LM3S812-EQN50-C2

TE X AS I NS TRUM E NTS - P RO DUCTION D ATA ® Stellaris LM3S812 Microcontroller D ATA SHE E T D S -LM3S 812- 1 5 8 5 2 . 2 7 4 3 S P M S 153I C o p yri g h t © 2 0 07-2014 Te xa s In stru me n ts In co rporated Copyright Copyright © 2007-2014 Texas Instruments Incorporated All rights reserved. Stellaris and StellarisWare® are registered trademarks of Texas Instruments Incorporated. ARM and Thumb are registered trademarks and Cortex is a trademark of ARM Limited. Other names and brands may be claimed as the property of others. PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. Texas Instruments Incorporated 108 Wild Basin, Suite 350 Austin, TX 78746 http://www.ti.com/stellaris http://www-k.ext.ti.com/sc/technical-support/product-information-centers.htm 2 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Table of Contents Revision History ............................................................................................................................. 20 About This Document .................................................................................................................... 24 Audience .............................................................................................................................................. About This Manual ................................................................................................................................ Related Documents ............................................................................................................................... Documentation Conventions .................................................................................................................. 24 24 24 25 1 Architectural Overview .......................................................................................... 27 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 1.4.9 Product Features .......................................................................................................... Target Applications ........................................................................................................ High-Level Block Diagram ............................................................................................. Functional Overview ...................................................................................................... ARM Cortex™-M3 ......................................................................................................... Motor Control Peripherals .............................................................................................. Analog Peripherals ........................................................................................................ Serial Communications Peripherals ................................................................................ System Peripherals ....................................................................................................... Memory Peripherals ...................................................................................................... Additional Features ....................................................................................................... Hardware Details .......................................................................................................... System Block Diagram .................................................................................................. 27 34 34 36 36 37 37 38 39 40 40 41 42 2 The Cortex-M3 Processor ...................................................................................... 43 2.1 2.2 2.2.1 2.2.2 2.2.3 2.2.4 2.3 2.3.1 2.3.2 2.3.3 2.3.4 2.3.5 2.3.6 2.4 2.4.1 2.4.2 2.4.3 2.4.4 2.4.5 2.4.6 2.4.7 2.5 2.5.1 2.5.2 Block Diagram .............................................................................................................. 44 Overview ...................................................................................................................... 45 System-Level Interface .................................................................................................. 45 Integrated Configurable Debug ...................................................................................... 45 Trace Port Interface Unit (TPIU) ..................................................................................... 46 Cortex-M3 System Component Details ........................................................................... 46 Programming Model ...................................................................................................... 47 Processor Mode and Privilege Levels for Software Execution ........................................... 47 Stacks .......................................................................................................................... 47 Register Map ................................................................................................................ 48 Register Descriptions .................................................................................................... 49 Exceptions and Interrupts .............................................................................................. 62 Data Types ................................................................................................................... 62 Memory Model .............................................................................................................. 62 Memory Regions, Types and Attributes ........................................................................... 63 Memory System Ordering of Memory Accesses .............................................................. 64 Behavior of Memory Accesses ....................................................................................... 64 Software Ordering of Memory Accesses ......................................................................... 65 Bit-Banding ................................................................................................................... 66 Data Storage ................................................................................................................ 68 Synchronization Primitives ............................................................................................. 69 Exception Model ........................................................................................................... 70 Exception States ........................................................................................................... 71 Exception Types ............................................................................................................ 71 July 14, 2014 3 Texas Instruments-Production Data Table of Contents 2.5.3 2.5.4 2.5.5 2.5.6 2.5.7 2.6 2.6.1 2.6.2 2.6.3 2.6.4 2.7 2.7.1 2.7.2 2.8 Exception Handlers ....................................................................................................... 74 Vector Table .................................................................................................................. 74 Exception Priorities ....................................................................................................... 75 Interrupt Priority Grouping .............................................................................................. 75 Exception Entry and Return ........................................................................................... 75 Fault Handling .............................................................................................................. 77 Fault Types ................................................................................................................... 78 Fault Escalation and Hard Faults .................................................................................... 78 Fault Status Registers and Fault Address Registers ........................................................ 79 Lockup ......................................................................................................................... 79 Power Management ...................................................................................................... 80 Entering Sleep Modes ................................................................................................... 80 Wake Up from Sleep Mode ............................................................................................ 80 Instruction Set Summary ............................................................................................... 81 3 Cortex-M3 Peripherals ........................................................................................... 85 3.1 3.1.1 3.1.2 3.1.3 3.1.4 3.2 3.3 3.4 3.5 3.6 Functional Description ................................................................................................... 85 System Timer (SysTick) ................................................................................................. 85 Nested Vectored Interrupt Controller (NVIC) .................................................................... 86 System Control Block (SCB) .......................................................................................... 88 Memory Protection Unit (MPU) ....................................................................................... 88 Register Map ................................................................................................................ 93 System Timer (SysTick) Register Descriptions ................................................................ 94 NVIC Register Descriptions ........................................................................................... 98 System Control Block (SCB) Register Descriptions ........................................................ 106 Memory Protection Unit (MPU) Register Descriptions .................................................... 133 4 JTAG Interface ...................................................................................................... 143 4.1 4.2 4.3 4.3.1 4.3.2 4.3.3 4.3.4 4.4 4.5 4.5.1 4.5.2 Block Diagram ............................................................................................................ Signal Description ....................................................................................................... Functional Description ................................................................................................. JTAG Interface Pins ..................................................................................................... JTAG TAP Controller ................................................................................................... Shift Registers ............................................................................................................ Operational Considerations .......................................................................................... Initialization and Configuration ..................................................................................... Register Descriptions .................................................................................................. Instruction Register (IR) ............................................................................................... Data Registers ............................................................................................................ 144 144 145 145 146 147 147 149 149 149 151 5 System Control ..................................................................................................... 153 5.1 5.2 5.2.1 5.2.2 5.2.3 5.2.4 5.2.5 5.3 5.4 5.5 Signal Description ....................................................................................................... Functional Description ................................................................................................. Device Identification .................................................................................................... Reset Control .............................................................................................................. Power Control ............................................................................................................. Clock Control .............................................................................................................. System Control ........................................................................................................... Initialization and Configuration ..................................................................................... Register Map .............................................................................................................. Register Descriptions .................................................................................................. 4 153 153 153 153 158 158 161 162 163 164 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 6 Internal Memory ................................................................................................... 212 6.1 6.2 6.2.1 6.2.2 6.3 6.3.1 6.3.2 6.4 6.5 6.6 Block Diagram ............................................................................................................ 212 Functional Description ................................................................................................. 212 SRAM Memory ............................................................................................................ 212 Flash Memory ............................................................................................................. 213 Flash Memory Initialization and Configuration ............................................................... 216 Changing Flash Protection Bits .................................................................................... 216 Flash Programming ..................................................................................................... 217 Register Map .............................................................................................................. 218 Flash Register Descriptions (Flash Control Offset) ......................................................... 218 Flash Register Descriptions (System Control Offset) ...................................................... 226 7 General-Purpose Input/Outputs (GPIOs) ........................................................... 230 7.1 7.2 7.3 7.3.1 7.3.2 7.3.3 7.3.4 7.3.5 7.4 7.5 7.6 Block Diagram ............................................................................................................ 231 Signal Description ....................................................................................................... 231 Functional Description ................................................................................................. 234 Data Control ............................................................................................................... 235 Interrupt Control .......................................................................................................... 236 Mode Control .............................................................................................................. 237 Pad Control ................................................................................................................. 237 Identification ............................................................................................................... 237 Initialization and Configuration ..................................................................................... 237 Register Map .............................................................................................................. 238 Register Descriptions .................................................................................................. 240 8 General-Purpose Timers ...................................................................................... 272 8.1 8.2 8.3 8.3.1 8.3.2 8.3.3 8.4 8.4.1 8.4.2 8.4.3 8.4.4 8.4.5 8.4.6 8.5 8.6 Block Diagram ............................................................................................................ Signal Description ....................................................................................................... Functional Description ................................................................................................. GPTM Reset Conditions .............................................................................................. 32-Bit Timer Operating Modes ...................................................................................... 16-Bit Timer Operating Modes ...................................................................................... Initialization and Configuration ..................................................................................... 32-Bit One-Shot/Periodic Timer Mode ........................................................................... 32-Bit Real-Time Clock (RTC) Mode ............................................................................. 16-Bit One-Shot/Periodic Timer Mode ........................................................................... 16-Bit Input Edge Count Mode ..................................................................................... 16-Bit Input Edge Timing Mode .................................................................................... 16-Bit PWM Mode ....................................................................................................... Register Map .............................................................................................................. Register Descriptions .................................................................................................. 273 273 274 274 274 276 279 279 280 280 281 281 282 282 283 9 Watchdog Timer ................................................................................................... 308 9.1 9.2 9.3 9.4 9.5 Block Diagram ............................................................................................................ Functional Description ................................................................................................. Initialization and Configuration ..................................................................................... Register Map .............................................................................................................. Register Descriptions .................................................................................................. 309 309 310 310 311 10 Analog-to-Digital Converter (ADC) ..................................................................... 332 10.1 Block Diagram ............................................................................................................ 332 July 14, 2014 5 Texas Instruments-Production Data Table of Contents 10.2 10.3 10.3.1 10.3.2 10.3.3 10.3.4 10.3.5 10.3.6 10.3.7 10.4 10.4.1 10.4.2 10.5 10.6 Signal Description ....................................................................................................... 333 Functional Description ................................................................................................. 333 Sample Sequencers .................................................................................................... 334 Module Control ............................................................................................................ 334 Hardware Sample Averaging Circuit ............................................................................. 335 Analog-to-Digital Converter .......................................................................................... 335 Differential Sampling ................................................................................................... 335 Test Modes ................................................................................................................. 338 Internal Temperature Sensor ........................................................................................ 338 Initialization and Configuration ..................................................................................... 339 Module Initialization ..................................................................................................... 339 Sample Sequencer Configuration ................................................................................. 339 Register Map .............................................................................................................. 340 Register Descriptions .................................................................................................. 341 11 Universal Asynchronous Receivers/Transmitters (UARTs) ............................. 368 11.1 11.2 11.3 11.3.1 11.3.2 11.3.3 11.3.4 11.3.5 11.3.6 11.4 11.5 11.6 Block Diagram ............................................................................................................ Signal Description ....................................................................................................... Functional Description ................................................................................................. Transmit/Receive Logic ............................................................................................... Baud-Rate Generation ................................................................................................. Data Transmission ...................................................................................................... FIFO Operation ........................................................................................................... Interrupts .................................................................................................................... Loopback Operation .................................................................................................... Initialization and Configuration ..................................................................................... Register Map .............................................................................................................. Register Descriptions .................................................................................................. 369 369 370 370 370 371 371 372 373 373 374 375 12 Synchronous Serial Interface (SSI) .................................................................... 408 12.1 12.2 12.3 12.3.1 12.3.2 12.3.3 12.3.4 12.4 12.5 12.6 Block Diagram ............................................................................................................ Signal Description ....................................................................................................... Functional Description ................................................................................................. Bit Rate Generation ..................................................................................................... FIFO Operation ........................................................................................................... Interrupts .................................................................................................................... Frame Formats ........................................................................................................... Initialization and Configuration ..................................................................................... Register Map .............................................................................................................. Register Descriptions .................................................................................................. 13 Inter-Integrated Circuit (I2C) Interface ................................................................ 446 13.1 13.2 13.3 13.3.1 13.3.2 13.3.3 13.3.4 13.3.5 13.4 Block Diagram ............................................................................................................ Signal Description ....................................................................................................... Functional Description ................................................................................................. I2C Bus Functional Overview ........................................................................................ Available Speed Modes ............................................................................................... Interrupts .................................................................................................................... Loopback Operation .................................................................................................... Command Sequence Flow Charts ................................................................................ Initialization and Configuration ..................................................................................... 6 408 408 409 409 409 410 410 418 419 420 447 447 447 448 450 451 451 451 459 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 13.5 13.6 13.7 Register Map .............................................................................................................. 460 Register Descriptions (I2C Master) ............................................................................... 461 Register Descriptions (I2C Slave) ................................................................................. 474 14 Analog Comparator .............................................................................................. 483 14.1 14.2 14.3 14.3.1 14.4 14.5 14.6 Block Diagram ............................................................................................................ Signal Description ....................................................................................................... Functional Description ................................................................................................. Internal Reference Programming .................................................................................. Initialization and Configuration ..................................................................................... Register Map .............................................................................................................. Register Descriptions .................................................................................................. 483 483 484 485 486 486 487 15 Pulse Width Modulator (PWM) ............................................................................ 495 15.1 15.2 15.3 15.3.1 15.3.2 15.3.3 15.3.4 15.3.5 15.3.6 15.3.7 15.3.8 15.4 15.5 15.6 Block Diagram ............................................................................................................ Signal Description ....................................................................................................... Functional Description ................................................................................................. PWM Timer ................................................................................................................. PWM Comparators ...................................................................................................... PWM Signal Generator ................................................................................................ Dead-Band Generator ................................................................................................. Interrupt/ADC-Trigger Selector ..................................................................................... Synchronization Methods ............................................................................................ Fault Conditions .......................................................................................................... Output Control Block ................................................................................................... Initialization and Configuration ..................................................................................... Register Map .............................................................................................................. Register Descriptions .................................................................................................. 16 Pin Diagram .......................................................................................................... 533 496 497 497 497 498 499 500 500 500 500 501 501 502 503 17 Signal Tables ........................................................................................................ 534 17.1 17.2 17.3 17.4 17.5 Signals by Pin Number ................................................................................................ 534 Signals by Signal Name ............................................................................................... 536 Signals by Function, Except for GPIO ........................................................................... 538 GPIO Pins and Alternate Functions .............................................................................. 539 Connections for Unused Signals ................................................................................... 540 18 Operating Characteristics ................................................................................... 542 19 Electrical Characteristics .................................................................................... 543 19.1 19.1.1 19.1.2 19.1.3 19.1.4 19.1.5 19.1.6 19.2 19.2.1 19.2.2 19.2.3 19.2.4 DC Characteristics ...................................................................................................... 543 Maximum Ratings ....................................................................................................... 543 Recommended DC Operating Conditions ...................................................................... 543 On-Chip Low Drop-Out (LDO) Regulator Characteristics ................................................ 544 GPIO Module Characteristics ....................................................................................... 544 Power Specifications ................................................................................................... 544 Flash Memory Characteristics ...................................................................................... 545 AC Characteristics ....................................................................................................... 545 Load Conditions .......................................................................................................... 545 Clocks ........................................................................................................................ 546 JTAG and Boundary Scan ............................................................................................ 546 Reset ......................................................................................................................... 548 July 14, 2014 7 Texas Instruments-Production Data Table of Contents 19.2.5 Sleep Modes ............................................................................................................... 19.2.6 General-Purpose I/O (GPIO) ........................................................................................ 19.2.7 Analog-to-Digital Converter .......................................................................................... 19.2.8 Synchronous Serial Interface (SSI) ............................................................................... 19.2.9 Inter-Integrated Circuit (I2C) Interface ........................................................................... 19.2.10 Analog Comparator ..................................................................................................... 550 550 551 552 554 555 A Serial Flash Loader .............................................................................................. 556 A.1 A.2 A.2.1 A.2.2 A.3 A.3.1 A.3.2 A.3.3 A.4 A.4.1 A.4.2 A.4.3 A.4.4 A.4.5 A.4.6 Serial Flash Loader ..................................................................................................... Interfaces ................................................................................................................... UART ......................................................................................................................... SSI ............................................................................................................................. Packet Handling .......................................................................................................... Packet Format ............................................................................................................ Sending Packets ......................................................................................................... Receiving Packets ....................................................................................................... Commands ................................................................................................................. COMMAND_PING (0X20) ............................................................................................ COMMAND_GET_STATUS (0x23) ............................................................................... COMMAND_DOWNLOAD (0x21) ................................................................................. COMMAND_SEND_DATA (0x24) ................................................................................. COMMAND_RUN (0x22) ............................................................................................. COMMAND_RESET (0x25) ......................................................................................... B Register Quick Reference ................................................................................... 561 556 556 556 556 557 557 557 557 558 558 558 558 559 559 559 C Ordering and Contact Information ..................................................................... 579 C.1 C.2 C.3 C.4 Ordering Information .................................................................................................... 579 Part Markings .............................................................................................................. 579 Kits ............................................................................................................................. 579 Support Information ..................................................................................................... 580 D Package Information ............................................................................................ 581 D.1 D.1.1 D.1.2 D.1.3 48-Pin LQFP Package ................................................................................................. Package Dimensions ................................................................................................... Tray Dimensions ......................................................................................................... Tape and Reel Dimensions .......................................................................................... 8 581 581 583 585 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller List of Figures Figure 1-1. Figure 1-2. Figure 2-1. Figure 2-2. Figure 2-3. Figure 2-4. Figure 2-5. Figure 2-6. Figure 2-7. Figure 3-1. Figure 4-1. Figure 4-2. Figure 4-3. Figure 4-4. Figure 4-5. Figure 5-1. Figure 5-2. Figure 5-3. Figure 5-4. Figure 6-1. Figure 7-1. Figure 7-2. Figure 7-3. Figure 7-4. Figure 8-1. Figure 8-2. Figure 8-3. Figure 8-4. Figure 9-1. Figure 10-1. Figure 10-2. Figure 10-3. Figure 10-4. Figure 10-5. Figure 11-1. Figure 11-2. Figure 12-1. Figure 12-2. Figure 12-3. Figure 12-4. Figure 12-5. Figure 12-6. Figure 12-7. Figure 12-8. Figure 12-9. Figure 12-10. Stellaris LM3S812 Microcontroller High-Level Block Diagram ................................. 35 LM3S812 Controller System-Level Block Diagram ................................................. 42 CPU Block Diagram ............................................................................................. 45 TPIU Block Diagram ............................................................................................ 46 Cortex-M3 Register Set ........................................................................................ 48 Bit-Band Mapping ................................................................................................ 68 Data Storage ....................................................................................................... 69 Vector Table ........................................................................................................ 74 Exception Stack Frame ........................................................................................ 76 SRD Use Example ............................................................................................... 91 JTAG Module Block Diagram .............................................................................. 144 Test Access Port State Machine ......................................................................... 147 IDCODE Register Format ................................................................................... 151 BYPASS Register Format ................................................................................... 152 Boundary Scan Register Format ......................................................................... 152 Basic RST Configuration .................................................................................... 155 External Circuitry to Extend Power-On Reset ....................................................... 155 Reset Circuit Controlled by Switch ...................................................................... 156 Main Clock Tree ................................................................................................ 159 Flash Block Diagram .......................................................................................... 212 GPIO Module Block Diagram .............................................................................. 231 GPIO Port Block Diagram ................................................................................... 235 GPIODATA Write Example ................................................................................. 236 GPIODATA Read Example ................................................................................. 236 GPTM Module Block Diagram ............................................................................ 273 16-Bit Input Edge Count Mode Example .............................................................. 277 16-Bit Input Edge Time Mode Example ............................................................... 278 16-Bit PWM Mode Example ................................................................................ 279 WDT Module Block Diagram .............................................................................. 309 ADC Module Block Diagram ............................................................................... 333 Differential Sampling Range, VIN_ODD = 1.5 V ...................................................... 337 Differential Sampling Range, VIN_ODD = 0.75 V .................................................... 337 Differential Sampling Range, VIN_ODD = 2.25 V .................................................... 338 Internal Temperature Sensor Characteristic ......................................................... 339 UART Module Block Diagram ............................................................................. 369 UART Character Frame ..................................................................................... 370 SSI Module Block Diagram ................................................................................. 408 TI Synchronous Serial Frame Format (Single Transfer) ........................................ 411 TI Synchronous Serial Frame Format (Continuous Transfer) ................................ 412 Freescale SPI Format (Single Transfer) with SPO=0 and SPH=0 .......................... 412 Freescale SPI Format (Continuous Transfer) with SPO=0 and SPH=0 .................. 413 Freescale SPI Frame Format with SPO=0 and SPH=1 ......................................... 414 Freescale SPI Frame Format (Single Transfer) with SPO=1 and SPH=0 ............... 414 Freescale SPI Frame Format (Continuous Transfer) with SPO=1 and SPH=0 ........ 415 Freescale SPI Frame Format with SPO=1 and SPH=1 ......................................... 416 MICROWIRE Frame Format (Single Frame) ........................................................ 416 July 14, 2014 9 Texas Instruments-Production Data Table of Contents Figure 12-11. Figure 12-12. 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 13-13. 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 15-6. Figure 16-1. Figure 19-1. Figure 19-2. Figure 19-3. Figure 19-4. Figure 19-5. Figure 19-6. Figure 19-7. Figure 19-8. Figure 19-9. Figure 19-10. Figure 19-11. Figure 19-12. MICROWIRE Frame Format (Continuous Transfer) ............................................. 417 MICROWIRE Frame Format, SSIFss Input Setup and Hold Requirements ............ 418 I2C Block Diagram ............................................................................................. 447 I2C Bus Configuration ........................................................................................ 448 START and STOP Conditions ............................................................................. 448 Complete Data Transfer with a 7-Bit Address ....................................................... 449 R/S Bit in First Byte ............................................................................................ 449 Data Validity During Bit Transfer on the I2C Bus ................................................... 449 Master Single SEND .......................................................................................... 453 Master Single RECEIVE ..................................................................................... 454 Master Burst SEND ........................................................................................... 455 Master Burst RECEIVE ...................................................................................... 456 Master Burst RECEIVE after Burst SEND ............................................................ 457 Master Burst SEND after Burst RECEIVE ............................................................ 458 Slave Command Sequence ................................................................................ 459 Analog Comparator Module Block Diagram ......................................................... 483 Structure of Comparator Unit .............................................................................. 484 Comparator Internal Reference Structure ............................................................ 485 PWM Unit Diagram ............................................................................................ 496 PWM Module Block Diagram .............................................................................. 497 PWM Count-Down Mode .................................................................................... 498 PWM Count-Up/Down Mode .............................................................................. 499 PWM Generation Example In Count-Up/Down Mode ........................................... 499 PWM Dead-Band Generator ............................................................................... 500 48-Pin QFP Package Pin Diagram ...................................................................... 533 Load Conditions ................................................................................................ 546 JTAG Test Clock Input Timing ............................................................................. 547 JTAG Test Access Port (TAP) Timing .................................................................. 548 JTAG TRST Timing ............................................................................................ 548 External Reset Timing (RST) .............................................................................. 549 Power-On Reset Timing ..................................................................................... 549 Brown-Out Reset Timing .................................................................................... 549 Software Reset Timing ....................................................................................... 550 Watchdog Reset Timing ..................................................................................... 550 LDO Reset Timing ............................................................................................. 550 ADC Input Equivalency Diagram ......................................................................... 552 SSI Timing for TI Frame Format (FRF=01), Single Transfer Timing Measurement .................................................................................................... 553 Figure 19-13. SSI Timing for MICROWIRE Frame Format (FRF=10), Single Transfer ................. 553 Figure 19-14. SSI Timing for SPI Frame Format (FRF=00), with SPH=1 ..................................... 554 Figure 19-15. I2C Timing ......................................................................................................... 555 Figure D-1. Stellaris LM3S812 48-Pin LQFP Package ........................................................... 581 Figure D-2. 48-Pin LQFP Tray Dimensions ........................................................................... 583 Figure D-3. 48-Pin LQFP Tape and Reel Dimensions ............................................................. 585 10 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller List of Tables Table 1. Table 2. Table 2-1. Table 2-2. Table 2-3. Table 2-4. Table 2-5. Table 2-6. Table 2-7. Table 2-8. Table 2-9. Table 2-10. Table 2-11. Table 2-12. Table 2-13. Table 3-1. Table 3-2. Table 3-3. Table 3-4. Table 3-5. Table 3-6. Table 3-7. Table 3-8. Table 3-9. Table 4-1. Table 4-2. Table 4-3. Table 5-1. Table 5-2. Table 5-3. Table 5-4. Table 5-5. Table 5-6. Table 6-1. Table 6-2. Table 7-1. Table 7-2. Table 7-3. Table 7-4. Table 7-5. Table 7-6. Table 8-1. Table 8-2. Table 8-3. Table 8-4. Table 9-1. Revision History .................................................................................................. 20 Documentation Conventions ................................................................................ 25 Summary of Processor Mode, Privilege Level, and Stack Use ................................ 48 Processor Register Map ....................................................................................... 49 PSR Register Combinations ................................................................................. 54 Memory Map ....................................................................................................... 62 Memory Access Behavior ..................................................................................... 64 SRAM Memory Bit-Banding Regions .................................................................... 66 Peripheral Memory Bit-Banding Regions ............................................................... 66 Exception Types .................................................................................................. 72 Interrupts ............................................................................................................ 73 Exception Return Behavior ................................................................................... 77 Faults ................................................................................................................. 78 Fault Status and Fault Address Registers .............................................................. 79 Cortex-M3 Instruction Summary ........................................................................... 81 Core Peripheral Register Regions ......................................................................... 85 Memory Attributes Summary ................................................................................ 88 TEX, S, C, and B Bit Field Encoding ..................................................................... 91 Cache Policy for Memory Attribute Encoding ......................................................... 92 AP Bit Field Encoding .......................................................................................... 92 Memory Region Attributes for Stellaris Microcontrollers .......................................... 92 Peripherals Register Map ..................................................................................... 93 Interrupt Priority Levels ...................................................................................... 112 Example SIZE Field Values ................................................................................ 140 JTAG_SWD_SWO Signals (48QFP) ................................................................... 144 JTAG Port Pins Reset State ............................................................................... 145 JTAG Instruction Register Commands ................................................................. 149 System Control & Clocks Signals (48QFP) .......................................................... 153 Reset Sources ................................................................................................... 154 Clock Source Options ........................................................................................ 158 Possible System Clock Frequencies Using the SYSDIV Field ............................... 159 System Control Register Map ............................................................................. 163 PLL Mode Control .............................................................................................. 176 Flash Protection Policy Combinations ................................................................. 213 Flash Register Map ............................................................................................ 218 GPIO Pins With Non-Zero Reset Values .............................................................. 232 GPIO Pins and Alternate Functions (48QFP) ....................................................... 232 GPIO Signals (48QFP) ....................................................................................... 233 GPIO Pad Configuration Examples ..................................................................... 238 GPIO Interrupt Configuration Example ................................................................ 238 GPIO Register Map ........................................................................................... 239 Available CCP Pins ............................................................................................ 273 General-Purpose Timers Signals (48QFP) ........................................................... 274 16-Bit Timer With Prescaler Configurations ......................................................... 276 Timers Register Map .......................................................................................... 283 Watchdog Timer Register Map ............................................................................ 310 July 14, 2014 11 Texas Instruments-Production Data Table of Contents Table 10-1. Table 10-2. Table 10-3. Table 10-4. Table 11-1. Table 11-2. Table 12-1. Table 12-2. Table 13-1. Table 13-2. Table 13-3. Table 13-4. Table 14-1. Table 14-2. Table 14-3. Table 14-4. Table 15-1. Table 15-2. Table 17-1. Table 17-2. Table 17-3. Table 17-4. Table 17-5. Table 18-1. Table 18-2. Table 18-3. Table 19-1. Table 19-2. Table 19-3. Table 19-4. Table 19-5. Table 19-6. Table 19-7. Table 19-8. Table 19-9. Table 19-10. Table 19-11. Table 19-12. Table 19-13. Table 19-14. Table 19-15. Table 19-16. Table 19-17. Table 19-18. Table 19-19. ADC Signals (48QFP) ........................................................................................ 333 Samples and FIFO Depth of Sequencers ............................................................ 334 Differential Sampling Pairs ................................................................................. 336 ADC Register Map ............................................................................................. 340 UART Signals (48QFP) ...................................................................................... 369 UART Register Map ........................................................................................... 374 SSI Signals (48QFP) .......................................................................................... 409 SSI Register Map .............................................................................................. 419 I2C Signals (48QFP) .......................................................................................... 447 Examples of I2C Master Timer Period versus Speed Mode ................................... 450 Inter-Integrated Circuit (I2C) Interface Register Map ............................................. 460 Write Field Decoding for I2CMCS[3:0] Field (Sheet 1 of 3) .................................... 465 Analog Comparators Signals (48QFP) ................................................................ 484 Comparator 0 Operating Modes .......................................................................... 485 Internal Reference Voltage and ACREFCTL Field Values ..................................... 485 Analog Comparators Register Map ..................................................................... 487 PWM Signals (48QFP) ....................................................................................... 497 PWM Register Map ............................................................................................ 502 Signals by Pin Number ....................................................................................... 534 Signals by Signal Name ..................................................................................... 536 Signals by Function, Except for GPIO ................................................................. 538 GPIO Pins and Alternate Functions ..................................................................... 539 Connections for Unused Signals ......................................................................... 541 Temperature Characteristics ............................................................................... 542 Thermal Characteristics ..................................................................................... 542 ESD Absolute Maximum Ratings ........................................................................ 542 Maximum Ratings .............................................................................................. 543 Recommended DC Operating Conditions ............................................................ 543 LDO Regulator Characteristics ........................................................................... 544 GPIO Module DC Characteristics ........................................................................ 544 Detailed Power Specifications ............................................................................ 545 Flash Memory Characteristics ............................................................................ 545 Phase Locked Loop (PLL) Characteristics ........................................................... 546 Clock Characteristics ......................................................................................... 546 System Clock Characteristics with ADC Operation ............................................... 546 JTAG Characteristics ......................................................................................... 546 Reset Characteristics ......................................................................................... 548 Sleep Modes AC Characteristics ......................................................................... 550 GPIO Characteristics ......................................................................................... 551 ADC Characteristics ........................................................................................... 551 ADC Module Internal Reference Characteristics .................................................. 552 SSI Characteristics ............................................................................................ 552 I2C Characteristics ............................................................................................. 554 Analog Comparator Characteristics ..................................................................... 555 Analog Comparator Voltage Reference Characteristics ........................................ 555 12 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller List of Registers The Cortex-M3 Processor ............................................................................................................. 43 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: Cortex General-Purpose Register 0 (R0) ........................................................................... 50 Cortex General-Purpose Register 1 (R1) ........................................................................... 50 Cortex General-Purpose Register 2 (R2) ........................................................................... 50 Cortex General-Purpose Register 3 (R3) ........................................................................... 50 Cortex General-Purpose Register 4 (R4) ........................................................................... 50 Cortex General-Purpose Register 5 (R5) ........................................................................... 50 Cortex General-Purpose Register 6 (R6) ........................................................................... 50 Cortex General-Purpose Register 7 (R7) ........................................................................... 50 Cortex General-Purpose Register 8 (R8) ........................................................................... 50 Cortex General-Purpose Register 9 (R9) ........................................................................... 50 Cortex General-Purpose Register 10 (R10) ....................................................................... 50 Cortex General-Purpose Register 11 (R11) ........................................................................ 50 Cortex General-Purpose Register 12 (R12) ....................................................................... 50 Stack Pointer (SP) ........................................................................................................... 51 Link Register (LR) ............................................................................................................ 52 Program Counter (PC) ..................................................................................................... 53 Program Status Register (PSR) ........................................................................................ 54 Priority Mask Register (PRIMASK) .................................................................................... 58 Fault Mask Register (FAULTMASK) .................................................................................. 59 Base Priority Mask Register (BASEPRI) ............................................................................ 60 Control Register (CONTROL) ........................................................................................... 61 Cortex-M3 Peripherals ................................................................................................................... 85 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: SysTick Control and Status Register (STCTRL), offset 0x010 ............................................. 95 SysTick Reload Value Register (STRELOAD), offset 0x014 ................................................ 97 SysTick Current Value Register (STCURRENT), offset 0x018 ............................................. 98 Interrupt 0-29 Set Enable (EN0), offset 0x100 .................................................................... 99 Interrupt 0-29 Clear Enable (DIS0), offset 0x180 .............................................................. 100 Interrupt 0-29 Set Pending (PEND0), offset 0x200 ........................................................... 101 Interrupt 0-29 Clear Pending (UNPEND0), offset 0x280 ................................................... 102 Interrupt 0-29 Active Bit (ACTIVE0), offset 0x300 ............................................................. 103 Interrupt 0-3 Priority (PRI0), offset 0x400 ......................................................................... 104 Interrupt 4-7 Priority (PRI1), offset 0x404 ......................................................................... 104 Interrupt 8-11 Priority (PRI2), offset 0x408 ....................................................................... 104 Interrupt 12-15 Priority (PRI3), offset 0x40C .................................................................... 104 Interrupt 16-19 Priority (PRI4), offset 0x410 ..................................................................... 104 Interrupt 20-23 Priority (PRI5), offset 0x414 ..................................................................... 104 Interrupt 24-27 Priority (PRI6), offset 0x418 ..................................................................... 104 Interrupt 28-29 Priority (PRI7), offset 0x41C .................................................................... 104 Software Trigger Interrupt (SWTRIG), offset 0xF00 .......................................................... 106 CPU ID Base (CPUID), offset 0xD00 ............................................................................... 107 Interrupt Control and State (INTCTRL), offset 0xD04 ........................................................ 108 Vector Table Offset (VTABLE), offset 0xD08 .................................................................... 111 Application Interrupt and Reset Control (APINT), offset 0xD0C ......................................... 112 System Control (SYSCTRL), offset 0xD10 ....................................................................... 114 July 14, 2014 13 Texas Instruments-Production Data Table of Contents Register 23: Register 24: Register 25: Register 26: Register 27: Register 28: Register 29: Register 30: Register 31: Register 32: Register 33: Register 34: Register 35: Register 36: Register 37: Register 38: Register 39: Register 40: Register 41: Register 42: Configuration and Control (CFGCTRL), offset 0xD14 ....................................................... 116 System Handler Priority 1 (SYSPRI1), offset 0xD18 ......................................................... 118 System Handler Priority 2 (SYSPRI2), offset 0xD1C ........................................................ 119 System Handler Priority 3 (SYSPRI3), offset 0xD20 ......................................................... 120 System Handler Control and State (SYSHNDCTRL), offset 0xD24 .................................... 121 Configurable Fault Status (FAULTSTAT), offset 0xD28 ..................................................... 125 Hard Fault Status (HFAULTSTAT), offset 0xD2C .............................................................. 131 Memory Management Fault Address (MMADDR), offset 0xD34 ........................................ 132 Bus Fault Address (FAULTADDR), offset 0xD38 .............................................................. 133 MPU Type (MPUTYPE), offset 0xD90 ............................................................................. 134 MPU Control (MPUCTRL), offset 0xD94 .......................................................................... 135 MPU Region Number (MPUNUMBER), offset 0xD98 ....................................................... 137 MPU Region Base Address (MPUBASE), offset 0xD9C ................................................... 138 MPU Region Base Address Alias 1 (MPUBASE1), offset 0xDA4 ....................................... 138 MPU Region Base Address Alias 2 (MPUBASE2), offset 0xDAC ...................................... 138 MPU Region Base Address Alias 3 (MPUBASE3), offset 0xDB4 ....................................... 138 MPU Region Attribute and Size (MPUATTR), offset 0xDA0 ............................................... 140 MPU Region Attribute and Size Alias 1 (MPUATTR1), offset 0xDA8 .................................. 140 MPU Region Attribute and Size Alias 2 (MPUATTR2), offset 0xDB0 .................................. 140 MPU Region Attribute and Size Alias 3 (MPUATTR3), offset 0xDB8 .................................. 140 System Control ............................................................................................................................ 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: Register 16: Register 17: Register 18: Register 19: Register 20: Register 21: Register 22: Register 23: Register 24: Register 25: Register 26: Register 27: Device Identification 0 (DID0), offset 0x000 ..................................................................... 165 Power-On and Brown-Out Reset Control (PBORCTL), offset 0x030 .................................. 167 LDO Power Control (LDOPCTL), offset 0x034 ................................................................. 168 Raw Interrupt Status (RIS), offset 0x050 .......................................................................... 169 Interrupt Mask Control (IMC), offset 0x054 ...................................................................... 170 Masked Interrupt Status and Clear (MISC), offset 0x058 .................................................. 171 Reset Cause (RESC), offset 0x05C ................................................................................ 172 Run-Mode Clock Configuration (RCC), offset 0x060 ......................................................... 173 XTAL to PLL Translation (PLLCFG), offset 0x064 ............................................................. 177 Deep Sleep Clock Configuration (DSLPCLKCFG), offset 0x144 ........................................ 178 Clock Verification Clear (CLKVCLR), offset 0x150 ............................................................ 179 Allow Unregulated LDO to Reset the Part (LDOARST), offset 0x160 ................................. 180 Device Identification 1 (DID1), offset 0x004 ..................................................................... 181 Device Capabilities 0 (DC0), offset 0x008 ........................................................................ 183 Device Capabilities 1 (DC1), offset 0x010 ........................................................................ 184 Device Capabilities 2 (DC2), offset 0x014 ........................................................................ 186 Device Capabilities 3 (DC3), offset 0x018 ........................................................................ 188 Device Capabilities 4 (DC4), offset 0x01C ....................................................................... 190 Run Mode Clock Gating Control Register 0 (RCGC0), offset 0x100 ................................... 191 Sleep Mode Clock Gating Control Register 0 (SCGC0), offset 0x110 ................................. 193 Deep Sleep Mode Clock Gating Control Register 0 (DCGC0), offset 0x120 ....................... 195 Run Mode Clock Gating Control Register 1 (RCGC1), offset 0x104 ................................... 197 Sleep Mode Clock Gating Control Register 1 (SCGC1), offset 0x114 ................................. 199 Deep Sleep Mode Clock Gating Control Register 1 (DCGC1), offset 0x124 ....................... 201 Run Mode Clock Gating Control Register 2 (RCGC2), offset 0x108 ................................... 203 Sleep Mode Clock Gating Control Register 2 (SCGC2), offset 0x118 ................................. 204 Deep Sleep Mode Clock Gating Control Register 2 (DCGC2), offset 0x128 ....................... 206 14 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 28: Register 29: Register 30: Software Reset Control 0 (SRCR0), offset 0x040 ............................................................. 208 Software Reset Control 1 (SRCR1), offset 0x044 ............................................................. 209 Software Reset Control 2 (SRCR2), offset 0x048 ............................................................. 211 Internal Memory ........................................................................................................................... 212 Register 1: Register 2: Register 3: Register 4: Register 5: Register 6: Register 7: Register 8: Register 9: Flash Memory Address (FMA), offset 0x000 .................................................................... 219 Flash Memory Data (FMD), offset 0x004 ......................................................................... 220 Flash Memory Control (FMC), offset 0x008 ..................................................................... 221 Flash Controller Raw Interrupt Status (FCRIS), offset 0x00C ............................................ 223 Flash Controller Interrupt Mask (FCIM), offset 0x010 ........................................................ 224 Flash Controller Masked Interrupt Status and Clear (FCMISC), offset 0x014 ..................... 225 USec Reload (USECRL), offset 0x140 ............................................................................ 227 Flash Memory Protection Read Enable (FMPRE), offset 0x130 ......................................... 228 Flash Memory Protection Program Enable (FMPPE), offset 0x134 .................................... 229 General-Purpose Input/Outputs (GPIOs) ................................................................................... 230 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 ............................................................................ 241 GPIO Direction (GPIODIR), offset 0x400 ......................................................................... 242 GPIO Interrupt Sense (GPIOIS), offset 0x404 .................................................................. 243 GPIO Interrupt Both Edges (GPIOIBE), offset 0x408 ........................................................ 244 GPIO Interrupt Event (GPIOIEV), offset 0x40C ................................................................ 245 GPIO Interrupt Mask (GPIOIM), offset 0x410 ................................................................... 246 GPIO Raw Interrupt Status (GPIORIS), offset 0x414 ........................................................ 247 GPIO Masked Interrupt Status (GPIOMIS), offset 0x418 ................................................... 248 GPIO Interrupt Clear (GPIOICR), offset 0x41C ................................................................ 249 GPIO Alternate Function Select (GPIOAFSEL), offset 0x420 ............................................ 250 GPIO 2-mA Drive Select (GPIODR2R), offset 0x500 ........................................................ 252 GPIO 4-mA Drive Select (GPIODR4R), offset 0x504 ........................................................ 253 GPIO 8-mA Drive Select (GPIODR8R), offset 0x508 ........................................................ 254 GPIO Open Drain Select (GPIOODR), offset 0x50C ......................................................... 255 GPIO Pull-Up Select (GPIOPUR), offset 0x510 ................................................................ 256 GPIO Pull-Down Select (GPIOPDR), offset 0x514 ........................................................... 257 GPIO Slew Rate Control Select (GPIOSLR), offset 0x518 ................................................ 258 GPIO Digital Enable (GPIODEN), offset 0x51C ................................................................ 259 GPIO Peripheral Identification 4 (GPIOPeriphID4), offset 0xFD0 ....................................... 260 GPIO Peripheral Identification 5 (GPIOPeriphID5), offset 0xFD4 ....................................... 261 GPIO Peripheral Identification 6 (GPIOPeriphID6), offset 0xFD8 ....................................... 262 GPIO Peripheral Identification 7 (GPIOPeriphID7), offset 0xFDC ...................................... 263 GPIO Peripheral Identification 0 (GPIOPeriphID0), offset 0xFE0 ....................................... 264 GPIO Peripheral Identification 1 (GPIOPeriphID1), offset 0xFE4 ....................................... 265 GPIO Peripheral Identification 2 (GPIOPeriphID2), offset 0xFE8 ....................................... 266 GPIO Peripheral Identification 3 (GPIOPeriphID3), offset 0xFEC ...................................... 267 GPIO PrimeCell Identification 0 (GPIOPCellID0), offset 0xFF0 .......................................... 268 GPIO PrimeCell Identification 1 (GPIOPCellID1), offset 0xFF4 .......................................... 269 GPIO PrimeCell Identification 2 (GPIOPCellID2), offset 0xFF8 .......................................... 270 GPIO PrimeCell Identification 3 (GPIOPCellID3), offset 0xFFC ......................................... 271 General-Purpose Timers ............................................................................................................. 272 Register 1: Register 2: Register 3: GPTM Configuration (GPTMCFG), offset 0x000 .............................................................. 284 GPTM TimerA Mode (GPTMTAMR), offset 0x004 ............................................................ 285 GPTM TimerB Mode (GPTMTBMR), offset 0x008 ............................................................ 287 July 14, 2014 15 Texas Instruments-Production Data Table of Contents 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: GPTM Control (GPTMCTL), offset 0x00C ........................................................................ 289 GPTM Interrupt Mask (GPTMIMR), offset 0x018 .............................................................. 292 GPTM Raw Interrupt Status (GPTMRIS), offset 0x01C ..................................................... 294 GPTM Masked Interrupt Status (GPTMMIS), offset 0x020 ................................................ 295 GPTM Interrupt Clear (GPTMICR), offset 0x024 .............................................................. 296 GPTM TimerA Interval Load (GPTMTAILR), offset 0x028 ................................................. 298 GPTM TimerB Interval Load (GPTMTBILR), offset 0x02C ................................................ 299 GPTM TimerA Match (GPTMTAMATCHR), offset 0x030 ................................................... 300 GPTM TimerB Match (GPTMTBMATCHR), offset 0x034 .................................................. 301 GPTM TimerA Prescale (GPTMTAPR), offset 0x038 ........................................................ 302 GPTM TimerB Prescale (GPTMTBPR), offset 0x03C ....................................................... 303 GPTM TimerA Prescale Match (GPTMTAPMR), offset 0x040 ........................................... 304 GPTM TimerB Prescale Match (GPTMTBPMR), offset 0x044 ........................................... 305 GPTM TimerA (GPTMTAR), offset 0x048 ........................................................................ 306 GPTM TimerB (GPTMTBR), offset 0x04C ....................................................................... 307 Watchdog Timer ........................................................................................................................... 308 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 ...................................................................... 312 Watchdog Value (WDTVALUE), offset 0x004 ................................................................... 313 Watchdog Control (WDTCTL), offset 0x008 ..................................................................... 314 Watchdog Interrupt Clear (WDTICR), offset 0x00C .......................................................... 315 Watchdog Raw Interrupt Status (WDTRIS), offset 0x010 .................................................. 316 Watchdog Masked Interrupt Status (WDTMIS), offset 0x014 ............................................. 317 Watchdog Test (WDTTEST), offset 0x418 ....................................................................... 318 Watchdog Lock (WDTLOCK), offset 0xC00 ..................................................................... 319 Watchdog Peripheral Identification 4 (WDTPeriphID4), offset 0xFD0 ................................. 320 Watchdog Peripheral Identification 5 (WDTPeriphID5), offset 0xFD4 ................................. 321 Watchdog Peripheral Identification 6 (WDTPeriphID6), offset 0xFD8 ................................. 322 Watchdog Peripheral Identification 7 (WDTPeriphID7), offset 0xFDC ................................ 323 Watchdog Peripheral Identification 0 (WDTPeriphID0), offset 0xFE0 ................................. 324 Watchdog Peripheral Identification 1 (WDTPeriphID1), offset 0xFE4 ................................. 325 Watchdog Peripheral Identification 2 (WDTPeriphID2), offset 0xFE8 ................................. 326 Watchdog Peripheral Identification 3 (WDTPeriphID3), offset 0xFEC ................................. 327 Watchdog PrimeCell Identification 0 (WDTPCellID0), offset 0xFF0 .................................... 328 Watchdog PrimeCell Identification 1 (WDTPCellID1), offset 0xFF4 .................................... 329 Watchdog PrimeCell Identification 2 (WDTPCellID2), offset 0xFF8 .................................... 330 Watchdog PrimeCell Identification 3 (WDTPCellID3 ), offset 0xFFC .................................. 331 Analog-to-Digital Converter (ADC) ............................................................................................. 332 Register 1: Register 2: Register 3: Register 4: Register 5: Register 6: Register 7: Register 8: Register 9: Register 10: Register 11: ADC Active Sample Sequencer (ADCACTSS), offset 0x000 ............................................. 342 ADC Raw Interrupt Status (ADCRIS), offset 0x004 ........................................................... 343 ADC Interrupt Mask (ADCIM), offset 0x008 ..................................................................... 344 ADC Interrupt Status and Clear (ADCISC), offset 0x00C .................................................. 345 ADC Overflow Status (ADCOSTAT), offset 0x010 ............................................................ 346 ADC Event Multiplexer Select (ADCEMUX), offset 0x014 ................................................. 347 ADC Underflow Status (ADCUSTAT), offset 0x018 ........................................................... 350 ADC Sample Sequencer Priority (ADCSSPRI), offset 0x020 ............................................. 351 ADC Processor Sample Sequence Initiate (ADCPSSI), offset 0x028 ................................. 353 ADC Sample Averaging Control (ADCSAC), offset 0x030 ................................................. 354 ADC Sample Sequence Input Multiplexer Select 0 (ADCSSMUX0), offset 0x040 ............... 355 16 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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: ADC Sample Sequence Control 0 (ADCSSCTL0), offset 0x044 ........................................ 357 ADC Sample Sequence Result FIFO 0 (ADCSSFIFO0), offset 0x048 ................................ 360 ADC Sample Sequence Result FIFO 1 (ADCSSFIFO1), offset 0x068 ................................ 360 ADC Sample Sequence Result FIFO 2 (ADCSSFIFO2), offset 0x088 ................................ 360 ADC Sample Sequence Result FIFO 3 (ADCSSFIFO3), offset 0x0A8 ............................... 360 ADC Sample Sequence FIFO 0 Status (ADCSSFSTAT0), offset 0x04C ............................. 361 ADC Sample Sequence FIFO 1 Status (ADCSSFSTAT1), offset 0x06C ............................. 361 ADC Sample Sequence FIFO 2 Status (ADCSSFSTAT2), offset 0x08C ............................ 361 ADC Sample Sequence FIFO 3 Status (ADCSSFSTAT3), offset 0x0AC ............................ 361 ADC Sample Sequence Input Multiplexer Select 1 (ADCSSMUX1), offset 0x060 ............... 362 ADC Sample Sequence Input Multiplexer Select 2 (ADCSSMUX2), offset 0x080 ............... 362 ADC Sample Sequence Control 1 (ADCSSCTL1), offset 0x064 ........................................ 363 ADC Sample Sequence Control 2 (ADCSSCTL2), offset 0x084 ........................................ 363 ADC Sample Sequence Input Multiplexer Select 3 (ADCSSMUX3), offset 0x0A0 ............... 365 ADC Sample Sequence Control 3 (ADCSSCTL3), offset 0x0A4 ........................................ 366 ADC Test Mode Loopback (ADCTMLB), offset 0x100 ....................................................... 367 Universal Asynchronous Receivers/Transmitters (UARTs) ..................................................... 368 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 ............................................................................... 376 UART Receive Status/Error Clear (UARTRSR/UARTECR), offset 0x004 ........................... 378 UART Flag (UARTFR), offset 0x018 ................................................................................ 380 UART Integer Baud-Rate Divisor (UARTIBRD), offset 0x024 ............................................ 382 UART Fractional Baud-Rate Divisor (UARTFBRD), offset 0x028 ....................................... 383 UART Line Control (UARTLCRH), offset 0x02C ............................................................... 384 UART Control (UARTCTL), offset 0x030 ......................................................................... 386 UART Interrupt FIFO Level Select (UARTIFLS), offset 0x034 ........................................... 388 UART Interrupt Mask (UARTIM), offset 0x038 ................................................................. 390 UART Raw Interrupt Status (UARTRIS), offset 0x03C ...................................................... 392 UART Masked Interrupt Status (UARTMIS), offset 0x040 ................................................. 393 UART Interrupt Clear (UARTICR), offset 0x044 ............................................................... 394 UART Peripheral Identification 4 (UARTPeriphID4), offset 0xFD0 ..................................... 396 UART Peripheral Identification 5 (UARTPeriphID5), offset 0xFD4 ..................................... 397 UART Peripheral Identification 6 (UARTPeriphID6), offset 0xFD8 ..................................... 398 UART Peripheral Identification 7 (UARTPeriphID7), offset 0xFDC ..................................... 399 UART Peripheral Identification 0 (UARTPeriphID0), offset 0xFE0 ...................................... 400 UART Peripheral Identification 1 (UARTPeriphID1), offset 0xFE4 ...................................... 401 UART Peripheral Identification 2 (UARTPeriphID2), offset 0xFE8 ...................................... 402 UART Peripheral Identification 3 (UARTPeriphID3), offset 0xFEC ..................................... 403 UART PrimeCell Identification 0 (UARTPCellID0), offset 0xFF0 ........................................ 404 UART PrimeCell Identification 1 (UARTPCellID1), offset 0xFF4 ........................................ 405 UART PrimeCell Identification 2 (UARTPCellID2), offset 0xFF8 ........................................ 406 UART PrimeCell Identification 3 (UARTPCellID3), offset 0xFFC ........................................ 407 Synchronous Serial Interface (SSI) ............................................................................................ 408 Register 1: Register 2: Register 3: Register 4: Register 5: Register 6: SSI Control 0 (SSICR0), offset 0x000 .............................................................................. SSI Control 1 (SSICR1), offset 0x004 .............................................................................. SSI Data (SSIDR), offset 0x008 ...................................................................................... SSI Status (SSISR), offset 0x00C ................................................................................... SSI Clock Prescale (SSICPSR), offset 0x010 .................................................................. SSI Interrupt Mask (SSIIM), offset 0x014 ......................................................................... July 14, 2014 421 423 425 426 428 429 17 Texas Instruments-Production Data Table of Contents 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: SSI Raw Interrupt Status (SSIRIS), offset 0x018 .............................................................. 431 SSI Masked Interrupt Status (SSIMIS), offset 0x01C ........................................................ 432 SSI Interrupt Clear (SSIICR), offset 0x020 ....................................................................... 433 SSI Peripheral Identification 4 (SSIPeriphID4), offset 0xFD0 ............................................. 434 SSI Peripheral Identification 5 (SSIPeriphID5), offset 0xFD4 ............................................. 435 SSI Peripheral Identification 6 (SSIPeriphID6), offset 0xFD8 ............................................. 436 SSI Peripheral Identification 7 (SSIPeriphID7), offset 0xFDC ............................................ 437 SSI Peripheral Identification 0 (SSIPeriphID0), offset 0xFE0 ............................................. 438 SSI Peripheral Identification 1 (SSIPeriphID1), offset 0xFE4 ............................................. 439 SSI Peripheral Identification 2 (SSIPeriphID2), offset 0xFE8 ............................................. 440 SSI Peripheral Identification 3 (SSIPeriphID3), offset 0xFEC ............................................ 441 SSI PrimeCell Identification 0 (SSIPCellID0), offset 0xFF0 ............................................... 442 SSI PrimeCell Identification 1 (SSIPCellID1), offset 0xFF4 ............................................... 443 SSI PrimeCell Identification 2 (SSIPCellID2), offset 0xFF8 ............................................... 444 SSI PrimeCell Identification 3 (SSIPCellID3), offset 0xFFC ............................................... 445 Inter-Integrated Circuit (I2C) Interface ........................................................................................ 446 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: I2C Master Slave Address (I2CMSA), offset 0x000 ........................................................... 462 I2C Master Control/Status (I2CMCS), offset 0x004 ........................................................... 463 I2C Master Data (I2CMDR), offset 0x008 ......................................................................... 467 I2C Master Timer Period (I2CMTPR), offset 0x00C ........................................................... 468 I2C Master Interrupt Mask (I2CMIMR), offset 0x010 ......................................................... 469 I2C Master Raw Interrupt Status (I2CMRIS), offset 0x014 ................................................. 470 I2C Master Masked Interrupt Status (I2CMMIS), offset 0x018 ........................................... 471 I2C Master Interrupt Clear (I2CMICR), offset 0x01C ......................................................... 472 I2C Master Configuration (I2CMCR), offset 0x020 ............................................................ 473 I2C Slave Own Address (I2CSOAR), offset 0x800 ............................................................ 475 I2C Slave Control/Status (I2CSCSR), offset 0x804 ........................................................... 476 I2C Slave Data (I2CSDR), offset 0x808 ........................................................................... 478 I2C Slave Interrupt Mask (I2CSIMR), offset 0x80C ........................................................... 479 I2C Slave Raw Interrupt Status (I2CSRIS), offset 0x810 ................................................... 480 I2C Slave Masked Interrupt Status (I2CSMIS), offset 0x814 .............................................. 481 I2C Slave Interrupt Clear (I2CSICR), offset 0x818 ............................................................ 482 Analog Comparator ..................................................................................................................... 