0 = 10
—
–10
—
mV
CP0HYN1–0 = 11
—
–19
—
mV
CP0HYP1–0 = 00
—
1.6
2.3
mV
CP0HYP1–0 = 01
2
4
6
mV
CP0HYP1–0 = 10
4.8
8
11
mV
CP0HYP1–0 = 11
10
15.5
21
mV
Common-Mode Rejection Ratio
Positive Hysteresis
Mode 0 (CPMD = 00)
Negative Hysteresis
Mode 0 (CPMD = 00)
Positive Hysteresis
Mode 1 (CPMD = 01)
Negative Hysteresis
Mode 1 (CPMD = 01)
Positive Hysteresis
Mode 2 (CPMD = 10)
Negative Hysteresis
Mode 2 (CPMD = 10)
Positive Hysteresis
Mode 3 (CPMD = 11)
42
Preliminary Rev. 0.71
C8051F39x/37x
Table 7.16. Comparator Electrical Characteristics (Continued)
VDD = 3.0 V, –40 to +105 °C (C8051F39x), –40 to +85 °C (C8051F37x), unless otherwise specified.
Parameter
Min
Typ
Max
Unit
CP0HYN1–0 = 00
—
1.6
2.3
mV
CP0HYN1–0 = 01
–6
–4
–2
mV
CP0HYN1–0 = 10
–11
–8
–4.8
mV
CP0HYN1–0 = 11
–21
–15.5
–10
mV
–0.25
—
VDD + 0.25
V
Input Capacitance
—
4
—
pF
Input Bias Current
—
0.001
—
nA
Input Offset Voltage
10
—
–10
mV
Power Supply Rejection
—
0.1
—
mV/V
Power-up Time
—
6.5
—
µs
Mode 0
—
32
48
µA
Mode 1
—
15
20
µA
Mode 2
—
5
10
µA
Mode 3
—
2
8
µA
Negative Hysteresis
Mode 3 (CPMD = 11)
Condition
Inverting or Non-Inverting Input
Voltage Range
Power Supply
Supply Current at DC
Note: Vcm is the common-mode voltage on CP0+ and CP0–.
Preliminary Rev. 0.71
43
C8051F39x/37x
7.3. Typical Performance Curves
VDD=1.8V
VDD=3.0V
VDD=3.6V
8.0
F < 9 MHz
Oneshot
Enabled
7.0
F > 9 MHz
Oneshot
Disabled
6.0
IDD(mA)
5.0
4.0
3.0
2.0
1.0
0.0
0
5
10
15
20
25
30
35
40
45
50
45
50
SYSCLK(MHz)
Figure 7.1. Normal Mode Digital Supply Current vs. Frequency
VDD=1.8V
VDD=3.0V
VDD=3.6V
4.0
3.5
3.0
IDD(mA)
2.5
2.0
1.5
1.0
0.5
0.0
0
5
10
15
20
25
30
35
40
SYSCLK(MHz)
Figure 7.2. Idle Mode Digital Supply Current vs. Frequency
44
Preliminary Rev. 0.71
C8051F39x/37x
8. Precision Temperature Sensor
(C8051F390/2/4/6/8 and C8051F370/4 Only)
The precision temperature sensor is a self-contained module that reports the die temperature in degrees
Celsius. For the temperature sensor accessed by the ADC, refer to Section 10.
The precision temperature sensor begins a conversion once the TS0STRT bit is set to 1 then cleared to 0
by firmware. The conversion length is specified by TS0CNVL, with a longer conversion time resulting in a
more accurate temperature measurement. The TS0DN bit is set by hardware once the temperature sensor
block has completed the measurement, and the temperature is available in TS0DATH:TS0DATL.
The precision temperature sensor may also be enabled as an interrupt source by setting the EPTS bit in
EIE2. When enabled, the interrupt occurs once TS0DN is set to 1 by hardware.
8.1. Temperature in Two’s Complement
The 16-bit word in TS0DATH:TS0DATL is the temperature in degrees Celsius represented in two's complement with 1 weighted sign bit, 8 integer bits, and 7 fractional bits. Equation 8.1 converts the value in
TS0DATH:TS0DATL from two’s complement binary to decimal.
7
 6

n+1
n – 7

Temperature in C = –  TS0DATH  7   2  +  TS0DATH  n   2
+  TS0DATL  n   2


n = 0

n=0
8
Equation 8.1. Temperature Conversion from Two’s Complement Binary to Decimal
Where:
th
 TS0DATH[n] is the n bit in TS0DATH

TS0DATL[n] is the nth bit in TS0DATL
Table 8.1 lists several 16-bit values in TS0DATH:TS0DATL and the corresponding temperature.
Table 8.1. Example Temperature Values in TS0DATH:TS0DATL
Hexadecimal
Binary
Temperature (°C)
0x3480
0011 0100 1000 0000
105
0x1400
0001 0100 0000 0000
40
0x0CE0
0000 1100 1110 0000
25.75
0x0080
0000 0000 1000 0000
1
0x0040
0000 0000 0100 0000
0.5
0x0001
0000 0000 0000 0001
1/128
0x0000
0000 0000 0000 0000
0
0xFFFF
1111 1111 1111 1111
–1/128
0xFFC0
1111 1111 1100 0000
–0.5
0xFF80
1111 1111 1000 0000
–1
0xF320
1111 0011 0010 0000
–25.75
0xEC00
1110 1100 0000 0000
–40
Preliminary Rev. 0.71
45
C8051F39x/37x
SFR Definition 8.1. TS0CN: Temperature Sensor Control
Bit
7
Name TS0STRT
6
5
4
3
2
TS0DN
Type
R/W
R
Reset
0
0
1
0
TS0CNVL
R/W
0
0
0
R/W
R/W
R/W
0
0
0
SFR Address = 0xD2; SFR Page = F
Bit
Name
7
TS0STRT
Function
Temperature Sensor Start.
Firmware must set this bit to 1, then clear this bit to 0 to start a temperature sensor
measurement.
6
TS0DN
Temperature Sensor Finished Flag.
Hardware will set TS0DN to 1 when a temperature sensor measurement is complete. If enabled, a temperature sensor interrupt will be generated. This bit must
be cleared to 0 by firmware.
5:3
Reserved
Must Write 000b.
2:0
TS0CNVL
Temperature Sensor Conversion Length.
This field sets the conversion length of time over which the temperature is calculated. A longer conversion length results in a more accurate measurement. The
conversion length in microseconds is derived from the following equation, where
TS0CNVL is the 3-bit value held in TS0CNVL[2:0] and FTS0 is the precision temperature sensor clock frequency given in Table 7.12.
6
TS0CNVL + 1
256
Conversion Length in s =  -----------  10    2
+ 1  + 32
 F TS0

46
Preliminary Rev. 0.71
C8051F39x/37x
SFR Definition 8.2. TS0DATH: Temperature Sensor Output High Byte
Bit
7
6
5
4
Name
TS0DATH
Type
R/W
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address = 0xD3; SFR Page = 0
Bit
Name
7:0
TS0DATH
Function
Temperature Sensor Data Word (MSB).
This byte represents the MSB of the temperature sensor
data word. The data word is a 16-bit, 2’s complement number.
SFR Definition 8.3. TS0DATL: Temperature Sensor Output Low Byte
Bit
7
6
5
4
Name
TS0DATL
Type
R/W
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address = 0xD2; SFR Page = 0
Bit
Name
7:0
TS0DATL
Function
Temperature Sensor Data Word (LSB).
This byte represents the LSB of the temperature sensor
data word. The data word is a 16-bit, 2’s complement number.
Preliminary Rev. 0.71
47
C8051F39x/37x
9. 10-Bit ADC (ADC0, C8051F390/2/4/6/8 and C8051F370/4 Only)
ADC0 on the C8051F390/2/4/6/8 and C8051F370/4 is a 500 ksps, 10-bit successive-approximation-register (SAR) ADC with integrated track-and-hold and a programmable window detector. The ADC is fully configurable under software control via Special Function Registers. The ADC may be configured to measure
various different signals using the analog multiplexer described in Section “9.4. ADC0 Analog Multiplexer
(C8051F390/2/4/6/8 and C8051F370/4 Only)” on page 59. The voltage reference for the ADC is selected
as described in Section “12. Voltage Reference Options” on page 71. The ADC0 subsystem 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.
AMX0P
AMX0P5
AMX0P4
AMX0P3
AMX0P2
AMX0P1
AMX0P0
AD0EN
AD0TM
AD0INT
AD0BUSY
AD0WINT
AD0CM2
AD0CM1
AD0CM0
ADC0CN
Temp
Sensor
ADC
Negative
Input
(AIN-)
AMUX
000
001
010
011
AD0BUSY (W)
Timer 0 Overflow
Timer 2 Overflow
Timer 1 Overflow
100
101
110
111
CNVSTR Input
Timer 3 Overflow
Timer 4 Overflow
Timer 5 Overflow
SYSCLK
REF
VREF
10-Bit
SAR
AIN+
AIN-
Port I/O
Pins*
Start
Conversion
ADC0L
VDD
VDD
Positive
Input
(AIN+)
AMUX
ADC0H
Port I/O
Pins*
AD0WINT
* 20 Selections on 24-pin package
16 Selections on 20-pin package
AMX0N
AD0SC4
AD0SC3
AD0SC2
AD0SC1
AD0SC0
AD0LJST
AMX0N5
AMX0N4
AMX0N3
AMX0N2
AMX0N1
AMX0N0
GND
ADC0CF
ADC0LTH ADC0LTL
ADC0GTH ADC0GTL
Figure 9.1. ADC0 Functional Block Diagram
48
Preliminary Rev. 0.71
32
Window
Compare
Logic
C8051F39x/37x
9.1. Output Code Formatting
The conversion code format differs between Single-ended and Differential modes. The registers ADC0H
and ADC0L contain the high and low bytes of the output conversion code from the ADC at the completion
of each conversion. Data can be right-justified or left-justified, depending on the setting of the AD0LJST bit
(ADC0CN.0). When in Single-ended Mode, conversion codes are represented as 10-bit unsigned integers.
Inputs are measured from 0 to VREF x 1023/1024. Example codes are shown below for both right-justified
and left-justified data. Unused bits in the ADC0H and ADC0L registers are set to 0.
Input Voltage
(Single-Ended)
Right-Justified ADC0H:ADC0L
(AD0LJST = 0)
Left-Justified ADC0H:ADC0L
(AD0LJST = 1)
VREF x 1023/1024
0x03FF
0xFFC0
VREF x 512/1024
0x0200
0x8000
VREF x 256/1024
0x0100
0x4000
0
0x0000
0x0000
When in Differential Mode, conversion codes are represented as 10-bit signed 2s complement numbers.
Inputs are measured from –VREF to VREF x 511/512. Example codes are shown below for both right-justified and left-justified data. For right-justified data, the unused MSBs of ADC0H are a sign-extension of the
data word. For left-justified data, the unused LSBs in the ADC0L register are set to 0.
Input Voltage
(Differential)
Right-Justified ADC0H:ADC0L
(AD0LJST = 0)
Left-Justified ADC0H:ADC0L
(AD0LJST = 1)
VREF x 511/512
0x01FF
0x7FC0
VREF x 256/512
0x0100
0x4000
0
0x0000
0x0000
–VREF x 256/512
0xFF00
0xC000
–VREF
0xFE00
0x8000
Preliminary Rev. 0.71
49
C8051F39x/37x
9.2. Modes of Operation
ADC0 has a maximum conversion speed of 500 ksps. The ADC0 conversion clock is a divided version of
the system clock, determined by the AD0SC bits in the ADC0CF register.
9.2.1. Starting a Conversion
A conversion can be initiated in one of several ways, depending on the programmed states of the ADC0
Start of Conversion Mode bits (AD0CM2–0) in register ADC0CN. Conversions may be initiated by one of
the following:
1. Writing a 1 to the AD0BUSY bit of register ADC0CN
2. A Timer 0 overflow (i.e., timed continuous conversions)
3. A Timer 2 overflow
4. A Timer 1 overflow
5. A rising edge on the CNVSTR input signal
6. A Timer 3 overflow
7. A Timer 4 overflow
8. A Timer 5 overflow
Writing a 1 to AD0BUSY provides software control of ADC0 whereby conversions are performed "ondemand". During conversion, the AD0BUSY bit is set to logic 1 and reset to logic 0 when the conversion is
complete. The falling edge of AD0BUSY triggers an interrupt (when enabled) and sets the ADC0 interrupt
flag (AD0INT). Note: When polling for ADC conversion completions, the ADC0 interrupt flag (AD0INT)
should be used. Converted data is available in the ADC0 data registers, ADC0H:ADC0L, when bit AD0INT
is logic 1. Note that when Timer 2, 3, 4, or 5 overflows are used as the conversion source, Low Byte overflows are used if the timer is in 8-bit mode; High byte overflows are used if the timer is in 16-bit mode. See
Section “31. Timers” on page 240 for timer configuration.
Important Note About Using CNVSTR: The CNVSTR input pin also functions as a Port I/O pin. When the
CNVSTR input is used as the ADC0 conversion source, the associated pin should be skipped by the Digital Crossbar. See Section “27. Port Input/Output” on page 171 for details on Port I/O configuration.
50
Preliminary Rev. 0.71
C8051F39x/37x
9.2.2. Tracking Modes
The AD0TM bit in register ADC0CN controls the ADC0 track-and-hold mode. In its default state, the ADC0
input is continuously tracked, except when a conversion is in progress. When the AD0TM bit is logic 1,
ADC0 operates in low-power track-and-hold mode. In this mode, each conversion is preceded by a tracking period of three SAR clocks (after the start-of-conversion signal). When the CNVSTR signal is used to
initiate conversions in low-power tracking mode, ADC0 tracks only when CNVSTR is low; conversion
begins on the rising edge of CNVSTR. See Figure 9.2 for track and convert timing details. Tracking can
also be disabled (shutdown) when the device is in low power standby or sleep modes. Low-power trackand-hold mode is also useful when AMUX settings are frequently changed, due to the settling time requirements described in Section “9.2.3. Settling Time Requirements” on page 52.
A. ADC0 Timing for External Trigger Source
CNVSTR
(AD0CM[2:0]=100)
1
2
3
4
5
6
7
8
9
1
0
1
1
SAR Clocks
AD0TM=1
AD0TM=0
Write '1' to AD0BUSY,
Timer 0, Timer 2,
Timer 1, Timer 3 Overflow
(AD0CM[2:0]=000, 001,010
011, 101)
Low Power
or Convert
Track or Convert
1
Low Power
or Convert
Track or
Convert
2
3
4
5
6
7
Track
1
SAR
Clocks
AD0TM=0
Convert
Low Power
Mode
Convert
Track
B. ADC0 Timing for Internal Trigger Source
SAR
Clocks
AD0TM=1
Track
2
3
8
9
1
0
1
1
Convert
4
5
6
7
Convert
8
9
1
0
1
2
1
3
1
4
Low Power Mode
1
1
Track
Figure 9.2. 10-Bit ADC Track and Conversion Example Timing
Preliminary Rev. 0.71
51
C8051F39x/37x
9.2.3. Settling Time Requirements
A minimum tracking time is required before each conversion to ensure that an accurate conversion is performed. This tracking time is determined by the AMUX0 resistance, the ADC0 sampling capacitance, any
external source resistance, and the accuracy required for the conversion. 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 minimum tracking time requirements.
Figure 9.3 shows the equivalent ADC0 input circuit. The required ADC0 settling time for a given settling
accuracy (SA) may be approximated by Equation 9.1. See Table 7.10 for ADC0 minimum settling time
requirements as well as the mux impedance and sampling capacitor values.
n
2
t = ln  -------  R TOTAL C SAMPLE
 SA
Equation 9.1. 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 AMUX0 resistance and any external source resistance.
n is the ADC resolution in bits (10).
Differential Mode
Single-Ended Mode
MUX
Select
MUX Select
Px.x
Px.x
R MUX
R MUX
C SAMPLE
RCInput= R MUX * C SAMPLE
C SAMPLE
RCInput= R MUX * C SAMPLE
C SAMPLE
Px.x
R MUX
MUX Select
Figure 9.3. ADC0 Equivalent Input Circuits
52
Preliminary Rev. 0.71
C8051F39x/37x
SFR Definition 9.1. ADC0CF: ADC0 Configuration
Bit
7
6
5
4
3
2
Name
AD0SC[4:0]
AD0LJST
Type
R/W
R/W
Reset
1
1
1
1
1
0
1
0
R/W
0
0
SFR Address = 0xBC; SFR Page = All Pages
Bit
Name
7:3
AD0SC[4:0]
Function
ADC0 SAR Conversion Clock Period Bits.
SAR Conversion clock is derived from system clock by the following equation, where AD0SC refers to the 5-bit value held in
bits AD0SC4–0. SAR Conversion clock requirements are given
in the ADC specification Table 7.10.
SYSCLK
AD0SC = ----------------------- – 1
CLK SAR
2
AD0LJST
ADC0 Left Justify Select.
0: Data in ADC0H:ADC0L registers are right-justified.
1: Data in ADC0H:ADC0L registers are left-justified.
1:0
Reserved
Must Write 00b.
Preliminary Rev. 0.71
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C8051F39x/37x
SFR Definition 9.2. ADC0H: ADC0 Data Word MSB
Bit
7
6
5
4
3
Name
ADC0H[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address = 0xBE; SFR Page = All Pages
Bit
7:0
Name
Function
ADC0H[7:0] ADC0 Data Word High-Order Bits.
For AD0LJST = 0: Bits 7–2 will read 000000b. Bits 1–0 are the upper 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.
SFR Definition 9.3. ADC0L: ADC0 Data Word LSB
Bit
7
6
5
4
3
Name
ADC0L[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address = 0xBD; SFR Page = All Pages
54
Bit
Name
Function
7:0
ADC0L[7:0]
ADC0 Data Word Low-Order Bits.
For AD0LJST = 0: Bits 7–0 are the lower 8 bits of the 10-bit Data Word.
For AD0LJST = 1: Bits 7–6 are the lower 2 bits of the 10-bit Data Word. Bits 5–
0 will read 000000b.
Preliminary Rev. 0.71
C8051F39x/37x
SFR Definition 9.4. ADC0CN: ADC0 Control
Bit
7
6
5
4
3
Name
AD0EN
AD0TM
AD0INT
Type
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
2
AD0BUSY AD0WINT
1
0
AD0CM[2:0]
R/W
0
0
0
SFR Address = 0xE8; SFR Page = All Pages; Bit-Addressable
Bit
Name
7
AD0EN
Function
ADC0 Enable Bit.
0: ADC0 Disabled. ADC0 is in low-power shutdown.
1: ADC0 Enabled. ADC0 is active and ready for data conversions.
6
AD0TM
ADC0 Track Mode Bit.
0: Normal Track Mode: When ADC0 is enabled, tracking is continuous unless a conversion is in progress. Conversion begins immediately on start-of-conversion event,
as defined by AD0CM[2:0].
1: Delayed Track Mode: When ADC0 is enabled, input is tracked when a conversion
is not in progress. A start-of-conversion signal initiates three SAR clocks of additional
tracking, and then begins the conversion. Note that there is not a tracking delay when
CNVSTR is used (AD0CM[2:0] = 100).
5
AD0INT
ADC0 Conversion Complete Interrupt Flag.
0: ADC0 has not completed a data conversion since AD0INT was last cleared.
1: ADC0 has completed a data conversion.
4
AD0BUSY ADC0 Busy Bit.
3
AD0WINT ADC0 Window Compare Interrupt Flag.
0: ADC0 Window Comparison Data match has not occurred since this flag was last
cleared.
1: ADC0 Window Comparison Data match has occurred.
2:0
AD0CM[2: ADC0 Start of Conversion Mode Select.
0]
000: ADC0 start-of-conversion source is write of 1 to AD0BUSY.
001: ADC0 start-of-conversion source is overflow of Timer 0.
010: ADC0 start-of-conversion source is overflow of Timer 2.
011: ADC0 start-of-conversion source is overflow of Timer 1.
100: ADC0 start-of-conversion source is rising edge of external CNVSTR.
101: ADC0 start-of-conversion source is overflow of Timer 3.
110: ADC0 start-of-conversion source is overflow of Timer 4.
111: ADC0 start-of-conversion source is overflow of Timer 5.
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55
C8051F39x/37x
9.3. Programmable Window Detector
The ADC Programmable Window Detector continuously compares the ADC0 output registers to user-programmed limits, and notifies the system when a desired condition 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 register ADC0CN) can also be used in
polled mode. The ADC0 Greater-Than (ADC0GTH, ADC0GTL) and Less-Than (ADC0LTH, ADC0LTL)
registers hold the comparison values. The window detector flag can be programmed to indicate when measured data is inside or outside of the user-programmed limits, depending on the contents of the ADC0
Less-Than and ADC0 Greater-Than registers.
SFR Definition 9.5. ADC0GTH: ADC0 Greater Than Data High Byte
Bit
7
6
5
4
3
Name
ADC0GTH[7:0]
Type
R/W
Reset
1
1
1
1
1
2
1
0
1
1
1
SFR Address = 0xC4; SFR Page = All Pages
Bit
Name
7:0
ADC0GTH[7:0]
Function
ADC0 Greater-Than Data Word High-Order Bits.
SFR Definition 9.6. ADC0GTL: ADC0 Greater-Than Data Low Byte
Bit
7
6
5
4
3
Name
ADC0GTL[7:0]
Type
R/W
Reset
1
1
1
1
1
2
1
0
1
1
1
SFR Address = 0xC3; SFR Page = All Pages
56
Bit
Name
7:0
ADC0GTL[7:0]
Function
ADC0 Greater-Than Data Word Low-Order Bits.
Preliminary Rev. 0.71
C8051F39x/37x
SFR Definition 9.7. ADC0LTH: ADC0 Less-Than Data High Byte
Bit
7
6
5
4
3
Name
ADC0LTH[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address = 0xC6; SFR Page = All Pages
Bit
Name
7:0
ADC0LTH[7:0]
Function
ADC0 Less-Than Data Word High-Order Bits.
SFR Definition 9.8. ADC0LTL: ADC0 Less-Than Data Low Byte
Bit
7
6
5
4
3
Name
ADC0LTL[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address = 0xC5; SFR Page = All Pages
Bit
Name
7:0
ADC0LTL[7:0]
Function
ADC0 Less-Than Data Word Low-Order Bits.
Preliminary Rev. 0.71
57
C8051F39x/37x
9.3.1. Window Detector Example
Figure 9.4 shows two example window comparisons for right-justified, single-ended data, with
ADC0LTH:ADC0LTL = 0x0080 (128d) and ADC0GTH:ADC0GTL = 0x0040 (64d). The input voltage can
range from 0 to VREF x (1023/1024) with respect to GND, and is represented by a 10-bit unsigned integer
value. In the left example, an AD0WINT interrupt will be generated if the ADC0 conversion word
(ADC0H:ADC0L) is within the range defined by ADC0GTH:ADC0GTL and ADC0LTH:ADC0LTL
(if 0x0040 < ADC0H:ADC0L < 0x0080). In the right example, and AD0WINT interrupt will be generated if
the ADC0 conversion word is outside of the range defined by the ADC0GT and ADC0LT registers
(if ADC0H:ADC0L < 0x0040 or ADC0H:ADC0L > 0x0080). Figure 9.5 shows an example using left-justified data with the same comparison values.
ADC0H:ADC0L
ADC0H:ADC0L
Input Voltage
(AIN - GND)
VREF x (1023/
1024)
Input Voltage
(AIN - GND)
0x03FF
VREF x (1023/
1024)
0x03FF
AD0WINT
not affected
AD0WINT=1
0x0081
VREF x (128/1024)
0x0080
0x0081
ADC0LTH:ADC0LTL
VREF x (128/1024)
0x007F
0x0080
0x007F
AD0WINT=1
VREF x (64/1024)
0x0041
0x0040
ADC0GTH:ADC0GTL
VREF x (64/1024)
0x003F
0x0041
0x0040
ADC0GTH:ADC0GTL
AD0WINT
not affected
ADC0LTH:ADC0LTL
0x003F
AD0WINT=1
AD0WINT
not affected
0
0x0000
0
0x0000
Figure 9.4. ADC Window Compare Example: Right-Justified, Single-Ended Data
ADC0H:ADC0L
ADC0H:ADC0L
Input Voltage
(AIN - GND)
VREF x (1023/
1024)
Input Voltage
(AIN - GND)
0xFFC0
VREF x (1023/
1024)
0xFFC0
AD0WINT
not affected
AD0WINT=1
0x2040
VREF x (128/1024)
0x2000
0x1FC0
0x2040
ADC0LTH:ADC0LTL
VREF x (128/1024)
0x2000
0x1FC0
AD0WINT=1
0x1040
VREF x (64/1024)
0x1000
0x1040
ADC0GTH:ADC0GTL
VREF x (64/1024)
0x0FC0
0x1000
0x0000
AD0WINT
not affected
ADC0LTH:ADC0LTL
0x0FC0
AD0WINT=1
AD0WINT
not affected
0
ADC0GTH:ADC0GTL
0
0x0000
Figure 9.5. ADC Window Compare Example: Left-Justified, Single-Ended Data
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9.4. ADC0 Analog Multiplexer (C8051F390/2/4/6/8 and C8051F370/4 Only)
ADC0 on the C8051F390/2/4/6/8 and C8051F370/4 has two analog multiplexers, referred to collectively as
AMUX0.
AMUX0 selects the positive and negative inputs to the ADC. Any of the following may be selected as the
positive input: Port I/O pins, the on-chip temperature sensor, or the positive power supply (VDD). Any of the
following may be selected as the negative input: Port I/O pins, VREF, or GND. When GND is selected as
the negative input, ADC0 operates in Single-ended Mode; all other times, ADC0 operates in Differential Mode. The ADC0 input channels are selected in the AMX0P and AMX0N registers as described in
SFR Definition 9.9 and SFR Definition 9.10.
P0.0
AMX0P1
AMX0P0
AMX0N0
AMX0P2
AMX0N1
AMX0P3
AMX0P4
AMX0P
AMUX
P2.3*
Temp
Sensor
VDD
AIN+
AIN-
P0.0
ADC0
AMUX
VREF
GND
AMX0N2
P2.3*
AMX0N3
AMX0N4
AMX0N
*P2.0-P2.3 Only available as
inputs on QFN24 Packaging
Figure 9.6. ADC0 Multiplexer Block Diagram
Important Note About ADC0 Input Configuration: Port pins selected as ADC0 inputs should be configured as analog inputs, and should be skipped by the Digital Crossbar. To configure a Port pin for analog
input, set to ‘0’ the corresponding bit in register PnMDIN. To force the Crossbar to skip a Port pin, set to ‘1’
the corresponding bit in register PnSKIP. See Section “27. Port Input/Output” on page 171 for more Port I/
O configuration details.
Preliminary Rev. 0.71
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C8051F39x/37x
SFR Definition 9.9. AMX0P: AMUX0 Positive Channel Select
Bit
7
6
5
4
3
2
Type
R
R
R
Reset
0
0
0
1
1
R/W
1
1
1
SFR Address = 0xBB; SFR Page = All Pages
Name
Function
7:5
Unused
Read = 000b; Write = Don’t Care.
4:0 AMX0P[4:0] AMUX0 Positive Input Selection.
00000:
00001:
00010:
00011:
00100:
00101:
00110:
00111:
01000:
01001:
01010:
01011:
01100:
01101:
01110:
01111:
10000:
10001:
10010:
10011:
10100:
10101:
10110 – 11111:
60
0
AMX0P[4:0]
Name
Bit
1
P0.0
P0.1
P0.2
P0.3
P0.4
P0.5
P0.6
P0.7
P1.0
P1.1
P1.2
P1.3
P1.4
P1.5
P1.6
P1.7
Temp Sensor
VDD
P2.0 (C8051F390/1/4/5 and C8051F37x Only)
P2.1 (C8051F390/1/4/5 and C8051F37x Only)
P2.2 (C8051F390/1/4/5 and C8051F37x Only)
P2.3 (C8051F390/1/4/5 and C8051F37x Only)
no input selected
Preliminary Rev. 0.71
C8051F39x/37x
SFR Definition 9.10. AMX0N: AMUX0 Negative Channel Select
Bit
7
6
5
4
3
2
1
0
1
1
AMX0N[4:0]
Name
Type
R
R
R
Reset
0
0
0
R/W
1
1
1
SFR Address = 0xBA; SFR Page = All Pages
Bit
Name
Function
7:5
Unused
Read = 000b; Write = Don’t Care.
4:0 AMX0N[4:0] AMUX0 Negative Input Selection.
00000:
00001:
00010:
00011:
00100:
00101:
00110:
00111:
01000:
01001:
01010:
01011:
01100:
01101:
01110:
01111:
10000:
10001:
10010:
10011:
10100:
10101:
10110 – 11111:
P0.0
P0.1
P0.2
P0.3
P0.4
P0.5
P0.6
P0.7
P1.0
P1.1
P1.2
P1.3
P1.4
P1.5
P1.6
P1.7
VREF
GND (ADC in Single-Ended Mode)
P2.0 (C8051F390/1/4/5 and C8051F37x Only)
P2.1 (C8051F390/1/4/5 and C8051F37x Only)
P2.2 (C8051F390/1/4/5 and C8051F37x Only)
P2.3 (C8051F390/1/4/5 and C8051F37x Only)
no input selected
Preliminary Rev. 0.71
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10. Temperature Sensor (C8051F390/2/4/6/8 and C8051F370/4 Only)
A fully C8051F33x-compatible temperature sensor is included on the C8051F390/2/4/6/8 and C8051F370/
4 and accessed via the ADC multiplexer in single-ended configuration. For the self-contained precision
temperature sensor, refer to Section 8.
To use the ADC to measure the temperature sensor, the ADC mux channel should be configured to connect to the temperature sensor. The temperature sensor transfer function is shown in Figure 10.1. The output voltage (VTEMP) is the positive ADC input when the ADC multiplexer is set correctly. The TEMPE bit in
register REF0CN enables/disables the temperature sensor, as described in SFR Definition 12.1. While disabled, the temperature sensor defaults to a high impedance state and any ADC measurements performed
on the sensor will result in meaningless data. Refer to Table 7.11 for the slope and offset parameters of the
temperature sensor.
VTEMP = (Slope x TempC) + Offset
Voltage
TempC = (VTEMP - Offset) / Slope
Slope (V / deg C)
Offset (V at 0 Celsius)
Temperature
Figure 10.1. Temperature Sensor Transfer Function
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10.1. Calibration
The uncalibrated temperature sensor output is extremely linear and suitable for relative temperature measurements (see Table 7.11 on page 39 for specifications). For absolute temperature measurements, offset
and/or gain calibration is recommended.
Error (degrees C)
Figure 10.2 shows the typical temperature sensor error assuming a 1-point calibration at 0 °C. Parameters that affect ADC measurement, in particular the voltage reference value, will also affect temperature measurement.
5.00
5.00
4.00
4.00
3.00
3.00
2.00
2.00
1.00
1.00
0.00
-40.00
-20.00
0.00
20.00
40.00
60.00
80.00
0.00
-1.00
-1.00
-2.00
-2.00
-3.00
-3.00
-4.00
-4.00
-5.00
-5.00
Temperature (degrees C)
Figure 10.2. Temperature Sensor Error with 1-Point Calibration at 0 °C
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11. 10-Bit Current Mode DACs (IDA0, IDA1, C8051F390/2/4/6/8 and
C8051F370/4 Only)
The C8051F390/2/4/6/8 and C8051F370/4 devices include two 10-bit current-mode Digital-to-Analog Converters (IDACs). The maximum current output of the IDACs can be adjusted for three different current settings; 0.5 mA, 1 mA, and 2 mA. The IDACs are enabled or disabled with the IDAnEN bit in the Control
Register for that IDAC (see SFR Definition 11.1 and SFR Definition 11.4). When IDAnEN is set to 0, the
IDAC output behaves as a normal GPIO pin. When IDAnEN is set to 1, the digital output drivers and weak
pullup for the IDAC pin are automatically disabled, and the pin is connected to the IDAC output. An internal
bandgap bias generator is used to generate a reference current for the IDAC whenever it is enabled. When
using an IDAC, the crossbar skip functionality should be enabled on the IDAC output pin, to force the
Crossbar to skip the output pin.
11.1. IDAC Output Scheduling
The IDACs feature a flexible output update mechanism which allows for seamless full-scale changes and
supports jitter-free updates for waveform generation. Three update modes are provided, allowing IDAC
output updates on a write to IDAnH, on a Timer overflow, or on an external pin edge.
11.1.1. Update Output On-Demand
IDA0CN
CNVSTR
Timer 3
Timer 2
Timer 1
IDA0EN
IDA0CM2
IDA0CM1
IDA0CM0
Timer 0
IDA0H
In its default mode (IDAnCN.[6:4] = 111) the IDAC output is updated “on-demand” on a write to the highbyte of the IDAC data register (IDAnH). It is important to note that writes to IDAnL are held in this mode,
and have no effect on the IDAC output until a write to IDAnH takes place. If writing a full 10-bit word to the
IDAC data registers, the 10-bit data word is written to the low byte (IDAnL) and high byte (IDAnH) data registers. Data is latched into the IDAC after a write to the IDAnH register, so the write sequence should be
IDAnL followed by IDAnH if the full 10-bit resolution is required. The IDAC can be used in 8-bit mode by
initializing IDAnL to the desired value (typically 0x00), and writing data to only IDAnH (see Section 11.3 for
information on the format of the 10-bit IDAC data word within the 16-bit SFR space).
IDA0H
8
IDA0L
IDA0OMD1
IDA0OMD0
2
Latch
10
IDA0
Figure 11.1. IDA0 Functional Block Diagram
64
Preliminary Rev. 0.71
IDA0
CNVSTR
Timer 3
Timer 2
Timer 5
Timer 0
IDA1H
IDA1EN
IDA1CM2
IDA1CM1
IDA1CM0
IDA1H
IDA1OMD1
IDA1OMD0
8
IDA1L
2
10
Latch
IDA1CN
C8051F39x/37x
IDA1
IDA1
Figure 11.2. IDA1 Functional Block Diagram
Preliminary Rev. 0.71
65
C8051F39x/37x
11.1.2. Update Output Based on Timer Overflow
The IDAC outputs can use a Timer overflow to schedule an output update event. This feature is useful in
systems where the IDAC is used to generate a waveform of a defined sampling rate by eliminating the
effects of variable interrupt latency and instruction execution on the timing of the IDAC output. When the
IDAnCM bits (IDAnCN.[6:4]) are set to 000, 001, 010 or 011, writes to both IDAC data registers (IDAnL and
IDAnH) are held until an associated Timer overflow event occurs, at which time the IDAnH:IDAnL contents
are copied to the IDAC input latches, allowing the IDAC output to change to the new value.
11.1.3. Update Output Based on CNVSTR Edge
The IDAC output can also be configured to update on a rising edge, falling edge, or both edges of the
external CNVSTR signal. When the IDAnCM bits (IDAnCN.[6:4]) are set to 100, 101, or 110, writes to both
IDAC data registers (IDAnL and IDAnH) are held until an edge occurs on the CNVSTR input pin. The particular setting of the IDAnCM bits determines whether IDAC outputs are updated on rising, falling, or both
edges of CNVSTR. When a corresponding edge occurs, the IDAnH:IDAnL contents are copied to the IDAC
input latches, allowing the IDAC output to change to the new value.
11.2. IDAC Reset Behavior
By default, both IDAC modules revert to a disabled state on any reset source. It is possible to keep the
IDAC outputs enabled through all but a POR or VDD monitor reset, however. When the IDAnRP bit in the
IDAnCN register is set to 1, any reset other than a POR or VDD monitor reset will not affect the IDAC output. The IDAC output will remain enabled and the value in the IDAC output word is maintained.
11.3. IDAC Output Mapping
The IDAC data registers (IDAnH and IDAnL) are left-justified, meaning that the eight MSBs of the IDAC
output word are mapped to bits 7–0 of the IDAnH register, and the two LSBs of the IDAC output word are
mapped to bits 7 and 6 of the IDAnL register. The data word mapping for the IDACs is shown in
Figure 11.3.
B9
B8
B7
IDAnH
B6
B5
IDAnL
B4
B3
B2
B1
B0
Input Data Word
(IDAn9–IDAn0)
Output Current
IDAnOMD[1:0] = 1x
Output Current
IDAnOMD[1:0] = 01
Output Current
IDAnOMD[1:0] = 00
0x000
0x001
0x200
0x3FF
0 mA
1/1024 x 2 mA
512/1024 x 2 mA
1023/1024 x 2 mA
0 mA
1/1024 x 1 mA
512/1024 x 1 mA
1023/1024 x 1 mA
0 mA
1/1024 x 0.5 mA
512/1024 x 0.5 mA
1023/1024 x 0.5 mA
Figure 11.3. IDA0 Data Word Mapping
The full-scale output current of the IDAC is selected using the IDAnOMD bits (IDAnCN[1:0]). By default,
the IDAC is set to a full-scale output current of 2 mA. The IDAnOMD bits can also be configured to provide
full-scale output currents of 1 mA or 0.5 mA, as shown in SFR Definition 11.1 and SFR Definition 11.4.
66
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SFR Definition 11.1. IDA0CN: IDA0 Control
Bit
7
6
5
Name
IDA0EN
IDA0CM[2:0]
Type
R/W
R/W
Reset
0
1
1
4
1
3
2
1
0
IDA0RP
IDA0OMD[1:0]
R
R/W
R/W
0
Varies
1
0
SFR Address = 0xB9; SFR Page = 0
Bit
Name
7
IDA0EN
Function
IDA0 Enable.
0: IDA0 Disabled.
1: IDA0 Enabled.
6:4
IDA0CM[2:0]
IDA0 Update Source Select bits.
000: DAC output updates on Timer 0 overflow.
001: DAC output updates on Timer 1 overflow.
010: DAC output updates on Timer 2 overflow.
011: DAC output updates on Timer 3 overflow.
100: DAC output updates on rising edge of CNVSTR.
101: DAC output updates on falling edge of CNVSTR.
110: DAC output updates on any edge of CNVSTR.
111: DAC output updates on write to IDA0H.
3
2
Reserved
IDA0RP
Write = 0b.
IDA0 Reset Persistence.
0: IDA0 is disabled by any reset source.
1: IDA0 will remain enabled through any reset source
except a power-on-reset.
This bit is reset to 0 by a power on reset, but is sticky
through all other reset sources. When setting IDA0RP to 1,
IDA0EN must be set to 1 also in the same mov instruction.
1:0
IDA0OMD[1:0]
IDA0 Output Mode Select bits.
00: 0.5 mA full-scale output current.
01: 1.0 mA full-scale output current.
1x: 2.0 mA full-scale output current.
Preliminary Rev. 0.71
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SFR Definition 11.2. IDA0H: IDA0 Data Word MSB
Bit
7
6
5
4
Name
IDA0[9:2]
Type
R/W
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address = 0x97; SFR Page = 0
Bit
Name
7:0
IDA0[9:2]
Function
IDA0 Data Word High-Order Bits.
Upper 8 bits of the 10-bit IDA0 Data Word.
SFR Definition 11.3. IDA0L: IDA0 Data Word LSB
Bit
7
6
Name
IDA0[1:0]
Type
R/W
Reset
0
0
5
4
3
2
1
0
R
R
R
R
R
R
0
0
0
0
0
0
SFR Address = 0x96; SFR Page = 0
Bit
Name
7:6
IDA0[1:0]
Function
IDA0 Data Word Low-Order Bits.
Lower 2 bits of the 10-bit IDA0 Data Word.
5:0
68
Unused
Unused. Read = 000000b. Write = Don’t care.
Preliminary Rev. 0.71
C8051F39x/37x
SFR Definition 11.4. IDA1CN: IDA1 Control
Bit
7
6
5
Name
IDA1EN
IDA1CM[2:0]
Type
R/W
R/W
Reset
0
1
1
4
1
3
2
1
0
IDA1RP
IDA1OMD[1:0]
R
R/W
R/W
0
Varies
1
0
SFR Address = 0xB9; SFR Page = F
Bit
Name
7
IDA1EN
Function
IDA1 Enable.
0: IDA1 Disabled.
1: IDA1 Enabled.
6:4
IDA1CM[2:0]
IDA0 Update Source Select bits.
000: DAC output updates on Timer 0 overflow.
001: DAC output updates on Timer 5 overflow.
010: DAC output updates on Timer 2 overflow.
011: DAC output updates on Timer 3 overflow.
100: DAC output updates on rising edge of CNVSTR.
101: DAC output updates on falling edge of CNVSTR.
110: DAC output updates on any edge of CNVSTR.
111: DAC output updates on write to IDA1H.
3
2
Reserved
IDA1RP
Write = 0b.
IDA1 Reset Persistence.
0: IDA1 is disabled by any reset source.
1: IDA1 will remain enabled through any reset source
except a power-on-reset.
This bit is reset to 0 by a power on reset, but is sticky
through all other reset sources. When setting IDA1RP to 1,
IDA1EN must be set to 1 also in the same move instruction.
1:0
IDA1OMD[1:0]
IDA1 Output Mode Select bits.
00: 0.5 mA full-scale output current.
01: 1.0 mA full-scale output current.
1x: 2.0 mA full-scale output current.
Preliminary Rev. 0.71
69
C8051F39x/37x
SFR Definition 11.5. IDA1H: IDA1 Data Word MSB
Bit
7
6
5
4
Name
IDA1[9:2]
Type
R/W
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address = 0x97; SFR Page = F
Bit
Name
7:0
IDA1[9:2]
Function
IDA1 Data Word High-Order Bits.
Upper 8 bits of the 10-bit IDA1 Data Word.
SFR Definition 11.6. IDA1L: IDA1 Data Word LSB
Bit
7
6
Name
IDA1[1:0]
Type
R/W
Reset
0
0
5
4
3
2
1
0
R
R
R
R
R
R
0
0
0
0
0
0
SFR Address = 0x96; SFR Page = F
Bit
Name
7:6
IDA1[1:0]
Function
IDA1 Data Word Low-Order Bits.
Lower 2 bits of the 10-bit IDA1 Data Word.
5:0
70
Unused
Unused. Read = 000000b. Write = Don’t care.
Preliminary Rev. 0.71
C8051F39x/37x
12. Voltage Reference Options
The Voltage reference multiplexer for the ADC is configurable to use an externally connected voltage reference, the on-chip reference voltage generator routed to the VREF pin, the unregulated power supply voltage (VDD), or the regulated 1.8 V internal supply (see Figure 12.1). The REFSL bit in the Reference
Control register (REF0CN, SFR Definition 12.1) selects the reference source for the ADC. For an external
source or the on-chip reference, REFSL should be set to 0 to select the VREF pin. To use VDD as the reference source, REFSL should be set to 1. To override this selection and use the internal regulator as the
reference source, the REGOVR bit can be set to 1.
The BIASE bit enables the internal voltage bias generator, which is used by many of the analog peripherals
on the device. This bias is automatically enabled when any peripheral which requires it is enabled, and it
does not need to be enabled manually. The bias generator may be enabled manually by writing a 1 to the
BIASE bit in register REF0CN. The electrical specifications for the voltage reference circuit are given in
Table 7.13.
The C8051F390/2/4/6/8 and C8051F370/4 devices also include an on-chip voltage reference circuit which
consists of a 1.2 V, temperature stable bandgap voltage reference generator and a selectable-gain output
buffer amplifier. The buffer is configured for 1x or 2x gain using the REFBGS bit in register REF0CN. On
the 1x gain setting the output voltage is nominally 1.2 V, and on the 2x gain setting the output voltage is
nominally 2.4 V. The on-chip voltage reference can be driven on the VREF pin by setting the REFBE bit in
register REF0CN to a 1. The maximum load seen by the VREF pin must be less than 200 µA to GND.
Bypass capacitors of 0.1 µF and 4.7 µF are recommended from the VREF pin to GND, and a minimum of
0.1uF is required. If the on-chip reference is not used, the REFBE bit should be cleared to 0. Electrical
specifications for the on-chip voltage reference are given in Table 7.13.
Important Note about the VREF Pin: When using either an external voltage reference or the on-chip reference circuitry, the VREF pin should be configured as an analog pin and skipped by the Digital Crossbar.
Refer to Section “27. Port Input/Output” on page 171 for the location of the VREF pin, as well as details of
how to configure the pin in analog mode and to be skipped by the crossbar.
REGOVR
REFSL
TEMPE
BIASE
REFBE
REFBGS
REF0CN
EN
To ADC, IDAC,
Internal Oscillators,
Reference,
TempSensor
Bias Generator
IOSCEN
VDD
External
Voltage
Reference
Circuit
R1
EN
VREF
1x/2x
GND
0
Temp Sensor
1.2V Reference
To Analog Mux
EN
REFBE
REFBGS
0
4.7F
+
0.1F
Recommended Bypass
Capacitors
VDD
VREF
(to ADC)
1
Internal
Regulator
1
REGOVR
Figure 12.1. Voltage Reference Functional Block Diagram
Preliminary Rev. 0.71
71
C8051F39x/37x
SFR Definition 12.1. REF0CN: Reference Control
Bit
7
6
Name
REFBGS
Type
R/W
R
Reset
0
0
5
4
3
2
1
0
REGOVR
REFSL
TEMPE
BIASE
REFBE
R
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
SFR Address = 0xD1; SFR Page = All Pages
Bit
Name
7
REFBGS
Function
Reference Buffer Gain Select.
This bit selects between 1x and 2x gain for the on-chip voltage reference buffer.
0: 2x Gain
1: 1x Gain
6:5
Unused
Read = 00b; Write = Don’t care.
4
REGOVR
Regulator Reference Override.
This bit “overrides” the REFSL bit, and allows the internal regulator
to be used as a reference source.
0: The voltage reference source is selected by the REFSL bit.
1: The internal regulator is used as the voltage reference.
3
REFSL
Voltage Reference Select.
This bit selects the ADCs voltage reference.
0: VREF pin used as voltage reference.
1: VDD used as voltage reference.
2
TEMPE
Temperature Sensor Enable Bit.
0: Internal Temperature Sensor off.
1: Internal Temperature Sensor on.
1
BIASE
Internal Analog Bias Generator Enable Bit.
0: Internal Bias Generator off.
1: Internal Bias Generator on.
0
REFBE
On-chip Reference Buffer Enable Bit.
0: On-chip Reference Buffer off.
1: On-chip Reference Buffer on. Internal voltage reference driven
on the VREF pin.
72
Preliminary Rev. 0.71
C8051F39x/37x
13. Voltage Regulator
C8051F39x/37x devices include an internal regulator that regulates the internal core supply from a VDD
supply of 1.8 to 3.6 V. The regulator has two power-saving modes built in to help reduce current consumption in low-power applications. These modes are accessed through the REG0CN register.
13.1. Power Modes
Under default conditions, the internal regulator will remain on when the device enters STOP mode. This
allows any enabled reset source to generate a reset for the device and bring the device out of STOP mode.
For additional power savings, the STOPCF bit can be used to shut down the regulator and the internal
power network of the device when the part enters STOP mode. When STOPCF is set to 1, the RST pin
and a full power cycle of the device are the only methods of generating a reset.
SFR Definition 13.1. REG0CN: Voltage Regulator Control
Bit
7
6
5
4
2
1
0
STOPCF
Name
R/W
Type
Reset
3
0
0
R/W
0
0
0
R/W
0
0
0
SFR Address = 0xC9; SFR Page = All Pages
Bit
Name
Function
7:4
Reserved
Must Write 0000b.
3
STOPCF
Stop Mode Configuration.
This bit configures the regulator’s behavior when the device enters
STOP mode.
0: Regulator is still active in STOP mode. Any enabled reset
source will reset the device.
1: Regulator is shut down in STOP mode. Only the RST pin or
power cycle can reset the device.
2:0
Reserved
Must Write 000b.
Preliminary Rev. 0.71
73
C8051F39x/37x
14. Comparator0
C8051F39x/37x devices include an on-chip programmable voltage comparator, Comparator0, shown in
Figure 14.1.
The Comparator offers programmable response time and hysteresis, an analog input multiplexer, and two
outputs that are optionally available at the Port pins: a synchronous “latched” output (CP0), or an asynchronous “raw” output (CP0A). The asynchronous CP0A signal is available even when the system clock is
not active. This allows the Comparator to operate and generate an output with the device in STOP mode.
When assigned to a Port pin, the Comparator output may be configured as open drain or push-pull (see
Section “27.4. Port I/O Initialization” on page 178). Comparator0 may also be used as a reset source (see
Section “24.5. Comparator0 Reset” on page 157), or as a trigger to kill a PCA output channel.
The Comparator0 inputs are selected by the comparator input multiplexer, as detailed in Section
“14.1. Comparator Multiplexer” on page 78.
CPT0CN
CP0EN
CP0OUT
CP0RIF
CP0FIF
CP0HYP1
CP0HYP0
CP0HYN1
CP0HYN0
VDD
CP0 +
Comparator
Input Mux
CP0 -
+
CP0
D
-
SET
CLR
D
Q
Q
SET
CLR
Q
Q
Crossbar
(SYNCHRONIZER)
CP0A
GND
CPT0MD
CP0FIE
CP0RIE
CP0MD1
CP0MD0
Reset
Decision
Tree
CP0RIF
CP0FIF
0
CP0EN
EA
1
0
0
0
1
1
CP0
Interrupt
1
Figure 14.1. Comparator0 Functional Block Diagram
The Comparator output can be polled in software, used as an interrupt source, and/or routed to a Port pin.
When routed to a Port pin, the Comparator output is available asynchronous or synchronous to the system
clock; the asynchronous output is available even in STOP mode (with no system clock active). When disabled, the Comparator output (if assigned to a Port I/O pin via the Crossbar) defaults to the logic low state,
and the power supply to the comparator is turned off. See Section “27.3. Priority Crossbar Decoder” on
page 176 for details on configuring Comparator outputs via the digital Crossbar. Comparator inputs can be
externally driven from –0.25 V to (VDD) + 0.25 V without damage or upset. The complete Comparator electrical specifications are given in Section “7. Electrical Characteristics” on page 32.
74
Preliminary Rev. 0.71
C8051F39x/37x
The Comparator response time may be configured in software via the CPT0MD register (see SFR Definition 14.2). Selecting a longer response time reduces the Comparator supply current.
VIN+
VIN-
CP0+
CP0-
+
CP0
_
OUT
CIRCUIT CONFIGURATION
Positive Hysteresis Voltage
(Programmed with CP0HYP Bits)
VIN-
INPUTS
Negative Hysteresis Voltage
(Programmed by CP0HYN Bits)
VIN+
VOH
OUTPUT
VOL
Negative Hysteresis
Disabled
Positive Hysteresis
Disabled
Maximum
Negative Hysteresis
Maximum
Positive Hysteresis
Figure 14.2. Comparator Hysteresis Plot
The Comparator hysteresis is software-programmable via its Comparator Control register CPT0CN. The
user can program both the amount of hysteresis voltage (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 CPT0CN
(shown in SFR Definition 14.1). The amount of negative hysteresis voltage is determined by the settings of
the CP0HYN bits. As shown in Figure 14.2, settings of 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 hysteresis is
determined by the setting the CP0HYP bits.
Comparator interrupts can be generated on both rising-edge and falling-edge output transitions. (For Interrupt enable and priority control, see Section “20.1. MCU Interrupt Sources and Vectors” on page 116). The
CP0FIF flag is set to logic 1 upon a Comparator falling-edge occurrence, and the CP0RIF flag is set to
logic 1 upon the Comparator rising-edge occurrence. Once set, these bits remain set until cleared by software. The Comparator rising-edge interrupt mask is enabled by setting CP0RIE to a logic 1. The
Comparator0 falling-edge interrupt mask is enabled by setting CP0FIE to a logic 1.
The output state of the Comparator can be obtained at any time by reading the CP0OUT bit. The Comparator is enabled by setting the CP0EN bit to logic 1, and is disabled by clearing this bit to logic 0.
Note that false rising edges and falling edges can be detected when the comparator is first powered on or
if changes are made to the hysteresis or response time control bits. Therefore, it is recommended that the
rising-edge and falling-edge flags be explicitly cleared to logic 0 a short time after the comparator is
enabled or its mode bits have been changed.
Preliminary Rev. 0.71
75
C8051F39x/37x
SFR Definition 14.1. CPT0CN: Comparator0 Control
Bit
7
6
5
4
3
2
Name
CP0EN
CP0OUT
CP0RIF
CP0FIF
CP0HYP[1:0]
CP0HYN[1:0]
Type
R/W
R
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
1
0
0
0
SFR Address = 0x9B; SFR Page = All Pages
Bit
Name
7
CP0EN
Function
Comparator0 Enable Bit.
0: Comparator0 Disabled.
1: Comparator0 Enabled.
6
CP0OUT
Comparator0 Output State Flag.
0: Voltage on CP0+ < CP0–.
1: Voltage on CP0+ > CP0–.
5
CP0RIF
Comparator0 Rising-Edge Flag. Must be cleared by
software.
0: No Comparator0 Rising Edge has occurred since this flag
was last cleared.
1: Comparator0 Rising Edge has occurred.
4
CP0FIF
Comparator0 Falling-Edge Flag. Must be cleared by
software.
0: No Comparator0 Falling-Edge has occurred since this flag
was last cleared.
1: Comparator0 Falling-Edge has occurred.
3:2
CP0HYP[1:0]
Comparator0 Positive Hysteresis Control Bits.
00: Positive Hysteresis Disabled.
01: Positive Hysteresis = 5 mV.
10: Positive Hysteresis = 10 mV.
11: Positive Hysteresis = 20 mV.
1:0
CP0HYN[1:0]
Comparator0 Negative Hysteresis Control Bits.
00: Negative Hysteresis Disabled.
01: Negative Hysteresis = 5 mV.
10: Negative Hysteresis = 10 mV.
11: Negative Hysteresis = 20 mV.
76
Preliminary Rev. 0.71
C8051F39x/37x
SFR Definition 14.2. CPT0MD: Comparator0 Mode Selection
Bit
7
6
Name
5
4
CP0RIE
CP0FIE
3
2
1
0
CP0MD[1:0]
Type
R
R
R/W
R/W
R
R
Reset
0
0
0
0
0
0
R/W
1
0
SFR Address = 0x9D; SFR Page = All Pages
Bit
Name
Function
7:6
5
Unused
CP0RIE
Unused. Read = 00b, Write = Don’t Care.
4
CP0FIE
Comparator0 Falling-Edge Interrupt Enable.
0: Comparator0 Falling-edge interrupt disabled.
1: Comparator0 Falling-edge interrupt enabled.
3:2
1:0
Unused
CP0MD[1:0]
Comparator0 Rising-Edge Interrupt Enable.
0: Comparator0 Rising-edge interrupt disabled.
1: Comparator0 Rising-edge interrupt enabled.
Unused. Read = 00b, Write = don’t care.
Comparator0 Mode Select.
These bits affect the response time and power consumption
for Comparator0.
00: Mode 0 (Fastest Response Time, Highest Power Consumption)
01: Mode 1
10: Mode 2
11: Mode 3 (Slowest Response Time, Lowest Power Consumption)
Preliminary Rev. 0.71
77
C8051F39x/37x
14.1. Comparator Multiplexer
C8051F39x/37x devices include an analog input multiplexer to connect Port I/O pins to the comparator
inputs. The Comparator0 inputs are selected in the CPT0MX register (SFR Definition 14.3). The CMX0P1–
CMX0P0 bits select the Comparator0 positive input; the CMX0N1–CMX0N0 bits select the Comparator0
negative input. Important Note About Comparator Inputs: The Port pins selected as comparator inputs
should be configured as analog inputs in their associated Port configuration register, and configured to be
skipped by the Crossbar (for details on Port configuration, see Section “27.6. Special Function Registers
for Accessing and Configuring Port I/O” on page 183).
CPT0MX
CMX0N3
CMX0N2
CMX0N1
CMX0N0
CMX0P3
CMX0P2
CMX0P1
CMX0P0
P0.0
P0.2
P0.4
P0.6
P1.0
P1.2
P1.4
P1.6
P2.0*
P2.2*
P0.1
P0.3
P0.5
P0.7
P1.1
P1.3
P1.5
P1.7
P2.1*
P2.3*
VDD
CP0 +
CP0 -
+
GND
*P2.0-P2.3 Only available as
inputs on QFN24 Packaging
Figure 14.3. Comparator Input Multiplexer Block Diagram
78
Preliminary Rev. 0.71
C8051F39x/37x
SFR Definition 14.3. CPT0MX: Comparator0 MUX Selection
Bit
7
6
5
4
3
2
1
Name
CMX0N[3:0]
CMX0P[3:0]
Type
R/W
R/W
Reset
1
1
1
1
1
1
1
0
1
SFR Address = 0x9F; SFR Page = All Pages
Bit
7:4
Name
Function
CMX0N[3:0] Comparator0 Negative Input MUX Selection.
0000:
0001:
0010:
0011:
0100:
0101:
0110:
0111:
1000:
1001:
1010-1111:
3:0
P0.1
P0.3
P0.5
P0.7
P1.1
P1.3
P1.5
P1.7
P2.1 (C8051F390/1/4/5 and C8051F37x Only)
P2.3 (C8051F390/1/4/5 and C8051F37x Only)
None
CMX0P[3:0] Comparator0 Positive Input MUX Selection.
0000:
0001:
0010:
0011:
0100:
0101:
0110:
0111:
1000:
1001:
1010-1111:
P0.0
P0.2
P0.4
P0.6
P1.0
P1.2
P1.4
P1.6
P2.0 (C8051F390/1/4/5 and C8051F37x Only)
P2.2 (C8051F390/1/4/5 and C8051F37x Only)
None
Preliminary Rev. 0.71
79
C8051F39x/37x
15. 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 software. The MCU family has a superset of all the peripherals included with a standard 8051. The CIP-51
also includes on-chip debug hardware (see description in Section 33), and interfaces directly with the analog and digital subsystems providing a complete 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 15.1 for a block diagram).
The CIP-51 includes the following features:
Fully Compatible with MCS-51 Instruction Set
50 MIPS Peak Throughput with 49 MHz Clock
 0 to 49 MHz Clock Frequency
 Extended Interrupt Handler
Reset Input
Power Management Modes
 On-chip Debug Logic
 Program and Data Memory Security




