BOOKHAM LM3S818

P REL I MIN AR Y
LM3S818 Microcontroller
D A TA S H E E T
DS-LM3S81 8-02
Co pyrigh t © 200 7 Lumin ary Micro, In c.
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2
May 4, 2007
Preliminary
LM3S818 Data Sheet
Table of Contents
Legal Disclaimers and Trademark Information.............................................................................. 2
Revision History ............................................................................................................................. 17
About This Document..................................................................................................................... 18
Audience........................................................................................................................................................... 18
About This Manual............................................................................................................................................ 18
Related Documents .......................................................................................................................................... 18
Documentation Conventions............................................................................................................................. 18
1.
Architectural Overview ....................................................................................................... 21
1.1
1.2
1.3
1.4
1.4.1
1.4.2
1.4.3
1.4.4
1.4.5
1.4.6
1.4.7
1.4.8
1.5
Product Features ................................................................................................................................. 21
Target Applications .............................................................................................................................. 25
High-Level Block Diagram ................................................................................................................... 26
Functional Overview ............................................................................................................................ 27
ARM Cortex™-M3 ............................................................................................................................... 27
Motor Control Peripherals .................................................................................................................... 27
Analog Peripherals .............................................................................................................................. 28
Serial Communications Peripherals..................................................................................................... 29
System Peripherals.............................................................................................................................. 29
Memory Peripherals............................................................................................................................. 30
Additional Features .............................................................................................................................. 30
Hardware Details ................................................................................................................................. 31
System Block Diagram ........................................................................................................................ 32
2.
ARM Cortex-M3 Processor Core........................................................................................ 33
2.1
2.2
2.2.1
2.2.2
2.2.3
2.2.4
2.2.5
2.2.6
Block Diagram ..................................................................................................................................... 34
Functional Description ......................................................................................................................... 34
Serial Wire and JTAG Debug .............................................................................................................. 34
Embedded Trace Macrocell (ETM) ...................................................................................................... 35
Trace Port Interface Unit (TPIU) .......................................................................................................... 35
ROM Table .......................................................................................................................................... 35
Memory Protection Unit (MPU) ............................................................................................................ 35
Nested Vectored Interrupt Controller (NVIC) ....................................................................................... 35
3.
Memory Map ........................................................................................................................ 41
4.
Interrupts ............................................................................................................................. 43
5.
JTAG Interface .................................................................................................................... 46
5.1
5.2
5.2.1
5.2.2
5.2.3
5.2.4
5.3
5.4
5.4.1
5.4.2
Block Diagram ..................................................................................................................................... 47
Functional Description ......................................................................................................................... 47
JTAG Interface Pins............................................................................................................................. 48
JTAG TAP Controller ........................................................................................................................... 49
Shift Registers ..................................................................................................................................... 50
Operational Considerations ................................................................................................................. 50
Initialization and Configuration............................................................................................................. 51
Register Descriptions........................................................................................................................... 52
Instruction Register (IR) ....................................................................................................................... 52
Data Registers ..................................................................................................................................... 54
6.
System Control.................................................................................................................... 56
6.1
6.1.1
Functional Description ......................................................................................................................... 56
Device Identification............................................................................................................................. 56
May 4, 2007
3
Preliminary
Table of Contents
6.1.2
6.1.3
6.1.4
6.1.5
6.2
6.3
6.4
Reset Control ....................................................................................................................................... 56
Power Control ...................................................................................................................................... 59
Clock Control ....................................................................................................................................... 59
System Control .................................................................................................................................... 61
Initialization and Configuration............................................................................................................. 62
Register Map ....................................................................................................................................... 62
Register Descriptions........................................................................................................................... 63
7.
Internal Memory .................................................................................................................. 98
7.1
7.2
7.2.1
7.2.2
7.3
7.3.1
7.3.2
7.4
7.5
Block Diagram ..................................................................................................................................... 98
Functional Description ......................................................................................................................... 98
SRAM Memory .................................................................................................................................... 98
Flash Memory ...................................................................................................................................... 99
Initialization and Configuration........................................................................................................... 101
Changing Flash Protection Bits ......................................................................................................... 101
Flash Programming ........................................................................................................................... 102
Register Map ..................................................................................................................................... 102
Register Descriptions......................................................................................................................... 103
8.
General-Purpose Input/Outputs (GPIOs) ........................................................................ 115
8.1
8.2
8.2.1
8.2.2
8.2.3
8.2.4
8.2.5
8.2.6
8.3
8.4
8.5
Block Diagram ................................................................................................................................... 116
Functional Description ....................................................................................................................... 116
Data Register Operation .................................................................................................................... 117
Data Direction .................................................................................................................................... 118
Interrupt Operation............................................................................................................................. 118
Mode Control ..................................................................................................................................... 119
Pad Configuration .............................................................................................................................. 119
Identification....................................................................................................................................... 119
Initialization and Configuration........................................................................................................... 119
Register Map ..................................................................................................................................... 121
Register Descriptions......................................................................................................................... 122
9.
General-Purpose Timers .................................................................................................. 153
9.1
9.2
9.2.1
9.2.2
9.2.3
9.3
9.3.1
9.3.2
9.3.3
9.3.4
9.3.5
9.3.6
9.4
9.5
Block Diagram ................................................................................................................................... 154
Functional Description ....................................................................................................................... 154
GPTM Reset Conditions .................................................................................................................... 154
32-Bit Timer Operating Modes........................................................................................................... 154
16-Bit Timer Operating Modes........................................................................................................... 156
Initialization and Configuration........................................................................................................... 160
32-Bit One-Shot/Periodic Timer Mode ............................................................................................... 160
32-Bit Real-Time Clock (RTC) Mode ................................................................................................. 161
16-Bit One-Shot/Periodic Timer Mode ............................................................................................... 161
16-Bit Input Edge Count Mode .......................................................................................................... 161
16-Bit Input Edge Timing Mode ......................................................................................................... 162
16-Bit PWM Mode.............................................................................................................................. 162
Register Map ..................................................................................................................................... 163
Register Descriptions......................................................................................................................... 164
10.
Watchdog Timer ................................................................................................................ 185
10.1
10.2
10.3
Block Diagram ................................................................................................................................... 185
Functional Description ....................................................................................................................... 186
Initialization and Configuration........................................................................................................... 186
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May 4, 2007
Preliminary
LM3S818 Data Sheet
10.4
10.5
Register Map ..................................................................................................................................... 186
Register Descriptions......................................................................................................................... 187
11.
Analog-to-Digital Converter (ADC) .................................................................................. 208
11.1
11.2
11.2.1
11.2.2
11.2.3
11.2.4
11.2.5
11.2.6
11.3
11.3.1
11.3.2
11.4
11.5
Block Diagram ................................................................................................................................... 209
Functional Description ....................................................................................................................... 209
Sample Sequencers .......................................................................................................................... 209
Module Control .................................................................................................................................. 210
Hardware Sample Averaging Circuit.................................................................................................. 211
Analog-to-Digital Converter ............................................................................................................... 211
Test Modes ........................................................................................................................................ 211
Internal Temperature Sensor ............................................................................................................. 211
Initialization and Configuration........................................................................................................... 211
Module Initialization ........................................................................................................................... 212
Sample Sequencer Configuration ...................................................................................................... 212
Register Map ..................................................................................................................................... 212
Register Descriptions......................................................................................................................... 213
12.
Universal Asynchronous Receivers/Transmitters (UARTs).......................................... 238
12.1
12.2
12.2.1
12.2.2
12.2.3
12.2.4
12.2.5
12.2.6
12.3
12.4
12.5
Block Diagram ................................................................................................................................... 239
Functional Description ....................................................................................................................... 239
Transmit/Receive Logic ..................................................................................................................... 239
Baud-Rate Generation ....................................................................................................................... 240
Data Transmission ............................................................................................................................. 241
FIFO Operation .................................................................................................................................. 241
Interrupts............................................................................................................................................ 241
Loopback Operation .......................................................................................................................... 242
Initialization and Configuration........................................................................................................... 242
Register Map ..................................................................................................................................... 243
Register Descriptions......................................................................................................................... 244
13.
Synchronous Serial Interface (SSI) ................................................................................. 274
13.1
13.2
13.2.1
13.2.2
13.2.3
13.2.4
13.3
13.4
13.5
Block Diagram ................................................................................................................................... 274
Functional Description ....................................................................................................................... 275
Bit Rate Generation ........................................................................................................................... 275
FIFO Operation .................................................................................................................................. 275
Interrupts............................................................................................................................................ 275
Frame Formats .................................................................................................................................. 276
Initialization and Configuration........................................................................................................... 283
Register Map ..................................................................................................................................... 284
Register Descriptions......................................................................................................................... 285
14.
Analog Comparator........................................................................................................... 309
14.1
14.2
14.2.1
14.3
14.4
14.5
Block Diagram ................................................................................................................................... 309
Functional Description ....................................................................................................................... 309
Internal Reference Programming....................................................................................................... 310
Initialization and Configuration........................................................................................................... 311
Register Map ..................................................................................................................................... 312
Register Descriptions......................................................................................................................... 312
15.
Pulse Width Modulator (PWM) ......................................................................................... 320
15.1
15.2
Block Diagram ................................................................................................................................... 320
Functional Description ....................................................................................................................... 320
May 4, 2007
5
Preliminary
Table of Contents
15.2.1
15.2.2
15.2.3
15.2.4
15.2.5
15.2.6
15.2.7
15.2.8
15.3
15.4
15.5
PWM Timer ........................................................................................................................................ 320
PWM Comparators ............................................................................................................................ 320
PWM Signal Generator ...................................................................................................................... 321
Dead-Band Generator ....................................................................................................................... 322
Interrupt Selector ............................................................................................................................... 322
Synchronization Methods .................................................................................................................. 322
Fault Conditions ................................................................................................................................. 323
Output Control Block.......................................................................................................................... 323
Initialization and Configuration........................................................................................................... 323
Register Map ..................................................................................................................................... 324
Register Descriptions......................................................................................................................... 325
16.
Quadrature Encoder Interface (QEI)................................................................................ 349
16.1
16.2
16.3
16.4
16.5
Block Diagram ................................................................................................................................... 349
Functional Description ....................................................................................................................... 349
Initialization and Configuration........................................................................................................... 352
Register Map ..................................................................................................................................... 352
Register Descriptions......................................................................................................................... 352
17.
Pin Diagram ....................................................................................................................... 365
18.
Signal Tables ..................................................................................................................... 366
19.
Operating Characteristics ................................................................................................ 376
20.
Electrical Characteristics ................................................................................................. 377
20.1
20.1.1
20.1.2
20.1.3
20.1.4
20.1.5
20.2
20.2.1
20.2.2
20.2.3
20.2.4
20.2.5
20.2.6
20.2.7
20.2.8
DC Characteristics ............................................................................................................................. 377
Maximum Ratings .............................................................................................................................. 377
Recommended DC Operating Conditions ......................................................................................... 377
On-Chip Low Drop-Out (LDO) Regulator Characteristics .................................................................. 378
Power Specifications ......................................................................................................................... 379
Flash Memory Characteristics ........................................................................................................... 380
AC Characteristics ............................................................................................................................. 380
Load Conditions ................................................................................................................................. 380
Clocks ................................................................................................................................................ 380
Analog-to-Digital Converter ............................................................................................................... 381
Analog Comparator............................................................................................................................ 382
Synchronous Serial Interface (SSI) ................................................................................................... 382
JTAG and Boundary Scan ................................................................................................................. 384
General-Purpose I/O.......................................................................................................................... 386
Reset ................................................................................................................................................. 386
21.
Package Information......................................................................................................... 389
Appendix A. Serial Flash Loader ............................................................................................... 390
22.1
22.1.1
22.1.2
22.2
22.2.1
22.2.2
22.2.3
22.3
22.3.1
22.3.2
22.3.3
Interfaces ........................................................................................................................................... 390
UART ................................................................................................................................................. 390
SSI ..................................................................................................................................................... 390
Packet Handling................................................................................................................................. 390
Packet Format ................................................................................................................................... 391
Sending Packets ................................................................................................................................ 391
Receiving Packets ............................................................................................................................. 391
Commands ........................................................................................................................................ 391
COMMAND_PING (0x20) .................................................................................................................. 392
COMMAND_GET_STATUS (0x23) ................................................................................................... 392
COMMAND_DOWNLOAD (0x21)...................................................................................................... 392
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May 4, 2007
Preliminary
LM3S818 Data Sheet
22.3.4 COMMAND_SEND_DATA (0x24) ..................................................................................................... 392
22.3.5 COMMAND_RUN (0x22) ................................................................................................................... 393
22.3.6 COMMAND_RESET (0x25)............................................................................................................... 393
Ordering and Contact Information .............................................................................................. 395
Ordering Information....................................................................................................................................... 395
Development Kit ............................................................................................................................................. 395
Company Information ..................................................................................................................................... 395
Support Information ........................................................................................................................................ 396
May 4, 2007
7
Preliminary
List of Figures
List of Figures
Figure 1-1.
Figure 1-2.
Figure 2-1.
Figure 2-2.
Figure 5-1.
Figure 5-2.
Figure 5-3.
Figure 5-4.
Figure 5-5.
Figure 6-1.
Figure 6-2.
Figure 7-1.
Figure 8-1.
Figure 8-2.
Figure 8-3.
Figure 8-4.
Figure 9-1.
Figure 9-2.
Figure 9-3.
Figure 9-4.
Figure 10-1.
Figure 11-1.
Figure 11-2.
Figure 12-1.
Figure 12-2.
Figure 13-1.
Figure 13-2.
Figure 13-3.
Figure 13-4.
Figure 13-5.
Figure 13-6.
Figure 13-7.
Figure 13-8.
Figure 13-9.
Figure 13-10.
Figure 13-11.
Figure 13-12.
Figure 14-1.
Figure 14-2.
Figure 14-3.
Figure 15-1.
Figure 15-2.
Figure 15-3.
Figure 15-4.
Figure 15-5.
Figure 16-1.
Stellaris® High-Level Block Diagram ........................................................................................ 26
LM3S818 Controller System-Level Block Diagram ................................................................... 32
CPU Block Diagram .................................................................................................................. 34
TPIU Block Diagram .................................................................................................................. 35
JTAG Module Block Diagram .................................................................................................... 47
Test Access Port State Machine ............................................................................................... 50
IDCODE Register Format.......................................................................................................... 54
BYPASS Register Format ......................................................................................................... 54
Boundary Scan Register Format ............................................................................................... 55
External Circuitry to Extend Reset............................................................................................. 57
Main Clock Tree ........................................................................................................................ 60
Flash Block Diagram ................................................................................................................. 98
GPIO Module Block Diagram .................................................................................................. 116
GPIO Port Block Diagram........................................................................................................ 117
GPIODATA Write Example...................................................................................................... 118
GPIODATA Read Example ..................................................................................................... 118
GPTM Module Block Diagram ................................................................................................. 154
16-Bit Input Edge Count Mode Example ................................................................................. 158
16-Bit Input Edge Time Mode Example................................................................................... 159
16-Bit PWM Mode Example .................................................................................................... 160
WDT Module Block Diagram ................................................................................................... 185
ADC Module Block Diagram.................................................................................................... 209
Internal Temperature Sensor Characteristic............................................................................ 211
UART Module Block Diagram.................................................................................................. 239
UART Character Frame........................................................................................................... 240
SSI Module Block Diagram...................................................................................................... 274
TI Synchronous Serial Frame Format (Single Transfer).......................................................... 276
TI Synchronous Serial Frame Format (Continuous Transfer) ................................................. 277
Freescale SPI Format (Single Transfer) with SPO=0 and SPH=0 .......................................... 278
Freescale SPI Format (Continuous Transfer) with SPO=0 and SPH=0 .................................. 278
Freescale SPI Frame Format with SPO=0 and SPH=1........................................................... 279
Freescale SPI Frame Format (Single Transfer) with SPO=1 and SPH=0............................... 279
Freescale SPI Frame Format (Continuous Transfer) with SPO=1 and SPH=0....................... 280
Freescale SPI Frame Format with SPO=1 and SPH=1........................................................... 280
MICROWIRE Frame Format (Single Frame)........................................................................... 281
MICROWIRE Frame Format (Continuous Transfer) ............................................................... 282
MICROWIRE Frame Format, SSIFss Input Setup and Hold Requirements............................ 283
Analog Comparator Module Block Diagram ............................................................................ 309
Structure of Comparator Unit................................................................................................... 310
Comparator Internal Reference Structure ............................................................................... 311
PWM Module Block Diagram................................................................................................... 320
PWM Count-Down Mode......................................................................................................... 321
PWM Count-Up/Down Mode ................................................................................................... 321
PWM Generation Example In Count-Up/Down Mode ............................................................. 322
PWM Dead-Band Generator ................................................................................................... 322
QEI Block Diagram .................................................................................................................. 349
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May 4, 2007
Preliminary
LM3S818 Data Sheet
Figure 16-2.
Figure 17-1.
Figure 20-1.
Figure 20-2.
Figure 20-3.
Figure 20-4.
Figure 20-5.
Figure 20-6.
Figure 20-7.
Figure 20-8.
Figure 20-9.
Figure 20-10.
Figure 20-11.
Figure 20-12.
Figure 20-13.
Figure 21-1.
Quadrature Encoder and Velocity Predivider Operation ......................................................... 350
Pin Connection Diagram ......................................................................................................... 365
Load Conditions....................................................................................................................... 380
SSI Timing for TI Frame Format (FRF=01), Single Transfer Timing Measurement ................ 383
SSI Timing for MICROWIRE Frame Format (FRF=10), Single Transfer................................. 383
SSI Timing for SPI Frame Format (FRF=00), with SPH=1...................................................... 383
JTAG Test Clock Input Timing................................................................................................. 385
JTAG Test Access Port (TAP) Timing ..................................................................................... 385
JTAG TRST Timing ................................................................................................................. 385
External Reset Timing (RST)................................................................................................... 387
Power-On Reset Timing .......................................................................................................... 387
Brown-Out Reset Timing ......................................................................................................... 387
Software Reset Timing ............................................................................................................ 387
Watchdog Reset Timing .......................................................................................................... 388
LDO Reset Timing ................................................................................................................... 388
48-Pin LQFP Package............................................................................................................. 389
May 4, 2007
9
Preliminary
List of Tables
List of Tables
Table 0-1.
Table 3-1.
Table 4-1.
Table 4-2.
Table 5-1.
Table 5-2.
Table 6-1.
Table 6-2.
Table 6-3.
Table 6-4.
Table 7-1.
Table 7-2.
Table 8-1.
Table 8-2.
Table 8-3.
Table 9-1.
Table 9-2.
Table 10-1.
Table 11-1.
Table 11-2.
Table 12-1.
Table 13-1.
Table 14-1.
Table 14-2.
Table 14-3.
Table 15-1.
Table 15-2.
Table 16-1.
Table 18-1.
Table 18-2.
Table 18-3.
Table 18-4.
Table 19-1.
Table 19-2.
Table 20-1.
Table 20-2.
Table 20-3.
Table 20-4.
Table 20-5.
Table 20-6.
Table 20-7.
Table 20-8.
Table 20-9.
Table 20-10.
Table 20-11.
Table 20-12.
Table 20-13.
Table 20-14.
Documentation Conventions ..................................................................................................... 18
Memory Map.............................................................................................................................. 41
Exception Types ........................................................................................................................ 43
Interrupts ................................................................................................................................... 44
JTAG Port Pins Reset State ...................................................................................................... 48
JTAG Instruction Register Commands ...................................................................................... 52
System Control Register Map.................................................................................................... 62
VADJ to VOUT .......................................................................................................................... 75
PLL Mode Control...................................................................................................................... 87
Default Crystal Field Values and PLL Programming ................................................................. 88
Flash Protection Policy Combinations ..................................................................................... 100
Flash Register Map ................................................................................................................. 103
GPIO Pad Configuration Examples ........................................................................................ 120
GPIO Interrupt Configuration Example ................................................................................... 120
GPIO Register Map ................................................................................................................. 121
16-Bit Timer with Prescaler Configurations ............................................................................. 157
GPTM Register Map................................................................................................................ 163
WDT Register Map .................................................................................................................. 186
Samples and FIFO Depth of Sequencers................................................................................ 209
ADC Register Map................................................................................................................... 212
UART Register Map ................................................................................................................ 243
SSI Register Map .................................................................................................................... 284
Comparator 0 Operating Modes .............................................................................................. 310
Internal Reference Voltage and ACREFCTL Field Values ...................................................... 311
Analog Comparator Register Map ........................................................................................... 312
PWM Register Map ................................................................................................................. 324
PWM Generator Action Encodings.......................................................................................... 344
QEI Register Map .................................................................................................................... 352
Signals by Pin Number ............................................................................................................ 366
Signals by Signal Name .......................................................................................................... 369
Signals by Function, Except for GPIO ..................................................................................... 372
GPIO Pins and Alternate Functions......................................................................................... 374
Temperature Characteristics ................................................................................................... 376
Thermal Characteristics........................................................................................................... 376
Maximum Ratings.................................................................................................................... 377
Recommended DC Operating Conditions ............................................................................... 377
LDO Regulator Characteristics................................................................................................ 378
Power Specifications ............................................................................................................... 379
Flash Memory Characteristics ................................................................................................. 380
Phase Locked Loop (PLL) Characteristics .............................................................................. 380
Clock Characteristics............................................................................................................... 381
ADC Characteristics ................................................................................................................ 381
Analog Comparator Characteristics......................................................................................... 382
Analog Comparator Voltage Reference Characteristics.......................................................... 382
SSI Characteristics .................................................................................................................. 382
JTAG Characteristics............................................................................................................... 384
GPIO Characteristics............................................................................................................... 386
Reset Characteristics .............................................................................................................. 386
10
May 4, 2007
Preliminary
LM3S818 Data Sheet
List of Registers
ARM Cortex-M3 Processor Core ................................................................................................... 33
Register 1:
Register 2:
Register 3:
SysTick Control and Status Register......................................................................................... 38
SysTick Reload Value Register ................................................................................................. 39
SysTick Current Value Register ................................................................................................ 40
System Control ............................................................................................................................... 56
Register 1:
Register 2:
Register 3:
Register 4:
Register 5:
Register 6:
Register 7:
Register 8:
Register 9:
Register 10:
Register 11:
Register 12:
Register 13:
Register 14:
Register 15:
Register 16:
Register 17:
Register 18:
Register 19:
Register 20:
Register 21:
Register 22:
Register 23:
Register 24:
Register 25:
Register 26:
Register 27:
Register 28:
Register 29:
Register 30:
Device Identification 0 (DID0), offset 0x000 .............................................................................. 64
Device Identification 1 (DID1), offset 0x004 .............................................................................. 65
Device Capabilities 0 (DC0), offset 0x008................................................................................. 67
Device Capabilities 1 (DC1), offset 0x010................................................................................. 68
Device Capabilities 2 (DC2), offset 0x014................................................................................. 70
Device Capabilities 3 (DC3), offset 0x018................................................................................. 71
Device Capabilities 4 (DC4), offset 0x01C ................................................................................ 73
Power-On and Brown-Out Reset Control (PBORCTL), offset 0x030 ........................................ 74
LDO Power Control (LDOPCTL), offset 0x034.......................................................................... 75
Software Reset Control 0 (SRCR0), offset 0x040 ..................................................................... 76
Software Reset Control 1 (SRCR1), offset 0x044 ..................................................................... 77
Software Reset Control 2 (SRCR2), offset 0x048 ..................................................................... 78
Raw Interrupt Status (RIS), offset 0x050................................................................................... 79
Interrupt Mask Control (IMC), offset 0x054 ............................................................................... 80
Masked Interrupt Status and Clear (MISC), offset 0x058.......................................................... 82
Reset Cause (RESC), offset 0x05C .......................................................................................... 83
Run-Mode Clock Configuration (RCC), offset 0x060................................................................. 84
XTAL to PLL Translation (PLLCFG), offset 0x064 .................................................................... 89
Run-Mode Clock Gating Control 0 (RCGC0), offset 0x100 ....................................................... 90
Sleep-Mode Clock Gating Control 0 (SCGC0), offset 0x110..................................................... 90
Deep-Sleep-Mode Clock Gating Control 0 (DCGC0), offset 0x120........................................... 90
Run-Mode Clock Gating Control 1 (RCGC1), offset 0x104 ....................................................... 92
Sleep-Mode Clock Gating Control 1 (SCGC1), offset 0x114..................................................... 92
Deep-Sleep-Mode Clock Gating Control 1 (DCGC1), offset 0x124........................................... 92
Run-Mode Clock Gating Control 2 (RCGC2), offset 0x108 ....................................................... 94
Sleep-Mode Clock Gating Control 2 (SCGC2), offset 0x118..................................................... 94
Deep-Sleep-Mode Clock Gating Control 2 (DCGC2), offset 0x128........................................... 94
Deep-Sleep Clock Configuration (DSLPCLKCFG), offset 0x144 .............................................. 95
Clock Verification Clear (CLKVCLR), offset 0x150.................................................................... 96
Allow Unregulated LDO to Reset the Part (LDOARST), offset 0x160 ....................................... 97
Internal Memory .............................................................................................................................. 98
Register 1:
Register 2:
Register 3:
Register 4:
Register 5:
Register 6:
Register 7:
Register 8:
Register 9:
Flash Memory Protection Read Enable (FMPRE), offset 0x130 ............................................. 104
Flash Memory Protection Program Enable (FMPPE), offset 0x134 ........................................ 105
USec Reload (USECRL), offset 0x140.................................................................................... 106
Flash Memory Address (FMA), offset 0x000 ........................................................................... 107
Flash Memory Data (FMD), offset 0x004 ................................................................................ 109
Flash Memory Control (FMC), offset 0x008 ............................................................................ 110
Flash Controller Raw Interrupt Status (FCRIS), offset 0x00C ................................................. 112
Flash Controller Interrupt Mask (FCIM), offset 0x010 ............................................................. 113
Flash Controller Masked Interrupt Status and Clear (FCMISC), offset 0x014......................... 114
May 4, 2007
11
Preliminary
List of Registers
General-Purpose Input/Outputs (GPIOs) .................................................................................... 115
Register 1:
Register 2:
Register 3:
Register 4:
Register 5:
Register 6:
Register 7:
Register 8:
Register 9:
Register 10:
Register 11:
Register 12:
Register 13:
Register 14:
Register 15:
Register 16:
Register 17:
Register 18:
Register 19:
Register 20:
Register 21:
Register 22:
Register 23:
Register 24:
Register 25:
Register 26:
Register 27:
Register 28:
Register 29:
Register 30:
GPIO Data (GPIODATA), offset 0x000 ................................................................................... 123
GPIO Direction (GPIODIR), offset 0x400 ................................................................................ 124
GPIO Interrupt Sense (GPIOIS), offset 0x404......................................................................... 125
GPIO Interrupt Both Edges (GPIOIBE), offset 0x408.............................................................. 126
GPIO Interrupt Event (GPIOIEV), offset 0x40C....................................................................... 127
GPIO Interrupt Mask (GPIOIM), offset 0x410.......................................................................... 128
GPIO Raw Interrupt Status (GPIORIS), offset 0x414.............................................................. 129
GPIO Masked Interrupt Status (GPIOMIS), offset 0x418 ........................................................ 130
GPIO Interrupt Clear (GPIOICR), offset 0x41C....................................................................... 131
GPIO Alternate Function Select (GPIOAFSEL), offset 0x420 ................................................. 132
GPIO 2-mA Drive Select (GPIODR2R), offset 0x500.............................................................. 133
GPIO 4-mA Drive Select (GPIODR4R), offset 0x504.............................................................. 134
GPIO 8-mA Drive Select (GPIODR8R), offset 0x508.............................................................. 135
GPIO Open Drain Select (GPIOODR), offset 0x50C............................................................... 136
GPIO Pull-Up Select (GPIOPUR), offset 0x510 ...................................................................... 137
GPIO Pull-Down Select (GPIOPDR), offset 0x514.................................................................. 138
GPIO Slew Rate Control Select (GPIOSLR), offset 0x518...................................................... 139
GPIO Digital Input Enable (GPIODEN), offset 0x51C ............................................................. 140
GPIO Peripheral Identification 4 (GPIOPeriphID4), offset 0xFD0 ........................................... 141
GPIO Peripheral Identification 5 (GPIOPeriphID5), offset 0xFD4 ........................................... 142
GPIO Peripheral Identification 6 (GPIOPeriphID6), offset 0xFD8 ........................................... 143
GPIO Peripheral Identification 7 (GPIOPeriphID7), offset 0xFDC........................................... 144
GPIO Peripheral Identification 0 (GPIOPeriphID0), offset 0xFE0 ........................................... 145
GPIO Peripheral Identification 1(GPIOPeriphID1), offset 0xFE4 ............................................ 146
GPIO Peripheral Identification 2 (GPIOPeriphID2), offset 0xFE8 ........................................... 147
GPIO Peripheral Identification 3 (GPIOPeriphID3), offset 0xFEC........................................... 148
GPIO PrimeCell Identification 0 (GPIOPCellID0), offset 0xFF0 .............................................. 149
GPIO PrimeCell Identification 1 (GPIOPCellID1), offset 0xFF4 .............................................. 150
GPIO PrimeCell Identification 2 (GPIOPCellID2), offset 0xFF8 .............................................. 151
GPIO PrimeCell Identification 3 (GPIOPCellID3), offset 0xFFC.............................................. 152
General-Purpose Timers .............................................................................................................. 153
Register 1:
Register 2:
Register 3:
Register 4:
Register 5:
Register 6:
Register 7:
Register 8:
Register 9:
Register 10:
Register 11:
Register 12:
Register 13:
Register 14:
Register 15:
GPTM Configuration (GPTMCFG), offset 0x000..................................................................... 165
GPTM TimerA Mode (GPTMTAMR), offset 0x004 .................................................................. 166
GPTM TimerB Mode (GPTMTBMR), offset 0x008 .................................................................. 167
GPTM Control (GPTMCTL), offset 0x00C............................................................................... 168
GPTM Interrupt Mask (GPTMIMR), offset 0x018 .................................................................... 170
GPTM Raw Interrupt Status (GPTMRIS), offset 0x01C .......................................................... 172
GPTM Masked Interrupt Status (GPTMMIS), offset 0x020 ..................................................... 173
GPTM Interrupt Clear (GPTMICR), offset 0x024..................................................................... 174
GPTM TimerA Interval Load (GPTMTAILR), offset 0x028 ...................................................... 175
GPTM TimerB Interval Load (GPTMTBILR), offset 0x02C...................................................... 176
GPTM TimerA Match (GPTMTAMATCHR), offset 0x030 ....................................................... 177
GPTM TimerB Match (GPTMTBMATCHR), offset 0x034 ....................................................... 178
GPTM TimerA Prescale (GPTMTAPR), offset 0x038.............................................................. 179
GPTM TimerB Prescale (GPTMTBPR), offset 0x03C ............................................................. 180
GPTM TimerA Prescale Match (GPTMTAPMR), offset 0x040................................................ 181
12
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 16:
Register 17:
Register 18:
GPTM TimerB Prescale Match (GPTMTBPMR), offset 0x044................................................ 182
GPTM TimerA (GPTMTAR), offset 0x048 ............................................................................... 183
GPTM TimerB (GPTMTBR), offset 0x04C .............................................................................. 184
Watchdog Timer............................................................................................................................ 185
Register 1:
Register 2:
Register 3:
Register 4:
Register 5:
Register 6:
Register 7:
Register 8:
Register 9:
Register 10:
Register 11:
Register 12:
Register 13:
Register 14:
Register 15:
Register 16:
Register 17:
Register 18:
Register 19:
Register 20:
Watchdog Load (WDTLOAD), offset 0x000 ............................................................................ 188
Watchdog Value (WDTVALUE), offset 0x004 ......................................................................... 189
Watchdog Control (WDTCTL), offset 0x008............................................................................ 190
Watchdog Interrupt Clear (WDTICR), offset 0x00C ................................................................ 191
Watchdog Raw Interrupt Status (WDTRIS), offset 0x010 ....................................................... 192
Watchdog Masked Interrupt Status (WDTMIS), offset 0x014.................................................. 193
Watchdog Lock (WDTLOCK), offset 0xC00 ............................................................................ 194
Watchdog Test (WDTTEST), offset 0x418 .............................................................................. 195
Watchdog Peripheral Identification 4 (WDTPeriphID4), offset 0xFD0..................................... 196
Watchdog Peripheral Identification 5 (WDTPeriphID5), offset 0xFD4..................................... 197
Watchdog Peripheral Identification 6 (WDTPeriphID6), offset 0xFD8..................................... 198
Watchdog Peripheral Identification 7 (WDTPeriphID7), offset 0xFDC .................................... 199
Watchdog Peripheral Identification 0 (WDTPeriphID0), offset 0xFE0 ..................................... 200
Watchdog Peripheral Identification 1 (WDTPeriphID1), offset 0xFE4 ..................................... 201
Watchdog Peripheral Identification 2 (WDTPeriphID2), offset 0xFE8 ..................................... 202
Watchdog Peripheral Identification 3 (WDTPeriphID3), offset 0xFEC .................................... 203
Watchdog PrimeCell Identification 0 (WDTPCellID0), offset 0xFF0........................................ 204
Watchdog PrimeCell Identification 1 (WDTPCellID1), offset 0xFF4........................................ 205
Watchdog PrimeCell Identification 2 (WDTPCellID2), offset 0xFF8........................................ 206
Watchdog PrimeCell Identification 3 (WDTPCellID3 ), offset 0xFFC ...................................... 207
Analog-to-Digital Converter (ADC).............................................................................................. 208
Register 1:
Register 2:
Register 3:
Register 4:
Register 5:
Register 6:
Register 7:
Register 8:
Register 9:
Register 10:
Register 11:
Register 12:
Register 13:
Register 14:
Register 15:
Register 16:
Register 17:
Register 18:
Register 19:
Register 20:
Register 21:
Register 22:
ADC Active Sample Sequencer (ADCACTSS), offset 0x000 .................................................. 214
ADC Raw Interrupt Status (ADCRIS), offset 0x004................................................................. 215
ADC Interrupt Mask (ADCIM), offset 0x008 ............................................................................ 216
ADC Interrupt Status and Clear (ADCISC), offset 0x00C........................................................ 217
ADC Overflow Status (ADCOSTAT), offset 0x010 .................................................................. 218
ADC Event Multiplexer Select (ADCEMUX), offset 0x014 ...................................................... 219
ADC Underflow Status (ADCUSTAT), offset 0x018 ................................................................ 220
ADC Sample Sequencer Priority (ADCSSPRI), offset 0x020.................................................. 221
ADC Processor Sample Sequence Initiate (ADCPSSI), offset 0x028 ..................................... 222
ADC Sample Averaging Control (ADCSAC), offset 0x030 ...................................................... 223
ADC Sample Sequence Input Multiplexer Select 0 (ADCSSMUX0), offset 0x040.................. 224
ADC Sample Sequence Control 0 (ADCSSCTL0), offset 0x044............................................. 226
ADC Sample Sequence Result FIFO 0 (ADCSSFIFO0), offset 0x048.................................... 228
ADC Sample Sequence FIFO 0 Status (ADCSSFSTAT0), offset 0x04C................................ 229
ADC Sample Sequence Input Multiplexer Select 1 (ADCSSMUX1), offset 0x060.................. 230
ADC Sample Sequence Control 1 (ADCSSCTL1), offset 0x064............................................. 231
ADC Sample Sequence Result FIFO 1 (ADCSSFIFO1), offset 0x068.................................... 231
ADC Sample Sequence FIFO 1 Status (ADCSSFSTAT1), offset 0x06C................................ 231
ADC Sample Sequence Input Multiplexer Select 2 (ADCSSMUX2), offset 0x080.................. 232
ADC Sample Sequence Control 2 (ADCSSCTL2), offset 0x084............................................. 233
ADC Sample Sequence Result FIFO 2 (ADCSSFIFO2), offset 0x088.................................... 233
ADC Sample Sequence FIFO 2 Status (ADCSSFSTAT2), offset 0x08C................................ 233
May 4, 2007
13
Preliminary
List of Registers
Register 23:
Register 24:
Register 25:
Register 26:
Register 27:
ADC Sample Sequence Input Multiplexer Select 3 (ADCSSMUX3), offset 0x0A0 ................. 234
ADC Sample Sequence Control 3 (ADCSSCTL3), offset 0x0A4 ............................................ 235
ADC Sample Sequence Result FIFO 3 (ADCSSFIFO3), offset 0x0A8 ................................... 235
ADC Sample Sequence FIFO 3 Status (ADCSSFSTAT3), offset 0x0AC ............................... 235
ADC Test Mode Loopback (ADCTMLB), offset 0x100 ............................................................ 236
Universal Asynchronous Receivers/Transmitters (UARTs) ..................................................... 238
Register 1:
Register 2:
Register 3:
Register 4:
Register 5:
Register 6:
Register 7:
Register 8:
Register 9:
Register 10:
Register 11:
Register 12:
Register 13:
Register 14:
Register 15:
Register 16:
Register 17:
Register 18:
Register 19:
Register 20:
Register 21:
Register 22:
Register 23:
Register 24:
UART Data (UARTDR), offset 0x000 ...................................................................................... 245
UART Receive Status/Error Clear (UARTRSR/UARTECR), offset 0x004 .............................. 247
UART Flag (UARTFR), offset 0x018 ....................................................................................... 249
UART Integer Baud-Rate Divisor (UARTIBRD), offset 0x024 ................................................. 251
UART Fractional Baud-Rate Divisor (UARTFBRD), offset 0x028 ........................................... 252
UART Line Control (UARTLCRH), offset 0x02C ..................................................................... 253
UART Control (UARTCTL), offset 0x030................................................................................. 255
UART Interrupt FIFO Level Select (UARTIFLS), offset 0x034 ................................................ 256
UART Interrupt Mask (UARTIM), offset 0x038 ........................................................................ 257
UART Raw Interrupt Status (UARTRIS), offset 0x03C............................................................ 259
UART Masked Interrupt Status (UARTMIS), offset 0x040 ...................................................... 260
UART Interrupt Clear (UARTICR), offset 0x044...................................................................... 261
UART Peripheral Identification 4 (UARTPeriphID4), offset 0xFD0.......................................... 262
UART Peripheral Identification 5 (UARTPeriphID5), offset 0xFD4.......................................... 263
UART Peripheral Identification 6 (UARTPeriphID6), offset 0xFD8.......................................... 264
UART Peripheral Identification 7 (UARTPeriphID7), offset 0xFDC ......................................... 265
UART Peripheral Identification 0 (UARTPeriphID0), offset 0xFE0.......................................... 266
UART Peripheral Identification 1 (UARTPeriphID1), offset 0xFE4.......................................... 267
UART Peripheral Identification 2 (UARTPeriphID2), offset 0xFE8.......................................... 268
UART Peripheral Identification 3 (UARTPeriphID3), offset 0xFEC ......................................... 269
UART PrimeCell Identification 0 (UARTPCellID0), offset 0xFF0............................................. 270
UART PrimeCell Identification 1 (UARTPCellID1), offset 0xFF4............................................. 271
UART PrimeCell Identification 2 (UARTPCellID2), offset 0xFF8............................................. 272
UART PrimeCell Identification 3 (UARTPCellID3), offset 0xFFC ............................................ 273
Synchronous Serial Interface (SSI) ............................................................................................. 274
Register 1:
Register 2:
Register 3:
Register 4:
Register 5:
Register 6:
Register 7:
Register 8:
Register 9:
Register 10:
Register 11:
Register 12:
Register 13:
Register 14:
Register 15:
Register 16:
SSI Control 0 (SSICR0), offset 0x000 ..................................................................................... 286
SSI Control 1 (SSICR1), offset 0x004 ..................................................................................... 288
SSI Data (SSIDR), offset 0x008 .............................................................................................. 290
SSI Status (SSISR), offset 0x00C ........................................................................................... 291
SSI Clock Prescale (SSICPSR), offset 0x010 ......................................................................... 292
SSI Interrupt Mask (SSIIM), offset 0x014 ................................................................................ 293
SSI Raw Interrupt Status (SSIRIS), offset 0x018 .................................................................... 294
SSI Masked Interrupt Status (SSIMIS), offset 0x01C.............................................................. 295
SSI Interrupt Clear (SSIICR), offset 0x020.............................................................................. 296
SSI Peripheral Identification 4 (SSIPeriphID4), offset 0xFD0.................................................. 297
SSI Peripheral Identification 5 (SSIPeriphID5), offset 0xFD4.................................................. 298
SSI Peripheral Identification 6 (SSIPeriphID6), offset 0xFD8.................................................. 299
SSI Peripheral Identification 7 (SSIPeriphID7), offset 0xFDC ................................................. 300
SSI Peripheral Identification 0 (SSIPeriphID0), offset 0xFE0.................................................. 301
SSI Peripheral Identification 1 (SSIPeriphID1), offset 0xFE4.................................................. 302
SSI Peripheral Identification 2 (SSIPeriphID2), offset 0xFE8.................................................. 303
14
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 17:
Register 18:
Register 19:
Register 20:
Register 21:
SSI Peripheral Identification 3 (SSIPeriphID3), offset 0xFEC ................................................. 304
SSI PrimeCell Identification 0 (SSIPCellID0), offset 0xFF0..................................................... 305
SSI PrimeCell Identification 1 (SSIPCellID1), offset 0xFF4..................................................... 306
SSI PrimeCell Identification 2 (SSIPCellID2), offset 0xFF8..................................................... 307
SSI PrimeCell Identification 3 (SSIPCellID3), offset 0xFFC .................................................... 308
Analog Comparator ...................................................................................................................... 309
Register 1:
Register 2:
Register 3:
Register 4:
Register 5:
Register 6:
Analog Comparator Masked Interrupt Status (ACMIS), offset 0x00........................................ 313
Analog Comparator Raw Interrupt Status (ACRIS), offset 0x04.............................................. 314
Analog Comparator Interrupt Enable (ACINTEN), offset 0x08 ................................................ 315
Analog Comparator Reference Voltage Control (ACREFCTL), offset 0x10 ............................ 316
Analog Comparator Status 0 (ACSTAT0), offset 0x20 ............................................................ 317
Analog Comparator Control 0 (ACCTL0), offset 0x24 ............................................................. 318
Pulse Width Modulator (PWM)..................................................................................................... 320
Register 1:
Register 2:
Register 3:
Register 4:
Register 5:
Register 6:
Register 7:
Register 8:
Register 9:
Register 10:
Register 11:
Register 12:
Register 13:
Register 14:
Register 15:
Register 16:
Register 17:
Register 18:
Register 19:
Register 20:
Register 21:
Register 22:
PWM Master Control (PWMCTL), offset 0x000....................................................................... 326
PWM Time Base Sync (PWMSYNC), offset 0x004................................................................. 327
PWM Output Enable (PWMENABLE), offset 0x008................................................................ 328
PWM Output Inversion (PWMINVERT), offset 0x00C............................................................. 329
PWM Output Fault (PWMFAULT), offset 0x010...................................................................... 330
PWM Interrupt Enable (PWMINTEN), offset 0x014................................................................. 331
PWM Raw Interrupt Status (PWMRIS), offset 0x018 .............................................................. 332
PWM Interrupt Status and Clear (PWMISC), offset 0x01C ..................................................... 333
PWM Status (PWMSTATUS), offset 0x020............................................................................. 334
PWM0 Control (PWM0CTL), offset 0x040............................................................................... 335
PWM0 Interrupt Enable (PWM0INTEN), offset 0x044............................................................. 336
PWM0 Raw Interrupt Status (PWM0RIS), offset 0x048 .......................................................... 337
PWM0 Interrupt Status and Clear (PWM0ISC), offset 0x04C ................................................. 338
PWM0 Load (PWM0LOAD), offset 0x050 ............................................................................... 339
PWM0 Counter (PWM0COUNT), offset 0x054 ....................................................................... 340
PWM0 Compare A (PWM0CMPA), offset 0x058 .................................................................... 341
PWM0 Compare B (PWM0CMPB), offset 0x05C.................................................................... 342
PWM0 Generator A Control (PWM0GENA), offset 0x060....................................................... 343
PWM0 Generator B Control (PWM0GENB), offset 0x064....................................................... 345
PWM0 Dead-Band Control (PWM0DBCTL), offset 0x068 ...................................................... 346
PWM0 Dead-Band Rising-Edge Delay (PWM0DBRISE), offset 0x06C .................................. 347
PWM0 Dead-Band Falling-Edge-Delay (PWM0DBFALL), offset 0x070.................................. 348
Quadrature Encoder Interface (QEI)............................................................................................ 349
Register 1:
Register 2:
Register 3:
Register 4:
Register 5:
Register 6:
Register 7:
Register 8:
Register 9:
Register 10:
Register 11:
QEI Control (QEICTL), offset 0x000........................................................................................ 353
QEI Status (QEISTAT), offset 0x004....................................................................................... 355
QEI Position (QEIPOS), offset 0x008...................................................................................... 356
QEI Maximum Position (QEIMAXPOS), offset 0x00C............................................................. 357
QEI Timer Load (QEILOAD), offset 0x010 .............................................................................. 358
QEI Timer (QEITIME), offset 0x014 ........................................................................................ 359
QEI Velocity Counter (QEICOUNT), offset 0x018 ................................................................... 360
QEI Velocity (QEISPEED), offset 0x01C................................................................................. 361
QEI Interrupt Enable (QEIINTEN), offset 0x020...................................................................... 362
QEI Raw Interrupt Status (QEIRIS), offset 0x024 ................................................................... 363
QEI Interrupt Status and Clear (QEIISC), offset 0x028 ........................................................... 364
May 4, 2007
15
Preliminary
LM3S818 Data Sheet
Revision History
This table provides a summary of the document revisions.
Date
Revision
Description
February 2007
00
Initial release of LM3S317, LM3S617, LM3S618, LM3S817 and LM3S818 data
sheet to customers.
March 2007
01
Second release of LM3S617 and LM3S818 data sheets. Includes the following
changes:
• Added information to the Thermal chapter.
• Added information to the Power Specifications section in the Electrical chapter.
April 2007
02
Third release of LM3S317, LM3S617, LM3S618, LM3S817, and LM3S818 data
sheets. Includes the following changes:
• In the Internal Memory chapter, added information on code protection.
• In the ARM Cortex-M3 Processor Core, Architecture Overview, and
General-Purpose Timers chapters, added information for the System Timer
(SysTick).
• In the Timers chapter, added note to the 16-Bit Input Edge Time Mode section.
May 4, 2007
17
Preliminary
About This Document
About This Document
This data sheet provides reference information for the LM3S818 microcontroller, describing the
functional blocks of the system-on-chip (SoC) device designed around the ARM® Cortex™-M3
core.
Audience
This manual is intended for system software developers, hardware designers, and application
developers.
About This Manual
This document is organized into sections that correspond to each major feature.
Related Documents
The following documents are referenced by the data sheet, and available on the documentation
CD or from the Luminary Micro web site at www.luminarymicro.com:
„
ARM® Cortex™-M3 Technical Reference Manual
„
CoreSight™ Design Kit Technical Reference Manual
„
ARM® v7-M Architecture Application Level Reference Manual
The following related documents are also referenced:
„
IEEE Standard 1149.1-Test Access Port and Boundary-Scan Architecture
This documentation list was current as of publication date. Please check the Luminary Micro web
site for additional documentation, including application notes and white papers.
Documentation Conventions
This document uses the conventions shown in Table 0-1.
Table 0-1. Documentation Conventions
Notation
Meaning
General Register Notation
REGISTER
APB registers are indicated in uppercase bold. For example,
PBORCTL is the Power-On and Brown-Out Reset Control register. If
a register name contains a lowercase n, it represents more than one
register. For example, SRCRn represents any (or all) of the three
Software Reset Control registers: SRCR0, SRCR1, and SRCR2.
bit
A single bit in a register.
bit field
Two or more consecutive and related bits.
offset 0xnnn
A hexadecimal increment to a register’s address, relative to that
module’s base address as specified in Table 3-1, "Memory Map," on
page 41.
18
May 4, 2007
Preliminary
LM3S818 Data Sheet
Table 0-1. Documentation Conventions
Notation
Meaning
Register N
Registers are numbered consecutively throughout the document to
aid in referencing them. The register number has no meaning to
software.
reserved
Register bits marked reserved are reserved for future use. Reserved
bits return an indeterminate value, and should never be changed.
Only write a reserved bit with its current value.
yy:xx
The range of register bits inclusive from xx to yy. For example, 31:15
means bits 15 through 31 in that register.
Register Bit/Field Types
This value in the register bit diagram indicates whether software
running on the controller can change the value of the bit field.
RO
Software can read this field. Always write the chip reset value.
R/W
Software can read or write this field.
R/W1C
Software can read or write this field. A write of a 0 to a W1C bit does
not affect the bit value in the register. A write of a 1 clears the value
of the bit in the register; the remaining bits remain unchanged.
This register type is primarily used for clearing interrupt status bits
where the read operation provides the interrupt status and the write
of the read value clears only the interrupts being reported at the time
the register was read.
W1C
Software can write this field. A write of a 0 to a W1C bit does not
affect the bit value in the register. A write of a 1 clears the value of
the bit in the register; the remaining bits remain unchanged. A read
of the register returns no meaningful data.
This register is typically used to clear the corresponding bit in an
interrupt register.
WO
Only a write by software is valid; a read of the register returns no
meaningful data.
Register Bit/Field Reset Value
This value in the register bit diagram shows the bit/field value after
any reset, unless noted.
0
Bit cleared to 0 on chip reset.
1
Bit set to 1 on chip reset.
–
Nondeterministic.
Pin/Signal Notation
[]
Pin alternate function; a pin defaults to the signal without the
brackets.
pin
Refers to the physical connection on the package.
signal
Refers to the electrical signal encoding of a pin.
May 4, 2007
19
Preliminary
About This Document
Table 0-1. Documentation Conventions
Notation
Meaning
assert a signal
Change the value of the signal from the logically False state to the
logically True state. For active High signals, the asserted signal
value is 1 (High); for active Low signals, the asserted signal value is
0 (Low). The active polarity (High or Low) is defined by the signal
name (see SIGNAL and SIGNAL below).
deassert a signal
Change the value of the signal from the logically True state to the
logically False state.
SIGNAL
Signal names are in uppercase and in the Courier font. An overbar
on a signal name indicates that it is active Low. To assert SIGNAL is
to drive it Low; to deassert SIGNAL is to drive it High.
SIGNAL
Signal names are in uppercase and in the Courier font. An active
High signal has no overbar. To assert SIGNAL is to drive it High; to
deassert SIGNAL is to drive it Low.
Numbers
X
An uppercase X indicates any of several values is allowed, where X
can be any legal pattern. For example, a binary value of 0X00 can be
either 0100 or 0000, a hex value of 0xX is 0x0 or 0x1, and so on.
0x
Hexadecimal numbers have a prefix of 0x. For example, 0x00FF is
the hexadecimal number FF. Binary numbers are indicated with a b
suffix, for example, 1011b. Decimal numbers are written without a
prefix or suffix.
20
May 4, 2007
Preliminary
LM3S818 Data Sheet
1
Architectural Overview
The Luminary Micro Stellaris® family of microcontrollers—the first ARM® Cortex™-M3 based
controllers—brings high-performance 32-bit computing to cost-sensitive embedded microcontroller
applications. These pioneering parts deliver customers 32-bit performance at a cost equivalent to
legacy 8- and 16-bit devices, all in a package with a small footprint.
The LM3S818 controller in the Stellaris family offers the advantages of ARM’s widely available
development tools, System-on-Chip (SoC) infrastructure IP applications, and a large user
community. Additionally, the controller uses ARM’s Thumb®-compatible Thumb-2 instruction set to
reduce memory requirements and, thereby, cost.
Luminary Micro offers a complete solution to get to market quickly, with a customer development
board, white papers and application notes, and a strong support, sales, and distributor network.
1.1
Product Features
The LM3S818 microcontroller includes the following product features:
„
32-Bit RISC Performance
– 32-bit ARM® Cortex™-M3 v7M architecture optimized for small-footprint embedded
applications
– System timer (SysTick) provides a simple, 24-bit clear-on-write, decrementing,
wrap-on-zero counter with a flexible control mechanism
– Thumb®-compatible Thumb-2-only instruction set processor core for high code density
– 50-MHz operation
– Hardware-division and single-cycle-multiplication
– Integrated Nested Vectored Interrupt Controller (NVIC) providing deterministic interrupt
handling
– 27 interrupts with eight priority levels
– Memory protection unit (MPU) provides a privileged mode for protected operating system
functionality
– Unaligned data access, enabling data to be efficiently packed into memory
– Atomic bit manipulation (bit-banding) delivers maximum memory utilization and
streamlined peripheral control
„
Internal Memory
– 64-KB single-cycle flash
•
User-managed flash block protection on a 2-KB block basis
•
User-managed flash data programming
•
User-defined and managed flash-protection block
– 8-KB single-cycle SRAM
„
General-Purpose Timers
– Three timers, each of which can be configured: as a single 32-bit timer, as two 16-bit
timers, or to initiate an ADC event
– 32-bit Timer modes:
•
Programmable one-shot timer
May 4, 2007
21
Preliminary
Architectural Overview
•
Programmable periodic timer
•
Real-Time Clock when using an external 32.768-KHz clock as the input
•
User-enabled stalling in periodic and one-shot mode when the controller asserts the
CPU Halt flag during debug
•
ADC event trigger
– 16-bit Timer modes:
•
General-purpose timer function with an 8-bit prescaler
•
Programmable one-shot timer
•
Programmable periodic timer
•
User-enabled stalling when the controller asserts CPU Halt flag during debug
•
ADC event trigger
– 16-bit Input Capture modes:
•
Input edge count capture
•
Input edge time capture
– 16-bit PWM mode:
•
„
Simple PWM mode with software-programmable output inversion of the PWM signal
ARM FiRM-compliant Watchdog Timer
– 32-bit down counter with a programmable load register
– Separate watchdog clock with an enable
– Programmable interrupt generation logic with interrupt masking
– Lock register protection from runaway software
– Reset generation logic with an enable/disable
– User-enabled stalling when the controller asserts the CPU Halt flag during debug
„
Synchronous Serial Interface (SSI)
– Master or slave operation
– Programmable clock bit rate and prescale
– Separate transmit and receive FIFOs, 16 bits wide, 8 locations deep
– Programmable interface operation for Freescale SPI, MICROWIRE, or Texas Instruments
synchronous serial interfaces
– Programmable data frame size from 4 to 16 bits
– Internal loopback test mode for diagnostic/debug testing
„
UART
– Two fully programmable 16C550-type UARTs
– Separate 16x8 transmit (TX) and 16x12 receive (RX) FIFOs to reduce CPU interrupt
service loading
– Programmable baud-rate generator with fractional divider
– Programmable FIFO length, including 1-byte deep operation providing conventional
double-buffered interface
22
May 4, 2007
Preliminary
LM3S818 Data Sheet
– FIFO trigger levels of 1/8, 1/4, 1/2, 3/4, and 7/8
– Standard asynchronous communication bits for start, stop, and parity
– False-start-bit detection
– Line-break generation and detection
„
ADC
– Single- and differential-input configurations
– Six 10-bit channels (inputs) when used as single-ended inputs
– Sample rate of one million samples/second
– Flexible, configurable analog-to-digital conversion
– Four programmable sample conversion sequences from one to eight entries long, with
corresponding conversion result FIFOs
– Each sequence triggered by software or internal event (timers, analog comparators, PWM
or GPIO)
„
Analog Comparator
– One independent integrated analog comparator
– Configurable for output to: drive an output pin, or generate an interrupt, or initiate an ADC
sample sequence
– Compare external pin input to external pin input or to internal programmable voltage
reference
„
PWM
– Three PWM generator blocks, each with one 16-bit counter, two comparators, a PWM
generator, and a dead-band generator
– One 16-bit counter
•
Runs in Down or Up/Down mode
•
Output frequency controlled by a 16-bit load value
•
Load value updates can be synchronized
•
Produces output signals at zero and load value
– Two comparators
•
Comparator value updates can be synchronized
•
Produces output signals on match
– PWM generator
•
Output PWM signal is constructed based on actions taken as a result of the counter
and comparator output signals
•
Produces two independent PWM signals
– Dead-band generator
•
Produces two PWM signals with programmable dead-band delays suitable for driving
a half-H bridge
•
Can be bypassed, leaving input PWM signals unmodified
– Flexible output control block with PWM output enable of each PWM signal
May 4, 2007
23
Preliminary
Architectural Overview
•
PWM output enable of each PWM signal
•
Optional output inversion of each PWM signal (polarity control)
•
Optional fault handling for each PWM signal
•
Synchronization of timers in the PWM generator blocks
•
Synchronization of timer/comparator updates across the PWM generator blocks
•
Interrupt status summary of the PWM generator blocks
– Can initiate an ADC sample sequence
„
QEI
– Hardware position integrator tracks the encoder position
– Velocity capture using built-in timer
– Interrupt generation on index pulse, velocity-timer expiration, direction change, and
quadrature error detection
„
GPIOs
– 0 to 30 GPIOs, depending on configuration
– 5-V-tolerant input/outputs
– Programmable interrupt generation as either edge-triggered or level-sensitive
– Bit masking in both read and write operations through address lines
– Can initiate an ADC sample sequence
– Programmable control for GPIO pad configuration:
„
•
Weak pull-up or pull-down resistors
•
2-mA, 4-mA, and 8-mA pad drive
•
Slew rate control for the 8-mA drive
•
Open drain enables
•
Digital input enables
Power
– On-chip Low Drop-Out (LDO) voltage regulator, with programmable output user-adjustable
from 2.25 V to 2.75 V
– Low-power options on controller: Sleep and Deep-sleep modes
– Low-power options for peripherals: software controls shutdown of individual peripherals
– User-enabled LDO unregulated voltage detection and automatic reset
– 3.3-V supply brownout detection and reporting via interrupt or reset
– On-chip temperature sensor
„
Flexible Reset Sources
– Power-on reset (POR)
– Reset pin assertion
– Brown-out (BOR) detector alerts to system power drops
– Software reset
– Watchdog timer reset
24
May 4, 2007
Preliminary
LM3S818 Data Sheet
– Internal low drop-out (LDO) regulator output goes unregulated
„
Additional Features
– Six reset sources
– Programmable clock source control
– Clock gating to individual peripherals for power savings
– IEEE 1149.1-1990 compliant Test Access Port (TAP) controller
– Debug access via JTAG and Serial Wire interfaces
– Full JTAG boundary scan
„
1.2
Industrial-range 48-pin RoHS-compliant LQFP package
Target Applications
„
Factory automation and control
„
Industrial control power devices
„
Building and home automation
„
Stepper motors
„
Brushless DC motors
„
AC induction motors
May 4, 2007
25
Preliminary
Architectural Overview
1.3
High-Level Block Diagram
Figure 1-1.
Stellaris® High-Level Block Diagram
ARM Cortex-M3
(including Nested DCode bus
Flash
Vectored Interrupt
Controller (NVIC)) ICode bus
System
Control
& Clocks
LMI JTAG
Test Access Port
(TAP)
Controller
APB Bridge
Memory
Peripherals
SRAM
General-Purpose
Timers
General-Purpose
Input/Outputs
(GPIOs)
System
Peripherals
Universal
Asynchronous
Receiver/
Transmitters
(UARTs)
Peripheral Bus
Watchdog
Timer
Analog-toDigital
Converter
(ADC)
Synchronous
Serial
Interface
(SSI)
Analog
Comparators
Serial
Communications
Peripherals
Analog
Peripherals
Temperature
Sensor
Quadrature
Encoder
Interface
(QEI)
Pulse
Width
Modulator
(PWM)
Motor
Control
Peripherals
LM3S818
26
May 4, 2007
Preliminary
LM3S818 Data Sheet
1.4
Functional Overview
The following sections provide an overview of the features of the LM3S818 microcontroller. The
chapter number in parenthesis indicates where that feature is discussed in detail. Ordering and
support information can be found in “Ordering and Contact Information” on page 395.
1.4.1
ARM Cortex™-M3
1.4.1.1
Processor Core (Section 2 on page 33)
All members of the Stellaris product family, including the LM3S818 microcontroller, are designed
around an ARM Cortex™-M3 processor core. The ARM Cortex-M3 processor provides the core
for a high-performance, low-cost platform that meets the needs of minimal memory
implementation, reduced pin count, and low power consumption, while delivering outstanding
computational performance and exceptional system response to interrupts.
Section 2, “ARM Cortex-M3 Processor Core,” on page 33 provides an overview of the ARM core;
the core is detailed in the ARM® Cortex™-M3 Technical Reference Manual.
1.4.1.2
Nested Vectored Interrupt Controller (NVIC)
The LM3S818 controller includes the ARM Nested Vectored Interrupt Controller (NVIC) on the
ARM Cortex-M3 core. The NVIC and Cortex-M3 prioritize and handle all exceptions. All exceptions
are handled in Handler Mode. The processor state is automatically stored to the stack on an
exception, and automatically restored from the stack at the end of the Interrupt Service Routine
(ISR). The vector is fetched in parallel to the state saving, which enables efficient interrupt entry.
The processor supports tail-chaining, which enables back-to-back interrupts to be performed
without the overhead of state saving and restoration. Software can set eight priority levels on 7
exceptions (system handlers) and 27 interrupts.
Section 4, “Interrupts,” on page 43 provides an overview of the NVIC controller and the interrupt
map. Exceptions and interrupts are detailed in the ARM® Cortex™-M3 Technical Reference
Manual.
1.4.2
Motor Control Peripherals
To enhance motor control, the LM3S818 controller features Pulse Width Modulation (PWM)
outputs and the Quadrature Encoder Interface (QEI).
1.4.2.1
PWM
Pulse width modulation (PWM) is a powerful technique for digitally encoding analog signal levels.
High-resolution counters are used to generate a square wave, and the duty cycle of the square
wave is modulated to encode an analog signal. Typical applications include switching power
supplies and motor control.
On the LM3S818, PWM motion control functionality can be achieved through dedicated, flexible
motion control hardware (the PWM pins) or through the motion control features of the
general-purpose timers (using the CCP pins).
PWM Pins (Section 15 on page 320)
The LM3S818 PWM module consists of three PWM generator blocks and a control block. Each
PWM generator block contains one timer (16-bit down or up/down counter), two comparators, a
PWM signal generator, a dead-band generator, and an interrupt/ADC-trigger selector. The control
block determines the polarity of the PWM signals, and which signals are passed through to the
pins.
May 4, 2007
27
Preliminary
Architectural Overview
Each PWM generator block produces two PWM signals that can either be independent signals or
a single pair of complementary signals with dead-band delays inserted. The output of the PWM
generation blocks are managed by the output control block before being passed to the device pins.
CCP Pins (“16-Bit PWM Mode” on page 162)
The General-Purpose Timer Module’s CCP (Capture Compare PWM) pins are software
programmable to support a simple PWM mode with a software-programmable output inversion of
the PWM signal.
1.4.2.2
QEI (Section 16 on page 349)
A quadrature encoder, also known as a 2-channel incremental encoder, converts linear
displacement into a pulse signal. By monitoring both the number of pulses and the relative phase
of the two signals, you can track the position, direction of rotation, and speed. In addition, a third
channel, or index signal, can be used to reset the position counter.
The quadrature encoder with index (QEI) module interprets the code produced by a quadrature
encoder wheel to integrate position over time and determine direction of rotation. In addition, it can
capture a running estimate of the velocity of the encoder wheel.
1.4.3
Analog Peripherals
To handle analog signals, the LM3S818 controller offers an Analog-to-Digital Converter (ADC) and
an analog comparator.
1.4.3.1
ADC (Section 11 on page 208)
An analog-to-digital converter (ADC) is a peripheral that converts a continuous analog voltage to a
discrete digital number.
The Stellaris ADC module features 10-bit conversion resolution and supports six input channels,
plus an internal temperature sensor. Four buffered sample sequences allow rapid sampling of up
to six analog input sources without controller intervention. Each sample sequence provides flexible
programming with fully configurable input source, trigger events, interrupt generation, and
sequence priority.
1.4.3.2
Analog Comparator (Section 14 on page 309)
An analog comparator is a peripheral that compares two analog voltages, and provides a logical
output that signals the comparison result.
The LM3S818 controller provides one independent integrated analog comparator that can be
configured to drive an output or generate an interrupt or ADC event.
A comparator can compare a test voltage against any one of these voltages:
„
An individual external reference voltage
„
A single external reference voltage
„
A shared internal reference voltage
The comparator can provide its output to a device pin, acting as a replacement for an analog
comparator on the board, or it can be used to signal the application via interrupts or triggers to the
ADC to cause it to start capturing a sample sequence. The interrupt generation and ADC triggering
logic is separate. This means, for example, that an interrupt can be generated on a rising edge and
the ADC triggered on a falling edge.
28
May 4, 2007
Preliminary
LM3S818 Data Sheet
1.4.4
Serial Communications Peripherals
The LM3S818 controller supports both asynchronous and synchronous serial communications
with two fully programmable 16C550-type UARTs and SSI serial communications.
1.4.4.1
UART (Section 12 on page 238)
A Universal Asynchronous Receiver/Transmitter (UART) is an integrated circuit used for RS-232C
serial communications, containing a transmitter (parallel-to-serial converter) and a receiver
(serial-to-parallel converter), each clocked separately.
The LM3S818 controller includes two fully programmable 16C550-type UARTs that support data
transfer speeds up to 460.8 Kbps. (Although similar in functionality to a 16C550 UART, it is not
register compatible.)
Separate 16x8 transmit (TX) and 16x12 receive (RX) FIFOs reduce CPU interrupt service loading.
The UART can generate individually masked interrupts from the RX, TX, modem status, and error
conditions. The module provides a single combined interrupt when any of the interrupts are
asserted and are unmasked.
1.4.4.2
SSI (Section 13 on page 274)
Synchronous Serial Interface (SSI) is a four-wire bi-directional communications interface.
The Stellaris SSI module provides the functionality for synchronous serial communications with
peripheral devices, and can be configured to use the Freescale SPI, MICROWIRE, or TI
synchronous serial interface frame formats. The size of the data frame is also configurable, and
can be set between 4 and 16 bits, inclusive.
The SSI module performs serial-to-parallel conversion on data received from a peripheral device,
and parallel-to-serial conversion on data transmitted to a peripheral device. The TX and RX paths
are buffered with internal FIFOs, allowing up to eight 16-bit values to be stored independently.
The SSI module can be configured as either a master or slave device. As a slave device, the SSI
module can also be configured to disable its output, which allows a master device to be coupled
with multiple slave devices.
The SSI module also includes a programmable bit rate clock divider and prescaler to generate the
output serial clock derived from the SSI module’s input clock. Bit rates are generated based on the
input clock and the maximum bit rate is determined by the connected peripheral.
1.4.5
1.4.5.1
System Peripherals
Programmable GPIOs (Section 8 on page 115)
General-purpose input/output (GPIO) pins offer flexibility for a variety of connections.
The Stellaris GPIO module is composed of five physical GPIO blocks, each corresponding to an
individual GPIO port. The GPIO module is FiRM-compliant (compliant to the ARM Foundation IP
for Real-Time Microcontrollers specification) and supports 0 to 30 programmable input/output pins.
The number of GPIOs available depends on the peripherals being used (see Table 18-4 on
page 374 for the signals available to each GPIO pin).
The GPIO module features programmable interrupt generation as either edge-triggered or
level-sensitive on all pins, programmable control for GPIO pad configuration, and bit masking in
both read and write operations through address lines.
1.4.5.2
Three Programmable Timers (Section 9 on page 153)
Programmable timers can be used to count or time external events that drive the Timer input pins.
May 4, 2007
29
Preliminary
Architectural Overview
The Stellaris General-Purpose Timer Module (GPTM) contains three GPTM blocks. Each GPTM
block provides two 16-bit timer/counters that can be configured to operate independently as timers
or event counters, or configured to operate as one 32-bit timer or one 32-bit Real-Time Clock
(RTC). Timers can also be used to trigger analog-to-digital (ADC) conversions.
When configured in 32-bit mode, a timer can run as a one-shot timer, periodic timer, or Real-Time
Clock (RTC). When in 16-bit mode, a timer can run as a one-shot timer or periodic timer, and can
extend its precision by using an 8-bit prescaler. A 16-bit timer can also be configured for event
capture or Pulse Width Modulation (PWM) generation.
1.4.5.3
Watchdog Timer (Section 10 on page 185)
A watchdog timer can generate nonmaskable interrupts (NMIs) or a reset when a time-out value is
reached. The watchdog timer is used to regain control when a system has failed due to a software
error or to the failure of an external device to respond in the expected way.
The Stellaris Watchdog Timer module consists of a 32-bit down counter, a programmable load
register, interrupt generation logic, and a locking register.