483 Register 1: Register 2: Register 3: Register 4: Register 5: Register 6: Analog Comparator Masked Interrupt Status (ACMIS), offset 0x000 .................................. Analog Comparator Raw Interrupt Status (ACRIS), offset 0x004 ....................................... Analog Comparator Interrupt Enable (ACINTEN), offset 0x008 ......................................... Analog Comparator Reference Voltage Control (ACREFCTL), offset 0x010 ....................... Analog Comparator Status 0 (ACSTAT0), offset 0x020 ..................................................... Analog Comparator Control 0 (ACCTL0), offset 0x024 ..................................................... 488 489 490 491 492 493 Pulse Width Modulator (PWM) .................................................................................................... 495 Register 1: Register 2: Register 3: Register 4: Register 5: Register 6: Register 7: PWM Master Control (PWMCTL), offset 0x000 ................................................................ 504 PWM Time Base Sync (PWMSYNC), offset 0x004 ........................................................... 505 PWM Output Enable (PWMENABLE), offset 0x008 .......................................................... 506 PWM Output Inversion (PWMINVERT), offset 0x00C ....................................................... 507 PWM Output Fault (PWMFAULT), offset 0x010 ................................................................ 508 PWM Interrupt Enable (PWMINTEN), offset 0x014 ........................................................... 509 PWM Raw Interrupt Status (PWMRIS), offset 0x018 ........................................................ 510 18 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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 Interrupt Status and Clear (PWMISC), offset 0x01C ................................................ 511 PWM Status (PWMSTATUS), offset 0x020 ...................................................................... 512 PWM0 Control (PWM0CTL), offset 0x040 ....................................................................... 513 PWM0 Interrupt and Trigger Enable (PWM0INTEN), offset 0x044 .................................... 515 PWM0 Raw Interrupt Status (PWM0RIS), offset 0x048 .................................................... 518 PWM0 Interrupt Status and Clear (PWM0ISC), offset 0x04C ........................................... 519 PWM0 Load (PWM0LOAD), offset 0x050 ....................................................................... 520 PWM0 Counter (PWM0COUNT), offset 0x054 ................................................................ 521 PWM0 Compare A (PWM0CMPA), offset 0x058 ............................................................. 522 PWM0 Compare B (PWM0CMPB), offset 0x05C ............................................................. 523 PWM0 Generator A Control (PWM0GENA), offset 0x060 ................................................ 524 PWM0 Generator B Control (PWM0GENB), offset 0x064 ................................................ 527 PWM0 Dead-Band Control (PWM0DBCTL), offset 0x068 ................................................ 530 PWM0 Dead-Band Rising-Edge Delay (PWM0DBRISE), offset 0x06C ............................. 531 PWM0 Dead-Band Falling-Edge-Delay (PWM0DBFALL), offset 0x070 ............................. 532 July 14, 2014 19 Texas Instruments-Production Data Revision History Revision History The revision history table notes changes made between the indicated revisions of the LM3S812 data sheet. Table 1. Revision History Date July 2014 June 2012 November 2011 Revision Description 15852.2743 ■ ■ In UART chapter: – Clarified that the transmit interrupt is based on a transition through level. – Corrected reset for UART Raw Interrupt Status (UARTRIS) register. ■ In Ordering and Contact Information appendix, moved orderable part numbers table to addendum. ■ Additional minor data sheet clarifications and corrections. 12739.2515 ■ 11107 In Internal Memory chapter, added sections on Execute-Only Protection, Read-Only Protection, and Permanently Disabling Debug. In Reset Characteristics table, changed values and units for Internal reset timeout after hardware reset (R7). ■ Removed 48QFN package. ■ Removed extended temperature package. ■ Minor data sheet clarifications and corrections. ■ Added module-specific pin tables to each chapter in the new Signal Description sections. ■ In Timer chapter, clarified that in 16-Bit Input Edge Time Mode, the timer is capable of capturing three types of events: rising edge, falling edge, or both. ■ In UART chapter, clarified interrupt behavior. ■ In SSI chapter, corrected SSIClk in the figure "Synchronous Serial Frame Format (Single Transfer)". ■ In Signal Tables chapter: ■ ■ – Corrected pin numbers in table "Connections for Unused Signals" (other pin tables were correct). – Corrected buffer type for PWMn signals in pin tables. In Electrical Characteristics chapter: – Added parameter "Input voltage for a GPIO configured as an analog input" to the "Maximum Ratings" table. – Corrected Nom values for parameters "TCK clock Low time" and "TCK clock High time" in "JTAG Characteristics" table. Additional minor data sheet clarifications and corrections. 20 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Table 1. Revision History (continued) Date Revision January 2011 9102 September 2010 June 2010 7783 7393 Description ■ In Application Interrupt and Reset Control (APINT) register, changed bit name from SYSRESETREQ to SYSRESREQ. ■ Added DEBUG (Debug Priority) bit field to System Handler Priority 3 (SYSPRI3) register. ■ Added "Reset Sources" table to System Control chapter. ■ Removed mention of false-start bit detection in the UART chapter. This feature is not supported. ■ Added note that specific module clocks must be enabled before that module's registers can be programmed. There must be a delay of 3 system clocks after the module clock is enabled before any of that module's registers are accessed. ■ Changed I2C slave register base addresses and offsets to be relative to the I2C module base address of 0x4002.0000 , so register bases and offsets were changed for all I2C slave registers. Note that ® the hw_i2c.h file in the StellarisWare Driver Library uses a base address of 0x4002.0800 for the 2 I C slave registers. Be aware when using registers with offsets between 0x800 and 0x818 that StellarisWare uses the old slave base address for these offsets. ■ Corrected nonlinearity and offset error parameters (EL, ED, and EO) in ADC Characteristics table. ■ Added specification for maximum input voltage on a non-power pin when the microcontroller is unpowered (VNON parameter in Maximum Ratings table). ■ Additional minor data sheet clarifications and corrections. ■ Reorganized ARM Cortex-M3 Processor Core, Memory Map and Interrupts chapters, creating two new chapters, The Cortex-M3 Processor and Cortex-M3 Peripherals. Much additional content was added, including all the Cortex-M3 registers. ■ Changed register names to be consistent with StellarisWare names: the Cortex-M3 Interrupt Control and Status (ICSR) register to the Interrupt Control and State (INTCTRL) register, and the Cortex-M3 Interrupt Set Enable (SETNA) register to the Interrupt 0-31 Set Enable (EN0) register. ■ Added clarification of instruction execution during Flash operations. ■ Modified Figure 7-2 on page 235 to clarify operation of the GPIO inputs when used as an alternate function. ■ Added caution not to apply a Low value to PB7 when debugging; a Low value on the pin causes the JTAG controller to be reset, resulting in a loss of JTAG communication. ■ In General-Purpose Timers chapter, clarified operation of the 32-bit RTC mode. ■ Added missing table "Connections for Unused Signals" (Table 17-5 on page 541). ■ In Electrical Characteristics chapter: – Added ILKG parameter (GPIO input leakage current) to Table 19-4 on page 544. – Corrected values for tCLKRF parameter (SSIClk rise/fall time) in Table 19-16 on page 552. ■ Added dimensions for Tray and Tape and Reel shipping mediums. ■ Corrected base address for SRAM in architectural overview chapter. ■ Clarified system clock operation, adding content to “Clock Control” on page 158. ■ In Signal Tables chapter, added table "Connections for Unused Signals." ■ In "Reset Characteristics" table, corrected value for supply voltage (VDD) rise time. ■ Additional minor data sheet clarifications and corrections. July 14, 2014 21 Texas Instruments-Production Data Revision History Table 1. Revision History (continued) Date Revision April 2010 7004 January 2010 6712 Description ■ Added caution note to the I2C Master Timer Period (I2CMTPR) register description and changed field width to 7 bits. ■ Added note about RST signal routing. ■ Clarified the function of the TnSTALL bit in the GPTMCTL register. ■ Additional minor data sheet clarifications and corrections. ■ In "System Control" section, clarified Debug Access Port operation after Sleep modes. ■ Clarified wording on Flash memory access errors. ■ Added section on Flash interrupts. ■ Changed the reset value of the ADC Sample Sequence Result FIFO n (ADCSSFIFOn) registers to be indeterminate. ■ Clarified operation of SSI transmit FIFO. ■ Made these changes to the Operating Characteristics chapter: ■ October 2009 July 2009 6438 5953 – Added storage temperature ratings to "Temperature Characteristics" table – Added "ESD Absolute Maximum Ratings" table Made these changes to the Electrical Characteristics chapter: – In "Flash Memory Characteristics" table, corrected Mass erase time – Added sleep and deep-sleep wake-up times ("Sleep Modes AC Characteristics" table) – In "Reset Characteristics" table, corrected supply voltage (VDD) rise time ■ The reset value for the DID1 register may change, depending on the package. ■ Deleted MAXADCSPD bit field from DCGC0 register as it is not applicable in Deep-Sleep mode. ■ Deleted reset value for 16-bit mode from GPTMTAILR, GPTMTAMATCHR, and GPTMTAR registers because the module resets in 32-bit mode. ■ Made these changes to the Electrical Characteristics chapter: – Removed VSIH and VSIL parameters from Operating Conditions table. – Changed SSI set up and hold times to be expressed in system clocks, not ns. – Revised ADC electrical specifications to clarify, including reorganizing and adding new data. ■ Added 48QFN package. ■ Additional minor data sheet clarifications and corrections. ■ Clarified Power-on reset and RST pin operation; added new diagrams. ■ Added DBG bits missing from FMPRE register. This changes register reset value. ■ In ADC characteristics table, changed Max value for GAIN parameter from ±1 to ±3 and added EIR (Internal voltage reference error) parameter. ■ Corrected ordering numbers. ■ Additional minor data sheet clarifications and corrections. 22 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Table 1. Revision History (continued) Date Revision April 2009 5369 January 2009 November 2008 October 2008 4644 4283 4149 Description ■ Added JTAG/SWD clarification (see “Communication with JTAG/SWD” on page 148). ■ Added "GPIO Module DC Characteristics" table (see Table 19-4 on page 544). ■ Additional minor data sheet clarifications and corrections. ■ Incorrect bit type for RELOAD bit field in SysTick Reload Value register; changed to R/W. ■ Clarification added as to what happens when the SSI in slave mode is required to transmit but there is no data in the TX FIFO. ■ Minor corrections to comparator operating mode tables. ■ Additional minor data sheet clarifications and corrections. ■ Revised High-Level Block Diagram. ■ Corrected descriptions for UART1 signals. ■ Additional minor data sheet clarifications and corrections were made. ■ Added note on clearing interrupts to the Interrupts chapter: Note: ■ It may take several processor cycles after a write to clear an interrupt source in order for NVIC to see the interrupt source de-assert. This means if the interrupt clear is done as the last action in an interrupt handler, it is possible for the interrupt handler to complete while NVIC sees the interrupt as still asserted, causing the interrupt handler to be re-entered errantly. This can be avoided by either clearing the interrupt source at the beginning of the interrupt handler or by performing a read or write after the write to clear the interrupt source (and flush the write buffer) Step 1 of the Initialization and Configuration procedure in the ADC chapter states the wrong register to use to enable the ADC clock. Sentence changed to: 1. Enable the ADC clock by writing a value of 0x0001.0000 to the RCGC0 register. ■ June 2008 2972 Additional minor data sheet clarifications and corrections were made. Started tracking revision history. July 14, 2014 23 Texas Instruments-Production Data About This Document About This Document This data sheet provides reference information for the LM3S812 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 related documents are available on the Stellaris web site at www.ti.com/stellaris: ■ Stellaris® Errata ■ ARM® Cortex™-M3 Errata ■ Cortex™-M3/M4 Instruction Set Technical User's Manual ■ Stellaris® Graphics Library User's Guide ■ Stellaris® Peripheral Driver Library User's Guide The following related documents are also referenced: ■ ARM® Debug Interface V5 Architecture Specification ■ ARM® Embedded Trace Macrocell Architecture Specification ■ IEEE Standard 1149.1-Test Access Port and Boundary-Scan Architecture This documentation list was current as of publication date. Please check the web site for additional documentation, including application notes and white papers. 24 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Documentation Conventions This document uses the conventions shown in Table 2 on page 25. Table 2. 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 2-4 on page 62. 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. In most cases, reserved bits are set to 0; however, user software should not rely on the value of a reserved bit. To provide software compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 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. RC Software can read this field. The bit or field is cleared by hardware after reading 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/WC Software can read or write this field. Writing to it with any value clears the register. 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. R/W1S Software can read or write a 1 to this field. A write of a 0 to a R/W1S bit does not affect the bit value in the register. 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. July 14, 2014 25 Texas Instruments-Production Data About This Document Table 2. Documentation Conventions (continued) 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. All other numbers within register tables are assumed to be binary. Within conceptual information, binary numbers are indicated with a b suffix, for example, 1011b, and decimal numbers are written without a prefix or suffix. 26 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 1 Architectural Overview ® The 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 LM3S812 microcontroller is targeted for industrial applications, including test and measurement equipment, factory automation, HVAC and building control, motion control, medical instrumentation, fire and security, and power/energy. In addition, the LM3S812 microcontroller offers the advantages of ARM's widely available development tools, System-on-Chip (SoC) infrastructure IP applications, and a large user community. Additionally, the microcontroller uses ARM's Thumb®-compatible Thumb-2 instruction set to reduce memory requirements and, thereby, cost. Finally, the LM3S812 microcontroller is code-compatible to all members of the extensive Stellaris family; providing flexibility to fit our customers' precise needs. Texas Instruments offers a complete solution to get to market quickly, with evaluation and development boards, white papers and application notes, an easy-to-use peripheral driver library, and a strong support, sales, and distributor network. See “Ordering and Contact Information” on page 579 for ordering information for Stellaris family devices. 1.1 Product Features The LM3S812 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), providing 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 – 24 interrupts with eight priority levels – Memory protection unit (MPU), providing a privileged mode for protected operating system functionality – Unaligned data access, enabling data to be efficiently packed into memory – Atomic bit manipulation (bit-banding), delivering maximum memory utilization and streamlined peripheral control ■ ARM® Cortex™-M3 Processor Core July 14, 2014 27 Texas Instruments-Production Data Architectural Overview – 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. – Rapid application execution through Harvard architecture characterized by separate buses for instruction and data. – Exceptional interrupt handling, by implementing the register manipulations required for handling an interrupt in hardware. – Deterministic, fast interrupt processing: always 12 cycles, or just 6 cycles with tail-chaining – Memory protection unit (MPU) to provide a privileged mode of operation for complex applications. – Migration from the ARM7™ processor family for better performance and power efficiency. – Full-featured debug solution • 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 – Optimized for single-cycle flash usage – Three sleep modes with clock gating for low power – Single-cycle multiply instruction and hardware divide – Atomic operations – ARM Thumb2 mixed 16-/32-bit instruction set – 1.25 DMIPS/MHz ■ JTAG – IEEE 1149.1-1990 compatible Test Access Port (TAP) controller – Four-bit Instruction Register (IR) chain for storing JTAG instructions – IEEE standard instructions: BYPASS, IDCODE, SAMPLE/PRELOAD, EXTEST and INTEST – ARM additional instructions: APACC, DPACC and ABORT – Integrated ARM Serial Wire Debug (SWD) 28 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller ■ 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 ■ GPIOs – 7-34 GPIOs, depending on configuration – 5-V-tolerant in input configuration – Fast toggle capable of a change every two clock cycles – Programmable control for GPIO interrupts • Interrupt generation masking • Edge-triggered on rising, falling, or both • Level-sensitive on High or Low values – Bit masking in both read and write operations through address lines – Can initiate an ADC sample sequence – Pins configured as digital inputs are Schmitt-triggered. – Programmable control for GPIO pad configuration • Weak pull-up or pull-down resistors • 2-mA, 4-mA, and 8-mA pad drive for digital communication • Slew rate control for the 8-mA drive • Open drain enables • Digital input enables ■ General-Purpose Timers – Three General-Purpose Timer Modules (GPTM), each of which provides two 16-bit timers/counters. Each GPTM can be configured to operate independently: • As a single 32-bit timer • As one 32-bit Real-Time Clock (RTC) to event capture • For Pulse Width Modulation (PWM) July 14, 2014 29 Texas Instruments-Production Data Architectural Overview • To trigger analog-to-digital conversions – 32-bit Timer modes • Programmable one-shot timer • Programmable periodic timer • Real-Time Clock when using an external 32.768-KHz clock as the input • User-enabled stalling when the controller asserts CPU Halt flag during debug • ADC event trigger – 16-bit Timer modes • General-purpose timer function with an 8-bit prescaler (for one-shot and periodic modes only) • 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 ■ ADC – Two analog input channels – Single-ended and differential-input configurations 30 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller – On-chip internal temperature sensor – Sample rate of 250 thousand samples/second – Flexible, configurable analog-to-digital conversion – Four programmable sample conversion sequences from one to eight entries long, with corresponding conversion result FIFOs – Flexible trigger control • Controller (software) • Timers • Analog Comparators • PWM • GPIO – Hardware averaging of up to 64 samples for improved accuracy – Converter uses an internal 3-V reference ■ UART – Two fully programmable 16C550-type UARTs – Separate 16x8 transmit (TX) and receive (RX) FIFOs to reduce CPU interrupt service loading – Programmable baud-rate generator allowing speeds up to 3.125 Mbps – 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 – Standard asynchronous communication bits for start, stop, and parity – 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 ■ 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 July 14, 2014 31 Texas Instruments-Production Data Architectural Overview – 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 ■ I2C – Devices on the I2C bus can be designated as either a master or a slave • Supports both sending and receiving data as either a master or a slave • Supports simultaneous master and slave operation – Four I2C modes • Master transmit • Master receive • Slave transmit • Slave receive – Two transmission speeds: Standard (100 Kbps) and Fast (400 Kbps) – Master and slave interrupt generation • Master generates interrupts when a transmit or receive operation completes (or aborts due to an error) • Slave generates interrupts when data has been sent or requested by a master – Master with arbitration and clock synchronization, multimaster support, and 7-bit addressing mode ■ Analog Comparators – One integrated analog comparator – Configurable for output to drive an output pin, generate an interrupt, or initiate an ADC sample sequence – Compare external pin input to external pin input or to internal programmable voltage reference – 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 ■ PWM 32 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller – One PWM generator blocks, each with one 16-bit counter, two PWM comparators, a PWM signal generator, a dead-band generator, and an interrupt/ADC-trigger selector – One fault input in hardware to promote low-latency shutdown – 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 PWM 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 PWM 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 • 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 • Interrupt status summary of the PWM generator blocks – Can initiate an ADC sample sequence ■ 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 July 14, 2014 33 Texas Instruments-Production Data Architectural Overview – User-enabled LDO unregulated voltage detection and automatic reset – 3.3-V supply brown-out detection and reporting via interrupt or reset ■ Flexible Reset Sources – Power-on reset (POR) – Reset pin assertion – Brown-out (BOR) detector alerts to system power drops – Software reset – Watchdog timer reset – Internal low drop-out (LDO) regulator output goes unregulated ■ Industrial temperature 48-pin RoHS-compliant LQFP package 1.2 Target Applications ■ Factory automation and control ■ Industrial control power devices ■ Building and home automation ■ Stepper motors ■ Brushless DC motors ■ AC induction motors 1.3 High-Level Block Diagram Figure 1-1 on page 35 depicts the features on the Stellaris LM3S812 microcontroller. 34 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Figure 1-1. Stellaris LM3S812 Microcontroller High-Level Block Diagram JTAG/SWD ARM® Cortex™-M3 (50MHz) System Control and Clocks (w/ Precis. Osc.) Flash (64KB) DCode bus NVIC MPU ICode bus System Bus LM3S812 Bus Matrix SRAM (8KB) SYSTEM PERIPHERALS GeneralPurpose Timer (3) Watchdog Timer (1) Advanced Peripheral Bus (APB) GPIOs (7-34) I2C (1) Analog Comparator (1) SERIAL PERIPHERALS UART (2) SSI (1) ANALOG PERIPHERALS 10- Bit ADC Channels (2) MOTION CONTROL PERIPHERALS PWM (2) July 14, 2014 35 Texas Instruments-Production Data Architectural Overview 1.4 Functional Overview The following sections provide an overview of the features of the LM3S812 microcontroller. The page 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 579. 1.4.1 ARM Cortex™-M3 1.4.1.1 Processor Core (see page 43) All members of the Stellaris product family, including the LM3S812 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. 1.4.1.2 Memory Map (see page 62) A memory map lists the location of instructions and data in memory. The memory map for the LM3S812 controller can be found in Table 2-4 on page 62. Register addresses are given as a hexadecimal increment, relative to the module's base address as shown in the memory map. 1.4.1.3 System Timer (SysTick) (see page 85) 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. 1.4.1.4 Nested Vectored Interrupt Controller (NVIC) (see page 86) The LM3S812 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 24 interrupts. 36 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 1.4.1.5 System Control Block (SCB) (see page 88) The SCB provides system implementation information and system control, including configuration, control, and reporting of system exceptions. 1.4.1.6 Memory Protection Unit (MPU) (see page 88) The MPU 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. 1.4.2 Motor Control Peripherals To enhance motor control, the LM3S812 controller features Pulse Width Modulation (PWM) outputs. 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 LM3S812, PWM motion control functionality can be achieved through: ■ Dedicated, flexible motion control hardware using the PWM pins ■ The motion control features of the general-purpose timers using the CCP pins PWM Pins (see page 495) The LM3S812 PWM module consists of one 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. 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 (see page 278) 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. Fault Pin (see page 500) The LM3S812 PWM module includes one fault-condition handling input to quickly provide low-latency shutdown and prevent damage to the motor being controlled. 1.4.3 Analog Peripherals To handle analog signals, the LM3S812 microcontroller offers an Analog-to-Digital Converter (ADC). For support of analog signals, the LM3S812 microcontroller offers one analog comparator. 1.4.3.1 ADC (see page 332) An analog-to-digital converter (ADC) is a peripheral that converts a continuous analog voltage to a discrete digital number. July 14, 2014 37 Texas Instruments-Production Data Architectural Overview The LM3S812 ADC module features 10-bit conversion resolution and supports two input channels, plus an internal temperature sensor. Four buffered sample sequences allow rapid sampling of up to eight 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 Comparators (see page 483) An analog comparator is a peripheral that compares two analog voltages, and provides a logical output that signals the comparison result. The LM3S812 microcontroller 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. 1.4.4 Serial Communications Peripherals The LM3S812 controller supports both asynchronous and synchronous serial communications with: ■ Two fully programmable 16C550-type UARTs ■ One SSI module ■ One I2C module 1.4.4.1 UART (see page 368) 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 LM3S812 controller includes two fully programmable 16C550-type UARTs that support data transfer speeds up to 3.125 Mbps. (Although similar in functionality to a 16C550 UART, it is not register-compatible.) Separate 16x8 transmit (TX) and 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 (see page 408) Synchronous Serial Interface (SSI) is a four-wire bi-directional full and low-speed communications interface. 38 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller The LM3S812 controller includes one SSI module that 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. 1.4.4.3 I2C (see page 446) The Inter-Integrated Circuit (I2C) bus provides bi-directional data transfer through a two-wire design (a serial data line SDA and a serial clock line SCL). The I2C bus interfaces to external I2C devices such as serial memory (RAMs and ROMs), networking devices, LCDs, tone generators, and so on. The I2C bus may also be used for system testing and diagnostic purposes in product development and manufacture. The LM3S812 controller includes one I2C module that provides the ability to communicate to other IC devices over an I2C bus. The I2C bus supports devices that can both transmit and receive (write and read) data. Devices on the I2C bus can be designated as either a master or a slave. The I2C module supports both sending and receiving data as either a master or a slave, and also supports the simultaneous operation as both a master and a slave. The four I2C modes are: Master Transmit, Master Receive, Slave Transmit, and Slave Receive. A Stellaris I2C module can operate at two speeds: Standard (100 Kbps) and Fast (400 Kbps). Both the I2C master and slave can generate interrupts. The I2C master generates interrupts when a transmit or receive operation completes (or aborts due to an error). The I2C slave generates interrupts when data has been sent or requested by a master. 1.4.5 System Peripherals 1.4.5.1 Programmable GPIOs (see page 230) General-purpose input/output (GPIO) pins offer flexibility for a variety of connections. The Stellaris GPIO module is comprised 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 7-34 programmable input/output pins. The number of GPIOs available depends on the peripherals being used (see “Signal Tables” on page 534 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. Pins configured as digital inputs are Schmitt-triggered. July 14, 2014 39 Texas Instruments-Production Data Architectural Overview 1.4.5.2 Three Programmable Timers (see page 272) Programmable timers can be used to count or time external events that drive the Timer input pins. The Stellaris General-Purpose Timer Module (GPTM) contains three GPTM blocks. Each GPTM block provides two 16-bit timers/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 Real-Time Clock (RTC), one-shot timer or periodic timer. 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 (see page 308) A watchdog timer can generate an interrupt 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 LM3S812 controller offers both single-cycle SRAM and single-cycle Flash memory. 1.4.6.1 SRAM (see page 212) The LM3S812 static random access memory (SRAM) controller supports 8 KB SRAM. The internal SRAM of the Stellaris devices starts at base 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 (see page 213) The LM3S812 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 JTAG TAP Controller (see page 143) 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) 40 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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 composed 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 Stellaris 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 Stellaris JTAG instructions select the Stellaris TDO outputs. The multiplexer is controlled by the Stellaris JTAG controller, which has comprehensive programming for the ARM, Stellaris, and unimplemented JTAG instructions. 1.4.7.2 System Control and Clocks (see page 153) 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: ■ “Pin Diagram” on page 533 ■ “Signal Tables” on page 534 ■ “Operating Characteristics” on page 542 ■ “Electrical Characteristics” on page 543 ■ “Package Information” on page 581 July 14, 2014 41 Texas Instruments-Production Data Architectural Overview 1.4.9 System Block Diagram Figure 1-2. LM3S812 Controller System-Level Block Diagram VDD_3.3V LDO LDO VDD_2.5V 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 Analog Comparator PA5/SSITx PA4/SSIRx PA3/SSIFss PA2/SSIClk SSI PA1/U0Tx PA0/U0Rx UART0 I2C Master PB6/C0+ PB4/C0PB3/I2CSDA PB2/I2CSCL GPIO Port C Peripheral Bus Slave PB1 GP Timer0 PB0/CCP0 PC6/CCP3 PC3/TDO/SWO PC2/TDI PC1/TMS/SWDIO PC0/TCK/SWCLK PB5/CCP5 JTAG SWD/SWO PC7/CCP4 GP Timer2 PC4 PC5 PE0 PE1 PWM0 PD6/Fault PD0/PWM0 PD1/PWM1 UART1 PD2/U1Rx PD3/U1Tx GPIO Port E PD4 GP Timer1 PE2 PE3/CCP1 ADC1 ADC0 GPIO Port D ADC PD5/CCP2 PD7/C0o Temperature Sensor LM3S812 42 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 2 The Cortex-M3 Processor The ARM® Cortex™-M3 processor provides a high-performance, low-cost platform that meets the system requirements 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. ■ Rapid application execution through Harvard architecture characterized by separate buses for instruction and data. ■ Exceptional interrupt handling, by implementing the register manipulations required for handling an interrupt in hardware. ■ Deterministic, fast interrupt processing: always 12 cycles, or just 6 cycles with tail-chaining ■ Memory protection unit (MPU) to provide a privileged mode of operation for complex applications. ■ Migration from the ARM7™ processor family for better performance and power efficiency. ■ Full-featured debug solution – 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 ■ Optimized for single-cycle flash usage ■ Three sleep modes with clock gating for low power ■ Single-cycle multiply instruction and hardware divide ■ Atomic operations ■ ARM Thumb2 mixed 16-/32-bit instruction set ■ 1.25 DMIPS/MHz ® 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, building and home automation, and stepper motor control. July 14, 2014 43 Texas Instruments-Production Data The Cortex-M3 Processor This chapter provides information on the Stellaris implementation of the Cortex-M3 processor, including the programming model, the memory model, the exception model, fault handling, and power management. For technical details on the instruction set, see the Cortex™-M3/M4 Instruction Set Technical User's Manual. 2.1 Block Diagram The Cortex-M3 processor is built on a high-performance processor core, with a 3-stage pipeline Harvard architecture, making it ideal for demanding embedded applications. The processor delivers exceptional power efficiency through an efficient instruction set and extensively optimized design, providing high-end processing hardware including a range of single-cycle and SIMD multiplication and multiply-with-accumulate capabilities, saturating arithmetic and dedicated hardware division. To facilitate the design of cost-sensitive devices, the Cortex-M3 processor implements tightly coupled system components that reduce processor area while significantly improving interrupt handling and system debug capabilities. The Cortex-M3 processor implements a version of the Thumb® instruction set based on Thumb-2 technology, ensuring high code density and reduced program memory requirements. The Cortex-M3 instruction set provides the exceptional performance expected of a modern 32-bit architecture, with the high code density of 8-bit and 16-bit microcontrollers. The Cortex-M3 processor closely integrates a nested interrupt controller (NVIC), to deliver industry-leading interrupt performance. The Stellaris NVIC includes a non-maskable interrupt (NMI) and provides eight interrupt priority levels. The tight integration of the processor core and NVIC provides fast execution of interrupt service routines (ISRs), dramatically reducing interrupt latency. The hardware stacking of registers and the ability to suspend load-multiple and store-multiple operations further reduce interrupt latency. Interrupt handlers do not require any assembler stubs which removes code overhead from the ISRs. Tail-chaining optimization also significantly reduces the overhead when switching from one ISR to another. To optimize low-power designs, the NVIC integrates with the sleep modes, including Deep-sleep mode, which enables the entire device to be rapidly powered down. 44 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Figure 2-1. CPU Block Diagram Nested Vectored Interrupt Controller Interrupts Sleep ARM Cortex-M3 CM3 Core Debug Instructions Data Trace Port Interface Unit Memory Protection Unit Flash Patch and Breakpoint Instrumentation Data Watchpoint Trace Macrocell and Trace ROM Table Private Peripheral Bus (internal) Adv. Peripheral Bus Bus Matrix Serial Wire JTAG Debug Port Debug Access Port 2.2 Overview 2.2.1 System-Level Interface Serial Wire Output Trace Port (SWO) I-code bus D-code bus System bus The Cortex-M3 processor provides multiple interfaces using AMBA® technology to provide high-speed, low-latency memory accesses. The core supports unaligned data accesses and implements atomic bit manipulation that enables faster peripheral controls, system spinlocks, and thread-safe Boolean data handling. The Cortex-M3 processor has a memory protection unit (MPU) that provides fine-grain memory control, enabling applications to implement security privilege levels and separate code, data and stack on a task-by-task basis. 2.2.2 Integrated Configurable Debug The Cortex-M3 processor implements a complete hardware debug solution, providing high system visibility of the processor and memory through either a traditional JTAG port or a 2-pin Serial Wire Debug (SWD) port that is ideal for microcontrollers and other small package devices. The Stellaris implementation replaces the ARM SW-DP and JTAG-DP with the ARM CoreSight™-compliant Serial Wire JTAG Debug Port (SWJ-DP) interface. The SWJ-DP interface combines the SWD and JTAG debug ports into one module. See the ARM® Debug Interface V5 Architecture Specification for details on SWJ-DP. For system trace, the processor integrates an Instrumentation Trace Macrocell (ITM) alongside data watchpoints and a profiling unit. To enable simple and cost-effective profiling of the system trace events, a Serial Wire Viewer (SWV) can export a stream of software-generated messages, data trace, and profiling information through a single pin. July 14, 2014 45 Texas Instruments-Production Data The Cortex-M3 Processor The Flash Patch and Breakpoint Unit (FPB) provides up to eight hardware breakpoint comparators that debuggers can use. The comparators in the FPB also provide remap functions of up to eight words in the program code in the CODE memory region. This enables applications stored in a read-only area of Flash memory to be patched in another area of on-chip SRAM or Flash memory. If a patch is required, the application programs the FPB to remap a number of addresses. When those addresses are accessed, the accesses are redirected to a remap table specified in the FPB configuration. For more information on the Cortex-M3 debug capabilities, see theARM® Debug Interface V5 Architecture Specification. 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, as shown in Figure 2-2 on page 46. Figure 2-2. TPIU Block Diagram 2.2.4 Debug ATB Slave Port ATB Interface APB Slave Port APB Interface Asynchronous FIFO Trace Out (serializer) Serial Wire Trace Port (SWO) Cortex-M3 System Component Details The Cortex-M3 includes the following system components: ■ SysTick A 24-bit count-down timer that can be used as a Real-Time Operating System (RTOS) tick timer or as a simple counter (see “System Timer (SysTick)” on page 85). ■ Nested Vectored Interrupt Controller (NVIC) An embedded interrupt controller that supports low latency interrupt processing (see “Nested Vectored Interrupt Controller (NVIC)” on page 86). ■ System Control Block (SCB) 46 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller The programming model interface to the processor. The SCB provides system implementation information and system control, including configuration, control, and reporting of system exceptions (see “System Control Block (SCB)” on page 88). ■ Memory Protection Unit (MPU) Improves system reliability by defining the memory attributes for different memory regions. The MPU provides up to eight different regions and an optional predefined background region (see “Memory Protection Unit (MPU)” on page 88). 2.3 Programming Model This section describes the Cortex-M3 programming model. In addition to the individual core register descriptions, information about the processor modes and privilege levels for software execution and stacks is included. 2.3.1 Processor Mode and Privilege Levels for Software Execution The Cortex-M3 has two modes of operation: ■ Thread mode Used to execute application software. The processor enters Thread mode when it comes out of reset. ■ Handler mode Used to handle exceptions. When the processor has finished exception processing, it returns to Thread mode. In addition, the Cortex-M3 has two privilege levels: ■ Unprivileged In this mode, software has the following restrictions: – Limited access to the MSR and MRS instructions and no use of the CPS instruction – No access to the system timer, NVIC, or system control block – Possibly restricted access to memory or peripherals ■ Privileged In this mode, software can use all the instructions and has access to all resources. In Thread mode, the CONTROL register (see page 61) controls whether software execution is privileged or unprivileged. In Handler mode, software execution is always privileged. Only privileged software can write to the CONTROL register to change the privilege level for software execution in Thread mode. Unprivileged software can use the SVC instruction to make a supervisor call to transfer control to privileged software. 2.3.2 Stacks The processor uses a full descending stack, meaning that the stack pointer indicates the last stacked item on the memory. When the processor pushes a new item onto the stack, it decrements the stack pointer and then writes the item to the new memory location. The processor implements two stacks: July 14, 2014 47 Texas Instruments-Production Data The Cortex-M3 Processor the main stack and the process stack, with a pointer for each held in independent registers (see the SP register on page 51). In Thread mode, the CONTROL register (see page 61) controls whether the processor uses the main stack or the process stack. In Handler mode, the processor always uses the main stack. The options for processor operations are shown in Table 2-1 on page 48. Table 2-1. Summary of Processor Mode, Privilege Level, and Stack Use Processor Mode Use Privilege Level Thread Applications Privileged or unprivileged Stack Used Handler Exception handlers Always privileged a Main stack or process stack a Main stack a. See CONTROL (page 61). 2.3.3 Register Map Figure 2-3 on page 48 shows the Cortex-M3 register set. Table 2-2 on page 49 lists the Core registers. The core registers are not memory mapped and are accessed by register name, so the base address is n/a (not applicable) and there is no offset. Figure 2-3. Cortex-M3 Register Set R0 R1 R2 Low registers R3 R4 R5 R6 General-purpose registers R7 R8 R9 High registers R10 R11 R12 Stack Pointer SP (R13) Link Register LR (R14) Program Counter PC (R15) PSR PSP‡ MSP‡ ‡ Banked version of SP Program status register PRIMASK FAULTMASK Exception mask registers Special registers BASEPRI CONTROL CONTROL register 48 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Table 2-2. Processor Register Map Offset Type Reset - R0 R/W - Cortex General-Purpose Register 0 50 - R1 R/W - Cortex General-Purpose Register 1 50 - R2 R/W - Cortex General-Purpose Register 2 50 - R3 R/W - Cortex General-Purpose Register 3 50 - R4 R/W - Cortex General-Purpose Register 4 50 - R5 R/W - Cortex General-Purpose Register 5 50 - R6 R/W - Cortex General-Purpose Register 6 50 - R7 R/W - Cortex General-Purpose Register 7 50 - R8 R/W - Cortex General-Purpose Register 8 50 - R9 R/W - Cortex General-Purpose Register 9 50 - R10 R/W - Cortex General-Purpose Register 10 50 - R11 R/W - Cortex General-Purpose Register 11 50 - R12 R/W - Cortex General-Purpose Register 12 50 - SP R/W - Stack Pointer 51 - LR R/W 0xFFFF.FFFF Link Register 52 - PC R/W - Program Counter 53 - PSR R/W 0x0100.0000 Program Status Register 54 - PRIMASK R/W 0x0000.0000 Priority Mask Register 58 - FAULTMASK R/W 0x0000.0000 Fault Mask Register 59 - BASEPRI R/W 0x0000.0000 Base Priority Mask Register 60 - CONTROL R/W 0x0000.0000 Control Register 61 2.3.4 Description See page Name Register Descriptions This section lists and describes the Cortex-M3 registers, in the order shown in Figure 2-3 on page 48. The core registers are not memory mapped and are accessed by register name rather than offset. Note: The register type shown in the register descriptions refers to type during program execution in Thread mode and Handler mode. Debug access can differ. July 14, 2014 49 Texas Instruments-Production Data The Cortex-M3 Processor Register 1: Cortex General-Purpose Register 0 (R0) Register 2: Cortex General-Purpose Register 1 (R1) Register 3: Cortex General-Purpose Register 2 (R2) Register 4: Cortex General-Purpose Register 3 (R3) Register 5: Cortex General-Purpose Register 4 (R4) Register 6: Cortex General-Purpose Register 5 (R5) Register 7: Cortex General-Purpose Register 6 (R6) Register 8: Cortex General-Purpose Register 7 (R7) Register 9: Cortex General-Purpose Register 8 (R8) Register 10: Cortex General-Purpose Register 9 (R9) Register 11: Cortex General-Purpose Register 10 (R10) Register 12: Cortex General-Purpose Register 11 (R11) Register 13: Cortex General-Purpose Register 12 (R12) The Rn registers are 32-bit general-purpose registers for data operations and can be accessed from either privileged or unprivileged mode. Cortex General-Purpose Register 0 (R0) Type R/W, reset 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 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 - R/W - R/W - 15 14 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 - R/W - R/W - DATA Type Reset DATA Type Reset Bit/Field Name Type Reset 31:0 DATA R/W - Description Register data. 50 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 14: Stack Pointer (SP) The Stack Pointer (SP) is register R13. In Thread mode, the function of this register changes depending on the ASP bit in the Control Register (CONTROL) register. When the ASP bit is clear, this register is the Main Stack Pointer (MSP). When the ASP bit is set, this register is the Process Stack Pointer (PSP). On reset, the ASP bit is clear, and the processor loads the MSP with the value from address 0x0000.0000. The MSP can only be accessed in privileged mode; the PSP can be accessed in either privileged or unprivileged mode. Stack Pointer (SP) Type R/W, reset 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 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 - R/W - R/W - 15 14 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 - R/W - R/W - SP Type Reset SP Type Reset Bit/Field Name Type Reset 31:0 SP R/W - Description This field is the address of the stack pointer. July 14, 2014 51 Texas Instruments-Production Data The Cortex-M3 Processor Register 15: Link Register (LR) The Link Register (LR) is register R14, and it stores the return information for subroutines, function calls, and exceptions. LR can be accessed from either privileged or unprivileged mode. EXC_RETURN is loaded into LR on exception entry. See Table 2-10 on page 77 for the values and description. Link Register (LR) Type R/W, reset 0xFFFF.FFFF 31 30 29 28 27 26 25 24 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 R/W 1 LINK Type Reset 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 LINK Type Reset R/W 1 R/W 1 R/W 1 R/W 1 R/W 1 R/W 1 Bit/Field Name Type 31:0 LINK R/W R/W 1 Reset R/W 1 Description 0xFFFF.FFFF This field is the return address. 52 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 16: Program Counter (PC) The Program Counter (PC) is register R15, and it contains the current program address. On reset, the processor loads the PC with the value of the reset vector, which is at address 0x0000.0004. Bit 0 of the reset vector is loaded into the THUMB bit of the EPSR at reset and must be 1. The PC register can be accessed in either privileged or unprivileged mode. Program Counter (PC) Type R/W, reset 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 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 - R/W - R/W - 15 14 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 - R/W - R/W - PC Type Reset PC Type Reset Bit/Field Name Type Reset 31:0 PC R/W - Description This field is the current program address. July 14, 2014 53 Texas Instruments-Production Data The Cortex-M3 Processor Register 17: Program Status Register (PSR) Note: This register is also referred to as xPSR. The Program Status Register (PSR) has three functions, and the register bits are assigned to the different functions: ■ Application Program Status Register (APSR), bits 31:27, ■ Execution Program Status Register (EPSR), bits 26:24, 15:10 ■ Interrupt Program Status Register (IPSR), bits 5:0 The PSR, IPSR, and EPSR registers can only be accessed in privileged mode; the APSR register can be accessed in either privileged or unprivileged mode. APSR contains the current state of the condition flags from previous instruction executions. EPSR contains the Thumb state bit and the execution state bits for the If-Then (IT) instruction or the Interruptible-Continuable Instruction (ICI) field for an interrupted load multiple or store multiple instruction. Attempts to read the EPSR directly through application software using the MSR instruction always return zero. Attempts to write the EPSR using the MSR instruction in application software are always ignored. Fault handlers can examine the EPSR value in the stacked PSR to determine the operation that faulted (see “Exception Entry and Return” on page 75). IPSR contains the exception type number of the current Interrupt Service Routine (ISR). These registers can be accessed individually or as a combination of any two or all three registers, using the register name as an argument to the MSR or MRS instructions. For example, all of the registers can be read using PSR with the MRS instruction, or APSR only can be written to using APSR with the MSR instruction. page 54 shows the possible register combinations for the PSR. See the MRS and MSR instruction descriptions in the Cortex™-M3/M4 Instruction Set Technical User's Manual for more information about how to access the program status registers. Table 2-3. PSR Register Combinations Register Type PSR R/W Combination APSR, EPSR, and IPSR IEPSR RO EPSR and IPSR a, b a APSR and IPSR b APSR and EPSR IAPSR R/W EAPSR R/W a. The processor ignores writes to the IPSR bits. b. Reads of the EPSR bits return zero, and the processor ignores writes to these bits. Program Status Register (PSR) Type R/W, reset 0x0100.0000 Type Reset 31 30 29 28 27 N Z C V Q 26 25 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 RO 0 RO 0 RO 1 RO 0 RO 0 RO 0 RO 0 15 14 13 12 11 10 9 8 7 6 5 4 ICI / IT ICI / IT Type Reset RO 0 RO 0 RO 0 24 23 22 21 20 THUMB reserved RO 0 RO 0 RO 0 RO 0 RO 0 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 RO 0 RO 0 RO 0 reserved RO 0 ISRNUM RO 0 54 RO 0 RO 0 RO 0 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Bit/Field Name Type Reset 31 N R/W 0 Description APSR Negative or Less Flag Value Description 1 The previous operation result was negative or less than. 0 The previous operation result was positive, zero, greater than, or equal. The value of this bit is only meaningful when accessing PSR or APSR. 30 Z R/W 0 APSR Zero Flag Value Description 1 The previous operation result was zero. 0 The previous operation result was non-zero. The value of this bit is only meaningful when accessing PSR or APSR. 29 C R/W 0 APSR Carry or Borrow Flag Value Description 1 The previous add operation resulted in a carry bit or the previous subtract operation did not result in a borrow bit. 0 The previous add operation did not result in a carry bit or the previous subtract operation resulted in a borrow bit. The value of this bit is only meaningful when accessing PSR or APSR. 28 V R/W 0 APSR Overflow Flag Value Description 1 The previous operation resulted in an overflow. 0 The previous operation did not result in an overflow. The value of this bit is only meaningful when accessing PSR or APSR. 27 Q R/W 0 APSR DSP Overflow and Saturation Flag Value Description 1 DSP Overflow or saturation has occurred. 0 DSP overflow or saturation has not occurred since reset or since the bit was last cleared. The value of this bit is only meaningful when accessing PSR or APSR. This bit is cleared by software using an MRS instruction. July 14, 2014 55 Texas Instruments-Production Data The Cortex-M3 Processor Bit/Field Name Type Reset 26:25 ICI / IT RO 0x0 Description EPSR ICI / IT status These bits, along with bits 15:10, contain the Interruptible-Continuable Instruction (ICI) field for an interrupted load multiple or store multiple instruction or the execution state bits of the IT instruction. When EPSR holds the ICI execution state, bits 26:25 are zero. The If-Then block contains up to four instructions following an IT instruction. Each instruction in the block is conditional. The conditions for the instructions are either all the same, or some can be the inverse of others. See the Cortex™-M3/M4 Instruction Set Technical User's Manual for more information. The value of this field is only meaningful when accessing PSR or EPSR. 24 THUMB RO 1 EPSR Thumb State This bit indicates the Thumb state and should always be set. The following can clear the THUMB bit: ■ The BLX, BX and POP{PC} instructions ■ Restoration from the stacked xPSR value on an exception return ■ Bit 0 of the vector value on an exception entry or reset Attempting to execute instructions when this bit is clear results in a fault or lockup. See “Lockup” on page 79 for more information. The value of this bit is only meaningful when accessing PSR or EPSR. 23:16 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 15:10 ICI / IT RO 0x0 EPSR ICI / IT status These bits, along with bits 26:25, contain the Interruptible-Continuable Instruction (ICI) field for an interrupted load multiple or store multiple instruction or the execution state bits of the IT instruction. When an interrupt occurs during the execution of an LDM, STM, PUSH or POP instruction, the processor stops the load multiple or store multiple instruction operation temporarily and stores the next register operand in the multiple operation to bits 15:12. After servicing the interrupt, the processor returns to the register pointed to by bits 15:12 and resumes execution of the multiple load or store instruction. When EPSR holds the ICI execution state, bits 11:10 are zero. The If-Then block contains up to four instructions following a 16-bit IT instruction. Each instruction in the block is conditional. The conditions for the instructions are either all the same, or some can be the inverse of others. See the Cortex™-M3/M4 Instruction Set Technical User's Manual for more information. The value of this field is only meaningful when accessing PSR or EPSR. 9:6 reserved RO 0x0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 56 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Bit/Field Name Type Reset Description 5:0 ISRNUM RO 0x00 IPSR ISR Number This field contains the exception type number of the current Interrupt Service Routine (ISR). Value Description 0x00 Thread mode 0x01 Reserved 0x02 NMI 0x03 Hard fault 0x04 Memory management fault 0x05 Bus fault 0x06 Usage fault 0x07-0x0A Reserved 0x0B SVCall 0x0C Reserved for Debug 0x0D Reserved 0x0E PendSV 0x0F SysTick 0x10 Interrupt Vector 0 0x11 Interrupt Vector 1 ... ... 0x2D Interrupt Vector 29 0x2E-0x3F Reserved See “Exception Types” on page 71 for more information. The value of this field is only meaningful when accessing PSR or IPSR. July 14, 2014 57 Texas Instruments-Production Data The Cortex-M3 Processor Register 18: Priority Mask Register (PRIMASK) The PRIMASK register prevents activation of all exceptions with programmable priority. Reset, non-maskable interrupt (NMI), and hard fault are the only exceptions with fixed priority. Exceptions should be disabled when they might impact the timing of critical tasks. This register is only accessible in privileged mode. The MSR and MRS instructions are used to access the PRIMASK register, and the CPS instruction may be used to change the value of the PRIMASK register. See the Cortex™-M3/M4 Instruction Set Technical User's Manual for more information on these instructions. For more information on exception priority levels, see “Exception Types” on page 71. Priority Mask Register (PRIMASK) Type R/W, reset 0x0000.0000 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 8 RO 0 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 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 Bit/Field Name Type Reset 31:1 reserved RO 0x0000.000 0 PRIMASK R/W 0 RO 0 PRIMASK R/W 0 Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. Priority Mask Value Description 1 Prevents the activation of all exceptions with configurable priority. 0 No effect. 58 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 19: Fault Mask Register (FAULTMASK) The FAULTMASK register prevents activation of all exceptions except for the Non-Maskable Interrupt (NMI). Exceptions should be disabled when they might impact the timing of critical tasks. This register is only accessible in privileged mode. The MSR and MRS instructions are used to access the FAULTMASK register, and the CPS instruction may be used to change the value of the FAULTMASK register. See the Cortex™-M3/M4 Instruction Set Technical User's Manual for more information on these instructions. For more information on exception priority levels, see “Exception Types” on page 71. Fault Mask Register (FAULTMASK) Type R/W, reset 0x0000.0000 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 8 RO 0 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 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 Bit/Field Name Type Reset 31:1 reserved RO 0x0000.000 0 FAULTMASK R/W 0 RO 0 FAULTMASK R/W 0 Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. Fault Mask Value Description 1 Prevents the activation of all exceptions except for NMI. 0 No effect. The processor clears the FAULTMASK bit on exit from any exception handler except the NMI handler. July 14, 2014 59 Texas Instruments-Production Data The Cortex-M3 Processor Register 20: Base Priority Mask Register (BASEPRI) The BASEPRI register defines the minimum priority for exception processing. When BASEPRI is set to a nonzero value, it prevents the activation of all exceptions with the same or lower priority level as the BASEPRI value. Exceptions should be disabled when they might impact the timing of critical tasks. This register is only accessible in privileged mode. For more information on exception priority levels, see “Exception Types” on page 71. Base Priority Mask Register (BASEPRI) Type R/W, reset 0x0000.0000 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 RO 0 RO 0 RO 0 RO 0 reserved Type Reset reserved Type Reset BASEPRI RO 0 Bit/Field Name Type Reset 31:8 reserved RO 0x0000.00 7:5 BASEPRI R/W 0x0 R/W 0 reserved RO 0 Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. Base Priority Any exception that has a programmable priority level with the same or lower priority as the value of this field is masked. The PRIMASK register can be used to mask all exceptions with programmable priority levels. Higher priority exceptions have lower priority levels. Value Description 4:0 reserved RO 0x0 0x0 All exceptions are unmasked. 0x1 All exceptions with priority level 1-7 are masked. 0x2 All exceptions with priority level 2-7 are masked. 0x3 All exceptions with priority level 3-7 are masked. 0x4 All exceptions with priority level 4-7 are masked. 0x5 All exceptions with priority level 5-7 are masked. 0x6 All exceptions with priority level 6-7 are masked. 0x7 All exceptions with priority level 7 are masked. Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 60 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 21: Control Register (CONTROL) The CONTROL register controls the stack used and the privilege level for software execution when the processor is in Thread mode. This register is only accessible in privileged mode. Handler mode always uses MSP, so the processor ignores explicit writes to the ASP bit of the CONTROL register when in Handler mode. The exception entry and return mechanisms automatically update the CONTROL register based on the EXC_RETURN value (see Table 2-10 on page 77). In an OS environment, threads running in Thread mode should use the process stack and the kernel and exception handlers should use the main stack. By default, Thread mode uses MSP. To switch the stack pointer used in Thread mode to PSP, either use the MSR instruction to set the ASP bit, as detailed in the Cortex™-M3/M4 Instruction Set Technical User's Manual, or perform an exception return to Thread mode with the appropriate EXC_RETURN value, as shown in Table 2-10 on page 77. Note: When changing the stack pointer, software must use an ISB instruction immediately after the MSR instruction, ensuring that instructions after the ISB execute use the new stack pointer. See the Cortex™-M3/M4 Instruction Set Technical User's Manual. Control Register (CONTROL) Type R/W, reset 0x0000.0000 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 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 ASP TMPL 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 31:2 reserved RO 0x0000.000 1 ASP R/W 0 Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. Active Stack Pointer Value Description 1 PSP is the current stack pointer. 0 MSP is the current stack pointer In Handler mode, this bit reads as zero and ignores writes. The Cortex-M3 updates this bit automatically on exception return. 0 TMPL R/W 0 Thread Mode Privilege Level Value Description 1 Unprivileged software can be executed in Thread mode. 0 Only privileged software can be executed in Thread mode. July 14, 2014 61 Texas Instruments-Production Data The Cortex-M3 Processor 2.3.5 Exceptions and Interrupts The Cortex-M3 processor supports interrupts and system exceptions. The processor and the Nested Vectored Interrupt Controller (NVIC) prioritize and handle all exceptions. An exception changes the normal flow of software control. The processor uses Handler mode to handle all exceptions except for reset. See “Exception Entry and Return” on page 75 for more information. The NVIC registers control interrupt handling. See “Nested Vectored Interrupt Controller (NVIC)” on page 86 for more information. 2.3.6 Data Types The Cortex-M3 supports 32-bit words, 16-bit halfwords, and 8-bit bytes. The processor also supports 64-bit data transfer instructions. All instruction and data memory accesses are little endian. See “Memory Regions, Types and Attributes” on page 63 for more information. 2.4 Memory Model This section describes the processor memory map, the behavior of memory accesses, and the bit-banding features. The processor has a fixed memory map that provides up to 4 GB of addressable memory. The memory map for the LM3S812 controller is provided in Table 2-4 on page 62. In this manual, register addresses are given as a hexadecimal increment, relative to the module’s base address as shown in the memory map. The regions for SRAM and peripherals include bit-band regions. Bit-banding provides atomic operations to bit data (see “Bit-Banding” on page 66). The processor reserves regions of the Private peripheral bus (PPB) address range for core peripheral registers (see “Cortex-M3 Peripherals” on page 85). Note: Within the memory map, all reserved space returns a bus fault when read or written. Table 2-4. Memory Map Start End Description For details, see page ... 0x0000.0000 0x0000.FFFF On-chip Flash 218 0x0001.0000 0x1FFF.FFFF Reserved - 0x2000.0000 0x2000.1FFF Bit-banded on-chip SRAM 212 0x2000.2000 0x21FF.FFFF Reserved - 0x2200.0000 0x2203.FFFF Bit-band alias of bit-banded on-chip SRAM starting at 0x2000.0000 212 0x2204.0000 0x3FFF.FFFF Reserved - 0x4000.0000 0x4000.0FFF Watchdog timer 0 311 0x4000.1000 0x4000.3FFF Reserved - 0x4000.4000 0x4000.4FFF GPIO Port A 240 0x4000.5000 0x4000.5FFF GPIO Port B 240 0x4000.6000 0x4000.6FFF GPIO Port C 240 0x4000.7000 0x4000.7FFF GPIO Port D 240 0x4000.8000 0x4000.8FFF SSI0 420 Memory FiRM Peripherals 62 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Table 2-4. Memory Map (continued) Start End Description For details, see page ... 0x4000.9000 0x4000.BFFF Reserved - 0x4000.C000 0x4000.CFFF UART0 375 0x4000.D000 0x4000.DFFF UART1 375 0x4000.E000 0x4001.FFFF Reserved - 0x4002.0000 0x4002.0FFF I2C 0 461 0x4002.1000 0x4002.3FFF Reserved - 0x4002.4000 0x4002.4FFF GPIO Port E 240 0x4002.5000 0x4002.7FFF Reserved - 0x4002.8000 0x4002.8FFF PWM 503 0x4002.9000 0x4002.FFFF Reserved - 0x4003.0000 0x4003.0FFF Timer 0 283 0x4003.1000 0x4003.1FFF Timer 1 283 0x4003.2000 0x4003.2FFF Timer 2 283 0x4003.3000 0x4003.7FFF Reserved - 0x4003.8000 0x4003.8FFF ADC0 341 0x4003.9000 0x4003.BFFF Reserved - 0x4003.C000 0x4003.CFFF Analog Comparators 483 0x4003.D000 0x400F.CFFF Reserved - 0x400F.D000 0x400F.DFFF Flash memory control 218 0x400F.E000 0x400F.EFFF System control 164 0x400F.F000 0x41FF.FFFF Reserved - 0x4200.0000 0x43FF.FFFF Bit-banded alias of 0x4000.0000 through 0x400F.FFFF - 0x4400.0000 0xDFFF.FFFF Reserved - 0xE000.0000 0xE000.0FFF Instrumentation Trace Macrocell (ITM) 45 0xE000.1000 0xE000.1FFF Data Watchpoint and Trace (DWT) 45 0xE000.2000 0xE000.2FFF Flash Patch and Breakpoint (FPB) 45 0xE000.3000 0xE000.DFFF Reserved - 0xE000.E000 0xE000.EFFF Cortex-M3 Peripherals (SysTick, NVIC, MPU and SCB) 93 0xE000.F000 0xE003.FFFF Reserved - 0xE004.0000 0xE004.0FFF Trace Port Interface Unit (TPIU) 46 0xE004.1000 0xFFFF.FFFF Reserved - Peripherals Private Peripheral Bus 2.4.1 Memory Regions, Types and Attributes The memory map and the programming of the MPU split the memory map into regions. Each region has a defined memory type, and some regions have additional memory attributes. The memory type and attributes determine the behavior of accesses to the region. The memory types are: ■ Normal: The processor can re-order transactions for efficiency and perform speculative reads. July 14, 2014 63 Texas Instruments-Production Data The Cortex-M3 Processor ■ Device: The processor preserves transaction order relative to other transactions to Device or Strongly Ordered memory. ■ Strongly Ordered: The processor preserves transaction order relative to all other transactions. The different ordering requirements for Device and Strongly Ordered memory mean that the memory system can buffer a write to Device memory but must not buffer a write to Strongly Ordered memory. An additional memory attribute is Execute Never (XN), which means the processor prevents instruction accesses. A fault exception is generated only on execution of an instruction executed from an XN region. 2.4.2 Memory System Ordering of Memory Accesses For most memory accesses caused by explicit memory access instructions, the memory system does not guarantee that the order in which the accesses complete matches the program order of the instructions, providing the order does not affect the behavior of the instruction sequence. Normally, if correct program execution depends on two memory accesses completing in program order, software must insert a memory barrier instruction between the memory access instructions (see “Software Ordering of Memory Accesses” on page 65). However, the memory system does guarantee ordering of accesses to Device and Strongly Ordered memory. For two memory access instructions A1 and A2, if both A1 and A2 are accesses to either Device or Strongly Ordered memory, and if A1 occurs before A2 in program order, A1 is always observed before A2. 2.4.3 Behavior of Memory Accesses Table 2-5 on page 64 shows the behavior of accesses to each region in the memory map. See “Memory Regions, Types and Attributes” on page 63 for more information on memory types and the XN attribute. Stellaris devices may have reserved memory areas within the address ranges shown below (refer to Table 2-4 on page 62 for more information). Table 2-5. Memory Access Behavior Address Range Memory Region Memory Type Execute Never (XN) Description 0x0000.0000 - 0x1FFF.FFFF Code Normal - This executable region is for program code. Data can also be stored here. 0x2000.0000 - 0x3FFF.FFFF SRAM Normal - This executable region is for data. Code can also be stored here. This region includes bit band and bit band alias areas (see Table 2-6 on page 66). 0x4000.0000 - 0x5FFF.FFFF Peripheral Device XN This region includes bit band and bit band alias areas (see Table 2-7 on page 66). 0x6000.0000 - 0x9FFF.FFFF External RAM Normal - This executable region is for data. 0xA000.0000 - 0xDFFF.FFFF External device Device XN This region is for external device memory. 0xE000.0000- 0xE00F.FFFF Private peripheral bus Strongly Ordered XN This region includes the NVIC, system timer, and system control block. 0xE010.0000- 0xFFFF.FFFF Reserved - - - The Code, SRAM, and external RAM regions can hold programs. However, it is recommended that programs always use the Code region because the Cortex-M3 has separate buses that can perform instruction fetches and data accesses simultaneously. 64 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller The MPU can override the default memory access behavior described in this section. For more information, see “Memory Protection Unit (MPU)” on page 88. The Cortex-M3 prefetches instructions ahead of execution and speculatively prefetches from branch target addresses. 2.4.4 Software Ordering of Memory Accesses The order of instructions in the program flow does not always guarantee the order of the corresponding memory transactions for the following reasons: ■ The processor can reorder some memory accesses to improve efficiency, providing this does not affect the behavior of the instruction sequence. ■ The processor has multiple bus interfaces. ■ Memory or devices in the memory map have different wait states. ■ Some memory accesses are buffered or speculative. “Memory System Ordering of Memory Accesses” on page 64 describes the cases where the memory system guarantees the order of memory accesses. Otherwise, if the order of memory accesses is critical, software must include memory barrier instructions to force that ordering. The Cortex-M3 has the following memory barrier instructions: ■ The Data Memory Barrier (DMB) instruction ensures that outstanding memory transactions complete before subsequent memory transactions. ■ The Data Synchronization Barrier (DSB) instruction ensures that outstanding memory transactions complete before subsequent instructions execute. ■ The Instruction Synchronization Barrier (ISB) instruction ensures that the effect of all completed memory transactions is recognizable by subsequent instructions. Memory barrier instructions can be used in the following situations: ■ MPU programming – If the MPU settings are changed and the change must be effective on the very next instruction, use a DSB instruction to ensure the effect of the MPU takes place immediately at the end of context switching. – Use an ISB instruction to ensure the new MPU setting takes effect immediately after programming the MPU region or regions, if the MPU configuration code was accessed using a branch or call. If the MPU configuration code is entered using exception mechanisms, then an ISB instruction is not required. ■ Vector table If the program changes an entry in the vector table and then enables the corresponding exception, use a DMB instruction between the operations. The DMB instruction ensures that if the exception is taken immediately after being enabled, the processor uses the new exception vector. ■ Self-modifying code July 14, 2014 65 Texas Instruments-Production Data The Cortex-M3 Processor If a program contains self-modifying code, use an ISB instruction immediately after the code modification in the program. The ISB instruction ensures subsequent instruction execution uses the updated program. ■ Memory map switching If the system contains a memory map switching mechanism, use a DSB instruction after switching the memory map in the program. The DSB instruction ensures subsequent instruction execution uses the updated memory map. ■ Dynamic exception priority change When an exception priority has to change when the exception is pending or active, use DSB instructions after the change. The change then takes effect on completion of the DSB instruction. Memory accesses to Strongly Ordered memory, such as the System Control Block, do not require the use of DMB instructions. For more information on the memory barrier instructions, see the Cortex™-M3/M4 Instruction Set Technical User's Manual. 2.4.5 Bit-Banding A bit-band region maps each word in a bit-band alias region to a single bit in the bit-band region. The bit-band regions occupy the lowest 1 MB of the SRAM and peripheral memory regions. Accesses to the 32-MB SRAM alias region map to the 1-MB SRAM bit-band region, as shown in Table 2-6 on page 66. Accesses to the 32-MB peripheral alias region map to the 1-MB peripheral bit-band region, as shown in Table 2-7 on page 66. For the specific address range of the bit-band regions, see Table 2-4 on page 62. Note: A word access to the SRAM or the peripheral bit-band alias region maps to a single bit in the SRAM or peripheral bit-band region. A word access to a bit band address results in a word access to the underlying memory, and similarly for halfword and byte accesses. This allows bit band accesses to match the access requirements of the underlying peripheral. Table 2-6. SRAM Memory Bit-Banding Regions Address Range Memory Region Instruction and Data Accesses Start End 0x2000.0000 0x2000.1FFF SRAM bit-band region Direct accesses to this memory range behave as SRAM memory accesses, but this region is also bit addressable through bit-band alias. 0x2200.0000 0x2203.FFFF SRAM bit-band alias Data accesses to this region are remapped to bit band region. A write operation is performed as read-modify-write. Instruction accesses are not remapped. Table 2-7. Peripheral Memory Bit-Banding Regions Address Range Start End 0x4000.0000 0x400F.FFFF Memory Region Instruction and Data Accesses Peripheral bit-band region Direct accesses to this memory range behave as peripheral memory accesses, but this region is also bit addressable through bit-band alias. 66 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Table 2-7. Peripheral Memory Bit-Banding Regions (continued) Address Range Memory Region Start End 0x4200.0000 0x43FF.FFFF Instruction and Data Accesses Peripheral bit-band alias Data accesses to this region are remapped to bit band region. A write operation is performed as read-modify-write. Instruction accesses are not permitted. The following formula shows how the alias region maps onto the bit-band region: bit_word_offset = (byte_offset x 32) + (bit_number x 4) bit_word_addr = bit_band_base + bit_word_offset where: bit_word_offset The position of the target bit in the bit-band memory region. bit_word_addr The address of the word in the alias memory region that maps to the targeted bit. bit_band_base The starting address of the alias region. byte_offset The number of the byte in the bit-band region that contains the targeted bit. bit_number The bit position, 0-7, of the targeted bit. Figure 2-4 on page 68 shows examples of bit-band mapping between the SRAM bit-band alias region and the SRAM bit-band region: ■ The alias word at 0x23FF.FFE0 maps to bit 0 of the bit-band byte at 0x200F.FFFF: 0x23FF.FFE0 = 0x2200.0000 + (0x000F.FFFF*32) + (0*4) ■ The alias word at 0x23FF.FFFC maps to bit 7 of the bit-band byte at 0x200F.FFFF: 0x23FF.FFFC = 0x2200.0000 + (0x000F.FFFF*32) + (7*4) ■ The alias word at 0x2200.0000 maps to bit 0 of the bit-band byte at 0x2000.0000: 0x2200.0000 = 0x2200.0000 + (0*32) + (0*4) ■ The alias word at 0x2200.001C maps to bit 7 of the bit-band byte at 0x2000.0000: 0x2200.001C = 0x2200.0000+ (0*32) + (7*4) July 14, 2014 67 Texas Instruments-Production Data The Cortex-M3 Processor Figure 2-4. Bit-Band Mapping 32-MB Alias Region 0x23FF.FFFC 0x23FF.FFF8 0x23FF.FFF4 0x23FF.FFF0 0x23FF.FFEC 0x23FF.FFE8 0x23FF.FFE4 0x23FF.FFE0 0x2200.001C 0x2200.0018 0x2200.0014 0x2200.0010 0x2200.000C 0x2200.0008 0x2200.0004 0x2200.0000 7 3 1-MB SRAM Bit-Band Region 7 6 5 4 3 2 1 0 7 6 0x200F.FFFF 7 6 5 4 3 2 0x2000.0003 2.4.5.1 5 4 3 2 1 0 7 6 0x200F.FFFE 1 0 7 6 5 4 3 2 5 4 3 2 1 0 6 0x200F.FFFD 1 0 0x2000.0002 7 6 5 4 3 2 0x2000.0001 5 4 2 1 0 1 0 0x200F.FFFC 1 0 7 6 5 4 3 2 0x2000.0000 Directly Accessing an Alias Region Writing to a word in the alias region updates a single bit in the bit-band region. Bit 0 of the value written to a word in the alias region determines the value written to the targeted bit in the bit-band region. Writing a value with bit 0 set writes a 1 to the bit-band bit, and writing a value with bit 0 clear writes a 0 to the bit-band bit. Bits 31:1 of the alias word have no effect on the bit-band bit. Writing 0x01 has the same effect as writing 0xFF. Writing 0x00 has the same effect as writing 0x0E. When reading a word in the alias region, 0x0000.0000 indicates that the targeted bit in the bit-band region is clear and 0x0000.0001 indicates that the targeted bit in the bit-band region is set. 2.4.5.2 Directly Accessing a Bit-Band Region “Behavior of Memory Accesses” on page 64 describes the behavior of direct byte, halfword, or word accesses to the bit-band regions. 2.4.6 Data Storage The processor views memory as a linear collection of bytes numbered in ascending order from zero. For example, bytes 0-3 hold the first stored word, and bytes 4-7 hold the second stored word. Data is stored in little-endian format, with the least-significant byte (lsbyte) of a word stored at the lowest-numbered byte, and the most-significant byte (msbyte) stored at the highest-numbered byte. Figure 2-5 on page 69 illustrates how data is stored. 68 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Figure 2-5. Data Storage Memory 7 Register 0 31 2.4.7 Address A B0 A+1 B1 A+2 B2 A+3 B3 lsbyte 24 23 B3 16 15 B2 8 7 B1 0 B0 msbyte Synchronization Primitives The Cortex-M3 instruction set includes pairs of synchronization primitives which provide a non-blocking mechanism that a thread or process can use to obtain exclusive access to a memory location. Software can use these primitives to perform a guaranteed read-modify-write memory update sequence or for a semaphore mechanism. A pair of synchronization primitives consists of: ■ A Load-Exclusive instruction, which is used to read the value of a memory location and requests exclusive access to that location. ■ A Store-Exclusive instruction, which is used to attempt to write to the same memory location and returns a status bit to a register. If this status bit is clear, it indicates that the thread or process gained exclusive access to the memory and the write succeeds; if this status bit is set, it indicates that the thread or process did not gain exclusive access to the memory and no write was performed. The pairs of Load-Exclusive and Store-Exclusive instructions are: ■ The word instructions LDREX and STREX ■ The halfword instructions LDREXH and STREXH ■ The byte instructions LDREXB and STREXB Software must use a Load-Exclusive instruction with the corresponding Store-Exclusive instruction. To perform an exclusive read-modify-write of a memory location, software must: 1. Use a Load-Exclusive instruction to read the value of the location. 2. Modify the value, as required. 3. Use a Store-Exclusive instruction to attempt to write the new value back to the memory location. 4. Test the returned status bit. If the status bit is clear, the read-modify-write completed successfully. If the status bit is set, no write was performed, which indicates that the value returned at step 1 might be out of date. The software must retry the entire read-modify-write sequence. Software can use the synchronization primitives to implement a semaphore as follows: July 14, 2014 69 Texas Instruments-Production Data The Cortex-M3 Processor 1. Use a Load-Exclusive instruction to read from the semaphore address to check whether the semaphore is free. 2. If the semaphore is free, use a Store-Exclusive to write the claim value to the semaphore address. 3. If the returned status bit from step 2 indicates that the Store-Exclusive succeeded, then the software has claimed the semaphore. However, if the Store-Exclusive failed, another process might have claimed the semaphore after the software performed step 1. The Cortex-M3 includes an exclusive access monitor that tags the fact that the processor has executed a Load-Exclusive instruction. The processor removes its exclusive access tag if: ■ It executes a CLREX instruction. ■ It executes a Store-Exclusive instruction, regardless of whether the write succeeds. ■ An exception occurs, which means the processor can resolve semaphore conflicts between different threads. For more information about the synchronization primitive instructions, see the Cortex™-M3/M4 Instruction Set Technical User's Manual. 2.5 Exception Model The ARM Cortex-M3 processor and the Nested Vectored Interrupt Controller (NVIC) prioritize and handle all exceptions 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, enabling 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 2-8 on page 72 lists all exception types. Software can set eight priority levels on seven of these exceptions (system handlers) as well as on 24 interrupts (listed in Table 2-9 on page 73). Priorities on the system handlers are set with the NVIC System Handler Priority n (SYSPRIn) registers. Interrupts are enabled through the NVIC Interrupt Set Enable n (ENn) register and prioritized with the NVIC Interrupt Priority n (PRIn) registers. Priorities can be grouped by splitting priority levels into preemption priorities and subpriorities. All the interrupt registers are described in “Nested Vectored Interrupt Controller (NVIC)” on page 86. Internally, the highest user-programmable priority (0) is treated as fourth priority, after a Reset, Non-Maskable Interrupt (NMI), and a Hard Fault, in that order. Note that 0 is the default priority for all the programmable priorities. Important: After a write to clear an interrupt source, it may take several processor cycles for the NVIC to see the interrupt source de-assert. Thus if the interrupt clear is done as the last action in an interrupt handler, it is possible for the interrupt handler to complete while the NVIC sees the interrupt as still asserted, causing the interrupt handler to be re-entered errantly. This situation can be avoided by either clearing the interrupt source at the beginning of the interrupt handler or by performing a read or write after the write to clear the interrupt source (and flush the write buffer). See “Nested Vectored Interrupt Controller (NVIC)” on page 86 for more information on exceptions and interrupts. 70 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 2.5.1 Exception States Each exception is in one of the following states: ■ Inactive. The exception is not active and not pending. ■ Pending. The exception is waiting to be serviced by the processor. An interrupt request from a peripheral or from software can change the state of the corresponding interrupt to pending. ■ Active. An exception that is being serviced by the processor but has not completed. Note: An exception handler can interrupt the execution of another exception handler. In this case, both exceptions are in the active state. ■ Active and Pending. The exception is being serviced by the processor, and there is a pending exception from the same source. 2.5.2 Exception Types The exception types are: ■ Reset. Reset is invoked on power up or a warm reset. The exception model treats reset as a special form of exception. When reset is asserted, the operation of the processor stops, potentially at any point in an instruction. When reset is deasserted, execution restarts from the address provided by the reset entry in the vector table. Execution restarts as privileged execution in Thread mode. ■ NMI. A non-maskable Interrupt (NMI) can be signaled using the NMI signal or triggered by software using the Interrupt Control and State (INTCTRL) register. This exception has the highest priority other than reset. NMI is permanently enabled and has a fixed priority of -2. NMIs cannot be masked or prevented from activation by any other exception or preempted by any exception other than reset. ■ Hard Fault. A hard fault is an exception that occurs because of an error during exception processing, or because an exception cannot be managed by any other exception mechanism. Hard faults have a fixed priority of -1, meaning they have higher priority than any exception with configurable priority. ■ Memory Management Fault. A memory management fault is an exception that occurs because of a memory protection related fault, including access violation and no match. The MPU or the fixed memory protection constraints determine this fault, for both instruction and data memory transactions. This fault is used to abort instruction accesses to Execute Never (XN) memory regions, even if the MPU is disabled. ■ Bus Fault. A bus fault is an exception that occurs because of a memory-related fault for an instruction or data memory transaction such as a prefetch fault or a memory access fault. This fault can be enabled or disabled. ■ Usage Fault. A usage fault is an exception that occurs because of a fault related to instruction execution, such as: – An undefined instruction – An illegal unaligned access – Invalid state on instruction execution July 14, 2014 71 Texas Instruments-Production Data The Cortex-M3 Processor – An error on exception return An unaligned address on a word or halfword memory access or division by zero can cause a usage fault when the core is properly configured. ■ SVCall. A supervisor call (SVC) is an exception that is triggered by the SVC instruction. In an OS environment, applications can use SVC instructions to access OS kernel functions and device drivers. ■ Debug Monitor. This exception is caused by the debug monitor (when not halting). This exception is only active when enabled. This exception does not activate if it is a lower priority than the current activation. ■ PendSV. PendSV is a pendable, interrupt-driven request for system-level service. In an OS environment, use PendSV for context switching when no other exception is active. PendSV is triggered using the Interrupt Control and State (INTCTRL) register. ■ SysTick. A SysTick exception is an exception that the system timer generates when it reaches zero when it is enabled to generate an interrupt. Software can also generate a SysTick exception using the Interrupt Control and State (INTCTRL) register. In an OS environment, the processor can use this exception as system tick. ■ Interrupt (IRQ). An interrupt, or IRQ, is an exception signaled by a peripheral or generated by a software request and fed through the NVIC (prioritized). All interrupts are asynchronous to instruction execution. In the system, peripherals use interrupts to communicate with the processor. Table 2-9 on page 73 lists the interrupts on the LM3S812 controller. For an asynchronous exception, other than reset, the processor can execute another instruction between when the exception is triggered and when the processor enters the exception handler. Privileged software can disable the exceptions that Table 2-8 on page 72 shows as having configurable priority (see the SYSHNDCTRL register on page 121 and the DIS0 register on page 100). For more information about hard faults, memory management faults, bus faults, and usage faults, see “Fault Handling” on page 77. Table 2-8. Exception Types Exception Type a Vector Number Priority Vector Address or b Offset - 0 - 0x0000.0000 Stack top is loaded from the first entry of the vector table on reset. Reset 1 -3 (highest) 0x0000.0004 Asynchronous Non-Maskable Interrupt (NMI) 2 -2 0x0000.0008 Asynchronous Hard Fault 3 -1 0x0000.000C - c 0x0000.0010 Synchronous c 0x0000.0014 Synchronous when precise and asynchronous when imprecise c Synchronous Memory Management 4 programmable Bus Fault 5 programmable Usage Fault 6 programmable 0x0000.0018 7-10 - - - Activation c c Reserved SVCall 11 programmable 0x0000.002C Synchronous Debug Monitor 12 programmable 0x0000.0030 Synchronous - 13 - - 72 Reserved July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Table 2-8. Exception Types (continued) Exception Type PendSV SysTick a Vector Number Priority 14 programmable 15 Interrupts Vector Address or b Offset c 0x0000.0038 Asynchronous c 0x0000.003C Asynchronous programmable 16 and above Activation d programmable 0x0000.0040 and above Asynchronous a. 0 is the default priority for all the programmable priorities. b. See “Vector Table” on page 74. c. See SYSPRI1 on page 118. d. See PRIn registers on page 104. Table 2-9. Interrupts Vector Number Interrupt Number (Bit in Interrupt Registers) Vector Address or Offset Description 0-15 - 0x0000.0000 0x0000.003C 16 0 0x0000.0040 GPIO Port A 17 1 0x0000.0044 GPIO Port B 18 2 0x0000.0048 GPIO Port C 19 3 0x0000.004C GPIO Port D 20 4 0x0000.0050 GPIO Port E 21 5 0x0000.0054 UART0 22 6 0x0000.0058 UART1 23 7 0x0000.005C SSI0 24 8 0x0000.0060 I2C0 25 9 - Processor exceptions Reserved 26 10 0x0000.0068 27-29 11-13 - PWM Generator 0 30 14 0x0000.0078 ADC0 Sequence 0 31 15 0x0000.007C ADC0 Sequence 1 32 16 0x0000.0080 ADC0 Sequence 2 33 17 0x0000.0084 ADC0 Sequence 3 34 18 0x0000.0088 Watchdog Timer 0 35 19 0x0000.008C Timer 0A 36 20 0x0000.0090 Timer 0B 37 21 0x0000.0094 Timer 1A 38 22 0x0000.0098 Timer 1B 39 23 0x0000.009C Timer 2A 40 24 0x0000.00A0 Timer 2B Analog Comparator 0 Reserved 41 25 0x0000.00A4 42-43 26-27 - 44 28 0x0000.00B0 System Control 45 29 0x0000.00B4 Flash Memory Control Reserved July 14, 2014 73 Texas Instruments-Production Data The Cortex-M3 Processor 2.5.3 Exception Handlers The processor handles exceptions using: ■ Interrupt Service Routines (ISRs). Interrupts (IRQx) are the exceptions handled by ISRs. ■ Fault Handlers. Hard fault, memory management fault, usage fault, and bus fault are fault exceptions handled by the fault handlers. ■ System Handlers. NMI, PendSV, SVCall, SysTick, and the fault exceptions are all system exceptions that are handled by system handlers. 