Performance
The CIP-51 employs a pipelined architecture that greatly increases its instruction throughput over the standard 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.
DATA BUS
D8
TMP2
B REGISTER
STACK POINTER
SRAM
ADDRESS
REGISTER
PSW
D8
D8
D8
ALU
SRAM
D8
D8
TMP1
ACCUMULATOR
D8
D8
D8
DATA BUS
DATA BUS
SFR_ADDRESS
BUFFER
D8
DATA POINTER
D8
D8
SFR
BUS
INTERFACE
SFR_CONTROL
SFR_WRITE_DATA
SFR_READ_DATA
DATA BUS
PC INCREMENTER
PROGRAM COUNTER (PC)
PRGM. ADDRESS REG.
PIPELINE
RESET
MEM_CONTROL
A16
MEMORY
INTERFACE
MEM_WRITE_DATA
MEM_READ_DATA
D8
CONTROL
LOGIC
SYSTEM_IRQs
CLOCK
D8
STOP
IDLE
MEM_ADDRESS
D8
POWER CONTROL
REGISTER
INTERRUPT
INTERFACE
EMULATION_IRQ
D8
Figure 15.1. CIP-51 Block Diagram
80
Preliminary Rev. 0.71
C8051F39x/37x
With the CIP-51's maximum system clock at 48 MHz, it has a peak throughput of 48 MIPS. The CIP-51 has
a total of 109 instructions. The table below shows the total number of instructions that require each execution time.
Clocks to Execute
1
2
2/4
3
3/5
4
5
4/6
6
8
Number of Instructions
26
50
5
10
7
5
2
1
2
1
Programming and Debugging Support
In-system programming of the EPROM program memory and communication with on-chip debug support
logic is accomplished via the Silicon Labs 2-Wire Development Interface (C2).
The on-chip debug support logic facilitates full speed in-circuit debugging, allowing the setting of hardware
breakpoints, starting, stopping and single stepping through program execution (including interrupt service
routines), examination of the program's call stack, and reading/writing the contents of registers and memory. This method of on-chip debugging is completely non-intrusive, requiring no RAM, Stack, timers, or
other on-chip resources. C2 details can be found in Section “33. C2 Interface” on page 295.
The CIP-51 is supported by development tools from Silicon Labs and third party vendors. Silicon Labs provides an integrated development environment (IDE) including editor, debugger and programmer. The IDE's
debugger and programmer interface to the CIP-51 via the C2 interface to provide fast and efficient in-system device programming and debugging. Third party macro assemblers and C compilers are also available.
15.1. Instruction Set
The instruction set of the CIP-51 System Controller is fully compatible with the standard MCS-51™ instruction 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 standard 8051.
15.1.1. 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 15.1 is the
CIP-51 Instruction Set Summary, which includes the mnemonic, number of bytes, and number of clock
cycles for each instruction.
Preliminary Rev. 0.71
81
C8051F39x/37x
Table 15.1. CIP-51 Instruction Set Summary
Mnemonic
Description
Bytes
Clock
Cycles
Add register to A
Add direct byte to A
Add indirect RAM to A
Add immediate to A
Add register to A with carry
Add direct byte to A with carry
Add indirect RAM to A with carry
Add immediate to A with carry
Subtract register from A with borrow
Subtract direct byte from A with borrow
Subtract indirect RAM from A with borrow
Subtract immediate from A with borrow
Increment A
Increment register
Increment direct byte
Increment indirect RAM
Decrement A
Decrement register
Decrement direct byte
Decrement indirect RAM
Increment Data Pointer
Multiply A and B
Divide A by B
Decimal adjust A
1
2
1
2
1
2
1
2
1
2
1
2
1
1
2
1
1
1
2
1
1
1
1
1
1
2
2
2
1
2
2
2
1
2
2
2
1
1
2
2
1
1
2
2
1
4
8
1
AND Register to A
AND direct byte to A
AND indirect RAM to A
AND immediate to A
AND A to direct byte
AND immediate to direct byte
OR Register to A
OR direct byte to A
OR indirect RAM to A
OR immediate to A
OR A to direct byte
OR immediate to direct byte
Exclusive-OR Register to A
Exclusive-OR direct byte to A
Exclusive-OR indirect RAM to A
Exclusive-OR immediate to A
Exclusive-OR A to direct byte
1
2
1
2
2
3
1
2
1
2
2
3
1
2
1
2
2
1
2
2
2
2
3
1
2
2
2
2
3
1
2
2
2
2
Arithmetic Operations
ADD A, Rn
ADD A, direct
ADD A, @Ri
ADD A, #data
ADDC A, Rn
ADDC A, direct
ADDC A, @Ri
ADDC A, #data
SUBB A, Rn
SUBB A, direct
SUBB A, @Ri
SUBB A, #data
INC A
INC Rn
INC direct
INC @Ri
DEC A
DEC Rn
DEC direct
DEC @Ri
INC DPTR
MUL AB
DIV AB
DA A
Logical Operations
ANL A, Rn
ANL A, direct
ANL A, @Ri
ANL A, #data
ANL direct, A
ANL direct, #data
ORL A, Rn
ORL A, direct
ORL A, @Ri
ORL A, #data
ORL direct, A
ORL direct, #data
XRL A, Rn
XRL A, direct
XRL A, @Ri
XRL A, #data
XRL direct, A
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Table 15.1. CIP-51 Instruction Set Summary (Continued)
Mnemonic
XRL direct, #data
CLR A
CPL A
RL A
RLC A
RR A
RRC A
SWAP A
Description
Bytes
Clock
Cycles
Exclusive-OR immediate to direct byte
Clear A
Complement A
Rotate A left
Rotate A left through Carry
Rotate A right
Rotate A right through Carry
Swap nibbles of A
3
1
1
1
1
1
1
1
3
1
1
1
1
1
1
1
Move Register to A
Move direct byte to A
Move indirect RAM to A
Move immediate to A
Move A to Register
Move direct byte to Register
Move immediate to Register
Move A to direct byte
Move Register to direct byte
Move direct byte to direct byte
Move indirect RAM to direct byte
Move immediate to direct byte
Move A to indirect RAM
Move direct byte to indirect RAM
Move immediate to indirect RAM
Load DPTR with 16-bit constant
Move code byte relative DPTR to A
Move code byte relative PC to A
Move external data (8-bit address) to A
Move A to external data (8-bit address)
Move external data (16-bit address) to A
Move A to external data (16-bit address)
Push direct byte onto stack
Pop direct byte from stack
Exchange Register with A
Exchange direct byte with A
Exchange indirect RAM with A
Exchange low nibble of indirect RAM with A
1
2
1
2
1
2
2
2
2
3
2
3
1
2
2
3
1
1
1
1
1
1
2
2
1
2
1
1
1
2
2
2
1
2
2
2
2
3
2
3
2
2
2
3
3
3
3
3
3
3
2
2
1
2
2
2
Clear Carry
Clear direct bit
Set Carry
Set direct bit
Complement Carry
Complement direct bit
1
2
1
2
1
2
1
2
1
2
1
2
Data Transfer
MOV A, Rn
MOV A, direct
MOV A, @Ri
MOV A, #data
MOV Rn, A
MOV Rn, direct
MOV Rn, #data
MOV direct, A
MOV direct, Rn
MOV direct, direct
MOV direct, @Ri
MOV direct, #data
MOV @Ri, A
MOV @Ri, direct
MOV @Ri, #data
MOV DPTR, #data16
MOVC A, @A+DPTR
MOVC A, @A+PC
MOVX A, @Ri
MOVX @Ri, A
MOVX A, @DPTR
MOVX @DPTR, A
PUSH direct
POP direct
XCH A, Rn
XCH A, direct
XCH A, @Ri
XCHD A, @Ri
Boolean Manipulation
CLR C
CLR bit
SETB C
SETB bit
CPL C
CPL bit
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Table 15.1. CIP-51 Instruction Set Summary (Continued)
Mnemonic
ANL C, bit
ANL C, /bit
ORL C, bit
ORL C, /bit
MOV C, bit
MOV bit, C
JC rel
JNC rel
JB bit, rel
JNB bit, rel
JBC bit, rel
Description
AND direct bit to Carry
AND complement of direct bit to Carry
OR direct bit to carry
OR complement of direct bit to Carry
Move direct bit to Carry
Move Carry to direct bit
Jump if Carry is set
Jump if Carry is not set
Jump if direct bit is set
Jump if direct bit is not set
Jump if direct bit is set and clear bit
Bytes
Clock
Cycles
2
2
2
2
2
2
2
2
3
3
3
2
2
2
2
2
2
2/4
2/4
3/5
3/5
3/5
2
3
1
1
2
3
2
1
2
2
3
3
3
4*
5*
6*
6*
4*
5*
4*
4*
2/4*
2/4*
4/6*
3/5*
3/5*
3
4/6*
2
3
1
2/4*
3/5*
1
Program Branching
ACALL addr11
LCALL addr16
RET
RETI
AJMP addr11
LJMP addr16
SJMP rel
JMP @A+DPTR
JZ rel
JNZ rel
CJNE A, direct, rel
CJNE A, #data, rel
CJNE Rn, #data, rel
Absolute subroutine call
Long subroutine call
Return from subroutine
Return from interrupt
Absolute jump
Long jump
Short jump (relative address)
Jump indirect relative to DPTR
Jump if A equals zero
Jump if A does not equal zero
Compare direct byte to A and jump if not equal
Compare immediate to A and jump if not equal
Compare immediate to Register and jump if not
equal
CJNE @Ri, #data, rel
Compare immediate to indirect and jump if not
equal
DJNZ Rn, rel
Decrement Register and jump if not zero
DJNZ direct, rel
Decrement direct byte and jump if not zero
NOP
No operation
* Clock cycles for branch instructions with prefetch enabled, Align = 0, FLRT = 0
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Notes on Registers, Operands and Addressing Modes:
Rn - Register R0–R7 of the currently selected register bank.
@Ri - Data RAM location addressed indirectly through R0 or R1.
rel - 8-bit, signed (two’s complement) offset 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
2 kB page of program memory as the first byte of the following instruction.
addr16 - 16-bit destination address used by LCALL and LJMP. The destination may be anywhere within
the 8 kB program memory space.
There is one unused opcode (0xA5) that performs the same function as NOP.
All mnemonics copyrighted © Intel Corporation 1980.
15.2. CIP-51 Register Descriptions
Following are descriptions of SFRs related to the operation of the CIP-51 System Controller. Reserved bits
should always be written to the value indicated in the SFR description. Future product versions may use
these bits to implement new features in which case the reset value of the bit will be the indicated value,
selecting the feature's default state. Detailed descriptions of the remaining SFRs are included in the sections of the datasheet associated with their corresponding system function.
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SFR Definition 15.1. DPL: Data Pointer Low Byte
Bit
7
6
5
4
Name
DPL[7:0]
Type
R/W
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address = 0x82; SFR Page = All Pages
Bit
Name
7:0
DPL[7:0]
Function
Data Pointer Low.
The DPL register is the low byte of the 16-bit DPTR.
SFR Definition 15.2. DPH: Data Pointer High Byte
Bit
7
6
5
4
Name
DPH[7:0]
Type
R/W
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address = 0x83; SFR Page = All Pages
Bit
Name
7:0
DPH[7:0]
Function
Data Pointer High.
The DPH register is the high byte of the 16-bit DPTR.
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SFR Definition 15.3. SP: Stack Pointer
Bit
7
6
5
4
Name
SP[7:0]
Type
R/W
Reset
0
0
0
0
3
2
1
0
0
1
1
1
SFR Address = 0x81; SFR Page = All Pages
Bit
Name
7:0
SP[7:0]
Function
Stack Pointer.
The Stack 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.
SFR Definition 15.4. ACC: Accumulator
Bit
7
6
5
4
Name
ACC[7:0]
Type
R/W
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address = 0xE0; SFR Page = All Pages; Bit-Addressable
Bit
Name
7:0
ACC[7:0]
Function
Accumulator.
This register is the accumulator for arithmetic operations.
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SFR Definition 15.5. B: B Register
Bit
7
6
5
4
Name
B[7:0]
Type
R/W
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address = 0xF0; SFR Page = All Pages; Bit-Addressable
Bit
Name
7:0
B[7:0]
Function
B Register.
This register serves as a second accumulator for certain arithmetic operations.
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SFR Definition 15.6. PSW: Program Status Word
Bit
7
6
5
Name
CY
AC
F0
Type
R/W
R/W
R/W
Reset
0
0
0
4
3
2
1
0
RS[1:0]
OV
F1
PARITY
R/W
R/W
R/W
R
0
0
0
0
0
SFR Address = 0xD0; SFR Page = All Pages; Bit-Addressable
Bit
Name
7
CY
Function
Carry Flag.
This bit is set when the last arithmetic operation resulted in a carry
(addition) or a borrow (subtraction). It is cleared to logic 0 by all
other arithmetic operations.
6
AC
Auxiliary Carry Flag.
This bit is set when the last arithmetic operation resulted in a carry
into (addition) or a borrow from (subtraction) the high order nibble.
It is cleared to logic 0 by all other arithmetic operations.
5
F0
User Flag 0.
This is a bit-addressable, general purpose flag for use under software control.
4:3
RS[1:0]
Register Bank Select.
These bits select which register bank is used during register
accesses.
00: Bank 0, Addresses 0x00-0x07
01: Bank 1, Addresses 0x08-0x0F
10: Bank 2, Addresses 0x10-0x17
11: Bank 3, Addresses 0x18-0x1F
2
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 instruction causes a divide-by-zero condition.
The OV bit is cleared to 0 by the ADD, ADDC, SUBB, MUL, and
DIV instructions in all other cases.
1
F1
User Flag 1.
This is a bit-addressable, general purpose flag for use under software control.
0
PARITY
Parity Flag.
This bit is set to logic 1 if the sum of the eight bits in the accumulator is odd and cleared if the sum is even.
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C8051F39x/37x
16. Prefetch Engine
The C8051F39x/37x family of devices incorporate a 2-byte prefetch engine. Because the access time of
the Flash memory is 40 ns, and the minimum instruction time is roughly 20 ns, the prefetch engine is necessary for full-speed code execution. Instructions are read from Flash memory two bytes at a time by the
prefetch engine and given to the CIP-51 processor core to execute. When running linear code (code without any jumps or branches), the prefetch engine allows instructions to be executed at full speed. When a
code branch occurs, the processor may be stalled for up to two clock cycles while the next set of code
bytes is retrieved from Flash memory.
Note: The prefetch engine should be disabled when the device is in suspend mode to save power.
SFR Definition 16.1. PFE0CN: Prefetch Engine Control
Bit
7
6
5
4
3
2
1
0
PFEN
Name
Type
R
R
R/W
R
R
R
R
R
Reset
0
0
1
0
0
0
0
0
SFR Address = 0xB5; SFR Page = All Pages
Bit
Name
7:6
5
Unused
PFEN
Function
Unused. Read = 00b, Write = don’t care.
Prefetch Enable.
This bit enables the prefetch engine.
0: Prefetch engine is disabled.
1: Prefetch engine is enabled.
4:0
90
Unused
Unused. Read = 00000b. Write = don’t care.
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17. 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. The memory organization of the
C8051F39x/37x device family is shown in Figure 17.1. Not shown in Figure 17.1 is 512 bytes of byteaddressable EEPROM available on C8051F37x, accessible by SMBUS/I2C (see Section 22).
PROGRAM/DATA MEMORY (FLASH)
DATA MEMORY (RAM)
C8051F390/1/2/3, C8051F370/1/4/5
INTERNAL DATA ADDRESS SPACE
0xFF
0x4000
0x80
0x7F
16 kB FLASH
(In-System
Programmable in 512
Byte Sectors)
0x30
0x2F
0x00
Special Function
Register's
(Direct Addressing Only)
0
F
(Direct and Indirect
Addressing)
0x20
0x1F
0x0000
Upper 128 RAM
(Indirect Addressing
Only)
Bit Addressable
Lower 128 RAM
(Direct and Indirect
Addressing)
General Purpose
Registers
EXTERNAL DATA ADDRESS SPACE
C8051F394/5/6/7
0xFFFF
0x2000
Same 1024 bytes as from
0x0000 to 0x03FF, wrapped
on 1024-byte boundaries
8 kB FLASH
(In-System
Programmable in 512
Byte Sectors)
0x0400
0x03FF
0x0300
0x02FF
0x0000
0x0000
Always Reads 0x00
XRAM - 768 Bytes
(accessable using MOVX
instruction)
C8051F398/9
0x1000
4 kB FLASH
(In-System
Programmable in 512
Byte Sectors)
0x0000
Figure 17.1. C8051F39x/37x Memory Map
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17.1. Program Memory
The CIP-51 core has a 64 kB program memory space. The C8051F39x/37x implements 16 kB of this program memory space as in-system, re-programmable Flash memory, organized in a contiguous block from
addresses 0x0000 to 0x3FFF. The address 0x3FFF serves as the security lock byte for the device, and
addresses above 0x3FFF are reserved.
C8051F390/1/2/3
C8051F370/1/4/5
Lock Byte
C8051F392/3/6/7
C8051F398/9
0x3FFF
0x3E00
Lock Byte
0x1FFF
0x1FFE
Lock Byte Page
0x1E00
Lock Byte
Flash Memory Space
0x0FFF
0x0FFE
Lock Byte Page
Flash Memory Space
0x0E00
FLASH memory organized in
512-byte pages
0x3FFE
Lock Byte Page
Flash Memory Space
0x0000
0x0000
0x0000
Figure 17.2. Flash Program Memory Map
17.1.1. MOVX Instruction and Program Memory
The MOVX instruction in an 8051 device is typically used to access external data memory. On the
C8051F39x/37x devices, the MOVX instruction is normally used to read and write on-chip XRAM, but can
be re-configured to write and erase on-chip Flash memory space. MOVC instructions are always used to
read Flash memory, while MOVX write instructions are used to erase and write Flash. This Flash access
feature provides a mechanism for the C8051F39x/37x to update program code and use the program memory space for non-volatile data storage. Refer to Section “21. Flash Memory” on page 129 for further
details.
17.2. Data Memory
The C8051F39x/37x device family includes 1024 bytes of RAM data memory. 256 bytes of this memory is
mapped into the internal RAM space of the 8051. 768 bytes of this memory is on-chip “external” memory.
The data memory map is shown in Figure 17.1 for reference.
17.2.1. Internal RAM
There are 256 bytes of internal RAM mapped into the data memory space from 0x00 through 0xFF. The
lower 128 bytes of data memory are used for general purpose registers and scratch pad memory. Either
direct or indirect addressing may be used to access the lower 128 bytes of data memory. Locations 0x00
through 0x1F are addressable as four banks of general purpose registers, 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 CPU accesses the upper 128 bytes of data memory space or the SFRs. Instructions that use
direct addressing will access the SFR space. Instructions using indirect addressing above 0x7F access the
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upper 128 bytes of data memory. Figure 17.1 illustrates the data memory organization of the C8051F39x/
37x.
17.2.1.1. General Purpose Registers
The lower 32 bytes of data memory, locations 0x00 through 0x1F, may be addressed as four banks of general-purpose registers. Each bank consists of eight byte-wide registers designated R0 through R7. Only
one of these banks may be enabled at a time. Two bits in the program status word, RS0 (PSW.3) and RS1
(PSW.4), select the active register bank (see description of the PSW in SFR Definition 15.6). This allows
fast context switching when entering subroutines and interrupt service routines. Indirect addressing modes
use registers R0 and R1 as index registers.
17.2.1.2. Bit Addressable Locations
In addition to direct access to data memory organized as bytes, the sixteen 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 bit7 of the byte at 0x20 has bit address
0x07. Bit 7 of the byte at 0x2F has bit address 0x7F. A bit 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 destination).
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.
17.2.1.3. Stack
A programmer's stack can be located anywhere in the 256-byte data memory. The stack area is designated using the Stack Pointer (SP) 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. Therefore, the first value pushed on the stack is placed at location 0x08, which is also the first register (R0) of register bank 1. Thus, if more 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.
17.2.2. External RAM
There are 768 bytes of on-chip RAM mapped into the external data memory space. All of these address
locations may be accessed using the external move instruction (MOVX) and the data pointer (DPTR), or
using MOVX indirect addressing mode. 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 Register (EMI0CN as shown in SFR Definition 17.1). Note: the MOVX instruction is also used for writes
to the Flash memory. See Section “21. Flash Memory” on page 129 for details. The MOVX instruction
accesses XRAM by default.
Memory locations between address 0x0300 and 0x03FF will all read back 0x00.
For a 16-bit MOVX operation (@DPTR), the upper 6 bits of the 16-bit external data memory address word
are "don't cares". As a result, addresses 0x0000 through 0x03FF are mapped modulo style over the entire
64 k external data memory address range. For example, the XRAM byte at address 0x0000 is shadowed
at addresses 0x0400, 0x0800, 0x0C00, 0x1000, etc.
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SFR Definition 17.1. EMI0CN: External Memory Interface Control
Bit
7
6
5
4
3
2
1
0
PGSEL
Name
Type
R
R
R
R
R
R
Reset
0
0
0
0
0
0
R/W
0
0
SFR Address = 0xAA; SFR Page = All Pages
Bit
Name
7:2
1:0
Unused
PGSEL
Function
Read = 000000b; Write = Don’t Care
XRAM Page Select.
The PGSEL field provides the high byte of the 16-bit external
data memory address when using an 8-bit MOVX command,
effectively selecting a 256-byte page of RAM. Since the upper
(unused) bits of the register are always zero, the PGSEL determines which page of XRAM is accessed.
For Example: If PGSEL = 0x01, addresses 0x0100 through
0x01FF will be accessed.
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18. Device ID Registers
The C8051F39x/37x has SFRs that identify the device family and derivative. These SFRs can be read by
firmware at runtime to determine the capabilities of the MCU that is executing code. This allows the same
firmware image to run on MCUs with different memory sizes and peripherals, and dynamically changing
functionality to suit the capabilities of that MCU.
In order for firmware to identify the MCU, it must read two SFRs. DERIVID describes the specific derivative
within that device family, and REVID describes the hardware revision of the MCU.
The C8051F39x/37x devices also include four SFRs, SN0 through SN3, that are pre-programmed during
production with a unique, 32-bit serial number. The serial number provides a unique identification number
for each device and can be read from the application firmware. If the serial number is not used in the application, these four registers can be used as general purpose SFRs.
SFR Definition 18.1. DERIVID: Device Derivative ID
Bit
7
6
5
4
3
2
1
0
Varies
Varies
Varies
Varies
Name
DERIVID
Type
R
Reset
Varies
Varies
Varies
Varies
SFR Address = 0xAB; SFR Page = 0
Bit
Name
7:0
DERIVID
Function
Derivative ID.
This read-only register returns the 8-bit derivative ID, which can
be used by firmware to identify which device in the product family
is being used.
0xD0: C8051F390
0xD1: C8051F391
0xD2: C8051F392
0xD3: C8051F393
0xD4: C8051F394
0xD5: C8051F395
0xD6: C8051F396
0xD7: C8051F397
0xD8: C8051F398
0xD9: C8051F399
0xE0: C8051F370
0xE1: C8051F371
0xE4: C8051F374
0xE5: C8051F375
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SFR Definition 18.2. REVISION: Device Revision ID
Bit
7
6
5
4
3
2
1
0
Varies
Varies
Varies
Varies
Name
REVISION
Type
R
Reset
Varies
Varies
Varies
Varies
SFR Address = 0xAC; SFR Page = 0
Bit
Name
7:0
REVISION
Function
Device Revision.
This read-only register returns the 8-bit revision ID. For example:
0x00 = Revision A.
SFR Definition 18.3. SN3: Serial Number Byte 3
Bit
7
6
5
4
Name
SN3
Type
R
Reset
Varies
Varies
Varies
Varies
3
2
1
0
Varies
Varies
Varies
Varies
SFR Address = 0xAE; SFR Page = F
Bit
Name
7:0
SN3
Function
Serial Number Byte 3.
This read-only register returns the MSB (byte 3) of the serial number.
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SFR Definition 18.4. SN2: Serial Number Byte 2
Bit
7
6
5
4
Name
SN2
Type
R
Reset
Varies
Varies
Varies
Varies
3
2
1
0
Varies
Varies
Varies
Varies
SFR Address = 0xAD; SFR Page = F
Bit
Name
7:0
SN2
Function
Serial Number Byte 2.
This read-only register returns the byte 2 of the serial number.
SFR Definition 18.5. SN1: Serial Number Byte 1
Bit
7
6
5
4
Name
SN1
Type
R
Reset
Varies
Varies
Varies
Varies
3
2
1
0
Varies
Varies
Varies
Varies
SFR Address = 0xAC; SFR Page = F
Bit
Name
7:0
SN1
Function
Serial Number Byte 1.
This read-only register returns byte 1 of the serial number.
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C8051F39x/37x
SFR Definition 18.6. SN0: Serial Number Byte 0
Bit
7
6
5
4
Name
SN0
Type
R
Reset
Varies
Varies
Varies
Varies
3
2
1
0
Varies
Varies
Varies
Varies
SFR Address = 0xAB; SFR Page = F
Bit
Name
7:0
SN0
Function
Serial Number Byte 0.
This read-only register returns the LSB (byte 0) of the serial number.
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19. Special Function Registers
The direct-access data memory locations from 0x80 to 0xFF constitute the special function registers
(SFRs). The SFRs provide control and data exchange with the C8051F39x/37x's resources and peripherals. The CIP-51 controller core duplicates the SFRs found in a typical 8051 implementation as well as
implementing additional SFRs used to configure and access the sub-systems unique to the C8051F39x/
37x. This allows the addition of new functionality while retaining compatibility with the MCS-51™ instruction set. Table 19.2 lists the SFRs implemented in the C8051F39x/37x device family.
The SFR registers are accessed anytime the direct addressing mode is used to access memory locations
from 0x80 to 0xFF. SFRs with addresses ending in 0x0 or 0x8 (e.g. P0, TCON, SCON0, IE, etc.) are bitaddressable as well as byte-addressable. All other SFRs 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 data sheet, as indicated in
Table 19.3, for a detailed description of each register.
19.1. SFR Paging
The CIP-51 features SFR paging, allowing the device to map many SFRs into the 0x80 to 0xFF memory
address space. The SFR memory space has 256 pages. In this way, each memory location from 0x80 to
0xFF can access up to 256 SFRs. The C8051F39x/37x devices utilize two SFR pages: 0x0, and 0xF. Most
SFRs are available on both pages. SFR pages are selected using the Special Function Register Page
Selection register, SFRPAGE. The procedure for reading and writing 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).
19.2. Interrupts and Automatic SFR Paging
When an interrupt occurs, the current SFRPAGE is pushed onto the SFR page stack. 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 five-byte SFR page stack, depicted in Figure 19.1. Firmware can read any element of the SFR page stack by setting the SFR Page Stack Index (SFRPGIDX) in the SFR Page Control
Register (SFRPGCN) and reading the SFRSTACK register:
Table 19.1. SFR Page Stack
SFRPGIDX Value
SFRSTACK Contains
000b
Value of the first/top* byte of the stack
001b
Value of the second byte of the stack
011b
Value of the third byte of the stack
010b
Value of the forth byte of the stack
100b
Value of the fifth/bottom byte of the stack
*Note: The first/top byte of the stack can also be directly accessed by reading SFRPAGE.
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C8051F39x/37x
SFRPGEN
Interrupt
Logic
SFRPAGE
SFRPGEN
SFRPGIDX2
SFRPGIDX1
SFRPGIDX0
SFRPGCN
000
001
SFR Page
Stack
010
SFRSTACK
011
100
Figure 19.1. SFR Page Stack
Upon an interrupt, hardware performs the five following operations:
1. The value (if any) in the SFRPGIDX = 011b location is pushed to the SFRPAGE = 100b location.
2. The value (if any) in the SFRPGIDX = 010b location is pushed to the SFRPAGE = 011b location.
3. The value (if any) in the SFRPGIDX = 001b location is pushed to the SFRPAGE = 010b location.
4. The current SFRPAGE value is pushed to the SFRPGIDX = 001b location in the stack.
5. SFRPAGE is set to the page corresponding to the flag which generated the interrupt.
On a return from interrupt, hardware performs the four following operations:
1. The SFR page stack is popped resulting in the value in the SFRPGIDX = 001b location returning to the
SFRPAGE register, thereby restoring the SFR page context without software intervention.
2. The value in the SFRPGIDX = 010b location of the stack is placed in the SFRPGIDX = 001b location.
3. The value in the SFRPGIDX = 011b location of the stack is placed in the SFRPGIDX = 010b location.
4. The value in the SFRPGIDX = 100b location of the stack is placed in the SFRPGIDX = 011b location.
Automatic switching of the SFR page by hardware upon interrupt entries and exits may be enabled or disabled using the SFR Automatic Page Control Enable Bit (SFRPGEN) located in SFRPGCN. The automatic
SFR page switching is enabled after a reset until disabled by firmware.
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19.3. SFR Page Stack Example
In this example, the SFR Control register is left in the default enabled state (SFRPGEN set to 1), and the
core is executing in-line code that is writing values to Temperature Sensor Control Register (TS0CN). The
device is also using the SPI peripheral (SPI0) and the Programmable Counter Array (PCA0) peripheral to
generate a PWM output. The PCA is timing a critical control function in its interrupt service routine, therefore, its associated ISR is set to high priority. At this point, the SFR page is set to 0x0F to access the
TS0CN SFR. See Figure 19.2.
SFRPGIDX[2:0]
SFRPAGE = 0x0F
(TS0CN)
000
001
010
SFRSTACK
011
100
Figure 19.2. SFR Page Stack While Using SFR Page 0x0F To Access TS0CN
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C8051F39x/37x
The SPI0 interrupt occurs while the core executes in-line code by writing a value to TS0CN. The core vectors to the SPI0 ISR and pushes the current SFR page value (in this case SFR page 0x0F for TS0CN) into
the 001b SFRPGIDX location in the SFR page stack. Also, the core automatically places the SFR page
(0x00) needed to access the SPI0’s special function registers into the SFRPAGE register. See Figure 19.3.
SFRPAGE is considered the top of the SFR page stack. Software may switch to any SFR page by writing
a new value to the SFRPAGE register at any time during the SPI0 ISR.
SFRPGIDX[2:0]
2) SFRPAGE automatically set
to 0x00 on SPI0 interrupt
1) SFRPAGE is pushed to
SFRPGIDX = 001b location
SFRPAGE = 0x00
(SPIO0)
0x0F
(TS0CN)
000
001
010
SFRSTACK
011
100
Figure 19.3. SFR Page Stack After SPI0 Interrupt Occurs
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While in the SPI0 ISR, a PCA interrupt occurs. Recall the PCA interrupt is configured as a high priority
interrupt, while the SPI0 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 value that was in the SFRPGIDX = 001b location before
the PCA interrupt (in this case SFR page 0x0F for TS0CN) is pushed down to the SFRPGIDX = 010b location. Likewise, the value that was in the SFRPAGE register before the PCA interrupt (SFR page 0x00 for
SPI0) is pushed down the stack into the SFRPGIDX = 001b location. Lastly, the CIP-51 will automatically
places the SFR page needed to access the PCA0’s special function registers into the SFRPAGE register,
SFR page 0x00. See Figure 19.4.
SFRPGIDX[2:0]
3) SFRPAGE automatically set
to 0x00 on PCA0 interrupt
2) SFRPAGE is pushed to
SFRPGIDX = 001b location
1) Value at SFRPGIDX = 001b location is
pushed to SFRPGIDX = 010b location
SFRPAGE = 0x00
(PCA0)
0x00
(SPI0)
0x0F
(TS0CN)
000
001
010
SFRSTACK
011
100
Figure 19.4. SFR Page Stack Upon PCA Interrupt Occurring During a SPI0 ISR
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On exit from the PCA0 interrupt service routine, the CIP-51 will return to the SPI0 ISR. On execution of the
RETI instruction, SFR page 0x00 used to access the PCA0 registers will be automatically popped off of the
SFR page stack, and the contents at the SFRPGIDX = 001b location will be moved to the SFRPAGE register. Software in the SPI0 ISR can continue to access SFRs as it did prior to the PCA interrupt. Likewise,
the contents at the SFRPGIDX = 010b location are moved to the SFRPGIDX = 001b location. Recall this
was the SFR Page value 0x0F being used to access TS0CN before the SPI0 interrupt occurred. See
Figure 19.5.
SFRPGIDX[2:0]
1) SFR page 0x00 from PCA0 ISR automatically
popped off on return from interrupt
2) Value at SFRPGIDX = 001b location is
popped to SFRPAGE
3) Value at SFRPGIDX = 001b location is
popped to SFRPGIDX = 010b location
SFRPAGE = 0x00
(SPI0)
0x0F
(TS0CN)
000
001
010
011
100
Figure 19.5. SFR Page Stack Upon Return from PCA0 Interrupt
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SFRSTACK
C8051F39x/37x
On the execution of the RETI instruction in the SPI0 ISR, the value in SFRPAGE register is overwritten
with the contents at the SFRPGIDX = 001b location. The CIP-51 may now access the TS0CN register as it
did prior to the interrupts occurring. See Figure 19.6.
SFRPGIDX[2:0]
1) SFR page 0x00 from SPI0 ISR automatically
popped off on return from interrupt
2) Value at SFRPGIDX = 001b location is
popped to SFRPAGE
SFRPAGE = 0x0F
(TS0CN)
000
001
010
SFRSTACK
011
100
Figure 19.6. SFR Page Stack Upon Return From SPI0 Interrupt
Push operations on the SFR page stack only occur on interrupt service, and pop operations 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).
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SFR Definition 19.1. SFRPAGE: SFR Page
Bit
7
6
5
4
3
Name
SFRPAGE[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address = 0xA7; SFR Page = All Pages
Bit
Name
7:0
SFRPAGE[7:0]
Function
SFR Page Bits.
Represents the SFR Page the C8051 core uses when
reading or modifying SFRs.
Write: Sets the SFR Page.
Read: Byte is the SFR page the C8051 core is using.
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SFR Definition 19.2. SFRPGCN: SFR Page Control
Bit
7
6
5
4
3
2
1
SFRPGIDX[2:0]
Name
Type
R/W
Reset
0
SFRPGEN
R/W
0
0
0
0
R/W
R/W
R/W
R/W
0
0
0
1
SFR Address = 0xCF; SFR Page = All Pages
Bit
Name
7
6:4
Reserved
SFRPGIDX[2:0]
Function
Must Write 0b
SFR Page Stack Index.
This field can be used to access the SFRPAGE values stored in
the SFR page stack. It selects which level of the stack is accessible when reading the SFRSTACK register.
000: SFRSTACK contains the value of SFRPAGE, the first/top
byte of the SFR page stack
001: SFRSTACK contains the value of the second byte of the SFR
page stack
010: SFRSTACK contains the value of the third byte of the SFR
page stack
011: SFRSTACK contains the value of the forth byte of the SFR
page stack
100: SFRSTACK contains the value of the fifth/bottom byte of the
SFR page stack
101: Invalid index
11x: Invalid index
3:1
0
Reserved
SFRPGEN
Must Write 000b
SFR Automatic Page Control Enable.
This bit is used to enable automatic page switching on ISR entry/
exit. When set to 1, the current SFRPAGE value will be pushed
onto the SFR page stack, and SFRPAGE will be set to the page
corresponding to the flag which generated the interrupt; upon ISR
exit, hardware will pop the value from the SFR page stack and
restore SFRPAGE.
0: Disable automatic SFR paging.
1: Enable automatic SFR paging.
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SFR Definition 19.3. SFRSTACK: SFR Page Stack
Bit
7
6
5
4
3
Name
SFRSTACK
Type
R
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address = 0xD3; SFR Page = F
Bit
Name
7:0
SFRSTACK
Function
SFR Page Stack.
This register is used to access the contents of the SFR
page stack. SFRPGIDX in the SFRPGCN register controls which level of the stack this register will access.
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Page
Address
Table 19.2. Special Function Register (SFR) Memory Map
F8
F0
E8
E0
1(9)
2(A)
3(B)
4(C)
SPI0CN PCA0L
PCA0H PCA0CPL0 PCA0CPH0
B
P0MDIN
P1MDIN
P2MDIN
CKCON1
ADC0CN PCA0CPL1 PCA0CPH1 PCA0CPL2 PCA0CPH2
0
F
D8
D0
0(8)
ACC
XBR0
PCA0CN PCA0MD
0
F
PSW
REF0CN
5(D)
6(E)
7(F)
P0MAT
P0MASK VDM0CN
EIP1
PCA0PWM
P1MAT
P1MASK RSTSRC
SMB0ADM
XBR1
OSCLCN
IT01CF
EIE1
SMB1ADM
PCA0CPM0 PCA0CPM1 PCA0CPM2 CRC0AUTO CRC0CNT CRC0CN
TS0DATL TS0DATH
SMB0ADR
P0SKIP
P1SKIP
P2SKIP
TS0CN SFRSTACK
SMB1ADR
TMR2RLL TMR2RLH
TMR2L
TMR2H
PCA0CLR SFRPGCN
TMR5RLL TMR5RLH
TMR5L
TMR5H
SMB0DAT
ADC0GTL ADC0GTH ADC0LTL ADC0LTH
SMBTC
SMB1DAT
TMR2CN
REG0CN
TMR5CN
0 SMB0CN SMB0CF
C0
F SMB1CN SMB1CF
0
IDA0CN
B8
IP
AMX0N
AMX0P
ADC0CF
ADC0L
ADC0H
EIP2
F
IDA1CN
B0
OSCXCN OSCICN
OSCICL
PFE0CN
FLSCL
FLKEY
0
DERIVID REVISION
A8
IE
CLKSEL
EMI0CN
EIE2
F
SN0
SN1
SN2
SN3
A0
P2
SPI0CFG SPI0CKR SPI0DAT P0MDOUT P1MDOUT P2MDOUT SFRPAGE
98
SCON0
SBUF0 CRC0FLIP CPT0CN
CRC0IN
CPT0MD CRC0DAT CPT0MX
0
TMR3CN TMR3RLL TMR3RLH
TMR3L
TMR3H
IDA0L
IDA0H
90
P1
F
TMR4CN TMR4RLL TMR4RLH
TMR4L
TMR4H
IDA1L
IDA1H
88
TCON
TMOD
TL0
TL1
TH0
TH1
CKCON
PSCTL
80
P0
SP
DPL
DPH
IPH
EIP1H
EIP2H
PCON
0(8)
1(9)
2(A)
3(B)
4(C)
5(D)
6(E)
7(F)
C8
Notes:
1. SFR Addresses ending in 0x0 or 0x8 are bit-addressable locations and can be used with bitwise instructions.
2. Unless indicated otherwise, SFRs are available on both page 0 and page F.
Preliminary Rev. 0.71
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C8051F39x/37x
Table 19.3. Special Function Registers
SFRs are listed in alphabetical order. All undefined SFR locations are reserved
Register
Address SFR Page Description
Page
ACC
0xE0
All Pages Accumulator
87
ADC0CF
0xBC
All Pages ADC0 Configuration
53
ADC0CN
0xE8
All Pages ADC0 Control
55
ADC0GTH
0xC4
All Pages ADC0 Greater-Than Compare High
56
ADC0GTL
0xC3
All Pages ADC0 Greater-Than Compare Low
56
ADC0H
0xBE
All Pages ADC0 High
54
ADC0L
0xBD
All Pages ADC0 Low
54
ADC0LTH
0xC6
All Pages ADC0 Less-Than Compare Word High
57
ADC0LTL
0xC5
All Pages ADC0 Less-Than Compare Word Low
57
AMX0N
0xBA
All Pages AMUX0 Negative Channel Select
61
AMX0P
0xBB
All Pages AMUX0 Positive Channel Select
60
B
0xF0
All Pages B Register
88
CKCON
0x8E
All Pages Clock Control
241
CKCON1
0xF4
All Pages Clock Control 1
242
CLKSEL
0xA9
All Pages Clock Select
163
CPT0CN
0x9B
All Pages Comparator0 Control
76
CPT0MD
0x9D
All Pages Comparator0 Mode Selection
77
CPT0MX
0x9F
All Pages Comparator0 MUX Selection
79
CRC0AUTO
0xDD
All Pages CRC0 Automatic Control
150
CRC0CN
0xDF
All Pages CRC0 Control
148
CRC0CNT
0xDE
All Pages CRC0 Automatic Flash Sector Count
151
CRC0DAT
0x9E
All Pages CRC0 Data Output
149
CRC0FLIP
0x9A
All Pages CRC0 Bit Flip
152
CRC0IN
0x9C
All Pages CRC0 Data Input
149
DERIVID
0xAB
DPH
0x83
All Pages Data Pointer High
86
DPL
0x82
All Pages Data Pointer Low
86
EIE1
0xE6
All Pages Extended Interrupt Enable 1
121
EIE2
0xAF
All Pages Extended Interrupt Enable 2
124
EIP1
0xF6
All Pages Extended Interrupt Priority 1
122
EIP1H
0x85
All Pages Extended Interrupt Priority 1 High
123
EIP2
0xBF
All Pages Extended Interrupt Priority 2
125
EIP2H
0x86
All Pages Extended Interrupt Priority 2 High
125
110
0
Device Derivative ID
Preliminary Rev. 0.71
95
C8051F39x/37x
Table 19.3. Special Function Registers (Continued)
SFRs are listed in alphabetical order. All undefined SFR locations are reserved
Register
Address SFR Page Description
Page
EMI0CN
0xAA
All Pages External Memory Interface Control
94
FLKEY
0xB7
All Pages Flash Lock and Key
136
FLSCL
0xB6
All Pages Flash Scale
137
IDA0CN
0xB9
0
Current Mode DAC0 Control
67
IDA0H
0x97
0
Current Mode DAC0 High
68
IDA0L
0x96
0
Current Mode DAC0 Low
68
IDA1CN
0xB9
F
Current Mode DAC1 Control
69
IDA1H
0x97
F
Current Mode DAC1 High
70
IDA1L
0x96
F
Current Mode DAC1 Low
70
IE
0xA8
All Pages Interrupt Enable
118
IP
0xB8
All Pages Interrupt Priority
119
IPH
0x84
All Pages Interrupt Priority High
120
IT01CF
0xE4
All Pages INT0/INT1 Configuration
127
OSCICL
0xB3
All Pages Internal Oscillator Calibration
164
OSCICN
0xB2
All Pages Internal Oscillator Control
165
OSCLCN
0xE3
All Pages Low-Frequency Oscillator Control
166
OSCXCN
0xB1
All Pages External Oscillator Control
170
P0
0x80
All Pages Port 0 Latch
184
P0MASK
0xFE
All Pages Port 0 Mask Configuration
181
P0MAT
0xFD
All Pages Port 0 Match Configuration
182
P0MDIN
0xF1
All Pages Port 0 Input Mode Configuration
184
P0MDOUT
0xA4
All Pages Port 0 Output Mode Configuration
185
P0SKIP
0xD4
All Pages Port 0 Skip
185
P1
0x90
All Pages Port 1 Latch
186
P1MASK
0xEE
All Pages Port 1Mask Configuration
182
P1MAT
0xED
All Pages Port 1 Match Configuration
183
P1MDIN
0xF2
All Pages Port 1 Input Mode Configuration
186
P1MDOUT
0xA5
All Pages Port 1 Output Mode Configuration
187
P1SKIP
0xD5
All Pages Port 1 Skip
187
P2
0xA0
All Pages Port 2 Latch
188
P2MDIN
0xF3
All Pages Port 2 Input Mode Configuration
188
P2MDOUT
0xA6
All Pages Port 2 Output Mode Configuration
189
P2SKIP
0xD6
All Pages Port 2 Skip
189
PCA0CLR
0xCE
All Pages PCA Comparator Clear Control
291
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Table 19.3. Special Function Registers (Continued)
SFRs are listed in alphabetical order. All undefined SFR locations are reserved
Register
Address SFR Page Description
Page
PCA0CN
0xD8
All Pages PCA Control
288
PCA0CPH0
0xFC
All Pages PCA Capture 0 High
294
PCA0CPH1
0xEA
All Pages PCA Capture 1 High
294
PCA0CPH2
0xEC
All Pages PCA Capture 2 High
294
PCA0CPL0
0xFB
All Pages PCA Capture 0 Low
294
PCA0CPL1
0xE9
All Pages PCA Capture 1 Low
294
PCA0CPL2
0xEB
All Pages PCA Capture 2 Low
294
PCA0CPM0
0xDA
All Pages PCA Module 0 Mode Register
292
PCA0CPM1
0xDB
All Pages PCA Module 1 Mode Register
292
PCA0CPM2
0xDC
All Pages PCA Module 2 Mode Register
292
PCA0H
0xFA
All Pages PCA Counter High
293
PCA0L
0xF9
All Pages PCA Counter Low
293
PCA0MD
0xD9
All Pages PCA Mode
289
PCA0PWM
0xF7
All Pages PCA PWM Configuration
290
PCON
0x87
All Pages Power Control
161
PFE0CN
0xB5
All Pages Prefetch Engine Control
90
PSCTL
0x8F
All Pages Program Store R/W Control
135
PSW
0xD0
All Pages Program Status Word
89
REF0CN
0xD1
All Pages Voltage Reference Control
72
REG0CN
0xC9
All Pages Voltage Regulator Control
73
REVISION
0xAC
RSTSRC
0xEF
All Pages Reset Source Configuration/Status
158