The Watchdog Timer can be configured to generate an interrupt to the controller on its first
time-out, and to generate a reset signal on its second time-out. Once the Watchdog Timer has
been configured, the lock register can be written to prevent the timer configuration from being
inadvertently altered.
1.4.6
Memory Peripherals
The Stellaris controllers offer both SRAM and Flash memory.
1.4.6.1
SRAM (Section 7.2.1 on page 98)
The LM3S818 static random access memory (SRAM) controller supports 8 KB SRAM. The
internal SRAM of the Stellaris devices is located at address 0x2000.0000 of the device memory
map. To reduce the number of time consuming read-modify-write (RMW) operations, ARM has
introduced bit-banding technology in the new Cortex-M3 processor. With a bit-band-enabled
processor, certain regions in the memory map (SRAM and peripheral space) can use address
aliases to access individual bits in a single, atomic operation.
1.4.6.2
Flash (Section 7.2.2 on page 99)
The LM3S818 Flash controller supports 64 KB of flash memory. The flash is organized as a set of
1-KB blocks that can be individually erased. Erasing a block causes the entire contents of the
block to be reset to all 1s. These blocks are paired into a set of 2-KB blocks that can be individually
protected. The blocks can be marked as read-only or execute-only, providing different levels of
code protection. Read-only blocks cannot be erased or programmed, protecting the contents of
those blocks from being modified. Execute-only blocks cannot be erased or programmed, and can
only be read by the controller instruction fetch mechanism, protecting the contents of those blocks
from being read by either the controller or by a debugger.
1.4.7
Additional Features
1.4.7.1
Memory Map (Section 3 on page 41)
A memory map lists the location of instructions and data in memory. The memory map for the
LM3S818 controller can be found on page 41. Register addresses are given as a hexadecimal
increment, relative to the module’s base address as shown in the memory map.
The ARM® Cortex™-M3 Technical Reference Manual provides further information on the memory
map.
30
May 4, 2007
Preliminary
LM3S818 Data Sheet
1.4.7.2
JTAG TAP Controller (Section 5 on page 46)
The Joint Test Action Group (JTAG) port provides a standardized serial interface for controlling the
Test Access Port (TAP) and associated test logic. The TAP, JTAG instruction register, and JTAG
data registers can be used to test the interconnects of assembled printed circuit boards, obtain
manufacturing information on the components, and observe and/or control the inputs and outputs
of the controller during normal operation. The JTAG port provides a high degree of testability and
chip-level access at a low cost.
The JTAG port is comprised of the standard five pins: TRST, TCK, TMS, TDI, and TDO. Data is
transmitted serially into the controller on TDI and out of the controller on TDO. The interpretation of
this data is dependent on the current state of the TAP controller. For detailed information on the
operation of the JTAG port and TAP controller, please refer to the IEEE Standard 1149.1-Test
Access Port and Boundary-Scan Architecture.
The LMI JTAG controller works with the ARM JTAG controller built into the Cortex-M3 core. This is
implemented by multiplexing the TDO outputs from both JTAG controllers. ARM JTAG instructions
select the ARM TDO output while LMI JTAG instructions select the LMI TDO outputs. The
multiplexer is controlled by the LMI JTAG controller, which has comprehensive programming for
the ARM, LMI, and unimplemented JTAG instructions.
1.4.7.3
System Control and Clocks (Section 6 on page 56)
System control determines the overall operation of the device. It provides information about the
device, controls the clocking of the device and individual peripherals, and handles reset detection
and reporting.
1.4.8
Hardware Details
Details on the pins and package can be found in the following sections:
„
Section 17, “Pin Diagram,” on page 365
„
Section 18, “Signal Tables,” on page 366
„
Section 19, “Operating Characteristics,” on page 376
„
Section 20, “Electrical Characteristics,” on page 377
„
Section 21, “Package Information,” on page 389
May 4, 2007
31
Preliminary
Architectural Overview
1.5
System Block Diagram
Figure 1-2.
LM3S818 Controller System-Level Block Diagram
VDD_3.3V
LDO
VDD_2.5V
LDO
GND
ARM Cortex-M3
(50 MHz)
CM3Core
DCode
Debug
OSC0
IOSC
Flash
(64 KB)
ICode
NVIC
Bus
PLL
APB Bridge
OSC1
SRAM
(8 KB)
POR
BOR
RST
Watchdog
Timer
System
Control
& Clocks
GPIO Port B
GPIO Port A
PB7/TRST
SSI
PA1/U0Tx
PA0/U0Rx
UART0
Analog
Comparator
Peripheral Bus
PA5/SSITx
PA4/SSIRx
PA3/SSIFss
PA2/SSIClk
GPIO Port C
PC3/TDO/SWO
PC2/TDI
PC1/TMS/SWDIO
PC0/TCK/SWCLK
PC7/CCP4
PC5/CCP1
JTAG
SWD/SWO
GP Timer2
PC4/PhA
PC6/PhB
QEI
GPIO Port E
PE0/PWM4
PE1/PWM5
ADC5
ADC4
ADC3
ADC2
ADC1
ADC0
LM3S818
PB6/C0+
PB4/C0PB5/C0o
PB2/IDX
PWM1
PB1/PWM3
PB0/PWM2
PB3/Fault
GPIO Port D
PWM0
PD0/PWM0
PD1/PWM1
UART1
PD2/U1Rx
PD3/U1Tx
GP Timer0
PD4/CCP0
GP Timer1
PD5/CCP2
PWM2
ADC
Temperature
Sensor
32
May 4, 2007
Preliminary
LM3S818 Data Sheet
2
ARM Cortex-M3 Processor Core
The ARM Cortex-M3 processor provides the core for a high-performance, low-cost platform that
meets the needs of minimal memory implementation, reduced pin count, and low power
consumption, while delivering outstanding computational performance and exceptional system
response to interrupts. Features include:
„
Compact core.
„
Thumb-2 instruction set, delivering the high-performance expected of an ARM core in the
memory size usually associated with 8- and 16-bit devices; typically in the range of a few
kilobytes of memory for microcontroller class applications.
„
Exceptional interrupt handling, by implementing the register manipulations required for
handling an interrupt in hardware.
„
Memory protection unit (MPU) to provide a privileged mode of operation for complex
applications.
„
Full-featured debug solution with a:
– Serial Wire JTAG Debug Port (SWJ-DP)
– Flash Patch and Breakpoint (FPB) unit for implementing breakpoints
– Data Watchpoint and Trigger (DWT) unit for implementing watchpoints, trigger resources,
and system profiling
– Instrumentation Trace Macrocell (ITM) for support of printf style debugging
– Trace Port Interface Unit (TPIU) for bridging to a Trace Port Analyzer
The Stellaris family of microcontrollers builds on this core to bring high-performance 32-bit
computing to cost-sensitive embedded microcontroller applications, such as factory automation
and control, industrial control power devices, and building and home automation.
For more information on the ARM Cortex-M3 processor core, see the ARM® Cortex™-M3
Technical Reference Manual. For information on SWJ-DP, see the CoreSight™ Design Kit
Technical Reference Manual.
May 4, 2007
33
Preliminary
ARM Cortex-M3 Processor Core
2.1
Block Diagram
Figure 2-1.
CPU Block Diagram
Nested
Vectored
Interrupt
Controller
Interrupts
Sleep
Debug
ARM
Cortex-M3
CM3 Core
Instructions
Data
Trace
Port
Interface
Unit
Memory
Protection
Unit
Flash
Patch and
Breakpoint
Data
Watchpoint
and Trace
2.2
Private
Peripheral
Bus
(external)
ROM
Table
Private Peripheral
Bus
(internal )
Serial Wire JTAG
Debug Port
Instrumentation
Trace Macrocell
Serial
Wire
Output
Trace
Port
(SWO)
Adv. Peripheral
Bus
Bus
Matrix
Adv. HighPerf. Bus
Access Port
I-code bus
D-code bus
System bus
Functional Description
Important: The ARM® Cortex™-M3 Technical Reference Manual describes all the features of
an ARM Cortex-M3 in detail. However, these features differ based on the
implementation. This section describes the Stellaris implementation.
Luminary Micro has implemented the ARM Cortex-M3 core as shown in Figure 2-1. As noted in
the ARM® Cortex™-M3 Technical Reference Manual, several Cortex-M3 components are flexible
in their implementation: SW/JTAG-DP, ETM, TPIU, the ROM table, the MPU, and the Nested
Vectored Interrupt Controller (NVIC). Each of these is addressed in the sections that follow.
2.2.1
Serial Wire and JTAG Debug
Luminary Micro has replaced the ARM SW-DP and JTAG-DP with the ARM
CoreSight™-compliant Serial Wire JTAG Debug Port (SWJ-DP) interface. This means Chapter 12,
“Debug Port,” of the ARM® Cortex™-M3 Technical Reference Manual does not apply to Stellaris
devices.
The SWJ-DP interface combines the SWD and JTAG debug ports into one module. See the
CoreSight™ Design Kit Technical Reference Manual for details on SWJ-DP.
34
May 4, 2007
Preliminary
LM3S818 Data Sheet
2.2.2
Embedded Trace Macrocell (ETM)
ETM was not implemented in the Stellaris devices. This means Chapters 15 and 16 of the ARM®
Cortex™-M3 Technical Reference Manual can be ignored.
2.2.3
Trace Port Interface Unit (TPIU)
The TPIU acts as a bridge between the Cortex-M3 trace data from the ITM, and an off-chip Trace
Port Analyzer. The Stellaris devices have implemented TPIU as shown in Figure 2-2. This is
similar to the non-ETM version described in the ARM® Cortex™-M3 Technical Reference Manual,
however, SWJ-DP only provides SWV output for the TPIU.
Figure 2-2.
2.2.4
TPIU Block Diagram
Debug
ATB
Slave
Port
ATB
Interface
APB
Slave
Port
APB
Interface
Asynchronous FIFO
Trace Out
(serializer)
Serial Wire
Trace Port
(SWO)
ROM Table
The default ROM table was implemented as described in the ARM® Cortex™-M3 Technical
Reference Manual.
2.2.5
Memory Protection Unit (MPU)
The Memory Protection Unit (MPU) is included on the LM3S818 controller and supports the
standard ARMv7 Protected Memory System Architecture (PMSA) model. The MPU provides full
support for protection regions, overlapping protection regions, access permissions, and exporting
memory attributes to the system.
2.2.6
Nested Vectored Interrupt Controller (NVIC)
The Nested Vectored Interrupt Controller (NVIC):
„
Facilitates low-latency exception and interrupt handling
„
Controls power management
„
Implements system control registers
The NVIC supports up to 240 dynamically reprioritizable interrupts each with up to 256 levels of
priority. The NVIC and the processor core interface are closely coupled, which enables low latency
May 4, 2007
35
Preliminary
ARM Cortex-M3 Processor Core
interrupt processing and efficient processing of late arriving interrupts. The NVIC maintains
knowledge of the stacked (nested) interrupts to enable tail-chaining of interrupts.
You can only fully access the NVIC from privileged mode, but you can pend interrupts in
user-mode if you enable the Configuration Control Register (see the ARM® Cortex™-M3
Technical Reference Manual). Any other user-mode access causes a bus fault.
All NVIC registers are accessible using byte, halfword, and word unless otherwise stated.
All NVIC registers and system debug registers are little endian regardless of the endianness state
of the processor.
2.2.6.1
Interrupts
The ARM® Cortex™-M3 Technical Reference Manual describes the maximum number of
interrupts and interrupt priorities. The LM3S818 microcontroller supports 27 interrupts with eight
priority levels.
2.2.6.2
System Timer (SysTick)
Cortex-M3 includes an integrated system timer, SysTick. SysTick provides a simple, 24-bit
clear-on-write, decrementing, wrap-on-zero counter with a flexible control mechanism. The
counter can be used in several different ways, for example:
„
An RTOS tick timer which fires at a programmable rate (for example, 100 Hz) and invokes a
SysTick routine.
„
A high-speed alarm timer using the system clock.
„
A variable rate alarm or signal timer—the duration is range-dependent on the reference clock
used and the dynamic range of the counter.
„
A simple counter. Software can use this to measure time to completion and time used.
„
An internal clock source control based on missing/meeting durations. The COUNTFLAG
bit-field in the control and status register can be used to determine if an action completed
within a set duration, as part of a dynamic clock management control loop.
Functional Description
The timer consists of three registers:
„
A control and status counter to configure its clock, enable the counter, enable the SysTick
interrupt, and determine counter status.
„
The reload value for the counter, used to provide the counter's wrap value.
„
The current value of the counter.
A fourth register, the SysTick Calibration Value Register, is not implemented in the Stellaris
devices.
When enabled, the timer counts down from the reload value to zero, reloads (wraps) to the value
in the SysTick Reload Value register on the next clock edge, then decrements on subsequent
clocks. Writing a value of zero to the Reload Value register disables the counter on the next wrap.
When the counter reaches zero, the COUNTFLAG status bit is set. The COUNTFLAG bit clears on
reads.
Writing to the Current Value register clears the register and the COUNTFLAG status bit. The write
does not trigger the SysTick exception logic. On a read, the current value is the value of the
register at the time the register is accessed.
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May 4, 2007
Preliminary
LM3S818 Data Sheet
If the core is in debug state (halted), the counter will not decrement. The timer is clocked with
respect to a reference clock. The reference clock can be the core clock or an external clock
source.
May 4, 2007
37
Preliminary
ARM Cortex-M3 Processor Core
Register 1: SysTick Control and Status Register
Use the SysTick Control and Status Register to enable the SysTick features.
SysTick Control and Status
Address: 0xE000E010
31
30
29
28
27
26
25
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
24
23
22
21
20
19
18
17
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
COUNTFLAG
reserved
Type
Reset
RO
0
16
CLKSOURCE
R/W
0
TICKINT ENABLE
R/W
0
R/W
0
Bit/Field
Name
Type
Reset
Description
31:17
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
16
COUNTFLAG
R/W
0
Returns 1 if timer counted to 0 since last time this was read.
Clears on read by application. If read by the debugger using the
DAP, this bit is cleared on read-only if the MasterType bit in the
AHB-AP Control Register is set to 0. Otherwise, the
COUNTFLAG bit is not changed by the debugger read.
15:3
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
2
CLKSOURCE
R/W
0
0 = external reference clock. (Not implemented for Stellaris
microcontrollers.)
1 = core clock.
If no reference clock is provided, it is held at 1 and so gives the
same time as the core clock. The core clock must be at least 2.5
times faster than the reference clock. If it is not, the count values
are Unpredictable.
1
TICKINT
R/W
0
1 = counting down to 0 pends the SysTick handler.
0 = counting down to 0 does not pend the SysTick handler.
Software can use the COUNTFLAG to determine if ever counted
to 0.
0
ENABLE
R/W
0
1 = counter operates in a multi-shot way. That is, counter loads
with the Reload value and then begins counting down. On
reaching 0, it sets the COUNTFLAG to 1 and optionally pends
the SysTick handler, based on TICKINT. It then loads the Reload
value again, and begins counting.
0 = counter disabled.
38
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 2: SysTick Reload Value Register
Use the SysTick Reload Value Register to specify the start value to load into the current value
register when the counter reaches 0. It can be any value between 1 and 0x00FFFFFF. A start
value of 0 is possible, but has no effect because the SysTick interrupt and COUNTFLAG are
activated when counting from 1 to 0.
Therefore, as a multi-shot timer, repeated over and over, it fires every N+1 clock pulse, where N is
any value from 1 to 0x00FFFFFF. So, if the tick interrupt is required every 100 clock pulses, 99
must be written into the RELOAD. If a new value is written on each tick interrupt, so treated as
single shot, then the actual count down must be written. For example, if a tick is next required after
400 clock pulses, 400 must be written into the RELOAD.
SysTick Reload Value
Address: 0xE000E014
31
30
29
28
27
26
25
24
23
22
21
20
RO
0
RO
0
RO
0
15
14
R/W
-
R/W
-
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
-
R/W
-
R/W
-
R/W
-
R/W
-
R/W
-
R/W
-
R/W
-
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R/W
-
R/W
-
R/W
-
R/W
-
R/W
-
R/W
-
R/W
-
R/W
-
R/W
-
R/W
-
R/W
-
R/W
-
R/W
-
R/W
-
reserved
Type
Reset
RELOAD
RELOAD
Type
Reset
Bit/Field
Name
Type
Reset
Description
31:24
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
23:0
RELOAD
W1C
-
Value to load into the SysTick Current Value Register when the
counter reaches 0.
May 4, 2007
39
Preliminary
ARM Cortex-M3 Processor Core
Register 3: SysTick Current Value Register
Use the SysTick Current Value Register to find the current value in the register.
SysTick Current Value
Address: 0xE000E018
31
30
29
28
27
26
25
24
23
22
21
20
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
W1C
-
W1C
-
W1C
-
W1C
-
15
14
13
12
11
10
9
8
W1C
-
W1C
-
W1C
-
W1C
-
W1C
-
W1C
-
reserved
Type
Reset
19
18
17
16
W1C
-
W1C
-
W1C
-
CURRENT
7
W1C
-
6
5
4
3
2
1
0
W1C
-
W1C
-
W1C
-
W1C
-
W1C
-
W1C
-
W1C
-
CURRENT
Type
Reset
W1C
-
W1C
-
W1C
-
SysTick Current Value Register bit assignments
Bit/Field
Name
Type
Reset
Description
31:24
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
23:0
CURRENT
W1C
-
Current value at the time the register is accessed. No
read-modify-write protection is provided, so change with care.
This register is write-clear. Writing to it with any value clears the
register to 0. Clearing this register also clears the COUNTFLAG
bit of the SysTick Control and Status Register.
2.2.6.3
SysTick Calibration Value Register
The SysTick Calibration Value register is not implemented.
40
May 4, 2007
Preliminary
LM3S818 Data Sheet
3
Memory Map
The memory map for the LM3S818 is provided in Table 3-1. In this manual, register addresses are
given as a hexadecimal increment, relative to the module’s base address as shown in the memory
map. See also Chapter 4, “Memory Map” in the ARM® Cortex™-M3 Technical Reference Manual.
Table 3-1. Memory Map (Sheet 1 of 2)
Start
End
Description
For details on
registers, see ...
page 103
Memory
0x00000000
0x00007FFF
On-chip flash
0x00008000
0x1FFFFFFF
Reserveda
0x20000000
0x20001FFF
Bit-banded on-chip SRAM
-
0x20002000
0x200FFFFF
Reserveda
-
0x22000000
0x2203FFFF
Bit-band alias of 0x20000000 through 0x20001FFF
-
0x22040000
0x23FFFFFF
Reserveda
-
0x40000000
0x40000FFF
Watchdog timer
page 187
0x40001000
0x40003FFF
Reserved for three additional watchdog timers (per FiRM
specification)a
-
0x40004000
0x40004FFF
GPIO Port A
page 122
0x40005000
0x40005FFF
GPIO Port B
page 122
0x40006000
0x40006FFF
GPIO Port C
page 122
0x40007000
0x40007FFF
GPIO Port D
0x40008000
0x40008FFF
SSI
page 285
0x40009000
0x4000BFFF
Reserved for three additional SSIs (per FiRM
specification)a
-
0x4000C000
0x4000CFFF
UART0
page 244
0x4000D000
0x4000DFFF
UART1
page 244
0x4000E000
0x4000FFFF
Reserved for two additional UARTs (per FiRM
specification)a
-
0x40010000
0x4001FFFF
Reserved for future FiRM peripheralsa
-
0x40020000
0x40023FFF
Reserveda
-
0x40025000
0x40027FFF
Reserveda
-
0x40028000
0x40028FFF
PWM
page 325
FiRM Peripherals
Peripherals
May 4, 2007
41
Preliminary
Memory Map
Table 3-1. Memory Map (Sheet 2 of 2)
Start
End
Description
For details on
registers, see ...
0x40029000
0x4002BFFF
Reserveda
-
0x4002C000
0x4002CFFF
QEI
page 352
0x4002D000
0x4002FFFF
Reserveda
-
0x40030000
0x40030FFF
Timer0
page 164
0x40031000
0x40031FFF
Timer1
page 164
0x40032000
0x40032FFF
Timer2
page 164
0x40033000
0x40037FFF
Reserveda
-
0x40038000
0x40038FFF
ADC
page 213
0x40039000
0x4003BFFF
Reserveda
-
0x4003C000
0x4003CFFF
Analog comparator
page 312
0x4003D000
0x400FCFFF
Reserveda
-
0x400FD000
0x400FDFFF
Flash control
page 103
0x400FE000
0x400FFFFF
System control
page 63
0x40100000
0x41FFFFFF
Reserveda
-
0x42000000
0x43FFFFFF
Bit-band alias of 0x40000000 through 0x400FFFFF
-
0xDFFFFFFF
Reserveda
-
ARM® Cortex™-M3
Technical Reference
Manual
0x44000000
Private Peripheral Bus
0xE0000000
0xE0000FFF
Instrumentation Trace Macrocell (ITM)
0xE0001000
0xE0001FFF
Data Watchpoint and Trace (DWT)
0xE0002000
0xE0002FFF
Flash Patch and Breakpoint (FPB)
0xE0003000
0xE000DFFF
Reserveda
0xE000E000
0xE000EFFF
Nested Vectored Interrupt Controller (NVIC)
0xE000F000
0xE003FFFF
Reserveda
0xE0040000
0xE0040FFF
Trace Port Interface Unit (TPIU)
0xE0041000
0xE0041FFF
Reserveda
-
0xE0042000
0xE00FFFFF
Reserveda
-
0xE0100000
0xFFFFFFFF
Reserved for vendor peripheralsa
-
a. All reserved space returns a bus fault when read or written.
42
May 4, 2007
Preliminary
LM3S818 Data Sheet
4
Interrupts
The ARM Cortex-M3 processor and the Nested Vectored Interrupt Controller (NVIC) prioritize and
handle all exceptions. All exceptions are handled in Handler Mode. The processor state is
automatically stored to the stack on an exception, and automatically restored from the stack at the
end of the Interrupt Service Routine (ISR). The vector is fetched in parallel to the state saving,
which enables efficient interrupt entry. The processor supports tail-chaining, which enables
back-to-back interrupts to be performed without the overhead of state saving and restoration.
Table 4-1 lists all the exceptions. Software can set eight priority levels on seven of these
exceptions (system handlers) as well as on 27 interrupts (listed in Table 4-2). Priorities on the
system handlers are set with the NVIC System Handler Priority registers. Interrupts are enabled
through the NVIC Interrupt Set Enable register and prioritized with the NVIC Interrupt Priority
registers. You can also group priorities by splitting priority levels into pre-emption priorities and
subpriorities. All the interrupt registers are described in Chapter 8, “Nested Vectored Interrupt
Controller” in the ARM® Cortex™-M3 Technical Reference Manual.
Internally, the highest user-settable priority (0) is treated as fourth priority, after a Reset, NMI, and
a Hard Fault. Note that 0 is the default priority for all the settable priorities.
If you assign the same priority level to two or more interrupts, their hardware priority (the lower the
position number) determines the order in which the processor activates them. For example, if both
GPIO Port A and GPIO Port B are priority level 1, then GPIO Port A has higher priority.
See Chapter 5, “Exceptions” and Chapter 8, “Nested Vectored Interrupt Controller” in the ARM®
Cortex™-M3 Technical Reference Manual for more information on exceptions and interrupts.
Table 4-1.
Exception Types
Position
Prioritya
-
0
-
Reset
1
-3 (highest)
Non-Maskable
Interrupt (NMI)
2
-2
Exception Type
Description
Stack top is loaded from first entry of vector table on
reset.
Invoked on power up and warm reset. On first
instruction, drops to lowest priority (and then is
called the base level of activation). This is
asynchronous.
Cannot be stopped or preempted by any exception
but reset. This is asynchronous.
An NMI is only producible by software, using the
NVIC Interrupt Control State register.
Hard Fault
3
-1
All classes of Fault, when the fault cannot activate
due to priority or the configurable fault handler has
been disabled. This is synchronous.
Memory
Management
4
settable
MPU mismatch, including access violation and no
match. This is synchronous.
The priority of this exception can be changed.
Bus Fault
5
settable
Pre-fetch fault, memory access fault, and other
address/memory related faults. This is synchronous
when precise and asynchronous when imprecise.
You can enable or disable this fault.
May 4, 2007
43
Preliminary
Interrupts
Table 4-1.
Exception Types (Continued)
Position
Prioritya
Description
6
settable
Usage fault, such as undefined instruction executed
or illegal state transition attempt. This is
synchronous.
7-10
-
SVCall
11
settable
System service call with SVC instruction. This is
synchronous.
Debug Monitor
12
settable
Debug monitor (when not halting). This is
synchronous, but only active when enabled. It does
not activate if lower priority than the current
activation.
-
13
-
PendSV
14
settable
Pendable request for system service. This is
asynchronous and only pended by software.
SysTick
15
settable
System tick timer has fired. This is asynchronous.
16 and
above
settable
Asserted from outside the ARM Cortex-M3 core and
fed through the NVIC (prioritized). These are all
asynchronous. Table 4-2 lists the interrupts on the
LM3S818 controller.
Exception Type
Usage Fault
-
Interrupts
Reserved.
Reserved.
a. 0 is the default priority for all the settable priorities.
Table 4-2.
Interrupts
Interrupt
(Bit in Interrupt Registers)
Description
0
GPIO Port A
1
GPIO Port B
2
GPIO Port C
3
GPIO Port D
4
GPIO Port E
5
UART0
6
UART1
7
SSI
8
Reserved
9
PWM Fault
10
PWM Generator 0
11
PWM Generator 1
12
PWM Generator 2
44
May 4, 2007
Preliminary
LM3S818 Data Sheet
Table 4-2.
Interrupts (Continued)
Interrupt
(Bit in Interrupt Registers)
Description
13
QEI
14
ADC Sequence 0
15
ADC Sequence 1
16
ADC Sequence 2
17
ADC Sequence 3
18
Watchdog timer
19
Timer0a
20
Timer0b
21
Timer1a
22
Timer1b
23
Timer2a
24
Timer2b
25
Analog Comparator 0
26-27
Reserved
28
System Control
29
Flash Control
30-31
Reserved
May 4, 2007
45
Preliminary
JTAG Interface
5
JTAG Interface
The Joint Test Action Group (JTAG) port is an IEEE standard that defines a Test Access Port and
Boundary Scan Architecture for digital integrated circuits and provides a standardized serial
interface for controlling the associated test logic. The TAP, Instruction Register (IR), and Data
Registers (DR) can be used to test the interconnections of assembled printed circuit boards and
obtain manufacturing information on the components. The JTAG Port also provides a means of
accessing and controlling design-for-test features such as I/O pin observation and control, scan
testing, and debugging.
The JTAG port is comprised of the standard five pins: TRST, TCK, TMS, TDI, and TDO. Data is
transmitted serially into the controller on TDI and out of the controller on TDO. The interpretation of
this data is dependent on the current state of the TAP controller. For detailed information on the
operation of the JTAG port and TAP controller, please refer to the IEEE Standard 1149.1-Test
Access Port and Boundary-Scan Architecture.
The LMI JTAG controller works with the ARM JTAG controller built into the Cortex-M3 core. This is
implemented by multiplexing the TDO outputs from both JTAG controllers. ARM JTAG instructions
select the ARM TDO output while LMI JTAG instructions select the LMI TDO outputs. The
multiplexer is controlled by the LMI JTAG controller, which has comprehensive programming for
the ARM, LMI, and unimplemented JTAG instructions.
The JTAG module has the following features:
„
IEEE 1149.1-1990 compatible Test Access Port (TAP) controller
„
Four-bit Instruction Register (IR) chain for storing JTAG instructions
„
IEEE standard instructions:
– BYPASS instruction
– IDCODE instruction
– SAMPLE/PRELOAD instruction
– EXTEST instruction
– INTEST instruction
„
ARM additional instructions:
– APACC instruction
– DPACC instruction
– ABORT instruction
„
Integrated ARM Serial Wire Debug (SWD)
See the ARM® Cortex™-M3 Technical Reference Manual for more information on the ARM JTAG
controller.
46
May 4, 2007
Preliminary
LM3S818 Data Sheet
5.1
Block Diagram
Figure 5-1.
TRST
TCK
TMS
TDI
JTAG Module Block Diagram
TAP Controller
Instruction Register (IR)
BYPASS Data Register
TDO
Boundary Scan Data Register
IDCODE Data Register
ABORT Data Register
DPACC Data Register
APACC Data Register
Cortex-M3
Debug
Port
5.2
Functional Description
A high-level conceptual drawing of the JTAG module is shown in Figure 5-1. The JTAG module is
composed of the Test Access Port (TAP) controller and serial shift chains with parallel update
registers. The TAP controller is a simple state machine controlled by the TRST, TCK and TMS
inputs. The current state of the TAP controller depends on the current value of TRST and the
sequence of values captured on TMS at the rising edge of TCK. The TAP controller determines
when the serial shift chains capture new data, shift data from TDI towards TDO, and update the
parallel load registers. The current state of the TAP controller also determines whether the
Instruction Register (IR) chain or one of the Data Register (DR) chains is being accessed.
The serial shift chains with parallel load registers are comprised of a single Instruction Register
(IR) chain and multiple Data Register (DR) chains. The current instruction loaded in the parallel
load register determines which DR chain is captured, shifted, or updated during the sequencing of
the TAP controller.
Some instructions, like EXTEST and INTEST, operate on data currently in a DR chain and do not
capture, shift, or update any of the chains. Instructions that are not implemented decode to the
BYPASS instruction to ensure that the serial path between TDI and TDO is always connected (see
Table 5-2 on page 52 for a list of implemented instructions).
See “JTAG and Boundary Scan” on page 384 for JTAG timing diagrams.
May 4, 2007
47
Preliminary
JTAG Interface
5.2.1
JTAG Interface Pins
The JTAG interface consists of five standard pins: TRST, TCK, TMS, TDI, and TDO. These pins and
their associated reset state are given in Table 5-1. Detailed information on each pin follows.
Table 5-1.
5.2.1.1
JTAG Port Pins Reset State
Pin Name
Data
Direction
Internal
Pull-Up
Internal
Pull-Down
Drive
Strength
Drive Value
TRST
Input
Enabled
Disabled
N/A
N/A
TCK
Input
Enabled
Disabled
N/A
N/A
TMS
Input
Enabled
Disabled
N/A
N/A
TDI
Input
Enabled
Disabled
N/A
N/A
TDO
Output
Enabled
Disabled
2-mA driver
High-Z
Test Reset Input (TRST)
The TRST pin is an asynchronous active Low input signal for initializing and resetting the JTAG
TAP controller and associated JTAG circuitry. When TRST is asserted, the TAP controller resets to
the Test-Logic-Reset state and remains there while TRST is asserted. When the TAP controller
enters the Test-Logic-Reset state, the JTAG Instruction Register (IR) resets to the default
instruction, IDCODE.
By default, the internal pull-up resistor on the TRST pin is enabled after reset. Changes to the
pull-up resistor settings on GPIO Port B should ensure that the internal pull-up resistor remains
enabled on PB7/TRST; otherwise JTAG communication could be lost.
5.2.1.2
Test Clock Input (TCK)
The TCK pin is the clock for the JTAG module. This clock is provided so the test logic can operate
independently of any other system clocks. In addition, it ensures that multiple JTAG TAP
controllers that are daisy-chained together can synchronously communicate serial test data
between components. During normal operation, TCK is driven by a free-running clock with a
nominal 50% duty cycle. When necessary, TCK can be stopped at 0 or 1 for extended periods of
time. While TCK is stopped at 0 or 1, the state of the TAP controller does not change and data in
the JTAG Instruction and Data Registers is not lost.
By default, the internal pull-up resistor on the TCK pin is enabled after reset. This assures that no
clocking occurs if the pin is not driven from an external source. The internal pull-up and pull-down
resistors can be turned off to save internal power as long as the TCK pin is constantly being driven
by an external source.
5.2.1.3
Test Mode Select (TMS)
The TMS pin selects the next state of the JTAG TAP controller. TMS is sampled on the rising edge
of TCK. Depending on the current TAP state and the sampled value of TMS, the next state is
entered. Because the TMS pin is sampled on the rising edge of TCK, the IEEE Standard 1149.1
expects the value on TMS to change on the falling edge of TCK.
Holding TMS high for five consecutive TCK cycles drives the TAP controller state machine to the
Test-Logic-Reset state. When the TAP controller enters the Test-Logic-Reset state, the JTAG
Instruction Register (IR) resets to the default instruction, IDCODE. Therefore, this sequence can
be used as a reset mechanism, similar to asserting TRST. The JTAG Test Access Port state
machine can be seen in its entirety in Figure 5-2 on page 50.
48
May 4, 2007
Preliminary
LM3S818 Data Sheet
By default, the internal pull-up resistor on the TMS pin is enabled after reset. Changes to the
pull-up resistor settings on GPIO Port C should ensure that the internal pull-up resistor remains
enabled on PC1/TMS; otherwise JTAG communication could be lost.
5.2.1.4
Test Data Input (TDI)
The TDI pin provides a stream of serial information to the IR chain and the DR chains. TDI is
sampled on the rising edge of TCK and, depending on the current TAP state and the current
instruction, presents this data to the proper shift register chain. Because the TDI pin is sampled on
the rising edge of TCK, the IEEE Standard 1149.1 expects the value on TDI to change on the
falling edge of TCK.
By default, the internal pull-up resistor on the TDI pin is enabled after reset. Changes to the
pull-up resistor settings on GPIO Port C should ensure that the internal pull-up resistor remains
enabled on PC2/TDI; otherwise JTAG communication could be lost.
5.2.1.5
Test Data Output (TDO)
The TDO pin provides an output stream of serial information from the IR chain or the DR chains.
The value of TDO depends on the current TAP state, the current instruction, and the data in the
chain being accessed. In order to save power when the JTAG port is not being used, the TDO pin is
placed in an inactive drive state when not actively shifting out data. Because TDO can be
connected to the TDI of another controller in a daisy-chain configuration, the IEEE Standard
1149.1 expects the value on TDO to change on the falling edge of TCK.
By default, the internal pull-up resistor on the TDO pin is enabled after reset. This assures that the
pin remains at a constant logic level when the JTAG port is not being used. The internal pull-up
and pull-down resistors can be turned off to save internal power if a High-Z output value is
acceptable during certain TAP controller states.
5.2.2
JTAG TAP Controller
The JTAG TAP controller state machine is shown in Figure 5-2 on page 50. The TAP controller
state machine is reset to the Test-Logic-Reset state on the assertion of a Power-On-Reset (POR)
or the assertion of TRST. Asserting the correct sequence on the TMS pin allows the JTAG module
to shift in new instructions, shift in data, or idle during extended testing sequences. For detailed
information on the function of the TAP controller and the operations that occur in each state,
please refer to IEEE Standard 1149.1.
May 4, 2007
49
Preliminary
JTAG Interface
Figure 5-2.
Test Access Port State Machine
Test Logic
1
0
Run Test Idle
0
Select DR Scan
1
Select IR Scan
1
0
1
Capture DR
1
Capture IR
0
0
Shift DR
Shift IR
0
1
Exit 1 DR
Exit 1 IR
1
Pause IR
0
1
Exit 2 DR
0
1
0
Exit 2 IR
1
1
Update DR
5.2.3
1
0
Pause DR
1
0
1
0
0
1
0
0
Update IR
1
0
Shift Registers
The Shift Registers consist of a serial shift register chain and a parallel load register. The serial
shift register chain samples specific information during the TAP controller’s CAPTURE states and
allows this information to be shifted out of TDO during the TAP controller’s SHIFT states. While the
sampled data is being shifted out of the chain on TDO, new data is being shifted into the serial shift
register on TDI. This new data is stored in the parallel load register during the TAP controller’s
UPDATE states. Each of the shift registers is discussed in detail in “Shift Registers” on page 50.
5.2.4
Operational Considerations
There are certain operational considerations when using the JTAG module. Because the JTAG
pins can be programmed to be GPIOs, board configuration and reset conditions on these pins
must be considered. In addition, because the JTAG module has integrated ARM Serial Wire
Debug, the method for switching between these two operational modes requires clarification.
5.2.4.1
GPIO Functionality
When the controller is reset with either a POR or RST, the JTAG port pins default to their JTAG
configurations. The default configuration includes enabling the pull-up resistors (setting GPIOPUR
50
May 4, 2007
Preliminary
LM3S818 Data Sheet
to 1 for PB7 and PC[3:0]) and enabling the alternate hardware function (setting GPIOAFSEL to 1
for PB7 and PC[3:0]) on the JTAG pins.
It is possible for software to configure these pins as GPIOs after reset by writing 0s to PB7 and
PC[3:0]in the GPIOAFSEL register. If the user does not require the JTAG port for debugging or
board-level testing, this provides five more GPIOs for use in the design.
Caution – If the JTAG pins are used as GPIOs in a design, PB7 and PC2 cannot have external
pull-down resistors connected to both of them at the same time. If both pins are pulled Low during
reset, the controller has unpredictable behavior. If this happens, remove one or both of the
pull-down resistors, and apply RST or power-cycle the part
In addition, it is possible to create a software sequence that prevents the debugger from connecting
to the Stellaris microcontroller. If the program code loaded into flash immediately changes the
JTAG pins to their GPIO functionality, the debugger does not have enough time to connect and
halt the controller before the JTAG pin functionality switches. This locks the debugger out of the
part. This can be avoided with a software routine that restores JTAG functionality using an
external trigger.
5.2.4.2
ARM Serial Wire Debug (SWD)
In order to seamlessly integrate the ARM Serial Wire Debug (SWD) functionality, a serial-wire
debugger must be able to connect to the Cortex-M3 core without having to perform, or have any
knowledge of, JTAG cycles. This is accomplished with a SWD preamble that is issued before the
SWD session begins.
The preamble used to enable the SWD interface of the SWJ-DP module starts with the TAP
controller in the Test-Logic-Reset state. From here, the preamble sequences the TAP controller
through the following states: Run Test Idle, Select DR, Select IR, Capture IR, Exit1 IR, Update IR,
Run Test Idle, Select DR, Select IR, Capture IR, Exit1 IR, Update IR, Run Test Idle, Select DR,
Select IR, and Test-Logic-Reset states.
Stepping through the JTAG TAP Instruction Register (IR) load sequences of the TAP state
machine twice without shifting in a new instruction enables the SWD interface and disables the
JTAG interface. For more information on this operation and the SWD interface, see the ARM®
Cortex™-M3 Technical Reference Manual and the ARM® CoreSight Technical Reference Manual.
Because this sequence is a valid series of JTAG operations that could be issued, the ARM JTAG
TAP controller is not fully compliant to the IEEE Standard 1149.1. This is the only instance where
the ARM JTAG TAP controller does not meet full compliance with the specification. Due to the low
probability of this sequence occurring during normal operation of the TAP controller, it should not
affect normal performance of the JTAG interface.
5.3
Initialization and Configuration
After a Power-On-Reset or an external reset (RST), the JTAG pins are automatically configured for
JTAG communication. No user-defined initialization or configuration is needed. However, if the
user application changes these pins to their GPIO function, they must be configured back to their
JTAG functionality before JTAG communication can be restored. This is done by enabling the five
JTAG pins (PB7 and PC[3:0]) for their alternate function using the GPIOAFSEL register.
May 4, 2007
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Preliminary
JTAG Interface
5.4
Register Descriptions
There are no APB-accessible registers in the JTAG TAP Controller or Shift Register chains. The
registers within the JTAG controller are all accessed serially through the TAP Controller. The
registers can be broken down into two main categories: Instruction Registers and Data Registers.
5.4.1
Instruction Register (IR)
The JTAG TAP Instruction Register (IR) is a four-bit serial scan chain with a parallel load register
connected between the JTAG TDI and TDO pins. When the TAP Controller is placed in the correct
states, bits can be shifted into the Instruction Register. Once these bits have been shifted into the
chain and updated, they are interpreted as the current instruction. The decode of the Instruction
Register bits is shown in Table 5-2. A detailed explanation of each instruction, along with its
associated Data Register, follows.
Table 5-2. JTAG Instruction Register Commands
IR[3:0]
Instruction
0000
EXTEST
Drives the values preloaded into the Boundary Scan Chain by the
SAMPLE/PRELOAD instruction onto the pads.
0001
INTEST
Drives the values preloaded into the Boundary Scan Chain by the
SAMPLE/PRELOAD instruction into the controller.
0010
SAMPLE / PRELOAD
1000
ABORT
Shifts data into the ARM Debug Port Abort Register.
1010
DPACC
Shifts data into and out of the ARM DP Access Register.
1011
APACC
Shifts data into and out of the ARM AC Access Register.
1110
IDCODE
Loads manufacturing information defined by the IEEE Standard 1149.1
into the IDCODE chain and shifts it out.
1111
BYPASS
Connects TDI to TDO through a single Shift Register chain.
All Others
Reserved
Defaults to the BYPASS instruction to ensure that TDI is always
connected to TDO.
5.4.1.1
Description
Captures the current I/O values and shifts the sampled values out of the
Boundary Scan Chain while new preload data is shifted in.
EXTEST Instruction
The EXTEST instruction does not have an associated Data Register chain. The EXTEST
instruction uses the data that has been preloaded into the Boundary Scan Data Register using the
SAMPLE/PRELOAD instruction. When the EXTEST instruction is present in the Instruction
Register, the preloaded data in the Boundary Scan Data Register associated with the outputs and
output enables are used to drive the GPIO pads rather than the signals coming from the core. This
allows tests to be developed that drive known values out of the controller, which can be used to
verify connectivity.
5.4.1.2
INTEST Instruction
The INTEST instruction does not have an associated Data Register chain. The INTEST instruction
uses the data that has been preloaded into the Boundary Scan Data Register using the SAMPLE/
PRELOAD instruction. When the INTEST instruction is present in the Instruction Register, the
preloaded data in the Boundary Scan Data Register associated with the inputs are used to drive
the signals going into the core rather than the signals coming from the GPIO pads. This allows
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May 4, 2007
Preliminary
LM3S818 Data Sheet
tests to be developed that drive known values into the controller, which can be used for testing. It
is important to note that although the RST input pin is on the Boundary Scan Data Register chain,
it is only observable.
5.4.1.3
SAMPLE/PRELOAD Instruction
The SAMPLE/PRELOAD instruction connects the Boundary Scan Data Register chain between
TDI and TDO. This instruction samples the current state of the pad pins for observation and
preloads new test data. Each GPIO pad has an associated input, output, and output enable signal.
When the TAP controller enters the Capture DR state during this instruction, the input, output, and
output-enable signals to each of the GPIO pads are captured. These samples are serially shifted
out of TDO while the TAP controller is in the Shift DR state and can be used for observation or
comparison in various tests.
While these samples of the inputs, outputs, and output enables are being shifted out of the
Boundary Scan Data Register, new data is being shifted into the Boundary Scan Data Register
from TDI. Once the new data has been shifted into the Boundary Scan Data Register, the data is
saved in the parallel load registers when the TAP controller enters the Update DR state. This
update of the parallel load register preloads data into the Boundary Scan Data Register that is
associated with each input, output, and output enable. This preloaded data can be used with the
EXTEST and INTEST instructions to drive data into or out of the controller. Please see “Boundary
Scan Data Register” on page 54 for more information.
5.4.1.4
ABORT Instruction
The ABORT instruction connects the associated ABORT Data Register chain between TDI and
TDO. This instruction provides read and write access to the ABORT Register of the ARM Debug
Access Port (DAP). Shifting the proper data into this Data Register clears various error bits or
initiates a DAP abort of a previous request. Please see the “ABORT Data Register” on page 55 for
more information.
5.4.1.5
DPACC Instruction
The DPACC instruction connects the associated DPACC Data Register chain between TDI and
TDO. This instruction provides read and write access to the DPACC Register of the ARM Debug
Access Port (DAP). Shifting the proper data into this register and reading the data output from this
register allows read and write access to the ARM debug and status registers. Please see “DPACC
Data Register” on page 55 for more information.
5.4.1.6
APACC Instruction
The APACC instruction connects the associated APACC Data Register chain between TDI and
TDO. This instruction provides read and write access to the APACC Register of the ARM Debug
Access Port (DAP). Shifting the proper data into this register and reading the data output from this
register allows read and write access to internal components and buses through the Debug Port.
Please see “APACC Data Register” on page 55 for more information.
5.4.1.7
IDCODE Instruction
The IDCODE instruction connects the associated IDCODE Data Register chain between TDI and
TDO. This instruction provides information on the manufacturer, part number, and version of the
ARM core. This information can be used by testing equipment and debuggers to automatically
configure their input and output data streams. IDCODE is the default instruction that is loaded into
the JTAG Instruction Register when a power-on-reset (POR) is asserted, TRST is asserted, or the
Test-Logic-Reset state is entered. Please see “IDCODE Data Register” on page 54 for more
information.
May 4, 2007
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Preliminary
JTAG Interface
5.4.1.8
BYPASS Instruction
The BYPASS instruction connects the associated BYPASS Data Register chain between TDI and
TDO. This instruction is used to create a minimum length serial path between the TDI and TDO
ports. The BYPASS Data Register is a single-bit shift register. This instruction improves test
efficiency by allowing components that are not needed for a specific test to be bypassed in the
JTAG scan chain by loading them with the BYPASS instruction. Please see “BYPASS Data
Register” on page 54 for more information.
5.4.2
Data Registers
The JTAG module contains six Data Registers. These include: IDCODE, BYPASS, Boundary
Scan, APACC, DPACC, and ABORT serial Data Register chains. Each of these Data Registers is
discussed in the following sections.
5.4.2.1
IDCODE Data Register
The format for the 32-bit IDCODE Data Register defined by the IEEE Standard 1149.1 is shown in
Figure 5-3. The standard requires that every JTAG-compliant device implement either the
IDCODE instruction or the BYPASS instruction as the default instruction. The LSB of the IDCODE
Data Register is defined to be a 1 to distinguish it from the BYPASS instruction, which has an LSB
of 0. This allows auto configuration test tools to determine which instruction is the default
instruction.
The major uses of the JTAG port are for manufacturer testing of component assembly, and
program development and debug. To facilitate the use of auto-configuration debug tools, the
IDCODE instruction outputs a value of 0x1BA00477. This value indicates an ARM Cortex-M3,
Version 1 processor. This allows the debuggers to automatically configure themselves to work
correctly with the Cortex-M3 during debug.
Figure 5-3.
IDCODE Register Format
31
TDI
5.4.2.2
28 27
12 11
Version
Part Number
1 0
Manufacturer ID
1
TDO
BYPASS Data Register
The format for the 1-bit BYPASS Data Register defined by the IEEE Standard 1149.1 is shown in
Figure 5-4. The standard requires that every JTAG-compliant device implement either the
BYPASS instruction or the IDCODE instruction as the default instruction. The LSB of the BYPASS
Data Register is defined to be a 0 to distinguish it from the IDCODE instruction, which has an LSB
of 1. This allows auto configuration test tools to determine which instruction is the default
instruction.
Figure 5-4.
BYPASS Register Format
0
TDI
5.4.2.3
0
TDO
Boundary Scan Data Register
The format of the Boundary Scan Data Register is shown in Figure 5-5. Each GPIO pin, in a
counter-clockwise direction from the JTAG port pins, is included in the Boundary Scan Data
Register. Each GPIO pin has three associated digital signals that are included in the chain. These
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May 4, 2007
Preliminary
LM3S818 Data Sheet
signals are input, output, and output enable, and are arranged in that order as can be seen in the
figure. In addition to the GPIO pins, the controller reset pin, RST, is included in the chain. Because
the reset pin is always an input, only the input signal is included in the Data Register chain.
When the Boundary Scan Data Register is accessed with the SAMPLE/PRELOAD instruction, the
input, output, and output enable from each digital pad are sampled and then shifted out of the
chain to be verified. The sampling of these values occurs on the rising edge of TCK in the Capture
DR state of the TAP controller. While the sampled data is being shifted out of the Boundary Scan
chain in the Shift DR state of the TAP controller, new data can be preloaded into the chain for use
with the EXTEST and INTEST instructions. These instructions either force data out of the
controller, with the EXTEST instruction, or into the controller, with the INTEST instruction.
Figure 5-5.
TDI
I
N
Boundary Scan Register Format
O
U
T
O
E
...
GPIO PB6
I
N
O
U
T
GPIO m
O
E
I
N
RST
I
N
O
U
T
GPIO m+1
O
E
...
I
N
O
U
T
O TDO
E
GPIO n
For detailed information on the order of the input, output, and output enable bits for each of the
GPIO ports, please refer to the Stellaris Family Boundary Scan Description Language (BSDL)
files, downloadable from www.luminarymicro.com.
5.4.2.4
APACC Data Register
The format for the 35-bit APACC Data Register defined by ARM is described in the ARM®
Cortex™-M3 Technical Reference Manual.
5.4.2.5
DPACC Data Register
The format for the 35-bit DPACC Data Register defined by ARM is described in the ARM®
Cortex™-M3 Technical Reference Manual.
5.4.2.6
ABORT Data Register
The format for the 35-bit ABORT Data Register defined by ARM is described in the ARM®
Cortex™-M3 Technical Reference Manual.
May 4, 2007
55
Preliminary
System Control
6
System Control
System control determines the overall operation of the device. It provides information about the
device, controls the clocking of the device and individual peripherals, and handles reset detection
and reporting.
6.1
Functional Description
The System Control module provides the following capabilities:
6.1.1
„
Device identification, see page 56
„
Local control, such as reset (see page 56), power (see page 59) and clock control (see
page 59)
„
System control (Run, Sleep, and Deep-Sleep modes), see page 61
Device Identification
Seven read-only registers provide software with information on the microcontroller, such as
version, part number, SRAM size, Flash size, and other features. See the DID0, DID1 and
DC0-DC4 registers starting on page 64.
6.1.2
Reset Control
This section discusses aspects of hardware functions during reset as well as system software
requirements following the reset sequence.
6.1.2.1
Reset Sources
The controller has six sources of reset:
1. External reset input pin (RST) assertion, see page 56.
2. Power-on reset (POR), see page 57.
3. Internal brown-out (BOR) detector, see page 57.
4. Software-initiated reset (with the software reset registers), see page 58.
5. A watchdog timer reset condition violation, see page 58.
6. Internal low drop-out (LDO) regulator output, see page 59.
After a reset, the Reset Cause (RESC) register (see page 83) is set with the reset cause. The bits
in this register are sticky and maintain their state across multiple reset sequences, except when an
external reset is the cause, and then all the other bits in the RESC register are cleared.
Note:
6.1.2.2
The main oscillator is used for external resets and power-on resets; the internal oscillator
is used during the internal process by internal reset and clock verification circuitry.
RST Pin Assertion
The external reset pin (RST) resets the controller. This resets the core and all the peripherals
except the JTAG TAP controller (see “JTAG Interface” on page 46). The external reset sequence is
as follows:
1. The external reset pin (RST) is asserted and then de-asserted.
2. After RST is de-asserted, the main crystal oscillator must be allowed to settle and there is an
internal main oscillator counter that takes from 15-30 ms to account for this. During this time,
internal reset to the rest of the controller is held active.
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May 4, 2007
Preliminary
LM3S818 Data Sheet
3. The internal reset is released and the controller fetches and loads the initial stack pointer, the
initial program counter, and the first instruction designated by the program counter, and then
begins execution.
The external reset timing is shown in Figure 20-8 on page 387.
6.1.2.3
Power-On Reset (POR)
The Power-On Reset (POR) circuitry detects a rise in power-supply voltage and generates an
on-chip reset pulse. To use the on-chip circuitry, the RST input needs a pull-up resistor (1K to
10K Ω).
The device must be operating within the specified operating parameters at the point when the
on-chip power-on reset pulse is complete. The specified operating parameters include supply
voltage, frequency, temperature, and so on. If the operating conditions are not met at the point of
POR end, the Stellaris controller does not operate correctly. In this case, the reset must be
extended using external circuitry. The RST input may be used with the circuit as shown in
Figure 6-1.
Figure 6-1.
External Circuitry to Extend Reset
Stellaris
D1
R1
RST
C1
R2
The R1 and C1 components define the power-on delay. The R2 resistor mitigates any leakage from
the RST input. The diode discharges C1 rapidly when the power supply is turned off.
The Power-On Reset sequence is as follows:
1. The controller waits for the later of external reset (RST) or internal POR to go inactive.
2. After the resets are inactive, the main crystal oscillator must be allowed to settle and there is
an internal main oscillator counter that takes from 15-30 ms to account for this. During this
time, internal reset to the rest of the controller is held active.
3. The internal reset is released and the controller fetches and loads the initial stack pointer, the
initial program counter, and the first instruction designated by the program counter, and then
begins execution.
The internal POR is only active on the initial power-up of the controller. The Power-On Reset
timing is shown in Figure 20-9 on page 387.
6.1.2.4
Brown-Out Reset (BOR)
A drop in the input voltage resulting in the assertion of the internal brown-out detector can be used
to reset the controller. This is initially disabled and may be enabled by software.
The system provides a brown-out detection circuit that triggers if VDD drops below VBTH. The
circuit is provided to guard against improper operation of logic and peripherals that operate off VDD
and not the LDO voltage. If a brown-out condition is detected, the system may generate a
controller interrupt or a system reset. The BOR circuit has a digital filter that protects against
noise-related detection. This feature may be optionally enabled.
May 4, 2007
57
Preliminary
System Control
Brown-out resets are controlled with the Power-On and Brown-Out Reset Control (PBORCTL)
register (see page 74). The BORIOR bit in the PBORCTL register must be set for a brown-out to
trigger a reset. The brown-out reset sequence is as follows:
1. When VDD drops below VBTH, an internal BOR condition is set.
2. If the BORWT bit in the PBORCTL register is set, the BOR condition is resampled sometime
later (specified by BORTIM) to determine if the original condition was caused by noise. If the
BOR condition is not met the second time, then no action is taken.
3. If the BOR condition exists, an internal reset is asserted.
4. The internal reset is released and the controller fetches and loads the initial stack pointer, the
initial program counter, and the first instruction designated by the program counter, and then
begins execution.
5. The internal BOR signal is released after 500 µs to prevent another BOR condition from being
set before software has a chance to investigate the original cause.
The internal Brown-Out Reset timing is shown in Figure 20-10 on page 387.
6.1.2.5
Software Reset
Each peripheral can be reset by software. There are three registers that control this function (see
the SRCRn registers, starting on page 76). If the bit position corresponding to a peripheral is set,
the peripheral is reset. The encoding of the reset registers is consistent with the encoding of the
clock gating control for peripherals and on-chip functions (see “System Control” on page 61).
Writing a bit lane with a value of 1 initiates a reset of the corresponding unit. Note that all reset
signals for all clocks of the specified unit are asserted as a result of a software-initiated reset.
The entire system can be reset by software also. Setting the SYSRESETREQ bit in the Cortex-M3
Application Interrupt and Reset Control register resets the entire system including the core. The
software-initiated system reset sequence is as follows:
1. A software system reset in initiated by writing the SYSRESETREQ bit in the ARM Cortex-M3
Application Interrupt and Reset Control register.
2. An internal reset is asserted.
3. The internal reset is released and the controller fetches and loads the initial stack pointer, the
initial program counter, and the first instruction designated by the program counter, and then
begins execution.
The software-initiated system reset timing is shown in Figure 20-11 on page 387.
6.1.2.6
Watchdog Timer Reset
The watchdog timer module's function is to prevent system hangs. The watchdog timer can be
configured to generate an interrupt to the controller on its first time-out, and to generate a reset
signal on its second time-out.
After the first time-out event, the 32-bit counter is reloaded with the value of the Watchdog Timer
Load (WDTLOAD) register (see page 188), and the timer resumes counting down from that value.
If the timer counts down to its zero state again before the first time-out interrupt is cleared, and the
reset signal has been enabled, the watchdog timer asserts its reset signal to the system. The
watchdog timer reset sequence is as follows:
1. The watchdog timer times out for the second time without being serviced.
2. An internal reset is asserted.
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May 4, 2007
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LM3S818 Data Sheet
3. The internal reset is released and the controller fetches and loads the initial stack pointer, the
initial program counter, and the first instruction designated by the program counter, and then
begins execution.
The watchdog reset timing is shown in Figure 20-12 on page 388.
6.1.2.7
Low Drop-Out
A reset can be initiated when the internal low drop-out (LDO) regulator output goes unregulated.
This is initially disabled and may be enabled by software. LDO is controlled with the LDO Power
Control (LDOPCTL) register (see page 75). The LDO reset sequence is as follows:
1. LDO goes unregulated and the LDOARST bit in the LDOARST register is set.
2. An internal reset is asserted.
3. The internal reset is released and the controller fetches and loads the initial stack pointer, the
initial program counter, and the first instruction designated by the program counter, and then
begins execution.
The LDO reset timing is shown in Figure 20-13 on page 388.
6.1.3
Power Control
The LDO regulator permits the adjustment of the on-chip output voltage (VOUT). The output may
be adjusted in 50 mV increments between the range of 2.25 V through 2.75 V. The adjustment is
made through the VADJ field of the LDO Power Control (LDOPCTL) register (see page 75).
6.1.4
Clock Control
System control determines the clocking and control of clocks in this part.
6.1.4.1
Fundamental Clock Sources
There are two fundamental clock sources for use in the device:
„
The main oscillator, driven from either an external crystal or a single-ended source. As a
crystal, the main oscillator source is specified to run from 1-8 MHz. However, when the crystal
is being used as the PLL source, it must be from 3.579545–8.192 MHz to meet PLL
requirements. As a single-ended source, the range is from DC to the specified speed of the
device.
„
The internal oscillator, which is an on-chip free running clock. The internal oscillator is
specified to run at 15 MHz ± 50%. It can be used to clock the system, but the tolerance of
frequency range must be met.
The internal system clock may be driven by either of the above two reference sources as well as
the internal PLL, provided that the PLL input is connected to a clock source that meets its AC
requirements.
Nearly all of the control for the clocks is provided by the Run-Mode Clock Configuration (RCC)
register (see page 84).
Figure 6-2 shows the logic for the main clock tree. The peripheral blocks are driven by the System
Clock signal and can be programmatically enabled/disabled. The ADC clock signal is
automatically divided down to 14-18 MHz for proper ADC operation. The PWM clock signal is a
synchronous divide by of the system clock to provide the PWM circuit with more range.
May 4, 2007
59
Preliminary
System Control
Figure 6-2.
Main Clock Tree
USESYSDIVa
OSC1
OSC2
Main
Osc
1-8 MHz
System Clock
SYSDIVa
Internal
Osc
15 MHz
PLL
(200 MHz
output )
÷4
a
OSCSRC
OEN
a
PWRDNa
PWM Clock
a
PWMDIV
XTALa
BYPASS a
USEPWMDIVa
Constant
Divide
a. These are bit fields within the Run-Mode Clock Configuration (RCC) register.
6.1.4.2
(16.667 MHz output )
ADC Clock
PLL Frequency Configuration
The user does not have direct control over the PLL frequency, but is required to match the external
crystal used to an internal PLL-Crystal table. This table is used to create the best fit for PLL
parameters to the crystal chosen. Not all crystals result in the PLL operating at exactly 200 MHz,
though the frequency is within ±1%. The result of the lookup is kept in the XTAL to PLL
Translation (PLLCFG) register (see page 89).
Table 6-4 on page 88 describes the available crystal choices and default programming of the
PLLCFG register. The crystal number is written into the XTAL field of the Run-Mode Clock
Configuration (RCC) register (see page 84). Any time the XTAL field changes, a read of the
internal table is performed to get the correct value. Table 6-4 on page 88 describes the available
crystal choices and default programming values.
6.1.4.3
PLL Modes
The PLL has two modes of operation: Normal and Power-Down
„
Normal: The PLL multiplies the input clock reference and drives the output.
„
Power-Down: Most of the PLL internal circuitry is disabled and the PLL does not drive the
output.
The modes are programmed using the RCC register fields as shown in Table 6-4 on page 88.
6.1.4.4
PLL Operation
If the PLL configuration is changed, the PLL output is not stable for a period of time (PLL
TREADY=0.5 ms) and during this time, the PLL is not usable as a clock reference.
The PLL is changed by one of the following:
„
Change to the XTAL value in the RCC register (see page 84)—writes of the same value do not
cause a relock.
„
Change in the PLL from Power-Down to Normal mode.
A counter is defined to measure the TREADY requirement. The counter is clocked by the main
oscillator. The range of the main oscillator has been taken into account and the down counter is
set to 0x1200 (that is, ~600 µs at a 8.192-MHz external oscillator clock). Hardware is provided to
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May 4, 2007
Preliminary
LM3S818 Data Sheet
keep the PLL from being used as a system clock until the TREADY condition is met after one of the
two changes above. It is the user's responsibility to have a stable clock source (like the main
oscillator) before the RCC register is switched to use the PLL.
6.1.4.5
Clock Verification Timers
There are three identical clock verification circuits that can be enabled though software. The circuit
checks the faster clock by a slower clock using timers:
„
The main oscillator checks the PLL.
„
The main oscillator checks the internal oscillator.
„
The internal oscillator divided by 64 checks the main oscillator.
If the verification timer function is enabled and a failure is detected, the main clock tree is
immediately switched to a working clock and an interrupt is generated to the controller. Software
can then determine the course of action to take. The actual failure indication and clock switching
does not clear without a write to the CLKVCLR register, an external reset, or a POR reset. The
clock verification timers are controlled by the PLLVER, IOSCVER, and MOSCVER bits in the RCC
register (see page 84).
6.1.5
System Control
For power-savings purposes, the RCGCn, SCGCn, and DCGCn registers control the clock gating
logic for each peripheral or block in the system while the controller is in Run, Sleep, and
Deep-Sleep mode, respectively. The DC1, DC2 and DC4 registers act as a write mask for the
RCGCn, SCGCn, and DCGCn registers.
In Run mode, the controller is actively executing code. In Sleep mode, the clocking of the device is
unchanged but the controller no longer executes code (and is no longer clocked). In Deep-Sleep
mode, the clocking of the device may change (depending on the Run mode clock configuration)
and the controller no longer executes code (and is no longer clocked). An interrupt returns the
device to Run mode from one of the sleep modes; the sleep modes are entered on request from
the code. Each mode is described in more detail in this section.
6.1.5.1
Run Mode
Run mode provides normal operation of the processor and all of the peripherals that are currently
enabled by the RCGCn registers. The system clock can be any of the available clock sources
including the PLL.
6.1.5.2
Sleep Mode
In Sleep mode, the Cortex-M3 processor core and the memory subsystem are not clocked.
Peripherals are clocked that are enabled in the SCGCn register when Auto Clock Gating is
enabled (see RCC register on page 84) or the RCGCn register when the Auto Clock Gating is
disabled. The System Clock has the same source and frequency as that during Run mode.
6.1.5.3
Deep-Sleep Mode
The Cortex-M3 processor core and the memory subsystem are not clocked. Peripherals are
clocked that are enabled in the DCGCn register when Auto Clock Gating is enabled (see RCC
register) or the RCGCn register when the Auto Clock Gating is disabled. The system clock source
is the main oscillator by default or the internal oscillator specified in the DSLPCLKCFG register if
one is enabled (see page 95). When the DSLPCLKCFG register is used, the internal oscillator is
powered up, if necessary, and the main oscillator is powered down. If the PLL is running at the
time of the WFI instruction, hardware powers the PLL down and overrides the SYSDIV field of the
active RCC register to be /16 or /64 respectively. When the Deep-Sleep exit event occurs,
May 4, 2007
61
Preliminary
System Control
hardware brings the system clock back to the source and frequency it had at the onset of
Deep-Sleep mode before enabling the clocks that were stopped during the Deep-Sleep duration.
6.2
Initialization and Configuration
The PLL is configured using direct register writes to the Run-Mode Clock Configuration (RCC)
register. The steps required to successfully change the PLL-based system clock are:
1. Bypass the PLL and system clock divider by setting the BYPASS bit and clearing the USESYS
bit in the RCC register. This configures the system to run off a “raw” clock source (using the
main oscillator or internal oscillator) and allows for the new PLL configuration to be validated
before switching the system clock to the PLL.
2. Select the crystal value (XTAL) and oscillator source (OSCSRC), and clear the PWRDN and OEN
bits in RCC. Setting the XTAL field automatically pulls valid PLL configuration data for the
appropriate crystal, and clearing the PWRDN and OEN bits powers and enables the PLL and its
output.
3. Select the desired system divider (SYSDIV) and set the USESYS bit in RCC. The SYSDIV field
determines the system frequency for the microcontroller.
4. Wait for the PLL to lock by polling the PLLLRIS bit in the Raw Interrupt Status (RIS) register.
If the PLL doesn’t lock, the configuration is invalid.
5. Enable use of the PLL by clearing the BYPASS bit in RCC.
Important: If the BYPASS bit is cleared before the PLL locks, it is possible to render the device
unusable.
6.3
Register Map
Table 6-1 lists the System Control registers, grouped by function. The offset listed is a
hexadecimal increment to the register’s address, relative to the System Control base address of
0x400FE000.
Table 6-1. System Control Register Map
Offset
Name
Reset
Type
Description
See
page
Device Identification and Capabilities
0x000
DID0
-
RO
Device identification 0
64
0x004
DID1
-
RO
Device identification 1
65
0x008
DC0
0x001F001F
RO
Device capabilities 0
67
0x010
DC1
0x001133BF
RO
Device capabilities 1
68
0x014
DC2
0x01070113
RO
Device capabilities 2
70
0x018
DC3
0x3F3F01FF0
x173F01FF
RO
Device Capabilities 3
71
0x01C
DC4
0x0000001F
RO
Device Capabilities 4
73
Local Control
62
May 4, 2007
Preliminary
LM3S818 Data Sheet
Table 6-1. System Control Register Map (Continued)
Offset
Name
0x030
See
page
Reset
Type
Description
PBORCTL
0x00007FFD
R/W
Power-On and Brown-Out Reset Control
74
0x034
LDOPCTL
0x00000000
R/W
LDO Power Control
75
0x040
SRCR0
0x00000000
R/W
Software Reset Control 0
76
0x044
SRCR1
0x00000000
R/W
Software Reset Control 1
77
0x048
SRCR2
0x00000000
R/W
Software Reset Control 2
78
0x050
RIS
0x00000000
RO
Raw Interrupt Status
79
0x054
IMC
0x00000000
R/W
Interrupt Mask Control
80
0x058
MISC
0x00000000
R/W1C
Masked Interrupt Status and Clear
82
0x05C
RESC
-
R/W
Reset Cause
83
0x060
RCC
0x078E3AC0
R/W
Run-Mode Clock Configuration
84
0x064
PLLCFG
-
RO
XTAL to PLL translation
89
System Control
0x100
RCGC0
0x00000000
R/W
Run-Mode Clock Gating Control 0
90
0x104
RCGC1
0x00000000
R/W
Run-Mode Clock Gating Control 1
92
0x108
RCGC2
0x00000000
R/W
Run-Mode Clock Gating Control 2
94
0x110
SCGC0
0x00000001
R/W
Sleep-Mode Clock Gating Control 0
90
0x114
SCGC1
0x00000000
R/W
Sleep-Mode Clock Gating Control 1
92
0x118
SCGC2
0x00000000
R/W
Sleep-Mode Clock Gating Control 2
94
0x120
DCGC0
0x00000001
R/W
Deep-Sleep-Mode Clock Gating Control 0
90
0x124
DCGC1
0x00000000
R/W
Deep-Sleep-Mode Clock Gating Control 1
92
0x128
DCGC2
0x00000000
R/W
Deep-Sleep-Mode Clock Gating Control 2
94
0x144
DSLPCLKCFG
0x07800000
R/W
Deep-Sleep Clock Configuration
95
0x150
CLKVCLR
0x00000000
R/W
Clock verification clear
96
0x160
LDOARST
0x00000000
R/W
Allow unregulated LDO to reset the part
97
6.4
Register Descriptions
The remainder of this section lists and describes the System Control registers, in numerical order
by address offset.
May 4, 2007
63
Preliminary
System Control
Register 1: Device Identification 0 (DID0), offset 0x000
This register identifies the version of the device.
Device Identification 0 (DID0)
Offset 0x000
31
30
reserved
Type
Reset
29
28
27
26
25
24
23
22
21
20
19
18
17
16
reserved
VER
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
MINOR
MAJOR
Type
Reset
Bit/Field
Name
Type
Reset
Description
31
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
30:28
VER
RO
0
This field defines the version of the DID0 register format:
0=Register version for the Stellaris microcontrollers
27:16
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
15:8
MAJOR
RO
-
This field specifies the major revision number of the device.
The major revision number is indicated in the part number
as a letter (A for first revision, B for second, and so on).
This field is encoded as follows:
0: Revision A (initial device)
1: Revision B (first revision)
and so on.
7:0
MINOR
RO
-
This field specifies the minor revision number of the device.