2.5.4 Vector Table The vector table contains the reset value of the stack pointer and the start addresses, also called exception vectors, for all exception handlers. The vector table is constructed using the vector address or offset shown in Table 2-8 on page 72. Figure 2-6 on page 74 shows the order of the exception vectors in the vector table. The least-significant bit of each vector must be 1, indicating that the exception handler is Thumb code Figure 2-6. Vector Table Exception number IRQ number 45 29 . . . 18 2 17 1 16 0 15 -1 14 -2 13 Offset 0x00B4 . . . 0x004C 0x0048 0x0044 0x0040 0x003C 0x0038 12 11 Vector IRQ29 . . . IRQ2 IRQ1 IRQ0 Systick PendSV Reserved Reserved for Debug -5 10 0x002C 9 SVCall Reserved 8 7 6 -10 5 -11 4 -12 3 -13 2 -14 1 0x0018 0x0014 0x0010 0x000C 0x0008 0x0004 0x0000 Usage fault Bus fault Memory management fault Hard fault NMI Reset Initial SP value On system reset, the vector table is fixed at address 0x0000.0000. Privileged software can write to the Vector Table Offset (VTABLE) register to relocate the vector table start address to a different 74 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller memory location, in the range 0x0000.0100 to 0x3FFF.FF00 (see “Vector Table” on page 74). Note that when configuring the VTABLE register, the offset must be aligned on a 256-byte boundary. 2.5.5 Exception Priorities As Table 2-8 on page 72 shows, all exceptions have an associated priority, with a lower priority value indicating a higher priority and configurable priorities for all exceptions except Reset, Hard fault, and NMI. If software does not configure any priorities, then all exceptions with a configurable priority have a priority of 0. For information about configuring exception priorities, see page 118 and page 104. Note: Configurable priority values for the Stellaris implementation are in the range 0-7. This means that the Reset, Hard fault, and NMI exceptions, with fixed negative priority values, always have higher priority than any other exception. For example, assigning a higher priority value to IRQ[0] and a lower priority value to IRQ[1] means that IRQ[1] has higher priority than IRQ[0]. If both IRQ[1] and IRQ[0] are asserted, IRQ[1] is processed before IRQ[0]. If multiple pending exceptions have the same priority, the pending exception with the lowest exception number takes precedence. For example, if both IRQ[0] and IRQ[1] are pending and have the same priority, then IRQ[0] is processed before IRQ[1]. When the processor is executing an exception handler, the exception handler is preempted if a higher priority exception occurs. If an exception occurs with the same priority as the exception being handled, the handler is not preempted, irrespective of the exception number. However, the status of the new interrupt changes to pending. 2.5.6 Interrupt Priority Grouping To increase priority control in systems with interrupts, the NVIC supports priority grouping. This grouping divides each interrupt priority register entry into two fields: ■ An upper field that defines the group priority ■ A lower field that defines a subpriority within the group Only the group priority determines preemption of interrupt exceptions. When the processor is executing an interrupt exception handler, another interrupt with the same group priority as the interrupt being handled does not preempt the handler. If multiple pending interrupts have the same group priority, the subpriority field determines the order in which they are processed. If multiple pending interrupts have the same group priority and subpriority, the interrupt with the lowest IRQ number is processed first. For information about splitting the interrupt priority fields into group priority and subpriority, see page 112. 2.5.7 Exception Entry and Return Descriptions of exception handling use the following terms: ■ Preemption. When the processor is executing an exception handler, an exception can preempt the exception handler if its priority is higher than the priority of the exception being handled. See “Interrupt Priority Grouping” on page 75 for more information about preemption by an interrupt. When one exception preempts another, the exceptions are called nested exceptions. See “Exception Entry” on page 76 more information. July 14, 2014 75 Texas Instruments-Production Data The Cortex-M3 Processor ■ Return. Return occurs when the exception handler is completed, and there is no pending exception with sufficient priority to be serviced and the completed exception handler was not handling a late-arriving exception. The processor pops the stack and restores the processor state to the state it had before the interrupt occurred. See “Exception Return” on page 77 for more information. ■ Tail-Chaining. This mechanism speeds up exception servicing. On completion of an exception handler, if there is a pending exception that meets the requirements for exception entry, the stack pop is skipped and control transfers to the new exception handler. ■ Late-Arriving. This mechanism speeds up preemption. If a higher priority exception occurs during state saving for a previous exception, the processor switches to handle the higher priority exception and initiates the vector fetch for that exception. State saving is not affected by late arrival because the state saved is the same for both exceptions. Therefore, the state saving continues uninterrupted. The processor can accept a late arriving exception until the first instruction of the exception handler of the original exception enters the execute stage of the processor. On return from the exception handler of the late-arriving exception, the normal tail-chaining rules apply. 2.5.7.1 Exception Entry Exception entry occurs when there is a pending exception with sufficient priority and either the processor is in Thread mode or the new exception is of higher priority than the exception being handled, in which case the new exception preempts the original exception. When one exception preempts another, the exceptions are nested. Sufficient priority means the exception has more priority than any limits set by the mask registers (see PRIMASK on page 58, FAULTMASK on page 59, and BASEPRI on page 60). An exception with less priority than this is pending but is not handled by the processor. When the processor takes an exception, unless the exception is a tail-chained or a late-arriving exception, the processor pushes information onto the current stack. This operation is referred to as stacking and the structure of eight data words is referred to as stack frame. Figure 2-7. Exception Stack Frame ... {aligner} xPSR PC LR R12 R3 R2 R1 R0 Pre-IRQ top of stack IRQ top of stack Immediately after stacking, the stack pointer indicates the lowest address in the stack frame. Unless stack alignment is disabled, the stack frame is aligned to a double-word address. If the STKALIGN bit of the Configuration Control (CCR) register is set, stack align adjustment is performed during stacking. The stack frame includes the return address, which is the address of the next instruction in the interrupted program. This value is restored to the PC at exception return so that the interrupted program resumes. 76 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller In parallel to the stacking operation, the processor performs a vector fetch that reads the exception handler start address from the vector table. When stacking is complete, the processor starts executing the exception handler. At the same time, the processor writes an EXC_RETURN value to the LR, indicating which stack pointer corresponds to the stack frame and what operation mode the processor was in before the entry occurred. If no higher-priority exception occurs during exception entry, the processor starts executing the exception handler and automatically changes the status of the corresponding pending interrupt to active. If another higher-priority exception occurs during exception entry, known as late arrival, the processor starts executing the exception handler for this exception and does not change the pending status of the earlier exception. 2.5.7.2 Exception Return Exception return occurs when the processor is in Handler mode and executes one of the following instructions to load the EXC_RETURN value into the PC: ■ An LDM or POP instruction that loads the PC ■ A BX instruction using any register ■ An LDR instruction with the PC as the destination EXC_RETURN is the value loaded into the LR on exception entry. The exception mechanism relies on this value to detect when the processor has completed an exception handler. The lowest four bits of this value provide information on the return stack and processor mode. Table 2-10 on page 77 shows the EXC_RETURN values with a description of the exception return behavior. EXC_RETURN bits 31:4 are all set. When this value is loaded into the PC, it indicates to the processor that the exception is complete, and the processor initiates the appropriate exception return sequence. Table 2-10. Exception Return Behavior EXC_RETURN[31:0] Description 0xFFFF.FFF0 Reserved 0xFFFF.FFF1 Return to Handler mode. Exception return uses state from MSP. Execution uses MSP after return. 0xFFFF.FFF2 - 0xFFFF.FFF8 Reserved 0xFFFF.FFF9 Return to Thread mode. Exception return uses state from MSP. Execution uses MSP after return. 0xFFFF.FFFA - 0xFFFF.FFFC Reserved 0xFFFF.FFFD Return to Thread mode. Exception return uses state from PSP. Execution uses PSP after return. 0xFFFF.FFFE - 0xFFFF.FFFF 2.6 Reserved Fault Handling Faults are a subset of the exceptions (see “Exception Model” on page 70). The following conditions generate a fault: July 14, 2014 77 Texas Instruments-Production Data The Cortex-M3 Processor ■ A bus error on an instruction fetch or vector table load or a data access. ■ An internally detected error such as an undefined instruction or an attempt to change state with a BX instruction. ■ Attempting to execute an instruction from a memory region marked as Non-Executable (XN). ■ An MPU fault because of a privilege violation or an attempt to access an unmanaged region. 2.6.1 Fault Types Table 2-11 on page 78 shows the types of fault, the handler used for the fault, the corresponding fault status register, and the register bit that indicates the fault has occurred. See page 125 for more information about the fault status registers. Table 2-11. Faults Fault Handler Fault Status Register Bit Name Bus error on a vector read Hard fault Hard Fault Status (HFAULTSTAT) VECT Fault escalated to a hard fault Hard fault Hard Fault Status (HFAULTSTAT) FORCED MPU or default memory mismatch on Memory management instruction access fault Memory Management Fault Status (MFAULTSTAT) IERR MPU or default memory mismatch on Memory management data access fault Memory Management Fault Status (MFAULTSTAT) DERR MPU or default memory mismatch on Memory management exception stacking fault Memory Management Fault Status (MFAULTSTAT) MSTKE MPU or default memory mismatch on Memory management exception unstacking fault Memory Management Fault Status (MFAULTSTAT) MUSTKE Bus error during exception stacking Bus fault Bus Fault Status (BFAULTSTAT) BSTKE Bus error during exception unstacking Bus fault Bus Fault Status (BFAULTSTAT) BUSTKE Bus error during instruction prefetch Bus fault Bus Fault Status (BFAULTSTAT) IBUS Precise data bus error Bus fault Bus Fault Status (BFAULTSTAT) PRECISE Imprecise data bus error Bus fault Bus Fault Status (BFAULTSTAT) IMPRE Attempt to access a coprocessor Usage fault Usage Fault Status (UFAULTSTAT) NOCP Undefined instruction Usage fault Usage Fault Status (UFAULTSTAT) UNDEF Attempt to enter an invalid instruction Usage fault b set state Usage Fault Status (UFAULTSTAT) INVSTAT a Invalid EXC_RETURN value Usage fault Usage Fault Status (UFAULTSTAT) INVPC Illegal unaligned load or store Usage fault Usage Fault Status (UFAULTSTAT) UNALIGN Divide by 0 Usage fault Usage Fault Status (UFAULTSTAT) DIV0 a. Occurs on an access to an XN region even if the MPU is disabled. b. Attempting to use an instruction set other than the Thumb instruction set, or returning to a non load-store-multiple instruction with ICI continuation. 2.6.2 Fault Escalation and Hard Faults All fault exceptions except for hard fault have configurable exception priority (see SYSPRI1 on page 118). Software can disable execution of the handlers for these faults (see SYSHNDCTRL on page 121). 78 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Usually, the exception priority, together with the values of the exception mask registers, determines whether the processor enters the fault handler, and whether a fault handler can preempt another fault handler as described in “Exception Model” on page 70. In some situations, a fault with configurable priority is treated as a hard fault. This process is called priority escalation, and the fault is described as escalated to hard fault. Escalation to hard fault occurs when: ■ A fault handler causes the same kind of fault as the one it is servicing. This escalation to hard fault occurs because a fault handler cannot preempt itself because it must have the same priority as the current priority level. ■ A fault handler causes a fault with the same or lower priority as the fault it is servicing. This situation happens because the handler for the new fault cannot preempt the currently executing fault handler. ■ An exception handler causes a fault for which the priority is the same as or lower than the currently executing exception. ■ A fault occurs and the handler for that fault is not enabled. If a bus fault occurs during a stack push when entering a bus fault handler, the bus fault does not escalate to a hard fault. Thus if a corrupted stack causes a fault, the fault handler executes even though the stack push for the handler failed. The fault handler operates but the stack contents are corrupted. Note: 2.6.3 Only Reset and NMI can preempt the fixed priority hard fault. A hard fault can preempt any exception other than Reset, NMI, or another hard fault. Fault Status Registers and Fault Address Registers The fault status registers indicate the cause of a fault. For bus faults and memory management faults, the fault address register indicates the address accessed by the operation that caused the fault, as shown in Table 2-12 on page 79. Table 2-12. Fault Status and Fault Address Registers Handler Status Register Name Address Register Name Register Description Hard fault Hard Fault Status (HFAULTSTAT) - page 131 Memory management Memory Management Fault Status fault (MFAULTSTAT) Memory Management Fault Address (MMADDR) page 125 Bus fault Bus Fault Address (FAULTADDR) page 125 - page 125 Bus Fault Status (BFAULTSTAT) Usage fault 2.6.4 Usage Fault Status (UFAULTSTAT) page 132 page 133 Lockup The processor enters a lockup state if a hard fault occurs when executing the NMI or hard fault handlers. When the processor is in the lockup state, it does not execute any instructions. The processor remains in lockup state until it is reset, an NMI occurs, or it is halted by a debugger. Note: If the lockup state occurs from the NMI handler, a subsequent NMI does not cause the processor to leave the lockup state. July 14, 2014 79 Texas Instruments-Production Data The Cortex-M3 Processor 2.7 Power Management The Cortex-M3 processor sleep modes reduce power consumption: ■ Sleep mode stops the processor clock. ■ Deep-sleep mode stops the system clock and switches off the PLL and Flash memory. The SLEEPDEEP bit of the System Control (SYSCTRL) register selects which sleep mode is used (see page 114). For more information about the behavior of the sleep modes, see “System Control” on page 161. This section describes the mechanisms for entering sleep mode and the conditions for waking up from sleep mode, both of which apply to Sleep mode and Deep-sleep mode. 2.7.1 Entering Sleep Modes This section describes the mechanisms software can use to put the processor into one of the sleep modes. The system can generate spurious wake-up events, for example a debug operation wakes up the processor. Therefore, software must be able to put the processor back into sleep mode after such an event. A program might have an idle loop to put the processor back to sleep mode. 2.7.1.1 Wait for Interrupt The wait for interrupt instruction, WFI, causes immediate entry to sleep mode unless the wake-up condition is true (see “Wake Up from WFI or Sleep-on-Exit” on page 81). When the processor executes a WFI instruction, it stops executing instructions and enters sleep mode. See the Cortex™-M3/M4 Instruction Set Technical User's Manual for more information. 2.7.1.2 Wait for Event The wait for event instruction, WFE, causes entry to sleep mode conditional on the value of a one-bit event register. When the processor executes a WFE instruction, it checks the event register. If the register is 0, the processor stops executing instructions and enters sleep mode. If the register is 1, the processor clears the register and continues executing instructions without entering sleep mode. If the event register is 1, the processor must not enter sleep mode on execution of a WFE instruction. Typically, this situation occurs if an SEV instruction has been executed. Software cannot access this register directly. See the Cortex™-M3/M4 Instruction Set Technical User's Manual for more information. 2.7.1.3 Sleep-on-Exit If the SLEEPEXIT bit of the SYSCTRL register is set, when the processor completes the execution of all exception handlers, it returns to Thread mode and immediately enters sleep mode. This mechanism can be used in applications that only require the processor to run when an exception occurs. 2.7.2 Wake Up from Sleep Mode The conditions for the processor to wake up depend on the mechanism that cause it to enter sleep mode. 80 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 2.7.2.1 Wake Up from WFI or Sleep-on-Exit Normally, the processor wakes up only when the NVIC detects an exception with sufficient priority to cause exception entry. Some embedded systems might have to execute system restore tasks after the processor wakes up and before executing an interrupt handler. Entry to the interrupt handler can be delayed by setting the PRIMASK bit and clearing the FAULTMASK bit. If an interrupt arrives that is enabled and has a higher priority than current exception priority, the processor wakes up but does not execute the interrupt handler until the processor clears PRIMASK. For more information about PRIMASK and FAULTMASK, see page 58 and page 59. 2.7.2.2 Wake Up from WFE The processor wakes up if it detects an exception with sufficient priority to cause exception entry. In addition, if the SEVONPEND bit in the SYSCTRL register is set, any new pending interrupt triggers an event and wakes up the processor, even if the interrupt is disabled or has insufficient priority to cause exception entry. For more information about SYSCTRL, see page 114. 2.8 Instruction Set Summary The processor implements a version of the Thumb instruction set. Table 2-13 on page 81 lists the supported instructions. Note: In Table 2-13 on page 81: ■ ■ ■ ■ ■ Angle brackets, , enclose alternative forms of the operand Braces, {}, enclose optional operands The Operands column is not exhaustive Op2 is a flexible second operand that can be either a register or a constant Most instructions can use an optional condition code suffix For more information on the instructions and operands, see the instruction descriptions in the Cortex™-M3/M4 Instruction Set Technical User's Manual. Table 2-13. Cortex-M3 Instruction Summary Mnemonic Operands Brief Description Flags ADC, ADCS {Rd,} Rn, Op2 Add with carry N,Z,C,V ADD, ADDS {Rd,} Rn, Op2 Add N,Z,C,V ADD, ADDW {Rd,} Rn , #imm12 Add N,Z,C,V ADR Rd, label Load PC-relative address - AND, ANDS {Rd,} Rn, Op2 Logical AND N,Z,C ASR, ASRS Rd, Rm, Arithmetic shift right N,Z,C B label Branch - BFC Rd, #lsb, #width Bit field clear - BFI Rd, Rn, #lsb, #width Bit field insert - BIC, BICS {Rd,} Rn, Op2 Bit clear N,Z,C BKPT #imm Breakpoint - BL label Branch with link - BLX Rm Branch indirect with link - BX Rm Branch indirect - CBNZ Rn, label Compare and branch if non-zero - July 14, 2014 81 Texas Instruments-Production Data The Cortex-M3 Processor Table 2-13. Cortex-M3 Instruction Summary (continued) Mnemonic Operands Brief Description Flags CBZ Rn, label Compare and branch if zero - CLREX - Clear exclusive - CLZ Rd, Rm Count leading zeros - CMN Rn, Op2 Compare negative N,Z,C,V CMP Rn, Op2 Compare N,Z,C,V CPSID i Change processor state, disable interrupts - CPSIE i Change processor state, enable interrupts - DMB - Data memory barrier - DSB - Data synchronization barrier - EOR, EORS {Rd,} Rn, Op2 Exclusive OR N,Z,C ISB - Instruction synchronization barrier - IT - If-Then condition block - LDM Rn{!}, reglist Load multiple registers, increment after - LDMDB, LDMEA Rn{!}, reglist Load multiple registers, decrement before LDMFD, LDMIA Rn{!}, reglist Load multiple registers, increment after - LDR Rt, [Rn, #offset] Load register with word - LDRB, LDRBT Rt, [Rn, #offset] Load register with byte - LDRD Rt, Rt2, [Rn, #offset] Load register with two bytes - LDREX Rt, [Rn, #offset] Load register exclusive - LDREXB Rt, [Rn] Load register exclusive with byte - LDREXH Rt, [Rn] Load register exclusive with halfword - LDRH, LDRHT Rt, [Rn, #offset] Load register with halfword - LDRSB, LDRSBT Rt, [Rn, #offset] Load register with signed byte - LDRSH, LDRSHT Rt, [Rn, #offset] Load register with signed halfword - LDRT Rt, [Rn, #offset] Load register with word - LSL, LSLS Rd, Rm, Logical shift left N,Z,C LSR, LSRS Rd, Rm, Logical shift right N,Z,C MLA Rd, Rn, Rm, Ra Multiply with accumulate, 32-bit result - MLS Rd, Rn, Rm, Ra Multiply and subtract, 32-bit result - MOV, MOVS Rd, Op2 Move N,Z,C MOV, MOVW Rd, #imm16 Move 16-bit constant N,Z,C MOVT Rd, #imm16 Move top - MRS Rd, spec_reg Move from special register to general register - MSR spec_reg, Rm Move from general register to special register N,Z,C,V MUL, MULS {Rd,} Rn, Rm Multiply, 32-bit result N,Z MVN, MVNS Rd, Op2 Move NOT N,Z,C NOP - No operation - ORN, ORNS {Rd,} Rn, Op2 Logical OR NOT N,Z,C 82 - July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Table 2-13. Cortex-M3 Instruction Summary (continued) Mnemonic Operands Brief Description Flags ORR, ORRS {Rd,} Rn, Op2 Logical OR N,Z,C POP reglist Pop registers from stack - PUSH reglist Push registers onto stack - RBIT Rd, Rn Reverse bits - REV Rd, Rn Reverse byte order in a word - REV16 Rd, Rn Reverse byte order in each halfword - REVSH Rd, Rn Reverse byte order in bottom halfword and sign extend - ROR, RORS Rd, Rm, Rotate right N,Z,C RRX, RRXS Rd, Rm Rotate right with extend N,Z,C RSB, RSBS {Rd,} Rn, Op2 Reverse subtract N,Z,C,V SBC, SBCS {Rd,} Rn, Op2 Subtract with carry N,Z,C,V SBFX Rd, Rn, #lsb, #width Signed bit field extract - SDIV {Rd,} Rn, Rm Signed divide - SEV - Send event - SMLAL RdLo, RdHi, Rn, Rm Signed multiply with accumulate (32x32+64), 64-bit result - SMULL RdLo, RdHi, Rn, Rm Signed multiply (32x32), 64-bit result - SSAT Rd, #n, Rm {,shift #s} Signed saturate Q STM Rn{!}, reglist Store multiple registers, increment after - STMDB, STMEA Rn{!}, reglist Store multiple registers, decrement before STMFD, STMIA Rn{!}, reglist Store multiple registers, increment after - STR Rt, [Rn {, #offset}] Store register word - STRB, STRBT Rt, [Rn {, #offset}] Store register byte - STRD Rt, Rt2, [Rn {, #offset}] Store register two words - STREX Rt, Rt, [Rn {, #offset}] Store register exclusive - STREXB Rd, Rt, [Rn] Store register exclusive byte - STREXH Rd, Rt, [Rn] Store register exclusive halfword - STRH, STRHT Rt, [Rn {, #offset}] Store register halfword - STRSB, STRSBT Rt, [Rn {, #offset}] Store register signed byte - STRSH, STRSHT Rt, [Rn {, #offset}] Store register signed halfword - STRT Rt, [Rn {, #offset}] Store register word - SUB, SUBS {Rd,} Rn, Op2 Subtract N,Z,C,V SUB, SUBW {Rd,} Rn, #imm12 Subtract 12-bit constant N,Z,C,V SVC #imm Supervisor call - SXTB {Rd,} Rm {,ROR #n} Sign extend a byte - SXTH {Rd,} Rm {,ROR #n} Sign extend a halfword - TBB [Rn, Rm] Table branch byte - TBH [Rn, Rm, LSL #1] Table branch halfword - TEQ Rn, Op2 Test equivalence N,Z,C TST Rn, Op2 Test N,Z,C July 14, 2014 - 83 Texas Instruments-Production Data The Cortex-M3 Processor Table 2-13. Cortex-M3 Instruction Summary (continued) Mnemonic Operands Brief Description Flags UBFX Rd, Rn, #lsb, #width Unsigned bit field extract - UDIV {Rd,} Rn, Rm Unsigned divide - UMLAL RdLo, RdHi, Rn, Rm Unsigned multiply with accumulate (32x32+32+32), 64-bit result - UMULL RdLo, RdHi, Rn, Rm Unsigned multiply (32x 2), 64-bit result - USAT Rd, #n, Rm {,shift #s} Unsigned Saturate Q UXTB {Rd,} Rm, {,ROR #n} Zero extend a Byte - UXTH {Rd,} Rm, {,ROR #n} Zero extend a Halfword - WFE - Wait for event - WFI - Wait for interrupt - 84 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 3 Cortex-M3 Peripherals ® This chapter provides information on the Stellaris implementation of the Cortex-M3 processor peripherals, including: ■ SysTick (see page 85) Provides a simple, 24-bit clear-on-write, decrementing, wrap-on-zero counter with a flexible control mechanism. ■ Nested Vectored Interrupt Controller (NVIC) (see page 86) – Facilitates low-latency exception and interrupt handling – Controls power management – Implements system control registers ■ System Control Block (SCB) (see page 88) Provides system implementation information and system control, including configuration, control, and reporting of system exceptions. ■ Memory Protection Unit (MPU) (see page 88) 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. Table 3-1 on page 85 shows the address map of the Private Peripheral Bus (PPB). Some peripheral register regions are split into two address regions, as indicated by two addresses listed. Table 3-1. Core Peripheral Register Regions Address Core Peripheral Description (see page ...) 0xE000.E010-0xE000.E01F System Timer 85 0xE000.E100-0xE000.E4EF Nested Vectored Interrupt Controller 86 0xE000.ED00-0xE000.ED3F System Control Block 88 0xE000.ED90-0xE000.EDB8 Memory Protection Unit 88 0xE000.EF00-0xE000.EF03 3.1 Functional Description This chapter provides information on the Stellaris implementation of the Cortex-M3 processor peripherals: SysTick, NVIC, SCB and MPU. 3.1.1 System Timer (SysTick) Cortex-M3 includes an integrated system timer, SysTick, which 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 as: ■ An RTOS tick timer that fires at a programmable rate (for example, 100 Hz) and invokes a SysTick routine. ■ A high-speed alarm timer using the system clock. July 14, 2014 85 Texas Instruments-Production Data Cortex-M3 Peripherals ■ 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 used to measure time to completion and time used. ■ An internal clock source control based on missing/meeting durations. The COUNT bit in the STCTRL 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. The timer consists of three registers: ■ SysTick Control and Status (STCTRL): A control and status counter to configure its clock, enable the counter, enable the SysTick interrupt, and determine counter status. ■ SysTick Reload Value (STRELOAD): The reload value for the counter, used to provide the counter's wrap value. ■ SysTick Current Value (STCURRENT): The current value of the counter. When enabled, the timer counts down on each clock from the reload value to zero, reloads (wraps) to the value in the STRELOAD register on the next clock edge, then decrements on subsequent clocks. Clearing the STRELOAD register disables the counter on the next wrap. When the counter reaches zero, the COUNT status bit is set. The COUNT bit clears on reads. Writing to the STCURRENT register clears the register and the COUNT 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. The SysTick counter runs on the system clock. If this clock signal is stopped for low power mode, the SysTick counter stops. Ensure software uses aligned word accesses to access the SysTick registers. Note: 3.1.2 When the processor is halted for debugging, the counter does not decrement. Nested Vectored Interrupt Controller (NVIC) This section describes the Nested Vectored Interrupt Controller (NVIC) and the registers it uses. The NVIC supports: ■ 24 interrupts. ■ A programmable priority level of 0-7 for each interrupt. A higher level corresponds to a lower priority, so level 0 is the highest interrupt priority. ■ Low-latency exception and interrupt handling. ■ Level and pulse detection of interrupt signals. ■ Dynamic reprioritization of interrupts. ■ Grouping of priority values into group priority and subpriority fields. ■ Interrupt tail-chaining. ■ An external Non-maskable interrupt (NMI). 86 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller The processor automatically stacks its state on exception entry and unstacks this state on exception exit, with no instruction overhead, providing low latency exception handling. 3.1.2.1 Level-Sensitive and Pulse Interrupts The processor supports both level-sensitive and pulse interrupts. Pulse interrupts are also described as edge-triggered interrupts. A level-sensitive interrupt is held asserted until the peripheral deasserts the interrupt signal. Typically this happens because the ISR accesses the peripheral, causing it to clear the interrupt request. A pulse interrupt is an interrupt signal sampled synchronously on the rising edge of the processor clock. To ensure the NVIC detects the interrupt, the peripheral must assert the interrupt signal for at least one clock cycle, during which the NVIC detects the pulse and latches the interrupt. When the processor enters the ISR, it automatically removes the pending state from the interrupt (see “Hardware and Software Control of Interrupts” on page 87 for more information). For a level-sensitive interrupt, if the signal is not deasserted before the processor returns from the ISR, the interrupt becomes pending again, and the processor must execute its ISR again. As a result, the peripheral can hold the interrupt signal asserted until it no longer needs servicing. 3.1.2.2 Hardware and Software Control of Interrupts The Cortex-M3 latches all interrupts. A peripheral interrupt becomes pending for one of the following reasons: ■ The NVIC detects that the interrupt signal is High and the interrupt is not active. ■ The NVIC detects a rising edge on the interrupt signal. ■ Software writes to the corresponding interrupt set-pending register bit, or to the Software Trigger Interrupt (SWTRIG) register to make a Software-Generated Interrupt pending. See the INT bit in the PEND0 register on page 101 or SWTRIG on page 106. A pending interrupt remains pending until one of the following: ■ The processor enters the ISR for the interrupt, changing the state of the interrupt from pending to active. Then: – For a level-sensitive interrupt, when the processor returns from the ISR, the NVIC samples the interrupt signal. If the signal is asserted, the state of the interrupt changes to pending, which might cause the processor to immediately re-enter the ISR. Otherwise, the state of the interrupt changes to inactive. – For a pulse interrupt, the NVIC continues to monitor the interrupt signal, and if this is pulsed the state of the interrupt changes to pending and active. In this case, when the processor returns from the ISR the state of the interrupt changes to pending, which might cause the processor to immediately re-enter the ISR. If the interrupt signal is not pulsed while the processor is in the ISR, when the processor returns from the ISR the state of the interrupt changes to inactive. ■ Software writes to the corresponding interrupt clear-pending register bit – For a level-sensitive interrupt, if the interrupt signal is still asserted, the state of the interrupt does not change. Otherwise, the state of the interrupt changes to inactive. July 14, 2014 87 Texas Instruments-Production Data Cortex-M3 Peripherals – For a pulse interrupt, the state of the interrupt changes to inactive, if the state was pending or to active, if the state was active and pending. 3.1.3 System Control Block (SCB) The System Control Block (SCB) provides system implementation information and system control, including configuration, control, and reporting of the system exceptions. 3.1.4 Memory Protection Unit (MPU) This section describes the Memory protection unit (MPU). The MPU divides the memory map into a number of regions and defines the location, size, access permissions, and memory attributes of each region. The MPU supports independent attribute settings for each region, overlapping regions, and export of memory attributes to the system. The memory attributes affect the behavior of memory accesses to the region. The Cortex-M3 MPU defines eight separate memory regions, 0-7, and a background region. When memory regions overlap, a memory access is affected by the attributes of the region with the highest number. For example, the attributes for region 7 take precedence over the attributes of any region that overlaps region 7. The background region has the same memory access attributes as the default memory map, but is accessible from privileged software only. The Cortex-M3 MPU memory map is unified, meaning that instruction accesses and data accesses have the same region settings. If a program accesses a memory location that is prohibited by the MPU, the processor generates a memory management fault, causing a fault exception and possibly causing termination of the process in an OS environment. In an OS environment, the kernel can update the MPU region setting dynamically based on the process to be executed. Typically, an embedded OS uses the MPU for memory protection. Configuration of MPU regions is based on memory types (see “Memory Regions, Types and Attributes” on page 63 for more information). Table 3-2 on page 88 shows the possible MPU region attributes. See the section called “MPU Configuration for a Stellaris Microcontroller” on page 92 for guidelines for programming a microcontroller implementation. Table 3-2. Memory Attributes Summary Memory Type Description Strongly Ordered All accesses to Strongly Ordered memory occur in program order. Device Memory-mapped peripherals Normal Normal memory To avoid unexpected behavior, disable the interrupts before updating the attributes of a region that the interrupt handlers might access. Ensure software uses aligned accesses of the correct size to access MPU registers: ■ Except for the MPU Region Attribute and Size (MPUATTR) register, all MPU registers must be accessed with aligned word accesses. ■ The MPUATTR register can be accessed with byte or aligned halfword or word accesses. 88 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller The processor does not support unaligned accesses to MPU registers. When setting up the MPU, and if the MPU has previously been programmed, disable unused regions to prevent any previous region settings from affecting the new MPU setup. 3.1.4.1 Updating an MPU Region To update the attributes for an MPU region, the MPU Region Number (MPUNUMBER), MPU Region Base Address (MPUBASE) and MPUATTR registers must be updated. Each register can be programmed separately or with a multiple-word write to program all of these registers. You can use the MPUBASEx and MPUATTRx aliases to program up to four regions simultaneously using an STM instruction. Updating an MPU Region Using Separate Words This example simple code configures one region: ; R1 = region number ; R2 = size/enable ; R3 = attributes ; R4 = address LDR R0,=MPUNUMBER STR R1, [R0, #0x0] STR R4, [R0, #0x4] STRH R2, [R0, #0x8] STRH R3, [R0, #0xA] ; ; ; ; ; 0xE000ED98, MPU region number register Region Number Region Base Address Region Size and Enable Region Attribute Disable a region before writing new region settings to the MPU if you have previously enabled the region being changed. For example: ; R1 = region number ; R2 = size/enable ; R3 = attributes ; R4 = address LDR R0,=MPUNUMBER STR R1, [R0, #0x0] BIC R2, R2, #1 STRH R2, [R0, #0x8] STR R4, [R0, #0x4] STRH R3, [R0, #0xA] ORR R2, #1 STRH R2, [R0, #0x8] ; ; ; ; ; ; ; ; 0xE000ED98, MPU region number register Region Number Disable Region Size and Enable Region Base Address Region Attribute Enable Region Size and Enable Software must use memory barrier instructions: ■ Before MPU setup, if there might be outstanding memory transfers, such as buffered writes, that might be affected by the change in MPU settings. ■ After MPU setup, if it includes memory transfers that must use the new MPU settings. However, memory barrier instructions are not required if the MPU setup process starts by entering an exception handler, or is followed by an exception return, because the exception entry and exception return mechanism cause memory barrier behavior. Software does not need any memory barrier instructions during MPU setup, because it accesses the MPU through the Private Peripheral Bus (PPB), which is a Strongly Ordered memory region. July 14, 2014 89 Texas Instruments-Production Data Cortex-M3 Peripherals For example, if all of the memory access behavior is intended to take effect immediately after the programming sequence, then a DSB instruction and an ISB instruction should be used. A DSB is required after changing MPU settings, such as at the end of context switch. An ISB is required if the code that programs the MPU region or regions is entered using a branch or call. If the programming sequence is entered using a return from exception, or by taking an exception, then an ISB is not required. Updating an MPU Region Using Multi-Word Writes The MPU can be programmed directly using multi-word writes, depending how the information is divided. Consider the following reprogramming: ; R1 = region number ; R2 = address ; R3 = size, attributes in one LDR R0, =MPUNUMBER ; 0xE000ED98, MPU region number register STR R1, [R0, #0x0] ; Region Number STR R2, [R0, #0x4] ; Region Base Address STR R3, [R0, #0x8] ; Region Attribute, Size and Enable An STM instruction can be used to optimize this: ; R1 = region number ; R2 = address ; R3 = size, attributes in one LDR R0, =MPUNUMBER ; 0xE000ED98, MPU region number register STM R0, {R1-R3} ; Region number, address, attribute, size and enable This operation can be done in two words for pre-packed information, meaning that the MPU Region Base Address (MPUBASE) register (see page 138) contains the required region number and has the VALID bit set. This method can be used when the data is statically packed, for example in a boot loader: ; R1 = address and region number in one ; R2 = size and attributes in one LDR R0, =MPUBASE ; 0xE000ED9C, MPU Region Base register STR R1, [R0, #0x0] ; Region base address and region number combined ; with VALID (bit 4) set STR R2, [R0, #0x4] ; Region Attribute, Size and Enable Subregions Regions of 256 bytes or more are divided into eight equal-sized subregions. Set the corresponding bit in the SRD field of the MPU Region Attribute and Size (MPUATTR) register (see page 140) to disable a subregion. The least-significant bit of the SRD field controls the first subregion, and the most-significant bit controls the last subregion. Disabling a subregion means another region overlapping the disabled range matches instead. If no other enabled region overlaps the disabled subregion, the MPU issues a fault. Regions of 32, 64, and 128 bytes do not support subregions. With regions of these sizes, the SRD field must be configured to 0x00, otherwise the MPU behavior is unpredictable. 90 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Example of SRD Use Two regions with the same base address overlap. Region one is 128 KB, and region two is 512 KB. To ensure the attributes from region one apply to the first 128 KB region, configure the SRD field for region two to 0x03 to disable the first two subregions, as Figure 3-1 on page 91 shows. Figure 3-1. SRD Use Example Region 2, with subregions Region 1 Base address of both regions 3.1.4.2 Offset from base address 512KB 448KB 384KB 320KB 256KB 192KB 128KB Disabled subregion 64KB Disabled subregion 0 MPU Access Permission Attributes The access permission bits, TEX, S, C, B, AP, and XN of the MPUATTR register, control access to the corresponding memory region. If an access is made to an area of memory without the required permissions, then the MPU generates a permission fault. Table 3-3 on page 91 shows the encodings for the TEX, C, B, and S access permission bits. All encodings are shown for completeness, however the current implementation of the Cortex-M3 does not support the concept of cacheability or shareability. Refer to the section called “MPU Configuration for a Stellaris Microcontroller” on page 92 for information on programming the MPU for Stellaris implementations. Table 3-3. TEX, S, C, and B Bit Field Encoding TEX S 000b x C B Memory Type Shareability Other Attributes a 0 0 Strongly Ordered Shareable - a - 000 x 0 1 Device Shareable 000 0 1 0 Normal Not shareable 000 1 1 0 Normal Shareable 000 0 1 1 Normal Not shareable 000 1 1 1 Normal Shareable 001 0 0 0 Normal Not shareable 001 1 0 0 Normal Shareable Outer and inner noncacheable. 001 x a 0 1 Reserved encoding - - a Outer and inner write-through. No write allocate. 001 x 1 0 Reserved encoding - - 001 0 1 1 Normal Not shareable 001 1 1 1 Normal Shareable Outer and inner write-back. Write and read allocate. 010 x a 0 0 Device Not shareable Nonshared Device. a 0 1 Reserved encoding - - a 1 x Reserved encoding - - 010 x 010 x a July 14, 2014 91 Texas Instruments-Production Data Cortex-M3 Peripherals Table 3-3. TEX, S, C, and B Bit Field Encoding (continued) TEX S C B Memory Type Shareability Other Attributes 1BB 0 A A Normal Not shareable 1BB 1 A A Normal Shareable Cached memory (BB = outer policy, AA = inner policy). See Table 3-4 for the encoding of the AA and BB bits. a. The MPU ignores the value of this bit. Table 3-4 on page 92 shows the cache policy for memory attribute encodings with a TEX value in the range of 0x4-0x7. Table 3-4. Cache Policy for Memory Attribute Encoding Encoding, AA or BB Corresponding Cache Policy 00 Non-cacheable 01 Write back, write and read allocate 10 Write through, no write allocate 11 Write back, no write allocate Table 3-5 on page 92 shows the AP encodings in the MPUATTR register that define the access permissions for privileged and unprivileged software. Table 3-5. AP Bit Field Encoding AP Bit Field Privileged Permissions Unprivileged Permissions Description 000 No access No access All accesses generate a permission fault. 001 R/W No access Access from privileged software only. 010 R/W RO Writes by unprivileged software generate a permission fault. 011 R/W R/W Full access. 100 Unpredictable Unpredictable Reserved. 101 RO No access Reads by privileged software only. 110 RO RO Read-only, by privileged or unprivileged software. 111 RO RO Read-only, by privileged or unprivileged software. MPU Configuration for a Stellaris Microcontroller Stellaris microcontrollers have only a single processor and no caches. As a result, the MPU should be programmed as shown in Table 3-6 on page 92. Table 3-6. Memory Region Attributes for Stellaris Microcontrollers Memory Region TEX S C B Memory Type and Attributes Flash memory 000b 0 1 0 Normal memory, non-shareable, write-through Internal SRAM 000b 1 1 0 Normal memory, shareable, write-through External SRAM 000b 1 1 1 Normal memory, shareable, write-back, write-allocate Peripherals 000b 1 0 1 Device memory, shareable 92 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller In current Stellaris microcontroller implementations, the shareability and cache policy attributes do not affect the system behavior. However, using these settings for the MPU regions can make the application code more portable. The values given are for typical situations. 3.1.4.3 MPU Mismatch When an access violates the MPU permissions, the processor generates a memory management fault (see “Exceptions and Interrupts” on page 62 for more information). The MFAULTSTAT register indicates the cause of the fault. See page 125 for more information. 3.2 Register Map Table 3-7 on page 93 lists the Cortex-M3 Peripheral SysTick, NVIC, MPU and SCB registers. The offset listed is a hexadecimal increment to the register's address, relative to the Core Peripherals base address of 0xE000.E000. Note: Register spaces that are not used are reserved for future or internal use. Software should not modify any reserved memory address. Table 3-7. Peripherals Register Map Offset Name Type Reset Description See page System Timer (SysTick) Registers 0x010 STCTRL R/W 0x0000.0000 SysTick Control and Status Register 95 0x014 STRELOAD R/W 0x0000.0000 SysTick Reload Value Register 97 0x018 STCURRENT R/WC 0x0000.0000 SysTick Current Value Register 98 Nested Vectored Interrupt Controller (NVIC) Registers 0x100 EN0 R/W 0x0000.0000 Interrupt 0-29 Set Enable 99 0x180 DIS0 R/W 0x0000.0000 Interrupt 0-29 Clear Enable 100 0x200 PEND0 R/W 0x0000.0000 Interrupt 0-29 Set Pending 101 0x280 UNPEND0 R/W 0x0000.0000 Interrupt 0-29 Clear Pending 102 0x300 ACTIVE0 RO 0x0000.0000 Interrupt 0-29 Active Bit 103 0x400 PRI0 R/W 0x0000.0000 Interrupt 0-3 Priority 104 0x404 PRI1 R/W 0x0000.0000 Interrupt 4-7 Priority 104 0x408 PRI2 R/W 0x0000.0000 Interrupt 8-11 Priority 104 0x40C PRI3 R/W 0x0000.0000 Interrupt 12-15 Priority 104 0x410 PRI4 R/W 0x0000.0000 Interrupt 16-19 Priority 104 0x414 PRI5 R/W 0x0000.0000 Interrupt 20-23 Priority 104 0x418 PRI6 R/W 0x0000.0000 Interrupt 24-27 Priority 104 0x41C PRI7 R/W 0x0000.0000 Interrupt 28-29 Priority 104 0xF00 SWTRIG WO 0x0000.0000 Software Trigger Interrupt 106 July 14, 2014 93 Texas Instruments-Production Data Cortex-M3 Peripherals Table 3-7. Peripherals Register Map (continued) Offset Name Type Reset Description See page System Control Block (SCB) Registers 0xD00 CPUID RO 0x410F.C231 CPU ID Base 107 0xD04 INTCTRL R/W 0x0000.0000 Interrupt Control and State 108 0xD08 VTABLE R/W 0x0000.0000 Vector Table Offset 111 0xD0C APINT R/W 0xFA05.0000 Application Interrupt and Reset Control 112 0xD10 SYSCTRL R/W 0x0000.0000 System Control 114 0xD14 CFGCTRL R/W 0x0000.0000 Configuration and Control 116 0xD18 SYSPRI1 R/W 0x0000.0000 System Handler Priority 1 118 0xD1C SYSPRI2 R/W 0x0000.0000 System Handler Priority 2 119 0xD20 SYSPRI3 R/W 0x0000.0000 System Handler Priority 3 120 0xD24 SYSHNDCTRL R/W 0x0000.0000 System Handler Control and State 121 0xD28 FAULTSTAT R/W1C 0x0000.0000 Configurable Fault Status 125 0xD2C HFAULTSTAT R/W1C 0x0000.0000 Hard Fault Status 131 0xD34 MMADDR R/W - Memory Management Fault Address 132 0xD38 FAULTADDR R/W - Bus Fault Address 133 Memory Protection Unit (MPU) Registers 0xD90 MPUTYPE RO 0x0000.0800 MPU Type 134 0xD94 MPUCTRL R/W 0x0000.0000 MPU Control 135 0xD98 MPUNUMBER R/W 0x0000.0000 MPU Region Number 137 0xD9C MPUBASE R/W 0x0000.0000 MPU Region Base Address 138 0xDA0 MPUATTR R/W 0x0000.0000 MPU Region Attribute and Size 140 0xDA4 MPUBASE1 R/W 0x0000.0000 MPU Region Base Address Alias 1 138 0xDA8 MPUATTR1 R/W 0x0000.0000 MPU Region Attribute and Size Alias 1 140 0xDAC MPUBASE2 R/W 0x0000.0000 MPU Region Base Address Alias 2 138 0xDB0 MPUATTR2 R/W 0x0000.0000 MPU Region Attribute and Size Alias 2 140 0xDB4 MPUBASE3 R/W 0x0000.0000 MPU Region Base Address Alias 3 138 0xDB8 MPUATTR3 R/W 0x0000.0000 MPU Region Attribute and Size Alias 3 140 3.3 System Timer (SysTick) Register Descriptions This section lists and describes the System Timer registers, in numerical order by address offset. 94 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 1: SysTick Control and Status Register (STCTRL), offset 0x010 Note: This register can only be accessed from privileged mode. The SysTick STCTRL register enables the SysTick features. SysTick Control and Status Register (STCTRL) Base 0xE000.E000 Offset 0x010 Type R/W, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 reserved Type Reset RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 15 14 13 12 11 10 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 9 8 7 6 5 4 3 reserved Type Reset RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 16 COUNT RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 2 1 0 CLK_SRC INTEN ENABLE R/W 0 R/W 0 R/W 0 Bit/Field Name Type Reset Description 31:17 reserved RO 0x000 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 16 COUNT RO 0 Count Flag Value Description 0 The SysTick timer has not counted to 0 since the last time this bit was read. 1 The SysTick timer has counted to 0 since the last time this bit was read. This bit is cleared by a read of the register or if the STCURRENT register is written with any value. If read by the debugger using the DAP, this bit is cleared only if the MasterType bit in the AHB-AP Control Register is clear. Otherwise, the COUNT bit is not changed by the debugger read. See the ARM® Debug Interface V5 Architecture Specification for more information on MasterType. 15:3 reserved RO 0x000 2 CLK_SRC R/W 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. Clock Source Value Description 0 External reference clock. (Not implemented for most Stellaris microcontrollers.) 1 System clock Because an external reference clock is not implemented, this bit must be set in order for SysTick to operate. July 14, 2014 95 Texas Instruments-Production Data Cortex-M3 Peripherals Bit/Field Name Type Reset 1 INTEN R/W 0 0 ENABLE R/W 0 Description Interrupt Enable Value Description 0 Interrupt generation is disabled. Software can use the COUNT bit to determine if the counter has ever reached 0. 1 An interrupt is generated to the NVIC when SysTick counts to 0. Enable Value Description 0 The counter is disabled. 1 Enables SysTick to operate in a multi-shot way. That is, the counter loads the RELOAD value and begins counting down. On reaching 0, the COUNT bit is set and an interrupt is generated if enabled by INTEN. The counter then loads the RELOAD value again and begins counting. 96 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 2: SysTick Reload Value Register (STRELOAD), offset 0x014 Note: This register can only be accessed from privileged mode. The STRELOAD register specifies the start value to load into the SysTick Current Value (STCURRENT) register when the counter reaches 0. The start value can be between 0x1 and 0x00FF.FFFF. A start value of 0 is possible but has no effect because the SysTick interrupt and the COUNT bit are activated when counting from 1 to 0. SysTick can be configured as a multi-shot timer, repeated over and over, firing every N+1 clock pulses, where N is any value from 1 to 0x00FF.FFFF. For example, if a tick interrupt is required every 100 clock pulses, 99 must be written into the RELOAD field. SysTick Reload Value Register (STRELOAD) Base 0xE000.E000 Offset 0x014 Type R/W, reset 0x0000.0000 31 30 29 28 RO 0 RO 0 RO 0 RO 0 15 14 13 R/W 0 R/W 0 R/W 0 27 26 25 24 23 22 21 20 18 17 16 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 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 reserved Type Reset 19 RELOAD RELOAD Type Reset Bit/Field Name Type Reset Description 31:24 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 23:0 RELOAD R/W 0x00.0000 Reload Value Value to load into the SysTick Current Value (STCURRENT) register when the counter reaches 0. July 14, 2014 97 Texas Instruments-Production Data Cortex-M3 Peripherals Register 3: SysTick Current Value Register (STCURRENT), offset 0x018 Note: This register can only be accessed from privileged mode. The STCURRENT register contains the current value of the SysTick counter. SysTick Current Value Register (STCURRENT) Base 0xE000.E000 Offset 0x018 Type R/WC, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 reserved Type Reset 20 19 18 17 16 CURRENT RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 R/WC 0 R/WC 0 R/WC 0 R/WC 0 R/WC 0 R/WC 0 R/WC 0 R/WC 0 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 R/WC 0 R/WC 0 R/WC 0 R/WC 0 R/WC 0 R/WC 0 R/WC 0 CURRENT Type Reset R/WC 0 R/WC 0 R/WC 0 R/WC 0 R/WC 0 R/WC 0 R/WC 0 R/WC 0 R/WC 0 Bit/Field Name Type Reset Description 31:24 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 23:0 CURRENT R/WC 0x00.0000 Current Value This field contains the 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. Clearing this register also clears the COUNT bit of the STCTRL register. 3.4 NVIC Register Descriptions This section lists and describes the NVIC registers, in numerical order by address offset. The NVIC registers can only be fully accessed from privileged mode, but interrupts can be pended while in unprivileged mode by enabling the Configuration and Control (CFGCTRL) register. Any other unprivileged mode access causes a bus fault. Ensure software uses correctly aligned register accesses. The processor does not support unaligned accesses to NVIC registers. An interrupt can enter the pending state even if it is disabled. Before programming the VTABLE register to relocate the vector table, ensure the vector table entries of the new vector table are set up for fault handlers, NMI, and all enabled exceptions such as interrupts. For more information, see page 111. 98 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 4: Interrupt 0-29 Set Enable (EN0), offset 0x100 Note: This register can only be accessed from privileged mode. The EN0 register enables interrupts and shows which interrupts are enabled. Bit 0 corresponds to Interrupt 0; bit 29 corresponds to Interrupt 29. See Table 2-9 on page 73 for interrupt assignments. If a pending interrupt is enabled, the NVIC activates the interrupt based on its priority. If an interrupt is not enabled, asserting its interrupt signal changes the interrupt state to pending, but the NVIC never activates the interrupt, regardless of its priority. Interrupt 0-29 Set Enable (EN0) Base 0xE000.E000 Offset 0x100 Type R/W, reset 0x0000.0000 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 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 reserved Type Reset INT RO 0 RO 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 INT Type Reset 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 31:30 reserved RO 0x0 29:0 INT R/W 0x000.0000 R/W 0 Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. Interrupt Enable Value Description 0 On a read, indicates the interrupt is disabled. On a write, no effect. 1 On a read, indicates the interrupt is enabled. On a write, enables the interrupt. A bit can only be cleared by setting the corresponding INT[n] bit in the DISn register. July 14, 2014 99 Texas Instruments-Production Data Cortex-M3 Peripherals Register 5: Interrupt 0-29 Clear Enable (DIS0), offset 0x180 Note: This register can only be accessed from privileged mode. The DIS0 register disables interrupts. Bit 0 corresponds to Interrupt 0; bit 29 corresponds to Interrupt 29. See Table 2-9 on page 73 for interrupt assignments. Interrupt 0-29 Clear Enable (DIS0) Base 0xE000.E000 Offset 0x180 Type R/W, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 reserved Type Reset 22 21 20 19 18 17 16 INT 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 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 INT Type Reset Bit/Field Name Type Reset 31:30 reserved RO 0x0 29:0 INT R/W 0x000.0000 Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. Interrupt Disable Value Description 0 On a read, indicates the interrupt is disabled. On a write, no effect. 1 On a read, indicates the interrupt is enabled. On a write, clears the corresponding INT[n] bit in the EN0 register, disabling interrupt [n]. 100 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 6: Interrupt 0-29 Set Pending (PEND0), offset 0x200 Note: This register can only be accessed from privileged mode. The PEND0 register forces interrupts into the pending state and shows which interrupts are pending. Bit 0 corresponds to Interrupt 0; bit 29 corresponds to Interrupt 29. See Table 2-9 on page 73 for interrupt assignments. Interrupt 0-29 Set Pending (PEND0) Base 0xE000.E000 Offset 0x200 Type R/W, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 reserved Type Reset 22 21 20 19 18 17 16 INT 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 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 INT Type Reset Bit/Field Name Type Reset 31:30 reserved RO 0x0 29:0 INT R/W 0x000.0000 Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. Interrupt Set Pending Value Description 0 On a read, indicates that the interrupt is not pending. On a write, no effect. 1 On a read, indicates that the interrupt is pending. On a write, the corresponding interrupt is set to pending even if it is disabled. If the corresponding interrupt is already pending, setting a bit has no effect. A bit can only be cleared by setting the corresponding INT[n] bit in the UNPEND0 register. July 14, 2014 101 Texas Instruments-Production Data Cortex-M3 Peripherals Register 7: Interrupt 0-29 Clear Pending (UNPEND0), offset 0x280 Note: This register can only be accessed from privileged mode. The UNPEND0 register shows which interrupts are pending and removes the pending state from interrupts. Bit 0 corresponds to Interrupt 0; bit 29 corresponds to Interrupt 29. See Table 2-9 on page 73 for interrupt assignments. Interrupt 0-29 Clear Pending (UNPEND0) Base 0xE000.E000 Offset 0x280 Type R/W, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 reserved Type Reset 22 21 20 19 18 17 16 INT 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 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 INT Type Reset Bit/Field Name Type Reset 31:30 reserved RO 0x0 29:0 INT R/W 0x000.0000 Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. Interrupt Clear Pending Value Description 0 On a read, indicates that the interrupt is not pending. On a write, no effect. 1 On a read, indicates that the interrupt is pending. On a write, clears the corresponding INT[n] bit in the PEND0 register, so that interrupt [n] is no longer pending. Setting a bit does not affect the active state of the corresponding interrupt. 102 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 8: Interrupt 0-29 Active Bit (ACTIVE0), offset 0x300 Note: This register can only be accessed from privileged mode. The ACTIVE0 register indicates which interrupts are active. Bit 0 corresponds to Interrupt 0; bit 29 corresponds to Interrupt 29. See Table 2-9 on page 73 for interrupt assignments. Caution – Do not manually set or clear the bits in this register. Interrupt 0-29 Active Bit (ACTIVE0) Base 0xE000.E000 Offset 0x300 Type RO, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 reserved Type Reset 22 21 20 19 18 17 16 INT RO 0 RO 0 RO 0 RO 0 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 INT Type Reset Bit/Field Name Type Reset 31:30 reserved RO 0x0 29:0 INT RO 0x000.0000 Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. Interrupt Active Value Description 0 The corresponding interrupt is not active. 1 The corresponding interrupt is active, or active and pending. July 14, 2014 103 Texas Instruments-Production Data Cortex-M3 Peripherals Register 9: Interrupt 0-3 Priority (PRI0), offset 0x400 Register 10: Interrupt 4-7 Priority (PRI1), offset 0x404 Register 11: Interrupt 8-11 Priority (PRI2), offset 0x408 Register 12: Interrupt 12-15 Priority (PRI3), offset 0x40C Register 13: Interrupt 16-19 Priority (PRI4), offset 0x410 Register 14: Interrupt 20-23 Priority (PRI5), offset 0x414 Register 15: Interrupt 24-27 Priority (PRI6), offset 0x418 Register 16: Interrupt 28-29 Priority (PRI7), offset 0x41C Note: This register can only be accessed from privileged mode. The PRIn registers provide 3-bit priority fields for each interrupt. These registers are byte accessible. Each register holds four priority fields that are assigned to interrupts as follows: PRIn Register Bit Field Interrupt Bits 31:29 Interrupt [4n+3] Bits 23:21 Interrupt [4n+2] Bits 15:13 Interrupt [4n+1] Bits 7:5 Interrupt [4n] See Table 2-9 on page 73 for interrupt assignments. Each priority level can be split into separate group priority and subpriority fields. The PRIGROUP field in the Application Interrupt and Reset Control (APINT) register (see page 112) indicates the position of the binary point that splits the priority and subpriority fields. These registers can only be accessed from privileged mode. Interrupt 0-3 Priority (PRI0) Base 0xE000.E000 Offset 0x400 Type R/W, reset 0x0000.0000 31 30 29 28 27 INTD Type Reset R/W 0 15 R/W 0 R/W 0 RO 0 RO 0 14 13 12 11 INTB Type Reset R/W 0 R/W 0 26 25 24 23 reserved RO 0 RO 0 RO 0 R/W 0 10 9 8 7 reserved R/W 0 RO 0 RO 0 RO 0 22 21 20 19 INTC R/W 0 R/W 0 RO 0 RO 0 6 5 4 3 INTA RO 0 Bit/Field Name Type Reset 31:29 INTD R/W 0x0 RO 0 R/W 0 R/W 0 18 17 16 RO 0 RO 0 RO 0 2 1 0 RO 0 RO 0 reserved reserved R/W 0 RO 0 RO 0 RO 0 Description Interrupt Priority for Interrupt [4n+3] This field holds a priority value, 0-7, for the interrupt with the number [4n+3], where n is the number of the Interrupt Priority register (n=0 for PRI0, and so on). The lower the value, the greater the priority of the corresponding interrupt. 104 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Bit/Field Name Type Reset Description 28:24 reserved RO 0x0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 23:21 INTC R/W 0x0 Interrupt Priority for Interrupt [4n+2] This field holds a priority value, 0-7, for the interrupt with the number [4n+2], where n is the number of the Interrupt Priority register (n=0 for PRI0, and so on). The lower the value, the greater the priority of the corresponding interrupt. 20:16 reserved RO 0x0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 15:13 INTB R/W 0x0 Interrupt Priority for Interrupt [4n+1] This field holds a priority value, 0-7, for the interrupt with the number [4n+1], where n is the number of the Interrupt Priority register (n=0 for PRI0, and so on). The lower the value, the greater the priority of the corresponding interrupt. 12:8 reserved RO 0x0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:5 INTA R/W 0x0 Interrupt Priority for Interrupt [4n] This field holds a priority value, 0-7, for the interrupt with the number [4n], where n is the number of the Interrupt Priority register (n=0 for PRI0, and so on). The lower the value, the greater the priority of the corresponding interrupt. 4:0 reserved RO 0x0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. July 14, 2014 105 Texas Instruments-Production Data Cortex-M3 Peripherals Register 17: Software Trigger Interrupt (SWTRIG), offset 0xF00 Note: Only privileged software can enable unprivileged access to the SWTRIG register. Writing an interrupt number to the SWTRIG register generates a Software Generated Interrupt (SGI). See Table 2-9 on page 73 for interrupt assignments. When the MAINPEND bit in the Configuration and Control (CFGCTRL) register (see page 116) is set, unprivileged software can access the SWTRIG register. Software Trigger Interrupt (SWTRIG) Base 0xE000.E000 Offset 0xF00 Type WO, reset 0x0000.0000 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 WO 0 WO 0 WO 0 WO 0 reserved Type Reset reserved Type Reset RO 0 INTID Bit/Field Name Type Reset 31:5 reserved RO 0x0000.00 4:0 INTID WO 0x00 WO 0 Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. Interrupt ID This field holds the interrupt ID of the required SGI. For example, a value of 0x3 generates an interrupt on IRQ3. 3.5 System Control Block (SCB) Register Descriptions This section lists and describes the System Control Block (SCB) registers, in numerical order by address offset. The SCB registers can only be accessed from privileged mode. All registers must be accessed with aligned word accesses except for the FAULTSTAT and SYSPRI1-SYSPRI3 registers, which can be accessed with byte or aligned halfword or word accesses. The processor does not support unaligned accesses to system control block registers. 106 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 18: CPU ID Base (CPUID), offset 0xD00 Note: This register can only be accessed from privileged mode. The CPUID register contains the ARM® Cortex™-M3 processor part number, version, and implementation information. CPU ID Base (CPUID) Base 0xE000.E000 Offset 0xD00 Type RO, reset 0x410F.C231 31 30 29 28 27 26 25 24 23 22 IMP Type Reset 21 20 19 18 VAR RO 0 RO 1 RO 0 RO 0 RO 0 RO 0 RO 0 RO 1 RO 0 RO 0 RO 0 RO 0 RO 1 RO 1 15 14 13 12 11 10 9 8 7 6 5 4 3 2 PARTNO Type Reset RO 1 RO 1 RO 0 RO 0 RO 0 RO 0 RO 1 17 16 RO 1 RO 1 1 0 RO 0 RO 1 CON REV RO 0 RO 0 RO 0 Bit/Field Name Type Reset Description 31:24 IMP RO 0x41 Implementer Code RO 1 RO 1 RO 0 RO 0 Value Description 0x41 ARM 23:20 VAR RO 0x0 Variant Number Value Description 0x0 19:16 CON RO 0xF The rn value in the rnpn product revision identifier, for example, the 0 in r0p1. Constant Value Description 0xF 15:4 PARTNO RO 0xC23 Always reads as 0xF. Part Number Value Description 0xC23 Cortex-M3 processor. 3:0 REV RO 0x1 Revision Number Value Description 0x1 The pn value in the rnpn product revision identifier, for example, the 1 in r0p1. July 14, 2014 107 Texas Instruments-Production Data Cortex-M3 Peripherals Register 19: Interrupt Control and State (INTCTRL), offset 0xD04 Note: This register can only be accessed from privileged mode. The INCTRL register provides a set-pending bit for the NMI exception, and set-pending and clear-pending bits for the PendSV and SysTick exceptions. In addition, bits in this register indicate the exception number of the exception being processed, whether there are preempted active exceptions, the exception number of the highest priority pending exception, and whether any interrupts are pending. When writing to INCTRL, the effect is unpredictable when writing a 1 to both the PENDSV and UNPENDSV bits, or writing a 1 to both the PENDSTSET and PENDSTCLR bits. Interrupt Control and State (INTCTRL) Base 0xE000.E000 Offset 0xD04 Type R/W, reset 0x0000.0000 31 NMISET Type Reset 30 29 reserved 28 26 PENDSV UNPENDSV 25 PENDSTSET PENDSTCLR 24 reserved 23 22 21 20 ISRPRE ISRPEND 19 18 17 reserved 16 VECPEND R/W 0 RO 0 RO 0 R/W 0 WO 0 R/W 0 WO 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 VECPEND Type Reset 27 RO 0 RETBASE RO 0 reserved RO 0 Bit/Field Name Type Reset 31 NMISET R/W 0 RO 0 VECACT Description NMI Set Pending Value Description 0 On a read, indicates an NMI exception is not pending. On a write, no effect. 1 On a read, indicates an NMI exception is pending. On a write, changes the NMI exception state to pending. Because NMI is the highest-priority exception, normally the processor enters the NMI exception handler as soon as it registers the setting of this bit, and clears this bit on entering the interrupt handler. A read of this bit by the NMI exception handler returns 1 only if the NMI signal is reasserted while the processor is executing that handler. 30:29 reserved RO 0x0 28 PENDSV R/W 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. PendSV Set Pending Value Description 0 On a read, indicates a PendSV exception is not pending. On a write, no effect. 1 On a read, indicates a PendSV exception is pending. On a write, changes the PendSV exception state to pending. Setting this bit is the only way to set the PendSV exception state to pending. This bit is cleared by writing a 1 to the UNPENDSV bit. 108 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Bit/Field Name Type Reset 27 UNPENDSV WO 0 Description PendSV Clear Pending Value Description 0 On a write, no effect. 1 On a write, removes the pending state from the PendSV exception. This bit is write only; on a register read, its value is unknown. 26 PENDSTSET R/W 0 SysTick Set Pending Value Description 0 On a read, indicates a SysTick exception is not pending. On a write, no effect. 1 On a read, indicates a SysTick exception is pending. On a write, changes the SysTick exception state to pending. This bit is cleared by writing a 1 to the PENDSTCLR bit. 25 PENDSTCLR WO 0 SysTick Clear Pending Value Description 0 On a write, no effect. 1 On a write, removes the pending state from the SysTick exception. This bit is write only; on a register read, its value is unknown. 24 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 23 ISRPRE RO 0 Debug Interrupt Handling Value Description 0 The release from halt does not take an interrupt. 1 The release from halt takes an interrupt. This bit is only meaningful in Debug mode and reads as zero when the processor is not in Debug mode. 22 ISRPEND RO 0 Interrupt Pending Value Description 0 No interrupt is pending. 1 An interrupt is pending. This bit provides status for all interrupts excluding NMI and Faults. 21:18 reserved RO 0x0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. July 14, 2014 109 Texas Instruments-Production Data Cortex-M3 Peripherals Bit/Field Name Type Reset Description 17:12 VECPEND RO 0x00 Interrupt Pending Vector Number This field contains the exception number of the highest priority pending enabled exception. The value indicated by this field includes the effect of the BASEPRI and FAULTMASK registers, but not any effect of the PRIMASK register. Value Description 0x00 No exceptions are pending 0x01 Reserved 0x02 NMI 0x03 Hard fault 0x04 Memory management fault 0x05 Bus fault 0x06 Usage fault 0x07-0x0A Reserved 0x0B SVCall 0x0C Reserved for Debug 0x0D Reserved 0x0E PendSV 0x0F SysTick 0x10 Interrupt Vector 0 0x11 Interrupt Vector 1 ... ... 0x2D Interrupt Vector 29 0x2E-0x3F Reserved 11 RETBASE RO 0 Return to Base Value Description 0 There are preempted active exceptions to execute. 1 There are no active exceptions, or the currently executing exception is the only active exception. This bit provides status for all interrupts excluding NMI and Faults. This bit only has meaning if the processor is currently executing an ISR (the Interrupt Program Status (IPSR) register is non-zero). 10:6 reserved RO 0x0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 5:0 VECACT RO 0x00 Interrupt Pending Vector Number This field contains the active exception number. The exception numbers can be found in the description for the VECPEND field. If this field is clear, the processor is in Thread mode. This field contains the same value as the ISRNUM field in the IPSR register. Subtract 16 from this value to obtain the IRQ number required to index into the Interrupt Set Enable (ENn), Interrupt Clear Enable (DISn), Interrupt Set Pending (PENDn), Interrupt Clear Pending (UNPENDn), and Interrupt Priority (PRIn) registers (see page 54). 110 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 20: Vector Table Offset (VTABLE), offset 0xD08 Note: This register can only be accessed from privileged mode. The VTABLE register indicates the offset of the vector table base address from memory address 0x0000.0000. Vector Table Offset (VTABLE) Base 0xE000.E000 Offset 0xD08 Type R/W, reset 0x0000.0000 31 30 reserved Type Reset 29 28 27 26 25 24 23 BASE 22 21 20 19 18 17 16 OFFSET 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 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 RO 0 RO 0 RO 0 RO 0 OFFSET Type Reset R/W 0 R/W 0 R/W 0 R/W 0 reserved R/W 0 R/W 0 R/W 0 Bit/Field Name Type Reset 31:30 reserved RO 0x0 29 BASE R/W 0 R/W 0 RO 0 RO 0 RO 0 RO 0 Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. Vector Table Base Value Description 28:8 OFFSET R/W 0x000.00 0 The vector table is in the code memory region. 1 The vector table is in the SRAM memory region. Vector Table Offset When configuring the OFFSET field, the offset must be aligned to the number of exception entries in the vector table. Because there are 29 interrupts, the offset must be aligned on a 256-byte boundary. 7:0 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. July 14, 2014 111 Texas Instruments-Production Data Cortex-M3 Peripherals Register 21: Application Interrupt and Reset Control (APINT), offset 0xD0C Note: This register can only be accessed from privileged mode. The APINT register provides priority grouping control for the exception model, endian status for data accesses, and reset control of the system. To write to this register, 0x05FA must be written to the VECTKEY field, otherwise the write is ignored. The PRIGROUP field indicates the position of the binary point that splits the INTx fields in the Interrupt Priority (PRIx) registers into separate group priority and subpriority fields. Table 3-8 on page 112 shows how the PRIGROUP value controls this split. The bit numbers in the Group Priority Field and Subpriority Field columns in the table refer to the bits in the INTA field. For the INTB field, the corresponding bits are 15:13; for INTC, 23:21; and for INTD, 31:29. Note: Determining preemption of an exception uses only the group priority field. Table 3-8. Interrupt Priority Levels a PRIGROUP Bit Field Binary Point Group Priority Field Subpriority Field Group Priorities Subpriorities 0x0 - 0x4 bxxx. [7:5] None 8 1 0x5 bxx.y [7:6] [5] 4 2 0x6 bx.yy [7] [6:5] 2 4 0x7 b.yyy None [7:5] 1 8 a. INTx field showing the binary point. An x denotes a group priority field bit, and a y denotes a subpriority field bit. Application Interrupt and Reset Control (APINT) Base 0xE000.E000 Offset 0xD0C Type R/W, reset 0xFA05.0000 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 1 R/W 0 R/W 1 5 4 3 2 1 0 VECTKEY Type Reset R/W 1 R/W 1 R/W 1 R/W 1 R/W 1 R/W 0 15 14 13 12 11 10 reserved ENDIANESS Type Reset RO 0 RO 0 RO 0 RO 0 R/W 1 R/W 0 R/W 0 R/W 0 9 8 7 6 PRIGROUP RO 0 R/W 0 R/W 0 Bit/Field Name Type Reset 31:16 VECTKEY R/W 0xFA05 reserved R/W 0 RO 0 RO 0 RO 0 SYSRESREQ VECTCLRACT VECTRESET RO 0 RO 0 WO 0 WO 0 WO 0 Description Register Key This field is used to guard against accidental writes to this register. 0x05FA must be written to this field in order to change the bits in this register. On a read, 0xFA05 is returned. 15 ENDIANESS RO 0 Data Endianess The Stellaris implementation uses only little-endian mode so this is cleared to 0. 14:11 reserved RO 0x0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 112 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Bit/Field Name Type Reset 10:8 PRIGROUP R/W 0x0 Description Interrupt Priority Grouping This field determines the split of group priority from subpriority (see Table 3-8 on page 112 for more information). 7:3 reserved RO 0x0 2 SYSRESREQ WO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. System Reset Request Value Description 0 No effect. 1 Resets the core and all on-chip peripherals except the Debug interface. This bit is automatically cleared during the reset of the core and reads as 0. 1 VECTCLRACT WO 0 Clear Active NMI / Fault This bit is reserved for Debug use and reads as 0. This bit must be written as a 0, otherwise behavior is unpredictable. 0 VECTRESET WO 0 System Reset This bit is reserved for Debug use and reads as 0. This bit must be written as a 0, otherwise behavior is unpredictable. July 14, 2014 113 Texas Instruments-Production Data Cortex-M3 Peripherals Register 22: System Control (SYSCTRL), offset 0xD10 Note: This register can only be accessed from privileged mode. The SYSCTRL register controls features of entry to and exit from low-power state. System Control (SYSCTRL) Base 0xE000.E000 Offset 0xD10 Type R/W, reset 0x0000.0000 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 2 1 reserved Type Reset RO 0 RO 0 RO 0 RO 0 RO 0 15 14 13 12 11 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 10 9 8 7 6 5 reserved Type Reset RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 Bit/Field Name Type Reset 31:5 reserved RO 0x0000.00 4 SEVONPEND R/W 0 RO 0 RO 0 RO 0 RO 0 4 3 SEVONPEND reserved R/W 0 RO 0 SLEEPDEEP SLEEPEXIT R/W 0 R/W 0 0 reserved RO 0 Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. Wake Up on Pending Value Description 0 Only enabled interrupts or events can wake up the processor; disabled interrupts are excluded. 1 Enabled events and all interrupts, including disabled interrupts, can wake up the processor. When an event or interrupt enters the pending state, the event signal wakes up the processor from WFE. If the processor is not waiting for an event, the event is registered and affects the next WFE. The processor also wakes up on execution of a SEV instruction or an external event. 3 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 2 SLEEPDEEP R/W 0 Deep Sleep Enable Value Description 0 Use Sleep mode as the low power mode. 1 Use Deep-sleep mode as the low power mode. 114 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Bit/Field Name Type Reset 1 SLEEPEXIT R/W 0 Description Sleep on ISR Exit Value Description 0 When returning from Handler mode to Thread mode, do not sleep when returning to Thread mode. 1 When returning from Handler mode to Thread mode, enter sleep or deep sleep on return from an ISR. Setting this bit enables an interrupt-driven application to avoid returning to an empty main application. 0 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. July 14, 2014 115 Texas Instruments-Production Data Cortex-M3 Peripherals Register 23: Configuration and Control (CFGCTRL), offset 0xD14 Note: This register can only be accessed from privileged mode. The CFGCTRL register controls entry to Thread mode and enables: the handlers for NMI, hard fault and faults escalated by the FAULTMASK register to ignore bus faults; trapping of divide by zero and unaligned accesses; and access to the SWTRIG register by unprivileged software (see page 106). Configuration and Control (CFGCTRL) Base 0xE000.E000 Offset 0xD14 Type R/W, reset 0x0000.0000 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 6 5 2 1 0 reserved Type Reset RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 15 14 13 12 11 10 reserved Type Reset RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 9 8 7 reserved STKALIGN BFHFNMIGN RO 0 RO 0 R/W 0 Bit/Field Name Type Reset 31:10 reserved RO 0x0000.00 9 STKALIGN R/W 0 R/W 0 RO 0 RO 0 RO 0 4 3 DIV0 UNALIGNED R/W 0 R/W 0 reserved MAINPEND BASETHR RO 0 R/W 0 R/W 0 Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. Stack Alignment on Exception Entry Value Description 0 The stack is 4-byte aligned. 1 The stack is 8-byte aligned. On exception entry, the processor uses bit 9 of the stacked PSR to indicate the stack alignment. On return from the exception, it uses this stacked bit to restore the correct stack alignment. 8 BFHFNMIGN R/W 0 Ignore Bus Fault in NMI and Fault This bit enables handlers with priority -1 or -2 to ignore data bus faults caused by load and store instructions. The setting of this bit applies to the hard fault, NMI, and FAULTMASK escalated handlers. Value Description 0 Data bus faults caused by load and store instructions cause a lock-up. 1 Handlers running at priority -1 and -2 ignore data bus faults caused by load and store instructions. Set this bit only when the handler and its data are in absolutely safe memory. The normal use of this bit is to probe system devices and bridges to detect control path problems and fix them. 7:5 reserved RO 0x0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 116 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Bit/Field Name Type Reset 4 DIV0 R/W 0 Description Trap on Divide by 0 This bit enables faulting or halting when the processor executes an SDIV or UDIV instruction with a divisor of 0. Value Description 3 UNALIGNED R/W 0 0 Do not trap on divide by 0. A divide by zero returns a quotient of 0. 1 Trap on divide by 0. Trap on Unaligned Access Value Description 0 Do not trap on unaligned halfword and word accesses. 1 Trap on unaligned halfword and word accesses. An unaligned access generates a usage fault. Unaligned LDM, STM, LDRD, and STRD instructions always fault regardless of whether UNALIGNED is set. 2 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 1 MAINPEND R/W 0 Allow Main Interrupt Trigger Value Description 0 BASETHR R/W 0 0 Disables unprivileged software access to the SWTRIG register. 1 Enables unprivileged software access to the SWTRIG register (see page 106). Thread State Control Value Description 0 The processor can enter Thread mode only when no exception is active. 1 The processor can enter Thread mode from any level under the control of an EXC_RETURN value (see “Exception Return” on page 77 for more information). July 14, 2014 117 Texas Instruments-Production Data Cortex-M3 Peripherals Register 24: System Handler Priority 1 (SYSPRI1), offset 0xD18 Note: This register can only be accessed from privileged mode. The SYSPRI1 register configures the priority level, 0 to 7 of the usage fault, bus fault, and memory management fault exception handlers. This register is byte-accessible. System Handler Priority 1 (SYSPRI1) Base 0xE000.E000 Offset 0xD18 Type R/W, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 reserved Type Reset RO 0 15 RO 0 RO 0 RO 0 RO 0 14 13 12 11 BUS Type Reset R/W 0 R/W 0 RO 0 RO 0 RO 0 R/W 0 10 9 8 7 reserved R/W 0 RO 0 22 21 20 19 USAGE RO 0 RO 0 R/W 0 R/W 0 RO 0 RO 0 6 5 4 3 MEM RO 0 RO 0 R/W 0 R/W 0 18 17 16 RO 0 RO 0 RO 0 2 1 0 RO 0 RO 0 reserved reserved R/W 0 RO 0 RO 0 RO 0 Bit/Field Name Type Reset Description 31:24 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 23:21 USAGE R/W 0x0 Usage Fault Priority This field configures the priority level of the usage fault. Configurable priority values are in the range 0-7, with lower values having higher priority. 20:16 reserved RO 0x0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 15:13 BUS R/W 0x0 Bus Fault Priority This field configures the priority level of the bus fault. Configurable priority values are in the range 0-7, with lower values having higher priority. 12:8 reserved RO 0x0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:5 MEM R/W 0x0 Memory Management Fault Priority This field configures the priority level of the memory management fault. Configurable priority values are in the range 0-7, with lower values having higher priority. 4:0 reserved RO 0x0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 118 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 25: System Handler Priority 2 (SYSPRI2), offset 0xD1C Note: This register can only be accessed from privileged mode. The SYSPRI2 register configures the priority level, 0 to 7 of the SVCall handler. This register is byte-accessible. System Handler Priority 2 (SYSPRI2) Base 0xE000.E000 Offset 0xD1C Type R/W, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 SVC Type Reset 22 21 20 19 18 17 16 reserved R/W 0 R/W 0 R/W 0 RO 0 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 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 Bit/Field Name Type Reset 31:29 SVC R/W 0x0 RO 0 Description SVCall Priority This field configures the priority level of SVCall. Configurable priority values are in the range 0-7, with lower values having higher priority. 28:0 reserved RO 0x000.0000 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. July 14, 2014 119 Texas Instruments-Production Data Cortex-M3 Peripherals Register 26: System Handler Priority 3 (SYSPRI3), offset 0xD20 Note: This register can only be accessed from privileged mode. The SYSPRI3 register configures the priority level, 0 to 7 of the SysTick exception and PendSV handlers. This register is byte-accessible. System Handler Priority 3 (SYSPRI3) Base 0xE000.E000 Offset 0xD20 Type R/W, reset 0x0000.0000 31 30 29 28 27 TICK Type Reset 26 25 24 23 reserved R/W 0 R/W 0 R/W 0 RO 0 RO 0 RO 0 RO 0 RO 0 R/W 0 15 14 13 12 11 10 9 8 7 reserved Type Reset RO 0 RO 0 RO 0 RO 0 22 21 20 19 PENDSV R/W 0 R/W 0 RO 0 RO 0 6 5 4 3 DEBUG RO 0 RO 0 RO 0 Bit/Field Name Type Reset 31:29 TICK R/W 0x0 RO 0 R/W 0 R/W 0 18 17 16 RO 0 RO 0 RO 0 2 1 0 RO 0 RO 0 reserved reserved R/W 0 RO 0 RO 0 RO 0 Description SysTick Exception Priority This field configures the priority level of the SysTick exception. Configurable priority values are in the range 0-7, with lower values having higher priority. 28:24 reserved RO 0x0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 23:21 PENDSV R/W 0x0 PendSV Priority This field configures the priority level of PendSV. Configurable priority values are in the range 0-7, with lower values having higher priority. 20:8 reserved RO 0x000 7:5 DEBUG R/W 0x0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. Debug Priority This field configures the priority level of Debug. Configurable priority values are in the range 0-7, with lower values having higher priority. 4:0 reserved RO 0x0.0000 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 120 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 27: System Handler Control and State (SYSHNDCTRL), offset 0xD24 Note: This register can only be accessed from privileged mode. The SYSHNDCTRL register enables the system handlers, and indicates the pending status of the usage fault, bus fault, memory management fault, and SVC exceptions as well as the active status of the system handlers. If a system handler is disabled and the corresponding fault occurs, the processor treats the fault as a hard fault. This register can be modified to change the pending or active status of system exceptions. An OS kernel can write to the active bits to perform a context switch that changes the current exception type. Caution – Software that changes the value of an active bit in this register without correct adjustment to the stacked content can cause the processor to generate a fault exception. Ensure software that writes to this register retains and subsequently restores the current active status. If the value of a bit in this register must be modified after enabling the system handlers, a read-modify-write procedure must be used to ensure that only the required bit is modified. System Handler Control and State (SYSHNDCTRL) Base 0xE000.E000 Offset 0xD24 Type R/W, reset 0x0000.0000 31 30 29 28 27 26 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 15 14 13 12 11 SVC BUSP MEMP USAGEP R/W 0 R/W 0 R/W 0 R/W 0 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 USAGE BUS MEM R/W 0 R/W 0 R/W 0 10 9 8 7 6 5 4 3 2 1 0 TICK PNDSV reserved MON SVCA R/W 0 R/W 0 RO 0 R/W 0 R/W 0 USGA reserved BUSA MEMA R/W 0 RO 0 R/W 0 R/W 0 reserved Type Reset Type Reset reserved RO 0 RO 0 RO 0 Bit/Field Name Type Reset Description 31:19 reserved RO 0x000 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 18 USAGE R/W 0 Usage Fault Enable Value Description 17 BUS R/W 0 0 Disables the usage fault exception. 1 Enables the usage fault exception. Bus Fault Enable Value Description 0 Disables the bus fault exception. 1 Enables the bus fault exception. July 14, 2014 121 Texas Instruments-Production Data Cortex-M3 Peripherals Bit/Field Name Type Reset 16 MEM R/W 0 Description Memory Management Fault Enable Value Description 15 SVC R/W 0 0 Disables the memory management fault exception. 1 Enables the memory management fault exception. SVC Call Pending Value Description 0 An SVC call exception is not pending. 1 An SVC call exception is pending. This bit can be modified to change the pending status of the SVC call exception. 14 BUSP R/W 0 Bus Fault Pending Value Description 0 A bus fault exception is not pending. 1 A bus fault exception is pending. This bit can be modified to change the pending status of the bus fault exception. 13 MEMP R/W 0 Memory Management Fault Pending Value Description 0 A memory management fault exception is not pending. 1 A memory management fault exception is pending. This bit can be modified to change the pending status of the memory management fault exception. 12 USAGEP R/W 0 Usage Fault Pending Value Description 0 A usage fault exception is not pending. 1 A usage fault exception is pending. This bit can be modified to change the pending status of the usage fault exception. 11 TICK R/W 0 SysTick Exception Active Value Description 0 A SysTick exception is not active. 1 A SysTick exception is active. This bit can be modified to change the active status of the SysTick exception, however, see the Caution above before setting this bit. 122 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Bit/Field Name Type Reset 10 PNDSV R/W 0 Description PendSV Exception Active Value Description 0 A PendSV exception is not active. 1 A PendSV exception is active. This bit can be modified to change the active status of the PendSV exception, however, see the Caution above before setting this bit. 9 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 8 MON R/W 0 Debug Monitor Active Value Description 7 SVCA R/W 0 0 The Debug monitor is not active. 1 The Debug monitor is active. SVC Call Active Value Description 0 SVC call is not active. 