SBUF0
0x99
All Pages UART0 Data Buffer
224
SCON0
0x98
All Pages UART0 Control
223
SFRPAGE
0xBF
All Pages SFR Page
106
SFRPGCN
0xBF
All Pages SFR Page Control
107
SFRSTACK
0xBF
F
SFR Page Stack
108
SMB0ADM
0xE7
0
SMBus0 Slave Address Mask
204
SMB0ADR
0xD7
0
SMBus0 Slave Address
203
SMB0CF
0xC1
0
SMBus0 Configuration
196
SMB0CN
0xC0
0
SMBus0 Control
200
SMB0DAT
0xC2
0
SMBus0 Data
207
SMB1ADM
0xE7
F
SMBus1 Slave Address Mask
206
SMB1ADR
0xD7
F
SMBus1 Slave Address
205
112
0
Device Revision
Preliminary Rev. 0.71
96
C8051F39x/37x
Table 19.3. Special Function Registers (Continued)
SFRs are listed in alphabetical order. All undefined SFR locations are reserved
Register
Address SFR Page Description
Page
SMB1CF
0xC1
F
SMBus1 Configuration
197
SMB1CN
0xC0
F
SMBus1 Control
201
SMB1DAT
0xC2
F
SMBus1 Data
208
SMBTC
0xC7
SN0
0xAB
F
Serial Number Byte 0
98
SN1
0xAC
F
Serial Number Byte 1
97
SN2
0xAD
F
Serial Number Byte 2
97
SN3
0xAE
F
Serial Number Byte 3
96
SP
0x81
All Pages Stack Pointer
87
SPI0CFG
0xA1
All Pages SPI Configuration
233
SPI0CKR
0xA2
All Pages SPI Clock Rate Control
235
SPI0CN
0xF8
All Pages SPI Control
234
SPI0DAT
0xA3
All Pages SPI Data
236
TCON
0x88
All Pages Timer/Counter Control
247
TH0
0x8C
All Pages Timer/Counter 0 High
250
TH1
0x8D
All Pages Timer/Counter 1 High
250
TL0
0x8A
All Pages Timer/Counter 0 Low
249
TL1
0x8B
All Pages Timer/Counter 1 Low
249
TMOD
0x89
All Pages Timer/Counter Mode
248
TMR2CN
0xC8
0
Timer/Counter 2 Control
254
TMR2H
0xCD
0
Timer/Counter 2 High
256
TMR2L
0xCC
0
Timer/Counter 2 Low
255
TMR2RLH
0xCB
0
Timer/Counter 2 Reload High
255
TMR2RLL
0xCA
0
Timer/Counter 2 Reload Low
255
TMR3CN
0x91
0
Timer/Counter 3 Control
260
TMR3H
0x95
0
Timer/Counter 3 High
262
TMR3L
0x94
0
Timer/Counter 3 Low
261
TMR3RLH
0x93
0
Timer/Counter 3 Reload High
261
TMR3RLL
0x92
0
Timer/Counter 3 Reload Low
261
TMR4CN
0x91
F
Timer/Counter 4 Control
265
TMR4H
0x95
F
Timer/Counter 4 High
267
TMR4L
0x94
F
Timer/Counter 4 Low
266
TMR4RLH
0x93
F
Timer/Counter 4 Reload High
266
TMR4RLL
0x92
F
Timer/Counter 4 Reload Low
266
All Pages SMBus Timing Control
Preliminary Rev. 0.71
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C8051F39x/37x
Table 19.3. Special Function Registers (Continued)
SFRs are listed in alphabetical order. All undefined SFR locations are reserved
Register
Address SFR Page Description
Page
TMR5CN
0xC8
F
Timer/Counter 5 Control
270
TMR5H
0xCD
F
Timer/Counter 5 High
272
TMR5L
0xCC
F
Timer/Counter 5 Low
271
TMR5RLH
0xCB
F
Timer/Counter 5 Reload High
271
TMR5RLL
0xCA
F
Timer/Counter 5 Reload Low
271
TS0CN
0xD2
F
Temperature Sensor Control
46
TS0DATH
0xD3
0
Temperature Sensor Data High
47
TS0DATL
0xD2
0
Temperature Sensor Data Low
47
VDM0CN
0xFF
All Pages VDD Monitor Control
156
XBR0
0xE1
All Pages Port I/O Crossbar Control 0
179
XBR1
0xE2
All Pages Port I/O Crossbar Control 1
180
114
Preliminary Rev. 0.71
C8051F39x/37x
20. Interrupts
The C8051F39x/37x includes an extended interrupt system supporting multiple interrupt sources with four
priority levels. The allocation of interrupt sources between on-chip peripherals and external input pins varies according to the specific version of the device. Each interrupt source has one or more associated interrupt-pending flag(s) located in an SFR. When a peripheral or external source meets a valid interrupt
condition, the associated interrupt-pending flag is set to logic 1.
If interrupts are enabled for the source, an interrupt request is generated when the interrupt-pending flag is
set. As soon as execution of the current instruction is complete, the CPU generates an LCALL to a predetermined address to begin execution 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 had not occurred. If interrupts are not enabled, the interrupt-pending flag is ignored by the
hardware and program execution continues as normal. (The interrupt-pending flag is set to logic 1 regardless 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, EIE1, and EIE2). However, interrupts must first be globally enabled by setting the
EA bit (IE.7) to logic 1 before the individual interrupt enables are recognized. Setting the EA bit to logic 0
disables all interrupt sources regardless of the individual interrupt-enable settings.
Note: Any instruction that clears a bit to disable an interrupt should be immediately followed by an instruction that has two or more opcode bytes. Using EA (global interrupt enable) as an example:
// in 'C':
EA = 0; // clear EA bit.
EA = 0; // this is a dummy instruction with two-byte opcode.
; in assembly:
CLR EA ; clear EA bit.
CLR EA ; this is a dummy instruction with two-byte opcode.
For example, if an interrupt is posted during the execution phase of a "CLR EA" opcode (or any instruction
which clears a bit to disable an interrupt source), and the instruction is followed by a single-cycle instruction, the interrupt may be taken. However, a read of the enable bit will return a '0' inside the interrupt service routine. When the bit-clearing opcode is followed by a multi-cycle instruction, the interrupt will not be
taken.
Some interrupt-pending flags are automatically cleared by the hardware when the CPU vectors to the ISR.
However, most are not cleared by the hardware and must be cleared by software before 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.
Preliminary Rev. 0.71
115
C8051F39x/37x
20.1. MCU Interrupt Sources and Vectors
The C8051F39x/37x MCUs support 18 interrupt sources. Software can simulate an interrupt 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 20.2. Refer
to the datasheet section associated with a particular on-chip peripheral for information regarding valid
interrupt conditions for the peripheral and the behavior of its interrupt-pending flag(s).
20.1.1. Interrupt Priorities
Each interrupt source can be individually programmed to one of four priority levels. This differs from the
traditional two priority levels on the 8051 core. However, the implementation of the extra levels is backwards-compatible with legacy 8051 code.
An interrupt service routine can be preempted by any interrupt of higher priority. Interrupts at the highest
priority level cannot be preempted. Each interrupt has two associated priority bits which are used to configure the priority level. For backwards compatibility, the bits are spread across two different registers. The
LSBs of the priority setting are stored in the IP, EIP1 and EIP2 registers, while the MSBs are store in the
IPH, EIP1H and EIP2H registers. Priority levels according to the MSB and LSB are decoded in Table 20.1.
The lowest priority setting is the default for all interrupts. If two or more interrupts are recognized simultaneously, the interrupt with the highest priority is serviced first. If both interrupts have the same priority level,
a fixed priority order is used to arbitrate, given in Table 20.2. If legacy 8051 operation is desired, the bits of
the “High” priority registers (IPH, EIP1H and EIP2H) should all be configured to 0 (this is the reset value of
these registers).
Priority MSB
(from IPH, EIP1H or
EIP2H)
Priority LSB
(from IP, EIP1 or
EIP2)
0
0
1
1
0
1
0
1
Priority Level
Priority 0 (lowest priority, default)
Priority 1
Priority 2
Priority 3 (highest priority)
Table 20.1. Configurable Interrupt Priority Decoding
20.1.2. Interrupt Latency
Interrupt response time depends on the state of the CPU when the interrupt occurs. Pending interrupts are
sampled and priority decoded each system clock cycle. Therefore, 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 the
ISR. If an interrupt is pending when a RETI is executed, a single instruction is executed before an LCALL
is made to service the pending interrupt. Therefore, the maximum response time for an interrupt (when no
other interrupt is currently being serviced or the new interrupt is of greater priority) occurs when the CPU is
performing 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 clock 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. If more than one interrupt is pending
when the CPU exits an ISR, the CPU will service the next highest priority interrupt that is pending.
116
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C8051F39x/37x
Interrupt
Vector
Priority
Order
Pending Flags
Reset
0x0000
Top
None
N/A N/A Always Enabled
External Interrupt 0 (INT0) 0x0003
0
IE0 (TCON.1)
Y
Y
EX0 (IE.0)
0x000B
1
TF0 (TCON.5)
Y
Y
ET0 (IE.1)
External Interrupt 1 (INT1) 0x0013
2
IE1 (TCON.3)
Y
Y
EX1 (IE.2)
Timer 1 Overflow
0x001B
3
TF1 (TCON.7)
Y
Y
ET1 (IE.3)
UART0
0x0023
4
RI0 (SCON0.0)
TI0 (SCON0.1)
Y
N
ES0 (IE.4)
Timer 2 Overflow
0x002B
5
TF2H (TMR2CN.7)
TF2L (TMR2CN.6)
Y
N
ET2 (IE.5)
SPI0
0x0033
6
SPIF (SPI0CN.7)
WCOL (SPI0CN.6)
MODF (SPI0CN.5)
RXOVRN (SPI0CN.4)
Y
N
ESPI0 (IE.6)
SMB0
0x003B
7
SI (SMB0CN.0)
Y
N
ESMB0 (EIE1.0)
Port Match
0x0043
8
None
N/A N/A EMAT (EIE1.1)
ADC0 Window Compare
0x004B
9
AD0WINT (ADC0CN.3) Y
N
EWADC0
(EIE1.2)
ADC0 Conversion Complete
0x0053
10
AD0INT (ADC0CN.5)
Y
N
EADC0 (EIE1.3)
Programmable Counter
Array
0x005B
11
CF (PCA0CN.7)
CCFn (PCA0CN.n)
COVF (PCA0PWM.6)
Y
N
EPCA0 (EIE1.4)
Comparator0
0x0063
12
CP0FIF (CPT0CN.4)
CP0RIF (CPT0CN.5)
N
N
ECP0 (EIE1.5)
Reserved
0x006B
13
N/A
N/A N/A N/A
Timer 3 Overflow
0x0073
14
TF3H (TMR3CN.7)
TF3L (TMR3CN.6)
N
N
ET3 (EIE1.7)
SMB1
0x007B
15
SI (SMB0CN.0)
Y
N
ESMB0 (EIE2.0)
Timer 4 Overflow
0x0083
16
TF4H (TMR4CN.7)
TF4L (TMR4CN.6)
Y
N
ET4 (EIE2.1)
Timer 5 Overflow
0x008B
17
TF5H (TMR5CN.7)
TF5L (TMR5CN.6)
N
N
ET5 (EIE2.2)
Precision Temp Sensor
0x0093
18
TS0DN (TS0CN.6)
N
N
EPTS (EIE2.3)
Timer 0 Overflow
Preliminary Rev. 0.71
Cleared by HW?
Interrupt Source
Bit addressable?
Table 20.2. Interrupt Summary
Enable Flag
117
C8051F39x/37x
20.2. Interrupt Register Descriptions
The SFRs used to enable the interrupt sources and set their priority level are described in this section.
Refer to the data sheet section associated with a particular on-chip peripheral for information regarding
valid interrupt conditions for the peripheral and the behavior of its interrupt-pending flag(s).
SFR Definition 20.1. IE: Interrupt Enable
Bit
7
6
5
4
3
2
1
0
Name
EA
ESPI0
ET2
ES0
ET1
EX1
ET0
EX0
Type
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
SFR Address = 0xA8; SFR Page = All Pages; Bit-Addressable
Bit
Name
7
EA
6
ESPI0
5
ET2
Enable 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 TF2L or TF2H flags.
4
ES0
Enable UART0 Interrupt.
This bit sets the masking of the UART0 interrupt.
0: Disable UART0 interrupt.
1: Enable UART0 interrupt.
3
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.
2
EX1
Enable External Interrupt 1.
This bit sets the masking of External Interrupt 1.
0: Disable external interrupt 1.
1: Enable interrupt requests generated by the /INT1 input.
1
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.
0
EX0
Enable External Interrupt 0.
This bit sets the masking of External Interrupt 0.
0: Disable external interrupt 0.
1: Enable interrupt requests generated by the INT0 input.
118
Function
Enable All Interrupts.
Globally enables/disables all interrupts. It overrides individual interrupt mask settings.
0: Disable all interrupt sources.
1: Enable each interrupt according to its individual mask setting.
Enable Serial Peripheral Interface (SPI0) Interrupt.
This bit sets the masking of the SPI0 interrupts.
0: Disable all SPI0 interrupts.
1: Enable interrupt requests generated by SPI0.
Preliminary Rev. 0.71
C8051F39x/37x
SFR Definition 20.2. IP: Interrupt Priority
Bit
7
Name
6
5
4
3
2
1
0
PSPI0
PT2
PS0
PT1
PX1
PT0
PX0
Type
R
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
1
0
0
0
0
0
0
0
SFR Address = 0xB8; SFR Page = All Pages; Bit-Addressable
Bit
Name
Function
7
6
Unused
PSPI0
5
PT2
Timer 2 Interrupt Priority Control LSB.
This bit sets the LSB of the priority field for the Timer 2 interrupt.
4
PS0
UART0 Interrupt Priority Control LSB.
This bit sets the LSB of the priority field for the UART0 interrupt.
3
PT1
Timer 1 Interrupt Priority Control LSB.
This bit sets the LSB of the priority field for the Timer 1 interrupt.
2
PX1
External Interrupt 1 Priority Control LSB.
This bit sets the LSB of the priority field for the External Interrupt 1
interrupt.
1
PT0
Timer 0 Interrupt Priority Control LSB.
This bit sets the LSB of the priority field for the Timer 0 interrupt.
0
PX0
External Interrupt 0 Priority Control LSB.
This bit sets the LSB of the priority field for the External Interrupt 0
interrupt.
Read = 1, Write = Don't Care.
Serial Peripheral Interface (SPI0) Interrupt Priority Control
LSB.
This bit sets the LSB of the priority field for the SPI0 interrupt.
Preliminary Rev. 0.71
119
C8051F39x/37x
SFR Definition 20.3. IPH: Interrupt Priority High
Bit
7
Name
6
5
4
3
2
1
0
PHSPI0
PHT2
PHS0
PHT1
PHX1
PHT0
PHX0
Type
R
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
1
0
0
0
0
0
0
0
SFR Address = 0x84; SFR Page = All Pages; Bit-Addressable
120
Bit
Name
Function
7
6
Unused
PHSPI0
5
PHT2
Timer 2 Interrupt Priority Control MSB.
This bit sets the MSB of the priority field for the Timer 2 interrupt.
4
PHS0
UART0 Interrupt Priority Control MSB.
This bit sets the MSB of the priority field for the UART0 interrupt.
3
PHT1
Timer 1 Interrupt Priority Control MSB.
This bit sets the MSB of the priority field for the Timer 1 interrupt.
2
PHX1
External Interrupt 1 Priority Control MSB.
This bit sets the MSB of the priority field for the External Interrupt 1 interrupt.
1
PHT0
Timer 0 Interrupt Priority Control MSB.
This bit sets the MSB of the priority field for the Timer 0 interrupt.
0
PHX0
External Interrupt 0 Priority Control MSB.
This bit sets the MSB of the priority field for the External Interrupt 0 interrupt.
Read = 1, Write = Don't Care.
Serial Peripheral Interface (SPI0) Interrupt Priority Control MSB.
This bit sets the MSB of the priority field for the SPI0 interrupt.
Preliminary Rev. 0.71
C8051F39x/37x
SFR Definition 20.4. EIE1: Extended Interrupt Enable 1
Bit
7
6
Name
ET3
Type
R/W
Reset
0
5
4
3
2
1
0
ECP0
EPCA0
EADC0
EWADC0
EMAT
ESMB0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
SFR Address = 0xE6; SFR Page = All Pages
Bit
Name
Function
7
ET3
6
5
Reserved
ECP0
4
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.
3
EADC0
Enable ADC0 Conversion Complete Interrupt.
This bit sets the masking of the ADC0 Conversion Complete interrupt.
0: Disable ADC0 Conversion Complete interrupt.
1: Enable interrupt requests generated by the AD0INT flag.
2
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 Compare flag
(AD0WINT).
1
EMAT
0
ESMB0
Enable Timer 3 Interrupt.
This bit sets the masking of the Timer 3 interrupt.
0: Disable Timer 3 interrupts.
1: Enable interrupt requests generated by the TF3L or TF3H flags.
Reserved. Must Write 0.
Enable Comparator0 (CP0) Interrupt.
This bit sets the masking of the CP0 interrupt.
0: Disable CP0 interrupts.
1: Enable interrupt requests generated by the CP0RIF or CP0FIF flags.
Enable Port Match Interrupts.
This bit sets the masking of the Port Match Event interrupt.
0: Disable all Port Match interrupts.
1: Enable interrupt requests generated by a Port Match.
Enable SMBus (SMB0) Interrupt.
This bit sets the masking of the SMB0 interrupt.
0: Disable all SMB0 interrupts.
1: Enable interrupt requests generated by SMB0.
Preliminary Rev. 0.71
121
C8051F39x/37x
SFR Definition 20.5. EIP1: Extended Interrupt Priority 1
Bit
7
Name
PT3
Type
R/W
Reset
0
6
5
4
3
2
1
0
PCP0
PPCA0
PADC0
PWADC0
PMAT
PSMB0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
SFR Address = 0xF6; SFR Page = All Pages
122
Bit
Name
Function
7
PT3
6
5
Reserved
PCP0
4
PPCA0
Programmable Counter Array (PCA0) Interrupt Priority
Control LSB.
This bit sets the LSB of the priority field for the PCA0 interrupt.
3
PADC0
ADC0 Conversion Complete Interrupt Priority Control LSB.
This bit sets the LSB of the priority field for the ADC0 Conversion
Complete interrupt.
2
PWADC0
1
PMAT
0
PSMB0
Timer 3 Interrupt Priority Control LSB.
This bit sets the LSB of the priority field for the Timer 3 interrupt.
Reserved. Must Write 0.
Comparator0 (CP0) Interrupt Priority Control LSB.
This bit sets the LSB of the priority field for the CP0 interrupt.
ADC0 Window Comparator Interrupt Priority Control LSB.
This bit sets the LSB of the priority field for the ADC0 Window
interrupt.
Port Match Interrupt Priority Control LSB.
This bit sets the LSB of the priority field for the Port Match Event
interrupt.
SMBus (SMB0) Interrupt Priority Control LSB.
This bit sets the LSB of the priority field for the SMB0 interrupt.
Preliminary Rev. 0.71
C8051F39x/37x
SFR Definition 20.6. EIP1H: Extended Interrupt Priority 1 High
Bit
7
Name
PHT3
Type
R/W
Reset
0
6
5
4
3
PHCP0
PHPCA0
R/W
R/W
R/W
R/W
0
0
0
0
2
1
0
PHMAT
PHSMB0
R/W
R/W
R/W
0
0
0
PHADC0 PHWADC0
SFR Address = 0x85; SFR Page = All Pages
Bit
Name
Function
7
PHT3
Timer 3 Interrupt Priority Control MSB.
This bit sets the MSB of the priority field for the Timer 3 interrupt.
6
5
Reserved
PHCP0
Reserved. Must Write 0.
4
PHPCA0
Programmable Counter Array (PCA0) Interrupt Priority
Control MSB.
This bit sets the MSB of the priority field for the PCA0 interrupt.
3
PHADC0
ADC0 Conversion Complete Interrupt Priority Control MSB.
This bit sets the MSB of the priority field for the ADC0 Conversion
Complete interrupt.
2
PHWADC0
1
PHMAT
0
PHSMB0
Comparator0 (CP0) Interrupt Priority Control MSB.
This bit sets the MSB of the priority field for the CP0 interrupt.
ADC0 Window Comparator Interrupt Priority Control MSB.
This bit sets the MSB of the priority field for the ADC0 Window
interrupt.
Port Match Interrupt Priority Control MSB.
This bit sets the MSB of the priority field for the Port Match Event
interrupt.
SMBus (SMB0) Interrupt Priority Control MSB.
This bit sets the MSB of the priority field for the SMB0 interrupt.
Preliminary Rev. 0.71
123
C8051F39x/37x
SFR Definition 20.7. EIE2: Extended Interrupt Enable 2
Bit
7
6
5
4
Name
3
2
1
0
EPTS
ET5
ET4
ESMB1
Type
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
SFR Address = 0xAF; SFR Page = All Pages
124
Bit
Name
Function
7:4
3
Reserved
EPTS
2
ET5
Enable Timer 5 Interrupt.
This bit sets the masking of the Timer 5 interrupt.
0: Disable Timer 5 interrupts.
1: Enable interrupt requests generated by the TF5L or TF5H
flags.
1
ET4
Enable Timer 4 Interrupt.
This bit sets the masking of the Timer 4 interrupt.
0: Disable Timer 4 interrupts.
1: Enable interrupt requests generated by the TF4L or TF4H
flags.
0
ESMB1
Must Write 0000b.
Enable Precision Temperature Sensor Interrupt.
This bit sets the masking of the Precision Temperature Sensor
interrupt.
0: Disable Precision Temperature Sensor interrupts.
1: Enable interrupt requests generated by the Precision Temperature Sensor.
Enable SMBus (SMB1) Interrupt.
This bit sets the masking of the SMB1 interrupt.
0: Disable all SMB1 interrupts.
1: Enable interrupt requests generated by SMB1.
Preliminary Rev. 0.71
C8051F39x/37x
SFR Definition 20.8. EIP2: Extended Interrupt Priority 2
Bit
7
6
5
4
Name
3
2
1
0
PPTS
PT5
PT4
PSMB1
Type
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
SFR Address = 0xBF; SFR Page = All Pages
Bit
7:4
3
Name
Reserved
PPTS
2
PT5
1
PT4
0
PSMB1
Function
Must Write 0000b.
Precision Temperature Sensor Interrupt Priority Control LSB.
This bit sets the LSB of the priority field for the Precision Temperature Sensor interrupt.
Timer 5 Interrupt Priority Control LSB.
This bit sets the LSB of the priority field for the Timer 5 interrupt.
Timer 4 Interrupt Priority Control LSB.
This bit sets the LSB of the priority field for the Timer 4 interrupt.
SMBus (SMB1) Interrupt Priority Control LSB.
This bit sets the LSB of the priority field for the SMB1 interrupt.
SFR Definition 20.9. EIP2H: Extended Interrupt Priority 2 High
Bit
7
6
5
4
Name
3
2
1
0
PHPTS
PHT5
PHT4
PHSMB1
Type
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
SFR Address = 0x86; SFR Page = All Pages
Bit
7:4
3
Name
Reserved
PHPTS
2
PHT5
1
PHT4
0
PHSMB1
Function
Must Write 0000b.
Precision Temperature Sensor Interrupt Priority Control
MSB.
This bit sets the MSB of the priority field for the Precision Temperature Sensor interrupt.
Timer 5 Interrupt Priority Control MSB.
This bit sets the MSB of the priority field for the Timer 5 interrupt.
Timer 4 Interrupt Priority Control MSB.
This bit sets the MSB of the priority field for the Timer 4 interrupt.
SMBus (SMB1) Interrupt Priority Control MSB.
This bit sets the MSB of the priority field for the SMB1 interrupt.
Preliminary Rev. 0.71
125
C8051F39x/37x
20.3. External Interrupts INT0 and INT1
The INT0 and INT1 external interrupt sources are configurable as active high or low, edge or level sensitive. The IN0PL (INT0 Polarity) and IN1PL (INT1 Polarity) bits in the IT01CF register select active high or
active low; the IT0 and IT1 bits in TCON (Section “31.1. Timer 0 and Timer 1” on page 243) select level or
edge sensitive. The table below lists the possible configurations.
IT0
IN0PL
INT0 Interrupt
IT1
IN1PL
INT1 Interrupt
1
0
Active low, edge sensitive
1
0
Active low, edge sensitive
1
1
Active high, edge sensitive
1
1
Active high, edge sensitive
0
0
Active low, level sensitive
0
0
Active low, level sensitive
0
1
Active high, level sensitive
0
1
Active high, level sensitive
INT0 and INT1 are assigned to Port pins as defined in the IT01CF register (see SFR Definition 20.10).
Note that INT0 and INT1 Port pin assignments are independent of any Crossbar assignments. INT0 and
INT1 will monitor their assigned Port pins without disturbing the peripheral that was assigned the Port pin
via the Crossbar. To assign a Port pin only to INT0 and/or INT1, configure the Crossbar to skip the selected
pin(s). This is accomplished by setting the associated bit in register XBR0 (see Section “27.3. Priority
Crossbar Decoder” on page 176 for complete details on configuring the Crossbar).
IE0 (TCON.1) and IE1 (TCON.3) serve as the interrupt-pending flags for the INT0 and INT1 external interrupts, respectively. 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 remains logic 1 while the input is active as defined
by the corresponding polarity bit (IN0PL or IN1PL); the flag remains logic 0 while the input is inactive. The
external interrupt source must hold the input active until the interrupt request is recognized. It must then
deactivate the interrupt request before execution of the ISR completes or another interrupt request will be
generated.
126
Preliminary Rev. 0.71
C8051F39x/37x
SFR Definition 20.10. IT01CF: INT0/INT1 Configuration
Bit
7
6
Name
IN1PL
IN1SL[2:0]
IN0PL
IN0SL[2:0]
Type
R/W
R/W
R/W
R/W
Reset
0
0
5
4
0
0
3
0
2
0
1
0
0
1
SFR Address = 0xE4; SFR Page = All Pages
Preliminary Rev. 0.71
127
C8051F39x/37x
128
Bit
Name
7
IN1PL
6:4
IN1SL[2:0]
3
IN0PL
2:0
IN0SL[2:0]
Function
INT1 Polarity.
0: /INT1 input is active low.
1: /INT1 input is active high.
INT1 Port Pin Selection Bits.
These bits select which Port pin is assigned to /INT1. Note that
this pin assignment is independent of the Crossbar; /INT1 will
monitor the assigned Port pin without disturbing the peripheral
that has been assigned the Port pin via the Crossbar. The Crossbar will not assign the Port pin to a peripheral if it is configured to
skip the selected pin.
000: Select P0.0
001: Select P0.1
010: Select P0.2
011: Select P0.3
100: Select P0.4
101: Select P0.5
110: Select P0.6
111: Select P0.7
INT0 Polarity.
0: INT0 input is active low.
1: INT0 input is active high.
INT0 Port Pin Selection Bits.
These bits select which Port pin is assigned to INT0. Note that
this pin assignment is independent of the Crossbar; INT0 will
monitor the assigned Port pin without disturbing the peripheral
that has been assigned the Port pin via the Crossbar. The Crossbar will not assign the Port pin to a peripheral if it is configured to
skip the selected pin.
000: Select P0.0
001: Select P0.1
010: Select P0.2
011: Select P0.3
100: Select P0.4
101: Select P0.5
110: Select P0.6
111: Select P0.7
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21. Flash Memory
On-chip, re-programmable Flash memory is included for program code and non-volatile data storage. The
Flash memory can be programmed in-system, a single byte at a time, through the C2 interface or by software using the MOVX instruction. Once cleared to logic 0, a Flash bit must be erased to set it back to
logic 1. Flash bytes would typically be erased (set to 0xFF) before being reprogrammed. The write and
erase operations are automatically timed by hardware for proper execution; data polling to determine the
end of the write/erase operation is not required. Code execution is stalled during a Flash write/erase operation. Refer to Section “7. Electrical Characteristics” on page 32 for complete Flash memory electrical
characteristics.
21.1. Programming The Flash Memory
The simplest means of programming the Flash memory is through the C2 interface using programming
tools provided by Silicon Labs or a third party vendor. This is the only means for programming a non-initialized device. For details on the C2 commands to program Flash memory, see Section “33. C2 Interface” on
page 295.
To ensure the integrity of Flash contents, it is strongly recommended that the on-chip VDD Monitor be
enabled in any system that includes code that writes and/or erases Flash memory from software. See Section 21.4 for more details.
21.1.1. Flash Lock and Key Functions
Flash writes and erases by user software are protected with a lock and key function. The Flash Lock and
Key Register (FLKEY) must be written with the correct key codes, in sequence, before Flash operations
may be performed. The key codes are: 0xA5, 0xF1. The timing does not matter, but the codes must be
written in order. If the key codes are written out of order, or the wrong codes are written, Flash writes and
erases will be disabled until the next system reset. Flash writes and erases will also be disabled if a Flash
write or erase is attempted before the key codes have been written properly. The Flash lock resets after
each write or erase; the key codes must be written again before a following Flash operation can be performed. The FLKEY register is detailed in SFR Definition 21.2.
21.1.2. Flash Erase Procedure
The Flash memory can be programmed by software 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 operations must be enabled by: (1) setting the PSWE Program Store Write Enable bit
(PSCTL.0) to logic 1 (this directs the MOVX writes to target Flash memory); and (2) Writing the Flash key
codes in sequence to the Flash Lock register (FLKEY). The PSWE bit remains set until cleared by software.
A write to Flash memory can clear bits to logic 0 but cannot set them; only an erase operation can set bits
to logic 1 in Flash. A byte location to be programmed should be erased before a new value is written.
The Flash memory is organized in 512-byte pages. The erase operation applies to an entire page (setting
all bytes in the page to 0xFF). To erase an entire 512-byte page, perform the following steps:
1. Disable interrupts (recommended).
2. Set thePSEE bit (register PSCTL).
3. Set the PSWE bit (register PSCTL).
4. Write the first key code to FLKEY: 0xA5.
5. Write the second key code to FLKEY: 0xF1.
6. Using the MOVX instruction, write a data byte to any location within the 512-byte page to be erased.
7. Clear the PSWE and PSEE bits.
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21.1.3. Flash Write Procedure
Flash bytes are programmed by software with the following sequence:
1. Disable interrupts (recommended).
2. Erase the 512-byte Flash page containing the target location, as described in Section 21.1.2.
3. Set the PSWE bit (register PSCTL).
4. Clear the PSEE bit (register PSCTL).
5. Write the first key code to FLKEY: 0xA5.
6. Write the second key code to FLKEY: 0xF1.
7. Using the MOVX instruction, write a single data byte to the desired location within the 512-byte sector.
8. Clear the PSWE bit.
Steps 5–7 must be repeated for each byte to be written. After Flash writes are complete, PSWE should be
cleared so that MOVX instructions do not target program memory.
21.2. 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 and read using the MOVC instruction. Note: MOVX read instructions always target XRAM.
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21.3. Security Options
The CIP-51 provides security options to protect the Flash memory from inadvertent modification by software as well as to prevent the viewing of proprietary program code and constants. The Program Store
Write Enable (bit PSWE in register PSCTL) and the Program Store Erase Enable (bit PSEE in register
PSCTL) bits protect the Flash memory from accidental modification by software. PSWE must be explicitly
set to ‘1’ before software can modify the Flash memory; both PSWE and PSEE must be set to ‘1’ before
software can erase Flash memory. Additional security features prevent proprietary program code and data
constants from being read or altered across the C2 interface.
A Security Lock Byte located in Flash user space offers protection of the Flash program memory from
access (reads, writes, or erases) by unprotected code or the C2 interface. See Section “17. Memory Organization” on page 91 for the location of the security byte. The Flash security mechanism allows the user to
lock n 512-byte Flash pages, starting at page 0 (addresses 0x0000 to 0x01FF), where n is the 1’s complement number represented by the Security Lock Byte. Note that the page containing the Flash Security
Lock Byte is unlocked when no other Flash pages are locked (all bits of the Lock Byte are ‘1’) and
locked when any other Flash pages are locked (any bit of the Lock Byte is ‘0’). An example is shown
in Figure 21.1.
Security Lock Byte:
1s Complement:
Flash pages locked:
11111101b
00000010b
3 (First two Flash pages + Lock Byte Page)
Figure 21.1. Security Byte Decoding
The level of Flash security depends on the Flash access method. The three Flash access methods that
can be restricted are reads, writes, and erases from the C2 debug interface, user firmware executing on
unlocked pages, and user firmware executing on locked pages. Table 21.1 summarizes the Flash security
features of the C8051F39x/37x devices.
Table 21.1. Flash Security Summary
Action
C2 Debug
Interface
User Firmware executing from:
an unlocked page
a locked page
Permitted
Permitted
Permitted
Not Permitted
Flash Error Reset
Permitted
Read or Write page containing Lock Byte
(if no pages are locked)
Permitted
Permitted
Permitted
Read or Write page containing Lock Byte
(if any page is locked)
Not Permitted
Flash Error Reset
Permitted
Read contents of Lock Byte
(if no pages are locked)
Permitted
Permitted
Permitted
Read contents of Lock Byte
(if any page is locked)
Not Permitted
Flash Error Reset
Permitted
Read, Write or Erase unlocked pages
(except page with Lock Byte)
Read, Write or Erase locked pages
(except page with Lock Byte)
Erase page containing Lock Byte
(if no pages are locked)
Permitted
Flash Error Reset Flash Error Reset
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Table 21.1. Flash Security Summary
Erase page containing Lock Byte—Unlock all
pages (if any page is locked)
C2 Device
Erase Only
Flash Error Reset Flash Error Reset
Lock additional pages
(change 1s to 0s in the Lock Byte)
Not Permitted
Flash Error Reset Flash Error Reset
Unlock individual pages
(change 0s to 1s in the Lock Byte)
Not Permitted
Flash Error Reset Flash Error Reset
Read, Write or Erase Reserved Area
Not Permitted
Flash Error Reset Flash Error Reset
C2 Device Erase—Erases all Flash pages including the page containing the Lock Byte.
Flash Error Reset —Not permitted; Causes Flash Error Device Reset (FERROR bit in RSTSRC is '1' after
reset).
- All prohibited operations that are performed via the C2 interface are ignored (do not cause device reset).
- Locking any Flash page also locks the page containing the Lock Byte.
- Once written to, the Lock Byte cannot be modified except by performing a C2 Device Erase.
- If user code writes to the Lock Byte, the Lock does not take effect until the next device reset.
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21.4. Flash Write and Erase Guidelines
Any system which contains routines which write or erase Flash memory from software involves some risk
that the write or erase routines will execute unintentionally if the CPU is operating outside its specified
operating range of VDD, system clock frequency, or temperature. This accidental execution of Flash modifying code can result in alteration of Flash memory contents causing a system failure that is only recoverable by re-Flashing the code in the device. The following guidelines are recommended for any system
which contains routines which write or erase Flash from code.
21.4.1. VDD Maintenance and the VDD Monitor
1. If the system power supply is subject to voltage or current "spikes," add sufficient transient protection
devices to the power supply to ensure that the supply voltages listed in the Absolute Maximum Ratings
table are not exceeded.
2. Make certain that the minimum VDD rise time specification of 1 ms is met. If the system cannot meet
this rise time specification, then add an external VDD brownout circuit to the RST pin of the device that
holds the device in reset until VDD reaches 2.7 V and re-asserts RST if VDD drops below 2.7 V.
3. Enable the on-chip VDD monitor and enable the VDD monitor as a reset source as early in code as
possible. This should be the first set of instructions executed after the Reset Vector. For 'C'-based
systems, this will involve modifying the startup code added by the C compiler. See your compiler
documentation for more details. Make certain that there are no delays in software between enabling the
VDD monitor and enabling the VDD monitor as a reset source. Code examples showing this can be
found in “AN201: Writing to Flash from Firmware", available from the Silicon Laboratories web site.
4. As an added precaution, explicitly enable the VDD monitor and enable the VDD monitor as a reset
source inside the functions that write and erase Flash memory. The VDD monitor enable instructions
should be placed just after the instruction to set PSWE to a 1, but before the Flash write or erase
operation instruction.
5. Make certain that all writes to the RSTSRC (Reset Sources) register use direct assignment operators
and explicitly DO NOT use the bit-wise operators (such as AND or OR). For example,
"RSTSRC = 0x02" is correct. "RSTSRC |= 0x02" is incorrect.
6. Make certain that all writes to the RSTSRC register explicitly set the PORSF bit to a '1'. Areas to check
are initialization code which enables other reset sources, such as the Missing Clock Detector or
Comparator, for example, and instructions which force a Software Reset. A global search on "RSTSRC"
can quickly verify this.
21.4.2. PSWE Maintenance
7. Reduce the number of places in code where the PSWE bit (b0 in PSCTL) is set to a '1'. There should be
exactly one routine in code that sets PSWE to a '1' to write Flash bytes and one routine in code that
sets PSWE and PSEE both to a '1' to erase Flash pages.
8. Minimize the number of variable accesses while PSWE is set to a '1'. Handle pointer address updates
and loop variable maintenance outside the "PSWE = 1;... PSWE = 0;" area. Code examples showing
this can be found in “AN201: Writing to Flash from Firmware", available from the Silicon Laboratories
web site.
9. Disable interrupts prior to setting PSWE to a '1' and leave them disabled until after PSWE has been
reset to 0. Any interrupts posted during the Flash write or erase operation will be serviced in priority
order after the Flash operation has been completed and interrupts have been re-enabled by software.
10.Make certain that the Flash write and erase pointer variables are not located in XRAM. See your
compiler documentation for instructions regarding how to explicitly locate variables in different memory
areas.
11. Add address bounds checking to the routines that write or erase Flash memory to ensure that a routine
called with an illegal address does not result in modification of the Flash.
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21.4.3. System Clock
12.If operating from an external crystal, be advised that crystal performance is susceptible to electrical
interference and is sensitive to layout and to changes in temperature. If the system is operating in an
electrically noisy environment, use the internal oscillator or use an external CMOS clock.
13.If operating from the external oscillator, switch to the internal oscillator during Flash write or erase
operations. The external oscillator can continue to run, and the CPU can switch back to the external
oscillator after the Flash operation has completed.
Additional Flash recommendations and example code can be found in “AN201: Writing to Flash from Firmware", available from the Silicon Laboratories web site.
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SFR Definition 21.1. PSCTL: Program Store R/W Control
Bit
7
6
5
4
3
2
Name
1
0
PSEE
PSWE
Type
R
R
R
R
R
R
R/W
R/W
Reset
0
0
0
0
0
0
0
0
SFR Address = 0x8F; SFR Page = All Pages
Bit
Name
7:2
1
Unused
PSEE
Function
Read = 000000b, Write = don’t care.
Program Store Erase Enable
Setting this bit (in combination with PSWE) allows an entire page
of Flash program memory to be erased. If this bit is logic 1 and
Flash writes are enabled (PSWE is logic 1), 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.
0: Flash program memory erasure disabled.
1: Flash program memory erasure enabled.
0
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 Flash location
should be erased before writing data.
0: Writes to Flash program memory disabled.
1: Writes to Flash program memory enabled; the MOVX write
instruction targets Flash memory.
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SFR Definition 21.2. FLKEY: Flash Lock and Key
Bit
7
6
5
4
3
Name
FLKEY[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address = 0xB7; SFR Page = All Pages
Bit
Name
7:0
FLKEY[7:0]
Function
Flash Lock and Key Register.
Write:
This register provides a lock and key function for Flash erasures
and writes. Flash writes and erases are enabled by writing 0xA5
followed by 0xF1 to the FLKEY register. Flash writes and erases
are automatically disabled after the next write or erase is complete. If any writes to FLKEY are performed incorrectly, or if a
Flash write or erase operation is attempted while these operations are disabled, the Flash will be permanently locked from
writes or erasures until the next device reset. If an application
never writes to Flash, it can intentionally lock the Flash by writing
a non-0xA5 value to FLKEY from software.
Read:
When read, bits 1–0 indicate the current Flash lock state.
00: Flash is write/erase locked.
01: The first key code has been written (0xA5).
10: Flash is unlocked (writes/erases allowed).
11: Flash writes/erases disabled until the next reset.
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SFR Definition 21.3. FLSCL: Flash Scale
Bit
7
6
5
Name
FOSE
Type
R/W
R/W
R/W
Reset
1
0
0
4
3
2
1
0
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
FLRT
SFR Address = 0xB6; SFR Page = All Pages
Bit
Name
7
FOSE
Function
Flash One-shot Enable
This bit enables the Flash read one-shot (recommended). If the
Flash one-shot is disabled, the Flash sense amps are enabled
for a full clock cycle during Flash reads, increasing the device
power consumption.
0: Flash one-shot disabled.
1: Flash one-shot enabled.
6:5
4
Reserved
FLRT
Must Write 00b.
Flash Read Timing
This bit should be programmed to the smallest allowed value,
according to the system clock speed.
0: SYSCLK < 25 MHz.
1: SYSCLK < 50 MHz.
3:0
Reserved
Must Write 0000b.
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22. EEPROM (C8051F37x)
The C8051F37x devices contain 512 bytes of byte-programmable EEPROM. The EEPROM is accessible
by a 2-wire bus, available on EESDA and EESCL pins, which correspond to P2.2 and P2.3 respectively.
The EEPROM operates as a slave. The master can be either the SMBUS1 peripheral of the C8051F37x,
internally connected to EESDA and EESCL, or an external master connected externally to the EESDA and
EESCL pins.
22.1. EEPROM Communication Protocol
Communication between the master and the EEPROM consists of two types of operations: writes and
reads. An overview of both operations is as follows:






The master generates the clock on EESCL.
Communication begins when the master generates a START condition by causing a falling edge in
EESDA when EESCL is logic high.
The master sends the slave address byte. See Section 22.1.1.
The EEPROM acknowledges the receipt of the slave address byte generating an ACK. See Section
22.1.2.
The master performs a read or write operation based on the setting of the R/W bit in the slave address
byte. See Section 22.2 and Section 22.3.
Throughout communication, the state of EESDA represents one bit of valid data when EESCL is logic
high:
The
master is permitted to change the state of EESDA when EESCL is logic high only to generate a START or
STOP condition. Any changes in the EESDA line while the EESCL line is logic high will be interpreted as a
START or STOP condition by the EEPROM.
The master or EEPROM is permitted to change the state of EESDA when EESCL is logic low.
Communication terminates when the master generates a STOP condition by causing a rising edge in
EESDA when EESCL is logic high.
 If necessary, the master can reset the communication with the EEPROM. See Section 22.1.4.

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22.1.1. Slave Address Byte
The master begins a transmission by sending a START condition followed by the slave address byte
(SAB).
Slave Address Byte (SAB) Definition
Bit
7
6
5
1
Bit
Name
7:2
SLA
1
3
2
SLA
Name
Value
4
0
1
0
0
1
0
ADDR MSB
R/W
Varies
Varies
0
Function
Slave Address of EEPROM.
Always 101000b.
ADDR MSB Most Significant Addressing Bit.
This bit is concatenated to the 8-bit address counter to create a 9-bit address used
by EEPROM read and write operations.
0: Address locations 0x000 to 0x0FF are targeted by the EEPROM operations.
1: Address locations 0x100 to 0x1FF are targeted by the EEPROM operations.
0
R/W
EEPROM Read/Write Direction Bit.
Instructs the EEPROM to perform a read or write operation
0: Perform an EEPROM write operation
1: Perform an EEPROM read operation
Figure 22.1. Slave Address Byte Definition
22.1.2. Acknowledgement (ACK)
During an acknowledgement (ACK), the master or EEPROM forces the EESDA line to a logic low when
EESCL is logic high.
22.1.3. Not-Acknowledgement (NACK)
During a not-acknowledgement (NACK), the master or EEPROM allows the EESDA line to be pulled up to
a logic high when EESCL is logic high.
22.1.4. Reset
The EEPROM can be reset in case the SMBus communication is accidentally interrupted (e.g. power loss)
or needs to be terminated mid-stream. The reset is initialized when the master device creates a START
condition. To do this, it may be necessary for the master device to monitor EESDA up to nine times while
cycling the EESCL signal. During this process, the master checks for a logic high on EESDA for each
rising edge of EESCL.
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22.2. Write Operation
Up to sixteen successive bytes may be written to the EEPROM within a single write operation. To write to
the EEPROM:
1. The master sends the START condition and the slave address byte with the R/W bit cleared to 0.
2. The EEPROM generates an ACK.
3. The master sends the write address location (A[7:0]) to the EEPROM.
4. The EEPROM stores the address location in its address counter and generates an ACK.
5. The master transmits the data byte (D[7:0]) to the EEPROM.
6. The EEPROM increments four least significant bits of the address counter and generates an ACK.
7. The master can repeat Steps 5 and 6 up to fifteen more times.
8. The master generates a STOP condition.
9. The EEPROM begins its internal programming cycle.
10.The master transmits a START condition and slave address with the R/W bit cleared to 0:
a. If the EEPROM does not generate an ACK, repeat Steps 8 and 9.
b. If the EEPROM does generate and ACK, the EEPROM internal programming cycle is complete.
Note: If the master transmits more than sixteen bytes prior to issuing a STOP condition, the last for bits of the address
counter will roll over and the previously written data will be overwritten.
Master
Slave
Master
Slave
Master
ACK
Address
Byte
(A[7:0])
ACK
Data Byte
(D[7:0])
Slave Master
EESCL
EESDA
SLA[5:0]
START
A[8]
W
Slave Address Byte
(SAB[7:0])
ACK
STOP
Figure 22.2. Write Operation (Single Byte)
Master
Slave Master Slave Master Slave Master Slave Master Slave
Master Slave Master
EESCL
EESDA
START
Slave
Address
Byte
(SAB[7:0])
ACK
Address
Byte
(A[7:0])
ACK
Data Byte
n
(D[7:0])
ACK
Data Byte
n+1
(D[7:0])
ACK
Data Byte
n+2
(D[7:0])
ACK
Figure 22.3. Write Operation (Multiple Bytes)
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Data Byte
n + m,
m < 255
(D[7:0])
ACK
STOP
C8051F39x/37x
22.3. Read Operation
There are two operations to read the EEPROM: current address read and selective address read. Both
read operations can read up to 256 bytes within a single read operation.
22.3.1. Current Address Read
A current address read accesses the data at the EEPROM internal address counter’s current location.
The address counter in the EEPROM maintains the address of the last byte accessed, incremented by
one. For example, if the previous operation was a read or write operation addressed to address location n,
the internal address counter automatically increments to address n+1.
To perform a current address read operation:
1. The master sends the START condition and the slave address byte with the R/W bit set to 1.
2. The EEPROM generates an ACK and transmits the byte of data (D[7:0]) stored at the address specified
by the address counter. This address will be the address from the last read or write operation
incremented by one.
3. The EEPROM increments the internal address counter by one.
4. (Optional) To read additional bytes:
a. The master generates an ACK.
b. The EEPROM transmits the byte of data stored at the address specified by the address counter.
c. The EEPROM increments the internal address counter by one.
d. Repeat Step 4a through 4c until the master is done reading bytes.
5. The master generates a NACK.
6. The master generates a STOP condition.
7. The EEPROM terminates the transmission.
Note: If the previous operation targeted the last byte of the EEPROM, the EEPROM will transmit the data from
address location 0x00 for a current address read operation.
Master
Slave
Master
EESCL
EESDA
SLA[5:0]
START
A[8]
Slave Address Byte
(SAB[7:0])
R
ACK
Data Byte
(D[7:0])
NACK
STOP
Figure 22.4. Current Address Read Operation (Single Byte)
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Master
Slave
Master Slave Master
Slave
Data Byte
n+1
(D[7:0])
Data Byte
n + m,
m < 255
(D[7:0])
Master
EESCL
EESDA
START
Slave
Address
Byte
(SAB[7:0])
ACK
Data Byte
n
(D[7:0])
ACK
ACK
NACK
Figure 22.5. Current Address Read Operation (Multiple Bytes)
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STOP
C8051F39x/37x
22.3.2. Selective Address Read
In a selective address read operation, the master selects the target memory location for the read
operation.
To perform a selective address read:
1. The master sends the START condition and the slave address byte with the R/W bit set to 1.
2. The EEPROM generates an ACK.
3. The master sends the read memory address (A[7:0]) to the EEPROM.
4. The EEPROM stores the address in the address counter and generates an ACK.
5. The master again sends the slave address byte with the R/W bit set to 1.
6. The EEPROM generates an ACK.
7. The EEPROM sends the byte of data (D[7:0]) specified by the address counter.
8. The EEPROM increments the internal address counter by one.
9. (Optional) To read additional bytes:
a. The master generates an ACK.
b. The EEPROM sends the byte of data (D[7:0]) specified by the address counter.
c. The EEPROM increments the internal address counter by one.
d. Repeat Steps9a through 9c until the master reads all of the desired bytes.
10.The master generates a NACK.
11. The master generates a STOP condition.
12.The EEPROM terminates the transmission.
Note: If the selective read operation overflows the top of memory, the EEPROM address counter will wrap, and the
EEPROM transmit the data from address location 0x00.
Master
Slave Master Slave Master
Slave
Master
EESCL
EESDA
START
Slave
Address
Byte
(SAB[7:0])
ACK
Address
Byte
(A[7:0])
ACK
Slave
Address
Byte
(SAB[7:0])
ACK
Data Byte
(D[7:0])
NACK
STOP
Figure 22.6. Selective Address Read (Single Byte)
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Master
Slave Master Slave Master
Slave
Master Slave Master
Slave
Data Byte
n+1
(D[7:0])
Data Byte
n + m,
m < 255
(D[7:0])
Master
EESCL
EESDA
START
Slave
Address
Byte
(SAB[7:0])
ACK
Address
Byte
(A[7:0])
ACK
Slave
Address
Byte
(SAB[7:0])
ACK
Data Byte
n
(D[7:0])
ACK
ACK
Figure 22.7. Selective Address Read (Multiple Bytes)
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NACK
STOP
C8051F39x/37x
23. Cyclic Redundancy Check Unit (CRC0)
C8051F39x/37x devices include a cyclic redundancy check unit (CRC0) that can perform a CRC using a
16-bit polynomial. CRC0 accepts a stream of 8-bit data written to the CRC0IN register. CRC0 posts the 16bit result to an internal register. The internal result register may be accessed indirectly using the CRC0PNT
bits and CRC0DAT register, as shown in Figure 23.1. CRC0 also has a bit reverse register for quick data
manipulation.
CRC0IN
8
8
Automatic CRC
Controller
Flash
Memory
CRC0INIT
CRC0VAL
CRC0ST[5]
CRC0ST[4]
CRC0ST[3]
CRC0ST[2]
CRC0ST[1]
CRC0ST[0]
CRC Engine
CRC0PNT
16
CRC0AUTO
CRC0CN
AUTOEN
CRC0FLIP
Write
RESULT
8
CRC0CNT[4]
CRC0CNT[3]
CRC0CNT[2]
CRC0CNT[1]
CRC0CNT[0]
8
CRC0CNT
CRC0DONE
2 to 1 MUX
CRC0FLIP
Read
8
CRC0DAT
Figure 23.1. CRC0 Block Diagram
23.1. CRC Algorithm
The C8051F39x/37x CRC unit generates a CRC result equivalent to the following algorithm:
1. XOR the input with the most-significant bits of the current CRC result. If this is the first iteration of the
CRC unit, the current CRC result will be the set initial value
(0x00000000 or 0xFFFFFFFF).
2a. If the MSB of the CRC result is set, shift the CRC result and XOR the result with the selected
polynomial.
2b. If the MSB of the CRC result is not set, shift the CRC result.
Repeat Steps 2a/2b for the number of input bits (8). The algorithm is also described in the following example.
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The 16-bit C8051F39x/37x CRC algorithm can be described by the following code:
unsigned short UpdateCRC (unsigned short CRC_acc, unsigned char CRC_input)
{
unsigned char i;
// loop counter
#define POLY 0x1021
// Create the CRC "dividend" for polynomial arithmetic (binary arithmetic
// with no carries)
CRC_acc = CRC_acc ^ (CRC_input << 8);
// "Divide" the poly into the dividend using CRC XOR subtraction
// CRC_acc holds the "remainder" of each divide
//
// Only complete this division for 8 bits since input is 1 byte
for (i = 0; i < 8; i++)
{
// Check if the MSB is set (if MSB is 1, then the POLY can "divide"
// into the "dividend")
if ((CRC_acc & 0x8000) == 0x8000)
{
// if so, shift the CRC value, and XOR "subtract" the poly
CRC_acc = CRC_acc << 1;
CRC_acc ^= POLY;
}
else
{
// if not, just shift the CRC value
CRC_acc = CRC_acc << 1;
}
}
// Return the final remainder (CRC value)
return CRC_acc;
}
Table 23.1 lists several input values and the associated outputs using the 16-bit C8051F39x/37x CRC
algorithm:
Table 23.1. Example 16-bit CRC Outputs
146
Input
Output
0x63
0x8C
0x7D
0xAA, 0xBB, 0xCC
0x00, 0x00, 0xAA, 0xBB, 0xCC
0xBD35
0xB1F4
0x4ECA
0x6CF6
0xB166
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23.2. Preparing for a CRC Calculation
To prepare CRC0 for a CRC calculation, software should set the initial value of the result. The polynomial
used for the CRC computation is 0x1021. The CRC0 result may be initialized to one of two values: 0x0000
or 0xFFFF. The following steps can be used to initialize CRC0.
1. Select the initial result value (Set CRC0VAL to 0 for 0x0000 or 1 for 0xFFFF).
2. Set the result to its initial value (Write 1 to CRC0INIT).
23.3. Performing a CRC Calculation
Once CRC0 is initialized, the input data stream is sequentially written to CRC0IN, one byte at a time. The
CRC0 result is automatically updated after each byte is written. The CRC engine may also be configured to
automatically perform a CRC on one or more 256 byte blocks read from Flash. The following steps can be
used to automatically perform a CRC on Flash memory.
1. Prepare CRC0 for a CRC calculation as shown above.
2. Write the index of the starting page to CRC0AUTO.
3. Set the AUTOEN bit to 1 in CRC0AUTO.
4. Write the number of 256 byte blocks to perform in the CRC calculation to CRC0CNT.
5. Write any value to CRC0CN (or OR its contents with 0x00) to initiate the CRC calculation. The CPU will
not execute code any additional code until the CRC operation completes. See the note in SFR
Definition 23.1. CRC0CN: CRC0 Control for more information on how to properly initiate a CRC
calculation.
6. Clear the AUTOEN bit in CRC0AUTO.
7. Read the CRC result using the procedure below.
23.4. Accessing the CRC0 Result
The internal CRC0 result is 16 bits. The CRC0PNT bits select the byte that is targeted by read and write
operations on CRC0DAT and increment after each read or write. The calculation result will remain in the
internal CR0 result register until it is set, overwritten, or additional data is written to CRC0IN.
23.5. CRC0 Bit Reverse Feature
CRC0 includes hardware to reverse the bit order of each bit in a byte as shown in Figure 23.2. Each byte
of data written to CRC0FLIP is read back bit reversed. For example, if 0xC0 is written to CRC0FLIP, the
data read back is 0x03. Bit reversal is a useful mathematical function used in algorithms such as the FFT.
CRC0FLIP
Write
CRC0FLIP
Read
Figure 23.2. Bit Reverse Register
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SFR Definition 23.1. CRC0CN: CRC0 Control
Bit
7
6
5
4
3
2
1
CRC0INIT CRC0VAL
Name
0
CRC0PNT
Type
R
R
R
R
R/W
R/W
R
R/W
Reset
0
0
0
1
0
0
0
0
SFR Address = 0xDF; SFR Page = All Pages
Bit
Name
7:4
3
Unused
CRC0INIT
Function
Read = 0001b; Write = Don’t Care.
CRC0 Result Initialization Bit.
Writing a 1 to this bit initializes the entire CRC result based
on CRC0VAL.
2
CRC0VAL
CRC0 Set Value Initialization Bit.
This bit selects the set value of the CRC result.
0: CRC result is set to 0x00000000 on write of 1 to
CRC0INIT.
1: CRC result is set to 0xFFFFFFFF on write of 1 to
CRC0INIT.
1
0
Unused
CRC0PNT
Read = 0b; Write = Don’t Care.
CRC0 Result Pointer.
Specifies the byte of the CRC result to be read/written on
the next access to CRC0DAT. The value of these bits will
auto-increment upon each read or write.
0: CRC0DAT accesses bits 7–0 of the 16-bit CRC result.
1: CRC0DAT accesses bits 15–8 of the 16-bit CRC result.
Note: Upon initiation of an automatic CRC calculation, the three cycles following a write to CRC0CN that initiate a
CRC operation must only contain instructions which execute in the same number of cycles as the number of
bytes in the instruction. An example of such an instruction is a 3-byte MOV that targets the CRC0FLIP
register. When programming in C, the dummy value written to CRC0FLIP should be a non-zero value to
prevent the compiler from generating a 2-byte MOV instruction.
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SFR Definition 23.2. CRC0IN: CRC0 Data Input
Bit
7
6
5
4
3
Name
CRC0IN[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address = 0x9C; SFR Page = All Pages
Bit
Name
7:0
CRC0IN[7:0]
Function
CRC0 Data Input.
Each write to CRC0IN results in the written data being computed into the existing CRC result according to the CRC
algorithm described in Section 23.1
SFR Definition 23.3. CRC0DAT: CRC0 Data Output
Bit
7
6
5
4
3
Name
CRC0DAT[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address = 0x9E; SFR Page = All Pages
Bit
Name
7:0
CRC0DAT[7:0]
Function
CRC0 Data Output.
Each read or write performed on CRC0DAT targets the
CRC result bits pointed to by the CRC0 Result Pointer
(CRC0PNT bits in CRC0CN).
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SFR Definition 23.4. CRC0AUTO: CRC0 Automatic Control
Bit
7
6
Name
AUTOEN
Type
R/W
R/W
Reset
0
0
5
4
3
2
1
0
0
0
CRC0ST[5:0]
R/W
0
0
0
0
SFR Address = 0xDD; SFR Page = All Pages
Bit
Name
7
AUTOEN
Function
Automatic CRC Calculation Enable.
When AUTOEN is set to 1, any write to CRC0CN will initiate an automatic CRC starting at Flash sector CRC0ST
and continuing for CRC0CNT sectors.
6
Reserved
5:0
CRC0ST[5:0]
Must write 0b.
Automatic CRC Calculation Starting Block.
These bits specify the Flash block to start the automatic
CRC calculation. The starting address of the first Flash
block included in the automatic CRC calculation is
CRC0ST x Block Size.
Note: The block size is 256 bytes.
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SFR Definition 23.5. CRC0CNT: CRC0 Automatic Flash Sector Count
Bit
7
6
5
4
3
Name CRCDONE
Type
R
Reset
1
2
1
0
0
0
CRC0CNT[4:0]
R/W
0
R/W
0
0
0
0
SFR Address = 0xDE; SFR Page = All Pages
Bit
Name
7
CRCDONE
Function
CRCDONE Automatic CRC Calculation Complete.
Set to 0 when a CRC calculation is in progress. Code execution is stopped during a CRC calculation; therefore,
reads from firmware will always return 1.
6:5
Reserved
4:0
CRC0CNT[4:0]
Must write 00b.
Automatic CRC Calculation Block Count.
These bits specify the number of Flash blocks to include in
an automatic CRC calculation. The last address of the last
Flash block included in the automatic CRC calculation is
(CRC0ST+CRC0CNT) x Block Size - 1.
Notes:
1. The block size is 256 bytes.
2. The maximum number of blocks that may be computed in
a single operation is 31. To compute a CRC on all 32
blocks, perform one operation on 31 blocks, then perform
a second operation on 1 block without clearing the CRC
result.
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SFR Definition 23.6. CRC0FLIP: CRC0 Bit Flip
Bit
7
6
5
4
3
Name
CRC0FLIP[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address = 0x9A; SFR Page = All Pages
Bit
Name
7:0
CRC0FLIP[7:0]
Function
CRC0 Bit Flip.
Any byte written to CRC0FLIP is read back in a bitreversed order, i.e., the written LSB becomes the MSB.
For example:
If 0xC0 is written to CRC0FLIP, the data read back will
be 0x03.
If 0x05 is written to CRC0FLIP, the data read back will be
0xA0.
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24. Reset Sources
Reset circuitry allows the controller to be easily placed in a predefined default condition. Upon entering this
reset state, the following events 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 stack is not altered.

The Port I/O latches are reset to 0xFF (all logic ones) in open-drain mode. Weak pullups are enabled during and after the reset. For VDD Monitor and power-on resets, the RST pin is driven low until the device
exits the reset state.
On exit from the reset state, the program counter (PC) is reset, and the system clock defaults to the internal oscillator. The Watchdog Timer is enabled with the system clock divided by 12 as its clock source. Program execution begins at location 0x0000.
VDD
Power On
Reset
Supply
Monitor
+
-
'0'
Enable
(wired-OR)
/RST
C0RSEF
Missing
Clock
Detector
(oneshot)
EN
Reset
Funnel
PCA
WDT
(Software Reset)
SWRSF
Errant
FLASH
Operation
EN
System
Clock
WDT
Enable
Px.x
+
-
Comparator 0
MCD
Enable
Px.x
CIP-51
Microcontroller
Core
System Reset
Extended Interrupt
Handler
Figure 24.1. Reset Sources
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24.1. Power-On Reset
During power-up, the device is held in a reset state and the RST pin is driven low until VDD settles above
VRST. A delay occurs before the device is released from reset; the delay decreases as the VDD ramp time
increases (VDD ramp time is defined as how fast VDD ramps from 0 V to VRST). Figure 24.2. plots the
power-on and VDD monitor reset timing. The maximum VDD ramp time is 1 ms; slower ramp times may
cause the device to be released from reset before VDD reaches the VRST level. For ramp times less than
1 ms, the power-on reset delay (TPORDelay) is typically less than 0.3 ms.
volts
On exit from a power-on reset, the PORSF flag (RSTSRC.1) is set by hardware to logic 1. When PORSF is
set, 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 content of internal data memory should be assumed to be undefined after a power-on reset. The VDD monitor is enabled following a
power-on reset.
VDD
2.70
2.55
VRST
VD
D
2.0
1.0
t
Logic HIGH
Logic LOW
/RST
TPORDelay
Power-On
Reset
VDD
Monitor
Reset
Figure 24.2. Power-On and VDD Monitor Reset Timing
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24.2. Power-Fail Reset / VDD Monitor
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 hold the CIP-51 in a reset state (see Figure 24.2). When VDD returns
to a level above VRST, the CIP-51 will be released from the reset state. 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 required for data retention. If the PORSF flag reads ‘1’, the data may no longer be valid. The VDD
monitor is enabled after power-on resets. Its defined state (enabled/disabled) is not altered by any other
reset source. For example, if the VDD monitor is disabled by code and a software reset is performed, the
VDD monitor will still be disabled after the reset.
Important Note: If the VDD monitor is being turned on from a disabled state, it should be enabled before it
is selected as a reset source. Selecting the VDD monitor as a reset source before it is enabled and stabilized may cause a system reset. In some applications, this reset may be undesirable. If this is not desirable
in the application, a delay should be introduced between enabling the monitor and selecting it as a reset
source. The procedure for enabling the VDD monitor and configuring it as a reset source from a disabled
state is shown below:
1. Enable the VDD monitor (VDMEN bit in VDM0CN = ‘1’).
2. If necessary, wait for the VDD monitor to stabilize.
3. Select the VDD monitor as a reset source (PORSF bit in RSTSRC = ‘1’).
See Figure 24.2 for VDD monitor timing; note that the power-on-reset delay is not incurred after a VDD
monitor reset. See Section “7. Electrical Characteristics” on page 32 for complete electrical characteristics
of the VDD monitor.
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SFR Definition 24.1. VDM0CN: VDD Monitor Control
Bit
7
6
5
4
3
2
1
0
Name
VDMEN
VDDSTAT
VDMLVL
Type
R/W
R
R/W
R
R
R
R
R
Reset
Varies
Varies
0
0
0
0
0
0
SFR Address = 0xFF; SFR Page = All Pages
Bit
Name
7
VDMEN
Function
VDD Monitor Enable.
This bit turns the VDD monitor circuit on/off. The VDD Monitor
cannot generate system resets until it is also selected as a
reset source in register RSTSRC (SFR Definition 24.2).
Selecting the VDD monitor as a reset source before it has
stabilized may generate a system reset. In systems where
this reset would be undesirable, a delay should be introduced between enabling the VDD Monitor and selecting it as
a reset source.
0: VDD Monitor Disabled.
1: VDD Monitor Enabled.
6
VDDSTAT
VDD Status.
This bit indicates the current power supply status (VDD Monitor output).
0: VDD is at or below the VDD monitor threshold.
1: VDD is above the VDD monitor threshold.
5
VDMLVL
VDD Monitor Level Select.
0: VDD Monitor Threshold is set to VRST-LOW.
1: VDD Monitor Threshold is set to VRST-HIGH. This setting
is required for any system with firmware that writes and/or
erases Flash.
4:0
156
Unused
Read = 000000b; Write = Don’t care.
Preliminary Rev. 0.71
C8051F39x/37x
24.3. External Reset
The external RST pin provides a means for external circuitry to force the device into a reset state. Asserting an active-low signal on the RST pin generates a reset; an external pullup and/or decoupling of the RST
pin may be necessary to avoid erroneous noise-induced resets. See Section “7. Electrical Characteristics”
on page 32 for complete RST pin specifications. The PINRSF flag (RSTSRC.0) is set on exit from an external reset.
24.4. Missing Clock Detector Reset
The Missing Clock Detector (MCD) is a one-shot circuit that is triggered by the system clock. If the system
clock remains high or low for more than 100 µs, the one-shot will time out and generate a reset. After a
MCD reset, the MCDRSF flag (RSTSRC.2) will read ‘1’, signifying the MCD as the reset source; otherwise,
this bit reads ‘0’. Writing a ‘1’ to the MCDRSF bit enables the Missing Clock Detector; writing a ‘0’ disables
it. The state of the RST pin is unaffected by this reset.
24.5. Comparator0 Reset
Comparator0 can be configured as a reset source by writing a ‘1’ to the C0RSEF flag (RSTSRC.5).
Comparator0 should be enabled and allowed to settle 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 noninverting input voltage (on CP0+) is less than the inverting input voltage (on CP0-), the device 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.
24.6. PCA Watchdog Timer Reset
The programmable Watchdog Timer (WDT) function of the Programmable Counter Array (PCA) can be
used to prevent software from running out of control during a system malfunction. The PCA WDT function
can be enabled or disabled by software as described in Section “32.4. Watchdog Timer Mode” on
page 284; the WDT is enabled and clocked by SYSCLK / 12 following any reset. If a system malfunction
prevents user software from updating the WDT, a reset is generated and the WDTRSF bit (RSTSRC.5) is
set to ‘1’. The state of the RST pin is unaffected by this reset.
24.7. Flash Error Reset
If a Flash read/write/erase or program read targets an illegal address, a system reset is generated. This
may occur due to any of the following:
A Flash write or erase is attempted above user code space. This occurs when PSWE is set to ‘1’ and a
MOVX write operation targets an address above address 0x3DFF.
 A Flash read is attempted above user code space. This occurs when a MOVC operation targets an
address above address 0x3DFF.
 A Program read is attempted above user code space. This occurs when user code attempts to branch
to an address above 0x3DFF.
 A Flash read, write or erase attempt is restricted due to a Flash security setting (see Section
“21.3. Security Options” on page 131).
The FERROR bit (RSTSRC.6) is set following a Flash error reset. The state of the RST pin is unaffected by
this reset.

24.8. Software Reset
Software may force a reset by writing a ‘1’ to the SWRSF bit (RSTSRC.4). The SWRSF bit will read ‘1’ following a software forced reset. The state of the RST pin is unaffected by this reset.
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SFR Definition 24.2. RSTSRC: Reset Source
Bit
7
Name
6
5
4
3
2
1
0
FERROR
C0RSEF
SWRSF
WDTRSF
MCDRSF
PORSF
PINRSF
Type
R
R
R/W
R/W
R
R/W
R/W
R
Reset
0
Varies
Varies
Varies
Varies
Varies
Varies
Varies
SFR Address = 0xEF; SFR Page = All Pages
Bit
Name
7
Unused
Description
Write
Unused.
Don’t care.
0
Set to ‘1’ if Flash read/
write/erase error caused
the last reset.
Set to ‘1’ if Comparator0
caused the last reset.
6
FERROR Flash Error Reset Flag.
N/A
5
C0RSEF Comparator0 Reset Enable
and Flag.
4
SWRSF
Writing a ‘1’ enables
Comparator0 as a reset
source (active-low).
Writing a ‘1’ forces a system reset.
Software Reset Force and
Flag.
3
WDTRSF Watchdog Timer Reset Flag. N/A
2
MCDRSF Missing Clock Detector
Enable and Flag.
1
PORSF
0
PINRSF
Writing a ‘1’ enables the
Missing Clock Detector.
The MCD triggers a reset
if a missing clock condition
is detected.
Writing a ‘1’ enables the
Power-On / VDD Monitor
Reset Flag, and VDD monitor VDD monitor as a reset
source.
Reset Enable.
Writing ‘1’ to this bit
before the VDD monitor
is enabled and stabilized
may cause a system
reset.
N/A
HW Pin Reset Flag.
Note: Do not use read-modify-write operations on this register
158
Read
Preliminary Rev. 0.71
Set to ‘1’ if last reset was
caused by a write to
SWRSF.
Set to ‘1’ if Watchdog
Timer overflow caused the
last reset.
Set to ‘1’ if Missing Clock
Detector timeout caused
the last reset.
Set to ‘1’ anytime a poweron or VDD monitor reset
occurs.
When set to ‘1’ all other
RSTSRC flags are indeterminate.
Set to ‘1’ if RST pin
caused the last reset.
C8051F39x/37x
25. Power Management Modes
The C8051F39x/37x devices have three software programmable power management modes: idle, stop,
and Suspend. Idle mode and stop mode are part of the standard 8051 architecture, while suspend mode is
an enhanced power-saving mode implemented by the high-speed oscillator.
Idle mode halts the CPU while leaving the peripherals and clocks active. In stop mode, the CPU is halted,
all interrupts and timers (except the Missing Clock Detector) are inactive, and the internal oscillator is
stopped (analog peripherals remain in their selected states; the external oscillator is not affected). Suspend mode is similar to Stop mode in that the internal oscillator and CPU are halted, but the device can
wake on events such as a Port Mismatch, Comparator low output, or a Timer 3 overflow. Since clocks are
running in Idle mode, power consumption is dependent upon the system clock frequency and the number
of peripherals left in active mode before entering Idle. Stop mode and suspend mode consume the least
power because the majority of the device is shut down with no clocks active. SFR Definition 25.1 describes
the Power Control Register (PCON) used to control the C8051F39x/37x's Stop and Idle power management modes. Suspend mode is controlled by the SUSPEND bit in the OSCICN register (SFR Definition
26.3).
Although the C8051F39x/37x has idle, stop, and suspend modes available, more control over the device
power can be achieved by enabling/disabling individual peripherals as needed. Each analog peripheral
can be disabled when not in use and placed in low power mode. Digital peripherals, such as timers or
serial buses, draw little power when they are not in use. Turning off oscillators lowers power consumption
considerably, at the expense of reduced functionality.
25.1. Idle Mode
Setting the Idle Mode Select bit (PCON.0) causes the hardware to halt the CPU and enter idle mode as
soon as the instruction that sets the bit completes execution. 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 is asserted or a reset occurs. The assertion of an
enabled interrupt 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 program execution at address 0x0000.
Note: If the instruction following the write of the IDLE bit is a single-byte instruction and an interrupt occurs during the
execution phase of the instruction that sets the IDLE bit, the CPU may not wake from Idle mode when a future
interrupt occurs. Therefore, instructions that set the IDLE bit should be followed by an instruction that has two
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
MOV PCON, PCON
; set IDLE bit
; ... followed by a 3-cycle dummy instruction
If enabled, the Watchdog Timer (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 opportunity 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 “24.6. PCA Watchdog Timer
Reset” on page 157 for more information on the use and configuration of the WDT.
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25.2. Stop Mode
Setting the Stop Mode Select bit (PCON.1) causes the controller core to enter Stop mode as soon as the
instruction that sets the bit completes execution. Before entering stop mode, the system clock must be
sourced by the internal high-frequency oscillator. In stop mode the internal oscillator, CPU, and all digital
peripherals are stopped; the state of the external oscillator circuit is not affected. Each analog peripheral
(including the external oscillator circuit) may be shut down individually prior to entering stop mode. Stop
mode can only be terminated by an internal or external reset. On reset, the device 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 in STOP mode for longer than the
MCD timeout.
By default, when in stop mode the internal regulator is still active. However, the regulator can be configured to shut down while in stop mode to save power. To shut down the regulator in stop mode, the
STOPCF bit in register REG01CN should be set to 1 prior to setting the STOP bit (see SFR Definition
25.1). If the regulator is shut down using the STOPCF bit, only the RST pin or a full power cycle are capable of resetting the device.
25.3. Suspend Mode
Setting the SUSPEND bit (OSCICN.5) causes the hardware to halt the CPU and the high-frequency internal oscillator, and go into suspend mode as soon as the instruction that sets the bit completes execution.
All internal registers and memory maintain their original data. Most digital peripherals are not active in suspend mode. The exception to this is the Port Match feature and Timer 3, when it is run from an external
oscillator source or the internal low-frequency oscillator.
Suspend mode can be terminated by four types of events, a port match (described in Section “27.5. Port
Match” on page 181), a Timer 3 overflow (described in Section “31.3. Timer 3” on page 257), a Comparator
low output (if enabled), or a device reset event. Note that in order to run Timer 3 in suspend mode, the
timer must be configured to clock from either the external clock source or the internal low-frequency oscillator source. When suspend mode is terminated, the device will continue execution on the instruction following the one that set the SUSPEND bit. If the wake event (port match or Timer 3 overflow) was
configured to generate an interrupt, the interrupt will be serviced upon waking the device. If suspend mode
is terminated by an internal or external reset, the CIP-51 performs a normal reset sequence and begins
program execution at address 0x0000.
160
Preliminary Rev. 0.71
C8051F39x/37x
SFR Definition 25.1. PCON: Power Control
Bit
7
6
5
4
3
2
1
0
Name
GF[5:0]
STOP
IDLE
Type
R/W
R/W
R/W
0
0
Reset
0
0
0
0
0
0
SFR Address = 0x87; SFR Page = All Pages
Bit
Name
7:2
GF[5:0]
Function
General Purpose Flags 5–0.
These are general purpose flags for use under software control.
1
STOP
Stop Mode Select.
Setting this bit will place the CIP-51 in Stop mode. This bit will
always be read as 0.
1: CPU goes into Stop mode (internal oscillator stopped).
0
IDLE
IDLE: Idle Mode Select.
Setting this bit will place the CIP-51 in Idle mode. This bit will
always be read as 0.
1: CPU goes into Idle mode. (Shuts off clock to CPU, but clock
to Timers, Interrupts, Serial Ports, and Analog Peripherals are
still active.)
Preliminary Rev. 0.71
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C8051F39x/37x
26. Oscillators and Clock Selection
C8051F39x/37x devices include a programmable internal high-frequency oscillator, a programmable internal low-frequency oscillator, an internal low-power oscillator, and an external oscillator drive circuit. The
internal high-frequency oscillator can be enabled/disabled and calibrated using the OSCICN and OSCICL
registers, as shown in Figure 26.1. The internal low-frequency oscillator can be enabled/disabled and calibrated using the OSCLCN register. The internal low-power oscillator is automatically enabled and disabled
when selected and deselected as the system clock. The system clock can be sourced by the external oscillator circuit or any internal oscillator. The internal high-frequency and low-frequency oscillators offer a
selectable post-scaling feature.
Option 2
VDD
CLKSL2
CLKSL1
CLKSL0
OSCLEN OSCLF OSCLD
Option 3
XTAL2
EN
2, 4, 8, 16
49 MHz High Frequency
Internal Oscillator
XTAL2
CLKSEL
OSCLEN
OSCLRDY
OSCLF3
OSCLF2
OSCLF1
OSCLF0
OSCLD1
OSCLD0
OSCLCN
IFCN1
IFCN0
OSCICN
IOSCEN
IFRDY
SUSPEND
STSYNC
OSCICL
OSCLF
(49 MHz)
OSCLEN
EN
80 kHz Low Frequency
Internal Oscillator
Option 1
Input
Circuit
OSC
XTAL2
(20 MHz)
20 MHz Low Power
Internal Oscillator
XFCN2
XFCN1
XFCN0
XOSCMD2
XOSCMD1
XOSCMD0
Option 4
XTAL2
OSCXCN
Figure 26.1. Oscillator Options
162
SYSCLK
OSCLD
XTAL1
10M:
1, 2, 4, 8
Preliminary Rev. 0.71
C8051F39x/37x
26.1. System Clock Selection
The CLKSL[2:0] bits in register CLKSEL select which oscillator source is used as the system clock.
CLKSL[2:0] must be set to 001b for the system clock to run from the external oscillator; however the external oscillator may still clock certain peripherals (timers, PCA) when the internal oscillator is selected as the
system clock. The system clock may be switched on-the-fly between any of the oscillator sources so long
as the selected clock source is enabled and has settled.
The internal high-frequency and low-frequency oscillators require little start-up time and may be selected
as the system clock immediately following the register write which enables the oscillator. The external RC
and C modes also typically require no startup time.
External crystals and ceramic resonators however, typically require a start-up time before they are settled
and ready for use. The Crystal Valid Flag (XTLVLD in register OSCXCN) is set to '1' by hardware when the
external crystal or ceramic resonator is settled. In crystal mode, to avoid reading a false XTLVLD, software should delay at least 1 ms between enabling the external oscillator and checking XTLVLD.
SFR Definition 26.1. CLKSEL: Clock Select
Bit
7
6
5
4
3
2
1
0
CLKSL[2:0]
Name
Type
R
R
R
R
R
Reset
0
0
0
0
0
R/W
0
0
0
SFR Address = 0xA9; SFR Page = All Pages
Bit
Name
7:3
2:0
Unused
CLKSL[2:0]
Function
Read = 00000b; Write = Don’t Care
System Clock Source Select Bits.
000: SYSCLK derived from the Internal High-Frequency Oscillator and scaled per the IFCN bits in register OSCICN.
001: SYSCLK derived from the External Oscillator circuit.
010: SYSCLK derived from the Internal Low-Frequency Oscillator and scaled per the OSCLD bits in register OSCLCN.
011: SYSCLK derived directly from the Internal High-Frequency
Oscillator.
100: Reserved.
101: SYSCLK derived from the Internal Low-Power Oscillator.
110: Reserved.
111: Reserved.
Preliminary Rev. 0.71
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C8051F39x/37x
26.2. Programmable Internal High-Frequency (H-F) Oscillator
All C8051F39x/37x devices include a programmable internal high-frequency oscillator that defaults as the
system clock after a system reset. The internal oscillator period can be adjusted via the OSCICL register
as defined by SFR Definition 26.2.
On C8051F39x/37x devices, OSCICL is factory calibrated to obtain a 49 MHz base frequency.
The system clock may be derived directly from the programmed internal oscillator, or from a divided version, with factors of 2, 4, 8, or 16, as defined by the IFCN bits in register OSCICN. The divide value
defaults to 16 following a reset.
26.2.1. Internal Oscillator Suspend Mode
When software writes a logic 1 to SUSPEND (OSCICN.5), the internal oscillator is suspended. If the system clock is derived from the internal oscillator, the input clock to the peripheral or CIP-51 will be stopped
until one of the following events occur:
Port 0 Match Event.
Port 1 Match Event.
 Comparator 0 enabled and output is logic 0.
 Timer3 Overflow Event.
When one of the oscillator awakening events occur, the internal oscillator, CIP-51, and affected peripherals
resume normal operation, regardless of whether the event also causes an interrupt. The CPU resumes
execution at the instruction following the write to SUSPEND.