This field is numeric and is encoded as follows:
0: No changes. Major revision was most recent update.
1: One interconnect change made since last major revision
update.
2: Two interconnect changes made since last major revision
update.
and so on.
64
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 2: Device Identification 1 (DID1), offset 0x004
This register identifies the device family, part number, temperature range, and package type.
Note:
The bit diagram indicates some values are device-specific. The table below indicates
values for your part.
Device Identification 1 (DID1)
Offset 0x004
31
30
29
28
27
26
RO
0
25
24
23
22
21
20
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
-
RO
-
RO
-
RO
-
15
14
13
12
11
10
9
8
7
6
5
4
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
0
FAM
VER
Type
Reset
18
17
16
RO
-
RO
-
RO
-
RO
-
3
2
1
0
PARTNO
reserved
Type
Reset
19
TEMP
Bit/Field
Name
Type
Reset
31:28
VER
RO
0x0
RO
0
RoHS
PKG
RO
1
RO
1
QUAL
RO
-
RO
-
Description
This field defines the version of the DID1 register format:
0=Register version for the Stellaris microcontrollers
27:24
FAM
RO
0x0
Family
This field provides the family identification of the device
within the Luminary Micro product portfolio.
The 0x0 value indicates the Stellaris family of
microcontrollers.
23:16
PARTNO
RO
0x37
Part Number
This field provides the part number of the device within the
family.
The 0x37 value indicates the LM3S818 microcontroller.
15:8
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
7:5
TEMP
RO
1
Temperature Range
This field specifies the temperature rating of the device. A
value of 1 indicates the industrial temperature range (-40°C
to 85°C).
4:3
PKG
RO
0x1
2
RoHS
RO
1
This field specifies the package type. A value of 1 indicates
a 48-pin LQFP package.
RoHS-Compliance
A 1 in this bit specifies the device is RoHS-compliant.
May 4, 2007
65
Preliminary
System Control
Bit/Field
Name
Type
Reset
1:0
QUAL
RO
see table
Description
This field specifies the qualification status of the device.
This field is encoded as follows:
QUAL
66
Description
00
Engineering Sample (unqualified)
01
Pilot Production (unqualified)
10
Fully Qualified
11
Reserved
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 3: Device Capabilities 0 (DC0), offset 0x008
This register is predefined by the part and can be used to verify features.
Note:
The bit diagram indicates the values are device-specific. The table below indicates values
for your specific part.
Device Capabilities Register 0 (DC0)
Offset 0x004
31
30
29
28
27
26
25
24
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
15
14
13
12
11
10
9
8
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
23
22
21
20
19
18
17
16
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
7
6
5
4
3
2
1
0
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
SRAMSZ
Type
Reset
FLSHSZ
Type
Reset
Bit/Field
Name
Type
Reset
Description
31:16
SRAMSZ
RO
0x001F
Indicates the size of the on-chip SRAM. A value of 0x001F
indicates 8 KB of SRAM.
15:0
FLSHSZ
RO
0x001F
Indicates the size of the on-chip flash memory. A value of
0x001F indicates 64 KB of Flash.
May 4, 2007
67
Preliminary
System Control
Register 4: Device Capabilities 1 (DC1), offset 0x010
This register is predefined by the part and can be used to verify features.
Device Capabilities 1 (DC1)
Offset 0x010
31
30
29
28
27
26
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
RO
1
RO
0
25
24
23
22
21
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
0
RO
0
RO
0
RO
1
10
9
8
7
6
5
4
3
2
1
0
MPU
reserved
TEMP
PLL
WDT
SWO
SWD
JTAG
RO
1
RO
0
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
reserved
Type
Reset
MINSYSDIV
Type
Reset
RO
0
RO
0
RO
1
19
PWM
MAXADCSPD
RO
0
20
RO
1
RO
1
18
17
16
ADC
reserved
Bit/Field
Name
Type
Reset
Description
31:21
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
20
PWMa
RO
1
A 1 in this bit indicates the presence of the PWM module.
19:17
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
16
ADCa
RO
1
A 1 in this bit indicates the presence of the ADC module.
15:12
MINSYSDIV
RO
0x03
The reset value is hardware-dependent. A value of 0x03
specifies a 50-MHz CPU clock with a PLL divider of 4.See
the RCC register (page 84) for how to change the system
clock divisor using the SYSDIV bit.
11:8
MAXADCSPDa
RO
0x3
This field indicates the maximum rate at which the ADC
samples data. A value of 0x3 indicates 1M samples per
second.
7
MPU
RO
1
This bit indicates whether the Memory Protection Unit
(MPU) in the Cortex-M3 is available. A 0 in this bit indicates
the MPU is not available; a 1 indicates the MPU is
available.
See the ARM® Cortex™-M3 Technical Reference Manual
for details on the MPU.
6
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
5
TEMP
RO
1
This bit specifies the presence of an internal temperature
sensor.
4
PLL
RO
1
A 1 in this bit indicates the presence of an implemented
PLL in the device.
3
WDTa
RO
1
A 1 in this bit indicates a watchdog timer on the device.
68
May 4, 2007
Preliminary
LM3S818 Data Sheet
Bit/Field
Name
Type
Reset
Description
2
SWOa
RO
1
A 1 in this bit indicates the presence of the ARM Serial Wire
Output (SWO) trace port capabilities.
1
SWDa
RO
1
A 1 in this bit indicates the presence of the ARM Serial Wire
Debug (SWD) capabilities.
0
JTAGa
RO
1
A 1 in this bit indicates the presence of a JTAG port.
a. These bits mask the Run-Mode Clock Gating Control 0 (RCGC0) register (see page 113), Sleep-Mode Clock Gating Control 0
(SCGC0) register (see page 113), and Deep-Sleep-Mode Clock Gating Control 0 (DCGC0) register (see page 113). Bits that are
not noted are passed as 0. ADCSP is clipped to the maximum value specified in DC1.
May 4, 2007
69
Preliminary
System Control
Register 5: Device Capabilities 2 (DC2), offset 0x014
This register is predefined by the part and can be used to verify features.
Device Capabilities 2 (DC2)
Offset 0x014
31
30
29
RO
0
RO
0
RO
0
15
14
RO
0
RO
0
28
27
26
25
RO
0
RO
0
RO
0
RO
0
13
12
11
10
9
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
23
22
RO
1
RO
0
RO
0
8
7
6
21
20
19
RO
0
RO
0
RO
0
RO
1
RO
1
RO
1
5
4
3
2
1
0
reserved
QEI
RO
1
18
reserved
COMP0
reserved
Type
Reset
24
RO
0
RO
0
16
GPTM2 GPTM1 GPTM0
SSI
RO
0
17
RO
1
reserved
RO
0
UART1 UART0
RO
0
RO
1
RO
1
Bit/Field
Name
Type
Reset
Description
31:25
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
24
COMP0
RO
1
A 1 in this bit indicates the presence of analog
comparator 0.
23:19
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
18
GPTM2
RO
1
A 1 in this bit indicates the presence of General-Purpose
Timer module 2.
17
GPTM1
RO
1
A 1 in this bit indicates the presence of General-Purpose
Timer module 1.
16
GPTM0
RO
1
A 1 in this bit indicates the presence of General-Purpose
Timer module 0.
15:9
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
8
QEI
RO
1
A 1 in this bit indicates the presence of the QEI module.
7:5
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
4
SSI
RO
1
A 1 in this bit indicates the presence of the SSI module.
3:2
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
1
UART1
RO
1
A 1 in this bit indicates the presence of the UART1 module.
0
UART0
RO
1
A 1 in this bit indicates the presence of the UART0 module.
70
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 6: Device Capabilities 3 (DC3), offset 0x018
This register is predefined by the part and can be used to verify features.
Device Capabilities 3 (DC3)
Offset 0x018
31
30
29
27
26
25
24
22
21
20
19
18
17
16
CCP4
reserved
CCP2
CCP1
CCP0
ADC5
ADC4
ADC3
ADC2
ADC1
ADC0
RO
0
RO
0
RO
1
RO
0
RO
1
RO
1
RO
1
RO
0
RO
0
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
C0o
C0+
C0-
PWM5
PWM4
PWM3
PWM2
PWM1
PWM0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
reserved
Type
Reset
23
RO
0
reserved
Type
Reset
28
RO
0
reserved
Bit/Field
Name
Type
Reset
Description
31:29
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
28
CCP4
RO
1
A 1 in this bit indicates the presence of the Capture/
Compare/PWM pin 4.
27
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
26
CCP2
RO
1
A 1 in this bit indicates the presence of the Capture/
Compare/PWM pin 2.
25
CCP1
RO
1
A 1 in this bit indicates the presence of the Capture/
Compare/PWM pin 1.
24
CCP0
RO
1
A 1 in this bit indicates the presence of the Capture/
Compare/PWM pin 0.
23:22
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
21
ADC5
RO
1
A 1 in this bit indicates the presence of the ADC5 pin.
20
ADC4
RO
1
A 1 in this bit indicates the presence of the ADC4 pin.
19
ADC3
RO
1
A 1 in this bit indicates the presence of the ADC3 pin.
18
ADC2
RO
1
A 1 in this bit indicates the presence of the ADC2 pin.
17
ADC1
RO
1
A 1 in this bit indicates the presence of the ADC1 pin.
16
ADC0
RO
1
A 1 in this bit indicates the presence of the ADC0 pin.
15:9
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
8
C0o
RO
1
A 1 in this bit indicates the presence of the C0o pin.
7
C0+
RO
1
A 1 in this bit indicates the presence of the C0+ pin.
6
C0-
RO
1
A 1 in this bit indicates the presence of the C0- pin.
May 4, 2007
71
Preliminary
System Control
Bit/Field
Name
Type
Reset
Description
5
PWM5
RO
1
A 1 in this bit indicates the presence of the PWM5 pin.
4
PWM4
RO
1
A 1 in this bit indicates the presence of the PWM4 pin.
3
PWM3
RO
1
A 1 in this bit indicates the presence of the PWM3 pin.
2
PWM2
RO
1
A 1 in this bit indicates the presence of the PWM2 pin.
1
PWM1
RO
1
A 1 in this bit indicates the presence of the PWM1 pin.
0
PWM0
RO
1
A 1 in this bit indicates the presence of the PWM0 pin.
72
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 7: Device Capabilities 4 (DC4), offset 0x01C
This register is predefined by the part and can be used to verify features.
Device Capabilities 4 (DC4)
Offset 0x01C
31
30
29
28
27
26
25
24
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
PORTE PORTD PORTC PORTB PORTA
RO
1
RO
1
RO
1
RO
1
RO
1
Bit/Field
Name
Type
Reset
Description
31:5
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
4
PORTE
RO
1
A 1 in this bit indicates the presence of GPIO Port E.
3
PORTD
RO
1
A 1 in this bit indicates the presence of GPIO Port D.
2
PORTC
RO
1
A 1 in this bit indicates the presence of GPIO Port C.
1
PORTB
RO
1
A 1 in this bit indicates the presence of GPIO Port B.
0
PORTA
RO
1
A 1 in this bit indicates the presence of GPIO Port A.
May 4, 2007
73
Preliminary
System Control
Register 8: Power-On and Brown-Out Reset Control (PBORCTL), offset 0x030
This register is responsible for controlling reset conditions after initial power-on reset.
Power-On and Brown-Out Reset Control (PBORCTL)
Offset 0x030
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R/W
0
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
reserved
Type
Reset
BORTIM
Type
Reset
Bit/Field
Name
Type
Reset
31:16
reserved
RO
0
15:2
BORTIM
R/W
0x1FFF
BORIOR BORWT
R/W
1
R/W
0
R/W
1
Description
Reserved bits return an indeterminate value, and should
never be changed.
This field specifies the number of internal oscillator clocks
delayed before the BOR output is resampled if the BORWT
bit is set.
The width of this field is derived by the tBOR width of 500 µs
and the internal oscillator (IOSC) frequency of 15 MHz ±
50%. At +50%, the counter value has to exceed 10,000.
1
BORIOR
R/W
0
BOR Interrupt or Reset
This bit controls how a BOR event is signaled to the
controller. If set, a reset is signaled. Otherwise, an interrupt
is signaled.
0
BORWT
R/W
1
BOR Wait and Check for Noise
This bit specifies the response to a brown-out signal
assertion. If BORWT is set to 1, the controller waits BORTIM
IOSC periods before resampling the BOR output, and if
asserted, it signals a BOR condition interrupt or reset. If the
BOR resample is deasserted, the cause of the initial
assertion was likely noise and the interrupt or reset is
suppressed. If BORWT is 0, BOR assertions do not resample
the output and any condition is reported immediately if
enabled.
74
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 9: LDO Power Control (LDOPCTL), offset 0x034
The VADJ field in this register adjusts the on-chip output voltage (VOUT).
LDO Power Control (LDOPCTL)
Offset 0x034
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
VADJ
Bit/Field
Name
Type
Reset
31:6
reserved
RO
0
5:0
VADJ
R/W
0x0
Table 6-2.
Description
Reserved bits return an indeterminate value, and should
never be changed.
This field sets the on-chip output voltage. The programming
values for the VADJ field are provided in Table 6-2.
VADJ to VOUT
VADJ Value
VOUT (V)
VADJ Value
VOUT (V)
VADJ Value
VOUT (V)
0x1B
2.75
0x1F
2.55
0x03
2.35
0x1C
2.70
0x00
2.50
0x04
2.30
0x1D
2.65
0x01
2.45
0x05
2.25
0x1E
2.60
0x02
2.40
0x06-0x3F
Reserved
May 4, 2007
75
Preliminary
System Control
Register 10: Software Reset Control 0 (SRCR0), offset 0x040
Writes to this register are masked by the bits in the Device Capabilities 1 (DC1) register (see
page 68).
Software Reset Control 0 (SRCR0)
Offset 0x040
31
30
29
28
27
26
25
24
23
22
21
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
RO
0
RO
0
RO
0
R/W
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
20
PWM
18
17
R/W
0
16
ADC
reserved
WDT
reserved
Type
Reset
19
reserved
RO
0
RO
0
RO
0
Bit/Field
Name
Type
Reset
Description
31:21
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
20
PWM
R/W
0
Reset control for the PWM units.
19:17
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
16
ADC
R/W
0
Reset control for the ADC unit.
15:4
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
3
WDT
R/W
0
Reset control for the Watchdog unit.
2:0
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
76
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 11: Software Reset Control 1 (SRCR1), offset 0x044
Writes to this register are masked by the bits in the Device Capabilities 2 (DC2) register (see
page 70).
Software Reset Control 1 (SRCR1)
Offset 0x044
31
30
29
28
27
26
25
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
RO
0
23
22
R/W
0
RO
0
RO
0
8
7
6
COMP0
reserved
Type
Reset
24
21
20
19
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
5
4
3
2
1
0
reserved
reserved
QEI
R/W
0
18
RO
0
RO
0
16
GPTM2 GPTM1 GPTM0
SSI
RO
0
17
R/W
0
reserved
RO
0
RO
0
UART1 UART0
R/W
0
R/W
0
Bit/Field
Name
Type
Reset
Description
31:25
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
24
COMP0
R/W
0
Reset control for analog comparator 0.
23:19
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
18
GPTM2
R/W
0
Reset control for General-Purpose Timer module 2.
17
GPTM1
R/W
0
Reset control for General-Purpose Timer module 1.
16
GPTM0
R/W
0
Reset control for General-Purpose Timer module 0.
15:9
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
8
QEI
R/W
0
Reset control for the QEI unit.
7:5
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
4
SSI
R/W
0
Reset control for the SSI units.
3:2
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
1
UART1
R/W
0
Reset control for the UART1 module.
0
UART0
R/W
0
Reset control for the UART0 module.
May 4, 2007
77
Preliminary
System Control
Register 12: Software Reset Control 2 (SRCR2), offset 0x048
Writes to this register are masked by the bits in the Device Capabilities 4 (DC4) register (see
page 73).
Software Reset Control (SRCR2)
Offset 0x048
31
30
29
28
27
26
25
24
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
PORTE PORTD PORTC PORTB PORTA
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
Bit/Field
Name
Type
Reset
Description
31:5
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
4
PORTE
R/W
0
Reset control for GPIO Port E.
3
PORTD
R/W
0
Reset control for GPIO Port D.
2
PORTC
R/W
0
Reset control for GPIO Port C.
1
PORTB
R/W
0
Reset control for GPIO Port B.
0
PORTA
R/W
0
Reset control for GPIO Port A.
78
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 13: Raw Interrupt Status (RIS), offset 0x050
Central location for system control raw interrupts. These are set and cleared by hardware.
Raw Interrupt Status (RIS)
Offset 0x050
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
PLLLRIS CLRIS
RO
0
RO
0
IOFRIS MOFRIS LDORIS BORRIS PLLFRIS
RO
0
RO
0
RO
0
RO
0
RO
0
Bit/Field
Name
Type
Reset
Description
31:7
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
6
PLLLRIS
RO
0
PLL Lock Raw Interrupt Status
This bit is set when the PLL TREADY Timer asserts.
5
CLRIS
RO
0
Current Limit Raw Interrupt Status
This bit is set if the LDO’s CLE output asserts.
4
IOFRIS
RO
0
Internal Oscillator Fault Raw Interrupt Status
This bit is set if an internal oscillator fault is detected.
3
MOFRIS
RO
0
Main Oscillator Fault Raw Interrupt Status
This bit is set if a main oscillator fault is detected.
2
LDORIS
RO
0
LDO Power Unregulated Raw Interrupt Status
This bit is set if a LDO voltage is unregulated.
1
BORRIS
RO
0
Brown-Out Reset Raw Interrupt Status
This bit is the raw interrupt status for any brown-out
conditions. If set, a brown-out condition was detected. An
interrupt is reported if the BORIM bit in the IMC register is
set and the BORIOR bit in the PBORCTL register is cleared.
0
PLLFRIS
RO
0
PLL Fault Raw Interrupt Status
This bit is set if a PLL fault is detected (stops oscillating).
May 4, 2007
79
Preliminary
System Control
Register 14: Interrupt Mask Control (IMC), offset 0x054
Central location for system control interrupt masks.
Interrupt Mask Control (IMC)
Offset 0x054
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
PLLLIM
CLIM
IOFIM
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
MOFIM LDOIM BORIM PLLFIM
R/W
0
R/W
0
R/W
0
R/W
0
Bit/Field
Name
Type
Reset
Description
31:7
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
6
PLLLIM
R/W
0
PLL Lock Interrupt Mask
This bit specifies whether a current limit detection is
promoted to a controller interrupt. If set, an interrupt is
generated if PLLLRIS in RIS is set; otherwise, an interrupt
is not generated.
5
CLIM
R/W
0
Current Limit Interrupt Mask
This bit specifies whether a current limit detection is
promoted to a controller interrupt. If set, an interrupt is
generated if CLRIS is set; otherwise, an interrupt is not
generated.
4
IOFIM
R/W
0
Internal Oscillator Fault Interrupt Mask
This bit specifies whether an internal oscillator fault
detection is promoted to a controller interrupt. If set, an
interrupt is generated if IOFRIS is set; otherwise, an
interrupt is not generated.
3
MOFIM
R/W
0
Main Oscillator Fault Interrupt Mask
This bit specifies whether a main oscillator fault detection is
promoted to a controller interrupt. If set, an interrupt is
generated if MOFRIS is set; otherwise, an interrupt is not
generated.
2
LDOIM
R/W
0
LDO Power Unregulated Interrupt Mask
This bit specifies whether an LDO unregulated power
situation is promoted to a controller interrupt. If set, an
interrupt is generated if LDORIS is set; otherwise, an
interrupt is not generated.
80
May 4, 2007
Preliminary
LM3S818 Data Sheet
Bit/Field
Name
Type
Reset
1
BORIM
R/W
0
Description
Brown-Out Reset Interrupt Mask
This bit specifies whether a brown-out condition is
promoted to a controller interrupt. If set, an interrupt is
generated if BORRIS is set; otherwise, an interrupt is not
generated.
0
PLLFIM
R/W
0
PLL Fault Interrupt Mask
This bit specifies whether a PLL fault detection is promoted
to a controller interrupt. If set, an interrupt is generated if
PLLFRIS is set; otherwise, an interrupt is not generated.
May 4, 2007
81
Preliminary
System Control
Register 15: Masked Interrupt Status and Clear (MISC), offset 0x058
Central location for system control result of RIS AND IMC to generate an interrupt to the controller.
All of the bits are R/W1C and this action also clears the corresponding raw interrupt bit in the RIS
register (see page 79).
Masked Interrupt Status and Clear (MISC)
Offset 0x058
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
PLLLMIS CLMIS IOFMIS MOFMIS LDOMIS BORMIS PLLFMIS
R/W1C
0
R/W1C
0
R/W1C
0
R/W1C
0
R/W1C
0
R/W1C
0
R/W1C
0
Bit/Field
Name
Type
Reset
Description
31:7
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
6
PLLLMIS
R/W1C
0
PLL Lock Masked Interrupt Status
This bit is set when the PLL TREADY timer asserts. The
interrupt is cleared by writing a 1 to this bit.
5
CLMIS
R/W1C
0
Current Limit Masked Interrupt Status
This bit is set if the LDO’s CLE output asserts. The interrupt
is cleared by writing a 1 to this bit.
4
IOFMIS
R/W1C
0
Internal Oscillator Fault Masked Interrupt Status
This bit is set if an internal oscillator fault is detected. The
interrupt is cleared by writing a 1 to this bit.
3
MOFMIS
R/W1C
0
Main Oscillator Fault Masked Interrupt Status
This bit is set if a main oscillator fault is detected. The
interrupt is cleared by writing a 1 to this bit.
2
LDOMIS
R/W1C
0
LDO Power Unregulated Masked Interrupt Status
This bit is set if LDO power is unregulated. The interrupt is
cleared by writing a 1 to this bit.
1
BORMIS
R/W1C
0
Brown-Out Reset Masked Interrupt Status
This bit is the masked interrupt status for any brown-out
conditions. If set, a brown-out condition was detected. An
interrupt is reported if the BORIM bit in the IMC register is
set and the BORIOR bit in the PBORCTL register is cleared.
The interrupt is cleared by writing a 1 to this bit.
0
PLLFMIS
R/W1C
0
PLL Fault Masked Interrupt Status
This bit is set if a PLL fault is detected (stops oscillating).
The interrupt is cleared by writing a 1 to this bit.
82
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 16: Reset Cause (RESC), offset 0x05C
This field specifies the cause of the reset event to software. The reset value is determined by the
cause of the reset. When an external reset is the cause (EXT is set), all other reset bits are
cleared. However, if the reset is due to any other cause, the remaining bits are sticky, allowing
software to see all causes.
Reset Cause (RESC)
Offset 0x05C
31
30
29
28
27
26
25
24
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
8
7
6
5
4
3
2
1
0
LDO
SW
WDT
BOR
POR
EXT
RO
0
RO
0
RO
0
R/W
-
R/W
-
R/W
-
R/W
-
R/W
-
R/W
-
reserved
Type
Reset
reserved
Type
Reset
RO
0
Bit/Field
Name
Type
Reset
Description
31:6
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
5
LDO
R/W
-
When set to 1, LDO power OK lost is the cause of the reset
event.
4
SW
R/W
-
When set to 1, a software reset is the cause of the reset
event.
3
WDT
R/W
-
When set to 1, a watchdog reset is the cause of the reset
event.
2
BOR
R/W
-
When set to 1, a brown-out reset is the cause of the reset
event.
1
POR
R/W
-
When set to 1, a power-on reset is the cause of the reset
event.
0
EXT
R/W
-
When set to 1, an external reset (RST assertion) is the
cause of the reset event.
May 4, 2007
83
Preliminary
System Control
Register 17: Run-Mode Clock Configuration (RCC), offset 0x060
This register is defined to provide source control and frequency speed.
Run-Mode Clock Configuration (RCC)
Offset 0x060
31
30
29
28
RO
0
15
26
25
RO
0
RO
0
RO
0
R/W
0
R/W
1
R/W
1
R/W
1
R/W
1
14
13
12
11
10
9
8
PWRDN
OEN
BYPASS
PLLVER
R/W
1
R/W
1
R/W
1
R/W
0
R/W
1
R/W
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
RO
0
27
ACG
24
23
22
21
20
USESYSDIV
reserved
USEPWMDIV
R/W
0
RO
0
R/W
0
R/W
1
R/W
1
R/W
1
RO
0
7
6
5
4
3
2
1
0
R/W
1
R/W
1
R/W
0
SYSDIV
XTAL
OSCSRC
R/W
0
19
18
17
16
reserved
PWMDIV
IOSCVER MOSCVER IOSCDIS MOSCDIS
R/W
0
R/W
0
RO
0
RO
0
Bit/Field
Name
Type
Reset
Description
31:28
Reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
27
ACG
R/W
0
Auto Clock Gating
This bit specifies whether the system uses the Sleep-Mode
Clock Gating Control (SCGCn) registers (see page 90)
and Deep-Sleep-Mode Clock Gating Control (DCGCn)
registers (see page 90) if the controller enters a Sleep or
Deep-Sleep mode (respectively). If set, the SCGCn or
DCGCn registers are used to control the clocks distributed
to the peripherals when the controller is in a sleep mode.
Otherwise, the Run-Mode Clock Gating Control (RCGCn)
registers (see page 90) are used when the controller enters
a sleep mode.
The RCGCn registers are always used to control the clocks
in Run mode.
This allows peripherals to consume less power when the
controller is in a sleep mode and the peripheral is unused.
84
May 4, 2007
Preliminary
LM3S818 Data Sheet
Bit/Field
Name
Type
Reset
26:23
SYSDIV
R/W
0xF
Description
System Clock Divisor
Specifies which divisor is used to generate the system clock
from the PLL output (200 MHz).
Binary
Value
Divisor
(BYPASS=1)
Frequency
(BYPASS=0)
0000
reserved
reserved
0001
/2
reserved
0010
/3
reserved
0011
/4
50 MHz
0100
/5
40 MHz
0101
/6
33.33 MHz
0110
/7
28.57 MHz
0111
/8
25 MHz
1000
/9
22.22 MHz
1001
/10
20 MHz
1010
/11
18.18 MHz
1011
/12
16.67 MHz
1100
/13
15.38 MHz
1101
/14
14.29 MHz
1110
/15
13.33 MHz
1111
/16
12.5 MHz (default)
When reading the Run-Mode Clock Configuration (RCC)
register (see page 84), the SYSDIV value is MINSYSDIV if
a lower divider was requested and the PLL is being used.
This lower value is allowed to divide a non-PLL source.
22
USESYSDIV
R/W
0
Use the system clock divider as the source for the system
clock. The system clock divider is forced to be used when
the PLL is selected as the source.
21
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
20
USEPWMDIV
R/W
0
Use the PWM clock divider as the source for the PWM
clock.
May 4, 2007
85
Preliminary
System Control
Bit/Field
Name
Type
Reset
19:17
PWMDIV
R/W
0x7
Description
PWM Unit Clock Divisor
This field specifies the binary divisor used to predivide the
system clock down for use as the timing reference for the
PWM module. This clock is only power 2 divide and rising
edge is synchronous without phase shift from the system
clock.
Value
Divisor
000
/2
001
/4
010
/8
011
/16
100
/32
101
/64
110
/64
111
/64 (default)
16:14
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
13
PWRDN
R/W
1
PLL Power Down
This bit connects to the PLL PWRDN input. The reset value
of 1 powers down the PLL. See Table 6-4 on page 88 for
PLL mode control.
12
OEN
R/W
1
PLL Output Enable
This bit specifies whether the PLL output driver is enabled.
If cleared, the driver transmits the PLL clock to the output.
Otherwise, the PLL clock does not oscillate outside the PLL
module.
Note:
11
BYPASS
R/W
1
Both PWRDN and OEN must be cleared to run the
PLL.
PLL Bypass
Chooses whether the system clock is derived from the PLL
output or the OSC source. If set, the clock that drives the
system is the OSC source. Otherwise, the clock that drives
the system is the PLL output clock divided by the system
divider.
Note:
86
The ADC module must be clocked from the PLL or
directly from a 14-MHz to an 18-MHz clock source
in order to operate properly.
May 4, 2007
Preliminary
LM3S818 Data Sheet
Bit/Field
Name
Type
Reset
10
PLLVER
R/W
0
Description
PLL Verification
This bit controls the PLL verification timer function. If set,
the verification timer is enabled and an interrupt is
generated if the PLL becomes inoperative. Otherwise, the
verification timer is not enabled.
9:6
XTAL
R/W
0xB
This field specifies the crystal value attached to the main
oscillator. The encoding for this field is provided in Table 6-4
on page 88.
R/W
0x0
Picks among the four input sources for the OSC. The
values are:
Oscillator-Related Bits
5:4
OSCSRC
Value
Input Source
00
Main oscillator (default)
01
Internal oscillator
10
Internal oscillator / 4 (this is necessary if used
as input to PLL)
11
reserved
3
IOSCVER
R/W
0
This bit controls the internal oscillator verification timer
function. If set, the verification timer is enabled and an
interrupt is generated if the timer becomes inoperative.
Otherwise, the verification timer is not enabled.
2
MOSCVER
R/W
0
This bit controls the main oscillator verification timer
function. If set, the verification timer is enabled and an
interrupt is generated if the timer becomes inoperative.
Otherwise, the verification timer is not enabled.
1
IOSCDIS
R/W
0
Internal Oscillator Disable
0: Internal oscillator is enabled.
1: Internal oscillator is disabled.
0
MOSCDIS
R/W
0
Main Oscillator Disable
0: Main oscillator is enabled.
1: Main oscillator is disabled.
Table 6-3.
PLL Mode Control
PWRDN
OEN
Mode
1
X
Power down
0
0
Normal
May 4, 2007
87
Preliminary
System Control
Table 6-4.
Default Crystal Field Values and PLL Programming
Crystal Number
(XTAL Binary Value)
0000-0011
Crystal Frequency (MHz)
reserved
0100
3.579545 MHz
0101
3.6864 MHz
0110
4 MHz
0111
4.096 MHz
1000
4.9152 MHz
1001
5 MHz
1010
5.12 MHz
1011
6 MHz (reset value)
1100
6.144 MHz
1101
7.3728 MHz
1110
8 MHz
1111
8.192 MHz
88
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 18: XTAL to PLL Translation (PLLCFG), offset 0x064
This register provides a means of translating external crystal frequencies into the appropriate PLL
settings. This register is initialized during the reset sequence and updated anytime that the XTAL
field changes in the Run-Mode Clock Configuration (RCC) register (see page 84).
XTAL to PLL Translation (PLLCFG)
Offset 0x064
31
30
29
28
27
26
25
24
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
8
7
6
5
4
3
2
1
0
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
reserved
Type
Reset
OD
Type
Reset
RO
-
F
R
Bit/Field
Name
Type
Reset
Description
31:16
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
15:14
OD
RO
-
This field specifies the value supplied to the PLL’s OD input.
13:5
F
RO
-
This field specifies the value supplied to the PLL’s F input.
4:0
R
RO
-
This field specifies the value supplied to the PLL’s R input.
May 4, 2007
89
Preliminary
System Control
Register 19: Run-Mode Clock Gating Control 0 (RCGC0), offset 0x100
Register 20: Sleep-Mode Clock Gating Control 0 (SCGC0), offset 0x110
Register 21: Deep-Sleep-Mode Clock Gating Control 0 (DCGC0), offset 0x120
These registers control the clock gating logic. Each bit controls a clock enable for a given
interface, function, or unit. If set, the unit receives a clock and functions. Otherwise, the unit is
unclocked and disabled (saving power). If the unit is unclocked, reads or writes to the unit will
generate a bus fault. The reset state of these bits is 0 (unclocked) unless otherwise noted, so that
all functional units are disabled. It is the responsibility of software to enable the ports necessary for
the application. Note that these registers may contain more bits than there are interfaces,
functions, or units to control. This is to assure reasonable code compatibility with other family and
future parts.
RCGC0 is the clock configuration register for running operation, SCGC0 for Sleep operation, and
DCGC0 for Deep-Sleep operation. Setting the ACG bit in the Run-Mode Clock Configuration
(RCC) register (see page 84) specifies that the system uses sleep modes.
Run-Mode, Sleep-Mode and Deep-Sleep-Mode Clock Gating Control 0 (RCGC0, SCG0, and DCGC0)
Offset 0x100, 0x110, 0x120
31
30
29
28
27
26
25
24
23
22
21
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
RO
0
RO
0
RO
0
R/W
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
R/W
0
19
PWM
MAXADCSPD
reserved
Type
Reset
20
R/W
0
18
R/W
0
16
ADC
reserved
WDT
reserved
17
reserved
RO
0
RO
0
RO
0
Bit/Field
Name
Type
Reset
Description
31:21
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
20
PWM
R/W
0
This bit controls the clock gating for the PWM module. If
set, the unit receives a clock and functions. Otherwise, the
unit is unclocked and disabled.a
19:17
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
16
ADC
R/W
0
This bit controls the clock gating for the ADC module. If
set, the unit receives a clock and functions. Otherwise, the
unit is unclocked and disabled.a
15:12
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
90
May 4, 2007
Preliminary
LM3S818 Data Sheet
Bit/Field
Name
Type
Reset
11:8
MAXADCSPD
R/W
0x0
Description
This field sets the rate at which the ADC samples data.
You can set the sample rate by setting the MAXADCSPD bit
as follows (you cannot set the rate higher than the
maximum rate.):
Value
a.
Sample Rate
0x0
125K samples/second
0x1
250K samples/second
0x2
500K samples/second
0x3
1M samples/second
7:4
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
3
WDT
R/W
0
This bit controls the clock gating for the WDT module. If
set, the unit receives a clock and functions. Otherwise, the
unit is unclocked and disabled.a
2:0
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
If the unit is unclocked, a read or write to the unit generates a bus fault.
May 4, 2007
91
Preliminary
System Control
Register 22: Run-Mode Clock Gating Control 1 (RCGC1), offset 0x104
Register 23: Sleep-Mode Clock Gating Control 1 (SCGC1), offset 0x114
Register 24: Deep-Sleep-Mode Clock Gating Control 1 (DCGC1), offset 0x124
These registers control the clock gating logic. Each bit controls a clock enable for a given
interface, function, or unit. If set, the unit receives a clock and functions. Otherwise, the unit is
unclocked and disabled (saving power). If the unit is unclocked, reads or writes to the unit will
generate a bus fault. The reset state of these bits is 0 (unclocked) unless otherwise noted, so that
all functional units are disabled. It is the responsibility of software to enable the ports necessary for
the application. Note that these registers may contain more bits than there are interfaces,
functions, or units to control. This is to assure reasonable code compatibility with other family and
future parts.
RCGC1 is the clock configuration register for running operation, SCGC1 for Sleep operation, and
DCGC1 for Deep-Sleep operation. Setting the ACG bit in the Run-Mode Clock Configuration
(RCC) register (see page 84) specifies that the system uses sleep modes.
Run-Mode, Sleep-Mode, and Deep-Sleep-Mode Clock Gating Control 1 (RCGC1, SCGC1, and DCGC1)
Offset 0x104, 0x114, and 0x124
31
30
29
RO
0
RO
0
RO
0
15
14
13
RO
0
RO
0
RO
0
28
27
26
25
RO
0
RO
0
RO
0
RO
0
12
11
10
9
RO
0
RO
0
RO
0
reserved
Type
Reset
RO
0
23
22
R/W
0
RO
0
RO
0
8
7
6
21
20
19
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
5
4
3
2
1
0
reserved
QEI
R/W
0
18
reserved
COMP0
reserved
Type
Reset
24
RO
0
RO
0
16
GPTM2 GPTM1 GPTM0
SSI
RO
0
17
R/W
0
reserved
RO
0
RO
0
UART1 UART0
R/W
0
R/W
0
Bit/Field
Name
Type
Reset
Description
31:25
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
24
COMP0
R/W
0
This bit controls the clock gating for the Comparator 0
module. If set, the unit receives a clock and functions.
Otherwise, the unit is unclocked and disabled.a
23:19
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
18
GPTM2
R/W
0
This bit controls the clock gating for the General Purpose
Timer 2 module. If set, the unit receives a clock and
functions. Otherwise, the unit is unclocked and disabled.a
17
GPTM1
R/W
0
This bit controls the clock gating for the General Purpose
Timer 1 module. If set, the unit receives a clock and
functions. Otherwise, the unit is unclocked and disabled.a
16
GPTM0
R/W
0
This bit controls the clock gating for the General Purpose
Timer 0 module. If set, the unit receives a clock and
functions. Otherwise, the unit is unclocked and disabled.a
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May 4, 2007
Preliminary
LM3S818 Data Sheet
a.
Bit/Field
Name
Type
Reset
Description
15:9
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
8
QEI
R/W
0
This bit controls the clock gating for the QEI module. If set,
the unit receives a clock and functions. Otherwise, the unit
is unclocked and disabled.a
7:5
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
4
SSI
R/W
0
This bit controls the clock gating for the SSI module. If set,
the unit receives a clock and functions. Otherwise, the unit
is unclocked and disabled.a
3:2
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
1
UART1
R/W
0
This bit controls the clock gating for the UART1 module. If
set, the unit receives a clock and functions. Otherwise, the
unit is unclocked and disabled.a
0
UART0
R/W
0
This bit controls the clock gating for the UART0 module. If
set, the unit receives a clock and functions. Otherwise, the
unit is unclocked and disabled.a
If the unit is unclocked, reads or writes to the unit will generate a bus fault.
May 4, 2007
93
Preliminary
System Control
Register 25: Run-Mode Clock Gating Control 2 (RCGC2), offset 0x108
Register 26: Sleep-Mode Clock Gating Control 2 (SCGC2), offset 0x118
Register 27: Deep-Sleep-Mode Clock Gating Control 2 (DCGC2), offset 0x128
These registers control the clock gating logic. Each bit controls a clock enable for a given
interface, function, or unit. If set, the unit receives a clock and functions. Otherwise, the unit is
unclocked and disabled (saving power). If the unit is unclocked, reads or writes to the unit will
generate a bus fault. The reset state of these bits is 0 (unclocked) unless otherwise noted, so that
all functional units are disabled. It is the responsibility of software to enable the ports necessary for
the application. Note that these registers may contain more bits than there are interfaces,
functions, or units to control. This is to assure reasonable code compatibility with other family and
future parts.
RCGC2 is the clock configuration register for running operation, SCGC2 for Sleep operation, and
DCGC2 for Deep-Sleep operation. Setting the ACG bit in the Run-Mode Clock Configuration
(RCC) register (see page 84) specifies that the system uses sleep modes.
Run-Mode, Sleep-Mode, and Deep-Sleep-Mode Clock Gating Control 2 (RCGC2, SCGC2, and DCGC2)
Offset 0x108, 0x118, and 0x128
31
30
29
28
27
26
25
24
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
a.
RO
0
PORTE PORTD PORTC PORTB PORTA
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
Bit/Field
Name
Type
Reset
Description
31:5
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
4
PORTE
R/W
0
This bit controls the clock gating for the GPIO Port E
module. If set, the unit receives a clock and functions.
Otherwise, the unit is unclocked and disabled.a
3
PORTD
R/W
0
This bit controls the clock gating for the GPIO Port D
module. If set, the unit receives a clock and functions.
Otherwise, the unit is unclocked and disabled.a
2
PORTC
R/W
0
This bit controls the clock gating for the GPIO Port C
module. If set, the unit receives a clock and functions.
Otherwise, the unit is unclocked and disabled.a
1
PORTB
R/W
0
This bit controls the clock gating for the GPIO Port B
module. If set, the unit receives a clock and functions.
Otherwise, the unit is unclocked and disabled.a
0
PORTA
R/W
0
This bit controls the clock gating for the GPIO Port A
module. If set, the unit receives a clock and functions.
Otherwise, the unit is unclocked and disabled.a
If the unit is unclocked, reads or writes to the unit will generate a bus fault.
94
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 28: Deep-Sleep Clock Configuration (DSLPCLKCFG), offset 0x144
This register is used to automatically switch from the main oscillator to the internal oscillator when
entering Deep-Sleep mode. The system clock source is the main oscillator by default. When this
register is set, the internal oscillator is powered up and the main oscillator is powered down. When
the Deep-Sleep exit event occurs, hardware brings the system clock back to the source and
frequency it had at the onset of Deep-Sleep mode.
Deep-Sleep Clock Configuration (DSLPCLKCFG)
Offset 0x144
31
30
29
28
27
26
25
24
23
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
IOSC
R/W
0
Bit/Field
Name
Type
Reset
Description
31:1
Reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
0
IOSC
R/W
0
This field allows an override of the main oscillator when
Deep-Sleep mode is running. When set, this field forces the
internal oscillator to be the clock source during Deep-Sleep
mode. Otherwise, the main oscillator remains as the default
system clock source.
May 4, 2007
95
Preliminary
System Control
Register 29: Clock Verification Clear (CLKVCLR), offset 0x150
This register is provided as a means of clearing the clock verification circuits by software. Since
the clock verification circuits force a known good clock to control the process, the controller is
allowed the opportunity to solve the problem and clear the verification fault. This register clears all
clock verification faults. To clear a clock verification fault, the VERCLR bit must be set and then
cleared by software. This bit is not self-clearing.
Clock Verification Clear (CLKVCLR)
Offset 0x150
31
30
29
28
27
26
25
24
23
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
VERCLR
R/W
0
Bit/Field
Name
Type
Reset
Description
31:1
Reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
0
VERCLR
R/W
0
Clear clock verification faults.
96
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 30: Allow Unregulated LDO to Reset the Part (LDOARST), offset 0x160
This register is provided as a means of allowing the LDO to reset the part if the voltage goes
unregulated. Use this register to choose whether to automatically reset the part if the LDO goes
unregulated, based on the design tolerance for LDO fluctuation.
Allow Unregulated LDO to Reset the Part (LDOARST)
Offset 0x160
31
30
29
28
27
26
25
24
23
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
LDOARST
R/W
0
Bit/Field
Name
Type
Reset
Description
31:1
Reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
0
LDOARST
R/W
0
Set to 1 to allow unregulated LDO output to reset the part.
May 4, 2007
97
Preliminary
Internal Memory
7
Internal Memory
The LM3S818 microcontroller comes with 8 KB of bit-banded SRAM and 64 KB of flash memory.
The flash controller provides a user-friendly interface, making flash programming a simple task.
Flash protection can be applied to the flash memory on a 2-KB block basis.
7.1
Block Diagram
Figure 7-1.
Flash Block Diagram
Flash Timing
USECRL
Flash Control
ICode
Cortex-M3
DCode
FMA
FMD
Flash Array
FMC
System Bus
FCRIS
FCIM
FCMISC
Bridge
APB
Flash Protection
FMPRE
SRAM Array
7.2
FMPPE
Functional Description
This section describes the functionality of both memories.
7.2.1
SRAM Memory
The internal SRAM of the Stellaris devices is located at address 0x20000000 of the device
memory map. To reduce the number of time consuming read-modify-write (RMW) operations,
ARM has introduced bit-banding technology in the new Cortex-M3 processor. With a
bit-band-enabled processor, certain regions in the memory map (SRAM and peripheral space) can
use address aliases to access individual bits in a single, atomic operation.
98
May 4, 2007
Preliminary
LM3S818 Data Sheet
The bit-band alias is calculated by using the formula:
bit-band alias = bit-band base + (byte offset * 32) + (bit number * 4)
For example, if bit 3 at address 0x20001000 is to be modified, the bit-band alias is calculated as:
0x22000000 + (0x1000 * 32) + (3 * 4) = 0x2202000C
With the alias address calculated, an instruction performing a read/write to address 0x2202000C
allows direct access to only bit 3 of the byte at address 0x20001000.
For details about bit-banding, please refer to Chapter 4, “Memory Map” in the ARM® Cortex™-M3
Technical Reference Manual.
7.2.2
Flash Memory
The flash is organized as a set of 1-KB blocks that can be individually erased. Erasing a block
causes the entire contents of the block to be reset to all 1s. These blocks are paired into a set of
2-KB blocks that can be individually protected. The blocks can be marked as read-only or
execute-only, providing different levels of code protection. Read-only blocks cannot be erased or
programmed, protecting the contents of those blocks from being modified. Execute-only blocks
cannot be erased or programmed, and can only be read by the controller instruction fetch
mechanism, protecting the contents of those blocks from being read by either the controller or by a
debugger.
7.2.2.1
Flash Memory Timing
The timing for the flash is automatically handled by the flash controller. However, in order to do so,
it must know the clock rate of the system in order to time its internal signals properly. The number
of clock cycles per microsecond must be provided to the flash controller for it to accomplish this
timing. It is software's responsibility to keep the flash controller updated with this information via
the USec Reload (USECRL) register (see page 106).
On reset, USECRL is loaded with a value that configures the flash timing so that it works with the
default crystal value of 6 MHz. If software changes the system operating frequency, the new
operating frequency must be loaded into USECRL before any flash modifications are attempted.
For example, if the device is operating at a speed of 20 MHz, a value of 0x13 must be written to
the USECRL register.
7.2.2.2
Flash Memory Protection
The user is provided two forms of flash protection per 2-KB flash blocks in two 32-bit wide
registers. The protection policy for each form is controlled by individual bits (per policy per block) in
the FMPPE (see page 105) and FMPRE registers (see page 104).
„
Flash Memory Protection Program Enable (FMPPE[Blockn:Block0]): If set, the block may
be programmed (written) or erased. If cleared, the block may not be changed.
„
Flash Memory Protection Read Enable (FMPRE[Blockn:Block0]): If set, the block may be
executed or read by software or debuggers. If cleared, the block may only be executed. The
contents of the memory block are prohibited from being accessed as data and traversing the
DCode bus.
May 4, 2007
99
Preliminary
Internal Memory
The policies may be combined as shown in Table 7-1.
Table 7-1.
Flash Protection Policy Combinations
FMPPE
FMPRE
Protection
0
0
Execute-only protection. The block may only be executed and may not be
written or erased. This mode is used to protect code.
1
0
The block may be written, erased, or executed, but not read. This
combination is unlikely to be used.
0
1
Read-only protection. The block may be read or executed but may not be
written or erased. This mode is used to lock the block from further modification
while allowing any read or execute access.
1
1
No protection. The block may be written, erased, executed, or read.
An access that attempts to program or erase a PE-protected block is prohibited. A controller
interrupt may be optionally generated (by setting the AMASK bit in the FIM register) to alert
software developers of poorly behaving software during the development and debug phases.
An access that attempts to read an RE-protected block is prohibited. Such accesses return data
filled with all 0s. A controller interrupt may be optionally generated to alert software developers of
poorly behaving software during the development and debug phases.
The factory settings for the FMPRE and FMPPE registers are a value of 1 for all implemented
banks. This implements a policy of open access and programmability. The register bits may be
changed by writing the specific register bit. The changes are not permanent until the register is
committed (saved), at which point the bit change is permanent. If a bit is changed from a 1 to a 0
and not committed, it may be restored by executing a power-on reset sequence.
7.2.2.3
Flash Protection by Disabling Debug Access
Flash memory may also be protected by permanently disabling access to the Debug Access Port
(DAP) through the JTAG and SWD interfaces. This is accomplished by clearing the DBG field of
the FMPRE register.
Flash Memory Protection Read Enable (DBG field): If set to 0x2, access to the DAP is enabled
through the JTAG and SWD interfaces. If clear, access to the DAP is disabled. The DBG field
programming becomes permanent, and irreversible, after a commit sequence is performed.
In the initial state, provided from the factory, access is enabled in order to facilitate code
development and debug. Access to the DAP may be disabled at the end of the manufacturing flow,
once all tests have passed and software loaded. This change will not take effect until the next
power-up of the device. Note that it is recommended that disabling access to the DAP be
combined with a mechanism for providing end-user installable updates (if necessary) such as the
Stellaris boot loader.
Important: Once the DBG field is cleared and committed, this field can never be restored to the
factory-programmed value—which means JTAG/SWD interface to the debug module
can never be re-enabled. This sequence does NOT disable the JTAG controller, it
only disables the access of the DAP through the JTAG or SWD interfaces. The JTAG
interface remains functional and access to the Test Access Port remains enabled,
allowing the user to execute the IEEE JTAG-defined instructions (for example, to
perform boundary scan operations).
100
May 4, 2007
Preliminary
LM3S818 Data Sheet
If the user will also be using the FMPRE bits to protect flash memory from being read as data (to
mark sets of 2 KB blocks of flash memory as execute-only), these one-time-programmable bits
should be written at the same time that the debug disable bits are programmed. Mechanisms to
execute the one-time code sequence to disable all debug access include:
7.2.2.4
„
Selecting the debug disable option in the Stellaris boot loader
„
Loading the debug disable sequence into SRAM and running it once from SRAM after
programming the final end application code into flash
Flash Memory Programming
Writing the flash memory requires that the code be executed out of SRAM to avoid corrupting or
interrupting the bus timing. Flash pages can be erased on a page basis (1 KB in size), or by
performing a mass erase of the entire flash.
All erase and program operations are performed using the Flash Memory Address (FMA), Flash
Memory Data (FMD) and Flash Memory Control (FMC) registers. See section 7.3 for examples.
7.3
Initialization and Configuration
This section shows examples for using the flash controller to perform various operations on the
contents of the flash memory.
7.3.1
Changing Flash Protection Bits
As discussed in Section 7.2.2.2, changes to the protection bits must be committed before they
take effect. The sequence below is used change and commit a block protection bit in the FMPRE
or FMPPE registers. The sequence to change and commit a bit in software is as follows:
1. The Flash Memory Protection Read Enable (FMPRE) and Flash Memory Protection
Program Enable (FMPPE) registers are written, changing the intended bit(s). The action of
these changes can be tested by software while in this state.
2. The Flash Memory Address (FMA) register (see page 107) bit 0 is set to 1 if the FMPPE
register is to be committed; otherwise, a 0 commits the FMPRE register.
3. The Flash Memory Control (FMC) register (see page 110) is written with the COMT bit set.
This initiates a write sequence and commits the changes.
There is a special sequence to change and commit the DBG bits in the Flash Memory Protection
Read Enable (FMPRE) register. This sequence also sets and commits any changes from 1 to 0 in
the block protection bits (for execute-only) in the FMPRE register.
1. 1. The Flash Memory Protection Read Enable (FMPRE) register is written, changing the
intended bit(s). The action of these changes can be tested by software while in this state.
2. 2. The Flash Memory Address (FMA) register (see page 102) is written with a value of 0x900.
3. 3. The Flash Memory Control (FMC) register (see page 104) is written with the COMT bit set.
This initiates a write sequence and commits the changes.
Below is an example code sequence to permanently disable the JTAG and SWD interface to the
debug module using Luminary Micro's DriverLib peripheral driver library:
#include "hw_types.h"
#include "hw_flash.h"
void
permanently_disable_jtag_swd(void)
{
May 4, 2007
101
Preliminary
Internal Memory
//
// Clear the DBG field of the FMPRE register. Note that the value
// used in this instance does not affect the state of the BlockN
// bits, but were the value different, all bits in the FMPRE are
// affected by this function!
//
HWREG(FLASH_FMPRE) &= 0x3fffffff;
//
// The following sequence activates the one-time
// programming of the FMPRE register.
//
HWREG(FLASH_FMA) = 0x900;
HWREG(FLASH_FMC) = (FLASH_FMC_WRKEY | FLASH_FMC_COMT);
//
// Wait until the operation is complete.
//
while (HWREG(FLASH_FMC) & FLASH_FMC_COMT)
{
}
}
7.3.2
Flash Programming
The Stellaris devices provide a user-friendly interface for flash programming. All erase/program
operations are handled via three registers: FMA, FMD and FMC.
The flash is programmed using the following sequence:
1. Write source data to the FMD register.
2. Write the target address to the FMA register.
3. Write the flash write key and the WRITE bit (a value of 0xA4420001) to the FMC register.
4. Poll the FMC register until the WRITE bit is cleared.
To perform an erase of a 1-KB page:
1. Write the page address to the FMA register.
2. Write the flash write key and the ERASE bit (a value of 0xA4420002) to the FMC register.
3. Poll the FMC register until the ERASE bit is cleared.
To perform a mass erase of the flash:
1. Write the flash write key and the MERASE bit (a value of 0xA4420004) to the FMC register.
2. Poll the FMC register until the MERASE bit is cleared.
7.4
Register Map
Table 7-2 lists the Flash memory and control registers. The offset listed is a hexadecimal
increment to the register’s address, relative to the Flash control base address of 0x400FD000,
102
May 4, 2007
Preliminary
LM3S818 Data Sheet
except for FMPRE and FMPPE, which are relative to the System Control base address of
0x400FE000.
Table 7-2. Flash Register Map
Offset
Name
0x130a
0x134a
0X140a
See
page
Reset
Type
Description
FMPRE
0xFFFFFFFF
R/W0
Flash memory read protect
104
FMPPE
0xFFFFFFFF
R/W0
Flash memory program protect
105
USECRL
0x00000031
R/W
USec reload
106
0x000
FMA
0x00000000
R/W
Flash memory address
107
0x004
FMD
0x00000000
R/W
Flash memory data
109
0x008
FMC
0x00000000
R/W
Flash memory control
110
0x00C
FCRIS
0x00000000
RO
Flash controller raw interrupt status
112
0x010
FCIM
0x00000000
R/W
Flash controller interrupt mask
113
0x014
FCMISC
0x00000000
R/W1C
Flash controller masked interrupt status and clear
114
a. Relative to System Control base address of 0x400FE000.
7.5
Register Descriptions
The remainder of this section lists and describes the Flash Memory registers, in numerical order
by address offset.
May 4, 2007
103
Preliminary
Internal Memory
Register 1: Flash Memory Protection Read Enable (FMPRE), offset 0x130
Note:
Offset is relative to System Control base address of 0x400FE000
This register stores the read-only (FMPRE) protection bits for each 2-KB flash block and bits to
disable debug access through JTAG and SWD. This register is loaded during the power-on reset
sequence.
The factory setting for the FMPRE register is a value of 1 for all implemented flash banks and 0x2
for the DBG field. These bits implement a policy of open access, programmability, and debug
access. The register bits may be changed by writing the specific register bit. However, this register
is R/W0; the user can only change the protection bit from a 1 to a 0 (and may NOT change a 0 to a
1). The last 4 KB of flash (from 60 KB to 64 KB) will always be readable as both code and data.
However, this region can still be write-protected through the use of the FMPPE register.
The changes are not permanent until the register is committed (saved), at which point the bit
change is permanent. If a bit is changed from a 1 to a 0 and not committed, it may be restored by
executing a power-on reset sequence.
For additional information, see “Flash Memory Protection” on page 87.
Flash Memory Protection Read Enable (FMPRE)
Offset 0x130 and 0x134
31
30
DBG
Type
Reset
28
27
26
24
23
22
20
19
18
16
Block28
Block25
Block24
Block21
Block20
Block17
Block15
R/W0
1
R/W0
1
R/W0
1
R/W0
1
R/W0
1
R/W0
1
R/W0
1
R/W0
1
R/W0
1
R/W0
1
R/W0
1
R/W0
1
R/W0
1
R/W0
1
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Block13
Block12
Block9
Block8
Block7
Block6
Block5
Block4
Block3
Block2
Block1
Block0
R/W0
1
R/W0
1
R/W0
1
R/W0
1
R/W0
1
R/W0
1
R/W0
1
R/W0
1
R/W0
1
R/W0
1
R/W0
1
R/W0
1
Block11 Block10
R/W0
1
R/W0
1
Block19 Block18
17
Block29
R/W0
1
Block23 Block22
21
R/W0
0
R/W0
1
Block27 Block26
25
R/W0
1
Block15 Block14
Type
Reset
29
Bit/Field
Name
Type
Reset
31:30
DBG
R/W0
0x2
Controls access to the debug access port (DAP)
through the JTAG and SWD interfaces. A value of
0x2 enables access. A value of 0 disables access.
29:0
Block29Block0
R/W0
0x3FFFFFFF
Enable 2-KB flash blocks to be executed or read.
The policies may be combined as shown in
Table 7-1 on page 100.
104
Description
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 2: Flash Memory Protection Program Enable (FMPPE), offset 0x134
Note:
Offset is relative to System Control base address of 0x400FE000
This register stores the execute-only (FMPPE) protection bits for each 2-KB flash block. This
register is loaded during the power-on reset sequence.
The factory setting for the FMPPE register is a value of 1 for all implemented banks. This
implements a policy of open access and programmability. The register bits may be changed by
writing the specific register bit. However, this register is R/W0; the user can only change the
protection bit from a 1 to a 0 (and may NOT change a 0 to a 1).
The changes are not permanent until the register is committed (saved), at which point the bit
change is permanent. If a bit is changed from a 1 to a 0 and not committed, it may be restored by
executing a power-on reset sequence.
For additional information, see “Flash Memory Protection” on page 99.
Flash Memory Protection Program Enable (FMPPE)
Offset 0x130 and 0x134
31
30
Block31 Block30
Type
Reset
28
27
26
24
22
20
19
18
16
Block28
Block21
Block20
Block17
Block15
R/W0
RO
01
R/W0
RO
01
R/W0
RO
01
R/W0
RO
01
R/W0
RO
01
R/W0
RO
01
R/W0
RO
01
R/W0
RO
01
R/W0
RO
01
R/W0
RO
01
R/W0
RO
01
R/W0
RO
01
R/W0
RO
01
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Block9
Block8
Block7
Block6
Block5
Block4
Block3
Block2
Block1
Block0
R/W0
RO
01
R/W0
RO
01
R/W0
1
R/W0
1
R/W0
1
R/W0
1
R/W0
1
R/W0
1
R/W0
1
R/W0
1
R/W0
RO
01
Block12
reserved
Block11 Block10
R/W0
RO
01
R/W0
RO
01
R/W0
RO
01
Bit/Field
Name
Type
Reset
31:0
Block31Block0
R/W0
1
May 4, 2007
Block19 Block18
17
R/W0
RO
01
Block13
Block24
Block23 Block22
reserved
21
Block29
R/W0
RO
01
Block25
23
R/W0
RO
01
R/W0
RO
01
Block27 Block26
25
R/W0
RO
01
Block15 Block14
Type
Reset
29
Description
Enable 2-KB flash blocks to be written or erased
(FMPPE register). This policy may be combined with
the FMPRE register as shown in Table 7-1 on
page 100.
105
Preliminary
Internal Memory
Register 3: USec Reload (USECRL), offset 0x140
Note:
Offset is relative to System Control base address of 0x400FE000
This register is provided as a means of creating a 1-µs tick divider reload value for the flash
controller. The internal flash has specific minimum and maximum requirements on the length of
time the high voltage write pulse can be applied. It is required that this register contain the
operating frequency (in MHz -1) whenever the flash is being erased or programmed. The user is
required to change this value if the clocking conditions are changed for a flash erase/program
operation.
Usec Reload (USECRL)
Offset 0x140
31
30
29
28
27
26
25
24
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
8
7
6
5
4
3
2
1
0
RO
0
R/W
0
R/W
0
R/W
1
R/W
1
R/W
0
R/W
0
R/W
0
R/W
1
reserved
Type
Reset
reserved
Type
Reset
RO
0
USEC
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
USEC
R/W
0x31
Description
Reserved bits return an indeterminate value, and should
never be changed.
MHz -1 of the controller clock when the flash is being
erased or programmed.
USEC should be set to 0x31 (49 MHz) whenever the flash is
being erased or programmed.
106
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 4: Flash Memory Address (FMA), offset 0x000
During a write operation, this register contains a 4-byte-aligned address and specifies where the
data is written. During erase operations, this register contains a 1 KB-aligned address and
May 4, 2007
107
Preliminary
Internal Memory
specifies which page is erased. Note that the alignment requirements must be met by software or
the results of the operation are unpredictable.
Flash Memory Address (FMA)
Offset 0x000
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
23
22
21
20
19
18
17
16
reserved
Type
Reset
OFFSET
Type
Reset
Flash Memory Address (FMA)
Offset 0x000
31
30
29
28
27
26
25
24
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
23
22
21
20
19
18
17
16
reserved
Type
Reset
reserved
Type
Reset
OFFSET
RO
0
Flash Memory Address (FMA)
Offset 0x000
31
30
29
28
27
26
25
24
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
23
22
21
20
19
18
17
16
reserved
Type
Reset
reserved
Type
Reset
RO
0
OFFSET
Flash Memory Address (FMA)
Offset 0x000
31
30
29
28
27
26
25
24
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
RO
0
OFFSET
R/W
0
Bit/Field
Name
Type
Reset
Description
31:16
reserved
RO
0x0
Reserved bits return an indeterminate value, and should
never be changed.
15:0
OFFSET
R/W
0x0
Address offset in flash where operation is performed.
108
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 5: Flash Memory Data (FMD), offset 0x004
This register contains the data to be written during the programming cycle or read during the read
cycle. Note that the contents of this register are undefined for a read access of an execute-only
block. This register is not used during the erase cycles.
Flash Memory Data (FMD)
Offset 0x004
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
DATA
Type
Reset
DATA
Type
Reset
Bit/Field
Name
Type
Reset
31:0
DATA
R/W
0x0
Description
Data value for write operation.
May 4, 2007
109
Preliminary
Internal Memory
Register 6: Flash Memory Control (FMC), offset 0x008
When this register is written, the flash controller initiates the appropriate access cycle for the
location specified by the Flash Memory Address (FMA) register (see page 107). If the access is
a write access, the data contained in the Flash Memory Data (FMD) register (see page 109) is
written.
This is the final register written and initiates the memory operation. There are four control bits in
the lower byte of this register that, when set, initiate the memory operation. The most used of
these register bits are the ERASE and WRITE bits.
It is a programming error to write multiple control bits and the results of such an operation are
unpredictable.
Flash Memory Control (FMC)
Offset 0x008
31
30
29
28
27
26
25
24
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
15
14
13
12
11
10
9
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
23
22
21
20
19
18
17
16
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
WRKEY
Type
Reset
COMT MERASE ERASE WRITE
reserved
Type
Reset
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
Bit/Field
Name
Type
Reset
Description
31:16
WRKEY
WO
0x0
15:4
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
3
COMT
R/W
0
Commit (write) of register value to nonvolatile storage. A
write of 0 has no effect on the state of this bit.
This field contains a write key, which is used to minimize the
incidence of accidental flash writes. The value 0xA442 must
be written into this field for a write to occur. Writes to the
FMC register without this WRKEY value are ignored. A
read of this field returns the value 0.
If read, the state of the previous commit access is provided.
If the previous commit access is complete, a 0 is returned;
otherwise, if the commit access is not complete, a 1 is
returned.
This can take up to 50 µs.
2
MERASE
R/W
0
Mass erase flash memory
If this bit is set, the flash main memory of the device is all
erased. A write of 0 has no effect on the state of this bit.
If read, the state of the previous mass erase access is
provided. If the previous mass erase access is complete, a
0 is returned; otherwise, if the previous mass erase access
is not complete, a 1 is returned.
This can take up to 250 ms.
110
May 4, 2007
Preliminary
LM3S818 Data Sheet
Bit/Field
Name
Type
Reset
1
ERASE
R/W
0
Description
Erase a page of flash memory
If this bit is set, the page of flash main memory as specified
by the contents of FMA is erased. A write of 0 has no effect
on the state of this bit.
If read, the state of the previous erase access is provided. If
the previous erase access is complete, a 0 is returned;
otherwise, if the previous erase access is not complete, a 1
is returned.
This can take up to 25 ms.
0
WRITE
R/W
0
Write a word into flash memory
If this bit is set, the data stored in FMD is written into the
location as specified by the contents of FMA. A write of 0
has no effect on the state of this bit.
If read, the state of the previous write update is provided. If
the previous write access is complete, a 0 is returned;
otherwise, if the write access is not complete, a 1 is
returned.
This can take up to 50 µs.
May 4, 2007
111
Preliminary
Internal Memory
Register 7: Flash Controller Raw Interrupt Status (FCRIS), offset 0x00C
This register indicates that the flash controller has an interrupt condition. An interrupt is only
signaled if the corresponding FCIM register bit is set.
Flash Controller Raw Interrupt Status (FCRIS)
Offset 0x00C
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
PRIS
ARIS
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
Bit/Field
Name
Type
Reset
Description
31:2
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
1
PRIS
RO
0
Programming Raw Interrupt Status
This bit indicates the current state of the programming
cycle. If set, the programming cycle completed; if cleared,
the programming cycle has not completed. Programming
cycles are either write or erase actions generated through
the Flash Memory Control (FMC) register bits (see
page 110).
0
ARIS
RO
0
Access Raw Interrupt Status
This bit indicates if the flash was improperly accessed. If
set, the program tried to access the flash counter to the
policy as set in the Flash Memory Protection Read
Enable (FMPRE) and Flash Memory Protection Program
Enable (FMPPE) registers (see page 104). Otherwise, no
access has tried to improperly access the flash.
112
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 8: Flash Controller Interrupt Mask (FCIM), offset 0x010
This register controls whether the flash controller generates interrupts to the controller.
Flash Controller Interrupt Mask (FCIM)
Offset 0x010
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
PMASK AMASK
reserved
Type
Reset
RO
0
R/W
0
R/W
0
Bit/Field
Name
Type
Reset
Description
31:2
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
1
PMASK
R/W
0
Programming Interrupt Mask
This bit controls the reporting of the programming raw
interrupt status to the controller. If set, a
programming-generated interrupt is promoted to the
controller. Otherwise, interrupts are recorded but
suppressed from the controller.
0
AMASK
R/W
0
Access Interrupt Mask
This bit controls the reporting of the access raw interrupt
status to the controller. If set, an access-generated interrupt
is promoted to the controller. Otherwise, interrupts are
recorded but suppressed from the controller.
May 4, 2007
113
Preliminary
Internal Memory
Register 9: Flash Controller Masked Interrupt Status and Clear (FCMISC), offset 0x014
This register provides two functions. First, it reports the cause of an interrupt by indicating which
interrupt source or sources are signaling the interrupt. Second, it serves as the method to clear the
interrupt reporting.
Flash Controller Masked Interrupt Status and Clear (FCMISC)
Offset 0x014
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
PMISC
AMISC
R/W1C
0
R/W1C
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
Bit/Field
Name
Type
Reset
Description
31:2
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
1
PMISC
R/W1C
0
Programming Masked Interrupt Status and Clear
This bit indicates whether an interrupt was signaled
because a programming cycle completed and was not
masked. This bit is cleared by writing a 1. The PRIS bit in
the FCRIS register (see page 112) is also cleared when the
PMISC bit is cleared.
0
AMISC
R/W1C
0
Access Masked Interrupt Status and Clear
This bit indicates whether an interrupt was signaled
because an improper access was attempted and was not
masked. This bit is cleared by writing a 1. The ARIS bit in
the FCRIS register is also cleared when the AMISC bit is
cleared.
114
May 4, 2007
Preliminary
LM3S818 Data Sheet
8
General-Purpose Input/Outputs (GPIOs)
The GPIO module is composed of five physical GPIO blocks, each corresponding to an individual
GPIO port (Port A, Port B, Port C, Port D, and Port E). The GPIO module is FiRM-compliant and
supports 0 to 30 programmable input/output pins, depending on the peripherals being used.
The GPIO module has the following features:
„
Programmable control for GPIO interrupts:
– Interrupt generation masking
– Edge-triggered on rising, falling, or both
– Level-sensitive on High or Low values
„
5-V-tolerant input/outputs
„
Bit masking in both read and write operations through address lines
„
Programmable control for GPIO pad configuration:
– Weak pull-up or pull-down resistors
– 2-mA, 4-mA, and 8-mA pad drive
– Slew rate control for the 8-mA drive
– Open drain enables
– Digital input enables
May 4, 2007
115
Preliminary
General-Purpose Input/Outputs (GPIOs)
Block Diagram
GPIO Module Block Diagram
U0Tx
PA2
PA3
PA4
PA5
SSICLK
SSIFss
SSIRx
SSITx
JTAG
SWD/SWO
UART0
PWM1
PWM3
Fault
PB5
PB6
GPIO Port B
PWM2
PB1
PB4
C0o
C0+
PC2
TDO/SWO
PC3
QEI
IDX
GP Timer 2
Fault
C0-
PC1
TDI
SSI
PB0
PB3
PC0
TMS/SWDIO
TRST
PhA
PB2
TCK/SWCLK
Analog
Comparators
PWM0
CCP1
GP Timer 1
Fault
PWM2
PC5
PC6
PC7
PWM0
PD0
PWM1
PD1
U1Tx
GP Timer 0
PC4
CCP4
U1Rx
UART1
PB7
PhB
GPIO Port C
U0Rx
PA1
GPIO Port A
PA0
CCP0
GPIO Port D
Figure 8-1.