1 SVC call is active. This bit can be modified to change the active status of the SVC call exception, however, see the Caution above before setting this bit. 6:4 reserved RO 0x0 3 USGA R/W 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. Usage Fault Active Value Description 0 Usage fault is not active. 1 Usage fault is active. This bit can be modified to change the active status of the usage fault exception, however, see the Caution above before setting this bit. 2 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 1 BUSA R/W 0 Bus Fault Active Value Description 0 Bus fault is not active. 1 Bus fault is active. This bit can be modified to change the active status of the bus fault exception, however, see the Caution above before setting this bit. July 14, 2014 123 Texas Instruments-Production Data Cortex-M3 Peripherals Bit/Field Name Type Reset 0 MEMA R/W 0 Description Memory Management Fault Active Value Description 0 Memory management fault is not active. 1 Memory management fault is active. This bit can be modified to change the active status of the memory management fault exception, however, see the Caution above before setting this bit. 124 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 28: Configurable Fault Status (FAULTSTAT), offset 0xD28 Note: This register can only be accessed from privileged mode. The FAULTSTAT register indicates the cause of a memory management fault, bus fault, or usage fault. Each of these functions is assigned to a subregister as follows: ■ Usage Fault Status (UFAULTSTAT), bits 31:16 ■ Bus Fault Status (BFAULTSTAT), bits 15:8 ■ Memory Management Fault Status (MFAULTSTAT), bits 7:0 FAULTSTAT is byte accessible. FAULTSTAT or its subregisters can be accessed as follows: ■ ■ ■ ■ ■ The complete FAULTSTAT register, with a word access to offset 0xD28 The MFAULTSTAT, with a byte access to offset 0xD28 The MFAULTSTAT and BFAULTSTAT, with a halfword access to offset 0xD28 The BFAULTSTAT, with a byte access to offset 0xD29 The UFAULTSTAT, with a halfword access to offset 0xD2A Bits are cleared by writing a 1 to them. In a fault handler, the true faulting address can be determined by: 1. Read and save the Memory Management Fault Address (MMADDR) or Bus Fault Address (FAULTADDR) value. 2. Read the MMARV bit in MFAULTSTAT, or the BFARV bit in BFAULTSTAT to determine if the MMADDR or FAULTADDR contents are valid. Software must follow this sequence because another higher priority exception might change the MMADDR or FAULTADDR value. For example, if a higher priority handler preempts the current fault handler, the other fault might change the MMADDR or FAULTADDR value. Configurable Fault Status (FAULTSTAT) Base 0xE000.E000 Offset 0xD28 Type R/W1C, reset 0x0000.0000 31 30 29 28 27 26 reserved Type Reset RO 0 RO 0 RO 0 15 14 13 BFARV Type Reset R/W1C 0 reserved RO 0 RO 0 RO 0 RO 0 RO 0 25 24 DIV0 UNALIGN R/W1C 0 R/W1C 0 23 22 21 20 reserved RO 0 RO 0 RO 0 6 5 12 11 10 9 8 7 BSTKE BUSTKE IMPRE PRECISE IBUS MMARV R/W1C 0 R/W1C 0 R/W1C 0 R/W1C 0 R/W1C 0 R/W1C 0 reserved RO 0 RO 0 RO 0 4 MSTKE R/W1C 0 19 18 17 16 NOCP INVPC INVSTAT UNDEF R/W1C 0 R/W1C 0 R/W1C 0 R/W1C 0 3 2 MUSTKE reserved R/W1C 0 RO 0 1 0 DERR IERR R/W1C 0 R/W1C 0 Bit/Field Name Type Reset Description 31:26 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. July 14, 2014 125 Texas Instruments-Production Data Cortex-M3 Peripherals Bit/Field Name Type Reset 25 DIV0 R/W1C 0 Description Divide-by-Zero Usage Fault Value Description 0 No divide-by-zero fault has occurred, or divide-by-zero trapping is not enabled. 1 The processor has executed an SDIV or UDIV instruction with a divisor of 0. When this bit is set, the PC value stacked for the exception return points to the instruction that performed the divide by zero. Trapping on divide-by-zero is enabled by setting the DIV0 bit in the Configuration and Control (CFGCTRL) register (see page 116). This bit is cleared by writing a 1 to it. 24 UNALIGN R/W1C 0 Unaligned Access Usage Fault Value Description 0 No unaligned access fault has occurred, or unaligned access trapping is not enabled. 1 The processor has made an unaligned memory access. Unaligned LDM, STM, LDRD, and STRD instructions always fault regardless of the configuration of this bit. Trapping on unaligned access is enabled by setting the UNALIGNED bit in the CFGCTRL register (see page 116). This bit is cleared by writing a 1 to it. 23:20 reserved RO 0x00 19 NOCP R/W1C 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. No Coprocessor Usage Fault Value Description 0 A usage fault has not been caused by attempting to access a coprocessor. 1 The processor has attempted to access a coprocessor. This bit is cleared by writing a 1 to it. 18 INVPC R/W1C 0 Invalid PC Load Usage Fault Value Description 0 A usage fault has not been caused by attempting to load an invalid PC value. 1 The processor has attempted an illegal load of EXC_RETURN to the PC as a result of an invalid context or an invalid EXC_RETURN value. When this bit is set, the PC value stacked for the exception return points to the instruction that tried to perform the illegal load of the PC. This bit is cleared by writing a 1 to it. 126 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Bit/Field Name Type Reset 17 INVSTAT R/W1C 0 Description Invalid State Usage Fault Value Description 0 A usage fault has not been caused by an invalid state. 1 The processor has attempted to execute an instruction that makes illegal use of the EPSR register. When this bit is set, the PC value stacked for the exception return points to the instruction that attempted the illegal use of the Execution Program Status Register (EPSR) register. This bit is not set if an undefined instruction uses the EPSR register. This bit is cleared by writing a 1 to it. 16 UNDEF R/W1C 0 Undefined Instruction Usage Fault Value Description 0 A usage fault has not been caused by an undefined instruction. 1 The processor has attempted to execute an undefined instruction. When this bit is set, the PC value stacked for the exception return points to the undefined instruction. An undefined instruction is an instruction that the processor cannot decode. This bit is cleared by writing a 1 to it. 15 BFARV R/W1C 0 Bus Fault Address Register Valid Value Description 0 The value in the Bus Fault Address (FAULTADDR) register is not a valid fault address. 1 The FAULTADDR register is holding a valid fault address. This bit is set after a bus fault, where the address is known. Other faults can clear this bit, such as a memory management fault occurring later. If a bus fault occurs and is escalated to a hard fault because of priority, the hard fault handler must clear this bit. This action prevents problems if returning to a stacked active bus fault handler whose FAULTADDR register value has been overwritten. This bit is cleared by writing a 1 to it. 14:13 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. July 14, 2014 127 Texas Instruments-Production Data Cortex-M3 Peripherals Bit/Field Name Type Reset 12 BSTKE R/W1C 0 Description Stack Bus Fault Value Description 0 No bus fault has occurred on stacking for exception entry. 1 Stacking for an exception entry has caused one or more bus faults. When this bit is set, the SP is still adjusted but the values in the context area on the stack might be incorrect. A fault address is not written to the FAULTADDR register. This bit is cleared by writing a 1 to it. 11 BUSTKE R/W1C 0 Unstack Bus Fault Value Description 0 No bus fault has occurred on unstacking for a return from exception. 1 Unstacking for a return from exception has caused one or more bus faults. This fault is chained to the handler. Thus, when this bit is set, the original return stack is still present. The SP is not adjusted from the failing return, a new save is not performed, and a fault address is not written to the FAULTADDR register. This bit is cleared by writing a 1 to it. 10 IMPRE R/W1C 0 Imprecise Data Bus Error Value Description 0 An imprecise data bus error has not occurred. 1 A data bus error has occurred, but the return address in the stack frame is not related to the instruction that caused the error. When this bit is set, a fault address is not written to the FAULTADDR register. This fault is asynchronous. Therefore, if the fault is detected when the priority of the current process is higher than the bus fault priority, the bus fault becomes pending and becomes active only when the processor returns from all higher-priority processes. If a precise fault occurs before the processor enters the handler for the imprecise bus fault, the handler detects that both the IMPRE bit is set and one of the precise fault status bits is set. This bit is cleared by writing a 1 to it. 9 PRECISE R/W1C 0 Precise Data Bus Error Value Description 0 A precise data bus error has not occurred. 1 A data bus error has occurred, and the PC value stacked for the exception return points to the instruction that caused the fault. When this bit is set, the fault address is written to the FAULTADDR register. This bit is cleared by writing a 1 to it. 128 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Bit/Field Name Type Reset 8 IBUS R/W1C 0 Description Instruction Bus Error Value Description 0 An instruction bus error has not occurred. 1 An instruction bus error has occurred. The processor detects the instruction bus error on prefetching an instruction, but sets this bit only if it attempts to issue the faulting instruction. When this bit is set, a fault address is not written to the FAULTADDR register. This bit is cleared by writing a 1 to it. 7 MMARV R/W1C 0 Memory Management Fault Address Register Valid Value Description 0 The value in the Memory Management Fault Address (MMADDR) register is not a valid fault address. 1 The MMADDR register is holding a valid fault address. If a memory management fault occurs and is escalated to a hard fault because of priority, the hard fault handler must clear this bit. This action prevents problems if returning to a stacked active memory management fault handler whose MMADDR register value has been overwritten. This bit is cleared by writing a 1 to it. 6:5 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 4 MSTKE R/W1C 0 Stack Access Violation Value Description 0 No memory management fault has occurred on stacking for exception entry. 1 Stacking for an exception entry has caused one or more access violations. When this bit is set, the SP is still adjusted but the values in the context area on the stack might be incorrect. A fault address is not written to the MMADDR register. This bit is cleared by writing a 1 to it. July 14, 2014 129 Texas Instruments-Production Data Cortex-M3 Peripherals Bit/Field Name Type Reset 3 MUSTKE R/W1C 0 Description Unstack Access Violation Value Description 0 No memory management fault has occurred on unstacking for a return from exception. 1 Unstacking for a return from exception has caused one or more access violations. This fault is chained to the handler. Thus, when this bit is set, the original return stack is still present. The SP is not adjusted from the failing return, a new save is not performed, and a fault address is not written to the MMADDR register. This bit is cleared by writing a 1 to it. 2 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 1 DERR R/W1C 0 Data Access Violation Value Description 0 A data access violation has not occurred. 1 The processor attempted a load or store at a location that does not permit the operation. When this bit is set, the PC value stacked for the exception return points to the faulting instruction and the address of the attempted access is written to the MMADDR register. This bit is cleared by writing a 1 to it. 0 IERR R/W1C 0 Instruction Access Violation Value Description 0 An instruction access violation has not occurred. 1 The processor attempted an instruction fetch from a location that does not permit execution. This fault occurs on any access to an XN region, even when the MPU is disabled or not present. When this bit is set, the PC value stacked for the exception return points to the faulting instruction and the address of the attempted access is not written to the MMADDR register. This bit is cleared by writing a 1 to it. 130 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 29: Hard Fault Status (HFAULTSTAT), offset 0xD2C Note: This register can only be accessed from privileged mode. The HFAULTSTAT register gives information about events that activate the hard fault handler. Bits are cleared by writing a 1 to them. Hard Fault Status (HFAULTSTAT) Base 0xE000.E000 Offset 0xD2C Type R/W1C, reset 0x0000.0000 Type Reset 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 DBG FORCED R/W1C 0 R/W1C 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 reserved 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 VECT reserved RO 0 RO 0 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/W1C 0 RO 0 reserved Type Reset Bit/Field Name Type Reset 31 DBG R/W1C 0 Description Debug Event This bit is reserved for Debug use. This bit must be written as a 0, otherwise behavior is unpredictable. 30 FORCED R/W1C 0 Forced Hard Fault Value Description 0 No forced hard fault has occurred. 1 A forced hard fault has been generated by escalation of a fault with configurable priority that cannot be handled, either because of priority or because it is disabled. When this bit is set, the hard fault handler must read the other fault status registers to find the cause of the fault. This bit is cleared by writing a 1 to it. 29:2 reserved RO 0x00 1 VECT R/W1C 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. Vector Table Read Fault Value Description 0 No bus fault has occurred on a vector table read. 1 A bus fault occurred on a vector table read. This error is always handled by the hard fault handler. When this bit is set, the PC value stacked for the exception return points to the instruction that was preempted by the exception. This bit is cleared by writing a 1 to it. 0 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. July 14, 2014 131 Texas Instruments-Production Data Cortex-M3 Peripherals Register 30: Memory Management Fault Address (MMADDR), offset 0xD34 Note: This register can only be accessed from privileged mode. The MMADDR register contains the address of the location that generated a memory management fault. When an unaligned access faults, the address in the MMADDR register is the actual address that faulted. Because a single read or write instruction can be split into multiple aligned accesses, the fault address can be any address in the range of the requested access size. Bits in the Memory Management Fault Status (MFAULTSTAT) register indicate the cause of the fault and whether the value in the MMADDR register is valid (see page 125). Memory Management Fault Address (MMADDR) Base 0xE000.E000 Offset 0xD34 Type R/W, reset 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 R/W - R/W - R/W - R/W - R/W - R/W - R/W - R/W - 7 6 5 4 3 2 1 0 R/W - R/W - R/W - R/W - R/W - R/W - R/W - R/W - ADDR Type Reset R/W - R/W - R/W - R/W - R/W - R/W - R/W - R/W - 15 14 13 12 11 10 9 8 ADDR Type Reset R/W - R/W - R/W - R/W - R/W - R/W - R/W - Bit/Field Name Type Reset 31:0 ADDR R/W - R/W - Description Fault Address When the MMARV bit of MFAULTSTAT is set, this field holds the address of the location that generated the memory management fault. 132 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 31: Bus Fault Address (FAULTADDR), offset 0xD38 Note: This register can only be accessed from privileged mode. The FAULTADDR register contains the address of the location that generated a bus fault. When an unaligned access faults, the address in the FAULTADDR register is the one requested by the instruction, even if it is not the address of the fault. Bits in the Bus Fault Status (BFAULTSTAT) register indicate the cause of the fault and whether the value in the FAULTADDR register is valid (see page 125). Bus Fault Address (FAULTADDR) Base 0xE000.E000 Offset 0xD38 Type R/W, reset 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 R/W - R/W - R/W - R/W - R/W - R/W - R/W - R/W - 7 6 5 4 3 2 1 0 R/W - R/W - R/W - R/W - R/W - R/W - R/W - R/W - ADDR Type Reset R/W - R/W - R/W - R/W - R/W - R/W - R/W - R/W - 15 14 13 12 11 10 9 8 ADDR Type Reset R/W - R/W - R/W - R/W - R/W - R/W - R/W - Bit/Field Name Type Reset 31:0 ADDR R/W - R/W - Description Fault Address When the FAULTADDRV bit of BFAULTSTAT is set, this field holds the address of the location that generated the bus fault. 3.6 Memory Protection Unit (MPU) Register Descriptions This section lists and describes the Memory Protection Unit (MPU) registers, in numerical order by address offset. The MPU registers can only be accessed from privileged mode. July 14, 2014 133 Texas Instruments-Production Data Cortex-M3 Peripherals Register 32: MPU Type (MPUTYPE), offset 0xD90 Note: This register can only be accessed from privileged mode. The MPUTYPE register indicates whether the MPU is present, and if so, how many regions it supports. MPU Type (MPUTYPE) Base 0xE000.E000 Offset 0xD90 Type RO, reset 0x0000.0800 31 30 29 28 27 26 25 24 23 22 21 20 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 15 14 13 12 11 10 9 8 7 6 5 DREGION Type Reset RO 0 RO 0 RO 0 RO 0 19 18 17 16 RO 0 IREGION RO 0 RO 0 RO 0 RO 0 4 3 2 1 reserved RO 1 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 0 SEPARATE RO 0 RO 0 RO 0 RO 0 Bit/Field Name Type Reset Description 31:24 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 23:16 IREGION RO 0x00 Number of I Regions This field indicates the number of supported MPU instruction regions. This field always contains 0x00. The MPU memory map is unified and is described by the DREGION field. 15:8 DREGION RO 0x08 Number of D Regions Value Description 0x08 Indicates there are eight supported MPU data regions. 7:1 reserved RO 0x00 0 SEPARATE RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. Separate or Unified MPU Value Description 0 Indicates the MPU is unified. 134 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 33: MPU Control (MPUCTRL), offset 0xD94 Note: This register can only be accessed from privileged mode. The MPUCTRL register enables the MPU, enables the default memory map background region, and enables use of the MPU when in the hard fault, Non-maskable Interrupt (NMI), and Fault Mask Register (FAULTMASK) escalated handlers. When the ENABLE and PRIVDEFEN bits are both set: ■ For privileged accesses, the default memory map is as described in “Memory Model” on page 62. Any access by privileged software that does not address an enabled memory region behaves as defined by the default memory map. ■ Any access by unprivileged software that does not address an enabled memory region causes a memory management fault. Execute Never (XN) and Strongly Ordered rules always apply to the System Control Space regardless of the value of the ENABLE bit. When the ENABLE bit is set, at least one region of the memory map must be enabled for the system to function unless the PRIVDEFEN bit is set. If the PRIVDEFEN bit is set and no regions are enabled, then only privileged software can operate. When the ENABLE bit is clear, the system uses the default memory map, which has the same memory attributes as if the MPU is not implemented (see Table 2-5 on page 64 for more information). The default memory map applies to accesses from both privileged and unprivileged software. When the MPU is enabled, accesses to the System Control Space and vector table are always permitted. Other areas are accessible based on regions and whether PRIVDEFEN is set. Unless HFNMIENA is set, the MPU is not enabled when the processor is executing the handler for an exception with priority –1 or –2. These priorities are only possible when handling a hard fault or NMI exception or when FAULTMASK is enabled. Setting the HFNMIENA bit enables the MPU when operating with these two priorities. MPU Control (MPUCTRL) Base 0xE000.E000 Offset 0xD94 Type R/W, reset 0x0000.0000 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 RO 0 RO 0 reserved Type Reset reserved Type Reset RO 0 Bit/Field Name Type Reset 31:3 reserved RO 0x0000.000 PRIVDEFEN HFNMIENA R/W 0 R/W 0 ENABLE R/W 0 Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. July 14, 2014 135 Texas Instruments-Production Data Cortex-M3 Peripherals Bit/Field Name Type Reset 2 PRIVDEFEN R/W 0 Description MPU Default Region This bit enables privileged software access to the default memory map. Value Description 0 If the MPU is enabled, this bit disables use of the default memory map. Any memory access to a location not covered by any enabled region causes a fault. 1 If the MPU is enabled, this bit enables use of the default memory map as a background region for privileged software accesses. When this bit is set, the background region acts as if it is region number -1. Any region that is defined and enabled has priority over this default map. If the MPU is disabled, the processor ignores this bit. 1 HFNMIENA R/W 0 MPU Enabled During Faults This bit controls the operation of the MPU during hard fault, NMI, and FAULTMASK handlers. Value Description 0 The MPU is disabled during hard fault, NMI, and FAULTMASK handlers, regardless of the value of the ENABLE bit. 1 The MPU is enabled during hard fault, NMI, and FAULTMASK handlers. When the MPU is disabled and this bit is set, the resulting behavior is unpredictable. 0 ENABLE R/W 0 MPU Enable Value Description 0 The MPU is disabled. 1 The MPU is enabled. When the MPU is disabled and the HFNMIENA bit is set, the resulting behavior is unpredictable. 136 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 34: MPU Region Number (MPUNUMBER), offset 0xD98 Note: This register can only be accessed from privileged mode. The MPUNUMBER register selects which memory region is referenced by the MPU Region Base Address (MPUBASE) and MPU Region Attribute and Size (MPUATTR) registers. Normally, the required region number should be written to this register before accessing the MPUBASE or the MPUATTR register. However, the region number can be changed by writing to the MPUBASE register with the VALID bit set (see page 138). This write updates the value of the REGION field. MPU Region Number (MPUNUMBER) Base 0xE000.E000 Offset 0xD98 Type R/W, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 1 0 reserved Type Reset RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 15 14 13 12 11 10 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 9 8 7 6 5 4 3 2 reserved Type Reset RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 Bit/Field Name Type Reset 31:3 reserved RO 0x0000.000 2:0 NUMBER R/W 0x0 NUMBER RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 R/W 0 R/W 0 R/W 0 Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. MPU Region to Access This field indicates the MPU region referenced by the MPUBASE and MPUATTR registers. The MPU supports eight memory regions. July 14, 2014 137 Texas Instruments-Production Data Cortex-M3 Peripherals Register 35: MPU Region Base Address (MPUBASE), offset 0xD9C Register 36: MPU Region Base Address Alias 1 (MPUBASE1), offset 0xDA4 Register 37: MPU Region Base Address Alias 2 (MPUBASE2), offset 0xDAC Register 38: MPU Region Base Address Alias 3 (MPUBASE3), offset 0xDB4 Note: This register can only be accessed from privileged mode. The MPUBASE register defines the base address of the MPU region selected by the MPU Region Number (MPUNUMBER) register and can update the value of the MPUNUMBER register. To change the current region number and update the MPUNUMBER register, write the MPUBASE register with the VALID bit set. The ADDR field is bits 31:N of the MPUBASE register. Bits (N-1):5 are reserved. The region size, as specified by the SIZE field in the MPU Region Attribute and Size (MPUATTR) register, defines the value of N where: N = Log2(Region size in bytes) If the region size is configured to 4 GB in the MPUATTR register, there is no valid ADDR field. In this case, the region occupies the complete memory map, and the base address is 0x0000.0000. The base address is aligned to the size of the region. For example, a 64-KB region must be aligned on a multiple of 64 KB, for example, at 0x0001.0000 or 0x0002.0000. MPU Region Base Address (MPUBASE) Base 0xE000.E000 Offset 0xD9C Type R/W, reset 0x0000.0000 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 VALID reserved R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 WO 0 RO 0 ADDR Type Reset ADDR Type Reset R/W 0 Bit/Field Name Type Reset 31:5 ADDR R/W 0x0000.000 REGION R/W 0 R/W 0 R/W 0 Description Base Address Mask Bits 31:N in this field contain the region base address. The value of N depends on the region size, as shown above. The remaining bits (N-1):5 are reserved. Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 138 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Bit/Field Name Type Reset 4 VALID WO 0 Description Region Number Valid Value Description 0 The MPUNUMBER register is not changed and the processor updates the base address for the region specified in the MPUNUMBER register and ignores the value of the REGION field. 1 The MPUNUMBER register is updated with the value of the REGION field and the base address is updated for the region specified in the REGION field. This bit is always read as 0. 3 reserved RO 0 2:0 REGION R/W 0x0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. Region Number On a write, contains the value to be written to the MPUNUMBER register. On a read, returns the current region number in the MPUNUMBER register. July 14, 2014 139 Texas Instruments-Production Data Cortex-M3 Peripherals Register 39: MPU Region Attribute and Size (MPUATTR), offset 0xDA0 Register 40: MPU Region Attribute and Size Alias 1 (MPUATTR1), offset 0xDA8 Register 41: MPU Region Attribute and Size Alias 2 (MPUATTR2), offset 0xDB0 Register 42: MPU Region Attribute and Size Alias 3 (MPUATTR3), offset 0xDB8 Note: This register can only be accessed from privileged mode. The MPUATTR register defines the region size and memory attributes of the MPU region specified by the MPU Region Number (MPUNUMBER) register and enables that region and any subregions. The MPUATTR register is accessible using word or halfword accesses with the most-significant halfword holding the region attributes and the least-significant halfword holds the region size and the region and subregion enable bits. The MPU access permission attribute bits, XN, AP, TEX, S, C, and B, control access to the corresponding memory region. If an access is made to an area of memory without the required permissions, then the MPU generates a permission fault. The SIZE field defines the size of the MPU memory region specified by the MPUNUMBER register as follows: (Region size in bytes) = 2(SIZE+1) The smallest permitted region size is 32 bytes, corresponding to a SIZE value of 4. Table 3-9 on page 140 gives example SIZE values with the corresponding region size and value of N in the MPU Region Base Address (MPUBASE) register. Table 3-9. Example SIZE Field Values a SIZE Encoding Region Size Value of N Note 00100b (0x4) 32 B 5 Minimum permitted size 01001b (0x9) 1 KB 10 - 10011b (0x13) 1 MB 20 - 11101b (0x1D) 1 GB 30 - 11111b (0x1F) 4 GB No valid ADDR field in MPUBASE; the Maximum possible size region occupies the complete memory map. a. Refers to the N parameter in the MPUBASE register (see page 138). MPU Region Attribute and Size (MPUATTR) Base 0xE000.E000 Offset 0xDA0 Type R/W, reset 0x0000.0000 31 30 29 28 27 reserved Type Reset 26 25 24 23 AP 21 reserved 20 19 18 TEX 17 16 XN reserved S C B RO 0 RO 0 RO 0 R/W 0 RO 0 R/W 0 R/W 0 R/W 0 RO 0 RO 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 RO 0 RO 0 R/W 0 R/W 0 R/W 0 R/W 0 SRD Type Reset 22 reserved SIZE 140 R/W 0 ENABLE R/W 0 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Bit/Field Name Type Reset Description 31:29 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 28 XN R/W 0 Instruction Access Disable Value Description 0 Instruction fetches are enabled. 1 Instruction fetches are disabled. 27 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 26:24 AP R/W 0 Access Privilege For information on using this bit field, see Table 3-5 on page 92. 23:22 reserved RO 0x0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 21:19 TEX R/W 0x0 Type Extension Mask For information on using this bit field, see Table 3-3 on page 91. 18 S R/W 0 Shareable For information on using this bit, see Table 3-3 on page 91. 17 C R/W 0 Cacheable For information on using this bit, see Table 3-3 on page 91. 16 B R/W 0 Bufferable For information on using this bit, see Table 3-3 on page 91. 15:8 SRD R/W 0x00 Subregion Disable Bits Value Description 0 The corresponding subregion is enabled. 1 The corresponding subregion is disabled. Region sizes of 128 bytes and less do not support subregions. When writing the attributes for such a region, configure the SRD field as 0x00. See the section called “Subregions” on page 90 for more information. 7:6 reserved RO 0x0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 5:1 SIZE R/W 0x0 Region Size Mask The SIZE field defines the size of the MPU memory region specified by the MPUNUMBER register. Refer to Table 3-9 on page 140 for more information. July 14, 2014 141 Texas Instruments-Production Data Cortex-M3 Peripherals Bit/Field Name Type Reset 0 ENABLE R/W 0 Description Region Enable Value Description 0 The region is disabled. 1 The region is enabled. 142 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 4 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 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 Stellaris 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 Stellaris JTAG instructions select the Stellaris TDO outputs. The multiplexer is controlled by the Stellaris JTAG controller, which has comprehensive programming for the ARM, Stellaris, and unimplemented JTAG instructions. The Stellaris 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, IDCODE, SAMPLE/PRELOAD, EXTEST and INTEST ■ ARM additional instructions: APACC, DPACC and ABORT ■ Integrated ARM Serial Wire Debug (SWD) See the ARM® Debug Interface V5 Architecture Specification for more information on the ARM JTAG controller. July 14, 2014 143 Texas Instruments-Production Data JTAG Interface 4.1 Block Diagram Figure 4-1. JTAG Module Block Diagram TRST TCK TMS TAP Controller TDI 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 4.2 Signal Description Table 4-1 on page 144 lists the external signals of the JTAG/SWD controller and describes the function of each. The JTAG/SWD controller signals are alternate functions for some GPIO signals, however note that the reset state of the pins is for the JTAG/SWD function. The column in the table below titled "Pin Assignment" lists the GPIO pin placement for the JTAG/SWD controller signals. The AFSEL bit in the GPIO Alternate Function Select (GPIOAFSEL) register (page 250) is set to choose the JTAG/SWD function. For more information on configuring GPIOs, see “General-Purpose Input/Outputs (GPIOs)” on page 230. Table 4-1. JTAG_SWD_SWO Signals (48QFP) a Pin Name Pin Number Pin Type Buffer Type SWCLK 40 I TTL Description JTAG/SWD CLK. SWDIO 39 I/O TTL JTAG TMS and SWDIO. SWO 37 O TTL JTAG TDO and SWO. TCK 40 I TTL JTAG/SWD CLK. TDI 38 I TTL JTAG TDI. TDO 37 O TTL JTAG TDO and SWO. TMS 39 I/O TTL JTAG TMS and SWDIO. TRST 41 I TTL JTAG TRST. a. The TTL designation indicates the pin has TTL-compatible voltage levels. 144 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 4.3 Functional Description A high-level conceptual drawing of the JTAG module is shown in Figure 4-1 on page 144. 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 4-3 on page 149 for a list of implemented instructions). See “JTAG and Boundary Scan” on page 546 for JTAG timing diagrams. 4.3.1 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 4-2 on page 145. Detailed information on each pin follows. Table 4-2. JTAG Port Pins Reset State 4.3.1.1 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. 4.3.1.2 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 July 14, 2014 145 Texas Instruments-Production Data JTAG Interface 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. 4.3.1.3 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 4-2 on page 147. 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. 4.3.1.4 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. 4.3.1.5 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. 4.3.2 JTAG TAP Controller The JTAG TAP controller state machine is shown in Figure 4-2 on page 147. The TAP controller state machine is reset to the Test-Logic-Reset state on the assertion of a Power-On-Reset (POR) 146 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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. Figure 4-2. Test Access Port State Machine Test Logic Reset 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 4.3.3 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 “Register Descriptions” on page 149. 4.3.4 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 July 14, 2014 147 Texas Instruments-Production Data JTAG Interface considered. In addition, because the JTAG module has integrated ARM Serial Wire Debug, the method for switching between these two operational modes is described below. 4.3.4.1 GPIO Functionality When the microcontroller 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 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. 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. 4.3.4.2 Communication with JTAG/SWD Because the debug clock and the system clock can be running at different frequencies, care must be taken to maintain reliable communication with the JTAG/SWD interface. In the Capture-DR state, the result of the previous transaction, if any, is returned, together with a 3-bit ACK response. Software should check the ACK response to see if the previous operation has completed before initiating a new transaction. Alternatively, if the system clock is at least 8 times faster than the debug clock (TCK or SWCLK), the previous operation has enough time to complete and the ACK bits do not have to be checked. 4.3.4.3 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 switching 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® Debug Interface V5 Architecture Specification. 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 148 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller probability of this sequence occurring during normal operation of the TAP controller, it should not affect normal performance of the JTAG interface. 4.4 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. In addition to enabling the alternate functions, any other changes to the GPIO pad configurations on the five JTAG pins (PB7 andPC[3:0]) should be reverted to their default settings. 4.5 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. 4.5.1 Instruction Register (IR) The JTAG TAP Instruction Register (IR) is a four-bit serial scan chain connected between the JTAG TDI and TDO pins with a parallel load register. 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 4-3 on page 149. A detailed explanation of each instruction, along with its associated Data Register, follows. Table 4-3. JTAG Instruction Register Commands 4.5.1.1 IR[3:0] Instruction Description 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. Captures the current I/O values and shifts the sampled values out of the Boundary Scan Chain while new preload data is shifted in. 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. EXTEST Instruction The EXTEST instruction is not associated with its own 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 July 14, 2014 149 Texas Instruments-Production Data JTAG Interface tests to be developed that drive known values out of the controller, which can be used to verify connectivity. While the EXTEST instruction is present in the Instruction Register, the Boundary Scan Data Register can be accessed to sample and shift out the current data and load new data into the Boundary Scan Data Register. 4.5.1.2 INTEST Instruction The INTEST instruction is not associated with its own 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 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. While the INTEXT instruction is present in the Instruction Register, the Boundary Scan Data Register can be accessed to sample and shift out the current data and load new data into the Boundary Scan Data Register. 4.5.1.3 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 152 for more information. 4.5.1.4 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 152 for more information. 4.5.1.5 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 152 for more information. 150 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 4.5.1.6 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 152 for more information. 4.5.1.7 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 151 for more information. 4.5.1.8 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 152 for more information. 4.5.2 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. 4.5.2.1 IDCODE Data Register The format for the 32-bit IDCODE Data Register defined by the IEEE Standard 1149.1 is shown in Figure 4-3 on page 151. 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 0x1BA0.0477. This allows the debuggers to automatically configure themselves to work correctly with the Cortex-M3 during debug. Figure 4-3. IDCODE Register Format 31 TDI 28 27 Version 12 11 Part Number July 14, 2014 1 0 Manufacturer ID 1 TDO 151 Texas Instruments-Production Data JTAG Interface 4.5.2.2 BYPASS Data Register The format for the 1-bit BYPASS Data Register defined by the IEEE Standard 1149.1 is shown in Figure 4-4 on page 152. 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 4-4. BYPASS Register Format 0 0 TDI 4.5.2.3 TDO Boundary Scan Data Register The format of the Boundary Scan Data Register is shown in Figure 4-5 on page 152. Each GPIO pin, starting with a GPIO pin next to 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 signals are input, output, and output enable, and are arranged in that order as can be seen in the figure. 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 4-5. Boundary Scan Register Format TDI I N O U T O E ... GPIO PB6 4.5.2.4 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 APACC Data Register The format for the 35-bit APACC Data Register defined by ARM is described in the ARM® Debug Interface V5 Architecture Specification. 4.5.2.5 DPACC Data Register The format for the 35-bit DPACC Data Register defined by ARM is described in the ARM® Debug Interface V5 Architecture Specification. 4.5.2.6 ABORT Data Register The format for the 35-bit ABORT Data Register defined by ARM is described in the ARM® Debug Interface V5 Architecture Specification. 152 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 5 System Control System control determines the overall operation of the device. It provides information about the device, controls the clocking to the core and individual peripherals, and handles reset detection and reporting. 5.1 Signal Description Table 5-1 on page 153 lists the external signals of the System Control module and describes the function of each. The NMI signal is the alternate function for and functions as a GPIO after reset. under commit protection and require a special process to be configured as any alternate function or to subsequently return to the GPIO function. The column in the table below titled "Pin Assignment" lists the GPIO pin placement for the NMI signal. The AFSEL bit in the GPIO Alternate Function Select (GPIOAFSEL) register (page 250) should be set to choose the NMI function. For more information on configuring GPIOs, see “General-Purpose Input/Outputs (GPIOs)” on page 230. The remaining signals (with the word "fixed" in the Pin Assignment column) have a fixed pin assignment and function. Table 5-1. System Control & Clocks Signals (48QFP) a Pin Name Pin Number Pin Type Buffer Type Description OSC0 9 I Analog Main oscillator crystal input or an external clock reference input. OSC1 10 O Analog Main oscillator crystal output. Leave unconnected when using a single-ended clock source. RST 5 I TTL System reset input. a. The TTL designation indicates the pin has TTL-compatible voltage levels. 5.2 Functional Description The System Control module provides the following capabilities: ■ Device identification (see “Device Identification” on page 153) ■ Local control, such as reset (see “Reset Control” on page 153), power (see “Power Control” on page 158) and clock control (see “Clock Control” on page 158) ■ System control (Run, Sleep, and Deep-Sleep modes); see “System Control” on page 161 5.2.1 Device Identification Several 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. 5.2.2 Reset Control This section discusses aspects of hardware functions during reset as well as system software requirements following the reset sequence. 5.2.2.1 Reset Sources The controller has six sources of reset: 1. External reset input pin (RST) assertion; see “External RST Pin” on page 155. July 14, 2014 153 Texas Instruments-Production Data System Control 2. Power-on reset (POR); see “Power-On Reset (POR)” on page 154. 3. Internal brown-out (BOR) detector; see “Brown-Out Reset (BOR)” on page 156. 4. Software-initiated reset (with the software reset registers); see “Software Reset” on page 157. 5. A watchdog timer reset condition violation; see “Watchdog Timer Reset” on page 157. 6. Internal low drop-out (LDO) regulator output. Table 5-2 provides a summary of results of the various reset operations. Table 5-2. Reset Sources Core Reset? JTAG Reset? On-Chip Peripherals Reset? Power-On Reset Reset Source Yes Yes Yes RST Yes Pin Config Only Yes Brown-Out Reset Yes No Yes Software System Request a Reset Yes No Yes Software Peripheral Reset No No Yes Watchdog Reset Yes No Yes LDO Reset Yes No Yes b a. By using the SYSRESREQ bit in the ARM Cortex-M3 Application Interrupt and Reset Control (APINT) register b. Programmable on a module-by-module basis using the Software Reset Control Registers. After a reset, the Reset Cause (RESC) register 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: 5.2.2.2 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. Power-On Reset (POR) Note: The power-on reset also resets the JTAG controller. An external reset does not. The internal Power-On Reset (POR) circuit monitors the power supply voltage (VDD) and generates a reset signal to all of the internal logic including JTAG when the power supply ramp reaches a threshold value (VTH). The microcontroller must be operating within the specified operating parameters when the on-chip power-on reset pulse is complete. The 3.3-V power supply to the microcontroller must reach 3.0 V within 10 msec of VDD crossing 2.0 V to guarantee proper operation. For applications that require the use of an external reset signal to hold the microcontroller in reset longer than the internal POR, the RST input may be used as discussed in “External RST Pin” on page 155. The Power-On Reset sequence is as follows: 1. The microcontroller waits for internal POR to go inactive. 2. The internal reset is released and the core loads from memory 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 microcontroller. The Power-On Reset timing is shown in Figure 19-6 on page 549. 154 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 5.2.2.3 External RST Pin Note: It is recommended that the trace for the RST signal must be kept as short as possible. Be sure to place any components connected to the RST signal as close to the microcontroller as possible. If the application only uses the internal POR circuit, the RST input must be connected to the power supply (VDD) through an optional pull-up resistor (0 to 100K Ω) as shown in Figure 5-1 on page 155. Figure 5-1. Basic RST Configuration VDD Stellaris® RPU RST RPU = 0 to 100 kΩ The external reset pin (RST) resets the microcontroller including the core and all the on-chip peripherals except the JTAG TAP controller (see “JTAG Interface” on page 143). The external reset sequence is as follows: 1. The external reset pin (RST) is asserted for the duration specified by TMIN and then de-asserted (see “Reset” on page 548). 2. The internal reset is released and the core loads from memory the initial stack pointer, the initial program counter, and the first instruction designated by the program counter, and then begins execution. To improve noise immunity and/or to delay reset at power up, the RST input may be connected to an RC network as shown in Figure 5-2 on page 155. Figure 5-2. External Circuitry to Extend Power-On Reset VDD Stellaris® RPU RST C1 RPU = 1 kΩ to 100 kΩ C1 = 1 nF to 10 µF If the application requires the use of an external reset switch, Figure 5-3 on page 156 shows the proper circuitry to use. July 14, 2014 155 Texas Instruments-Production Data System Control Figure 5-3. Reset Circuit Controlled by Switch VDD Stellaris® RPU RST C1 RS Typical RPU = 10 kΩ Typical RS = 470 Ω C1 = 10 nF The RPU and C1 components define the power-on delay. The external reset timing is shown in Figure 19-5 on page 549. 5.2.2.4 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 the power supply (VDD) drops below a brown-out threshold voltage (VBTH). The circuit is provided to guard against improper operation of logic and peripherals that operate off the power supply voltage (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 for the interrupt condition. This feature may be optionally enabled. Brown-out resets are controlled with the Power-On and Brown-Out Reset Control (PBORCTL) register. The BORIOR bit in the PBORCTL register must be set for a brown-out condition 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 and BORIOR is not set, the BOR condition is resampled, after a delay 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 further 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, the first instruction designated by the program counter, and begins execution. 5. The internal BOR condition is reset 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 19-7 on page 549. 156 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 5.2.2.5 Software Reset Software can reset a specific peripheral or generate a reset to the entire system . Peripherals can be individually reset by software via three registers that control reset signals to each peripheral (see the SRCRn registers). If the bit position corresponding to a peripheral is set and subsequently cleared, 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 161). 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 by 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 is 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 deasserted and the controller loads from memory 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 19-8 on page 550. 5.2.2.6 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, 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. 3. The internal reset is released and the controller loads from memory the initial stack pointer, the initial program counter, the first instruction designated by the program counter, and begins execution. The watchdog reset timing is shown in Figure 19-9 on page 550. 5.2.2.7 Low Drop-Out (LDO) 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. 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. July 14, 2014 157 Texas Instruments-Production Data System Control 3. The internal reset is released and the controller fetches and loads the initial stack pointer, the initial program counter, the first instruction designated by the program counter, and begins execution. The LDO reset timing is shown in Figure 19-10 on page 550. 5.2.3 Power Control ® The Stellaris microcontroller provides an integrated LDO regulator that is used to provide power to the majority of the controller's internal logic. For power reduction, the LDO regulator provides software a mechanism to adjust the regulated value, in small increments (VSTEP), over the range of 2.25 V to 2.75 V (inclusive)—or 2.5 V ± 10%. The adjustment is made by changing the value of the VADJ field in the LDO Power Control (LDOPCTL) register. 5.2.4 Clock Control System control determines the control of clocks in this part. 5.2.4.1 Fundamental Clock Sources There are multiple clock sources for use in the device: ■ Internal Oscillator (IOSC). The internal oscillator is an on-chip clock source. It does not require the use of any external components. The frequency of the internal oscillator is 12 MHz ± 30%. ■ Main Oscillator (MOSC). The main oscillator provides a frequency-accurate clock source by one of two means: an external single-ended clock source is connected to the OSC0 input pin, or an external crystal is connected across the OSC0 input and OSC1 output pins. The crystal value allowed depends on whether the main oscillator is used as the clock reference source to the PLL. If so, the crystal must be one of the supported frequencies between 3.579545 MHz through 8.192 MHz (inclusive). If the PLL is not being used, the crystal may be any one of the supported frequencies between 1 MHz and 8.192 MHz. The single-ended clock source range is from DC through the specified speed of the device. The supported crystals are listed in the XTAL bit field in the RCC register (see page 173). The internal system clock (SysClk), is derived from any of the above sources plus two others: the output of the main internal PLL, and the internal oscillator divided by four (3 MHz ± 30%). The frequency of the PLL clock reference must be in the range of 3.579545 MHz to 8.192 MHz (inclusive). Table 5-3 on page 158 shows how the various clock sources can be used in a system. Table 5-3. Clock Source Options 5.2.4.2 Clock Source Drive PLL? Internal Oscillator (12 MHz) Yes BYPASS = 0, OSCSRC = 0x1 Yes BYPASS = 1, OSCSRC = 0x1 Internal Oscillator divide by 4 (3 Yes MHz) BYPASS = 0, OSCSRC = 0x2 Yes BYPASS = 1, OSCSRC = 0x2 Main Oscillator BYPASS = 0, OSCSRC = 0x0 Yes BYPASS = 1, OSCSRC = 0x0 Yes Used as SysClk? Clock Configuration Nearly all of the control for the clocks is provided by the Run-Mode Clock Configuration (RCC) register. This register controls the following clock functionality: ■ Source of clocks in sleep and deep-sleep modes 158 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller ■ System clock derived from PLL or other clock source ■ Enabling/disabling of oscillators and PLL ■ Clock divisors ■ Crystal input selection Figure 5-4 on page 159 shows the logic for the main clock tree. The peripheral blocks are driven by the system clock signal and can be individually enabled/disabled. The ADC clock signal is automatically divided down to 16.67 MHz for proper ADC operation. The PWM clock signal is a synchronous divide of the system clock to provide the PWM circuit with more range (set with PWMDIV in RCC). Note: When the ADC module is in operation, the system clock must be at least 16.667 MHz. Figure 5-4. Main Clock Tree USESYSDIVa OSC1 OSC2 Main Osc 1-8 MHz System Clock SYSDIVa Internal Osc 12 MHz PLL (200 MHz output) ÷4 OSCSRCa OENa PWRDNa PWM Clock PWMDIVa XTALa BYPASSa USEPWMDIVa Constant Divide (16.667 MHz output) a. These are bit fields within the Run-Mode Clock Configuration (RCC) register. ADC Clock In the RCC register, the SYSDIV field specifies which divisor is used to generate the system clock from either the PLL output or the oscillator source (depending on how the BYPASS bit in this register is configured). Table 5-4 shows how the SYSDIV encoding affects the system clock frequency, depending on whether the PLL is used (BYPASS=0) or another clock source is used (BYPASS=1). The divisor is equivalent to the SYSDIV encoding plus 1. For a list of possible clock sources, see Table 5-3 on page 158. Table 5-4. Possible System Clock Frequencies Using the SYSDIV Field SYSDIV Divisor a Frequency (BYPASS=0) Frequency (BYPASS=1) StellarisWare Parameter b 0x0 /1 reserved Clock source frequency/2 SYSCTL_SYSDIV_1 0x1 /2 reserved Clock source frequency/2 SYSCTL_SYSDIV_2 0x2 /3 reserved Clock source frequency/3 SYSCTL_SYSDIV_3 0x3 /4 50 MHz Clock source frequency/4 SYSCTL_SYSDIV_4 0x4 /5 40 MHz Clock source frequency/5 SYSCTL_SYSDIV_5 0x5 /6 33.33 MHz Clock source frequency/6 SYSCTL_SYSDIV_6 0x6 /7 28.57 MHz Clock source frequency/7 SYSCTL_SYSDIV_7 July 14, 2014 159 Texas Instruments-Production Data System Control Table 5-4. Possible System Clock Frequencies Using the SYSDIV Field (continued) Frequency (BYPASS=1) StellarisWare Parameter /8 25 MHz Clock source frequency/8 SYSCTL_SYSDIV_8 0x8 /9 22.22 MHz Clock source frequency/9 SYSCTL_SYSDIV_9 0x9 /10 20 MHz Clock source frequency/10 SYSCTL_SYSDIV_10 0xA /11 18.18 MHz Clock source frequency/11 SYSCTL_SYSDIV_11 0xB /12 16.67 MHz Clock source frequency/12 SYSCTL_SYSDIV_12 0xC /13 15.38 MHz Clock source frequency/13 SYSCTL_SYSDIV_13 0xD /14 14.29 MHz Clock source frequency/14 SYSCTL_SYSDIV_14 0xE /15 13.33 MHz Clock source frequency/15 SYSCTL_SYSDIV_15 0xF /16 12.5 MHz (default) Clock source frequency/16 SYSCTL_SYSDIV_16 0x7 Divisor a Frequency (BYPASS=0) SYSDIV a. This parameter is used in functions such as SysCtlClockSet() in the Stellaris Peripheral Driver Library. b. SYSCTL_SYSDIV_1 does not set the USESYSDIV bit. As a result, using this parameter without enabling the PLL results in the system clock having the same frequency as the clock source. 5.2.4.3 Crystal Configuration for the Main Oscillator (MOSC) The main oscillator supports the use of a select number of crystals. If the main oscillator is used by the PLL as a reference clock, the supported range of crystals is 3.579545 to 8.192 MHz, otherwise, the range of supported crystals is 1 to 8.192 MHz. The XTAL bit in the RCC register (see page 173) describes the available crystal choices and default programming values. Software configures the RCC register XTAL field with the crystal number. If the PLL is used in the design, the XTAL field value is internally translated to the PLL settings. 5.2.4.4 Main PLL Frequency Configuration The main PLL is disabled by default during power-on reset and is enabled later by software if required. Software configures the main PLL input reference clock source, specifies the output divisor to set the system clock frequency, and enables the main PLL to drive the output. If the main oscillator provides the clock reference to the main PLL, the translation provided by hardware and used to program the PLL is available for software in the XTAL to PLL Translation (PLLCFG) register (see page 177). The internal translation provides a translation within ± 1% of the targeted PLL VCO frequency. The Crystal Value field (XTAL) in the Run-Mode Clock Configuration (RCC) register (see page 173) describes the available crystal choices and default programming of the PLLCFG register. Any time the XTAL field changes, the new settings are translated and the internal PLL settings are updated. 5.2.4.5 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 (see page 173). 160 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 5.2.4.6 PLL Operation If a PLL configuration is changed, the PLL output frequency is unstable until it reconverges (relocks) to the new setting. The time between the configuration change and relock is TREADY (see Table 19-7 on page 546). During the relock time, the affected PLL is not usable as a clock reference. PLL is changed by one of the following: ■ Change to the XTAL value in the RCC register—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 an 8.192 MHz external oscillator clock). Hardware is provided to 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. If the main PLL is enabled and the system clock is switched to use the PLL in one step, the system control hardware continues to clock the controller from the oscillator selected by the RCC register until the main PLL is stable (TREADY time met), after which it changes to the PLL. Software can use many methods to ensure that the system is clocked from the main PLL, including periodically polling the PLLLRIS bit in the Raw Interrupt Status (RIS) register, and enabling the PLL Lock interrupt. 5.2.4.7 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. 5.2.5 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. There are three levels of operation for the device defined as: ■ Run Mode. In Run mode, the controller actively executes code. 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. ■ Sleep Mode. In Sleep mode, the clock frequency of the active peripherals is unchanged, but the processor and the memory subsystem are not clocked and therefore no longer execute code. July 14, 2014 161 Texas Instruments-Production Data System Control Sleep mode is entered by the Cortex-M3 core executing a WFI(Wait for Interrupt) instruction. Any properly configured interrupt event in the system will bring the processor back into Run mode. See “Power Management” on page 80 for more details. Peripherals are clocked that are enabled in the SCGCn register when auto-clock gating is enabled (see the RCC register) 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. ■ Deep-Sleep Mode. In Deep-Sleep mode, the clock frequency of the active peripherals may change (depending on the Run mode clock configuration) in addition to the processor clock being stopped. An interrupt returns the device to Run mode from one of the sleep modes. Deep-Sleep mode is entered by first writing the Deep Sleep Enable bit in the ARM Cortex-M3 NVIC system control register and then executing a WFI instruction. Any properly configured interrupt event in the system will bring the processor back into Run mode. See “Power Management” on page 80 for more details. 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 the RCC register) or the RCGCn register when 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. 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 will power the PLL 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 before enabling the clocks that had been stopped during the Deep-Sleep duration. Caution – If the Cortex-M3 Debug Access Port (DAP) has been enabled, and the device wakes from a low power sleep or deep-sleep mode, the core may start executing code before all clocks to peripherals have been restored to their run mode configuration. The DAP is usually enabled by software tools accessing the JTAG or SWD interface when debugging or flash programming. If this condition occurs, a Hard Fault is triggered when software accesses a peripheral with an invalid clock. A software delay loop can be used at the beginning of the interrupt routine that is used to wake up a system from a WFI (Wait For Interrupt) instruction. This stalls the execution of any code that accesses a peripheral register that might cause a fault. This loop can be removed for production software as the DAP is most likely not enabled during normal execution. Because the DAP is disabled by default (power on reset), the user can also power-cycle the device. The DAP is not enabled unless it is enabled through the JTAG or SWD interface. 5.3 Initialization and Configuration The PLL is configured using direct register writes to the 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 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. 162 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 3. Select the desired system divider (SYSDIV) in RCC 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. 5. Enable use of the PLL by clearing the BYPASS bit in RCC. Note: 5.4 If the BYPASS bit is cleared before the PLL locks, it is possible to render the device unusable. Register Map Table 5-5 on page 163 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 0x400F.E000. Note: Spaces in the System Control register space that are not used are reserved for future or internal use. Software should not modify any reserved memory address. Table 5-5. System Control Register Map Description See page Offset Name Type Reset 0x000 DID0 RO - Device Identification 0 165 0x004 DID1 RO - Device Identification 1 181 0x008 DC0 RO 0x001F.001F Device Capabilities 0 183 0x010 DC1 RO 0x0011.31BF Device Capabilities 1 184 0x014 DC2 RO 0x0107.1013 Device Capabilities 2 186 0x018 DC3 RO 0xBF03.01C3 Device Capabilities 3 188 0x01C DC4 RO 0x0000.001F Device Capabilities 4 190 0x030 PBORCTL R/W 0x0000.7FFD Power-On and Brown-Out Reset Control 167 0x034 LDOPCTL R/W 0x0000.0000 LDO Power Control 168 0x040 SRCR0 R/W 0x00000000 Software Reset Control 0 208 0x044 SRCR1 R/W 0x00000000 Software Reset Control 1 209 0x048 SRCR2 R/W 0x00000000 Software Reset Control 2 211 0x050 RIS RO 0x0000.0000 Raw Interrupt Status 169 0x054 IMC R/W 0x0000.0000 Interrupt Mask Control 170 0x058 MISC R/W1C 0x0000.0000 Masked Interrupt Status and Clear 171 0x05C RESC R/W - Reset Cause 172 0x060 RCC R/W 0x078E.3AC0 Run-Mode Clock Configuration 173 0x064 PLLCFG RO - XTAL to PLL Translation 177 0x100 RCGC0 R/W 0x00000040 Run Mode Clock Gating Control Register 0 191 0x104 RCGC1 R/W 0x00000000 Run Mode Clock Gating Control Register 1 197 0x108 RCGC2 R/W 0x00000000 Run Mode Clock Gating Control Register 2 203 July 14, 2014 163 Texas Instruments-Production Data System Control Table 5-5. System Control Register Map (continued) Name Type Reset 0x110 SCGC0 R/W 0x00000040 Sleep Mode Clock Gating Control Register 0 193 0x114 SCGC1 R/W 0x00000000 Sleep Mode Clock Gating Control Register 1 199 0x118 SCGC2 R/W 0x00000000 Sleep Mode Clock Gating Control Register 2 204 0x120 DCGC0 R/W 0x00000040 Deep Sleep Mode Clock Gating Control Register 0 195 0x124 DCGC1 R/W 0x00000000 Deep Sleep Mode Clock Gating Control Register 1 201 0x128 DCGC2 R/W 0x00000000 Deep Sleep Mode Clock Gating Control Register 2 206 0x144 DSLPCLKCFG R/W 0x0780.0000 Deep Sleep Clock Configuration 178 0x150 CLKVCLR R/W 0x0000.0000 Clock Verification Clear 179 0x160 LDOARST R/W 0x0000.0000 Allow Unregulated LDO to Reset the Part 180 5.5 Description See page Offset Register Descriptions All addresses given are relative to the System Control base address of 0x400F.E000. 164 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 1: Device Identification 0 (DID0), offset 0x000 This register identifies the version of the microcontroller. Each microcontroller is uniquely identified by the combined values of the CLASS field in the DID0 register and the PARTNO field in the DID1 register. Device Identification 0 (DID0) Base 0x400F.E000 Offset 0x000 Type RO, reset 31 30 reserved Type Reset 29 28 27 26 25 24 23 22 VER 21 20 19 18 17 16 reserved RO 0 RO 0 RO 0 RO 0 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 - MAJOR Type Reset MINOR Bit/Field Name Type Reset 31 reserved RO 0 30:28 VER RO 0x0 Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. DID0 Version This field defines the DID0 register format version. The version number is numeric. The value of the VER field is encoded as follows: Value Description 0x0 27:16 reserved RO 0x0 15:8 MAJOR RO - Initial DID0 register format definition for Stellaris® Sandstorm-class devices. Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. Major Revision This field specifies the major revision number of the device. The major revision reflects changes to base layers of the design. 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: Value Description 0x0 Revision A (initial device) 0x1 Revision B (first base layer revision) 0x2 Revision C (second base layer revision) and so on. July 14, 2014 165 Texas Instruments-Production Data System Control Bit/Field Name Type Reset 7:0 MINOR RO - Description Minor Revision This field specifies the minor revision number of the device. The minor revision reflects changes to the metal layers of the design. The MINOR field value is reset when the MAJOR field is changed. This field is numeric and is encoded as follows: Value Description 0x0 Initial device, or a major revision update. 0x1 First metal layer change. 0x2 Second metal layer change. and so on. 166 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 2: 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) Base 0x400F.E000 Offset 0x030 Type R/W, reset 0x0000.7FFD 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 R/W 0 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 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 BORIOR BORWT R/W 1 R/W 1 R/W 1 R/W 1 R/W 1 R/W 1 R/W 1 R/W 0 R/W 1 reserved Type Reset BORTIM Type Reset Bit/Field Name Type Reset 31:16 reserved RO 0x0 15:2 BORTIM R/W 0x1FFF Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. BOR Time Delay 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 t BOR width of 500 μs and the internal oscillator (IOSC) frequency of 12 MHz ± 30%. At +30%, the counter value has to exceed 7,800. 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 BORIOR is not set. If BORWT is set to 1 and BORIOR is cleared to 0, the controller waits BORTIM IOSC periods and resamples the BOR output. If still asserted, a BOR interrupt is signalled. If no longer asserted, the initial assertion is suppressed (attributable to noise). If BORWT is 0, BOR assertions do not resample the output and any condition is reported immediately if enabled. July 14, 2014 167 Texas Instruments-Production Data System Control Register 3: LDO Power Control (LDOPCTL), offset 0x034 The VADJ field in this register adjusts the on-chip output voltage (VOUT). LDO Power Control (LDOPCTL) Base 0x400F.E000 Offset 0x034 Type R/W, reset 0x0000.0000 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 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 VADJ Bit/Field Name Type Reset 31:6 reserved RO 0 5:0 VADJ R/W 0x0 Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. LDO Output Voltage This field sets the on-chip output voltage. The programming values for the VADJ field are provided below. Value VOUT (V) 0x00 2.50 0x01 2.45 0x02 2.40 0x03 2.35 0x04 2.30 0x05 2.25 0x06-0x3F Reserved 0x1B 2.75 0x1C 2.70 0x1D 2.65 0x1E 2.60 0x1F 2.55 168 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 4: Raw Interrupt Status (RIS), offset 0x050 Central location for system control raw interrupts. These are set and cleared by hardware. Raw Interrupt Status (RIS) Base 0x400F.E000 Offset 0x050 Type RO, reset 0x0000.0000 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 PLLLRIS CLRIS IOFRIS MOFRIS LDORIS RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 reserved Type Reset reserved Type Reset RO 0 BORRIS PLLFRIS RO 0 RO 0 Bit/Field Name Type Reset Description 31:7 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 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 is currently active. This is an unregistered signal from the brown-out detection circuit. 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). July 14, 2014 169 Texas Instruments-Production Data System Control Register 5: Interrupt Mask Control (IMC), offset 0x054 Central location for system control interrupt masks. Interrupt Mask Control (IMC) Base 0x400F.E000 Offset 0x054 Type R/W, reset 0x0000.0000 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 PLLLIM CLIM IOFIM MOFIM LDOIM BORIM PLLFIM 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 RO 0 Bit/Field Name Type Reset Description 31:7 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 6 PLLLIM R/W 0 PLL Lock Interrupt Mask This bit specifies whether a PLL Lock interrupt 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. 1 BORIM R/W 0 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. 170 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 6: Masked Interrupt Status and Clear (MISC), offset 0x058 On a read, this register gives the current masked status value of the corresponding interrupt. All of the bits are R/W1C and this action also clears the corresponding raw interrupt bit in the RIS register (see page 169). Masked Interrupt Status and Clear (MISC) Base 0x400F.E000 Offset 0x058 Type R/W1C, reset 0x0000.0000 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 PLLLMIS CLMIS IOFMIS RO 0 RO 0 R/W1C 0 R/W1C 0 R/W1C 0 reserved Type Reset reserved Type Reset RO 0 MOFMIS LDOMIS R/W1C 0 R/W1C 0 BORMIS reserved R/W1C 0 RO 0 Bit/Field Name Type Reset Description 31:7 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 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 BOR 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 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. July 14, 2014 171 Texas Instruments-Production Data System Control Register 7: 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) Base 0x400F.E000 Offset 0x05C Type R/W, reset 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 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 5 LDO R/W - LDO Reset When set, indicates the LDO circuit has lost regulation and has generated a reset event. 4 SW R/W - Software Reset When set, indicates a software reset is the cause of the reset event. 3 WDT R/W - Watchdog Timer Reset When set, indicates a watchdog reset is the cause of the reset event. 2 BOR R/W - Brown-Out Reset When set, indicates a brown-out reset is the cause of the reset event. 1 POR R/W - Power-On Reset When set, indicates a power-on reset is the cause of the reset event. 0 EXT R/W - External Reset When set, indicates an external reset (RST assertion) is the cause of the reset event. 172 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 8: Run-Mode Clock Configuration (RCC), offset 0x060 This register is defined to provide source control and frequency speed. Run-Mode Clock Configuration (RCC) Base 0x400F.E000 Offset 0x060 Type R/W, reset 0x078E.3AC0 31 30 29 28 26 25 RO 0 RO 0 RO 0 RO 0 R/W 0 R/W 1 15 14 13 12 11 10 PWRDN OEN BYPASS PLLVER R/W 1 R/W 1 R/W 1 R/W 0 reserved Type Reset reserved Type Reset RO 0 RO 0 27 24 23 R/W 1 R/W 1 R/W 1 9 8 R/W 1 R/W 0 ACG 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 Bit/Field Name Type Reset 31:28 reserved RO 0x0 27 ACG R/W 0 OSCSRC R/W 0 19 18 17 PWMDIV 16 reserved IOSCVER MOSCVER IOSCDIS MOSCDIS R/W 0 R/W 0 R/W 0 R/W 0 Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. Auto Clock Gating This bit specifies whether the system uses the Sleep-Mode Clock Gating Control (SCGCn) registers and Deep-Sleep-Mode Clock Gating Control (DCGCn) registers 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 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. 26:23 SYSDIV R/W 0xF System Clock Divisor Specifies which divisor is used to generate the system clock from either the PLL output or the oscillator source (depending on how the BYPASS bit in this register is configured). See Table 5-4 on page 159 for bit encodings. The PLL VCO frequency is 200 MHz. If the SYSDIV value is less than MINSYSDIV (see page 184), and the PLL is being used, then the MINSYSDIV value is used as the divisor. If the PLL is not being used, the SYSDIV value can be less than MINSYSDIV. 22 USESYSDIV R/W 0 Enable System Clock Divider 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. If the USERCC2 bit in the RCC2 register is set, then the SYSDIV2 field in the RCC2 register is used as the system clock divider rather than the SYSDIV field in this register. July 14, 2014 173 Texas Instruments-Production Data System Control Bit/Field Name Type Reset Description 21 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 20 USEPWMDIV R/W 0 Enable PWM Clock Divisor Use the PWM clock divider as the source for the PWM clock. 19:17 PWMDIV R/W 0x7 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 0x0 /2 0x1 /4 0x2 /8 0x3 /16 0x4 /32 0x5 /64 0x6 /64 0x7 /64 (default) 16:14 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 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 5-6 on page 176 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. See Table 5-4 on page 159 for programming guidelines. Note: 10 PLLVER R/W 0 The ADC must be clocked from the PLL or directly from a 14-MHz to 18-MHz clock source to operate properly. 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. 174 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Bit/Field Name Type Reset 9:6 XTAL R/W 0xB Description Crystal Value This field specifies the crystal value attached to the main oscillator. The encoding for this field is provided below. Value Crystal Frequency (MHz) Not Using the PLL 5:4 OSCSRC R/W 0x0 Crystal Frequency (MHz) Using the PLL 0x0 1.000 reserved 0x1 1.8432 reserved 0x2 2.000 reserved 0x3 2.4576 reserved 0x4 3.579545 MHz 0x5 3.6864 MHz 0x6 4 MHz 0x7 4.096 MHz 0x8 4.9152 MHz 0x9 5 MHz 0xA 5.12 MHz 0xB 6 MHz (reset value) 0xC 6.144 MHz 0xD 7.3728 MHz 0xE 8 MHz 0xF 8.192 MHz Oscillator Source Selects the input source for the OSC. The values are: Value Input Source 0x0 MOSC Main oscillator (default) 0x1 IOSC Internal oscillator 0x2 IOSC/4 Internal oscillator / 4 (this is necessary if used as input to PLL) 0x3 3 IOSCVER R/W 0 reserved Internal Oscillator Verification Timer 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 Main Oscillator Verification Timer 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. July 14, 2014 175 Texas Instruments-Production Data System Control Bit/Field Name Type Reset 1 IOSCDIS R/W 0 Description Internal Oscillator Disable 0: Internal oscillator (IOSC) is enabled. 1: Internal oscillator is disabled. 0 MOSCDIS R/W 0 Main Oscillator Disable 0: Main oscillator is enabled (default). 1: Main oscillator is disabled . Table 5-6. PLL Mode Control PWRDN OEN Mode 1 X Power down 0 0 Normal 176 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 9: 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 173). The PLL frequency is calculated using the PLLCFG field values, as follows: PLLFreq = OSCFreq * (F + 2) / (R + 2) XTAL to PLL Translation (PLLCFG) Base 0x400F.E000 Offset 0x064 Type RO, reset 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 Bit/Field Name Type Reset 31:16 reserved RO 0x0 15:14 OD RO - R Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. PLL OD Value This field specifies the value supplied to the PLL’s OD input. Value Description 13:5 F RO - 0x0 Divide by 1 0x1 Divide by 2 0x2 Divide by 4 0x3 Reserved PLL F Value This field specifies the value supplied to the PLL’s F input. 4:0 R RO - PLL R Value This field specifies the value supplied to the PLL’s R input. July 14, 2014 177 Texas Instruments-Production Data System Control Register 10: 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) Base 0x400F.E000 Offset 0x144 Type R/W, reset 0x0780.0000 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 8 RO 0 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 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 Bit/Field Name Type Reset 31:1 reserved RO 0x0 0 IOSC R/W 0 RO 0 IOSC R/W 0 Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. IOSC Clock Source When set, forces IOSC to be clock source during Deep-Sleep (overrides DSOSCSRC field if set) 178 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 11: 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) Base 0x400F.E000 Offset 0x150 Type R/W, reset 0x0000.0000 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 8 RO 0 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 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 RO 0 VERCLR R/W 0 Bit/Field Name Type Reset Description 31:1 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 0 VERCLR R/W 0 Clock Verification Clear Clears clock verification faults. July 14, 2014 179 Texas Instruments-Production Data System Control Register 12: 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) Base 0x400F.E000 Offset 0x160 Type R/W, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 reserved Type Reset 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 RO 0 8 7 6 5 4 3 2 1 reserved Type Reset RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 0 LDOARST RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 R/W 0 Bit/Field Name Type Reset Description 31:1 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 0 LDOARST R/W 0 LDO Reset When set, allows unregulated LDO output to reset the part. 180 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 13: Device Identification 1 (DID1), offset 0x004 This register identifies the device family, part number, temperature range, pin count, and package type. Each microcontroller is uniquely identified by the combined values of the CLASS field in the DID0 register and the PARTNO field in the DID1 register. Device Identification 1 (DID1) Base 0x400F.E000 Offset 0x004 Type RO, reset 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 0 RO 0 RO 1 RO 1 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 - RO - RO - VER Type Reset FAM TEMP RO 0 18 17 16 RO 0 RO 0 RO 1 RO 1 3 2 1 0 PARTNO reserved Type Reset 19 Bit/Field Name Type Reset 31:28 VER RO 0x0 RO - PKG ROHS RO - RO 1 QUAL RO - RO - Description DID1 Version This field defines the DID1 register format version. The version number is numeric. The value of the VER field is encoded as follows (all other encodings are reserved): Value Description 0x0 27:24 FAM RO 0x0 Initial DID1 register format definition, indicating a Stellaris LM3Snnn device. Family This field provides the family identification of the device within the Luminary Micro product portfolio. The value is encoded as follows (all other encodings are reserved): Value Description 0x0 23:16 PARTNO RO 0x33 Stellaris family of microcontollers, that is, all devices with external part numbers starting with LM3S. Part Number This field provides the part number of the device within the family. The value is encoded as follows (all other encodings are reserved): Value Description 0x33 LM3S812 15:8 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. July 14, 2014 181 Texas Instruments-Production Data System Control Bit/Field Name Type Reset 7:5 TEMP RO - Description Temperature Range This field specifies the temperature rating of the device. The value is encoded as follows (all other encodings are reserved): Value Description 4:3 PKG RO - 0x0 Commercial temperature range (0°C to 70°C) 0x1 Industrial temperature range (-40°C to 85°C) 0x2 Extended temperature range (-40°C to 105°C) Package Type This field specifies the package type. The value is encoded as follows (all other encodings are reserved): Value Description 2 ROHS RO 1 0x0 28-pin SOIC package 0x1 48-pin LQFP package 0x3 48-pin QFN package RoHS-Compliance This bit specifies whether the device is RoHS-compliant. A 1 indicates the part is RoHS-compliant. 1:0 QUAL RO - Qualification Status This field specifies the qualification status of the device. The value is encoded as follows (all other encodings are reserved): Value Description 0x0 Engineering Sample (unqualified) 0x1 Pilot Production (unqualified) 0x2 Fully Qualified 182 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 14: Device Capabilities 0 (DC0), offset 0x008 This register is predefined by the part and can be used to verify features. Device Capabilities 0 (DC0) Base 0x400F.E000 Offset 0x008 Type RO, reset 0x001F.001F 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 8 RO 0 RO 0 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 1 RO 1 RO 1 RO 1 RO 1 7 6 5 4 3 2 1 0 RO 0 RO 0 RO 1 RO 1 RO 1 RO 1 RO 1 SRAMSZ Type Reset FLASHSZ Type Reset RO 0 Bit/Field Name Type Reset Description 31:16 SRAMSZ RO 0x001F SRAM Size Indicates the size of the on-chip SRAM memory. Value Description 0x001F 8 KB of SRAM 15:0 FLASHSZ RO 0x001F Flash Size Indicates the size of the on-chip flash memory. Value Description 0x001F 64 KB of Flash July 14, 2014 183 Texas Instruments-Production Data System Control Register 15: Device Capabilities 1 (DC1), offset 0x010 This register provides a list of features available in the system. The Stellaris family uses this register format to indicate the availability of the following family features in the specific device: PWM, ADC, Watchdog timer, and debug capabilities. This register also indicates the maximum clock frequency and maximum ADC sample rate. The format of this register is consistent with the RCGC0, SCGC0, and DCGC0 clock control registers and the SRCR0 software reset control register. Device Capabilities 1 (DC1) Base 0x400F.E000 Offset 0x010 Type RO, reset 0x0011.31BF 31 30 29 28 27 RO 0 RO 0 RO 0 RO 0 RO 0 15 14 13 12 11 RO 0 RO 0 RO 1 RO 0 26 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 PLL WDT SWO SWD JTAG RO 1 RO 1 RO 1 RO 1 RO 1 reserved Type Reset MINSYSDIV Type Reset RO 1 reserved RO 0 20 19 PWM MAXADCSPD RO 0 RO 1 MPU RO 1 reserved TEMPSNS RO 0 RO 1 18 17 reserved 16 ADC Bit/Field Name Type Reset Description 31:21 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 20 PWM RO 1 PWM Module Present When set, indicates that the PWM module is present. 19:17 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 16 ADC RO 1 ADC Module Present When set, indicates that the ADC module is present. 15:12 MINSYSDIV RO 0x3 System Clock Divider Minimum 4-bit divider value for system clock. The reset value is hardware-dependent. See the RCC register for how to change the system clock divisor using the SYSDIV bit. Value Description 0x3 11:10 reserved RO 0 9:8 MAXADCSPD RO 0x1 Specifies a 50-MHz CPU clock with a PLL divider of 4. Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. Max ADC Speed Indicates the maximum rate at which the ADC samples data. Value Description 0x1 250K samples/second 184 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Bit/Field Name Type Reset 7 MPU RO 1 Description MPU Present When set, indicates that the Cortex-M3 Memory Protection Unit (MPU) module is present. See the "Cortex-M3 Peripherals" chapter in the Stellaris Data Sheet for details on the MPU. 6 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 5 TEMPSNS RO 1 Temp Sensor Present When set, indicates that the on-chip temperature sensor is present. 4 PLL RO 1 PLL Present When set, indicates that the on-chip Phase Locked Loop (PLL) is present. 3 WDT RO 1 Watchdog Timer Present When set, indicates that a watchdog timer is present. 2 SWO RO 1 SWO Trace Port Present When set, indicates that the Serial Wire Output (SWO) trace port is present. 1 SWD RO 1 SWD Present When set, indicates that the Serial Wire Debugger (SWD) is present. 0 JTAG RO 1 JTAG Present When set, indicates that the JTAG debugger interface is present. July 14, 2014 185 Texas Instruments-Production Data System Control Register 16: Device Capabilities 2 (DC2), offset 0x014 This register provides a list of features available in the system. The Stellaris family uses this register format to indicate the availability of the following family features in the specific device: Analog Comparators, General-Purpose Timers, I2Cs, QEIs, SSIs, and UARTs. The format of this register is consistent with the RCGC1, SCGC1, and DCGC1 clock control registers and the SRCR1 software reset control register. Device Capabilities 2 (DC2) Base 0x400F.E000 Offset 0x014 Type RO, reset 0x0107.1013 31 30 29 RO 0 RO 0 RO 0 15 14 13 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 reserved Type Reset RO 0 RO 0 RO 1 23 22 20 19 RO 1 RO 0 RO 0 RO 0 RO 0 RO 0 8 7 6 5 4 3 RO 0 RO 0 RO 0 COMP0 I2C0 RO 0 24 21 reserved reserved RO 0 SSI0 RO 1 18 17 16 TIMER2 TIMER1 TIMER0 RO 1 RO 1 RO 1 2 1 0 UART1 UART0 RO 1 RO 1 reserved RO 0 RO 0 Bit/Field Name Type Reset Description 31:25 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 24 COMP0 RO 1 Analog Comparator 0 Present When set, indicates that analog comparator 0 is present. 23:19 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 18 TIMER2 RO 1 Timer 2 Present When set, indicates that General-Purpose Timer module 2 is present. 17 TIMER1 RO 1 Timer 1 Present When set, indicates that General-Purpose Timer module 1 is present. 16 TIMER0 RO 1 Timer 0 Present When set, indicates that General-Purpose Timer module 0 is present. 15:13 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 12 I2C0 RO 1 I2C Module 0 Present When set, indicates that I2C module 0 is present. 11:5 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 4 SSI0 RO 1 SSI0 Present When set, indicates that SSI module 0 is present. 186 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Bit/Field Name Type Reset Description 3:2 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 1 UART1 RO 1 UART1 Present When set, indicates that UART module 1 is present. 0 UART0 RO 1 UART0 Present When set, indicates that UART module 0 is present. July 14, 2014 187 Texas Instruments-Production Data System Control Register 17: Device Capabilities 3 (DC3), offset 0x018 This register provides a list of features available in the system. The Stellaris family uses this register format to indicate the availability of the following family features in the specific device: Analog Comparator I/Os, CCP I/Os, ADC I/Os, and PWM I/Os. Device Capabilities 3 (DC3) Base 0x400F.E000 Offset 0x018 Type RO, reset 0xBF03.01C3 Type Reset 31 30 29 28 27 26 25 24 32KHZ reserved CCP5 CCP4 CCP3 CCP2 CCP1 CCP0 RO 1 RO 0 RO 1 RO 1 RO 1 RO 1 RO 1 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 21 RO 1 RO 0 RO 0 RO 0 8 7 6 C0O Bit/Field Name Type Reset 31 32KHZ RO 1 RO 1 20 19 18 RO 0 RO 0 RO 0 5 4 3 2 RO 0 RO 0 RO 0 RO 0 reserved C0PLUS C0MINUS RO 1 RO 1 reserved 17 16 ADC1 ADC0 RO 1 RO 1 1 0 PWM1 PWM0 RO 1 RO 1 Description 32KHz Input Clock Available When set, indicates the 32KHz pin or an even CCP pin is present and can be used as a 32-KHz input clock. 30 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 29 CCP5 RO 1 CCP5 Pin Present When set, indicates that Capture/Compare/PWM pin 5 is present. 28 CCP4 RO 1 CCP4 Pin Present When set, indicates that Capture/Compare/PWM pin 4 is present. 27 CCP3 RO 1 CCP3 Pin Present When set, indicates that Capture/Compare/PWM pin 3 is present. 26 CCP2 RO 1 CCP2 Pin Present When set, indicates that Capture/Compare/PWM pin 2 is present. 25 CCP1 RO 1 CCP1 Pin Present When set, indicates that Capture/Compare/PWM pin 1 is present. 24 CCP0 RO 1 CCP0 Pin Present When set, indicates that Capture/Compare/PWM pin 0 is present. 23:18 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 17 ADC1 RO 1 ADC1 Pin Present When set, indicates that ADC pin 1 is present. 16 ADC0 RO 1 ADC0 Pin Present When set, indicates that ADC pin 0 is present. 188 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Bit/Field Name Type Reset Description 15:9 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 8 C0O RO 1 C0o Pin Present When set, indicates that the analog comparator 0 output pin is present. 7 C0PLUS RO 1 C0+ Pin Present When set, indicates that the analog comparator 0 (+) input pin is present. 6 C0MINUS RO 1 C0- Pin Present When set, indicates that the analog comparator 0 (-) input pin is present. 5:2 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 1 PWM1 RO 1 PWM1 Pin Present When set, indicates that the PWM pin 1 is present. 0 PWM0 RO 1 PWM0 Pin Present When set, indicates that the PWM pin 0 is present. July 14, 2014 189 Texas Instruments-Production Data System Control Register 18: Device Capabilities 4 (DC4), offset 0x01C This register provides a list of features available in the system. The Stellaris family uses this register format to indicate the availability of GPIOs in the specific device. The format of this register is consistent with the RCGC2, SCGC2, and DCGC2 clock control registers and the SRCR2 software reset control register. Device Capabilities 4 (DC4) Base 0x400F.E000 Offset 0x01C Type RO, reset 0x0000.001F 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 GPIOE GPIOD GPIOC GPIOB GPIOA RO 0 RO 0 RO 0 RO 0 RO 1 RO 1 RO 1 RO 1 RO 1 reserved Type Reset reserved Type Reset RO 0 Bit/Field Name Type Reset Description 31:5 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 4 GPIOE RO 1 GPIO Port E Present When set, indicates that GPIO Port E is present. 3 GPIOD RO 1 GPIO Port D Present When set, indicates that GPIO Port D is present. 2 GPIOC RO 1 GPIO Port C Present When set, indicates that GPIO Port C is present. 1 GPIOB RO 1 GPIO Port B Present When set, indicates that GPIO Port B is present. 0 GPIOA RO 1 GPIO Port A Present When set, indicates that GPIO Port A is present. 190 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 19: Run Mode Clock Gating Control Register 0 (RCGC0), offset 0x100 This register controls 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 specifies that the system uses sleep modes. Run Mode Clock Gating Control Register 0 (RCGC0) Base 0x400F.E000 Offset 0x100 Type R/W, reset 0x00000040 31 30 29 28 27 RO 0 RO 0 RO 0 RO 0 RO 0 15 14 13 12 RO 0 RO 0 RO 0 26 25 24 23 22 21 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 R/W 0 RO 0 RO 0 RO 0 R/W 0 11 10 9 8 7 6 5 4 3 2 1 0 RO 0 RO 0 R/W 0 RO 0 RO 0 RO 0 RO 0 reserved Type Reset reserved Type Reset RO 0 20 19 PWM MAXADCSPD R/W 0 reserved 18 17 reserved WDT R/W 0 16 ADC reserved RO 0 RO 0 RO 0 Bit/Field Name Type Reset Description 31:21 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 20 PWM R/W 0 PWM Clock Gating Control 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. If the unit is unclocked, a read or write to the unit generates a bus fault. 19:17 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 16 ADC R/W 0 ADC0 Clock Gating Control This bit controls the clock gating for SAR ADC module 0. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, a read or write to the unit generates a bus fault. 15:10 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. July 14, 2014 191 Texas Instruments-Production Data System Control Bit/Field Name Type Reset 9:8 MAXADCSPD R/W 0 Description ADC Sample Speed This field sets the rate at which the ADC samples data. You cannot set the rate higher than the maximum rate. You can set the sample rate by setting the MAXADCSPD bit as follows: Value Description 0x1 250K samples/second 0x0 125K samples/second 7:4 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 3 WDT R/W 0 WDT Clock Gating Control 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. If the unit is unclocked, a read or write to the unit generates a bus fault. 2:0 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 192 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 20: Sleep Mode Clock Gating Control Register 0 (SCGC0), offset 0x110 This register controls 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 specifies that the system uses sleep modes. Sleep Mode Clock Gating Control Register 0 (SCGC0) Base 0x400F.E000 Offset 0x110 Type R/W, reset 0x00000040 31 30 29 28 27 26 25 24 23 22 21 reserved Type Reset RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 15 14 13 12 11 10 reserved Type Reset RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 R/W 0 9 8 7 6 5 4 MAXADCSPD RO 0 RO 0 20 19 PWM R/W 0 R/W 0 reserved RO 0 RO 0 RO 0 18 RO 0 RO 0 3 2 WDT RO 0 17 reserved R/W 0 16 ADC RO 0 R/W 0 1 0 reserved RO 0 RO 0 RO 0 Bit/Field Name Type Reset Description 31:21 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 20 PWM R/W 0 PWM Clock Gating Control 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. If the unit is unclocked, a read or write to the unit generates a bus fault. 19:17 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 16 ADC R/W 0 ADC0 Clock Gating Control This bit controls the clock gating for SAR ADC module 0. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, a read or write to the unit generates a bus fault. 15:10 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. July 14, 2014 193 Texas Instruments-Production Data System Control Bit/Field Name Type Reset 9:8 MAXADCSPD R/W 0 Description ADC Sample Speed This field sets the rate at which the ADC samples data. You cannot set the rate higher than the maximum rate. You can set the sample rate by setting the MAXADCSPD bit as follows: Value Description 0x1 250K samples/second 0x0 125K samples/second 7:4 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 3 WDT R/W 0 WDT Clock Gating Control 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. If the unit is unclocked, a read or write to the unit generates a bus fault. 2:0 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 194 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 21: Deep Sleep Mode Clock Gating Control Register 0 (DCGC0), offset 0x120 This register controls 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 specifies that the system uses sleep modes. Deep Sleep Mode Clock Gating Control Register 0 (DCGC0) Base 0x400F.E000 Offset 0x120 Type R/W, reset 0x00000040 31 30 29 28 27 26 25 24 23 22 21 reserved Type Reset 20 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 19 PWM 18 RO 0 RO 0 3 2 WDT RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 17 reserved R/W 0 16 ADC RO 0 R/W 0 1 0 reserved RO 0 RO 0 RO 0 Bit/Field Name Type Reset Description 31:21 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 20 PWM R/W 0 PWM Clock Gating Control 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. If the unit is unclocked, a read or write to the unit generates a bus fault. 19:17 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 16 ADC R/W 0 ADC0 Clock Gating Control This bit controls the clock gating for SAR ADC module 0. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, a read or write to the unit generates a bus fault. 15:4 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. July 14, 2014 195 Texas Instruments-Production Data System Control Bit/Field Name Type Reset 3 WDT R/W 0 Description WDT Clock Gating Control 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. If the unit is unclocked, a read or write to the unit generates a bus fault. 2:0 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 196 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 22: Run Mode Clock Gating Control Register 1 (RCGC1), offset 0x104 This register controls 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 specifies that the system uses sleep modes. Run Mode Clock Gating Control Register 1 (RCGC1) Base 0x400F.E000 Offset 0x104 Type R/W, reset 0x00000000 31 30 29 RO 0 RO 0 RO 0 15 14 13 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 reserved Type Reset RO 0 RO 0 R/W 0 23 22 20 19 R/W 0 RO 0 RO 0 RO 0 RO 0 RO 0 8 7 6 5 4 3 RO 0 RO 0 RO 0 COMP0 I2C0 RO 0 24 21 reserved reserved RO 0 SSI0 R/W 0 18 17 16 TIMER2 TIMER1 TIMER0 R/W 0 R/W 0 R/W 0 2 1 0 UART1 UART0 R/W 0 R/W 0 reserved RO 0 RO 0 Bit/Field Name Type Reset Description 31:25 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 24 COMP0 R/W 0 Analog Comparator 0 Clock Gating This bit controls the clock gating for analog comparator 0. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. 23:19 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 18 TIMER2 R/W 0 Timer 2 Clock Gating Control This bit controls the clock gating for General-Purpose Timer module 2. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. 17 TIMER1 R/W 0 Timer 1 Clock Gating Control This bit controls the clock gating for General-Purpose Timer module 1. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. July 14, 2014 197 Texas Instruments-Production Data System Control Bit/Field Name Type Reset 16 TIMER0 R/W 0 Description Timer 0 Clock Gating Control This bit controls the clock gating for General-Purpose Timer module 0. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. 15:13 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 12 I2C0 R/W 0 I2C0 Clock Gating Control This bit controls the clock gating for I2C module 0. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. 11:5 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 4 SSI0 R/W 0 SSI0 Clock Gating Control This bit controls the clock gating for SSI module 0. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. 3:2 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 1 UART1 R/W 0 UART1 Clock Gating Control This bit controls the clock gating for UART module 1. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. 0 UART0 R/W 0 UART0 Clock Gating Control This bit controls the clock gating for UART module 0. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. 198 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 23: Sleep Mode Clock Gating Control Register 1 (SCGC1), offset 0x114 This register controls 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 specifies that the system uses sleep modes. Sleep Mode Clock Gating Control Register 1 (SCGC1) Base 0x400F.E000 Offset 0x114 Type R/W, reset 0x00000000 31 30 29 28 27 26 25 reserved Type Reset RO 0 RO 0 RO 0 14 13 15 reserved Type Reset RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 12 11 10 9 I2C0 RO 0 R/W 0 24 23 22 COMP0 21 R/W 0 RO 0 RO 0 RO 0 8 7 6 5 reserved RO 0 RO 0 RO 0 RO 0 20 19 reserved RO 0 RO 0 17 16 TIMER1 TIMER0 R/W 0 R/W 0 RO 0 RO 0 R/W 0 4 3 2 SSI0 RO 0 18 TIMER2 R/W 0 reserved RO 0 RO 0 1 0 UART1 UART0 R/W 0 R/W 0 Bit/Field Name Type Reset Description 31:25 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 24 COMP0 R/W 0 Analog Comparator 0 Clock Gating This bit controls the clock gating for analog comparator 0. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. 23:19 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 18 TIMER2 R/W 0 Timer 2 Clock Gating Control This bit controls the clock gating for General-Purpose Timer module 2. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. 17 TIMER1 R/W 0 Timer 1 Clock Gating Control This bit controls the clock gating for General-Purpose Timer module 1. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. July 14, 2014 199 Texas Instruments-Production Data System Control Bit/Field Name Type Reset 16 TIMER0 R/W 0 Description Timer 0 Clock Gating Control This bit controls the clock gating for General-Purpose Timer module 0. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. 15:13 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 12 I2C0 R/W 0 I2C0 Clock Gating Control This bit controls the clock gating for I2C module 0. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. 11:5 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 4 SSI0 R/W 0 SSI0 Clock Gating Control This bit controls the clock gating for SSI module 0. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. 3:2 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 1 UART1 R/W 0 UART1 Clock Gating Control This bit controls the clock gating for UART module 1. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. 0 UART0 R/W 0 UART0 Clock Gating Control This bit controls the clock gating for UART module 0. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. 200 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 24: Deep Sleep Mode Clock Gating Control Register 1 (DCGC1), offset 0x124 This register controls 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 specifies that the system uses sleep modes. Deep Sleep Mode Clock Gating Control Register 1 (DCGC1) Base 0x400F.E000 Offset 0x124 Type R/W, reset 0x00000000 31 30 29 28 27 26 25 reserved Type Reset RO 0 RO 0 RO 0 14 13 15 reserved Type Reset RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 12 11 10 9 I2C0 RO 0 R/W 0 24 23 22 COMP0 21 R/W 0 RO 0 RO 0 RO 0 8 7 6 5 reserved RO 0 RO 0 RO 0 RO 0 20 19 reserved RO 0 RO 0 17 16 TIMER1 TIMER0 R/W 0 R/W 0 RO 0 RO 0 R/W 0 4 3 2 SSI0 RO 0 18 TIMER2 R/W 0 reserved RO 0 RO 0 1 0 UART1 UART0 R/W 0 R/W 0 Bit/Field Name Type Reset Description 31:25 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 24 COMP0 R/W 0 Analog Comparator 0 Clock Gating This bit controls the clock gating for analog comparator 0. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. 23:19 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 18 TIMER2 R/W 0 Timer 2 Clock Gating Control This bit controls the clock gating for General-Purpose Timer module 2. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. 17 TIMER1 R/W 0 Timer 1 Clock Gating Control This bit controls the clock gating for General-Purpose Timer module 1. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. July 14, 2014 201 Texas Instruments-Production Data System Control Bit/Field Name Type Reset 16 TIMER0 R/W 0 Description Timer 0 Clock Gating Control This bit controls the clock gating for General-Purpose Timer module 0. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. 15:13 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 12 I2C0 R/W 0 I2C0 Clock Gating Control This bit controls the clock gating for I2C module 0. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. 11:5 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 4 SSI0 R/W 0 SSI0 Clock Gating Control This bit controls the clock gating for SSI module 0. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. 3:2 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 1 UART1 R/W 0 UART1 Clock Gating Control This bit controls the clock gating for UART module 1. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. 0 UART0 R/W 0 UART0 Clock Gating Control This bit controls the clock gating for UART module 0. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. 202 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 25: Run Mode Clock Gating Control Register 2 (RCGC2), offset 0x108 This register controls 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 specifies that the system uses sleep modes. Run Mode Clock Gating Control Register 2 (RCGC2) Base 0x400F.E000 Offset 0x108 Type R/W, reset 0x00000000 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 GPIOE GPIOD GPIOC GPIOB GPIOA 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 RO 0 Bit/Field Name Type Reset Description 31:5 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 4 GPIOE R/W 0 Port E Clock Gating Control This bit controls the clock gating for Port E. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. 3 GPIOD R/W 0 Port D Clock Gating Control This bit controls the clock gating for Port D. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. 2 GPIOC R/W 0 Port C Clock Gating Control This bit controls the clock gating for Port C. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. 1 GPIOB R/W 0 Port B Clock Gating Control This bit controls the clock gating for Port B. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. 0 GPIOA R/W 0 Port A Clock Gating Control This bit controls the clock gating for Port A. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. July 14, 2014 203 Texas Instruments-Production Data System Control Register 26: Sleep Mode Clock Gating Control Register 2 (SCGC2), offset 0x118 This register controls 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 specifies that the system uses sleep modes. Sleep Mode Clock Gating Control Register 2 (SCGC2) Base 0x400F.E000 Offset 0x118 Type R/W, reset 0x00000000 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 reserved Type Reset RO 0 RO 0 RO 0 RO 0 RO 0 15 14 13 12 11 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 10 9 8 7 6 5 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 4 3 2 1 0 GPIOE GPIOD GPIOC GPIOB GPIOA 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 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 4 GPIOE R/W 0 Port E Clock Gating Control This bit controls the clock gating for Port E. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. 3 GPIOD R/W 0 Port D Clock Gating Control This bit controls the clock gating for Port D. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. 2 GPIOC R/W 0 Port C Clock Gating Control This bit controls the clock gating for Port C. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. 1 GPIOB R/W 0 Port B Clock Gating Control This bit controls the clock gating for Port B. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. 204 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Bit/Field Name Type Reset 0 GPIOA R/W 0 Description Port A Clock Gating Control This bit controls the clock gating for Port A. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. July 14, 2014 205 Texas Instruments-Production Data System Control Register 27: Deep Sleep Mode Clock Gating Control Register 2 (DCGC2), offset 0x128 This register controls 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 specifies that the system uses sleep modes. Deep Sleep Mode Clock Gating Control Register 2 (DCGC2) Base 0x400F.E000 Offset 0x128 Type R/W, reset 0x00000000 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 reserved Type Reset RO 0 RO 0 RO 0 RO 0 RO 0 15 14 13 12 11 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 10 9 8 7 6 5 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 4 3 2 1 0 GPIOE GPIOD GPIOC GPIOB GPIOA 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 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 4 GPIOE R/W 0 Port E Clock Gating Control This bit controls the clock gating for Port E. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. 3 GPIOD R/W 0 Port D Clock Gating Control This bit controls the clock gating for Port D. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. 2 GPIOC R/W 0 Port C Clock Gating Control This bit controls the clock gating for Port C. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. 1 GPIOB R/W 0 Port B Clock Gating Control This bit controls the clock gating for Port B. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. 206 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Bit/Field Name Type Reset 0 GPIOA R/W 0 Description Port A Clock Gating Control This bit controls the clock gating for Port A. If set, the unit receives a clock and functions. Otherwise, the unit is unclocked and disabled. If the unit is unclocked, reads or writes to the unit will generate a bus fault. July 14, 2014 207 Texas Instruments-Production Data System Control Register 28: Software Reset Control 0 (SRCR0), offset 0x040 Writes to this register are masked by the bits in the Device Capabilities 1 (DC1) register. Software Reset Control 0 (SRCR0) Base 0x400F.E000 Offset 0x040 Type R/W, reset 0x00000000 31 30 29 28 27 RO 0 RO 0 RO 0 RO 0 RO 0 15 14 13 12 RO 0 RO 0 RO 0 RO 0 26 25 24 23 22 21 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 R/W 0 RO 0 RO 0 RO 0 R/W 0 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 20 PWM reserved Type Reset 19 18 17 reserved WDT R/W 0 16 ADC reserved RO 0 RO 0 RO 0 Bit/Field Name Type Reset Description 31:21 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 20 PWM R/W 0 PWM Reset Control Reset control for PWM module. 19:17 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 16 ADC R/W 0 ADC0 Reset Control Reset control for SAR ADC module 0. 15:4 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 3 WDT R/W 0 WDT Reset Control Reset control for Watchdog unit. 2:0 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 208 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 29: Software Reset Control 1 (SRCR1), offset 0x044 Writes to this register are masked by the bits in the Device Capabilities 2 (DC2) register. Software Reset Control 1 (SRCR1) Base 0x400F.E000 Offset 0x044 Type R/W, reset 0x00000000 31 30 29 RO 0 RO 0 RO 0 15 14 13 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 reserved Type Reset RO 0 RO 0 R/W 0 23 22 20 19 R/W 0 RO 0 RO 0 RO 0 RO 0 RO 0 8 7 6 5 4 3 RO 0 RO 0 RO 0 COMP0 I2C0 RO 0 24 21 reserved reserved RO 0 SSI0 R/W 0 18 17 16 TIMER2 TIMER1 TIMER0 R/W 0 R/W 0 R/W 0 2 1 0 UART1 UART0 R/W 0 R/W 0 reserved RO 0 RO 0 Bit/Field Name Type Reset Description 31:25 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 24 COMP0 R/W 0 Analog Comp 0 Reset Control Reset control for analog comparator 0. 23:19 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 18 TIMER2 R/W 0 Timer 2 Reset Control Reset control for General-Purpose Timer module 2. 17 TIMER1 R/W 0 Timer 1 Reset Control Reset control for General-Purpose Timer module 1. 16 TIMER0 R/W 0 Timer 0 Reset Control Reset control for General-Purpose Timer module 0. 15:13 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 12 I2C0 R/W 0 I2C0 Reset Control Reset control for I2C unit 0. 11:5 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 4 SSI0 R/W 0 SSI0 Reset Control Reset control for SSI unit 0. 3:2 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. July 14, 2014 209 Texas Instruments-Production Data System Control Bit/Field Name Type Reset 1 UART1 R/W 0 Description UART1 Reset Control Reset control for UART unit 1. 0 UART0 R/W 0 UART0 Reset Control Reset control for UART unit 0. 210 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 30: Software Reset Control 2 (SRCR2), offset 0x048 Writes to this register are masked by the bits in the Device Capabilities 4 (DC4) register. Software Reset Control 2 (SRCR2) Base 0x400F.E000 Offset 0x048 Type R/W, reset 0x00000000 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 GPIOE GPIOD GPIOC GPIOB GPIOA 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 RO 0 Bit/Field Name Type Reset Description 31:5 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 4 GPIOE R/W 0 Port E Reset Control Reset control for GPIO Port E. 3 GPIOD R/W 0 Port D Reset Control Reset control for GPIO Port D. 2 GPIOC R/W 0 Port C Reset Control Reset control for GPIO Port C. 1 GPIOB R/W 0 Port B Reset Control Reset control for GPIO Port B. 0 GPIOA R/W 0 Port A Reset Control Reset control for GPIO Port A. July 14, 2014 211 Texas Instruments-Production Data Internal Memory 6 Internal Memory The LM3S812 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. 6.1 Block Diagram Figure 6-1 on page 212 illustrates the Flash functions. The dashed boxes in the figure indicate registers residing in the System Control module rather than the Flash Control module. Figure 6-1. Flash Block Diagram Flash Control Icode Bus Cortex-M3 System Bus Dcode Bus FMA FMD FMC FCRIS FCIM FCMISC Flash Array Flash Protection Bridge FMPRE FMPPE Flash Timing USECRL SRAM Array 6.2 Functional Description This section describes the functionality of the SRAM and Flash memories. 6.2.1 SRAM Memory ® 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 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. 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 0x2000.1000 is to be modified, the bit-band alias is calculated as: 212 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 0x2200.0000 + (0x1000 * 32) + (3 * 4) = 0x2202.000C With the alias address calculated, an instruction performing a read/write to address 0x2202.000C allows direct access to only bit 3 of the byte at address 0x2000.1000. For details about bit-banding, see “Bit-Banding” on page 66. 6.2.2 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. An individual 32-bit word can be programmed to change bits that are currently 1 to a 0. These blocks are paired into a set of 2-KB blocks that can be individually protected. The protection allows blocks to 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. See also “Serial Flash Loader” on page 556 for a preprogrammed flash-resident utility used to download code to the flash memory of a device without the use of a debug interface. 6.2.2.1 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. On reset, the USECRL register is loaded with a value that configures the flash timing so that it works with the maximum clock rate of the part. If software changes the system operating frequency, the new operating frequency minus 1 (in MHz) 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 (20-1) must be written to the USECRL register. 6.2.2.2 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 FMPPEn and FMPREn registers. ■ Flash Memory Protection Program Enable (FMPPEn): If set, the block may be programmed (written) or erased. If cleared, the block may not be changed. ■ Flash Memory Protection Read Enable (FMPREn): If a bit is set, the corresponding block may be executed or read by software or debuggers. If a bit is cleared, the corresponding block may only be executed, and contents of the memory block are prohibited from being read as data. The policies may be combined as shown in Table 6-1 on page 213. Table 6-1. Flash Protection Policy Combinations FMPPEn FMPREn 0 0 Protection Execute-only protection. The block may only be executed and may not be written or erased. This mode is used to protect code. July 14, 2014 213 Texas Instruments-Production Data Internal Memory Table 6-1. Flash Protection Policy Combinations (continued) FMPPEn FMPREn Protection 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. A Flash memory access that attempts to read a read-protected block (FMPREn bit is set) is prohibited and generates a bus fault. A Flash memory access that attempts to program or erase a program-protected block (FMPPEn bit is set) is prohibited and can optionally generate an interrupt (by setting the AMASK bit in the Flash Controller Interrupt Mask (FCIM) register) to alert software developers of poorly behaving software during the development and debug phases. The factory settings for the FMPREn and FMPPEn registers are a value of 1 for all implemented banks. These settings create a policy of open access and programmability. The register bits may be changed by clearing 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. The changes are committed using the Flash Memory Control (FMC) register. 6.2.2.3 Execute-Only Protection Execute-only protection prevents both modification and visibility to a protected flash block. This mode is intended to be used in situations where a device requires debug capability, yet portions of the application space must be protected from external access. An example of this is a company who wishes to sell Stellaris devices with their proprietary software pre-programmed, yet allow the end user to add custom code to an unprotected region of the flash (such as a motor control module with a customizable motor configuration section in flash). Literal data introduces a complication to the protection mechanism. When C code is compiled and linked, literal data (constants, and so on) is typically placed in the text section, between functions, by the compiler. The literal data is accessed at run time through the use of the LDR instruction, which loads the data from memory using a PC-relative memory address. The execution of the LDR instruction generates a read transaction across the Cortex-M3's DCode bus, which is subject to the execute-only protection mechanism. If the accessed block is marked as execute only, the transaction is blocked, and the processor is prevented from loading the constant data and, therefore, inhibiting correct execution. Therefore, using execute-only protection requires that literal data be handled differently. There are three ways to address this: 1. Use a compiler that allows literal data to be collected into a separate section that is put into one or more read-enabled flash blocks. Note that the LDR instruction may use a PC-relative address–-in which case the literal pool cannot be located outside the span of the offset–-or the software may reserve a register to point to the base address of the literal pool and the LDR offset is relative to the beginning of the pool. 2. Use a compiler that generates literal data from arithmetic instruction immediate data and subsequent computation. 3. Use method 1 or 2, but in assembly language, if the compiler does not support either method. 214 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 6.2.2.4 Read-Only Protection Read-only protection prevents the contents of the flash block from being re-programmed, while still allowing the content to be read by processor or the debug interface. Note that if a FMPREn bit is cleared, all read accesses to the Flash memory block are disallowed, including any data accesses. Care must be taken not to store required data in a Flash memory block that has the associated FMPREn bit cleared. The read-only mode does not prevent read access to the stored program, but it does provide protection against accidental (or malicious) erasure or programming. Read-only is especially useful for utilities like the boot loader when the debug interface is permanently disabled. In such combinations, the boot loader, which provides access control to the Flash memory, is protected from being erased or modified. 6.2.2.5 Permanently Disabling Debug For extremely sensitive applications, the debug interface to the processor and peripherals can be permanently disabled, blocking all accesses to the device through the JTAG or SWD interfaces. With the debug interface disabled, it is still possible to perform standard IEEE instructions (such as boundary scan operations), but access to the processor and peripherals is blocked. The two most-significant bits of the FMPRE register are the DBG bits, and control whether or not the debug interface is turned on or off. Since the DBG bits are part of the FMPRE register, the user loses the capability to mark the upper two flash blocks in a 64 KB flash device as execute-only. The debug interface should not be permanently disabled without providing some mechanism–-such as the boot loader–-to provide customer-installable updates or bug fixes. Disabling the debug interface is permanent and cannot be reversed. 6.2.2.6 Interrupts The Flash memory controller can generate interrupts when the following conditions are observed: ■ Programming Interrupt - signals when a program or erase action is complete. ■ Access Interrupt - signals when a program or erase action has been attempted on a 2-kB block of memory that is protected by its corresponding FMPPEn bit. The interrupt events that can trigger a controller-level interrupt are defined in the Flash Controller Masked Interrupt Status (FCMIS) register (see page 224) by setting the corresponding MASK bits. If interrupts are not used, the raw interrupt status is always visible via the Flash Controller Raw Interrupt Status (FCRIS) register (see page 223). Interrupts are always cleared (for both the FCMIS and FCRIS registers) by writing a 1 to the corresponding bit in the Flash Controller Masked Interrupt Status and Clear (FCMISC) register (see page 225). 6.2.2.7 Flash Memory 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. Access is disabled by clearing the DBG field of the FMPRE register. If the DBG field in the Flash Memory Protection Read Enable (FMPRE) register is programmed 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. July 14, 2014 215 Texas Instruments-Production Data Internal Memory 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 has been loaded. This change does 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 the 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). When 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: ■ 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 memory 6.3 Flash Memory Initialization and Configuration This section shows examples for using the flash controller to perform various operations on the contents of the flash memory. 6.3.1 Changing Flash Protection Bits As discussed in “Flash Memory Protection” on page 213, 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 219) 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 221) 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. 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. The Flash Memory Address (FMA) register (see page 219) is written with a value of 0x900. 216 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 3. The Flash Memory Control (FMC) register (see page 221) 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 DriverLib: #include "hw_types.h" #include "hw_flash.h" void permanently_disable_jtag_swd(void) { // // 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) { } } 6.3.2 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. During a Flash memory operation (write, page erase, or mass erase) access to the Flash memory is inhibited. As a result, instruction and literal fetches are held off until the Flash memory operation is complete. If instruction execution is required during a Flash memory operation, the code that is executing must be placed in SRAM and executed from there while the flash operation is in progress. 6.3.2.1 To program a 32-bit word 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 0xA442.0001) to the FMC register. 4. Poll the FMC register until the WRITE bit is cleared. 6.3.2.2 To perform an erase of a 1-KB page 1. Write the page address to the FMA register. July 14, 2014 217 Texas Instruments-Production Data Internal Memory 2. Write the flash write key and the ERASE bit (a value of 0xA442.0002) to the FMC register. 3. Poll the FMC register until the ERASE bit is cleared. 6.3.2.3 To perform a mass erase of the flash 1. Write the flash write key and the MERASE bit (a value of 0xA442.0004) to the FMC register. 2. Poll the FMC register until the MERASE bit is cleared. 6.4 Register Map Table 6-2 on page 218 lists the Flash memory and control registers. The offset listed is a hexadecimal increment to the register's address. The FMA, FMD, FMC, FCRIS, FCIM, and FCMISC register offsets are relative to the Flash memory control base address of 0x400F.D000. The Flash memory protection register offsets are relative to the System Control base address of 0x400F.E000. Table 6-2. Flash Register Map Offset Name Type Reset See page Description Flash Memory Control Registers (Flash Control Offset) 0x000 FMA R/W 0x0000.0000 Flash Memory Address 219 0x004 FMD R/W 0x0000.0000 Flash Memory Data 220 0x008 FMC R/W 0x0000.0000 Flash Memory Control 221 0x00C FCRIS RO 0x0000.0000 Flash Controller Raw Interrupt Status 223 0x010 FCIM R/W 0x0000.0000 Flash Controller Interrupt Mask 224 0x014 FCMISC R/W1C 0x0000.0000 Flash Controller Masked Interrupt Status and Clear 225 Flash Memory Protection Registers (System Control Offset) 0x130 FMPRE R/W 0xBFFF.FFFF Flash Memory Protection Read Enable 228 0x134 FMPPE R/W 0xFFFF.FFFF Flash Memory Protection Program Enable 229 0x140 USECRL R/W 0x31 USec Reload 227 6.5 Flash Register Descriptions (Flash Control Offset) This section lists and describes the Flash Memory registers, in numerical order by address offset. Registers in this section are relative to the Flash control base address of 0x400F.D000. 218 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 1: 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 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) Base 0x400F.D000 Offset 0x000 Type R/W, reset 0x0000.0000 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 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 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 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 R/W 0 reserved Type Reset OFFSET Type Reset Bit/Field Name Type Reset Description 31:16 reserved RO 0x0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 15:0 OFFSET R/W 0x0 Address Offset Address offset in flash where operation is performed. July 14, 2014 219 Texas Instruments-Production Data Internal Memory Register 2: 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) Base 0x400F.D000 Offset 0x004 Type R/W, reset 0x0000.0000 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 Description 31:0 DATA R/W 0x0 Data Value Data value for write operation. 220 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 3: 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 219). If the access is a write access, the data contained in the Flash Memory Data (FMD) register (see page 220) 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) Base 0x400F.D000 Offset 0x008 Type R/W, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 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 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 COMT MERASE ERASE WRITE RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 R/W 0 R/W 0 R/W 0 R/W 0 WRKEY Type Reset reserved Type Reset Bit/Field Name Type Reset 31:16 WRKEY WO 0x0 Description Flash Write Key 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. 15:4 reserved RO 0x0 3 COMT R/W 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. Commit Register Value Commit (write) of register value to nonvolatile storage. A write of 0 has no effect on the state of this bit. 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. July 14, 2014 221 Texas Instruments-Production Data Internal Memory 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. 222 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 4: 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) Base 0x400F.D000 Offset 0x00C Type RO, reset 0x0000.0000 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 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 PRIS ARIS 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 31:2 reserved RO 0x0 1 PRIS RO 0 Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. Programming Raw Interrupt Status This bit provides status on programming cycles which are write or erase actions generated through the FMC register bits (see page 221). Value Description 1 The programming cycle has completed. 0 The programming cycle has not completed. This status is sent to the interrupt controller when the PMASK bit in the FCIM register is set. This bit is cleared by writing a 1 to the PMISC bit in the FCMISC register. 0 ARIS RO 0 Access Raw Interrupt Status Value Description 1 A program or erase action was attempted on a block of Flash memory that contradicts the protection policy for that block as set in the FMPPEn registers. 0 No access has tried to improperly program or erase the Flash memory. This status is sent to the interrupt controller when the AMASK bit in the FCIM register is set. This bit is cleared by writing a 1 to the AMISC bit in the FCMISC register. July 14, 2014 223 Texas Instruments-Production Data Internal Memory Register 5: Flash Controller Interrupt Mask (FCIM), offset 0x010 This register controls whether the flash controller generates interrupts to the controller. Flash Controller Interrupt Mask (FCIM) Base 0x400F.D000 Offset 0x010 Type R/W, reset 0x0000.0000 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 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 PMASK AMASK 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 31:2 reserved RO 0x0 1 PMASK R/W 0 Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. Programming Interrupt Mask This bit controls the reporting of the programming raw interrupt status to the interrupt controller. Value Description 0 AMASK R/W 0 1 An interrupt is sent to the interrupt controller when the PRIS bit is set. 0 The PRIS interrupt is suppressed and not sent to the interrupt controller. Access Interrupt Mask This bit controls the reporting of the access raw interrupt status to the interrupt controller. Value Description 1 An interrupt is sent to the interrupt controller when the ARIS bit is set. 0 The ARIS interrupt is suppressed and not sent to the interrupt controller. 224 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 6: 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 signalling the interrupt. Second, it serves as the method to clear the interrupt reporting. Flash Controller Masked Interrupt Status and Clear (FCMISC) Base 0x400F.D000 Offset 0x014 Type R/W1C, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 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 15 14 13 12 11 10 9 8 7 6 5 4 3 2 reserved Type Reset RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 Bit/Field Name Type Reset 31:2 reserved RO 0x0 1 PMISC R/W1C 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 1 0 PMISC AMISC R/W1C 0 R/W1C 0 Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. Programming Masked Interrupt Status and Clear Value Description 1 When read, a 1 indicates that an unmasked interrupt was signaled because a programming cycle completed. Writing a 1 to this bit clears PMISC and also the PRIS bit in the FCRIS register (see page 223). 0 When read, a 0 indicates that a programming cycle complete interrupt has not occurred. A write of 0 has no effect on the state of this bit. 0 AMISC R/W1C 0 Access Masked Interrupt Status and Clear Value Description 1 When read, a 1 indicates that an unmasked interrupt was signaled because a program or erase action was attempted on a block of Flash memory that contradicts the protection policy for that block as set in the FMPPEn registers. Writing a 1 to this bit clears AMISC and also the ARIS bit in the FCRIS register (see page 223). 0 When read, a 0 indicates that no improper accesses have occurred. A write of 0 has no effect on the state of this bit. July 14, 2014 225 Texas Instruments-Production Data Internal Memory 6.6 Flash Register Descriptions (System Control Offset) The remainder of this section lists and describes the Flash Memory registers, in numerical order by address offset. Registers in this section are relative to the System Control base address of 0x400F.E000. 226 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 7: USec Reload (USECRL), offset 0x140 Note: Offset is relative to System Control base address of 0x400F.E000 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) Base 0x400F.E000 Offset 0x140 Type R/W, reset 0x31 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 R/W 0 R/W 0 R/W 0 R/W 1 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 USEC RO 0 RO 0 RO 0 RO 0 R/W 0 R/W 0 R/W 1 R/W 1 Bit/Field Name Type Reset Description 31:8 reserved RO 0x0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 USEC R/W 0x31 Microsecond Reload Value MHz -1 of the controller clock when the flash is being erased or programmed. If the maximum system frequency is being used, USEC should be set to 0x31 (50 MHz) whenever the flash is being erased or programmed. July 14, 2014 227 Texas Instruments-Production Data Internal Memory Register 8: 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 protection bits for each 2-KB flash block (see the FMPPE registers for the execute-only protection bits). This register is loaded during the power-on reset sequence. The factory settingsare 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 the “Flash Memory Protection” section. Flash Memory Protection Read Enable (FMPRE) Base 0x400F.E000 Offset 0x130 Type R/W, reset 0xBFFF.FFFF 31 30 29 28 27 26 25 24 DBG Type Reset 23 22 21 20 19 18 17 16 READ_ENABLE R/W 1 R/W 0 R/W 1 R/W 1 R/W 1 R/W 1 R/W 1 15 14 13 12 11 10 9 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 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 READ_ENABLE Type Reset R/W 1 R/W 1 R/W 1 R/W 1 R/W 1 R/W 1 R/W 1 Bit/Field Name Type Reset 31:30 DBG R/W 0x2 R/W 1 R/W 1 Description User Controlled Debug Enable Each bit position maps 2 Kbytes of Flash to be read-enabled. Value Description 0x2 29:0 READ_ENABLE R/W Debug access allowed 0x3FFFFFFF Flash Read Enable Each bit position maps 2 Kbytes of Flash to be read-enabled. Value Description 0x3FFFFFFF Enables 64 KB of flash. 228 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 9: 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 protection bits for each 2-KB flash block (see the FMPRE registers for the read-only protection bits). This register is loaded during the power-on reset sequence. The factory settings 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. 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 the “Flash Memory Protection” section. Flash Memory Protection Program Enable (FMPPE) Base 0x400F.E000 Offset 0x134 Type R/W, reset 0xFFFF.FFFF 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 PROG_ENABLE Type Reset 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 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 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 PROG_ENABLE Type Reset R/W 1 R/W 1 R/W 1 R/W 1 R/W 1 R/W 1 Bit/Field Name Type 31:0 PROG_ENABLE R/W R/W 1 Reset R/W 1 R/W 1 Description 0xFFFFFFFF Flash Programming Enable Each bit position maps 2 Kbytes of Flash to be write-enabled. Value Description 0xFFFFFFFF Enables 64 KB of flash. July 14, 2014 229 Texas Instruments-Production Data General-Purpose Input/Outputs (GPIOs) 7 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, Port E). The GPIO module supports 7-34 programmable input/output pins, depending on the peripherals being used. The GPIO module has the following features: ■ 7-34 GPIOs, depending on configuration ■ 5-V-tolerant in input configuration ■ Fast toggle capable of a change every two clock cycles ■ Programmable control for GPIO interrupts – Interrupt generation masking – Edge-triggered on rising, falling, or both – Level-sensitive on High or Low values ■ Bit masking in both read and write operations through address lines ■ Can initiate an ADC sample sequence ■ Pins configured as digital inputs are Schmitt-triggered. ■ Programmable control for GPIO pad configuration – Weak pull-up or pull-down resistors – 2-mA, 4-mA, and 8-mA pad drive for digital communication – Slew rate control for the 8-mA drive – Open drain enables – Digital input enables 230 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 7.1 Block Diagram Figure 7-1. GPIO Module Block Diagram PA1 U0Tx PA3 PA4 SSIClk SSIFss GPIO Port E PA2 UART0 SSI SSIRx PA5 SSITx PB0 CCP0 Timer0 CCP1 PWM0 Fault PB2 PB3 PB4 PB5 GPIO Port B PB1 I2CSCL I2CSDA UART1 I2C CCP3 C0o Timer1 PE2 PE3 U1Rx U1Tx PD2 CCP2 PD1 PD3 PD4 PD5 PD6 C0+ PB6 PE1 PD0 C0Analog Comparator PE0 PWM0 PWM1 GPIO Port D U0Rx GPIO Port A PA0 PD7 Timer 2 CCP5 TRST PB7 CCP4 TDO/SWO TDI TMS/SWDIO TCK/SWCLK JTAG 7.2 PC7 PC6 PC5 PC4 PC3 PC2 PC1 PC0 GPIO Port C Signal Description GPIO signals have alternate hardware functions. Table 7-3 on page 233 lists the GPIO pins and their analog and digital alternate functions. The AINx analog signals are not 5-V tolerant and go through an isolation circuit before reaching their circuitry. These signals are configured by clearing the corresponding DEN bit in the GPIO Digital Enable (GPIODEN) register. Other analog signals are 5-V tolerant and are connected directly to their circuitry (C0-, C0+). These signals are configured by clearing the DEN bit in the GPIO Digital Enable (GPIODEN) register. The digital alternate hardware functions are enabled by setting the appropriate bit in the GPIO Alternate Function Select (GPIOAFSEL) and GPIODEN registers and configuring the PMCx bit field in the GPIO Port Control July 14, 2014 231 Texas Instruments-Production Data General-Purpose Input/Outputs (GPIOs) (GPIOPCTL) register to the numeric enoding shown in the table below. Note that each pin must be programmed individually; no type of grouping is implied by the columns in the table. Important: All GPIO pins are configured as GPIOs and tri-stated by default (GPIOAFSEL=0, GPIODEN=0, GPIOPDR=0, GPIOPUR=0, and GPIOPCTL=0, with the exception of the four JTAG/SWD pins (shown in the table below). A Power-On-Reset (POR) or asserting RST puts the pins back to their default state. Table 7-1. GPIO Pins With Non-Zero Reset Values GPIO Pins Default State PA[1:0] UART0 GPIOAFSEL GPIODEN GPIOPDR GPIOPUR 1 1 0 GPIOPCTL 0 0x1 PA[5:2] SSI0 1 1 0 0 0x1 PB[3:2] I2C0 1 1 0 0 0x1 PC[3:0] JTAG/SWD 1 1 0 1 0x3 Table 7-2. GPIO Pins and Alternate Functions (48QFP) IO Pin Number Multiplexed Function PA0 17 U0Rx PA1 18 U0Tx PA2 19 SSIClk PA3 20 SSIFss PA4 21 SSIRx Multiplexed Function PA5 22 SSITx PB0 29 CCP0 PB1 30 PB2 33 I2CSCL PB3 34 I2CSDA PB4 44 C0- PB5 43 CCP5 PB6 42 C0+ PB7 41 TRST PC0 40 TCK SWCLK PC1 39 TMS SWDIO PC2 38 TDI PC3 37 TDO PC4 14 PC5 13 PC6 12 CCP3 PC7 11 CCP4 PD0 25 PWM0 PD1 26 PWM1 PD2 27 U1Rx PD3 28 U1Tx PD4 45 232 SWO July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Table 7-2. GPIO Pins and Alternate Functions (48QFP) (continued) IO Pin Number Multiplexed Function PD5 46 CCP2 PD6 47 Fault PD7 48 C0o PE0 35 PE1 36 PE2 4 PE3 3 Multiplexed Function CCP1 Table 7-3. GPIO Signals (48QFP) a Pin Name Pin Number Pin Type Buffer Type Description PA0 17 I/O TTL GPIO port A bit 0. PA1 18 I/O TTL GPIO port A bit 1. 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. PD6 47 I/O TTL GPIO port D bit 6. PD7 48 I/O TTL GPIO port D bit 7. PE0 35 I/O TTL GPIO port E bit 0. July 14, 2014 233 Texas Instruments-Production Data General-Purpose Input/Outputs (GPIOs) Table 7-3. GPIO Signals (48QFP) (continued) a Pin Name Pin Number Pin Type Buffer Type Description PE1 36 I/O TTL GPIO port E bit 1. PE2 4 I/O TTL GPIO port E bit 2. PE3 3 I/O TTL GPIO port E bit 3. a. The TTL designation indicates the pin has TTL-compatible voltage levels. 7.3 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). A Power-On-Reset (POR) or asserting an external reset (RST) puts both groups of pins back to their default state. While debugging systems where PB7 is being used as a GPIO, care must be taken to ensure that a Low value is not applied to the pin when the part is reset. Because PB7 reverts to the TRST function after reset, a Low value on the pin causes the JTAG controller to be reset, resulting in a loss of JTAG communication. Each GPIO port is a separate hardware instantiation of the same physical block (see Figure 7-2 on page 235). The LM3S812 microcontroller contains five ports and thus five of these physical GPIO blocks. 234 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Figure 7-2. GPIO Port Block Diagram Mode Control GPIOAFSEL DEMUX Alternate Input Alternate Output Pad Input Alternate Output Enable Pad Output MUX Pad Output Enable Digital I/O Pad Package I/O Pin GPIO Output GPIODATA GPIODIR Interrupt MUX GPIO Input Data Control GPIO Output Enable Interrupt Control Pad Control GPIOIS GPIOIBE GPIOIEV GPIOIM GPIORIS GPIOMIS GPIOICR GPIODR2R GPIODR4R GPIODR8R GPIOSLR GPIOPUR GPIOPDR GPIOODR GPIODEN Identification Registers GPIOPeriphID0 GPIOPeriphID1 GPIOPeriphID2 GPIOPeriphID3 7.3.1 GPIOPeriphID4 GPIOPeriphID5 GPIOPeriphID6 GPIOPeriphID7 GPIOPCellID0 GPIOPCellID1 GPIOPCellID2 GPIOPCellID3 Data Control The data control registers allow software to configure the operational modes of the GPIOs. The data direction register configures the GPIO as an input or an output while the data register either captures incoming data or drives it out to the pads. 7.3.1.1 Data Direction Operation The GPIO Direction (GPIODIR) register (see page 242) is used to configure each individual pin as an input or output. When the data direction bit is set to 0, the GPIO is configured as an input and the corresponding data register bit will capture and store the value on the GPIO port. When the data direction bit is set to 1, the GPIO is configured as an output and the corresponding data register bit will be driven out on the GPIO port. 7.3.1.2 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 241) 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. July 14, 2014 235 Texas Instruments-Production Data General-Purpose Input/Outputs (GPIOs) 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 7-3 on page 236, where u is data unchanged by the write. Figure 7-3. GPIODATA Write Example ADDR[9:2] 0x098 9 8 7 6 5 4 3 2 1 0 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 7-4 on page 236. Figure 7-4. GPIODATA Read Example 7.3.2 ADDR[9:2] 0x0C4 9 8 7 6 5 4 3 2 1 0 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 Interrupt Control 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 243) ■ GPIO Interrupt Both Edges (GPIOIBE) register (see page 244) ■ GPIO Interrupt Event (GPIOIEV) register (see page 245) Interrupts are enabled/disabled via the GPIO Interrupt Mask (GPIOIM) register (see page 246). 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 page 247 and page 248). As the name implies, the GPIOMIS register only shows interrupt 236 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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. 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 (the appropriate bit of 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 Interrupt 0-31 Set Enable (EN0) 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 PB4, and wait for the ADC interrupt or the ADC interrupt must be disabled in the EN0 register and the PortB interrupt handler must poll the ADC registers until the conversion is completed. See page 99 for more information. Interrupts are cleared by writing a 1 to the appropriate bit of the GPIO Interrupt Clear (GPIOICR) register (see page 249). When programming the following interrupt control registers, 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. 7.3.3 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 250), 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. 7.3.4 Pad Control The pad control registers allow for GPIO pad configuration by software based on the application requirements. The pad control registers include the GPIODR2R, GPIODR4R, GPIODR8R, GPIOODR, GPIOPUR, GPIOPDR, GPIOSLR, and GPIODEN registers. These registers control drive strength, open-drain configuration, pull-up and pull-down resistors, slew-rate control and digital enable. 7.3.5 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. 7.4 Initialization and Configuration To use the GPIO, the peripheral clock must be enabled by setting the appropriate GPIO Port bit field (GPIOn) in the RCGC2 register. On reset, all GPIO pins (except for the five JTAG pins) default to general-purpose input mode (GPIODIR=0 and GPIOAFSEL=0). Table 7-4 on page 238 shows all possible configurations of the GPIO pads and the control register settings required to achieve them. Table 7-5 on page 238 shows how a rising edge interrupt would be configured for pin 2 of a GPIO port. July 14, 2014 237 Texas Instruments-Production Data General-Purpose Input/Outputs (GPIOs) Table 7-4. GPIO Pad Configuration Examples a GPIO Register Bit Value Configuration AFSEL Digital Input (GPIO) DIR 0 ODR 0 DEN 0 PUR 1 PDR ? ? DR2R DR4R DR8R X X X SLR X Digital Output (GPIO) 0 1 0 1 ? ? ? ? ? ? Open Drain Output (GPIO) 0 1 1 1 X X ? ? ? ? Open Drain Input/Output (I2C) 1 X 1 1 X X ? ? ? ? Digital Input (Timer CCP) 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 ? ? ? ? ? ? a. X=Ignored (don’t care bit) ?=Can be either 0 or 1, depending on the configuration Table 7-5. GPIO Interrupt Configuration Example Register GPIOIS Desired Interrupt Event Trigger a Pin 2 Bit Value 7 0=edge 6 5 4 3 2 1 0 X X X X X 0 X X X X X X X 0 X X X X X X X 1 X X 0 0 0 0 0 1 0 0 1=level GPIOIBE 0=single edge 1=both edges GPIOIEV 0=Low level, or negative edge 1=High level, or positive edge GPIOIM 0=masked 1=not masked a. X=Ignored (don’t care bit) 7.5 Register Map Table 7-6 on page 239 lists the GPIO registers. The offset listed is a hexadecimal increment to the register’s address, relative to that GPIO port’s base address: 238 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller ■ ■ ■ ■ ■ GPIO Port A: 0x4000.4000 GPIO Port B: 0x4000.5000 GPIO Port C: 0x4000.6000 GPIO Port D: 0x4000.7000 GPIO Port E: 0x4002.4000 Note that the GPIO module clock must be enabled before the registers can be programmed (see page 203). There must be a delay of 3 system clocks after the GPIO module clock is enabled before any GPIO module registers are accessed. 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. In those cases, writing to those unconnected bits has no effect, and reading those unconnected bits returns no meaningful data. Note: The default reset value for the GPIOAFSEL register is 0x0000.0000 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 0x0000.0080 while the default reset value for Port C is 0x0000.000F. Table 7-6. GPIO Register Map Description See page Offset Name Type Reset 0x000 GPIODATA R/W 0x0000.0000 GPIO Data 241 0x400 GPIODIR R/W 0x0000.0000 GPIO Direction 242 0x404 GPIOIS R/W 0x0000.0000 GPIO Interrupt Sense 243 0x408 GPIOIBE R/W 0x0000.0000 GPIO Interrupt Both Edges 244 0x40C GPIOIEV R/W 0x0000.0000 GPIO Interrupt Event 245 0x410 GPIOIM R/W 0x0000.0000 GPIO Interrupt Mask 246 0x414 GPIORIS RO 0x0000.0000 GPIO Raw Interrupt Status 247 0x418 GPIOMIS RO 0x0000.0000 GPIO Masked Interrupt Status 248 0x41C GPIOICR W1C 0x0000.0000 GPIO Interrupt Clear 249 0x420 GPIOAFSEL R/W - GPIO Alternate Function Select 250 0x500 GPIODR2R R/W 0x0000.00FF GPIO 2-mA Drive Select 252 0x504 GPIODR4R R/W 0x0000.0000 GPIO 4-mA Drive Select 253 0x508 GPIODR8R R/W 0x0000.0000 GPIO 8-mA Drive Select 254 0x50C GPIOODR R/W 0x0000.0000 GPIO Open Drain Select 255 0x510 GPIOPUR R/W 0x0000.00FF GPIO Pull-Up Select 256 0x514 GPIOPDR R/W 0x0000.0000 GPIO Pull-Down Select 257 0x518 GPIOSLR R/W 0x0000.0000 GPIO Slew Rate Control Select 258 0x51C GPIODEN R/W 0x0000.00FF GPIO Digital Enable 259 0xFD0 GPIOPeriphID4 RO 0x0000.0000 GPIO Peripheral Identification 4 260 July 14, 2014 239 Texas Instruments-Production Data General-Purpose Input/Outputs (GPIOs) Table 7-6. GPIO Register Map (continued) Offset Name 0xFD4 Reset GPIOPeriphID5 RO 0x0000.0000 GPIO Peripheral Identification 5 261 0xFD8 GPIOPeriphID6 RO 0x0000.0000 GPIO Peripheral Identification 6 262 0xFDC GPIOPeriphID7 RO 0x0000.0000 GPIO Peripheral Identification 7 263 0xFE0 GPIOPeriphID0 RO 0x0000.0061 GPIO Peripheral Identification 0 264 0xFE4 GPIOPeriphID1 RO 0x0000.0000 GPIO Peripheral Identification 1 265 0xFE8 GPIOPeriphID2 RO 0x0000.0018 GPIO Peripheral Identification 2 266 0xFEC GPIOPeriphID3 RO 0x0000.0001 GPIO Peripheral Identification 3 267 0xFF0 GPIOPCellID0 RO 0x0000.000D GPIO PrimeCell Identification 0 268 0xFF4 GPIOPCellID1 RO 0x0000.00F0 GPIO PrimeCell Identification 1 269 0xFF8 GPIOPCellID2 RO 0x0000.0005 GPIO PrimeCell Identification 2 270 0xFFC GPIOPCellID3 RO 0x0000.00B1 GPIO PrimeCell Identification 3 271 7.6 Description See page Type Register Descriptions The remainder of this section lists and describes the GPIO registers, in numerical order by address offset. 240 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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 242). 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) GPIO Port A base: 0x4000.4000 GPIO Port B base: 0x4000.5000 GPIO Port C base: 0x4000.6000 GPIO Port D base: 0x4000.7000 GPIO Port E base: 0x4002.4000 Offset 0x000 Type R/W, reset 0x0000.0000 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 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 reserved Type Reset reserved Type Reset DATA RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 DATA R/W 0x00 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 235 for examples of reads and writes. July 14, 2014 241 Texas Instruments-Production Data 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) GPIO Port A base: 0x4000.4000 GPIO Port B base: 0x4000.5000 GPIO Port C base: 0x4000.6000 GPIO Port D base: 0x4000.7000 GPIO Port E base: 0x4002.4000 Offset 0x400 Type R/W, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 R/W 0 R/W 0 R/W 0 R/W 0 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 DIR RO 0 RO 0 RO 0 RO 0 R/W 0 R/W 0 R/W 0 R/W 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 DIR R/W 0x00 GPIO Data Direction The DIR values are defined as follows: Value Description 0 Pins are inputs. 1 Pins are outputs. 242 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) GPIO Port A base: 0x4000.4000 GPIO Port B base: 0x4000.5000 GPIO Port C base: 0x4000.6000 GPIO Port D base: 0x4000.7000 GPIO Port E base: 0x4002.4000 Offset 0x404 Type R/W, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 R/W 0 R/W 0 R/W 0 R/W 0 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 IS RO 0 RO 0 RO 0 RO 0 R/W 0 R/W 0 R/W 0 R/W 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 IS R/W 0x00 GPIO Interrupt Sense The IS values are defined as follows: Value Description 0 Edge on corresponding pin is detected (edge-sensitive). 1 Level on corresponding pin is detected (level-sensitive). July 14, 2014 243 Texas Instruments-Production Data 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 243) 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 245). Clearing a bit configures the pin to be controlled by GPIOIEV. All bits are cleared by a reset. GPIO Interrupt Both Edges (GPIOIBE) GPIO Port A base: 0x4000.4000 GPIO Port B base: 0x4000.5000 GPIO Port C base: 0x4000.6000 GPIO Port D base: 0x4000.7000 GPIO Port E base: 0x4002.4000 Offset 0x408 Type R/W, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 R/W 0 R/W 0 R/W 0 R/W 0 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 IBE RO 0 RO 0 RO 0 RO 0 R/W 0 R/W 0 R/W 0 R/W 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 IBE R/W 0x00 GPIO Interrupt Both Edges The IBE values are defined as follows: Value Description 0 Interrupt generation is controlled by the GPIO Interrupt Event (GPIOIEV) register (see page 245). 1 Both edges on the corresponding pin trigger an interrupt. Note: Single edge is determined by the corresponding bit in GPIOIEV. 244 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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 243). 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) GPIO Port A base: 0x4000.4000 GPIO Port B base: 0x4000.5000 GPIO Port C base: 0x4000.6000 GPIO Port D base: 0x4000.7000 GPIO Port E base: 0x4002.4000 Offset 0x40C Type R/W, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 R/W 0 R/W 0 R/W 0 R/W 0 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 IEV RO 0 RO 0 RO 0 RO 0 R/W 0 R/W 0 R/W 0 R/W 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 IEV R/W 0x00 GPIO Interrupt Event The IEV values are defined as follows: Value Description 0 Falling edge or Low levels on corresponding pins trigger interrupts. 1 Rising edge or High levels on corresponding pins trigger interrupts. July 14, 2014 245 Texas Instruments-Production Data 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) GPIO Port A base: 0x4000.4000 GPIO Port B base: 0x4000.5000 GPIO Port C base: 0x4000.6000 GPIO Port D base: 0x4000.7000 GPIO Port E base: 0x4002.4000 Offset 0x410 Type R/W, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 R/W 0 R/W 0 R/W 0 R/W 0 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 IME RO 0 RO 0 RO 0 RO 0 R/W 0 R/W 0 R/W 0 R/W 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 IME R/W 0x00 GPIO Interrupt Mask Enable The IME values are defined as follows: Value Description 0 Corresponding pin interrupt is masked. 1 Corresponding pin interrupt is not masked. 246 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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 246). 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) GPIO Port A base: 0x4000.4000 GPIO Port B base: 0x4000.5000 GPIO Port C base: 0x4000.6000 GPIO Port D base: 0x4000.7000 GPIO Port E base: 0x4002.4000 Offset 0x414 Type RO, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 RO 0 RO 0 RO 0 RO 0 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 RIS RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 RIS RO 0x00 GPIO Interrupt Raw Status Reflects the status of interrupt trigger condition detection on pins (raw, prior to masking). The RIS values are defined as follows: Value Description 0 Corresponding pin interrupt requirements not met. 1 Corresponding pin interrupt has met requirements. July 14, 2014 247 Texas Instruments-Production Data 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 (the appropriate bit of 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 Interrupt 0-31 Set Enable (EN0) 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 PB4, and wait for the ADC interrupt or the ADC interrupt must be disabled in the EN0 register and the PortB interrupt handler must poll the ADC registers until the conversion is completed. See page 99 for more information. GPIOMIS is the state of the interrupt after masking. GPIO Masked Interrupt Status (GPIOMIS) GPIO Port A base: 0x4000.4000 GPIO Port B base: 0x4000.5000 GPIO Port C base: 0x4000.6000 GPIO Port D base: 0x4000.7000 GPIO Port E base: 0x4002.4000 Offset 0x418 Type RO, reset 0x0000.0000 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 RO 0 RO 0 RO 0 RO 0 RO 0 reserved Type Reset reserved Type Reset MIS RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 MIS RO 0x00 GPIO Masked Interrupt Status Masked value of interrupt due to corresponding pin. The MIS values are defined as follows: Value Description 0 Corresponding GPIO line interrupt not active. 1 Corresponding GPIO line asserting interrupt. 248 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) GPIO Port A base: 0x4000.4000 GPIO Port B base: 0x4000.5000 GPIO Port C base: 0x4000.6000 GPIO Port D base: 0x4000.7000 GPIO Port E base: 0x4002.4000 Offset 0x41C Type W1C, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 W1C 0 W1C 0 W1C 0 W1C 0 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 IC RO 0 RO 0 RO 0 RO 0 W1C 0 W1C 0 W1C 0 W1C 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 IC W1C 0x00 GPIO Interrupt Clear The IC values are defined as follows: Value Description 0 Corresponding interrupt is unaffected. 1 Corresponding interrupt is cleared. July 14, 2014 249 Texas Instruments-Production Data 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. 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). A Power-On-Reset (POR) or asserting an external reset (RST) puts both groups of pins back to their default state. While debugging systems where PB7 is being used as a GPIO, care must be taken to ensure that a Low value is not applied to the pin when the part is reset. Because PB7 reverts to the TRST function after reset, a Low value on the pin causes the JTAG controller to be reset, resulting in a loss of JTAG communication. 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. 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) GPIO Port A base: 0x4000.4000 GPIO Port B base: 0x4000.5000 GPIO Port C base: 0x4000.6000 GPIO Port D base: 0x4000.7000 GPIO Port E base: 0x4002.4000 Offset 0x420 Type R/W, reset 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 R/W - R/W - R/W - R/W - 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 AFSEL RO 0 RO 0 RO 0 RO 0 R/W - R/W - R/W - R/W - Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 250 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Bit/Field Name Type Reset 7:0 AFSEL R/W - Description GPIO Alternate Function Select The AFSEL values are defined as follows: Value Description 0 Software control of corresponding GPIO line (GPIO mode). 1 Hardware control of corresponding GPIO line (alternate hardware function). Note: The default reset value for the GPIOAFSEL register is 0x0000.0000 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 0x0000.0080 while the default reset value for Port C is 0x0000.000F. July 14, 2014 251 Texas Instruments-Production Data General-Purpose Input/Outputs (GPIOs) 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) GPIO Port A base: 0x4000.4000 GPIO Port B base: 0x4000.5000 GPIO Port C base: 0x4000.6000 GPIO Port D base: 0x4000.7000 GPIO Port E base: 0x4002.4000 Offset 0x500 Type R/W, reset 0x0000.00FF 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 R/W 1 R/W 1 R/W 1 R/W 1 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 DRV2 RO 0 RO 0 RO 0 RO 0 R/W 1 R/W 1 R/W 1 R/W 1 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 DRV2 R/W 0xFF 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. 252 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) GPIO Port A base: 0x4000.4000 GPIO Port B base: 0x4000.5000 GPIO Port C base: 0x4000.6000 GPIO Port D base: 0x4000.7000 GPIO Port E base: 0x4002.4000 Offset 0x504 Type R/W, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 R/W 0 R/W 0 R/W 0 R/W 0 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 DRV4 RO 0 RO 0 RO 0 RO 0 R/W 0 R/W 0 R/W 0 R/W 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 DRV4 R/W 0x00 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. July 14, 2014 253 Texas Instruments-Production Data General-Purpose Input/Outputs (GPIOs) 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) GPIO Port A base: 0x4000.4000 GPIO Port B base: 0x4000.5000 GPIO Port C base: 0x4000.6000 GPIO Port D base: 0x4000.7000 GPIO Port E base: 0x4002.4000 Offset 0x508 Type R/W, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 R/W 0 R/W 0 R/W 0 R/W 0 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 DRV8 RO 0 RO 0 RO 0 RO 0 R/W 0 R/W 0 R/W 0 R/W 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 DRV8 R/W 0x00 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. 254 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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 Enable (GPIODEN) register (see page 259). 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 cleared. If open drain is selected while the GPIO is configured as an input, the GPIO will remain an input and the open-drain selection has no effect until the GPIO is changed to an output. When using the I2C module, in addition to configuring the pin to open drain, the GPIO Alternate Function Select (GPIOAFSEL) register bits for the I2C clock and data pins should be set to 1 (see examples in “Initialization and Configuration” on page 237). GPIO Open Drain Select (GPIOODR) GPIO Port A base: 0x4000.4000 GPIO Port B base: 0x4000.5000 GPIO Port C base: 0x4000.6000 GPIO Port D base: 0x4000.7000 GPIO Port E base: 0x4002.4000 Offset 0x50C Type R/W, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 R/W 0 R/W 0 R/W 0 R/W 0 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 ODE RO 0 RO 0 RO 0 RO 0 R/W 0 R/W 0 R/W 0 R/W 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 ODE R/W 0x00 Output Pad Open Drain Enable The ODE values are defined as follows: Value Description 0 Open drain configuration is disabled. 1 Open drain configuration is enabled. July 14, 2014 255 Texas Instruments-Production Data General-Purpose Input/Outputs (GPIOs) 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 257). GPIO Pull-Up Select (GPIOPUR) GPIO Port A base: 0x4000.4000 GPIO Port B base: 0x4000.5000 GPIO Port C base: 0x4000.6000 GPIO Port D base: 0x4000.7000 GPIO Port E base: 0x4002.4000 Offset 0x510 Type R/W, reset 0x0000.00FF 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 R/W 1 R/W 1 R/W 1 R/W 1 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 PUE RO 0 RO 0 RO 0 RO 0 R/W 1 R/W 1 R/W 1 R/W 1 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 PUE R/W 0xFF Pad Weak Pull-Up Enable Value Description 0 The corresponding pin's weak pull-up resistor is disabled. 1 The corresponding pin's weak pull-up resistor is enabled. 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. 256 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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 256). GPIO Pull-Down Select (GPIOPDR) GPIO Port A base: 0x4000.4000 GPIO Port B base: 0x4000.5000 GPIO Port C base: 0x4000.6000 GPIO Port D base: 0x4000.7000 GPIO Port E base: 0x4002.4000 Offset 0x514 Type R/W, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 R/W 0 R/W 0 R/W 0 R/W 0 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 PDE RO 0 RO 0 RO 0 RO 0 R/W 0 R/W 0 R/W 0 R/W 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 PDE R/W 0x00 Pad Weak Pull-Down Enable Value Description 0 The corresponding pin's weak pull-down resistor is disabled. 1 The corresponding pin's weak pull-down resistor is enabled. 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. July 14, 2014 257 Texas Instruments-Production Data General-Purpose Input/Outputs (GPIOs) 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 254). GPIO Slew Rate Control Select (GPIOSLR) GPIO Port A base: 0x4000.4000 GPIO Port B base: 0x4000.5000 GPIO Port C base: 0x4000.6000 GPIO Port D base: 0x4000.7000 GPIO Port E base: 0x4002.4000 Offset 0x518 Type R/W, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 R/W 0 R/W 0 R/W 0 R/W 0 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 SRL RO 0 RO 0 RO 0 RO 0 R/W 0 R/W 0 R/W 0 R/W 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 SRL R/W 0x00 Slew Rate Limit Enable (8-mA drive only) The SRL values are defined as follows: Value Description 0 Slew rate control disabled. 1 Slew rate control enabled. 258 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 18: GPIO Digital Enable (GPIODEN), offset 0x51C Note: Pins configured as digital inputs are Schmitt-triggered. The GPIODEN register is the digital enable register. By default, all GPIO signals are configured as digital inputs at reset. If a pin is being used as a GPIO or its Alternate Hardware Function, it should be configured as a digital input. 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 comparators. GPIO Digital Enable (GPIODEN) GPIO Port A base: 0x4000.4000 GPIO Port B base: 0x4000.5000 GPIO Port C base: 0x4000.6000 GPIO Port D base: 0x4000.7000 GPIO Port E base: 0x4002.4000 Offset 0x51C Type R/W, reset 0x0000.00FF 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 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 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 DEN R/W 0xFF Digital Enable The DEN values are defined as follows: Value Description 0 Digital functions disabled. 1 Digital functions enabled. July 14, 2014 259 Texas Instruments-Production Data General-Purpose Input/Outputs (GPIOs) 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) GPIO Port A base: 0x4000.4000 GPIO Port B base: 0x4000.5000 GPIO Port C base: 0x4000.6000 GPIO Port D base: 0x4000.7000 GPIO Port E base: 0x4002.4000 Offset 0xFD0 Type RO, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 RO 0 RO 0 RO 0 RO 0 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 PID4 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 PID4 RO 0x00 GPIO Peripheral ID Register[7:0] 260 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) GPIO Port A base: 0x4000.4000 GPIO Port B base: 0x4000.5000 GPIO Port C base: 0x4000.6000 GPIO Port D base: 0x4000.7000 GPIO Port E base: 0x4002.4000 Offset 0xFD4 Type RO, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 RO 0 RO 0 RO 0 RO 0 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 PID5 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 PID5 RO 0x00 GPIO Peripheral ID Register[15:8] July 14, 2014 261 Texas Instruments-Production Data General-Purpose Input/Outputs (GPIOs) 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) GPIO Port A base: 0x4000.4000 GPIO Port B base: 0x4000.5000 GPIO Port C base: 0x4000.6000 GPIO Port D base: 0x4000.7000 GPIO Port E base: 0x4002.4000 Offset 0xFD8 Type RO, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 RO 0 RO 0 RO 0 RO 0 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 PID6 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 PID6 RO 0x00 GPIO Peripheral ID Register[23:16] 262 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) GPIO Port A base: 0x4000.4000 GPIO Port B base: 0x4000.5000 GPIO Port C base: 0x4000.6000 GPIO Port D base: 0x4000.7000 GPIO Port E base: 0x4002.4000 Offset 0xFDC Type RO, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 RO 0 RO 0 RO 0 RO 0 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 PID7 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 PID7 RO 0x00 GPIO Peripheral ID Register[31:24] July 14, 2014 263 Texas Instruments-Production Data General-Purpose Input/Outputs (GPIOs) 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) GPIO Port A base: 0x4000.4000 GPIO Port B base: 0x4000.5000 GPIO Port C base: 0x4000.6000 GPIO Port D base: 0x4000.7000 GPIO Port E base: 0x4002.4000 Offset 0xFE0 Type RO, reset 0x0000.0061 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 RO 0 RO 0 RO 0 RO 1 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 PID0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 1 RO 1 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 PID0 RO 0x61 GPIO Peripheral ID Register[7:0] Can be used by software to identify the presence of this peripheral. 264 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) GPIO Port A base: 0x4000.4000 GPIO Port B base: 0x4000.5000 GPIO Port C base: 0x4000.6000 GPIO Port D base: 0x4000.7000 GPIO Port E base: 0x4002.4000 Offset 0xFE4 Type RO, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 RO 0 RO 0 RO 0 RO 0 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 PID1 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 PID1 RO 0x00 GPIO Peripheral ID Register[15:8] Can be used by software to identify the presence of this peripheral. July 14, 2014 265 Texas Instruments-Production Data General-Purpose Input/Outputs (GPIOs) 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) GPIO Port A base: 0x4000.4000 GPIO Port B base: 0x4000.5000 GPIO Port C base: 0x4000.6000 GPIO Port D base: 0x4000.7000 GPIO Port E base: 0x4002.4000 Offset 0xFE8 Type RO, reset 0x0000.0018 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 RO 1 RO 0 RO 0 RO 0 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 PID2 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 1 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 PID2 RO 0x18 GPIO Peripheral ID Register[23:16] Can be used by software to identify the presence of this peripheral. 266 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) GPIO Port A base: 0x4000.4000 GPIO Port B base: 0x4000.5000 GPIO Port C base: 0x4000.6000 GPIO Port D base: 0x4000.7000 GPIO Port E base: 0x4002.4000 Offset 0xFEC Type RO, reset 0x0000.0001 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 RO 0 RO 0 RO 0 RO 1 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 PID3 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 PID3 RO 0x01 GPIO Peripheral ID Register[31:24] Can be used by software to identify the presence of this peripheral. July 14, 2014 267 Texas Instruments-Production Data General-Purpose Input/Outputs (GPIOs) 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) GPIO Port A base: 0x4000.4000 GPIO Port B base: 0x4000.5000 GPIO Port C base: 0x4000.6000 GPIO Port D base: 0x4000.7000 GPIO Port E base: 0x4002.4000 Offset 0xFF0 Type RO, reset 0x0000.000D 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 RO 1 RO 1 RO 0 RO 1 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 CID0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 CID0 RO 0x0D GPIO PrimeCell ID Register[7:0] Provides software a standard cross-peripheral identification system. 268 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) GPIO Port A base: 0x4000.4000 GPIO Port B base: 0x4000.5000 GPIO Port C base: 0x4000.6000 GPIO Port D base: 0x4000.7000 GPIO Port E base: 0x4002.4000 Offset 0xFF4 Type RO, reset 0x0000.00F0 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 RO 0 RO 0 RO 0 RO 0 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 CID1 RO 0 RO 0 RO 0 RO 0 RO 1 RO 1 RO 1 RO 1 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 CID1 RO 0xF0 GPIO PrimeCell ID Register[15:8] Provides software a standard cross-peripheral identification system. July 14, 2014 269 Texas Instruments-Production Data General-Purpose Input/Outputs (GPIOs) 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) GPIO Port A base: 0x4000.4000 GPIO Port B base: 0x4000.5000 GPIO Port C base: 0x4000.6000 GPIO Port D base: 0x4000.7000 GPIO Port E base: 0x4002.4000 Offset 0xFF8 Type RO, reset 0x0000.0005 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 RO 0 RO 1 RO 0 RO 1 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 CID2 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 CID2 RO 0x05 GPIO PrimeCell ID Register[23:16] Provides software a standard cross-peripheral identification system. 270 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) GPIO Port A base: 0x4000.4000 GPIO Port B base: 0x4000.5000 GPIO Port C base: 0x4000.6000 GPIO Port D base: 0x4000.7000 GPIO Port E base: 0x4002.4000 Offset 0xFFC Type RO, reset 0x0000.00B1 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 RO 0 RO 0 RO 0 RO 1 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 CID3 RO 0 RO 0 RO 0 RO 0 RO 1 RO 0 RO 1 RO 1 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 CID3 RO 0xB1 GPIO PrimeCell ID Register[31:24] Provides software a standard cross-peripheral identification system. July 14, 2014 271 Texas Instruments-Production Data General-Purpose Timers 8 General-Purpose Timers Programmable timers can be used to count or time external events that drive the Timer input pins. ® The Stellaris General-Purpose Timer Module (GPTM) contains three GPTM blocks (Timer0, Timer1, and Timer 2). Each GPTM block provides two 16-bit timers/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). In addition, timers can be used to trigger analog-to-digital conversions (ADC). The ADC 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 GPT Module is one timing resource available on the Stellaris microcontrollers. Other timer resources include the System Timer (SysTick) (see 85) and the PWM timer in the PWM module (see “PWM Timer” on page 497). The General-Purpose Timers provide the following features: ■ Three General-Purpose Timer Modules (GPTM), each of which provides two 16-bit timers/counters. Each GPTM can be configured to operate independently: – As a single 32-bit timer – As one 32-bit Real-Time Clock (RTC) to event capture – For Pulse Width Modulation (PWM) – To trigger analog-to-digital conversions ■ 32-bit Timer modes – Programmable one-shot timer – Programmable periodic timer – Real-Time Clock when using an external 32.768-KHz clock as the input – User-enabled stalling when the controller asserts CPU Halt flag during debug – ADC event trigger ■ 16-bit Timer modes – General-purpose timer function with an 8-bit prescaler (for one-shot and periodic modes only) – 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 272 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller – Input edge time capture ■ 16-bit PWM mode – Simple PWM mode with software-programmable output inversion of the PWM signal 8.1 Block Diagram Note: In Figure 8-1 on page 273, the specific CCP pins available depend on the Stellaris device. See Table 8-1 on page 273 for the available CCPs. Figure 8-1. 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 GPTMTAMR GPTMCTL GPTMIMR TimerB Interrupt 32 KHz or Even CCP Pin RTC Divider GPTMRIS GPTMMIS TimerB Control GPTMICR GPTMTBPMR GPTMTBR En Clock / Edge Detect GPTMTBPR GPTMTBMATCHR GPTMTBILR Odd CCP Pin TB Comparator GPTMTBMR 0x0000 (Down Counter Modes) System Clock Table 8-1. Available CCP Pins Timer 16-Bit Up/Down Counter Even CCP Pin Odd CCP Pin Timer 0 TimerA CCP0 - TimerB - CCP1 TimerA CCP2 - TimerB - CCP3 TimerA CCP4 - TimerB - CCP5 Timer 1 Timer 2 8.2 Signal Description Table 8-2 on page 274lists the external signals of the GP Timer module and describes the function of each. The GP Timer signals are alternate functions for some GPIO signals and default to be GPIO signals at reset. The column in the table below titled "Pin Assignment" lists the possible GPIO July 14, 2014 273 Texas Instruments-Production Data General-Purpose Timers pin placements for these GP Timer signals. The AFSEL bit in the GPIO Alternate Function Select (GPIOAFSEL) register (page 250) should be set to choose the GP Timer function. For more information on configuring GPIOs, see “General-Purpose Input/Outputs (GPIOs)” on page 230. Table 8-2. General-Purpose Timers Signals (48QFP) a Pin Name Pin Number Pin Type Buffer Type Description CCP0 29 I/O TTL Capture/Compare/PWM 0. CCP1 3 I/O TTL Capture/Compare/PWM 1. CCP2 46 I/O TTL Capture/Compare/PWM 2. CCP3 12 I/O TTL Capture/Compare/PWM 3. CCP4 11 I/O TTL Capture/Compare/PWM 4. CCP5 43 I/O TTL Capture/Compare/PWM 5. a. The TTL designation indicates the pin has TTL-compatible voltage levels. 8.3 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 284), the GPTM TimerA Mode (GPTMTAMR) register (see page 285), and the GPTM TimerB Mode (GPTMTBMR) register (see page 287). 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. 8.3.1 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 298) and the GPTM TimerB Interval Load (GPTMTBILR) register (see page 299). The prescale counters are initialized to 0x00: the GPTM TimerA Prescale (GPTMTAPR) register (see page 302) and the GPTM TimerB Prescale (GPTMTBPR) register (see page 303). 8.3.2 32-Bit Timer Operating Modes 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 298 ■ GPTM TimerB Interval Load (GPTMTBILR) register [15:0], see page 299 ■ GPTM TimerA (GPTMTAR) register [15:0], see page 306 ■ GPTM TimerB (GPTMTBR) register [15:0], see page 307 274 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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] 8.3.2.1 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 285), 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 289), the timer begins counting down from its preloaded value. Once the 0x0000.0000 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 triggers when it reaches the 0x000.0000 state. The GPTM sets the TATORIS bit in the GPTM Raw Interrupt Status (GPTMRIS) register (see page 294), and holds it until it is cleared by writing the GPTM Interrupt Clear (GPTMICR) register (see page 296). If the time-out interrupt is enabled in the GPTM Interrupt Mask (GPTMIMR) register (see page 292), the GPTM also sets the TATOMIS bit in the GPTM Masked Interrupt Status (GPTMMIS) register (see page 295). The ADC trigger is enabled by setting the TAOTE bit in GPTMCTL. 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 set, the timer freezes counting while the processor is halted by the debugger. The timer resumes counting when the processor resumes execution. 8.3.2.2 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 0x0000.0001. All subsequent load values must be written to the GPTM TimerA Match (GPTMTAMATCHR) register (see page 300) by the controller. The input clock on an even CCP input 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. When software writes the TAEN bit inthe GPTMCTL register, the counter starts counting up from its preloaded value of 0x0000.0001. When the current count value matches the preloaded value in the GPTMTAMATCHR register, it rolls over to a value of 0x0000.0000 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 GPTMIMR, the GPTM also sets the RTCMIS bit in GPTMMIS 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. July 14, 2014 275 Texas Instruments-Production Data General-Purpose Timers 8.3.3 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 284). This section describes each of the GPTM 16-bit modes of operation. TimerA and TimerB have identical modes, so a single description is given using an n to reference both. 8.3.3.1 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 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 GPTMIMR, the GPTM also sets the TnTOMIS bit in GPTMISR and generates a controller interrupt. The ADC trigger is enabled by setting the TnOTE bit in the GPTMCTL register. 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 set, the timer freezes counting while the processor is halted by the debugger. The timer resumes counting when the processor resumes execution. 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). Table 8-3. 16-Bit Timer With Prescaler Configurations a Prescale #Clock (T c) Max Time Units 00000000 1 1.3107 mS 00000001 2 2.6214 mS 00000010 3 3.9322 mS ------------ -- -- -- 11111101 254 332.9229 mS 11111110 255 334.2336 mS 11111111 256 335.5443 mS a. Tc is the clock period. 8.3.3.2 16-Bit Input Edge Count Mode Note: For rising-edge detection, the input signal must be High for at least two system clock periods following the rising edge. Similarly, for falling-edge detection, the input signal must be Low for at least two system clock periods following the falling edge. Based on this criteria, the maximum input frequency for edge detection is 1/4 of the system frequency. Note: The prescaler is not available in 16-Bit Input Edge Count mode. 276 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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 8-2 on page 277 shows how input edge count mode works. In this case, the timer start value is set to GPTMTnILR =0x000A and the match value is set to GPTMTnMATCHR =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 GPTMTnMATCHR register. Figure 8-2. 16-Bit Input Edge Count Mode Example Timer stops, flags asserted Count Timer reload on next cycle Ignored Ignored 0x000A 0x0009 0x0008 0x0007 0x0006 Input Signal 8.3.3.3 16-Bit Input Edge Time Mode Note: For rising-edge detection, the input signal must be High for at least two system clock periods following the rising edge. Similarly, for falling edge detection, the input signal must be Low for at least two system clock periods following the falling edge. Based on this criteria, the maximum input frequency for edge detection is 1/4 of the system frequency. Note: The prescaler is not available in 16-Bit Input Edge Time mode. July 14, 2014 277 Texas Instruments-Production Data General-Purpose Timers 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). The timer is capable of capturing three types of events: rising edge, falling edge, or both. 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. 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 GPTMTnILR register. Figure 8-3 on page 278 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). Figure 8-3. 16-Bit Input Edge Time Mode Example Count 0xFFFF GPTMTnR=X GPTMTnR=Y GPTMTnR=Z Z X Y Time Input Signal 8.3.3.4 16-Bit PWM Mode Note: The prescaler is not available in 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. In this mode, the PWM frequency and period are synchronous events and therefore guaranteed to be glitch free. 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. 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 278 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller GPTMTnILR 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 (GPTMTnMATCHR). Software has the capability of inverting the output PWM signal by setting the TnPWML bit in the GPTMCTL register. Figure 8-4 on page 279 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 GPTMTnIRL=0xC350 and the match value is GPTMTnMATCHR=0x411A. Figure 8-4. 16-Bit PWM Mode Example Count GPTMTnR=GPTMnMR GPTMTnR=GPTMnMR 0xC350 0x411A Time TnEN set TnPWML = 0 Output Signal TnPWML = 1 8.4 Initialization and Configuration To use the general-purpose timers, the peripheral clock must be enabled by setting the TIMER0, TIMER1, and TIMER2 bits in the RCGC1 register. This section shows module initialization and configuration examples for each of the supported timer modes. 8.4.1 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. July 14, 2014 279 Texas Instruments-Production Data General-Purpose Timers 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). In One-Shot mode, the timer stops counting after step 7 on page 280. To re-enable the timer, repeat the sequence. A timer configured in Periodic mode does not stop counting after it times out. 8.4.2 32-Bit Real-Time Clock (RTC) Mode To use the RTC mode, the timer must have a 32.768-KHz input signal on an even CCP input. 