SFR Definition 26.2. OSCICL: Internal H-F Oscillator Calibration
Bit
7
6
5
4
3
2
1
0
Varies
Varies
Varies
OSCICL[6:0]
Name
Type
R
Reset
0
R/W
Varies
Varies
Varies
Varies
SFR Address = 0xB3; SFR Page = All Pages
Bit
Name
7
6:0
Unused
OSCICL[6:0]
Function
Unused. Read = 0; Write = Don’t Care
Internal Oscillator Calibration Bits.
These bits determine the internal oscillator period. When set to
0000000b, the H-F oscillator operates at its fastest setting.
When set to 1111111b, the H-F oscillator operates at its slowest setting. The reset value is factory calibrated to generate an
internal oscillator frequency of 49 MHz.
164
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C8051F39x/37x
SFR Definition 26.3. OSCICN: Internal H-F Oscillator Control
Bit
7
6
5
4
3
2
Name
IOSCEN
IFRDY
SUSPEND
STSYNC
Type
R/W
R
R/W
R
R
R
Reset
1
1
0
0
0
0
1
0
IFCN[1:0]
R/W
0
0
SFR Address = 0xB2; SFR Page = All Pages
Bit
Name
7
IOSCEN
Function
Internal H-F Oscillator Enable Bit.
0: Internal H-F Oscillator Disabled.
1: Internal H-F Oscillator Enabled.
6
IFRDY
Internal H-F Oscillator Frequency Ready Flag.
0: Internal H-F Oscillator is not running at programmed frequency.
1: Internal H-F Oscillator is running at programmed frequency.
5
SUSPEND
Internal Oscillator Suspend Enable Bit.
Setting this bit to logic 1 places the internal oscillator in SUSPEND mode. The internal oscillator resumes operation when
one of the SUSPEND mode awakening events occurs.
4
STSYNC
Suspend Timer Synchronization Bit.
This bit is used to indicate when it is safe to read and write the
registers associated with the suspend wake-up timer. If a
suspend wake-up source other than the timer has brought the
oscillator out of suspend mode, it may take up to three timer
clocks before the timer can be read or written. When STSYNC
reads '1', reads and writes of the timer register should not be
performed. When STSYNC reads '0', it is safe to read and
write the timer registers.
3:2
1:0
Unused
IFCN[1:0]
Unused. Read = 00b; Write = Don’t Care
Internal H-F Oscillator Frequency Divider Control Bits.
These bits control the oscillator clock divider when the clock
divider is selected as the system clock source.
00: Internal H-F divide ratio = 16.
01: Internal H-F divide ratio = 8.
10: Internal H-F divide ratio = 4.
11: Internal H-F divide ratio = 2.
Preliminary Rev. 0.71
165
C8051F39x/37x
26.3. Programmable Internal Low-Frequency (L-F) Oscillator
All C8051F39x/37x devices include a programmable low-frequency internal oscillator, which is calibrated
to a nominal frequency of 80 kHz. The low-frequency oscillator circuit includes a divider that can be
changed to divide the clock by 1, 2, 4, or 8, using the OSCLD bits in the OSCLCN register (see SFR Definition 26.4). Additionally, the OSCLF[3:0] bits can be used to adjust the oscillator’s output frequency.
26.3.1. Calibrating the Internal L-F Oscillator
Timers 2 and 3 include capture functions that can be used to capture the oscillator frequency, when running from a known time base. When either Timer 2 or Timer 3 is configured for L-F Oscillator Capture
Mode, a falling edge (Timer 2) or rising edge (Timer 3) of the low-frequency oscillator’s output will cause a
capture event on the corresponding timer. As a capture event occurs, the current timer value
(TMRnH:TMRnL) is copied into the timer reload registers (TMRnRLH:TMRnRLL). By recording the difference between two successive timer capture values, the low-frequency oscillator’s period can be calculated. The OSCLF bits can then be adjusted to produce the desired oscillator frequency.
SFR Definition 26.4. OSCLCN: Internal L-F Oscillator Control
Bit
7
6
5
4
Name
OSCLEN
OSCLRDY
OSCLF[3:0]
OSCLD[1:0]
Type
R/W
R
R.W
R/W
Reset
0
0
Varies
Varies
3
Varies
2
Varies
1
0
0
0
SFR Address = 0xE3; SFR Page = All Pages
Bit
Name
7
OSCLEN
Function
Internal L-F Oscillator Enable.
0: Internal L-F Oscillator Disabled.
1: Internal L-F Oscillator Enabled.
6
OSCLRDY
Internal L-F Oscillator Ready.
0: Internal L-F Oscillator frequency not stabilized.
1: Internal L-F Oscillator frequency stabilized.
Note: OSCLRDY is only set back to 0 in the event of a device reset
or a change to the OSCLD[1:0] bits.
5:2
OSCLF[3:0]
Internal L-F Oscillator Frequency Control Bits.
Fine-tune control bits for the Internal L-F oscillator frequency.
When set to 0000b, the L-F oscillator operates at its fastest
setting. When set to 1111b, the L-F oscillator operates at its
slowest setting. The OSCLF bits should only be changed by
firmware when the L-F oscillator is disabled (OSCLEN = 0).
1:0
OSCLD[1:0]
Internal L-F Oscillator Divider Select.
00: Divide by 8 selected.
01: Divide by 4 selected.
10: Divide by 2 selected.
11: Divide by 1 selected.
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Preliminary Rev. 0.71
C8051F39x/37x
26.4. Internal Low-Power Oscillator
All C8051F39x/37x devices include a low-power internal oscillator with a nominal frequency of 20 MHz.
The low-power oscillator is automatically enabled when selected as the system clock and disabled when
not in use. See Table 7.9, “Internal Low-Power Oscillator Electrical Characteristics,” on page 37 for complete oscillator specifications.
26.5. External Oscillator Drive Circuit
The external oscillator circuit may drive an external crystal, ceramic resonator, capacitor, or RC network. A
CMOS clock may also provide a clock input. Figure 26.1 shows a block diagram of the four external oscillator options. The external oscillator is enabled and configured using the OSCXCN register (see SFR Definition 26.5).
Important Note on External Oscillator Usage: Port pins must be configured when using the external
oscillator circuit. When the external oscillator drive circuit is enabled in crystal/resonator mode, Port pins
P0.2 and P0.3 are used as XTAL1 and XTAL2, respectively. When the external oscillator drive circuit is
enabled in capacitor, RC, or CMOS clock mode, Port pin P0.3 is used as XTAL2. The Port I/O Crossbar
should be configured to skip the Port pin used by the oscillator circuit; see Section “27.3. Priority Crossbar
Decoder” on page 176 for Crossbar configuration. Additionally, when using the external oscillator circuit in
crystal/resonator, capacitor, or RC mode, the associated Port pins should be configured as analog inputs.
In CMOS clock mode, the associated pin should be configured as a digital input. See Section “27.4. Port
I/O Initialization” on page 178 for details on Port input mode selection.
The external oscillator output may be selected as the system clock or used to clock some of the digital
peripherals (e.g. Timers, PCA, etc.). See the data sheet chapters for each digital peripheral for details. See
Section “7. Electrical Characteristics” on page 32 for complete oscillator specifications.
26.5.1. External Crystal Mode
If a crystal or ceramic resonator is used as the external oscillator, the crystal/resonator and a 10 Mresistor must be wired across the XTAL1 and XTAL2 pins as shown in Figure 26.1, “Crystal Mode”. Appropriate
loading capacitors should be added to XTAL1 and XTAL2, and both pins should be configured for analog I/
O with the digital output drivers disabled.
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 recommended load capacitance depends upon the crystal and the manufacturer. Refer to the
crystal data sheet when completing these calculations.
The equation for determining the load capacitance for two capacitors is
CA  CB
C L = -------------------- + C S
CA + CB
Where:
CA and CB are the capacitors connected to the crystal leads.
CS is the total stray capacitance of the PCB.
The stray capacitance for a typical layout where the crystal is as close as possible to the pins is 2-5 pF per
pin.
If CA and CB are the same (C), then the equation becomes
C
C L = ---- + C S
2
Preliminary Rev. 0.71
167
C8051F39x/37x
For example, a tuning-fork crystal of 32 kHz with a recommended load capacitance of 12.5 pF should use
the configuration shown in Figure 26.1, Option 1. With a stray capacitance of 3 pF per pin (6 pF total), the
13 pF capacitors yield an equivalent capacitance of 12.5 pF across the crystal, as shown in Figure 26.2.
13 pF
XTAL1
10 M
32 kHz
XTAL2
13 pF
Figure 26.2. 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.
When using an external crystal, the external oscillator drive circuit must be configured by software for Crystal Oscillator Mode or Crystal Oscillator Mode with divide by 2 stage. The divide by 2 stage ensures that the
clock derived from the external oscillator has a duty cycle of 50%. The External Oscillator Frequency Control value (XFCN) must also be specified based on the crystal frequency (see SFR Definition 26.5).
When the crystal oscillator is first enabled, the external oscillator valid detector allows software to determine when the external system clock is valid and running. Switching to the external oscillator before the
crystal oscillator has stabilized can result in unpredictable behavior. The recommended procedure for starting the crystal is:
1. Configure XTAL1 and XTAL2 for analog I/O.
2. Disable the XTAL1 and XTAL2 digital output drivers by writing 1s to the appropriate bits in the Port
Latch register.
3. Configure and enable the external oscillator.
4. Wait at least 1 ms.
5. Poll for XTLVLD > 1.
6. Switch the system clock to the external oscillator.
168
Preliminary Rev. 0.71
C8051F39x/37x
26.5.2. External RC Example
If an RC network is used as an external oscillator source for the MCU, the circuit should be configured as
shown in Figure 26.1, “RC Mode”. 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, first
select the RC network value to produce the desired frequency of oscillation, according to Equation , where
f = the frequency of oscillation in MHz, C = the capacitor value in pF, and R = the pull-up resistor value in
k..
3
f = 1.23  10   R  C 
Equation 26.1. RC Mode Oscillator Frequency
For example: 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 26.5, the required XFCN setting is 010b.
26.5.3. External Capacitor Example
If a capacitor is used as an external oscillator for the MCU, the circuit should be configured as shown in
Figure 26.1, “C Mode”. 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 capacitor to be used and find the frequency of oscillation according to Equation , where f = the frequency of oscillation in MHz, C = the capacitor value in pF, and VDD = the MCU power supply in Volts.
f =  KF    C  V DD 
Equation 26.2. C Mode Oscillator Frequency
For example: Assume VDD = 3.0 V and f = 150 kHz:
f = KF / (C x VDD)
0.150 MHz = KF / (C x 3.0)
Since the frequency of roughly 150 kHz is desired, select the K Factor from the table in SFR Definition 26.5
(OSCXCN) as KF = 22:
0.150 MHz = 22 / (C x 3.0)
C x 3.0 = 22 / 0.150 MHz
C = 146.6 / 3.0 pF = 48.8 pF
Therefore, the XFCN value to use in this example is 011b and C = 50 pF.
Preliminary Rev. 0.71
169
C8051F39x/37x
SFR Definition 26.5. OSCXCN: External Oscillator Control
Bit
7
6
Name XCLKVLD
Type
R
Reset
0
5
4
3
2
XOSCMD[2:0]
R
0
0
XFCN[2:0]
R/W
0
1
0
0
R/W
0
0
0
SFR Address = 0xB1; SFR Page = All Pages
Bit
Name
Function
7
XCLKVLD
External Oscillator Valid Flag.
Provides External Oscillator status and is valid at all times for all modes of operation except External CMOS Clock Mode and External CMOS Clock Mode with
divide by 2. In these modes, XCLKVLD always returns 0.
0: External Oscillator is unused or not yet stable.
1: External Oscillator is running and stable.
6:4
XOSCMD[2:0] External Oscillator Mode Select.
00x: External Oscillator circuit off.
010: External CMOS Clock Mode.
011: External CMOS Clock Mode with divide-by-2 stage.
100: RC Oscillator Mode with divide-by-2 stage.
101: Capacitor Oscillator Mode with divide-by-2 stage.
110: Crystal Oscillator Mode.
111: Crystal Oscillator Mode with divide-by-2 stage.
3
Unused
2:0
XFCN[2:0]
Read = 0; Write = don’t care
External Oscillator Frequency Control Bits.
Set according to the desired frequency for RC mode.
Set according to the desired K Factor for C mode.
170
XFCN
Crystal Mode
RC Mode
C Mode
000
001
010
011
100
101
110
111
f 20 kHz
20 kHz f 58 kHz
58 kHz f 155 kHz
155 kHz f 415 kHz
415 kHz f 1.1 MHz
1.1 MHz f 3.1 MHz
3.1 MHz f 8.2 MHz
8.2 MHz f 25 MHz
f 25 kHz
25 kHz f 50 kHz
50 kHz f 100 kHz
100 kHz f 200 kHz
200 kHz f 400 kHz
400 kHz f 800 kHz
800 kHz f 1.6 MHz
1.6 MHz f 3.2 MHz
K Factor = 0.87
K Factor = 2.6
K Factor = 7.7
K Factor = 22
K Factor = 65
K Factor = 180
K Factor = 664
K Factor = 1590
Preliminary Rev. 0.71
C8051F39x/37x
27. Port Input/Output
Digital and analog resources are available through 17 (C8051F392/3/6/7/8/9) or 21 (C8051F390/1/4/5 and
C8051F37x) I/O pins. Port pins P0.0-P2.3 can be defined as general-purpose I/O (GPIO), assigned to one
of the internal digital resources, or assigned to an analog function as shown in Figure 27.3. Port pin P2.4
on the C8051F390/1/4/5 and C8051F37x and P2.0 on the C8051F392/3/6/7/8/9 can be used as GPIO and
are shared with the C2 Interface Data signal (C2D). The designer has complete control over which functions are assigned, limited only by the number of physical I/O pins. This resource assignment flexibility is
achieved through the use of a Priority Crossbar Decoder. Note that the state of a Port I/O pin can always
be read in the corresponding Port latch, regardless of the Crossbar settings.
The Crossbar assigns the selected internal digital resources to the I/O pins based on the Priority Decoder
(Figure 27.3 and Figure 27.4). The registers XBR0 and XBR1, defined in SFR Definition 27.1 and SFR
Definition 27.2, are used to select internal digital functions.
The Port I/O cells are configured as either push-pull or open-drain in the Port Output Mode registers
(PnMDOUT, where n = 0,1). Complete Electrical Specifications for Port I/O are given in Section
“7. Electrical Characteristics” on page 32.
Port Match
P0MASK, P0MAT
P1MASK, P1MAT
XBR0, XBR1,
PnSKIP Registers
External Interrupts
EX0 and EX1
Priority
Decoder
Highest
Priority
UART
4
(Internal Digital Signals)
SPI
SMBus0
CP0
Outputs
2
2
P0.0
Digital
Crossbar
8
P0.7
4
PCA
SMBus1
8
2
P0
P1.0
P1
I/O
Cells
P1.7
2
8
(Port Latches)
P0
I/O
Cells
SYSCLK
T0, T1
Lowest
Priority
PnMDOUT,
PnMDIN Registers
2
(P0.0-P0.7)
4
P2.0*
P2
I/O
Cell
P2.3*
8
P1
(P1.0-P1.7)
P2
(P2.0-P2.3*)
4
To Analog Peripherals
(ADC0, CP0, VREF, XTAL)
*P2.0-P2.3 are only available through
the crossbar on QFN24 Packages.
Figure 27.1. Port I/O Functional Block Diagram
Preliminary Rev. 0.71
171
C8051F39x/37x
27.1. Port I/O Modes of Operation
Port pins P0.0 - P2.3 use the Port I/O cell shown in Figure 27.2. Each Port I/O cell can be configured by
software for analog I/O or digital I/O using the PnMDIN registers. On reset, all Port I/O cells default to a
high impedance state with weak pull-ups enabled. Until the crossbar is enabled (XBARE = ‘1’), both the
high and low port I/O drive circuits are explicitly disabled on all crossbar pins.
27.1.1. Port Pins Configured for Analog I/O
Any pins to be used as Comparator or ADC input, external oscillator input/output, VREF, or IDAC output
should be configured for analog I/O (PnMDIN.n = ‘1’). When a pin is configured for analog I/O, its weak
pullup, digital driver, and digital receiver are disabled. Port pins configured for analog I/O will always read
back a value of ‘0’.
Configuring pins as analog I/O saves power and isolates the Port pin from digital interference. Port pins
configured as digital I/O may still be used by analog peripherals; however, this practice is not recommended and may result in measurement errors.
27.1.2. Port Pins Configured For Digital I/O
Any pins to be used by digital peripherals (UART, SPI, SMBus, etc.), external event trigger functions, or as
GPIO should be configured as digital I/O (PnMDIN.n = ‘1’). For digital I/O pins, one of two output modes
(push-pull or open-drain) must be selected using the PnMDOUT registers.
Push-pull outputs (PnMDOUT.n = ‘1’) drive the Port pad to the VDD or GND supply rails based on the output logic value of the Port pin. Open-drain outputs have the high side driver disabled; therefore, they only
drive the Port pad to GND when the output logic value is ‘0’ and become high impedance inputs (both high
low drivers turned off) when the output logic value is ‘1’.
When a digital I/O cell is placed in the high impedance state, a weak pull-up transistor pulls the Port pad to
the VDD supply voltage to ensure the digital input is at a defined logic state. Weak pull-ups are disabled
when the I/O cell is driven to GND to minimize power consumption, and they may be globally disabled by
setting WEAKPUD to ‘1’. The user should ensure that digital I/O are always internally or externally pulled
or driven to a valid logic state to minimize power consumption. Port pins configured for digital I/O always
read back the logic state of the Port pad, regardless of the output logic value of the Port pin.
WEAKPUD
(Weak Pull-Up Disable)
PxMDOUT.x
(1 for push-pull)
(0 for open-drain)
VDD
XBARE
(Crossbar
Enable)
(WEAK)
PORT
PAD
Px.x – Output
Logic Value
(Port Latch or
Crossbar)
PxMDIN.x
(1 for digital)
(0 for analog)
To/From Analog
Peripheral
GND
Px.x – Input Logic Value
(Reads 0 when pin is configured as an analog I/O)
Figure 27.2. Port I/O Cell Block Diagram
172
VDD
Preliminary Rev. 0.71
C8051F39x/37x
27.2. Assigning Port I/O Pins to Analog and Digital Functions
Port I/O pins P0.0 - P2.3 can be assigned to various analog, digital, and external interrupt functions. The
Port pins assigned to analog functions should be configured for analog I/O, and Port pins assigned to digital or external interrupt functions should be configured for digital I/O.
27.2.1. Assigning Port I/O Pins to Analog Functions
Table 27.1 shows all available analog functions that require Port I/O assignments. Port pins selected for
these analog functions should have their corresponding bit in PnSKIP set to ‘1’. This reserves the
pin for use by the analog function and does not allow it to be claimed by the Crossbar. Table 27.1 shows
the potential mapping of Port I/O to each analog function.
Table 27.1. Port I/O Assignment for Analog Functions
Analog Function
Potentially Assignable
Port Pins
SFR(s) used for
Assignment
ADC Input
P0.0 - P2.3
AMX0P, AMX0N,
PnSKIP, PnMDIN
Comparator0 Input
P0.0 - P2.3
CPT0MX, PnSKIP,
PnMDIN
Voltage Reference (VREF0)
P0.0
REF0CN, PnSKIP,
PnMDIN
Current DAC Output (IDA0)
P0.1
IDA0CN, PnSKIP,
PnMDIN
Current DAC Output (IDA1)
P1.0 (20-pin devices)
P1.2 (24-pin devices)
IDA1CN, PnSKIP,
PnMDIN
External Oscillator in Crystal Mode (XTAL1)
P0.2
OSCXCN, PnSKIP,
PnMDIN
External Oscillator in RC, C, or Crystal Mode (XTAL2)
P0.3
OSCXCN, PnSKIP,
PnMDIN
Preliminary Rev. 0.71
173
C8051F39x/37x
27.2.2. Assigning Port I/O Pins to Digital Functions
Any Port pins not assigned to analog functions may be assigned to digital functions or used as GPIO. Most
digital functions rely on the Crossbar for pin assignment; however, some digital functions bypass the
Crossbar in a manner similar to the analog functions listed above. Port pins used by these digital functions and any Port pins selected for use as GPIO should have their corresponding bit in PnSKIP set
to ‘1’. Table 27.2 shows all available digital functions and the potential mapping of Port I/O to each digital
function.
Table 27.2. Port I/O Assignment for Digital Functions
Digital Function
UART0, SPI0, SMBus0,
SMBus1, CP0, CP0A,
SYSCLK, PCA0 (CEX0-2
and ECI), T0 or T1.
Any pin used for GPIO
174
Potentially Assignable Port Pins
Any Port pin available for assignment by the
Crossbar. This includes P0.0 - P2.3 pins which
have their PnSKIP bit set to ‘0’.
Note: The Crossbar will always assign UART0
pins to P0.4 and P0.5.
P0.0 - P2.4
Preliminary Rev. 0.71
SFR(s) Used for
Assignment
XBR0, XBR1
P0SKIP, P1SKIP,
P2SKIP
C8051F39x/37x
27.2.3. Assigning Port I/O Pins to External Event Trigger Functions
External event trigger functions can be used to trigger an interrupt or wake the device from a low power
mode when a transition occurs on a digital I/O pin. The event trigger functions do not require dedicated
pins and will function on both GPIO pins (PnSKIP = ’1’) and pins in use by the Crossbar (PnSKIP = ‘0’).
External event trigger functions cannot be used on pins configured for analog I/O. Table 27.3 shows all
available external event trigger functions.
Table 27.3. Port I/O Assignment for External Event Trigger Functions
Event Trigger Function
Potentially Assignable Port Pins
SFR(s) used for
Assignment
External Interrupt 0
P0.0 - P0.7
IT01CF
External Interrupt 1
P0.0 - P0.7
IT01CF
Port Match
P0.0 - P1.7
P0MASK, P0MAT
P1MASK, P1MAT
Preliminary Rev. 0.71
175
C8051F39x/37x
27.3. Priority Crossbar Decoder
The Priority Crossbar Decoder (Figure 27.3) assigns a priority to each I/O function, starting at the top with
UART0. When a digital resource is selected, the least-significant unassigned Port pin is assigned to that
resource (excluding UART0, which is always at pins 4 and 5). If a Port pin is assigned, the Crossbar skips
that pin when assigning the next selected resource. Additionally, the Crossbar will skip Port pins whose
associated bits in the PnSKIP registers are set. The PnSKIP registers allow software to skip Port pins that
are to be used for analog input, dedicated functions, or GPIO.
Important Note on Crossbar Configuration: If a Port pin is claimed by a peripheral without use of the
Crossbar, its corresponding PnSKIP bit should be set. This applies to P0.0 if VREF is used, P0.3 and/or
P0.2 if the external oscillator circuit is enabled, P0.6 if the ADC or IDAC is configured to use the external
conversion start signal (CNVSTR), and any selected ADC or Comparator inputs. The Crossbar skips
selected pins as if they were already assigned, and moves to the next unassigned pin.
Figure 27.3 shows all of the potential peripheral-to-pin assignments available to the crossbar. Note that
this does not mean any peripheral can always be assigned to the highlighted pins. The actual pin assignments are determined by the priority of the enabled peripherals.
2
3
4
5
6
7
0
1
2
3
4
5
6
7
04
13
EESCL 5
x2
x2
1
EESDA 5
x1
x1
0
IDA1
IDA0
IDA0
PIN I/O
IDA1
VREF
SF Signals
(24-pin)
P2
P1
CNVSTR CNVSTR
SF Signals
(20-pin)
VREF
P0
23
33
43
TX0
RX0
SCK
Pin not available for crossbar peripherals.
MISO
MOSI
NSS1
SDA02
SCL02
CP0
CP0A
SYSCLK
CEX0
CEX1
CEX2
ECI
T0
T1
SDA12
SCL12
SF Signals
Port pin potentially available to peripheral
Notes:
Special Function Signals are not assigned by the crossbar.
When these signals are enabled, the Crossbar must be
manually configured to skip their corresponding port pins.
1.
2.
3.
4.
5.
NSS is only pinned out in 4-wire SPI Mode
SMBus pins can be re-ordered using SMBTC register
Pins P2.1-P2.4 only on QFN24 Package
Pin 2.0 unavailable on crossbar in QFN20 Package
C8051F37x only
Figure 27.3. Crossbar Priority Decoder - Possible Pin Assignments
176
Preliminary Rev. 0.71
C8051F39x/37x
Registers XBR0 and XBR1 are used to assign the digital I/O resources to the physical I/O Port pins. Note
that when the SMBus is selected, the Crossbar assigns both pins associated with the SMBus (SDA and
SCL); when the UART is selected, the Crossbar assigns both pins associated with the UART (TX and RX).
UART0 pin assignments are fixed for bootloading purposes: UART TX0 is always assigned to P0.4; UART
RX0 is always assigned to P0.5. Standard Port I/Os appear contiguously after the prioritized functions
have been assigned.
Figure 27.4 shows an example of the resulting pin assignments of the device with UART0, SMBus, and
CEX0 enabled, the XTAL1 (P0.2) and XTAL2 (P0.3) pins skipped (P0SKIP = 0x0C). UART0 is the highest
priority and it will be assigned first. The UART can only appear on P0.4 and P0.5, so that is where it is
assigned. The next-highest enabled peripheral is SMBus0. P0.0 and P0.1 are free, so SMBus0 takes
these two pins. The last peripheral enabled is the PCA’s CEX0 pin. P0.0, P0.1, P0.4 and P0.5 are already
occupied by higher-priority peripherals. Additionally, P0.2 and P0.3 are set to be skipped by the crossbar.
The CEX0 signal ends up getting routed to P0.6, as it is the next available pin. The other pins on the
device are available for use as general-purpose digital I/O or analog functions.
4
5
6
7
0
1
2
1
0
0
0
0
0
0
0
12
22
32
0
0
0
IDA1
3
EESCL 5
1
2
EESDA 5
0
P2
IDA1
0
CNVSTR CNVSTR
1
x2
0
x2
IDA0
IDA0
PIN I/O
x1
VREF
SF Signals
(24-pin)
P1
x1
SF Signals
(20-pin)
VREF
P0
3
4
5
6
7
0
0
0
0
0
0
0
42
TX0
RX0
SCK
Pin not available for crossbar peripherals.
MISO
MOSI
NSS1
SDA
SCL
CP0
CP0A
SYSCLK
CEX0
CEX1
CEX2
ECI
T0
T1
SDA12
SCL12
P1SKIP[0:7]
P0SKIP[0:7]
SF Signals
Port pin potentially available to peripheral
Notes:
Special Function Signals are not assigned by the crossbar.
When these signals are enabled, the CrossBar must be
manually configured to skip their corresponding port pins.
1.
2.
3.
4.
5.
P2SKIP[0:3]
NSS is only pinned out in 4-wire SPI Mode
SMBus pins can be re-ordered using SMBTC register
Pins P2.1-P2.4 only on QFN24 Package
Pin 2.0 unavailable on crossbar in QFN20 Package
C8051F37x only
Figure 27.4. Crossbar Priority Decoder Example
Important Notes: The SPI can be operated in either 3-wire or 4-wire modes, pending the state of the
NSSMD1–NSSMD0 bits in register SPI0CN. According to the SPI mode, the NSS signal may or may not
be routed to a Port pin. The order in which SMBus pins are assigned is defined by the SMBnSWAP bits in
the SMBTC register.
Preliminary Rev. 0.71
177
C8051F39x/37x
27.4. Port I/O Initialization
Port I/O initialization consists of the following steps:
1. Select the input mode (analog or digital) for all Port pins, using the Port Input Mode register (PnMDIN).
2. Select the output mode (open-drain or push-pull) for all Port pins, using the Port Output Mode register
(PnMDOUT).
3. Select any pins to be skipped by the I/O Crossbar using the Port Skip registers (PnSKIP).
4. Assign Port pins to desired peripherals.
5. Enable the Crossbar (XBARE = ‘1’).
All Port pins must be configured as either analog or digital inputs. Any pins to be used as Comparator or
ADC inputs should be configured as an analog inputs. When a pin is configured as an analog input, its
weak pullup, digital driver, and digital receiver are disabled. This process saves power and reduces noise
on the analog input. Pins configured as digital inputs may still be used by analog peripherals; however this
practice is not recommended.
Additionally, all analog input pins should be configured to be skipped by the Crossbar (accomplished by
setting the associated bits in PnSKIP). Port input mode is set in the PnMDIN register, where a ‘1’ indicates
a digital input, and a ‘0’ indicates an analog input. All pins default to digital inputs on reset. See SFR Definition 27.8 for the PnMDIN register details.
The output driver characteristics of the I/O pins are defined using the Port Output Mode registers (PnMDOUT). Each Port Output driver can be configured as either open drain or push-pull. This selection is
required even for the digital resources selected in the XBRn registers, and is not automatic. The only
exception to this is the SMBus (SDA, SCL) pins, which are configured as open-drain regardless of the
PnMDOUT settings. When the WEAKPUD bit in XBR1 is ‘0’, a weak pullup is enabled for all Port I/O configured as open-drain. WEAKPUD does not affect the push-pull Port I/O. Furthermore, the weak pullup is
turned off on an output that is driving a ‘0’ to avoid unnecessary power dissipation.
Registers XBR0 and XBR1 must be loaded with the appropriate values to select the digital I/O functions
required by the design. Setting the XBARE bit in XBR1 to ‘1’ enables the Crossbar. Until the Crossbar is
enabled, the external pins remain as standard Port I/O (in input mode), regardless of the XBRn Register
settings. For given XBRn Register settings, one can determine the I/O pin-out using the Priority Decode
Table; as an alternative, the Configuration Wizard utility of the Silicon Labs IDE software will determine the
Port I/O pin-assignments based on the XBRn Register settings.
The Crossbar must be enabled to use Port pins as standard Port I/O in output mode. Port output drivers
are disabled while the Crossbar is disabled.
178
Preliminary Rev. 0.71
C8051F39x/37x
SFR Definition 27.1. XBR0: Port I/O Crossbar Register 0
Bit
7
6
5
4
3
2
1
0
Name
EEPUE
SMB1E
CP0AE
CP0E
SYSCKE
SMB0E
SPI0E
URT0E
Type
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
SFR Address = 0xE1; SFR Page = All Pages
Bit
Name
7
EEPUE
Function
EEPROM Pullup Enable.
0: On-chip strong pullups not active.
1: On-chip strong pullups active on pins P2.2 and P2.3.
6
SMB1E
SMBus1 I/O Enable.
0: SMBus1 I/O unavailable at Port pins.
1: SMBus1 I/O routed to Port pins.
5
CP0AE
Comparator0 Asynchronous Output Enable.
0: Asynchronous CP0 unavailable at Port pin.
1: Asynchronous CP0 routed to Port pin.
4
CP0E
Comparator0 Output Enable.
0: CP0 unavailable at Port pin.
1: CP0 routed to Port pin.
3
SYSCKE
/SYSCLK Output Enable.
0: /SYSCLK unavailable at Port pin.
1: /SYSCLK output routed to Port pin.
2
SMB0E
SMBus0 I/O Enable.
0: SMBus0 I/O unavailable at Port pins.
1: SMBus0 I/O routed to Port pins.
1
SPI0E
SPI I/O Enable.
0: SPI I/O unavailable at Port pins.
1: SPI I/O routed to Port pins. Note that the SPI can be assigned
either 3 or 4 GPIO pins.
0
URT0E
UART I/O Output Enable.
0: UART I/O unavailable at Port pin.
1: UART TX0, RX0 routed to Port pins P0.4 and P0.5.
Preliminary Rev. 0.71
179
C8051F39x/37x
SFR Definition 27.2. XBR1: Port I/O Crossbar Register 1
Bit
7
Name WEAKPUD
6
5
4
3
XBARE
T1E
T0E
ECIE
2
1
0
PCA0ME[1:0]
Type
R/W
R/W
R/W
R/W
R/W
R
R/W
R/W
Reset
0
0
0
0
0
0
0
0
SFR Address = 0xE2; SFR Page = All Pages
Bit
Name
7
WEAKPUD
Function
Port I/O Weak Pullup Disable.
0: Weak Pullups enabled (except for Ports whose I/O are configured for analog mode).
1: Weak Pullups disabled.
6
XBARE
Crossbar Enable.
0: Crossbar disabled.
1: Crossbar enabled.
5
T1E
T1 Enable.
0: T1 unavailable at Port pin.
1: T1 routed to Port pin.
4
T0E
T0 Enable.
0: T0 unavailable at Port pin.
1: T0 routed to Port pin.
3
ECIE
PCA0 External Counter Input Enable.
0: ECI unavailable at Port pin.
1: ECI routed to Port pin.
2
1:0
Unused
PCA0ME[1:0]
Read = 0b; Write = Don’t Care.
PCA Module I/O Enable Bits.
00: All PCA I/O unavailable at Port pins.
01: CEX0 routed to Port pin.
10: CEX0, CEX1 routed to Port pins.
11: CEX0, CEX1, CEX2 routed to Port pins.
180
Preliminary Rev. 0.71
C8051F39x/37x
27.5. Port Match
Port match functionality allows system events to be triggered by a logic value change on P0 or P1. A software controlled value stored in the PnMATCH registers specifies the expected or normal logic values of P0
and P1. A Port mismatch event occurs if the logic levels of the Port’s input pins no longer match the software controlled value. This allows Software to be notified if a certain change or pattern occurs on P0 or P1
input pins regardless of the XBRn settings.
The PnMASK registers can be used to individually select which P0 and P1 pins should be compared
against the PnMATCH registers. A Port mismatch event is generated if (P0 & P0MASK) does not equal
(P0MATCH & P0MASK) or if (P1 & P1MASK) does not equal (P1MATCH & P1MASK).
A Port mismatch event may be used to generate an interrupt or wake the device from a low power mode,
such as IDLE or SUSPEND. See the Interrupts and Power Options chapters for more details on interrupt
and wake-up sources.
SFR Definition 27.3. P0MASK: Port 0 Mask Register
Bit
7
6
5
4
3
Name
P0MASK[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address = 0xFE; SFR Page = All Pages
Bit
Name
7:0
P0MASK[7:0]
Function
Port 0 Mask Value.
Selects P0 pins to be compared to the corresponding bits
in P0MAT.
0: P0.n pin logic value is ignored and cannot cause a Port
Mismatch event.
1: P0.n pin logic value is compared to P0MAT.n.
Preliminary Rev. 0.71
181
C8051F39x/37x
SFR Definition 27.4. P0MAT: Port 0 Match Register
Bit
7
6
5
4
3
Name
P0MAT[7:0]
Type
R/W
Reset
1
1
1
1
1
2
1
0
1
1
1
SFR Address = 0xFD; SFR Page = All Pages
Bit
Name
7:0
P0MAT[7:0]
Function
Port 0 Match Value.
Match comparison value used on Port 0 for bits in
P0MASK which are set to ‘1’.
0: P0.n pin logic value is compared with logic LOW.
1: P0.n pin logic value is compared with logic HIGH.
SFR Definition 27.5. P1MASK: Port 1 Mask Register
Bit
7
6
5
4
3
Name
P1MASK[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address = 0xEE; SFR Page = All Pages
Bit
Name
7:0
P1MASK[7:0]
Function
Port 1 Mask Value.
Selects P1 pins to be compared to the corresponding bits
in P1MAT.
0: P1.n pin logic value is ignored and cannot cause a Port
Mismatch event.
1: P1.n pin logic value is compared to P1MAT.n.
182
Preliminary Rev. 0.71
C8051F39x/37x
SFR Definition 27.6. P1MAT: Port 1 Match Register
Bit
7
6
5
4
3
Name
P1MAT[7:0]
Type
R/W
Reset
1
1
1
1
1
2
1
0
1
1
1
SFR Address = 0xED; SFR Page = All Pages
Bit
Name
7:0
P1MAT[7:0]
Function
Port 1 Match Value.
Match comparison value used on Port 1 for bits in
P1MASK which are set to ‘1’.
0: P1.n pin logic value is compared with logic LOW.
1: P1.n pin logic value is compared with logic HIGH.
27.6. Special Function Registers for Accessing and Configuring Port I/O
All Port I/O are accessed through corresponding special function registers (SFRs) that are both byte
addressable and bit addressable. When writing to a Port, the value written to the SFR is latched to maintain the output data value at each pin. When reading, the logic levels of the Port's input pins are returned
regardless of the XBRn settings (i.e., even when the pin is assigned to another signal by the Crossbar, the
Port register can always read its corresponding Port I/O pin). The exception to this is the execution of the
read-modify-write instructions that target a Port Latch register as the destination. The read-modify-write
instructions when operating on a Port SFR are the following: ANL, ORL, XRL, JBC, CPL, INC, DEC, DJNZ
and MOV, CLR or SETB, when the destination is an individual bit in a Port SFR. For these instructions, the
value of the latch register (not the pin) is read, modified, and written back to the SFR.
Each Port has a corresponding PnSKIP register which allows its individual Port pins to be assigned to digital functions or skipped by the Crossbar. All Port pins used for analog functions, GPIO, or dedicated digital
functions such as the EMIF should have their PnSKIP bit set to ‘1’.
The Port input mode of the I/O pins is defined using the Port Input Mode registers (PnMDIN). Each Port
cell can be configured for analog or digital I/O. This selection is required even for the digital resources
selected in the XBRn registers, and is not automatic. The only exception to this is P2.4, which can only be
used for digital I/O.
The output driver characteristics of the I/O pins are defined using the Port Output Mode registers (PnMDOUT). Each Port Output driver can be configured as either open drain or push-pull. This selection is
required even for the digital resources selected in the XBRn registers, and is not automatic. The only
exception to this is the SMBus (SDA, SCL) pins, which are configured as open-drain regardless of the
PnMDOUT settings.
Preliminary Rev. 0.71
183
C8051F39x/37x
SFR Definition 27.7. P0: Port 0
Bit
7
6
5
4
Name
P0[7:0]
Type
R/W
Reset
1
1
1
1
3
2
1
0
1
1
1
1
SFR Address = 0x80; SFR Page = All Pages; Bit Addressable
Bit
Name
7:0
P0[7:0]
Description
Write
Port 0 Data.
Sets the Port latch logic
value or reads the Port pin
logic state in Port cells configured for digital I/O.
Read
0: Set output latch to logic
LOW.
1: Set output latch to logic
HIGH.
0: P0.n Port pin is logic
LOW.
1: P0.n Port pin is logic
HIGH.
SFR Definition 27.8. P0MDIN: Port 0 Input Mode
Bit
7
6
5
4
3
Name
P0MDIN[7:0]
Type
R/W
Reset
1
1
1
1
1
2
1
0
1
1
1
SFR Address = 0xF1; SFR Page = All Pages
Bit
Name
Function
7:0
P0MDIN[7:0]
Analog Configuration Bits for P0.7–P0.0 (respectively).
Port pins configured for analog mode have their weak pullup, digital driver, and digital receiver disabled.
0: Corresponding P0.n pin is configured for analog mode.
1: Corresponding P0.n pin is not configured for analog
mode.
184
Preliminary Rev. 0.71
C8051F39x/37x
SFR Definition 27.9. P0MDOUT: Port 0 Output Mode
Bit
7
6
5
4
3
Name
P0MDOUT[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address = 0xA4; SFR Page = All Pages
Bit
Name
Function
7:0
P0MDOUT[7:0]
Output Configuration Bits for P0.7–P0.0 (respectively).
These bits are ignored if the corresponding bit in register
P0MDIN is logic 0.
0: Corresponding P0.n Output is open-drain.
1: Corresponding P0.n Output is push-pull.
SFR Definition 27.10. P0SKIP: Port 0 Skip
Bit
7
6
5
4
3
Name
P0SKIP[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address = 0xD4; SFR Page = All Pages
Bit
Name
7:0
P0SKIP[7:0]
Function
Port 0 Crossbar Skip Enable Bits.
These bits select Port 0 pins to be skipped by the Crossbar
Decoder. Port pins used for analog, special functions or
GPIO should be skipped by the Crossbar.
0: Corresponding P0.n pin is not skipped by the Crossbar.
1: Corresponding P0.n pin is skipped by the Crossbar.
Preliminary Rev. 0.71
185
C8051F39x/37x
SFR Definition 27.11. P1: Port 1
Bit
7
6
5
4
Name
P1[7:0]
Type
R/W
Reset
1
1
1
1
3
2
1
0
1
1
1
1
SFR Address = 0x90; SFR Page = All Pages; Bit Addressable
Bit
Name
7:0
P1[7:0]
Description
Write
Port 1 Data.
Sets the Port latch logic
value or reads the Port pin
logic state in Port cells configured for digital I/O.
Read
0: Set output latch to logic
LOW.
1: Set output latch to logic
HIGH.
0: P1.n Port pin is logic
LOW.
1: P1.n Port pin is logic
HIGH.
SFR Definition 27.12. P1MDIN: Port 1 Input Mode
Bit
7
6
5
4
3
Name
P1MDIN[7:0]
Type
R/W
Reset
1
1
1
1
1
2
1
0
1
1
1
SFR Address = 0xF2; SFR Page = All Pages
Bit
Name
Function
7:0
P1MDIN[7:0]
Analog Configuration Bits for P1.7–P1.0 (respectively).
Port pins configured for analog mode have their weak pullup, digital driver, and digital receiver disabled.
0: Corresponding P1.n pin is configured for analog mode.
1: Corresponding P1.n pin is not configured for analog
mode.
186
Preliminary Rev. 0.71
C8051F39x/37x
SFR Definition 27.13. P1MDOUT: Port 1 Output Mode
Bit
7
6
5
4
3
Name
P1MDOUT[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address = 0xA5; SFR Page = All Pages
Bit
Name
Function
7:0
P1MDOUT[7:0]
Output Configuration Bits for P1.7–P1.0 (respectively).
These bits are ignored if the corresponding bit in register
P1MDIN is logic 0.
0: Corresponding P1.n Output is open-drain.
1: Corresponding P1.n Output is push-pull.
SFR Definition 27.14. P1SKIP: Port 1 Skip
Bit
7
6
5
4
3
Name
P1SKIP[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address = 0xD5; SFR Page = All Pages
Bit
Name
7:0
P1SKIP[7:0]
Function
Port 1 Crossbar Skip Enable Bits.
These bits select Port 1 pins to be skipped by the Crossbar
Decoder. Port pins used for analog, special functions or
GPIO should be skipped by the Crossbar.
0: Corresponding P1.n pin is not skipped by the Crossbar.
1: Corresponding P1.n pin is skipped by the Crossbar.
Preliminary Rev. 0.71
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C8051F39x/37x
SFR Definition 27.15. P2: Port 2
Bit
7
6
5
4
3
2
1
0
1
1
P2[4:0]
Name
Type
R
R
R
Reset
0
0
0
R/W
1
1
1
SFR Address = 0xA0; SFR Page = All Pages; Bit Addressable
Bit
Name
Description
Write
7:5
Unused
Unused.
Don’t Care
000b
4:0
P2[4:0]
Port 2 Data.
0: Set output latch to logic
LOW.
1: Set output latch to logic
HIGH.
0: P2.n Port pin is logic
LOW.
1: P2.n Port pin is logic
HIGH.
Sets the Port latch logic
value or reads the Port pin
logic state in Port cells configured for digital I/O.
Read
Note: Pins P2.1-P2.4 are only available in QFN24-packaged devices.
SFR Definition 27.16. P2MDIN: Port 2 Input Mode
Bit
7
6
5
4
3
2
1
0
P2MDIN[7:0]
Name
Type
R
R
R
R
Reset
0
0
0
0
R/W
1
1
1
1
SFR Address = 0xF3; SFR Page = All Pages
Bit
Name
7:4
3:0
Unused
P2MDIN[3:0]
Function
Read = 0000b; Write = Don’t Care
Analog Configuration Bits for P2.3–P2.0 (respectively).
Port pins configured for analog mode have their weak pullup, digital
driver, and digital receiver disabled.
0: Corresponding P2.n pin is configured for analog mode.
1: Corresponding P2.n pin is not configured for analog mode.
Note: Pins P2.1-P2.4 are only available in QFN24-packaged devices.
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SFR Definition 27.17. P2MDOUT: Port 2 Output Mode
Bit
7
6
5
4
3
2
1
0
0
0
P2MDOUT[4:0]
Name
Type
R
R
R
Reset
0
0
0
R/W
0
0
0
SFR Address = 0xA6; SFR Page = All Pages
Bit
Name
7:5
4:0
Unused
P2MDOUT[4:0]
Function
Read = 000b; Write = Don’t Care
Output Configuration Bits for P2.4–P2.0 (respectively).
These bits are ignored if the corresponding bit in register
P2MDIN is logic 0.
0: Corresponding P2.n Output is open-drain.
1: Corresponding P2.n Output is push-pull.
Note: P2.0 is not available for analog input in the QFN20-packaged devices, and P2.1-P2.4 are only available in the
QFN24-packaged devices.
SFR Definition 27.18. P2SKIP: Port 2 Skip
Bit
7
6
5
4
3
2
1
0
P2SKIP[7:0]
Name
Type
R
R
R
R
Reset
0
0
0
0
R/W
0
0
0
0
SFR Address = 0xD6; SFR Page = All Pages
Bit
Name
7:4
3:0
Unused
P2SKIP[3:0]
Function
Read = 0000b; Write = Don’t Care
Port 2 Crossbar Skip Enable Bits.
These bits select Port 2 pins to be skipped by the Crossbar
Decoder. Port pins used for analog, special functions or
GPIO should be skipped by the Crossbar.
0: Corresponding P2.n pin is not skipped by the Crossbar.
1: Corresponding P2.n pin is skipped by the Crossbar.
Note: P2.0 is not available for crossbar peripherals in the QFN20-packaged devices, and P2.1-P2.4 are only
available in the QFN24-packaged devices.
Preliminary Rev. 0.71
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C8051F39x/37x
28. SMBus0 and SMBus1 (I2C Compatible)
The SMBus I/O interface is a two-wire, bi-directional serial bus. The SMBus is compliant with the System
Management Bus Specification, version 1.1, and compatible with the I2C serial bus. The C8051F39x/37x
devices contain two SMBus interfaces, SMBus0 and SMBus1.
Reads and writes to the SMBus by the system controller are byte oriented with the SMBus interface autonomously controlling the serial transfer of the data. Data can be transferred at up to 1/20th of the system
clock as a master or slave (this can be faster than allowed by the SMBus specification, depending on the
system clock used). A method of extending the clock-low duration is available to accommodate devices
with different speed capabilities on the same bus.
The SMBus may operate as a master and/or slave, and may function on a bus with multiple masters. The
SMBus provides control of SDA (serial data), SCL (serial clock) generation and synchronization, arbitration
logic, and START/STOP control and generation. The SMBus peripherals can be fully driven by software
(i.e., software accepts/rejects slave addresses, and generates ACKs), or hardware slave address recognition and automatic ACK generation can be enabled to minimize software overhead. A block diagram of the
SMBus0 peripheral and the associated SFRs is shown in Figure 28.1. SMBus1 is identical, with the exception of the available timer options for the clock source, and the timer used to implement the SCL low timeout feature. Refer to the specific SFR definitions for more details.
SMB0CN
M T S S A A A S
A X T T CR C I
SMAOK B K
T O
R L
E D
QO
R E
S
T
SMB0CF
E I B E S S S S
N N U XMMMM
S H S T B B B B
M Y H T F CC
B
OO T S S
L E E 1 0
D
SMBUS CONTROL LOGIC
Arbitration
SCL Synchronization
SCL Generation (Master Mode)
SDA Control
Hardware Slave Address Recognition
Hardware ACK Generation
Data Path
IRQ Generation
Control
Interrupt
Request
00
T0 Overflow
01
T1 Overflow
10
TMR2H Overflow
11
TMR2L Overflow
SCL
Control
S
L
V
5
S
L
V
4
S
L
V
3
S
L
V
2
S
L
V
1
SMB0ADR
SG
L C
V
0
S S S S S S S
L L L L L L L
V V V V V V V
MMMMMMM
6 5 4 3 2 1 0
SMB0ADM
SDA
FILTER
E
H
A
C
K
N
Figure 28.1. SMBus0 Block Diagram
190
C
R
O
S
S
B
A
R
N
SDA
Control
SMB0DAT
7 6 5 4 3 2 1 0
S
L
V
6
SCL
FILTER
Preliminary Rev. 0.71
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C8051F39x/37x
28.1. Supporting Documents
It is assumed the reader is familiar with or has access to the following supporting documents:
1. The I2C-Bus and How to Use It (including specifications), Philips Semiconductor.
2. The I2C-Bus Specification—Version 2.0, Philips Semiconductor.
3. System Management Bus Specification—Version 1.1, SBS Implementers Forum.
28.2. SMBus Configuration
Figure 28.2 shows a typical SMBus configuration. The SMBus specification allows any recessive voltage
between 3.0 V and 5.0 V; different devices on the bus may operate at different voltage levels. However, the
maximum voltage on any port pin must conform to Table 7.1. 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 (recessive state) 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 not
exceed 300 ns and 1000 ns, respectively.
3.0V < VDD < 3.6V
Master
Device
Slave
Device 1
Slave
Device 2
SDA
SCL
Figure 28.2. Typical SMBus Configuration
28.3. SMBus Operation
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 serial clock pulses on SCL. The
SMBus interface may operate as a master or a slave, and multiple master devices on the same bus are
supported. If two or more masters attempt to initiate a data transfer simultaneously, an arbitration scheme
is employed with a single master always winning the arbitration. It is not necessary to specify one device
as the Master in a system; any device who transmits a START and a slave address becomes the master
for the duration of 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. Bytes that are
received (by a master or slave) are acknowledged (ACK) with a low SDA during a high SCL (see
Figure 28.3). If the receiving device does not ACK, the transmitting device will read a NACK (not acknowledge), which is a high SDA during a high SCL.
The direction bit (R/W) occupies the least-significant bit position of the address byte. The direction bit is set
to logic 1 to indicate a "READ" operation and cleared to logic 0 to indicate a "WRITE" operation.
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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 transaction is a WRITE operation from the master to the slave, the master transmits the data a byte at a time
waiting for an ACK from the slave at the end of each byte. For READ operations, the slave transmits the
data waiting for an ACK from the master at the end of each byte. At the end of the data transfer, the master
generates a STOP condition to terminate the transaction and free the bus. Figure 28.3 illustrates a typical
SMBus transaction.
SCL
SDA
SLA6
START
SLA5-0
R/W
Slave Address + R/W
D7
ACK
D6-0
Data Byte
NACK
STOP
Figure 28.3. SMBus Transaction
28.3.1. Transmitter vs. Receiver
On the SMBus communications interface, a device is the “transmitter” when it is sending an address or
data byte to another device on the bus. A device is a “receiver” when an address or data byte is being sent
to it from another device on the bus. The transmitter controls the SDA line during the address or data byte.
After each byte of address or data information is sent by the transmitter, the receiver sends an ACK or
NACK bit during the ACK phase of the transfer, during which time the receiver controls the SDA line.
28.3.2. Arbitration
A master may start a transfer only if the bus is free. The bus is free after a STOP condition or after the SCL
and SDA lines remain high for a specified time (see Section “28.3.5. SCL High (SMBus Free) Timeout” on
page 193). In the event that two or more devices attempt to begin a transfer at the same time, an arbitration scheme is employed to force one master to give up the bus. The master devices continue transmitting
until one attempts a HIGH while the other transmits 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 lose the arbitration. The winning
master continues its transmission without interruption; the losing master becomes a slave and receives the
rest of the transfer if addressed. This arbitration scheme is non-destructive: one device always wins, and
no data is lost.
28.3.3. 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.
28.3.4. SCL Low Timeout
If the SCL line is held low by a slave device on the bus, no further communication is possible. Furthermore,
the master cannot force the SCL line high to correct the 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 communication no later than 10 ms after detecting the timeout condition.
For the SMBus0 interface, Timer 3 is used to implement SCL low timeouts. Timer 4 is used on the SMBus1
interface for SCL low timeouts. The SCL low timeout feature is enabled by setting the SMBnTOE bit in
SMBnCF. The associated timer is forced to reload when SCL is high, and allowed to count when SCL is
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low. With the associated timer enabled and configured to overflow after 25 ms (and SMBnTOE set), the
timer interrupt service routine can be used to reset (disable and re-enable) the SMBus in the event of an
SCL low timeout.
28.3.5. 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. When the SMBnFTE bit in SMBnCF is set, the bus will be considered free if SCL and
SDA remain high for more than 10 SMBus clock source periods (as defined by the timer configured for the
SMBus clock source). If the SMBus is waiting to generate a Master START, the START will be generated
following this timeout. A clock source is required for free timeout detection, even in a slave-only implementation.
28.4. Using the SMBus
The SMBus can operate in both Master and Slave modes. The interface provides timing and shifting control for serial transfers; higher level protocol is determined by user software. The SMBus interface provides
the following application-independent features:








Byte-wise serial data transfers
Clock signal generation on SCL (Master Mode only) and SDA data synchronization
Timeout/bus error recognition, as defined by the SMB0CF configuration register
START/STOP timing, detection, and generation
Bus arbitration
Interrupt generation
Status information
Optional hardware recognition of slave address and automatic acknowledgement of address/data
SMBus interrupts are generated for each data byte or slave address that is transferred. When hardware
acknowledgement is disabled, the point at which the interrupt is generated depends on whether the hardware is acting as a data transmitter or receiver. When a transmitter (i.e., sending address/data, receiving
an ACK), this interrupt is generated after the ACK cycle so that software may read the received ACK value;
when receiving data (i.e., receiving address/data, sending an ACK), this interrupt is generated before the
ACK cycle so that software may define the outgoing ACK value. If hardware acknowledgement is enabled,
these interrupts are always generated after the ACK cycle. See Section 28.5 for more details on transmission sequences.
Interrupts are also generated to indicate the beginning of a transfer when a master (START generated), or
the end of a transfer when a slave (STOP detected). Software should read the SMBnCN (SMBus Control
register) to find the cause of the SMBus interrupt. The SMBnCN register is described in Section 28.4.4;
Table 28.5 provides a quick SMBnCN decoding reference.
28.4.1. SMBus Configuration Register
The SMBus Configuration register (SMBnCF) is used to enable the SMBus Master and/or Slave modes,
select the SMBus clock source, and select the SMBus timing and timeout options. When the ENSMB bit is
set, the SMBus is enabled for all master and slave events. Slave events may be disabled by setting the
INH bit. With slave events inhibited, the SMBus interface will still monitor the SCL and SDA pins; however,
the interface will NACK all received addresses and will not generate any slave interrupts. When the INH bit
is set, all slave events will be inhibited following the next START (interrupts will continue for the duration of
the current transfer).
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Table 28.1. SMBus Clock Source Selection
SMBnCS1 SMBnCS0
0
0
1
1
0
1
0
1
SMBus0 Clock Source
SMBus1 Clock Source
Timer 0 Overflow
Timer 1 Overflow
Timer 2 High Byte Overflow
Timer 2 Low Byte Overflow
Timer 0 Overflow
Timer 5 Overflow
Timer 2 High Byte Overflow
Timer 2 Low Byte Overflow
The SMBnCS1–0 bits select the SMBus clock source, which is used only when operating as a master or
when the Free Timeout detection is enabled. When operating as a master, overflows from the selected
source determine the absolute minimum SCL low and high times as defined in Equation 28.1.The selected
clock source may be shared by other peripherals so long as the timer is left running at all times. For example, Timer 1 overflows may generate the SMBus0 and SMBus1 clock rates simultaneously. Timer configuration is covered in Section “31. Timers” on page 240.
1
T HighMin = T LowMin = ---------------------------------------------f ClockSourceOverflow
Equation 28.1. Minimum SCL High and Low Times
The selected clock source should be configured to establish the minimum SCL High and Low times as per
Equation 28.1. When the interface is operating as a master (and SCL is not driven or extended by any
other devices on the bus), the typical SMBus bit rate is approximated by Equation 28.2.
f ClockSourceOverflow
BitRate = ---------------------------------------------3
Equation 28.2. Typical SMBus Bit Rate
Figure 28.4 shows the typical SCL generation described by Equation 28.2. Notice that THIGH is typically
twice as large as TLOW. The actual SCL output may vary due to other devices on the bus (SCL may be
extended low by slower slave devices, or driven low by contending master devices). The bit rate when
operating as a master will never exceed the limits defined by equation Equation 28.1.
Timer Source
Overflows
SCL
TLow
SCL High Timeout
THigh
Figure 28.4. Typical SMBus SCL Generation
Setting the EXTHOLD bit extends the minimum setup and hold times for the SDA line. The minimum SDA
setup time defines the absolute minimum time that SDA is stable before SCL transitions from low-to-high.
The minimum SDA hold time defines the absolute minimum time that the current SDA value remains stable
after SCL transitions from high-to-low. EXTHOLD should be set so that the minimum setup and hold times
meet the SMBus Specification requirements of 250 ns and 300 ns, respectively. Table 28.2 shows the min-
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imum setup and hold times for the two EXTHOLD settings. Setup and hold time extensions are typically
necessary when SYSCLK is above 10 MHz.
Table 28.2. Minimum SDA Setup and Hold Times
EXTHOLD
0
1
Minimum SDA Setup Time
Tlow – 4 system clocks
or
1 system clock + s/w delay*
11 system clocks
Minimum SDA Hold Time
3 system clocks
12 system clocks
Note: Setup Time for ACK bit transmissions and the MSB of all data transfers. When using
software acknowledgement, the s/w delay occurs between the time SMB0DAT or
ACK is written and when SI is cleared. Note that if SI is cleared in the same write
that defines the outgoing ACK value, s/w delay is zero.
With the SMBnTOE bit set, Timer 3 (SMBus0) and Timer 5 (SMBus1) should be configured to overflow
after 25 ms in order to detect SCL low timeouts (see Section “28.3.4. SCL Low Timeout” on page 192).
The SMBus interface will force the associated timer to reload while SCL is high, and allow the timer to
count when SCL is low. The timer interrupt service routine should be used to reset SMBus communication
by disabling and re-enabling the SMBus.
SMBus Free Timeout detection can be enabled by setting the SMBnFTE bit. When this bit is set, the bus
will be considered free if SDA and SCL remain high for more than 10 SMBus clock source periods (see
Figure 28.4).
28.4.2. SMBus Pin Swap
The SMBus peripherals are assigned to pins using the priority crossbar decoder. By default, the SMBus
signals are assigned to port pins starting with SDA on the lower-numbered pin, and SCL on the next available pin. The SMBnSWAP bits in the SMBTC register can be set to 1 to reverse the order in which the
SMBus signals are assigned.
28.4.3. SMBus Timing Control
The SMBnSDD field in the SMBTC register are used to restrict the detection of a START condition under
certain circumstances. In some systems where there is significant mis-match between the impedance or
the capacitance on the SDA and SCL lines, it may be possible for SCL to fall after SDA during an address
or data transfer. Such an event can cause a false START detection on the bus. These kind of events are
not expected in a standard SMBus or I2C-compliant system. In most systems this parameter should
not be adjusted, and it is recommended that it be left at its default value.
By default, if the SCL falling edge is detected after the falling edge of SDA (i.e. one SYSCLK cycle or
more), the device will detect this as a START condition. The SMBnSDD field is used to increase the
amount of hold time that is required between SDA and SCL falling before a START is recognized. An additional 2, 4, or 8 SYSCLKs can be added to prevent false START detection in systems where the bus conditions warrant this.
Preliminary Rev. 0.71
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SFR Definition 28.1. SMB0CF: SMBus Clock/Configuration
Bit
7
6
5
4
3
2
Name
ENSMB0
INH0
BUSY0
Type
R/W
R/W
R
R/W
R/W
R/W
Reset
0
0
0
0
0
0
EXTHOLD0 SMB0TOE SMB0FTE
1
0
SMB0CS[1:0]
R/W
0
0
SFR Address = 0xC1; SFR Page = 0
196
Bit
Name
Function
7
ENSMB0
SMBus0 Enable.
This bit enables the SMBus0 interface when set to 1. When enabled,
the interface constantly monitors the SDA0 and SCL0 pins.
6
INH0
5
BUSY0
4
EXTHOLD0
SMBus0 Setup and Hold Time Extension Enable.
This bit controls the SDA0 setup and hold times according to
Table 28.2.
0: SDA0 Extended Setup and Hold Times disabled.
1: SDA0 Extended Setup and Hold Times enabled.
3
SMB0TOE
SMBus0 SCL Timeout Detection Enable.
This bit enables SCL low timeout detection. If set to logic 1, the
SMBus0 forces Timer 3 to reload while SCL0 is high and allows
Timer 3 to count when SCL0 goes low. If Timer 3 is configured to
Split Mode, only the High Byte of the timer is held in reload while
SCL0 is high. Timer 3 should be programmed to generate interrupts
at 25 ms, and the Timer 3 interrupt service routine should reset
SMBus0 communication.
2
SMB0FTE
SMBus0 Free Timeout Detection Enable.
When this bit is set to logic 1, the bus will be considered free if SCL0
and SDA0 remain high for more than 10 SMBus clock source periods.
1:0
SMB0CS[1:0]
SMBus0 Clock Source Selection.
These two bits select the SMBus0 clock source, which is used to
generate the SMBus0 bit rate. The selected device should be configured according to Equation 28.1.
00: Timer 0 Overflow
01: Timer 1 Overflow
10: Timer 2 High Byte Overflow
11: Timer 2 Low Byte Overflow
SMBus0 Slave Inhibit.
When this bit is set to logic 1, the SMBus0 does not generate an
interrupt when slave events occur. This effectively removes the
SMBus0 slave from the bus. Master Mode interrupts are not
affected.
SMBus0 Busy Indicator.
This bit is set to logic 1 by hardware when a transfer is in progress. It
is cleared to logic 0 when a STOP or free-timeout is sensed.
Preliminary Rev. 0.71
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SFR Definition 28.2. SMB1CF: SMBus Clock/Configuration
Bit
7
6
5
4
3
2
Name
ENSMB1
INH1
BUSY1
Type
R/W
R/W
R
R/W
R/W
R/W
Reset
0
0
0
0
0
0
EXTHOLD1 SMB1TOE SMB1FTE
1
0
SMB1CS[1:0]
R/W
0
0
SFR Address = 0xC1; SFR Page = F
Bit
Name
Function
7
ENSMB1
SMBus1 Enable.
This bit enables the SMBus1 interface when set to 1. When enabled,
the interface constantly monitors the SDA1 and SCL1 pins.
6
INH1
5
BUSY1
4
EXTHOLD1
SMBus1 Setup and Hold Time Extension Enable.
This bit controls the SDA1 setup and hold times according to
Table 28.2.
0: SDA1 Extended Setup and Hold Times disabled.
1: SDA1 Extended Setup and Hold Times enabled.
3
SMB1TOE
SMBus1 SCL Timeout Detection Enable.
This bit enables SCL low timeout detection. If set to logic 1, the
SMBus1 forces Timer 4 to reload while SCL1 is high and allows
Timer 4 to count when SCL1 goes low. If Timer 4 is configured to
Split Mode, only the High Byte of the timer is held in reload while
SCL1 is high. Timer 4 should be programmed to generate interrupts
at 25 ms, and the Timer 4 interrupt service routine should reset
SMBus1 communication.
2
SMB1FTE
SMBus1 Free Timeout Detection Enable.
When this bit is set to logic 1, the bus will be considered free if SCL1
and SDA1 remain high for more than 10 SMBus clock source periods.
1:0
SMB1CS[1:0]
SMBus1 Clock Source Selection.
These two bits select the SMBus1 clock source, which is used to
generate the SMBus1 bit rate. The selected device should be configured according to Equation 28.1.
00: Timer 0 Overflow
01: Timer 5 Overflow
10: Timer 2 High Byte Overflow
11: Timer 2 Low Byte Overflow
SMBus1 Slave Inhibit.
When this bit is set to logic 1, the SMBus1 does not generate an
interrupt when slave events occur. This effectively removes the
SMBus1 slave from the bus. Master Mode interrupts are not
affected.
SMBus1 Busy Indicator.
This bit is set to logic 1 by hardware when a transfer is in progress. It
is cleared to logic 0 when a STOP or free-timeout is sensed.
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SFR Definition 28.3. SMBTC: SMBus Timing and Pin Control
Bit
7
6
5
4
Name SMB1SWAP SMB0SWAP
Type
R/W
R/W
R/W
R/W
Reset
0
0
0
0
3
2
1
0
SMB1SDD[1:0]
SMB0SDD[1:0]
R/W
R/W
0
0
0
0
SFR Address = 0xC7; SFR Page = All Pages
Bit
Name
7
SMB1SWAP
Function
SMBus1 Swap Pins
This bit swaps the order of the SMBus1 pins on the crossbar. This should be set to 1 when accessing the EEPROM.
0: SDA1 is mapped to the lower-numbered port pin, and
SCL1 is mapped to the higher-numbered port pin.
1: SCL1 is mapped to the lower-numbered port pin, and
SDA1 is mapped to the higher-numbered port pin.
6
SMB0SWAP
SMBus0 Swap Pins
This bit swaps the order of the SMBus1 pins on the crossbar. This should be set to 1 when accessing the EEPROM.
0: SDA0 is mapped to the lower-numbered port pin, and
SCL0 is mapped to the higher-numbered port pin.
1: SCL0 is mapped to the lower-numbered port pin, and
SDA0 is mapped to the higher-numbered port pin.
5:4
Reserved
3:2
SMB1SDD[1:0]
Must Write 00b.
SMBus1 Start Detection Window
These bits increase the hold time requirement between
SDA falling and SCL falling for START detection.
00: No additional hold time requirement (0-1 SYSCLK).
01: Increase hold time window to 2-3 SYSCLKs.
10: Increase hold time window to 4-5 SYSCLKs.
11: Increase hold time window to 8-9 SYSCLKs.
1:0
SMB0SDD[1:0]
SMBus0 Start Detection Window
These bits increase the hold time requirement between
SDA falling and SCL falling for START detection.
00: No additional hold time window (0-1 SYSCLK).
01: Increase hold time window to 2-3 SYSCLKs.
10: Increase hold time window to 4-5 SYSCLKs.
11: Increase hold time window to 8-9 SYSCLKs.
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28.4.4. SMBnCN Control Register
SMBnCN is used to control the interface and to provide status information (see SFR Definition 28.4). The
higher four bits of SMBnCN (MASTER, TXMODE, STA, and STO) form a status vector that can be used to
jump to service routines. MASTER indicates whether a device is the master or slave during the current
transfer. TXMODE indicates whether the device is transmitting or receiving data for the current byte.
STA and STO indicate that a START and/or STOP has been detected or generated since the last SMBus
interrupt. STA and STO are also used to generate START and STOP conditions when operating as a master. Writing a 1 to STA will cause the SMBus interface to enter Master Mode and generate a START when
the bus becomes free (STA is not cleared by hardware after the START is generated). Writing a 1 to STO
while in Master Mode will cause the interface to generate a STOP and end the current transfer after the
next ACK cycle. If STO and STA are both set (while in Master Mode), a STOP followed by a START will be
generated.
The ARBLOST bit indicates that the interface has lost an arbitration. This may occur anytime the interface
is transmitting (master or slave). A lost arbitration while operating as a slave indicates a bus error condition. ARBLOST is cleared by hardware each time SI is cleared.
The SI bit (SMBus Interrupt Flag) is set at the beginning and end of each transfer, after each byte frame, or
when an arbitration is lost; see Table 28.3 for more details.
Important Note About the SI Bit: The SMBus interface is stalled while SI is set; thus SCL is held low, and
the bus is stalled until software clears SI.
28.4.4.1. Software ACK Generation
When the EHACK bit in register SMBnADM is cleared to 0, the firmware on the device must detect incoming slave addresses and ACK or NACK the slave address and incoming data bytes. As a receiver, writing
the ACK bit defines the outgoing ACK value; as a transmitter, reading the ACK bit indicates the value
received during the last ACK cycle. ACKRQ is set each time a byte is received, indicating that an outgoing
ACK value is needed. When ACKRQ is set, software should write the desired outgoing value to the ACK
bit before clearing SI. A NACK will be generated if software does not write the ACK bit before clearing SI.
SDA will reflect the defined ACK value immediately following a write to the ACK bit; however SCL will
remain low until SI is cleared. If a received slave address is not acknowledged, further slave events will be
ignored until the next START is detected.
28.4.4.2. Hardware ACK Generation
When the EHACK bit in register SMB0ADM is set to 1, automatic slave address recognition and ACK generation is enabled. More detail about automatic slave address recognition can be found in Section 28.4.5.
As a receiver, the value currently specified by the ACK bit will be automatically sent on the bus during the
ACK cycle of an incoming data byte. As a transmitter, reading the ACK bit indicates the value received on
the last ACK cycle. The ACKRQ bit is not used when hardware ACK generation is enabled. If a received
slave address is NACKed by hardware, further slave events will be ignored until the next START is
detected, and no interrupt will be generated.
Table 28.3 lists all sources for hardware changes to the SMBnCN bits. Refer to Table 28.5 for SMBus status decoding using the SMBnCN register.
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SFR Definition 28.4. SMB0CN: SMBus Control
Bit
7
6
Name MASTER0 TXMODE0
5
4
STA0
STO0
3
2
ACKRQ0 ARBLOST0
1
0
ACK0
SI0
Type
R
R
R/W
R/W
R
R
R/W
R/W
Reset
0
0
0
0
0
0
0
0
SFR Address = 0xC0; SFR Page = 0; Bit-Addressable
Bit
Name
Description
Read
Write
N/A
7
MASTER0 SMBus0 Master/Slave
Indicator. This read-only bit
indicates when the SMBus0 is
operating as a master.
0: SMBus0 operating in
slave mode.
1: SMBus0 operating in
master mode.
6
TXMODE0 SMBus0 Transmit Mode
Indicator. This read-only bit
indicates when the SMBus0 is
operating as a transmitter.
N/A
0: SMBus0 in Receiver
Mode.
1: SMBus0 in Transmitter
Mode.
5
STA0
SMBus0 Start Flag.
0: No Start or repeated
Start detected.
1: Start or repeated Start
detected.
0: No Start generated.
1: When Configured as a
Master, initiates a START
or repeated START.
4
STO0
SMBus0 Stop Flag.
0: No Stop condition
detected.
1: Stop condition detected
(if in Slave Mode) or
pending (if in Master
Mode).
0: No STOP condition is
transmitted.
1: When configured as a
Master, causes a STOP
condition to be transmitted after the next ACK
cycle.
Cleared by Hardware.
3
ACKRQ0
SMBus0 Acknowledge
Request.
0: No ACK requested
1: ACK requested
N/A
0: No arbitration error.
1: Arbitration Lost
N/A
0: NACK received.
1: ACK received.
0: Send NACK
1: Send ACK
2
ARBLOST0 SMBus0 Arbitration Lost
Indicator.
1
ACK0
0
SI0
200
SMBus0 Acknowledge.
0: No interrupt pending
SMBus0 Interrupt Flag.
1: Interrupt Pending
This bit is set by hardware
under the conditions listed in
Table 28.3. SI0 must be
cleared by software. While SI0
is set, SCL0 is held low and
the SMBus0 is stalled.
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0: Clear interrupt, and initiate next state machine
event.
1: Force interrupt.
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SFR Definition 28.5. SMB1CN: SMBus Control
Bit
7
6
Name MASTER1 TXMODE1
5
4
STA1
STO1
3
2
ACKRQ1 ARBLOST1
1
0
ACK1
SI1
Type
R
R
R/W
R/W
R
R
R/W
R/W
Reset
0
0
0
0
0
0
0
0
SFR Address = 0xC0; SFR Page = F; Bit-Addressable
Bit
Name
Description
Read
Write
N/A
7
MASTER1 SMBus1 Master/Slave
Indicator. This read-only bit
indicates when the SMBus1 is
operating as a master.
0: SMBus1 operating in
slave mode.
1: SMBus1 operating in
master mode.
6
TXMODE1 SMBus1 Transmit Mode
Indicator. This read-only bit
indicates when the SMBus1 is
operating as a transmitter.
N/A
0: SMBus1 in Receiver
Mode.
1: SMBus1 in Transmitter
Mode.
5
STA1
SMBus1 Start Flag.
0: No Start or repeated
Start detected.
1: Start or repeated Start
detected.
0: No Start generated.
1: When Configured as a
Master, initiates a START
or repeated START.
4
STO1
SMBus1 Stop Flag.
0: No Stop condition
detected.
1: Stop condition detected
(if in Slave Mode) or
pending (if in Master
Mode).
0: No STOP condition is
transmitted.
1: When configured as a
Master, causes a STOP
condition to be transmitted after the next ACK
cycle.
Cleared by Hardware.
3
ACKRQ1
SMBus1 Acknowledge
Request.
0: No ACK requested
1: ACK requested
N/A
0: No arbitration error.
1: Arbitration Lost
N/A
0: NACK received.
1: ACK received.
0: Send NACK
1: Send ACK
2
ARBLOST1 SMBus1 Arbitration Lost
Indicator.
1
ACK1
0
SI1
SMBus1 Acknowledge.
0: No interrupt pending
SMBus1 Interrupt Flag.
1: Interrupt Pending
This bit is set by hardware
under the conditions listed in
Table 28.3. SI1 must be
cleared by software. While SI1
is set, SCL1 is held low and
the SMBus1 is stalled.
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0: Clear interrupt, and initiate next state machine
event.
1: Force interrupt.
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Table 28.3. Sources for Hardware Changes to SMBnCN
Bit
MASTERn
Set by Hardware When:

A START is generated.
STAn


STOn


ACKRQn

ARBLOSTn


ACKn




SIn


A pending STOP is generated.