PWM4
PWM5
PD2
PD3
PD4
PD5
CCP2
GPIO Block E
8.1
PE0
PE1
LM3S818
8.2
Functional Description
Important: All GPIO pins are inputs by default (GPIODIR=0 and GPIOAFSEL=0), with the
exception of the five JTAG pins (PB7 and PC[3:0]. The JTAG pins default to their
JTAG functionality (GPIOAFSEL=1). Asserting a Power-On-Reset (POR) or an
external reset (RST) puts both groups of pins back to their default state.
Each GPIO port is a separate hardware instantiation of the same physical block (see Figure 8-2).
The LM3S818 microcontroller contains five ports and thus five of these physical GPIO blocks.
116
May 4, 2007
Preliminary
LM3S818 Data Sheet
Figure 8-2.
GPIO Port Block Diagram
Function
Selection
GPIOAFSEL
D
E
M
U
X
Alternate Input
Alternate Output
Alternate Output Enable
GPIO Input
I/O
Data
M
U
X
Pad Output
M
U
X
Pad Output Enable
I/O
Pad
Package I/O Pin
GPIO Output
GPIODATA
GPIODIR
Interrupt
Pad Input
GPIO Output Enable
Interrupt
Control
I/O Pad
Control
GPIOIS
GPIOIBE
GPIOIEV
GPIOIM
GPIORIS
GPIOMIS
GPIOICR
GPIODR2R
GPIODR4R
GPIODR8R
GPIOSLR
GPIOPUR
GPIOPDR
GPIOODR
GPIODEN
Identification Registers
GPIOPeriphID0
GPIOPeriphID1
GPIOPeriphID2
GPIOPeriphID3
8.2.1
GPIOPeriphID4
GPIOPeriphID5
GPIOPeriphID6
GPIOPeriphID7
GPIOPCellID0
GPIOPCellID1
GPIOPCellID2
GPIOPCellID3
Data Register Operation
To aid in the efficiency of software, the GPIO ports allow for the modification of individual bits in the
GPIO Data (GPIODATA) register (see page 123) by using bits [9:2] of the address bus as a mask.
This allows software drivers to modify individual GPIO pins in a single instruction, without affecting
the state of the other pins. This is in contrast to the "typical" method of doing a read-modify-write
operation to set or clear an individual GPIO pin. To accommodate this feature, the GPIODATA
register covers 256 locations in the memory map.
During a write, if the address bit associated with that data bit is set to 1, the value of the
GPIODATA register is altered. If it is cleared to 0, it is left unchanged.
For example, writing a value of 0xEB to the address GPIODATA + 0x098 would yield as shown in
Figure 8-3, where u is data unchanged by the write.
May 4, 2007
117
Preliminary
General-Purpose Input/Outputs (GPIOs)
Figure 8-3.
GPIODATA Write Example
ADDR[9:2]
9
8
7
6
5
4
3
2
1
0
0x098
0
0
1
0
0
1
1
0
0
0
0xEB
1
1
1
0
1
0
1
1
GPIODATA
u
u
1
u
u
0
1
u
7
6
5
4
3
2
1
0
During a read, if the address bit associated with the data bit is set to 1, the value is read. If the
address bit associated with the data bit is set to 0, it is read as a zero, regardless of its actual
value. For example, reading address GPIODATA + 0x0C4 yields as shown in Figure 8-4.
Figure 8-4.
8.2.2
GPIODATA Read Example
ADDR[9:2]
9
8
7
6
5
4
3
2
1
0
0x0C4
0
0
1
1
0
0
0
1
0
0
GPIODATA
1
0
1
1
1
1
1
0
Returned Value
0
0
1
1
0
0
0
0
7
6
5
4
3
2
1
0
Data Direction
The GPIO Direction (GPIODIR) register (see page 124) is used to configure each individual pin
as an input or output.
8.2.3
Interrupt Operation
The interrupt capabilities of each GPIO port are controlled by a set of seven registers. With these
registers, it is possible to select the source of the interrupt, its polarity, and the edge properties.
When one or more GPIO inputs cause an interrupt, a single interrupt output is sent to the interrupt
controller for the entire GPIO port. For edge-triggered interrupts, software must clear the interrupt
to enable any further interrupts. For a level-sensitive interrupt, it is assumed that the external
source holds the level constant for the interrupt to be recognized by the controller.
Three registers are required to define the edge or sense that causes interrupts:
„
GPIO Interrupt Sense (GPIOIS) register (see page 125)
„
GPIO Interrupt Both Edges (GPIOIBE) register (see page 126)
„
GPIO Interrupt Event (GPIOIEV) register (see page 127)
Interrupts are enabled/disabled via the GPIO Interrupt Mask (GPIOIM) register (see page 128).
When an interrupt condition occurs, the state of the interrupt signal can be viewed in two locations:
the GPIO Raw Interrupt Status (GPIORIS) and GPIO Masked Interrupt Status (GPIOMIS)
registers (see pages 129 and 130). As the name implies, the GPIOMIS register only shows
interrupt conditions that are allowed to be passed to the controller. The GPIORIS register indicates
that a GPIO pin meets the conditions for an interrupt, but has not necessarily been sent to the
controller.
118
May 4, 2007
Preliminary
LM3S818 Data Sheet
In addition to providing GPIO functionality, PB4 can also be used as an external trigger for the
ADC. If PB4 is configured as a non-masked interrupt pin (GPIOIM is set to 1), not only is an
interrupt for PortB generated, but an external trigger signal is sent to the ADC. If the ADC Event
Multiplexer Select (ADCEMUX) register is configured to use the external trigger, an ADC
conversion is initiated.
If no other PortB pins are being used to generate interrupts, the ARM Integrated Nested Vectored
Interrupt Controller (NVIC) Interrupt Set Enable (SETNA) register can disable the PortB interrupts
and the ADC interrupt can be used to read back the converted data. Otherwise, the PortB interrupt
handler needs to ignore and clear interrupts on B4, and wait for the ADC interrupt or the ADC
interrupt needs to be disabled in the SETNA register and the PortB interrupt handler polls the ADC
registers until the conversion is completed.
Interrupts are cleared by writing a 1 to the GPIO Interrupt Clear (GPIOICR) register (see
page 131).
When programming interrupts, the interrupts should be masked (GPIOIM set to 0). Writing any
value to an interrupt control register (GPIOIS, GPIOIBE, or GPIOIEV) can generate a spurious
interrupt if the corresponding bits are enabled.
8.2.4
Mode Control
The GPIO pins can be controlled by either hardware or software. When hardware control is
enabled via the GPIO Alternate Function Select (GPIOAFSEL) register (see page 132), the pin
state is controlled by its alternate function (that is, the peripheral). Software control corresponds to
GPIO mode, where the GPIODATA register is used to read/write the corresponding pins.
8.2.5
Pad Configuration
The pad configuration registers allow for GPIO pad configuration by software based on the
application requirements. The pad configuration registers include the GPIODR2R, GPIODR4R,
GPIODR8R, GPIOODR, GPIOPUR, GPIOPDR, GPIOSLR, and GPIODEN registers.
8.2.6
Identification
The identification registers configured at reset allow software to detect and identify the module as
a GPIO block. The identification registers include the GPIOPeriphID0-GPIOPeriphID7 registers
as well as the GPIOPCellID0-GPIOPCellID3 registers.
8.3
Initialization and Configuration
To use the GPIO, the peripheral clock must be enabled by setting PORTA, PORTB, PORTC, PORTD,
and PORTE in the RCGC2 register.
On reset, all GPIO pins (except for the five JTAG pins) default to general-purpose input mode
(GPIODIR and GPIOAFSEL both set to 0). Table 8-1 shows all possible configurations of the
May 4, 2007
119
Preliminary
General-Purpose Input/Outputs (GPIOs)
GPIO pads and the control register settings required to achieve them. Table 8-2 shows how a
rising edge interrupt would be configured for pin 2 of a GPIO port.
Table 8-1.
GPIO Pad Configuration Examples
GPIOAFSEL
GPIODIR
GPIOODR
GPIODEN
GPIOPUR
GPIOPDR
GPIODR2R
GPIODR4R
GPIODR8R
GPIOSLR
Register Bit Valuea
Digital Input (GPIO)
0
0
0
1
?
?
X
X
X
X
Digital Output (GPIO)
0
1
0
1
?
?
?
?
?
?
Open Drain Input (GPIO)
0
0
1
1
X
X
X
X
X
X
Open Drain Output (GPIO)
0
1
1
1
X
X
?
?
?
?
Digital Input (Timer CCP)
1
X
0
1
?
?
X
X
X
X
Digital Input (QEI)
1
X
0
1
?
?
X
X
X
X
Digital Output (PWM)
1
X
0
1
?
?
?
?
?
?
Digital Output (Timer PWM)
1
X
0
1
?
?
?
?
?
?
Digital Input/Output (SSI)
1
X
0
1
?
?
?
?
?
?
Digital Input/Output (UART)
1
X
0
1
?
?
?
?
?
?
Analog Input (Comparator)
0
0
0
0
0
0
X
X
X
X
Digital Output (Comparator)
1
X
0
1
?
?
?
?
?
?
Configuration
a. X=Ignored (don’t care bit)
?=Can be either 0 or 1, depending on the configuration
Table 8-2.
Register
GPIO Interrupt Configuration Example
Desired Interrupt
Event Trigger
Pin 2 Bit Valuea
7
6
5
4
3
2
1
0
0=edge
1=level
X
X
X
X
X
0
X
X
GPIOIBE
0=single edge
1=both edges
X
X
X
X
X
0
X
X
GPIOIEV
0=Low level, or
negative edge
1=High level, or
positive edge
X
X
X
X
X
1
X
X
0=masked
1=not masked
0
0
0
0
0
1
0
0
GPIOIS
GPIOIM
a. X=Ignored (don’t care bit)
120
May 4, 2007
Preliminary
LM3S818 Data Sheet
8.4
Register Map
Table 8-2 lists the GPIO registers. The offset listed is a hexadecimal increment to the register’s
address, relative to that GPIO port’s base address:
„
GPIO Port A: 0x40004000
„
GPIO Port B: 0x40005000
„
GPIO Port C: 0x40006000
„
GPIO Port D: 0x40007000
„
GPIO Port E: 0x40024000
Important: The GPIO registers in this chapter are duplicated in each GPIO block, however,
depending on the block, all eight bits may not be connected to a GPIO pad (see
Figure 8-1 on page 116). In those cases, writing to those unconnected bits has no
effect and reading those unconnected bits returns no meaningful data.
Table 8-3. GPIO Register Map
Offset
Name
0x000
See
page
Reset
Type
Description
GPIODATA
0x00000000
R/W
Data
123
0x400
GPIODIR
0x00000000
R/W
Data direction
124
0x404
GPIOIS
0x00000000
R/W
Interrupt sense
125
0x408
GPIOIBE
0x00000000
R/W
Interrupt both edges
126
0x40C
GPIOIEV
0x00000000
R/W
Interrupt event
127
0x410
GPIOIM
0x00000000
R/W
Interrupt mask enable
128
0x414
GPIORIS
0x00000000
RO
Raw interrupt status
129
0x418
GPIOMIS
0x00000000
RO
Masked interrupt status
130
0x41C
GPIOICR
0x00000000
W1C
Interrupt clear
131
0x420
GPIOAFSEL
see notea
R/W
Alternate function select
132
0x500
GPIODR2R
0x000000FF
R/W
2-mA drive select
133
0x504
GPIODR4R
0x00000000
R/W
4-mA drive select
134
0x508
GPIODR8R
0x00000000
R/W
8-mA drive select
135
0x50C
GPIOODR
0x00000000
R/W
Open drain select
136
0x510
GPIOPUR
0x000000FF
R/W
Pull-up select
137
0x514
GPIOPDR
0x00000000
R/W
Pull-down select
138
0x518
GPIOSLR
0x00000000
R/W
Slew rate control select
139
0x51C
GPIODEN
0x000000FF
R/W
Digital input enable
140
0xFD0
GPIOPeriphID4
0x00000000
RO
Peripheral identification 4
141
May 4, 2007
121
Preliminary
General-Purpose Input/Outputs (GPIOs)
Table 8-3. GPIO Register Map (Continued)
Offset
Name
0xFD4
See
page
Reset
Type
Description
GPIOPeriphID5
0x00000000
RO
Peripheral identification 5
142
0xFD8
GPIOPeriphID6
0x00000000
RO
Peripheral identification 6
143
0xFDC
GPIOPeriphID7
0x00000000
RO
Peripheral identification 7
144
0xFE0
GPIOPeriphID0
0x00000061
RO
Peripheral identification 0
145
0xFE4
GPIOPeriphID1
0x00000000
RO
Peripheral identification 1
146
0xFE8
GPIOPeriphID2
0x00000018
RO
Peripheral identification 2
147
0xFEC
GPIOPeriphID3
0x00000001
RO
Peripheral identification 3
148
0xFF0
GPIOPCellID0
0x0000000D
RO
GPIO PrimeCell identification 0
149
0xFF4
GPIOPCellID1
0x000000F0
RO
GPIO PrimeCell identification 1
150
0xFF8
GPIOPCellID2
0x00000005
RO
GPIO PrimeCell identification 2
151
0xFFC
GPIOPCellID3
0x000000B1
RO
GPIO PrimeCell identification 3
152
a. The default reset value for the GPIOAFSEL register is 0x00000000 for all GPIO pins, with the exception of the five JTAG pins
(PB7 and PC[3:0]. These five pins default to JTAG functionality. Because of this, the default reset value of GPIOAFSEL for
GPIO Port B is 0x00000080 while the default reset value of GPIOAFSEL for Port C is 0x0000000F.
8.5
Register Descriptions
The remainder of this section lists and describes the GPIO registers, in numerical order by
address offset.
122
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 1: GPIO Data (GPIODATA), offset 0x000
The GPIODATA register is the data register. In software control mode, values written in the
GPIODATA register are transferred onto the GPIO port pins if the respective pins have been
configured as outputs through the GPIO Direction (GPIODIR) register (see page 124).
In order to write to GPIODATA, the corresponding bits in the mask, resulting from the address bus
bits [9:2], must be High. Otherwise, the bit values remain unchanged by the write.
Similarly, the values read from this register are determined for each bit by the mask bit derived
from the address used to access the data register, bits [9:2]. Bits that are 1 in the address mask
cause the corresponding bits in GPIODATA to be read, and bits that are 0 in the address mask
cause the corresponding bits in GPIODATA to be read as 0, regardless of their value.
A read from GPIODATA returns the last bit value written if the respective pins are configured as
outputs, or it returns the value on the corresponding input pin when these are configured as inputs.
All bits are cleared by a reset.
GPIO Data (GPIODATA)
Offset 0x000
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
DATA
Bit/Field
Name
Type
Reset
Description
31:8
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
7:0
DATA
R/W
0
GPIO Data
This register is virtually mapped to 256 locations in the address
space. To facilitate the reading and writing of data to these
registers by independent drivers, the data read from and the data
written to the registers are masked by the eight address lines
ipaddr[9:2]. Reads from this register return its current
state. Writes to this register only affect bits that are not masked
by ipaddr[9:2] and are configured as outputs. See “Data
Register Operation” on page 117 for examples of reads and
writes.
May 4, 2007
123
Preliminary
General-Purpose Input/Outputs (GPIOs)
Register 2: GPIO Direction (GPIODIR), offset 0x400
The GPIODIR register is the data direction register. Bits set to 1 in the GPIODIR register configure
the corresponding pin to be an output, while bits set to 0 configure the pins to be inputs. All bits are
cleared by a reset, meaning all GPIO pins are inputs by default.
GPIO Direction (GPIODIR)
Offset 0x400
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
DIR
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
DIR
R/W
0x00
Description
Reserved bits return an indeterminate value, and should never
be changed.
GPIO Data Direction
0: Pins are inputs.
1: Pins are outputs.
124
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 3: GPIO Interrupt Sense (GPIOIS), offset 0x404
The GPIOIS register is the interrupt sense register. Bits set to 1 in GPIOIS configure the
corresponding pins to detect levels, while bits set to 0 configure the pins to detect edges. All bits
are cleared by a reset.
GPIO Interrupt Sense (GPIOIS)
Offset 0x404
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
IS
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
IS
R/W
0x00
Description
Reserved bits return an indeterminate value, and should never
be changed.
GPIO Interrupt Sense
0: Edge on corresponding pin is detected (edge-sensitive).
1: Level on corresponding pin is detected (level-sensitive).
May 4, 2007
125
Preliminary
General-Purpose Input/Outputs (GPIOs)
Register 4: GPIO Interrupt Both Edges (GPIOIBE), offset 0x408
The GPIOIBE register is the interrupt both-edges register. When the corresponding bit in the GPIO
Interrupt Sense (GPIOIS) register (see page 125) is set to detect edges, bits set to High in
GPIOIBE configure the corresponding pin to detect both rising and falling edges, regardless of the
corresponding bit in the GPIO Interrupt Event (GPIOIEV) register (see page 127). Clearing a bit
configures the pin to be controlled by GPIOIEV. All bits are cleared by a reset.
GPIO Interrupt Both Edges (GPIOIBE)
Offset 0x408
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
IBE
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
IBE
R/W
0x00
Description
Reserved bits return an indeterminate value, and should never
be changed.
GPIO Interrupt Both Edges
0: Interrupt generation is controlled by the GPIO Interrupt Event
(GPIOIEV) register (see page 142).
1: Both edges on the corresponding pin trigger an interrupt.
Note:
126
Single edge is determined by the corresponding bit in
GPIOIEV.
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 5: GPIO Interrupt Event (GPIOIEV), offset 0x40C
The GPIOIEV register is the interrupt event register. Bits set to High in GPIOIEV configure the
corresponding pin to detect rising edges or high levels, depending on the corresponding bit value
in the GPIO Interrupt Sense (GPIOIS) register (see page 125). Clearing a bit configures the pin to
detect falling edges or low levels, depending on the corresponding bit value in GPIOIS. All bits are
cleared by a reset.
GPIO Interrupt Event (GPIOIEV)
Offset 0x40C
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
IEV
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
IEV
R/W
0x00
Description
Reserved bits return an indeterminate value, and should never
be changed.
GPIO Interrupt Event
0: Falling edge or Low levels on corresponding pins trigger
interrupts.
1: Rising edge or High levels on corresponding pins trigger
interrupts.
May 4, 2007
127
Preliminary
General-Purpose Input/Outputs (GPIOs)
Register 6: GPIO Interrupt Mask (GPIOIM), offset 0x410
The GPIOIM register is the interrupt mask register. Bits set to High in GPIOIM allow the
corresponding pins to trigger their individual interrupts and the combined GPIOINTR line. Clearing
a bit disables interrupt triggering on that pin. All bits are cleared by a reset.
GPIO Interrupt Mask (GPIOIM)
Offset 0x410
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
IME
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
IME
R/W
0x00
Description
Reserved bits return an indeterminate value, and should never
be changed.
GPIO Interrupt Mask Enable
0: Corresponding pin interrupt is masked.
1: Corresponding pin interrupt is not masked.
128
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 7: GPIO Raw Interrupt Status (GPIORIS), offset 0x414
The GPIORIS register is the raw interrupt status register. Bits read High in GPIORIS reflect the
status of interrupt trigger conditions detected (raw, prior to masking), indicating that all the
requirements have been met, before they are finally allowed to trigger by the GPIO Interrupt
Mask (GPIOIM) register (see page 128). Bits read as zero indicate that corresponding input pins
have not initiated an interrupt. All bits are cleared by a reset.
GPIO Raw Interrupt Status (GPIORIS)
Offset 0x414
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RIS
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
RIS
RO
0x00
Description
Reserved bits return an indeterminate value, and should never
be changed.
GPIO Interrupt Raw Status
Reflect the status of interrupt trigger condition detection on pins
(raw, prior to masking).
0: Corresponding pin interrupt requirements not met.
1: Corresponding pin interrupt has met requirements.
May 4, 2007
129
Preliminary
General-Purpose Input/Outputs (GPIOs)
Register 8: GPIO Masked Interrupt Status (GPIOMIS), offset 0x418
The GPIOMIS register is the masked interrupt status register. Bits read High in GPIOMIS reflect
the status of input lines triggering an interrupt. Bits read as Low indicate that either no interrupt has
been generated, or the interrupt is masked.
In addition to providing GPIO functionality, PB4 can also be used as an external trigger for the
ADC. If PB4 is configured as a non-masked interrupt pin (GPIOIM is set to 1), not only is an
interrupt for PortB generated, but an external trigger signal is sent to the ADC. If the ADC Event
Multiplexer Select (ADCEMUX) register (see page 219) is configured to use the external trigger,
an ADC conversion is initiated.
If no other PortB pins are being used to generate interrupts, the ARM Integrated Nested Vectored
Interrupt Controller (NVIC) Interrupt Set Enable (SETNA) register can disable the PortB interrupts
and the ADC interrupt can be used to read back the converted data. Otherwise, the PortB interrupt
handler needs to ignore and clear interrupts on B4, and wait for the ADC interrupt or the ADC
interrupt needs to be disabled in the SETNA register and the PortB interrupt handler polls the ADC
registers until the conversion is completed.
GPIOMIS is the state of the interrupt after masking.
GPIO Masked Interrupt Status (GPIOMIS)
Offset 0x418
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
MIS
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
MIS
RO
0x00
Description
Reserved bits return an indeterminate value, and should never
be changed.
GPIO Masked Interrupt Status
Masked value of interrupt due to corresponding pin.
0: Corresponding GPIO line interrupt not active.
1: Corresponding GPIO line asserting interrupt.
130
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 9: GPIO Interrupt Clear (GPIOICR), offset 0x41C
The GPIOICR register is the interrupt clear register. Writing a 1 to a bit in this register clears the
corresponding interrupt edge detection logic register. Writing a 0 has no effect.
GPIO Interrupt Clear (GPIOICR)
Offset 0x41C
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
W1C
0
W1C
0
W1C
0
W1C
0
W1C
0
W1C
0
W1C
0
W1C
0
reserved
Type
Reset
reserved
Type
Reset
IC
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
IC
W1C
0x00
Description
Reserved bits return an indeterminate value, and should never
be changed.
GPIO Interrupt Clear
0: Corresponding interrupt is unaffected.
1: Corresponding interrupt is cleared.
May 4, 2007
131
Preliminary
General-Purpose Input/Outputs (GPIOs)
Register 10: GPIO Alternate Function Select (GPIOAFSEL), offset 0x420
The GPIOAFSEL register is the mode control select register. Writing a 1 to any bit in this register
selects the hardware control for the corresponding GPIO line. All bits are cleared by a reset,
therefore no GPIO line is set to hardware control by default.
Caution – All GPIO pins are inputs by default (GPIODIR=0 and GPIOAFSEL=0), with the
exception of the five JTAG pins (PB7 and PC[3:0]). The JTAG pins default to their JTAG
functionality (GPIOAFSEL=1). Asserting a Power-On-Reset (POR) or an external reset (RST)
puts both groups of pins back to their default state.
If the JTAG pins are used as GPIOs in a design, PB7 and PC2 cannot have external pull-down
resistors connected to both of them at the same time. If both pins are pulled Low during reset, the
controller has unpredictable behavior. If this happens, remove one or both of the pull-down
resistors, and apply RST or power-cycle the part.
In addition, it is possible to create a software sequence that prevents the debugger from connecting
to the Stellaris microcontroller. If the program code loaded into flash immediately changes the
JTAG pins to their GPIO functionality, the debugger may not have enough time to connect and
halt the controller before the JTAG pin functionality switches. This may lock the debugger out of
the part. This can be avoided with a software routine that restores JTAG functionality based on an
external or software trigger.
GPIO Alternate Function Select (GPIOAFSEL)
Offset 0x420
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
-
R/W
-
R/W
-
R/W
-
R/W
-
R/W
-
R/W
-
R/W
-
reserved
Type
Reset
reserved
Type
Reset
AFSEL
Bit/Field
Name
Type
Reset
Description
31:8
reserved
RO
0
7:0
AFSEL
R/W
see note
Reserved bits return an indeterminate value, and should never
be changed.
GPIO Alternate Function Select
0: Software control of corresponding GPIO line (GPIO mode).
1: Hardware control of corresponding GPIO line (alternate
hardware function).
Note:
132
The default reset value for the GPIOAFSEL register is
0x00 for all GPIO pins, with the exception of the five
JTAG pins (PB7 and PC[3:0]). These five pins
default to JTAG functionality. Because of this, the
default reset value of GPIOAFSEL for GPIO Port B is
0x80 while the default reset value of GPIOAFSEL for
Port C is 0x0F.
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 11: GPIO 2-mA Drive Select (GPIODR2R), offset 0x500
The GPIODR2R register is the 2-mA drive control register. It allows for each GPIO signal in the
port to be individually configured without affecting the other pads. When writing a DRV2 bit for a
GPIO signal, the corresponding DRV4 bit in the GPIODR4R register and the DRV8 bit in the
GPIODR8R register are automatically cleared by hardware.
GPIO 2-mA Drive Select (GPIODR2R)
Offset 0x500
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
reserved
Type
Reset
reserved
Type
Reset
DRV2
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
DRV2
R/W
0xFF
Description
Reserved bits return an indeterminate value, and should never
be changed.
Output Pad 2-mA Drive Enable
A write of 1 to either GPIODR4[n] or GPIODR8[n] clears the
corresponding 2-mA enable bit. The change is effective on the
second clock cycle after the write.
May 4, 2007
133
Preliminary
General-Purpose Input/Outputs (GPIOs)
Register 12: GPIO 4-mA Drive Select (GPIODR4R), offset 0x504
The GPIODR4R register is the 4-mA drive control register. It allows for each GPIO signal in the
port to be individually configured without affecting the other pads. When writing the DRV4 bit for a
GPIO signal, the corresponding DRV2 bit in the GPIODR2R register and the DRV8 bit in the
GPIODR8R register are automatically cleared by hardware.
GPIO 4-mA Drive Select (GPIODR4R)
Offset 0x504
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
DRV4
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
DRV4
R/W
0x00
Description
Reserved bits return an indeterminate value, and should never
be changed.
Output Pad 4-mA Drive Enable
A write of 1 to either GPIODR2[n] or GPIODR8[n] clears the
corresponding 4-mA enable bit. The change is effective on the
second clock cycle after the write.
134
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 13: GPIO 8-mA Drive Select (GPIODR8R), offset 0x508
The GPIODR8R register is the 8-mA drive control register. It allows for each GPIO signal in the
port to be individually configured without affecting the other pads. When writing the DRV8 bit for a
GPIO signal, the corresponding DRV2 bit in the GPIODR2R register and the DRV4 bit in the
GPIODR4R register are automatically cleared by hardware.
GPIO 8-mA Drive Select (GPIODR8R)
Offset 0x508
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
DRV8
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
DRV8
R/W
0x00
Description
Reserved bits return an indeterminate value, and should never
be changed.
Output Pad 8-mA Drive Enable
A write of 1 to either GPIODR2[n] or GPIODR4[n] clears the
corresponding 8-mA enable bit. The change is effective on the
second clock cycle after the write.
May 4, 2007
135
Preliminary
General-Purpose Input/Outputs (GPIOs)
Register 14: GPIO Open Drain Select (GPIOODR), offset 0x50C
The GPIOODR register is the open drain control register. Setting a bit in this register enables the
open drain configuration of the corresponding GPIO pad. When open drain mode is enabled, the
corresponding bit should also be set in the GPIO Digital Input Enable (GPIODEN) register (see
page 140). Corresponding bits in the drive strength registers (GPIODR2R, GPIODR4R,
GPIODR8R, and GPIOSLR) can be set to achieve the desired rise and fall times. The GPIO acts
as an open drain input if the corresponding bit in the GPIODIR register is set to 0; and as an open
drain output when set to 1.
GPIO Open Drain Select (GPIOODR)
Offset 0x50C
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
ODE
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
ODE
R/W
0x00
Description
Reserved bits return an indeterminate value, and should never
be changed.
Output Pad Open Drain Enable
0: Open drain configuration is disabled.
1: Open drain configuration is enabled.
136
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 15: GPIO Pull-Up Select (GPIOPUR), offset 0x510
The GPIOPUR register is the pull-up control register. When a bit is set to 1, it enables a weak
pull-up resistor on the corresponding GPIO signal. Setting a bit in GPIOPUR automatically clears
the corresponding bit in the GPIO Pull-Down Select (GPIOPDR) register (see page 138).
GPIO Pull-Up Select (GPIOPUR)
Offset 0x510
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
reserved
Type
Reset
reserved
Type
Reset
PUE
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PUE
R/W
0xFF
Description
Reserved bits return an indeterminate value, and should never
be changed.
Pad Weak Pull-Up Enable
A write of 1 to GPIOPDR[n] clears the corresponding
GPIOPUR[n] enables. The change is effective on the second
clock cycle after the write.
May 4, 2007
137
Preliminary
General-Purpose Input/Outputs (GPIOs)
Register 16: GPIO Pull-Down Select (GPIOPDR), offset 0x514
The GPIOPDR register is the pull-down control register. When a bit is set to 1, it enables a weak
pull-down resistor on the corresponding GPIO signal. Setting a bit in GPIOPDR automatically
clears the corresponding bit in the GPIO Pull-Up Select (GPIOPUR) register (see page 137).
GPIO Pull-Down Select (GPIOPDR)
Offset 0x514
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
PDE
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PDE
R/W
0x00
Description
Reserved bits return an indeterminate value, and should never
be changed.
Pad Weak Pull-Down Enable
A write of 1 to GPIOPUR[n] clears the corresponding
GPIOPDR[n] enables. The change is effective on the second
clock cycle after the write.
138
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 17: GPIO Slew Rate Control Select (GPIOSLR), offset 0x518
The GPIOSLR register is the slew rate control register. Slew rate control is only available when
using the 8-mA drive strength option via the GPIO 8-mA Drive Select (GPIODR8R) register (see
page 135).
GPIO Slew Rate Control Select (GPIOSLR)
Offset 0x518
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
SRL
Bit/Field
Name
Type
Reset
Description
31:8
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
7:0
SRL
R/W
0
Slew Rate Limit Enable (8-mA drive only)
0: Slew rate control disabled.
1: Slew rate control enabled.
May 4, 2007
139
Preliminary
General-Purpose Input/Outputs (GPIOs)
Register 18: GPIO Digital Input Enable (GPIODEN), offset 0x51C
The GPIODEN register is the digital input enable register. By default, all GPIO signals are
configured as digital inputs at reset. The only time that a pin should not be configured as a digital
input is when the GPIO pin is configured to be one of the analog input signals for the analog
comparator.
GPIO Digital Input Enable (GPIODEN)
Offset 0x51C
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
reserved
Type
Reset
reserved
Type
Reset
DEN
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
DEN
R/W
0xFF
Description
Reserved bits return an indeterminate value, and should never
be changed.
Digital-Input Enable
0: Digital input disabled
1: Digital input enabled
140
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 19: GPIO Peripheral Identification 4 (GPIOPeriphID4), offset 0xFD0
The GPIOPeriphID4, GPIOPeriphID5, GPIOPeriphID6, and GPIOPeriphID7 registers can
conceptually be treated as one 32-bit register; each register contains eight bits of the 32-bit
register, used by software to identify the peripheral.
GPIO Peripheral Identification 4 (GPIOPeriphID4)
Offset 0xFD0
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID4
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID4
RO
0x00
Description
Reserved bits return an indeterminate value, and should
never be changed.
GPIO Peripheral ID Register[7:0]
May 4, 2007
141
Preliminary
General-Purpose Input/Outputs (GPIOs)
Register 20: GPIO Peripheral Identification 5 (GPIOPeriphID5), offset 0xFD4
The GPIOPeriphID4, GPIOPeriphID5, GPIOPeriphID6, and GPIOPeriphID7 registers can
conceptually be treated as one 32-bit register; each register contains eight bits of the 32-bit
register, used by software to identify the peripheral.
GPIO Peripheral Identification 5 (GPIOPeriphID5)
Offset 0xFD4
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID5
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID5
RO
0x00
Description
Reserved bits return an indeterminate value, and should
never be changed.
GPIO Peripheral ID Register[15:8]
142
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 21: GPIO Peripheral Identification 6 (GPIOPeriphID6), offset 0xFD8
The GPIOPeriphID4, GPIOPeriphID5, GPIOPeriphID6, and GPIOPeriphID7 registers can
conceptually be treated as one 32-bit register; each register contains eight bits of the 32-bit
register, used by software to identify the peripheral.
GPIO Peripheral Identification 6 (GPIOPeriphID6)
Offset 0xFD8
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID6
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID6
RO
0x00
Description
Reserved bits return an indeterminate value, and should
never be changed.
GPIO Peripheral ID Register[23:16]
May 4, 2007
143
Preliminary
General-Purpose Input/Outputs (GPIOs)
Register 22: GPIO Peripheral Identification 7 (GPIOPeriphID7), offset 0xFDC
The GPIOPeriphID4, GPIOPeriphID5, GPIOPeriphID6, and GPIOPeriphID7 registers can
conceptually be treated as one 32-bit register; each register contains eight bits of the 32-bit
register, used by software to identify the peripheral.
GPIO Peripheral Identification 7 (GPIOPeriphID7)
Offset 0xFDC
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID7
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID7
RO
0x00
Description
Reserved bits return an indeterminate value, and should
never be changed.
GPIO Peripheral ID Register[31:24]
144
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 23: GPIO Peripheral Identification 0 (GPIOPeriphID0), offset 0xFE0
The GPIOPeriphID0, GPIOPeriphID1, GPIOPeriphID2, and GPIOPeriphID3 registers can
conceptually be treated as one 32-bit register; each register contains eight bits of the 32-bit
register, used by software to identify the peripheral.
GPIO Peripheral Identification 0 (GPIOPeriphID0)
Offset 0xFE0
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
1
RO
0
RO
0
RO
0
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
PID0
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID0
RO
0x61
Description
Reserved bits return an indeterminate value, and should never
be changed.
GPIO Peripheral ID Register[7:0]
Can be used by software to identify the presence of this
peripheral.
May 4, 2007
145
Preliminary
General-Purpose Input/Outputs (GPIOs)
Register 24: GPIO Peripheral Identification 1(GPIOPeriphID1), offset 0xFE4
The GPIOPeriphID0, GPIOPeriphID1, GPIOPeriphID2, and GPIOPeriphID3 registers can
conceptually be treated as one 32-bit register; each register contains eight bits of the 32-bit
register, used by software to identify the peripheral.
GPIO Peripheral Identification 1 (GPIOPeriphID1)
Offset 0xFE4
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID1
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID1
RO
0x00
Description
Reserved bits return an indeterminate value, and should never
be changed.
GPIO Peripheral ID Register[15:8]
Can be used by software to identify the presence of this
peripheral.
146
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 25: GPIO Peripheral Identification 2 (GPIOPeriphID2), offset 0xFE8
The GPIOPeriphID0, GPIOPeriphID1, GPIOPeriphID2, and GPIOPeriphID3 registers can
conceptually be treated as one 32-bit register; each register contains eight bits of the 32-bit
register, used by software to identify the peripheral.
GPIO Peripheral Identification 2 (GPIOPeriphID2)
Offset 0xFE8
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
1
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID2
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID2
RO
0x18
Description
Reserved bits return an indeterminate value, and should never
be changed.
GPIO Peripheral ID Register[23:16]
Can be used by software to identify the presence of this
peripheral.
May 4, 2007
147
Preliminary
General-Purpose Input/Outputs (GPIOs)
Register 26: GPIO Peripheral Identification 3 (GPIOPeriphID3), offset 0xFEC
The GPIOPeriphID0, GPIOPeriphID1, GPIOPeriphID2, and GPIOPeriphID3 registers can
conceptually be treated as one 32-bit register; each register contains eight bits of the 32-bit
register, used by software to identify the peripheral.
GPIO Peripheral Identification 3 (GPIOPeriphID3)
Offset 0xFEC
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
PID3
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID3
RO
0x01
Description
Reserved bits return an indeterminate value, and should never
be changed.
GPIO Peripheral ID Register[31:24]
Can be used by software to identify the presence of this
peripheral.
148
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 27: GPIO PrimeCell Identification 0 (GPIOPCellID0), offset 0xFF0
The GPIOPCellID0, GPIOPCellID1, GPIOPCellID2, and GPIOPCellID3 registers are four 8-bit
wide registers, that can conceptually be treated as one 32-bit register. The register is used as a
standard cross-peripheral identification system.
GPIO Primecell Identification 0 (GPIOPCellID0)
Offset 0xFF0
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
1
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
CID0
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
CID0
RO
0x0D
Description
Reserved bits return an indeterminate value, and should never
be changed.
GPIO PrimeCell ID Register[7:0]
Provides software a standard cross-peripheral identification
system.
May 4, 2007
149
Preliminary
General-Purpose Input/Outputs (GPIOs)
Register 28: GPIO PrimeCell Identification 1 (GPIOPCellID1), offset 0xFF4
The GPIOPCellID0, GPIOPCellID1, GPIOPCellID2, and GPIOPCellID3 registers are four 8-bit
wide registers, that can conceptually be treated as one 32-bit register. The register is used as a
standard cross-peripheral identification system.
GPIO Primecell Identification 1 (GPIOPCellID1)
Offset 0xFF4
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
1
RO
1
RO
1
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
CID1
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
CID1
RO
0xF0
Description
Reserved bits return an indeterminate value, and should never
be changed.
GPIO PrimeCell ID Register[15:8]
Provides software a standard cross-peripheral identification
system.
150
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 29: GPIO PrimeCell Identification 2 (GPIOPCellID2), offset 0xFF8
The GPIOPCellID0, GPIOPCellID1, GPIOPCellID2, and GPIOPCellID3 registers are four 8-bit
wide registers, that can conceptually be treated as one 32-bit register. The register is used as a
standard cross-peripheral identification system.
GPIO Primecell Identification 2 (GPIOPCellID2)
Offset 0xFF8
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
CID2
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
CID2
RO
0x05
Description
Reserved bits return an indeterminate value, and should never
be changed.
GPIO PrimeCell ID Register[23:16]
Provides software a standard cross-peripheral identification
system.
May 4, 2007
151
Preliminary
General-Purpose Input/Outputs (GPIOs)
Register 30: GPIO PrimeCell Identification 3 (GPIOPCellID3), offset 0xFFC
The GPIOPCellID0, GPIOPCellID1, GPIOPCellID2, and GPIOPCellID3 registers are four 8-bit
wide registers, that can conceptually be treated as one 32-bit register. The register is used as a
standard cross-peripheral identification system.
GPIO Primecell Identification 3 (GPIOPCellID3)
Offset 0xFFC
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
0
RO
1
RO
1
RO
0
RO
0
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
CID3
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
CID3
RO
0xB1
Description
Reserved bits return an indeterminate value, and should never
be changed.
GPIO PrimeCell ID Register[31:24]
Provides software a standard cross-peripheral identification
system.
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9
General-Purpose Timers
Programmable timers can be used to count or time external events that drive the Timer input pins.
The LM3S818 controller General-Purpose Timer Module (GPTM) contains three GPTM blocks
(Timer0, Timer1, and Timer 2). Each GPTM block provides two 16-bit timer/counters (referred to
as TimerA and TimerB) that can be configured to operate independently as timers or event
counters, or configured to operate as one 32-bit timer or one 32-bit Real-Time Clock (RTC).
Timers can also be used to trigger analog-to-digital (ADC) conversions. The trigger signals from all
of the general-purpose timers are ORed together before reaching the ADC module, so only one
timer should be used to trigger ADC events.
The General-Purpose Timer Module is one timing resource available on the Stellaris
microcontrollers. Other timer resources include the System Timer (SysTick) (see “System Timer
(SysTick)” on page 36) and the PWM timer in the PWM module (see “PWM Timer” on page 320).
The following modes are supported:
„
32-bit Timer modes:
– Programmable one-shot timer
– Programmable periodic timer
– Real-Time Clock using 32.768-KHz input clock
– Software-controlled event stalling (excluding RTC mode)
„
16-bit Timer modes:
– General-purpose timer function with an 8-bit prescaler
– Programmable one-shot timer
– Programmable periodic timer
– Software-controlled event stalling
„
16-bit Input Capture modes:
– Input edge count capture
– Input edge time capture
„
16-bit PWM mode:
– Simple PWM mode with software-programmable output inversion of the PWM signal
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9.1
Block Diagram
Figure 9-1.
GPTM Module Block Diagram
0x0000 (Down Counter Modes )
TimerA Control
GPTMTAPMR
TA Comparator
GPTMTAPR
Clock / Edge
Detect
GPTMTAMATCHR
Interrupt / Config
TimerA
Interrupt
GPTMCFG
GPTMTAILR
GPTMAR
En
GPTMCTL
GPTMIMR
TimerB
Interrupt
CCP (even)
GPTMTAMR
RTC Divider
GPTMRIS
GPTMMIS
GPTMICR
TimerB Control
GPTMTBPMR
GPTMTBR En
Clock / Edge
Detect
GPTMTBPR
GPTMTBMATCHR
GPTMTBILR
CCP (odd)
TB Comparator
GPTMTBMR
0x0000 (Down Counter Modes )
System
Clock
9.2
Functional Description
The main components of each GPTM block are two free-running 16-bit up/down counters (referred
to as TimerA and TimerB), two 16-bit match registers, two prescaler match registers, and two
16-bit load/initialization registers and their associated control functions. The exact functionality of
each GPTM is controlled by software and configured through the register interface.
Software configures the GPTM using the GPTM Configuration (GPTMCFG) register (see
page 165), the GPTM TimerA Mode (GPTMTAMR) register (see page 166), and the GPTM
TimerB Mode (GPTMTBMR) register (see page 167). When in one of the 32-bit modes, the timer
can only act as a 32-bit timer. However, when configured in 16-bit mode, the GPTM can have its
two 16-bit timers configured in any combination of the 16-bit modes.
9.2.1
GPTM Reset Conditions
After reset has been applied to the GPTM module, the module is in an inactive state, and all
control registers are cleared and in their default states. Counters TimerA and TimerB are initialized
to 0xFFFF, along with their corresponding load registers: the GPTM TimerA Interval Load
(GPTMTAILR) register (see page 175) and the GPTM TimerB Interval Load (GPTMTBILR)
register (see page 176). The prescale counters are initialized to 0x00: the GPTM TimerA
Prescale (GPTMTAPR) register (see page 179) and the GPTM TimerB Prescale (GPTMTBPR)
register (see page 180).
9.2.2
32-Bit Timer Operating Modes
Note:
Both the odd- and even-numbered CCP pins are used for 16-bit mode. Only the
even-numbered CCP pins are used for 32-bit mode.
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This section describes the three GPTM 32-bit timer modes (One-Shot, Periodic, and RTC) and
their configuration.
The GPTM is placed into 32-bit mode by writing a 0 (One-Shot/Periodic 32-bit timer mode) or a 1
(RTC mode) to the GPTM Configuration (GPTMCFG) register. In both configurations, certain
GPTM registers are concatenated to form pseudo 32-bit registers. These registers include:
„
GPTM TimerA Interval Load (GPTMTAILR) register [15:0], see page 175
„
GPTM TimerB Interval Load (GPTMTBILR) register [15:0], see page 176
„
GPTM TimerA (GPTMTAR) register [15:0], see page 183
„
GPTM TimerB (GPTMTBR) register [15:0], see page 184
In the 32-bit modes, the GPTM translates a 32-bit write access to GPTMTAILR into a write access
to both GPTMTAILR and GPTMTBILR. The resulting word ordering for such a write operation is:
GPTMTBILR[15:0]:GPTMTAILR[15:0]. Likewise, a read access to GPTMTAR returns the
value: GPTMTBR[15:0]:GPTMTAR[15:0].
9.2.2.1
32-Bit One-Shot/Periodic Timer Mode
In 32-bit one-shot and periodic timer modes, the concatenated versions of the TimerA and TimerB
registers are configured as a 32-bit down-counter. The selection of one-shot or periodic mode is
determined by the value written to the TAMR field of the GPTM TimerA Mode (GPTMTAMR)
register (see page 166), and there is no need to write to the GPTM TimerB Mode (GPTMTBMR)
register.
When software writes the TAEN bit in the GPTM Control (GPTMCTL) register (see page 168), the
timer begins counting down from its preloaded value. Once the 0x00000000 state is reached, the
timer reloads its start value from the concatenated GPTMTAILR on the next cycle. If configured to
be a one-shot timer, the timer stops counting and clears the TAEN bit in the GPTMCTL register. If
configured as a periodic timer, it continues counting.
In addition to reloading the count value, the GPTM generates interrupts and output triggers when it
reaches the 0x0000000 state. The GPTM sets the TATORIS bit in the GPTM Raw Interrupt
Status (GPTMRIS) register (see page 172), and holds it until it is cleared by writing the GPTM
Interrupt Clear (GPTMICR) register (see page 174). If the time-out interrupt is enabled in the
GPTM Interrupt Mask (GPTIMR) register (see page 170), the GPTM also sets the TATOMIS bit in
the GPTM Masked Interrupt Status (GPTMISR) register (see page 173).
The output trigger is a one-clock-cycle pulse that is asserted when the counter hits the
0x00000000 state, and deasserted on the following clock cycle. It is enabled by setting the TAOTE
bit in GPTMCTL, and can trigger SoC-level events such as ADC conversions.
If software reloads the GPTMTAILR register while the counter is running, the counter loads the
new value on the next clock cycle and continues counting from the new value.
If the TASTALL bit in the GPTMCTL register is asserted, the timer freezes counting until the signal
is deasserted.
9.2.2.2
32-Bit Real-Time Clock Timer Mode
In Real-Time Clock (RTC) mode, the concatenated versions of the TimerA and TimerB registers
are configured as a 32-bit up-counter. When RTC mode is selected for the first time, the counter is
loaded with a value of 0x00000001. All subsequent load values must be written to the GPTM
TimerA Match (GPTMTAMATCHR) register (see page 177) by the controller.
The input clock on the CCP0, CCP2 or CCP4 pins is required to be 32.768 KHz in RTC mode. The
clock signal is then divided down to a 1 Hz rate and is passed along to the input of the 32-bit
counter.
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When software writes the TAEN bit in GPTMCTL, the counter starts counting up from its preloaded
value of 0x00000001. When the current count value matches the preloaded value in
GPTMTAMATCHR, it rolls over to a value of 0x00000000 and continues counting until either a
hardware reset, or it is disabled by software (clearing the TAEN bit). When a match occurs, the
GPTM asserts the RTCRIS bit in GPTMRIS. If the RTC interrupt is enabled in GPTIMR, the GPTM
also sets the RTCMIS bit in GPTMISR and generates a controller interrupt. The status flags are
cleared by writing the RTCCINT bit in GPTMICR.
If the TASTALL and/or TBSTALL bits in the GPTMCTL register are set, the timer does not freeze if
the RTCEN bit is set in GPTMCTL.
9.2.3
16-Bit Timer Operating Modes
The GPTM is placed into global 16-bit mode by writing a value of 0x4 to the GPTM Configuration
(GPTMCFG) register (see page 165). This section describes each of the GPTM 16-bit modes of
operation. Timer A and Timer B have identical modes, so a single description is given using an n
to reference both.
9.2.3.1
16-Bit One-Shot/Periodic Timer Mode
In 16-bit one-shot and periodic timer modes, the timer is configured as a 16-bit down-counter with
an optional 8-bit prescaler that effectively extends the counting range of the timer to 24 bits. The
selection of one-shot or periodic mode is determined by the value written to the TnMR field of the
GPTMTnMR register. The optional prescaler is loaded into the GPTM Timern Prescale
(GPTMTnPR) register.
When software writes the TnEN bit in the GPTMCTL register, the timer begins counting down from
its preloaded value. Once the 0x0000 state is reached, the timer reloads its start value from
GPTMTnILR and GPTMTnPR on the next cycle. If configured to be a one-shot timer, the timer
stops counting and clears the TnEN bit in the GPTMCTL register. If configured as a periodic timer,
it continues counting.
In addition to reloading the count value, the timer generates interrupts and output triggers when it
reaches the 0x0000 state. The GPTM sets the TnTORIS bit in the GPTMRIS register, and holds it
until it is cleared by writing the GPTMICR register. If the time-out interrupt is enabled in GPTIMR,
the GPTM also sets the TnTOMIS bit in GPTMISR and generates a controller interrupt.
The output trigger is a one-clock-cycle pulse that is asserted when the counter hits the 0x0000
state, and deasserted on the following clock cycle. It is enabled by setting the TnOTE bit in the
GPTMCTL register, and can trigger SoC-level events such as ADC conversions.
If software reloads the GPTMTAILR register while the counter is running, the counter loads the
new value on the next clock cycle and continues counting from the new value.
If the TnSTALL bit in the GPTMCTL register is enabled, the timer freezes counting until the signal
is deasserted.
The following example shows a variety of configurations for a 16-bit free running timer while using
the prescaler. All values assume a 50-MHz clock with Tc=20 ns (clock period).
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Table 9-1.
16-Bit Timer with Prescaler Configurations
Prescale
#Clock (TC)a
Max Time
Units
00000000
1
1.3107
mS
00000001
2
2.6214
mS
00000010
3
3.9321
mS
------------
--
11111100
254
332.9229
mS
11111110
255
334.2336
mS
11111111
256
335.5443
mS
a. TC is the clock period.
9.2.3.2
16-Bit Input Edge Count Mode
In Edge Count mode, the timer is configured as a down-counter capable of capturing three types
of events: rising edge, falling edge, or both. To place the timer in Edge Count mode, the TnCMR bit
of the GPTMTnMR register must be set to 0. The type of edge that the timer counts is determined
by the TnEVENT fields of the GPTMCTL register. During initialization, the GPTM Timern Match
(GPTMTnMATCHR) register is configured so that the difference between the value in the
GPTMTnILR register and the GPTMTnMATCHR register equals the number of edge events that
must be counted.
When software writes the TnEN bit in the GPTM Control (GPTMCTL) register, the timer is enabled
for event capture. Each input event on the CCP pin decrements the counter by 1 until the event
count matches GPTMTnMATCHR. When the counts match, the GPTM asserts the CnMRIS bit in
the GPTMRIS register (and the CnMMIS bit, if the interrupt is not masked). The counter is then
reloaded using the value in GPTMTnILR, and stopped since the GPTM automatically clears the
TnEN bit in the GPTMCTL register. Once the event count has been reached, all further events are
ignored until TnEN is re-enabled by software.
Figure 9-2 shows how input edge count mode works. In this case, the timer start value is set to
GPTMnILR=0x000A and the match value is set to GPTMnMATCHR=0x0006 so that four edge
events are counted. The counter is configured to detect both edges of the input signal.
Note that the last two edges are not counted since the timer automatically clears the TnEN bit after
the current count matches the value in the GPTMnMR register.
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Figure 9-2.
16-Bit Input Edge Count Mode Example
Timer reload
on next cycle
Count
Ignored
Ignored
0x000A
0x0009
0x0008
0x0007
0x0006
Timer stops,
flags
asserted
Input Signal
9.2.3.3
16-Bit Input Edge Time Mode
In Edge Time mode, the timer is configured as a free-running down-counter initialized to the value
loaded in the GPTMTnILR register (or 0xFFFF at reset). This mode allows for event capture of
both rising and falling edges. The timer is placed into Edge Time mode by setting the TnCMR bit in
the GPTMTnMR register, and the type of event that the timer captures is determined by the
TnEVENT fields of the GPTMCTL register.
Note:
Prescaler is not available in 16-Bit Input Edge Time mode.
When software writes the TnEN bit in the GPTMCTL register, the timer is enabled for event
capture. When the selected input event is detected, the current Tn counter value is captured in the
GPTMTnR register and is available to be read by the controller. The GPTM then asserts the
CnERIS bit (and the CnEMIS bit, if the interrupt is not masked).
After an event has been captured, the timer does not stop counting. It continues to count until the
TnEN bit is cleared. When the timer reaches the 0x0000 state, it is reloaded with the value from the
GPTMnILR register.
Figure 9-3 shows how input edge timing mode works. In the diagram, it is assumed that the start
value of the timer is the default value of 0xFFFF, and the timer is configured to capture rising edge
events.
Each time a rising edge event is detected, the current count value is loaded into the GPTMTnR
register, and is held there until another rising edge is detected (at which point the new count value
is loaded into GPTMTnR).
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Figure 9-3.
16-Bit Input Edge Time Mode Example
Count
0xFFFF
GPTMTnR=X
GPTMTnR=Y
GPTMTnR=Z
Z
X
Y
Time
Input Signal
9.2.3.4
16-Bit PWM Mode
The GPTM supports a simple PWM generation mode. In PWM mode, the timer is configured as a
down-counter with a start value (and thus period) defined by GPTMTnILR. PWM mode is enabled
with the GPTMTnMR register by setting the TnAMS bit to 0x1, the TNCMR bit to 0x0, and the TnMR
field to 0x2.
PWM mode can take advantage of the 8-bit prescaler by using the GPTM Timern Prescale
Register (GPTMTnPR) and the GPTM Timern Prescale Match Register (GPTMTnPMR). This
effectively extends the range of the timer to 24 bits.
When software writes the TnEN bit in the GPTMCTL register, the counter begins counting down
until it reaches the 0x0000 state. On the next counter cycle, the counter reloads its start value from
GPTMTnILR (and GPTMTnPR if using a prescaler) and continues counting until disabled by
software clearing the TnEN bit in the GPTMCTL register. No interrupts or status bits are asserted
in PWM mode.
The output PWM signal asserts when the counter is at the value of the GPTMTnILR register (its
start state), and is deasserted when the counter value equals the value in the GPTM Timern
Match Register (GPTMnMATCHR). Software has the capability of inverting the output PWM
signal by setting the TnPWML bit in the GPTMCTL register.
Figure 9-4 shows how to generate an output PWM with a 1-ms period and a 66% duty cycle
assuming a 50-MHz input clock and TnPWML=0 (duty cycle would be 33% for the TnPWML=1
configuration). For this example, the start value is GPTMnIRL=0xC350 and the match value is
GPTMnMR=0x411A.
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Figure 9-4.
16-Bit PWM Mode Example
Count
GPTMTnR=GPTMnMR
GPTMTnR=GPTMnMR
0xC350
0x411A
Time
TnEN set
TnPWML = 0
Output
Signal
TnPWML = 1
9.3
Initialization and Configuration
To use the general purpose timers, the peripheral clock must be enabled by setting the GPTM0,
GPTM1, and GPTM2 bits in the RCGC1 register.
This section shows module initialization and configuration examples for each of the supported
timer modes.
9.3.1
32-Bit One-Shot/Periodic Timer Mode
The GPTM is configured for 32-bit One-Shot and Periodic modes by the following sequence:
1. Ensure the timer is disabled (the TAEN bit in the GPTMCTL register is cleared) before making
any changes.
2. Write the GPTM Configuration Register (GPTMCFG) with a value of 0x0.
3. Set the TAMR field in the GPTM TimerA Mode Register (GPTMTAMR):
a. Write a value of 0x1 for One-Shot mode.
b. Write a value of 0x2 for Periodic mode.
4. Load the start value into the GPTM TimerA Interval Load Register (GPTMTAILR).
5. If interrupts are required, set the TATOIM bit in the GPTM Interrupt Mask Register
(GPTMIMR).
6. Set the TAEN bit in the GPTMCTL register to enable the timer and start counting.
7. Poll the TATORIS bit in the GPTMRIS register or wait for the interrupt to be generated (if
enabled). In both cases, the status flags are cleared by writing a 1 to the TATOCINT bit of the
GPTM Interrupt Clear Register (GPTMICR).
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In One-Shot mode, the timer stops counting after step 7. To re-enable the timer, repeat the
sequence. A timer configured in Periodic mode does not stop counting after it times out.
9.3.2
32-Bit Real-Time Clock (RTC) Mode
To use the RTC mode, the timer must have a 32.768-KHz input signal on its CCP0, CCP2 or CCP4
pins. To enable the RTC feature, follow these steps:
1. Ensure the timer is disabled (the TAEN bit is cleared) before making any changes.
2. Write the GPTM Configuration Register (GPTMCFG) with a value of 0x1.
3. Write the desired match value to the GPTM TimerA Match Register (GPTMTAMATCHR).
4. Set/clear the RTCEN bit in the GPTM Control Register (GPTMCTL) as desired.
5. If interrupts are required, set the RTCIM bit in the GPTM Interrupt Mask Register
(GPTMIMR).
6. Set the TAEN bit in the GPTMCTL register to enable the timer and start counting.
When the timer count equals the value in the GPTMTAMATCHR register, the counter is re-loaded
with 0x00000000 and begins counting. If an interrupt is enabled, it does not have to be cleared.
9.3.3
16-Bit One-Shot/Periodic Timer Mode
A timer is configured for 16-bit One-Shot and Periodic modes by the following sequence:
1. Ensure the timer is disabled (the TnEN bit is cleared) before making any changes.
2. Write the GPTM Configuration Register (GPTMCFG) with a value of 0x4.
3. Set the TnMR field in the GPTM Timer Mode (GPTMTnMR) register:
a. Write a value of 0x1 for One-Shot mode.
b. Write a value of 0x2 for Periodic mode.
4. If a prescaler is to be used, write the prescale value to the GPTM Timern Prescale Register
(GPTMTnPR).
5. Load the start value into the GPTM Timer Interval Load Register (GPTMTnILR).
6. If interrupts are required, set the TnTOIM bit in the GPTM Interrupt Mask Register
(GPTMIMR).
7. Set the TnEN bit in the GPTM Control Register (GPTMCTL) to enable the timer and start
counting.
8. Poll the TnTORIS bit in the GPTMRIS register or wait for the interrupt to be generated (if
enabled). In both cases, the status flags are cleared by writing a 1 to the TnTOCINT bit of the
GPTM Interrupt Clear Register (GPTMICR).
In One-Shot mode, the timer stops counting after step 8. To re-enable the timer, repeat the
sequence. A timer configured in Periodic mode does not stop counting after it times out.
9.3.4
16-Bit Input Edge Count Mode
A timer is configured to Input Edge Count mode by the following sequence:
1. Ensure the timer is disabled (the TnEN bit is cleared) before making any changes.
2. Write the GPTM Configuration (GPTMCFG) register with a value of 0x4.
3. In the GPTM Timer Mode (GPTMTnMR) register, write the TnCMR field to 0x0 and the TnMR
field to 0x3.
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4. Configure the type of event(s) that the timer captures by writing the TnEVENT field of the
GPTM Control (GPTMCTL) register.
5. Load the timer start value into the GPTM Timern Interval Load (GPTMTnILR) register.
6. Load the desired event count into the GPTM Timern Match (GPTMTnMATCHR) register.
7. If interrupts are required, set the CnMIM bit in the GPTM Interrupt Mask (GPTMIMR) register.
8. Set the TnEN bit in the GPTMCTL register to enable the timer and begin waiting for edge
events.
9. Poll the CnMRIS bit in the GPTMRIS register or wait for the interrupt to be generated (if
enabled). In both cases, the status flags are cleared by writing a 1 to the CnMCINT bit of the
GPTM Interrupt Clear (GPTMICR) register.
In Input Edge Count Mode, the timer stops after the desired number of edge events has been
detected. To re-enable the timer, ensure that the TnEN bit is cleared and repeat steps 4-9.
9.3.5
16-Bit Input Edge Timing Mode
A timer is configured to Input Edge Timing mode by the following sequence:
1. Ensure the timer is disabled (the TnEN bit is cleared) before making any changes.
2. Write the GPTM Configuration (GPTMCFG) register with a value of 0x4.
3. In the GPTM Timer Mode (GPTMTnMR) register, write the TnCMR field to 0x1 and the TnMR
field to 0x3.
4. Configure the type of event that the timer captures by writing the TnEVENT field of the GPTM
Control (GPTMCTL) register.
5. Load the timer start value into the GPTM Timern Interval Load (GPTMTnILR) register.
6. If interrupts are required, set the CnEIM bit in the GPTM Interrupt Mask (GPTMIMR) register.
7. Set the TnEN bit in the GPTM Control (GPTMCTL) register to enable the timer and start
counting.
8. Poll the CnERIS bit in the GPTMRIS register or wait for the interrupt to be generated (if
enabled). In both cases, the status flags are cleared by writing a 1 to the CnECINT bit of the
GPTM Interrupt Clear (GPTMICR) register. The time at which the event happened can be
obtained by reading the GPTM Timern (GPTMTnR) register.
In Input Edge Timing mode, the timer continues running after an edge event has been detected,
but the timer interval can be changed at any time by writing the GPTMTnILR register. The change
takes effect at the next cycle after the write.
9.3.6
16-Bit PWM Mode
A timer is configured to PWM mode using the following sequence:
1. Ensure the timer is disabled (the TnEN bit is cleared) before making any changes.
2. Write the GPTM Configuration (GPTMCFG) register with a value of 0x4.
3. In the GPTM Timer Mode (GPTMTnMR) register, set the TnAMS bit to 0x1, the TNCMR bit to
0x0, and the TnMR field to 0x2.
4. Configure the output state of the PWM signal (whether or not it is inverted) in the TnEVENT
field of the GPTM Control (GPTMCTL) register.
5. Load the timer start value into the GPTM Timern Interval Load (GPTMTnILR) register.
6. Load the GPTM Timern Match (GPTMTnMATCHR) register with the desired value.
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7. If a prescaler is going to be used, configure the GPTM Timern Prescale (GPTMTnPR)
register and the GPTM Timern Prescale Match (GPTMTnPMR) register.
8. Set the TnEN bit in the GPTM Control (GPTMCTL) register to enable the timer and begin
generation of the output PWM signal.
In PWM Timing mode, the timer continues running after the PWM signal has been generated. The
PWM period can be adjusted at any time by writing the GPTMTnILR register, and the change
takes effect at the next cycle after the write.
9.4
Register Map
Table 9-1 lists the GPTM registers. The offset listed is a hexadecimal increment to the register’s
address, relative to that timer’s base address:
„
Timer0: 0x40030000
„
Timer1: 0x40031000
„
Timer2: 0x40032000
Table 9-2. GPTM Register Map
Type
Description
See
page
0x00000000
R/W
Configuration
165
GPTMTAMR
0x00000000
R/W
TimerA mode
166
0x008
GPTMTBMR
0x00000000
R/W
TimerB mode
167
0x00C
GPTMCTL
0x00000000
R/W
Control
168
0x018
GPTMIMR
0x00000000
R/W
Interrupt mask
170
0x01C
GPTMRIS
0x00000000
RO
Interrupt status
172
0x020
GPTMMIS
0x00000000
RO
Masked interrupt status
173
0x024
GPTMICR
0x00000000
W1C
Interrupt clear
174
0x028
GPTMTAILR
0x0000FFFFa
0xFFFFFFFF
R/W
TimerA interval load
175
0x02C
GPTMTBILR
0x0000FFFF
R/W
TimerB interval load
176
0x030
GPTMTAMATCHR
0x0000FFFFa
0xFFFFFFFF
R/W
TimerA match
177
0x034
GPTMTBMATCHR
0x0000FFFF
R/W
TimerB match
178
0x038
GPTMTAPR
0x00000000
R/W
TimerA prescale
179
0x03C
GPTMTBPR
0x00000000
R/W
TimerB prescale
180
0x040
GPTMTAPMR
0x00000000
R/W
TimerA prescale match
181
0x044
GPTMTBPMR
0x00000000
R/W
TimerB prescale match
182
Offset
Name
0x000
GPTMCFG
0x004
Reset
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General-Purpose Timers
Table 9-2. GPTM Register Map (Continued)
Offset
Name
0x048
0x04C
See
page
Reset
Type
Description
GPTMTAR
0x0000FFFFa
0xFFFFFFFF
RO
TimerA
183
GPTMTBR
0x0000FFFF
RO
TimerB
184
a. The default reset value for the GPTMTAILR, GPTMTAMATCHR, and GPTMTAR registers is 0x0000FFFF when in 16-bit mode
and 0xFFFFFFFF when in 32-bit mode.
9.5
Register Descriptions
The remainder of this section lists and describes the GPTM registers, in numerical order by
address offset.
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LM3S818 Data Sheet
Register 1: GPTM Configuration (GPTMCFG), offset 0x000
This register configures the global operation of the GPTM module. The value written to this
register determines whether the GPTM is in 32- or 16-bit mode.
GPTM Configuration (GPTMCFG)
Offset 0x000
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
GPTMCFG
R/W
0
R/W
0
Bit/Field
Name
Type
Reset
Description
31:3
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
2:0
GPTMCFG
R/W
0
GPTM Configuration
0x0: 32-bit timer configuration.
0x1: 32-bit real-time clock (RTC) counter configuration.
0x2: Reserved.
0x3: Reserved.
0x4-0x7: 16-bit timer configuration, function is controlled by bits
1:0 of GPTMTAMR and GPTMTBMR.
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Preliminary
General-Purpose Timers
Register 2: GPTM TimerA Mode (GPTMTAMR), offset 0x004
This register configures the GPTM based on the configuration selected in the GPTMCFG register.
When in 16-bit PWM mode, set the TAAMS bit to 0x1, the TACMR bit to 0x0, and the TAMR field to
0x2.
GPTM TimerA Mode (GPTMTAMR)
Offset 0x004
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
TAAMS TACMR
reserved
Type
Reset
R/W
0
R/W
0
TAMR
R/W
0
R/W
0
Bit/Field
Name
Type
Reset
Description
31:4
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
3
TAAMS
R/W
0
GPTM TimerA Alternate Mode Select
0: Capture mode is enabled.
1: PWM mode is enabled.
Note:
2
TACMR
R/W
0
To enable PWM mode, you must also clear the TACMR
bit and set the TAMR field to 0x2.
GPTM TimerA Capture Mode
0: Edge-Count mode.
1: Edge-Time mode.
1:0
TAMR
R/W
0
GPTM TimerA Mode
0x0: Reserved.
0x1: One-Shot Timer mode.
0x2: Periodic Timer mode.
0x3: Capture mode.
The Timer mode is based on the timer configuration defined by
bits 2:0 in the GPTMCFG register (16-or 32-bit).
In 16-bit timer configuration, TAMR controls the 16-bit timer
modes for TimerA.
In 32-bit timer configuration, this register controls the mode and
the contents of GPTMTBMR are ignored.
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Register 3: GPTM TimerB Mode (GPTMTBMR), offset 0x008
This register configures the GPTM based on the configuration selected in the GPTMCFG register.
When in 16-bit PWM mode, set the TBAMS bit to 0x1, the TBCMR bit to 0x0, and the TBMR field to
0x2.
GPTM TimerB Mode (GPTMTBMR)
Offset 0x008
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
TBAMS TBCMR
reserved
Type
Reset
R/W
0
R/W
0
TBMR
R/W
0
R/W
0
Bit/Field
Name
Type
Reset
Description
31:4
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
3
TBAMS
R/W
0
GPTM TimerB Alternate Mode Select
0: Capture mode is enabled.
1: PWM mode is enabled.
Note:
2
TBCMR
R/W
0
To enable PWM mode, you must also clear the TBCMR
bit and set the TBMR field to 0x2.
GPTM TimerB Capture Mode
0: Edge-Count mode.
1: Edge-Time mode.
1:0
TBMR
R/W
0
GPTM TimerB Mode
0x0: Reserved.
0x1: One-Shot Timer mode.
0x2: Periodic Timer mode.
0x3: Capture mode.
The timer mode is based on the timer configuration defined by
bits 2:0 in the GPTMCFG register.
In 16-bit timer configuration, these bits control the 16-bit timer
modes for TimerB.
In 32-bit timer configuration, this register’s contents are ignored
and GPTMTAMR is used.
May 4, 2007
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Preliminary
General-Purpose Timers
Register 4: GPTM Control (GPTMCTL), offset 0x00C
This register is used alongside the GPTMCFG and GMTMTnMR registers to fine-tune the timer
configuration, and to enable other features such as timer stall and the output trigger. The output
trigger can be used to initiate transfers on the ADC module.
GPTM Control (GPTMCTL)
Offset 0x00C
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
res
TBPWML
TBOTE
res
RO
0
R/W
0
R/W
0
RO
0
TBSTALL
TBEN
res
TASTALL
TAEN
R/W
0
R/W
0
RO
0
R/W
0
R/W
0
reserved
Type
Reset
Type
Reset
TBEVENT
R/W
0
R/W
0
TAPWML TAOTE
R/W
0
R/W
0
RTCEN
R/W
0
TAEVENT
R/W
0
R/W
0
Bit/Field
Name
Type
Reset
Description
31:15
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
14
TBPWML
R/W
0
GPTM TimerB PWM Output Level
0: Output is unaffected.
1: Output is inverted.
13
TBOTE
R/W
0
GPTM TimerB Output Trigger Enable
0: The output TimerB trigger is disabled.
1: The output TimerB trigger is enabled.
12
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
11:10
TBEVENT
R/W
0
GPTM TimerB Event Mode
00: Positive edge.
01: Negative edge.
10: Reserved.