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 GPTM asserts the RTCRIS bit in the GPTMRIS register and continues counting until Timer A is disabled or a hardware reset. The interrupt is cleared by writing the RTCCINT bit in the GPTMICR register. 8.4.3 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). 280 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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 on page 281. To re-enable the timer, repeat the sequence. A timer configured in Periodic mode does not stop counting after it times out. 8.4.4 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. 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 step 4 on page 281 through step 9 on page 281. 8.4.5 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. July 14, 2014 281 Texas Instruments-Production Data General-Purpose Timers 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. 8.4.6 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 TnPWML 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. 7. 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. 8.5 Register Map Table 8-4 on page 283 lists the GPTM registers. The offset listed is a hexadecimal increment to the register’s address, relative to that timer’s base address: ■ Timer0: 0x4003.0000 ■ Timer1: 0x4003.1000 ■ Timer2: 0x4003.2000 Note that the Timer module clock must be enabled before the registers can be programmed (see page 197). There must be a delay of 3 system clocks after the Timer module clock is enabled before any Timer module registers are accessed. 282 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Table 8-4. Timers Register Map Name Type Reset 0x000 GPTMCFG R/W 0x0000.0000 GPTM Configuration 284 0x004 GPTMTAMR R/W 0x0000.0000 GPTM TimerA Mode 285 0x008 GPTMTBMR R/W 0x0000.0000 GPTM TimerB Mode 287 0x00C GPTMCTL R/W 0x0000.0000 GPTM Control 289 0x018 GPTMIMR R/W 0x0000.0000 GPTM Interrupt Mask 292 0x01C GPTMRIS RO 0x0000.0000 GPTM Raw Interrupt Status 294 0x020 GPTMMIS RO 0x0000.0000 GPTM Masked Interrupt Status 295 0x024 GPTMICR W1C 0x0000.0000 GPTM Interrupt Clear 296 0x028 GPTMTAILR R/W 0xFFFF.FFFF GPTM TimerA Interval Load 298 0x02C GPTMTBILR R/W 0x0000.FFFF GPTM TimerB Interval Load 299 0x030 GPTMTAMATCHR R/W 0xFFFF.FFFF GPTM TimerA Match 300 0x034 GPTMTBMATCHR R/W 0x0000.FFFF GPTM TimerB Match 301 0x038 GPTMTAPR R/W 0x0000.0000 GPTM TimerA Prescale 302 0x03C GPTMTBPR R/W 0x0000.0000 GPTM TimerB Prescale 303 0x040 GPTMTAPMR R/W 0x0000.0000 GPTM TimerA Prescale Match 304 0x044 GPTMTBPMR R/W 0x0000.0000 GPTM TimerB Prescale Match 305 0x048 GPTMTAR RO 0xFFFF.FFFF GPTM TimerA 306 0x04C GPTMTBR RO 0x0000.FFFF GPTM TimerB 307 8.6 Description See page Offset Register Descriptions The remainder of this section lists and describes the GPTM registers, in numerical order by address offset. July 14, 2014 283 Texas Instruments-Production Data General-Purpose Timers 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) Timer0 base: 0x4003.0000 Timer1 base: 0x4003.1000 Timer2 base: 0x4003.2000 Offset 0x000 Type R/W, reset 0x0000.0000 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 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 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 2:0 GPTMCFG R/W 0x0 GPTM Configuration The GPTMCFG values are defined as follows: Value Description 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. 284 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) Timer0 base: 0x4003.0000 Timer1 base: 0x4003.1000 Timer2 base: 0x4003.2000 Offset 0x004 Type R/W, reset 0x0000.0000 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 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 TAAMS TACMR RO 0 RO 0 RO 0 RO 0 RO 0 R/W 0 R/W 0 reserved Type Reset reserved Type Reset TAMR R/W 0 R/W 0 Bit/Field Name Type Reset Description 31:4 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 3 TAAMS R/W 0 GPTM TimerA Alternate Mode Select The TAAMS values are defined as follows: Value Description 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 The TACMR values are defined as follows: Value Description 0 Edge-Count mode 1 Edge-Time mode July 14, 2014 285 Texas Instruments-Production Data General-Purpose Timers Bit/Field Name Type Reset 1:0 TAMR R/W 0x0 Description GPTM TimerA Mode The TAMR values are defined as follows: Value Description 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. 286 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) Timer0 base: 0x4003.0000 Timer1 base: 0x4003.1000 Timer2 base: 0x4003.2000 Offset 0x008 Type R/W, reset 0x0000.0000 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 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 TBAMS TBCMR RO 0 RO 0 RO 0 RO 0 RO 0 R/W 0 R/W 0 reserved Type Reset reserved Type Reset TBMR R/W 0 R/W 0 Bit/Field Name Type Reset Description 31:4 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 3 TBAMS R/W 0 GPTM TimerB Alternate Mode Select The TBAMS values are defined as follows: Value Description 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 The TBCMR values are defined as follows: Value Description 0 Edge-Count mode 1 Edge-Time mode July 14, 2014 287 Texas Instruments-Production Data General-Purpose Timers Bit/Field Name Type Reset 1:0 TBMR R/W 0x0 Description GPTM TimerB Mode The TBMR values are defined as follows: Value Description 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. 288 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) Timer0 base: 0x4003.0000 Timer1 base: 0x4003.1000 Timer2 base: 0x4003.2000 Offset 0x00C Type R/W, reset 0x0000.0000 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 8 TBOTE reserved TBSTALL TBEN R/W 0 RO 0 R/W 0 R/W 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 7 6 5 4 3 2 1 0 TAOTE RTCEN TASTALL TAEN R/W 0 R/W 0 R/W 0 R/W 0 reserved Type Reset reserved TBPWML Type Reset RO 0 R/W 0 TBEVENT R/W 0 R/W 0 reserved TAPWML RO 0 R/W 0 TAEVENT R/W 0 R/W 0 Bit/Field Name Type Reset Description 31:15 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 14 TBPWML R/W 0 GPTM TimerB PWM Output Level The TBPWML values are defined as follows: Value Description 13 TBOTE R/W 0 0 Output is unaffected. 1 Output is inverted. GPTM TimerB Output Trigger Enable The TBOTE values are defined as follows: Value Description 0 The output TimerB ADC trigger is disabled. 1 The output TimerB ADC trigger is enabled. In addition, the ADC must be enabled and the timer selected as a trigger source with the EMn bit in the ADCEMUX register (see page 347). 12 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. July 14, 2014 289 Texas Instruments-Production Data General-Purpose Timers Bit/Field Name Type Reset 11:10 TBEVENT R/W 0x0 Description GPTM TimerB Event Mode The TBEVENT values are defined as follows: Value Description 0x0 Positive edge 0x1 Negative edge 0x2 Reserved 0x3 Both edges 9 TBSTALL R/W 0 GPTM Timer B Stall Enable The TBSTALL values are defined as follows: Value Description 0 Timer B continues counting while the processor is halted by the debugger. 1 Timer B freezes counting while the processor is halted by the debugger. If the processor is executing normally, the TBSTALL bit is ignored. 8 TBEN R/W 0 GPTM TimerB Enable The TBEN values are defined as follows: Value Description 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 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 6 TAPWML R/W 0 GPTM TimerA PWM Output Level The TAPWML values are defined as follows: Value Description 5 TAOTE R/W 0 0 Output is unaffected. 1 Output is inverted. GPTM TimerA Output Trigger Enable The TAOTE values are defined as follows: Value Description 0 The output TimerA ADC trigger is disabled. 1 The output TimerA ADC trigger is enabled. In addition, the ADC must be enabled and the timer selected as a trigger source with the EMn bit in the ADCEMUX register (see page 347). 290 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Bit/Field Name Type Reset 4 RTCEN R/W 0 Description GPTM RTC Enable The RTCEN values are defined as follows: Value Description 3:2 TAEVENT R/W 0x0 0 RTC counting is disabled. 1 RTC counting is enabled. GPTM TimerA Event Mode The TAEVENT values are defined as follows: Value Description 0x0 Positive edge 0x1 Negative edge 0x2 Reserved 0x3 Both edges 1 TASTALL R/W 0 GPTM Timer A Stall Enable The TASTALL values are defined as follows: Value Description 0 Timer A continues counting while the processor is halted by the debugger. 1 Timer A freezes counting while the processor is halted by the debugger. If the processor is executing normally, the TASTALL bit is ignored. 0 TAEN R/W 0 GPTM TimerA Enable The TAEN values are defined as follows: Value Description 0 TimerA is disabled. 1 TimerA is enabled and begins counting or the capture logic is enabled based on the GPTMCFG register. July 14, 2014 291 Texas Instruments-Production Data 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) Timer0 base: 0x4003.0000 Timer1 base: 0x4003.1000 Timer2 base: 0x4003.2000 Offset 0x018 Type R/W, reset 0x0000.0000 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 CBEIM CBMIM TBTOIM RO 0 RO 0 RO 0 RO 0 R/W 0 R/W 0 R/W 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 RTCIM CAEIM CAMIM TATOIM 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 RO 0 reserved Bit/Field Name Type Reset Description 31:11 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 10 CBEIM R/W 0 GPTM CaptureB Event Interrupt Mask The CBEIM values are defined as follows: Value Description 9 CBMIM R/W 0 0 Interrupt is disabled. 1 Interrupt is enabled. GPTM CaptureB Match Interrupt Mask The CBMIM values are defined as follows: Value Description 8 TBTOIM R/W 0 0 Interrupt is disabled. 1 Interrupt is enabled. GPTM TimerB Time-Out Interrupt Mask The TBTOIM values are defined as follows: Value Description 7:4 reserved RO 0 0 Interrupt is disabled. 1 Interrupt is enabled. Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 292 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Bit/Field Name Type Reset 3 RTCIM R/W 0 Description GPTM RTC Interrupt Mask The RTCIM values are defined as follows: Value Description 2 CAEIM R/W 0 0 Interrupt is disabled. 1 Interrupt is enabled. GPTM CaptureA Event Interrupt Mask The CAEIM values are defined as follows: Value Description 1 CAMIM R/W 0 0 Interrupt is disabled. 1 Interrupt is enabled. GPTM CaptureA Match Interrupt Mask The CAMIM values are defined as follows: Value Description 0 TATOIM R/W 0 0 Interrupt is disabled. 1 Interrupt is enabled. GPTM TimerA Time-Out Interrupt Mask The TATOIM values are defined as follows: Value Description 0 Interrupt is disabled. 1 Interrupt is enabled. July 14, 2014 293 Texas Instruments-Production Data 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) Timer0 base: 0x4003.0000 Timer1 base: 0x4003.1000 Timer2 base: 0x4003.2000 Offset 0x01C Type RO, reset 0x0000.0000 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 8 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 7 6 5 4 3 2 1 0 RTCRIS CAERIS RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 reserved Type Reset reserved Type Reset RO 0 CBERIS RO 0 CBMRIS TBTORIS RO 0 RO 0 reserved CAMRIS TATORIS RO 0 RO 0 Bit/Field Name Type Reset Description 31:11 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 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 0x0 3 RTCRIS RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 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. 294 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) Timer0 base: 0x4003.0000 Timer1 base: 0x4003.1000 Timer2 base: 0x4003.2000 Offset 0x020 Type RO, reset 0x0000.0000 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 8 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 7 6 5 4 3 2 1 0 RO 0 RO 0 RO 0 RO 0 reserved Type Reset reserved Type Reset RO 0 CBEMIS CBMMIS TBTOMIS RO 0 RO 0 RO 0 reserved RTCMIS RO 0 CAEMIS CAMMIS TATOMIS RO 0 RO 0 RO 0 Bit/Field Name Type Reset Description 31:11 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 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 0x0 3 RTCMIS RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 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. July 14, 2014 295 Texas Instruments-Production Data 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) Timer0 base: 0x4003.0000 Timer1 base: 0x4003.1000 Timer2 base: 0x4003.2000 Offset 0x024 Type W1C, reset 0x0000.0000 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 8 23 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 reserved Type Reset reserved Type Reset RO 0 RO 0 RO 0 CBECINT CBMCINT RO 0 RO 0 W1C 0 W1C 0 reserved TBTOCINT W1C 0 RO 0 RO 0 RO 0 RTCCINT CAECINT CAMCINT RO 0 W1C 0 W1C 0 W1C 0 0 TATOCINT W1C 0 Bit/Field Name Type Reset Description 31:11 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 10 CBECINT W1C 0 GPTM CaptureB Event Interrupt Clear The CBECINT values are defined as follows: Value Description 9 CBMCINT W1C 0 0 The interrupt is unaffected. 1 The interrupt is cleared. GPTM CaptureB Match Interrupt Clear The CBMCINT values are defined as follows: Value Description 8 TBTOCINT W1C 0 0 The interrupt is unaffected. 1 The interrupt is cleared. GPTM TimerB Time-Out Interrupt Clear The TBTOCINT values are defined as follows: Value Description 7:4 reserved RO 0x0 0 The interrupt is unaffected. 1 The interrupt is cleared. Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 296 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Bit/Field Name Type Reset 3 RTCCINT W1C 0 Description GPTM RTC Interrupt Clear The RTCCINT values are defined as follows: Value Description 2 CAECINT W1C 0 0 The interrupt is unaffected. 1 The interrupt is cleared. GPTM CaptureA Event Interrupt Clear The CAECINT values are defined as follows: Value Description 1 CAMCINT W1C 0 0 The interrupt is unaffected. 1 The interrupt is cleared. GPTM CaptureA Match Interrupt Clear The CAMCINT values are defined as follows: Value Description 0 TATOCINT W1C 0 0 The interrupt is unaffected. 1 The interrupt is cleared. GPTM TimerA Time-Out Interrupt Clear The TATOCINT values are defined as follows: Value Description 0 The interrupt is unaffected. 1 The interrupt is cleared. July 14, 2014 297 Texas Instruments-Production Data General-Purpose Timers 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) Timer0 base: 0x4003.0000 Timer1 base: 0x4003.1000 Timer2 base: 0x4003.2000 Offset 0x028 Type R/W, reset 0xFFFF.FFFF 31 30 29 28 27 26 25 24 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 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 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 TAILRH Type Reset TAILRL Type Reset Bit/Field Name Type Reset 31:16 TAILRH R/W 0xFFFF Description 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. 15:0 TAILRL R/W 0xFFFF 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. 298 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) Timer0 base: 0x4003.0000 Timer1 base: 0x4003.1000 Timer2 base: 0x4003.2000 Offset 0x02C Type R/W, reset 0x0000.FFFF 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 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 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 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 R/W 1 reserved Type Reset TBILRL Type Reset Bit/Field Name Type Reset Description 31:16 reserved RO 0x0000 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 15:0 TBILRL R/W 0xFFFF 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. July 14, 2014 299 Texas Instruments-Production Data General-Purpose Timers 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) Timer0 base: 0x4003.0000 Timer1 base: 0x4003.1000 Timer2 base: 0x4003.2000 Offset 0x030 Type R/W, reset 0xFFFF.FFFF 31 30 29 28 27 26 25 24 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 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 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 TAMRH Type Reset TAMRL Type Reset Bit/Field Name Type Reset 31:16 TAMRH R/W 0xFFFF Description 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. 15:0 TAMRL R/W 0xFFFF 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. 300 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 12: GPTM TimerB Match (GPTMTBMATCHR), offset 0x034 This register is used in 16-bit PWM and Input Edge Count modes. GPTM TimerB Match (GPTMTBMATCHR) Timer0 base: 0x4003.0000 Timer1 base: 0x4003.1000 Timer2 base: 0x4003.2000 Offset 0x034 Type R/W, reset 0x0000.FFFF 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 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 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 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 R/W 1 reserved Type Reset TBMRL Type Reset Bit/Field Name Type Reset Description 31:16 reserved RO 0x0000 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 15:0 TBMRL R/W 0xFFFF 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. July 14, 2014 301 Texas Instruments-Production Data General-Purpose Timers Register 13: GPTM TimerA Prescale (GPTMTAPR), offset 0x038 This register allows software to extend the range of the 16-bit timers when operating in one-shot or periodic mode. GPTM TimerA Prescale (GPTMTAPR) Timer0 base: 0x4003.0000 Timer1 base: 0x4003.1000 Timer2 base: 0x4003.2000 Offset 0x038 Type R/W, reset 0x0000.0000 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 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 reserved Type Reset reserved Type Reset TAPSR RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 TAPSR R/W 0x00 GPTM TimerA Prescale The register loads this value on a write. A read returns the current value of the register. Refer to Table 8-3 on page 276 for more details and an example. 302 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 14: GPTM TimerB Prescale (GPTMTBPR), offset 0x03C This register allows software to extend the range of the 16-bit timers when operating in one-shot or periodic mode. GPTM TimerB Prescale (GPTMTBPR) Timer0 base: 0x4003.0000 Timer1 base: 0x4003.1000 Timer2 base: 0x4003.2000 Offset 0x03C Type R/W, reset 0x0000.0000 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 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 reserved Type Reset reserved Type Reset TBPSR RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 TBPSR R/W 0x00 GPTM TimerB Prescale The register loads this value on a write. A read returns the current value of this register. Refer to Table 8-3 on page 276 for more details and an example. July 14, 2014 303 Texas Instruments-Production Data General-Purpose Timers Register 15: GPTM TimerA Prescale Match (GPTMTAPMR), offset 0x040 This register effectively extends the range of GPTMTAMATCHR to 24 bits when operating in 16-bit one-shot or periodic mode. GPTM TimerA Prescale Match (GPTMTAPMR) Timer0 base: 0x4003.0000 Timer1 base: 0x4003.1000 Timer2 base: 0x4003.2000 Offset 0x040 Type R/W, reset 0x0000.0000 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 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 reserved Type Reset reserved Type Reset TAPSMR RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 TAPSMR R/W 0x00 GPTM TimerA Prescale Match This value is used alongside GPTMTAMATCHR to detect timer match events while using a prescaler. 304 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 16: GPTM TimerB Prescale Match (GPTMTBPMR), offset 0x044 This register effectively extends the range of GPTMTBMATCHR to 24 bits when operating in 16-bit one-shot or periodic mode. GPTM TimerB Prescale Match (GPTMTBPMR) Timer0 base: 0x4003.0000 Timer1 base: 0x4003.1000 Timer2 base: 0x4003.2000 Offset 0x044 Type R/W, reset 0x0000.0000 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 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 reserved Type Reset reserved Type Reset TBPSMR RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 TBPSMR R/W 0x00 GPTM TimerB Prescale Match This value is used alongside GPTMTBMATCHR to detect timer match events while using a prescaler. July 14, 2014 305 Texas Instruments-Production Data General-Purpose Timers 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 number of edges that have occurred. GPTM TimerA (GPTMTAR) Timer0 base: 0x4003.0000 Timer1 base: 0x4003.1000 Timer2 base: 0x4003.2000 Offset 0x048 Type RO, reset 0xFFFF.FFFF 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 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 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 Bit/Field Name Type Reset 31:16 TARH RO 0xFFFF Description 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. 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 number of edges that have occurred. 306 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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 number of edges that have occurred. GPTM TimerB (GPTMTBR) Timer0 base: 0x4003.0000 Timer1 base: 0x4003.1000 Timer2 base: 0x4003.2000 Offset 0x04C Type RO, reset 0x0000.FFFF 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 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 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 7 6 5 4 3 2 1 0 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 0x0000 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 15:0 TBRL RO 0xFFFF GPTM TimerB A read returns the current value of the GPTM TimerB Count Register, except in Input Edge-Count mode, when it returns the number of edges that have occurred. July 14, 2014 307 Texas Instruments-Production Data Watchdog Timer 9 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 has the following features: ■ 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 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. 308 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 9.1 Block Diagram Figure 9-1. 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 9.2 WDTPCellID0 WDTPeriphID0 WDTPeriphID4 WDTPCellID1 WDTPeriphID1 WDTPeriphID5 WDTPCellID2 WDTPeriphID2 WDTPeriphID6 WDTPCellID3 WDTPeriphID3 WDTPeriphID7 Functional Description 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. 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. 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. July 14, 2014 309 Texas Instruments-Production Data Watchdog Timer 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. 9.3 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 0x1ACC.E551. 9.4 Register Map Table 9-1 on page 310 lists the Watchdog registers. The offset listed is a hexadecimal increment to the register’s address, relative to the Watchdog Timer base address of 0x4000.0000. Table 9-1. Watchdog Timer Register Map Description See page Offset Name Type Reset 0x000 WDTLOAD R/W 0xFFFF.FFFF Watchdog Load 312 0x004 WDTVALUE RO 0xFFFF.FFFF Watchdog Value 313 0x008 WDTCTL R/W 0x0000.0000 Watchdog Control 314 0x00C WDTICR WO - Watchdog Interrupt Clear 315 0x010 WDTRIS RO 0x0000.0000 Watchdog Raw Interrupt Status 316 0x014 WDTMIS RO 0x0000.0000 Watchdog Masked Interrupt Status 317 0x418 WDTTEST R/W 0x0000.0000 Watchdog Test 318 0xC00 WDTLOCK R/W 0x0000.0000 Watchdog Lock 319 0xFD0 WDTPeriphID4 RO 0x0000.0000 Watchdog Peripheral Identification 4 320 0xFD4 WDTPeriphID5 RO 0x0000.0000 Watchdog Peripheral Identification 5 321 0xFD8 WDTPeriphID6 RO 0x0000.0000 Watchdog Peripheral Identification 6 322 0xFDC WDTPeriphID7 RO 0x0000.0000 Watchdog Peripheral Identification 7 323 0xFE0 WDTPeriphID0 RO 0x0000.0005 Watchdog Peripheral Identification 0 324 0xFE4 WDTPeriphID1 RO 0x0000.0018 Watchdog Peripheral Identification 1 325 0xFE8 WDTPeriphID2 RO 0x0000.0018 Watchdog Peripheral Identification 2 326 310 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Table 9-1. Watchdog Timer Register Map (continued) Offset Name 0xFEC Reset WDTPeriphID3 RO 0x0000.0001 Watchdog Peripheral Identification 3 327 0xFF0 WDTPCellID0 RO 0x0000.000D Watchdog PrimeCell Identification 0 328 0xFF4 WDTPCellID1 RO 0x0000.00F0 Watchdog PrimeCell Identification 1 329 0xFF8 WDTPCellID2 RO 0x0000.0005 Watchdog PrimeCell Identification 2 330 0xFFC WDTPCellID3 RO 0x0000.00B1 Watchdog PrimeCell Identification 3 331 9.5 Description See page Type Register Descriptions The remainder of this section lists and describes the WDT registers, in numerical order by address offset. July 14, 2014 311 Texas Instruments-Production Data 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 0x0000.0000, an interrupt is immediately generated. Watchdog Load (WDTLOAD) Base 0x4000.0000 Offset 0x000 Type R/W, reset 0xFFFF.FFFF 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 31:0 WDTLoad R/W Reset R/W 1 Description 0xFFFF.FFFF Watchdog Load Value 312 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 2: Watchdog Value (WDTVALUE), offset 0x004 This register contains the current count value of the timer. Watchdog Value (WDTVALUE) Base 0x4000.0000 Offset 0x004 Type RO, reset 0xFFFF.FFFF 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 31:0 WDTValue RO Reset RO 1 Description 0xFFFF.FFFF Watchdog Value Current value of the 32-bit down counter. July 14, 2014 313 Texas Instruments-Production Data 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 (on 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) Base 0x4000.0000 Offset 0x008 Type R/W, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 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 15 14 13 12 11 10 9 8 7 6 5 4 3 2 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 1 0 RESEN INTEN R/W 0 R/W 0 Bit/Field Name Type Reset Description 31:2 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 1 RESEN R/W 0 Watchdog Reset Enable The RESEN values are defined as follows: Value Description 0 INTEN R/W 0 0 Disabled. 1 Enable the Watchdog module reset output. Watchdog Interrupt Enable The INTEN values are defined as follows: Value Description 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. 314 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) Base 0x4000.0000 Offset 0x00C Type WO, reset 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 July 14, 2014 315 Texas Instruments-Production Data 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) Base 0x4000.0000 Offset 0x010 Type RO, reset 0x0000.0000 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 8 RO 0 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 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 RO 0 WDTRIS RO 0 Bit/Field Name Type Reset Description 31:1 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 0 WDTRIS RO 0 Watchdog Raw Interrupt Status Gives the raw interrupt state (prior to masking) of WDTINTR. 316 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) Base 0x4000.0000 Offset 0x014 Type RO, reset 0x0000.0000 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 8 RO 0 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 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 RO 0 WDTMIS RO 0 Bit/Field Name Type Reset Description 31:1 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 0 WDTMIS RO 0 Watchdog Masked Interrupt Status Gives the masked interrupt state (after masking) of the WDTINTR interrupt. July 14, 2014 317 Texas Instruments-Production Data Watchdog Timer Register 7: Watchdog Test (WDTTEST), offset 0x418 This register provides user-enabled stalling when the microcontroller asserts the CPU halt flag during debug. Watchdog Test (WDTTEST) Base 0x4000.0000 Offset 0x418 Type R/W, reset 0x0000.0000 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 8 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 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 STALL R/W 0 reserved Bit/Field Name Type Reset Description 31:9 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 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 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 318 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 8: Watchdog Lock (WDTLOCK), offset 0xC00 Writing 0x1ACC.E551 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 0x0000.0001 (when locked; otherwise, the returned value is 0x0000.0000 (unlocked)). Watchdog Lock (WDTLOCK) Base 0x4000.0000 Offset 0xC00 Type R/W, reset 0x0000.0000 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 0x1ACC.E551 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: Value Description 0x0000.0001 Locked 0x0000.0000 Unlocked July 14, 2014 319 Texas Instruments-Production Data 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) Base 0x4000.0000 Offset 0xFD0 Type RO, reset 0x0000.0000 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 RO 0 RO 0 RO 0 RO 0 RO 0 reserved Type Reset reserved Type Reset PID4 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 PID4 RO 0x00 WDT Peripheral ID Register[7:0] 320 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) Base 0x4000.0000 Offset 0xFD4 Type RO, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 RO 0 RO 0 RO 0 RO 0 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 PID5 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 PID5 RO 0x00 WDT Peripheral ID Register[15:8] July 14, 2014 321 Texas Instruments-Production Data 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) Base 0x4000.0000 Offset 0xFD8 Type RO, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 RO 0 RO 0 RO 0 RO 0 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 PID6 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 PID6 RO 0x00 WDT Peripheral ID Register[23:16] 322 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) Base 0x4000.0000 Offset 0xFDC Type RO, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 RO 0 RO 0 RO 0 RO 0 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 PID7 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 PID7 RO 0x00 WDT Peripheral ID Register[31:24] July 14, 2014 323 Texas Instruments-Production Data 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) Base 0x4000.0000 Offset 0xFE0 Type RO, reset 0x0000.0005 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 RO 0 RO 1 RO 0 RO 1 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 PID0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 PID0 RO 0x05 Watchdog Peripheral ID Register[7:0] 324 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) Base 0x4000.0000 Offset 0xFE4 Type RO, reset 0x0000.0018 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 RO 1 RO 0 RO 0 RO 0 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 PID1 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 1 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 PID1 RO 0x18 Watchdog Peripheral ID Register[15:8] July 14, 2014 325 Texas Instruments-Production Data 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) Base 0x4000.0000 Offset 0xFE8 Type RO, reset 0x0000.0018 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 RO 1 RO 0 RO 0 RO 0 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 PID2 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 1 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 PID2 RO 0x18 Watchdog Peripheral ID Register[23:16] 326 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) Base 0x4000.0000 Offset 0xFEC Type RO, reset 0x0000.0001 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 RO 0 RO 0 RO 0 RO 1 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 PID3 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 PID3 RO 0x01 Watchdog Peripheral ID Register[31:24] July 14, 2014 327 Texas Instruments-Production Data 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) Base 0x4000.0000 Offset 0xFF0 Type RO, reset 0x0000.000D 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 RO 0 RO 1 RO 1 RO 0 RO 1 reserved Type Reset reserved Type Reset CID0 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 CID0 RO 0x0D Watchdog PrimeCell ID Register[7:0] 328 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) Base 0x4000.0000 Offset 0xFF4 Type RO, reset 0x0000.00F0 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 1 RO 1 RO 1 RO 1 RO 0 RO 0 RO 0 RO 0 reserved Type Reset reserved Type Reset CID1 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 CID1 RO 0xF0 Watchdog PrimeCell ID Register[15:8] July 14, 2014 329 Texas Instruments-Production Data 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) Base 0x4000.0000 Offset 0xFF8 Type RO, reset 0x0000.0005 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 RO 0 RO 0 RO 1 RO 0 RO 1 reserved Type Reset reserved Type Reset CID2 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 CID2 RO 0x05 Watchdog PrimeCell ID Register[23:16] 330 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) Base 0x4000.0000 Offset 0xFFC Type RO, reset 0x0000.00B1 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 1 RO 0 RO 1 RO 1 RO 0 RO 0 RO 0 RO 1 reserved Type Reset reserved Type Reset CID3 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 CID3 RO 0xB1 Watchdog PrimeCell ID Register[31:24] July 14, 2014 331 Texas Instruments-Production Data Analog-to-Digital Converter (ADC) 10 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 two input channels, plus an internal temperature sensor. The ADC module contains four 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 module provides the following features: ■ Two analog input channels ■ Single-ended and differential-input configurations ■ On-chip internal temperature sensor ■ Sample rate of 250 thousand samples/second ■ Flexible, configurable analog-to-digital conversion ■ Four programmable sample conversion sequences from one to eight entries long, with corresponding conversion result FIFOs ■ Flexible trigger control – Controller (software) – Timers – Analog Comparators – PWM – GPIO ■ Hardware averaging of up to 64 samples for improved accuracy ■ Converter uses an internal 3-V reference 10.1 Block Diagram Figure 10-1 on page 333 provides details on the internal configuration of the ADC controls and data registers. 332 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Figure 10-1. ADC Module Block Diagram Trigger Events Comparator GPIO (PB4) Timer PWM Analog Inputs SS3 Comparator GPIO (PB4) Timer PWM Control/Status Sample Sequencer 0 ADCACTSS ADCSSMUX0 ADCOSTAT ADCSSCTL0 ADCUSTAT ADCSSFSTAT0 Analog-to-Digital Converter ADCSSPRI SS2 Sample Sequencer 1 ADCSSMUX1 Comparator GPIO (PB4) Timer PWM ADCSSCTL1 SS1 Hardware Averager ADCSSFSTAT1 ADCSAC Sample Sequencer 2 Comparator GPIO (PB4) Timer PWM SS0 ADCSSMUX2 ADCSSCTL2 FIFO Block ADCSSFSTAT2 ADCSSFIFO0 ADCEMUX ADCPSSI ADCSSFIFO1 Interrupt Control Sample Sequencer 3 ADCIM ADCSSMUX3 SS0 Interrupt SS1 Interrupt SS2 Interrupt SS3 Interrupt 10.2 ADCSSFIFO2 ADCSSFIFO3 ADCRIS ADCSSCTL3 ADCISC ADCSSFSTAT3 Signal Description The signals are analog functions for some GPIO signals. The column in the table below titled "Pin Assignment" lists the GPIO pin placement for the ADC signals. The AINx analog signals are not 5-V tolerant and go through an isolation circuit before reaching their circuitry. These signals are configured by clearing the corresponding DEN bit in the GPIO Digital Enable (GPIODEN) register. For more information on configuring GPIOs, see “General-Purpose Input/Outputs (GPIOs)” on page 230. Table 10-1. ADC Signals (48QFP) a Pin Name Pin Number Pin Type Buffer Type Description ADC0 1 I Analog Analog-to-digital converter input 0. ADC1 2 I Analog Analog-to-digital converter input 1. a. The TTL designation indicates the pin has TTL-compatible voltage levels. 10.3 Functional Description The Stellaris ADC collects sample data by using a programmable sequence-based approach instead of the traditional single or double-sampling approaches 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. July 14, 2014 333 Texas Instruments-Production Data Analog-to-Digital Converter (ADC) 10.3.1 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 10-2 on page 334 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 10-2. 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 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, and should 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 IEn 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. 10.3.2 Module Control Outside of the sample sequencers, the remainder of the control logic is responsible for tasks such as: ■ Interrupt generation ■ Sequence prioritization ■ 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. 334 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 10.3.2.1 Interrupts The register configurations of the sample sequencers dictate which events generate raw interrupts, but do not have control over whether the interrupt is actually sent to the interrupt controller. The ADC module's interrupt signals are 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 the various interrupt signals, and the ADC Interrupt Status and Clear (ADCISC) register, which shows active interrupts that are enabled by the ADCIM register. Sequencer interrupts are cleared by writing a 1 to the corresponding IN bit in ADCISC. 10.3.2.2 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. 10.3.2.3 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 SSx bits in the ADC Processor Sample Sequence Initiate (ADCPSSI) register. Care must be taken when using the "Always" trigger. If a sequence's priority is too high, it is possible to starve other lower priority sequences. 10.3.3 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 354). There is a single averaging circuit and all input channels receive the same amount of averaging whether they are single-ended or differential. 10.3.4 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. An internal 3 V reference is used by the converter resulting in sample values ranging from 0x000 at 0 V input to 0x3FF at 3 V input when in single-ended input mode. 10.3.5 Differential Sampling In addition to traditional single-ended sampling, the ADC module supports differential sampling of two analog input channels. To enable differential sampling, software must set the Dn bit in the ADCSSCTL0n register in a step's configuration nibble. When a sequence step is configured for differential sampling, its corresponding value in the ADCSSMUXn register must be set to one of the four differential pairs, numbered 0-3. Differential July 14, 2014 335 Texas Instruments-Production Data Analog-to-Digital Converter (ADC) pair 0 samples analog inputs 0 and 1; differential pair 1 samples analog inputs 2 and 3; and so on (see Table 10-3 on page 336). The ADC does not support other differential pairings such as analog input 0 with analog input 3. The number of differential pairs supported is dependent on the number of analog inputs (see Table 10-3 on page 336). Table 10-3. Differential Sampling Pairs Differential Pair Analog Inputs 0 0 and 1 The voltage sampled in differential mode is the difference between the odd and even channels: ∆V (differential voltage) = VIN_EVEN (even channels) – VIN_ODD (odd channels), therefore: ■ If ∆V = 0, then the conversion result = 0x1FF ■ If ∆V > 0, then the conversion result > 0x1FF (range is 0x1FF–0x3FF) ■ If ∆V < 0, then the conversion result < 0x1FF (range is 0–0x1FF) The differential pairs assign polarities to the analog inputs: the even-numbered input is always positive, and the odd-numbered input is always negative. In order for a valid conversion result to appear, the negative input must be in the range of ± 1.5 V of the positive input. If an analog input is greater than 3 V or less than 0 V (the valid range for analog inputs), the input voltage is clipped, meaning it appears as either 3 V or 0 V, respectively, to the ADC. Figure 10-2 on page 337 shows an example of the negative input centered at 1.5 V. In this configuration, the differential range spans from -1.5 V to 1.5 V. Figure 10-3 on page 337 shows an example where the negative input is centered at -0.75 V, meaning inputs on the positive input saturate past a differential voltage of -0.75 V since the input voltage is less than 0 V. Figure 10-4 on page 338 shows an example of the negative input centered at 2.25 V, where inputs on the positive channel saturate past a differential voltage of 0.75 V since the input voltage would be greater than 3 V. 336 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Figure 10-2. Differential Sampling Range, VIN_ODD = 1.5 V ADC Conversion Result 0x3FF 0x1FF 0V -1.5 V 1.5 V 0V 3.0 V VIN_EVEN 1.5 V DV VIN_ODD = 1.5 V - Input Saturation Figure 10-3. Differential Sampling Range, VIN_ODD = 0.75 V ADC Conversion Result 0x3FF 0x1FF 0x0FF -1.5 V 0V -0.75 V +0.75 V +2.25 V +1.5 V VIN_EVEN DV - Input Saturation July 14, 2014 337 Texas Instruments-Production Data Analog-to-Digital Converter (ADC) Figure 10-4. Differential Sampling Range, VIN_ODD = 2.25 V ADC Conversion Result 0x3FF 0x2FF 0x1FF 0.75 V -1.5 V 2.25 V 3.0 V 0.75 V 1.5 V VIN_EVEN DV - Input Saturation 10.3.6 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 367). 10.3.7 Internal Temperature Sensor The temperature sensor does not have a separate enable, since it also contains the bandgap reference and must always be enabled. The reference is supplied to other analog modules; not just the ADC. 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 10-5 on page 339. 338 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Figure 10-5. Internal Temperature Sensor Characteristic 10.4 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). Using unsupported frequencies can cause faulty operation in the ADC module. 10.4.1 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 0x0001.0000 to the RCGC0 register (see page 191). 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. 10.4.2 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 ASENn 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. July 14, 2014 339 Texas Instruments-Production Data Analog-to-Digital Converter (ADC) 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 ASENn bit in the ADCACTSS register. 10.5 Register Map Table 10-4 on page 340 lists the ADC registers. The offset listed is a hexadecimal increment to the register’s address, relative to the ADC base address of 0x4003.8000. Note that the ADC module clock must be enabled before the registers can be programmed (see page 191). There must be a delay of 3 system clocks after the ADC module clock is enabled before any ADC module registers are accessed. Table 10-4. ADC Register Map Description See page Offset Name Type Reset 0x000 ADCACTSS R/W 0x0000.0000 ADC Active Sample Sequencer 342 0x004 ADCRIS RO 0x0000.0000 ADC Raw Interrupt Status 343 0x008 ADCIM R/W 0x0000.0000 ADC Interrupt Mask 344 0x00C ADCISC R/W1C 0x0000.0000 ADC Interrupt Status and Clear 345 0x010 ADCOSTAT R/W1C 0x0000.0000 ADC Overflow Status 346 0x014 ADCEMUX R/W 0x0000.0000 ADC Event Multiplexer Select 347 0x018 ADCUSTAT R/W1C 0x0000.0000 ADC Underflow Status 350 0x020 ADCSSPRI R/W 0x0000.3210 ADC Sample Sequencer Priority 351 0x028 ADCPSSI WO - ADC Processor Sample Sequence Initiate 353 0x030 ADCSAC R/W 0x0000.0000 ADC Sample Averaging Control 354 0x040 ADCSSMUX0 R/W 0x0000.0000 ADC Sample Sequence Input Multiplexer Select 0 355 0x044 ADCSSCTL0 R/W 0x0000.0000 ADC Sample Sequence Control 0 357 0x048 ADCSSFIFO0 RO - ADC Sample Sequence Result FIFO 0 360 0x04C ADCSSFSTAT0 RO 0x0000.0100 ADC Sample Sequence FIFO 0 Status 361 0x060 ADCSSMUX1 R/W 0x0000.0000 ADC Sample Sequence Input Multiplexer Select 1 362 0x064 ADCSSCTL1 R/W 0x0000.0000 ADC Sample Sequence Control 1 363 0x068 ADCSSFIFO1 RO - ADC Sample Sequence Result FIFO 1 360 0x06C ADCSSFSTAT1 RO 0x0000.0100 ADC Sample Sequence FIFO 1 Status 361 0x080 ADCSSMUX2 R/W 0x0000.0000 ADC Sample Sequence Input Multiplexer Select 2 362 0x084 ADCSSCTL2 R/W 0x0000.0000 ADC Sample Sequence Control 2 363 0x088 ADCSSFIFO2 RO - ADC Sample Sequence Result FIFO 2 360 340 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Table 10-4. ADC Register Map (continued) Offset Name 0x08C Reset ADCSSFSTAT2 RO 0x0000.0100 ADC Sample Sequence FIFO 2 Status 361 0x0A0 ADCSSMUX3 R/W 0x0000.0000 ADC Sample Sequence Input Multiplexer Select 3 365 0x0A4 ADCSSCTL3 R/W 0x0000.0002 ADC Sample Sequence Control 3 366 0x0A8 ADCSSFIFO3 RO - ADC Sample Sequence Result FIFO 3 360 0x0AC ADCSSFSTAT3 RO 0x0000.0100 ADC Sample Sequence FIFO 3 Status 361 0x100 ADCTMLB R/W 0x0000.0000 ADC Test Mode Loopback 367 10.6 Description See page Type Register Descriptions The remainder of this section lists and describes the ADC registers, in numerical order by address offset. July 14, 2014 341 Texas Instruments-Production Data 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 or disabled independently. ADC Active Sample Sequencer (ADCACTSS) Base 0x4003.8000 Offset 0x000 Type R/W, reset 0x0000.0000 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 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 ASEN3 ASEN2 ASEN1 ASEN0 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 31:4 reserved RO 0x0000.000 3 ASEN3 R/W 0 Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. ADC SS3 Enable 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 ADC SS2 Enable 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 ADC SS1 Enable 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 ADC SS0 Enable Specifies whether Sample Sequencer 0 is enabled. If set, the sample sequence logic for Sequencer 0 is active. Otherwise, the sequencer is inactive. 342 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) Base 0x4003.8000 Offset 0x004 Type RO, reset 0x0000.0000 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 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 INR3 INR2 INR1 INR0 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 0x000 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 3 INR3 RO 0 SS3 Raw Interrupt Status This bit is set by hardware when a sample with its respective ADCSSCTL3 IE bit has completed conversion. This bit is cleared by setting the IN3 bit in the ADCISC register. 2 INR2 RO 0 SS2 Raw Interrupt Status This bit is set by hardware when a sample with its respective ADCSSCTL2 IE bit has completed conversion. This bit is cleared by setting the IN2 bit in the ADCISC register. 1 INR1 RO 0 SS1 Raw Interrupt Status This bit is set by hardware when a sample with its respective ADCSSCTL1 IE bit has completed conversion. This bit is cleared by setting the IN1 bit in the ADCISC register. 0 INR0 RO 0 SS0 Raw Interrupt Status This bit is set by hardware when a sample with its respective ADCSSCTL0 IE bit has completed conversion. This bit is cleared by setting the IN30 bit in the ADCISC register. July 14, 2014 343 Texas Instruments-Production Data 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. Each raw interrupt signal can be masked independently. ADC Interrupt Mask (ADCIM) Base 0x4003.8000 Offset 0x008 Type R/W, reset 0x0000.0000 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 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 MASK3 MASK2 MASK1 MASK0 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 0x000 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 3 MASK3 R/W 0 SS3 Interrupt Mask When set, this bit allows the raw interrupt signal from Sample Sequencer 3 (ADCRIS register INR3 bit) to be promoted to a controller interrupt. When clear, the status of Sample Sequencer 3 does not affect the SS3 interrupt status. 2 MASK2 R/W 0 SS2 Interrupt Mask When set, this bit allows the raw interrupt signal from Sample Sequencer 2 (ADCRIS register INR2 bit) to be promoted to a controller interrupt. When clear, the status of Sample Sequencer 2 does not affect the SS2 interrupt status. 1 MASK1 R/W 0 SS1 Interrupt Mask When set, this bit allows the raw interrupt signal from Sample Sequencer 1 (ADCRIS register INR1 bit) to be promoted to a controller interrupt. When clear, the status of Sample Sequencer 1 does not affect the SS1 interrupt status. 0 MASK0 R/W 0 SS0 Interrupt Mask When set, this bit allows the raw interrupt signal from Sample Sequencer 0 (ADCRIS register INR0 bit) to be promoted to a controller interrupt. When clear, the status of Sample Sequencer 0 does not affect the SS0 interrupt status. 344 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 4: ADC Interrupt Status and Clear (ADCISC), offset 0x00C This register provides the mechanism for clearing sample sequence 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. Sample sequence nterrupts are cleared by setting the corresponding bit position. If software is polling the ADCRIS instead of generating interrupts, the sample sequence INR bits are still cleared via the ADCISC register, even if the IN bit is not set. ADC Interrupt Status and Clear (ADCISC) Base 0x4003.8000 Offset 0x00C Type R/W1C, reset 0x0000.0000 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 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 IN3 IN2 IN1 IN0 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 0x000 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 3 IN3 R/W1C 0 SS3 Interrupt Status and Clear This bit is set when both the INR3 bit in the ADCRIS register and the MASK3 bit in the ADCIM register are set, providing a level-based interrupt to the controller. This bit is cleared by writing a 1. Clearing this bit also clears the INR3 bit. 2 IN2 R/W1C 0 SS2 Interrupt Status and Clear This bit is set when both the INR2 bit in the ADCRIS register and the MASK2 bit in the ADCIM register are set, providing a level-based interrupt to the controller. This bit is cleared by writing a 1. Clearing this bit also clears the INR2 bit. 1 IN1 R/W1C 0 SS1 Interrupt Status and Clear This bit is set when both the INR1 bit in the ADCRIS register and the MASK1 bit in the ADCIM register are set, providing a level-based interrupt to the controller. This bit is cleared by writing a 1. Clearing this bit also clears the INR1 bit. 0 IN0 R/W1C 0 SS0 Interrupt Status and Clear This bit is set when both the INR0 bit in the ADCRIS register and the MASK0 bit in the ADCIM register are set, providing a level-based interrupt to the controller. This bit is cleared by writing a 1. Clearing this bit also clears the INR0 bit. July 14, 2014 345 Texas Instruments-Production Data 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) Base 0x4003.8000 Offset 0x010 Type R/W1C, reset 0x0000.0000 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 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 OV3 OV2 OV1 OV0 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 31:4 reserved RO 0x0000.000 3 OV3 R/W1C 0 Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. SS3 FIFO Overflow When set, 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. This bit is cleared by writing a 1. 2 OV2 R/W1C 0 SS2 FIFO Overflow When set, 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. This bit is cleared by writing a 1. 1 OV1 R/W1C 0 SS1 FIFO Overflow When set, 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. This bit is cleared by writing a 1. 0 OV0 R/W1C 0 SS0 FIFO Overflow When set, 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. This bit is cleared by writing a 1. 346 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) Base 0x4003.8000 Offset 0x014 Type R/W, reset 0x0000.0000 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 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 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 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 0x0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 15:12 EM3 R/W 0x0 SS3 Trigger Select This field selects the trigger source for Sample Sequencer 3. The valid configurations for this field are: Value Event 0x0 Controller (default) 0x1 Analog Comparator 0 0x2 Reserved 0x3 Reserved 0x4 External (GPIO PB4) 0x5 Timer In addition, the trigger must be enabled with the TnOTE bit in the GPTMCTL register (see page 289). 0x6 PWM0 The PWM module 0 trigger can be configured with the PWM0 Interrupt and Trigger Enable (PWM0INTEN) register, see page 515. 0x7 PWM1 The PWM module 1 trigger can be configured with the PWM1INTEN register, see page 515. 0x8 reserved 0x9-0xE reserved 0xF Always (continuously sample) July 14, 2014 347 Texas Instruments-Production Data Analog-to-Digital Converter (ADC) Bit/Field Name Type Reset 11:8 EM2 R/W 0x0 Description SS2 Trigger Select This field selects the trigger source for Sample Sequencer 2. The valid configurations for this field are: Value Event 0x0 Controller (default) 0x1 Analog Comparator 0 0x2 Reserved 0x3 Reserved 0x4 External (GPIO PB4) 0x5 Timer In addition, the trigger must be enabled with the TnOTE bit in the GPTMCTL register (see page 289). 0x6 PWM0 The PWM module 0 trigger can be configured with the PWM0 Interrupt and Trigger Enable (PWM0INTEN) register, see page 515. 0x7 PWM1 The PWM module 1 trigger can be configured with the PWM1INTEN register, see page 515. 0x8 reserved 0x9-0xE reserved 0xF 7:4 EM1 R/W 0x0 Always (continuously sample) SS1 Trigger Select This field selects the trigger source for Sample Sequencer 1. The valid configurations for this field are: Value Event 0x0 Controller (default) 0x1 Analog Comparator 0 0x2 Reserved 0x3 Reserved 0x4 External (GPIO PB4) 0x5 Timer In addition, the trigger must be enabled with the TnOTE bit in the GPTMCTL register (see page 289). 0x6 PWM0 The PWM module 0 trigger can be configured with the PWM0 Interrupt and Trigger Enable (PWM0INTEN) register, see page 515. 0x7 PWM1 The PWM module 1 trigger can be configured with the PWM1INTEN register, see page 515. 0x8 reserved 0x9-0xE reserved 0xF Always (continuously sample) 348 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Bit/Field Name Type Reset 3:0 EM0 R/W 0x0 Description SS0 Trigger Select This field selects the trigger source for Sample Sequencer 0. The valid configurations for this field are: Value Event 0x0 Controller (default) 0x1 Analog Comparator 0 0x2 Reserved 0x3 Reserved 0x4 External (GPIO PB4) 0x5 Timer In addition, the trigger must be enabled with the TnOTE bit in the GPTMCTL register (see page 289). 0x6 PWM0 The PWM module 0 trigger can be configured with the PWM0 Interrupt and Trigger Enable (PWM0INTEN) register, see page 515. 0x7 PWM1 The PWM module 1 trigger can be configured with the PWM1INTEN register, see page 515. 0x8 reserved 0x9-0xE reserved 0xF Always (continuously sample) July 14, 2014 349 Texas Instruments-Production Data 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 is cleared by writing a 1 to the relevant bit position. ADC Underflow Status (ADCUSTAT) Base 0x4003.8000 Offset 0x018 Type R/W1C, reset 0x0000.0000 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 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 UV3 UV2 UV1 UV0 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 31:4 reserved RO 0x0000.000 3 UV3 R/W1C 0 Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. SS3 FIFO Underflow When set, 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 SS2 FIFO Underflow When set, 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 SS1 FIFO Underflow When set, 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 SS0 FIFO Underflow When set, 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. 350 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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 Sequencer 3 has the lowest priority. When reconfiguring sequence priorities, each sequence must have a unique priority for the ADC to operate properly. ADC Sample Sequencer Priority (ADCSSPRI) Base 0x4003.8000 Offset 0x020 Type R/W, reset 0x0000.3210 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 R/W 1 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 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 RO 0 SS3 R/W 1 reserved RO 0 SS2 R/W 1 Bit/Field Name Type Reset 31:14 reserved RO 0x0000.0 13:12 SS3 R/W 0x3 reserved SS1 reserved SS0 R/W 0 Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. SS3 Priority This 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. The ADC may not operate properly if two or more fields are equal. 11:10 reserved RO 0x0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 9:8 SS2 R/W 0x2 SS2 Priority This field contains a binary-encoded value that specifies the priority encoding of Sample Sequencer 2. A priority encoding of 0 is highest and 3 is lowest. The priorities assigned to the sequencers must be uniquely mapped. The ADC may not operate properly if two or more fields are equal. 7:6 reserved RO 0x0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 5:4 SS1 R/W 0x1 SS1 Priority This field contains a binary-encoded value that specifies the priority encoding of Sample Sequencer 1. A priority encoding of 0 is highest and 3 is lowest. The priorities assigned to the sequencers must be uniquely mapped. The ADC may not operate properly if two or more fields are equal. 3:2 reserved RO 0x0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. July 14, 2014 351 Texas Instruments-Production Data Analog-to-Digital Converter (ADC) Bit/Field Name Type Reset Description 1:0 SS0 R/W 0x0 SS0 Priority This field contains a binary-encoded value that specifies the priority encoding of Sample Sequencer 0. A priority encoding of 0 is highest and 3 is lowest. The priorities assigned to the sequencers must be uniquely mapped. The ADC may not operate properly if two or more fields are equal. 352 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) Base 0x4003.8000 Offset 0x028 Type WO, reset 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 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 SS3 SS2 SS1 SS0 RO 0 RO 0 RO 0 RO 0 RO 0 WO - WO - WO - WO - reserved Type Reset reserved Type Reset Bit/Field Name Type Reset Description 31:4 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 3 SS3 WO - SS3 Initiate When set, this bit triggers sampling on Sample Sequencer 3 if the sequencer is enabled in the ADCACTSS register. Only a write by software is valid; a read of this register returns no meaningful data. 2 SS2 WO - SS2 Initiate When set, this bit triggers sampling on Sample Sequencer 2 if the sequencer is enabled in the ADCACTSS register. Only a write by software is valid; a read of this register returns no meaningful data. 1 SS1 WO - SS1 Initiate When set, this bit triggers sampling on Sample Sequencer 1 if the sequencer is enabled in the ADCACTSS register. Only a write by software is valid; a read of this register returns no meaningful data. 0 SS0 WO - SS0 Initiate When set, this bit triggers sampling on Sample Sequencer 0 if the sequencer is enabled in the ADCACTSS register. Only a write by software is valid; a read of this register returns no meaningful data. July 14, 2014 353 Texas Instruments-Production Data Analog-to-Digital Converter (ADC) 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 2 AVG consecutive ADC samples at the specified ADC speed. If AVG is 0, the sample is passed directly through without any averaging. If AVG=6, then 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) Base 0x4003.8000 Offset 0x030 Type R/W, reset 0x0000.0000 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 RO 0 RO 0 R/W 0 reserved Type Reset reserved Type Reset RO 0 Bit/Field Name Type Reset 31:3 reserved RO 0x0000.000 2:0 AVG R/W 0x0 AVG R/W 0 R/W 0 Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. Hardware Averaging Control 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. Value Description 0x0 No hardware oversampling 0x1 2x hardware oversampling 0x2 4x hardware oversampling 0x3 8x hardware oversampling 0x4 16x hardware oversampling 0x5 32x hardware oversampling 0x6 64x hardware oversampling 0x7 Reserved 354 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) Base 0x4003.8000 Offset 0x040 Type R/W, reset 0x0000.0000 31 30 29 reserved Type Reset RO 0 RO 0 RO 0 14 13 15 reserved Type Reset RO 0 RO 0 28 27 MUX7 R/W 0 RO 0 12 11 MUX3 RO 0 R/W 0 26 25 reserved RO 0 RO 0 10 9 reserved RO 0 RO 0 24 23 MUX6 R/W 0 RO 0 8 7 MUX2 RO 0 Bit/Field Name Type Reset 31:29 reserved RO 0 28 MUX7 R/W 0x0 R/W 0 22 21 reserved RO 0 RO 0 6 5 reserved RO 0 RO 0 20 19 MUX5 R/W 0 RO 0 4 3 MUX1 RO 0 R/W 0 18 17 reserved RO 0 RO 0 2 1 reserved RO 0 RO 0 16 MUX4 R/W 0 0 MUX0 RO 0 R/W 0 Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 8th Sample Input Select The MUX7 field is used during the eighth sample of a sequence executed with the sample sequencer. 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. 27:25 reserved RO 0 24 MUX6 R/W 0x0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7th Sample Input Select The MUX6 field is used during the seventh sample of a sequence executed with the sample sequencer. It specifies which of the analog inputs is sampled for the analog-to-digital conversion. 23:21 reserved RO 0 20 MUX5 R/W 0x0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 6th Sample Input Select The MUX5 field is used during the sixth sample of a sequence executed with the sample sequencer. It specifies which of the analog inputs is sampled for the analog-to-digital conversion. 19:17 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. July 14, 2014 355 Texas Instruments-Production Data Analog-to-Digital Converter (ADC) Bit/Field Name Type Reset 16 MUX4 R/W 0x0 Description 5th Sample Input Select The MUX4 field is used during the fifth sample of a sequence executed with the sample sequencer. It specifies which of the analog inputs is sampled for the analog-to-digital conversion. 15:13 reserved RO 0 12 MUX3 R/W 0x0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 4th Sample Input Select The MUX3 field is used during the fourth sample of a sequence executed with the sample sequencer. It specifies which of the analog inputs is sampled for the analog-to-digital conversion. 11:9 reserved RO 0 8 MUX2 R/W 0x0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 3rd Sample Input Select The MUX72 field is used during the third sample of a sequence executed with the sample sequencer. It specifies which of the analog inputs is sampled for the analog-to-digital conversion. 7:5 reserved RO 0 4 MUX1 R/W 0x0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 2nd Sample Input Select The MUX1 field is used during the second sample of a sequence executed with the sample sequencer. It specifies which of the analog inputs is sampled for the analog-to-digital conversion. 3:1 reserved RO 0 0 MUX0 R/W 0x0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 1st Sample Input Select The MUX0 field is used during the first sample of a sequence executed with the sample sequencer. It specifies which of the analog inputs is sampled for the analog-to-digital conversion. 356 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 12: ADC Sample Sequence Control 0 (ADCSSCTL0), offset 0x044 This register contains the configuration information for each sample for a sequence executed with a sample sequencer. 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) Base 0x4003.8000 Offset 0x044 Type R/W, reset 0x0000.0000 31 Type Reset Type Reset 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 TS7 IE7 END7 D7 TS6 IE6 END6 D6 TS5 IE5 END5 D5 TS4 IE4 END4 D4 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 TS3 IE3 END3 D3 TS2 IE2 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 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 Bit/Field Name Type Reset 31 TS7 R/W 0 Description 8th Sample Temp Sensor Select This bit is used during the eighth sample of the sample sequence and and specifies the input source of the sample. When set, the temperature sensor is read. When clear, the input pin specified by the ADCSSMUX register is read. 30 IE7 R/W 0 8th Sample Interrupt Enable This 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. When this bit is clear, the raw interrupt is not asserted. It is legal to have multiple samples within a sequence generate interrupts. 29 END7 R/W 0 8th Sample is End of Sequence 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 8th Sample Diff Input Select 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 7th Sample Temp Sensor Select Same definition as TS7 but used during the seventh sample. July 14, 2014 357 Texas Instruments-Production Data Analog-to-Digital Converter (ADC) Bit/Field Name Type Reset 26 IE6 R/W 0 Description 7th Sample Interrupt Enable Same definition as IE7 but used during the seventh sample. 25 END6 R/W 0 7th Sample is End of Sequence Same definition as END7 but used during the seventh sample. 24 D6 R/W 0 7th Sample Diff Input Select Same definition as D7 but used during the seventh sample. 23 TS5 R/W 0 6th Sample Temp Sensor Select Same definition as TS7 but used during the sixth sample. 22 IE5 R/W 0 6th Sample Interrupt Enable Same definition as IE7 but used during the sixth sample. 21 END5 R/W 0 6th Sample is End of Sequence Same definition as END7 but used during the sixth sample. 20 D5 R/W 0 6th Sample Diff Input Select Same definition as D7 but used during the sixth sample. 19 TS4 R/W 0 5th Sample Temp Sensor Select Same definition as TS7 but used during the fifth sample. 18 IE4 R/W 0 5th Sample Interrupt Enable Same definition as IE7 but used during the fifth sample. 17 END4 R/W 0 5th Sample is End of Sequence Same definition as END7 but used during the fifth sample. 16 D4 R/W 0 5th Sample Diff Input Select Same definition as D7 but used during the fifth sample. 15 TS3 R/W 0 4th Sample Temp Sensor Select Same definition as TS7 but used during the fourth sample. 14 IE3 R/W 0 4th Sample Interrupt Enable Same definition as IE7 but used during the fourth sample. 13 END3 R/W 0 4th Sample is End of Sequence Same definition as END7 but used during the fourth sample. 12 D3 R/W 0 4th Sample Diff Input Select Same definition as D7 but used during the fourth sample. 11 TS2 R/W 0 3rd Sample Temp Sensor Select Same definition as TS7 but used during the third sample. 10 IE2 R/W 0 3rd Sample Interrupt Enable Same definition as IE7 but used during the third sample. 9 END2 R/W 0 3rd Sample is End of Sequence Same definition as END7 but used during the third sample. 358 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Bit/Field Name Type Reset 8 D2 R/W 0 Description 3rd Sample Diff Input Select Same definition as D7 but used during the third sample. 7 TS1 R/W 0 2nd Sample Temp Sensor Select Same definition as TS7 but used during the second sample. 6 IE1 R/W 0 2nd Sample Interrupt Enable Same definition as IE7 but used during the second sample. 5 END1 R/W 0 2nd Sample is End of Sequence Same definition as END7 but used during the second sample. 4 D1 R/W 0 2nd Sample Diff Input Select Same definition as D7 but used during the second sample. 3 TS0 R/W 0 1st Sample Temp Sensor Select Same definition as TS7 but used during the first sample. 2 IE0 R/W 0 1st Sample Interrupt Enable Same definition as IE7 but used during the first sample. 1 END0 R/W 0 1st Sample is End of Sequence Same definition as END7 but used during the first sample. 0 D0 R/W 0 1st Sample Diff Input Select Same definition as D7 but used during the first sample. July 14, 2014 359 Texas Instruments-Production Data Analog-to-Digital Converter (ADC) Register 13: ADC Sample Sequence Result FIFO 0 (ADCSSFIFO0), offset 0x048 Register 14: ADC Sample Sequence Result FIFO 1 (ADCSSFIFO1), offset 0x068 Register 15: ADC Sample Sequence Result FIFO 2 (ADCSSFIFO2), offset 0x088 Register 16: ADC Sample Sequence Result FIFO 3 (ADCSSFIFO3), offset 0x0A8 Important: This register is read-sensitive. See the register description for details. This register contains the conversion results for samples collected with the sample sequencer (the ADCSSFIFO0 register is used for Sample Sequencer 0, ADCSSFIFO1 for Sequencer 1, ADCSSFIFO2 for Sequencer 2, and ADCSSFIFO3 for Sequencer 3). 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) Base 0x4003.8000 Offset 0x048 Type RO, reset 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO - RO - RO - RO - RO - 4 3 2 1 0 RO - RO - RO - RO - RO - reserved Type Reset RO - RO - RO - RO - RO - RO - RO - RO - RO - RO - RO - 15 14 13 12 11 10 9 8 7 6 5 reserved Type Reset RO - RO - RO - RO - DATA RO - RO - RO - RO - RO - RO - RO - Bit/Field Name Type Reset Description 31:10 reserved RO - Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 9:0 DATA RO - Conversion Result Data 360 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 17: ADC Sample Sequence FIFO 0 Status (ADCSSFSTAT0), offset 0x04C Register 18: ADC Sample Sequence FIFO 1 Status (ADCSSFSTAT1), offset 0x06C Register 19: ADC Sample Sequence FIFO 2 Status (ADCSSFSTAT2), offset 0x08C Register 20: ADC Sample Sequence FIFO 3 Status (ADCSSFSTAT3), offset 0x0AC This register provides a window into the sample sequencer, 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. The ADCSSFSTAT0 register provides status on FIFO0, ADCSSFSTAT1 on FIFO1, ADCSSFSTAT2 on FIFO2, and ADCSSFSTAT3 on FIFO3. ADC Sample Sequence FIFO 0 Status (ADCSSFSTAT0) Base 0x4003.8000 Offset 0x04C Type RO, reset 0x0000.0100 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 8 23 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 RO 0 reserved Type Reset reserved Type Reset RO 0 RO 0 FULL RO 0 RO 0 reserved RO 0 RO 0 EMPTY RO 0 Bit/Field Name Type Reset 31:13 reserved RO 0x0 12 FULL RO 0 RO 1 HPTR TPTR Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. FIFO Full When set, this bit indicates that the FIFO is currently full. 11:9 reserved RO 0x0 8 EMPTY RO 1 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. FIFO Empty When set, this bit indicates that the FIFO is currently empty. 7:4 HPTR RO 0x0 FIFO Head Pointer This field contains the current "head" pointer index for the FIFO, that is, the next entry to be written. 3:0 TPTR RO 0x0 FIFO Tail Pointer This field contains the current "tail" pointer index for the FIFO, that is, the next entry to be read. July 14, 2014 361 Texas Instruments-Production Data Analog-to-Digital Converter (ADC) Register 21: ADC Sample Sequence Input Multiplexer Select 1 (ADCSSMUX1), offset 0x060 Register 22: 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 1 or 2. These registers are 16-bits wide and contain information for four possible samples. See the ADCSSMUX0 register on page 355 for detailed bit descriptions. The ADCSSMUX1 register affects Sample Sequencer 1 and the ADCSSMUX2 register affects Sample Sequencer 2. ADC Sample Sequence Input Multiplexer Select 1 (ADCSSMUX1) Base 0x4003.8000 Offset 0x060 Type R/W, reset 0x0000.0000 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 8 23 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 reserved Type Reset reserved Type Reset RO 0 RO 0 MUX3 RO 0 R/W 0 reserved RO 0 RO 0 MUX2 RO 0 Bit/Field Name Type Reset 31:13 reserved RO 0x0000 12 MUX3 R/W 0x0 11:9 reserved RO 0 8 MUX2 R/W 0x0 7:5 reserved RO 0 4 MUX1 R/W 0x0 3:1 reserved RO 0 0 MUX0 R/W 0x0 R/W 0 reserved RO 0 RO 0 MUX1 RO 0 R/W 0 reserved RO 0 RO 0 MUX0 RO 0 R/W 0 Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 4th Sample Input Select Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 3rd Sample Input Select Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 2nd Sample Input Select Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 1st Sample Input Select 362 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 23: ADC Sample Sequence Control 1 (ADCSSCTL1), offset 0x064 Register 24: ADC Sample Sequence Control 2 (ADCSSCTL2), offset 0x084 These registers contain the configuration information for each sample for a sequence executed with Sample Sequencer 1 or 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. These registers are 16-bits wide and contain information for four possible samples. See the ADCSSCTL0 register on page 357 for detailed bit descriptions. The ADCSSCTL1 register configures Sample Sequencer 1 and the ADCSSCTL2 register configures Sample Sequencer 2. ADC Sample Sequence Control 1 (ADCSSCTL1) Base 0x4003.8000 Offset 0x064 Type R/W, reset 0x0000.0000 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 8 TS3 IE3 END3 D3 TS2 IE2 END2 D2 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 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 7 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 reserved Type Reset Type Reset Bit/Field Name Type Reset 31:16 reserved RO 0x0000 15 TS3 R/W 0 Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 4th Sample Temp Sensor Select Same definition as TS7 but used during the fourth sample. 14 IE3 R/W 0 4th Sample Interrupt Enable Same definition as IE7 but used during the fourth sample. 13 END3 R/W 0 4th Sample is End of Sequence Same definition as END7 but used during the fourth sample. 12 D3 R/W 0 4th Sample Diff Input Select Same definition as D7 but used during the fourth sample. 11 TS2 R/W 0 3rd Sample Temp Sensor Select Same definition as TS7 but used during the third sample. 10 IE2 R/W 0 3rd Sample Interrupt Enable Same definition as IE7 but used during the third sample. 9 END2 R/W 0 3rd Sample is End of Sequence Same definition as END7 but used during the third sample. 8 D2 R/W 0 3rd Sample Diff Input Select Same definition as D7 but used during the third sample. 7 TS1 R/W 0 2nd Sample Temp Sensor Select Same definition as TS7 but used during the second sample. July 14, 2014 363 Texas Instruments-Production Data Analog-to-Digital Converter (ADC) Bit/Field Name Type Reset 6 IE1 R/W 0 Description 2nd Sample Interrupt Enable Same definition as IE7 but used during the second sample. 5 END1 R/W 0 2nd Sample is End of Sequence Same definition as END7 but used during the second sample. 4 D1 R/W 0 2nd Sample Diff Input Select Same definition as D7 but used during the second sample. 3 TS0 R/W 0 1st Sample Temp Sensor Select Same definition as TS7 but used during the first sample. 2 IE0 R/W 0 1st Sample Interrupt Enable Same definition as IE7 but used during the first sample. 1 END0 R/W 0 1st Sample is End of Sequence Same definition as END7 but used during the first sample. 0 D0 R/W 0 1st Sample Diff Input Select Same definition as D7 but used during the first sample. 364 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 25: ADC Sample Sequence Input Multiplexer Select 3 (ADCSSMUX3), offset 0x0A0 This register defines the analog input configuration for a sample executed with Sample Sequencer 3. This register is 4-bits wide and contains information for one possible sample. See the ADCSSMUX0 register on page 355 for detailed bit descriptions. ADC Sample Sequence Input Multiplexer Select 3 (ADCSSMUX3) Base 0x4003.8000 Offset 0x0A0 Type R/W, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 reserved Type Reset 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 RO 0 8 7 6 5 4 3 2 1 reserved Type Reset RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 Bit/Field Name Type Reset 31:1 reserved RO 0x0000.000 0 MUX0 R/W 0 RO 0 0 MUX0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 R/W 0 Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 1st Sample Input Select July 14, 2014 365 Texas Instruments-Production Data Analog-to-Digital Converter (ADC) Register 26: ADC Sample Sequence Control 3 (ADCSSCTL3), offset 0x0A4 This register contains the configuration information for a sample 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. See the ADCSSCTL0 register on page 357 for detailed bit descriptions. ADC Sample Sequence Control 3 (ADCSSCTL3) Base 0x4003.8000 Offset 0x0A4 Type R/W, reset 0x0000.0002 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 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 TS0 IE0 END0 D0 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 Bit/Field Name Type Reset 31:4 reserved RO 0x0000.000 3 TS0 R/W 0 Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 1st Sample Temp Sensor Select Same definition as TS7 but used during the first sample. 2 IE0 R/W 0 1st Sample Interrupt Enable Same definition as IE7 but used during the first sample. 1 END0 R/W 1 1st Sample is End of Sequence 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 1st Sample Diff Input Select Same definition as D7 but used during the first sample. 366 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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 0x0000.0001 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) Base 0x4003.8000 Offset 0x100 Type R/W, reset 0x0000.0000 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 8 RO 0 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 7 6 5 4 3 2 1 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 R/W 0 reserved Type Reset reserved Type Reset Bit/Field Name Type Reset 31:1 reserved RO 0x0000.000 0 LB R/W 0 RO 0 LB Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. Loopback Mode Enable When set, forces a loopback within the digital block to provide information on input and unique numbering. The ADCSSFIFOn registers do not provide sample data, but instead provide the 10-bit loopback data as shown below. Bit/Field Name Description 9:6 Continuous Sample Counter CNT 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 Continuation Sample Indicator 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 Differential Sample Indicator When set, indicates that this is a differential sample. 3 TS Temp Sensor Sample Indicator When set, indicates that this is a temperature sensor sample. 2:0 MUX Analog Input Indicator Indicates which analog input is to be sampled. July 14, 2014 367 Texas Instruments-Production Data Universal Asynchronous Receivers/Transmitters (UARTs) 11 Universal Asynchronous Receivers/Transmitters (UARTs) ® Each Stellaris Universal Asynchronous Receiver/Transmitter (UART) has the following features: ■ Two fully programmable 16C550-type UARTs ■ Separate 16x8 transmit (TX) and receive (RX) FIFOs to reduce CPU interrupt service loading ■ Programmable baud-rate generator allowing speeds up to 3.125 Mbps ■ 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 ■ Standard asynchronous communication bits for start, stop, and parity ■ 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 368 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 11.1 Block Diagram Figure 11-1. UART Module Block Diagram System Clock Interrupt Interrupt Control UARTIFLS UARTIM UARTMIS UARTRIS UARTICR Identification Registers UARTPCellID0 UARTPCellID1 UARTPCellID2 UARTPCellID3 UARTPeriphID0 UARTPeriphID1 UARTPeriphID2 UARTPeriphID3 UARTPeriphID4 UARTPeriphID5 UARTPeriphID6 UARTPeriphID7 11.2 TxFIFO 16 x 8 . . . Transmitter UnTx Baud Rate Generator UARTIBRD UARTFBRD UARTDR Receiver Control/Status UnRx RxFIFO 16 x 8 UARTRSR/ECR UARTFR UARTLCRH UARTCTL UARTILPR . . . Signal Description Table 11-1 on page 369 lists the external signals of the UART module and describes the function of each. The UART signals are alternate functions for some GPIO signals and default to be GPIO signals at reset, with the exception of the U0Rx and U0Tx pins which default to the UART function. The column in the table below titled "Pin Assignment" lists the possible GPIO pin placements for these UART signals. The AFSEL bit in the GPIO Alternate Function Select (GPIOAFSEL) register (page 250) should be set to choose the UART function. For more information on configuring GPIOs, see “General-Purpose Input/Outputs (GPIOs)” on page 230. Table 11-1. UART Signals (48QFP) a Pin Name Pin Number Pin Type Buffer Type U0Rx 17 I TTL Description UART module 0 receive. U0Tx 18 O TTL UART module 0 transmit. U1Rx 27 I TTL UART module 1 receive. U1Tx 28 O TTL UART module 1 transmit. a. The TTL designation indicates the pin has TTL-compatible voltage levels. July 14, 2014 369 Texas Instruments-Production Data Universal Asynchronous Receivers/Transmitters (UARTs) 11.3 Functional Description Each 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 386). 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. 11.3.1 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 bits (LSB first), parity bit, and the stop bits according to the programmed configuration in the control registers. See Figure 11-2 on page 370 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 11-2. UART Character Frame UnTX LSB 1 5-8 data bits 0 n Parity bit if enabled Start 11.3.2 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 382) and the 6-bit fractional part is loaded with the UART Fractional Baud-Rate Divisor (UARTFBRD) register (see page 383). 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 = UARTSysClk / (16 * Baud Rate) where UARTSysClk is the system clock connected to the UART. 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. 370 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Along with the UART Line Control, High Byte (UARTLCRH) register (see page 384), 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 11.3.3 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 380) 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 (the UnRx 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 370). The start bit is valid and recognized if UnRx is still low on the eighth cycle of Baud16, otherwise it is ignored. After a valid start bit is detected, 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 UnRx 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. 11.3.4 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 376). 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 384). FIFO status can be monitored via the UART Flag (UARTFR) register (see page 380) 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. July 14, 2014 371 Texas Instruments-Production Data Universal Asynchronous Receivers/Transmitters (UARTs) The trigger points at which the FIFOs generate interrupts is controlled via the UART Interrupt FIFO Level Select (UARTIFLS) register (see page 388). Both FIFOs can be individually configured to trigger interrupts at different levels. Available configurations include 1/8, ¼, ½, ¾, and 7/8. For example, if the ¼ 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 ½ mark. 11.3.5 Interrupts The UART can generate interrupts when the following conditions are observed: ■ Overrun Error ■ Break Error ■ Parity Error ■ Framing Error ■ 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 393). The interrupt events that can trigger a controller-level interrupt are defined in the UART Interrupt Mask (UARTIM ) register (see page 390) 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 392). 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 394). The receive interrupt changes state when one of the following events occurs: ■ If the FIFOs are enabled and the receive FIFO reaches the programmed trigger level, the RXRIS bit is set. The receive interrupt is cleared by reading data from the receive FIFO until it becomes less than the trigger level, or by clearing the interrupt by writing a 1 to the RXIC bit. ■ If the FIFOs are disabled (have a depth of one location) and data is received thereby filling the location, the RXRIS bit is set. The receive interrupt is cleared by performing a single read of the receive FIFO, or by clearing the interrupt by writing a 1 to the RXIC bit. The transmit interrupt changes state when one of the following events occurs: ■ If the FIFOs are enabled and the transmit FIFO progresses through the programmed trigger level, the TXRIS bit is set. The transmit interrupt is based on a transition through level, therefore the FIFO must be written past the programmed trigger level otherwise no further transmit interrupts will be generated. The transmit interrupt is cleared by writing data to the transmit FIFO until it becomes greater than the trigger level, or by clearing the interrupt by writing a 1 to the TXIC bit. 372 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller ■ If the FIFOs are disabled (have a depth of one location) and there is no data present in the transmitters single location, the TXRIS bit is set. It is cleared by performing a single write to the transmit FIFO, or by clearing the interrupt by writing a 1 to the TXIC bit. 11.3.6 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 386). In loopback mode, data transmitted on UnTx is received on the UnRx input. 11.4 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 to use a UART module. For this example, the UART 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 370, 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 382) should be set to 10. The value to be loaded into the UARTFBRD register (see page 383) 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. 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 0x0000.0060). 5. Enable the UART by setting the UARTEN bit in the UARTCTL register. July 14, 2014 373 Texas Instruments-Production Data Universal Asynchronous Receivers/Transmitters (UARTs) 11.5 Register Map Table 11-2 on page 374 lists the UART registers. The offset listed is a hexadecimal increment to the register’s address, relative to that UART’s base address: ■ UART0: 0x4000.C000 ■ UART1: 0x4000.D000 Note that the UART module clock must be enabled before the registers can be programmed (see page 197). There must be a delay of 3 system clocks after the UART module clock is enabled before any UART module registers are accessed. Note: The UART must be disabled (see the UARTEN bit in the UARTCTL register on page 386) 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. Table 11-2. UART Register Map Offset Name Type Reset Description See page 0x000 UARTDR R/W 0x0000.0000 UART Data 376 0x004 UARTRSR/UARTECR R/W 0x0000.0000 UART Receive Status/Error Clear 378 0x018 UARTFR RO 0x0000.0090 UART Flag 380 0x024 UARTIBRD R/W 0x0000.0000 UART Integer Baud-Rate Divisor 382 0x028 UARTFBRD R/W 0x0000.0000 UART Fractional Baud-Rate Divisor 383 0x02C UARTLCRH R/W 0x0000.0000 UART Line Control 384 0x030 UARTCTL R/W 0x0000.0300 UART Control 386 0x034 UARTIFLS R/W 0x0000.0012 UART Interrupt FIFO Level Select 388 0x038 UARTIM R/W 0x0000.0000 UART Interrupt Mask 390 0x03C UARTRIS RO 0x0000.0000 UART Raw Interrupt Status 392 0x040 UARTMIS RO 0x0000.0000 UART Masked Interrupt Status 393 0x044 UARTICR W1C 0x0000.0000 UART Interrupt Clear 394 0xFD0 UARTPeriphID4 RO 0x0000.0000 UART Peripheral Identification 4 396 0xFD4 UARTPeriphID5 RO 0x0000.0000 UART Peripheral Identification 5 397 0xFD8 UARTPeriphID6 RO 0x0000.0000 UART Peripheral Identification 6 398 0xFDC UARTPeriphID7 RO 0x0000.0000 UART Peripheral Identification 7 399 0xFE0 UARTPeriphID0 RO 0x0000.0011 UART Peripheral Identification 0 400 0xFE4 UARTPeriphID1 RO 0x0000.0000 UART Peripheral Identification 1 401 0xFE8 UARTPeriphID2 RO 0x0000.0018 UART Peripheral Identification 2 402 0xFEC UARTPeriphID3 RO 0x0000.0001 UART Peripheral Identification 3 403 0xFF0 UARTPCellID0 RO 0x0000.000D UART PrimeCell Identification 0 404 0xFF4 UARTPCellID1 RO 0x0000.00F0 UART PrimeCell Identification 1 405 374 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Table 11-2. UART Register Map (continued) Offset Name 0xFF8 0xFFC 11.6 Description See page Type Reset UARTPCellID2 RO 0x0000.0005 UART PrimeCell Identification 2 406 UARTPCellID3 RO 0x0000.00B1 UART PrimeCell Identification 3 407 Register Descriptions The remainder of this section lists and describes the UART registers, in numerical order by address offset. July 14, 2014 375 Texas Instruments-Production Data Universal Asynchronous Receivers/Transmitters (UARTs) Register 1: UART Data (UARTDR), offset 0x000 Important: This register is read-sensitive. See the register description for details. 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) UART0 base: 0x4000.C000 UART1 base: 0x4000.D000 Offset 0x000 Type R/W, reset 0x0000.0000 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 8 OE BE PE FE RO 0 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 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 reserved Type Reset reserved Type Reset RO 0 DATA Bit/Field Name Type Reset Description 31:12 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 11 OE RO 0 UART Overrun Error The OE values are defined as follows: Value Description 10 BE RO 0 0 There has been no data loss due to a FIFO overrun. 1 New data was received when the FIFO was full, resulting in data loss. 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 full-word 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. 376 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Bit/Field Name Type Reset 9 PE RO 0 Description 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. 8 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). 7:0 DATA R/W 0 Data Transmitted or Received When written, the data that is to be transmitted via the UART. When read, the data that was received by the UART. July 14, 2014 377 Texas Instruments-Production Data Universal Asynchronous Receivers/Transmitters (UARTs) 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. The UARTRSR register cannot be written. 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. Reads UART Receive Status/Error Clear (UARTRSR/UARTECR) UART0 base: 0x4000.C000 UART1 base: 0x4000.D000 Offset 0x004 Type RO, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 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 15 14 13 12 11 10 9 8 7 6 5 4 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 3 2 1 0 OE BE PE FE RO 0 RO 0 RO 0 RO 0 Bit/Field Name Type Reset Description 31:4 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 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. 2 BE RO 0 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 full-word 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. 