After each ACK cycle.

Each time SIn is cleared.

START is generated.
 SMBnDAT is written before the start of an
SMBus frame.

TXMODEn
Cleared by Hardware When:
A STOP is generated.
Arbitration is lost.
A START is detected.
Arbitration is lost.
SMBnDAT is not written before the
start of an SMBus frame.
Must be cleared by software.




A START followed by an address byte is
received.
A STOP is detected while addressed as a
slave.
Arbitration is lost due to a detected STOP.
A byte has been received and an ACK
response value is needed (only when
hardware ACK is not enabled).
A repeated START is detected as a
MASTER when STAn is low (unwanted
repeated START).
SCLn is sensed low while attempting to
generate a STOP or repeated START
condition.
SDAn is sensed low while transmitting a 1
(excluding ACK bits).
The incoming ACK value is low
(ACKNOWLEDGE).
A START has been generated.
Lost arbitration.
A byte has been transmitted and an ACK/
NACK received.
A byte has been received.
A START or repeated START followed by a
slave address + R/W has been received.
A STOP has been received.



The incoming ACK value is high
(NOT ACKNOWLEDGE).
 Must be cleared by software.

28.4.5. Hardware Slave Address Recognition
The SMBus hardware has the capability to automatically recognize incoming slave addresses and send an
ACK without software intervention. Automatic slave address recognition is enabled by setting the EHACK
bit in register SMB0ADM to 1. This will enable both automatic slave address recognition and automatic
hardware ACK generation for received bytes (as a master or slave). More detail on automatic hardware
ACK generation can be found in Section 28.4.4.2.
The registers used to define which address(es) are recognized by the hardware are the SMBus Slave
Address register and the SMBus Slave Address Mask register. A single address or range of addresses
(including the General Call Address 0x00) can be specified using these two registers. The most-significant
seven bits of the two registers are used to define which addresses will be ACKed. A 1 in bit positions of the
slave address mask SLVM[6:0] enable a comparison between the received slave address and the hardware’s slave address SLV[6:0] for those bits. A 0 in a bit of the slave address mask means that bit will be
treated as a “don’t care” for comparison purposes. In this case, either a 1 or a 0 value are acceptable on
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the incoming slave address. Additionally, if the GCn bit in register SMBnADR is set to 1, hardware will recognize the General Call Address (0x00). Table 28.4 shows some example parameter settings and the
slave addresses that will be recognized by hardware under those conditions.
Table 28.4. Hardware Address Recognition Examples (EHACK = 1)
Hardware Slave Address
SLVn[6:0]
Slave Address Mask
SLVMn[6:0]
GCn bit Slave Addresses Recognized by
Hardware
0x34
0x34
0x34
0x34
0x70
0x7F
0x7F
0x7E
0x7E
0x73
0
1
0
1
0
0x34
0x34, 0x00 (General Call)
0x34, 0x35
0x34, 0x35, 0x00 (General Call)
0x70, 0x74, 0x78, 0x7C
SFR Definition 28.6. SMB0ADR: SMBus0 Slave Address
Bit
7
6
5
4
3
2
1
0
Name
SLV0[6:0]
GC0
Type
R/W
R/W
Reset
0
0
0
0
0
0
0
0
SFR Address = 0xD7; SFR Page = 0
Bit
Name
7:1
SLV0[6:0]
Function
SMBus Hardware Slave Address.
Defines the SMBus0 Slave Address(es) for automatic
hardware acknowledgement. Only address bits which
have a 1 in the corresponding bit position in SLVM0[6:0]
are checked against the incoming address. This allows
multiple addresses to be recognized.
0
GC0
General Call Address Enable.
When hardware address recognition is enabled
(EHACK0 = 1), this bit will determine whether the General
Call Address (0x00) is also recognized by hardware.
0: General Call Address is ignored.
1: General Call Address is recognized.
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SFR Definition 28.7. SMB0ADM: SMBus0 Slave Address Mask
Bit
7
6
5
4
3
2
1
0
Name
SLVM0[6:0]
EHACK0
Type
R/W
R/W
Reset
1
1
1
1
1
1
1
0
SFR Address = 0xE7; SFR Page = 0
Bit
Name
7:1
SLVM0[6:0]
Function
SMBus0 Slave Address Mask.
Defines which bits of register SMB0ADR are compared
with an incoming address byte, and which bits are ignored.
Any bit set to 1 in SLVM0[6:0] enables comparisons with
the corresponding bit in SLV0[6:0]. Bits set to 0 are ignored
(can be either 0 or 1 in the incoming address).
0
EHACK0
Hardware Acknowledge Enable.
Enables hardware acknowledgement of slave address and
received data bytes.
0: Firmware must manually acknowledge all incoming
address and data bytes.
1: Automatic Slave Address Recognition and Hardware
Acknowledge is Enabled.
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SFR Definition 28.8. SMB1ADR: SMBus1 Slave Address
Bit
7
6
5
4
3
2
1
0
Name
SLV1[6:0]
GC1
Type
R/W
R/W
Reset
0
0
0
0
0
0
0
0
SFR Address = 0xD7; SFR Page = F
Bit
Name
7:1
SLV1[6:0]
Function
SMBus1 Hardware Slave Address.
Defines the SMBus1 Slave Address(es) for automatic
hardware acknowledgement. Only address bits which
have a 1 in the corresponding bit position in SLVM1[6:0]
are checked against the incoming address. This allows
multiple addresses to be recognized.
0
GC1
General Call Address Enable.
When hardware address recognition is enabled
(EHACK1 = 1), this bit will determine whether the General
Call Address (0x00) is also recognized by hardware.
0: General Call Address is ignored.
1: General Call Address is recognized.
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SFR Definition 28.9. SMB1ADM: SMBus1 Slave Address Mask
Bit
7
6
5
4
3
2
1
0
Name
SLVM1[6:0]
EHACK1
Type
R/W
R/W
Reset
1
1
1
1
1
1
1
0
SFR Address = 0xE7; SFR Page = F
Bit
Name
7:1
SLVM1[6:0]
Function
SMBus1 Slave Address Mask.
Defines which bits of register SMB1ADR are compared
with an incoming address byte, and which bits are ignored.
Any bit set to 1 in SLVM1[6:0] enables comparisons with
the corresponding bit in SLV1[6:0]. Bits set to 0 are ignored
(can be either 0 or 1 in the incoming address).
0
EHACK1
Hardware Acknowledge Enable.
Enables hardware acknowledgement of slave address and
received data bytes.
0: Firmware must manually acknowledge all incoming
address and data bytes.
1: Automatic Slave Address Recognition and Hardware
Acknowledge is Enabled.
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28.4.6. Data Register
The SMBus Data register SMBnDAT holds a byte of serial data to be transmitted or one that has just been
received. Software may safely read or write to the data register when the SIn flag is set. Software should
not attempt to access the SMBnDAT register when the SMBus is enabled and the SIn flag is cleared to
logic 0, as the interface may be in the process of shifting a byte of data into or out of the register.
Data in SMBnDAT is always shifted out MSB first. After a byte has been received, the first bit of received
data is located at the MSB of SMBnDAT. While data is being shifted out, data on the bus is simultaneously
being shifted in. SMBnDAT always contains the last data byte present on the bus. In the event of lost arbitration, the transition from master transmitter to slave receiver is made with the correct data or address in
SMBnDAT.
SFR Definition 28.10. SMB0DAT: SMBus Data
Bit
7
6
5
4
3
Name
SMB0DAT[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address = 0xC2; SFR Page = 0
Bit
Name
7:0
SMB0DAT[7:0]
Function
SMBus0 Data.
The SMB0DAT register contains a byte of data to be transmitted on the SMBus0 serial interface or a byte that has just
been received on the SMBus0 serial interface. The CPU
can read from or write to this register whenever the SI0
serial interrupt flag (SMB0CN.0) is set to logic 1. The serial
data in the register remains stable as long as the SI0 flag is
set. When the SI0 flag is not set, the system may be in the
process of shifting data in/out and the CPU should not
attempt to access this register.
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SFR Definition 28.11. SMB1DAT: SMBus Data
Bit
7
6
5
4
3
Name
SMB1DAT[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address = 0xC2; SFR Page = F
Bit
Name
7:0
SMB1DAT[7:0]
Function
SMBus1 Data.
The SMB1DAT register contains a byte of data to be transmitted on the SMBus1 serial interface or a byte that has just
been received on the SMBus1 serial interface. The CPU
can read from or write to this register whenever the SI1
serial interrupt flag (SMB1CN.0) is set to logic 1. The serial
data in the register remains stable as long as the SI1 flag is
set. When the SI1 flag is not set, the system may be in the
process of shifting data in/out and the CPU should not
attempt to access this register.
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28.5. SMBus Transfer Modes
The SMBus interface may be configured to operate as master and/or slave. At any particular time, it will be
operating in one of the following four modes: Master Transmitter, Master Receiver, Slave Transmitter, or
Slave Receiver. The SMBus interface enters Master Mode any time a START is generated, and remains in
Master Mode until it loses an arbitration or generates a STOP. An SMBus interrupt is generated at the end
of all SMBus byte frames. The position of the ACK interrupt when operating as a receiver depends on
whether hardware ACK generation is enabled. As a receiver, the interrupt for an ACK occurs before the
ACK with hardware ACK generation disabled, and after the ACK when hardware ACK generation is
enabled. As a transmitter, interrupts occur after the ACK, regardless of whether hardware ACK generation
is enabled or not.
28.5.1. Write Sequence (Master)
During a write sequence, an SMBus master writes data to a slave device. The master in this transfer will be
a transmitter during the address byte, and a transmitter during all data bytes. The SMBus interface generates the START condition and transmits the first 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 0 (WRITE). The master then transmits one or more bytes of serial data. After each byte is transmitted, an acknowledge bit is generated by
the slave. The transfer is ended when the STO bit is set and a STOP is generated. The interface will switch
to Master Receiver Mode if SMB0DAT is not written following a Master Transmitter interrupt. Figure 28.5
shows a typical master write sequence. Two transmit data bytes are shown, though any number of bytes
may be transmitted. Notice that all of the “data byte transferred” interrupts occur after the ACK cycle in this
mode, regardless of whether hardware ACK generation is enabled.
Interrupts with Hardware ACK Enabled (EHACK = 1)
S
SLA
W
A
Data Byte
A
Data Byte
A
P
Interrupts with Hardware ACK Disabled (EHACK = 0)
S = START
P = STOP
A = ACK
W = WRITE
SLA = Slave Address
Received by SMBus
Interface
Transmitted by
SMBus Interface
Figure 28.5. Typical Master Write Sequence
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28.5.2. Read Sequence (Master)
During a read sequence, an SMBus master reads data from a slave device. The master in this transfer will
be a transmitter during the address byte, and a receiver during all data bytes. The SMBus interface generates the START condition and transmits the first 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 (READ). Serial data is then
received from the slave on SDA while the SMBus outputs the serial clock. The slave transmits one or more
bytes of serial data.
If hardware ACK generation is disabled, the ACKRQ is set to 1 and an interrupt is generated after each
received byte. Software must write the ACK bit at that time to ACK or NACK the received byte.
With hardware ACK generation enabled, the SMBus hardware will automatically generate the ACK/NACK,
and then post the interrupt. It is important to note that the appropriate ACK or NACK value should be
set up by the software prior to receiving the byte when hardware ACK generation is enabled.
Writing a 1 to the ACK bit generates an ACK; writing a 0 generates a NACK. Software should write a 0 to
the ACK bit for the last data transfer, to transmit a NACK. The interface exits Master Receiver Mode after
the STO bit is set and a STOP is generated. The interface will switch to Master Transmitter Mode if
SMB0DAT is written while an active Master Receiver. Figure 28.6 shows a typical master read sequence.
Two received data bytes are shown, though any number of bytes may be received. Notice that the ‘data
byte transferred’ interrupts occur at different places in the sequence, depending on whether hardware ACK
generation is enabled. The interrupt occurs before the ACK with hardware ACK generation disabled, and
after the ACK when hardware ACK generation is enabled.
Interrupts with Hardware ACK Enabled (EHACK = 1)
S
SLA
R
A
Data Byte
A
Data Byte
N
Interrupts with Hardware ACK Disabled (EHACK = 0)
S = START
P = STOP
A = ACK
N = NACK
R = READ
SLA = Slave Address
Received by SMBus
Interface
Transmitted by
SMBus Interface
Figure 28.6. Typical Master Read Sequence
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28.5.3. Write Sequence (Slave)
During a write sequence, an SMBus master writes data to a slave device. The slave in this transfer will be
a receiver during the address byte, and a receiver during all data bytes. When slave events are enabled
(INH = 0), the interface enters Slave Receiver Mode when a START followed by a slave address and direction bit (WRITE in this case) is received. If hardware ACK generation is disabled, upon entering Slave
Receiver Mode, an interrupt is generated and the ACKRQ bit is set. The software must respond to the
received slave address with an ACK, or ignore the received slave address with a NACK. If hardware ACK
generation is enabled, the hardware will apply the ACK for a slave address which matches the criteria set
up by SMB0ADR and SMB0ADM. The interrupt will occur after the ACK cycle.
If the received slave address is ignored (by software or hardware), slave interrupts will be inhibited until the
next START is detected. If the received slave address is acknowledged, zero or more data bytes are
received.
If hardware ACK generation is disabled, the ACKRQ is set to 1 and an interrupt is generated after each
received byte. Software must write the ACK bit at that time to ACK or NACK the received byte.
With hardware ACK generation enabled, the SMBus hardware will automatically generate the ACK/NACK,
and then post the interrupt. It is important to note that the appropriate ACK or NACK value should be
set up by the software prior to receiving the byte when hardware ACK generation is enabled.
The interface exits Slave Receiver Mode after receiving a STOP. The interface will switch to Slave Transmitter Mode if SMB0DAT is written while an active Slave Receiver. Figure 28.7 shows a typical slave write
sequence. Two received data bytes are shown, though any number of bytes may be received. Notice that
the ‘data byte transferred’ interrupts occur at different places in the sequence, depending on whether hardware ACK generation is enabled. The interrupt occurs before the ACK with hardware ACK generation disabled, and after the ACK when hardware ACK generation is enabled.
Interrupts with Hardware ACK Enabled (EHACK = 1)
S
SLA
W
A
Data Byte
A
Data Byte
A
P
Interrupts with Hardware ACK Disabled (EHACK = 0)
S = START
P = STOP
A = ACK
W = WRITE
SLA = Slave Address
Received by SMBus
Interface
Transmitted by
SMBus Interface
Figure 28.7. Typical Slave Write Sequence
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28.5.4. Read Sequence (Slave)
During a read sequence, an SMBus master reads data from a slave device. The slave in this transfer will
be a receiver during the address byte, and a transmitter during all data bytes. When slave events are
enabled (INH = 0), the interface enters Slave Receiver Mode (to receive the slave address) when a START
followed by a slave address and direction bit (READ in this case) is received. If hardware ACK generation
is disabled, upon entering Slave Receiver Mode, an interrupt is generated and the ACKRQ bit is set. The
software must respond to the received slave address with an ACK, or ignore the received slave address
with a NACK. If hardware ACK generation is enabled, the hardware will apply the ACK for a slave address
which matches the criteria set up by SMB0ADR and SMB0ADM. The interrupt will occur after the ACK
cycle.
If the received slave address is ignored (by software or hardware), slave interrupts will be inhibited until the
next START is detected. If the received slave address is acknowledged, zero or more data bytes are transmitted. If the received slave address is acknowledged, data should be written to SMB0DAT to be transmitted. The interface enters slave transmitter mode, and transmits one or more bytes of data. After each byte
is transmitted, the master sends an acknowledge bit; if the acknowledge bit is an ACK, SMB0DAT should
be written with the next data byte. If the acknowledge bit is a NACK, SMB0DAT should not be written to
before SI is cleared (an error condition may be generated if SMB0DAT is written following a received
NACK while in slave transmitter mode). The interface exits slave transmitter mode after receiving a STOP.
The interface will switch to slave receiver mode if SMB0DAT is not written following a Slave Transmitter
interrupt. Figure 28.8 shows a typical slave read sequence. Two transmitted data bytes are shown, though
any number of bytes may be transmitted. Notice that all of the “data byte transferred” interrupts occur after
the ACK cycle in this mode, regardless of whether hardware ACK generation is enabled.
Interrupts with Hardware ACK Enabled (EHACK = 1)
S
SLA
R
A
Data Byte
A
Data Byte
N
P
Interrupts with Hardware ACK Disabled (EHACK = 0)
S = START
P = STOP
N = NACK
R = READ
SLA = Slave Address
Received by SMBus
Interface
Transmitted by
SMBus Interface
Figure 28.8. Typical Slave Read Sequence
28.6. SMBus Status Decoding
The current SMBus status can be easily decoded using the SMB0CN register. The appropriate actions to
take in response to an SMBus event depend on whether hardware slave address recognition and ACK
generation is enabled or disabled. Table 28.5 describes the typical actions when hardware slave address
recognition and ACK generation is disabled. Table 28.6 describes the typical actions when hardware slave
address recognition and ACK generation is enabled. In the tables, STATUS VECTOR refers to the four
upper bits of SMB0CN: MASTER, TXMODE, STA, and STO. The shown response options are only the typical responses; application-specific procedures are allowed as long as they conform to the SMBus specification. Highlighted responses are allowed by hardware but do not conform to the SMBus specification.
212
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ARBLOST
0 X
0
0
1000
1
0
ACK
STO
0
STA
1100
Typical Response Options
ACK
ACKRQ
0
Status
Vector
Mode
Master Transmitter
Master Receiver
1110
Current SMbus State
Vector Expected
Values to
Write
Values Read
Next Status
Table 28.5. SMBus Status Decoding: Hardware ACK Disabled (EHACK = 0)
0
0 X
1100
1
0 X
1110
0
1 X
—
Load next data byte into
SMB0DAT.
0
0 X
1100
End transfer with STOP.
0
1 X
—
A master data or address byte End transfer with STOP and start 1
another transfer.
1 was transmitted; ACK
received.
Send repeated START.
1
1 X
—
0 X
1110
Switch to Master Receiver Mode 0
(clear SI without writing new data
to SMB0DAT).
0 X
1000
Acknowledge received byte;
Read SMB0DAT.
0
0
1
1000
Send NACK to indicate last byte, 0
and send STOP.
1
0
—
Send NACK to indicate last byte, 1
and send STOP followed by
START.
1
0
1110
Send ACK followed by repeated
START.
1
0
1
1110
Send NACK to indicate last byte, 1
and send repeated START.
0
0
1110
Send ACK and switch to Master
Transmitter Mode (write to
SMB0DAT before clearing SI).
0
0
1
1100
Send NACK and switch to Master Transmitter Mode (write to
SMB0DAT before clearing SI).
0
0
0
1100
A master START was generated.
Load slave address + R/W into
SMB0DAT.
A master data or address byte Set STA to restart transfer.
0 was transmitted; NACK
Abort transfer.
received.
0 X
A master data byte was
received; ACK requested.
Preliminary Rev. 0.71
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C8051F39x/37x
ARBLOST
ACK
STA
STO
0101
ACKRQ
0
0
0
A slave byte was transmitted; No action required (expecting
NACK received.
STOP condition).
0
0 X
0001
0
0
1
A slave byte was transmitted; Load SMB0DAT with next data
ACK received.
byte to transmit.
0
0 X
0100
0
1 X
A Slave byte was transmitted; No action required (expecting
error detected.
Master to end transfer).
0
0 X
0001
0
0 X
—
0
0
1
0000
If Read, Load SMB0DAT with
0
data byte; ACK received address
0
1
0100
NACK received address.
0
0
0
—
If Write, Acknowledge received
address
0
0
1
0000
If Read, Load SMB0DAT with
0
Lost arbitration as master;
1 X slave address + R/W received; data byte; ACK received address
ACK requested.
NACK received address.
0
0
1
0100
0
0
—
1
0
0
1110
0
0 X
—
Lost arbitration while attempt- No action required (transfer
ing a STOP.
complete/aborted).
0
0
0
—
Acknowledge received byte;
Read SMB0DAT.
0
0
1
0000
NACK received byte.
0
0
0
—
Current SMbus State
Typical Response Options
An illegal STOP or bus error
0 X X was detected while a Slave
Clear STO.
Transmission was in progress.
If Write, Acknowledge received
address
1
0 X
A slave address + R/W was
received; ACK requested.
Slave Receiver
0010
1
Reschedule failed transfer;
NACK received address.
0
A STOP was detected while
0 X addressed as a Slave Transmitter or Slave Receiver.
1
1 X
1
A slave byte was received;
0 X
ACK requested.
0001
0000
214
ACK
Status
Vector
Mode
Slave Transmitter
0100
Vector Expected
Values to
Write
Values Read
Next Status
Table 28.5. SMBus Status Decoding: Hardware ACK Disabled (EHACK = 0) (Continued)
Clear STO.
Preliminary Rev. 0.71
C8051F39x/37x
ACKRQ
ARBLOST
0
1 X
Lost arbitration while attempt- Abort failed transfer.
ing a repeated START.
Reschedule failed transfer.
0001
0
1 X
Lost arbitration due to a
detected STOP.
0000
1
1 X
STA
STO
ACK
Typical Response Options
ACK
Status
Vector
Mode
Bus Error Condition
0010
Current SMbus State
Vector Expected
Values to
Write
Values Read
Next Status
Table 28.5. SMBus Status Decoding: Hardware ACK Disabled (EHACK = 0) (Continued)
0
0 X
—
1
0 X
1110
Abort failed transfer.
0
0 X
—
Reschedule failed transfer.
1
0 X
1110
Lost arbitration while transmit- Abort failed transfer.
ting a data byte as master.
Reschedule failed transfer.
0
0
0
—
1
0
0
1110
ARBLOST
0
0 X
0
0
0
ACK
STO
0
STA
1100
Typical Response Options
ACK
ACKRQ
Vector
Status
Mode
Master Transmitter
1110
Current SMbus State
Vector Expected
Values to
Write
Values Read
Next Status
Table 28.6. SMBus Status Decoding: Hardware ACK Enabled (EHACK = 1)
0
0 X
1100
1
0 X
1110
0
1 X
—
Load next data byte into
SMB0DAT.
0
0 X
1100
End transfer with STOP.
0
1 X
—
End transfer with STOP and start 1
A master data or address byte
another transfer.
1 was transmitted; ACK
Send repeated START.
1
received.
Switch to Master Receiver Mode 0
(clear SI without writing new data
to SMB0DAT). Set ACK for initial
data byte.
1 X
—
0 X
1110
0
1000
A master START was generated.
Load slave address + R/W into
SMB0DAT.
A master data or address byte Set STA to restart transfer.
0 was transmitted; NACK
Abort transfer.
received.
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215
C8051F39x/37x
Values to
Write
Slave Transmitter
0100
0101
STO
ACK
Next Status
0
Set ACK for next data byte;
Read SMB0DAT.
0
0
1
1000
Set NACK to indicate next data
byte as the last data byte;
Read SMB0DAT.
0
0
0
1000
Initiate repeated START.
1
0
0
1110
Switch to Master Transmitter
0
Mode (write to SMB0DAT before
clearing SI).
0 X
1100
Read SMB0DAT; send STOP.
0
1
0
—
Read SMB0DAT; Send STOP
followed by START.
1
1
0
1110
Initiate repeated START.
1
0
0
1110
0 X
1100
Typical Response Options
ACK
1
A master data byte was
received; ACK sent.
1000
0
216
0
Current SMbus State
STA
Master Receiver
0
ARBLOST
ACKRQ
Vector
Status
Mode
Values Read
A master data byte was
0 received; NACK sent (last
byte).
Vector Expected
Table 28.6. SMBus Status Decoding: Hardware ACK Enabled (EHACK = 1) (Continued)
Switch to Master Transmitter
0
Mode (write to SMB0DAT before
clearing SI).
0
0
0
A slave byte was transmitted; No action required (expecting
NACK received.
STOP condition).
0
0 X
0001
0
0
1
A slave byte was transmitted; Load SMB0DAT with next data
ACK received.
byte to transmit.
0
0 X
0100
0
1 X
A Slave byte was transmitted; No action required (expecting
error detected.
Master to end transfer).
0
0 X
0001
0
0 X
—
An illegal STOP or bus error
0 X X was detected while a Slave
Clear STO.
Transmission was in progress.
Preliminary Rev. 0.71
C8051F39x/37x
Values to
Write
STA
STO
ACK
Next Status
0
0
1
0000
If Read, Load SMB0DAT with
data byte
0
0 X
0100
If Write, Set ACK for first data
byte.
0
0
1
0000
0
0 X
0100
1
0 X
1110
0
0 X
—
Lost arbitration while attempt- No action required (transfer
ing a STOP.
complete/aborted).
0
0
0
—
Set ACK for next data byte;
Read SMB0DAT.
0
0
1
0000
Set NACK for next data byte;
Read SMB0DAT.
0
0
0
0000
0
0 X
—
1
0 X
1110
Abort failed transfer.
0
0 X
—
ARBLOST
If Write, Set ACK for first data
byte.
ACKRQ
0
A slave address + R/W was
0 X
received; ACK sent.
Current SMbus State
Bus Error Condition
Slave Receiver
0010
0
Typical Response Options
ACK
Vector
Status
Mode
Values Read
Lost arbitration as master;
1 X slave address + R/W received; If Read, Load SMB0DAT with
ACK sent.
data byte
Reschedule failed transfer
0
A STOP was detected while
0 X addressed as a Slave Transmitter or Slave Receiver.
0
1 X
0001
Vector Expected
Table 28.6. SMBus Status Decoding: Hardware ACK Enabled (EHACK = 1) (Continued)
Clear STO.
0000
0
0 X A slave byte was received.
0010
0
1 X
Lost arbitration while attempt- Abort failed transfer.
ing a repeated START.
Reschedule failed transfer.
0001
0
1 X
Lost arbitration due to a
detected STOP.
Reschedule failed transfer.
1
0 X
1110
0000
0
1 X
Lost arbitration while transmit- Abort failed transfer.
ting a data byte as master.
Reschedule failed transfer.
0
0 X
—
1
0 X
1110
Preliminary Rev. 0.71
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C8051F39x/37x
29. UART0
UART0 is an asynchronous, full duplex serial port offering modes 1 and 3 of the standard 8051 UART.
Enhanced baud rate support allows a wide range of clock sources to generate standard baud rates (details
in Section “29.1. Enhanced Baud Rate Generation” on page 219). Received data buffering allows UART0
to start reception of a second incoming data byte before software has finished reading the previous data
byte.
UART0 has two associated SFRs: Serial Control Register 0 (SCON0) and Serial Data Buffer 0 (SBUF0).
The single SBUF0 location provides access to both transmit and receive registers. Writes to SBUF0
always access the Transmit register. Reads of SBUF0 always access the buffered Receive register;
it is not possible to read data from the Transmit register.
With UART0 interrupts enabled, an interrupt is generated each time a transmit is completed (TI0 is set in
SCON0), or a data byte has been received (RI0 is set in SCON0). The UART0 interrupt flags are not
cleared by hardware when the CPU vectors to the interrupt service routine. They must be cleared manually
by software, allowing software to determine the cause of the UART0 interrupt (transmit complete or receive
complete).
SFR Bus
Write to
SBUF
TB8
SBUF
(TX Shift)
SET
D
Q
TX
CLR
Crossbar
Zero Detector
Stop Bit
Shift
Start
Data
Tx Control
Tx Clock
Send
Tx IRQ
TI
MCE
REN
TB8
RB8
TI
RI
SMODE
SCON
UART Baud
Rate Generator
RI
Serial
Port
Interrupt
Port I/O
Rx IRQ
Rx Clock
Rx Control
Start
Shift
0x1FF
RB8
Load
SBUF
Input Shift Register
(9 bits)
Load SBUF
SBUF
(RX Latch)
Read
SBUF
SFR Bus
RX
Figure 29.1. UART0 Block Diagram
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C8051F39x/37x
29.1. Enhanced Baud Rate Generation
The UART0 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 29.2), which is not useraccessible. 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.
Timer 1
TL1
UART
Overflow
2
TX Clock
Overflow
2
RX Clock
TH1
Start
Detected
RX Timer
Figure 29.2. UART0 Baud Rate Logic
Timer 1 should be configured for Mode 2, 8-bit auto-reload (see Section “31.1.3. Mode 2: 8-bit Counter/
Timer with Auto-Reload” on page 245). The Timer 1 reload value should be set so that overflows will occur
at two times the desired UART baud rate frequency. Note that Timer 1 may be clocked by one of six
sources: SYSCLK, SYSCLK/4, SYSCLK/12, SYSCLK/48, the external oscillator clock/8, or an external
input T1. For any given Timer 1 clock source, the UART0 baud rate is determined by Equation 29.1-A and
Equation 29.1-B.
A)
1
UartBaudRate = ---  T1_Overflow_Rate
2
B)
T1 CLK
T1_Overflow_Rate = -------------------------256 – TH1
Equation 29.1. UART0 Baud Rate
Where T1CLK is the frequency of the clock supplied to Timer 1, and T1H is the high byte of Timer 1 (reload
value). Timer 1 clock frequency is selected as described in Section “31. Timers” on page 240. A quick reference for typical baud rates and system clock frequencies is given in Table 29.1 through Table 29.2. The
internal oscillator may still generate the system clock when the external oscillator is driving Timer 1.
Preliminary Rev. 0.71
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C8051F39x/37x
29.2. Operational Modes
UART0 provides standard asynchronous, full duplex communication. The UART mode (8-bit or 9-bit) is
selected by the S0MODE bit (SCON0.7). Typical UART connection options are shown in Figure 29.3.
TX
RS-232
LEVEL
XLTR
RS-232
RX
C8051xxxx
OR
TX
TX
RX
RX
MCU
C8051xxxx
Figure 29.3. UART Interconnect Diagram
29.2.1. 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 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 software 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 MCE0 is logic 1, the stop bit must be logic 1. In the event of a receive data overrun, the first received 8 bits are latched into the SBUF0 receive register and the following overrun data bits
are lost.
If these conditions are met, the eight 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 is set.
MARK
SPACE
START
BIT
D0
D1
D2
D3
D4
D5
BIT TIMES
BIT SAMPLING
Figure 29.4. 8-Bit UART Timing Diagram
220
Preliminary Rev. 0.71
D6
D7
STOP
BIT
C8051F39x/37x
29.2.2. 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 programmable ninth data bit, and a stop bit. The state of the ninth transmit data bit is determined by the value in TB80
(SCON0.3), which is assigned by user software. It can be assigned the value of the parity flag (bit P in register PSW) for error detection, 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 1. After the stop bit is
received, the data byte will be loaded into the SBUF0 receive register if the following conditions are met:
(1) RI0 must be logic 0, and (2) if MCE0 is logic 1, the 9th bit must be logic 1 (when MCE0 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
SBUF0, the ninth bit is stored in RB80, and the RI0 flag is set to 1. If the above conditions are not met,
SBUF0 and RB80 will not be loaded and the RI0 flag will not be set to 1. A UART0 interrupt will occur if
enabled when either TI0 or RI0 is set to 1.
MARK
SPACE
START
BIT
D0
D1
D2
D3
D4
D5
D6
D7
D8
STOP
BIT
BIT TIMES
BIT SAMPLING
Figure 29.5. 9-Bit UART Timing Diagram
Preliminary Rev. 0.71
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29.3. 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 data bit. When a master processor wants 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 MCE0 bit (SCON0.5) 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 1 (RB80 = 1) signifying an address
byte has been received. In the UART interrupt handler, software will compare the received address with
the slave's own assigned 8-bit address. If the addresses match, the slave will clear its MCE0 bit to enable
interrupts on the reception of the following data byte(s). Slaves that weren't addressed leave their MCE0
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 resets its MCE0 bit to ignore all transmissions until it receives the next address byte.
Multiple addresses can be assigned to a single 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).
Master
Device
RX
TX
Slave
Device
RX
TX
Slave
Device
RX
TX
Slave
Device
RX
TX
Figure 29.6. UART Multi-Processor Mode Interconnect Diagram
222
Preliminary Rev. 0.71
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SFR Definition 29.1. SCON0: Serial Port 0 Control
Bit
7
6
Name
S0MODE
Type
R/W
Reset
0
5
4
3
2
1
0
MCE0
REN0
TB80
RB80
TI0
RI0
R
R/W
R/W
R/W
R/W
R/W
R/W
1
0
0
0
0
0
0
SFR Address = 0x98; SFR Page = All Pages; Bit-Addressable
Bit
7
Name
S0MODE
6
5
Unused
MCE0
Function
Serial Port 0 Operation Mode.
Selects the UART0 Operation Mode.
0: 8-bit UART with Variable Baud Rate.
1: 9-bit UART with Variable Baud Rate.
Unused. Read = 1b, Write = Don’t Care.
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: RI0 will only be activated if stop bit is logic level 1.
Mode 1: Multiprocessor Communications Enable.
4
3
2
1
0
REN0
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.
Receive Enable.
TB80
0: UART0 reception disabled.
1: UART0 reception enabled.
Ninth Transmission Bit.
RB80
The logic level of this bit will be sent as the ninth transmission bit in 9-bit UART
Mode (Mode 1). Unused in 8-bit mode (Mode 0).
Ninth Receive Bit.
TI0
RB80 is assigned the value of the STOP bit in Mode 0; it is assigned the value
of the 9th data bit in Mode 1.
Transmit Interrupt Flag.
RI0
Set by hardware when a byte of data has been transmitted by UART0 (after
the 8th bit in 8-bit UART Mode, or at the beginning of the STOP bit in 9-bit
UART Mode). When the UART0 interrupt is enabled, setting this bit causes the
CPU to vector to the UART0 interrupt service routine. This bit must be cleared
manually by software.
Receive Interrupt Flag.
Set to 1 by hardware when a byte of data has been received by UART0 (set at
the STOP bit sampling time). When the UART0 interrupt is enabled, setting
this bit to 1 causes the CPU to vector to the UART0 interrupt service routine.
This bit must be cleared manually by software.
Preliminary Rev. 0.71
223
C8051F39x/37x
SFR Definition 29.2. SBUF0: Serial (UART0) Port Data Buffer
Bit
7
6
5
4
3
Name
SBUF0[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address = 0x99; SFR Page = All Pages
Bit
Name
7:0
SBUF0[7:0]
Function
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 SBUF0, it goes to
the transmit shift register and is held for serial transmission.
Writing a byte to SBUF0 initiates the transmission. A read of
SBUF0 returns the contents of the receive latch.
224
Preliminary Rev. 0.71
C8051F39x/37x
Table 29.1. Timer Settings for Standard Baud Rates
Using The Internal 49 MHz Oscillator
Internal Osc.
SYSCLK from
Frequency: 49 MHz
Target
Baud Rate
(bps)
Baud Rate
% Error
230400
115200
57600
28800
9600
2400
–0.32%
0.15%
–0.32%
0.15%
–0.32%
0.15%
Oscillator Timer Clock
Divide
Source
Factor
212
426
848
1704
5088
20448
SCA1–SCA0
(pre-scale
select)1
T1M1
Timer 1
Reload
Value (hex)
XX2
XX
01
00
00
10
1
1
0
0
0
0
0x96
0x2B
0x96
0xB9
0xCB
0x2B
SCA1–SCA0
(pre-scale
select)1
T1M1
Timer 1
Reload
Value (hex)
XX2
XX
XX
00
00
00
10
10
11
11
11
11
11
11
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0xD0
0xA0
0x40
0xE0
0xC0
0xA0
0xA0
0x40
0xFA
0xF4
0xE8
0xD0
0xA0
0x70
SYSCLK
SYSCLK
SYSCLK/4
SYSCLK/12
SYSCLK/48
SYSCLK/48
Notes:
1. SCA1–SCA0 and T1M bit definitions can be found in Section 31.1.
2. X = Don’t care.
Table 29.2. Timer Settings for Standard Baud Rates
Using an External 22.1184 MHz Oscillator
SYSCLK from
External Osc.
SYSCLK from
Internal Osc.
Frequency: 22.1184 MHz
Target
Baud Rate
(bps)
Baud Rate
% Error
230400
115200
57600
28800
14400
9600
2400
1200
230400
115200
57600
28800
14400
9600
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
Oscillator Timer Clock
Divide
Source
Factor
96
192
384
768
1536
2304
9216
18432
96
192
384
768
1536
2304
SYSCLK
SYSCLK
SYSCLK
SYSCLK / 12
SYSCLK / 12
SYSCLK / 12
SYSCLK / 48
SYSCLK / 48
EXTCLK / 8
EXTCLK / 8
EXTCLK / 8
EXTCLK / 8
EXTCLK / 8
EXTCLK / 8
Notes:
1. SCA1–SCA0 and T1M bit definitions can be found in Section 31.1.
2. X = Don’t care.
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30. 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 multiple 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, avoiding
contention on the SPI bus when more than one master attempts simultaneous data transfers. NSS can
also be configured as a chip-select output in master mode, or disabled for 3-wire operation. Additional general purpose port I/O pins can be used to select multiple slave devices in master mode.
SFR Bus
SYSCLK
SPI0CN
SPIBSY
MSTEN
CKPHA
CKPOL
SLVSEL
NSSIN
SRMT
RXBMT
SPIF
WCOL
MODF
RXOVRN
NSSMD1
NSSMD0
TXBMT
SPIEN
SPI0CFG
SCR7
SCR6
SCR5
SCR4
SCR3
SCR2
SCR1
SCR0
SPI0CKR
Clock Divide
Logic
SPI CONTROL LOGIC
Data Path
Control
SPI IRQ
Pin Interface
Control
MOSI
Tx Data
SPI0DAT
SCK
Transmit Data Buffer
Shift Register
7 6 5 4 3 2 1 0
Rx Data
Pin
Control
Logic
Receive Data Buffer
MISO
NSS
Read
SPI0DAT
Write
SPI0DAT
SFR Bus
Figure 30.1. SPI Block Diagram
226
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C
R
O
S
S
B
A
R
Port I/O
C8051F39x/37x
30.1. Signal Descriptions
The four signals used by SPI0 (MOSI, MISO, SCK, NSS) are described below.
30.1.1. Master Out, Slave In (MOSI)
The master-out, slave-in (MOSI) signal is an output from a master device and an input to slave devices. It
is used to serially transfer data from the master to the slave. This signal is an output when SPI0 is operating 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.
30.1.2. 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 operating as a master and an output when SPI0 is operating as a slave. Data is transferred most-significant bit
first. The MISO pin is placed in a high-impedance state when the SPI module is disabled 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.
30.1.3. Serial Clock (SCK)
The serial clock (SCK) signal is an output from the master 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 generates 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.
30.1.4. 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 must be the only slave on the bus in 3-wire mode. This is intended for point-topoint 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 enabled 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 30.2, Figure 30.3, and Figure 30.4 for typical connection diagrams of the various operational
modes. Note that the setting of NSSMD bits affects the pinout of the device. When in 3-wire master 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 “27. Port Input/Output” on page 171 for general purpose
port I/O and crossbar information.
Preliminary Rev. 0.71
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30.2. SPI0 Master Mode Operation
A SPI master device initiates all data transfers on a SPI bus. SPI0 is placed in master mode by setting 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 register, and a data transfer 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 shift 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 different 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 slave devices while they are not acting as the system master device. In multi-master mode, slave devices can be addressed individually (if needed) using general-purpose I/O pins.
Figure 30.2 shows a connection diagram between two master devices in multiple-master mode.
3-wire single-master mode is active when NSSMD1 (SPI0CN.3) = 0 and NSSMD0 (SPI0CN.2) = 0. In this
mode, NSS is not used, and is not 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 30.3
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 general-purpose I/O pins. Figure 30.4 shows a connection diagram for a master device in
4-wire master mode and two slave devices.
Master
Device 1
NSS
GPIO
MISO
MISO
MOSI
MOSI
SCK
SCK
GPIO
NSS
Master
Device 2
Figure 30.2. Multiple-Master Mode Connection Diagram
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Master
Device
MISO
MISO
MOSI
MOSI
SCK
SCK
Slave
Device
Figure 30.3. 3-Wire Single Master and 3-Wire Single Slave Mode Connection Diagram
Master
Device
GPIO
MISO
MISO
MOSI
MOSI
SCK
SCK
NSS
NSS
MISO
MOSI
Slave
Device
Slave
Device
SCK
NSS
Figure 30.4. 4-Wire Single Master Mode and 4-Wire Slave Mode Connection Diagram
30.3. 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 signal. A bit counter in the SPI0 logic counts SCK edges. When 8 bits have been shifted through the shift register, 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 doublebuffered, and are placed in the transmit buffer first. If the shift register is empty, the contents of the transmit
buffer will immediately be transferred into the shift register. When the shift register already contains data,
the SPI will load the shift register with the transmit buffer’s contents after the last SCK edge of the next (or
current) SPI transfer.
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 signal must be driven low at least 2 system clocks before the first active edge of SCK for each byte transfer.
Figure 30.4 shows a connection diagram between two slave devices in 4-wire slave mode and a master
device.
The 3-wire slave mode is active when NSSMD1 (SPI0CN.3) = 0 and NSSMD0 (SPI0CN.2) = 0. NSS is not
used in this mode, and is not mapped to an external port pin through the crossbar. Since there is no way of
Preliminary Rev. 0.71
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C8051F39x/37x
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 reenabling SPI0 with the SPIEN bit. Figure 30.3 shows a connection diagram between a slave device in 3wire slave mode and a master device.
30.4. SPI0 Interrupt Sources
When SPI0 interrupts are enabled, the following four flags will generate an interrupt when they are set to
logic 1:
All of the following bits must be cleared by software.
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.
 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.
 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 logic 0 to disable SPI0 and allow another master device to access the bus.
 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
byte is not transferred to the receive buffer, allowing the previously received data byte to be read. The
data byte which caused the overrun is lost.