11: Both edges.
9
TBSTALL
R/W
0
GPTM TimerB Stall Enable
0: TimerB stalling is disabled.
1: TimerB stalling is enabled.
8
TBEN
R/W
0
GPTM TimerB Enable
0: TimerB is disabled.
1: TimerB is enabled and begins counting or the capture logic is
enabled based on the GPTMCFG register.
7
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
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LM3S818 Data Sheet
Bit/Field
Name
Type
Reset
6
TAPWML
R/W
0
Description
GPTM TimerA PWM Output Level
0: Output is unaffected.
1: Output is inverted.
5
TAOTE
R/W
0
GPTM TimerA Output Trigger Enable
0: The output TimerA trigger is disabled.
1: The output TimerA trigger is enabled.
4
RTCEN
R/W
0
GPTM RTC Enable
0: RTC counting is disabled.
1: RTC counting is enabled.
3:2
TAEVENT
R/W
0
GPTM TimerA Event Mode
00: Positive edge.
01: Negative edge.
10: Reserved.
11: Both edges.
1
TASTALL
R/W
0
GPTM TimerA Stall Enable
0: TimerA stalling is disabled.
1: TimerA stalling is enabled.
0
TAEN
R/W
0
GPTM TimerA Enable
0: TimerA is disabled.
1: TimerA is enabled and begins counting or the capture logic is
enabled based on the GPTMCFG register.
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General-Purpose Timers
Register 5: GPTM Interrupt Mask (GPTMIMR), offset 0x018
This register allows software to enable/disable GPTM controller-level interrupts. Writing a 1
enables the interrupt, while writing a 0 disables it.
GPTM Interrupt Mask (GPTMIMR)
Offset 0x018
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
CBEIM CBMIM TBTOIM
reserved
Type
Reset
RO
0
R/W
0
R/W
0
R/W
0
reserved
RTCIM
R/W
0
CAEIM CAMIM TATOIM
R/W
0
R/W
0
R/W
0
Bit/Field
Name
Type
Reset
Description
31:11
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
10
CBEIM
R/W
0
GPTM CaptureB Event Interrupt Mask
0: Interrupt is disabled.
1: Interrupt is enabled.
9
CBMIM
R/W
0
GPTM CaptureB Match Interrupt Mask
0: Interrupt is disabled.
1: Interrupt is enabled.
8
TBTOIM
R/W
0
GPTM TimerB Time-Out Interrupt Mask
0: Interrupt is disabled.
1: Interrupt is enabled.
7:4
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
3
RTCIM
R/W
0
GPTM RTC Interrupt Mask
0: Interrupt is disabled.
1: Interrupt is enabled.
2
CAEIM
R/W
0
GPTM CaptureA Event Interrupt Mask
0: Interrupt is disabled.
1: Interrupt is enabled.
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LM3S818 Data Sheet
Bit/Field
Name
Type
Reset
1
CAMIM
R/W
0
Description
GPTM CaptureA Match Interrupt Mask
0: Interrupt is disabled.
1: Interrupt is enabled.
0
TATOIM
R/W
0
GPTM TimerA Time-Out Interrupt Mask
0: Interrupt is disabled.
1: Interrupt is enabled.
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Preliminary
General-Purpose Timers
Register 6: GPTM Raw Interrupt Status (GPTMRIS), offset 0x01C
This register shows the state of the GPTM's internal interrupt signal. These bits are set whether or
not the interrupt is masked in the GPTMIMR register. Each bit can be cleared by writing a 1 to its
corresponding bit in GPTMICR.
GPTM Raw Interrupt Status (GPTMRIS)
Offset 0x01C
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RTCRIS
CAERIS
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
CBERIS
reserved
CBMRIS TBTORIS
RO
0
RO
0
RO
0
CAMRIS TATORIS
RO
0
RO
0
Bit/Field
Name
Type
Reset
Description
31:11
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
10
CBERIS
RO
0
GPTM CaptureB Event Raw Interrupt
This is the CaptureB Event interrupt status prior to masking.
9
CBMRIS
RO
0
GPTM CaptureB Match Raw Interrupt
This is the CaptureB Match interrupt status prior to masking.
8
TBTORIS
RO
0
GPTM TimerB Time-Out Raw Interrupt
This is the TimerB time-out interrupt status prior to masking.
7:4
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
3
RTCRIS
RO
0
GPTM RTC Raw Interrupt
This is the RTC Event interrupt status prior to masking.
2
CAERIS
RO
0
GPTM CaptureA Event Raw Interrupt
This is the CaptureA Event interrupt status prior to masking.
1
CAMRIS
RO
0
GPTM CaptureA Match Raw Interrupt
This is the CaptureA Match interrupt status prior to masking.
0
TATORIS
RO
0
GPTM TimerA Time-Out Raw Interrupt
This the TimerA time-out interrupt status prior to masking.
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LM3S818 Data Sheet
Register 7: GPTM Masked Interrupt Status (GPTMMIS), offset 0x020
This register show the state of the GPTM's controller-level interrupt. If an interrupt is unmasked in
GPTMIMR, and there is an event that causes the interrupt to be asserted, the corresponding bit is
set in this register. All bits are cleared by writing a 1 to the corresponding bit in GPTMICR.
GPTM Masked Interrupt Status (GPTMMIS)
Offset 0x020
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
CBEMIS
reserved
CBMMIS TBTOMIS
RO
0
RO
0
RO
0
RTCMIS
RO
0
CAEMIS CAMMIS TATOMIS
RO
0
RO
0
RO
0
Bit/Field
Name
Type
Reset
Description
31:11
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
10
CBEMIS
RO
0
GPTM CaptureB Event Masked Interrupt
This is the CaptureB event interrupt status after masking.
9
CBMMIS
RO
0
GPTM CaptureB Match Masked Interrupt
This is the CaptureB match interrupt status after masking.
8
TBTOMIS
RO
0
GPTM TimerB Time-Out Masked Interrupt
This is the TimerB time-out interrupt status after masking.
7:4
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
3
RTCMIS
RO
0
GPTM RTC Masked Interrupt
This is the RTC event interrupt status after masking.
2
CAEMIS
RO
0
GPTM CaptureA Event Masked Interrupt
This is the CaptureA event interrupt status after masking.
1
CAMMIS
RO
0
GPTM CaptureA Match Masked Interrupt
This is the CaptureA match interrupt status after masking.
0
TATOMIS
RO
0
GPTM TimerA Time-Out Masked Interrupt
This is the TimerA time-out interrupt status after masking.
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General-Purpose Timers
Register 8: GPTM Interrupt Clear (GPTMICR), offset 0x024
This register is used to clear the status bits in the GPTMRIS and GPTMMIS registers. Writing a 1
to a bit clears the corresponding bit in the GPTMRIS and GPTMMIS registers.
GPTM Interrupt Clear (GPTMICR)
Offset 0x024
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
W1C
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
reserved
CBECINT CBMCINT TBTOCINT
W1C
0
W1C
0
W1C
0
RTCCINT CAECINT CAMCINTTATOCINT
W1C
0
W1C
0
W1C
0
W1C
0
Bit/Field
Name
Type
Reset
Description
31:11
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
10
CBECINT
W1C
0
GPTM CaptureB Event Interrupt Clear
0: The interrupt is unaffected.
1: The interrupt is cleared.
9
CBMCINT
W1C
0
GPTM CaptureB Match Interrupt Clear
0: The interrupt is unaffected.
1: The interrupt is cleared.
8
TBTOCINT
W1C
0
GPTM TimerB Time-Out Interrupt Clear
0: The interrupt is unaffected.
1: The interrupt is cleared.
7:4
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
3
RTCCINT
W1C
0
GPTM RTC Interrupt Clear
0: The interrupt is unaffected.
1: The interrupt is cleared.
2
CAECINT
W1C
0
GPTM CaptureA Event Interrupt Clear
0: The interrupt is unaffected.
1: The interrupt is cleared.
1
CAMCINT
W1C
0
GPTM CaptureA Match Raw Interrupt
This is the CaptureA match interrupt status after masking.
0
TATOCINT
W1C
0
GPTM TimerA Time-Out Raw Interrupt
0: The interrupt is unaffected.
1: The interrupt is cleared.
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LM3S818 Data Sheet
Register 9: GPTM TimerA Interval Load (GPTMTAILR), offset 0x028
This register is used to load the starting count value into the timer. When GPTM is configured to
one of the 32-bit modes, GPTMTAILR appears as a 32-bit register (the upper 16-bits correspond
to the contents of the GPTM TimerB Interval Load (GPTMTBILR) register). In 16-bit mode, the
upper 16 bits of this register read as 0s and have no effect on the state of GPTMTBILR.
GPTM TimerA Interval Load (GPTMTAILR)
Offset 0x028
31
30
29
28
27
26
25
24
23
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
15
14
13
12
11
10
9
8
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
22
21
20
19
18
17
16
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
7
6
5
4
3
2
1
0
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
TAILRH
Type
Reset
TAILRL
Type
Reset
R/W
1
1/0 = 1 if timer is configured in 32-bit mode; 0 if timer is configured in 16-bit mode.
Bit/Field
Name
Type
Reset
Description
31:16
TAILRH
R/W
0xFFFF
(32-bit
mode)
0x0000
(16-bit
mode)
15:0
TAILRL
R/W
0xFFFF
GPTM TimerA Interval Load Register High
When configured for 32-bit mode via the GPTMCFG register,
the GPTM TimerB Interval Load (GPTMTBILR) register loads
this value on a write. A read returns the current value of
GPTMTBILR.
In 16-bit mode, this field reads as 0 and does not have an effect
on the state of GPTMTBILR.
GPTM TimerA Interval Load Register Low
For both 16- and 32-bit modes, writing this field loads the
counter for TimerA. A read returns the current value of
GPTMTAILR.
May 4, 2007
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Preliminary
General-Purpose Timers
Register 10: GPTM TimerB Interval Load (GPTMTBILR), offset 0x02C
This register is used to load the starting count value into TimerB. When the GPTM is configured to
a 32-bit mode, GPTMTBILR returns the current value of TimerB and ignores writes.
GPTM TimerB Interval Load (GPTMTBILR)
Offset 0x02C
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
reserved
Type
Reset
TBILRL
Type
Reset
Bit/Field
Name
Type
Reset
Description
31:16
reserved
RO
0
15:0
TBILRL
R/W
0xFFFF
Reserved bits return an indeterminate value, and should never
be changed.
GPTM TimerB Interval Load Register
When the GPTM is not configured as a 32-bit timer, a write to
this field updates GPTMTBILR. In 32-bit mode, writes are
ignored, and reads return the current value of GPTMTBILR.
176
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 11: GPTM TimerA Match (GPTMTAMATCHR), offset 0x030
This register is used in 32-bit Real-Time Clock mode and 16-bit PWM and Input Edge Count
modes.
GPTM TimerA Match (GPTMTAMATCHR)
Offset 0x030
31
30
29
28
27
26
25
24
23
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
15
14
13
12
11
10
9
8
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
22
21
20
19
18
17
16
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
7
6
5
4
3
2
1
0
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
TAMRH
Type
Reset
TAMRL
Type
Reset
R/W
1
1/0 = 1 if timer is configured in 32-bit mode; 0 if timer is configured in 16-bit mode.
Bit/Field
Name
Type
Reset
Description
31:16
TAMRH
R/W
0xFFFF
(32-bit
mode)
0x0000
(16-bit
mode)
15:0
TAMRL
R/W
0xFFFF
GPTM TimerA Match Register High
When configured for 32-bit Real-Time Clock (RTC) mode via
the GPTMCFG register, this value is compared to the upper
half of GPTMTAR, to determine match events.
In 16-bit mode, this field reads as 0 and does not have an effect
on the state of GPTMTBMATCHR.
GPTM TimerA Match Register Low
When configured for 32-bit Real-Time Clock (RTC) mode via
the GPTMCFG register, this value is compared to the lower half
of GPTMTAR, to determine match events.
When configured for PWM mode, this value along with
GPTMTAILR, determines the duty cycle of the output PWM
signal.
When configured for Edge Count mode, this value along with
GPTMTAILR, determines how many edge events are counted.
The total number of edge events counted is equal to the value
in GPTMTAILR minus this value.
May 4, 2007
177
Preliminary
General-Purpose Timers
Register 12: GPTM TimerB Match (GPTMTBMATCHR), offset 0x034
This register is used in 32-bit Real-Time Clock mode and 16-bit PWM and Input Edge Count
modes.
GPTM TimerB Match (GPTMTBMATCHR)
Offset 0x034
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
TBMRL
Type
Reset
Bit/Field
Name
Type
Reset
31:16
reserved
RO
0
15:0
TBMRL
R/W
0xFFFF
R/W
0
Description
Reserved bits return an indeterminate value, and should never
be changed.
GPTM TimerB Match Register Low
When configured for PWM mode, this value along with
GPTMTBILR, determines the duty cycle of the output PWM
signal.
When configured for Edge Count mode, this value along with
GPTMTBILR, determines how many edge events are counted.
The total number of edge events counted is equal to the value
in GPTMTBILR minus this value.
178
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 13: GPTM TimerA Prescale (GPTMTAPR), offset 0x038
This register allows software to extend the range of the 16-bit timers.
GPTM TimerA Prescale (GPTMTAPR)
Offset 0x038
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
TAPSR
R/W
0
Bit/Field
Name
Type
Reset
Description
31:8
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
7:0
TAPSR
R/W
0
GPTM TimerA Prescale
The register loads this value on a write. A read returns the
current value of the register.
Refer to Table 9-1 on page 157 for more details and an
example.
May 4, 2007
179
Preliminary
General-Purpose Timers
Register 14: GPTM TimerB Prescale (GPTMTBPR), offset 0x03C
This register allows software to extend the range of the 16-bit timers.
GPTM TimerB Prescale (GPTMTBPR)
Offset 0x03C
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
TBPSR
R/W
0
Bit/Field
Name
Type
Reset
Description
31:8
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
7:0
TBPSR
R/W
0
GPTM TimerB Prescale
The register loads this value on a write. A read returns the
current value of this register.
Refer to Table 9-1 on page 157 for more details and an
example.
180
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 15: GPTM TimerA Prescale Match (GPTMTAPMR), offset 0x040
This register effectively extends the range of GPTMTAMATCHR to 24 bits.
GPTM TimerA Prescale Match (GPTMTAPMR)
Offset 0x040
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
TAPSMR
R/W
0
Bit/Field
Name
Type
Reset
Description
31:8
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
7:0
TAPSMR
R/W
0
GPTM TimerA Prescale Match
This value is used alongside GPTMTAMATCHR to detect timer
match events while using a prescaler.
May 4, 2007
181
Preliminary
General-Purpose Timers
Register 16: GPTM TimerB Prescale Match (GPTMTBPMR), offset 0x044
This register effectively extends the range of GPTMTBMATCHR to 24 bits.
GPTM TimerB Prescale Match (GPTMTBPMR)
Offset 0x044
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
TBPSMR
R/W
0
Bit/Field
Name
Type
Reset
Description
31:8
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
7:0
TBPSMR
R/W
0
GPTM TimerB Prescale Match
This value is used alongside GPTMTBMATCHR to detect timer
match events while using a prescaler.
182
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 17: GPTM TimerA (GPTMTAR), offset 0x048
This register shows the current value of the TimerA counter in all cases except for Input Edge
Count mode. When in this mode, this register contains the time at which the last edge event took
place.
GPTM TimerA (GPTMTAR)
Offset 0x048
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
1/0
RO
1/0
RO
1/0
RO
1/0
RO
1/0
RO
1/0
RO
1/0
RO
1/0
RO
1/0
RO
1/0
RO
1/0
RO
1/0
RO
1/0
RO
1/0
RO
1/0
RO
1/0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
TARH
Type
Reset
TARL
Type
Reset
1/0 = 1 if timer is configured in 32-bit mode; 0 if timer is configured in 16-bit mode.
Bit/Field
Name
Type
Reset
Description
31:16
TARH
RO
0xFFFF
(32-bit
mode)
GPTM TimerA Register High
If the GPTMCFG is in a 32-bit mode, TimerB value is read. If the
GPTMCFG is in a 16-bit mode, this is read as zero.
0x0000
(16-bit
mode)
15:0
TARL
RO
0xFFFF
GPTM TimerA Register Low
A read returns the current value of the GPTM TimerA Count
Register, except in Input Edge Count mode, when it returns the
timestamp from the last edge event.
May 4, 2007
183
Preliminary
General-Purpose Timers
Register 18: GPTM TimerB (GPTMTBR), offset 0x04C
This register shows the current value of the TimerB counter in all cases except for Input Edge
Count mode. When in this mode, this register contains the time at which the last edge event took
place.
GPTM TimerB (GPTMTBR)
Offset 0x04C
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
reserved
Type
Reset
TBRL
Type
Reset
Bit/Field
Name
Type
Reset
Description
31:16
reserved
RO
0
15:0
TBRL
RO
0xFFFF
Reserved bits return an indeterminate value, and should never
be changed.
GPTM TimerB
A read returns the current value of the GPTM TimerB Count
Register, except in Input Edge Count mode, when it returns the
timestamp from the last edge event.
184
May 4, 2007
Preliminary
LM3S818 Data Sheet
10
Watchdog Timer
A watchdog timer can generate nonmaskable interrupts (NMIs) or a reset when a time-out value is
reached. The watchdog timer is used to regain control when a system has failed due to a software
error or due to the failure of an external device to respond in the expected way.
The Stellaris Watchdog Timer module consists of a 32-bit down counter, a programmable load
register, interrupt generation logic, a locking register, and user-enabled stalling.
The Watchdog Timer can be configured to generate an interrupt to the controller on its first
time-out, and to generate a reset signal on its second time-out. Once the Watchdog Timer has
been configured, the lock register can be written to prevent the timer configuration from being
inadvertently altered.
10.1
Block Diagram
Figure 10-1. WDT Module Block Diagram
WDTLOAD
Control / Clock /
Interrupt
Generation
WDTCTL
WDTICR
Interrupt
WDTRIS
32-Bit Down
Counter
WDTMIS
0x00000000
WDTLOCK
System Clock
WDTTEST
Comparator
WDTVALUE
Identification Registers
WDTPCellID0
WDTPeriphID0
WDTPeriphID4
WDTPCellID1
WDTPeriphID1
WDTPeriphID5
WDTPCellID2
WDTPeriphID2
WDTPeriphID6
WDTPCellID3
WDTPeriphID3
WDTPeriphID7
May 4, 2007
185
Preliminary
Watchdog Timer
10.2
Functional Description
The Watchdog Timer module consists of a 32-bit down counter, a programmable load register,
interrupt generation logic, and a locking register. Once the Watchdog Timer has been configured,
the Watchdog Timer Lock (WDTLOCK) register is written, which prevents the timer configuration
from being inadvertently altered by software.
The Watchdog Timer module generates the first time-out signal when the 32-bit counter reaches
the zero state after being enabled; enabling the counter also enables the watchdog timer interrupt.
After the first time-out event, the 32-bit counter is re-loaded with the value of the Watchdog Timer
Load (WDTLOAD) register, and the timer resumes counting down from that value.
If the timer counts down to its zero state again before the first time-out interrupt is cleared, and the
reset signal has been enabled (via the WatchdogResetEnable function), the Watchdog timer
asserts its reset signal to the system. If the interrupt is cleared before the 32-bit counter reaches its
second time-out, the 32-bit counter is loaded with the value in the WDTLOAD register, and
counting resumes from that value.
If WDTLOAD is written with a new value while the Watchdog Timer counter is counting, then the
counter is loaded with the new value and continues counting.
Writing to WDTLOAD does not clear an active interrupt. An interrupt must be specifically cleared
by writing to the Watchdog Interrupt Clear (WDTICR) register.
The Watchdog module interrupt and reset generation can be enabled or disabled as required.
When the interrupt is re-enabled, the 32-bit counter is preloaded with the load register value and
not its last state.
10.3
Initialization and Configuration
To use the WDT, its peripheral clock must be enabled by setting the WDT bit in the RCGC0 register.
The Watchdog Timer is configured using the following sequence:
1. Load the WDTLOAD register with the desired timer load value.
2. If the Watchdog is configured to trigger system resets, set the RESEN bit in the WDTCTL
register.
3. Set the INTEN bit in the WDTCTL register to enable the Watchdog and lock the control
register.
If software requires that all of the watchdog registers are locked, the Watchdog Timer module can
be fully locked by writing any value to the WDTLOCK register. To unlock the Watchdog Timer,
write a value of 0x1ACCE551.
10.4
Register Map
Table 10-1 lists the Watchdog registers. The offset listed is a hexadecimal increment to the
register’s address, relative to the Watchdog Timer base address of 0x40000000.
Table 10-1.
WDT Register Map
Offset
Name
0x000
See
page
Reset
Type
Description
WDTLOAD
0xFFFFFFFF
R/W
Load
188
0x004
WDTVALUE
0xFFFFFFFF
RO
Current value
189
0x008
WDTCTL
0x00000000
R/W
Control
190
186
May 4, 2007
Preliminary
LM3S818 Data Sheet
Table 10-1.
WDT Register Map (Continued)
Offset
Name
0x00C
See
page
Reset
Type
Description
WDTICR
-
WO
Interrupt clear
191
0x010
WDTRIS
0x00000000
RO
Raw interrupt status
192
0x014
WDTMIS
0x00000000
RO
Masked interrupt status
193
0x418
WDTTEST
0x00000000
R/W
Watchdog stall enable
195
0xC00
WDTLOCK
0x00000000
R/W
Lock
194
0xFD0
WDTPeriphID4
0x00000000
RO
Peripheral identification 4
196
0xFD4
WDTPeriphID5
0x00000000
RO
Peripheral identification 5
197
0xFD8
WDTPeriphID6
0x00000000
RO
Peripheral identification 6
198
0xFDC
WDTPeriphID7
0x00000000
RO
Peripheral identification 7
199
0xFE0
WDTPeriphID0
0x00000005
RO
Peripheral identification 0
200
0xFE4
WDTPeriphID1
0x00000018
RO
Peripheral identification 1
201
0xFE8
WDTPeriphID2
0x00000018
RO
Peripheral identification 2
202
0xFEC
WDTPeriphID3
0x00000001
RO
Peripheral identification 3
203
0xFF0
WDTPCellID0
0x0000000D
RO
PrimeCell identification 0
204
0xFF4
WDTPCellID1
0x000000F0
RO
PrimeCell identification 1
205
0xFF8
WDTPCellID2
0x00000005
RO
PrimeCell identification 2
206
0xFFC
WDTPCellID3
0x000000B1
RO
PrimeCell identification 3
207
10.5
Register Descriptions
The remainder of this section lists and describes the WDT registers, in numerical order by address
offset.
May 4, 2007
187
Preliminary
Watchdog Timer
Register 1: Watchdog Load (WDTLOAD), offset 0x000
This register is the 32-bit interval value used by the 32-bit counter. When this register is written, the
value is immediately loaded and the counter restarts counting down from the new value. If the
WDTLOAD register is loaded with 0x00000000, an interrupt is immediately generated.
Watchdog Load (WDTLOAD)
Offset 0x000
31
30
29
28
27
26
25
24
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
15
14
13
12
11
10
9
8
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
23
22
21
20
19
18
17
16
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
7
6
5
4
3
2
1
0
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
WDTLoad
Type
Reset
WDTLoad
Type
Reset
Bit/Field
Name
Type
Reset
31:0
WDTLoad
R/W
0xFFFFFFFF
R/W
1
Description
Watchdog Load Value
188
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 2: Watchdog Value (WDTVALUE), offset 0x004
This register contains the current count value of the timer.
Watchdog Value (WDTVALUE)
Offset 0x004
31
30
29
28
27
26
25
24
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
15
14
13
12
11
10
9
8
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
23
22
21
20
19
18
17
16
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
7
6
5
4
3
2
1
0
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
WDTValue
Type
Reset
WDTValue
Type
Reset
Bit/Field
Name
Type
Reset
31:0
WDTValue
RO
0xFFFFFFFF
RO
1
Description
Watchdog Value
Current value of the 32-bit down counter.
May 4, 2007
189
Preliminary
Watchdog Timer
Register 3: Watchdog Control (WDTCTL), offset 0x008
This register is the watchdog control register. The watchdog timer can be configured to generate a
reset signal (upon second time-out) or an interrupt on time-out.
When the watchdog interrupt has been enabled, all subsequent writes to the control register are
ignored. The only mechanism that can re-enable writes is a hardware reset.
Watchdog Control (WDTCTL)
Offset 0x008
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RESEN
INTEN
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
Bit/Field
Name
Type
Reset
Description
31:2
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
1
RESEN
R/W
0
Watchdog Reset Enable
0: Disabled.
1: Enable the Watchdog module reset output.
0
INTEN
R/W
0
Watchdog Interrupt Enable
0: Interrupt event disabled (once this bit is set, it can only
be cleared by a hardware reset)
1: Interrupt event enabled. Once enabled, all writes are
ignored.
190
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 4: Watchdog Interrupt Clear (WDTICR), offset 0x00C
This register is the interrupt clear register. A write of any value to this register clears the Watchdog
interrupt and reloads the 32-bit counter from the WDTLOAD register. Value for a read or reset is
indeterminate.
Watchdog Interrupt Clear (WDTICR)
Offset 0x00C
31
30
29
28
27
26
25
24
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
15
14
13
12
11
10
9
8
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
23
22
21
20
19
18
17
16
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
7
6
5
4
3
2
1
0
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
WDTIntClr
Type
Reset
WDTIntClr
Type
Reset
Bit/Field
Name
Type
Reset
31:0
WDTIntClr
WO
-
WO
-
Description
Watchdog Interrupt Clear
May 4, 2007
191
Preliminary
Watchdog Timer
Register 5: Watchdog Raw Interrupt Status (WDTRIS), offset 0x010
This register is the raw interrupt status register. Watchdog interrupt events can be monitored via
this register if the controller interrupt is masked.
Watchdog Raw Interrupt Status (WDTRIS)
Offset 0x010
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
WDTRIS
RO
0
Bit/Field
Name
Type
Reset
Description
31:1
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
0
WDTRIS
RO
0
Watchdog Raw Interrupt Status
Gives the raw interrupt state (prior to masking) of
WDTINTR.
192
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 6: Watchdog Masked Interrupt Status (WDTMIS), offset 0x014
This register is the masked interrupt status register. The value of this register is the logical AND of
the raw interrupt bit and the Watchdog interrupt enable bit.
Watchdog Masked Interrupt Status (WDTMIS)
Offset 0x014
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
WDTMIS
reserved
Type
Reset
RO
0
RO
0
Bit/Field
Name
Type
Reset
Description
31:1
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
0
WDTMIS
RO
0
Watchdog Masked Interrupt Status
Gives the masked interrupt state (after masking) of the
WDTINTR interrupt.
May 4, 2007
193
Preliminary
Watchdog Timer
Register 7: Watchdog Lock (WDTLOCK), offset 0xC00
Writing 0x1ACCE551 to the WDTLOCK register enables write access to all other registers. Writing
any other value to the WDTLOCK register re-enables the locked state for register writes to all the
other registers. Reading the WDTLOCK register returns the lock status rather than the 32-bit
value written. Therefore, when write accesses are disabled, reading the WDTLOCK register
returns 0x00000001 (when locked; otherwise, the returned value is 0x00000000 (unlocked)).
Watchdog Lock (WDTLOCK)
Offset 0xC00
31
30
29
28
27
26
25
24
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
15
14
13
12
11
10
9
8
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
23
22
21
20
19
18
17
16
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
7
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
WDTLock
Type
Reset
WDTLock
Type
Reset
Bit/Field
Name
Type
Reset
31:0
WDTLock
R/W
0x0000
R/W
0
Description
Watchdog Lock
A write of the value 0x1ACCE551 unlocks the watchdog
registers for write access. A write of any other value
reapplies the lock, preventing any register updates.
A read of this register returns the following values:
Locked: 0x00000001
Unlocked: 0x00000000
194
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 8: Watchdog Test (WDTTEST), offset 0x418
This register provides user-enabled stalling when the microcontroller asserts the CPU halt flag
during debug.
Watchdog Test (WDTTEST)
Offset 0x418
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
reserved
STALL
R/W
0
Bit/Field
Name
Type
Reset
Description
31:9
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
8
STALL
R/W
0
Watchdog Stall Enable
When set to 1, if the Stellaris microcontroller is stopped
with a debugger, the watchdog timer stops counting. Once
the microcontroller is restarted, the watchdog timer
resumes counting.
7:0
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
May 4, 2007
195
Preliminary
Watchdog Timer
Register 9: Watchdog Peripheral Identification 4 (WDTPeriphID4), offset 0xFD0
The WDTPeriphIDn registers are hard-coded and the fields within the register determine the reset
value.
Watchdog Peripheral Identification 4 (WDTPeriphID4)
Offset 0xFD0
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID4
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID4
RO
0x00
Description
Reserved bits return an indeterminate value, and should
never be changed.
WDT Peripheral ID Register[7:0]
196
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 10: Watchdog Peripheral Identification 5 (WDTPeriphID5), offset 0xFD4
The WDTPeriphIDn registers are hard-coded and the fields within the register determine the reset
value.
Watchdog Peripheral Identification 5 (WDTPeriphID5)
Offset 0xFD4
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID5
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID5
RO
0x00
Description
Reserved bits return an indeterminate value, and should
never be changed.
WDT Peripheral ID Register[15:8]
May 4, 2007
197
Preliminary
Watchdog Timer
Register 11: Watchdog Peripheral Identification 6 (WDTPeriphID6), offset 0xFD8
The WDTPeriphIDn registers are hard-coded and the fields within the register determine the reset
value.
Watchdog Peripheral Identification 6 (WDTPeriphID6)
Offset 0xFD8
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID6
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID6
RO
0x00
Description
Reserved bits return an indeterminate value, and should
never be changed.
WDT Peripheral ID Register[23:16]
198
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 12: Watchdog Peripheral Identification 7 (WDTPeriphID7), offset 0xFDC
The WDTPeriphIDn registers are hard-coded and the fields within the register determine the reset
value.
Watchdog Peripheral Identification 7 (WDTPeriphID7)
Offset 0xFDC
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID7
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID7
RO
0x00
Description
Reserved bits return an indeterminate value, and should
never be changed.
WDT Peripheral ID Register[31:24]
May 4, 2007
199
Preliminary
Watchdog Timer
Register 13: Watchdog Peripheral Identification 0 (WDTPeriphID0), offset 0xFE0
The WDTPeriphIDn registers are hard-coded and the fields within the register determine the reset
value.
Watchdog Peripheral Identification 0 (WDTPeriphID0)
Offset 0xFE0
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
PID0
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID0
RO
0x05
Description
Reserved bits return an indeterminate value, and should
never be changed.
Watchdog Peripheral ID Register[7:0]
200
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 14: Watchdog Peripheral Identification 1 (WDTPeriphID1), offset 0xFE4
The WDTPeriphIDn registers are hard-coded and the fields within the register determine the reset
value.
Watchdog Peripheral Identification 1 (WDTPeriphID1)
Offset 0xFE4
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
1
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID1
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID1
RO
0x18
Description
Reserved bits return an indeterminate value, and should
never be changed.
Watchdog Peripheral ID Register[15:8]
May 4, 2007
201
Preliminary
Watchdog Timer
Register 15: Watchdog Peripheral Identification 2 (WDTPeriphID2), offset 0xFE8
The WDTPeriphIDn registers are hard-coded and the fields within the register determine the reset
value.
Watchdog Peripheral Identification 2 (WDTPeriphID2)
Offset 0xFE8
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
1
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID2
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID2
RO
0x18
Description
Reserved bits return an indeterminate value, and should
never be changed.
Watchdog Peripheral ID Register[23:16]
202
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 16: Watchdog Peripheral Identification 3 (WDTPeriphID3), offset 0xFEC
The WDTPeriphIDn registers are hard-coded and the fields within the register determine the reset
value.
Watchdog Peripheral Identification 3 (WDTPeriphID3)
Offset 0xFEC
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
PID3
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID3
RO
0x01
Description
Reserved bits return an indeterminate value, and should
never be changed.
Watchdog Peripheral ID Register[31:24]
May 4, 2007
203
Preliminary
Watchdog Timer
Register 17: Watchdog PrimeCell Identification 0 (WDTPCellID0), offset 0xFF0
The WDTPCellIDn registers are hard-coded and the fields within the register determine the reset
value.
Watchdog Primecell Identification 0 (WDTPCellID0)
Offset 0xFF0
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
1
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
CID0
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
CID0
RO
0x0D
Description
Reserved bits return an indeterminate value, and should
never be changed.
Watchdog PrimeCell ID Register[7:0]
204
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 18: Watchdog PrimeCell Identification 1 (WDTPCellID1), offset 0xFF4
The WDTPCellIDn registers are hard-coded and the fields within the register determine the reset
value.
Watchdog Primecell Identification 1 (WDTPCellID1)
Offset 0xFF4
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
1
RO
1
RO
1
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
CID1
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
CID1
RO
0xF0
Description
Reserved bits return an indeterminate value, and should
never be changed.
Watchdog PrimeCell ID Register[15:8]
May 4, 2007
205
Preliminary
Watchdog Timer
Register 19: Watchdog PrimeCell Identification 2 (WDTPCellID2), offset 0xFF8
The WDTPCellIDn registers are hard-coded and the fields within the register determine the reset
value.
Watchdog Primecell Identification 2 (WDTPCellID2)
Offset 0xFF8
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
CID2
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
CID2
RO
0x05
Description
Reserved bits return an indeterminate value, and should
never be changed.
Watchdog PrimeCell ID Register[23:16]
206
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 20: Watchdog PrimeCell Identification 3 (WDTPCellID3 ), offset 0xFFC
The WDTPCellIDn registers are hard-coded and the fields within the register determine the reset
value.
Watchdog Primecell Identification 3 (WDTPCellID3)
Offset 0xFFC
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
0
RO
1
RO
1
RO
0
RO
0
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
CID3
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
CID3
RO
0xB1
Description
Reserved bits return an indeterminate value, and should
never be changed.
Watchdog PrimeCell ID Register[31:24]
May 4, 2007
207
Preliminary
Analog-to-Digital Converter (ADC)
11
Analog-to-Digital Converter (ADC)
An analog-to-digital converter (ADC) is a peripheral that converts a continuous analog voltage to a
discrete digital number.
The Stellaris ADC module features 10-bit conversion resolution and supports six input channels,
plus an internal temperature sensor. The ADC module contains a programmable sequencer which
allows for the sampling of multiple analog input sources without controller intervention. Each
sample sequence provides flexible programming with fully configurable input source, trigger
events, interrupt generation, and sequence priority.
The Stellaris ADC provides the following features:
„
Six analog input channels
„
Single-ended and differential-input configurations
„
Internal temperature sensor
„
Sample rate of one million samples/second
„
Four programmable sample conversion sequences from one to eight entries long, with
corresponding conversion result FIFOs
„
Flexible trigger control
– Controller (software)
– Timers
– Analog Comparator
– PWM
– GPIO
„
Hardware averaging of up to 64 samples for improved accuracy
208
May 4, 2007
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LM3S818 Data Sheet
11.1
Block Diagram
Figure 11-1.
ADC Module Block Diagram
Trigger Events
Comparator
GPIO (PB4)
Timer
PWM
Comparator
GPIO (PB4)
Timer
PWM
Comparator
GPIO (PB4)
Timer
PWM
Comparator
GPIO (PB4)
Timer
PWM
SS3
Control/Status
Sample
Sequencer 0
ADCACTSS
ADCSSMUX0
ADCOSTAT
ADCSSCTL0
ADCUSTAT
ADCSSFSTAT0
ADCSSPRI
SS2
Sample
Sequencer 1
ADCSSMUX1
ADCSSCTL1
SS1
ADCSSFSTAT1
Hardware Averager
ADCSAC
Sample
Sequencer 2
SS0
ADCSSMUX2
ADCSSCTL2
ADCSSFSTAT2
ADCEMUX
FIFO Block
ADCSSFIFO0
ADCSSFIFO1
ADCPSSI
Interrupt Control
Sample
Sequencer 3
ADCIM
ADCSSMUX3
SS0 Interrupt
SS1 Interrupt
SS2 Interrupt
SS3 Interrupt
11.2
Analog-to-Digital
Converter
ADCRIS
ADCSSCTL3
ADCISC
ADCSSFSTAT3
ADCSSFIFO2
ADCSSFIFO3
Functional Description
The Stellaris ADC collects sample data by using a programmable sequence-based approach
instead of the traditional single or double-sampling approach found on many ADC modules. Each
sample sequence is a fully programmed series of consecutive (back-to-back) samples, allowing
the ADC to collect data from multiple input sources without having to be re-configured or serviced
by the controller. The programming of each sample in the sample sequence includes parameters
such as the input source and mode (differential versus single-ended input), interrupt generation on
sample completion, and the indicator for the last sample in the sequence.
11.2.1
Sample Sequencers
The sampling control and data capture is handled by the Sample Sequencers. All of the
sequencers are identical in implementation except for the number of samples that can be captured
and the depth of the FIFO. Table 11-1 shows the maximum number of samples that each
Sequencer can capture and its corresponding FIFO depth. In this implementation, each FIFO entry
is a 32-bit word, with the lower 10 bits containing the conversion result.
Table 11-1.
Samples and FIFO Depth of Sequencers
Sequencer
Number of
Samples
Depth of FIFO
SS3
1
1
SS2
4
4
SS1
4
4
SS0
8
8
May 4, 2007
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Preliminary
Analog-to-Digital Converter (ADC)
For a given sample sequence, each sample is defined by two 4-bit nibbles in the ADC Sample
Sequence Input Multiplexer Select (ADCSSMUXn) and ADC Sample Sequence Control
(ADCSSCTLn) registers, where "n" corresponds to the sequence number. The ADCSSMUXn
nibbles select the input pin, while the ADCSSCTLn nibbles contain the sample control bits
corresponding to parameters such as temperature sensor selection, interrupt enable, end of
sequence, and differential input mode. Sample Sequencers are enabled by setting the respective
ASENn bit in the ADC Active Sample Sequencer (ADCACTSS) register, but can be configured
before being enabled.
When configuring a sample sequence, multiple uses of the same input pin within the same
sequence is allowed. In the ADCSSCTLn register, the Interrupt Enable (IE) bits can be set
for any combination of samples, allowing interrupts to be generated after every sample in the
sequence if necessary. Also, the END bit can be set at any point within a sample sequence. For
example, if Sequencer 0 is used, the END bit can be set in the nibble associated with the fifth
sample, allowing Sequencer 0 to complete execution of the sample sequence after the fifth
sample.
After a sample sequence completes execution, the result data can be retrieved from the ADC
Sample Sequence Result FIFO (ADCSSFIFOn) registers. The FIFOs are simple circular buffers
that read a single address to "pop" result data. For software debug purposes, the positions of the
FIFO head and tail pointers are visible in the ADC Sample Sequence FIFO Status
(ADCSSFSTATn) registers along with FULL and EMPTY status flags. Overflow and underflow
conditions are monitored using the ADCOSTAT and ADCUSTAT registers.
11.2.2
Module Control
Outside of the Sample Sequencers, the remainder of the control logic is responsible for tasks such
as interrupt generation, sequence prioritization, and trigger configuration.
Most of the ADC control logic runs at the ADC clock rate of 14-18 MHz. The internal ADC divider is
configured automatically by hardware when the system XTAL is selected. The automatic clock
divider configuration targets 16.667 MHz operation for all Stellaris devices.
11.2.2.1
Interrupts
The Sample Sequencers dictate the events that cause interrupts, but they don't have control over
whether the interrupt is actually sent to the interrupt controller. The ADC module's interrupt signal
is controlled by the state of the MASK bits in the ADC Interrupt Mask (ADCIM) register. Interrupt
status can be viewed at two locations: the ADC Raw Interrupt Status (ADCRIS) register, which
shows the raw status of a Sample Sequencer's interrupt signal, and the ADC Interrupt Status
and Clear (ADCISC) register, which shows the logical AND of the ADCRIS register’s INR bit and
the ADCIM register’s MASK bits. Interrupts are cleared by writing a 1 to the corresponding IN bit in
ADCISC.
11.2.2.2
Prioritization
When sampling events (triggers) happen concurrently, they are prioritized for processing by the
values in the ADC Sample Sequencer Priority (ADCSSPRI) register. Valid priority values are in
the range of 0-3, with 0 being the highest priority and 3 being the lowest. Multiple active Sample
Sequencer units with the same priority do not provide consistent results, so software must ensure
that all active Sample Sequencer units have a unique priority value.
11.2.2.3
Sampling Events
Sample triggering for each Sample Sequencer is defined in the ADC Event Multiplexer Select
(ADCEMUX) register. The external peripheral triggering sources vary by Stellaris family member,
but all devices share the "Controller" and "Always" triggers. Software can initiate sampling by
setting the CH bits in the ADC Processor Sample Sequence Initiate (ADCPSSI) register.
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May 4, 2007
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LM3S818 Data Sheet
When using the "Always" trigger, care must be taken. If a sequence's priority is too high, it is
possible to starve other lower priority sequences.
11.2.3
Hardware Sample Averaging Circuit
Higher precision results can be generated using the hardware averaging circuit, however, the
improved results are at the cost of throughput. Up to 64 samples can be accumulated and
averaged to form a single data entry in the sequencer FIFO. Throughput is decreased
proportionally to the number of samples in the averaging calculation. For example, if the averaging
circuit is configured to average 16 samples, the throughput is decreased by a factor of 16.
By default the averaging circuit is off and all data from the converter passes through to the
sequencer FIFO. The averaging hardware is controlled by the ADC Sample Averaging Control
(ADCSAC) register (see page 223). There is a single averaging circuit and all input channels
receive the same amount of averaging whether they are single-ended or differential.
11.2.4
Analog-to-Digital Converter
The converter itself generates a 10-bit output value for selected analog input. Special analog pads
are used to minimize the distortion on the input.
11.2.5
Test Modes
There is a user-available test mode that allows for loopback operation within the digital portion of
the ADC module. This can be useful for debugging software without having to provide actual
analog stimulus. This mode is available through the ADC Test Mode Loopback (ADCTMLB)
register (see page 236).
11.2.6
Internal Temperature Sensor
The internal temperature sensor provides an analog temperature reading as well as a reference
voltage. The voltage at the output terminal SENSO is given by the following equation:
SENSO = 2.7 - ((T + 55) / 75)
This relation is shown in Figure 11-2 on page 211.
Figure 11-2.
11.3
Internal Temperature Sensor Characteristic
Initialization and Configuration
In order for the ADC module to be used, the PLL must be enabled and using a supported crystal
frequency (see the RCC register on page 84). Using unsupported frequencies can cause faulty
operation in the ADC module.
May 4, 2007
211
Preliminary
Analog-to-Digital Converter (ADC)
11.3.1
Module Initialization
Initialization of the ADC module is a simple process with very few steps. The main steps include
enabling the clock to the ADC and reconfiguring the Sample Sequencer priorities (if needed).
The initialization sequence for the ADC is as follows:
1. Enable the ADC clock by writing a value of 0x00010000 to the RCGC1 register in the System
Control module.
2. If required by the application, reconfigure the Sample Sequencer priorities in the ADCSSPRI
register. The default configuration has Sample Sequencer 0 with the highest priority, and
Sample Sequencer 3 as the lowest priority.
11.3.2
Sample Sequencer Configuration
Configuration of the Sample Sequencers is slightly more complex than the module initialization
since each sample sequence is completely programmable.
The configuration for each Sample Sequencer should be as follows:
1. Ensure that the Sample Sequencer is disabled by writing a 0 to the corresponding ASEN bit in
the ADCACTSS register. Programming of the Sample Sequencers is allowed without having
them enabled. Disabling the Sequencer during programming prevents erroneous execution if
a trigger event were to occur during the configuration process.
2. Configure the trigger event for the Sample Sequencer in the ADCEMUX register.
3. For each sample in the sample sequence, configure the corresponding input source in the
ADCSSMUXn register.
4. For each sample in the sample sequence, configure the sample control bits in the
corresponding nibble in the ADCSSCTLn register. When programming the last nibble, ensure
that the END bit is set. Failure to set the END bit causes unpredictable behavior.
5. If interrupts are to be used, write a 1 to the corresponding MASK bit in the ADCIM register.
6. Enable the Sample Sequencer logic by writing a 1 to the corresponding ASEN bit in the
ADCACTSS register.
11.4
Register Map
Table 11-2 lists the ADC registers. The offset listed is a hexadecimal increment to the register’s
address, relative to the ADC base address of 0x40038000.
Table 11-2.
ADC Register Map
Offset
Name
0x000
See
page
Reset
Type
Description
ADCACTSS
0x00000000
R/W
Active sample sequencer
214
0x004
ADCRIS
0x00000000
RO
Raw interrupt status and clear
215
0x008
ADCIM
0x00000000
R/W
Interrupt mask
216
0x00C
ADCISC
0x00000000
R/W1C
Interrupt status and clear
217
0x010
ADCOSTAT
0x00000000
R/W1C
Overflow status
218
0x014
ADCEMUX
0x00000000
R/W
Event multiplexer select
219
0x018
ADCUSTAT
0x00000000
R/W1C
Underflow status
220
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Preliminary
LM3S818 Data Sheet
Table 11-2.
ADC Register Map (Continued)
Offset
Name
0x020
ADCSSPRI
0x028
See
page
Reset
Type
Description
0x00003210
R/W
Sample sequencer priority
221
ADCPSSI
-
WO
Processor sample sequence initiate
222
0x030
ADCSAC
0x00000000
R/W
Sample averaging control
223
0x040
ADCSSMUX0
0x00000000
R/W
Sample sequence input multiplexer select 0
224
0x044
ADCSSCTL0
0x00000000
R/W
Sample sequence control 0
226
0x048
ADCSSFIFO0
0x00000000
RO
Sample sequence result FIFO 0
228
0x04C
ADCSSFSTAT0
0x00000100
RO
Sample sequence FIFO 0 status
229
0x060
ADCSSMUX1
0x00000000
R/W
Sample sequence input multiplexer select 1
230
0x064
ADCSSCTL1
0x00000000
R/W
Sample sequence control 1
231
0x068
ADCSSFIFO1
0x00000000
RO
Sample sequence result FIFO 1
231
0x06C
ADCSSFSTAT1
0x00000100
RO
Sample sequence FIFO 1 status
231
0x080
ADCSSMUX2
0x00000000
R/W
Sample sequence input multiplexer select 2
232
0x084
ADCSSCTL2
0x00000000
R/W
Sample sequence control 2
233
0x088
ADCSSFIFO2
0x00000000
RO
Sample sequence result FIFO 2
233
0x08C
ADCSSFSTAT2
0x00000100
RO
Sample sequence FIFO 2 status
233
0x0A0
ADCSSMUX3
0x00000000
R/W
Sample sequence input multiplexer select 3
234
0x0A4
ADCSSCTL3
0x00000002
R/W
Sample sequence control 3
235
0x0A8
ADCSSFIFO3
0x00000000
RO
Sample sequence result FIFO 3
235
0x0AC
ADCSSFSTAT3
0x00000100
RO
Sample sequence FIFO 3 status
235
0x100
ADCTMLB
0x00000000
R/W
Test mode loopback
236
11.5
Register Descriptions
The remainder of this section lists and describes the ADC registers, in numerical order by address
offset.
May 4, 2007
213
Preliminary
Analog-to-Digital Converter (ADC)
Register 1: ADC Active Sample Sequencer (ADCACTSS), offset 0x000
This register controls the activation of the Sample Sequencers. Each Sample Sequencer can be
enabled/disabled independently.
ADC Active Sample Sequencer (ADCACTSS)
Offset 0x000
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
ASEN3
ASEN2
ASEN1
ASEN0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
Bit/Field
Name
Type
Reset
Description
31:4
reserved
RO
0
Reserved bits return an indeterminate value, and should never be
changed.
3
ASEN3
R/W
0
Specifies whether Sample Sequencer 3 is enabled. If set, the
sample sequence logic for Sequencer 3 is active. Otherwise, the
Sequencer is inactive.
2
ASEN2
R/W
0
Specifies whether Sample Sequencer 2 is enabled. If set, the
sample sequence logic for Sequencer 2 is active. Otherwise, the
Sequencer is inactive.
1
ASEN1
R/W
0
Specifies whether Sample Sequencer 1 is enabled. If set, the
sample sequence logic for Sequencer 1 is active. Otherwise, the
Sequencer is inactive.
0
ASEN0
R/W
0
Specifies whether Sample Sequencer 0 is enabled. If set, the
sample sequence logic for Sequencer 0 is active. Otherwise, the
Sequencer is inactive.
214
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 2: ADC Raw Interrupt Status (ADCRIS), offset 0x004
This register shows the status of the raw interrupt signal of each Sample Sequencer. These bits
may be polled by software to look for interrupt conditions without having to generate controller
interrupts.
ADC Raw Interrupt Status (ADCRIS)
Offset 0x004
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
INR3
INR2
INR1
INR0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
Bit/Field
Name
Type
Reset
Description
31:4
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
3
INR3
RO
0
Set by hardware when a sample with its respective
ADCSSCTL3 IE bit has completed conversion. This bit is
cleared by writing a 1 to the ADCISC IN3 bit.
2
INR2
RO
0
Set by hardware when a sample with its respective
ADCSSCTL2 IE bit has completed conversion. This bit is
cleared by writing a 1 to the ADCISC IN2 bit.
1
INR1
RO
0
Set by hardware when a sample with its respective
ADCSSCTL1 IE bit has completed conversion. This bit is
cleared by writing a 1 to the ADCISC IN1 bit.
0
INR0
RO
0
Set by hardware when a sample with its respective
ADCSSCTL0 IE bit has completed conversion. This bit is
cleared by writing a 1 to the ADCISC IN0 bit.
May 4, 2007
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Preliminary
Analog-to-Digital Converter (ADC)
Register 3: ADC Interrupt Mask (ADCIM), offset 0x008
This register controls whether the Sample Sequencer raw interrupt signals are promoted to
controller interrupts. The raw interrupt signal for each Sample Sequencer can be masked
independently.
ADC Interrupt Mask (ADCIM)
Offset 0x008
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
MASK3 MASK2 MASK1 MASK0
reserved
Type
Reset
R/W
0
R/W
0
R/W
0
R/W
0
Bit/Field
Name
Type
Reset
Description
31:4
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
3
MASK3
R/W
0
Specifies whether the raw interrupt signal from Sample
Sequencer 3 (ADCRIS register INR3 bit) is promoted to a
controller interrupt. If set, the raw interrupt signal is promoted to
a controller interrupt. Otherwise, it is not.
2
MASK2
R/W
0
Specifies whether the raw interrupt signal from Sample
Sequencer 2 (ADCRIS register INR2 bit) is promoted to a
controller interrupt. If set, the raw interrupt signal is promoted to
a controller interrupt. Otherwise, it is not.
1
MASK1
R/W
0
Specifies whether the raw interrupt signal from Sample
Sequencer 1 (ADCRIS register INR1 bit) is promoted to a
controller interrupt. If set, the raw interrupt signal is promoted to
a controller interrupt. Otherwise, it is not.
0
MASK0
R/W
0
Specifies whether the raw interrupt signal from Sample
Sequencer 0 (ADCRIS register INR0 bit) is promoted to a
controller interrupt. If set, the raw interrupt signal is promoted to
a controller interrupt. Otherwise, it is not.
216
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 4: ADC Interrupt Status and Clear (ADCISC), offset 0x00C
This register provides the mechanism for clearing interrupt conditions, and shows the status of
controller interrupts generated by the Sample Sequencers. When read, each bit field is the logical
AND of the respective INR and MASK bits. Interrupts are cleared by writing a 1 to the
corresponding bit position. If software is polling the ADCRIS instead of generating interrupts, the
INR bits are still cleared via the ADCISC register, even if the IN bit is not set.
ADC Interrupt Status and Clear (ADCISC)
Offset 0x00C
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
IN3
IN2
IN1
IN0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W1C
0
R/W1C
0
R/W1C
0
R/W1C
0
reserved
Type
Reset
reserved
Type
Reset
Bit/Field
Name
Type
Reset
Description
31:4
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
3
IN3
R/W1C
0
This bit is set by hardware when the MASK3 and INR3 bits are
both 1, providing a level-based interrupt to the controller. It is
cleared by writing a 1, and also clears the INR3 bit.
2
IN2
R/W1C
0
This bit is set by hardware when the MASK2 and INR2 bits are
both 1, providing a level based interrupt to the controller. It is
cleared by writing a 1, and also clears the INR2 bit.
1
IN1
R/W1C
0
This bit is set by hardware when the MASK1 and INR1 bits are
both 1, providing a level based interrupt to the controller. It is
cleared by writing a 1, and also clears the INR1 bit.
0
IN0
R/W1C
0
This bit is set by hardware when the MASK0 and INR0 bits are
both 1, providing a level based interrupt to the controller. It is
cleared by writing a 1, and also clears the INR0 bit.
May 4, 2007
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Preliminary
Analog-to-Digital Converter (ADC)
Register 5: ADC Overflow Status (ADCOSTAT), offset 0x010
This register indicates overflow conditions in the Sample Sequencer FIFOs. Once the overflow
condition has been handled by software, the condition can be cleared by writing a 1 to the
corresponding bit position.
ADC Overflow Status (ADCOSTAT)
Offset 0x010
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
OV3
OV2
OV1
OV0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W1C
0
R/W1C
0
R/W1C
0
R/W1C
0
reserved
Type
Reset
reserved
Type
Reset
Bit/Field
Name
Type
Reset
Description
31:4
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
3
OV3
R/W1C
0
This bit specifies that the FIFO for Sample Sequencer 3 has
hit an overflow condition where the FIFO is full and a write
was requested. When an overflow is detected, the most
recent write is dropped and this bit is set by hardware to
indicate the occurrence of dropped data. This bit is cleared by
writing a 1.
2
OV2
R/W1C
0
This bit specifies that the FIFO for Sample Sequencer 2 has
hit an overflow condition where the FIFO is full and a write
was requested. When an overflow is detected, the most
recent write is dropped and this bit is set by hardware to
indicate the occurrence of dropped data. This bit is cleared by
writing a 1.
1
OV1
R/W1C
0
This bit specifies that the FIFO for Sample Sequencer 1 has
hit an overflow condition where the FIFO is full and a write
was requested. When an overflow is detected, the most
recent write is dropped and this bit is set by hardware to
indicate the occurrence of dropped data. This bit is cleared by
writing a 1.
0
OV0
R/W1C
0
This bit specifies that the FIFO for Sample Sequencer 0 has
hit an overflow condition where the FIFO is full and a write
was requested. When an overflow is detected, the most
recent write is dropped and this bit is set by hardware to
indicate the occurrence of dropped data. This bit is cleared by
writing a 1.
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May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 6: ADC Event Multiplexer Select (ADCEMUX), offset 0x014
The ADCEMUX selects the event (trigger) that initiates sampling for each Sample Sequencer.
Each Sample Sequencer can be configured with a unique trigger source.
ADC Event Multiplexer Select (ADCEMUX)
Offset 0x014
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
EM3
Type
Reset
EM2
EM1
EM0
Bit/Field
Name
Type
Reset
Description
31:16
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
15:12
EM3
R/W
0
This field selects the trigger source for Sample Sequencer 3.
The valid configurations for this field are:
EM Binary Value
Event
0000
Controller (default)
0001
Analog Comparator 0
0010
Reserved
0011
Reserved
0100
External (GPIO PB4)
0101
Timer
0110
PWM0
0111
PWM1
1000
PWM2
1001-1110
1111
Reserved
Always (continuously sample)
11:8
EM2
R/W
0
This field selects the trigger source for Sample Sequencer 2.
The encodings are the same as those for EM3.
7:4
EM1
R/W
0
This field selects the trigger source for Sample Sequencer 1.
The encodings are the same as those for EM3.
3:0
EM0
R/W
0
This field selects the trigger source for Sample Sequencer 0.
The encodings are the same as those for EM3.
May 4, 2007
219
Preliminary
Analog-to-Digital Converter (ADC)
Register 7: ADC Underflow Status (ADCUSTAT), offset 0x018
This register indicates underflow conditions in the Sample Sequencer FIFOs. The corresponding
underflow condition can be cleared by writing a 1 to the relevant bit position.
ADC Underflow Status (ADCUSTAT)
Offset 0x010
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
UV3
UV2
UV1
UV0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W1C
0
R/W1C
0
R/W1C
0
R/W1C
0
reserved
Type
Reset
reserved
Type
Reset
Bit/Field
Name
Type
Reset
Description
31:4
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
3
UV3
R/W1C
0
This bit specifies that the FIFO for Sample Sequencer 3 has
hit an underflow condition where the FIFO is empty and a
read was requested. The problematic read does not move
the FIFO pointers, and 0s are returned. This bit is cleared by
writing a 1.
2
UV2
R/W1C
0
This bit specifies that the FIFO for Sample Sequencer 2 has
hit an underflow condition where the FIFO is empty and a
read was requested. The problematic read does not move the
FIFO pointers, and 0s are returned. This bit is cleared by
writing a 1.
1
UV1
R/W1C
0
This bit specifies that the FIFO for Sample Sequencer 1 has
hit an underflow condition where the FIFO is empty and a
read was requested. The problematic read does not move the
FIFO pointers, and 0s are returned. This bit is cleared by
writing a 1.
0
UV0
R/W1C
0
This bit specifies that the FIFO for Sample Sequencer 0 has
hit an underflow condition where the FIFO is empty and a
read was requested. The problematic read does not move the
FIFO pointers, and 0s are returned. This bit is cleared by
writing a 1.
220
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 8: ADC Sample Sequencer Priority (ADCSSPRI), offset 0x020
This register sets the priority for each of the Sample Sequencers. Out of reset, Sequencer 0 has
the highest priority, and sample sequence 3 has the lowest priority. When reconfiguring sequence
priorities, each sequence must have a unique priority or the ADC behavior is inconsistent.
ADC Sample Sequencer Priority (ADCSSPRI)
Offset 0x020
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
R/W
1
R/W
1
RO
0
RO
0
R/W
1
R/W
0
RO
0
RO
0
R/W
0
R/W
1
RO
0
RO
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
reserved
SS3
reserved
SS2
Bit/Field
Name
Type
Reset
31:14
reserved
RO
0
13:12
SS3
R/W
0x3
11:10
reserved
RO
0
9:8
SS2
R/W
0x2
7:6
reserved
RO
0
5:4
SS1
R/W
0x1
3:2
reserved
RO
0
1:0
SS0
R/W
0x0
reserved
SS1
SS0
R/W
0
Description
Reserved bits return an indeterminate value, and should
never be changed.
The SS3 field contains a binary-encoded value that specifies
the priority encoding of Sample Sequencer 3. A priority
encoding of 0 is highest and 3 is lowest. The priorities
assigned to the Sequencers must be uniquely mapped. ADC
behavior is not consistent if two or more fields are equal.
Reserved bits return an indeterminate value, and should
never be changed.
The SS2 field contains a binary-encoded value that specifies
the priority encoding of Sample Sequencer 2.
Reserved bits return an indeterminate value, and should
never be changed.
The SS1 field contains a binary-encoded value that specifies
the priority encoding of Sample Sequencer 1.
Reserved bits return an indeterminate value, and should
never be changed.
The SS0 field contains a binary-encoded value that specifies
the priority encoding of Sample Sequencer 0.
May 4, 2007
221
Preliminary
Analog-to-Digital Converter (ADC)
Register 9: ADC Processor Sample Sequence Initiate (ADCPSSI), offset 0x028
This register provides a mechanism for application software to initiate sampling in the Sample
Sequencers. Sample sequences can be initiated individually or in any combination. When multiple
sequences are triggered simultaneously, the priority encodings in ADCSSPRI dictate execution
order.
ADC Processor Sample Sequence Initiate (ADCPSSI)
Offset 0x028
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
SS3
SS2
SS1
SS0
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
reserved
Type
Reset
reserved
Type
Reset
Bit/Field
Name
Type
Reset
Description
31:4
reserved
WO
-
Only a write by software is valid; a read of the register
returns no meaningful data.
3
SS3
WO
-
Only a write by software is valid; a read of the register
returns no meaningful data. When set by software, sampling
is triggered on Sample Sequencer 3, assuming the
Sequencer is enabled in the ADCACTSS register.
2
SS2
WO
-
Only a write by software is valid; a read of the register
returns no meaningful data. When set by software, sampling
is triggered on Sample Sequencer 2, assuming the
Sequencer is enabled in the ADCACTSS register.
1
SS1
WO
-
Only a write by software is valid; a read of the register
returns no meaningful data. When set by software, sampling
is triggered on Sample Sequencer 1, assuming the
Sequencer is enabled in the ADCACTSS register.
0
SS0
WO
-
Only a write by software is valid; a read of the register
returns no meaningful data. When set by software, sampling
is triggered on Sample Sequencer 0, assuming the
Sequencer is enabled in the ADCACTSS register.
222
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 10: ADC Sample Averaging Control (ADCSAC), offset 0x030
This register controls the amount of hardware averaging applied to conversion results. The final
conversion result stored in the FIFO is averaged from 2AVG consecutive ADC samples at the
specified ADC speed. If AVG is 0, the sample is passed directly through without any averaging. If
AVG is 6, 64 consecutive ADC samples are averaged to generate one result in the sequencer
FIFO. An AVG = 7 provides unpredictable results.
ADC Sample Averaging Control (ADCSAC)
Offset 0x030
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
reserved
Type
Reset
AVG
reserved
Type
Reset
RO
0
R/W
0
R/W
0
Bit/Field
Name
Type
Reset
Description
31:3
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
2:0
AVG
R/W
0
Specifies the amount of hardware averaging that will be
applied to ADC samples. The AVG field can be any value
between 0 and 6. Entering a value of 7 creates unpredictable
results.
May 4, 2007
223
Preliminary
Analog-to-Digital Converter (ADC)
Register 11: ADC Sample Sequence Input Multiplexer Select 0 (ADCSSMUX0), offset 0x040
This register defines the analog input configuration for each sample in a sequence executed with
Sample Sequencer 0.
This register is 32-bits wide and contains information for eight possible samples.
ADC Sample Sequence Input Multiplexer Select 0 (ADCSSMUX0)
Offset 0x040
31
30
reserved
Type
Reset
28
27
26
25
reserved
MUX7
24
23
22
reserved
MUX6
21
20
MUX5
19
18
17
16
MUX4
reserved
RO
0
R/W
0
R/W
0
R/W
0
RO
0
R/W
0
R/W
0
R/W
0
RO
0
R/W
0
R/W
0
R/W
0
RO
0
R/W
0
R/W
0
R/W
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
reserved
Type
Reset
29
RO
0
MUX3
R/W
0
R/W
0
MUX2
reserved
R/W
0
RO
0
R/W
0
R/W
0
RO
0
reserved
MUX1
reserved
R/W
0
R/W
0
R/W
0
R/W
0
RO
0
MUX0
R/W
0
R/W
0
R/W
0
Bit/Field
Name
Type
Reset
Description
31:30
reserved
RO
0
Reserved bits return an indeterminate value, and should never be
changed.
29:28
MUX7
R/W
0
The MUX7 field is used during the eighth sample of a sequence
executed with Sample Sequencer 0. It specifies which of the
analog inputs is sampled for the analog-to-digital conversion. The
value set here indicates the corresponding pin, for example, a
value of 1 indicates the input is ADC1.
27:26
reserved
RO
0
Reserved bits return an indeterminate value, and should never be
changed.
25:24
MUX6
R/W
0
The MUX6 field is used during the seventh sample of a sequence
executed with Sample Sequencer 0 and specifies which of the
analog inputs is sampled for the analog-to-digital conversion.
23:22
reserved
RO
0
Reserved bits return an indeterminate value, and should never be
changed.
21:20
MUX5
R/W
0
The MUX5 field is used during the sixth sample of a sequence
executed with Sample Sequencer 0 and specifies which of the
analog inputs is sampled for the analog-to-digital conversion.
19:18
reserved
RO
0
Reserved bits return an indeterminate value, and should never be
changed.
17:16
MUX4
R/W
0
The MUX4 field is used during the fifth sample of a sequence
executed with Sample Sequencer 0 and specifies which of the
analog inputs is sampled for the analog-to-digital conversion.
15:14
reserved
RO
0
Reserved bits return an indeterminate value, and should never be
changed.
13:12
MUX3
R/W
0
The MUX3 field is used during the fourth sample of a sequence
executed with Sample Sequencer 0 and specifies which of the
analog inputs is sampled for the analog-to-digital conversion.
224
May 4, 2007
Preliminary
LM3S818 Data Sheet
Bit/Field
Name
Type
Reset
Description
11:10
reserved
RO
0
Reserved bits return an indeterminate value, and should never be
changed.
9:8
MUX2
R/W
0
The MUX2 field is used during the third sample of a sequence
executed with Sample Sequencer 0 and specifies which of the
analog inputs is sampled for the analog-to-digital conversion.
7:6
reserved
RO
0
Reserved bits return an indeterminate value, and should never be
changed.
5:4
MUX1
R/W
0
The MUX1 field is used during the second sample of a sequence
executed with Sample Sequencer 0 and specifies which of the
analog inputs is sampled for the analog-to-digital conversion.
3:2
reserved
RO
0
Reserved bits return an indeterminate value, and should never be
changed.
1:0
MUX0
R/W
0
The MUX0 field is used during the first sample of a sequence
executed with Sample Sequencer 0 and specifies which of the
analog inputs is sampled for the analog-to-digital conversion.
May 4, 2007
225
Preliminary
Analog-to-Digital Converter (ADC)
Register 12: ADC Sample Sequence Control 0 (ADCSSCTL0), offset 0x044
This register contains the configuration information for each sample for a sequence executed with
Sample Sequencer 0. When configuring a sample sequence, the END bit must be set at some
point, whether it be after the first sample, last sample, or any sample in between.
This register is 32-bits wide and contains information for eight possible samples.
ADC Sample Sequence Control 0 (ADCSSCTL0)
Offset 0x044
Type
Reset
Type
Reset
31
30
29
28
27
26
25
TS7
IE7
R/W
0
R/W
0
15
24
23
22
21
END7
D7
TS6
IE6
R/W
0
R/W
0
R/W
0
R/W
0
14
13
12
11
TS3
IE3
END3
D3
R/W
0
R/W
0
R/W
0
R/W
0
20
19
18
17
END6
D6
TS5
IE5
R/W
0
R/W
0
R/W
0
R/W
0
10
9
8
7
TS2
IE2
END2
D2
R/W
0
R/W
0
R/W
0
R/W
0
16
END5
D5
TS4
IE4
END4
D4
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
6
5
4
3
2
1
0
TS1
IE1
END1
D1
TS0
IE0
END0
D0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
Bit/Field
Name
Type
Reset
Description
31
TS7
R/W
0
The TS7 bit is used during the eighth sample of the sample
sequence and specifies the input source of the sample. If set,
the temperature sensor is read. Otherwise, the input pin
specified by the ADCSSMUX register is read.
30
IE7
R/W
0
The IE7 bit is used during the eighth sample of the sample
sequence and specifies whether the raw interrupt signal (INR0
bit) is asserted at the end of the sample's conversion. If the
MASK0 bit in the ADCIM register is set, the interrupt is
promoted to a controller-level interrupt. When this bit is set, the
raw interrupt is asserted, otherwise it is not. It is legal to have
multiple samples within a sequence generate interrupts.
29
END7
R/W
0
The END7 bit indicates that this is the last sample of the
sequence. It is possible to end the sequence on any sample
position. Samples defined after the sample containing a set
END are not requested for conversion even though the fields
may be non-zero. It is required that software write the END bit
somewhere within the sequence. (Sample Sequencer 3,
which only has a single sample in the sequence, is hardwired
to have the END0 bit set.)
Setting this bit indicates that this sample is the last in the
sequence.
28
D7
R/W
0
The D7 bit indicates that the analog input is to be differentially
sampled. The corresponding ADCSSMUXx nibble must be set
to the pair number "i", where the paired inputs are "2i and 2i+1".
The temperature sensor does not have a differential option.
When set, the analog inputs are differentially sampled.
27
TS6
R/W
0
Same definition as TS7 but used during the seventh sample.
26
IE6
R/W
0
Same definition as IE7 but used during the seventh sample.
25
END6
R/W
0
Same definition as END7 but used during the seventh sample.
226
May 4, 2007
Preliminary
LM3S818 Data Sheet
Bit/Field
Name
Type
Reset
Description
24
D6
R/W
0
Same definition as D7 but used during the seventh sample.
23
TS5
R/W
0
Same definition as TS7 but used during the sixth sample.
22
IE5
R/W
0
Same definition as IE7 but used during the sixth sample.
21
END5
R/W
0
Same definition as END7 but used during the sixth sample.