378 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Bit/Field Name Type Reset 1 PE RO 0 Description 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. Writes UART Receive Status/Error Clear (UARTRSR/UARTECR) UART0 base: 0x4000.C000 UART1 base: 0x4000.D000 Offset 0x004 Type WO, reset 0x0000.0000 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 WO 0 WO 0 WO 0 WO 0 WO 0 WO 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 WO 0 WO 0 WO 0 WO 0 WO 0 WO 0 WO 0 WO 0 WO 0 reserved Type Reset reserved Type Reset DATA WO 0 Bit/Field Name Type Reset Description 31:8 reserved WO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 DATA WO 0 Error Clear A write to this register of any data clears the framing, parity, break, and overrun flags. July 14, 2014 379 Texas Instruments-Production Data Universal Asynchronous Receivers/Transmitters (UARTs) 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) UART0 base: 0x4000.C000 UART1 base: 0x4000.D000 Offset 0x018 Type RO, reset 0x0000.0090 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 8 RO 0 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 7 6 5 4 3 2 1 0 TXFE RXFF TXFF RXFE BUSY 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 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 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. 4 RXFE RO 1 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. 380 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Bit/Field Name Type Reset Description 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 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. July 14, 2014 381 Texas Instruments-Production Data Universal Asynchronous Receivers/Transmitters (UARTs) 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 370 for configuration details. UART Integer Baud-Rate Divisor (UARTIBRD) UART0 base: 0x4000.C000 UART1 base: 0x4000.D000 Offset 0x024 Type R/W, reset 0x0000.0000 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 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 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 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 31:16 reserved RO 0 15:0 DIVINT R/W 0x0000 Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. Integer Baud-Rate Divisor 382 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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 370 for configuration details. UART Fractional Baud-Rate Divisor (UARTFBRD) UART0 base: 0x4000.C000 UART1 base: 0x4000.D000 Offset 0x028 Type R/W, reset 0x0000.0000 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 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 reserved Type Reset reserved Type Reset RO 0 DIVFRAC R/W 0 Bit/Field Name Type Reset Description 31:6 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 5:0 DIVFRAC R/W 0x000 Fractional Baud-Rate Divisor July 14, 2014 383 Texas Instruments-Production Data Universal Asynchronous Receivers/Transmitters (UARTs) 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) UART0 base: 0x4000.C000 UART1 base: 0x4000.D000 Offset 0x02C Type R/W, reset 0x0000.0000 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 7 6 reserved Type Reset RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 15 14 13 12 11 10 9 8 reserved Type Reset RO 0 RO 0 RO 0 RO 0 SPS RO 0 RO 0 RO 0 RO 0 R/W 0 5 WLEN R/W 0 R/W 0 4 3 2 1 0 FEN STP2 EPS PEN BRK R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 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: Value Description 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. 384 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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. July 14, 2014 385 Texas Instruments-Production Data Universal Asynchronous Receivers/Transmitters (UARTs) 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. Note: The UARTCTL register should not be changed while the UART is enabled or else the results are unpredictable. The following sequence is recommended for making changes to the UARTCTL register. 1. Disable the UART. 2. Wait for the end of transmission or reception of the current character. 3. Flush the transmit FIFO by disabling bit 4 (FEN) in the line control register (UARTLCRH). 4. Reprogram the control register. 5. Enable the UART. UART Control (UARTCTL) UART0 base: 0x4000.C000 UART1 base: 0x4000.D000 Offset 0x030 Type R/W, reset 0x0000.0300 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 RXE TXE LBE RO 0 RO 0 RO 0 RO 0 RO 0 R/W 1 R/W 1 R/W 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 reserved Type Reset reserved Type Reset RO 0 reserved UARTEN R/W 0 Bit/Field Name Type Reset Description 31:10 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 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. Note: 8 TXE R/W 1 To enable reception, the UARTEN bit must also be set. 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. Note: To enable transmission, the UARTEN bit must also be set. 386 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Bit/Field Name Type Reset 7 LBE R/W 0 Description 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 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 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. July 14, 2014 387 Texas Instruments-Production Data 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) UART0 base: 0x4000.C000 UART1 base: 0x4000.D000 Offset 0x034 Type R/W, reset 0x0000.0012 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 R/W 0 R/W 0 R/W 0 reserved Type Reset reserved Type Reset RO 0 RXIFLSEL R/W 1 TXIFLSEL R/W 1 R/W 0 Bit/Field Name Type Reset Description 31:6 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 5:3 RXIFLSEL R/W 0x2 UART Receive Interrupt FIFO Level Select The trigger points for the receive interrupt are as follows: Value Description 0x0 RX FIFO ≥ ⅛ full 0x1 RX FIFO ≥ ¼ full 0x2 RX FIFO ≥ ½ full (default) 0x3 RX FIFO ≥ ¾ full 0x4 RX FIFO ≥ ⅞ full 0x5-0x7 Reserved 388 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Bit/Field Name Type Reset 2:0 TXIFLSEL R/W 0x2 Description UART Transmit Interrupt FIFO Level Select The trigger points for the transmit interrupt are as follows: Value Description 0x0 TX FIFO ≤ ⅞ empty 0x1 TX FIFO ≤ ¾ empty 0x2 TX FIFO ≤ ½ empty (default) 0x3 TX FIFO ≤ ¼ empty 0x4 TX FIFO ≤ ⅛ empty 0x5-0x7 Reserved July 14, 2014 389 Texas Instruments-Production Data Universal Asynchronous Receivers/Transmitters (UARTs) 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) UART0 base: 0x4000.C000 UART1 base: 0x4000.D000 Offset 0x038 Type R/W, reset 0x0000.0000 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 3 2 1 0 RO 0 RO 0 reserved Type Reset RO 0 RO 0 15 14 RO 0 RO 0 RO 0 13 12 11 RO 0 reserved Type Reset RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 10 9 8 7 6 5 4 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 reserved RO 0 RO 0 Bit/Field Name Type Reset Description 31:11 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 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. 5 TXIM R/W 0 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. 390 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Bit/Field Name Type Reset Description 3:0 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. July 14, 2014 391 Texas Instruments-Production Data Universal Asynchronous Receivers/Transmitters (UARTs) 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) UART0 base: 0x4000.C000 UART1 base: 0x4000.D000 Offset 0x03C Type RO, reset 0x0000.0000 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 OERIS 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 BERIS PERIS FERIS RTRIS TXRIS RXRIS 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 Bit/Field Name Type Reset Description 31:11 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 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 0x0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 392 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) UART0 base: 0x4000.C000 UART1 base: 0x4000.D000 Offset 0x040 Type RO, reset 0x0000.0000 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 OEMIS 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 BEMIS PEMIS FEMIS RTMIS TXMIS RXMIS 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 Bit/Field Name Type Reset Description 31:11 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 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 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. July 14, 2014 393 Texas Instruments-Production Data Universal Asynchronous Receivers/Transmitters (UARTs) 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) UART0 base: 0x4000.C000 UART1 base: 0x4000.D000 Offset 0x044 Type W1C, reset 0x0000.0000 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 OEIC RO 0 RO 0 RO 0 RO 0 W1C 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 BEIC PEIC FEIC RTIC TXIC RXIC 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 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 10 OEIC W1C 0 Overrun Error Interrupt Clear The OEIC values are defined as follows: Value Description 9 BEIC W1C 0 0 No effect on the interrupt. 1 Clears interrupt. Break Error Interrupt Clear The BEIC values are defined as follows: Value Description 8 PEIC W1C 0 0 No effect on the interrupt. 1 Clears interrupt. Parity Error Interrupt Clear The PEIC values are defined as follows: Value Description 7 FEIC W1C 0 0 No effect on the interrupt. 1 Clears interrupt. Framing Error Interrupt Clear The FEIC values are defined as follows: Value Description 0 No effect on the interrupt. 1 Clears interrupt. 394 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Bit/Field Name Type Reset 6 RTIC W1C 0 Description Receive Time-Out Interrupt Clear The RTIC values are defined as follows: Value Description 5 TXIC W1C 0 0 No effect on the interrupt. 1 Clears interrupt. Transmit Interrupt Clear The TXIC values are defined as follows: Value Description 4 RXIC W1C 0 0 No effect on the interrupt. 1 Clears interrupt. Receive Interrupt Clear The RXIC values are defined as follows: Value Description 3:0 reserved RO 0x00 0 No effect on the interrupt. 1 Clears interrupt. Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. July 14, 2014 395 Texas Instruments-Production Data 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) UART0 base: 0x4000.C000 UART1 base: 0x4000.D000 Offset 0xFD0 Type RO, reset 0x0000.0000 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 RO 0 RO 0 RO 0 RO 0 RO 0 reserved Type Reset reserved Type Reset PID4 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 PID4 RO 0x0000 UART Peripheral ID Register[7:0] Can be used by software to identify the presence of this peripheral. 396 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) UART0 base: 0x4000.C000 UART1 base: 0x4000.D000 Offset 0xFD4 Type RO, reset 0x0000.0000 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 RO 0 RO 0 RO 0 RO 0 RO 0 reserved Type Reset reserved Type Reset PID5 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 PID5 RO 0x0000 UART Peripheral ID Register[15:8] Can be used by software to identify the presence of this peripheral. July 14, 2014 397 Texas Instruments-Production Data 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) UART0 base: 0x4000.C000 UART1 base: 0x4000.D000 Offset 0xFD8 Type RO, reset 0x0000.0000 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 RO 0 RO 0 RO 0 RO 0 RO 0 reserved Type Reset reserved Type Reset PID6 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 PID6 RO 0x0000 UART Peripheral ID Register[23:16] Can be used by software to identify the presence of this peripheral. 398 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) UART0 base: 0x4000.C000 UART1 base: 0x4000.D000 Offset 0xFDC Type RO, reset 0x0000.0000 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 RO 0 RO 0 RO 0 RO 0 RO 0 reserved Type Reset reserved Type Reset PID7 RO 0 Bit/Field Name Type Reset 31:8 reserved RO 0 7:0 PID7 RO 0x0000 Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. UART Peripheral ID Register[31:24] Can be used by software to identify the presence of this peripheral. July 14, 2014 399 Texas Instruments-Production Data 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) UART0 base: 0x4000.C000 UART1 base: 0x4000.D000 Offset 0xFE0 Type RO, reset 0x0000.0011 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 RO 1 RO 0 RO 0 RO 0 RO 1 reserved Type Reset reserved Type Reset PID0 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 PID0 RO 0x11 UART Peripheral ID Register[7:0] Can be used by software to identify the presence of this peripheral. 400 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) UART0 base: 0x4000.C000 UART1 base: 0x4000.D000 Offset 0xFE4 Type RO, reset 0x0000.0000 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 RO 0 RO 0 RO 0 RO 0 RO 0 reserved Type Reset reserved Type Reset PID1 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 PID1 RO 0x00 UART Peripheral ID Register[15:8] Can be used by software to identify the presence of this peripheral. July 14, 2014 401 Texas Instruments-Production Data 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) UART0 base: 0x4000.C000 UART1 base: 0x4000.D000 Offset 0xFE8 Type RO, reset 0x0000.0018 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 RO 1 RO 1 RO 0 RO 0 RO 0 reserved Type Reset reserved Type Reset PID2 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 PID2 RO 0x18 UART Peripheral ID Register[23:16] Can be used by software to identify the presence of this peripheral. 402 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) UART0 base: 0x4000.C000 UART1 base: 0x4000.D000 Offset 0xFEC Type RO, reset 0x0000.0001 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 RO 0 RO 0 RO 0 RO 0 RO 1 reserved Type Reset reserved Type Reset PID3 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 PID3 RO 0x01 UART Peripheral ID Register[31:24] Can be used by software to identify the presence of this peripheral. July 14, 2014 403 Texas Instruments-Production Data 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) UART0 base: 0x4000.C000 UART1 base: 0x4000.D000 Offset 0xFF0 Type RO, reset 0x0000.000D 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 RO 0 RO 1 RO 1 RO 0 RO 1 reserved Type Reset reserved Type Reset CID0 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 CID0 RO 0x0D UART PrimeCell ID Register[7:0] Provides software a standard cross-peripheral identification system. 404 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) UART0 base: 0x4000.C000 UART1 base: 0x4000.D000 Offset 0xFF4 Type RO, reset 0x0000.00F0 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 1 RO 1 RO 1 RO 1 RO 0 RO 0 RO 0 RO 0 reserved Type Reset reserved Type Reset CID1 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 CID1 RO 0xF0 UART PrimeCell ID Register[15:8] Provides software a standard cross-peripheral identification system. July 14, 2014 405 Texas Instruments-Production Data 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) UART0 base: 0x4000.C000 UART1 base: 0x4000.D000 Offset 0xFF8 Type RO, reset 0x0000.0005 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 RO 0 RO 0 RO 1 RO 0 RO 1 reserved Type Reset reserved Type Reset CID2 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 CID2 RO 0x05 UART PrimeCell ID Register[23:16] Provides software a standard cross-peripheral identification system. 406 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) UART0 base: 0x4000.C000 UART1 base: 0x4000.D000 Offset 0xFFC Type RO, reset 0x0000.00B1 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 1 RO 0 RO 1 RO 1 RO 0 RO 0 RO 0 RO 1 reserved Type Reset reserved Type Reset CID3 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 CID3 RO 0xB1 UART PrimeCell ID Register[31:24] Provides software a standard cross-peripheral identification system. July 14, 2014 407 Texas Instruments-Production Data Synchronous Serial Interface (SSI) 12 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 module has the following features: ■ 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 12.1 Block Diagram Figure 12-1. SSI Module Block Diagram Interrupt Interrupt Control SSIIM SSIMIS Control/ Status SSIRIS SSIICR SSICR0 SSICR1 TxFIFO 8 x16 . . . SSITx SSISR SSIRx SSIDR RxFIFO 8 x16 System Clock SSIPCellID0 Identification Registers SSIPeriphID0 SSIPeriphID 4 SSIPCellID1 SSIPeriphID 1 SSIPeriphID 5 SSIPCellID2 SSIPeriphID 2 SSIPeriphID 6 SSIPCellID3 SSIPeriphID 3 SSIPeriphID7 12.2 Clock Prescaler Transmit / Receive Logic SSIClk SSIFss . . . SSICPSR Signal Description Table 12-1 on page 409 lists the external signals of the SSI module and describes the function of each. The SSI signals are alternate functions for some GPIO signals and default to be GPIO signals 408 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller at reset., with the exception of the SSI0Clk, SSI0Fss, SSI0Rx, and SSI0Tx pins which default to the SSI function. The column in the table below titled "Pin Assignment" lists the possible GPIO pin placements for the SSI signals. The AFSEL bit in the GPIO Alternate Function Select (GPIOAFSEL) register (page 250) should be set to choose the SSI function. For more information on configuring GPIOs, see “General-Purpose Input/Outputs (GPIOs)” on page 230. Table 12-1. SSI Signals (48QFP) a Pin Name Pin Number Pin Type Buffer Type Description SSIClk 19 I/O TTL SSI clock. SSIFss 20 I/O TTL SSI frame. SSIRx 21 I TTL SSI receive. SSITx 22 O TTL SSI transmit. a. The TTL designation indicates the pin has TTL-compatible voltage levels. 12.3 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. 12.3.1 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 1.5 MHz and higher, although maximum bit rate is determined by peripheral devices. The serial bit rate is derived by dividing down the input clock (FSysClk). 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 428). 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 421). The frequency of the output clock SSIClk is defined by: SSIClk = FSysClk / (CPSDVSR * (1 + SCR)) Note: 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 “Synchronous Serial Interface (SSI)” on page 552 to view SSI timing parameters. 12.3.2 FIFO Operation 12.3.2.1 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 425), 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. In slave mode, the SSI transmits data each time the master initiates a transaction. If the transmit FIFO is empty and the master initiates, the slave transmits the 8th most recent value in the transmit FIFO. If less than 8 values have been written to the transmit FIFO since the SSI module clock was July 14, 2014 409 Texas Instruments-Production Data Synchronous Serial Interface (SSI) enabled using the SSI bit in the RGCG1 register, then 0 is transmitted. Care should be taken to ensure that valid data is in the FIFO as needed. The SSI can be configured to generate an interrupt when the FIFO is empty. 12.3.2.2 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. 12.3.3 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 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 429). 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 431 and page 432, respectively). 12.3.4 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. 410 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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. 12.3.4.1 Texas Instruments Synchronous Serial Frame Format Figure 12-2 on page 411 shows the Texas Instruments synchronous serial frame format for a single transmitted frame. Figure 12-2. TI Synchronous Serial Frame Format (Single Transfer) SSIClk SSIFss SSITx/SSIRx MSB LSB 4 to 16 bits 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 12-3 on page 412 shows the Texas Instruments synchronous serial frame format when back-to-back frames are transmitted. July 14, 2014 411 Texas Instruments-Production Data Synchronous Serial Interface (SSI) Figure 12-3. TI Synchronous Serial Frame Format (Continuous Transfer) SSIClk SSIFss SSITx/SSIRx MSB LSB 4 to 16 bits 12.3.4.2 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. 12.3.4.3 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 12-4 on page 412 and Figure 12-5 on page 413. Figure 12-4. Freescale SPI Format (Single Transfer) with SPO=0 and SPH=0 SSIClk SSIFss SSIRx LSB MSB Q 4 to 16 bits SSITx MSB Note: LSB Q is undefined. 412 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Figure 12-5. Freescale SPI Format (Continuous Transfer) with SPO=0 and SPH=0 SSIClk SSIFss SSIRx LSB LSB MSB MSB 4 to16 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. 12.3.4.4 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 12-6 on page 414, which covers both single and continuous transfers. July 14, 2014 413 Texas Instruments-Production Data Synchronous Serial Interface (SSI) Figure 12-6. Freescale SPI Frame Format with SPO=0 and SPH=1 SSIClk SSIFss SSIRx Q MSB Q LSB Q 4 to 16 bits SSITx LSB MSB Note: Q is undefined. 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. 12.3.4.5 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 12-7 on page 414 and Figure 12-8 on page 415. Figure 12-7. Freescale SPI Frame Format (Single Transfer) with SPO=1 and SPH=0 SSIClk SSIFss SSIRx MSB LSB Q 4 to 16 bits SSITx LSB MSB Note: Q is undefined. 414 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Figure 12-8. Freescale SPI Frame Format (Continuous Transfer) with SPO=1 and SPH=0 SSIClk SSIFss SSITx/SSIRx MSB LSB 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. 12.3.4.6 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 12-9 on page 416, which covers both single and continuous transfers. July 14, 2014 415 Texas Instruments-Production Data Synchronous Serial Interface (SSI) Figure 12-9. Freescale SPI Frame Format with SPO=1 and SPH=1 SSIClk SSIFss SSIRx Q MSB LSB Q 4 to 16 bits MSB SSITx Note: LSB Q is undefined. 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. 12.3.4.7 MICROWIRE Frame Format Figure 12-10 on page 416 shows the MICROWIRE frame format, again for a single frame. Figure 12-11 on page 417 shows the same format when back-to-back frames are transmitted. Figure 12-10. MICROWIRE Frame Format (Single Frame) SSIClk SSIFss SSITx LSB MSB 8-bit control SSIRx 0 MSB LSB 4 to 16 bits output data 416 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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 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 12-11. 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. July 14, 2014 417 Texas Instruments-Production Data Synchronous Serial Interface (SSI) Figure 12-12 on page 418 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. Figure 12-12. 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 12.4 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 0x0000.0000. b. For slave mode (output enabled), set the SSICR1 register to 0x0000.0004. c. For slave mode (output disabled), set the SSICR1 register to 0x0000.000C. 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 418 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller ■ 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 0x0000.0000. 3. Write the SSICPSR register with a value of 0x0000.0002. 4. Write the SSICR0 register with a value of 0x0000.09C7. 5. The SSI is then enabled by setting the SSE bit in the SSICR1 register to 1. 12.5 Register Map Table 12-2 on page 419 lists the SSI registers. The offset listed is a hexadecimal increment to the register’s address, relative to that SSI module’s base address: ■ SSI0: 0x4000.8000 Note that the SSI module clock must be enabled before the registers can be programmed (see page 197). There must be a delay of 3 system clocks after the SSI module clock is enabled before any SSI module registers are accessed. Note: The SSI must be disabled (see the SSE bit in the SSICR1 register) before any of the control registers are reprogrammed. Table 12-2. SSI Register Map Offset Name Type Reset Description See page 0x000 SSICR0 R/W 0x0000.0000 SSI Control 0 421 0x004 SSICR1 R/W 0x0000.0000 SSI Control 1 423 0x008 SSIDR R/W 0x0000.0000 SSI Data 425 0x00C SSISR RO 0x0000.0003 SSI Status 426 0x010 SSICPSR R/W 0x0000.0000 SSI Clock Prescale 428 0x014 SSIIM R/W 0x0000.0000 SSI Interrupt Mask 429 0x018 SSIRIS RO 0x0000.0008 SSI Raw Interrupt Status 431 0x01C SSIMIS RO 0x0000.0000 SSI Masked Interrupt Status 432 July 14, 2014 419 Texas Instruments-Production Data Synchronous Serial Interface (SSI) Table 12-2. SSI Register Map (continued) Name Type Reset 0x020 SSIICR W1C 0x0000.0000 SSI Interrupt Clear 433 0xFD0 SSIPeriphID4 RO 0x0000.0000 SSI Peripheral Identification 4 434 0xFD4 SSIPeriphID5 RO 0x0000.0000 SSI Peripheral Identification 5 435 0xFD8 SSIPeriphID6 RO 0x0000.0000 SSI Peripheral Identification 6 436 0xFDC SSIPeriphID7 RO 0x0000.0000 SSI Peripheral Identification 7 437 0xFE0 SSIPeriphID0 RO 0x0000.0022 SSI Peripheral Identification 0 438 0xFE4 SSIPeriphID1 RO 0x0000.0000 SSI Peripheral Identification 1 439 0xFE8 SSIPeriphID2 RO 0x0000.0018 SSI Peripheral Identification 2 440 0xFEC SSIPeriphID3 RO 0x0000.0001 SSI Peripheral Identification 3 441 0xFF0 SSIPCellID0 RO 0x0000.000D SSI PrimeCell Identification 0 442 0xFF4 SSIPCellID1 RO 0x0000.00F0 SSI PrimeCell Identification 1 443 0xFF8 SSIPCellID2 RO 0x0000.0005 SSI PrimeCell Identification 2 444 0xFFC SSIPCellID3 RO 0x0000.00B1 SSI PrimeCell Identification 3 445 12.6 Description See page Offset Register Descriptions The remainder of this section lists and describes the SSI registers, in numerical order by address offset. 420 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) SSI0 base: 0x4000.8000 Offset 0x000 Type R/W, reset 0x0000.0000 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 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 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 SPH SPO 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 FRF R/W 0 DSS Bit/Field Name Type Reset Description 31:16 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 15:8 SCR R/W 0x0000 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. 5:4 FRF R/W 0x0 SSI Frame Format Select The FRF values are defined as follows: Value Frame Format 0x0 Freescale SPI Frame Format 0x1 Texas Instruments Synchronous Serial Frame Format 0x2 MICROWIRE Frame Format 0x3 Reserved July 14, 2014 421 Texas Instruments-Production Data Synchronous Serial Interface (SSI) Bit/Field Name Type Reset Description 3:0 DSS R/W 0x00 SSI Data Size Select The DSS values are defined as follows: Value Data Size 0x0-0x2 Reserved 0x3 4-bit data 0x4 5-bit data 0x5 6-bit data 0x6 7-bit data 0x7 8-bit data 0x8 9-bit data 0x9 10-bit data 0xA 11-bit data 0xB 12-bit data 0xC 13-bit data 0xD 14-bit data 0xE 15-bit data 0xF 16-bit data 422 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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 (SSICR1) SSI0 base: 0x4000.8000 Offset 0x004 Type R/W, reset 0x0000.0000 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 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 SOD MS SSE LBM 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 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 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. The SOD values are defined as follows: Value Description 2 MS R/W 0 0 SSI can drive SSITx output in Slave Output mode. 1 SSI must not drive the SSITx output in Slave mode. SSI Master/Slave Select This bit selects Master or Slave mode and can be modified only when SSI is disabled (SSE=0). The MS values are defined as follows: Value Description 0 Device configured as a master. 1 Device configured as a slave. July 14, 2014 423 Texas Instruments-Production Data Synchronous Serial Interface (SSI) Bit/Field Name Type Reset 1 SSE R/W 0 Description SSI Synchronous Serial Port Enable Setting this bit enables SSI operation. The SSE values are defined as follows: Value Description 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. The LBM values are defined as follows: Value Description 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. 424 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 3: SSI Data (SSIDR), offset 0x008 Important: This register is read-sensitive. See the register description for details. 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) SSI0 base: 0x4000.8000 Offset 0x008 Type R/W, reset 0x0000.0000 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 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 reserved Type Reset RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 15 14 13 12 11 10 9 8 DATA Type Reset 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 31:16 reserved RO 0x0000 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 15:0 DATA R/W 0x0000 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. July 14, 2014 425 Texas Instruments-Production Data Synchronous Serial Interface (SSI) 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) SSI0 base: 0x4000.8000 Offset 0x00C Type RO, reset 0x0000.0003 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 BSY RFF RNE TNF TFE RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 1 R0 1 reserved Type Reset reserved Type Reset RO 0 Bit/Field Name Type Reset Description 31:5 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 4 BSY RO 0 SSI Busy Bit The BSY values are defined as follows: Value Description 3 RFF RO 0 0 SSI is idle. 1 SSI is currently transmitting and/or receiving a frame, or the transmit FIFO is not empty. SSI Receive FIFO Full The RFF values are defined as follows: Value Description 2 RNE RO 0 0 Receive FIFO is not full. 1 Receive FIFO is full. SSI Receive FIFO Not Empty The RNE values are defined as follows: Value Description 1 TNF RO 1 0 Receive FIFO is empty. 1 Receive FIFO is not empty. SSI Transmit FIFO Not Full The TNF values are defined as follows: Value Description 0 Transmit FIFO is full. 1 Transmit FIFO is not full. 426 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Bit/Field Name Type Reset 0 TFE R0 1 Description SSI Transmit FIFO Empty The TFE values are defined as follows: Value Description 0 Transmit FIFO is not empty. 1 Transmit FIFO is empty. July 14, 2014 427 Texas Instruments-Production Data 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) SSI0 base: 0x4000.8000 Offset 0x010 Type R/W, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 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 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 reserved Type Reset RO 0 RO 0 RO 0 RO 0 CPSDVSR RO 0 RO 0 RO 0 RO 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 CPSDVSR R/W 0x00 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. 428 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) SSI0 base: 0x4000.8000 Offset 0x014 Type R/W, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 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 15 14 13 12 11 10 9 8 7 6 5 4 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 3 2 1 0 TXIM RXIM RTIM RORIM R/W 0 R/W 0 R/W 0 R/W 0 Bit/Field Name Type Reset Description 31:4 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 3 TXIM R/W 0 SSI Transmit FIFO Interrupt Mask The TXIM values are defined as follows: Value Description 2 RXIM R/W 0 0 TX FIFO half-empty or less condition interrupt is masked. 1 TX FIFO half-empty or less condition interrupt is not masked. SSI Receive FIFO Interrupt Mask The RXIM values are defined as follows: Value Description 1 RTIM R/W 0 0 RX FIFO half-full or more condition interrupt is masked. 1 RX FIFO half-full or more condition interrupt is not masked. SSI Receive Time-Out Interrupt Mask The RTIM values are defined as follows: Value Description 0 RX FIFO time-out interrupt is masked. 1 RX FIFO time-out interrupt is not masked. July 14, 2014 429 Texas Instruments-Production Data Synchronous Serial Interface (SSI) Bit/Field Name Type Reset 0 RORIM R/W 0 Description SSI Receive Overrun Interrupt Mask The RORIM values are defined as follows: Value Description 0 RX FIFO overrun interrupt is masked. 1 RX FIFO overrun interrupt is not masked. 430 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) SSI0 base: 0x4000.8000 Offset 0x018 Type RO, reset 0x0000.0008 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 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 TXRIS RXRIS RTRIS RORRIS RO 0 RO 0 RO 0 RO 0 RO 0 RO 1 RO 0 RO 0 RO 0 reserved Type Reset reserved Type Reset Bit/Field Name Type Reset Description 31:4 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 3 TXRIS RO 1 SSI Transmit FIFO Raw Interrupt Status Indicates that the transmit FIFO is half empty 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. July 14, 2014 431 Texas Instruments-Production Data Synchronous Serial Interface (SSI) 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) SSI0 base: 0x4000.8000 Offset 0x01C Type RO, reset 0x0000.0000 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 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 TXMIS RXMIS RTMIS RORMIS 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 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 3 TXMIS RO 0 SSI Transmit FIFO Masked Interrupt Status Indicates that the transmit FIFO is half empty 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. 432 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) SSI0 base: 0x4000.8000 Offset 0x020 Type W1C, reset 0x0000.0000 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 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 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 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 1 RTIC W1C 0 SSI Receive Time-Out Interrupt Clear The RTIC values are defined as follows: Value Description 0 RORIC W1C 0 0 No effect on interrupt. 1 Clears interrupt. SSI Receive Overrun Interrupt Clear The RORIC values are defined as follows: Value Description 0 No effect on interrupt. 1 Clears interrupt. July 14, 2014 433 Texas Instruments-Production Data Synchronous Serial Interface (SSI) 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) SSI0 base: 0x4000.8000 Offset 0xFD0 Type RO, reset 0x0000.0000 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 RO 0 RO 0 RO 0 RO 0 RO 0 reserved Type Reset reserved Type Reset PID4 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 PID4 RO 0x00 SSI Peripheral ID Register[7:0] Can be used by software to identify the presence of this peripheral. 434 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) SSI0 base: 0x4000.8000 Offset 0xFD4 Type RO, reset 0x0000.0000 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 RO 0 RO 0 RO 0 RO 0 RO 0 reserved Type Reset reserved Type Reset PID5 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 PID5 RO 0x00 SSI Peripheral ID Register[15:8] Can be used by software to identify the presence of this peripheral. July 14, 2014 435 Texas Instruments-Production Data Synchronous Serial Interface (SSI) 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) SSI0 base: 0x4000.8000 Offset 0xFD8 Type RO, reset 0x0000.0000 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 RO 0 RO 0 RO 0 RO 0 RO 0 reserved Type Reset reserved Type Reset PID6 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 PID6 RO 0x00 SSI Peripheral ID Register[23:16] Can be used by software to identify the presence of this peripheral. 436 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) SSI0 base: 0x4000.8000 Offset 0xFDC Type RO, reset 0x0000.0000 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 RO 0 RO 0 RO 0 RO 0 RO 0 reserved Type Reset reserved Type Reset PID7 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 PID7 RO 0x00 SSI Peripheral ID Register[31:24] Can be used by software to identify the presence of this peripheral. July 14, 2014 437 Texas Instruments-Production Data Synchronous Serial Interface (SSI) 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) SSI0 base: 0x4000.8000 Offset 0xFE0 Type RO, reset 0x0000.0022 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 1 RO 0 RO 0 RO 0 RO 1 RO 0 reserved Type Reset reserved Type Reset PID0 RO 0 Bit/Field Name Type Reset 31:8 reserved RO 0 7:0 PID0 RO 0x22 Description Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. SSI Peripheral ID Register[7:0] Can be used by software to identify the presence of this peripheral. 438 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) SSI0 base: 0x4000.8000 Offset 0xFE4 Type RO, reset 0x0000.0000 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 RO 0 RO 0 RO 0 RO 0 RO 0 reserved Type Reset reserved Type Reset PID1 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 PID1 RO 0x00 SSI Peripheral ID Register [15:8] Can be used by software to identify the presence of this peripheral. July 14, 2014 439 Texas Instruments-Production Data Synchronous Serial Interface (SSI) 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) SSI0 base: 0x4000.8000 Offset 0xFE8 Type RO, reset 0x0000.0018 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 RO 1 RO 1 RO 0 RO 0 RO 0 reserved Type Reset reserved Type Reset PID2 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 PID2 RO 0x18 SSI Peripheral ID Register [23:16] Can be used by software to identify the presence of this peripheral. 440 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) SSI0 base: 0x4000.8000 Offset 0xFEC Type RO, reset 0x0000.0001 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 RO 0 RO 0 RO 0 RO 0 RO 1 reserved Type Reset reserved Type Reset PID3 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 PID3 RO 0x01 SSI Peripheral ID Register [31:24] Can be used by software to identify the presence of this peripheral. July 14, 2014 441 Texas Instruments-Production Data Synchronous Serial Interface (SSI) 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) SSI0 base: 0x4000.8000 Offset 0xFF0 Type RO, reset 0x0000.000D 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 RO 0 RO 1 RO 1 RO 0 RO 1 reserved Type Reset reserved Type Reset CID0 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 CID0 RO 0x0D SSI PrimeCell ID Register [7:0] Provides software a standard cross-peripheral identification system. 442 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) SSI0 base: 0x4000.8000 Offset 0xFF4 Type RO, reset 0x0000.00F0 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 1 RO 1 RO 1 RO 1 RO 0 RO 0 RO 0 RO 0 reserved Type Reset reserved Type Reset CID1 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 CID1 RO 0xF0 SSI PrimeCell ID Register [15:8] Provides software a standard cross-peripheral identification system. July 14, 2014 443 Texas Instruments-Production Data Synchronous Serial Interface (SSI) 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) SSI0 base: 0x4000.8000 Offset 0xFF8 Type RO, reset 0x0000.0005 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 RO 0 RO 0 RO 1 RO 0 RO 1 reserved Type Reset reserved Type Reset CID2 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 CID2 RO 0x05 SSI PrimeCell ID Register [23:16] Provides software a standard cross-peripheral identification system. 444 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) SSI0 base: 0x4000.8000 Offset 0xFFC Type RO, reset 0x0000.00B1 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 1 RO 0 RO 1 RO 1 RO 0 RO 0 RO 0 RO 1 reserved Type Reset reserved Type Reset CID3 RO 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 CID3 RO 0xB1 SSI PrimeCell ID Register [31:24] Provides software a standard cross-peripheral identification system. July 14, 2014 445 Texas Instruments-Production Data Inter-Integrated Circuit (I2C) Interface 13 Inter-Integrated Circuit (I2C) Interface The Inter-Integrated Circuit (I2C) bus provides bi-directional data transfer through a two-wire design (a serial data line SDA and a serial clock line SCL), and interfaces to external I2C devices such as serial memory (RAMs and ROMs), networking devices, LCDs, tone generators, and so on. The I2C bus may also be used for system testing and diagnostic purposes in product development and manufacture. The LM3S812 microcontroller includes one I2C module, providing the ability to interact (both send and receive) with other I2C devices on the bus. ® The Stellaris I2C interface has the following features: ■ Devices on the I2C bus can be designated as either a master or a slave – Supports both sending and receiving data as either a master or a slave – Supports simultaneous master and slave operation ■ Four I2C modes – Master transmit – Master receive – Slave transmit – Slave receive ■ Two transmission speeds: Standard (100 Kbps) and Fast (400 Kbps) ■ Master and slave interrupt generation – Master generates interrupts when a transmit or receive operation completes (or aborts due to an error) – Slave generates interrupts when data has been sent or requested by a master ■ Master with arbitration and clock synchronization, multimaster support, and 7-bit addressing mode 446 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 13.1 Block Diagram Figure 13-1. I2C Block Diagram I2CSCL I2C Control Interrupt I2CMSA I2CSOAR I2CMCS I2CSCSR I2CMDR I2CSDR I2CMTPR I2CSIM I2CMIMR I2CSRIS I2CMRIS I2CSMIS I2CMMIS I2CSICR I2C Master Core I2CSCL I2C I/O Select I2CSDA I2CSCL I2C Slave Core I2CMICR I2CSDA I2CMCR 13.2 I2CSDA Signal Description Table 13-1 on page 447 lists the external signals of the I2C interface and describes the function of each. The I2C interface signals are alternate functions for some GPIO signals and default to be GPIO signals at reset., with the exception of the I2C0SCL and I2CSDA pins which default to the I2C function. The column in the table below titled "Pin Assignment" lists the possible GPIO pin placements for the I2C signals. The AFSEL bit in the GPIO Alternate Function Select (GPIOAFSEL) register (page 250) should be set to choose the I2C function. Note that the I2C pins should be set to open drain using the GPIO Open Drain Select (GPIOODR) register. For more information on configuring GPIOs, see “General-Purpose Input/Outputs (GPIOs)” on page 230. Table 13-1. I2C Signals (48QFP) a Pin Name Pin Number Pin Type Buffer Type Description I2CSCL 33 I/O OD I2C clock. I2CSDA 34 I/O OD I2C data. a. The TTL designation indicates the pin has TTL-compatible voltage levels. 13.3 Functional Description I2C module is comprised of both master and slave functions which are implemented as separate peripherals. For proper operation, the SDA and SCL pins must be connected to bi-directional open-drain pads. A typical I2C bus configuration is shown in Figure 13-2 on page 448. See “Inter-Integrated Circuit (I2C) Interface” on page 554 for I2C timing diagrams. July 14, 2014 447 Texas Instruments-Production Data Inter-Integrated Circuit (I2C) Interface Figure 13-2. I2C Bus Configuration RPUP SCL SDA I2C Bus I2CSCL I2CSDA Stellaris® 13.3.1 RPUP SCL SDA 3rd Party Device with I2C Interface SCL SDA 3rd Party Device with I2C Interface I2C Bus Functional Overview The I2C bus uses only two signals: SDA and SCL, named I2CSDA and I2CSCL on Stellaris microcontrollers. SDA is the bi-directional serial data line and SCL is the bi-directional serial clock line. The bus is considered idle when both lines are High. Every transaction on the I2C bus is nine bits long, consisting of eight data bits and a single acknowledge bit. The number of bytes per transfer (defined as the time between a valid START and STOP condition, described in “START and STOP Conditions” on page 448) is unrestricted, but each byte has to be followed by an acknowledge bit, and data must be transferred MSB first. When a receiver cannot receive another complete byte, it can hold the clock line SCL Low and force the transmitter into a wait state. The data transfer continues when the receiver releases the clock SCL. 13.3.1.1 START and STOP Conditions The protocol of the I2C bus defines two states to begin and end a transaction: START and STOP. A High-to-Low transition on the SDA line while the SCL is High is defined as a START condition, and a Low-to-High transition on the SDA line while SCL is High is defined as a STOP condition. The bus is considered busy after a START condition and free after a STOP condition. See Figure 13-3 on page 448. Figure 13-3. START and STOP Conditions SDA SDA SCL SCL START condition 13.3.1.2 STOP condition Data Format with 7-Bit Address Data transfers follow the format shown in Figure 13-4 on page 449. After the START condition, a slave address is sent. This address is 7-bits long followed by an eighth bit, which is a data direction bit (R/S bit in the I2CMSA register). A zero indicates a transmit operation (send), and a one indicates a request for data (receive). A data transfer is always terminated by a STOP condition generated by the master, however, a master can initiate communications with another device on the bus by generating a repeated START condition and addressing another slave without first generating a STOP condition. Various combinations of receive/send formats are then possible within a single transfer. 448 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Figure 13-4. Complete Data Transfer with a 7-Bit Address SDA MSB SCL 1 2 LSB R/S ACK 7 8 9 MSB 1 2 Slave address 7 LSB ACK 8 9 Data The first seven bits of the first byte make up the slave address (see Figure 13-5 on page 449). The eighth bit determines the direction of the message. A zero in the R/S position of the first byte means that the master will write (send) data to the selected slave, and a one in this position means that the master will receive data from the slave. Figure 13-5. R/S Bit in First Byte MSB LSB R/S Slave address 13.3.1.3 Data Validity The data on the SDA line must be stable during the high period of the clock, and the data line can only change when SCL is Low (see Figure 13-6 on page 449). Figure 13-6. Data Validity During Bit Transfer on the I2C Bus SDA SCL 13.3.1.4 Data line Change stable of data allowed Acknowledge All bus transactions have a required acknowledge clock cycle that is generated by the master. During the acknowledge cycle, the transmitter (which can be the master or slave) releases the SDA line. To acknowledge the transaction, the receiver must pull down SDA during the acknowledge clock cycle. The data sent out by the receiver during the acknowledge cycle must comply with the data validity requirements described in “Data Validity” on page 449. When a slave receiver does not acknowledge the slave address, SDA must be left High by the slave so that the master can generate a STOP condition and abort the current transfer. If the master device is acting as a receiver during a transfer, it is responsible for acknowledging each transfer made by the slave. Since the master controls the number of bytes in the transfer, it signals the end of data to the slave transmitter by not generating an acknowledge on the last data byte. The slave transmitter must then release SDA to allow the master to generate the STOP or a repeated START condition. 13.3.1.5 Arbitration A master may start a transfer only if the bus is idle. It's possible for two or more masters to generate a START condition within minimum hold time of the START condition. In these situations, an July 14, 2014 449 Texas Instruments-Production Data Inter-Integrated Circuit (I2C) Interface arbitration scheme takes place on the SDA line, while SCL is High. During arbitration, the first of the competing master devices to place a '1' (High) on SDA while another master transmits a '0' (Low) will switch off its data output stage and retire until the bus is idle again. Arbitration can take place over several bits. Its first stage is a comparison of address bits, and if both masters are trying to address the same device, arbitration continues on to the comparison of data bits. 13.3.2 Available Speed Modes The I2C clock rate is determined by the parameters: CLK_PRD, TIMER_PRD, SCL_LP, and SCL_HP. where: CLK_PRD is the system clock period SCL_LP is the low phase of SCL (fixed at 6) SCL_HP is the high phase of SCL (fixed at 4) TIMER_PRD is the programmed value in the I2C Master Timer Period (I2CMTPR) register (see page 468). The I2C clock period is calculated as follows: SCL_PERIOD = 2*(1 + TIMER_PRD)*(SCL_LP + SCL_HP)*CLK_PRD For example: CLK_PRD = 50 ns TIMER_PRD = 2 SCL_LP=6 SCL_HP=4 yields a SCL frequency of: 1/T = 333 Khz Table 13-2 on page 450 gives examples of timer period, system clock, and speed mode (Standard or Fast). Table 13-2. Examples of I2C Master Timer Period versus Speed Mode System Clock Timer Period Standard Mode Timer Period Fast Mode 4 MHz 0x01 100 Kbps - - 6 MHz 0x02 100 Kbps - - 12.5 MHz 0x06 89 Kbps 0x01 312 Kbps 16.7 MHz 0x08 93 Kbps 0x02 278 Kbps 20 MHz 0x09 100 Kbps 0x02 333 Kbps 25 MHz 0x0C 96.2 Kbps 0x03 312 Kbps 33 MHz 0x10 97.1 Kbps 0x04 330 Kbps 40 MHz 0x13 100 Kbps 0x04 400 Kbps 50 MHz 0x18 100 Kbps 0x06 357 Kbps 450 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 13.3.3 Interrupts The I2C can generate interrupts when the following conditions are observed: ■ Master transaction completed ■ Master arbitration lost ■ Master transaction error ■ Slave transaction received ■ Slave transaction requested There is a separate interrupt signal for the I2C master and I2C slave modules. While both modules can generate interrupts for multiple conditions, only a single interrupt signal is sent to the interrupt controller. 13.3.3.1 I2C Master Interrupts The I2C master module generates an interrupt when a transaction completes (either transmit or receive), when arbitration is lost, or when an error occurs during a transaction. To enable the I2C master interrupt, software must set the IM bit in the I2C Master Interrupt Mask (I2CMIMR) register. When an interrupt condition is met, software must check the ERROR and ARBLST bits in the I2C Master Control/Status (I2CMCS) register to verify that an error didn't occur during the last transaction and to ensure that arbitration has not been lost. An error condition is asserted if the last transaction wasn't acknowledged by the slave. If an error is not detected and the master has not lost arbitration, the application can proceed with the transfer. The interrupt is cleared by writing a 1 to the IC bit in the I2C Master Interrupt Clear (I2CMICR) register. If the application doesn't require the use of interrupts, the raw interrupt status is always visible via the I2C Master Raw Interrupt Status (I2CMRIS) register. 13.3.3.2 I2C Slave Interrupts The slave module can generate an interrupt when data has been received or requested. This interrupt is enabled by writing a 1 to the DATAIM bit in the I2C Slave Interrupt Mask (I2CSIMR) register. Software determines whether the module should write (transmit) or read (receive) data from the I2C Slave Data (I2CSDR) register, by checking the RREQ and TREQ bits of the I2C Slave Control/Status (I2CSCSR) register. If the slave module is in receive mode and the first byte of a transfer is received, the FBR bit is set along with the RREQ bit. The interrupt is cleared by writing a 1 to the DATAIC bit in the I2C Slave Interrupt Clear (I2CSICR) register. If the application doesn't require the use of interrupts, the raw interrupt status is always visible via the I2C Slave Raw Interrupt Status (I2CSRIS) register. 13.3.4 Loopback Operation The I2C modules can be placed into an internal loopback mode for diagnostic or debug work. This is accomplished by setting the LPBK bit in the I2C Master Configuration (I2CMCR) register. In loopback mode, the SDA and SCL signals from the master and slave modules are tied together. 13.3.5 Command Sequence Flow Charts This section details the steps required to perform the various I2C transfer types in both master and slave mode. July 14, 2014 451 Texas Instruments-Production Data Inter-Integrated Circuit (I2C) Interface 13.3.5.1 I2C Master Command Sequences The figures that follow show the command sequences available for the I2C master. 452 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Figure 13-7. Master Single SEND Idle Write Slave Address to I2CMSA Sequence may be omitted in a Single Master system Write data to I2CMDR Read I2CMCS NO BUSBSY bit=0? YES Write ---0-111 to I2CMCS Read I2CMCS NO BUSY bit=0? YES Error Service NO ERROR bit=0? YES Idle July 14, 2014 453 Texas Instruments-Production Data Inter-Integrated Circuit (I2C) Interface Figure 13-8. Master Single RECEIVE Idle Write Slave Address to I2CMSA Sequence may be omitted in a Single Master system Read I2CMCS NO BUSBSY bit=0? YES Write ---00111 to I2CMCS Read I2CMCS NO BUSY bit=0? YES Error Service NO ERROR bit=0? YES Read data from I2CMDR Idle 454 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Figure 13-9. Master Burst SEND Idle Write Slave Address to I2CMSA Sequence may be omitted in a Single Master system Read I2CMCS Write data to I2CMDR BUSY bit=0? YES Read I2CMCS ERROR bit=0? NO NO NO BUSBSY bit=0? YES Write data to I2CMDR YES Write ---0-011 to I2CMCS NO ARBLST bit=1? YES Write ---0-001 to I2CMCS NO Index=n? YES Write ---0-101 to I2CMCS Write ---0-100 to I2CMCS Error Service Idle Read I2CMCS NO BUSY bit=0? YES Error Service NO ERROR bit=0? YES Idle July 14, 2014 455 Texas Instruments-Production Data Inter-Integrated Circuit (I2C) Interface Figure 13-10. Master Burst RECEIVE Idle Write Slave Address to I2CMSA Sequence may be omitted in a Single Master system Read I2CMCS BUSY bit=0? Read I2CMCS NO YES NO BUSBSY bit=0? ERROR bit=0? NO YES Write ---01011 to I2CMCS NO Read data from I2CMDR ARBLST bit=1? YES Write ---01001 to I2CMCS NO Write ---0-100 to I2CMCS Index=m-1? Error Service YES Write ---00101 to I2CMCS Idle Read I2CMCS BUSY bit=0? NO YES NO ERROR bit=0? YES Error Service Read data from I2CMDR Idle 456 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Figure 13-11. Master Burst RECEIVE after Burst SEND Idle Master operates in Master Transmit mode STOP condition is not generated Write Slave Address to I2CMSA Write ---01011 to I2CMCS Master operates in Master Receive mode Repeated START condition is generated with changing data direction Idle July 14, 2014 457 Texas Instruments-Production Data Inter-Integrated Circuit (I2C) Interface Figure 13-12. Master Burst SEND after Burst RECEIVE Idle Master operates in Master Receive mode STOP condition is not generated Write Slave Address to I2CMSA Write ---0-011 to I2CMCS Master operates in Master Transmit mode Repeated START condition is generated with changing data direction Idle 13.3.5.2 I2C Slave Command Sequences Figure 13-13 on page 459 presents the command sequence available for the I2C slave. 458 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Figure 13-13. Slave Command Sequence Idle Write OWN Slave Address to I2CSOAR Write -------1 to I2CSCSR Read I2CSCSR NO TREQ bit=1? YES Write data to I2CSDR 13.4 NO RREQ bit=1? FBR is also valid YES Read data from I2CSDR Initialization and Configuration The following example shows how to configure the I2C module to send a single byte as a master. This assumes the system clock is 20 MHz. 1. Enable the I2C clock by writing a value of 0x0000.1000 to the RCGC1 register in the System Control module. 2. Enable the clock to the appropriate GPIO module via the RCGC2 register in the System Control module. 3. In the GPIO module, enable the appropriate pins for their alternate function using the GPIOAFSEL register. Also, be sure to enable the same pins for Open Drain operation. 4. Initialize the I2C Master by writing the I2CMCR register with a value of 0x0000.0020. 5. Set the desired SCL clock speed of 100 Kbps by writing the I2CMTPR register with the correct value. The value written to the I2CMTPR register represents the number of system clock periods in one SCL clock period. The TPR value is determined by the following equation: July 14, 2014 459 Texas Instruments-Production Data Inter-Integrated Circuit (I2C) Interface TPR = (System Clock / (2 * (SCL_LP + SCL_HP) * SCL_CLK)) - 1; TPR = (20MHz / (2 * (6 + 4) * 100000)) - 1; TPR = 9 Write the I2CMTPR register with the value of 0x0000.0009. 6. Specify the slave address of the master and that the next operation will be a Send by writing the I2CMSA register with a value of 0x0000.0076. This sets the slave address to 0x3B. 7. Place data (byte) to be sent in the data register by writing the I2CMDR register with the desired data. 8. Initiate a single byte send of the data from Master to Slave by writing the I2CMCS register with a value of 0x0000.0007 (STOP, START, RUN). 9. Wait until the transmission completes by polling the I2CMCS register’s BUSBSY bit until it has been cleared. 13.5 Register Map Table 13-3 on page 460 lists the I2C registers. All addresses given are relative to the I2C base addresses for the master and slave: ■ I2C 0: 0x4002.0000 Note that the I2C module clock must be enabled before the registers can be programmed (see page 197). There must be a delay of 3 system clocks after the I2C module clock is enabled before any I2C module registers are accessed. ® The hw_i2c.h file in the StellarisWare Driver Library uses a base address of 0x800 for the I2C slave registers. Be aware when using registers with offsets between 0x800 and 0x818 that StellarisWare uses an offset between 0x000 and 0x018 with the slave base address. Table 13-3. Inter-Integrated Circuit (I2C) Interface Register Map Offset Description See page Name Type Reset 0x000 I2CMSA R/W 0x0000.0000 I2C Master Slave Address 462 0x004 I2CMCS R/W 0x0000.0000 I2C Master Control/Status 463 0x008 I2CMDR R/W 0x0000.0000 I2C Master Data 467 0x00C I2CMTPR R/W 0x0000.0001 I2C Master Timer Period 468 0x010 I2CMIMR R/W 0x0000.0000 I2C Master Interrupt Mask 469 0x014 I2CMRIS RO 0x0000.0000 I2C Master Raw Interrupt Status 470 0x018 I2CMMIS RO 0x0000.0000 I2C Master Masked Interrupt Status 471 0x01C I2CMICR WO 0x0000.0000 I2C Master Interrupt Clear 472 0x020 I2CMCR R/W 0x0000.0000 I2C Master Configuration 473 I2C Master 460 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Table 13-3. Inter-Integrated Circuit (I2C) Interface Register Map (continued) Offset Description See page Name Type Reset 0x800 I2CSOAR R/W 0x0000.0000 I2C Slave Own Address 475 0x804 I2CSCSR RO 0x0000.0000 I2C Slave Control/Status 476 0x808 I2CSDR R/W 0x0000.0000 I2C Slave Data 478 0x80C I2CSIMR R/W 0x0000.0000 I2C Slave Interrupt Mask 479 0x810 I2CSRIS RO 0x0000.0000 I2C Slave Raw Interrupt Status 480 0x814 I2CSMIS RO 0x0000.0000 I2C Slave Masked Interrupt Status 481 0x818 I2CSICR WO 0x0000.0000 I2C Slave Interrupt Clear 482 I2C Slave 13.6 Register Descriptions (I2C Master) The remainder of this section lists and describes the I2C master registers, in numerical order by address offset. See also “Register Descriptions (I2C Slave)” on page 474. July 14, 2014 461 Texas Instruments-Production Data Inter-Integrated Circuit (I2C) Interface Register 1: I2C Master Slave Address (I2CMSA), offset 0x000 This register consists of eight bits: seven address bits (A6-A0), and a Receive/Send bit, which determines if the next operation is a Receive (High), or Send (Low). I2C Master Slave Address (I2CMSA) I2C 0 base: 0x4002.0000 Offset 0x000 Type R/W, reset 0x0000.0000 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 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 reserved Type Reset reserved Type Reset SA RO 0 R/S Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:1 SA R/W 0 I2C Slave Address This field specifies bits A6 through A0 of the slave address. 0 R/S R/W 0 Receive/Send The R/S bit specifies if the next operation is a Receive (High) or Send (Low). Value Description 0 Send. 1 Receive. 462 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 2: I2C Master Control/Status (I2CMCS), offset 0x004 This register accesses four control bits when written, and accesses seven status bits when read. The status register consists of seven bits, which when read determine the state of the I2C bus controller. The control register consists of four bits: the RUN, START, STOP, and ACK bits. The START bit causes the generation of the START, or REPEATED START condition. The STOP bit determines if the cycle stops at the end of the data cycle, or continues on to a burst. To generate a single send cycle, the I2C Master Slave Address (I2CMSA) register is written with the desired address, the R/S bit is set to 0, and the Control register is written with ACK=X (0 or 1), STOP=1, START=1, and RUN=1 to perform the operation and stop. When the operation is completed (or aborted due an error), the interrupt pin becomes active and the data may be read from the I2CMDR register. When the I2C module operates in Master receiver mode, the ACK bit must be set normally to logic 1. This causes the I2C bus controller to send an acknowledge automatically after each byte. This bit must be reset when the I2C bus controller requires no further data to be sent from the slave transmitter. Reads I2C Master Control/Status (I2CMCS) I2C 0 base: 0x4002.0000 Offset 0x004 Type RO, reset 0x0000.0000 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 BUSBSY IDLE ARBLST ERROR BUSY RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 reserved Type Reset reserved Type Reset RO 0 DATACK ADRACK RO 0 RO 0 Bit/Field Name Type Reset Description 31:7 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 6 BUSBSY RO 0 Bus Busy This bit specifies the state of the I2C bus. If set, the bus is busy; otherwise, the bus is idle. The bit changes based on the START and STOP conditions. 5 IDLE RO 0 I2C Idle This bit specifies the I2C controller state. If set, the controller is idle; otherwise the controller is not idle. 4 ARBLST RO 0 Arbitration Lost This bit specifies the result of bus arbitration. If set, the controller lost arbitration; otherwise, the controller won arbitration. July 14, 2014 463 Texas Instruments-Production Data Inter-Integrated Circuit (I2C) Interface Bit/Field Name Type Reset 3 DATACK RO 0 Description Acknowledge Data This bit specifies the result of the last data operation. If set, the transmitted data was not acknowledged; otherwise, the data was acknowledged. 2 ADRACK RO 0 Acknowledge Address This bit specifies the result of the last address operation. If set, the transmitted address was not acknowledged; otherwise, the address was acknowledged. 1 ERROR RO 0 Error This bit specifies the result of the last bus operation. If set, an error occurred on the last operation; otherwise, no error was detected. The error can be from the slave address not being acknowledged or the transmit data not being acknowledged. 0 BUSY RO 0 I2C Busy This bit specifies the state of the controller. If set, the controller is busy; otherwise, the controller is idle. When the BUSY bit is set, the other status bits are not valid. Writes I2C Master Control/Status (I2CMCS) I2C 0 base: 0x4002.0000 Offset 0x004 Type WO, reset 0x0000.0000 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 WO 0 WO 0 WO 0 WO 0 WO 0 WO 0 WO 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 ACK STOP START RUN 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 Type Reset Description 31:4 reserved WO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 3 ACK WO 0 Data Acknowledge Enable When set, causes received data byte to be acknowledged automatically by the master. See field decoding in Table 13-4 on page 465. 2 STOP WO 0 Generate STOP When set, causes the generation of the STOP condition. See field decoding in Table 13-4 on page 465. 1 START WO 0 Generate START When set, causes the generation of a START or repeated START condition. See field decoding in Table 13-4 on page 465. 464 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Bit/Field Name Type Reset 0 RUN WO 0 Description I2C Master Enable When set, allows the master to send or receive data. See field decoding in Table 13-4 on page 465. Table 13-4. Write Field Decoding for I2CMCS[3:0] Field (Sheet 1 of 3) Current I2CMSA[0] State R/S Idle I2CMCS[3:0] ACK STOP START RUN 1 0 X a 0 1 0 X 1 1 1 START condition followed by a SEND and STOP condition (master remains in Idle state). 1 0 0 1 1 START condition followed by RECEIVE operation with negative ACK (master goes to the Master Receive state). 1 0 1 1 1 START condition followed by RECEIVE and STOP condition (master remains in Idle state). 1 1 0 1 1 START condition followed by RECEIVE (master goes to the Master Receive state). 1 1 1 1 1 Illegal. All other combinations not listed are non-operations. Master Transmit Description START condition followed by SEND (master goes to the Master Transmit state). NOP. X X 0 0 1 SEND operation (master remains in Master Transmit state). X X 1 0 0 STOP condition (master goes to Idle state). X X 1 0 1 SEND followed by STOP condition (master goes to Idle state). 0 X 0 1 1 Repeated START condition followed by a SEND (master remains in Master Transmit state). 0 X 1 1 1 Repeated START condition followed by SEND and STOP condition (master goes to Idle state). 1 0 0 1 1 Repeated START condition followed by a RECEIVE operation with a negative ACK (master goes to Master Receive state). 1 0 1 1 1 Repeated START condition followed by a SEND and STOP condition (master goes to Idle state). 1 1 0 1 1 Repeated START condition followed by RECEIVE (master goes to Master Receive state). 1 1 1 1 1 Illegal. All other combinations not listed are non-operations. NOP. July 14, 2014 465 Texas Instruments-Production Data Inter-Integrated Circuit (I2C) Interface Table 13-4. Write Field Decoding for I2CMCS[3:0] Field (Sheet 1 of 3) (continued) Current I2CMSA[0] State R/S I2CMCS[3:0] Description ACK STOP START RUN X 0 0 0 1 RECEIVE operation with negative ACK (master remains in Master Receive state). X X 1 0 0 STOP condition (master goes to Idle state). X 0 1 0 1 RECEIVE followed by STOP condition (master goes to Idle state). X 1 0 0 1 RECEIVE operation (master remains in Master Receive state). X 1 1 0 1 Illegal. 1 0 0 1 1 Repeated START condition followed by RECEIVE operation with a negative ACK (master remains in Master Receive state). 1 0 1 1 1 Repeated START condition followed by RECEIVE and STOP condition (master goes to Idle state). 1 1 0 1 1 Repeated START condition followed by RECEIVE (master remains in Master Receive state). 0 X 0 1 1 Repeated START condition followed by SEND (master goes to Master Transmit state). 0 X 1 1 1 Repeated START condition followed by SEND and STOP condition (master goes to Idle state). Master Receive All other combinations not listed are non-operations. b NOP. a. An X in a table cell indicates the bit can be 0 or 1. b. In Master Receive mode, a STOP condition should be generated only after a Data Negative Acknowledge executed by the master or an Address Negative Acknowledge executed by the slave. 466 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 3: I2C Master Data (I2CMDR), offset 0x008 Important: This register is read-sensitive. See the register description for details. This register contains the data to be transmitted when in the Master Transmit state, and the data received when in the Master Receive state. I2C Master Data (I2CMDR) I2C 0 base: 0x4002.0000 Offset 0x008 Type R/W, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 R/W 0 R/W 0 R/W 0 R/W 0 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 DATA RO 0 RO 0 RO 0 RO 0 R/W 0 R/W 0 R/W 0 R/W 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 DATA R/W 0x00 Data Transferred Data transferred during transaction. July 14, 2014 467 Texas Instruments-Production Data Inter-Integrated Circuit (I2C) Interface Register 4: I2C Master Timer Period (I2CMTPR), offset 0x00C This register specifies the period of the SCL clock. Caution – Take care not to set bit 7 when accessing this register as unpredictable behavior can occur. I2C Master Timer Period (I2CMTPR) I2C 0 base: 0x4002.0000 Offset 0x00C Type R/W, reset 0x0000.0001 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 R/W 0 R/W 0 R/W 1 reserved Type Reset RO 0 RO 0 RO 0 RO 0 15 14 13 12 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 TPR RO 0 RO 0 RO 0 RO 0 RO 0 R/W 0 R/W 0 R/W 0 R/W 0 Bit/Field Name Type Reset Description 31:7 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 6:0 TPR R/W 0x1 SCL Clock Period This field specifies the period of the SCL clock. SCL_PRD = 2*(1 + TPR)*(SCL_LP + SCL_HP)*CLK_PRD where: SCL_PRD is the SCL line period (I2C clock). TPR is the Timer Period register value (range of 1 to 127). SCL_LP is the SCL Low period (fixed at 6). SCL_HP is the SCL High period (fixed at 4). 468 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 5: I2C Master Interrupt Mask (I2CMIMR), offset 0x010 This register controls whether a raw interrupt is promoted to a controller interrupt. I2C Master Interrupt Mask (I2CMIMR) I2C 0 base: 0x4002.0000 Offset 0x010 Type R/W, reset 0x0000.0000 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 8 RO 0 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 7 6 5 4 3 2 1 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 IM Bit/Field Name Type Reset Description 31:1 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 0 IM R/W 0 Interrupt Mask This bit controls whether a raw interrupt is promoted to a controller interrupt. If set, the interrupt is not masked and the interrupt is promoted; otherwise, the interrupt is masked. July 14, 2014 469 Texas Instruments-Production Data Inter-Integrated Circuit (I2C) Interface Register 6: I2C Master Raw Interrupt Status (I2CMRIS), offset 0x014 This register specifies whether an interrupt is pending. I2C Master Raw Interrupt Status (I2CMRIS) I2C 0 base: 0x4002.0000 Offset 0x014 Type RO, reset 0x0000.0000 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 8 RO 0 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 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 RO 0 RIS RO 0 Bit/Field Name Type Reset Description 31:1 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 0 RIS RO 0 Raw Interrupt Status This bit specifies the raw interrupt state (prior to masking) of the I2C master block. If set, an interrupt is pending; otherwise, an interrupt is not pending. 470 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 7: I2C Master Masked Interrupt Status (I2CMMIS), offset 0x018 This register specifies whether an interrupt was signaled. I2C Master Masked Interrupt Status (I2CMMIS) I2C 0 base: 0x4002.0000 Offset 0x018 Type RO, reset 0x0000.0000 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 8 RO 0 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 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 RO 0 MIS RO 0 Bit/Field Name Type Reset Description 31:1 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 0 MIS RO 0 Masked Interrupt Status This bit specifies the raw interrupt state (after masking) of the I2C master block. If set, an interrupt was signaled; otherwise, an interrupt has not been generated since the bit was last cleared. July 14, 2014 471 Texas Instruments-Production Data Inter-Integrated Circuit (I2C) Interface Register 8: I2C Master Interrupt Clear (I2CMICR), offset 0x01C This register clears the raw interrupt. I2C Master Interrupt Clear (I2CMICR) I2C 0 base: 0x4002.0000 Offset 0x01C Type WO, reset 0x0000.0000 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 8 RO 0 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 7 6 5 4 3 2 1 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 WO 0 reserved Type Reset reserved Type Reset RO 0 IC Bit/Field Name Type Reset Description 31:1 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 0 IC WO 0 Interrupt Clear This bit controls the clearing of the raw interrupt. A write of 1 clears the interrupt; otherwise, a write of 0 has no affect on the interrupt state. A read of this register returns no meaningful data. 472 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 9: I2C Master Configuration (I2CMCR), offset 0x020 This register configures the mode (Master or Slave) and sets the interface for test mode loopback. I2C Master Configuration (I2CMCR) I2C 0 base: 0x4002.0000 Offset 0x020 Type R/W, reset 0x0000.0000 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 SFE MFE RO 0 RO 0 RO 0 R/W 0 R/W 0 reserved Type Reset reserved Type Reset RO 0 reserved RO 0 RO 0 LPBK RO 0 R/W 0 Bit/Field Name Type Reset Description 31:6 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 5 SFE R/W 0 I2C Slave Function Enable This bit specifies whether the interface may operate in Slave mode. If set, Slave mode is enabled; otherwise, Slave mode is disabled. 4 MFE R/W 0 I2C Master Function Enable This bit specifies whether the interface may operate in Master mode. If set, Master mode is enabled; otherwise, Master mode is disabled and the interface clock is disabled. 3:1 reserved RO 0x00 0 LPBK R/W 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. I2C Loopback This bit specifies whether the interface is operating normally or in Loopback mode. If set, the device is put in a test mode loopback configuration; otherwise, the device operates normally. July 14, 2014 473 Texas Instruments-Production Data Inter-Integrated Circuit (I2C) Interface 13.7 Register Descriptions (I2C Slave) The remainder of this section lists and describes the I2C slave registers, in numerical order by address offset. See also “Register Descriptions (I2C Master)” on page 461. 474 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 10: I2C Slave Own Address (I2CSOAR), offset 0x800 This register consists of seven address bits that identify the Stellaris I2C device on the I2C bus. I2C Slave Own Address (I2CSOAR) I2C 0 base: 0x4002.0000 Offset 0x800 Type R/W, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 R/W 0 R/W 0 R/W 0 reserved Type Reset RO 0 RO 0 RO 0 RO 0 15 14 13 12 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 OAR RO 0 RO 0 RO 0 RO 0 RO 0 R/W 0 R/W 0 R/W 0 R/W 0 Bit/Field Name Type Reset Description 31:7 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 6:0 OAR R/W 0x00 I2C Slave Own Address This field specifies bits A6 through A0 of the slave address. July 14, 2014 475 Texas Instruments-Production Data Inter-Integrated Circuit (I2C) Interface Register 11: I2C Slave Control/Status (I2CSCSR), offset 0x804 This register accesses one control bit when written, and three status bits when read. The read-only Status register consists of three bits: the FBR, RREQ, and TREQ bits. The First Byte Received (FBR) bit is set only after the Stellaris device detects its own slave address and receives the first data byte from the I2C master. The Receive Request (RREQ) bit indicates that the Stellaris I2C device has received a data byte from an I2C master. Read one data byte from the I2C Slave Data (I2CSDR) register to clear the RREQ bit. The Transmit Request (TREQ) bit indicates that the Stellaris I2C device is addressed as a Slave Transmitter. Write one data byte into the I2C Slave Data (I2CSDR) register to clear the TREQ bit. The write-only Control register consists of one bit: the DA bit. The DA bit enables and disables the Stellaris I2C slave operation. Reads I2C Slave Control/Status (I2CSCSR) I2C 0 base: 0x4002.0000 Offset 0x804 Type RO, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 reserved Type Reset RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 15 14 13 12 11 10 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 9 8 7 6 5 4 3 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 2 1 0 FBR TREQ RREQ RO 0 RO 0 RO 0 Bit/Field Name Type Reset Description 31:3 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 2 FBR RO 0 First Byte Received Indicates that the first byte following the slave’s own address is received. This bit is only valid when the RREQ bit is set, and is automatically cleared when data has been read from the I2CSDR register. Note: 1 TREQ RO 0 This bit is not used for slave transmit operations. Transmit Request This bit specifies the state of the I2C slave with regards to outstanding transmit requests. If set, the I2C unit has been addressed as a slave transmitter and uses clock stretching to delay the master until data has been written to the I2CSDR register. Otherwise, there is no outstanding transmit request. 0 RREQ RO 0 Receive Request This bit specifies the status of the I2C slave with regards to outstanding receive requests. If set, the I2C unit has outstanding receive data from the I2C master and uses clock stretching to delay the master until the data has been read from the I2CSDR register. Otherwise, no receive data is outstanding. 476 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Writes I2C Slave Control/Status (I2CSCSR) I2C 0 base: 0x4002.0000 Offset 0x804 Type WO, reset 0x0000.0000 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 8 RO 0 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 7 6 5 4 3 2 1 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 WO 0 reserved Type Reset reserved Type Reset RO 0 DA Bit/Field Name Type Reset Description 31:1 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 0 DA WO 0 Device Active Value Description 0 Disables the I2C slave operation. 1 Enables the I2C slave operation. Once this bit has been set, it should not be set again unless it has been cleared by writing a 0 or by a reset, otherwise transfer failures may occur. July 14, 2014 477 Texas Instruments-Production Data Inter-Integrated Circuit (I2C) Interface Register 12: I2C Slave Data (I2CSDR), offset 0x808 Important: This register is read-sensitive. See the register description for details. This register contains the data to be transmitted when in the Slave Transmit state, and the data received when in the Slave Receive state. I2C Slave Data (I2CSDR) I2C 0 base: 0x4002.0000 Offset 0x808 Type R/W, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 RO 0 RO 0 3 2 1 0 R/W 0 R/W 0 R/W 0 R/W 0 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 15 14 13 12 11 10 9 8 7 6 5 4 reserved Type Reset RO 0 RO 0 RO 0 RO 0 DATA RO 0 RO 0 RO 0 RO 0 R/W 0 R/W 0 R/W 0 R/W 0 Bit/Field Name Type Reset Description 31:8 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7:0 DATA R/W 0x0 Data for Transfer This field contains the data for transfer during a slave receive or transmit operation. 478 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 13: I2C Slave Interrupt Mask (I2CSIMR), offset 0x80C This register controls whether a raw interrupt is promoted to a controller interrupt. I2C Slave Interrupt Mask (I2CSIMR) I2C 0 base: 0x4002.0000 Offset 0x80C Type R/W, reset 0x0000.0000 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 8 RO 0 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 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 RO 0 DATAIM R/W 0 Bit/Field Name Type Reset Description 31:1 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 0 DATAIM R/W 0 Data Interrupt Mask This bit controls whether the raw interrupt for data received and data requested is promoted to a controller interrupt. If set, the interrupt is not masked and the interrupt is promoted; otherwise, the interrupt is masked. July 14, 2014 479 Texas Instruments-Production Data Inter-Integrated Circuit (I2C) Interface Register 14: I2C Slave Raw Interrupt Status (I2CSRIS), offset 0x810 This register specifies whether an interrupt is pending. I2C Slave Raw Interrupt Status (I2CSRIS) I2C 0 base: 0x4002.0000 Offset 0x810 Type RO, reset 0x0000.0000 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 8 RO 0 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 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 RO 0 DATARIS RO 0 Bit/Field Name Type Reset Description 31:1 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 0 DATARIS RO 0 Data Raw Interrupt Status This bit specifies the raw interrupt state for data received and data requested (prior to masking) of the I2C slave block. If set, an interrupt is pending; otherwise, an interrupt is not pending. 480 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 15: I2C Slave Masked Interrupt Status (I2CSMIS), offset 0x814 This register specifies whether an interrupt was signaled. I2C Slave Masked Interrupt Status (I2CSMIS) I2C 0 base: 0x4002.0000 Offset 0x814 Type RO, reset 0x0000.0000 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 8 RO 0 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 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 RO 0 DATAMIS RO 0 Bit/Field Name Type Reset Description 31:1 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 0 DATAMIS RO 0 Data Masked Interrupt Status This bit specifies the interrupt state for data received and data requested (after masking) of the I2C slave block. If set, an interrupt was signaled; otherwise, an interrupt has not been generated since the bit was last cleared. July 14, 2014 481 Texas Instruments-Production Data Inter-Integrated Circuit (I2C) Interface Register 16: I2C Slave Interrupt Clear (I2CSICR), offset 0x818 This register clears the raw interrupt. A read of this register returns no meaningful data. I2C Slave Interrupt Clear (I2CSICR) I2C 0 base: 0x4002.0000 Offset 0x818 Type WO, reset 0x0000.0000 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 8 RO 0 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 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 RO 0 DATAIC WO 0 Bit/Field Name Type Reset Description 31:1 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 0 DATAIC WO 0 Data Interrupt Clear This bit controls the clearing of the raw interrupt for data received and data requested. When set, it clears the DATARIS interrupt bit; otherwise, it has no effect on the DATARIS bit value. 482 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 14 Analog Comparator An analog comparator is a peripheral that compares two analog voltages, and provides a logical output that signals the comparison result. Note: Not all comparators have the option to drive an output pin. See the Comparator Operating Mode tables in “Functional Description” on page 484 for more information. 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. ® The Stellaris Analog Comparators module has the following features: ■ One integrated analog comparator ■ Configurable for output to drive an output pin, generate an interrupt, or initiate an ADC sample sequence ■ Compare external pin input to external pin input or to internal programmable voltage reference ■ 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 14.1 Block Diagram Figure 14-1. Analog Comparator Module Block Diagram C0- -ve input C0+ +ve input Comparator 0 output +ve input (alternate) trigger ACCTL0 C0o trigger ACSTAT0 interrupt reference input Interrupt Control Voltage Ref internal bus ACRIS ACMIS ACREFCTL ACINTEN interrupt 14.2 Signal Description Table 14-1 on page 484 lists the external signals of the Analog Comparators and describes the function of each. The Analog Comparator output signal is an alternate functions for a GPIO signal and default to be a GPIO signal at reset. The column in the table below titled "Pin Assignment" lists July 14, 2014 483 Texas Instruments-Production Data Analog Comparator the possible GPIO pin placements for the Analog Comparator signals. The AFSEL bit in the GPIO Alternate Function Select (GPIOAFSEL) register (page 250) should be set to choose the Analog Comparator function. The positive and negative input signal are configured by clearing the DEN bit in the GPIO Digital Enable (GPIODEN) register. For more information on configuring GPIOs, see “General-Purpose Input/Outputs (GPIOs)” on page 230. Table 14-1. Analog Comparators Signals (48QFP) a Pin Name Pin Number Pin Type Buffer Type Description C0+ 42 I Analog Analog comparator 0 positive input. C0- 44 I Analog Analog comparator 0 negative input. C0o 48 O TTL Analog comparator 0 output. a. The TTL designation indicates the pin has TTL-compatible voltage levels. 14.3 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. VIN- < VIN+, VOUT = 1 VIN- > VIN+, VOUT = 0 As shown in Figure 14-2 on page 484, 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. Figure 14-2. Structure of Comparator Unit - ve input + ve input (alternate) reference input 0 output CINV 1 IntGen 2 TrigGen internal bus ACCTL ACSTAT trigger 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 the Comparator Operating Mode tables. 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. 484 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Important: The ASRCP bits in the ACCTLn register must be set before using the analog comparators. The proper pad configuration for the comparator input and output pins are described in the Comparator Operating Mode tables. Table 14-2. Comparator 0 Operating Modes 14.3.1 ACCTL0 Comparator 0 ASRCP VIN- VIN+ Output Interrupt ADC Trigger 00 C0- C0+ C0o yes yes 01 C0- C0+ C0o yes yes 10 C0- Vref C0o yes yes 11 C0- reserved C0o yes yes Internal Reference Programming The structure of the internal reference is shown in Figure 14-3 on page 485. This is controlled by a single configuration register (ACREFCTL). Table 14-3 on page 485 shows the programming options to develop specific internal reference values, to compare an external voltage against a particular voltage generated internally. Figure 14-3. Comparator Internal Reference Structure 8R AVDD 8R R R R ••• EN 15 14 ••• 1 0 Decoder VREF internal reference RNG Table 14-3. Internal Reference Voltage and ACREFCTL Field Values ACREFCTL Register EN Bit Value EN=0 RNG Bit Value RNG=X Output Reference Voltage Based on VREF Field Value 0 V (GND) for any value of VREF; however, it is recommended that RNG=1 and VREF=0 for the least noisy ground reference. July 14, 2014 485 Texas Instruments-Production Data Analog Comparator Table 14-3. Internal Reference Voltage and ACREFCTL Field Values (continued) ACREFCTL Register EN Bit Value RNG Bit Value RNG=0 EN=1 Output Reference Voltage Based on VREF Field Value Total resistance in ladder is 31 R. The range of internal reference in this mode is 0.85-2.448 V. RNG=1 Total resistance in ladder is 23 R. The range of internal reference for this mode is 0-2.152 V. 14.4 Initialization and Configuration The following example shows how to configure an analog comparator to read back its output value from an internal register. 1. Enable the analog comparator 0 clock by writing a value of 0x0010.0000 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 0x0000.030C. 4. Configure comparator 0 to use the internal voltage reference and to not invert the output by writing the ACCTL0 register with the value of 0x0000.040C. 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. 14.5 Register Map Table 14-4 on page 487 lists the comparator registers. The offset listed is a hexadecimal increment to the register’s address, relative to the Analog Comparator base address of 0x4003.C000. Note that the analog comparator module clock must be enabled before the registers can be programmed (see page 197). There must be a delay of 3 system clocks after the ADC module clock is enabled before any ADC module registers are accessed. 486 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Table 14-4. Analog Comparators Register Map Name Type Reset 0x000 ACMIS R/W1C 0x0000.0000 Analog Comparator Masked Interrupt Status 488 0x004 ACRIS RO 0x0000.0000 Analog Comparator Raw Interrupt Status 489 0x008 ACINTEN R/W 0x0000.0000 Analog Comparator Interrupt Enable 490 0x010 ACREFCTL R/W 0x0000.0000 Analog Comparator Reference Voltage Control 491 0x020 ACSTAT0 RO 0x0000.0000 Analog Comparator Status 0 492 0x024 ACCTL0 R/W 0x0000.0000 Analog Comparator Control 0 493 14.6 Description See page Offset Register Descriptions The remainder of this section lists and describes the Analog Comparator registers, in numerical order by address offset. July 14, 2014 487 Texas Instruments-Production Data Analog Comparator Register 1: Analog Comparator Masked Interrupt Status (ACMIS), offset 0x000 This register provides a summary of the interrupt status (masked) of the comparator. Analog Comparator Masked Interrupt Status (ACMIS) Base 0x4003.C000 Offset 0x000 Type R/W1C, reset 0x0000.0000 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 8 RO 0 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 7 6 5 4 3 2 1 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 R/W1C 0 reserved Type Reset reserved Type Reset RO 0 IN0 Bit/Field Name Type Reset Description 31:1 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 0 IN0 R/W1C 0 Comparator 0 Masked Interrupt Status Gives the masked interrupt state of this interrupt. Write 1 to this bit to clear the pending interrupt. 488 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 2: Analog Comparator Raw Interrupt Status (ACRIS), offset 0x004 This register provides a summary of the interrupt status (raw) of the comparator. Analog Comparator Raw Interrupt Status (ACRIS) Base 0x4003.C000 Offset 0x004 Type RO, reset 0x0000.0000 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 8 RO 0 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 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 RO 0 IN0 RO 0 Bit/Field Name Type Reset Description 31:1 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 0 IN0 RO 0 Comparator 0 Interrupt Status When set, indicates that an interrupt has been generated by comparator 0. July 14, 2014 489 Texas Instruments-Production Data Analog Comparator Register 3: Analog Comparator Interrupt Enable (ACINTEN), offset 0x008 This register provides the interrupt enable for the comparator. Analog Comparator Interrupt Enable (ACINTEN) Base 0x4003.C000 Offset 0x008 Type R/W, reset 0x0000.0000 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 8 RO 0 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 7 6 5 4 3 2 1 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 IN0 Bit/Field Name Type Reset Description 31:1 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 0 IN0 R/W 0 Comparator 0 Interrupt Enable When set, enables the controller interrupt from the comparator 0 output. 