30.5. Serial Clock Phase and Polarity
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 phases
(edge used to latch the data). The CKPOL bit (SPI0CFG.4) selects between an active-high or active-low
clock. Both master and slave devices must be configured to use the same clock phase and polarity. SPI0
should be disabled (by clearing the SPIEN bit, SPI0CN.0) when changing the clock phase or polarity. The
clock and data line relationships for master mode are shown in Figure 30.5. For slave mode, the clock and
data relationships are shown in Figure 30.6 and Figure 30.7. Note that CKPHA should be set to 0 on both
the master and slave SPI when communicating between two Silicon Labs C8051 devices.
The SPI0 Clock Rate Register (SPI0CKR) as shown in SFR Definition 30.3 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 or 12.5 MHz,
whichever is slower. 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 4wire slave mode), and the serial input data synchronously with the slave’s 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 frequency. In the special case where the master only wants to
transmit data to the slave and does not 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 slave’s
system clock.
230
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SCK
(CKPOL=0, CKPHA=0)
SCK
(CKPOL=0, CKPHA=1)
SCK
(CKPOL=1, CKPHA=0)
SCK
(CKPOL=1, CKPHA=1)
MISO/MOSI
MSB
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
NSS (Must Remain High
in Multi-Master Mode)
Figure 30.5. Master Mode Data/Clock Timing
SCK
(CKPOL=0, CKPHA=0)
SCK
(CKPOL=1, CKPHA=0)
MOSI
MSB
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
MISO
MSB
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
NSS (4-Wire Mode)
Figure 30.6. Slave Mode Data/Clock Timing (CKPHA = 0)
Preliminary Rev. 0.71
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C8051F39x/37x
SCK
(CKPOL=0, CKPHA=1)
SCK
(CKPOL=1, CKPHA=1)
MOSI
MSB
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
MISO
MSB
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Bit 0
NSS (4-Wire Mode)
Figure 30.7. Slave Mode Data/Clock Timing (CKPHA = 1)
30.6. 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 figures.
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SFR Definition 30.1. SPI0CFG: SPI0 Configuration
Bit
7
6
5
4
3
2
1
0
Name
SPIBSY
MSTEN
CKPHA
CKPOL
SLVSEL
NSSIN
SRMT
RXBMT
Type
R
R/W
R/W
R/W
R
R
R
R
Reset
0
0
0
0
0
1
1
1
SFR Address = 0xA1; SFR Page = All Pages
Bit
Name
7
SPIBSY
Function
SPI Busy.
This bit is set to logic 1 when a SPI transfer is in progress (master or slave mode).
6
MSTEN
Master Mode Enable.
0: Disable master mode. Operate in slave mode.
1: Enable master mode. Operate as a master.
5
CKPHA
SPI0 Clock Phase.
0: Data centered on first edge of SCK period.*
1: Data centered on second edge of SCK period.*
4
CKPOL
SPI0 Clock Polarity.
0: SCK line low in idle state.
1: SCK line high in idle state.
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.
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.
1
SRMT
Shift Register Empty (valid in slave mode only).
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 transferred to the
shift register from the transmit buffer or by a transition on SCK. SRMT = 1 when in
Master Mode.
0
RXBMT
Receive Buffer Empty (valid in slave mode only).
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 available in the receive buffer that has
not been read, this bit will return to logic 0. RXBMT = 1 when in Master Mode.
Note: In slave mode, data on MOSI is sampled in the center of each data bit. In master mode, data on MISO is
sampled one SYSCLK before the end of each data bit, to provide maximum settling time for the slave device.
See Table 30.1 for timing parameters.
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SFR Definition 30.2. SPI0CN: SPI0 Control
Bit
7
6
5
4
Name
SPIF
WCOL
MODF
RXOVRN
Type
R/W
R/W
R/W
R/W
Reset
0
0
0
0
3
2
1
0
NSSMD[1:0]
TXBMT
SPIEN
R/W
R
R/W
1
0
0
1
SFR Address = 0xF8; SFR Page = All Pages; Bit-Addressable
Bit
Name
7
SPIF
Function
SPI0 Interrupt Flag.
This bit is set to logic 1 by hardware at the end of a data transfer. If SPI interrupts
are enabled, an interrupt will be generated. This bit is not automatically cleared by
hardware, and must be cleared by software.
6
WCOL
Write Collision Flag.
This bit is set to logic 1 if a write to SPI0DAT is attempted when TXBMT is 0. When
this occurs, the write to SPI0DAT will be ignored, and the transmit buffer will not be
written. If SPI interrupts are enabled, an interrupt will be generated. This bit is not
automatically cleared by hardware, and must be cleared by software.
5
MODF
Mode Fault Flag.
This bit is set to logic 1 by hardware when a master mode collision is detected (NSS
is low, MSTEN = 1, and NSSMD[1:0] = 01). If SPI interrupts are enabled, an interrupt will be generated. This bit is not automatically cleared by hardware, and must
be cleared by software.
4
RXOVRN
Receive Overrun Flag (valid in slave mode only).
This bit is set to logic 1 by hardware 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. If SPI interrupts are enabled, an interrupt will be generated. This
bit is not automatically cleared by hardware, and must be cleared by software.
3:2
NSSMD[1:0] Slave Select Mode.
Selects between the following NSS operation modes:
(See Section 30.2 and Section 30.3).
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 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.
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.
0
SPIEN
SPI0 Enable.
0: SPI disabled.
1: SPI enabled.
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SFR Definition 30.3. SPI0CKR: SPI0 Clock Rate
Bit
7
6
5
4
Name
SCR[7:0]
Type
R/W
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address = 0xA2; SFR Page = All Pages
Bit
Name
7:0
SCR[7:0]
Function
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 given in the following equation, where SYSCLK
is the system clock frequency and SPI0CKR is the 8-bit
value held in the SPI0CKR register.
SYSCLK
f SCK = ----------------------------------------------------------2   SPI0CKR[7:0] + 1 
for 0 <= SPI0CKR <= 255
Example: If SYSCLK = 2 MHz and SPI0CKR = 0x04,
2000000
f SCK = -------------------------2  4 + 1
f SCK = 200kHz
Preliminary Rev. 0.71
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C8051F39x/37x
SFR Definition 30.4. SPI0DAT: SPI0 Data
Bit
7
6
5
4
3
Name
SPI0DAT[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address = 0xA3; SFR Page = All Pages
Bit
Name
7:0
SPI0DAT[7:0]
Function
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.
SCK*
T
MCKH
T
MCKL
T
MIS
T
MIH
MISO
MOSI
* SCK is shown for CKPOL = 0. SCK is the opposite polarity for CKPOL = 1.
Figure 30.8. SPI Master Timing (CKPHA = 0)
236
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SCK*
T
T
MCKH
MCKL
T
T
MIS
MIH
MISO
MOSI
* SCK is shown for CKPOL = 0. SCK is the opposite polarity for CKPOL = 1.
Figure 30.9. SPI Master Timing (CKPHA = 1)
NSS
T
T
SE
T
CKL
SD
SCK*
T
CKH
T
SIS
T
SIH
MOSI
T
SEZ
T
SOH
T
SDZ
MISO
* SCK is shown for CKPOL = 0. SCK is the opposite polarity for CKPOL = 1.
Figure 30.10. SPI Slave Timing (CKPHA = 0)
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NSS
T
T
SE
T
CKL
SD
SCK*
T
CKH
T
SIS
T
SIH
MOSI
T
SEZ
T
T
SOH
SLH
MISO
* SCK is shown for CKPOL = 0. SCK is the opposite polarity for CKPOL = 1.
Figure 30.11. SPI Slave Timing (CKPHA = 1)
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SDZ
C8051F39x/37x
Table 30.1. SPI Slave Timing Parameters
Parameter
Description
Min
Max
Units
Master Mode Timing (See Figure 30.8 and Figure 30.9)
TMCKH
SCK High Time
1 x TSYSCLK
—
ns
TMCKL
SCK Low Time
1 x TSYSCLK
—
ns
TMIS
MISO Valid to SCK Shift Edge
1 x TSYSCLK + 20
—
ns
TMIH
SCK Shift Edge to MISO Change
0
—
ns
Slave Mode Timing (See Figure 30.10 and Figure 30.11)
TSE
NSS Falling to First SCK Edge
2 x TSYSCLK
—
ns
TSD
Last SCK Edge to NSS Rising
2 x TSYSCLK
—
ns
TSEZ
NSS Falling to MISO Valid
—
4 x TSYSCLK
ns
TSDZ
NSS Rising to MISO High-Z
—
4 x TSYSCLK
ns
TCKH
SCK High Time
5 x TSYSCLK
—
ns
TCKL
SCK Low Time
5 x TSYSCLK
—
ns
TSIS
MOSI Valid to SCK Sample Edge
2 x TSYSCLK
—
ns
TSIH
SCK Sample Edge to MOSI Change
2 x TSYSCLK
—
ns
TSOH
SCK Shift Edge to MISO Change
—
4 x TSYSCLK
ns
TSLH
Last SCK Edge to MISO Change
(CKPHA = 1 ONLY)
6 x TSYSCLK
8 x TSYSCLK
ns
Note: TSYSCLK is equal to one period of the device system clock (SYSCLK).
Preliminary Rev. 0.71
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31. Timers
Each MCU includes six counter/timers: two are 16-bit counter/timers compatible with those found in the
standard 8051, and four are 16-bit auto-reload timer for use with the SMBus or for general purpose use.
These timers can be used to measure time intervals, count external events and generate periodic interrupt
requests. Timer 0 and Timer 1 are nearly identical and have four primary modes of operation. Timer 2, 3, 4,
and 5 offer 16-bit and split 8-bit timer functionality with auto-reload.
Timer 0 and Timer 1 Modes:
Timer 2, 3, 4, and 5 Modes:
13-bit counter/timer
16-bit counter/timer
8-bit counter/timer with auto-reload
Two 8-bit counter/timers (Timer 0 only)
16-bit timer with auto-reload
Two 8-bit timers with auto-reload
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 from which
Timer 0 and/or Timer 1 may be clocked (See SFR Definition 31.1 for pre-scaled clock selection).
Timer 0/1 may then be configured to use this pre-scaled clock signal or the system clock. Timer 2, 3, 4,
and 5 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 (T0 or T1). Events with a frequency of up to one-fourth the system clock frequency can be counted. The input signal need not be periodic, but it should be held at a given level for at least two full system clock cycles to ensure the level is
properly sampled.
240
Preliminary Rev. 0.71
C8051F39x/37x
SFR Definition 31.1. CKCON: Clock Control
Bit
7
6
5
4
3
2
1
0
Name
T3MH
T3ML
T2MH
T2ML
T1M
T0M
SCA[1:0]
Type
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
SFR Address = 0x8E; SFR Page = All Pages
Bit
Name
7
T3MH
Function
Timer 3 High Byte Clock Select.
Selects the clock supplied to the Timer 3 high byte (split 8-bit timer mode only).
0: Timer 3 high byte uses the clock defined by the T3XCLK bit in TMR3CN.
1: Timer 3 high byte uses the system clock.
6
T3ML
Timer 3 Low Byte Clock Select.
Selects the clock supplied to Timer 3. Selects the clock supplied to the lower 8bit timer in split 8-bit timer mode.
0: Timer 3 low byte uses the clock defined by the T3XCLK bit in TMR3CN.
1: Timer 3 low byte uses the system clock.
5
T2MH
Timer 2 High Byte Clock Select.
Selects the clock supplied to the Timer 2 high byte (split 8-bit timer mode only).
0: Timer 2 high byte uses the clock defined by the T2XCLK bit in TMR2CN.
1: Timer 2 high byte uses the system clock.
4
T2ML
Timer 2 Low Byte Clock Select.
Selects the clock supplied to Timer 2. If Timer 2 is configured in split 8-bit timer
mode, this bit selects the clock supplied to the lower 8-bit timer.
0: Timer 2 low byte uses the clock defined by the T2XCLK bit in TMR2CN.
1: Timer 2 low byte uses the system clock.
3
T1
Timer 1 Clock Select.
Selects the clock source supplied to Timer 1. Ignored when C/T1 is set to 1.
0: Timer 1 uses the clock defined by the prescale bits SCA[1:0].
1: Timer 1 uses the system clock.
2
T0
Timer 0 Clock Select.
Selects the clock source supplied to Timer 0. Ignored when C/T0 is set to 1.
0: Counter/Timer 0 uses the clock defined by the prescale bits SCA[1:0].
1: Counter/Timer 0 uses the system clock.
1:0
SCA[1:0]
Timer 0/1 Prescale Bits.
These bits control the Timer 0/1 Clock Prescaler:
00: System clock divided by 12
01: System clock divided by 4
10: System clock divided by 48
11: External clock divided by 8 (synchronized with the system clock)
Preliminary Rev. 0.71
241
C8051F39x/37x
SFR Definition 31.2. CKCON1: Clock Control 1
Bit
7
6
5
4
Name
3
2
1
0
T5MH
T5ML
T4MH
T4ML
Type
R
R
R
R
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
SFR Address = 0xF4; SFR Page = All Pages
Bit
Name
Function
7:4
Unused
Read = 0000b; Write = don’t care
3
T5MH
Timer 5 High Byte Clock Select.
Selects the clock supplied to the Timer 5 high byte (split 8-bit timer
mode only).
0: Timer 5 high byte uses the clock defined by the T5XCLK bit in
TMR5CN.
1: Timer 5 high byte uses the system clock.
2
T5ML
Timer 5 Low Byte Clock Select.
Selects the clock supplied to Timer 5. Selects the clock supplied to
the lower 8-bit timer in split 8-bit timer mode.
0: Timer 5 low byte uses the clock defined by the T5XCLK bit in
TMR5CN.
1: Timer 5 low byte uses the system clock.
1
T4MH
Timer 4 High Byte Clock Select.
Selects the clock supplied to the Timer 4 high byte (split 8-bit timer
mode only).
0: Timer 4 high byte uses the clock defined by the T4XCLK bit in
TMR4CN.
1: Timer 4 high byte uses the system clock.
0
T4ML
Timer 4 Low Byte Clock Select.
Selects the clock supplied to Timer 4. If Timer 4 is configured in split
8-bit timer mode, this bit selects the clock supplied to the lower 8-bit
timer.
0: Timer 4 low byte uses the clock defined by the T4XCLK bit in
TMR4CN.
1: Timer 4 low byte uses the system clock.
242
Preliminary Rev. 0.71
C8051F39x/37x
31.1. Timer 0 and Timer 1
Each timer is implemented as a 16-bit register accessed as two separate bytes: a low byte (TL0 or TL1)
and a high byte (TH0 or TH1). The Counter/Timer Control register (TCON) is used to enable Timer 0 and
Timer 1 as well as indicate status. Timer 0 interrupts can be enabled by setting the ET0 bit in the IE register (Section “20.2. Interrupt Register Descriptions” on page 118); Timer 1 interrupts can be enabled by setting the ET1 bit in the IE register (Section “20.2. Interrupt Register Descriptions” on page 118). 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. Each operating
mode is described below.
31.1.1. 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 in TCON is set and an interrupt will occur if Timer 0 interrupts are
enabled.
The C/T0 bit in the TMOD register 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
“27.3. Priority Crossbar Decoder” on page 176 for information on selecting and configuring external I/O
pins). Clearing C/T selects the clock defined by the T0M bit in register CKCON. When T0M is set, Timer 0
is clocked by the system clock. When T0M is cleared, Timer 0 is clocked by the source selected by the
Clock Scale bits in CKCON (see SFR Definition 31.1).
Setting the TR0 bit (TCON.4) enables the timer when either GATE0 in the TMOD register is logic 0 or the
input signal INT0 is active as defined by bit IN0PL in register IT01CF (see SFR Definition 20.10). Setting
GATE0 to 1 allows the timer to be controlled by the external input signal INT0 (see Section “20.2. Interrupt
Register Descriptions” on page 118), facilitating pulse width measurements
TR0
GATE0
INT0
Counter/Timer
0
1
1
1
X
0
1
1
X
X
0
1
Disabled
Enabled
Disabled
Enabled
Note: X = Don't Care
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 register for Timer 1 in the same manner as described above for TL0 and TH0.
Timer 1 is configured and controlled using the relevant TCON and TMOD bits just as with Timer 0. The
input signal INT0 is used with Timer 1; the /INT1 polarity is defined by bit IN1PL in register IT01CF (see
SFR Definition 20.10).
Preliminary Rev. 0.71
243
C8051F39x/37x
TMOD
G
A
T
E
1
T0M
Pre-scaled Clock
C
/
T
1
T T
1 1
MM
1 0
G
A
T
E
0
C
/
T
0
IT01CF
T T
0 0
MM
1 0
I
N
1
P
L
I
N
1
S
L
2
I
N
1
S
L
1
I
N
1
S
L
0
I
N
0
P
L
I
N
0
S
L
2
I
N
0
S
L
1
I
N
0
S
L
0
0
0
SYSCLK
1
1
TR0
Crossbar
/INT0
TCLK
TL0
(5 bits)
TH0
(8 bits)
GATE0
IN0PL
TCON
T0
TF1
TR1
TF0
TR0
IE1
IT1
IE0
IT0
Interrupt
XOR
Figure 31.1. T0 Mode 0 Block Diagram
31.1.2. 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 counter/timers are enabled and configured in Mode 1 in the same manner as for Mode 0.
244
Preliminary Rev. 0.71
C8051F39x/37x
31.1.3. Mode 2: 8-bit Counter/Timer with Auto-Reload
Mode 2 configures Timer 0 and Timer 1 to operate as 8-bit counter/timers with automatic reload of the start
value. TL0 holds the count and TH0 holds the reload value. When the counter in TL0 overflows from all
ones to 0x00, the timer overflow flag TF0 in the TCON register 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 correct. 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 the timer when either GATE0 in the TMOD register is logic 0 or when the input
signal INT0 is active as defined by bit IN0PL in register IT01CF (see Section “20.3. External Interrupts
INT0 and INT1” on page 126 for details on the external input signals INT0 and INT1).
TMOD
G
A
T
E
1
T0M
Pre-scaled Clock
C
/
T
1
T T
1 1
MM
1 0
G
A
T
E
0
C
/
T
0
IT01CF
T T
0 0
MM
1 0
I
N
1
P
L
I
N
1
S
L
2
I
N
1
S
L
1
I
N
1
S
L
0
I
N
0
P
L
I
N
0
S
L
2
I
N
0
S
L
1
I
N
0
S
L
0
0
0
SYSCLK
1
1
T0
TL0
(8 bits)
TCON
TCLK
TR0
Crossbar
GATE0
TH0
(8 bits)
/INT0
IN0PL
TF1
TR1
TF0
TR0
IE1
IT1
IE0
IT0
Interrupt
Reload
XOR
Figure 31.2. T0 Mode 2 Block Diagram
Preliminary Rev. 0.71
245
C8051F39x/37x
31.1.4. Mode 3: Two 8-bit Counter/Timers (Timer 0 Only)
In Mode 3, Timer 0 is configured as two separate 8-bit counter/timers held in TL0 and TH0. The counter/
timer in TL0 is controlled using the Timer 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 interrupt.
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 ADC
conversions. While Timer 0 is operating in Mode 3, Timer 1 run control is handled through its mode settings. 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.
TMOD
G
A
T
E
1
T0M
Pre-scaled Clock
C
/
T
1
T T
1 1
MM
1 0
G
A
T
E
0
C
/
T
0
T T
0 0
MM
1 0
0
TR1
1
0
TCON
SYSCLK
TH0
(8 bits)
1
T0
TL0
(8 bits)
TR0
Crossbar
/INT0
GATE0
IN0PL
XOR
Figure 31.3. T0 Mode 3 Block Diagram
246
Preliminary Rev. 0.71
TF1
TR1
TF0
TR0
IE1
IT1
IE0
IT0
Interrupt
Interrupt
C8051F39x/37x
SFR Definition 31.3. TCON: Timer Control
Bit
7
6
5
4
3
2
1
0
Name
TF1
TR1
TF0
TR0
IE1
IT1
IE0
IT0
Type
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
SFR Address = 0x88; SFR Page = All Pages; Bit-Addressable
Bit
Name
7
TF1
Function
Timer 1 Overflow Flag.
Set to 1 by hardware when Timer 1 overflows. This flag can be cleared by software
but is automatically cleared when the CPU vectors to the Timer 1 interrupt service
routine.
6
TR1
Timer 1 Run Control.
Timer 1 is enabled by setting this bit to 1.
5
TF0
Timer 0 Overflow Flag.
Set to 1 by hardware when Timer 0 overflows. This flag can be cleared by software
but is automatically cleared when the CPU vectors to the Timer 0 interrupt service
routine.
4
TR0
Timer 0 Run Control.
Timer 0 is enabled by setting this bit to 1.
3
IE1
External Interrupt 1.
This flag is set by hardware when an edge/level of type defined by IT1 is detected.
It can be cleared by software but is automatically cleared when the CPU vectors to
the External Interrupt 1 service routine in edge-triggered mode.
2
IT1
Interrupt 1 Type Select.
This bit selects whether the configured /INT1 interrupt will be edge or level sensitive. /INT1 is configured active low or high by the IN1PL bit in the IT01CF register
(see SFR Definition 20.10).
0: /INT1 is level triggered.
1: /INT1 is edge triggered.
1
IE0
External Interrupt 0.
This flag is set by hardware when an edge/level of type defined by IT1 is detected.
It can be cleared by software but is automatically cleared when the CPU vectors to
the External Interrupt 0 service routine in edge-triggered mode.
0
IT0
Interrupt 0 Type Select.
This bit selects whether the configured INT0 interrupt will be edge or level sensitive. INT0 is configured active low or high by the IN0PL bit in register IT01CF (see
SFR Definition 20.10).
0: INT0 is level triggered.
1: INT0 is edge triggered.
Preliminary Rev. 0.71
247
C8051F39x/37x
SFR Definition 31.4. TMOD: Timer Mode
Bit
7
6
Name
GATE1
C/T1
Type
R/W
R/W
Reset
0
0
5
4
3
2
T1M[1:0]
GATE0
C/T0
T0M[1:0]
R/W
R/W
R/W
R/W
0
0
0
0
1
0
0
0
SFR Address = 0x89; SFR Page = All Pages
Bit
Name
7
GATE1
Function
Timer 1 Gate Control.
0: Timer 1 enabled when TR1 = 1 irrespective of INT1 logic level.
1: Timer 1 enabled only when TR1 = 1 AND INT1 is active as defined by bit IN1PL in
register IT01CF (see SFR Definition 20.10).
6
C/T1
Counter/Timer 1 Select.
0: Timer: Timer 1 incremented by clock defined by T1M bit in register CKCON.
1: Counter: Timer 1 incremented by high-to-low transitions on external pin (T1).
5:4
T1M[1:0] Timer 1 Mode Select.
These bits select the Timer 1 operation mode.
00: Mode 0, 13-bit Counter/Timer
01: Mode 1, 16-bit Counter/Timer
10: Mode 2, 8-bit Counter/Timer with Auto-Reload
11: Mode 3, Timer 1 Inactive
3
GATE0
Timer 0 Gate Control.
0: Timer 0 enabled when TR0 = 1 irrespective of INT0 logic level.
1: Timer 0 enabled only when TR0 = 1 AND INT0 is active as defined by bit IN0PL in
register IT01CF (see SFR Definition 20.10).
2
C/T0
Counter/Timer 0 Select.
0: Timer: Timer 0 incremented by clock defined by T0M bit in register CKCON.
1: Counter: Timer 0 incremented by high-to-low transitions on external pin (T0).
1:0
T0M[1:0] Timer 0 Mode Select.
These bits select the Timer 0 operation mode.
00: Mode 0, 13-bit Counter/Timer
01: Mode 1, 16-bit Counter/Timer
10: Mode 2, 8-bit Counter/Timer with Auto-Reload
11: Mode 3, Two 8-bit Counter/Timers
248
Preliminary Rev. 0.71
C8051F39x/37x
SFR Definition 31.5. TL0: Timer 0 Low Byte
Bit
7
6
5
4
Name
TL0[7:0]
Type
R/W
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address = 0x8A; SFR Page = All Pages
Bit
Name
7:0
TL0[7:0]
Function
Timer 0 Low Byte.
The TL0 register is the low byte of the 16-bit Timer 0.
SFR Definition 31.6. TL1: Timer 1 Low Byte
Bit
7
6
5
4
Name
TL1[7:0]
Type
R/W
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address = 0x8B; SFR Page = All Pages
Bit
Name
7:0
TL1[7:0]
Function
Timer 1 Low Byte.
The TL1 register is the low byte of the 16-bit Timer 1.
Preliminary Rev. 0.71
249
C8051F39x/37x
SFR Definition 31.7. TH0: Timer 0 High Byte
Bit
7
6
5
4
Name
TH0[7:0]
Type
R/W
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address = 0x8C; SFR Page = All Pages
Bit
Name
7:0
TH0[7:0]
Function
Timer 0 High Byte.
The TH0 register is the high byte of the 16-bit Timer 0.
SFR Definition 31.8. TH1: Timer 1 High Byte
Bit
7
6
5
4
Name
TH1[7:0]
Type
R/W
Reset
0
0
0
0
3
2
1
0
0
0
0
0
SFR Address = 0x8D; SFR Page = All Pages
Bit
7:0
Name
Function
TH1[7:0] Timer 1 High Byte.
The TH1 register is the high byte of the 16-bit Timer 1.
250
Preliminary Rev. 0.71
C8051F39x/37x
31.2. Timer 2
Timer 2 is a 16-bit timer formed by two 8-bit SFRs: TMR2L (low byte) and TMR2H (high byte). Timer 2 may
operate in 16-bit auto-reload mode or (split) 8-bit auto-reload mode. The T2SPLIT bit (TMR2CN.3) defines
the Timer 2 operation mode.
Timer 2 may be clocked by the system clock, the system clock divided by 12, or the external oscillator
source divided by 8. The external clock mode is ideal for real-time clock (RTC) functionality, where the
internal oscillator drives the system clock while Timer 2 (and/or the PCA) is clocked by an external precision oscillator. Note that the external oscillator source divided by 8 is synchronized with the system clock.
31.2.1. 16-bit Timer with Auto-Reload
When T2SPLIT (TMR2CN.3) is zero, Timer 2 operates as a 16-bit timer with auto-reload. Timer 2 can be
clocked by SYSCLK, SYSCLK divided by 12, or the external oscillator clock source divided by 8. As the
16-bit timer register increments and overflows from 0xFFFF to 0x0000, the 16-bit value in the Timer 2
reload registers (TMR2RLH and TMR2RLL) is loaded into the Timer 2 register as shown in Figure 31.4,
and the Timer 2 High Byte Overflow Flag (TMR2CN.7) is set. If Timer 2 interrupts are enabled (if IE.5 is
set), an interrupt will be generated on each Timer 2 overflow. Additionally, if Timer 2 interrupts are enabled
and the TF2LEN bit is set (TMR2CN.5), an interrupt will be generated each time the lower 8 bits (TMR2L)
overflow from 0xFF to 0x00.
CKCON
T2XCLK
S
C
A
0
0
TL2
Overflow
0
External Clock / 8
SYSCLK
TR2
1
TCLK
TMR2L
To ADC,
SMBus
To SMBus
TMR2H
TMR2CN
SYSCLK / 12
T T T T T T S
3 3 2 2 1 0 C
MMMMMMA
H L H L
1
1
TF2H
TF2L
TF2LEN
TF2CEN
T2SPLIT
TR2
Interrupt
T2XCLK
TMR2RLL TMR2RLH
Reload
Figure 31.4. Timer 2 16-Bit Mode Block Diagram
Preliminary Rev. 0.71
251
C8051F39x/37x
31.2.2. 8-bit Timers with Auto-Reload
When T2SPLIT is set, Timer 2 operates as two 8-bit timers (TMR2H and TMR2L). Both 8-bit timers operate in auto-reload mode as shown in Figure 31.5. TMR2RLL holds the reload value for TMR2L; TMR2RLH
holds the reload value for TMR2H. The TR2 bit in TMR2CN handles the run control for TMR2H. TMR2L is
always running when configured for 8-bit Mode.
Each 8-bit timer may be configured to use SYSCLK, SYSCLK divided by 12, or the external oscillator clock
source divided by 8. The Timer 2 Clock Select bits (T2MH and T2ML in CKCON) select either SYSCLK or
the clock defined by the Timer 2 External Clock Select bit (T2XCLK in TMR2CN), as follows:
T2MH
T2XCLK
0
0
1
0
1
X
TMR2H Clock Source
SYSCLK / 12
External Clock / 8
SYSCLK
T2ML
T2XCLK
0
0
1
0
1
X
TMR2L Clock Source
SYSCLK / 12
External Clock / 8
SYSCLK
The TF2H bit is set when TMR2H overflows from 0xFF to 0x00; the TF2L bit is set when TMR2L overflows
from 0xFF to 0x00. When Timer 2 interrupts are enabled (IE.5), an interrupt is generated each time
TMR2H overflows. If Timer 2 interrupts are enabled and TF2LEN (TMR2CN.5) is set, an interrupt is generated each time either TMR2L or TMR2H overflows. When TF2LEN is enabled, software must check the
TF2H and TF2L flags to determine the source of the Timer 2 interrupt. The TF2H and TF2L interrupt flags
are not cleared by hardware and must be manually cleared by software.
CKCON
T T T T T T S
3 3 2 2 1 0 C
MMMMMMA
H L H L
1
T2XCLK
SYSCLK / 12
0
External Clock / 8
1
S
C
A
0
TMR2RLH
Reload
To SMBus
0
TCLK
TR2
TMR2H
TMR2RLL
SYSCLK
Reload
TMR2CN
1
TF2H
TF2L
TF2LEN
TF2CEN
T2SPLIT
TR2
T2XCLK
1
TCLK
TMR2L
To ADC,
SMBus
0
Figure 31.5. Timer 2 8-Bit Mode Block Diagram
252
Preliminary Rev. 0.71
Interrupt
C8051F39x/37x
31.2.3. Low-Frequency Oscillator (LFO) Capture Mode
The Low-Frequency Oscillator Capture Mode allows the LFO clock to be measured against the system
clock or an external oscillator source. Timer 2 can be clocked from the system clock, the system clock
divided by 12, or the external oscillator divided by 8, depending on the T2ML (CKCON.4), and T2XCLK
settings.
Setting TF2CEN to 1 enables the LFO Capture Mode for Timer 2. In this mode, T2SPLIT should be set to
0, as the full 16-bit timer is used. Upon a falling edge of the low-frequency oscillator, the contents of Timer
2 (TMR2H:TMR2L) are loaded into the Timer 2 reload registers (TMR2RLH:TMR2RLL) and the TF2H flag
is set. By recording the difference between two successive timer capture values, the LFO clock frequency
can be determined with respect to the Timer 2 clock. The Timer 2 clock should be much faster than the
LFO to achieve an accurate reading.
CKCON
T2XCLK
SYSCLK / 12
TTTTTTSS
3 3 2 2 1 0CC
MMMMMM A A
HLHL
1 0
0
0
SYSCLK
Low-Frequency
Oscillator
TR2
TCLK
1
TMR2L
TMR2H
Capture
1
TF2CEN
TMR2RLL TMR2RLH
TMR2CN
External Clock / 8
TF2H
TF2L
TF2LEN
TF2CEN
T2SPLIT
TR2
Interrupt
T2XCLK
Figure 31.6. Timer 2 Low-Frequency Oscillation Capture Mode Block Diagram
Preliminary Rev. 0.71
253
C8051F39x/37x
SFR Definition 31.9. TMR2CN: Timer 2 Control
Bit
7
6
5
4
3
2
1
0
Name
TF2H
TF2L
TF2LEN
TF2CEN
T2SPLIT
TR2
Type
R/W
R/W
R/W
R/W
R/W
R/W
R
R/W
Reset
0
0
0
0
0
0
0
0
T2XCLK
SFR Address = 0xC8; SFR Page = 0; Bit-Addressable
Bit
Name
7
TF2H
Function
Timer 2 High Byte Overflow Flag.
Set by hardware when the Timer 2 high byte overflows from 0xFF to 0x00. In 16 bit
mode, this will occur when Timer 2 overflows from 0xFFFF to 0x0000. When the
Timer 2 interrupt is enabled, setting this bit causes the CPU to vector to the Timer 2
interrupt service routine. This bit is not automatically cleared by hardware.
6
TF2L
Timer 2 Low Byte Overflow Flag.
Set by hardware when the Timer 2 low byte overflows from 0xFF to 0x00. TF2L will be
set when the low byte overflows regardless of the Timer 2 mode. This bit is not automatically cleared by hardware.
5
TF2LEN
Timer 2 Low Byte Interrupt Enable.
When set to 1, this bit enables Timer 2 Low Byte interrupts. If Timer 2 interrupts are
also enabled, an interrupt will be generated when the low byte of Timer 2 overflows.
4
TF2CEN Timer 2 Low-Frequency Oscillator Capture Enable.
When set to 1, this bit enables Timer 2 Low-Frequency Oscillator Capture Mode. If
TF2CEN is set and Timer 2 interrupts are enabled, an interrupt will be generated on a
falling edge of the low-frequency oscillator output, and the current 16-bit timer value in
TMR2H:TMR2L will be copied to TMR2RLH:TMR2RLL.
3
T2SPLIT Timer 2 Split Mode Enable.
When this bit is set, Timer 2 operates as two 8-bit timers with auto-reload.
0: Timer 2 operates in 16-bit auto-reload mode.
1: Timer 2 operates as two 8-bit auto-reload timers.
2
TR2
Timer 2 Run Control.
Timer 2 is enabled by setting this bit to 1. In 8-bit mode, this bit enables/disables
TMR2H only; TMR2L is always enabled in split mode.
1
0
Unused Unused. Read = 0b; Write = Don’t Care
T2XCLK Timer 2 External Clock Select.
This bit selects the external clock source for Timer 2. If Timer 2 is in 8-bit mode, this bit
selects the external oscillator clock source for both timer bytes. However, the Timer 2
Clock Select bits (T2MH and T2ML in register CKCON) may still be used to select
between the external clock and the system clock for either timer.
0: Timer 2 clock is the system clock divided by 12.
1: Timer 2 clock is the external clock divided by 8 (synchronized with SYSCLK).
254
Preliminary Rev. 0.71
C8051F39x/37x
SFR Definition 31.10. TMR2RLL: Timer 2 Reload Register Low Byte
Bit
7
6
5
4
3
Name
TMR2RLL[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address = 0xCA; SFR Page = 0
Bit
Name
7:0
Function
TMR2RLL[7:0] Timer 2 Reload Register Low Byte.
TMR2RLL holds the low byte of the reload value for Timer 2.
SFR Definition 31.11. TMR2RLH: Timer 2 Reload Register High Byte
Bit
7
6
5
4
3
Name
TMR2RLH[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address = 0xCB; SFR Page = 0
Bit
Name
7:0
Function
TMR2RLH[7:0] Timer 2 Reload Register High Byte.
TMR2RLH holds the high byte of the reload value for Timer 2.
SFR Definition 31.12. TMR2L: Timer 2 Low Byte
Bit
7
6
5
4
3
Name
TMR2L[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address = 0xCC; SFR Page = 0
Bit
7:0
Name
Function
TMR2L[7:0] Timer 2 Low Byte.
In 16-bit mode, the TMR2L register contains the low byte of the 16-bit Timer
2. In 8-bit mode, TMR2L contains the 8-bit low byte timer value.
Preliminary Rev. 0.71
255
C8051F39x/37x
SFR Definition 31.13. TMR2H Timer 2 High Byte
Bit
7
6
5
4
3
Name
TMR2H[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address = 0xCD; SFR Page = 0
Bit
7:0
Name
Function
TMR2H[7:0] Timer 2 Low Byte.
In 16-bit mode, the TMR2H register contains the high byte of the 16-bit Timer 2.
In 8-bit mode, TMR2H contains the 8-bit high byte timer value.
256
Preliminary Rev. 0.71
C8051F39x/37x
31.3. Timer 3
Timer 3 is a 16-bit timer formed by two 8-bit SFRs: TMR3L (low byte) and TMR3H (high byte). Timer 3 may
operate in 16-bit auto-reload mode or (split) 8-bit auto-reload mode. The T3SPLIT bit (TMR3CN.3) defines
the Timer 3 operation mode.
Timer 3 may be clocked by the system clock, the system clock divided by 12, the external oscillator source
divided by 8, or the internal low-frequency oscillator divided by 8. The external clock mode is ideal for realtime clock (RTC) functionality, where the internal high-frequency oscillator drives the system clock while
Timer 3 is clocked by an external oscillator source. Note that the external oscillator source divided by 8 and
the LFO source divided by 8 are synchronized with the system clock when in all operating modes except
suspend. When the internal oscillator is placed in suspend mode, The external clock/8 signal or the LFO/8
output can directly drive the timer. This allows the use of an external clock or the LFO to wake up the
device from suspend mode. The timer will continue to run in suspend mode and count up. When the timer
overflow occurs, the device will wake from suspend mode, and begin executing code again. The timer
value may be set prior to entering suspend, to overflow in the desired amount of time (number of clocks) to
wake the device. If a wake-up source other than the timer wakes the device from suspend mode, it may
take up to three timer clocks before the timer registers can be read or written. During this time, the
STSYNC bit in register OSCICN will be set to 1, to indicate that it is not safe to read or write the timer registers.
Important Note: In internal LFO/8 mode, the divider for the internal LFO must be set to 1 for proper
functionality. The timer will not operate if the LFO divider is not set to 1.
31.3.1. 16-bit Timer with Auto-Reload
When T3SPLIT (TMR3CN.3) is zero, Timer 3 operates as a 16-bit timer with auto-reload. Timer 3 can be
clocked by SYSCLK, SYSCLK divided by 12, or the external oscillator clock source divided by 8. As the
16-bit timer register increments and overflows from 0xFFFF to 0x0000, the 16-bit value in the Timer 3
reload registers (TMR3RLH and TMR3RLL) is loaded into the Timer 3 register as shown in Figure 31.7,
and the Timer 3 High Byte Overflow Flag (TMR3CN.7) is set. If Timer 3 interrupts are enabled (if EIE1.7 is
set), an interrupt will be generated on each Timer 3 overflow. Additionally, if Timer 3 interrupts are enabled
and the TF3LEN bit is set (TMR3CN.5), an interrupt will be generated each time the lower 8 bits (TMR3L)
overflow from 0xFF to 0x00.
CKCON
T T T T T T S
3 3 2 2 1 0 C
MMMMMMA
H L H L
1
T3XCLK[1:0]
SYSCLK / 12
S
C
A
0
00
To ADC
0
01
TR3
Internal LFO / 8
TCLK
TMR3L
TMR3H
11
TMR3CN
External Clock / 8
1
SYSCLK
TMR3RLL TMR3RLH
TF3H
TF3L
TF3LEN
TF3CEN
T3SPLIT
TR3
T3XCLK1
T3XCLK0
Interrupt
Reload
Figure 31.7. Timer 3 16-Bit Mode Block Diagram
Preliminary Rev. 0.71
257
C8051F39x/37x
31.3.2. 8-bit Timers with Auto-Reload
When T3SPLIT is set, Timer 3 operates as two 8-bit timers (TMR3H and TMR3L). Both 8-bit timers operate in auto-reload mode as shown in Figure 31.8. TMR3RLL holds the reload value for TMR3L; TMR3RLH
holds the reload value for TMR3H. The TR3 bit in TMR3CN handles the run control for TMR3H. TMR3L is
always running when configured for 8-bit Mode.
Each 8-bit timer may be configured to use SYSCLK, SYSCLK divided by 12, the external oscillator clock
source divided by 8, or the internal Low-frequency Oscillator. The Timer 3 Clock Select bits (T3MH and
T3ML in CKCON) select either SYSCLK or the clock defined by the Timer 3 External Clock Select bits
(T3XCLK[1:0] in TMR3CN), as follows:
T3MH
T3XCLK[1:0] TMR3H Clock
Source
0
0
0
0
1
00
01
10
11
X
T3ML
SYSCLK / 12
External Clock / 8
Reserved
Internal LFO
SYSCLK
T3XCLK[1:0] TMR3L Clock
Source
0
0
0
0
1
00
01
10
11
X
SYSCLK / 12
External Clock / 8
Reserved
Internal LFO
SYSCLK
The TF3H bit is set when TMR3H overflows from 0xFF to 0x00; the TF3L bit is set when TMR3L overflows
from 0xFF to 0x00. When Timer 3 interrupts are enabled, an interrupt is generated each time TMR3H overflows. If Timer 3 interrupts are enabled and TF3LEN (TMR3CN.5) is set, an interrupt is generated each
time either TMR3L or TMR3H overflows. When TF3LEN is enabled, software must check the TF3H and
TF3L flags to determine the source of the Timer 3 interrupt. The TF3H and TF3L interrupt flags are not
cleared by hardware and must be manually cleared by software.
CKCON
TTTTTTSS
3 3 2 2 1 0 CC
MMMMMM A A
HLHL
1 0
T3XCLK[1:0]
SYSCLK / 12
00
External Clock / 8
01
TMR3RLH
Reload
0
TCLK
TR3
11
TMR3RLL
SYSCLK
Reload
TMR3CN
Internal LFO / 8
TMR3H
1
TF3H
TF3L
TF3LEN
TF3CEN
T3SPLIT
TR3
T3XCLK1
T3XCLK0
1
TCLK
TMR3L
To ADC
0
Figure 31.8. Timer 3 8-Bit Mode Block Diagram
258
Preliminary Rev. 0.71
Interrupt
C8051F39x/37x
31.3.3. Low-Frequency Oscillator (LFO) Capture Mode
The Low-Frequency Oscillator Capture Mode allows the LFO clock to be measured against the system
clock or an external oscillator source. Timer 3 can be clocked from the system clock, the system clock
divided by 12, or the external oscillator divided by 8, depending on the T3ML (CKCON.6), and
T3XCLK[1:0] settings.
Setting TF3CEN to 1 enables the LFO Capture Mode for Timer 3. In this mode, T3SPLIT should be set to
0, as the full 16-bit timer is used. Upon a falling edge of the low-frequency oscillator, the contents of
Timer 3 (TMR3H:TMR3L) are loaded into the Timer 3 reload registers (TMR3RLH:TMR3RLL) and the
TF3H flag is set. By recording the difference between two successive timer capture values, the LFO clock
frequency can be determined with respect to the Timer 3 clock. The Timer 3 clock should be much faster
than the LFO to achieve an accurate reading. This means that the LFO/8 should not be selected as the
timer clock source in this mode.
CKCON
T3XCLK[1:0]
SYSCLK / 12
TTTTTTSS
3 3 2 2 1 0CC
MMMMMM A A
HLHL
1 0
00
0
SYSCLK
Low-Frequency
Oscillator
TR3
TCLK
01
TMR3L
TMR3H
Capture
1
TF3CEN
TMR3RLL TMR3RLH
TMR3CN
External Clock / 8
TF3H
TF3L
TF3LEN
TF3CEN
T3SPLIT
TR3
T3XCLK1
T3XCLK0
Interrupt
Figure 31.9. Timer 3 Low-Frequency Oscillation Capture Mode Block Diagram
Preliminary Rev. 0.71
259
C8051F39x/37x
SFR Definition 31.14. TMR3CN: Timer 3 Control
Bit
7
6
5
4
3
2
1
0
Name
TF3H
TF3L
TF3LEN
TF3CEN
T3SPLIT
TR3
T3XCLK[1:0]
Type
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
SFR Address = 0x91; SFR Page = 0
Bit
7
6
5
4
3
2
1:0
Name
TF3H
Timer 3 High Byte Overflow Flag.
TF3L
Set by hardware when the Timer 3 high byte overflows from 0xFF to 0x00. In 16 bit
mode, this will occur when Timer 3 overflows from 0xFFFF to 0x0000. When the
Timer 3 interrupt is enabled, setting this bit causes the CPU to vector to the Timer 3
interrupt service routine. This bit is not automatically cleared by hardware.
Timer 3 Low Byte Overflow Flag.
TF3LEN
Set by hardware when the Timer 3 low byte overflows from 0xFF to 0x00. TF3L will
be set when the low byte overflows regardless of the Timer 3 mode. This bit is not
automatically cleared by hardware.
Timer 3 Low Byte Interrupt Enable.
TF3CEN
When set to 1, this bit enables Timer 3 Low Byte interrupts. If Timer 3 interrupts are
also enabled, an interrupt will be generated when the low byte of Timer 3 overflows.
Timer 3 Low-Frequency Oscillator Capture Enable.
T3SPLIT
When set to 1, this bit enables Timer 3 Low-Frequency Oscillator Capture Mode. If
TF3CEN is set and Timer 3 interrupts are enabled, an interrupt will be generated on
a falling edge of the low-frequency oscillator output, and the current 16-bit timer
value in TMR3H:TMR3L will be copied to TMR3RLH:TMR3RLL.
Timer 3 Split Mode Enable.
TR3
Function
When this bit is set, Timer 3 operates as two 8-bit timers with auto-reload.
0: Timer 3 operates in 16-bit auto-reload mode.
1: Timer 3 operates as two 8-bit auto-reload timers.
Timer 3 Run Control.
Timer 3 is enabled by setting this bit to 1. In 8-bit mode, this bit enables/disables
TMR3H only; TMR3L is always enabled in split mode.
T3XCLK[1:0] Timer 3 External Clock Select.
This bit selects the “external” clock source for Timer 3. If Timer 3 is in 8-bit mode,
this bit selects the external oscillator clock source for both timer bytes. However,
the Timer 3 Clock Select bits (T3MH and T3ML in register CKCON) may still be
used to select between the external clock and the system clock for either timer.
00: System clock divided by 12.
01: External clock divided by 8 (synchronized with SYSCLK when not in suspend).
10: Reserved.
11: Internal LFO/8 (synchronized with SYSCLK when not in suspend).
260
Preliminary Rev. 0.71
C8051F39x/37x
SFR Definition 31.15. TMR3RLL: Timer 3 Reload Register Low Byte
Bit
7
6
5
4
3
Name
TMR3RLL[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address = 0x92; SFR Page = 0
Bit
Name
Function
7:0
TMR3RLL[7:0]
Timer 3 Reload Register Low Byte.
TMR3RLL holds the low byte of the reload value for Timer 3.
SFR Definition 31.16. TMR3RLH: Timer 3 Reload Register High Byte
Bit
7
6
5
4
3
Name
TMR3RLH[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address = 0x93; SFR Page = 0
Bit
Name
Function
7:0
TMR3RLH[7:0]
Timer 3 Reload Register High Byte.
TMR3RLH holds the high byte of the reload value for Timer 3.
SFR Definition 31.17. TMR3L: Timer 3 Low Byte
Bit
7
6
5
4
3
Name
TMR3L[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address = 0x94; SFR Page = 0
Bit
Name
7:0
TMR3L[7:0]
Function
Timer 3 Low Byte.
In 16-bit mode, the TMR3L register contains the low byte of the 16-bit Timer 3. In
8-bit mode, TMR3L contains the 8-bit low byte timer value.
Preliminary Rev. 0.71
261
C8051F39x/37x
SFR Definition 31.18. TMR3H Timer 3 High Byte
Bit
7
6
5
4
3
Name
TMR3H[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address = 0x95; SFR Page = 0
Bit
7:0
Name
Function
TMR3H[7:0] Timer 3 High Byte.
In 16-bit mode, the TMR3H register contains the high byte of the 16-bit
Timer 3. In 8-bit mode, TMR3H contains the 8-bit high byte timer value.
262
Preliminary Rev. 0.71
C8051F39x/37x
31.4. Timer 4
Timer 4 is a 16-bit timer formed by two 8-bit SFRs: TMR4L (low byte) and TMR4H (high byte). Timer 4 may
operate in 16-bit auto-reload mode or (split) 8-bit auto-reload mode. The T4SPLIT bit (TMR4CN.3) defines
Timer 4 may be clocked by the system clock, the system clock divided by 12, or the external oscillator
source divided by 8. Note that the external oscillator source divided by 8 is synchronized with the system
clock.
31.4.1. 16-bit Timer with Auto-Reload
When T4SPLIT (TMR4CN.3) is zero, Timer 4 operates as a 16-bit timer with auto-reload. Timer 4 can be
clocked by SYSCLK, SYSCLK divided by 12, or the external oscillator clock source divided by 8. As the
16-bit timer register increments and overflows from 0xFFFF to 0x0000, the 16-bit value in the Timer 4
reload registers (TMR4RLH and TMR4RLL) is loaded into the Timer 4 register as shown in Figure 31.10,
and the Timer 4 High Byte Overflow Flag (TMR4CN.7) is set. If Timer 4 interrupts are enabled (if EIE1.7 is
set), an interrupt will be generated on each Timer 4 overflow. Additionally, if Timer 4 interrupts are enabled
and the TF4LEN bit is set (TMR4CN.5), an interrupt will be generated each time the lower 8 bits (TMR4L)
overflow from 0xFF to 0x00.
CKCON1
TTTT
5 5 4 4
MMMM
HLHL
T4XCLK
To ADC
0
0
External Clock / 8
SYSCLK
TR4
1
TCLK
TMR4L
TMR4H
TMR4CN
SYSCLK / 12
1
TMR4RLL TMR4RLH
TF4H
TF4L
TF4LEN
T4CE
T4SPLIT
TR4
T4CSS
T4XCLK
Interrupt
Reload
Figure 31.10. Timer 4 16-Bit Mode Block Diagram
Preliminary Rev. 0.71
263
C8051F39x/37x
31.4.2. 8-bit Timers with Auto-Reload
When T4SPLIT is 1 and T4CE = 0, Timer 4 operates as two 8-bit timers (TMR4H and TMR4L). Both 8-bit
timers operate in auto-reload mode as shown in Figure 31.11. TMR4RLL holds the reload value for
TMR4L; TMR4RLH holds the reload value for TMR4H. The TR4 bit in TMR4CN handles the run control for
TMR4H. TMR4L is always running when configured for 8-bit Mode.
Each 8-bit timer may be configured to use SYSCLK, SYSCLK divided by 12, or the external oscillator clock
source divided by 8. The Timer 4 Clock Select bits (T4MH and T4ML in CKCON1) select either SYSCLK or
the clock defined by the Timer 4 External Clock Select bit (T4XCLK in TMR4CN), as follows:
T4MH
T4XCLK
TMR4H Clock Source
T4ML
T4XCLK
TMR4L Clock Source
0
0
1
0
1
X
SYSCLK/12
External Clock/8
SYSCLK
0
0
1
0
1
X
SYSCLK/12
External Clock/8
SYSCLK
The TF4H bit is set when TMR4H overflows from 0xFF to 0x00; the TF4L bit is set when TMR4L overflows
from 0xFF to 0x00. When Timer 4 interrupts are enabled, an interrupt is generated each time TMR4H overflows. If Timer 4 interrupts are enabled and TF4LEN (TMR4CN.5) is set, an interrupt is generated each
time either TMR4L or TMR4H overflows. When TF4LEN is enabled, software must check the TF4H and
TF4L flags to determine the source of the Timer 4 interrupt. The TF4H and TF4L interrupt flags are not
cleared by hardware and must be manually cleared by software.
CKCON1
TTTT
5 5 4 4
MMMM
HLHL
T4XCLK
SYSCLK / 12
TMR4RLH
Reload
0
To ADC
0
External Clock / 8
1
TCLK
TR4
TMR4H
TMR4RLL
SYSCLK
Reload
TMR4CN
1
TF4H
TF4L
TF4LEN
T4CE
T4SPLIT
TR4
T4CSS
T4XCLK
1
TCLK
TMR4L
0
Figure 31.11. Timer 4 8-Bit Mode Block Diagram
264
Preliminary Rev. 0.71
Interrupt
C8051F39x/37x
SFR Definition 31.19. TMR4CN: Timer 4 Control
Bit
7
6
5
4
Name
TF4H
TF4L
TF4LEN
Type
R/W
R/W
R/W
Reset
0
0
0
3
2
1
0
T4SPLIT
TR4
R
R/W
R/W
R
R/W
0
0
0
0
0
T4XCLK
SFR Address = 0x91; SFR Page = F
Bit
Name
7
TF4H
Function
Timer 4 High Byte Overflow Flag.
Set by hardware when the Timer 4 high byte overflows from 0xFF to
0x00. In 16 bit mode, this will occur when Timer 4 overflows from
0xFFFF to 0x0000. When the Timer 4 interrupt is enabled, setting this bit
causes the CPU to vector to the Timer 4 interrupt service routine. This bit
is not automatically cleared by hardware.
6
TF4L
Timer 4 Low Byte Overflow Flag.
Set by hardware when the Timer 4 low byte overflows from 0xFF to 0x00.
TF4L will be set when the low byte overflows regardless of the Timer 4
mode. This bit is not automatically cleared by hardware.
5
TF4LEN
Timer 4 Low Byte Interrupt Enable.
When set to 1, this bit enables Timer 4 Low Byte interrupts. If Timer 4
interrupts are also enabled, an interrupt will be generated when the low
byte of Timer 4 overflows.
4
Unused
Read = 0b; Write = don’t care.
3
T4SPLIT
Timer 4 Split Mode Enable.
When this bit is set, Timer 4 operates as two 8-bit timers with autoreload.
0: Timer 4 operates in 16-bit auto-reload mode.
1: Timer 4 operates as two 8-bit auto-reload timers.
2
TR4
Timer 4 Run Control.
Timer 4 is enabled by setting this bit to 1. In 8-bit mode, this bit enables/
disables TMR4H only; TMR4L is always enabled in split mode.
1
Unused
Read = 0b; Write = don’t care.
0
T4XCLK
Timer 4 External Clock Select.
This bit selects the external clock source for Timer 4. However, the
Timer 4 Clock Select bits (T4MH and T4ML in register CKCON1) may
still be used to select between the external clock and the system clock
for either timer.
0: Timer 4 clock is the system clock divided by 12.
1: Timer 4 clock is the external clock divided by 8 (synchronized with
SYSCLK).
Preliminary Rev. 0.71
265
C8051F39x/37x
SFR Definition 31.20. TMR4RLL: Timer 4 Reload Register Low Byte
Bit
7
6
5
4
3
Name
TMR4RLL[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address = 0x92; SFR Page = F
Bit
Name
7:0
Function
TMR4RLL[7:0] Timer 4 Reload Register Low Byte.
TMR4RLL holds the low byte of the reload value for Timer 4.
SFR Definition 31.21. TMR4RLH: Timer 4 Reload Register High Byte
Bit
7
6
5
4
3
Name
TMR4RLH[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address = 0x93; SFR Page = F
Bit
Name
7:0
Function
TMR4RLH[7:0] Timer 4 Reload Register High Byte.
TMR4RLH holds the high byte of the reload value for Timer 4.
SFR Definition 31.22. TMR4L: Timer 4 Low Byte
Bit
7
6
5
4
3
Name
TMR4L[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address = 0x94; SFR Page = F
Bit
Name
7:0
TMR4L[7:0]
Function
Timer 4 Low Byte.
In 16-bit mode, the TMR4L register contains the low byte of the 16-bit
Timer 4. In 8-bit mode, TMR4L contains the 8-bit low byte timer value.
266
Preliminary Rev. 0.71
C8051F39x/37x
SFR Definition 31.23. TMR4H Timer 4 High Byte
Bit
7
6
5
4
3
Name
TMR4H[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address = 0x95; SFR Page = F
Bit
Name
7:0
TMR4H[7:0]
Function
Timer 4 High Byte.
In 16-bit mode, the TMR4H register contains the high byte of the 16-bit
Timer 4. In 8-bit mode, TMR4H contains the 8-bit high byte timer value.
Preliminary Rev. 0.71
267
C8051F39x/37x
31.5. Timer 5
Timer 5 is a 16-bit timer formed by two 8-bit SFRs: TMR5L (low byte) and TMR5H (high byte). Timer 5 may
operate in 16-bit auto-reload mode or (split) 8-bit auto-reload mode. The T5SPLIT bit (TMR5CN.3) defines
Timer 5 may be clocked by the system clock, the system clock divided by 12, or the external oscillator
source divided by 8. Note that the external oscillator source divided by 8 is synchronized with the system
clock.
31.5.1. 16-bit Timer with Auto-Reload
When T5SPLIT (TMR5CN.3) is zero, Timer 5 operates as a 16-bit timer with auto-reload. Timer 5 can be
clocked by SYSCLK, SYSCLK divided by 12, or the external oscillator clock source divided by 8. As the
16-bit timer register increments and overflows from 0xFFFF to 0x0000, the 16-bit value in the Timer 5
reload registers (TMR5RLH and TMR5RLL) is loaded into the Timer 5 register as shown in Figure 31.12,
and the Timer 5 High Byte Overflow Flag (TMR5CN.7) is set. If Timer 5 interrupts are enabled (if EIE1.7 is
set), an interrupt will be generated on each Timer 5 overflow. Additionally, if Timer 5 interrupts are enabled
and the TF5LEN bit is set (TMR5CN.5), an interrupt will be generated each time the lower 8 bits (TMR5L)
overflow from 0xFF to 0x00.
CKCON1
TTTT
5 5 4 4
MMMM
HLHL
T5XCLK
To ADC
0
0
External Clock / 8
SYSCLK
TR5
1
TCLK
TMR5L
TMR5H
TMR5CN
SYSCLK / 12
1
TMR5RLL TMR5RLH
TF5H
TF5L
TF5LEN
T5CE
T5SPLIT
TR5
T5CSS
T5XCLK
Reload
Figure 31.12. Timer 5 16-Bit Mode Block Diagram
268
Preliminary Rev. 0.71
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C8051F39x/37x
31.5.2. 8-bit Timers with Auto-Reload
When T5SPLIT is 1 and T5CE = 0, Timer 5 operates as two 8-bit timers (TMR5H and TMR5L). Both 8-bit
timers operate in auto-reload mode as shown in Figure 31.13. TMR5RLL holds the reload value for
TMR5L; TMR5RLH holds the reload value for TMR5H. The TR5 bit in TMR5CN handles the run control for
TMR5H. TMR5L is always running when configured for 8-bit Mode.
Each 8-bit timer may be configured to use SYSCLK, SYSCLK divided by 12, or the external oscillator clock
source divided by 8. The Timer 5 Clock Select bits (T5MH and T5ML in CKCON1) select either SYSCLK or
the clock defined by the Timer 5 External Clock Select bit (T5XCLK in TMR5CN), as follows:
T5MH
T5XCLK
TMR5H Clock Source
T5ML
T5XCLK
TMR5L Clock Source
0
0
1
0
1
X
SYSCLK/12
External Clock/8
SYSCLK
0
0
1
0
1
X
SYSCLK/12
External Clock/8
SYSCLK
The TF5H bit is set when TMR5H overflows from 0xFF to 0x00; the TF5L bit is set when TMR5L overflows
from 0xFF to 0x00. When Timer 5 interrupts are enabled, an interrupt is generated each time TMR5H overflows. If Timer 5 interrupts are enabled and TF5LEN (TMR5CN.5) is set, an interrupt is generated each
time either TMR5L or TMR5H overflows. When TF5LEN is enabled, software must check the TF5H and
TF5L flags to determine the source of the Timer 5 interrupt. The TF5H and TF5L interrupt flags are not
cleared by hardware and must be manually cleared by software.
CKCON1
TTTT
5 5 4 4
MMMM
HLHL
T5XCLK
SYSCLK / 12
TMR5RLH
Reload
0
To ADC
0
1
TCLK
TR5
TMR5H
1
TMR5RLL
SYSCLK
Reload
TMR5CN
External Clock / 8
TF5H
TF5L
TF5LEN
T5CE
T5SPLIT
TR5
T5CSS
T5XCLK
Interrupt
1
TCLK
TMR5L
0
Figure 31.13. Timer 5 8-Bit Mode Block Diagram
Preliminary Rev. 0.71
269
C8051F39x/37x
SFR Definition 31.24. TMR5CN: Timer 5 Control
Bit
7
6
5
4
Name
TF5H
TF5L
TF5LEN
Type
R/W
R/W
R/W
Reset
0
0
0
3
2
1
0
T5SPLIT
TR5
R
R/W
R/W
R
R/W
0
0
0
0
0
T5XCLK
SFR Address = 0xC8; SFR Page = F; Bit-Addressable
Bit
Name
7
TF5H
Function
Timer 5 High Byte Overflow Flag.
Set by hardware when the Timer 5 high byte overflows from 0xFF to 0x00.
In 16 bit mode, this will occur when Timer 5 overflows from 0xFFFF to
0x0000. When the Timer 5 interrupt is enabled, setting this bit causes the
CPU to vector to the Timer 5 interrupt service routine. This bit is not automatically cleared by hardware.
6
TF5L
Timer 5 Low Byte Overflow Flag.
Set by hardware when the Timer 5 low byte overflows from 0xFF to 0x00.
TF5L will be set when the low byte overflows regardless of the Timer 5
mode. This bit is not automatically cleared by hardware.
5
TF5LEN
Timer 5 Low Byte Interrupt Enable.
When set to 1, this bit enables Timer 5 Low Byte interrupts. If Timer 5
interrupts are also enabled, an interrupt will be generated when the low
byte of Timer 5 overflows.
4
Unused
Read = 0b; Write = don’t care.
3
T5SPLIT
Timer 5 Split Mode Enable.
When this bit is set, Timer 5 operates as two 8-bit timers with auto-reload.
0: Timer 5 operates in 16-bit auto-reload mode.
1: Timer 5 operates as two 8-bit auto-reload timers.
2
TR5
Timer 5 Run Control.
Timer 5 is enabled by setting this bit to 1. In 8-bit mode, this bit enables/
disables TMR5H only; TMR5L is always enabled in split mode.
1
Unused
Read = 0b; Write = don’t care.
0
T5XCLK
Timer 5 External Clock Select.
This bit selects the external clock source for Timer 5. However, the Timer 5
Clock Select bits (T5MH and T5ML in register CKCON1) may still be used
to select between the external clock and the system clock for either timer.
0: Timer 5 clock is the system clock divided by 12.
1: Timer 5 clock is the external clock divided by 8 (synchronized with SYSCLK).
270
Preliminary Rev. 0.71
C8051F39x/37x
SFR Definition 31.25. TMR5RLL: Timer 5 Reload Register Low Byte
Bit
7
6
5
4
3
Name
TMR5RLL[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address = 0xCA; SFR Page = F
Bit
Name
7:0
Function
TMR5RLL[7:0] Timer 5 Reload Register Low Byte.
TMR5RLL holds the low byte of the reload value for Timer 5.
SFR Definition 31.26. TMR5RLH: Timer 5 Reload Register High Byte
Bit
7
6
5
4
3
Name
TMR5RLH[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address = 0xCB; SFR Page = F
Bit
Name
7:0
Function
TMR5RLH[7:0] Timer 5 Reload Register High Byte.
TMR5RLH holds the high byte of the reload value for Timer 5.
SFR Definition 31.27. TMR5L: Timer 5 Low Byte
Bit
7
6
5
4
3
Name
TMR5L[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address = 0xCC; SFR Page = F
Bit
Name
7:0
TMR5L[7:0]
Function
Timer 5 Low Byte.
In 16-bit mode, the TMR5L register contains the low byte of the 16-bit
Timer 5. In 8-bit mode, TMR5L contains the 8-bit low byte timer value.
Preliminary Rev. 0.71
271
C8051F39x/37x
SFR Definition 31.28. TMR5H Timer 5 High Byte
Bit
7
6
5
4
3
Name
TMR5H[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
SFR Address = 0xCD; SFR Page = F
Bit
Name
7:0
TMR5H[7:0]
Function
Timer 5 High Byte.
In 16-bit mode, the TMR5H register contains the high byte of the 16bit Timer 5. In 8-bit mode, TMR5H contains the 8-bit high byte timer
value.
272
Preliminary Rev. 0.71
C8051F39x/37x
32. Programmable Counter Array
The Programmable Counter Array (PCA0) provides enhanced timer functionality while requiring less CPU
intervention than the standard 8051 counter/timers. The PCA consists of a dedicated 16-bit counter/timer
and three 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. The counter/timer is driven by a
programmable timebase that can select between seven sources: system clock, system clock divided by
four, system clock divided by twelve, the external oscillator clock source divided by 8, low frequency oscillator divided by 8, Timer 0 overflows, or an external clock signal on the ECI input pin. Each capture/compare module may be configured to operate independently in one of six modes: Edge-Triggered Capture,
Software Timer, High-Speed Output, Frequency Output, 8 to 11-Bit PWM, or 16-Bit PWM (each mode is
described in Section “32.3. Capture/Compare Modules” on page 276). The external oscillator clock option
is ideal for real-time clock (RTC) functionality, allowing the PCA to be clocked by a precision external oscillator while the internal oscillator drives the system clock. The PCA is configured and controlled through the
system controller's Special Function Registers. The PCA block diagram is shown in Figure 32.1
Important Note: The PCA Module 2 may be used as a watchdog timer (WDT), and is enabled in this mode
following a system reset. Access to certain PCA registers is restricted while WDT mode is enabled.
See Section 32.4 for details.
SYSCLK/12
SYSCLK/4
Timer 0 Overflow
PCA
CLOCK
MUX
ECI
SYSCLK
16-Bit Counter/Timer
External Clock/8
LFO/8
Capture/Compare
Module 0
Capture/Compare
Module 1
Capture/Compare
Module 2 / WDT
CEX2
CEX1
CEX0
ECI
Crossbar
Port I/O
Figure 32.1. PCA Block Diagram
Preliminary Rev. 0.71
273
C8051F39x/37x
32.1. 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 Register first guarantees an accurate reading of the entire 16-bit PCA0 counter.
Reading PCA0H or PCA0L does not disturb the counter operation. The CPS2–CPS0 bits in the PCA0MD
register select the timebase for the counter/timer as shown in Table 32.1.
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 software. Clearing the CIDL bit in the PCA0MD register allows the PCA to continue normal operation while the
CPU is in Idle mode.
Table 32.1. PCA Timebase Input Options
CPS2
0
0
0
CPS1
0
0
1
CPS0
0
1
0
0
1
1
1
1
1
1
0
0
1
1
0
1
0
1
Timebase
System clock divided by 12
System clock divided by 4
Timer 0 overflow
High-to-low transitions on ECI (max rate = system clock divided
by 4)
System clock
External oscillator source divided by 8*
Low frequency oscillator divided by 8*
Reserved
Note: Synchronized with the system clock.
IDLE
PCA0MD
C WW
I DD
DT L
L EC
K
SYSCLK/12
SYSCLK/4
Timer 0 Overflow
ECI
SYSCLK
External Clock/8
LFO/8
CCCE
PPPC
SSSF
2 1 0
PCA0CN
CC
FR
CCC
CCC
FFF
2 1 0
To SFR Bus
PCA0L
read
Snapshot
Register
000
001
010
011
0
1
PCA0H
PCA0L
Overflow
100
CF
101
To PCA Modules
110
Figure 32.2. PCA Counter/Timer Block Diagram
274
To PCA Interrupt System
Preliminary Rev. 0.71
C8051F39x/37x
32.2. PCA0 Interrupt Sources
Figure 32.3 shows a diagram of the PCA interrupt tree. There are five independent event flags that can be
used to generate a PCA0 interrupt. They are: the main PCA counter overflow flag (CF), which is set upon
a 16-bit overflow of the PCA0 counter, an intermediate overflow flag (COVF), which can be set on an overflow from the 8th, 9th, 10th, or 11th bit of the PCA0 counter, and the individual flags for each PCA channel
(CCF0, CCF1, and CCF2), which are set according to the operation mode of that module. These event
flags are always set when the trigger condition occurs. Each of these flags can be individually selected to
generate a PCA0 interrupt, using the corresponding interrupt enable flag (ECF for CF, ECOV for COVF,
and ECCFn for each CCFn). PCA0 interrupts must be globally enabled before any individual interrupt
sources are recognized by the processor. PCA0 interrupts are globally enabled by setting the EA bit and
the EPCA0 bit to logic 1.
(for n = 0 to 2)
PCA0CPMn
P ECCMT P E
WC A A A O WC
MO P P T G MC
1 MP N n n n F
6 n n n
n
n
PCA0CN
CC
FR
CCC
CCC
FFF
2 1 0
PCA0MD
C WW
I DD
DT L
LEC
K
PCA0PWM
CCCE
PPPC
SSSF
2 1 0
AEC
RCO
SOV
EVF
L
CC
L L
SS
EE
L L
1 0
PCA Counter/Timer 8, 9,
10 or 11-bit Overflow
Set 8, 9, 10, or 11 bit Operation
0
PCA Counter/Timer 16bit Overflow
1
ECCF0
PCA Module 0
(CCF0)
0
1
EPCA0
EA
0
0
0
1
1
1
Interrupt
Priority
Decoder
ECCF1
0
PCA Module 1
(CCF1)
1
ECCF2
PCA Module 2
(CCF2)
0
1
Figure 32.3. PCA Interrupt Block Diagram
Preliminary Rev. 0.71
275
C8051F39x/37x
32.3. 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 to 11-bit pulse width modulator, or 16-bit
pulse width modulator. Each module has Special Function Registers (SFRs) associated with it in the CIP51 system controller. These registers are used to exchange data with a module and configure the module's
mode of operation. Table 32.2 summarizes the bit settings in the PCA0CPMn and PCA0PWM registers
used to select the PCA capture/compare module’s operating mode. Note that all modules set to use 8, 9,
10, or 11-bit PWM mode must use the same cycle length (8–11 bits). Setting the ECCFn bit in a
PCA0CPMn register enables the module's CCFn interrupt.
Table 32.2. PCA0CPM and PCA0PWM Bit Settings for PCA Capture/Compare Modules
Operational Mode
PCA0CPMn
PCA0PWM
Bit Number 7 6 5 4 3 2 1 0 7 6 5
4–2
1–0
Capture triggered by positive edge on CEXn
X X 1 0 0 0 0 A 0 X B XXX
XX
Capture triggered by negative edge on CEXn
X X 0 1 0 0 0 A 0 X B XXX
XX
Capture triggered by any transition on CEXn
X X 1 1 0 0 0 A 0 X B XXX
XX
Software Timer
X C 0 0 1 0 0 A 0 X B XXX
XX
High Speed Output
X C 0 0 1 1 0 A 0 X B XXX
XX
Frequency Output
X C 0 0 0 1 1 A 0 X B XXX
XX
8-Bit Pulse Width Modulator (Note 7)
0 C 0 0 E 0 1 A 0 X B XXX
00
9-Bit Pulse Width Modulator (Note 7)
0 C 0 0 E 0 1 A D X B XXX
01
10-Bit Pulse Width Modulator (Note 7)
0 C 0 0 E 0 1 A D X B XXX
10
11-Bit Pulse Width Modulator (Note 7)
0 C 0 0 E 0 1 A D X B XXX
11
16-Bit Pulse Width Modulator
1 C 0 0 E 0 1 A 0 X B XXX
XX
Notes:
1. X = Don’t Care (no functional difference for individual module if 1 or 0).
2. A = Enable interrupts for this module (PCA interrupt triggered on CCFn set to 1).
3. B = Enable 8th, 9th, 10th or 11th bit overflow interrupt (Depends on setting of CLSEL[1:0]).
4. C = When set to 0, the digital comparator is off. For high speed and frequency output modes, the
associated pin will not toggle. In any of the PWM modes, this generates a 0% duty cycle (output = 0).
5. D = Selects whether the Capture/Compare register (0) or the Auto-Reload register (1) for the associated
channel is accessed via addresses PCA0CPHn and PCA0CPLn.
6. E = When set, a match event will cause the CCFn flag for the associated channel to be set.
7. All modules set to 8, 9, 10 or 11-bit PWM mode use the same cycle length setting.
276
Preliminary Rev. 0.71
C8051F39x/37x
32.3.1. Edge-triggered Capture Mode
In this mode, a valid transition on the CEXn pin causes the PCA to capture the value of the PCA 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 register are used to select the type of transition 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. An interrupt request is generated if the CCFn interrupt for that module is
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. If both CAPPn and CAPNn bits are set to logic 1, then the
state of the Port pin associated with CEXn can be read directly to determine whether a rising-edge or falling-edge caused the capture.
PCA Interrupt
PCA0CPMn
P ECCMT P E
WC A A A O WC
MO P P T G MC
1 MP N n n n F
6 n n n
n
n
0 0 0 x
0
Port I/O
Crossbar
CEXn
CCC
CCC
FFF
2 1 0
(to CCFn)
x x
PCA0CN
CC
FR
1
PCA0CPLn
PCA0CPHn
Capture
0
1
PCA
Timebase
PCA0L
PCA0H
Figure 32.4. PCA Capture Mode Diagram
Note: The CEXn input signal must remain high or low for at least 2 system clock cycles to be recognized by the
hardware.
Preliminary Rev. 0.71
277
C8051F39x/37x
32.3.2. Software Timer (Compare) Mode
In Software Timer mode, the PCA counter/timer value is compared to the module's 16-bit capture/compare
register (PCA0CPHn and PCA0CPLn). When a match occurs, the Capture/Compare Flag (CCFn) in
PCA0CN is set to logic 1. An interrupt request is generated if the CCFn interrupt for that module is
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 mode.
Important Note About Capture/Compare Registers: When writing a 16-bit value to the PCA0 Capture/
Compare registers, the low byte should always be written first. Writing to PCA0CPLn clears the ECOMn bit
to 0; writing to PCA0CPHn sets ECOMn to 1.
Write to
PCA0CPLn
0
ENB
Reset
Write to
PCA0CPHn
PCA Interrupt
ENB
1
PCA0CPMn
PCA0CN
P ECCMT P E
WC A A A O WC
MO P P T G MC
1 MP N n n n F
6 n n n
n
n
x
0 0
PCA0CPLn
CC
FR
PCA0CPHn
0 0 x
Enable
16-bit Comparator
PCA
Timebase
PCA0L
Match
PCA0H
Figure 32.5. PCA Software Timer Mode Diagram
278
CCC
CCC
FFF
2 1 0
Preliminary Rev. 0.71
0
1
C8051F39x/37x
32.3.3. 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). When a match occurs, the Capture/Compare Flag (CCFn) in PCA0CN is set to logic 1. An
interrupt request is generated if the CCFn interrupt for that module is 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 TOGn, MATn, and ECOMn bits in the PCA0CPMn register enables the HighSpeed Output mode. If ECOMn is cleared, the associated pin will retain its state, and not toggle on the next
match event.
Important Note About Capture/Compare Registers: When writing a 16-bit value to the PCA0 Capture/
Compare registers, the low byte should always be written first. Writing to PCA0CPLn clears the ECOMn bit
to 0; writing to PCA0CPHn sets ECOMn to 1.
Write to
PCA0CPLn
0
ENB
Reset
Write to
PCA0CPHn
PCA0CPMn
P ECCMT P E
WC A A A O WC
MO P P T G MC
1 MPN n n n F
6 n n n
n
n
ENB
1
x
0 0
0 x
PCA Interrupt
PCA0CN
PCA0CPLn
Enable
CC
FR
PCA0CPHn
16-bit Comparator
Match
0
1
Toggle
PCA
Timebase
CCC
CCC
FFF
2 1 0
TOGn
0 CEXn
1
PCA0L
Crossbar
Port I/O
PCA0H
Figure 32.6. PCA High-Speed Output Mode Diagram
Preliminary Rev. 0.71
279
C8051F39x/37x
32.3.4. 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 output is toggled. The frequency of the square wave is then defined by Equation 32.1.
F PCA
F CEXn = ----------------------------------------2  PCA0CPHn
Note: A value of 0x00 in the PCA0CPHn register is equal to 256 for this equation.
Equation 32.1. Square Wave Frequency Output
Where FPCA is the frequency of the clock selected by the CPS2–0 bits in the PCA mode register,
PCA0MD. The lower byte of the capture/compare module is compared to the PCA counter low byte; on a
match, n is toggled and the offset held in the high byte is added to the matched value in PCA0CPLn. Frequency Output Mode is enabled by setting the ECOMn, TOGn, and PWMn bits in the PCA0CPMn register.
Note that the MATn bit should normally be set to 0 in this mode. If the MATn bit is set to 1, the CCFn flag
for the channel will be set when the 16-bit PCA0 counter and the 16-bit capture/compare register for the
channel are equal.
Write to
PCA0CPLn
0
ENB
Reset
PCA0CPMn
Write to
PCA0CPHn
ENB
1
P ECCMT P E
WC A A A O WC
MO P P T G MC
1 MP N n n n F
6 n n n
n
n
x
0 0 0
PCA0CPLn
8-bit Adder
Adder
Enable
Toggle
x
Enable
PCA Timebase
8-bit
Comparator
PCA0CPHn
TOGn
match
0 CEXn
1
Crossbar
Port I/O
PCA0L
Figure 32.7. PCA Frequency Output Mode
32.3.5. 8-bit, 9-bit, 10-bit and 11-bit Pulse Width Modulator Modes
Each module can be used independently to generate a pulse width modulated (PWM) output on its associated CEXn pin. The frequency of the output is dependent on the timebase for the PCA counter/timer, and
the setting of the PWM cycle length (8, 9, 10 or 11-bits). For backwards-compatibility with the 8-bit PWM
mode available on other devices, the 8-bit PWM mode operates slightly different than 9, 10 and 11-bit
PWM modes. It is important to note that all channels configured for 8/9/10/11-bit PWM mode will use
the same cycle length. It is not possible to configure one channel for 8-bit PWM mode and another for 11bit mode (for example). However, other PCA channels can be configured to Pin Capture, High-Speed Output, Software Timer, Frequency Output, or 16-bit PWM mode independently.
280
Preliminary Rev. 0.71
C8051F39x/37x
32.3.5.1. 8-bit Pulse Width Modulator Mode
The duty cycle of the PWM output signal in 8-bit PWM mode is varied using the module's PCA0CPLn capture/compare register. When the value in the low byte of the PCA counter/timer (PCA0L) is equal to the
value in PCA0CPLn, the output on the CEXn pin will be set. When the count value in PCA0L overflows, the
CEXn output will be reset (see Figure 32.8). Also, when the counter/timer low byte (PCA0L) overflows from
0xFF to 0x00, PCA0CPLn is reloaded automatically with the value stored in the module’s capture/compare
high byte (PCA0CPHn) without software intervention. Setting the ECOMn and PWMn bits in the
PCA0CPMn register, and setting the CLSEL bits in register PCA0PWM to 00b enables 8-Bit Pulse Width
Modulator mode. If the MATn bit is set to 1, the CCFn flag for the module will be set each time an 8-bit
comparator match (rising edge) occurs. The COVF flag in PCA0PWM can be used to detect the overflow
(falling edge), which will occur every 256 PCA clock cycles. The duty cycle for 8-Bit PWM Mode is given in
Equation 32.2.
Important Note About Capture/Compare Registers: When writing a 16-bit value to the PCA0 Capture/
Compare registers, the low byte should always be written first. Writing to PCA0CPLn clears the ECOMn bit
to 0; writing to PCA0CPHn sets ECOMn to 1.
 256 – PCA0CPHn 
Duty Cycle = --------------------------------------------------256
Equation 32.2. 8-Bit PWM Duty Cycle
Using Equation 32.2, the largest duty cycle is 100% (PCA0CPHn = 0), and the smallest duty cycle is
0.39% (PCA0CPHn = 0xFF). A 0% duty cycle may be generated by clearing the ECOMn bit to 0.
Write to
PCA0CPLn
0
ENB
Reset
PCA0CPHn
Write to
PCA0CPHn
ENB
COVF
1
PCA0PWM
PCA0CPMn
AEC
RCO
SOV
EVF
L
CC
L L
SS
EE
L L
1 0
P ECCMT P E
WC A A A O WC
MO P P T GMC
1 MP N n n n F
6 n n n
n
n
0 x
0 0
0
0 0 x 0
PCA0CPLn
x
Enable
8-bit
Comparator
match
S
R
PCA Timebase
PCA0L
SET
CLR
Q
CEXn
Crossbar
Port I/O
Q
Overflow
Figure 32.8. PCA 8-Bit PWM Mode Diagram
Preliminary Rev. 0.71
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32.3.5.2. 9/10/11-bit Pulse Width Modulator Mode
The duty cycle of the PWM output signal in 9/10/11-bit PWM mode should be varied by writing to an “AutoReload” Register, which is dual-mapped into the PCA0CPHn and PCA0CPLn register locations. The data
written to define the duty cycle should be right-justified in the registers. The auto-reload registers are
accessed (read or written) when the bit ARSEL in PCA0PWM is set to 1. The capture/compare registers
are accessed when ARSEL is set to 0.
When the least-significant N bits of the PCA0 counter match the value in the associated module’s capture/
compare register (PCA0CPn), the output on CEXn is asserted high. When the counter overflows from the
Nth bit, CEXn is asserted low (see Figure 32.9). Upon an overflow from the Nth bit, the COVF flag is set,
and the value stored in the module’s auto-reload register is loaded into the capture/compare register. The
value of N is determined by the CLSEL bits in register PCA0PWM.
The 9, 10 or 11-bit PWM mode is selected by setting the ECOMn and PWMn bits in the PCA0CPMn register, and setting the CLSEL bits in register PCA0PWM to the desired cycle length (other than 8-bits). If the
MATn bit is set to 1, the CCFn flag for the module will be set each time a comparator match (rising edge)
occurs. The COVF flag in PCA0PWM can be used to detect the overflow (falling edge), which will occur
every 512 (9-bit), 1024 (10-bit) or 2048 (11-bit) PCA clock cycles. The duty cycle for 9/10/11-Bit PWM
Mode is given in Equation 32.2, where N is the number of bits in the PWM cycle.
Important Note About PCA0CPHn and PCA0CPLn Registers: When writing a 16-bit value to the
PCA0CPn registers, the low byte should always be written first. Writing to PCA0CPLn clears the ECOMn
bit to 0; writing to PCA0CPHn sets ECOMn to 1.
 2 N – PCA0CPn Duty Cycle = ------------------------------------------2N
Equation 32.3. 9, 10, and 11-Bit PWM Duty Cycle
A 0% duty cycle may be generated by clearing the ECOMn bit to 0.
Write to
PCA0CPLn
0
R/W when
ARSEL = 1
ENB
Reset
Write to
PCA0CPHn
(Auto-Reload)
PCA0PWM
PCA0CPH:Ln
AEC
RCO
SOV
EVF
L
(right-justified)
ENB
1
CC
L L
SS
EE
L L
1 0
PCA0CPMn
P ECCMT P E
WC A A A O WC
MO P P T G MC
1 MP N n n n F
6 n n n
n
n
0
0 0 x 0
R/W when
ARSEL = 0
x
(Capture/Compare)
Set “N” bits:
01 = 9 bits
10 = 10 bits
11 = 11 bits
PCA0CPH:Ln
(right-justified)
x
Enable
match
N-bit Comparator
S
R
PCA Timebase
SET
CLR
Q
CEXn
Crossbar
Q
PCA0H:L
Overflow of Nth Bit
Figure 32.9. PCA 9, 10 and 11-Bit PWM Mode Diagram
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32.3.6. 16-Bit Pulse Width Modulator Mode
A PCA module may also be operated in 16-Bit PWM mode. 16-bit PWM mode is independent of the other
(8/9/10/11-bit) PWM modes. In this mode, the 16-bit capture/compare module defines the number of PCA
clocks for the low time of the PWM signal. When the PCA counter matches the module contents, the output on CEXn is asserted high; when the 16-bit counter overflows, CEXn is asserted low. To output a varying duty cycle, new value writes should be synchronized with PCA 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, match interrupts should be enabled (ECCFn = 1 AND MATn = 1) to help synchronize the
capture/compare register writes. If the MATn bit is set to 1, the CCFn flag for the module will be set each
time a 16-bit comparator match (rising edge) occurs. The CF flag in PCA0CN can be used to detect the
overflow (falling edge). The duty cycle for 16-Bit PWM Mode is given by Equation 32.4.
Important Note About Capture/Compare Registers: When writing a 16-bit value to the PCA0 Capture/
Compare registers, the low byte should always be written first. Writing to PCA0CPLn clears the ECOMn bit
to 0; writing to PCA0CPHn sets ECOMn to 1.
 65536 – PCA0CPn 
Duty Cycle = ----------------------------------------------------65536
Equation 32.4. 16-Bit PWM Duty Cycle
Using Equation 32.4, the largest duty cycle is 100% (PCA0CPn = 0), and the smallest duty cycle is
0.0015% (PCA0CPn = 0xFFFF). A 0% duty cycle may be generated by clearing the ECOMn bit to 0.
Write to
PCA0CPLn
0
ENB
Reset
Write to
PCA0CPHn
ENB
1
PCA0CPMn
P ECCMT P E
WC A A A O WC
MO P P T G MC
1 MPN n n n F
6 n n n
n
n
1
0 0 x 0
PCA0CPHn
PCA0CPLn
x
Enable
16-bit Comparator
match
S
R
PCA Timebase
PCA0H
PCA0L
SET
CLR
Q
CEXn
Crossbar
Port I/O
Q
Overflow
Figure 32.10. PCA 16-Bit PWM Mode
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32.4. Watchdog Timer Mode
A programmable watchdog timer (WDT) function is available through the PCA Module 2. The WDT is used
to generate a reset if the time between writes to the WDT update register (PCA0CPH2) exceed a specified
limit. The WDT can be configured and enabled/disabled as needed by software.
With the WDTE bit set in the PCA0MD register, Module 2 operates as a watchdog timer (WDT). The Module 2 high byte is compared to the PCA counter high byte; the Module 2 low byte holds the offset to be
used when WDT updates are performed. The Watchdog Timer is enabled on reset. Writes to some
PCA registers are restricted while the Watchdog Timer is enabled. The WDT will generate a reset
shortly after code begins execution. To avoid this reset, the WDT should be explicitly disabled (and optionally re-configured and re-enabled if it is used in the system).
32.4.1. Watchdog Timer Operation
While the WDT is enabled:






PCA counter is forced on.
Writes to PCA0L and PCA0H are not allowed.
PCA clock source bits (CPS2–CPS0) are frozen.
PCA Idle control bit (CIDL) is frozen.
Module 2 is forced into software timer mode.
Writes to the Module 2 mode register (PCA0CPM2) are disabled.
While the WDT is enabled, writes to the CR bit will not change the PCA counter state; the counter will run
until the WDT is disabled. The PCA counter run control bit (CR) will read zero if the WDT is enabled but
user software has not enabled the PCA counter. If a match occurs between PCA0CPH2 and PCA0H while
the WDT is enabled, a reset will be generated. To prevent a WDT reset, the WDT may be updated with a
write of any value to PCA0CPH2. Upon a PCA0CPH2 write, PCA0H plus the offset held in PCA0CPL2 is
loaded into PCA0CPH2 (See Figure 32.11).
PCA0MD
C WW
I DD
DT L
L EC
K
CCCE
PPPC
SSSF
2 1 0
PCA0CPH2
Enable
PCA0CPL2
Write to
PCA0CPH2
8-bit Adder
8-bit
Comparator
PCA0H
Match
Reset
PCA0L Overflow
Adder
Enable
Figure 32.11. PCA Module 2 with Watchdog Timer Enabled
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The 8-bit offset held in PCA0CPH2 is compared to the upper byte of the 16-bit PCA counter. This offset
value is the number of PCA0L overflows before a reset. Up to 256 PCA clocks may pass before the first
PCA0L overflow occurs, depending on the value of the PCA0L when the update is performed. The total offset is then given (in PCA clocks) by Equation 32.5, where PCA0L is the value of the PCA0L register at the
time of the update.
Offset =  256  PCA0CPL2  +  256 – PCA0L 
Equation 32.5. Watchdog Timer Offset in PCA Clocks
The WDT reset is generated when PCA0L overflows while there is a match between PCA0CPH2 and
PCA0H. Software may force a WDT reset by writing a 1 to the CCF2 flag (PCA0CN.2) while the WDT is
enabled.
32.4.2. Watchdog Timer Usage
To configure the WDT, perform the following tasks:
1. Disable the WDT by writing a 0 to the WDTE bit.
2. Select the desired PCA clock source (with the CPS2–CPS0 bits).
3. Load PCA0CPL2 with the desired WDT update offset value.
4. Configure the PCA Idle mode (set CIDL if the WDT should be suspended while the CPU is in Idle
mode).
5. Enable the WDT by setting the WDTE bit to 1.
6. Reset the WDT timer by writing to PCA0CPH2.
The PCA clock source and Idle mode select cannot be changed while the WDT is enabled. The watchdog
timer is enabled by setting the WDTE or WDLCK bits in the PCA0MD register. When WDLCK is set, the
WDT cannot be disabled until the next system reset. If WDLCK is not set, the WDT is disabled by clearing
the WDTE bit.
The WDT is enabled following any reset. The PCA0 counter clock defaults to the system clock divided by
12, PCA0L defaults to 0x00, and PCA0CPL2 defaults to 0x00. Using Equation 32.5, this results in a WDT
timeout interval of 256 PCA clock cycles, or 3072 system clock cycles. Table 32.3 lists some example timeout intervals for typical system clocks.
Table 32.3. Watchdog Timer Timeout Intervals1
System Clock (Hz)
PCA0CPL2
Timeout Interval (ms)
24,500,000
24,500,000
24,500,000
3,062,5002
3,062,5002
3,062,5002
32,000
32,000
32,000
255
128
32
255
128
32
255
128
32
32.1
16.2
4.1
257
129.5
33.1
24576
12384
3168
Notes:
1. Assumes SYSCLK/12 as the PCA clock source, and a PCA0L value
of 0x00 at the update time.
2. Internal SYSCLK reset frequency = Internal Oscillator divided by 8.
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32.5. Comparator Clear Function
In 8/9/10/11/16-bit PWM modes, the comparator clear function utilizes the Comparator0 output synchronized to the system clock to clear CEXn to logic low for the current PWM cycle. This comparator clear function can be enabled for each PWM channel by setting the CPCEn bits to 1 in the PCA0CLR SFR (see SFR
Definition 32.4). When the comparator clear function is disabled, CEXn is unaffected. See Figure 32.12.
PCA0CPMn
PCA0CLR
PWMn
ECCFn
MATn
TOGn
CAPNn
CAPPn
ECOMn
PWM16n
CPCE0
CPCE1
CPCE2
CPCPOL
Clear CEXn to logic low
for current PWM cycle
CP0 +
Comparator0
Input Mux
CP0 -
0
1
Figure 32.12. Comparator Clear Function Diagram
The asynchronous Comparator0 output is logic high when the voltage of CP0+ is greater than CP0- and
logic low when the voltage of CP0+ is less than CP0-. The polarity of the Comparator0 output is used to
clear CEXn as follows: when CPCPOL = 0, CEXn is forced to logic low on the falling edge of the
Comparator0 output (see Figure 32.13); when CPCPOL = 0, CEXn is forced logic low on the rising edge of
the Compartor0 output (see Figure 32.14).
CEXn (CPCEn = 0)
Comparator0 Output
(CPCPOL = 0)
CEXn (CPCEn = 1)
Figure 32.13. CEXn with CPCEn = 1, CPCPOL = 0
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CEXn (CPCEn = 0)
Comparator0 Output
(CPCPOL = 1)
CEXn (CPCEn = 1)
Figure 32.14. CEXn with CPCEn = 1, CPCPOL = 1
In the PWM cycle following the current cycle, should the Comparator0 output remain logic low when
CPCPOL = 0 or logic high when CPCPOL = 1, CEXn will continue to be logic low. See Figure 32.15 and
Figure 32.16.
CEXn (CPCEn = 0)
Comparator0 Output
(CPCPOL = 0)
CEXn (CPCEn = 1)
Figure 32.15. CEXn with CPCEn = 1, CPCPOL = 0
CEXn (CPCEn = 0)
Comparator0 Output
(CPCPOL = 1)
CEXn (CPCEn = 1)
Figure 32.16. CEXn with CPCEn = 1, CPCPOL = 1
Preliminary Rev. 0.71
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32.6. Register Descriptions for PCA0
Following are detailed descriptions of the special function registers related to the operation of the PCA.
SFR Definition 32.1. PCA0CN: PCA Control
Bit
7
6
5
4
Name
CF
CR
Type
R/W
R/W
R
R
Reset
0
0
0
0
3
2
1
0
CCF2
CCF1
CCF0
R
R/W
R/W
R/W
0
0
0
0
SFR Address = 0xD8; SFR Page = All Pages; Bit-Addressable
Bit
Name
7
CF
Function
PCA Counter/Timer Overflow Flag.
Set by hardware when the PCA Counter/Timer overflows from 0xFFFF to
0x0000. When the Counter/Timer Overflow (CF) interrupt is enabled, setting
this bit causes the CPU to vector to the PCA interrupt service routine. This bit
is not automatically cleared by hardware and must be cleared by software.
6
CR
PCA Counter/Timer Run Control.
This bit enables/disables the PCA Counter/Timer.
0: PCA Counter/Timer disabled.
1: PCA Counter/Timer enabled.
5:3
2
Unused
CCF2
Unused. Read = 000b, Write = Don't care.
PCA Module 2 Capture/Compare Flag.
This bit is set by hardware when a match or capture occurs. When the CCF2
interrupt is enabled, setting this bit causes the CPU to vector to the PCA interrupt service routine. This bit is not automatically cleared by hardware and
must be cleared by software.
1
CCF1
PCA Module 1 Capture/Compare Flag.
This bit is set by hardware when a match or capture occurs. When the CCF1
interrupt is enabled, setting this bit causes the CPU to vector to the PCA interrupt service routine. This bit is not automatically cleared by hardware and
must be cleared by software.
0
CCF0
PCA Module 0 Capture/Compare Flag.
This bit is set by hardware when a match or capture occurs. When the CCF0
interrupt is enabled, setting this bit causes the CPU to vector to the PCA interrupt service routine. This bit is not automatically cleared by hardware and
must be cleared by software.
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SFR Definition 32.2. PCA0MD: PCA Mode
Bit
7
6
5
4
Name
CIDL
WDTE
WDLCK
Type
R/W
R/W
R/W
Reset
0
1
0
3
2
1
0
CPS2
CPS1
CPS0
ECF
R
R/W
R/W
R/W
R/W
0
0
0
0
0
SFR Address = 0xD9; SFR Page = All Pages
Bit
Name
7
CIDL
Function
PCA Counter/Timer Idle Control.
Specifies PCA behavior when CPU is in Idle Mode.
0: PCA continues to function normally while the system controller is in Idle
Mode.
1: PCA operation is suspended while the system controller is in Idle Mode.
6
WDTE
Watchdog Timer Enable.
If this bit is set, PCA Module 2 is used as the watchdog timer.
0: Watchdog Timer disabled.
1: PCA Module 2 enabled as Watchdog Timer.
5
WDLCK
Watchdog Timer Lock.
This bit locks/unlocks the Watchdog Timer Enable. When WDLCK is set,
the Watchdog Timer may not be disabled until the next system reset.
0: Watchdog Timer Enable unlocked.
1: Watchdog Timer Enable locked.
4
3:1
Unused
CPS[2:0]
Unused. Read = 0b, Write = Don't care.
PCA Counter/Timer Pulse Select.
These bits select the timebase source for the PCA counter
000: System clock divided by 12
001: System clock divided by 4
010: Timer 0 overflow
011: High-to-low transitions on ECI (max rate = system clock divided by 4)
100: System clock
101: External clock divided by 8 (synchronized with the system clock)
110: Low frequency oscillator divided by 8
111: Reserved
0
ECF
PCA Counter/Timer Overflow Interrupt Enable.
This bit sets the masking of the PCA Counter/Timer Overflow (CF) interrupt.
0: Disable the CF interrupt.
1: Enable a PCA Counter/Timer Overflow interrupt request when CF
(PCA0CN.7) is set.
Note: When the WDTE bit is set to 1, the other bits in the PCA0MD register cannot be modified. To change the
contents of the PCA0MD register, the Watchdog Timer must first be disabled.
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SFR Definition 32.3. PCA0PWM: PCA PWM Configuration
Bit
7
6
5
4
3
2
Name
ARSEL
ECOV
COVF
Type
R/W
R/W
R/W
R
R
R
Reset
0
0
0
0
0
0
1
0
CLSEL[1:0]
R/W
0
0
SFR Address = 0xF7; SFR Page = All Pages
Bit
Name
7
ARSEL
Function
Auto-Reload Register Select.
This bit selects whether to read and write the normal PCA capture/compare registers (PCA0CPn), or the Auto-Reload registers at the same
SFR addresses. This function is used to define the reload value for 9,
10, and 11-bit PWM modes. In all other modes, the Auto-Reload registers have no function.
0: Read/Write Capture/Compare Registers at PCA0CPHn and
PCA0CPLn.
1: Read/Write Auto-Reload Registers at PCA0CPHn and PCA0CPLn.
6
ECOV
Cycle Overflow Interrupt Enable.
This bit sets the masking of the Cycle Overflow Flag (COVF) interrupt.
0: COVF will not generate PCA interrupts.
1: A PCA interrupt will be generated when COVF is set.
5
COVF
Cycle Overflow Flag.
This bit indicates an overflow of the 8th, 9th, 10th, or 11th bit of the
main PCA counter (PCA0). The specific bit used for this flag depends
on the setting of the Cycle Length Select bits. The bit can be set by
hardware or software, but must be cleared by software.
0: No overflow has occurred since the last time this bit was cleared.
1: An overflow has occurred since the last time this bit was cleared.
4:2
1:0
Unused
CLSEL[1:0]
Unused. Read = 000b; Write = Don’t care.
Cycle Length Select.
When 16-bit PWM mode is not selected, these bits select the length of
the PWM cycle, between 8, 9, 10, or 11 bits. This affects all channels
configured for PWM which are not using 16-bit PWM mode. These bits
are ignored for individual channels configured to16-bit PWM mode.
00: 8 bits.
01: 9 bits.
10: 10 bits.
11: 11 bits.
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SFR Definition 32.4. PCA0CLR: PCA Comparator Clear Control
Bit
7
6
5
4
Name
CPCPOL
Type
R/W
R/W
R/W
R/W
Reset
0
0
0
0
3
2
1
0
CPCE2
CPCE1
CPCE0
R/W
R/W
R/W
R/W
0
0
0
0
SFR Address = 0xCE; SFR Page = All Pages
Bit
Name
7
CPCPOL
Function
Comparator Clear Polarity.
Selects the polarity of the comparator result that will clear the PCA
channel(s).
0: PCA channel(s) will be cleared when comparator result goes logic
high
1: PCA channel(s) will be cleared when comparator result goes logic
low
6:3
2
Reserved
CPCE2
Must write 0000b.
Comparator Clear Enable for CEX2.
Enables the comparator clear function on PCA channel 2.
1
CPCE1
Comparator Clear Enable for CEX1.
Enables the comparator clear function on PCA channel 1.
0
CPCE0
Comparator Clear Enable for CEX0.
Enables the comparator clear function on PCA channel 0.
Preliminary Rev. 0.71
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SFR Definition 32.5. PCA0CPMn: PCA Capture/Compare Mode
Bit
7
6
5
4
3
2
1
0
Name
PWM16n
ECOMn
CAPPn
CAPNn
MATn
TOGn
PWMn
ECCFn
Type
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
SFR Addresses: PCA0CPM0 = 0xDA, PCA0CPM1 = 0xDB, PCA0CPM2 = 0xDC
SFR Pages: PCA0CPM0 = All Pages, PCA0CPM1 = All Pages, PCA0CPM2 = All Pages
Bit
7
Name
Function
PWM16n 16-bit Pulse Width Modulation Enable.
6
ECOMn
This bit enables 16-bit mode when Pulse Width Modulation mode is enabled.
0: 8 to 11-bit PWM selected.
1: 16-bit PWM selected.
Comparator Function Enable.
5
CAPPn
This bit enables the comparator function for PCA module n when set to 1.
Capture Positive Function Enable.
4
CAPNn
This bit enables the positive edge capture for PCA module n when set to 1.
Capture Negative Function Enable.
MATn
This bit enables the negative edge capture for PCA module n when set to 1.
Match Function Enable.
TOGn
This bit enables the match function for PCA module n when set to 1. When enabled,
matches of the PCA counter with a module's capture/compare register cause the
CCFn bit in PCA0MD register to be set to logic 1.
Toggle Function Enable.
PWMn
This bit enables the toggle function for PCA module n when set to 1. When enabled,
matches of the PCA counter with a module's capture/compare register cause the
logic level on the CEXn pin to toggle. If the PWMn bit is also set to logic 1, the module operates in Frequency Output Mode.
Pulse Width Modulation Mode Enable.
ECCFn
This bit enables the PWM function for PCA module n when set to 1. When enabled,
a pulse width modulated signal is output on the CEXn pin. 8 to 11-bit PWM is used if
PWM16n is cleared; 16-bit mode is used if PWM16n is set to logic 1. If the TOGn bit
is also set, the module operates in Frequency Output Mode.
Capture/Compare Flag Interrupt Enable.
3
2
1
0
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.
Note: When the WDTE bit is set to 1, the PCA0CPM2 register cannot be modified, and module 2 acts as the
watchdog timer. To change the contents of the PCA0CPM2 register or the function of module 2, the Watchdog
Timer must be disabled.
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SFR Definition 32.6. PCA0L: PCA Counter/Timer Low Byte
Bit
7
6
5
4
3
2
1
0
PCA0[7:0]
Name
Type
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
SFR Address = 0xF9; SFR Page = All Pages
Bit
Name
7:0
PCA0[7:0]
Function
PCA Counter/Timer Low Byte.
The PCA0L register holds the low byte (LSB) of the 16-bit PCA Counter/
Timer.
Note: When the WDTE bit is set to 1, the PCA0L register cannot be modified by software. To change the contents of
the PCA0L register, the Watchdog Timer must first be disabled.
SFR Definition 32.7. PCA0H: PCA Counter/Timer High Byte
Bit
7
6
5
4
3
2
1
0
PCA0[15:8]
Name
Type
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
SFR Address = 0xFA; SFR Page = All Pages
Bit
Name
7:0
PCA0[15:8]
Function
PCA Counter/Timer High Byte.
The PCA0H register holds the high byte (MSB) of the 16-bit PCA
Counter/Timer. Reads of this register will read the contents of a
“snapshot” register, whose contents are updated only when the contents of PCA0L are read (see Section 32.1).
Note: When the WDTE bit is set to 1, the PCA0H register cannot be modified by software. To change the contents of
the PCA0H register, the Watchdog Timer must first be disabled.
Preliminary Rev. 0.71
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SFR Definition 32.8. PCA0CPLn: PCA Capture Module Low Byte
Bit
7
6
5
4
3
2
1
0
PCA0CPn[7:0]
Name
Type
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
SFR Addresses: PCA0CPL0 = 0xFB, PCA0CPL1 = 0xE9, PCA0CPL2 = 0xEB
SFR Pages: PCA0CPL0 = All Pages, PCA0CPL1 = All Pages, PCA0CPL2 = All Pages
Bit
Name
7:0
PCA0CPn[7:0]
Function
PCA Capture Module Low Byte.
The PCA0CPLn register holds the low byte (LSB) of the 16-bit
capture module n.
This register address also allows access to the low byte of the
corresponding PCA channel’s auto-reload value for 9, 10, or 11bit PWM mode. The ARSEL bit in register PCA0PWM controls
which register is accessed.
Note: A write to this register will clear the module’s ECOMn bit to a 0.
SFR Definition 32.9. PCA0CPHn: PCA Capture Module High Byte
Bit
7
6
5
4
3
2
1
0
PCA0CPn[15:8]
Name
Type
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Reset
0
0
0
0
0
0
0
0
SFR Addresses: PCA0CPH0 = 0xFC, PCA0CPH1 = 0xEA, PCA0CPH2 = 0xEC
SFR Pages: PCA0CPH0 = All Pages, PCA0CPH1 = All Pages, PCA0CPH2 = All Pages
Bit
Name
7:0
PCA0CPn[15:8]
Function
PCA Capture Module High Byte.
The PCA0CPHn register holds the high byte (MSB) of the 16-bit capture module n.
This register address also allows access to the high byte of the corresponding PCA channel’s auto-reload value for 9, 10, or 11-bit PWM
mode. The ARSEL bit in register PCA0PWM controls which register is
accessed.
Note: A write to this register will set the module’s ECOMn bit to a 1.
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33. C2 Interface
C8051F39x/37x devices include an on-chip Silicon Labs 2-Wire (C2) debug interface to allow Flash programming and in-system debugging with the production part installed in the end application. The C2 interface uses a clock signal (C2CK) and a bi-directional C2 data signal (C2D) to transfer information between
the device and a host system. See the C2 Interface Specification for details on the C2 protocol.
33.1. C2 Interface Registers
The following describes the C2 registers necessary to perform Flash programming through the C2 interface. All C2 registers are accessed through the C2 interface as described in the C2 Interface Specification.
C2 Register Definition 33.1. C2ADD: C2 Address
Bit
7
6
5
4
3
Name
C2ADD[7:0]
Type
R/W
Reset
Bit
0
0
0
0
Name
0
2
1
0
0
0
0
Function
7:0 C2ADD[7:0] C2 Address.
The C2ADD register is accessed via the C2 interface to select the target Data register
for C2 Data Read and Data Write commands.
Address
Description
0x00
0x01
0x02
Selects the Device ID register for Data Read instructions
Selects the Revision ID register for Data Read instructions
Selects the C2 Flash Programming Control register for Data
Read/Write instructions
Selects the C2 Flash Programming Data register for Data Read/
Write instructions
0xB4
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C2 Register Definition 33.2. DEVICEID: C2 Device ID
Bit
7
6
5
4
3
Name
DEVICEID[7:0]
Type
R/W
Reset
0
0
1
0
1
2
1
0
0
1
1
C2 Address: 0x00
Bit
Name
Function
7:0
DEVICEID[7:0]
Device ID.
This read-only register returns the 8-bit device ID: 0x2B (C8051F39x/37x).
C2 Register Definition 33.3. REVID: C2 Revision ID
Bit
7
6
5
4
3
Name
REVID[7:0]
Type
R/W
Reset
Varies
Varies
Varies
Varies
Varies
2
1
0
Varies
Varies
Varies
C2 Address: 0x01
Bit
7:0
Name
Function
REVID[7:0] Revision ID.
This read-only register returns the 8-bit revision ID. For example: 0x00 = Revision A.
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C2 Register Definition 33.4. FPCTL: C2 Flash Programming Control
Bit
7
6
5
4
3
Name
FPCTL[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
C2 Address: 0x02
Bit
Name
7:0
Function
FPCTL[7:0] Flash Programming Control Register.
This register is used to enable Flash programming via the C2 interface. To enable
C2 Flash programming, the following codes must be written in order: 0x02, 0x01.
Note that once C2 Flash programming is enabled, a system reset must be issued to
resume normal operation.
C2 Register Definition 33.5. FPDAT: C2 Flash Programming Data
Bit
7
6
5
4
3
Name
FPDAT[7:0]
Type
R/W
Reset
0
0
0
0
0
2
1
0
0
0
0
C2 Address: 0xB4
Bit
7:0
Name
Function
FPDAT[7:0] C2 Flash Programming Data Register.
This register is used to pass Flash commands, addresses, and data during C2 Flash
accesses. Valid commands are listed below.
Code
Command
0x06
0x07
0x08
0x03
Flash Block Read
Flash Block Write
Flash Page Erase
Device Erase
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33.2. C2 Pin Sharing
The C2 protocol allows the C2 pins to be shared with user functions so that in-system debugging and
Flash programming may be performed. This is possible because C2 communication is typically performed
when the device is in the halt state, where all on-chip peripherals and user software are stalled. In this
halted state, the C2 interface can safely ‘borrow’ the C2CK (RST) and C2D pins. In most applications,
external resistors are required to isolate C2 interface traffic from the user application. A typical isolation
configuration is shown in Figure 33.1.
C8051Fxxx
/Reset (a)
C2CK
Input (b)
C2D
Output (c)
C2 Interface Master
Figure 33.1. Typical C2 Pin Sharing
The configuration in Figure 33.1 assumes the following:
1. The user input (b) cannot change state while the target device is halted.
2. The RST pin on the target device is used as an input only.
Additional resistors may be necessary depending on the specific application.
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DOCUMENT CHANGE LIST
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Revision 0.1 to Revision 0.7
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
Added Section 8.1 “Temperature in Two’s
Complement”
Changed clock cycles for “CJNE A, direct, re” to “4/
6” in Section 15. “CIP-15 Microcontroller”
Changed bit 5 of CRC0CNT to reserved in Section
23. “Cyclic Redundancy Check Unit” (CRC0)
Changed SFRPGCN reset value to “0x01” in Section
19. “Special Function Registers”
Added Section 19.2 “Interrupts and Automatic SFR
Paging”
Added Section 19.3 “SFR Page Stack Example”
Corrected incorrect references to C8501F34x in
Section 2. “Ordering Information”
Removed “The C8051F37x does not include the 4x
clock multiplier” bullet point from Section 3.1
Removed “External Oscillator C and RC Modes”
bullet point from Section 3.1
Updated the block diagram on the front page to
show EEPROM and 500 ksps ADC
Removed references to the REG0MD bit and low
power mode in Section 13.1
Removed REG0MD bit in the REG0CN SFR
definition. This bit (bit 2) is now reserved.
Section 22. “EEPROM” completely rewritten
Moved the “from IPH, EIPH1 or EIPH2” text from the
LSB column to the MSB column in Table 20.1
Moved the “from IP, EIP1 or EIP2” text from the MSB
column to the LSB column in Table 20.1
Changed Figure 27.4 to show all five footnotes
Changed Figure 27.5 to show correct SF signals and
all five footnotes
Added 5 V tolerance and lock byte address bullet
points to Section 3.1. “Hardware Incompatibilities”




Added maximum EESCL clock frequency to
Table 7.6 on page 36.
Updated typical INL and DNL in Table 7.10 on
page 38.
Updated resolution in Table 7.12 on page 39.
Updated typical and maximum INL and DNL in
Table 7.15 on page 41.
Updated typical full scale error in Table 7.15 on
page 41.
Updated references to Table 28.3 in the SMB0CN
and SMB1CN SFR definitions.
Revision 0.7 to Revision 0.71
Updated part numbers in Table 2.1 on page 20.
 Updated replacement part numbers in Table 3.1 on
page 21 to match Flash sizes.
 Corrected units for normal and active mode IDD
(VDD = 3.0 V, F = 80 kHz) in Table 7.2 on page 33.

Updated maximum normal mode IDD in Table 7.2 on
page 33.
 Added EESDA and EESCL DC electrical
characteristics to Table 7.3 on page 34.
 Added EEPROM supply current to Table 7.6 on
page 36.
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CONTACT INFORMATION
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