20
D5
R/W
0
Same definition as D7 but used during the sixth sample.
19
TS4
R/W
0
Same definition as TS7 but used during the fifth sample.
18
IE4
R/W
0
Same definition as IE7 but used during the fifth sample.
17
END4
R/W
0
Same definition as END7 but used during the fifth sample.
16
D4
R/W
0
Same definition as D7 but used during the fifth sample.
15
TS3
R/W
0
Same definition as TS7 but used during the fourth sample.
14
IE3
R/W
0
Same definition as IE7 but used during the fourth sample.
13
END3
R/W
0
Same definition as END7 but used during the fourth sample.
12
D3
R/W
0
Same definition as D7 but used during the fourth sample.
11
TS2
R/W
0
Same definition as TS7 but used during the third sample.
10
IE2
R/W
0
Same definition as IE7 but used during the third sample.
9
END2
R/W
0
Same definition as END7 but used during the third sample.
8
D2
R/W
0
Same definition as D7 but used during the third sample.
7
TS1
R/W
0
Same definition as TS7 but used during the second sample.
6
IE1
R/W
0
Same definition as IE7 but used during the second sample.
5
END1
R/W
0
Same definition as END7 but used during the second sample.
4
D1
R/W
0
Same definition as D7 but used during the second sample.
3
TS0
R/W
0
Same definition as TS7 but used during the first sample.
2
IE0
R/W
0
Same definition as IE7 but used during the first sample.
1
END0
R/W
0
Same definition as END7 but used during the first sample.
Since this sequencer has only one entry, this bit must be set.
0
D0
R/W
0
Same definition as D7 but used during the first sample.
May 4, 2007
227
Preliminary
Analog-to-Digital Converter (ADC)
Register 13: ADC Sample Sequence Result FIFO 0 (ADCSSFIFO0), offset 0x048
This register contains the conversion results for samples collected with Sample Sequencer 0.
Reads of this register return conversion result data in the order sample 0, sample 1, and so on,
until the FIFO is empty. If the FIFO is not properly handled by software, overflow and underflow
conditions are registered in the ADCOSTAT and ADCUSTAT registers.
ADC Sample Sequence Result FIFO 0 (ADCSSFIFO0)
Offset 0x048
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
DATA
Bit/Field
Name
Type
Reset
Description
31:10
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
9:0
DATA
RO
0
Conversion result data.
228
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 14: ADC Sample Sequence FIFO 0 Status (ADCSSFSTAT0), offset 0x04C
This register provides a window into the Sample Sequencer FIFO 0, providing full/empty status
information as well as the positions of the head and tail pointers. The reset value of 0x100
indicates an empty FIFO.
ADC Sample Sequence FIFO 0 Status (ADCSSFSTAT0)
Offset 0x04C
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
RO
0
FULL
RO
0
RO
0
reserved
RO
0
EMPTY
RO
0
RO
0
RO
1
HPTR
TPTR
Bit/Field
Name
Type
Reset
Description
31:13
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
12
FULL
RO
0
When set, indicates that the FIFO is currently full.
11:9
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
8
EMPTY
RO
1
When set, indicates that the FIFO is currently empty.
7:4
HPTR
RO
0
This field contains the current "head" pointer index for the
FIFO, that is, the next entry to be written.
3:0
TPTR
RO
0
This field contains the current "tail" pointer index for the FIFO,
that is, the next entry to be read.
May 4, 2007
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Preliminary
Analog-to-Digital Converter (ADC)
Register 15: ADC Sample Sequence Input Multiplexer Select 1 (ADCSSMUX1), offset 0x060
This register defines the analog input configuration for each sample in a sequence executed with
Sample Sequencer 1.
This register is 16-bits wide and contains information for four possible samples. This register’s bit
fields are as shown in the diagram below. Bit field definitions are the same as those in the
ADCSSMUX0 register (see page 224) but are for Sample Sequencer 1.
ADC Sample Sequence Input Multiplexer Select 1 (ADCSSMUX1)
Offset 0x060
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
MUX3
R/W
0
R/W
0
MUX2
reserved
R/W
0
RO
0
R/W
0
R/W
0
230
RO
0
reserved
MUX1
reserved
R/W
0
R/W
0
R/W
0
R/W
0
RO
0
MUX0
R/W
0
R/W
0
R/W
0
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 16: ADC Sample Sequence Control 1 (ADCSSCTL1), offset 0x064
This register contains the configuration information for each sample for a sequence executed with
Sample Sequencer 1. When configuring a sample sequence, the END bit must be set at some
point, whether it be after the first sample, last sample, or any sample in between.
This register is 16-bits wide and contains information for four possible samples. This register’s bit
fields are as shown in the diagram below. Bit field definitions are the same as those in the
ADCSSCTL0 register (see page 226) but are for Sample Sequencer 1.
ADC Sample Sequence Control 1 (ADCSSCTL1)
Offset 0x064
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
TS3
IE3
END3
D3
TS2
IE2
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
END2
D2
TS1
IE1
END1
D1
TS0
IE0
END0
D0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
Type
Reset
Register 17: ADC Sample Sequence Result FIFO 1 (ADCSSFIFO1), offset 0x068
This register contains the conversion results for samples collected with Sample Sequencer 1.
Reads of this register return conversion result data in the order sample 0, sample 1, and so on,
until the FIFO is empty. If the FIFO is not properly handled by software, overflow and underflow
conditions are registered in the ADCOSTAT and ADCUSTAT registers.
Bit fields and definitions are the same as ADCSSFIFO0 (see page 228) but are for FIFO 1.
Register 18: ADC Sample Sequence FIFO 1 Status (ADCSSFSTAT1), offset 0x06C
This register provides a window into the Sample Sequencer FIFO 1, providing full/empty status
information as well as the positions of the head and tail pointers. The reset value of 0x100
indicates an empty FIFO.
This register has the same bit fields and definitions as ADCSSFSTAT0 (see page 229) but is for
FIFO 1.
May 4, 2007
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Preliminary
Analog-to-Digital Converter (ADC)
Register 19: ADC Sample Sequence Input Multiplexer Select 2 (ADCSSMUX2), offset 0x080
This register defines the analog input configuration for each sample in a sequence executed with
Sample Sequencer 2.
This register is 16-bits wide and contains information for four possible samples. This register’s bit
fields are as shown in the diagram below. Bit field definitions are the same as those in the
ADCSSMUX0 register (see page 224) but are for Sample Sequencer 2.
ADC Sample Sequence Input Multiplexer Select 2 (ADCSSMUX2)
Offset 0x080
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
MUX3
R/W
0
R/W
0
MUX2
reserved
R/W
0
RO
0
R/W
0
R/W
0
232
RO
0
reserved
MUX1
reserved
R/W
0
R/W
0
R/W
0
R/W
0
RO
0
MUX0
R/W
0
R/W
0
R/W
0
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 20: ADC Sample Sequence Control 2 (ADCSSCTL2), offset 0x084
This register contains the configuration information for each sample for a sequence executed with
Sample Sequencer 2. When configuring a sample sequence, the END bit must be set at some
point, whether it be after the first sample, last sample, or any sample in between.
This register is 16-bits wide and contains information for four possible samples. This register’s bit
fields are as shown in the diagram below. Bit field definitions are the same as those in the
ADCSSCTL0 register (see page 226) but are for Sample Sequencer 2.
ADC Sample Sequence Control 2 (ADCSSCTL2)
Offset 0x084
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
TS3
IE3
END3
D3
TS2
IE2
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
END2
D2
TS1
IE1
END1
D1
TS0
IE0
END0
D0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
Type
Reset
Register 21: ADC Sample Sequence Result FIFO 2 (ADCSSFIFO2), offset 0x088
This register contains the conversion results for samples collected with Sample Sequencer 2.
Reads of this register return conversion result data in the order sample 0, sample 1, and so on,
until the FIFO is empty. If the FIFO is not properly handled by software, overflow and underflow
conditions are registered in the ADCOSTAT and ADCUSTAT registers.
Bit fields and definitions are the same as ADCSSFIFO0 (see page 228) but are for FIFO 2.
Register 22: ADC Sample Sequence FIFO 2 Status (ADCSSFSTAT2), offset 0x08C
This register provides a window into the Sample Sequencer FIFO 2, providing full/empty status
information as well as the positions of the head and tail pointers. The reset value of 0x100
indicates an empty FIFO.
This register has the same bit fields and definitions as ADCSSFSTAT0 (see page 229) but is for
FIFO 2.
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Preliminary
Analog-to-Digital Converter (ADC)
Register 23: ADC Sample Sequence Input Multiplexer Select 3 (ADCSSMUX3), offset 0x0A0
This register defines the analog input configuration for each sample in a sequence executed with
Sample Sequencer 3.
This register is 4-bits wide and contains information for one possible sample. This register’s bit
fields are as shown in the diagram below. Bit field definitions are the same as those in the
ADCSSMUX0 register ( see page 224) but are for Sample Sequencer 3.
ADC Sample Sequence Input Multiplexer Select 3 (ADCSSMUX3)
Offset 0x0A0
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
MUX0
234
R/W
0
R/W
0
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 24: ADC Sample Sequence Control 3 (ADCSSCTL3), offset 0x0A4
This register contains the configuration information for each sample for a sequence executed with
Sample Sequencer 3. The END bit is always set since there is only one sample in this sequencer.
This register is 4-bits wide and contains information for one possible sample. This register’s bit
fields are as shown in the diagram below. Bit field definitions are the same as those in the
ADCSSCTL0 register (see page 226) but are for Sample Sequencer 3.
ADC Sample Sequence Control 3 (ADCSSCTL3)
Offset 0x0A4
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
TS0
IE0
END0
D0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
1
R/W
0
reserved
Type
Reset
reserved
Type
Reset
Register 25: ADC Sample Sequence Result FIFO 3 (ADCSSFIFO3), offset 0x0A8
This register contains the conversion results for samples collected with Sample Sequencer 3.
Reads of this register return the conversion result data. If the FIFO is not properly handled by
software, overflow and underflow conditions are registered in the ADCOSTAT and ADCUSTAT
registers.
Bit fields and definitions are the same as ADCSSFIFO0 (see page 228) but are for FIFO 3.
Register 26: ADC Sample Sequence FIFO 3 Status (ADCSSFSTAT3), offset 0x0AC
This register provides a window into the Sample Sequencer FIFO 3, providing full/empty status
information as well as the positions of the head and tail pointers. The reset value of 0x100
indicates an empty FIFO.
This register has the same bit fields and definitions as ADCSSFSTAT0 (see page 229) but is for
FIFO 3.
May 4, 2007
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Preliminary
Analog-to-Digital Converter (ADC)
Register 27: ADC Test Mode Loopback (ADCTMLB), offset 0x100
This register provides loopback operation within the digital logic of the ADC, which can be useful in
debugging software without having to provide actual analog stimulus. This test mode is entered by
writing a value of 0x00000001 to this register. When data is read from the FIFO in loopback mode,
the read-only portion of this register is returned.
ADC Test Mode Loopback (ADCTMLB): Read
Offset 0x100
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
CONT
DIFF
TS
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
23
22
21
20
19
18
17
16
reserved
Type
Reset
reserved
Type
Reset
CNT
MUX
ADC Test Mode Loopback (ADCTMLB):Write
Offset 0x100
31
30
29
28
27
26
25
24
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
WO
0
reserved
Type
Reset
reserved
Type
Reset
Bit/Field
Name
Type
Reset
RO
0
LB
Description
Read-Only Register
31:10
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
9:6
CNT
RO
0
Continuous sample counter that is initialized to 0 and counts
each sample as it processed. This helps provide a unique value
for the data received.
5
CONT
RO
0
When set, indicates that this is a continuation sample. For
example if two sequencers were to run back-to-back, this
indicates that the controller kept continuously sampling at full
rate.
4
DIFF
RO
0
When set, indicates that this was to be a differential sample.
3
TS
RO
0
When set, indicates that this was to be a temperature sensor
sample.
2:0
MUX
RO
0
Indicate which analog input was to be sampled.
236
May 4, 2007
Preliminary
LM3S818 Data Sheet
Bit/Field
Name
Type
Reset
Description
Write-Only Register
31:1
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
0
LB
WO
0
When set, forces a loopback within the digital block to provide
information on input and unique numbering.
The 10-bit loopback data is defined as shown in the read for
bits 9:0 below.
May 4, 2007
237
Preliminary
Universal Asynchronous Receivers/Transmitters (UARTs)
12
Universal Asynchronous Receivers/Transmitters
(UARTs)
The Universal Asynchronous Receivers/Transmitters (UARTs) provide fully programmable,
16C550-type serial interface characteristics. The LM3S818 controller is equipped with two UART
modules.
Each UART has the following features:
„
Separate transmit and receive FIFOs
„
Programmable FIFO length, including 1-byte deep operation providing conventional
double-buffered interface
„
FIFO trigger levels of 1/8, 1/4, 1/2, 3/4, and 7/8
„
Programmable baud-rate generator allowing rates up to 460.8 Kbps
„
Standard asynchronous communication bits for start, stop and parity
„
False start bit detection
„
Line-break generation and detection
„
Fully programmable serial interface characteristics:
– 5, 6, 7, or 8 data bits
– Even, odd, stick, or no-parity bit generation/detection
– 1 or 2 stop bit generation
238
May 4, 2007
Preliminary
LM3S818 Data Sheet
12.1
Block Diagram
Figure 12-1. UART Module Block Diagram
System Clock
TXFIFO
16x8
Interrupt Control
Interrupt
UARTIFLS
.
.
.
UARTIM
UARTMIS
Identification
Registers
UARTRIS
UARTICR
Transmitter
UnTx
Receiver
UnRx
UARTPCellID0
UARTPCellID1
Baud Rate
Generator
UARTDR
UARTPCellID2
UARTIBRD
UARTPCellID3
UARTFBRD
UARTPeriphID0
UARTPeriphID1
UARTPeriphID2
UARTPeriphID3
UART PeriphID4
RXFIFO
16x8
Control / Status
UARTPeriphID5
UARTPeriphID6
UARTPeriphID7
UARTRSR/ECR
.
.
.
UARTFR
UARTLCRH
UARTCTL
12.2
Functional Description
The Stellaris UART performs the functions of parallel-to-serial and serial-to-parallel conversions. It
is similar in functionality to a 16C550 UART, but is not register compatible.
The UART is configured for transmit and/or receive via the TXE and RXE bits of the UART Control
(UARTCTL) register (see page 255). Transmit and receive are both enabled out of reset. Before
any control registers are programmed, the UART must be disabled by clearing the UARTEN bit in
UARTCTL. If the UART is disabled during a TX or RX operation, the current transaction is
completed prior to the UART stopping.
12.2.1
Transmit/Receive Logic
The transmit logic performs parallel-to-serial conversion on the data read from the transmit FIFO.
The control logic outputs the serial bit stream beginning with a start bit, and followed by the data
May 4, 2007
239
Preliminary
Universal Asynchronous Receivers/Transmitters (UARTs)
bits (LSB first), parity bit, and the stop bits according to the programmed configuration in the
control registers. See Figure 12-2 for details.
The receive logic performs serial-to-parallel conversion on the received bit stream after a valid
start pulse has been detected. Overrun, parity, frame error checking, and line-break detection are
also performed, and their status accompanies the data that is written to the receive FIFO.
Figure 12-2. UART Character Frame
UnTX
LSB
1
5-8 data bits
0
n
Parity bit
if enabled
Start
12.2.2
1-2
stop bits
MSB
Baud-Rate Generation
The baud-rate divisor is a 22-bit number consisting of a 16-bit integer and a 6-bit fractional part.
The number formed by these two values is used by the baud-rate generator to determine the bit
period. Having a fractional baud-rate divider allows the UART to generate all the standard baud
rates.
The 16-bit integer is loaded through the UART Integer Baud-Rate Divisor (UARTIBRD) register
(see page 251) and the 6-bit fractional part is loaded with the UART Fractional Baud-Rate
Divisor (UARTFBRD) register (see page 252). The baud-rate divisor (BRD) has the following
relationship to the system clock (where BRDI is the integer part of the BRD and BRDF is the
fractional part, separated by a decimal place.):
BRD = BRDI + BRDF = SysClk / (16 * Baud Rate)
The 6-bit fractional number (that is to be loaded into the DIVFRAC bit field in the UARTFBRD
register) can be calculated by taking the fractional part of the baud-rate divisor, multiplying it by 64,
and adding 0.5 to account for rounding errors:
UARTFBRD[DIVFRAC] = integer(BRDF * 64 + 0.5)
The UART generates an internal baud-rate reference clock at 16x the baud-rate (referred to as
Baud16). This reference clock is divided by 16 to generate the transmit clock, and is used for
error detection during receive operations.
Along with the UART Line Control, High Byte (UARTLCRH) register (see page 253), the
UARTIBRD and UARTFBRD registers form an internal 30-bit register. This internal register is only
updated when a write operation to UARTLCRH is performed, so any changes to the baud-rate
divisor must be followed by a write to the UARTLCRH register for the changes to take effect.
To update the baud-rate registers, there are four possible sequences:
„
UARTIBRD write, UARTFBRD write, and UARTLCRH write
„
UARTFBRD write, UARTIBRD write, and UARTLCRH write
„
UARTIBRD write and UARTLCRH write
„
UARTFBRD write and UARTLCRH write
240
May 4, 2007
Preliminary
LM3S818 Data Sheet
12.2.3
Data Transmission
Data received or transmitted is stored in two 16-byte FIFOs, though the receive FIFO has an extra
four bits per character for status information. For transmission, data is written into the transmit
FIFO. If the UART is enabled, it causes a data frame to start transmitting with the parameters
indicated in the UARTLCRH register. Data continues to be transmitted until there is no data left in
the transmit FIFO. The BUSY bit in the UART Flag (UARTFR) register (see page 249) is asserted
as soon as data is written to the transmit FIFO (that is, if the FIFO is non-empty) and remains
asserted while data is being transmitted. The BUSY bit is negated only when the transmit FIFO is
empty, and the last character has been transmitted from the shift register, including the stop bits.
The UART can indicate that it is busy even though the UART may no longer be enabled.
When the receiver is idle (U0Rx or U1Rx is continuously 1) and the data input goes Low (a start bit
has been received), the receive counter begins running and data is sampled on the eighth cycle of
Baud16 (described in “Transmit/Receive Logic” on page 239).
The start bit is valid if U0Rx or U1Rx is still low on the eighth cycle of Baud16, otherwise a false
start bit is detected and it is ignored. Start bit errors can be viewed in the UART Receive Status
(UARTRSR) register (see page 247). If the start bit was valid, successive data bits are sampled on
every 16th cycle of Baud16 (that is, one bit period later) according to the programmed length of
the data characters. The parity bit is then checked if parity mode was enabled. Data length and
parity are defined in the UARTLCRH register.
Lastly, a valid stop bit is confirmed if U0Rx or U1Rx is High, otherwise a framing error has
occurred. When a full word is received, the data is stored in the receive FIFO, with any error bits
associated with that word.
12.2.4
FIFO Operation
The UART has two 16-entry FIFOs; one for transmit and one for receive. Both FIFOs are accessed
via the UART Data (UARTDR) register (see page 245). Read operations of the UARTDR register
return a 12-bit value consisting of 8 data bits and 4 error flags while write operations place 8-bit
data in the transmit FIFO.
Out of reset, both FIFOs are disabled and act as 1-byte-deep holding registers. The FIFOs are
enabled by setting the FEN bit in UARTLCRH (page 253).
FIFO status can be monitored via the UART Flag (UARTFR) register (see page 249) and the
UART Receive Status (UARTRSR) register. Hardware monitors empty, full and overrun
conditions. The UARTFR register contains empty and full flags (TXFE, TXFF, RXFE and RXFF bits)
and the UARTRSR register shows overrun status via the OE bit.
The trigger points at which the FIFOs generate interrupts is controlled via the UART Interrupt
FIFO Level Select (UARTIFLS) register (see page 256). Both FIFOs can be individually
configured to trigger interrupts at different levels. Available configurations include 1/8, 1/4, 1/2, 3/4
and 7/8. For example, if the 1/4 option is selected for the receive FIFO, the UART generates a
receive interrupt after 4 data bytes are received. Out of reset, both FIFOs are configured to trigger
an interrupt at the 1/2 mark.
12.2.5
Interrupts
The UART can generate interrupts when the following conditions are observed:
„
Overrun Error
„
Break Error
„
Parity Error
„
Framing Error
May 4, 2007
241
Preliminary
Universal Asynchronous Receivers/Transmitters (UARTs)
„
Receive Timeout
„
Transmit (when condition defined in the TXIFLSEL bit in the UARTIFLS register is met)
„
Receive (when condition defined in the RXIFLSEL bit in the UARTIFLS register is met)
All of the interrupt events are ORed together before being sent to the interrupt controller, so the
UART can only generate a single interrupt request to the controller at any given time. Software can
service multiple interrupt events in a single interrupt service routine by reading the UART Masked
Interrupt Status (UARTMIS) register (see page 260).
The interrupt events that can trigger a controller-level interrupt are defined in the UART Interrupt
Mask (UARTIM) register (see page 257) by setting the corresponding IM bit to 1. If interrupts are
not used, the raw interrupt status is always visible via the UART Raw Interrupt Status (UARTRIS)
register (see page 259).
Interrupts are always cleared (for both the UARTMIS and UARTRIS registers) by setting the
corresponding bit in the UART Interrupt Clear (UARTICR) register (see page 261).
12.2.6
Loopback Operation
The UART can be placed into an internal loopback mode for diagnostic or debug work. This is
accomplished by setting the LBE bit in the UARTCTL register (see page 255). In loopback mode,
data transmitted on the U0Tx output is received on the U0Rx input, and data transmitted on U1Tx
is received on U1Rx.
12.3
Initialization and Configuration
To use the UARTs, the peripheral clock must be enabled by setting the UART0 or UART1 bits in the
RCGC1 register.
This section discusses the steps that are required for using a UART module. For this example, the
system clock is assumed to be 20 MHz and the desired UART configuration is:
„
115200 baud rate
„
Data length of 8 bits
„
One stop bit
„
No parity
„
FIFOs disabled
„
No interrupts
The first thing to consider when programming the UART is the baud-rate divisor (BRD), since the
UARTIBRD and UARTFBRD registers must be written before the UARTLCRH register. Using the
equation described in “Baud-Rate Generation” on page 240, the BRD can be calculated:
BRD = 20,000,000 / (16 * 115,200) = 10.8507
which means that the DIVINT field of the UARTIBRD register (see page 251) should be set to 10.
The value to be loaded into the UARTFBRD register (see page 252) is calculated by the equation:
UARTFBRD[DIVFRAC] = integer(0.8507 * 64 + 0.5) = 54
With the BRD values in hand, the UART configuration is written to the module in the following
order:
1. Disable the UART by clearing the UARTEN bit in the UARTCTL register.
2. Write the integer portion of the BRD to the UARTIBRD register.
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May 4, 2007
Preliminary
LM3S818 Data Sheet
3. Write the fractional portion of the BRD to the UARTFBRD register.
4. Write the desired serial parameters to the UARTLCRH register (in this case, a value of
0x00000060).
5. Enable the UART by setting the UARTEN bit in the UARTCTL register.
12.4
Register Map
Table 12-1 lists the UART registers. The offset listed is a hexadecimal increment to the register’s
address, relative to that UART’s base address:
„
UART0: 0x4000C000
„
UART1: 0x4000D000
Note:
Table 12-1.
The UART must be disabled (see the UARTEN bit in the UARTCTL register on page 255)
before any of the control registers are reprogrammed. When the UART is disabled during
a TX or RX operation, the current transaction is completed prior to the UART stopping.
UART Register Map
Offset
Name
0x000
0x004
See
page
Reset
Type
Description
UARTDR
0x00000000
R/W
Data
245
UARTRSR
0x00000000
R/W
Receive Status (read)
247
UARTECR
Error Clear (write)
0x018
UARTFR
0x00000090
RO
Flag Register (read only)
249
0x024
UARTIBRD
0x00000000
R/W
Integer Baud-Rate Divisor
251
0x028
UARTFBRD
0x00000000
R/W
Fractional Baud-Rate Divisor
252
0x02C
UARTLCRH
0x00000000
R/W
Line Control Register, High byte
253
0x030
UARTCTL
0x00000300
R/W
Control Register
255
0x034
UARTIFLS
0x00000012
R/W
Interrupt FIFO Level Select
256
0x038
UARTIM
0x00000000
R/W
Interrupt Mask
257
0x03C
UARTRIS
0x0000000F
RO
Raw Interrupt Status
259
0x040
UARTMIS
0x00000000
RO
Masked Interrupt Status
260
0x044
UARTICR
0x00000000
W1C
Interrupt Clear
261
0xFD0
UARTPeriphID4
0x00000000
RO
Peripheral identification 4
262
0xFD4
UARTPeriphID5
0x00000000
RO
Peripheral identification 5
263
0xFD8
UARTPeriphID6
0x00000000
RO
Peripheral identification 6
264
0xFDC
UARTPeriphID7
0x00000000
RO
Peripheral identification 7
265
0xFE0
UARTPeriphID0
0x00000011
RO
Peripheral identification 0
266
0xFE4
UARTPeriphID1
0x00000000
RO
Peripheral identification 1
267
0xFE8
UARTPeriphID2
0x00000018
RO
Peripheral identification 2
268
May 4, 2007
243
Preliminary
Universal Asynchronous Receivers/Transmitters (UARTs)
Table 12-1.
UART Register Map (Continued)
Offset
Name
0xFEC
See
page
Reset
Type
UARTPeriphID3
0x00000001
RO
Peripheral identification 3
269
0xFF0
UARTPCellID0
0x0000000D
RO
PrimeCell identification 0
270
0xFF4
UARTPCellID1
0x000000F0
RO
PrimeCell identification 1
271
0xFF8
UARTPCellID2
0x00000005
RO
PrimeCell identification 2
272
0xFFC
UARTPCellID3
0x000000B1
RO
PrimeCell identification 3
273
12.5
Description
Register Descriptions
The remainder of this section lists and describes the UART registers, in numerical order by
address offset.
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May 4, 2007
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LM3S818 Data Sheet
Register 1: UART Data (UARTDR), offset 0x000
This register is the data register (the interface to the FIFOs).
When FIFOs are enabled, data written to this location is pushed onto the transmit FIFO. If FIFOs
are disabled, data is stored in the transmitter holding register (the bottom word of the transmit
FIFO). A write to this register initiates a transmission from the UART.
For received data, if the FIFO is enabled, the data byte and the 4-bit status (break, frame, parity
and overrun) is pushed onto the 12-bit wide receive FIFO. If FIFOs are disabled, the data byte and
status are stored in the receiving holding register (the bottom word of the receive FIFO). The
received data can be retrieved by reading this register.
UART Data (UARTDR)
Offset 0x000
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
OE
RO
0
RO
0
RO
0
RO
0
RO
0
BE
PE
FE
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
DATA
Bit/Field
Name
Type
Reset
Description
31:12
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
11
OE
RO
0
UART Overrun Error
1=New data was received when the FIFO was full, resulting in
data loss.
0=There has been no data loss due to a FIFO overrun.
10
BE
RO
0
UART Break Error
This bit is set to 1 when a break condition is detected, indicating
that the receive data input was held Low for longer than a fullword transmission time (defined as start, data, parity, and stop
bits).
In FIFO mode, this error is associated with the character at the
top of the FIFO. When a break occurs, only one 0 character is
loaded into the FIFO. The next character is only enabled after
the received data input goes to a 1 (marking state) and the next
valid start bit is received.
9
PE
RO
0
UART Parity Error
This bit is set to 1 when the parity of the received data character
does not match the parity defined by bits 2 and 7 of the
UARTLCRH register.
In FIFO mode, this error is associated with the character at the
top of the FIFO.
May 4, 2007
245
Preliminary
Universal Asynchronous Receivers/Transmitters (UARTs)
Bit/Field
Name
Type
Reset
8
FE
RO
0
Description
UART Framing Error
This bit is set to 1 when the received character does not have a
valid stop bit (a valid stop bit is 1).
7:0
DATA
R/W
0
When written, the data that is to be transmitted via the UART.
When read, the data that was received by the UART.
246
May 4, 2007
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LM3S818 Data Sheet
Register 2: UART Receive Status/Error Clear (UARTRSR/UARTECR), offset 0x004
The UARTRSR/UARTECR register is the receive status register/error clear register.
In addition to the UARTDR register, receive status can also be read from the UARTRSR register. If
the status is read from this register, then the status information corresponds to the entry read from
UARTDR prior to reading UARTRSR. The status information for overrun is set immediately when
an overrun condition occurs.
A write of any value to the UARTECR register clears the framing, parity, break, and overrun errors.
All the bits are cleared to 0 on reset.
UART Receive Status (UARTRSR): Read
Offset 0x004
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
OE
BE
PE
FE
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
23
22
21
20
19
18
17
16
reserved
Type
Reset
reserved
Type
Reset
UART Error Clear (UARTECR): Write
Offset 0x004
31
30
29
28
27
26
25
24
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
reserved
Type
Reset
reserved
Type
Reset
Bit/Field
Name
WO
0
Type
DATA
Reset
Description
Read-Only Receive Status (UARTRSR) Register
31:4
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed. The UARTRSR register cannot be written.
3
OE
RO
0
UART Overrun Error
When this bit is set to 1, data is received and the FIFO is already
full. This bit is cleared to 0 by a write to UARTECR.
The FIFO contents remain valid since no further data is written
when the FIFO is full, only the contents of the shift register are
overwritten. The CPU must now read the data in order to empty
the FIFO.
May 4, 2007
247
Preliminary
Universal Asynchronous Receivers/Transmitters (UARTs)
Bit/Field
Name
Type
Reset
2
BE
RO
0
Description
UART Break Error
This bit is set to 1 when a break condition is detected, indicating
that the received data input was held Low for longer than a fullword transmission time (defined as start, data, parity, and stop
bits).
This bit is cleared to 0 by a write to UARTECR.
In FIFO mode, this error is associated with the character at the
top of the FIFO. When a break occurs, only one 0 character is
loaded into the FIFO. The next character is only enabled after
the receive data input goes to a 1 (marking state) and the next
valid start bit is received.
1
PE
RO
0
UART Parity Error
This bit is set to 1 when the parity of the received data character
does not match the parity defined by bits 2 and 7 of the
UARTLCRH register.
This bit is cleared to 0 by a write to UARTECR.
0
FE
RO
0
UART Framing Error
This bit is set to 1 when the received character does not have a
valid stop bit (a valid stop bit is 1).
This bit is cleared to 0 by a write to UARTECR.
In FIFO mode, this error is associated with the character at the
top of the FIFO.
Write-Only Error Clear (UARTECR) Register
31:8
reserved
WO
0
Reserved bits return an indeterminate value, and should never
be changed.
7:0
DATA
WO
0
A write to this register of any data clears the framing, parity,
break and overrun flags.
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May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 3: UART Flag (UARTFR), offset 0x018
The UARTFR register is the flag register. After reset, the TXFF, RXFF, and BUSY bits are 0, and
TXFE and RXFE bits are 1.
UART Flag (UARTFR)
Offset 0x018
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
TXFE
RXFF
TXFF
RXFE
BUSY
RO
0
RO
0
RO
1
RO
0
RO
0
RO
1
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
reserved
RO
0
RO
0
RO
0
Bit/Field
Name
Type
Reset
Description
31:8
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
7
TXFE
RO
1
UART Transmit FIFO Empty
The meaning of this bit depends on the state of the FEN bit in the
UARTLCRH register.
If the FIFO is disabled (FEN is 0), this bit is set when the transmit
holding register is empty.
If the FIFO is enabled (FEN is 1), this bit is set when the transmit
FIFO is empty.
6
RXFF
RO
0
UART Receive FIFO Full
The meaning of this bit depends on the state of the FEN bit in the
UARTLCRH register.
If the FIFO is disabled, this bit is set when the receive holding
register is full.
If the FIFO is enabled, this bit is set when the receive FIFO is
full.
5
TXFF
RO
0
UART Transmit FIFO Full
The meaning of this bit depends on the state of the FEN bit in the
UARTLCRH register.
If the FIFO is disabled, this bit is set when the transmit holding
register is full.
If the FIFO is enabled, this bit is set when the transmit FIFO is
full.
May 4, 2007
249
Preliminary
Universal Asynchronous Receivers/Transmitters (UARTs)
Bit/Field
Name
Type
Reset
4
RXFE
RO
1
Description
UART Receive FIFO Empty
The meaning of this bit depends on the state of the FEN bit in the
UARTLCRH register.
If the FIFO is disabled, this bit is set when the receive holding
register is empty.
If the FIFO is enabled, this bit is set when the receive FIFO is
empty.
3
BUSY
RO
0
UART Busy
When this bit is 1, the UART is busy transmitting data. This bit
remains set until the complete byte, including all stop bits, has
been sent from the shift register.
This bit is set as soon as the transmit FIFO becomes non-empty
(regardless of whether UART is enabled).
2:0
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
250
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 4: UART Integer Baud-Rate Divisor (UARTIBRD), offset 0x024
The UARTIBRD register is the integer part of the baud-rate divisor value. All the bits are cleared
on reset. The minimum possible divide ratio is 1 (when UARTIBRD=0), in which case the
UARTFBRD register is ignored. When changing the UARTIBRD register, the new value does not
take effect until transmission/reception of the current character is complete. Any changes to the
baud-rate divisor must be followed by a write to the UARTLCRH register. See “Baud-Rate
Generation” on page 240 for configuration details.
UART Integer Baud-Rate Divisor
Offset 0x024
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
DIVINT
Type
Reset
Bit/Field
Name
Type
Reset
Description
31:16
reserved
RO
0
15:0
DIVINT
R/W
0x0000
Reserved bits return an indeterminate value, and should never
be changed.
Integer Baud-Rate Divisor
May 4, 2007
251
Preliminary
Universal Asynchronous Receivers/Transmitters (UARTs)
Register 5: UART Fractional Baud-Rate Divisor (UARTFBRD), offset 0x028
The UARTFBRD register is the fractional part of the baud-rate divisor value. All the bits are
cleared on reset. When changing the UARTFBRD register, the new value does not take effect until
transmission/reception of the current character is complete. Any changes to the baud-rate divisor
must be followed by a write to the UARTLCRH register. See “Baud-Rate Generation” on page 240
for configuration details.
UART Fractional Baud-Rate Divisor (UARTFBRD)
Offset 0x028
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
DIVFRAC
Bit/Field
Name
Type
Reset
31:6
reserved
RO
0
5:0
DIVFRAC
R/W
0x00
R/W
0
Description
Reserved bits return an indeterminate value, and should never
be changed.
Fractional Baud-Rate Divisor
252
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 6: UART Line Control (UARTLCRH), offset 0x02C
The UARTLCRH register is the line control register. Serial parameters such as data length, parity
and stop bit selection are implemented in this register.
When updating the baud-rate divisor (UARTIBRD and/or UARTIFRD), the UARTLCRH register
must also be written. The write strobe for the baud-rate divisor registers is tied to the UARTLCRH
register.
UART Line Control (UARTLCRH)
Offset 0x02C
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
FEN
STP2
EPS
PEN
BRK
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
SPS
reserved
Type
Reset
R/W
0
WLEN
R/W
0
R/W
0
Bit/Field
Name
Type
Reset
Description
31:8
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
7
SPS
R/W
0
UART Stick Parity Select
When bits 1, 2 and 7 of UARTLCRH are set, the parity bit is
transmitted and checked as a 0. When bits 1 and 7 are set and 2
is cleared, the parity bit is transmitted and checked as a 1.
When this bit is cleared, stick parity is disabled.
6:5
WLEN
R/W
0
UART Word Length
The bits indicate the number of data bits transmitted or received
in a frame as follows:
0x3: 8 bits
0x2: 7 bits
0x1: 6 bits
0x0: 5 bits (default)
4
FEN
R/W
0
UART Enable FIFOs
If this bit is set to 1, transmit and receive FIFO buffers are
enabled (FIFO mode).
When cleared to 0, FIFOs are disabled (Character mode). The
FIFOs become 1-byte-deep holding registers.
3
STP2
R/W
0
UART Two Stop Bits Select
If this bit is set to 1, two stop bits are transmitted at the end of a
frame. The receive logic does not check for two stop bits being
received.
May 4, 2007
253
Preliminary
Universal Asynchronous Receivers/Transmitters (UARTs)
Bit/Field
Name
Type
Reset
2
EPS
R/W
0
Description
UART Even Parity Select
If this bit is set to 1, even parity generation and checking is
performed during transmission and reception, which checks for
an even number of 1s in data and parity bits.
When cleared to 0, then odd parity is performed, which checks
for an odd number of 1s.
This bit has no effect when parity is disabled by the PEN bit.
1
PEN
R/W
0
UART Parity Enable
If this bit is set to 1, parity checking and generation is enabled;
otherwise, parity is disabled and no parity bit is added to the data
frame.
0
BRK
R/W
0
UART Send Break
If this bit is set to 1, a Low level is continually output on the UNTX
output, after completing transmission of the current character.
For the proper execution of the break command, the software
must set this bit for at least two frames (character periods). For
normal use, this bit must be cleared to 0.
254
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 7: UART Control (UARTCTL), offset 0x030
The UARTCTL register is the control register. All the bits are cleared on reset except for the
Transmit Enable (TXE) and Receive Enable (RXE) bits, which are set to 1.
To enable the UART module, the UARTEN bit must be set to 1. If software requires a configuration
change in the module, the UARTEN bit must be cleared before the configuration changes are
written. If the UART is disabled during a transmit or receive operation, the current transaction is
completed prior to the UART stopping.
UART Control (UARTCR)
Offset 0x030
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RXE
TXE
LBE
R/W
1
R/W
1
R/W
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
reserved
RO
0
UARTEN
R/W
0
Bit/Field
Name
Type
Reset
Description
31:10
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
9
RXE
R/W
1
UART Receive Enable
If this bit is set to 1, the receive section of the UART is enabled.
When the UART is disabled in the middle of a receive, it
completes the current character before stopping.
8
TXE
R/W
1
UART Transmit Enable
If this bit is set to 1, the transmit section of the UART is enabled.
When the UART is disabled in the middle of a transmission, it
completes the current character before stopping.
7
LBE
R/W
0
UART Loop Back Enable
If this bit is set to 1, the UNTX path is fed through the UNRX path.
6:1
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
0
UARTEN
R/W
0
UART Enable
If this bit is set to 1, the UART is enabled. When the UART is
disabled in the middle of transmission or reception, it completes
the current character before stopping.
May 4, 2007
255
Preliminary
Universal Asynchronous Receivers/Transmitters (UARTs)
Register 8: UART Interrupt FIFO Level Select (UARTIFLS), offset 0x034
The UARTIFLS register is the interrupt FIFO level select register. You can use this register to
define the FIFO level at which the TXRIS and RXRIS bits in the UARTRIS register are triggered.
The interrupts are generated based on a transition through a level rather than being based on the
level. That is, the interrupts are generated when the fill level progresses through the trigger level.
For example, if the receive trigger level is set to the half-way mark, the interrupt is triggered as the
module is receiving the 9th character.
Out of reset, the TXIFLSEL and RXIFLSEL bits are configured so that the FIFOs trigger an
interrupt at the half-way mark.
UART Interrupt FIFO Level Select (UARTIFLS)
Offset 0x034
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
TXIFLSEL
RXIFLSEL
Bit/Field
Name
Type
Reset
31:6
reserved
RO
0
5:3
RXIFLSEL
R/W
0X2
R/W
1
R/W
1
R/W
0
Description
Reserved bits return an indeterminate value, and should never
be changed.
UART Receive Interrupt FIFO Level Select
The trigger points for the receive interrupt are as follows:
000: RX FIFO ≥ 1/8 full
001: RX FIFO ≥ 1/4 full
010: RX FIFO ≥ 1/2 full (default)
011: RX FIFO ≥ 3/4 full
100: RX FIFO ≥ 7/8 full
101-111: Reserved
2:0
TXIFLSEL
R/W
0X2
UART Transmit Interrupt FIFO Level Select
The trigger points for the transmit interrupt are as follows:
000: TX FIFO ≤ 1/8 full
001: TX FIFO ≤ 1/4 full
010: TX FIFO ≤ 1/2 full (default)
011: TX FIFO ≤ 3/4 full
100: TX FIFO ≤ 7/8 full
101-111: Reserved
256
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 9: UART Interrupt Mask (UARTIM), offset 0x038
The UARTIM register is the interrupt mask set/clear register.
On a read, this register gives the current value of the mask on the relevant interrupt. Writing a 1 to
a bit allows the corresponding raw interrupt signal to be routed to the interrupt controller. Writing a
0 prevents the raw interrupt signal from being sent to the interrupt controller.
UART Interrupt Mask (UARTIM)
Offset 0x038
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
OEIM
BEIM
PEIM
FEIM
RTIM
TXIM
RXIM
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
reserved
Bit/Field
Name
Type
Reset
Description
31:11
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
10
OEIM
R/W
0
UART Overrun Error Interrupt Mask
On a read, the current mask for the OEIM interrupt is returned.
Setting this bit to 1 promotes the OEIM interrupt to the interrupt
controller.
9
BEIM
R/W
0
UART Break Error Interrupt Mask
On a read, the current mask for the BEIM interrupt is returned.
Setting this bit to 1 promotes the BEIM interrupt to the interrupt
controller.
8
PEIM
R/W
0
UART Parity Error Interrupt Mask
On a read, the current mask for the PEIM interrupt is returned.
Setting this bit to 1 promotes the PEIM interrupt to the interrupt
controller.
7
FEIM
R/W
0
UART Framing Error Interrupt Mask
On a read, the current mask for the FEIM interrupt is returned.
Setting this bit to 1 promotes the FEIM interrupt to the interrupt
controller.
6
RTIM
R/W
0
UART Receive Time-Out Interrupt Mask
On a read, the current mask for the RTIM interrupt is returned.
Setting this bit to 1 promotes the RTIM interrupt to the interrupt
controller.
May 4, 2007
257
Preliminary
Universal Asynchronous Receivers/Transmitters (UARTs)
Bit/Field
Name
Type
Reset
5
TXIM
R/W
0
Description
UART Transmit Interrupt Mask
On a read, the current mask for the TXIM interrupt is returned.
Setting this bit to 1 promotes the TXIM interrupt to the interrupt
controller.
4
RXIM
R/W
0
UART Receive Interrupt Mask
On a read, the current mask for the RXIM interrupt is returned.
Setting this bit to 1 promotes the RXIM interrupt to the interrupt
controller.
3:0
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
258
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 10: UART Raw Interrupt Status (UARTRIS), offset 0x03C
The UARTRIS register is the raw interrupt status register. On a read, this register gives the current
raw status value of the corresponding interrupt. A write has no effect.
UART Raw Interrupt Status (UARTRIS)
Offset 0x03C
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
OERIS
BERIS
PERIS
FERIS
RTRIS
TXRIS
RXRIS
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
1
RO
1
RO
1
reserved
Type
Reset
reserved
Type
Reset
RO
0
reserved
Bit/Field
Name
Type
Reset
Description
31:11
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
10
OERIS
RO
0
UART Overrun Error Raw Interrupt Status
Gives the raw interrupt state (prior to masking) of this interrupt.
9
BERIS
RO
0
UART Break Error Raw Interrupt Status
Gives the raw interrupt state (prior to masking) of this interrupt.
8
PERIS
RO
0
UART Parity Error Raw Interrupt Status
Gives the raw interrupt state (prior to masking) of this interrupt.
7
FERIS
RO
0
UART Framing Error Raw Interrupt Status
Gives the raw interrupt state (prior to masking) of this interrupt.
6
RTRIS
RO
0
UART Receive Time-Out Raw Interrupt Status
Gives the raw interrupt state (prior to masking) of this interrupt.
5
TXRIS
RO
0
UART Transmit Raw Interrupt Status
Gives the raw interrupt state (prior to masking) of this interrupt.
4
RXRIS
RO
0
UART Receive Raw Interrupt Status
Gives the raw interrupt state (prior to masking) of this interrupt.
3:0
reserved
RO
0xF
This reserved bit is read-only and has a reset value of 0xF.
May 4, 2007
259
Preliminary
Universal Asynchronous Receivers/Transmitters (UARTs)
Register 11: UART Masked Interrupt Status (UARTMIS), offset 0x040
The UARTMIS register is the masked interrupt status register. On a read, this register gives the
current masked status value of the corresponding interrupt. A write has no effect.
UART Masked Interrupt Status (UARTMIS)
Offset 0x040
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
OEMIS
BEMIS
PEMIS
FEMIS
RTMIS
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
reserved
TXMIS RXMIS
RO
0
RO
0
RO
0
RO
0
Bit/Field
Name
Type
Reset
Description
31:11
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
10
OEMIS
RO
0
UART Overrun Error Masked Interrupt Status
Gives the masked interrupt state of this interrupt.
9
BEMIS
RO
0
UART Break Error Masked Interrupt Status
Gives the masked interrupt state of this interrupt.
8
PEMIS
RO
0
UART Parity Error Masked Interrupt Status
Gives the masked interrupt state of this interrupt.
7
FEMIS
RO
0
UART Framing Error Masked Interrupt Status
Gives the masked interrupt state of this interrupt.
6
RTMIS
RO
0
UART Receive Time-Out Masked Interrupt Status
Gives the masked interrupt state of this interrupt.
5
TXMIS
RO
0
UART Transmit Masked Interrupt Status
Gives the masked interrupt state of this interrupt.
4
RXMIS
RO
0
UART Receive Masked Interrupt Status
Gives the masked interrupt state of this interrupt.
3:0
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
260
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 12: UART Interrupt Clear (UARTICR), offset 0x044
The UARTICR register is the interrupt clear register. On a write of 1, the corresponding interrupt
(both raw interrupt and masked interrupt, if enabled) is cleared. A write of 0 has no effect.
UART Interrupt Clear (UARTICR)
Offset 0x044
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
OEIC
BEIC
PEIC
FEIC
RTIC
TXIC
RXIC
W1C
0
W1C
0
W1C
0
W1C
0
W1C
0
W1C
0
W1C
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
reserved
Bit/Field
Name
Type
Reset
Description
31:11
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
10
OEIC
W1C
0
Overrun Error Interrupt Clear
0: No effect on the interrupt.
1: Clears interrupt.
9
BEIC
W1C
0
Break Error Interrupt Clear
0: No effect on the interrupt.
1: Clears interrupt.
8
PEIC
W1C
0
Parity Error Interrupt Clear
0: No effect on the interrupt.
1: Clears interrupt.
7
FEIC
W1C
0
Framing Error Interrupt Clear
0: No effect on the interrupt.
1: Clears interrupt.
6
RTIC
W1C
0
Receive Time-Out Interrupt Clear
0: No effect on the interrupt.
1: Clears interrupt.
5
TXIC
W1C
0
Transmit Interrupt Clear
0: No effect on the interrupt.
1: Clears interrupt.
4
RXIC
W1C
0
Receive Interrupt Clear
0: No effect on the interrupt.
1: Clears interrupt.
3:0
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
May 4, 2007
261
Preliminary
Universal Asynchronous Receivers/Transmitters (UARTs)
Register 13: UART Peripheral Identification 4 (UARTPeriphID4), offset 0xFD0
The UARTPeriphIDn registers are hard-coded and the fields within the registers determine the
reset values.
UART Peripheral Identification 4 (UARTPeriphID4)
Offset 0xFD0
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID4
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID4
RO
0x00
Description
Reserved bits return an indeterminate value, and should
never be changed.
UART Peripheral ID Register[7:0]
262
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 14: UART Peripheral Identification 5 (UARTPeriphID5), offset 0xFD4
The UARTPeriphIDn registers are hard-coded and the fields within the registers determine the
reset values.
UART Peripheral Identification 5 (UARTPeriphID5)
Offset 0xFD4
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID5
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID5
RO
0x00
Description
Reserved bits return an indeterminate value, and should
never be changed.
UART Peripheral ID Register[15:8]
May 4, 2007
263
Preliminary
Universal Asynchronous Receivers/Transmitters (UARTs)
Register 15: UART Peripheral Identification 6 (UARTPeriphID6), offset 0xFD8
The UARTPeriphIDn registers are hard-coded and the fields within the registers determine the
reset values.
UART Peripheral Identification 6 (UARTPeriphID6)
Offset 0xFD8
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID6
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID6
RO
0x00
Description
Reserved bits return an indeterminate value, and should
never be changed.
UART Peripheral ID Register[23:16]
264
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 16: UART Peripheral Identification 7 (UARTPeriphID7), offset 0xFDC
The UARTPeriphIDn registers are hard-coded and the fields within the registers determine the
reset values.
UART Peripheral Identification 7 (UARTPeriphID7)
Offset 0xFDC
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID7
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID7
RO
0x00
Description
Reserved bits return an indeterminate value, and should
never be changed.
UART Peripheral ID Register[31:24]
May 4, 2007
265
Preliminary
Universal Asynchronous Receivers/Transmitters (UARTs)
Register 17: UART Peripheral Identification 0 (UARTPeriphID0), offset 0xFE0
The UARTPeriphIDn registers are hard-coded and the fields within the registers determine the
reset values.
UART Peripheral Identification 0 (UARTPeriphID0)
Offset 0xFE0
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
0
RO
0
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
PID0
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID0
RO
0x11
Description
Reserved bits return an indeterminate value, and should never
be changed.
UART Peripheral ID Register[7:0]
Can be used by software to identify the presence of this
peripheral.
266
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 18: UART Peripheral Identification 1 (UARTPeriphID1), offset 0xFE4
The UARTPeriphIDn registers are hard-coded and the fields within the registers determine the
reset values.
UART Peripheral Identification 1 (UARTPeriphID1)
Offset 0xFE4
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID1
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID1
RO
0x00
Description
Reserved bits return an indeterminate value, and should never
be changed.
UART Peripheral ID Register[15:8]
Can be used by software to identify the presence of this
peripheral.
May 4, 2007
267
Preliminary
Universal Asynchronous Receivers/Transmitters (UARTs)
Register 19: UART Peripheral Identification 2 (UARTPeriphID2), offset 0xFE8
The UARTPeriphIDn registers are hard-coded and the fields within the registers determine the
reset values.
UART Peripheral Identification 2 (UARTPeriphID2)
Offset 0xFE8
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
1
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID2
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID2
RO
0x18
Description
Reserved bits return an indeterminate value, and should never
be changed.
UART Peripheral ID Register[23:16]
Can be used by software to identify the presence of this
peripheral.
268
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 20: UART Peripheral Identification 3 (UARTPeriphID3), offset 0xFEC
The UARTPeriphIDn registers are hard-coded and the fields within the registers determine the
reset values.
UART Peripheral Identification 3 (UARTPeriphID3)
Offset 0xFEC
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
PID3
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID3
RO
0x01
Description
Reserved bits return an indeterminate value, and should never
be changed.
UART Peripheral ID Register[31:24]
Can be used by software to identify the presence of this
peripheral.
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Preliminary
Universal Asynchronous Receivers/Transmitters (UARTs)
Register 21: UART PrimeCell Identification 0 (UARTPCellID0), offset 0xFF0
The UARTPCellIDn registers are hard-coded and the fields within the registers determine the
reset values.
UART Primecell Identification 0 (UARTPCellID0)
Offset 0xFF0
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
1
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
CID0
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
CID0
RO
0x0D
Description
Reserved bits return an indeterminate value, and should never
be changed.
UART PrimeCell ID Register[7:0]
Provides software a standard cross-peripheral identification
system.
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LM3S818 Data Sheet
Register 22: UART PrimeCell Identification 1 (UARTPCellID1), offset 0xFF4
The UARTPCellIDn registers are hard-coded and the fields within the registers determine the
reset values.
UART Primecell Identification 1 (UARTPCellID1)
Offset 0xFF4
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
1
RO
1
RO
1
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
CID1
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
CID1
RO
0xF0
Description
Reserved bits return an indeterminate value, and should never
be changed.
UART PrimeCell ID Register[15:8]
Provides software a standard cross-peripheral identification
system.
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271
Preliminary
Universal Asynchronous Receivers/Transmitters (UARTs)
Register 23: UART PrimeCell Identification 2 (UARTPCellID2), offset 0xFF8
The UARTPCellIDn registers are hard-coded and the fields within the registers determine the
reset values.
UART Primecell Identification 2 (UARTPCellID2)
Offset 0xFF8
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
CID2
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
CID2
RO
0x05
Description
Reserved bits return an indeterminate value, and should never
be changed.
UART PrimeCell ID Register[23:16]
Provides software a standard cross-peripheral identification
system.
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LM3S818 Data Sheet
Register 24: UART PrimeCell Identification 3 (UARTPCellID3), offset 0xFFC
The UARTPCellIDn registers are hard-coded and the fields within the registers determine the
reset values.
UART Primecell Identification 3 (UARTPCellID3)
Offset 0xFFC
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
0
RO
1
RO
1
RO
0
RO
0
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
CID3
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
CID3
RO
0xB1
Description
Reserved bits return an indeterminate value, and should never
be changed.
UART PrimeCell ID Register[31:24]
Provides software a standard cross-peripheral identification
system.
May 4, 2007
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Preliminary
Synchronous Serial Interface (SSI)
13
Synchronous Serial Interface (SSI)
The Stellaris Synchronous Serial Interface (SSI) is a master or slave interface for synchronous
serial communication with peripheral devices that have either Freescale SPI, MICROWIRE, or
Texas Instruments synchronous serial interfaces.
The Stellaris SSI has the following features:
13.1
„
Master or slave operation
„
Programmable clock bit rate and prescale
„
Separate transmit and receive FIFOs, 16 bits wide, 8 locations deep
„
Programmable interface operation for Freescale SPI, MICROWIRE, or Texas Instruments
synchronous serial interfaces
„
Programmable data frame size from 4 to 16 bits
„
Internal loopback test mode for diagnostic/debug testing
Block Diagram
Figure 13-1. SSI Module Block Diagram
Interrupt
Interrupt Control
SSIIM
SSIMIS
Control / Status
SSICR0
SSIRIS
SSIICR
SSICR1
TxFIFO
8 x 16
.
.
.
SSITx
SSISR
SSIDR
RxFIFO
8 x 16
Transmit /
Receive
Logic
SSIRx
SSIClk
SSIFss
System Clock
Clock
Prescaler
Identification Registers
SSIPCellID0
SSIPeriphID 0
SSIPeriphID 4
SSIPCellID1
SSIPeriphID 1
SSIPeriphID 5
SSIPCellID2
SSIPeriphID 2
SSIPeriphID 6
SSIPCellID3
SSIPeriphID 3
SSIPeriphID 7
.
.
.
SSICPSR
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LM3S818 Data Sheet
13.2
Functional Description
The SSI performs serial-to-parallel conversion on data received from a peripheral device. The
CPU accesses data, control, and status information. The transmit and receive paths are buffered
with internal FIFO memories allowing up to eight 16-bit values to be stored independently in both
transmit and receive modes.
13.2.1
Bit Rate Generation
The SSI includes a programmable bit rate clock divider and prescaler to generate the serial output
clock. Bit rates are supported to 2 MHz and higher, although maximum bit rate is determined by
peripheral devices.
The serial bit rate is derived by dividing down the 50-MHz input clock. The clock is first divided by
an even prescale value CPSDVSR from 2 to 254, which is programmed in the SSI Clock Prescale
(SSICPSR) register (see page 292). The clock is further divided by a value from 1 to 256, which is
1 + SCR, where SCR is the value programmed in the SSI Control0 (SSICR0) register (see
page 286).
The frequency of the output clock SSICLK is defined by:
FSSIClk = FSysClk / (CPSDVSR * (1 + SCR))
Note that although the SSICLK transmit clock can theoretically be 25 MHz, the module may not be
able to operate at that speed. For master mode, the system clock must be at least two times faster
than the SSICLK. For slave mode, the system clock must be at least 12 times faster than the
SSICLK.
See “Electrical Characteristics” on page 377 to view SSI timing parameters.
13.2.2
FIFO Operation
13.2.2.1
Transmit FIFO
The common transmit FIFO is a 16-bit wide, 8-locations deep, first-in, first-out memory buffer. The
CPU writes data to the FIFO by writing the SSI Data (SSIDR) register (see page 290), and data is
stored in the FIFO until it is read out by the transmission logic.
When configured as a master or a slave, parallel data is written into the transmit FIFO prior to
serial conversion and transmission to the attached slave or master, respectively, through the
SSITX pin.
13.2.2.2
Receive FIFO
The common receive FIFO is a 16-bit wide, 8-locations deep, first-in, first-out memory buffer.
Received data from the serial interface is stored in the buffer until read out by the CPU, which
accesses the read FIFO by reading the SSIDR register.
When configured as a master or slave, serial data received through the SSIRX pin is registered
prior to parallel loading into the attached slave or master receive FIFO, respectively.
13.2.3
Interrupts
The SSI can generate interrupts when the following conditions are observed:
„
Transmit FIFO service
„
Receive FIFO service
„
Receive FIFO time-out
„
Receive FIFO overrun
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Synchronous Serial Interface (SSI)
All of the interrupt events are ORed together before being sent to the interrupt controller, so the
SSI can only generate a single interrupt request to the controller at any given time. You can mask
each of the four individual maskable interrupts by setting the appropriate bits in the SSI Interrupt
Mask (SSIIM) register (see page 293). Setting the appropriate mask bit to 1 enables the interrupt.
Provision of the individual outputs, as well as a combined interrupt output, allows use of either a
global interrupt service routine, or modular device drivers to handle interrupts. The transmit and
receive dynamic dataflow interrupts have been separated from the status interrupts so that data
can be read or written in response to the FIFO trigger levels. The status of the individual interrupt
sources can be read from the SSI Raw Interrupt Status (SSIRIS) and SSI Masked Interrupt
Status (SSIMIS) registers (see page 294 and page 295, respectively).
13.2.4
Frame Formats
Each data frame is between 4 and 16 bits long, depending on the size of data programmed, and is
transmitted starting with the MSB. There are three basic frame types that can be selected:
„
Texas Instruments synchronous serial
„
Freescale SPI
„
MICROWIRE
For all three formats, the serial clock (SSICLK) is held inactive while the SSI is idle, and SSICLK
transitions at the programmed frequency only during active transmission or reception of data. The
idle state of SSICLK is utilized to provide a receive timeout indication that occurs when the receive
FIFO still contains data after a timeout period.
For Freescale SPI and MICROWIRE frame formats, the serial frame (SSIFSS) pin is active Low,
and is asserted (pulled down) during the entire transmission of the frame.
For Texas Instruments synchronous serial frame format, the SSIFSS pin is pulsed for one serial
clock period starting at its rising edge, prior to the transmission of each frame. For this frame
format, both the SSI and the off-chip slave device drive their output data on the rising edge of
SSICLK, and latch data from the other device on the falling edge.
Unlike the full-duplex transmission of the other two frame formats, the MICROWIRE format uses a
special master-slave messaging technique, which operates at half-duplex. In this mode, when a
frame begins, an 8-bit control message is transmitted to the off-chip slave. During this transmit, no
incoming data is received by the SSI. After the message has been sent, the off-chip slave decodes
it and, after waiting one serial clock after the last bit of the 8-bit control message has been sent,
responds with the requested data. The returned data can be 4 to 16 bits in length, making the total
frame length anywhere from 13 to 25 bits.
13.2.4.1
Texas Instruments Synchronous Serial Frame Format
Figure 13-2 shows the Texas Instruments synchronous serial frame format for a single transmitted
frame.
Figure 13-2. TI Synchronous Serial Frame Format (Single Transfer)
SSIClk
SSIFss
SSITx/SSIRx
MSB
LSB
4 to 16 bits
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LM3S818 Data Sheet
In this mode, SSICLK and SSIFSS are forced Low, and the transmit data line SSITX is tristated
whenever the SSI is idle. Once the bottom entry of the transmit FIFO contains data, SSIFSS is
pulsed High for one SSICLK period. The value to be transmitted is also transferred from the
transmit FIFO to the serial shift register of the transmit logic. On the next rising edge of SSICLK,
the MSB of the 4 to 16-bit data frame is shifted out on the SSITX pin. Likewise, the MSB of the
received data is shifted onto the SSIRX pin by the off-chip serial slave device.
Both the SSI and the off-chip serial slave device then clock each data bit into their serial shifter on
the falling edge of each SSICLK. The received data is transferred from the serial shifter to the
receive FIFO on the first rising edge of SSICLK after the LSB has been latched.
Figure 13-3 shows the Texas Instruments synchronous serial frame format when back-to-back
frames are transmitted.
Figure 13-3. TI Synchronous Serial Frame Format (Continuous Transfer)
SSIClk
SSIFss
SSITx/SSIRx
MSB
LSB
4 to 16 bits
13.2.4.2
Freescale SPI Frame Format
The Freescale SPI interface is a four-wire interface where the SSIFSS signal behaves as a slave
select. The main feature of the Freescale SPI format is that the inactive state and phase of the
SSICLK signal are programmable through the SPO and SPH bits within the SSISCR0 control
register.
SPO Clock Polarity Bit
When the SPO clock polarity control bit is Low, it produces a steady state Low value on the
SSICLK pin. If the SPO bit is High, a steady state High value is placed on the SSICLK pin when
data is not being transferred.
SPH Phase Control Bit
The SPH phase control bit selects the clock edge that captures data and allows it to change state.
It has the most impact on the first bit transmitted by either allowing or not allowing a clock
transition before the first data capture edge. When the SPH phase control bit is Low, data is
captured on the first clock edge transition. If the SPH bit is High, data is captured on the second
clock edge transition.
13.2.4.3
Freescale SPI Frame Format with SPO=0 and SPH=0
Single and continuous transmission signal sequences for Freescale SPI format with SPO=0 and
SPH=0 are shown in Figure 13-4 and Figure 13-5.
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Preliminary
Synchronous Serial Interface (SSI)
Figure 13-4. Freescale SPI Format (Single Transfer) with SPO=0 and SPH=0
SSIClk
SSIFss
MSB
SSIRx
LSB
Q
4 to 16 bits
MSB
SSITx
LSB
Figure 13-5. Freescale SPI Format (Continuous Transfer) with SPO=0 and SPH=0
SSIClk
SSIFss
SSIRx LSB
MSB
LSB
MSB
4 to 16 bits
SSITx LSB
MSB
LSB
MSB
In this configuration, during idle periods:
„
SSICLK is forced Low
„
SSIFSS is forced High
„
The transmit data line SSITX is arbitrarily forced Low
„
When the SSI is configured as a master, it enables the SSICLK pad
„
When the SSI is configured as a slave, it disables the SSICLK pad
If the SSI is enabled and there is valid data within the transmit FIFO, the start of transmission is
signified by the SSIFSS master signal being driven Low. This causes slave data to be enabled
onto the SSIRX input line of the master. The master SSITX output pad is enabled.
One half SSICLK period later, valid master data is transferred to the SSITX pin. Now that both the
master and slave data have been set, the SSICLK master clock pin goes High after one further
half SSICLK period.
The data is now captured on the rising and propagated on the falling edges of the SSICLK signal.
In the case of a single word transmission, after all bits of the data word have been transferred, the
SSIFSS line is returned to its idle High state one SSICLK period after the last bit has been
captured.
However, in the case of continuous back-to-back transmissions, the SSIFSS signal must be
pulsed High between each data word transfer. This is because the slave select pin freezes the
data in its serial peripheral register and does not allow it to be altered if the SPH bit is logic zero.
Therefore, the master device must raise the SSIFSS pin of the slave device between each data
transfer to enable the serial peripheral data write. On completion of the continuous transfer, the
SSIFSS pin is returned to its idle state one SSICLK period after the last bit has been captured.
13.2.4.4
Freescale SPI Frame Format with SPO=0 and SPH=1
The transfer signal sequence for Freescale SPI format with SPO=0 and SPH=1 is shown in
Figure 13-6, which covers both single and continuous transfers.
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LM3S818 Data Sheet
Figure 13-6. Freescale SPI Frame Format with SPO=0 and SPH=1
SSIClk
SSIFss
SSIRx
Q
LSB
MSB
Q
4 to 16 bits
SSITx
MSB
LSB
In this configuration, during idle periods:
„
SSICLK is forced Low
„
SSIFSS is forced High
„
The transmit data line SSITX is arbitrarily forced Low
„
When the SSI is configured as a master, it enables the SSICLK pad
„
When the SSI is configured as a slave, it disables the SSICLK pad
If the SSI is enabled and there is valid data within the transmit FIFO, the start of transmission is
signified by the SSIFSS master signal being driven Low. The master SSITX output is enabled.
After a further one half SSICLK period, both master and slave valid data is enabled onto their
respective transmission lines. At the same time, the SSICLK is enabled with a rising edge
transition.
Data is then captured on the falling edges and propagated on the rising edges of the SSICLK
signal.
In the case of a single word transfer, after all bits have been transferred, the SSIFSS line is
returned to its idle High state one SSICLK period after the last bit has been captured.
For continuous back-to-back transfers, the SSIFSS pin is held Low between successive data
words and termination is the same as that of the single word transfer.
13.2.4.5
Freescale SPI Frame Format with SPO=1 and SPH=0
Single and continuous transmission signal sequences for Freescale SPI format with SPO=1 and
SPH=0 are shown in Figure 13-7 and Figure 13-8.
Figure 13-7. Freescale SPI Frame Format (Single Transfer) with SPO=1 and SPH=0
SSIClk
SSIFss
SSIRx
MSB
LSB
Q
4 to 16 bits
SSITx
MSB
LSB
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Preliminary
Synchronous Serial Interface (SSI)
Figure 13-8. Freescale SPI Frame Format (Continuous Transfer) with SPO=1 and SPH=0
SSIClk
SSIFss
SSITx/SSIRx
LSB
MSB
LSB
MSB
4 to 16 bits
In this configuration, during idle periods:
„
SSICLK is forced High
„
SSIFSS is forced High
„
The transmit data line SSITX is arbitrarily forced Low
„
When the SSI is configured as a master, it enables the SSICLK pad
„
When the SSI is configured as a slave, it disables the SSICLK pad
If the SSI is enabled and there is valid data within the transmit FIFO, the start of transmission is
signified by the SSIFSS master signal being driven Low, which causes slave data to be
immediately transferred onto the SSIRX line of the master. The master SSITX output pad is
enabled.
One half period later, valid master data is transferred to the SSITX line. Now that both the master
and slave data have been set, the SSICLK master clock pin becomes Low after one further half
SSICLK period. This means that data is captured on the falling edges and propagated on the rising
edges of the SSICLK signal.
In the case of a single word transmission, after all bits of the data word are transferred, the
SSIFSS line is returned to its idle High state one SSICLK period after the last bit has been
captured.
However, in the case of continuous back-to-back transmissions, the SSIFSS signal must be
pulsed High between each data word transfer. This is because the slave select pin freezes the
data in its serial peripheral register and does not allow it to be altered if the SPH bit is logic zero.
Therefore, the master device must raise the SSIFSS pin of the slave device between each data
transfer to enable the serial peripheral data write. On completion of the continuous transfer, the
SSIFSS pin is returned to its idle state one SSICLK period after the last bit has been captured.
13.2.4.6
Freescale SPI Frame Format with SPO=1 and SPH=1
The transfer signal sequence for Freescale SPI format with SPO=1 and SPH=1 is shown in
Figure 13-9, which covers both single and continuous transfers.
Figure 13-9. Freescale SPI Frame Format with SPO=1 and SPH=1
SSIClk
SSIFss
SSIRx
Q
LSB
MSB
Q
4 to 16 bits
SSITx
Note:
MSB
LSB
Q is undefined in Figure 13-9.
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LM3S818 Data Sheet
In this configuration, during idle periods:
„
SSICLK is forced High
„
SSIFSS is forced High
„
The transmit data line SSITX is arbitrarily forced Low
„
When the SSI is configured as a master, it enables the SSICLK pad
„
When the SSI is configured as a slave, it disables the SSICLK pad
If the SSI is enabled and there is valid data within the transmit FIFO, the start of transmission is
signified by the SSIFSS master signal being driven Low. The master SSITX output pad is enabled.
After a further one-half SSICLK period, both master and slave data are enabled onto their
respective transmission lines. At the same time, SSICLK is enabled with a falling edge transition.
Data is then captured on the rising edges and propagated on the falling edges of the SSICLK
signal.
After all bits have been transferred, in the case of a single word transmission, the SSIFSS line is
returned to its idle high state one SSICLK period after the last bit has been captured.
For continuous back-to-back transmissions, the SSIFSS pin remains in its active Low state, until
the final bit of the last word has been captured, and then returns to its idle state as described
above.
For continuous back-to-back transfers, the SSIFSS pin is held Low between successive data
words and termination is the same as that of the single word transfer.
13.2.4.7
MICROWIRE Frame Format
Figure 13-10 shows the MICROWIRE frame format, again for a single frame. Figure 13-11 shows
the same format when back-to-back frames are transmitted.
Figure 13-10.
MICROWIRE Frame Format (Single Frame)
SSIClk
SSIFss
SSITx
MSB
LSB
8-bit control
SSIRx
0
MSB
LSB
4 to 16 bits
output data
MICROWIRE format is very similar to SPI format, except that transmission is half-duplex instead
of full-duplex, using a master-slave message passing technique. Each serial transmission begins
with an 8-bit control word that is transmitted from the SSI to the off-chip slave device. During this
transmission, no incoming data is received by the SSI. After the message has been sent, the
off-chip slave decodes it and, after waiting one serial clock after the last bit of the 8-bit control
message has been sent, responds with the required data. The returned data is 4 to 16 bits in
length, making the total frame length anywhere from 13 to 25 bits.
In this configuration, during idle periods:
„
SSICLK is forced Low
„
SSIFSS is forced High
„
The transmit data line SSITX is arbitrarily forced Low
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Synchronous Serial Interface (SSI)
A transmission is triggered by writing a control byte to the transmit FIFO. The falling edge of
SSIFSS causes the value contained in the bottom entry of the transmit FIFO to be transferred to
the serial shift register of the transmit logic, and the MSB of the 8-bit control frame to be shifted out
onto the SSITX pin. SSIFSS remains Low for the duration of the frame transmission. The SSIRX
pin remains tristated during this transmission.
The off-chip serial slave device latches each control bit into its serial shifter on the rising edge of
each SSICLK. After the last bit is latched by the slave device, the control byte is decoded during a
one clock wait-state, and the slave responds by transmitting data back to the SSI. Each bit is
driven onto the SSIRX line on the falling edge of SSICLK. The SSI in turn latches each bit on the
rising edge of SSICLK. At the end of the frame, for single transfers, the SSIFSS signal is pulled
High one clock period after the last bit has been latched in the receive serial shifter, which causes
the data to be transferred to the receive FIFO.
Note:
The off-chip slave device can tristate the receive line either on the falling edge of SSICLK
after the LSB has been latched by the receive shifter, or when the SSIFSS pin goes High.
For continuous transfers, data transmission begins and ends in the same manner as a single
transfer. However, the SSIFSS line is continuously asserted (held Low) and transmission of data
occurs back-to-back. The control byte of the next frame follows directly after the LSB of the
received data from the current frame. Each of the received values is transferred from the receive
shifter on the falling edge of SSICLK, after the LSB of the frame has been latched into the SSI.
Figure 13-11.
MICROWIRE Frame Format (Continuous Transfer)
SSIClk
SSIFss
SSITx
LSB
MSB
LSB
8-bit control
SSIRx
0
MSB
LSB
MSB
4 to 16 bits
output data
In the MICROWIRE mode, the SSI slave samples the first bit of receive data on the rising edge of
SSICLK after SSIFSS has gone Low. Masters that drive a free-running SSICLK must ensure that
the SSIFSS signal has sufficient setup and hold margins with respect to the rising edge of
SSICLK.
Figure 13-12 illustrates these setup and hold time requirements. With respect to the SSICLK rising
edge on which the first bit of receive data is to be sampled by the SSI slave, SSIFSS must have a
setup of at least two times the period of SSICLK on which the SSI operates. With respect to the
SSICLK rising edge previous to this edge, SSIFSS must have a hold of at least one SSICLK
period.
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LM3S818 Data Sheet
Figure 13-12.
MICROWIRE Frame Format, SSIFss Input Setup and Hold Requirements
tSetup =(2*tSSIClk )
tHold=tSSIClk
SSIClk
SSIFss
SSIRx
First RX data to be
sampled by SSI slave
13.3
Initialization and Configuration
To use the SSI, its peripheral clock must be enabled by setting the SSI bit in the RCGC1 register.
For each of the frame formats, the SSI is configured using the following steps:
1. Ensure that the SSE bit in the SSICR1 register is disabled before making any configuration
changes.
2. Select whether the SSI is a master or slave:
a. For master operations, set the SSICR1 register to 0x00000000.
b. For slave mode (output enabled), set the SSICR1 register to 0x00000004.
c. For slave mode (output disabled), set the SSICR1 register to 0x0000000C.
3. Configure the clock prescale divisor by writing the SSICPSR register.
4. Write the SSICR0 register with the following configuration:
– Serial clock rate (SCR)
– Desired clock phase/polarity, if using Freescale SPI mode (SPH and SPO)
– The protocol mode: Freescale SPI, TI SSF, MICROWIRE (FRF)
– The data size (DSS)
5. Enable the SSI by setting the SSE bit in the SSICR1 register.
As an example, assume the SSI must be configured to operate with the following parameters:
„
Master operation
„
Freescale SPI mode (SPO=1, SPH=1)
„
1 Mbps bit rate
„
8 data bits
Assuming the system clock is 20 MHz, the bit rate calculation would be:
FSSIClk = FSysClk / (CPSDVSR * (1 + SCR)) ' 1x106 = 20x106 / (CPSDVSR * (1 +
SCR))
In this case, if CPSDVSR=2, SCR must be 9.
The configuration sequence would be as follows:
1. Ensure that the SSE bit in the SSICR1 register is disabled.
2. Write the SSICR1 register with a value of 0x00000000.
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Synchronous Serial Interface (SSI)
3. Write the SSICPSR register with a value of 0x00000002.
4. Write the SSICR0 register with a value of 0x000009C7.
5. The SSI is then enabled by setting the SSE bit in the SSICR1 register to 1.
13.4
Register Map
Table 13-1 lists the SSI registers. The offset listed is a hexadecimal increment to the register’s
address, relative to the SSI base address of 0x40008000.
Note:
Table 13-1.
The SSI must be disabled (see the SSE bit in the SSICR1 register) before any of the
control registers are reprogrammed.
SSI Register Map
Offset
Name
0x000
See
page
Reset
Type
Description
SSICR0
0x00000000
R/W
Control 0
286
0x004
SSICR1
0x00000000
R/W
Control 1
288
0x008
SSIDR
0x00000000
R/W
Data
290
0x00C
SSISR
0x00000003
RO
Status
291
0x010
SSICPSR
0x00000000
R/W
Clock prescale
292
0x014
SSIIM
0x00000000
R/W
Interrupt mask
293
0x018
SSIRIS
0x00000008
RO
Raw interrupt status
294
0x01C
SSIMIS
0x00000000
RO
Masked interrupt status
295
0x020
SSIICR
0x00000000
W1C
Interrupt clear
296
0xFD0
SSIPeriphID4
0x00000000
RO
Peripheral identification 4
297
0xFD4
SSIPeriphID5
0x00000000
RO
Peripheral identification 5
298
0xFD8
SSIPeriphID6
0x00000000
RO
Peripheral identification 6
299
0xFDC
SSIPeriphID7
0x00000000
RO
Peripheral identification 7
300
0xFE0
SSIPeriphID0
0x00000022
RO
Peripheral identification 0
301
0xFE4
SSIPeriphID1
0x00000000
RO
Peripheral identification 1
302
0xFE8
SSIPeriphID2
0x00000018
RO
Peripheral identification 2
303
0xFEC
SSIPeriphID3
0x00000001
RO
Peripheral identification 3
304
0xFF0
SSIPCellID0
0x0000000D
RO
PrimeCell identification 0
305
0xFF4
SSIPCellID1
0x000000F0
RO
PrimeCell identification 1
306
0xFF8
SSIPCellID2
0x00000005
RO
PrimeCell identification 2
307
0xFFC
SSIPCellID3
0x000000B1
RO
PrimeCell identification 3
308
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LM3S818 Data Sheet
13.5
Register Descriptions
The remainder of this section lists and describes the SSI registers, in numerical order by address
offset.
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Synchronous Serial Interface (SSI)
Register 1: SSI Control 0 (SSICR0), offset 0x000
SSICR0 is control register 0 and contains bit fields that control various functions within the SSI
module. Functionality such as protocol mode, clock rate and data size are configured in this
register.
SSI Control 0 (SSICR0)
Offset 0x000
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
SPH
SPO
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
SCR
Type
Reset
DSS
FRF
R/W
0
Bit/Field
Name
Type
Reset
Description
31:16
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
15:8
SCR
R/W
0
SSI Serial Clock Rate
The value SCR is used to generate the transmit and receive bit
rate of the SSI. The bit rate is:
BR= FSSICLK/(CPSDVSR * (1 + SCR))
where CPSDVSR is an even value from 2-254 programmed in the
SSICPSR register, and SCR is a value from 0-255.
7
SPH
R/W
0
SSI Serial Clock Phase
This bit is only applicable to the Freescale SPI Format.
The SPH control bit selects the clock edge that captures data
and allows it to change state. It has the most impact on the first
bit transmitted by either allowing or not allowing a clock
transition before the first data capture edge.
When the SPH bit is 0, data is captured on the first clock edge
transition. If SPH is 1, data is captured on the second clock edge
transition.
6
SPO
R/W
0
SSI Serial Clock Polarity
This bit is only applicable to the Freescale SPI Format.
When the SPO bit is 0, it produces a steady state Low value on
the SSICLK pin. If SPO is 1, a steady state High value is placed
on the SSICLK pin when data is not being transferred.
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LM3S818 Data Sheet
Bit/Field
Name
Type
Reset
5:4
FRF
R/W
0
Description
SSI Frame Format Select.
The FRF values are defined as follows:
FRF Value
3:0
DSS
R/W
0
Frame Format
00
Freescale SPI Frame Format
01
Texas Instruments Synchronous
Serial Frame Format
10
MICROWIRE Frame Format
11
Reserved
SSI Data Size Select
The DSS values are defined as follows:
DSS Value
Data Size
0000-0010
Reserved
0011
4-bit data
0100
5-bit data
0101
6-bit data
0110
7-bit data
0111
8-bit data
1000
9-bit data
1001
10-bit data
1010
11-bit data
1011
12-bit data
1100
13-bit data
1101
14-bit data
1110
15-bit data
1111
16-bit data
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Synchronous Serial Interface (SSI)
Register 2: SSI Control 1 (SSICR1), offset 0x004
SSICR1 is control register 1 and contains bit fields that control various functions within the SSI
module. Master and slave mode functionality is controlled by this register.
SSI Control 1 (SSCR1)
Offset 0x004
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
SOD
MS
SSE
LBM
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
Bit/Field
Name
Type
Reset
Description
31:4
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
3
SOD
R/W
0
SSI Slave Mode Output Disable
This bit is relevant only in the Slave mode (MS=1). In
multiple-slave systems, it is possible for the SSI master to
broadcast a message to all slaves in the system while
ensuring that only one slave drives data onto the serial output
line. In such systems, the TXD lines from multiple slaves
could be tied together. To operate in such a system, the SOD
bit can be configured so that the SSI slave does not drive the
SSITX pin.
0: SSI can drive SSITX output in Slave Output mode.
1: SSI must not drive the SSITX output in Slave mode.
2
MS
R/W
0
SSI Master/Slave Select
This bit selects Master or Slave mode and can be modified
only when SSI is disabled (SSE=0).
0: Device configured as a master.
1: Device configured as a slave.
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LM3S818 Data Sheet
Bit/Field
Name
Type
Reset
1
SSE
R/W
0
Description
SSI Synchronous Serial Port Enable
Setting this bit enables SSI operation.
0: SSI operation disabled.
1: SSI operation enabled.
Note:
0
LBM
R/W
0
This bit must be set to 0 before any control registers
are reprogrammed.
SSI Loopback Mode
Setting this bit enables Loopback Test mode.
0: Normal serial port operation enabled.
1: Output of the transmit serial shift register is connected
internally to the input of the receive serial shift register.
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Synchronous Serial Interface (SSI)
Register 3: SSI Data (SSIDR), offset 0x008
SSIDR is the data register and is 16-bits wide. When SSIDR is read, the entry in the receive FIFO
(pointed to by the current FIFO read pointer) is accessed. As data values are removed by the SSI
receive logic from the incoming data frame, they are placed into the entry in the receive FIFO
(pointed to by the current FIFO write pointer).
When SSIDR is written to, the entry in the transmit FIFO (pointed to by the write pointer) is written
to. Data values are removed from the transmit FIFO one value at a time by the transmit logic. It is
loaded into the transmit serial shifter, then serially shifted out onto the SSITx pin at the
programmed bit rate.
When a data size of less than 16 bits is selected, the user must right-justify data written to the
transmit FIFO. The transmit logic ignores the unused bits. Received data less than 16 bits is
automatically right-justified in the receive buffer.
When the SSI is programmed for MICROWIRE frame format, the default size for transmit data is
eight bits (the most significant byte is ignored). The receive data size is controlled by the
programmer. The transmit FIFO and the receive FIFO are not cleared even when the SSE bit in the
SSICR1 register is set to zero. This allows the software to fill the transmit FIFO before enabling the
SSI.
SSI Data (SSIDR)
Offset 0x008
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
DATA
Type
Reset
Bit/Field
Name
Type
Reset
Description
31:16
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
15:0
DATA
R/W
0
SSI Receive/Transmit Data
A read operation reads the receive FIFO. A write operation
writes the transmit FIFO.
Software must right-justify data when the SSI is programmed
for a data size that is less than 16 bits. Unused bits at the top
are ignored by the transmit logic. The receive logic
automatically right-justifies the data.
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LM3S818 Data Sheet
Register 4: SSI Status (SSISR), offset 0x00C
SSISR is a status register that contains bits that indicate the FIFO fill status and the SSI busy
status.
SSI Status (SSISR)
Offset 0x00C
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
BSY
RFF
RNE
TNF
TFE
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
1
reserved
Type
Reset
reserved
Type
Reset
RO
0
Bit/Field
Name
Type
Reset
Description
31:5
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
4
BSY
RO
0
SSI Busy Bit
0: SSI is idle.
1: SSI is currently transmitting and/or receiving a frame, or the
transmit FIFO is not empty.
3
RFF
RO
0
SSI Receive FIFO Full
0: Receive FIFO is not full.
1: Receive FIFO is full.
2
RNE
RO
0
SSI Receive FIFO Not Empty
0: Receive FIFO is empty.
1: Receive FIFO is not empty.
1
TNF
RO
1
SSI Transmit FIFO Not Full
0: Transmit FIFO is full.
1: Transmit FIFO is not full.
0
TFE
R0
1
SSI Transmit FIFO Empty
0: Transmit FIFO is not empty.
1: Transmit FIFO is empty.
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Synchronous Serial Interface (SSI)
Register 5: SSI Clock Prescale (SSICPSR), offset 0x010
SSICPSR is the clock prescale register and specifies the division factor by which the system clock
must be internally divided before further use.
The value programmed into this register must be an even number between 2 and 254. The
least-significant bit of the programmed number is hard-coded to zero. If an odd number is written
to this register, data read back from this register has the least-significant bit as zero.
SSI Clock Prescale (SSICPSR)
Offset 0x010
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
CPSDVSR
R/W
0
Bit/Field
Name
Type
Reset
Description
31:8
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
7:0
CPSDVSR
R/W
0
SSI Clock Prescale Divisor
This value must be an even number from 2 to 254, depending
on the frequency of SSICLK. The LSB always returns 0 on
reads.
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LM3S818 Data Sheet
Register 6: SSI Interrupt Mask (SSIIM), offset 0x014
The SSIIM register is the interrupt mask set or clear register. It is a read/write register and all bits
are cleared to 0 on reset.
On a read, this register gives the current value of the mask on the relevant interrupt. A write of 1 to
the particular bit sets the mask, enabling the interrupt to be read. A write of 0 clears the
corresponding mask.
SSI Interrupt Mask (SSIIM)
Offset 0x014
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
TXIM
RXIM
RTIM
RORIM
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
Bit/Field
Name
Type
Reset
Description
31:4
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
3
TXIM
R/W
0
SSI Transmit FIFO Interrupt Mask
0: TX FIFO half-full or less condition interrupt is masked.
1: TX FIFO half-full or less condition interrupt is not masked.
2
RXIM
R/W
0
SSI Receive FIFO Interrupt Mask
0: RX FIFO half-full or more condition interrupt is masked.
1: RX FIFO half-full or more condition interrupt is not masked.
1
RTIM
R/W
0
SSI Receive Time-Out Interrupt Mask
0: RX FIFO time-out interrupt is masked.
1: RX FIFO time-out interrupt is not masked.
0
RORIM
R/W
0
SSI Receive Overrun Interrupt Mask
0: RX FIFO overrun interrupt is masked.
1: RX FIFO overrun interrupt is not masked.
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Synchronous Serial Interface (SSI)
Register 7: SSI Raw Interrupt Status (SSIRIS), offset 0x018
The SSIRIS register is the raw interrupt status register. On a read, this register gives the current
raw status value of the corresponding interrupt prior to masking. A write has no effect.
SSI Raw Interrupt Status (SSIRIS)
Offset 0x018
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
TXRIS
RXRIS
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
0
reserved
Type
Reset
reserved
Type
Reset
RTRIS RORRIS
RO
0
Bit/Field
Name
Type
Reset
31:4
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
3
TXRIS
RO
1
SSI Transmit FIFO Raw Interrupt Status
RO
0
Description
Indicates that the transmit FIFO is half full or less, when set.
2
RXRIS
RO
0
SSI Receive FIFO Raw Interrupt Status
Indicates that the receive FIFO is half full or more, when set.
1
RTRIS
RO
0
SSI Receive Time-Out Raw Interrupt Status
Indicates that the receive time-out has occurred, when set.
0
RORRIS
RO
0
SSI Receive Overrun Raw Interrupt Status
Indicates that the receive FIFO has overflowed, when set.
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LM3S818 Data Sheet
Register 8: SSI Masked Interrupt Status (SSIMIS), offset 0x01C
The SSIMIS register is the masked interrupt status register. On a read, this register gives the
current masked status value of the corresponding interrupt. A write has no effect.
SSI Masked Interrupt Status (SSIMIS)
Offset 0x01C
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
TXMIS RXMIS
reserved
Type
Reset
RO
0
RO
0
RTMIS RORMIS
RO
0
Bit/Field
Name
Type
Reset
31:4
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
3
TXMIS
RO
0
SSI Transmit FIFO Masked Interrupt Status
RO
0
Description
Indicates that the transmit FIFO is half full or less, when set.
2
RXMIS
RO
0
SSI Receive FIFO Masked Interrupt Status
Indicates that the receive FIFO is half full or more, when set.
1
RTMIS
RO
0
SSI Receive Time-Out Masked Interrupt Status
Indicates that the receive time-out has occurred, when set.
0
RORMIS
RO
0
SSI Receive Overrun Masked Interrupt Status
Indicates that the receive FIFO has overflowed, when set.
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Synchronous Serial Interface (SSI)
Register 9: SSI Interrupt Clear (SSIICR), offset 0x020
The SSIICR register is the interrupt clear register. On a write of 1, the corresponding interrupt is
cleared. A write of 0 has no effect.
SSI Interrupt Clear (SSIICR)
Offset 0x020
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RTIC
RORIC
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
W1C
0
W1C
0
reserved
Type
Reset
reserved
Type
Reset
Bit/Field
Name
Type
Reset
Description
31:2
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
1
RTIC
W1C
0
SSI Receive Time-Out Interrupt Clear
0: No effect on interrupt.
1: Clears interrupt.
0
RORIC
W1C
0
SSI Receive Overrun Interrupt Clear
0: No effect on interrupt.
1: Clears interrupt.
296
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 10: SSI Peripheral Identification 4 (SSIPeriphID4), offset 0xFD0
The SSIPeriphIDn registers are hard-coded and the fields within the register determine the reset
value.
SSI Peripheral Identification 4 (SSIPeriphID4)
Offset 0xFD0
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
PID4
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID4
RO
0x00
Description
Reserved bits return an indeterminate value, and should
never be changed.
SSI Peripheral ID Register[7:0]
May 4, 2007
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Preliminary
Synchronous Serial Interface (SSI)
Register 11: SSI Peripheral Identification 5 (SSIPeriphID5), offset 0xFD4
The SSIPeriphIDn registers are hard-coded and the fields within the register determine the reset
value.
SSI Peripheral Identification 5 (SSIPeriphID5)
Offset 0xFD4
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
PID5
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID5
RO
0x00
Description
Reserved bits return an indeterminate value, and should
never be changed.
SSI Peripheral ID Register[15:8]
298
May 4, 2007
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LM3S818 Data Sheet
Register 12: SSI Peripheral Identification 6 (SSIPeriphID6), offset 0xFD8
The SSIPeriphIDn registers are hard-coded and the fields within the register determine the reset
value.
SSI Peripheral Identification 6 (SSIPeriphID6)
Offset 0xFD8
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
PID6
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID6
RO
0x00
Description
Reserved bits return an indeterminate value, and should
never be changed.
SSI Peripheral ID Register[23:16]
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Preliminary
Synchronous Serial Interface (SSI)
Register 13: SSI Peripheral Identification 7 (SSIPeriphID7), offset 0xFDC
The SSIPeriphIDn registers are hard-coded and the fields within the register determine the reset
value.
SSI Peripheral Identification 7 (SSIPeriphID7)
Offset 0xFDC
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
PID7
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID7
RO
0x00
Description
Reserved bits return an indeterminate value, and should
never be changed.
SSI Peripheral ID Register[31:24]
300
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 14: SSI Peripheral Identification 0 (SSIPeriphID0), offset 0xFE0
The SSIPeriphIDn registers are hard-coded and the fields within the register determine the reset
value.
SSI Peripheral Identification 0 (SSIPeriphID0)
Offset 0xFEO
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
0
RO
0
RO
0
RO
1
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID0
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID0
RO
0x22
Description
Reserved bits return an indeterminate value, and should
never be changed.
SSI Peripheral ID Register[7:0]
Can be used by software to identify the presence of this
peripheral.
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Preliminary
Synchronous Serial Interface (SSI)
Register 15: SSI Peripheral Identification 1 (SSIPeriphID1), offset 0xFE4
The SSIPeriphIDn registers are hard-coded and the fields within the register determine the reset
value.
SSI Peripheral Identification 1 (SSIPeriphID1)
Offset 0xFE4
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID1
RO
0
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID1
RO
0x00
Description
Reserved bits return an indeterminate value, and should
never be changed.
SSI Peripheral ID Register [15:8]
Can be used by software to identify the presence of this
peripheral.
302
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 16: SSI Peripheral Identification 2 (SSIPeriphID2), offset 0xFE8
The SSIPeriphIDn registers are hard-coded and the fields within the register determine the reset
value.
SSI Peripheral Identification 2 (SSIPeriphID2)
Offset 0xFE8
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
1
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID2
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID2
RO
0x18
Description
Reserved bits return an indeterminate value, and should
never be changed.
SSI Peripheral ID Register [23:16]
Can be used by software to identify the presence of this
peripheral.
May 4, 2007
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Preliminary
Synchronous Serial Interface (SSI)
Register 17: SSI Peripheral Identification 3 (SSIPeriphID3), offset 0xFEC
The SSIPeriphIDn registers are hard-coded and the fields within the register determine the reset
value.
SSI Peripheral Identification 3 (SSIPeriphID3)
Offset 0xFEC
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
PID3
RO
0
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID3
RO
0x01
Description
Reserved bits return an indeterminate value, and should
never be changed.
SSI Peripheral ID Register [31:24]
Can be used by software to identify the presence of this
peripheral.
304
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 18: SSI PrimeCell Identification 0 (SSIPCellID0), offset 0xFF0
The SSIPCellIDn registers are hard-coded and the fields within the register determine the reset
value.
SSI Primecell Identification 0 (SSIPCellID0)
Offset 0xFF0
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
1
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
CID0
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
CID0
RO
0x0D
Description
Reserved bits return an indeterminate value, and should
never be changed.
SSI PrimeCell ID Register [7:0]
Provides software a standard cross-peripheral identification
system.
May 4, 2007
305
Preliminary
Synchronous Serial Interface (SSI)
Register 19: SSI PrimeCell Identification 1 (SSIPCellID1), offset 0xFF4
The SSIPCellIDn registers are hard-coded and the fields within the register determine the reset
value.
SSI Primecell Identification 1 (SSIPCellID1)
Offset 0xFF4
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
1
RO
1
RO
1
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
CID1
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
CID1
RO
0xF0
Description
Reserved bits return an indeterminate value, and should
never be changed.
SSI PrimeCell ID Register [15:8]
Provides software a standard cross-peripheral identification
system.
306
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 20: SSI PrimeCell Identification 2 (SSIPCellID2), offset 0xFF8
The SSIPCellIDn registers are hard-coded and the fields within the register determine the reset
value.
SSI Primecell Identification 2 (SSIPCellID2)
Offset 0xFF8
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
CID2
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
CID2
RO
0x05
Description
Reserved bits return an indeterminate value, and should
never be changed.
SSI PrimeCell ID Register [23:16]
Provides software a standard cross-peripheral identification
system.
May 4, 2007
307
Preliminary
Synchronous Serial Interface (SSI)
Register 21: SSI PrimeCell Identification 3 (SSIPCellID3), offset 0xFFC
The SSIPCellIDn registers are hard-coded and the fields within the register determine the reset
value.
SSI Primecell Identification 3 (SSIPCellID3)
Offset 0xFFC
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
0
RO
1
RO
1
RO
0
RO
0
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
CID3
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
CID3
RO
0xB1
Description
Reserved bits return an indeterminate value, and should
never be changed.
SSI PrimeCell ID Register [31:24]
Provides software a standard cross-peripheral identification
system.
308
May 4, 2007
Preliminary
LM3S818 Data Sheet
14
Analog Comparator
An analog comparator is a peripheral that compares two analog voltages, and provides a logical
output that signals the comparison result.
The LM3S818 controller provides one analog comparator that can be configured to drive an output
or generate an interrupt or ADC event.
A comparator can compare a test voltage against any one of these voltages:
„
An individual external reference voltage
„
A shared single external reference voltage
„
A shared internal reference voltage
The comparator can provide its output to a device pin, acting as a replacement for an analog
comparator on the board, or it can be used to signal the application via interrupts or triggers to the
ADC to cause it to start capturing a sample sequence. The interrupt generation and ADC triggering
logic is separate. This means, for example, that an interrupt can be generated on a rising edge and
the ADC triggered on a falling edge.
14.1
Block Diagram
Figure 14-1. Analog Comparator Module Block Diagram
C0-
-ve input
C0+
+ve input
Comparator 0
output
C0o
+ve input (alternate)
ACCTL0
ACSTAT0
interrupt
reference input
interrupt
Voltage
Ref
internal
bus
14.2
ACREFCTL
Functional Description
Important: It is recommended that the Digital-Input enable (the GPIODEN bit in the GPIO
module) for the analog input pin be disabled to prevent excessive current draw from
the I/O pads.
The comparator compares the VIN- and VIN+ inputs to produce an output, VOUT.
As shown in Figure 14-2, the input source for VIN- is an external input. In addition to an external
input, input sources for VIN+ can be the +ve input of comparator 0 or an internal reference.
May 4, 2007
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Preliminary
Analog Comparator
Figure 14-2. Structure of Comparator Unit
-ve input
+ve input (alternate)
reference input
output
0
CINV
1
IntGen
2
TrigGen
ACCTL
trigger
internal
bus
ACSTAT
interrupt
+ve input
A comparator is configured through two status/control registers (ACCTL and ACSTAT). The
internal reference is configured through one control register (ACREFCTL). Interrupt status and
control is configured through three registers (ACMIS, ACRIS, and ACINTEN). The operating
modes of the comparators are shown in Table 14-1.
Typically, the comparator output is used internally to generate controller interrupts. It may also be
used to drive an external pin or generate an analog-to-digital converter (ADC) trigger.
Important: Certain register bit values must be set before using the analog comparators. The
proper pad configuration for the comparator input and output pins are described in
Table 8-1 on page 120.
Table 14-1.
Comparator 0 Operating Modes
ACCNTL0
ASRCP
14.2.1
Comparator 0
VIN-
VIN+
Output
Interrupt
00
C0-
C0+
C0o
yes
01
C0-
C0+
C0o
yes
10
C0-
Vref
C0o
yes
11
C0-
reserved
C0o
yes
Internal Reference Programming
The structure of the internal reference is shown in Figure 14-3. This is controlled by a single
configuration register (ACREFCTL). Table 14-2 shows the programming options to develop
specific internal reference values, to compare an external voltage against a particular voltage
generated internally.
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May 4, 2007
Preliminary
LM3S818 Data Sheet
Figure 14-3. Comparator Internal Reference Structure
8R
AVDD
8R
R
R
R
R
•••
EN
15
14
1
•••
0
Decoder
VREF
internal
reference
RNG
Table 14-2.
Internal Reference Voltage and ACREFCTL Field Values
ACREFCTL Register
Output Reference Voltage Based on VREF Field Value
EN Bit Value
RNG Bit Value
EN=0
RNG=X
0 V (GND) for any value of VREF; however, it is recommended that
RNG=1 and VREF=0 for the least noisy ground reference.
EN=1
RNG=0
Total resistance in ladder is 32 R.
R VREF
V REF = AV DD × ---------------RT
( VREF + 8 )
V REF = AV DD × ----------------------------32
V REF = 0.825 + 0.103 ⋅ VREF
The range of internal reference in this mode is 0.825–2.37 V.
RNG=1
Total resistance in ladder is 24 R.
R VREF
V REF = AV DD × ---------------RT
( VREF )
V REF = AV DD × -------------------24
V REF = 0.1375 ⋅ VREF
The range of internal reference for this mode is 0.0–2.0625 V.
14.3
Initialization and Configuration
The following example shows how to configure analog comparator to read back its output value
from an internal register.
1. Enable the analog comparator 0 clock by writing a value of 0x00100000 to the RCGC1 register
in the System Control module.
2. In the GPIO module, enable the GPIO port/pin associated with C0- as a GPIO input.
3. Configure the internal voltage reference to 1.65 V by writing the ACREFCTL register with the
value 0x0000030C.
4. Configure comparator 0 to use the internal voltage reference and to not invert the output on
the C0O pin by writing the ACCTL0 register with the value of 0x0000040C.
May 4, 2007
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Preliminary
Analog Comparator
5. Delay for some time.
6. Read the comparator output value by reading the ACSTAT0 register’s OVAL value.
Change the level of the signal input on C0- to see the OVAL value change.
14.4
Register Map
Table 14-3 lists the comparator registers. The offset listed is a hexadecimal increment to the
register’s address, relative to the Analog Comparator base address of 0x4003C000.
Table 14-3.
Analog Comparator Register Map
Offset
Name
Reset
Type
0x00
ACMIS
0x00000000
R/W1C
0X04
ACRIS
0x00000000
0X08
ACINTEN
0x10
Description
See
page
Interrupt status
313
RO
Raw interrupt status
314
0x00000000
R/W
Interrupt enable
315
ACREFCTL
0x00000000
R/W
Reference voltage control
316
0x20
ACSTAT0
0x00000000
RO
Comparator 0 status
317
0x24
ACCTL0
0x00000000
R/W
Comparator 0 control
318
14.5
Register Descriptions
The remainder of this section lists and describes the Analog Comparator registers, in numerical
order by address offset.
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May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 1: Analog Comparator Masked Interrupt Status (ACMIS), offset 0x00
This register provides a summary of the interrupt status (masked) of the comparator.
Analog Comparator Masked Interrupt Status (ACMIS)
Offset 0x000
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
IN0
RO
0
Bit/Field
Name
Type
Reset
Description
31:1
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
0
IN0
R/1WC
0
Comparator 0 Masked Interrupt Status
Gives the masked interrupt state of this interrupt. Write 1 to this
field to clear the pending interrupt.
May 4, 2007
313
Preliminary
Analog Comparator
Register 2: Analog Comparator Raw Interrupt Status (ACRIS), offset 0x04
This register provides a summary of the interrupt status (raw) of the comparator.
Analog Comparator Raw Interrupt Status (ACRIS)
Offset 0x04
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
IN0
RO
0
Bit/Field
Name
Type
Reset
Description
31:1
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
0
IN0
RO
0
When set, indicates that an interrupt has been generated by
comparator 0.
314
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 3: Analog Comparator Interrupt Enable (ACINTEN), offset 0x08
This register provides the interrupt enable for the comparator.
Analog Comparator Interrupt Enable (ACINTEN)
Offset 0x08
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
IN0
RO
R/W
0
Bit/Field
Name
Type
Reset
Description
31:1
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
0
IN0
R/W
0
When set, enables the controller interrupt from the comparator 0
output.
May 4, 2007
315
Preliminary
Analog Comparator
Register 4: Analog Comparator Reference Voltage Control (ACREFCTL), offset 0x10
This register specifies whether the resistor ladder is powered on as well as the range and tap.
Analog Comparator Reference Voltage Control (ACREFCTL)
Offset 0x010
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
RO
0
RO
0
RO
0
RO
0
RO
0
RO
R/W
0
R/W
RO
0
RO
R/W
0
R/W
RO
0
reserved
Type
Reset
VREF
ENreserved
RNG
Type
Reset
RO
R/W
0
Bit/Field
Name
Type
Reset
Description
31:10
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
9
EN
R/W
0
The EN bit specifies whether the resistor ladder is powered
on. If 0, the resistor ladder is unpowered. If 1, the resistor
ladder is connected to the analog VDD.
This bit is reset to 0 so that the internal reference consumes
the least amount of power if not used and programmed.
8
RNG
R/W
0
The RNG bit specifies the range of the resistor ladder. If 0, the
resistor ladder has a total resistance of 32 R. If 1, the resistor
ladder has a total resistance of 24 R.
7:4
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
3:0
VREF
R/W
0
The VREF bit field specifies the resistor ladder tap that is
passed through an analog multiplexer. The voltage
corresponding to the tap position is the internal reference
voltage available for comparison. See Table 14-2 on page 311
for some output reference voltage examples.
316
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 5: Analog Comparator Status 0 (ACSTAT0), offset 0x20
This register specifies the current output value of that comparator.
Analog Comparator Status 0 (ACSTAT0)
Offset 0x020
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
OVAL
reserved
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
Bit/Field
Name
Type
Reset
Description
31:2
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
1
OVAL
RO
0
The OVAL bit specifies the current output value of the
comparator.
0
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
May 4, 2007
317
Preliminary
Analog Comparator
Register 6: Analog Comparator Control 0 (ACCTL0), offset 0x24
This register configures that comparator’s input and output.
Analog Comparator Control 0 (ACCTL0)
Offset 0x024
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
CINV
reserved
R/W
RO
0
RO
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
TOEN
RO
0
R/W
0
ASRCP
RO
R/W
0
TSEN
reserved TSLVAL
RO
R/W
0
RO
0
R/W
RO
0
RO
R/W
0
ISEN
ISLVAL
RO
R/W
0
R/W
RO
0
RO
R/W
0
RO
R/W
0
Bit/Field
Name
Type
Reset
Description
31:12
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
11
TOEN
R/W
0
The TOEN bit enables the ADC event transmission to the
ADC. If 0, the event is suppressed and not sent to the ADC. If
1, the event is transmitted to the ADC.
10:9
ASRCP
R/W
0
The ASRCP field specifies the source of input voltage to the
VIN+ terminal of the comparator. The encodings for this field
are as follows:
ASRCP
Function
00
Pin value
01
Pin value of C0+
10
Internal voltage reference
11
Reserved
8
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
7
TSLVAL
R/W
0
The TSLVAL bit specifies the sense value of the input that
generates an ADC event if in Level Sense mode. If 0, an ADC
event is generated if the comparator output is Low. Otherwise,
an ADC event is generated if the comparator output is High.
6:5
TSEN
R/W
0
The TSEN field specifies the sense of the comparator output
that generates an ADC event. The sense conditioning is as
follows:
TSEN
318
Function
00
Level sense, see TSLVAL
01
Falling edge
10
Rising edge
11
Either edge
May 4, 2007
Preliminary
LM3S818 Data Sheet
Bit/Field
Name
Type
Reset
Description
4
ISLVAL
R/W
0
The ISLVAL bit specifies the sense value of the input that
generates an interrupt if in Level Sense mode. If 0, an
interrupt is generated if the comparator output is Low.
Otherwise, an interrupt is generated if the comparator output
is High.
3:2
ISEN
R/W
0
The ISEN field specifies the sense of the comparator output
that generates an interrupt. The sense conditioning is as
follows:
ISEN
Function
00
Level sense, see ISLVAL
01
Falling edge
10
Rising edge
11
Either edge
1
CINV
R/W
0
The CINV bit conditionally inverts the output of the
comparator. If 0, the output of the comparator is unchanged. If
1, the output of the comparator is inverted prior to being
processed by hardware.
0
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
May 4, 2007
319
Preliminary
Pulse Width Modulator (PWM)
15
Pulse Width Modulator (PWM)
Pulse width modulation (PWM) is a powerful technique for digitally encoding analog signal levels.
High-resolution counters are used to generate a square wave, and the duty cycle of the square
wave is modulated to encode an analog signal. Typical applications include switching power
supplies and motor control.
The LM3S818 PWM module consists of PWM generator block and a control block. PWM
generator block contains one timer (16-bit down or up/down counter), two comparators, a PWM
signal generator, a dead-band generator, and an interrupt selector. The control block determines
the polarity of the PWM signals, and which signals are passed through to the pins.
PWM generator block produces two PWM signals that can either be independent signals (other
than being based on the same timer and therefore having the same frequency) or a single pair of
complementary signals with dead-band delays inserted. The output of the PWM generation block
managed by the output control block before being passed to the device pins.
The LM3S818 PWM module provides a great deal of flexibility. It can generate simple PWM
signals, such as those required by a simple charge pump. It can also generate paired PWM
signals with dead-band delays, such as those required by a half-H bridge driver.
15.1
Block Diagram
Figure 15-1 provides a block diagram of a Stellaris PWM module.
Figure 15-1. PWM Module Block Diagram
15.2
Functional Description
15.2.1
PWM Timer
The timer runs in one of two modes: Count-Down mode or Count-Up/Down mode. In Count-Down
mode, the timer counts from the load value to zero, goes back to the load value, and continues
counting down. In Count-Up/Down mode, the timer counts from zero up to the load value, back
down to zero, back up to the load value, and so on. Generally, Count-Down mode is used for
generating left- or right-aligned PWM signals, while the Count-Up/Down mode is used for
generating center-aligned PWM signals.
The timers output three signals that are used in the PWM generation process: the direction signal
(this is always Low in Count-Down mode, but alternates between Low and High in Count-Up/Down
mode), a single-clock-cycle-width High pulse when the counter is zero, and a
single-clock-cycle-width High pulse when the counter is equal to the load value. Note that in
Count-Down mode, the zero pulse is immediately followed by the load pulse.
15.2.2
PWM Comparators
There are two comparators in PWM generator that monitor the value of the counter; when either
match the counter, they output a single-clock-cycle-width High pulse. When in Count-Up/Down
mode, these comparators match both when counting up and when counting down; they are
therefore qualified by the counter direction signal. These qualified pulses are used in the PWM
generation process. If either comparator match value is greater than the counter load value, then
that comparator never outputs a High pulse.
Figure 15-2 shows the behavior of the counter and the relationship of these pulses when the
counter is in Count-Down mode. Figure 15-3 shows the behavior of the counter and the
relationship of these pulses when the counter is in Count-Up/Down mode.
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May 4, 2007
Preliminary
LM3S818 Data Sheet
Figure 15-2. PWM Count-Down Mode
Load
CompA
CompB
Zero
Load
Zero
A
B
Dir
BDown
ADown
Figure 15-3. PWM Count-Up/Down Mode
Load
CompA
CompB
Zero
Load
Zero
A
B
Dir
BUp
AUp
15.2.3
BDown
ADown
PWM Signal Generator
The PWM generator takes these pulses (qualified by the direction signal), and generates two
PWM signals. In Count-Down mode, there are four events that can affect the PWM signal: zero,
load, match A down, and match B down. In Count-Up/Down mode, there are six events that can
affect the PWM signal: zero, load, match A down, match A up, match B down, and match B up.
The match A or match B events are ignored when they coincide with the zero or load events. If the
match A and match B events coincide, the first signal, PWMA, is generated based only on the match
A event, and the second signal, PWMB, is generated based only on the match B event.
For each event, the effect on each output PWM signal is programmable: it can be left alone
(ignoring the event), it can be toggled, it can be driven Low, or it can be driven High. These actions
can be used to generate a pair of PWM signals of various positions and duty cycles, which do or
do not overlap. Figure 15-4 shows the use of Count-Up/Down mode to generate a pair of
center-aligned, overlapped PWM signals that have different duty cycles.
May 4, 2007
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Preliminary
Pulse Width Modulator (PWM)
Figure 15-4. PWM Generation Example In Count-Up/Down Mode
Load
CompA
CompB
Zero
PWMA
PWMB
In this example, the first generator is set to drive High on match A up, drive Low on match A down,
and ignore the other four events. The second generator is set to drive High on match B up, drive
Low on match B down, and ignore the other four events. Changing the value of comparator A
changes the duty cycle of the PWMA signal, and changing the value of comparator B changes the
duty cycle of the PWMB signal.
15.2.4
Dead-Band Generator
The two PWM signals produced by the PWM generator are passed to the dead-band generator. If
disabled, the PWM signals simply pass through unmodified. If enabled, the second PWM signal is
lost and two PWM signals are generated based on the first PWM signal. The first output PWM
signal is the input signal with the rising edge delayed by a programmable amount. The second
output PWM signal is the inversion of the input signal with a programmable delay added between
the falling edge of the input signal and the rising edge of this new signal.
This is therefore a pair of active High signals where one is always High, except for a
programmable amount of time at transitions where both are Low. These signals are therefore
suitable for driving a half-H bridge, with the dead-band delays preventing shoot-through current
from damaging the power electronics. Figure 15-5 shows the effect of the dead-band generator on
an input PWM signal.
Figure 15-5. PWM Dead-Band Generator
Input
PWMA
PWMB
Rising Edge
Delay
15.2.5
Falling Edge
Delay
Interrupt Selector
The PWM generator also takes the same four (or six) counter events and uses them to generate
an interrupt. Any of these events or a set of these events can be selected as a source for an
interrupt; when any of the selected events occur, an interrupt is generated. The selection of events
allows the interrupt to occur at a specific position within the PWM signal. Note that interrupts are
based on the raw events; delays in the PWM signal edges caused by the dead-band generator are
not taken into account.
15.2.6
Synchronization Methods
There is a global reset capability that can synchronously reset any or all of the counters in the
PWM generator.
322
May 4, 2007
Preliminary
LM3S818 Data Sheet
The counter load values and comparator match values of the PWM generator can be updated in
two ways. The first is immediate update mode, where a new value is used as soon as the counter
reaches zero. By waiting for the counter to reach zero, a guaranteed behavior is defined, and
overly short or overly long output PWM pulses are prevented.
The other update method is synchronous, where the new value is not used until a global
synchronized update signal is asserted, at which point the new value is used as soon as the
counter reaches zero. This second mode allows multiple items to be updated simultaneously
without odd effects during the update; everything runs from the old values until a point at which
they all run from the new values.
15.2.7
Fault Conditions
There are two external conditions that affect the PWM block; the signal input on the Fault pin and
the stalling of the controller by a debugger. There are two mechanisms available to handle such
conditions: the output signals can be forced into an inactive state and/or the PWM timers can be
stopped.
Each output signal has a fault bit. If set, a fault input signal causes the corresponding output signal
to go into the inactive state. If the inactive state is a safe condition for the signal to be in for an
extended period of time, this keeps the output signal from driving the outside world in a dangerous
manner during the fault condition. A fault condition can also generate a controller interrupt.
Each PWM generator can also be configured to stop counting during a stall condition. The user
can select for the counters to run until they reach zero then stop, or to continue counting and
reloading. A stall condition does not generate a controller interrupt.
15.2.8
Output Control Block
With PWM generator block producing two raw PWM signals, the output control block takes care of
the final conditioning of the PWM signals before they go to the pins. Via a single register, the set of
PWM signals that are actually enabled to the pins can be modified; this can be used, for example,
to perform commutation of a brushless DC motor with a single register write (and without
modifying the individual PWM generators, which are modified by the feedback control loop).
Similarly, fault control can disable any of the PWM signals as well. A final inversion can be applied
to any of the PWM signals, making them active Low instead of the default active High.
15.3
Initialization and Configuration
The following example shows how to initialize the PWM Generator 0 with a 25-KHz frequency, and
with a 25% duty cycle on the PWM0 pin and a 75% duty cycle on the PWM1 pin. This example
assumes the system clock is 20 MHz.
1. Enable the PWM clock by writing a value of 0x00100000 to the RCGC0 register in the System
Control module.
2. In the GPIO module, enable the appropriate pins for their alternate function using the
GPIOAFSEL register.
3. Configure the Run-Mode Clock Configuration (RCC) register in the System Control module
to use the PWM divide (USEPWMDIV) and set the divider (PWMDIV) to divide by 2 (000).
4. Configure the PWM generator for countdown mode with immediate updates to the
parameters.
– Write the PWM0CTL register with a value of 0x00000000.
– Write the PWM0GENA register with a value of 0x0000008C.
– Write the PWM0GENB register with a value of 0x0000080C.
May 4, 2007
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Preliminary
Pulse Width Modulator (PWM)
5. Set the period. For a 25-KHz frequency, the period = 1/25,000, or 40 microseconds. The PWM
clock source is 10 MHz; the system clock divided by 2. This translates to 400 clock ticks per
period. Use this value to set the PWM0LOAD register. In Count-Down mode, set the LOAD
field in the PWM0LOAD register to the requested period minus one.
– Write the PWM0LOAD register with a value of 0x0000018F.
6. Set the pulse width of the PWM0 pin for a 25% duty cycle.
– Write the PWM0CMPA register with a value of 0x0000012B.
7. Set the pulse width of the PWM1 pin for a 75% duty cycle.
– Write the PWM0CMPB register with a value of 0x00000063.
8. Start the timers in PWM generator 0.
– Write the PWM0CTL register with a value of 0x00000001.
9. Enable PWM outputs.
– Write the PWMENABLE register with a value of 0x00000003.
15.4
Register Map
Table 15-2 lists the PWM registers. The offset listed is a hexadecimal increment to the register’s
address, relative to the PWM base address of 0x40028000.
Table 15-1.
Offset
PWM Register Map (Sheet 1 of 2)
Name
Reset
Type
Description
See
page
PWM Module Control
0x000
PWMCTL
0x00000000
R/W
Master control of the PWM module
326
0x004
PWMSYNC
0x00000000
R/W
Counter synchronization for the PWM generators
327
0x008
PWMENABLE
0x00000000
R/W
Master enable for the PWM output pins
328
0x00C
PWMINVERT
0x00000000
R/W
Inversion control for the PWM output pins
329
0x010
PWMFAULT
0x00000000
R/W
Fault handling for the PWM output pins
330
0x014
PWMINTEN
0x00000000
R/W
Interrupt enable
331
0x018
PWMRIS
0x00000000
RO
Raw interrupt status
332
0x01C
PWMISC
0x00000000
R/W1C
Interrupt status and clear
333
0x020
PWMSTATUS
0x00000000
RO
Value of the Fault input signal
334
PWM Generator 0
0x040
PWM0CTL
0x00000000
R/W
Master control of the PWM0 generator block
335
0x044
PWM0INTEN
0x00000000
R/W
Interrupt enable
336
0x048
PWM0RIS
0x00000000
RO
Raw interrupt status
337
0x04C
PWM0ISC
0x00000000
R/W1C
Interrupt status and clear
338
0x050
PWM0LOAD
0x00000000
R/W
Load value for the counter
339
324
May 4, 2007
Preliminary
LM3S818 Data Sheet
Table 15-1.
PWM Register Map (Sheet 2 of 2)
Offset
Name
0x054
Type
PWM0COUNT
0x00000000
RO
Current counter value
339
0x058
PWM0CMPA
0x00000000
R/W
Comparator A value
341
0x05C
PWM0CMPB
0x00000000
R/W
Comparator B value
342
0x060
PWM0GENA
0x00000000
R/W
Controls PWM generator A
343
0x064
PWM0GENB
0x00000000
R/W
Controls PWM generator B
345
0x068
PWM0DBCTL
0x00000000
R/W
Control the dead-band generator
346
0x06C
PWM0DBRISE
0x00000000
R/W
Dead-band rising-edge delay count
347
0x070
PWM0DBFALL
0x00000000
R/W
Dead-band falling-edge delay count
348
15.5
Description
See
page
Reset
Register Descriptions
The remainder of this section lists and describes the PWM registers, in numerical order by address
offset.
May 4, 2007
325
Preliminary
Pulse Width Modulator (PWM)
Register 1: PWM Master Control (PWMCTL), offset 0x000
This register provides master control over the PWM generation block.
Bit/Field
Name
Type
Reset
Description
31:
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
0
GlobalSync0
R/W
0
Setting this bit causes any queued update to a load or
comparator register in PWM generator 0 to be applied the
next time the corresponding counter becomes zero. This bit
automatically clears when the updates have completed; it
cannot be cleared by software.
326
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 2: PWM Time Base Sync (PWMSYNC), offset 0x004
This register provides a method to perform synchronization of the counters in the PWM generation
blocks. Writing a bit in this register to 1 causes the specified counter to reset back to 0; writing
multiple bits resets multiple counters simultaneously. The bits auto-clear after the reset has
occurred; reading them back as zero indicates that the synchronization has completed.
Bit/Field
Name
Type
Reset
Description
31:
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
0
Sync0
R/W
0
Performs a reset of the PWM generator 0 counter.
May 4, 2007
327
Preliminary
Pulse Width Modulator (PWM)
Register 3: PWM Output Enable (PWMENABLE), offset 0x008
This register provides a master control of which generated PWM signals are output to device pins.
By disabling a PWM output, the generation process can continue (for example when the time
bases are synchronized) without driving PWM signals to the pins. When bits in this register are
set, the corresponding PWM signal is passed through to the output stage, which is controlled by
the PWMINVERT register. When bits are not set, the PWM signal is replaced by a zero value
which is also passed to the output stage.
Bit/Field
Name
Type
Reset
Description
31:
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
1
PWM1En
R/W
0
When set, allows the generated PWM1 signal to be passed
to the device pin.
0
PWM0En
R/W
0
When set, allows the generated PWM0 signal to be passed
to the device pin.
328
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 4: PWM Output Inversion (PWMINVERT), offset 0x00C
This register provides a master control of the polarity of the PWM signals on the device pins. The
PWM signals generated by the dead-band block are active High; they can optionally be made
active Low via this register. Disabled PWM channels are also passed through the output inverter (if
so configured) so that inactive channels maintain the correct polarity.
Bit/Field
Name
Type
Reset
Description
31:
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
1
PWM1Inv
R/W
0
When set, the generated PWM1 signal is inverted.
0
PWM0Inv
R/W
0
When set, the generated PWM0 signal is inverted.
May 4, 2007
329
Preliminary
Pulse Width Modulator (PWM)
Register 5: PWM Output Fault (PWMFAULT), offset 0x010
This register controls the behavior of the PWM outputs in the presence of fault conditions. Both the
fault input and debug events are considered fault conditions. On a fault condition, each PWM
signal can either be passed through unmodified or driven Low. For outputs that are configured for
pass-through, the debug event handling on the corresponding PWM generator also determines if
the PWM signal continues to be generated.
Fault condition control happens before the output inverter, so PWM signals driven Low on fault are
inverted if the channel is configured for inversion (therefore, the pin is driven High on a fault
condition).
Bit/Field
Name
Type
Reset
Description
31:
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
1
Fault1
R/W
0
When set, the PWM1 output signal is driven Low on a fault
condition.
0
Fault0
R/W
0
When set, the PWM0 output signal is driven Low on a fault
condition.
330
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 6: PWM Interrupt Enable (PWMINTEN), offset 0x014
This register controls the global interrupt generation capabilities of the PWM module. The events
that can cause an interrupt are the fault input and the individual interrupts from the PWM
generator.
Bit/Field
Name
Type
Reset
Description
31:17
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
16
IntFault
R/W
0
When 1, an interrupt occurs when the fault input is
asserted.
15:
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
0
IntPWM0
R/W
0
When 1, an interrupt occurs when the PWM generator 0
block asserts an interrupt.
May 4, 2007
331
Preliminary
Pulse Width Modulator (PWM)
Register 7: PWM Raw Interrupt Status (PWMRIS), offset 0x018
This register provides the current set of interrupt sources that are asserted, regardless of whether
they cause an interrupt to be asserted to the controller. The fault interrupt is latched on detection; it
must be cleared through the PWM Interrupt Status and Clear (PWMISC) register (see
page 333). The PWM generator interrupts simply reflect the status of the PWM generator; they are
cleared via the interrupt status register in the PWM generator block. Bits set to 1 indicate the
events that are active; a zero bit indicates that the event in question is not active.
332
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 8: PWM Interrupt Status and Clear (PWMISC), offset 0x01C
This register provides a summary of the interrupt status of the PWM generator block. A bit set to 1
indicates that the generator block is asserting an interrupt. The individual interrupt status registers
must be consulted to determine the reason for the interrupt, and used to clear the interrupt. For the
fault interrupt, a write of 1 to that bit position clears the latched interrupt status.
PWM Interrupt Status and Clear (PWMISC)
Offset 0x01C
31
30
29
28
27
26
25
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
24
23
22
21
20
19
18
17
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W1C
0
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
IntFault
IntPWM2 IntPWM1 IntPWM0
reserved
Type
Reset
RO
0
16
RO
0
RO
0
RO
0
Bit/Field
Name
Type
Reset
Description
31:17
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
16
IntFault
R/W1C
0
Indicates if the fault input is asserting an interrupt.
15:
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
0
IntPWM0
RO
0
Indicates if the PWM generator 0 block is asserting an
interrupt.
May 4, 2007
333
Preliminary
Pulse Width Modulator (PWM)
Register 9: PWM Status (PWMSTATUS), offset 0x020
This register provides the status of the Fault input signal.
PWM Status (PWMSTATUS)
Offset 0x020
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
Fault
RO
0
Bit/Field
Name
Type
Reset
Description
31:1
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
0
Fault
RO
0
When set to 1, indicates the fault input is asserted.
334
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 10: PWM0 Control (PWM0CTL), offset 0x040
The Register Update mode, Debug mode, Counting mode, and Block Enable mode are all
controlled via . The block produce the PWM signals, which can be either two independent PWM
signals (from the same counter), or a paired set of PWM signals with dead-band delays added.
PWMn Control (PWMnCTL)
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
Debug
Mode
Enable
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
CmpBUpd CmpAUpd LoadUpd
R/W
0
R/W
0
R/W
0
Bit/Field
Name
Type
Reset
Description
31:6
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
5
CmpBUpd
R/W
0
Same as CmpAUpd but for the comparator B register.
4
CmpAUpd
R/W
0
The Update mode for the comparator A register. If 0,
updates to the register are reflected to the comparator the
next time the counter is 0. If 1, updates to the register are
delayed until the next time the counter is 0 after a
synchronous update has been requested through the PWM
Master Control (PWMCTL) register (see page 326).
3
LoadUpd
R/W
0
The Update mode for the load register. If 0, updates to the
register are reflected to the counter the next time the
counter is 0. If 1, updates to the register are delayed until
the next time the counter is 0 after a synchronous update
has been requested through the PWM Master Control
(PWMCTL) register.
2
Debug
R/W
0
The behavior of the counter in Debug mode. If 0, the
counter stops running when it next reaches 0, and
continues running again when no longer in Debug mode. If
1, the counter always runs.
1
Mode
R/W
0
The mode for the counter. If 0, the counter counts down
from the load value to 0 and then wraps back to the load
value (Count-Down mode). If 1, the counter counts up from
0 to the load value, back down to 0, and then repeats
(Count-Up/Down mode).
0
Enable
R/W
0
Master enable for the PWM generation block. If 0, the entire
block is disabled and not clocked. If 1, the block is enabled
and produces PWM signals.
May 4, 2007
335
Preliminary
Pulse Width Modulator (PWM)
Register 11: PWM0 Interrupt Enable (PWM0INTEN), offset 0x044
These registers control the interrupt generation capabilities of the PWM generator. The events that
can cause an interrupt are:
„
The counter being equal to the load register
„
The counter being equal to zero
„
The counter being equal to the comparator A register while counting up
„
The counter being equal to the comparator A register while counting down
„
The counter being equal to the comparator B register while counting up
„
The counter being equal to the comparator B register while counting down
Any combination of these events can generate either an interrupt.
Bit/Field
Name
Type
Reset
Description
31:
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
5
IntCmpBD
R/W
0
When 1, an interrupt occurs when the counter matches the
comparator B value and the counter is counting down.
4
IntCmpBU
R/W
0
When 1, an interrupt occurs when the counter matches the
comparator B value and the counter is counting up.
3
IntCmpAD
R/W
0
When 1, an interrupt occurs when the counter matches the
comparator A value and the counter is counting down.
2
IntCmpAU
R/W
0
When 1, an interrupt occurs when the counter matches the
comparator A value and the counter is counting up.
1
IntCntLoad
R/W
0
When 1, an interrupt occurs when the counter matches the
PWMnLOAD register.
0
IntCntZero
R/W
0
When 1, an interrupt occurs when the counter is 0.
336
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 12: PWM0 Raw Interrupt Status (PWM0RIS), offset 0x048
provide the current set of interrupt sources that are asserted, regardless of whether they cause an
interrupt to be asserted to the controller. Bits set to 1 indicate the latched events that have
occurred; a 0 bit indicates that the event in question has not occurred.
PWMn Raw Interrupt Status (PWMnRIS)
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
IntCmpBD IntCmpBU IntCmpAD IntCmpAU IntCntLoad IntCntZero
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
Bit/Field
Name
Type
Reset
Description
31:6
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
5
IntCmpBD
RO
0
Indicates that the counter has matched the comparator B
value while counting down.
4
IntCmpBU
RO
0
Indicates that the counter has matched the comparator B
value while counting up.
3
IntCmpAD
RO
0
Indicates that the counter has matched the comparator A
value while counting down.
2
IntCmpAU
RO
0
Indicates that the counter has matched the comparator A
value while counting up.
1
IntCntLoad
RO
0
Indicates that the counter has matched the PWMnLOAD
register.
0
IntCntZero
RO
0
Indicates that the counter has matched 0.
May 4, 2007
337
Preliminary
Pulse Width Modulator (PWM)
Register 13: PWM0 Interrupt Status and Clear (PWM0ISC), offset 0x04C
provide the current set of interrupt sources that are asserted to the controller. Bits set to 1 indicate
the latched events that have occurred; a 0 bit indicates that the event in question has not occurred.
These are R/W1C registers; writing a 1 to a bit position clears the corresponding interrupt reason.
PWMn Interrupt Status (PWMnISC)
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
IntCmpBD IntCmpBU IntCmpAD IntCmpAU IntCntLoad IntCntZero
R/W1C
0
R/W1C
0
R/W1C
0
R/W1C
0
R/W1C
0
R/W1C
0
Bit/Field
Name
Type
Reset
Description
31:6
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
5
IntCmpBD
R/W1C
0
Indicates that the counter has matched the comparator B
value while counting down.
4
IntCmpBU
R/W1C
0
Indicates that the counter has matched the comparator B
value while counting up.
3
IntCmpAD
R/W1C
0
Indicates that the counter has matched the comparator A
value while counting down.
2
IntCmpAU
R/W1C
0
Indicates that the counter has matched the comparator A
value while counting up.
1
IntCntLoad
R/W1C
0
Indicates that the counter has matched the PWMnLOAD
register.
0
IntCntZero
R/W1C
0
Indicates that the counter has matched 0.
338
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 14: PWM0 Load (PWM0LOAD), offset 0x050
contain the load value for the PWM counter. Based on the counter mode, either this value is
loaded into the counter after it reaches zero, or it is the limit of up-counting after which the counter
decrements back to zero. If the Load Value Update mode is immediate, this value is used the next
time the counter reaches zero; if the mode is synchronous, it is used the next time the counter
reaches zero after a synchronous update has been requested through the PWM Master Control
(PWMCTL) register (see page 326). If this register is re-written before the actual update occurs,
the previous value is never used and is lost.
PWMn Load (PWMnLOAD)
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
Load
Type
Reset
Bit/Field
Name
Type
Reset
Description
31:16
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
15:0
Load
R/W
0
The counter load value.
May 4, 2007
339
Preliminary
Pulse Width Modulator (PWM)
Register 15: PWM0 Counter (PWM0COUNT), offset 0x054
contain the current value of the PWM counter. When this value matches the load register, a pulse
is output; this can drive the generation of a PWM signal (via the PWMnGENA/PWMnGENB
registers, see page 343 and 345) or drive an interrupt (via the PWMnINTEN register, see
page 336). A pulse with the same capabilities is generated when this value is zero.
PWMn Counter (PWMnCOUNT)
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
Count
Type
Reset
Bit/Field
Name
Type
Reset
Description
31:16
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
15:0
Count
RO
0
The current value of the counter.
340
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 16: PWM0 Compare A (PWM0CMPA), offset 0x058
contain a value to be compared against the counter. When this value matches the counter, a
pulse is output; this can drive the generation of a PWM signal (via the PWMnGENA/PWMnGENB
registers) or drive an interrupt (via the PWMnINTEN register). If the value of this register is greater
than the PWMnLOAD register (see page 339), then no pulse is ever output.
For comparator A, if the update mode is immediate (based on the CmpAUpd bit in the PWMnCTL
register), then this 16-bit CompA value is used the next time the counter reaches zero. If the update
mode is synchronous, it is used the next time the counter reaches zero after a synchronous
update has been requested through the PWM Master Control (PWMCTL) register (see
page 326). If this register is rewritten before the actual update occurs, the previous value is never
used and is lost.
PWMn Compare A (PWMnCMPA)
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
CompA
Type
Reset
Bit/Field
Name
Type
Reset
Description
31:16
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
15:0
CompA
R/W
0
The value to be compared against the counter.
May 4, 2007
341
Preliminary
Pulse Width Modulator (PWM)
Register 17: PWM0 Compare B (PWM0CMPB), offset 0x05C
contain a value to be compared against the counter. When this value matches the counter, a
pulse is output; this can drive the generation of a PWM signal (via the PWMnGENA/PWMnGENB
registers) or drive an interrupt (via the PWMnINTEN register). If the value of this register is greater
than the PWMnLOAD register, then no pulse is ever output.
For comparator B, if the update mode is immediate (based on the CmpBUpd bit in the PWMnCTL
register), then this 16-bit CompB value is used the next time the counter reaches zero after a
synchronous update has been requested through the PWM Master Control (PWMCTL) register
(see page 326). If this register is rewritten before the actual update occurs, the previous value is
never used and is lost.
PWMn Compare B (PWMnCMPB)
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
CompB
Type
Reset
Bit/Field
Name
Type
Reset
Description
31:16
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
15:0
CompB
R/W
0
The value to be compared against the counter.
342
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 18: PWM0 Generator A Control (PWM0GENA), offset 0x060
control the generation of the PWMNA signal based on the load and zero output pulses from the
counter, as well as the compare A and compare B pulses from the comparators. When the counter
is running in Count-Down mode, only four of these events occur; when running in Count-Up/Down
mode, all six occur. These events provide great flexibility in the positioning and duty cycle of the
PWM signal that is produced.
The PWM0GENA register controls generation of the PWM0A signal.
Each field can take on one of the values defined in Table 15-2, which defines the effect of the
event on the output signal.
If a zero or load event coincides with a compare A or compare B event, the zero or load action is
taken and the compare A or compare B action is ignored. If a compare A event coincides with a
compare B event, the compare A action is taken and the compare B action is ignored.
PWMn Generator A Control (PWMnGENA)
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
ActCmpBD
reserved
Type
Reset
R/W
0
ActCmpBU
R/W
0
ActCmpAD
R/W
0
R/W
0
R/W
0
ActCmpAU
R/W
0
R/W
0
ActLoad
R/W
0
ActZero
R/W
0
Bit/Field
Name
Type
Reset
Description
31:12
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
11:10
ActCmpBD
R/W
0
The action to be taken when the counter matches
comparator B while counting down.
9:8
ActCmpBU
R/W
0
The action to be taken when the counter matches
comparator B while counting up. Occurs only when the
Mode bit in the PWMnCTL register (see page 335) is set
to 1.
7:6
ActCmpAD
R/W
0
The action to be taken when the counter matches
comparator A while counting down.
5:4
ActCmpAU
R/W
0
The action to be taken when the counter matches
comparator A while counting up.Occurs only when the
Mode bit in the PWMnCTL register is set to 1.
3:2
ActLoad
R/W
0
The action to be taken when the counter matches the load
value.
1:0
ActZero
R/W
0
The action to be taken when the counter is zero.
May 4, 2007
343
Preliminary
Pulse Width Modulator (PWM)
Table 15-2.
PWM Generator Action Encodings
Value
Description
00
Do nothing.
01
Invert the output signal.
10
Set the output signal to 0.
11
Set the output signal to 1.
344
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 19: PWM0 Generator B Control (PWM0GENB), offset 0x064
control the generation of the PWMNB signal based on the load and zero output pulses from the
counter, as well as the compare A and compare B pulses from the comparators. When the counter
is running in Down mode, only four of these events occur; when running in Up/Down mode, all six
occur. These events provide great flexibility in the positioning and duty cycle of the PWM signal
that is produced.
The PWM0GENB register controls generation of the PWM0B signal.
Each field can take on one of the values defined in Table 15-2 on page 344, which defines the
effect of the event on the output signal.
If a zero or load event coincides with a compare A or compare B event, the zero or load action is
taken and the compare A or compare B action is ignored. If a compare A event coincides with a
compare B event, the compare B action is taken and the compare A action is ignored.
PWMn Generator B Control (PWMnGENB)
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
ActCmpBD
reserved
Type
Reset
R/W
0
ActCmpBU
R/W
0
ActCmpAD
R/W
0
R/W
0
R/W
0
ActCmpAU
R/W
0
R/W
0
ActLoad
R/W
0
ActZero
R/W
0
Bit/Field
Name
Type
Reset
Description
31:12
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
11:10
ActCmpBD
R/W
0
The action to be taken when the counter matches
comparator B while counting down.
9:8
ActCmpBU
R/W
0
The action to be taken when the counter matches
comparator B while counting up. Occurs only when the
Mode bit in the PWMnCTL register (see page 335) is set
to 1.
7:6
ActCmpAD
R/W
0
The action to be taken when the counter matches
comparator A while counting down.
5:4
ActCmpAU
R/W
0
The action to be taken when the counter matches
comparator A while counting up. Occurs only when the
Mode bit in the PWMnCTL register is set to 1.
3:2
ActLoad
R/W
0
The action to be taken when the counter matches the load
value.
1:0
ActZero
R/W
0
The action to be taken when the counter is 0.
May 4, 2007
345
Preliminary
Pulse Width Modulator (PWM)
Register 20: PWM0 Dead-Band Control (PWM0DBCTL), offset 0x068
The PWM0DBCTL register controls the dead-band generator, which produces the PWM0 and PWM1
signals based on the PWM0A and PWM0B signals. When disabled, the PWM0A signal passes through
to the PWM0 signal and the PWM0B signal passes through to the PWM1 signal. When enabled, the
PWM0B signal is ignored; the PWM0 signal is generated by delaying the rising edge(s) of the PWM0A
signal by the value in the PWM0DBRISE register (see page 347), and the PWM1 signal is
generated by delaying the falling edge(s) of the PWM0A signal by the value in the PWM0DBFALL
register (see page 348).
PWMn Dead-Band Control (PWMnDBCTL)
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
Enable
R/W
0
Bit/Field
Name
Type
Reset
Description
31:1
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
0
Enable
R/W
0
When set, the dead-band generator inserts dead bands into
the output signals; when clear, it simply passes the PWM
signals through.
346
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 21: PWM0 Dead-Band Rising-Edge Delay (PWM0DBRISE), offset 0x06C
The PWM0DBRISE register contains the number of clock ticks to delay the rising edge of the
PWM0A signal when generating the PWM0 signal. If the dead-band generator is disabled through the
PWMnDBCTL register, the PWM0DBRISE register is ignored. If the value of this register is larger
than the width of a High pulse on the input PWM signal, the rising-edge delay consumes the entire
High time of the signal, resulting in no High time on the output. Care must be taken to ensure that
the input High time always exceeds the rising-edge delay.
PWMn Dead-Band Rising-Edge Delay (PWMnDBRISE)
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
RiseDelay
R/W
0
Bit/Field
Name
Type
Reset
Description
31:12
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
11:0
RiseDelay
R/W
0
The number of clock ticks to delay the rising edge.
May 4, 2007
347
Preliminary
Pulse Width Modulator (PWM)
Register 22: PWM0 Dead-Band Falling-Edge-Delay (PWM0DBFALL), offset 0x070
The PWM0DBFALL register contains the number of clock ticks to delay the falling edge of the
PWM0A signal when generating the PWM1 signal. If the dead-band generator is disabled, this
register is ignored. If the value of this register is larger than the width of a Low pulse on the input
PWM signal, the falling-edge delay consumes the entire Low time of the signal, resulting in no Low
time on the output. Care must be taken to ensure that the input Low time always exceeds the
falling-edge delay.
PWMn Dead-Band Falling-Edge-Delay Register (PWMnDBFALL)
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
Bit/Field
Name
31:12
reserved
11:0
FallDelay
FallDelay
Type
R/W
0
Reset
Description
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
R/W
0
The number of clock ticks to delay the falling edge.
348
May 4, 2007
Preliminary
LM3S818 Data Sheet
16
Quadrature Encoder Interface (QEI)
A quadrature encoder, also known as a 2-channel incremental encoder, converts linear
displacement into a pulse signal. By monitoring both the number of pulses and the relative phase
of the two signals, you can track the position, direction of rotation, and speed. In addition, a third
channel, or index signal, can be used to reset the position counter.
The Stellaris quadrature encoder interface (QEI) module interprets the code produced by a
quadrature encoder wheel to integrate position over time and determine direction of rotation. In
addition, it can capture a running estimate of the velocity of the encoder wheel.
The Stellaris quadrature encoder has the following features:
„
Position integrator that tracks the encoder position
„
Velocity capture using built-in timer
„
Interrupt generation on:
– Index pulse
– Velocity-timer expiration
– Direction change
– Quadrature error detection
16.1
Block Diagram
Figure 16-1 provides a block diagram of the QEI module.
Figure 16-1. QEI Block Diagram
QEILOAD
Control & Status
Velocity Timer
QEITIME
QEICTL
QEISTAT
Velocity Accumulator
Velocity
Predivider
clk
PhA
PhB
QEICOUNT
QEISPEED
QEIMAXPOS
Quadrature
Encoder dir
Position Integrator
QEIPOS
IDX
QEIINTEN
Interrupt Control
Interrupt
QEIRIS
QEIISC
16.2
Functional Description
The QEI module interprets the two-bit gray code produced by a quadrature encoder wheel to
integrate position over time and determine direction of rotation. In addition, it can capture a running
estimate of the velocity of the encoder wheel.
The position integrator and velocity capture can be independently enabled, though the position
integrator must be enabled before the velocity capture can be enabled. The two phase signals,
PHA and PHB, can be swapped in software before being interpreted by the QEI module to change
May 4, 2007
349
Preliminary
Quadrature Encoder Interface (QEI)
the meaning of forward and backward, and to correct for miswiring of the system. Alternatively, the
phase signals can be interpreted as a clock and direction signal as output by some encoders.
The QEI module supports two modes of signal operation: quadrature phase mode and clock/
direction mode. In quadrature phase mode, the encoder produces two clocks that are 90 degrees
out of phase; the edge relationship is used to determine the direction of rotation. In clock/direction
mode, the encoder produces a clock signal to indicate steps and a direction signal to indicate the
direction of rotation. This mode is determined by the SigMode bit of the QEI Control (QEICTL)
register (see page 353).
When the QEI module is set to use the quadrature phase mode (SigMode bit equals zero), the
capture mode for the position integrator can be set to update the position counter on every edge of
the PHA signal or to update on every edge of both PHA and PHB. Updating the position counter on
every PHA and PHB provides more positional resolution at the cost of less range in the positional
counter.
When edges on PHA lead edges on PHB, the position counter is incremented. When edges on PHB
lead edges on PHA, the position counter is decremented. When a rising and falling edge pair is
seen on one of the phases without any edges on the other, the direction of rotation has changed.
The positional counter is automatically reset on one of two conditions: sensing the index pulse or
reaching the maximum position value. Which mode is determined by the ResMode bit of the QEI
Control (QEICTL) register.
When ResMode is 0, the positional counter is reset when the index pulse is sensed. This limits the
positional counter to the values [0:N-1], where N is the number of phase edges in a full revolution
of the encoder wheel. The QEIMAXPOS register must be programmed with N-1 so that the
reverse direction from position 0 can move the position counter to N-1. In this mode, the position
register contains the absolute position of the encoder relative to the index (or home) position once
an index pulse has been seen.
When ResMode is 1, the positional counter is constrained to the range [0:M], where M is the
programmable maximum value. The index pulse is ignored by the positional counter in this mode.
The velocity capture has a configurable timer and a count register. It counts the number of phase
edges (using the same configuration as for the position integrator) in a given time period. The
edge count from the previous time period is available to the controller via the QEISPEED register,
while the edge count for the current time period is being accumulated in the QEICOUNT register.
As soon as the current time period is complete, the total number of edges counted in that time
period is made available in the QEISPEED register (losing the previous value), the QEICOUNT is
reset to 0, and counting commences on a new time period. The number of edges counted in a
given time period is directly proportional to the velocity of the encoder.
Figure 16-2 shows how the Stellaris quadrature encoder converts the phase input signals into
clock pulses, the direction signal, and how the velocity predivider operates (in Divide by 4 mode).
Figure 16-2. Quadrature Encoder and Velocity Predivider Operation
350
May 4, 2007
Preliminary
LM3S818 Data Sheet
The period of the timer is configurable by specifying the load value for the timer in the QEILOAD
register. When the timer reaches zero, an interrupt can be triggered, and the hardware reloads the
timer with the QEILOAD value and continues to count down. At lower encoder speeds, a longer
timer period is needed to be able to capture enough edges to have a meaningful result. At higher
encoder speeds, both a shorter timer period and/or the velocity predivider can be used.
The following equation converts the velocity counter value into an rpm value:
rpm = (clock * (2 ^ VelDiv) * Speed * 60) ÷ (Load * ppr * edges)
where:
clock is the controller clock rate
ppr is the number of pulses per revolution of the physical encoder
edges is 2 or 4, based on the capture mode set in the QEICTL register (2 for CapMode set to 0
and 4 for CapMode set to 1)
For example, consider a motor running at 600 rpm. A 2048 pulse per revolution quadrature
encoder is attached to the motor, producing 8192 phase edges per revolution. With a velocity
predivider of ÷1 (VelDiv set to 0)and clocking on both PHA and PHB edges, this results in 81,920
pulses per second (the motor turns 10 times per second). If the timer were clocked at 10,000 Hz,
and the load value was 2,500 (¼ of a second), it would count 20,480 pulses per update. Using the
above equation:
rpm = (10000 * 1 * 20480 * 60) ÷ (2500 * 2048 * 4) = 600 rpm
Now, consider that the motor is sped up to 3000 rpm. This results in 409,600 pulses per second, or
102,400 every ¼ of a second. Again, the above equation gives:
rpm = (10000 * 1 * 102400 * 60) ÷ (2500 * 2048 * 4) = 3000 rpm
Care must be taken when evaluating this equation since intermediate values may exceed the
capacity of a 32-bit integer. In the above examples, the clock is 10,000 and the divider is 2,500;
both could be predivided by 100 (at compile time if they are constants) and therefore be 100 and
25. In fact, if they were compile-time constants, they could also be reduced to a simple multiply by
4, cancelled by the ÷4 for the edge-count factor.
Important: Reducing constant factors at compile time is the best way to control the intermediate
values of this equation, as well as reducing the processing requirement of computing
this equation.
The division can be avoided by selecting a timer load value such that the divisor is a power of 2; a
simple shift can therefore be done in place of the division. For encoders with a power of 2 pulses
per revolution, this is a simple matter of selecting a power of 2 load value. For other encoders, a
load value must be selected such that the product is very close to a power of two. For example, a
100 pulse per revolution encoder could use a load value of 82, resulting in 32,800 as the divisor,
which is 0.09% above 214; in this case a shift by 15 would be an adequate approximation of the
divide in most cases. If absolute accuracy were required, the controller’s divide instruction could
be used.
The QEI module can produce a controller interrupt on several events: phase error, direction
change, reception of the index pulse, and expiration of the velocity timer. Standard masking, raw
interrupt status, interrupt status, and interrupt clear capabilities are provided.
May 4, 2007
351
Preliminary
Quadrature Encoder Interface (QEI)
16.3
Initialization and Configuration
The following example shows how to configure the Quadrature Encoder module to read back an
absolute position:
1. Enable the QEI clock by writing a value of 0x00000100 to the RCGC1 register in the System
Control module.
2. In the GPIO module, enable the appropriate pins for their alternate function using the
GPIOAFSEL register.
3. Configure the quadrature encoder to capture edges on both signals and maintain an absolute
position by resetting on index pulses. Using a 1000-line encoder at four edges per line, there
are 4000 pulses per revolution; therefore, set the maximum position to 3999 (0xF9F) since the
count is zero-based.
– Write the QEICTL register with the value of 0x00000018.
– Write the QEIMAXPOS register with the value of 0x00000F9F.
4. Enable the quadrature encoder by setting bit 0 of the QEICTL register.
5. Delay for some time.
6. Read the encoder position by reading the QEIPOS register value.
16.4
Register Map
Table 16-1 lists the QEI registers. All addresses given are relative to the QEI base address of
0x4002C000.
Table 16-1.
QEI Register Map
Description
See
page
R/W
Configuration
353
0x00000000
RO
Status
355
QEIPOS
0x00000000
R/W
Current encoder position
356
0x00C
QEIMAXPOS
0x00000000
R/W
Maximum encoder position
357
0x010
QEILOAD
0x00000000
R/W
Load value for the velocity timer
358
0x014
QEITIME
0x00000000
RO
Current value of the velocity timer
359
0x018
QEICOUNT
0x00000000
RO
Current count of encoder pulses
360
0x01C
QEISPEED
0x00000000
RO
Velocity of the quadrature encoder
361
0x020
QEIINTEN
0x00000000
R/W
Interrupt enables
362
0x024
QEIRIS
0x00000000
RO
Raw interrupt status
363
0x028
QEIISC
0x00000000
R/W1C
Interrupt status and clear
364
Offset
Name
Reset
0x000
QEICTL
0x00000000
0x004
QEISTAT
0x008
16.5
Type
Register Descriptions
The remainder of this section lists and describes the QEI registers, in numerical order by address
offset.
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May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 1: QEI Control (QEICTL), offset 0x000
This register contains the configuration of the QEI module. Separate enables are provided for the
quadrature encoder and the velocity capture blocks; the quadrature encoder must be enabled in
order to capture the velocity, but the velocity does not need to be captured in applications that do
not need it. The phase signal interpretation, phase swap, Position Update mode, Position Reset
mode, and velocity predivider are all set via this register.
QEI Control (QEICTL)
Offset 0x000
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
STALLEN
INVI
INVB
INVA
R/W
0
R/W
0
R/W
0
R/W
0
Swap
Enable
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
RO
0
RO
0
VelDiv
R/W
0
R/W
0
VelEn
R/W
0
ResMode CapMode SigMode
R/W
0
R/W
0
R/W
0
R/W
0
Bit/Field
Name
Type
Reset
31:13
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
12
STALLEN
R/W
0
When set, the QEI stalls when the microcontroller asserts
Halt.
11
INVI
R/W
0
When set , the input Index Pulse is inverted.
10
INVB
R/W
0
When set, the PHB input is inverted.
9
INVA
R/W
0
When set, the PHA input is inverted.
8:6
VelDiv
R/W
0
A predivider of the input quadrature pulses before being
applied to the QEICOUNT accumulator. This field can be
set to the following values:
5
VelEn
R/W
0
Description
Binary Value
Predivider
000
÷1
001
÷2
010
÷4
011
÷8
100
÷16
101
÷32
110
÷64
111
÷128
When set, enables capture of the velocity of the quadrature
encoder.
May 4, 2007
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Preliminary
Quadrature Encoder Interface (QEI)
Bit/Field
Name
Type
Reset
Description
4
ResMode
R/W
0
The Reset mode for the position counter. When 0, the
position counter is reset when it reaches the maximum;
when 1, the position counter is reset when the index pulse
is captured.
3
CapMode
R/W
0
The Capture mode defines the phase edges that are
counted in the position. When 0, only the PHA edges are
counted; when one, the PHA and PHB edges are counted,
providing twice the positional resolution but half the range.
2
SigMode
R/W
0
When 1, the PHA and PHB signals are clock and direction;
when 0, they are quadrature phase signals.
1
Swap
R/W
0
Swaps the PHA and PHB signals.
0
Enable
R/W
0
Enables the quadrature encoder module.
354
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 2: QEI Status (QEISTAT), offset 0x004
This register provides status about the operation of the QEI module.
QEI Status (QEISTAT)
Offset 0x004
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
Direction
Error
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
Bit/Field
Name
Type
Reset
Description
31:2
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
1
Direction
RO
0
Indicates the direction the encoder is rotating.
0: Forward rotation
1: Reverse rotation
0
Error
RO
0
Indicates that an error was detected in the gray code
sequence (that is, both signals changing at the same time).
May 4, 2007
355
Preliminary
Quadrature Encoder Interface (QEI)
Register 3: QEI Position (QEIPOS), offset 0x008
This register contains the current value of the position integrator. Its value is updated by inputs on
the QEI phase inputs, and can be set to a specific value by writing to it.
QEI Position (QEIPOS)
Offset 0x008
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
Position
Type
Reset
Position
Type
Reset
Bit/Field
Name
Type
Reset
31:0
Position
R/W
0
Description
The current position integrator value.
356
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 4: QEI Maximum Position (QEIMAXPOS), offset 0x00C
This register contains the maximum value of the position integrator. When moving forward, the
position register resets to zero when it increments past this register. When moving backward, the
position register resets to this register when it decrements from zero.
QEI Maximum Position (QEIMAXPOS)
Offset 0x00C
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
MaxPos
Type
Reset
MaxPos
Type
Reset
Bit/Field
Name
Type
Reset
31:0
MaxPos
R/W
0
Description
The maximum position integrator value.
May 4, 2007
357
Preliminary
Quadrature Encoder Interface (QEI)
Register 5: QEI Timer Load (QEILOAD), offset 0x010
This register contains the load value for the velocity timer. Since this value is loaded into the timer
when the clock cycle after the timer is zero, this value should be one less than the number of
clocks in the desired period. So, for example, to have 2000 clocks per timer period, this register
should contain 1999.
QEI Timer Load (QEILOAD)
Offset 0x010
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
Load
Type
Reset
Load
Type
Reset
Bit/Field
Name
Type
Reset
31:0
Load
R/W
0
Description
The velocity timer load value.
358
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 6: QEI Timer (QEITIME), offset 0x014
This register contains the current value of the velocity timer. This counter does not increment when
VelEn in QEICTL is 0.
QEI Timer (QEITIME)
Offset 0x014
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
Time
Type
Reset
Time
Type
Reset
Bit/Field
Name
Type
Reset
31:0
Time
RO
0
Description
The current value of the velocity timer.
May 4, 2007
359
Preliminary
Quadrature Encoder Interface (QEI)
Register 7: QEI Velocity Counter (QEICOUNT), offset 0x018
This register contains the running count of velocity pulses for the current time period. Since this is
a running total, the time period to which it applies cannot be known with precision (that is, a read of
this register does not necessarily correspond to the time returned by the QEITIME register since
there is a small window of time between the two reads, during which time either value may have
changed). The QEISPEED register should be used to determine the actual encoder velocity; this
register is exposed for information purposes only. This counter does not increment when VelEn in
QEICTL is 0.
QEI Velocity Counter (QEICOUNT)
Offset 0x018
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
Count
Type
Reset
Count
Type
Reset
Bit/Field
Name
Type
Reset
31:0
Count
RO
0
Description
The running total of encoder pulses during this velocity
timer period.
360
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 8: QEI Velocity (QEISPEED), offset 0x01C
This register contains the most recently measured velocity of the quadrature encoder. This
corresponds to the number of velocity pulses counted in the previous velocity timer period. This
register does not update when VelEn in QEICTL is 0.
QEI Velocity (QEISPEED)
Offset 0x01C
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
Speed
Type
Reset
Speed
Type
Reset
Bit/Field
Name
Type
Reset
31:0
Speed
RO
0
Description
The measured speed of the quadrature encoder in pulses
per period.
May 4, 2007
361
Preliminary
Quadrature Encoder Interface (QEI)
Register 9: QEI Interrupt Enable (QEIINTEN), offset 0x020
This register contains enables for each of the QEI module’s interrupts. An interrupt is asserted to
the controller if its corresponding bit in this register is set to 1.
QEI Interrupt Enable (QEIINTEN)
Offset 0x020
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
IntError
IntDir
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
IntTimer IntIndex
R/W
0
R/W
0
Bit/Field
Name
Type
Reset
Description
31:4
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
3
IntError
R/W
0
When 1, an interrupt occurs when a phase error is
detected.
2
IntDir
R/W
0
When 1, an interrupt occurs when the direction changes.
1
IntTimer
R/W
0
When 1, an interrupt occurs when the velocity timer
expires.
0
IntIndex
R/W
0
When 1, an interrupt occurs when the index pulse is
detected.
362
May 4, 2007
Preliminary
LM3S818 Data Sheet
Register 10: QEI Raw Interrupt Status (QEIRIS), offset 0x024
This register provides the current set of interrupt sources that are asserted, regardless of whether
they cause an interrupt to be asserted to the controller (this is set through the QEIINTEN register).
Bits set to 1 indicate the latched events that have occurred; a zero bit indicates that the event in
question has not occurred.
QEI Raw Interrupt Status (QEIRIS)
Offset 0x024
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
IntError
IntDir
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
IntTimer IntIndex
RO
0
RO
0
Bit/Field
Name
Type
Reset
Description
31:4
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
3
IntError
RO
0
Indicates that a phase error was detected.
2
IntDir
RO
0
Indicates that the direction has changed.
1
IntTimer
RO
0
Indicates that the velocity timer has expired.
0
IntIndex
RO
0
Indicates that the index pulse has occurred.
May 4, 2007
363
Preliminary
Quadrature Encoder Interface (QEI)
Register 11: QEI Interrupt Status and Clear (QEIISC), offset 0x028
This register provides the current set of interrupt sources that are asserted to the controller. Bits
set to 1 indicate the latched events that have occurred; a zero bit indicates that the event in
question has not occurred. This is a R/W1C register; writing a 1 to a bit position clears the
corresponding interrupt reason.
QEI Interrupt Status and Clear (QEIISC)
Offset 0x028
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
IntError
IntDir
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W1C
0
R/W1C
0
reserved
Type
Reset
reserved
Type
Reset
IntTimer IntIndex
R/W1C
0
R/W1C
0
Bit/Field
Name
Type
Reset
Description
31:4
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
3
IntError
R/W1C
0
Indicates that a phase error was detected.
2
IntDir
R/W1C
0
Indicates that the direction has changed.
1
IntTimer
R/W1C
0
Indicates that the velocity timer has expired.
0
IntIndex
R/W1C
0
Indicates that the index pulse has occurred.
364
May 4, 2007
Preliminary
LM3S818 Data Sheet
17
Pin Diagram
Figure 17-1 shows the pin diagram and pin-to-signal-name mapping.
PB4/C0PB5/C0o
PB6/C0+
PB7/TRST
PC0/TCK/SWCLK
PC1/TMS/SWDIO
PC2/TDI
PC3/TDO/SWO
48
47
46
45
44
43
42
41
40
39
38
37
ADC4
ADC5
PD5/CCP2
PD4/CCP0
Figure 17-1. Pin Connection Diagram
36
35
34
33
32
31
30
29
28
27
26
25
PA4/SSIRx
PA5/SSITx
VDD
GND
13
14
15
16
17
18
19
20
21
22
23
24
1
2
3
4
5
6
7
8
9
10
11
12
PC5/CCP1
PC4/PhA
VDD
GND
PA0/U0Rx
PA1/U0Tx
PA2/SSIClk
PA3/SSIFss
ADC0
ADC1
ADC2
ADC3
RST
LDO
VDD
GND
OSC0
OSC1
PC7/CCP4
PC6/PhB
May 4, 2007
PE1/PWM5
PE0/PWM4
PB3/Fault
PB2/IDX
VDD
GND
PB1/PWM3
PB0/PWM2
PD3/U1Tx
PD2/U1Rx
PD1/PWM1
PD0/PWM0
LM3S818
365
Preliminary
Signal Tables
18
Signal Tables
The following tables list the signals available for each pin. Functionality is enabled by software with
the GPIOAFSEL register (see page 132).
Important: All multiplexed pins are GPIOs by default, with the exception of the five JTAG pins
(PB7 and PC[3:0]) which default to the JTAG functionality.
shows the pin-to-signal-name mapping, including functional characteristics of the signals. lists the
signals in alphabetical order by signal name. groups the signals by functionality, except for
GPIOs. lists the GPIO pins and their alternate functionality.
Table 18-1.
Pin
Number
Signals by Pin Number (Sheet 1 of 4)
Pin Name
Pin
Type
Buffer
Type
Description
1
ADC0
I
Analog
Analog-to-digital converter input 0.
2
ADC1
I
Analog
Analog-to-digital converter input 1.
3
ADC2
I
Analog
Analog-to-digital converter input 2.
4
ADC3
I
Analog
Analog-to-digital converter input 3.
5
RST
I
TTL
6
LDO
-
Power
The low drop-out regulator output voltage. This pin requires an
external capacitor between the pin and GND of 1 µF or greater.
7
VDD
-
Power
Positive supply for logic and I/O pins.
8
GND
-
Power
Ground reference for logic and I/O pins.
9
OSC0
I
Analog
Oscillator crystal input or an external clock reference input.
10
OSC1
O
Analog
Oscillator crystal output.
11
PC7
I/O
TTL
GPIO port C bit 7.
CCP4
I/O
TTL
Timer 2 capture input, compare output, or PWM output channel 4.
PC6
I/O
TTL
GPIO port C bit 6.
PhB
I
TTL
Quadrature encoder phase B input.
PC5
I/O
TTL
GPIO port C bit 5.
CCP1
I/O
TTL
Timer 0 capture input, compare output, or PWM output channel 1.
PC4
I/O
TTL
GPIO port C bit 4.
PhA
I
TTL
Quadrature encoder phase A input.
15
VDD
-
Power
Positive supply for logic and I/O pins.
16
GND
-
Power
Ground reference for logic and I/O pins.
17
PA0
I/O
TTL
GPIO port A bit 0.
I
TTL
UART0 receive data input.
12
13
14
U0Rx
System reset input.
366
May 4, 2007
Preliminary
LM3S818 Data Sheet
Table 18-1.
Pin
Number
Signals by Pin Number (Sheet 2 of 4)
Pin
Type
Buffer
Type
PA1
I/O
TTL
GPIO port A bit 1.
U0Tx
O
TTL
UART0 transmit data output.
PA2
I/O
TTL
GPIO port A bit 2.
SSIClk
I/O
TTL
SSI clock reference (input when in slave mode and output in
master mode).
PA3
I/O
TTL
GPIO port A bit 3.
SSIFss
I/O
TTL
SSI frame enable (input for an SSI slave device and output for an
SSI master device).
PA4
I/O
TTL
GPIO port A bit 4.
I
TTL
SSI receive data input.
PA5
I/O
TTL
GPIO port A bit 5.
SSITx
O
TTL
SSI transmit data output.
23
VDD
-
Power
Positive supply for logic and I/O pins.
24
GND
-
Power
Ground reference for logic and I/O pins.
25
PD0
I/O
TTL
GPIO port D bit 0.
PWM0
O
TTL
Pulse width modulator channel 0 output.
PD1
I/O
TTL
GPIO port D bit 1.
PWM1
O
TTL
Pulse width modulator channel 1 output.
PD2
I/O
TTL
GPIO port D bit 2.
U1Rx
I
TTL
UART1 receive data input.
PD3
I/O
TTL
GPIO port D bit 3.
U1Tx
O
TTL
UART1 transmit data output.
PB0
I/O
TTL
GPIO port B bit 0.
PWM2
O
TTL
Pulse width modulator channel 2 output.
PB1
I/O
TTL
GPIO port B bit 1.
PWM3
O
TTL
Pulse width modulator channel 3 output.
31
GND
-
Power
Ground reference for logic and I/O pins.
32
VDD
-
Power
Positive supply for logic and I/O pins.
33
PB2
I/O
TTL
GPIO port B bit 2.
IDX
I
TTL
Quadrature encoder index input.
18
19
20
21
Pin Name
SSIRx
22
26
27
28
29
30
Description
May 4, 2007
367
Preliminary
Signal Tables
Table 18-1.
Pin
Number
34
Signals by Pin Number (Sheet 3 of 4)
Pin
Type
Buffer
Type
I/O
TTL
GPIO port B bit 3.
I
TTL
Motion control 0 fault.
PE0
I/O
TTL
GPIO port E bit 0.
PWM4
O
TTL
Pulse width modulator channel 4 output.
PE1
I/O
TTL
GPIO port E bit 1.
PWM5
O
TTL
Pulse width modulator channel 5 output.
PC3
I/O
TTL
GPIO port C bit 3.
TDO
O
TTL
JTAG scan test data output.
SWO
O
TTL
Serial-wire output.
PC2
I/O
TTL
GPIO port C bit 2.
TDI
I
TTL
JTAG scan test data input.
PC1
I/O
TTL
GPIO port C bit 1.
TMS
I
TTL
JTAG scan test mode select input.
SWDIO
I/O
TTL
Serial-wire debug input/output.
PC0
I/O
TTL
GPIO port C bit 0.
TCK
I
TTL
JTAG scan test clock reference input.
SWCLK
I
TTL
Serial wire clock reference input.
I/O
TTL
GPIO port B bit 7.
I
TTL
JTAG scan test reset input.
PB6
I/O
TTL
GPIO port B bit 6.
C0+
I
Analog
PB5
I/O
TTL
GPIO port B bit 5.
C0o
O
TTL
Analog comparator 0 output.
PB4
I/O
TTL
GPIO port B bit 4.
C0–
I
Analog
PD4
I/O
TTL
GPIO port D bit 4.
CCP0
I/O
TTL
Timer 0 capture input, compare output, or PWM output channel 0.
PD5
I/O
TTL
GPIO port D bit 5.
CCP2
I/O
TTL
Timer 1 capture input, compare output, or PWM output channel 2.
Pin Name
PB3
FAULT
35
36
37
38
39
40
41
PB7
TRST
42
43
44
45
46
Description
Analog comparator 0 positive-reference input.
Analog comparator 0 negative-reference input.
368
May 4, 2007
Preliminary
LM3S818 Data Sheet
Table 18-1.
Signals by Pin Number (Sheet 4 of 4)
Pin
Number
Pin Name
Pin
Type
Buffer
Type
Description
47
ADC5
I
Analog
Analog-to-digital converter input 5.
48
ADC4
I
Analog
Analog-to-digital converter input 4.
Table 18-2.
Signals by Signal Name (Sheet 1 of 3)
Pin
Number
Pin
Type
Buffer
Type
ADC0
1
I
Analog
Analog-to-digital converter input 0.
ADC1
2
I
Analog
Analog-to-digital converter input 1.
ADC2
3
I
Analog
Analog-to-digital converter input 2.
ADC3
4
I
Analog
Analog-to-digital converter input 3.
ADC4
48
I
Analog
Analog-to-digital converter input 4.
ADC5
47
I
Analog
Analog-to-digital converter input 5.
C0+
42
I
Analog
Analog comparator 0 positive-reference input.
C0–
44
I
Analog
Analog comparator 0 negative-reference input.
C0o
43
O
TTL
Analog comparator 0 output.
CCP0
45
I/O
TTL
Timer 0 capture input, compare output, or PWM output channel 0.
CCP1
13
I/O
TTL
Timer 0 capture input, compare output, or PWM output channel 1.
CCP2
46
I/O
TTL
Timer 1 capture input, compare output, or PWM output channel 2.
CCP4
11
I/O
TTL
Timer 2 capture input, compare output, or PWM output channel 4.
Fault
34
I
TTL
Motion control 0 fault.
GND
8
-
Power
Ground reference for logic and I/O pins.
GND
16
-
Power
Ground reference for logic and I/O pins.
GND
24
-
Power
Ground reference for logic and I/O pins.
GND
31
-
Power
Ground reference for logic and I/O pins.
IDX
33
I
TTL
LDO
6
-
Power
The low drop-out regulator output voltage. This pin requires an
external capacitor between the pin and GND of 1 µF or greater.
OSC0
9
I
Analog
Oscillator crystal input or an external clock reference input.
OSC1
10
O
Analog
Oscillator crystal output.
PA0
17
I/O
TTL
GPIO port A bit 0.
PA1
18
I/O
TTL
GPIO port A bit 1.
Pin Name
Description
Quadrature encoder index input.
May 4, 2007
369
Preliminary
Signal Tables
Table 18-2.
Signals by Signal Name (Sheet 2 of 3)
Pin
Number
Pin
Type
Buffer
Type
PA2
19
I/O
TTL
GPIO port A bit 2.
PA3
20
I/O
TTL
GPIO port A bit 3.
PA4
21
I/O
TTL
GPIO port A bit 4.
PA5
22
I/O
TTL
GPIO port A bit 5.
PB0
29
I/O
TTL
GPIO port B bit 0.
PB1
30
I/O
TTL
GPIO port B bit 1.
PB2
33
I/O
TTL
GPIO port B bit 2.
PB3
34
I/O
TTL
GPIO port B bit 3.
PB4
44
I/O
TTL
GPIO port B bit 4.
PB5
43
I/O
TTL
GPIO port B bit 5.
PB6
42
I/O
TTL
GPIO port B bit 6.
PB7
41
I/O
TTL
GPIO port B bit 7.
PC0
40
I/O
TTL
GPIO port C bit 0.
PC1
39
I/O
TTL
GPIO port C bit 1.
PC2
38
I/O
TTL
GPIO port C bit 2.
PC3
37
I/O
TTL
GPIO port C bit 3.
PC4
14
I/O
TTL
GPIO port C bit 4.
PC5
13
I/O
TTL
GPIO port C bit 5.
PC6
12
I/O
TTL
GPIO port C bit 6.
PC7
11
I/O
TTL
GPIO port C bit 7.
PD0
25
I/O
TTL
GPIO port D bit 0.
PD1
26
I/O
TTL
GPIO port D bit 1.
PD2
27
I/O
TTL
GPIO port D bit 2.
PD3
28
I/O
TTL
GPIO port D bit 3.
PD4
45
I/O
TTL
GPIO port D bit 4.
PD5
46
I/O
TTL
GPIO port D bit 5.
PE0
35
I/O
TTL
GPIO port E bit 0.
PE1
36
I/O
TTL
GPIO port E bit 1.
PhA
14
I
TTL
Quadrature encoder phase A input.
PhB
12
I
TTL
Quadrature encoder phase B input.
Pin Name
Description
370
May 4, 2007
Preliminary
LM3S818 Data Sheet
Table 18-2.
Signals by Signal Name (Sheet 3 of 3)
Pin
Number
Pin
Type
Buffer
Type
PWM0
25
O
TTL
Pulse width modulator channel 0 output.
PWM1
26
O
TTL
Pulse width modulator channel 1 output.
PWM2
29
O
TTL
Pulse width modulator channel 2 output.
PWM3
30
O
TTL
Pulse width modulator channel 3 output.
PWM4
35
O
TTL
Pulse width modulator channel 4 output.
PWM5
36
O
TTL
Pulse width modulator channel 5 output.
RST
5
I
TTL
System reset input.
SSIClk
19
I/O
TTL
SSI clock reference (input when in slave mode and output in
master mode).
SSIFss
20
I/O
TTL
SSI frame enable (input for an SSI slave device and output for an
SSI master device).
SSIRx
21
I
TTL
SSI receive data input.
SSITx
22
O
TTL
SSI transmit data output.
SWCLK
40
I
TTL
Serial wire clock reference input.
SWDIO
39
I/O
TTL
Serial-wire debug input/output.
SWO
37
O
TTL
Serial-wire output.
TCK
40
I
TTL
JTAG scan test clock reference input.
TDI
38
I
TTL
JTAG scan test data input.
TDO
37
O
TTL
JTAG scan test data output.
TMS
39
I
TTL
JTAG scan test mode select input.
TRST
41
I
TTL
JTAG scan test reset input.
U0Rx
17
I
TTL
UART0 receive data input.
U0Tx
18
O
TTL
UART0 transmit data output.
U1Rx
27
I
TTL
UART1 receive data input.
U1Tx
28
O
TTL
UART1 transmit data output.
VDD
7
-
Power
Positive supply for logic and I/O pins.
VDD
15
-
Power
Positive supply for logic and I/O pins.
VDD
23
-
Power
Positive supply for logic and I/O pins.
VDD
32
-
Power
Positive supply for logic and I/O pins.
Pin Name
Description
May 4, 2007
371
Preliminary
Signal Tables
Table 18-3.
Signals by Function, Except for GPIO (Sheet 1 of 3)
Function
ADC
Analog
Comparators
General-Purpose
Timers
JTAG/SWD/SWO
Pin
Number
Pin
Type
Buffer
Type
ADC0
1
I
Analog
Analog-to-digital converter input 0.
ADC1
2
I
Analog
Analog-to-digital converter input 1.
ADC2
3
I
Analog
Analog-to-digital converter input 2.
ADC3
4
I
Analog
Analog-to-digital converter input 3.
ADC4
48
I
Analog
Analog-to-digital converter input 4.
ADC5
47
I
Analog
Analog-to-digital converter input 5.
C0+
42
I
Analog
Analog comparator 0 positive-reference
input.
C0–
44
I
Analog
Analog comparator 0 negative-reference
input.
C0o
43
O
TTL
Analog comparator 0 output.
CCP0
45
I/O
TTL
Timer 0 capture input, compare output, or
PWM output channel 0.
CCP1
13
I/O
TTL
Timer 0 capture input, compare output, or
PWM output channel 1.
CCP2
46
I/O
TTL
Timer 1 capture input, compare output, or
PWM output channel 2.
PhB
12
I
TTL
Quadrature encoder phase A input.
CCP4
11
I/O
TTL
Timer 2 capture input, compare output, or
PWM output channel 4.
PhA
12
I
TTL
Quadrature encoder phase B input.
SWCLK
40
I
TTL
Serial-wire clock reference input.
SWDIO
39
I/O
TTL
Serial-wire debug input/output.
SWO
37
O
TTL
Serial-wire output.
TCK
40
I
TTL
JTAG scan test clock reference input.
TDI
38
I
TTL
JTAG scan test data input.
TDO
37
O
TTL
JTAG scan test data output.
TMS
39
I
TTL
JTAG scan test mode select input.
TRST
41
I
TTL
JTAG scan test reset input.
Pin Name
372
Description
May 4, 2007
Preliminary
LM3S818 Data Sheet
Table 18-3.
Signals by Function, Except for GPIO (Sheet 2 of 3)
Function
Power
PWM
QEI
SSI
System Control &
Clocks
Pin
Number
Pin
Type
Buffer
Type
GND
8
-
Power
Ground reference for logic and I/O pins.
GND
16
-
Power
Ground reference for logic and I/O pins.
GND
24
-
Power
Ground reference for logic and I/O pins.
GND
31
-
Power
Ground reference for logic and I/O pins.
LDO
6
-
Power
The low drop-out regulator output voltage.
This pin requires an external capacitor
between the pin and GND of 1 µF or greater.
VDD
7
-
Power
Positive supply for logic and I/O pins.
VDD
15
-
Power
Positive supply for logic and I/O pins.
VDD
23
-
Power
Positive supply for logic and I/O pins.
VDD
32
-
Power
Positive supply for logic and I/O pins.
PWM0
25
O
TTL
Pulse width modulator channel 0 output.
PWM1
26
O
TTL
Pulse width modulator channel 1 output.
PWM2
29
O
TTL
Pulse width modulator channel 2 output.
PWM3
30
O
TTL
Pulse width modulator channel 3 output.
PWM4
35
O
TTL
Pulse width modulator channel 4 output.
PWM5
36
O
TTL
Pulse width modulator channel 5 output.
IDX
33
I
TTL
Quadrature encoder index input.
PhA
14
I
TTL
Quadrature encoder phase A input.
PhB
12
I
TTL
Quadrature encoder phase B input.
SSIClk
19
I/O
TTL
SSI clock reference (input when in slave
mode and output in master mode).
SSIFss
20
I/O
TTL
SSI frame enable (input for an SSI slave
device and output for an SSI master device).
SSIRx
21
I
TTL
SSI receive data input.
SSITx
22
O
TTL
SSI transmit data output.
OSC0
9
I
Analog
Oscillator crystal input or an external clock
reference input.
OSC1
10
O
Analog
Oscillator crystal output.
RST
5
I
TTL
Pin Name
May 4, 2007
Description
System reset input.
373
Preliminary
Signal Tables
Table 18-3.
Signals by Function, Except for GPIO (Sheet 3 of 3)
Function
UART
Table 18-4.
GPIO Pin
Pin
Number
Pin
Type
Buffer
Type
U0Rx
17
I
TTL
UART0 receive data input.
U0Tx
18
O
TTL
UART0 transmit data output.
U1Rx
27
I
TTL
UART1 receive data input.
U1Tx
28
O
TTL
UART1 transmit data output.
Pin Name
Description
GPIO Pins and Alternate Functions (Sheet 1 of 2)
Pin
Number
Multiplexed
Function
Multiplexed
Function
PA0
17
U0Rx
PA1
18
U0Tx
PA2
19
SSIClk
PA3
20
SSIFss
PA4
21
SSIRx
PA5
22
SSITx
PB0
29
PWM2
PB1
30
PWM3
PB2
33
IDX
PB3
34
FAULT
PB4
44
C0-
PB5
43
C0o
PB6
42
C0+
PB7
41
TRST
PC0
40
TCK
SWCLK
PC1
39
TMS
SWDIO
PC2
38
TDI
PC3
37
TDO
PC4
14
PhA
PC5
13
CCP1
PC6
12
PhB
PC7
11
CCP4
PD0
25
PWM0
SWO
374
May 4, 2007
Preliminary
LM3S818 Data Sheet
Table 18-4.
GPIO Pin
GPIO Pins and Alternate Functions (Sheet 2 of 2)
Pin
Number
Multiplexed
Function
PD1
26
PWM1
PD2
27
U1Rx
PD3
28
U1Tx
PD4
45
CCP0
PD5
46
CCP2
PD6
47
ADC5
PD7
48
ADC4
PE0
35
PWM4
PE1
36
PWM5
PE2
4
ADC3
PE3
3
ADC2
PE4
2
ADC1
PE5
1
ADC0
Multiplexed
Function
May 4, 2007
375
Preliminary
Operating Characteristics
19
Table 19-1.
Operating Characteristics
Temperature Characteristics
Characteristic
Symbol
Value
Unit
Operating temperature rangea
TA
-40 to +85 for industrial
Characteristic
Symbol
Value
Unit
Thermal resistance (junction to ambient)a
θJA
76
°C/W
Average junction temperatureb
TJ
TA + (PAVG • θJA)
°C
Maximum junction temperature
TJMAX
115c
°C
°C
a. Maximum storage temperature is 150°C.
Table 19-2.
Thermal Characteristics
a. Junction to ambient thermal resistance θJA numbers are determined by a package simulator.
b. Power dissipation is a function of temperature.
c. TJMAX calculation is based on power consumption values and conditions as specified in “Power Specifications” on page 379 of
the data sheet.
376
May 4, 2007
Preliminary
LM3S818 Data Sheet
20
Electrical Characteristics
20.1
DC Characteristics
20.1.1
Maximum Ratings
The maximum ratings are the limits to which the device can be subjected without permanently
damaging the device.
Note:
The device is not guaranteed to operate properly at the maximum ratings.
Table 20-1.
Maximum Ratings
Characteristica
Symbol
Value
Unit
Supply voltage range (VDD)
VDD
0.0 to +3.6
V
Input voltage
VIN
-0.3 to 5.5
V
Maximum current for pins, excluding pins
operating as GPIOs
I
100
mA
Maximum current for GPIO pins
I
100
mA
a. Voltages are measured with respect to GND.
Important: This device contains circuitry to protect the inputs against damage due to high-static
voltages or electric fields; however, it is advised that normal precautions be taken to
avoid application of any voltage higher than maximum-rated voltages to this
high-impedance circuit. Reliability of operation is enhanced if unused inputs are
connected to an appropriate logic voltage level (for example, either GND or VDD).
20.1.2
Recommended DC Operating Conditions
Table 20-2.
Parameter
Recommended DC Operating Conditions
Parameter Name
Min
Nom
Max
Unit
VDD
Supply voltage
3.0
3.3
3.6
V
VIH
High-level input voltage
2.0
-
5.0
V
VIL
Low-level input voltage
-0.3
-
1.3
V
VSIH
High-level input voltage for Schmitt trigger inputs
0.8 * VDD
-
VDD
V
VSIL
Low-level input voltage for Schmitt trigger inputs
0
-
0.2 * VDD
V
VOH
High-level output voltage
2.4
-
-
V
VOL
Low-level output voltage
-
-
0.4
V
May 4, 2007
377
Preliminary
Electrical Characteristics
Table 20-2.
Parameter
IOH
IOL
20.1.3
Recommended DC Operating Conditions (Continued)
Parameter Name
Min
Nom
Max
Unit
2-mA Drive
2.0
-
-
mA
4-mA Drive
4.0
-
-
mA
8-mA Drive
8.0
-
-
mA
2-mA Drive
2.0
-
-
mA
4-mA Drive
4.0
-
-
mA
8-mA Drive
8.0
-
-
mA
High-level source current, VOH=2.4 V
Low-level sink current, VOL=0.4 V
On-Chip Low Drop-Out (LDO) Regulator Characteristics
Table 20-3.
Parameter
LDO Regulator Characteristics
Parameter Name
Min
Nom
Max
Unit
Programmable internal (logic) power supply
output value
2.25
-
2.75
V
Output voltage accuracy
-
2%
-
%
tPON
Power-on time
-
-
100
µs
tON
Time on
-
-
200
µs
tOFF
Time off
-
-
100
µs
VSTEP
Step programming incremental voltage
-
50
-
mV
CLDO
External filter capacitor size for internal
power supply
-
1
-
µF
VLDOOUT
378
May 4, 2007
Preliminary
LM3S818 Data Sheet
20.1.4
Power Specifications
The power measurements specified in Table 20-4 are run on the core processor using SRAM with
the following specifications:
„
VDD = 3.3 V
„
Temperature = 25°C
Table 20-4.
Power Specifications
Parameter
IDD_RUN
Parameter
Name
Run mode 1
(Flash loop)
Conditions
LDO = 2.50 V
Nom
Max
Unit
95
110
mA
60
75
mA
85
95
mA
50
60
mA
19
22
mA
950
1150
µA
Code = while(1){} executed in Flash
Peripherals = All clock-gated ON
System Clock = 50 MHz (with PLL)
Run mode 2
(Flash loop)
LDO = 2.50 V
Code = while(1){} executed in Flash
Peripherals = All clock-gated OFF
System Clock = 50 MHz (with PLL)
Run mode 1
(SRAM loop)
LDO = 2.50 V
Code = while(1){} executed in SRAM
Peripherals = All clock-gated ON
System Clock = 50 MHz (with PLL)
Run mode 2
(SRAM loop)
LDO = 2.50 V
Code = while(1){} executed in SRAM
Peripherals = All clock-gated OFF
System Clock = 50 MHz (with PLL)
IDD_SLEEP
Sleep mode
LDO = 2.50 V
Peripherals = All clock-gated OFF
System Clock = 50 MHz (with PLL)
IDD_DEEPSLEEP
Deep-Sleep
mode
LDO = 2.25 V
Peripherals = All clock-gated OFF
System Clock = MOSC/16
May 4, 2007
379
Preliminary
Electrical Characteristics
20.1.5
Flash Memory Characteristics
Table 20-5.
Flash Memory Characteristics
Parameter
Parameter Name
Min
Nom
Max
Unit
10,000
-
-
cycles
Data retention at average operating
temperature of 85°C
10
-
-
years
TPROG
Word program time
20
-
-
µs
TERASE
Page erase time
20
-
-
ms
TME
Mass erase time
200
-
-
ms
PECYC
Number of guaranteed program/erase
cyclesa before failure
TRET
a. A program/erase cycle is defined as switching the bits from 1-> 0 -> 1.
20.2
AC Characteristics
20.2.1
Load Conditions
Unless otherwise specified, the following conditions are true for all timing measurements. Timing
measurements are for 4-mA drive strength.
Figure 20-1. Load Conditions
pin
CL = 50 pF
GND
20.2.2
Clocks
Table 20-6.
Phase Locked Loop (PLL) Characteristics
Parameter
Parameter Name
Min
Nom
Max
Unit
fREF_CRYSTAL
Crystal referencea
3.579545
-
8.192
MHz
fREF_EXT
External clock referencea
3.579545
-
8.192
MHz
-
200
-
MHz
-
-
0.5
ms
fPLL
PLL frequency
TREADY
PLL lock time
b
a. The exact value is determined by the crystal value programmed into the XTAL field of the Run-Mode Clock
Configuration (RCC) register (see page 84).
b. PLL frequency is automatically calculated by the hardware based on the XTAL field of the RCC register.
380
May 4, 2007
Preliminary
LM3S818 Data Sheet
Table 20-7.
Clock Characteristics
Parameter
Parameter Name
Min
Nom
Max
Unit
fIOSC
Internal oscillator
frequency
7
15
22
MHz
fMOSC
Main oscillator frequency
1
-
8
MHz
tMOSC_PER
Main oscillator period
125
-
1000
ns
fREF_CRYSTAL_BYPASS
Crystal reference using the
main oscillator (PLL in
BYPASS mode)a
1
-
8
MHz
fREF_EXT_BYPASS
External clock reference
(PLL in BYPASS mode)a
0
-
50
MHz
fSYSTEM_CLOCK
System clock
0
-
50
MHz
a. The ADC must be clocked from the PLL or directly from a 14-MHz to 18-MHz clock source in order to operate
properly.
20.2.3
Table 20-8.
Analog-to-Digital Converter
ADC Characteristics
Parameter
Min
Nom
Max
Unit
Maximum single-ended, full-scale
analog input voltage
-
-
3.0
V
Minimum single-ended, full-scale
analog input voltage
-
-
0
V
Maximum differential, full-scale
analog input voltage
-
-
1.5
V
Minimum differential, full-scale analog
input voltage
-
-
-1.5
V
CADCIN
Equivalent input capacitance
-
1
-
pF
N
Resolution
-
10
-
bits
fADC
ADC internal clock frequency
14
16
18
MHz
tADCCONV
Conversion time
-
-
16
tADC cyclesa
fADCCONV
Conversion rate
875
1000
1125
k samples/s
INL
Integral nonlinearity
-
-
±1
LSB
DNL
Differential nonlinearity
-
-
±1
LSB
OFF
Offset
-
-
+2
LSB
GAIN
Gain
-
-
±2
LSB
VADCIN
Parameter Name
a. tADC = 1/fADC clock
May 4, 2007
381
Preliminary
Electrical Characteristics
20.2.4
Analog Comparator
Table 20-9.
Analog Comparator Characteristics
Parameter
Parameter Name
Min
Nom
Max
Unit
VOS
Input offset voltage
-
± 10
± 25
mV
VCM
Input common mode voltage range
0
-
VDD-1.5
V
Common mode rejection ratio
50
-
-
dB
CMRR
TRT
Response time
-
-
1
µs
TMC
Comparator mode change to Output Valid
-
-
10
µs
Min
Nom
Max
Unit
Table 20-10.
Parameter
Analog Comparator Voltage Reference Characteristics
Parameter Name
RHR
Resolution high range
-
VDD/32
-
LSB
RLR
Resolution low range
-
VDD/24
-
LSB
AHR
Absolute accuracy high range
-
-
± 1/2
LSB
ALR
Absolute accuracy low range
-
-
± 1/4
LSB
20.2.5
Synchronous Serial Interface (SSI)
Table 20-11.
SSI Characteristics
Parameter
No.
Parameter
Parameter Name
Min
Nom
Max
Unit
S1
tCLK_PER
SSICLK cycle time
2
-
65024
system
clocks
S2
tCLK_HIGH
SSICLK high time
-
1/2
-
tCLK_PER
S3
tCLK_LOW
SSICLK low time
-
1/2
-
tCLK_PER
S4
tCLKRF
SSICLK rise/fall time
-
7.4
26
ns
S5
tDMD
Data from master valid delay time
0
-
20
ns
S6
tDMS
Data from master setup time
20
-
-
ns
S7
tDMH
Data from master hold time
40
-
-
ns
S8
tDSS
Data from slave setup time
20
-
-
ns
S9
tDSH
Data from slave hold time
40
-
-
ns
382
May 4, 2007
Preliminary
LM3S818 Data Sheet
Figure 20-2. SSI Timing for TI Frame Format (FRF=01), Single Transfer Timing Measurement
S1
S2
S4
SSIClk
S3
SSIFss
SSITx
SSIRx
MSB
LSB
4 to 16 bits
Figure 20-3. SSI Timing for MICROWIRE Frame Format (FRF=10), Single Transfer
S2
S1
SSIClk
S3
SSIFss
SSITx
MSB
LSB
8-bit control
SSIRx
0
MSB
LSB
4 to 16 bits output data
Figure 20-4. SSI Timing for SPI Frame Format (FRF=00), with SPH=1
S1
S4
S2
SSIClk
(SPO=0)
S3
SSIClk
(SPO=1)
S6
SSITx
(master)
MSB
S5
SSIRx
(slave)
S7
S8
LSB
S9
MSB
LSB
SSIFss
May 4, 2007
383
Preliminary
Electrical Characteristics
20.2.6
JTAG and Boundary Scan
Table 20-12.
JTAG Characteristics
Parameter
No.
Parameter
J1
fTCK
TCK operational clock frequency
J2
tTCK
TCK operational clock period
J3
tTCK_LOW
J4
tTCK_HIGH
J5
Min
Nom
Max
Unit
0
-
10
MHz
100
-
-
ns
TCK clock Low time
-
½ tTCK
-
ns
TCK clock High time
-
½ tTCK
-
ns
tTCK_R
TCK rise time
0
-
10
ns
J6
tTCK_F
TCK fall time
0
-
10
ns
J7
tTMS_SU
TMS setup time to TCK rise
20
-
-
ns
J8
tTMS_HLD
TMS hold time from TCK rise
20
-
-
ns
J9
tTDI_SU
TDI setup time to TCK rise
25
-
-
ns
J10
tTDI_HLD
TDI hold time from TCK rise
25
-
-
ns
J11
tTDO_ZDV
TCK fall to
Data Valid
from High-Z
-
23
35
ns
4-mA drive
15
26
ns
8-mA drive
14
25
ns
8-mA drive with slew rate control
18
29
ns
21
35
ns
4-mA drive
14
25
ns
8-mA drive
13
24
ns
8-mA drive with slew rate control
18
28
ns
9
11
ns
4-mA drive
7
9
ns
8-mA drive
6
8
ns
8-mA drive with slew rate control
7
9
ns
J12
tTDO_DV
J13
tTDO_DVZ
TCK fall to
Data Valid
from Data
Valid
TCK fall to
High-Z from
Data Valid
J14
tTRST
J15
tTRST_SU
Parameter Name
2-mA drive
2-mA drive
2-mA drive
-
-
TRST assertion time
100
-
-
ns
TRST setup time to TCK rise
10
-
-
ns
384
May 4, 2007
Preliminary
LM3S818 Data Sheet
Figure 20-5. JTAG Test Clock Input Timing
J2
J3
J4
TCK
J6
J5
Figure 20-6. JTAG Test Access Port (TAP) Timing
TCK
J7
TMS
TDI
J8
J7
J8
TMS Input Valid
TMS Input Valid
J9
J9
J10
TDI Input Valid
TDI Input Valid
J11
TDO
J10
J12
J13
TDO Output Valid
TDO Output Valid
Figure 20-7. JTAG TRST Timing
TCK
J14
J15
TRST
May 4, 2007
385
Preliminary
Electrical Characteristics
20.2.7
General-Purpose I/O
Table 20-13.
GPIO Characteristicsa
Parameter
Parameter Name
Condition
Min
Nom
Max
Unit
tGPIOR
GPO Rise Time
(from 20% to 80%
of VDD)
2-mA drive
-
17
26
ns
4-mA drive
9
13
ns
8-mA drive
6
9
ns
8-mA drive with slew rate control
10
12
ns
17
25
ns
4-mA drive
8
12
ns
8-mA drive
6
10
ns
8-mA drive with slew rate control
11
13
ns
tGPIOF
GPO Fall Time
(from 80% to 20%
of VDD)
2-mA drive
-
a. All GPIOs are 5 V-tolerant.
20.2.8
Reset
Table 20-14.
Reset Characteristics
Parameter
No.
Parameter
R1
VTH
Reset threshold
R2
VBTH
Brown-Out threshold
R3
TPOR
R4
TBOR
R5
TIRPOR
R6
Parameter Name
Min
Nom
Max
Unit
-
2.0
-
V
2.85
2.9
2.95
V
Power-On Reset timeout
-
10
-
ms
Brown-Out timeout
-
500
-
µs
Internal reset timeout after POR
15
-
30
ms
TIRBOR
Internal reset timeout after BORa
2.5
-
20
µs
R7
TIRHWR
Internal reset timeout after hardware
reset (RST pin)
15
-
30
ms
R8
TIRSWR
Internal reset timeout after
software-initiated system reseta
2.5
-
20
µs
R9
TIRWDR
Internal reset timeout after watchdog
reseta
2.5
-
20
µs
R10
TIRLDOR
Internal reset timeout after LDO reseta
2.5
-
20
µs
R11
TVDDRISE
Supply voltage (VDD) rise time (0V-3.3V)
100
ms
a. 20 * tMOSC_PER
386
May 4, 2007
Preliminary
LM3S818 Data Sheet
Figure 20-8. External Reset Timing (RST)
RST
R7
/Reset
(Internal)
Figure 20-9. Power-On Reset Timing
R1
VDD
R3
/POR
(Internal)
R5
/Reset
(Internal)
Figure 20-10.
Brown-Out Reset Timing
R2
VDD
R4
/BOR
(Internal)
R6
/Reset
(Internal)
Figure 20-11.
Software Reset Timing
SW Reset
R8
/Reset
(Internal)
May 4, 2007
387
Preliminary
Electrical Characteristics
Figure 20-12.
Watchdog Reset Timing
WDT
Reset
(Internal)
R9
/Reset
(Internal)
Figure 20-13.
LDO Reset Timing
LDO Reset
(Internal)
R10
/Reset
(Internal)
388
May 4, 2007
Preliminary
LM3S818 Data Sheet
21
Package Information
Figure 21-1.
48-Pin LQFP Package
aaa
bbb
ccc
NOTES:
1.
2.
3.
4.
5.
ddd
aaa
bbb
ccc
ddd
48LD LQFP
NOTE
SYMBOL
A
A1
A2
D
D1
E
E1
L
e
b
b1
c
c1
6.
PACKAGE TYPE
7.
MIN
===
0.05
1.35
NOM
MAX
===
1.60
===
0.15
1.40
1.45
9.00 BSC
7.00 BSC
9.00 BSC
7.00 BSC
0.45
0.80
0.75
0.50 BSC
0.17
0.22
0.27
0.17
0.20
0.23
0.09
===
0.20
0.09
===
0.16
Tolerances of form and position
0.20
0.20
0.08
0.08
8.
9.
10.
11.
12.
13.
14.
15.
May 4, 2007
All dimensions are in mm. All dimensioning and tolerancing
conform to ANSI Y14.5M-1982.
The top package body size may be smaller than the bottom
package body size by as much as 0.20.
Datums A-B and -D- to be determined at datum plane -H- .
To be determined at seating plane -C- .
Dimensions D1 and E1 do not include mold protrusion.
Allowable protrusion is 0.25 per side. D1 and E1 are
maximum plastic body size dimensions including mold
mismatch.
Surface finish of the package is #24-27 Charmille
(1.6-2.3µmR0) Pin 1 and ejector pin may be less than
0.1µmR0.
Dambar removal protrusion does not exceed 0.08. Intrusion
does not exceed 0.03.
Burr does not exceed 0.08 in any direction.
Dimension b does not include Dambar protrusion.
Allowable Dambar protrusion shall not cause the lead width
to exceed the maximum b dimension by more than 0.08.
Dambar cannot be located on the lower radius or the foot.
Minimum space between protrusion and adjacent lead is
0.07 for 0.40 and 0.50 pitch package.
Corner radius of plastic body does not exceed 0.20.
These dimensions apply to the flat section of the lead
between 0.10 and 0.25 from the lead tip.
A1 is defined as the distance from the seating plane to the
lowest point of the package body.
Finish of leads is tin plated.
All specifications and dimensions are subjected to IPAC’S
manufacturing process flow and materials.
The packages described in the drawing conform to JEDEC
M5-026A. Where discrepancies between the JEDEC and
IPAC documents exist, this drawing will take the
precedence.
389
Preliminary
Appendix A. Serial Flash Loader
The Stellaris serial flash loader is used to download code to the flash memory of a device without
the use of a debug interface. The serial flash loader uses a simple packet interface to provide
synchronous communication with the device. The flash loader runs off the crystal and does not
enable the PLL, so its speed is determined by the crystal used. The two serial interfaces that can
be used are the UART0 and SSI interfaces. For simplicity, both the data format and
communication protocol are identical for both serial interfaces.
22.1
Interfaces
Once communication with the flash loader is established via one of the serial interfaces, that
interface is used until the flash loader is reset or new code takes over. For example, once you start
communicating using the SSI port, communications with the flash loader via the UART are
disabled until the device is reset.
22.1.1
UART
The Universal Asynchronous Receivers/Transmitters (UART) communication uses a fixed serial
format of 8 bits of data, no parity, and 1 stop bit. The baud rate used for communication is
automatically detected by the flash loader and can be any valid baud rate supported by the host
and the device. The auto detection sequence requires that the baud rate should be no more than
1/32 the crystal frequency of the board that is running the serial flash loader. This is actually the
same as the hardware limitation for the maximum baud rate for any UART on a Stellaris device.
In order to determine the baud rate, the serial flash loader needs to determine the relationship
between its own crystal frequency and the baud rate. This is enough information for the flash
loader to configure its UART to the same baud rate as the host. This automatic baud rate detection
allows the host to use any valid baud rate that it wants to communicate with the device.
The method used to perform this automatic synchronization relies on the host sending the flash
loader two bytes that are both 0x55. This generates a series of pulses to the flash loader that it can
use to calculate the ratios needed to program the UART to match the host’s baud rate. After the
host sends the pattern, it attempts to read back one byte of data from the UART. The flash loader
returns the value of 0xCC to indicate successful detection of the baud rate. If this byte is not
received after at least twice the time required to transfer the two bytes, the host can resend
another pattern of 0x55, 0x55, and wait for the 0xCC byte again until the flash loader
acknowledges that it has received a synchronization pattern correctly. For example, the time to
wait for data back from the flash loader should be calculated as at least 2*(20(bits/sync)/baud rate
(bits/sec)). For a baud rate of 115200, this time is 2*(20/115200) or 0.35ms.
22.1.2
SSI
The Synchronous Serial Interface (SSI) port also uses a fixed serial format for communications,
with the framing defined as Motorola format with SPH set to 1 and SPO set to 1. See the section
on SSI formats for more details on this transfer protocol. Like the UART, this interface has
hardware requirements that limit the maximum speed that the SSI clock can run. This allows the
SSI clock to be at most 1/12 the crystal frequency of the board running the flash loader. Since the
host device is the master, the SSI on the flash loader device does not need to determine the clock
as it is provided directly by the host.
22.2
Packet Handling
All communications, with the exception of the UART auto-baud, are done via defined packets that
are acknowledged (ACK) or not acknowledged (NAK) by the devices. The packets use the same
390
May 4, 2007
Preliminary
LM3S818 Data Sheet
format for receiving and sending packets, including the method used to acknowledge successful or
unsuccessful reception of a packet.
22.2.1
Packet Format
All packets sent and received from the device use the following byte-packed format.
struct
{
unsigned char ucSize;
unsigned char ucCheckSum;
unsigned char Data[];
};
ucSize – The first byte received holds the total size of the transfer including the size and checksum
bytes.
ucChecksum – This holds a simple checksum of the bytes in the data buffer only. The algorithm is
Data[0]+Data[1]+…+ Data[ucSize-3].
Data – This is the raw data intended for the device, which is formatted in some form of command
interface. There should be ucSize – 2 bytes of data provided in this buffer to or from the device.
22.2.2
Sending Packets
The actual bytes of the packet can be sent individually or all at once, the only limitation is that
commands that cause flash memory access should limit the download sizes to prevent losing
bytes during flash programming. This limitation is discussed further in the commands that interact
with the flash.
Once the packet has been formatted correctly by the host, it should be sent out over the UART or
SSI interface. Then the host should poll the UART or SSI interface for the first non-zero data
returned from the device. The first non-zero byte will either be an ACK (0xCC) or a NAK (0x33)
byte from the device indicating the packet was received successfully (ACK) or unsuccessfully
(NAK). This does not indicate that the actual contents of the command issued in the data portion of
the packet were valid, just that the packet was received correctly.
22.2.3
Receiving Packets
The flash loader sends a packet of data in the same format that it receives a packet. The flash
loader may transfer leading zero data before the first actual byte of data is sent out. The first
non-zero byte is the size of the packet followed by a checksum byte, and finally followed by the
data itself. There is no break in the data after the first non-zero byte is sent from the flash loader.
Once the device communicating with the flash loader receives all the bytes, it must either ACK or
NAK the packet to indicate that the transmission was successful. The appropriate response after
sending a NAK to the flash loader is to resend the command that failed and request the data
again. If needed, the host may send leading zeros before sending down the ACK/NAK signal to
the flash loader, as the flash loader only accepts the first non-zero data as a valid response. This
zero padding is needed by the SSI interface in order to receive data to or from the flash loader.
22.3
Commands
The next section defines the list of commands that can be sent to the flash loader. The first byte of
the data should always be one of the defined commands, followed by data or parameters as
determined by the command that is sent.
May 4, 2007
391
Preliminary
22.3.1
COMMAND_PING (0x20)
This command simply accepts the command and sets the global status to success. The format of
the packet is as follows:
Byte[0] = 0x03;
Byte[1] = checksum(Byte[2]);
Byte[2] = COMMAND_PING;
The ping command has 3 bytes and the value for COMMAND_PING is 0x20 and the checksum of
one byte is that same byte, making Byte[1] also 0x20. Since the ping command has no real return
status, the receipt of an ACK can be interpreted as a successful ping to the flash loader.
22.3.2
COMMAND_GET_STATUS (0x23)
This command returns the status of the last command that was issued. Typically, this command
should be sent after every command to ensure that the previous command was successful or to
properly respond to a failure. The command requires one byte in the data of the packet and should
be followed by reading a packet with one byte of data that contains a status code. The last step is
to ACK or NAK the received data so the flash loader knows that the data has been read.
Byte[0] = 0x03
Byte[1] = checksum(Byte[2])
Byte[2] = COMMAND_GET_STATUS
22.3.3
COMMAND_DOWNLOAD (0x21)
This command is sent to the flash loader to indicate where to store data and how many bytes will
be sent by the COMMAND_SEND_DATA commands that follow. The command consists of two
32-bit values that are both transferred MSB first. The first 32-bit value is the address to start
programming data into, while the second is the 32-bit size of the data that will be sent. This
command also triggers an erase of the full area to be programmed so this command takes longer
than other commands. This results in a longer time to receive the ACK/NAK back from the board.
This command should be followed by a COMMAND_GET_STATUS to ensure that the Program
Address and Program size are valid for the device running the flash loader.
The format of the packet to send this command is a follows:
Byte[0] = 11
Byte[1] = checksum(Bytes[2:10])
Byte[2] = COMMAND_DOWNLOAD
Byte[3] = Program Address [31:24]
Byte[4] = Program Address [23:16]
Byte[5] = Program Address [15:8]
Byte[6] = Program Address [7:0]
Byte[7] = Program Size [31:24]
Byte[8] = Program Size [23:16]
Byte[9] = Program Size [15:8]
Byte[10] = Program Size [7:0]
22.3.4
COMMAND_SEND_DATA (0x24)
This command should only follow a COMMAND_DOWNLOAD command or another
COMMAND_SEND_DATA command if more data is needed. Consecutive send data commands
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May 4, 2007
Preliminary
LM3S818 Data Sheet
automatically increment address and continue programming from the previous location. The caller
should limit transfers of data to a maximum 8 bytes of packet data to allow the flash to program
successfully and not overflow input buffers of the serial interfaces. The command terminates
programming once the number of bytes indicated by the COMMAND_DOWNLOAD command has
been received. Each time this function is called it should be followed by a
COMMAND_GET_STATUS to ensure that the data was successfully programmed into the flash. If
the flash loader sends a NAK to this command, the flash loader does not increment the current
address to allow retransmission of the previous data.
Byte[0] = 11
Byte[1] = checksum(Bytes[2:10])
Byte[2] = COMMAND_SEND_DATA
Byte[3] = Data[0]
Byte[4] = Data[1]
Byte[5] = Data[2]
Byte[6] = Data[3]
Byte[7] = Data[4]
Byte[8] = Data[5]
Byte[9] = Data[6]
Byte[10] = Data[7]
22.3.5
COMMAND_RUN (0x22)
This command is used to tell the flash loader to execute from the address passed as the
parameter in this command. This command consists of a single 32-bit value that is interpreted as
the address to execute. The 32-bit value is transmitted MSB first and the flash loader responds
with an ACK signal back to the host device before actually executing the code at the given
address. This allows the host to know that the command was received successfully and the code
is now running.
Byte[0]
Byte[1]
Byte[2]
Byte[3]
Byte[4]
Byte[5]
Byte[6]
22.3.6
=
=
=
=
=
=
=
7
checksum(Bytes[2:6])
COMMAND_RUN
Execute Address[31:24]
Execute Address[23:16]
Execute Address[15:8]
Execute Address[7:0]
COMMAND_RESET (0x25)
This command is used to tell the flash loader device to reset. This is useful when downloading a
new image that overwrote the flash loader and wants to start from a full reset. Unlike the
COMMAND_RUN command, this allows the initial stack pointer to be read by the hardware and
set up for the new code. It can also be used to reset the flash loader if a critical error occurs and
the host device wants to restart communication with the flash loader.
Byte[0] = 3
Byte[1] = checksum(Byte[2])
Byte[2] = COMMAND_RESET
May 4, 2007
393
Preliminary
The flash loader responds with an ACK signal back to the host device before actually executing
the software reset to the device running the flash loader. This allows the host to know that the
command was received successfully and the part will be reset.
394
May 4, 2007
Preliminary
LM3S818 Data Sheet
Ordering and Contact Information
Ordering Information
PWM
1
6
4
√
I
Packagee
−
Operating
Temperatured
√
QEI
2
CCP Pins
6
c
PWM Pins
1M
Analog
Comparator(s)
3
I2C
0
to
30
SSI
8
UART(s)
Timersb
LM3S818-IQN50(T)
# of 10-Bit
Channels
GPIOsa
64
LM3S818-IQN50
Samples Per
Second
SRAM (KB)
Order Number
Flash (KB)
ADC
Speed (Clock
Frequency in MHz)
Features
QN
50
a. Minimum is number of pins dedicated to GPIO; additional pins are available if certain peripherals are not used. See
data sheet for details.
b. One timer available as RTC.
c. PWM motion control functionality can be achieved through dedicated motion control hardware (using the PWM pins)
or through the motion control features of the general-purpose timers (using the CCP pins). See data sheet for details.
d. I=Industrial (–40 to 85°C).
e. QN=48-pin RoHS-compliant LQFP.
Development Kit
The Luminary Micro Stellaris® Family Development Kit
provides the hardware and software tools that engineers
need to begin development quickly. Ask your Luminary Micro
distributor for part number DK-LM3S818. See the Luminary
Micro website for the latest tools available.
Tools to
begin
development
quickly
Company Information
Founded in 2004, Luminary Micro, Inc. designs, markets, and sells ARM Cortex-M3-based microcontrollers
(MCUs). Austin, Texas-based Luminary Micro is the lead partner for the Cortex-M3 processor, delivering the
world's first silicon implementation of the Cortex-M3 processor. Luminary Micro's introduction of the Stellaris®
family of products provides 32-bit performance for the same price as current 8- and 16-bit microcontroller
designs. With entry-level pricing at $1.00 for an ARM technology-based MCU, Luminary Micro's Stellaris
product line allows for standardization that eliminates future architectural upgrades or software tool changes.
Luminary Micro, Inc.
108 Wild Basin, Suite 350
Austin, TX 78746
Main: +1-512-279-8800
Fax: +1-512-279-8879
http://www.luminarymicro.com
May 4, 2007
395
Preliminary
Support Information
For support on Luminary Micro products, contact:
support@luminarymicro.com
+1-512-279-8800, ext. 3
396
May 4, 2007
Preliminary