490 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 4: Analog Comparator Reference Voltage Control (ACREFCTL), offset 0x010 This register specifies whether the resistor ladder is powered on as well as the range and tap. Analog Comparator Reference Voltage Control (ACREFCTL) Base 0x4003.C000 Offset 0x010 Type R/W, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 1 0 R/W 0 R/W 0 reserved Type Reset RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 15 14 13 12 11 10 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 7 6 5 4 3 2 9 8 EN RNG R/W 0 R/W 0 reserved RO 0 RO 0 RO 0 VREF RO 0 R/W 0 R/W 0 Bit/Field Name Type Reset Description 31:10 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 9 EN R/W 0 Resistor Ladder Enable 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 Resistor Ladder Range The RNG bit specifies the range of the resistor ladder. If 0, the resistor ladder has a total resistance of 31 R. If 1, the resistor ladder has a total resistance of 23 R. 7:4 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 3:0 VREF R/W 0x00 Resistor Ladder Voltage Ref 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 14-3 on page 485 for some output reference voltage examples. July 14, 2014 491 Texas Instruments-Production Data Analog Comparator Register 5: Analog Comparator Status 0 (ACSTAT0), offset 0x020 This register specifies the current output value of the comparator. Analog Comparator Status 0 (ACSTAT0) Base 0x4003.C000 Offset 0x020 Type RO, reset 0x0000.0000 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 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 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 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 1 OVAL RO 0 Comparator Output Value The OVAL bit specifies the current output value of the comparator. 0 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 492 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 6: Analog Comparator Control 0 (ACCTL0), offset 0x024 This register configures the comparator’s input and output. Analog Comparator Control 0 (ACCTL0) Base 0x4003.C000 Offset 0x024 Type R/W, reset 0x0000.0000 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 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 reserved TSLVAL CINV reserved RO 0 R/W 0 R/W 0 RO 0 reserved Type Reset reserved Type Reset TOEN RO 0 RO 0 ASRCP R/W 0 R/W 0 R/W 0 TSEN R/W 0 ISLVAL R/W 0 R/W 0 ISEN R/W 0 R/W 0 Bit/Field Name Type Reset Description 31:12 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 11 TOEN R/W 0 Trigger Output Enable 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 0x00 Analog Source Positive The ASRCP field specifies the source of input voltage to the VIN+ terminal of the comparator. The encodings for this field are as follows: Value Function 0x0 Pin value 0x1 Pin value of C0+ 0x2 Internal voltage reference 0x3 Reserved 8 reserved RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 7 TSLVAL R/W 0 Trigger Sense Level Value 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. July 14, 2014 493 Texas Instruments-Production Data Analog Comparator Bit/Field Name Type Reset 6:5 TSEN R/W 0x0 Description Trigger Sense The TSEN field specifies the sense of the comparator output that generates an ADC event. The sense conditioning is as follows: Value Function 4 ISLVAL R/W 0 0x0 Level sense, see TSLVAL 0x1 Falling edge 0x2 Rising edge 0x3 Either edge Interrupt Sense Level Value 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 0x0 Interrupt Sense The ISEN field specifies the sense of the comparator output that generates an interrupt. The sense conditioning is as follows: Value Function 1 CINV R/W 0 0x0 Level sense, see ISLVAL 0x1 Falling edge 0x2 Rising edge 0x3 Either edge Comparator Output Invert 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 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 494 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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 Stellaris PWM module consists of one PWM generator block and a control block. The control block determines the polarity of the PWM signals, and which signals are passed through to the pins. The 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 is managed by the output control block before being passed to the device pins. The Stellaris 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. The Stellaris PWM module has the following features: ■ One PWM generator blocks, each with one 16-bit counter, two PWM comparators, a PWM signal generator, a dead-band generator, and an interrupt/ADC-trigger selector ■ One fault input in hardware to promote low-latency shutdown ■ 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 PWM 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 PWM 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 July 14, 2014 495 Texas Instruments-Production Data Pulse Width Modulator (PWM) ■ Flexible output control block with PWM output enable of each PWM signal – 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 – Interrupt status summary of the PWM generator blocks ■ Can initiate an ADC sample sequence 15.1 Block Diagram Figure 15-1 on page 496 provides the Stellaris PWM module unit diagram and Figure 15-2 on page 497 provides a more detailed diagram of a Stellaris PWM generator. The LM3S812 controller contains one generator block (PWM0) and generates two independent PWM signals or one paired PWM signal with dead-band delays inserted. Figure 15-1. PWM Unit Diagram PWM Clock Fault System Clock PWM0_A Control and Status PWM Generator 0 PWM0_B PWM0_Fault PWM Output Control Logic PWM 0 PWM 1 PWMCTL PWMSYNC PWMSTATUS Interrupt Interrupts PWMINTEN PWMRIS PWMISC Triggers Output PWMENABLE PWMINVERT PWMFAULT 496 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Figure 15-2. PWM Module Block Diagram PWM Generator Block Interrupts / Triggers Interrupt and Trigger Generator Control PWMnINTEN PWMnRIS PWMnISC PWMnCTL PWMn_Fault load dir PWMnLOAD PWMnCOUNT Signal Generator Comparators 15.2 Fault(s) PWMnFLTSRC0 PWMnMINFLTPER PWMnFLTSEN PWMnFLTSTAT0 zero Timer cmp A PWMnCMPA PWMnCMPB PWM Clock Fault Condition PWMnGENA PWMnGENB cmp B Dead-Band Generator PWMnDBCTL PWMnDBRISE PWMnDBFALL PWMn_A PWMn_B Signal Description Table 15-1 on page 497 lists the external signals of the PWM module module and describes the function of each. The PWM controller signals are alternate functions for some GPIO signals and default to be GPIO signals at reset. The column in the table below titled "Pin Assignment" lists the possible GPIO pin placements for these PWM signals. The AFSEL bit in the GPIO Alternate Function Select (GPIOAFSEL) register (page 250) should be set to choose the PWM function. For more information on configuring GPIOs, see “General-Purpose Input/Outputs (GPIOs)” on page 230. Table 15-1. PWM Signals (48QFP) Pin Name Pin Number Fault PWM0 PWM1 a Pin Type Buffer Type Description 47 I TTL PWM Fault. 25 O TTL PWM 0. This signal is controlled by PWM Generator 0. 26 O TTL PWM 1. This signal is controlled by PWM Generator 0. a. The TTL designation indicates the pin has TTL-compatible voltage levels. 15.3 Functional Description 15.3.1 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 July 14, 2014 497 Texas Instruments-Production Data Pulse Width Modulator (PWM) 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. 15.3.2 PWM Comparators There are two comparators in the 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 15-3 on page 498 shows the behavior of the counter and the relationship of these pulses when the counter is in Count-Down mode. Figure 15-4 on page 499 shows the behavior of the counter and the relationship of these pulses when the counter is in Count-Up/Down mode. Figure 15-3. PWM Count-Down Mode Load CompA CompB Zero Load Zero A B Dir BDown ADown 498 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Figure 15-4. PWM Count-Up/Down Mode Load CompA CompB Zero Load Zero A B Dir BUp AUp 15.3.3 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 15-5 on page 499 shows the use of Count-Up/Down mode to generate a pair of center-aligned, overlapped PWM signals that have different duty cycles. Figure 15-5. 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. July 14, 2014 499 Texas Instruments-Production Data Pulse Width Modulator (PWM) 15.3.4 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 15-6 on page 500 shows the effect of the dead-band generator on an input PWM signal. Figure 15-6. PWM Dead-Band Generator Input PWMA PWMB Rising Edge Delay 15.3.5 Falling Edge Delay Interrupt/ADC-Trigger Selector The PWM generator also takes the same four (or six) counter events and uses them to generate an interrupt or an ADC trigger. 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. Additionally, the same event, a different event, the same set of events, or a different set of events can be selected as a source for an ADC trigger; when any of these selected events occur, an ADC trigger pulse is generated. The selection of events allows the interrupt or ADC trigger to occur at a specific position within the PWM signal. Note that interrupts and ADC triggers are based on the raw events; delays in the PWM signal edges caused by the dead-band generator are not taken into account. 15.3.6 Synchronization Methods There is a global reset capability that can reset the counter of the PWM generator. 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. 15.3.7 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 500 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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. 15.3.8 Output Control Block With the 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. 15.4 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 0x0010.0000 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 0x0000.0000. ■ Write the PWM0GENA register with a value of 0x0000.008C. ■ Write the PWM0GENB register with a value of 0x0000.080C. 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 0x0000.018F. 6. Set the pulse width of the PWM0 pin for a 25% duty cycle. ■ Write the PWM0CMPA register with a value of 0x0000.012B. July 14, 2014 501 Texas Instruments-Production Data Pulse Width Modulator (PWM) 7. Set the pulse width of the PWM1 pin for a 75% duty cycle. ■ Write the PWM0CMPB register with a value of 0x0000.0063. 8. Start the timers in PWM generator 0. ■ Write the PWM0CTL register with a value of 0x0000.0001. 9. Enable PWM outputs. ■ Write the PWMENABLE register with a value of 0x0000.0003. 15.5 Register Map Table 15-2 on page 502 lists the PWM registers. The offset listed is a hexadecimal increment to the register’s address, relative to the PWM base address of 0x4002.8000. Note that the PWM module clock must be enabled before the registers can be programmed (see page 191). There must be a delay of 3 system clocks after the PWM module clock is enabled before any PWM module registers are accessed. Table 15-2. PWM Register Map Description See page Offset Name Type Reset 0x000 PWMCTL R/W 0x0000.0000 PWM Master Control 504 0x004 PWMSYNC R/W 0x0000.0000 PWM Time Base Sync 505 0x008 PWMENABLE R/W 0x0000.0000 PWM Output Enable 506 0x00C PWMINVERT R/W 0x0000.0000 PWM Output Inversion 507 0x010 PWMFAULT R/W 0x0000.0000 PWM Output Fault 508 0x014 PWMINTEN R/W 0x0000.0000 PWM Interrupt Enable 509 0x018 PWMRIS RO 0x0000.0000 PWM Raw Interrupt Status 510 0x01C PWMISC R/W1C 0x0000.0000 PWM Interrupt Status and Clear 511 0x020 PWMSTATUS RO 0x0000.0000 PWM Status 512 0x040 PWM0CTL R/W 0x0000.0000 PWM0 Control 513 0x044 PWM0INTEN R/W 0x0000.0000 PWM0 Interrupt and Trigger Enable 515 0x048 PWM0RIS RO 0x0000.0000 PWM0 Raw Interrupt Status 518 0x04C PWM0ISC R/W1C 0x0000.0000 PWM0 Interrupt Status and Clear 519 0x050 PWM0LOAD R/W 0x0000.0000 PWM0 Load 520 0x054 PWM0COUNT RO 0x0000.0000 PWM0 Counter 521 0x058 PWM0CMPA R/W 0x0000.0000 PWM0 Compare A 522 0x05C PWM0CMPB R/W 0x0000.0000 PWM0 Compare B 523 0x060 PWM0GENA R/W 0x0000.0000 PWM0 Generator A Control 524 0x064 PWM0GENB R/W 0x0000.0000 PWM0 Generator B Control 527 502 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Table 15-2. PWM Register Map (continued) Name Type Reset 0x068 PWM0DBCTL R/W 0x0000.0000 PWM0 Dead-Band Control 530 0x06C PWM0DBRISE R/W 0x0000.0000 PWM0 Dead-Band Rising-Edge Delay 531 0x070 PWM0DBFALL R/W 0x0000.0000 PWM0 Dead-Band Falling-Edge-Delay 532 15.6 Description See page Offset Register Descriptions The remainder of this section lists and describes the PWM registers, in numerical order by address offset. July 14, 2014 503 Texas Instruments-Production Data Pulse Width Modulator (PWM) Register 1: PWM Master Control (PWMCTL), offset 0x000 This register provides master control over the PWM generation block. PWM Master Control (PWMCTL) Base 0x4002.8000 Offset 0x000 Type R/W, reset 0x0000.0000 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 8 23 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 R/W 0 GlobalSync0 reserved Type Reset reserved Type Reset RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 Bit/Field Name Type Reset Description 31:1 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 0 GlobalSync0 R/W 0 Update PWM Generator 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. 504 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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. PWM Time Base Sync (PWMSYNC) Base 0x4002.8000 Offset 0x004 Type R/W, reset 0x0000.0000 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 8 RO 0 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 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 RO 0 Sync0 R/W 0 Bit/Field Name Type Reset Description 31:1 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 0 Sync0 R/W 0 Reset Generator 0 Counter Performs a reset of the PWM generator 0 counter. July 14, 2014 505 Texas Instruments-Production Data 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. PWM Output Enable (PWMENABLE) Base 0x4002.8000 Offset 0x008 Type R/W, reset 0x0000.0000 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 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 RO 0 RO 0 RO 0 reserved Type Reset reserved Type Reset PWM1En PWM0En R/W 0 R/W 0 Bit/Field Name Type Reset Description 31:2 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 1 PWM1En R/W 0 PWM1 Output Enable When set, allows the generated PWM1 signal to be passed to the device pin. 0 PWM0En R/W 0 PWM0 Output Enable When set, allows the generated PWM0 signal to be passed to the device pin. 506 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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 PWM generator 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. PWM Output Inversion (PWMINVERT) Base 0x4002.8000 Offset 0x00C Type R/W, reset 0x0000.0000 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 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 RO 0 RO 0 RO 0 reserved Type Reset reserved Type Reset PWM1Inv PWM0Inv R/W 0 R/W 0 Bit/Field Name Type Reset Description 31:2 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 1 PWM1Inv R/W 0 Invert PWM1 Signal When set, the generated PWM1 signal is inverted. 0 PWM0Inv R/W 0 Invert PWM0 Signal When set, the generated PWM0 signal is inverted. July 14, 2014 507 Texas Instruments-Production Data 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 inputs and debug events are considered fault conditions. On a fault condition, each PWM signal can 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 occurs 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). PWM Output Fault (PWMFAULT) Base 0x4002.8000 Offset 0x010 Type R/W, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 RO 0 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 15 14 13 12 11 10 9 8 7 6 5 4 3 2 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 1 0 Fault1 Fault0 R/W 0 R/W 0 Bit/Field Name Type Reset Description 31:2 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 1 Fault1 R/W 0 PWM1 Fault When set, the PWM1 output signal is driven Low on a fault condition. 0 Fault0 R/W 0 PWM0 Fault When set, the PWM0 output signal is driven Low on a fault condition. 508 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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. PWM Interrupt Enable (PWMINTEN) Base 0x4002.8000 Offset 0x014 Type R/W, reset 0x0000.0000 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 RO 0 RO 0 reserved Type Reset IntFault reserved Type Reset RO 0 16 IntPWM0 R/W 0 Bit/Field Name Type Reset Description 31:17 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 16 IntFault R/W 0 Fault Interrupt Enable When set, an interrupt occurs when the fault input is asserted. 15:1 reserved RO 0x00 0 IntPWM0 R/W 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. PWM0 Interrupt Enable When set, an interrupt occurs when the PWM generator 0 block asserts an interrupt. July 14, 2014 509 Texas Instruments-Production Data 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 511). 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; zero bits indicate that the event in question is not active. PWM Raw Interrupt Status (PWMRIS) Base 0x4002.8000 Offset 0x018 Type RO, reset 0x0000.0000 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 RO 0 8 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 IntFault reserved Type Reset RO 0 16 IntPWM0 RO 0 Bit/Field Name Type Reset Description 31:17 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 16 IntFault RO 0 Fault Interrupt Asserted Indicates that the fault input is asserting. 15:1 reserved RO 0x00 0 IntPWM0 RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. PWM0 Interrupt Asserted Indicates that the PWM generator 0 block is asserting its interrupt. 510 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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) Base 0x4002.8000 Offset 0x01C Type R/W1C, reset 0x0000.0000 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 16 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 RO 0 reserved Type Reset IntFault reserved Type Reset RO 0 IntPWM0 RO 0 Bit/Field Name Type Reset Description 31:17 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 16 IntFault R/W1C 0 Fault Interrupt Asserted Indicates that the fault input is asserting an interrupt. 15:1 reserved RO 0x00 0 IntPWM0 RO 0 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. PWM0 Interrupt Status Indicates if the PWM generator 0 block is asserting an interrupt. July 14, 2014 511 Texas Instruments-Production Data Pulse Width Modulator (PWM) Register 9: PWM Status (PWMSTATUS), offset 0x020 This register provides the status of the FAULT input signal. PWM Status (PWMSTATUS) Base 0x4002.8000 Offset 0x020 Type RO, reset 0x0000.0000 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 8 RO 0 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 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 RO 0 Fault RO 0 Bit/Field Name Type Reset Description 31:1 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 0 Fault RO 0 Fault Interrupt Status When set, indicates the fault input is asserted. 512 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 10: PWM0 Control (PWM0CTL), offset 0x040 This register configures the PWM signal generation block. The Register Update mode, Debug mode, Counting mode, and Block Enable mode are all controlled via this register. The block produces 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. The PWM0 block produces the PWM0 and PWM1 outputs. PWM0 Control (PWM0CTL) Base 0x4002.8000 Offset 0x040 Type R/W, reset 0x0000.0000 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 5 4 3 reserved Type Reset 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 reserved Type Reset RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 CmpBUpd CmpAUpd LoadUpd RO 0 RO 0 RO 0 RO 0 R/W 0 R/W 0 R/W 0 2 1 0 Debug Mode Enable R/W 0 R/W 0 R/W 0 Bit/Field Name Type Reset Description 31:6 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 5 CmpBUpd R/W 0 Comparator B Update Mode Same as CmpAUpd but for the comparator B register. 4 CmpAUpd R/W 0 Comparator A Update Mode The Update mode for the comparator A register. When not set, updates to the register are reflected to the comparator the next time the counter is 0. When set, 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 504). 3 LoadUpd R/W 0 Load Register Update Mode The Update mode for the load register. When not set, updates to the register are reflected to the counter the next time the counter is 0. When set, 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 Debug Mode The behavior of the counter in Debug mode. When not set, the counter stops running when it next reaches 0, and continues running again when no longer in Debug mode. When set, the counter always runs. 1 Mode R/W 0 Counter Mode The mode for the counter. When not set, the counter counts down from the load value to 0 and then wraps back to the load value (Count-Down mode). When set, the counter counts up from 0 to the load value, back down to 0, and then repeats (Count-Up/Down mode). July 14, 2014 513 Texas Instruments-Production Data Pulse Width Modulator (PWM) Bit/Field Name Type Reset 0 Enable R/W 0 Description PWM Block Enable Master enable for the PWM generation block. When not set, the entire block is disabled and not clocked. When set, the block is enabled and produces PWM signals. 514 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 11: PWM0 Interrupt and Trigger Enable (PWM0INTEN), offset 0x044 This register controls the interrupt and ADC trigger generation capabilities of the PWM generator. The events that can cause an interrupt or an ADC trigger 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, or an ADC trigger; though no determination can be made as to the actual event that caused an ADC trigger if more than one is specified. PWM0 Interrupt and Trigger Enable (PWM0INTEN) Base 0x4002.8000 Offset 0x044 Type R/W, reset 0x0000.0000 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 reserved Type Reset RO 0 RO 0 15 14 reserved Type Reset RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 13 12 11 10 TrCmpBD TrCmpBU TrCmpAD TrCmpAU R/W 0 R/W 0 R/W 0 R/W 0 RO 0 RO 0 RO 0 RO 0 7 6 9 8 TrCntLoad TrCntZero R/W 0 R/W 0 reserved RO 0 RO 0 5 4 3 2 1 0 IntCmpBD IntCmpBU IntCmpAD IntCmpAU IntCntLoad IntCntZero R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 Bit/Field Name Type Reset Description 31:14 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 13 TrCmpBD R/W 0 Trigger for Counter=Comparator B Down Value Description 12 TrCmpBU R/W 0 1 An ADC trigger pulse is output when the counter matches the value in the PWMnCMPB register value while counting down. 0 No ADC trigger is output. Trigger for Counter=Comparator B Up Value Description 1 An ADC trigger pulse is output when the counter matches the value in the PWMnCMPB register value while counting up. 0 No ADC trigger is output. July 14, 2014 515 Texas Instruments-Production Data Pulse Width Modulator (PWM) Bit/Field Name Type Reset 11 TrCmpAD R/W 0 Description Trigger for Counter=Comparator A Down Value Description 10 TrCmpAU R/W 0 1 An ADC trigger pulse is output when the counter matches the value in the PWMnCMPA register value while counting down. 0 No ADC trigger is output. Trigger for Counter=Comparator A Up Value Description 9 TrCntLoad R/W 0 1 An ADC trigger pulse is output when the counter matches the value in the PWMnCMPA register value while counting up. 0 No ADC trigger is output. Trigger for Counter=Load Value Description 8 TrCntZero R/W 0 1 An ADC trigger pulse is output when the counter matches the PWMnLOAD register. 0 No ADC trigger is output. Trigger for Counter=0 Value Description 7:6 reserved RO 0x0 5 IntCmpBD R/W 0 1 An ADC trigger pulse is output when the counter is 0. 0 No ADC trigger is output. Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. Interrupt for Counter=Comparator B Down Value Description 4 IntCmpBU R/W 0 1 A raw interrupt occurs when the counter matches the value in the PWMnCMPB register value while counting down. 0 No interrupt. Interrupt for Counter=Comparator B Up Value Description 1 A raw interrupt occurs when the counter matches the value in the PWMnCMPB register value while counting up. 0 No interrupt. 516 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Bit/Field Name Type Reset 3 IntCmpAD R/W 0 Description Interrupt for Counter=Comparator A Down Value Description 2 IntCmpAU R/W 0 1 A raw interrupt occurs when the counter matches the value in the PWMnCMPA register value while counting down. 0 No interrupt. Interrupt for Counter=Comparator A Up Value Description 1 IntCntLoad R/W 0 1 A raw interrupt occurs when the counter matches the value in the PWMnCMPA register value while counting up. 0 No interrupt. Interrupt for Counter=Load Value Description 0 IntCntZero R/W 0 1 A raw interrupt occurs when the counter matches the value in the PWMnLOAD register value. 0 No interrupt. Interrupt for Counter=0 Value Description 1 A raw interrupt occurs when the counter is zero. 0 No interrupt. July 14, 2014 517 Texas Instruments-Production Data Pulse Width Modulator (PWM) Register 12: PWM0 Raw Interrupt Status (PWM0RIS), offset 0x048 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. Bits set to 1 indicate the latched events that have occurred; bits set to 0 indicate that the event in question has not occurred. PWM0 Raw Interrupt Status (PWM0RIS) Base 0x4002.8000 Offset 0x048 Type RO, reset 0x0000.0000 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 IntCmpBD IntCmpBU IntCmpAD IntCmpAU IntCntLoad IntCntZero 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 Bit/Field Name Type Reset Description 31:6 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 5 IntCmpBD RO 0 Comparator B Down Interrupt Status Indicates that the counter has matched the comparator B value while counting down. 4 IntCmpBU RO 0 Comparator B Up Interrupt Status Indicates that the counter has matched the comparator B value while counting up. 3 IntCmpAD RO 0 Comparator A Down Interrupt Status Indicates that the counter has matched the comparator A value while counting down. 2 IntCmpAU RO 0 Comparator A Up Interrupt Status Indicates that the counter has matched the comparator A value while counting up. 1 IntCntLoad RO 0 Counter=Load Interrupt Status Indicates that the counter has matched the PWMnLOAD register. 0 IntCntZero RO 0 Counter=0 Interrupt Status Indicates that the counter has matched 0. 518 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 13: PWM0 Interrupt Status and Clear (PWM0ISC), offset 0x04C 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; bits set to 0 indicate 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. PWM0 Interrupt Status and Clear (PWM0ISC) Base 0x4002.8000 Offset 0x04C Type R/W1C, reset 0x0000.0000 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 IntCmpBD IntCmpBU IntCmpAD IntCmpAU IntCntLoad IntCntZero RO 0 RO 0 RO 0 R/W1C 0 R/W1C 0 R/W1C 0 R/W1C 0 R/W1C 0 R/W1C 0 reserved Type Reset reserved Type Reset RO 0 Bit/Field Name Type Reset Description 31:6 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 5 IntCmpBD R/W1C 0 Comparator B Down Interrupt Indicates that the counter has matched the comparator B value while counting down. 4 IntCmpBU R/W1C 0 Comparator B Up Interrupt Indicates that the counter has matched the comparator B value while counting up. 3 IntCmpAD R/W1C 0 Comparator A Down Interrupt Indicates that the counter has matched the comparator A value while counting down. 2 IntCmpAU R/W1C 0 Comparator A Up Interrupt Indicates that the counter has matched the comparator A value while counting up. 1 IntCntLoad R/W1C 0 Counter=Load Interrupt Indicates that the counter has matched the PWMnLOAD register. 0 IntCntZero R/W1C 0 Counter=0 Interrupt Indicates that the counter has matched 0. July 14, 2014 519 Texas Instruments-Production Data Pulse Width Modulator (PWM) Register 14: PWM0 Load (PWM0LOAD), offset 0x050 This register contains 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 504). If this register is re-written before the actual update occurs, the previous value is never used and is lost. PWM0 Load (PWM0LOAD) Base 0x4002.8000 Offset 0x050 Type R/W, reset 0x0000.0000 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 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 reserved Type Reset RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 15 14 13 12 11 10 9 8 Load Type Reset 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 31:16 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 15:0 Load R/W 0 Counter Load Value The counter load value. 520 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 15: PWM0 Counter (PWM0COUNT), offset 0x054 This register contains 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 524 and page 527) or drive an interrupt or ADC trigger (via the PWMnINTEN register, see page 515). A pulse with the same capabilities is generated when this value is zero. PWM0 Counter (PWM0COUNT) Base 0x4002.8000 Offset 0x054 Type RO, reset 0x0000.0000 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 8 RO 0 RO 0 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 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 Count Type Reset Bit/Field Name Type Reset Description 31:16 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 15:0 Count RO 0x00 Counter Value The current value of the counter. July 14, 2014 521 Texas Instruments-Production Data Pulse Width Modulator (PWM) Register 16: PWM0 Compare A (PWM0CMPA), offset 0x058 This register contains 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 or ADC trigger (via the PWMnINTEN register). If the value of this register is greater than the PWMnLOAD register (see page 520), then no pulse is ever output. If the comparator A update mode is immediate (based on the CmpAUpd bit in the PWMnCTL register), 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 504). If this register is rewritten before the actual update occurs, the previous value is never used and is lost. PWM0 Compare A (PWM0CMPA) Base 0x4002.8000 Offset 0x058 Type R/W, reset 0x0000.0000 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 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 reserved Type Reset RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 15 14 13 12 11 10 9 8 CompA Type Reset 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 31:16 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 15:0 CompA R/W 0x00 Comparator A Value The value to be compared against the counter. 522 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 17: PWM0 Compare B (PWM0CMPB), offset 0x05C This register contains 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 or ADC trigger (via the PWMnINTEN register). If the value of this register is greater than the PWMnLOAD register, no pulse is ever output. If the comparator B update mode is immediate (based on the CmpBUpd bit in the PWMnCTL register), this 16-bit CompB 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 504). If this register is rewritten before the actual update occurs, the previous value is never used and is lost. PWM0 Compare B (PWM0CMPB) Base 0x4002.8000 Offset 0x05C Type R/W, reset 0x0000.0000 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 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 reserved Type Reset RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 15 14 13 12 11 10 9 8 CompB Type Reset 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 31:16 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 15:0 CompB R/W 0x00 Comparator B Value The value to be compared against the counter. July 14, 2014 523 Texas Instruments-Production Data Pulse Width Modulator (PWM) Register 18: PWM0 Generator A Control (PWM0GENA), offset 0x060 This register controls 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. 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. PWM0 Generator A Control (PWM0GENA) Base 0x4002.8000 Offset 0x060 Type R/W, reset 0x0000.0000 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 8 RO 0 RO 0 RO 0 R/W 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 7 6 5 4 3 2 1 0 R/W 0 R/W 0 reserved Type Reset reserved Type Reset ActCmpBD RO 0 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 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 11:10 ActCmpBD R/W 0x0 Action for Comparator B Down The action to be taken when the counter matches comparator B while counting down. The table below defines the effect of the event on the output signal. Value Description 0x0 Do nothing. 0x1 Invert the output signal. 0x2 Set the output signal to 0. 0x3 Set the output signal to 1. 524 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Bit/Field Name Type Reset 9:8 ActCmpBU R/W 0x0 Description Action for Comparator B Up 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 513) is set to 1. The table below defines the effect of the event on the output signal. Value Description 0x0 Do nothing. 0x1 Invert the output signal. 0x2 Set the output signal to 0. 0x3 Set the output signal to 1. 7:6 ActCmpAD R/W 0x0 Action for Comparator A Down The action to be taken when the counter matches comparator A while counting down. The table below defines the effect of the event on the output signal. Value Description 0x0 Do nothing. 0x1 Invert the output signal. 0x2 Set the output signal to 0. 0x3 Set the output signal to 1. 5:4 ActCmpAU R/W 0x0 Action for Comparator A Up 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. The table below defines the effect of the event on the output signal. Value Description 0x0 Do nothing. 0x1 Invert the output signal. 0x2 Set the output signal to 0. 0x3 Set the output signal to 1. 3:2 ActLoad R/W 0x0 Action for Counter=Load The action to be taken when the counter matches the load value. The table below defines the effect of the event on the output signal. Value Description 0x0 Do nothing. 0x1 Invert the output signal. 0x2 Set the output signal to 0. 0x3 Set the output signal to 1. July 14, 2014 525 Texas Instruments-Production Data Pulse Width Modulator (PWM) Bit/Field Name Type Reset 1:0 ActZero R/W 0x0 Description Action for Counter=0 The action to be taken when the counter is zero. The table below defines the effect of the event on the output signal. Value Description 0x0 Do nothing. 0x1 Invert the output signal. 0x2 Set the output signal to 0. 0x3 Set the output signal to 1. 526 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Register 19: PWM0 Generator B Control (PWM0GENB), offset 0x064 This register controls 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. 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. PWM0 Generator B Control (PWM0GENB) Base 0x4002.8000 Offset 0x064 Type R/W, reset 0x0000.0000 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 8 RO 0 RO 0 RO 0 R/W 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 7 6 5 4 3 2 1 0 R/W 0 R/W 0 reserved Type Reset reserved Type Reset ActCmpBD RO 0 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 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 11:10 ActCmpBD R/W 0x0 Action for Comparator B Down The action to be taken when the counter matches comparator B while counting down. The table below defines the effect of the event on the output signal. Value Description 0x0 Do nothing. 0x1 Invert the output signal. 0x2 Set the output signal to 0. 0x3 Set the output signal to 1. July 14, 2014 527 Texas Instruments-Production Data Pulse Width Modulator (PWM) Bit/Field Name Type Reset 9:8 ActCmpBU R/W 0x0 Description Action for Comparator B Up The action to be taken when the counter matches comparator B while counting up. Occurs only when the Mode bit in the PWMnCTL register is set to 1. The table below defines the effect of the event on the output signal. Value Description 0x0 Do nothing. 0x1 Invert the output signal. 0x2 Set the output signal to 0. 0x3 Set the output signal to 1. 7:6 ActCmpAD R/W 0x0 Action for Comparator A Down The action to be taken when the counter matches comparator A while counting down. The table below defines the effect of the event on the output signal. Value Description 0x0 Do nothing. 0x1 Invert the output signal. 0x2 Set the output signal to 0. 0x3 Set the output signal to 1. 5:4 ActCmpAU R/W 0x0 Action for Comparator A Up 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. The table below defines the effect of the event on the output signal. Value Description 0x0 Do nothing. 0x1 Invert the output signal. 0x2 Set the output signal to 0. 0x3 Set the output signal to 1. 3:2 ActLoad R/W 0x0 Action for Counter=Load The action to be taken when the counter matches the load value. The table below defines the effect of the event on the output signal. Value Description 0x0 Do nothing. 0x1 Invert the output signal. 0x2 Set the output signal to 0. 0x3 Set the output signal to 1. 528 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Bit/Field Name Type Reset 1:0 ActZero R/W 0x0 Description Action for Counter=0 The action to be taken when the counter is 0. The table below defines the effect of the event on the output signal. Value Description 0x0 Do nothing. 0x1 Invert the output signal. 0x2 Set the output signal to 0. 0x3 Set the output signal to 1. July 14, 2014 529 Texas Instruments-Production Data 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 and inverting the resulting waveform, 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 531), 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 532). PWM0 Dead-Band Control (PWM0DBCTL) Base 0x4002.8000 Offset 0x068 Type R/W, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 RO 0 reserved Type Reset 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 RO 0 8 7 6 5 4 3 2 1 reserved Type Reset RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 0 Enable RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 RO 0 R/W 0 Bit/Field Name Type Reset Description 31:1 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 0 Enable R/W 0 Dead-Band Generator Enable When set, the dead-band generator inserts dead bands into the output signals; when clear, it simply passes the PWM signals through. 530 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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. PWM0 Dead-Band Rising-Edge Delay (PWM0DBRISE) Base 0x4002.8000 Offset 0x06C Type R/W, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 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 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 reserved Type Reset RO 0 RO 0 RiseDelay 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 Bit/Field Name Type Reset Description 31:12 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 11:0 RiseDelay R/W 0 Dead-Band Rise Delay The number of clock ticks to delay the rising edge. July 14, 2014 531 Texas Instruments-Production Data 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. PWM0 Dead-Band Falling-Edge-Delay (PWM0DBFALL) Base 0x4002.8000 Offset 0x070 Type R/W, reset 0x0000.0000 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 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 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 reserved Type Reset RO 0 RO 0 FallDelay RO 0 RO 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 31:12 reserved RO 0x00 Software should not rely on the value of a reserved bit. To provide compatibility with future products, the value of a reserved bit should be preserved across a read-modify-write operation. 11:0 FallDelay R/W 0x00 Dead-Band Fall Delay The number of clock ticks to delay the falling edge. 532 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 16 Pin Diagram The LM3S812 microcontroller pin diagrams are shown below. Figure 16-1. 48-Pin QFP Package Pin Diagram July 14, 2014 533 Texas Instruments-Production Data Signal Tables 17 Signal Tables 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. The following tables list the signals available for each pin. Functionality is enabled by software with the GPIOAFSEL register. All digital inputs are Schmitt triggered. ■ ■ ■ ■ ■ 17.1 Signals by Pin Number Signals by Signal Name Signals by Function, Except for GPIO GPIO Pins and Alternate Functions Connections for Unused Signals Signals by Pin Number Table 17-1. Signals by Pin Number a Pin Number Pin Name Pin Type Buffer Type 1 ADC0 I Analog Analog-to-digital converter input 0. 2 ADC1 I Analog Analog-to-digital converter input 1. PE3 I/O TTL GPIO port E bit 3. 3 Description CCP1 I/O TTL Capture/Compare/PWM 1. 4 PE2 I/O TTL GPIO port E bit 2. 5 RST I TTL System reset input. LDO - Power 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 I/O and some logic. 8 GND - Power Ground reference for logic and I/O pins. 9 OSC0 I Analog Main oscillator crystal input or an external clock reference input. OSC1 O Analog Main oscillator crystal output. Leave unconnected when using a single-ended clock source. PC7 I/O TTL GPIO port C bit 7. CCP4 I/O TTL Capture/Compare/PWM 4. 6 10 11 PC6 I/O TTL GPIO port C bit 6. CCP3 I/O TTL Capture/Compare/PWM 3. 13 PC5 I/O TTL GPIO port C bit 5. 14 PC4 I/O TTL GPIO port C bit 4. 15 VDD - Power Positive supply for I/O and some logic. 16 GND - Power Ground reference for logic and I/O pins. PA0 I/O TTL GPIO port A bit 0. U0Rx I TTL UART module 0 receive. PA1 I/O TTL GPIO port A bit 1. U0Tx O TTL UART module 0 transmit. PA2 I/O TTL GPIO port A bit 2. SSIClk I/O TTL SSI clock. 12 17 18 19 534 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Table 17-1. Signals by Pin Number (continued) Pin Number a Pin Name Pin Type Buffer Type Description PA3 I/O TTL GPIO port A bit 3. SSIFss I/O TTL SSI frame. PA4 I/O TTL GPIO port A bit 4. SSIRx I TTL SSI receive. PA5 I/O TTL GPIO port A bit 5. SSI transmit. 20 21 22 SSITx O TTL 23 VDD - Power Positive supply for I/O and some logic. 24 GND - Power Ground reference for logic and I/O pins. PD0 I/O TTL GPIO port D bit 0. PWM0 O TTL PWM 0. This signal is controlled by PWM Generator 0. 25 PD1 I/O TTL GPIO port D bit 1. PWM1 O TTL PWM 1. This signal is controlled by PWM Generator 0. PD2 I/O TTL GPIO port D bit 2. U1Rx I TTL UART module 1 receive. PD3 I/O TTL GPIO port D bit 3. U1Tx O TTL UART module 1 transmit. PB0 I/O TTL GPIO port B bit 0. CCP0 I/O TTL Capture/Compare/PWM 0. 30 PB1 I/O TTL GPIO port B bit 1. 31 GND - Power Ground reference for logic and I/O pins. 32 VDD - Power Positive supply for I/O and some logic. 26 27 28 29 PB2 I/O TTL GPIO port B bit 2. I2CSCL I/O OD I2C clock. 33 PB3 I/O TTL GPIO port B bit 3. I2CSDA I/O OD I2C data. 35 PE0 I/O TTL GPIO port E bit 0. 36 PE1 I/O TTL GPIO port E bit 1. PC3 I/O TTL GPIO port C bit 3. SWO O TTL JTAG TDO and SWO. TDO O TTL JTAG TDO and SWO. PC2 I/O TTL GPIO port C bit 2. TDI I TTL JTAG TDI. PC1 I/O TTL GPIO port C bit 1. SWDIO I/O TTL JTAG TMS and SWDIO. TMS I/O TTL JTAG TMS and SWDIO. PC0 I/O TTL GPIO port C bit 0. SWCLK I TTL JTAG/SWD CLK. TCK I TTL JTAG/SWD CLK. PB7 I/O TTL GPIO port B bit 7. TRST I TTL JTAG TRST. 34 37 38 39 40 41 July 14, 2014 535 Texas Instruments-Production Data Signal Tables Table 17-1. Signals by Pin Number (continued) Pin Number Pin Type PB6 I/O TTL C0+ I Analog PB5 I/O TTL GPIO port B bit 5. CCP5 I/O TTL Capture/Compare/PWM 5. PB4 I/O TTL GPIO port B bit 4. C0- I Analog PD4 I/O TTL GPIO port D bit 4. PD5 I/O TTL GPIO port D bit 5. CCP2 I/O TTL Capture/Compare/PWM 2. PD6 I/O TTL GPIO port D bit 6. Fault I TTL PWM Fault. PD7 I/O TTL GPIO port D bit 7. C0o O TTL Analog comparator 0 output. 42 43 44 45 a Pin Name 46 47 48 Buffer Type Description GPIO port B bit 6. Analog comparator 0 positive input. Analog comparator 0 negative input. a. The TTL designation indicates the pin has TTL-compatible voltage levels. 17.2 Signals by Signal Name Table 17-2. Signals by Signal Name a Pin Name Pin Number Pin Type Buffer Type ADC0 1 I Analog Description Analog-to-digital converter input 0. ADC1 2 I Analog Analog-to-digital converter input 1. C0+ 42 I Analog Analog comparator 0 positive input. C0- 44 I Analog Analog comparator 0 negative input. C0o 48 O TTL Analog comparator 0 output. CCP0 29 I/O TTL Capture/Compare/PWM 0. CCP1 3 I/O TTL Capture/Compare/PWM 1. CCP2 46 I/O TTL Capture/Compare/PWM 2. CCP3 12 I/O TTL Capture/Compare/PWM 3. CCP4 11 I/O TTL Capture/Compare/PWM 4. CCP5 43 I/O TTL Capture/Compare/PWM 5. Fault 47 I TTL PWM Fault. GND 8 16 24 31 - Power I2CSCL 33 I/O OD I2C clock. I2CSDA 34 I/O OD I2C data. LDO 6 - Power 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 Main oscillator crystal input or an external clock reference input. OSC1 10 O Analog Main oscillator crystal output. Leave unconnected when using a single-ended clock source. Ground reference for logic and I/O pins. 536 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Table 17-2. Signals by Signal Name (continued) a Pin Name Pin Number Pin Type Buffer Type Description PA0 17 I/O TTL GPIO port A bit 0. PA1 18 I/O TTL GPIO port A bit 1. 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. PD6 47 I/O TTL GPIO port D bit 6. PD7 48 I/O TTL GPIO port D bit 7. PE0 35 I/O TTL GPIO port E bit 0. PE1 36 I/O TTL GPIO port E bit 1. PE2 4 I/O TTL GPIO port E bit 2. PE3 3 I/O TTL GPIO port E bit 3. PWM0 25 O TTL PWM 0. This signal is controlled by PWM Generator 0. PWM1 26 O TTL PWM 1. This signal is controlled by PWM Generator 0. RST 5 I TTL System reset input. SSIClk 19 I/O TTL SSI clock. SSIFss 20 I/O TTL SSI frame. SSIRx 21 I TTL SSI receive. SSITx 22 O TTL SSI transmit. July 14, 2014 537 Texas Instruments-Production Data Signal Tables Table 17-2. Signals by Signal Name (continued) Pin Name Pin Number SWCLK SWDIO a Pin Type Buffer Type Description 40 I TTL JTAG/SWD CLK. 39 I/O TTL JTAG TMS and SWDIO. SWO 37 O TTL JTAG TDO and SWO. TCK 40 I TTL JTAG/SWD CLK. TDI 38 I TTL JTAG TDI. TDO 37 O TTL JTAG TDO and SWO. TMS 39 I/O TTL JTAG TMS and SWDIO. TRST 41 I TTL JTAG TRST. U0Rx 17 I TTL UART module 0 receive. U0Tx 18 O TTL UART module 0 transmit. U1Rx 27 I TTL UART module 1 receive. U1Tx 28 O TTL UART module 1 transmit. VDD 7 15 23 32 - Power Positive supply for I/O and some logic. a. The TTL designation indicates the pin has TTL-compatible voltage levels. 17.3 Signals by Function, Except for GPIO Table 17-3. Signals by Function, Except for GPIO Function Pin Name Pin Type Buffer Type ADC0 1 I Analog Analog-to-digital converter input 0. ADC1 2 I Analog Analog-to-digital converter input 1. C0+ 42 I Analog Analog comparator 0 positive input. C0- 44 I Analog Analog comparator 0 negative input. C0o 48 O TTL Analog comparator 0 output. CCP0 29 I/O TTL Capture/Compare/PWM 0. CCP1 3 I/O TTL Capture/Compare/PWM 1. CCP2 46 I/O TTL Capture/Compare/PWM 2. CCP3 12 I/O TTL Capture/Compare/PWM 3. CCP4 11 I/O TTL Capture/Compare/PWM 4. CCP5 43 I/O TTL Capture/Compare/PWM 5. I2CSCL 33 I/O OD I2C clock. I2CSDA 34 I/O OD I2C data. ADC Analog Comparators General-Purpose Timers a Pin Number I2C Description 538 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Table 17-3. Signals by Function, Except for GPIO (continued) Function Pin Name Pin Number a Pin Type Buffer Type SWCLK 40 I TTL JTAG/SWD CLK. SWDIO 39 I/O TTL JTAG TMS and SWDIO. SWO 37 O TTL JTAG TDO and SWO. TCK 40 I TTL JTAG/SWD CLK. TDI 38 I TTL JTAG TDI. TDO 37 O TTL JTAG TDO and SWO. TMS 39 I/O TTL JTAG TMS and SWDIO. TRST 41 I TTL JTAG TRST. Fault 47 I TTL PWM Fault. PWM0 25 O TTL PWM 0. This signal is controlled by PWM Generator 0. PWM1 26 O TTL PWM 1. This signal is controlled by PWM Generator 0. GND 8 16 24 31 - Power Ground reference for logic and I/O pins. LDO 6 - Power Low drop-out regulator output voltage. This pin requires an external capacitor between the pin and GND of 1 µF or greater. VDD 7 15 23 32 - Power Positive supply for I/O and some logic. SSIClk 19 I/O TTL SSI clock. SSIFss 20 I/O TTL SSI frame. SSIRx 21 I TTL SSI receive. SSITx 22 O TTL SSI transmit. OSC0 9 I Analog Main oscillator crystal input or an external clock reference input. OSC1 10 O Analog Main oscillator crystal output. Leave unconnected when using a single-ended clock source. RST 5 I TTL System reset input. U0Rx 17 I TTL UART module 0 receive. U0Tx 18 O TTL UART module 0 transmit. U1Rx 27 I TTL UART module 1 receive. U1Tx 28 O TTL UART module 1 transmit. JTAG/SWD/SWO PWM Power SSI System Control & Clocks Description UART a. The TTL designation indicates the pin has TTL-compatible voltage levels. 17.4 GPIO Pins and Alternate Functions Table 17-4. GPIO Pins and Alternate Functions IO Pin Number Multiplexed Function PA0 17 U0Rx PA1 18 U0Tx July 14, 2014 Multiplexed Function 539 Texas Instruments-Production Data Signal Tables Table 17-4. GPIO Pins and Alternate Functions (continued) 17.5 IO Pin Number Multiplexed Function PA2 19 SSIClk PA3 20 SSIFss PA4 21 SSIRx PA5 22 SSITx PB0 29 CCP0 PB1 30 PB2 33 I2CSCL PB3 34 I2CSDA PB4 44 C0- PB5 43 CCP5 PB6 42 C0+ PB7 41 TRST PC0 40 TCK SWCLK PC1 39 TMS SWDIO PC2 38 TDI PC3 37 TDO PC4 14 PC5 13 PC6 12 CCP3 PC7 11 CCP4 PD0 25 PWM0 PD1 26 PWM1 PD2 27 U1Rx PD3 28 U1Tx PD4 45 PD5 46 CCP2 PD6 47 Fault PD7 48 C0o PE0 35 PE1 36 PE2 4 PE3 3 Multiplexed Function SWO CCP1 Connections for Unused Signals Table 17-5 on page 541 show how to handle signals for functions that are not used in a particular system implementation. Two options are shown in the table: an acceptable practice and a preferred practice for reduced power consumption and improved EMC characteristics. 540 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Table 17-5. Connections for Unused Signals Function ADC GPIO System Control Signal Name Pin Number Acceptable Practice Preferred Practice ADC0 1 NC GNDA ADC1 2 All unused GPIOs - NC GND OSC0 9 NC GND OSC1 10 NC NC RST 5 Pull up as shown in Figure 5-1 on page 155 Connect through a capacitor to GND as close to pin as possible July 14, 2014 541 Texas Instruments-Production Data Operating Characteristics 18 Operating Characteristics Table 18-1. Temperature Characteristics Characteristic Symbol Value Industrial operating temperature range TA -40 to +85 Unit °C Unpowered storage temperature range TS -65 to +150 °C Table 18-2. Thermal Characteristics Characteristic a Thermal resistance (junction to ambient) b Symbol Value ΘJA 50 (48-pin QFP) Unit °C/W Junction temperature TJ TA + (P • ΘJA) °C Maximum junction temperature TJMAX 115 °C c 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”. a Table 18-3. ESD Absolute Maximum Ratings Parameter Name VESDHBM Min Nom Max Unit - - 2.0 kV VESDCDM - - 1.0 kV VESDMM - - 100 V a. All Stellaris parts are ESD tested following the JEDEC standard. 542 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 19 Electrical Characteristics 19.1 DC Characteristics 19.1.1 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 19-1. Maximum Ratings a Characteristic Supply voltage range (VDD) Input voltage Symbol Value VDD 0.0 to +3.6 V -0.3 to 5.5 V VIN Input voltage for a GPIO configured as an analog input Unit -0.3 to VDD + 0.3 V Maximum current for pins, excluding pins operating as GPIOs I 100 mA Maximum current for GPIO pins I 100 mA VNON 300 mV Maximum input voltage on a non-power pin when the microcontroller is unpowered 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). 19.1.2 Recommended DC Operating Conditions Table 19-2. Recommended DC Operating Conditions Parameter Parameter Name Min Nom Max Unit 3.0 3.3 3.6 V VDD Supply voltage VIH High-level input voltage 2.0 - 5.0 V VIL Low-level input voltage -0.3 - 1.3 V VOH High-level output voltage 2.4 - - V VOL Low-level output voltage - - 0.4 V 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 IOH Low-level sink current, VOL=0.4 V IOL July 14, 2014 543 Texas Instruments-Production Data Electrical Characteristics 19.1.3 On-Chip Low Drop-Out (LDO) Regulator Characteristics Table 19-3. LDO Regulator Characteristics Parameter 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 1.0 - 3.0 µF VLDOOUT 19.1.4 GPIO Module Characteristics Table 19-4. GPIO Module DC Characteristics Parameter Min Nom Max Unit RGPIOPU GPIO internal pull-up resistor 50 - 110 kΩ RGPIOPD GPIO internal pull-down resistor 55 - 180 kΩ - - 2 µA ILKG Parameter Name a GPIO input leakage current a. The leakage current is measured with GND or VDD applied to the corresponding pin(s). The leakage of digital port pins is measured individually. The port pin is configured as an input and the pullup/pulldown resistor is disabled. 19.1.5 Power Specifications The power measurements specified in the tables that follow are run on the core processor using SRAM with the following specifications (except as noted): ■ VDD = 3.3 V ■ Temperature = 25°C 544 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Table 19-5. Detailed Power Specifications Parameter Parameter Name Conditions Run mode 1 (Flash loop) 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 out of 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 out of Flash Peripherals = All clock-gated OFF IDD_RUN 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 OFF System Clock = MOSC/16 19.1.6 Flash Memory Characteristics Table 19-6. Flash Memory Characteristics Parameter Min Nom Max Unit 10,000 100,000 - 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 - - 250 ms PECYC TRET Parameter Name Number of guaranteed program/erase cycles a before failure a. A program/erase cycle is defined as switching the bits from 1-> 0 -> 1. 19.2 AC Characteristics 19.2.1 Load Conditions Unless otherwise specified, the following conditions are true for all timing measurements. Timing measurements are for 4-mA drive strength. July 14, 2014 545 Texas Instruments-Production Data Electrical Characteristics Figure 19-1. Load Conditions CL = 50 pF pin GND 19.2.2 Clocks Table 19-7. Phase Locked Loop (PLL) Characteristics Min Nom Max Unit fref_crystal Parameter Crystal reference Parameter Name 3.579545 - 8.192 MHz fref_ext External clock referencea 3.579545 - 8.192 MHz a b fpll PLL frequency - 200 - MHz TREADY PLL lock time - - 0.5 ms a. The exact value is determined by the crystal value programmed into the XTAL field of the Run-Mode Clock Configuration (RCC) register. b. PLL frequency is automatically calculated by the hardware based on the XTAL field of the RCC register. Table 19-8. Clock Characteristics Min Nom Max Unit fIOSC Parameter Parameter Name Internal oscillator frequency 7 12 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 a (PLL in BYPASS mode) 1 - 8 MHz fref_ext_bypass External clock reference (PLL in BYPASS a mode) 0 - 50 MHz fsystem_clock System clock 0 - 50 MHz a. The ADC must be clocked from the PLL or directly from a 16.667-MHz clock source to operate properly. 19.2.2.1 System Clock Specifications with ADC Operation Table 19-9. System Clock Characteristics with ADC Operation Parameter fsysadc 19.2.3 Parameter Name System clock frequency when the ADC module is operating (when PLL is bypassed) Min Nom Max Unit 16 - - MHz Min Nom Max Unit 0 - 10 MHz 100 - - ns JTAG and Boundary Scan Table 19-10. JTAG Characteristics Parameter No. Parameter Parameter Name J1 fTCK TCK operational clock frequency J2 tTCK TCK operational clock period 546 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Table 19-10. JTAG Characteristics (continued) Parameter No. Parameter J3 tTCK_LOW J4 tTCK_HIGH Parameter Name Min Nom Max Unit TCK clock Low time - tTCK/2 - ns TCK clock High time - tTCK/2 - ns J5 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 t TDO_ZDV TCK fall to Data Valid from High-Z 2-mA drive 23 35 ns 4-mA drive 15 26 ns - 8-mA drive 8-mA drive with slew rate control J12 t TDO_DV J13 TCK fall to Data Valid from Data Valid t TDO_DVZ TCK fall to High-Z from Data Valid J14 tTRST J15 tTRST_SU 14 25 ns 18 29 ns 2-mA drive 21 35 ns 4-mA drive 14 25 ns 13 24 ns 8-mA drive with slew rate control 18 28 ns 2-mA drive 9 11 ns 7 9 ns 6 8 ns - 8-mA drive 4-mA drive - 8-mA drive 7 9 ns TRST assertion time 8-mA drive with slew rate control 100 - - ns TRST setup time to TCK rise 10 - - ns Figure 19-2. JTAG Test Clock Input Timing J2 J3 J4 TCK J6 J5 July 14, 2014 547 Texas Instruments-Production Data Electrical Characteristics Figure 19-3. JTAG Test Access Port (TAP) Timing TCK J7 TMS TDI J8 J7 TMS Input Valid TMS Input Valid J9 J9 J10 TDI Input Valid J11 TDO J8 J10 TDI Input Valid J12 J13 TDO Output Valid TDO Output Valid Figure 19-4. JTAG TRST Timing TCK J14 J15 TRST 19.2.4 Reset Table 19-11. Reset Characteristics Parameter No. Parameter Parameter Name R1 VTH Reset threshold R2 VBTH Brown-Out threshold R3 TPOR R4 TBOR R5 TIRPOR Internal reset timeout after POR R6 TIRBOR Internal reset timeout after BOR R7 TIRHWR Internal reset timeout after hardware reset (RST pin) R8 TIRSWR Internal reset timeout after software-initiated system reset a R9 TIRWDR Internal reset timeout after watchdog reseta 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 15 - 30 ms 2.5 - 20 µs 2.9 - 29 µs 2.5 - 20 µs 2.5 - 20 µs 2.5 - 20 µs - - 100 ms a reseta R10 TIRLDOR Internal reset timeout after LDO R11 TVDDRISE Supply voltage (VDD) rise time (0 V-3.3 V) a. 20 * t MOSC_per 548 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Figure 19-5. External Reset Timing (RST) RST R7 /Reset (Internal) Figure 19-6. Power-On Reset Timing R1 VDD R3 /POR (Internal) R5 /Reset (Internal) Figure 19-7. Brown-Out Reset Timing R2 VDD R4 /BOR (Internal) R6 /Reset (Internal) July 14, 2014 549 Texas Instruments-Production Data Electrical Characteristics Figure 19-8. Software Reset Timing SW Reset R8 /Reset (Internal) Figure 19-9. Watchdog Reset Timing WDOG Reset (Internal) R9 /Reset (Internal) Figure 19-10. LDO Reset Timing LDO Reset (Internal) R10 /Reset (Internal) 19.2.5 Sleep Modes a Table 19-12. Sleep Modes AC Characteristics Parameter No Parameter D1 tWAKE_S D2 tWAKE_PLL_S Parameter Name Min Nom Max Unit Time to wake from interrupt in sleep or deep-sleep mode, not using the PLL - - 7 system clocks Time to wake from interrupt in sleep or deep-sleep mode when using the PLL - - TREADY ms a. Values in this table assume the IOSC is the clock source during sleep or deep-sleep mode. 19.2.6 General-Purpose I/O (GPIO) Note: All GPIOs are 5 V-tolerant. 550 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Table 19-13. GPIO Characteristics Parameter Parameter Name Condition tGPIOR tGPIOF Min GPIO Rise Time (from 20% to 80% of VDD) Nom Max Unit 2-mA drive 17 26 ns 4-mA drive 9 13 ns - 6 9 ns 8-mA drive with slew rate control 8-mA drive 10 12 ns 2-mA drive 17 25 ns 4-mA drive 8 12 ns 6 10 ns 11 13 ns GPIO Fall Time (from 80% to 20% of VDD) - 8-mA drive 8-mA drive with slew rate control 19.2.7 Analog-to-Digital Converter a Table 19-14. ADC Characteristics Parameter VADCIN Parameter Name Min Nom Max Unit Maximum single-ended, full-scale analog input voltage - - 3.0 V Minimum single-ended, full-scale analog input voltage 0.0 - - V - - 1.5 V 0.0 - - V 14 16.667 18 MHz Maximum differential, full-scale analog input voltage Minimum differential, full-scale analog input voltage N fADC Resolution 10 b ADC internal clock frequency bits tADCCONV Conversion time c 4 µs f ADCCONV c 260.417 k samples/s Conversion rate tLT Latency from trigger to start of conversion - 2 - system clocks IL ADC input leakage - - ±3.0 µA RADC ADC equivalent resistance - - 10 kΩ CADC ADC equivalent capacitance 0.9 1.0 1.1 pF EL Integral nonlinearity error - - ±3 LSB ED Differential nonlinearity error - - ±2 LSB d EO Offset error - - +6 LSB EG Full-scale gain error - - ±3 LSB ETS Temperature sensor accuracy - - ±5 °C a. The ADC reference voltage is 3.0 V. This reference voltage is internally generated from the 3.3 VDDA supply by a band gap circuit. b. The ADC must be clocked from the PLL or directly from an external clock source to operate properly. c. The conversion time and rate scale from the specified number if the ADC internal clock frequency is any value other than 16.667 MHz. d. The offset error listed above is the conversion result with 0 V applied to the ADC input. July 14, 2014 551 Texas Instruments-Production Data Electrical Characteristics Figure 19-11. ADC Input Equivalency Diagram Stellaris® Microcontroller VDD RADC 10-bit converter IL VIN CADC Sample and hold ADC converter Table 19-15. ADC Module Internal Reference Characteristics Parameter VREFI EIR 19.2.8 Parameter Name Min Nom Max Unit Internal voltage reference for ADC - 3.0 - V Internal voltage reference error - - ±2.5 % Synchronous Serial Interface (SSI) Table 19-16. SSI Characteristics Parameter No. Parameter Parameter Name Min S1 tclk_per SSIClk cycle time S2 tclk_high SSIClk high time S3 tclk_low SSIClk low time a Nom Max Unit 2 - 65024 system clocks - 0.5 - t clk_per - 0.5 - t clk_per - 6 10 ns S4 tclkrf SSIClk rise/fall time S5 tDMd Data from master valid delay time 0 - 1 system clocks S6 tDMs Data from master setup time 1 - - system clocks S7 tDMh Data from master hold time 2 - - system clocks S8 tDSs Data from slave setup time 1 - - system clocks S9 tDSh Data from slave hold time 2 - - system clocks a. Note that the delays shown are using 8-mA drive strength. 552 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Figure 19-12. SSI Timing for TI Frame Format (FRF=01), Single Transfer Timing Measurement S1 S4 S2 SSIClk S3 SSIFss SSITx SSIRx MSB LSB 4 to 16 bits Figure 19-13. 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 July 14, 2014 553 Texas Instruments-Production Data Electrical Characteristics Figure 19-14. SSI Timing for SPI Frame Format (FRF=00), with SPH=1 S1 S2 S4 SSIClk (SPO=0) S3 SSIClk (SPO=1) S6 SSITx (master) S7 MSB S5 SSIRx (slave) S8 LSB S9 MSB LSB SSIFss 19.2.9 Inter-Integrated Circuit (I2C) Interface Table 19-17. I2C Characteristics Parameter No. Parameter Parameter Name Min Nom Max Unit a tSCH Start condition hold time 36 - - system clocks a tLP Clock Low period 36 - - system clocks b tSRT I2CSCL/I2CSDA rise time (VIL =0.5 V to V IH =2.4 V) - - (see note b) ns a tDH Data hold time 2 - - system clocks c tSFT I2CSCL/I2CSDA fall time (VIH =2.4 V to V IL =0.5 V) - 9 10 ns I1 I2 I3 I4 I5 a tHT Clock High time 24 - - system clocks a tDS Data setup time 18 - - system clocks a tSCSR Start condition setup time (for repeated start condition only) 36 - - system clocks a tSCS Stop condition setup time 24 - - system clocks I6 I7 I8 I9 I2C a. Values depend on the value programmed into the TPR bit in the Master Timer Period (I2CMTPR) register; a TPR programmed for the maximum I2CSCL frequency (TPR=0x2) results in a minimum output timing as shown in the table above. The I 2C interface is designed to scale the actual data transition time to move it to the middle of the I2CSCL Low period. The actual position is affected by the value programmed into the TPR; however, the numbers given in the above values are minimum values. b. Because I2CSCL and I2CSDA are open-drain-type outputs, which the controller can only actively drive Low, the time I2CSCL or I2CSDA takes to reach a high level depends on external signal capacitance and pull-up resistor values. c. Specified at a nominal 50 pF load. 554 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Figure 19-15. I2C Timing I2 I6 I5 I2CSCL I1 I4 I7 I8 I3 I9 I2CSDA 19.2.10 Analog Comparator Table 19-18. 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 CMRR Common mode rejection ratio 50 - - dB TRT Response time - - 1 µs TMC Comparator mode change to Output Valid - - 10 µs Table 19-19. Analog Comparator Voltage Reference Characteristics Parameter Parameter Name Min Nom Max Unit RHR Resolution high range - VDD/31 - LSB RLR Resolution low range - VDD/23 - LSB AHR Absolute accuracy high range - - ±1/2 LSB ALR Absolute accuracy low range - - ±1/4 LSB July 14, 2014 555 Texas Instruments-Production Data Serial Flash Loader A Serial Flash Loader A.1 Serial Flash Loader ® The Stellaris serial flash loader is a preprogrammed flash-resident utility 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 SSI0 interfaces. For simplicity, both the data format and communication protocol are identical for both serial interfaces. A.2 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. A.2.1 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 which is calculated as follows: Max Baud Rate = System Clock Frequency / 16 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 0.35 ms. A.2.2 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 “Frame Formats” on page 410 in the SSI chapter for more information on formats for 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 556 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 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. A.3 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 format for receiving and sending packets, including the method used to acknowledge successful or unsuccessful reception of a packet. A.3.1 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[]; }; A.3.2 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. 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 section that describes the serial flash loader command, COMMAND_SEND_DATA (see “COMMAND_SEND_DATA (0x24)” on page 559). 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. A.3.3 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 July 14, 2014 557 Texas Instruments-Production Data Serial Flash Loader 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. A.4 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. A.4.1 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. A.4.2 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 A.4.3 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] Byte[1] Byte[2] Byte[3] Byte[4] Byte[5] Byte[6] Byte[7] = = = = = = = = 11 checksum(Bytes[2:10]) COMMAND_DOWNLOAD Program Address [31:24] Program Address [23:16] Program Address [15:8] Program Address [7:0] Program Size [31:24] 558 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller Byte[8] = Program Size [23:16] Byte[9] = Program Size [15:8] Byte[10] = Program Size [7:0] A.4.4 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 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] A.4.5 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] A.4.6 = = = = = = = 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. July 14, 2014 559 Texas Instruments-Production Data Serial Flash Loader Byte[0] = 3 Byte[1] = checksum(Byte[2]) Byte[2] = COMMAND_RESET 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. 560 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller B Register Quick Reference 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 The Cortex-M3 Processor R0, type R/W, , reset - (see page 50) DATA DATA R1, type R/W, , reset - (see page 50) DATA DATA R2, type R/W, , reset - (see page 50) DATA DATA R3, type R/W, , reset - (see page 50) DATA DATA R4, type R/W, , reset - (see page 50) DATA DATA R5, type R/W, , reset - (see page 50) DATA DATA R6, type R/W, , reset - (see page 50) DATA DATA R7, type R/W, , reset - (see page 50) DATA DATA R8, type R/W, , reset - (see page 50) DATA DATA R9, type R/W, , reset - (see page 50) DATA DATA R10, type R/W, , reset - (see page 50) DATA DATA R11, type R/W, , reset - (see page 50) DATA DATA R12, type R/W, , reset - (see page 50) DATA DATA SP, type R/W, , reset - (see page 51) SP SP LR, type R/W, , reset 0xFFFF.FFFF (see page 52) LINK LINK PC, type R/W, , reset - (see page 53) PC PC July 14, 2014 561 Texas Instruments-Production Data Register Quick Reference 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 PSR, type R/W, , reset 0x0100.0000 (see page 54) N Z C V Q ICI / IT THUMB ICI / IT ISRNUM PRIMASK, type R/W, , reset 0x0000.0000 (see page 58) PRIMASK FAULTMASK, type R/W, , reset 0x0000.0000 (see page 59) FAULTMASK BASEPRI, type R/W, , reset 0x0000.0000 (see page 60) BASEPRI CONTROL, type R/W, , reset 0x0000.0000 (see page 61) ASP TMPL INTEN ENABLE Cortex-M3 Peripherals System Timer (SysTick) Registers Base 0xE000.E000 STCTRL, type R/W, offset 0x010, reset 0x0000.0000 COUNT CLK_SRC STRELOAD, type R/W, offset 0x014, reset 0x0000.0000 RELOAD RELOAD STCURRENT, type R/WC, offset 0x018, reset 0x0000.0000 CURRENT CURRENT Cortex-M3 Peripherals Nested Vectored Interrupt Controller (NVIC) Registers Base 0xE000.E000 EN0, type R/W, offset 0x100, reset 0x0000.0000 INT INT DIS0, type R/W, offset 0x180, reset 0x0000.0000 INT INT PEND0, type R/W, offset 0x200, reset 0x0000.0000 INT INT UNPEND0, type R/W, offset 0x280, reset 0x0000.0000 INT INT ACTIVE0, type RO, offset 0x300, reset 0x0000.0000 INT INT PRI0, type R/W, offset 0x400, reset 0x0000.0000 INTD INTC INTB INTA PRI1, type R/W, offset 0x404, reset 0x0000.0000 INTD INTC INTB INTA 562 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 PRI2, type R/W, offset 0x408, reset 0x0000.0000 INTD INTC INTB INTA PRI3, type R/W, offset 0x40C, reset 0x0000.0000 INTD INTC INTB INTA PRI4, type R/W, offset 0x410, reset 0x0000.0000 INTD INTC INTB INTA PRI5, type R/W, offset 0x414, reset 0x0000.0000 INTD INTC INTB INTA PRI6, type R/W, offset 0x418, reset 0x0000.0000 INTD INTC INTB INTA PRI7, type R/W, offset 0x41C, reset 0x0000.0000 INTD INTC INTB INTA SWTRIG, type WO, offset 0xF00, reset 0x0000.0000 INTID Cortex-M3 Peripherals System Control Block (SCB) Registers Base 0xE000.E000 CPUID, type RO, offset 0xD00, reset 0x410F.C231 IMP VAR CON PARTNO REV INTCTRL, type R/W, offset 0xD04, reset 0x0000.0000 NMISET PENDSV UNPENDSV VECPEND ISRPRE PENDSTSET PENDSTCLR ISRPEND VECPEND RETBASE VECACT VTABLE, type R/W, offset 0xD08, reset 0x0000.0000 BASE OFFSET OFFSET APINT, type R/W, offset 0xD0C, reset 0xFA05.0000 VECTKEY PRIGROUP ENDIANESS SYSRESREQ VECTCLRACT VECTRESET SYSCTRL, type R/W, offset 0xD10, reset 0x0000.0000 SEVONPEND SLEEPDEEP SLEEPEXIT CFGCTRL, type R/W, offset 0xD14, reset 0x0000.0000 DIV0 STKALIGN BFHFNMIGN UNALIGNED MAINPEND BASETHR SYSPRI1, type R/W, offset 0xD18, reset 0x0000.0000 USAGE BUS MEM SYSPRI2, type R/W, offset 0xD1C, reset 0x0000.0000 SVC SYSPRI3, type R/W, offset 0xD20, reset 0x0000.0000 TICK PENDSV DEBUG July 14, 2014 563 Texas Instruments-Production Data Register Quick Reference 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 MON SVCA SYSHNDCTRL, type R/W, offset 0xD24, reset 0x0000.0000 USAGE SVC BUSP MEMP USAGEP TICK PNDSV USGA BUS MEM BUSA MEMA INVSTAT UNDEF DERR IERR FAULTSTAT, type R/W1C, offset 0xD28, reset 0x0000.0000 BFARV BSTKE BUSTKE IMPRE DIV0 UNALIGN PRECISE IBUS NOCP MMARV MSTKE INVPC MUSTKE HFAULTSTAT, type R/W1C, offset 0xD2C, reset 0x0000.0000 DBG FORCED VECT MMADDR, type R/W, offset 0xD34, reset ADDR ADDR FAULTADDR, type R/W, offset 0xD38, reset ADDR ADDR Cortex-M3 Peripherals Memory Protection Unit (MPU) Registers Base 0xE000.E000 MPUTYPE, type RO, offset 0xD90, reset 0x0000.0800 IREGION DREGION SEPARATE MPUCTRL, type R/W, offset 0xD94, reset 0x0000.0000 PRIVDEFEN HFNMIENA ENABLE MPUNUMBER, type R/W, offset 0xD98, reset 0x0000.0000 NUMBER MPUBASE, type R/W, offset 0xD9C, reset 0x0000.0000 ADDR ADDR VALID REGION VALID REGION VALID REGION VALID REGION MPUBASE1, type R/W, offset 0xDA4, reset 0x0000.0000 ADDR ADDR MPUBASE2, type R/W, offset 0xDAC, reset 0x0000.0000 ADDR ADDR MPUBASE3, type R/W, offset 0xDB4, reset 0x0000.0000 ADDR ADDR MPUATTR, type R/W, offset 0xDA0, reset 0x0000.0000 XN AP TEX SRD S C SIZE B ENABLE MPUATTR1, type R/W, offset 0xDA8, reset 0x0000.0000 XN AP TEX SRD S C SIZE B ENABLE MPUATTR2, type R/W, offset 0xDB0, reset 0x0000.0000 XN AP TEX SRD S C SIZE B ENABLE MPUATTR3, type R/W, offset 0xDB8, reset 0x0000.0000 XN AP SRD TEX S SIZE 564 C B ENABLE July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 BORIOR BORWT System Control Base 0x400F.E000 DID0, type RO, offset 0x000, reset - (see page 165) VER MAJOR MINOR PBORCTL, type R/W, offset 0x030, reset 0x0000.7FFD (see page 167) BORTIM LDOPCTL, type R/W, offset 0x034, reset 0x0000.0000 (see page 168) VADJ RIS, type RO, offset 0x050, reset 0x0000.0000 (see page 169) PLLLRIS CLRIS IOFRIS MOFRIS LDORIS BORRIS PLLFRIS PLLLIM CLIM IOFIM MOFIM LDOIM BORIM PLLFIM PLLLMIS CLMIS IOFMIS MOFMIS LDOMIS BORMIS LDO SW WDT BOR POR IMC, type R/W, offset 0x054, reset 0x0000.0000 (see page 170) MISC, type R/W1C, offset 0x058, reset 0x0000.0000 (see page 171) RESC, type R/W, offset 0x05C, reset - (see page 172) EXT RCC, type R/W, offset 0x060, reset 0x078E.3AC0 (see page 173) ACG PWRDN OEN BYPASS SYSDIV USESYSDIV PLLVER PWMDIV USEPWMDIV XTAL OSCSRC IOSCVER MOSCVER IOSCDIS MOSCDIS PLLCFG, type RO, offset 0x064, reset - (see page 177) OD F R DSLPCLKCFG, type R/W, offset 0x144, reset 0x0780.0000 (see page 178) IOSC CLKVCLR, type R/W, offset 0x150, reset 0x0000.0000 (see page 179) VERCLR LDOARST, type R/W, offset 0x160, reset 0x0000.0000 (see page 180) LDOARST DID1, type RO, offset 0x004, reset - (see page 181) VER FAM PARTNO TEMP PKG ROHS QUAL DC0, type RO, offset 0x008, reset 0x001F.001F (see page 183) SRAMSZ FLASHSZ DC1, type RO, offset 0x010, reset 0x0011.31BF (see page 184) PWM MINSYSDIV MAXADCSPD MPU TEMPSNS PLL ADC WDT SWO SWD JTAG TIMER2 TIMER1 TIMER0 UART1 UART0 DC2, type RO, offset 0x014, reset 0x0107.1013 (see page 186) COMP0 I2C0 SSI0 DC3, type RO, offset 0x018, reset 0xBF03.01C3 (see page 188) 32KHZ CCP5 CCP4 CCP3 CCP2 CCP1 CCP0 C0O C0PLUS C0MINUS July 14, 2014 ADC1 ADC0 PWM1 PWM0 565 Texas Instruments-Production Data Register Quick Reference 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 GPIOE GPIOD GPIOC GPIOB GPIOA DC4, type RO, offset 0x01C, reset 0x0000.001F (see page 190) RCGC0, type R/W, offset 0x100, reset 0x00000040 (see page 191) PWM MAXADCSPD ADC WDT SCGC0, type R/W, offset 0x110, reset 0x00000040 (see page 193) PWM MAXADCSPD ADC WDT DCGC0, type R/W, offset 0x120, reset 0x00000040 (see page 195) PWM ADC WDT RCGC1, type R/W, offset 0x104, reset 0x00000000 (see page 197) COMP0 I2C0 TIMER2 SSI0 TIMER1 TIMER0 UART1 UART0 TIMER1 TIMER0 UART1 UART0 TIMER1 TIMER0 UART1 UART0 SCGC1, type R/W, offset 0x114, reset 0x00000000 (see page 199) COMP0 I2C0 TIMER2 SSI0 DCGC1, type R/W, offset 0x124, reset 0x00000000 (see page 201) COMP0 I2C0 TIMER2 SSI0 RCGC2, type R/W, offset 0x108, reset 0x00000000 (see page 203) GPIOE GPIOD GPIOC GPIOB GPIOA GPIOE GPIOD GPIOC GPIOB GPIOA GPIOE GPIOD GPIOC GPIOB GPIOA SCGC2, type R/W, offset 0x118, reset 0x00000000 (see page 204) DCGC2, type R/W, offset 0x128, reset 0x00000000 (see page 206) SRCR0, type R/W, offset 0x040, reset 0x00000000 (see page 208) PWM ADC WDT SRCR1, type R/W, offset 0x044, reset 0x00000000 (see page 209) COMP0 I2C0 TIMER2 SSI0 TIMER1 TIMER0 UART1 UART0 SRCR2, type R/W, offset 0x048, reset 0x00000000 (see page 211) GPIOE GPIOD GPIOC GPIOB GPIOA COMT MERASE ERASE WRITE Internal Memory Flash Memory Control Registers (Flash Control Offset) Base 0x400F.D000 FMA, type R/W, offset 0x000, reset 0x0000.0000 OFFSET FMD, type R/W, offset 0x004, reset 0x0000.0000 DATA DATA FMC, type R/W, offset 0x008, reset 0x0000.0000 WRKEY 566 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 PRIS ARIS PMASK AMASK PMISC AMISC FCRIS, type RO, offset 0x00C, reset 0x0000.0000 FCIM, type R/W, offset 0x010, reset 0x0000.0000 FCMISC, type R/W1C, offset 0x014, reset 0x0000.0000 Internal Memory Flash Memory Protection Registers (System Control Offset) Base 0x400F.E000 USECRL, type R/W, offset 0x140, reset 0x31 USEC FMPRE, type R/W, offset 0x130, reset 0xBFFF.FFFF DBG READ_ENABLE READ_ENABLE FMPPE, type R/W, offset 0x134, reset 0xFFFF.FFFF PROG_ENABLE PROG_ENABLE General-Purpose Input/Outputs (GPIOs) GPIO Port A base: 0x4000.4000 GPIO Port B base: 0x4000.5000 GPIO Port C base: 0x4000.6000 GPIO Port D base: 0x4000.7000 GPIO Port E base: 0x4002.4000 GPIODATA, type R/W, offset 0x000, reset 0x0000.0000 (see page 241) DATA GPIODIR, type R/W, offset 0x400, reset 0x0000.0000 (see page 242) DIR GPIOIS, type R/W, offset 0x404, reset 0x0000.0000 (see page 243) IS GPIOIBE, type R/W, offset 0x408, reset 0x0000.0000 (see page 244) IBE GPIOIEV, type R/W, offset 0x40C, reset 0x0000.0000 (see page 245) IEV GPIOIM, type R/W, offset 0x410, reset 0x0000.0000 (see page 246) IME GPIORIS, type RO, offset 0x414, reset 0x0000.0000 (see page 247) RIS GPIOMIS, type RO, offset 0x418, reset 0x0000.0000 (see page 248) MIS GPIOICR, type W1C, offset 0x41C, reset 0x0000.0000 (see page 249) IC July 14, 2014 567 Texas Instruments-Production Data Register Quick Reference 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 GPIOAFSEL, type R/W, offset 0x420, reset - (see page 250) AFSEL GPIODR2R, type R/W, offset 0x500, reset 0x0000.00FF (see page 252) DRV2 GPIODR4R, type R/W, offset 0x504, reset 0x0000.0000 (see page 253) DRV4 GPIODR8R, type R/W, offset 0x508, reset 0x0000.0000 (see page 254) DRV8 GPIOODR, type R/W, offset 0x50C, reset 0x0000.0000 (see page 255) ODE GPIOPUR, type R/W, offset 0x510, reset 0x0000.00FF (see page 256) PUE GPIOPDR, type R/W, offset 0x514, reset 0x0000.0000 (see page 257) PDE GPIOSLR, type R/W, offset 0x518, reset 0x0000.0000 (see page 258) SRL GPIODEN, type R/W, offset 0x51C, reset 0x0000.00FF (see page 259) DEN GPIOPeriphID4, type RO, offset 0xFD0, reset 0x0000.0000 (see page 260) PID4 GPIOPeriphID5, type RO, offset 0xFD4, reset 0x0000.0000 (see page 261) PID5 GPIOPeriphID6, type RO, offset 0xFD8, reset 0x0000.0000 (see page 262) PID6 GPIOPeriphID7, type RO, offset 0xFDC, reset 0x0000.0000 (see page 263) PID7 GPIOPeriphID0, type RO, offset 0xFE0, reset 0x0000.0061 (see page 264) PID0 GPIOPeriphID1, type RO, offset 0xFE4, reset 0x0000.0000 (see page 265) PID1 GPIOPeriphID2, type RO, offset 0xFE8, reset 0x0000.0018 (see page 266) PID2 GPIOPeriphID3, type RO, offset 0xFEC, reset 0x0000.0001 (see page 267) PID3 568 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 GPIOPCellID0, type RO, offset 0xFF0, reset 0x0000.000D (see page 268) CID0 GPIOPCellID1, type RO, offset 0xFF4, reset 0x0000.00F0 (see page 269) CID1 GPIOPCellID2, type RO, offset 0xFF8, reset 0x0000.0005 (see page 270) CID2 GPIOPCellID3, type RO, offset 0xFFC, reset 0x0000.00B1 (see page 271) CID3 General-Purpose Timers Timer0 base: 0x4003.0000 Timer1 base: 0x4003.1000 Timer2 base: 0x4003.2000 GPTMCFG, type R/W, offset 0x000, reset 0x0000.0000 (see page 284) GPTMCFG GPTMTAMR, type R/W, offset 0x004, reset 0x0000.0000 (see page 285) TAAMS TACMR TAMR TBAMS TBCMR TBMR GPTMTBMR, type R/W, offset 0x008, reset 0x0000.0000 (see page 287) GPTMCTL, type R/W, offset 0x00C, reset 0x0000.0000 (see page 289) TBPWML TBOTE TBEVENT TBSTALL TBEN TAPWML TAOTE RTCEN TAEVENT TASTALL TAEN GPTMIMR, type R/W, offset 0x018, reset 0x0000.0000 (see page 292) CBEIM CBMIM TBTOIM RTCIM CAEIM CAMIM TATOIM CBMRIS TBTORIS RTCRIS CAERIS CAMRIS TATORIS RTCMIS CAEMIS CAMMIS TATOMIS GPTMRIS, type RO, offset 0x01C, reset 0x0000.0000 (see page 294) CBERIS GPTMMIS, type RO, offset 0x020, reset 0x0000.0000 (see page 295) CBEMIS CBMMIS TBTOMIS GPTMICR, type W1C, offset 0x024, reset 0x0000.0000 (see page 296) CBECINT CBMCINT TBTOCINT RTCCINT CAECINT CAMCINT TATOCINT GPTMTAILR, type R/W, offset 0x028, reset 0xFFFF.FFFF (see page 298) TAILRH TAILRL GPTMTBILR, type R/W, offset 0x02C, reset 0x0000.FFFF (see page 299) TBILRL GPTMTAMATCHR, type R/W, offset 0x030, reset 0xFFFF.FFFF (see page 300) TAMRH TAMRL GPTMTBMATCHR, type R/W, offset 0x034, reset 0x0000.FFFF (see page 301) TBMRL July 14, 2014 569 Texas Instruments-Production Data Register Quick Reference 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 RESEN INTEN GPTMTAPR, type R/W, offset 0x038, reset 0x0000.0000 (see page 302) TAPSR GPTMTBPR, type R/W, offset 0x03C, reset 0x0000.0000 (see page 303) TBPSR GPTMTAPMR, type R/W, offset 0x040, reset 0x0000.0000 (see page 304) TAPSMR GPTMTBPMR, type R/W, offset 0x044, reset 0x0000.0000 (see page 305) TBPSMR GPTMTAR, type RO, offset 0x048, reset 0xFFFF.FFFF (see page 306) TARH TARL GPTMTBR, type RO, offset 0x04C, reset 0x0000.FFFF (see page 307) TBRL Watchdog Timer Base 0x4000.0000 WDTLOAD, type R/W, offset 0x000, reset 0xFFFF.FFFF (see page 312) WDTLoad WDTLoad WDTVALUE, type RO, offset 0x004, reset 0xFFFF.FFFF (see page 313) WDTValue WDTValue WDTCTL, type R/W, offset 0x008, reset 0x0000.0000 (see page 314) WDTICR, type WO, offset 0x00C, reset - (see page 315) WDTIntClr WDTIntClr WDTRIS, type RO, offset 0x010, reset 0x0000.0000 (see page 316) WDTRIS WDTMIS, type RO, offset 0x014, reset 0x0000.0000 (see page 317) WDTMIS WDTTEST, type R/W, offset 0x418, reset 0x0000.0000 (see page 318) STALL WDTLOCK, type R/W, offset 0xC00, reset 0x0000.0000 (see page 319) WDTLock WDTLock WDTPeriphID4, type RO, offset 0xFD0, reset 0x0000.0000 (see page 320) PID4 WDTPeriphID5, type RO, offset 0xFD4, reset 0x0000.0000 (see page 321) PID5 WDTPeriphID6, type RO, offset 0xFD8, reset 0x0000.0000 (see page 322) PID6 570 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 ASEN3 ASEN2 ASEN1 ASEN0 INR3 INR2 INR1 INR0 MASK3 MASK2 MASK1 MASK0 IN3 IN2 IN1 IN0 OV3 OV2 OV1 OV0 UV1 UV0 WDTPeriphID7, type RO, offset 0xFDC, reset 0x0000.0000 (see page 323) PID7 WDTPeriphID0, type RO, offset 0xFE0, reset 0x0000.0005 (see page 324) PID0 WDTPeriphID1, type RO, offset 0xFE4, reset 0x0000.0018 (see page 325) PID1 WDTPeriphID2, type RO, offset 0xFE8, reset 0x0000.0018 (see page 326) PID2 WDTPeriphID3, type RO, offset 0xFEC, reset 0x0000.0001 (see page 327) PID3 WDTPCellID0, type RO, offset 0xFF0, reset 0x0000.000D (see page 328) CID0 WDTPCellID1, type RO, offset 0xFF4, reset 0x0000.00F0 (see page 329) CID1 WDTPCellID2, type RO, offset 0xFF8, reset 0x0000.0005 (see page 330) CID2 WDTPCellID3, type RO, offset 0xFFC, reset 0x0000.00B1 (see page 331) CID3 Analog-to-Digital Converter (ADC) Base 0x4003.8000 ADCACTSS, type R/W, offset 0x000, reset 0x0000.0000 (see page 342) ADCRIS, type RO, offset 0x004, reset 0x0000.0000 (see page 343) ADCIM, type R/W, offset 0x008, reset 0x0000.0000 (see page 344) ADCISC, type R/W1C, offset 0x00C, reset 0x0000.0000 (see page 345) ADCOSTAT, type R/W1C, offset 0x010, reset 0x0000.0000 (see page 346) ADCEMUX, type R/W, offset 0x014, reset 0x0000.0000 (see page 347) EM3 EM2 EM1 EM0 ADCUSTAT, type R/W1C, offset 0x018, reset 0x0000.0000 (see page 350) UV3 UV2 ADCSSPRI, type R/W, offset 0x020, reset 0x0000.3210 (see page 351) SS3 SS2 July 14, 2014 SS1 SS0 571 Texas Instruments-Production Data Register Quick Reference 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 SS3 SS2 SS1 SS0 ADCPSSI, type WO, offset 0x028, reset - (see page 353) ADCSAC, type R/W, offset 0x030, reset 0x0000.0000 (see page 354) AVG ADCSSMUX0, type R/W, offset 0x040, reset 0x0000.0000 (see page 355) MUX7 MUX6 MUX5 MUX4 MUX3 MUX2 MUX1 MUX0 ADCSSCTL0, type R/W, offset 0x044, reset 0x0000.0000 (see page 357) TS7 IE7 END7 D7 TS6 IE6 END6 D6 TS5 IE5 END5 D5 TS4 IE4 END4 D4 TS3 IE3 END3 D3 TS2 IE2 END2 D2 TS1 IE1 END1 D1 TS0 IE0 END0 D0 ADCSSFIFO0, type RO, offset 0x048, reset - (see page 360) DATA ADCSSFIFO1, type RO, offset 0x068, reset - (see page 360) DATA ADCSSFIFO2, type RO, offset 0x088, reset - (see page 360) DATA ADCSSFIFO3, type RO, offset 0x0A8, reset - (see page 360) DATA ADCSSFSTAT0, type RO, offset 0x04C, reset 0x0000.0100 (see page 361) FULL EMPTY HPTR TPTR EMPTY HPTR TPTR EMPTY HPTR TPTR EMPTY HPTR TPTR ADCSSFSTAT1, type RO, offset 0x06C, reset 0x0000.0100 (see page 361) FULL ADCSSFSTAT2, type RO, offset 0x08C, reset 0x0000.0100 (see page 361) FULL ADCSSFSTAT3, type RO, offset 0x0AC, reset 0x0000.0100 (see page 361) FULL ADCSSMUX1, type R/W, offset 0x060, reset 0x0000.0000 (see page 362) MUX3 MUX2 MUX1 MUX0 MUX2 MUX1 MUX0 ADCSSMUX2, type R/W, offset 0x080, reset 0x0000.0000 (see page 362) MUX3 ADCSSCTL1, type R/W, offset 0x064, reset 0x0000.0000 (see page 363) TS3 IE3 END3 D3 TS2 IE2 END2 D2 TS1 IE1 END1 D1 TS0 IE0 END0 D0 D2 TS1 IE1 END1 D1 TS0 IE0 END0 D0 ADCSSCTL2, type R/W, offset 0x084, reset 0x0000.0000 (see page 363) TS3 IE3 END3 D3 TS2 IE2 END2 ADCSSMUX3, type R/W, offset 0x0A0, reset 0x0000.0000 (see page 365) MUX0 572 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 TS0 IE0 END0 D0 ADCSSCTL3, type R/W, offset 0x0A4, reset 0x0000.0002 (see page 366) ADCTMLB, type R/W, offset 0x100, reset 0x0000.0000 (see page 367) LB Universal Asynchronous Receivers/Transmitters (UARTs) UART0 base: 0x4000.C000 UART1 base: 0x4000.D000 UARTDR, type R/W, offset 0x000, reset 0x0000.0000 (see page 376) OE BE PE FE DATA UARTRSR/UARTECR, type RO, offset 0x004, reset 0x0000.0000 (Reads) (see page 378) OE BE PE FE PEN BRK UARTRSR/UARTECR, type WO, offset 0x004, reset 0x0000.0000 (Writes) (see page 378) DATA UARTFR, type RO, offset 0x018, reset 0x0000.0090 (see page 380) TXFE RXFF TXFF RXFE BUSY UARTIBRD, type R/W, offset 0x024, reset 0x0000.0000 (see page 382) DIVINT UARTFBRD, type R/W, offset 0x028, reset 0x0000.0000 (see page 383) DIVFRAC UARTLCRH, type R/W, offset 0x02C, reset 0x0000.0000 (see page 384) SPS WLEN FEN STP2 EPS UARTCTL, type R/W, offset 0x030, reset 0x0000.0300 (see page 386) RXE TXE LBE UARTEN UARTIFLS, type R/W, offset 0x034, reset 0x0000.0012 (see page 388) RXIFLSEL TXIFLSEL UARTIM, type R/W, offset 0x038, reset 0x0000.0000 (see page 390) OEIM BEIM PEIM FEIM RTIM TXIM RXIM PERIS FERIS RTRIS TXRIS RXRIS PEMIS FEMIS RTMIS TXMIS RXMIS PEIC FEIC RTIC TXIC RXIC UARTRIS, type RO, offset 0x03C, reset 0x0000.0000 (see page 392) OERIS BERIS UARTMIS, type RO, offset 0x040, reset 0x0000.0000 (see page 393) OEMIS BEMIS UARTICR, type W1C, offset 0x044, reset 0x0000.0000 (see page 394) OEIC BEIC UARTPeriphID4, type RO, offset 0xFD0, reset 0x0000.0000 (see page 396) PID4 July 14, 2014 573 Texas Instruments-Production Data Register Quick Reference 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 UARTPeriphID5, type RO, offset 0xFD4, reset 0x0000.0000 (see page 397) PID5 UARTPeriphID6, type RO, offset 0xFD8, reset 0x0000.0000 (see page 398) PID6 UARTPeriphID7, type RO, offset 0xFDC, reset 0x0000.0000 (see page 399) PID7 UARTPeriphID0, type RO, offset 0xFE0, reset 0x0000.0011 (see page 400) PID0 UARTPeriphID1, type RO, offset 0xFE4, reset 0x0000.0000 (see page 401) PID1 UARTPeriphID2, type RO, offset 0xFE8, reset 0x0000.0018 (see page 402) PID2 UARTPeriphID3, type RO, offset 0xFEC, reset 0x0000.0001 (see page 403) PID3 UARTPCellID0, type RO, offset 0xFF0, reset 0x0000.000D (see page 404) CID0 UARTPCellID1, type RO, offset 0xFF4, reset 0x0000.00F0 (see page 405) CID1 UARTPCellID2, type RO, offset 0xFF8, reset 0x0000.0005 (see page 406) CID2 UARTPCellID3, type RO, offset 0xFFC, reset 0x0000.00B1 (see page 407) CID3 Synchronous Serial Interface (SSI) SSI0 base: 0x4000.8000 SSICR0, type R/W, offset 0x000, reset 0x0000.0000 (see page 421) SCR SPH SPO FRF DSS SSICR1, type R/W, offset 0x004, reset 0x0000.0000 (see page 423) SOD MS SSE LBM RFF RNE TNF TFE RXIM RTIM RORIM SSIDR, type R/W, offset 0x008, reset 0x0000.0000 (see page 425) DATA SSISR, type RO, offset 0x00C, reset 0x0000.0003 (see page 426) BSY SSICPSR, type R/W, offset 0x010, reset 0x0000.0000 (see page 428) CPSDVSR SSIIM, type R/W, offset 0x014, reset 0x0000.0000 (see page 429) TXIM 574 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 TXRIS RXRIS RTRIS RORRIS TXMIS RXMIS RTMIS RORMIS RTIC RORIC SSIRIS, type RO, offset 0x018, reset 0x0000.0008 (see page 431) SSIMIS, type RO, offset 0x01C, reset 0x0000.0000 (see page 432) SSIICR, type W1C, offset 0x020, reset 0x0000.0000 (see page 433) SSIPeriphID4, type RO, offset 0xFD0, reset 0x0000.0000 (see page 434) PID4 SSIPeriphID5, type RO, offset 0xFD4, reset 0x0000.0000 (see page 435) PID5 SSIPeriphID6, type RO, offset 0xFD8, reset 0x0000.0000 (see page 436) PID6 SSIPeriphID7, type RO, offset 0xFDC, reset 0x0000.0000 (see page 437) PID7 SSIPeriphID0, type RO, offset 0xFE0, reset 0x0000.0022 (see page 438) PID0 SSIPeriphID1, type RO, offset 0xFE4, reset 0x0000.0000 (see page 439) PID1 SSIPeriphID2, type RO, offset 0xFE8, reset 0x0000.0018 (see page 440) PID2 SSIPeriphID3, type RO, offset 0xFEC, reset 0x0000.0001 (see page 441) PID3 SSIPCellID0, type RO, offset 0xFF0, reset 0x0000.000D (see page 442) CID0 SSIPCellID1, type RO, offset 0xFF4, reset 0x0000.00F0 (see page 443) CID1 SSIPCellID2, type RO, offset 0xFF8, reset 0x0000.0005 (see page 444) CID2 SSIPCellID3, type RO, offset 0xFFC, reset 0x0000.00B1 (see page 445) CID3 Inter-Integrated Circuit (I2C) Interface I2C Master I2C 0 base: 0x4002.0000 I2CMSA, type R/W, offset 0x000, reset 0x0000.0000 SA July 14, 2014 R/S 575 Texas Instruments-Production Data Register Quick Reference 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 BUSBSY IDLE ARBLST DATACK ADRACK ERROR BUSY ACK STOP START RUN I2CMCS, type RO, offset 0x004, reset 0x0000.0000 (Reads) I2CMCS, type WO, offset 0x004, reset 0x0000.0000 (Writes) I2CMDR, type R/W, offset 0x008, reset 0x0000.0000 DATA I2CMTPR, type R/W, offset 0x00C, reset 0x0000.0001 TPR I2CMIMR, type R/W, offset 0x010, reset 0x0000.0000 IM I2CMRIS, type RO, offset 0x014, reset 0x0000.0000 RIS I2CMMIS, type RO, offset 0x018, reset 0x0000.0000 MIS I2CMICR, type WO, offset 0x01C, reset 0x0000.0000 IC I2CMCR, type R/W, offset 0x020, reset 0x0000.0000 SFE MFE LPBK Inter-Integrated Circuit (I2C) Interface I2C Slave I2C 0 base: 0x4002.0000 I2CSOAR, type R/W, offset 0x800, reset 0x0000.0000 OAR I2CSCSR, type RO, offset 0x804, reset 0x0000.0000 (Reads) FBR TREQ RREQ I2CSCSR, type WO, offset 0x804, reset 0x0000.0000 (Writes) DA I2CSDR, type R/W, offset 0x808, reset 0x0000.0000 DATA I2CSIMR, type R/W, offset 0x80C, reset 0x0000.0000 DATAIM I2CSRIS, type RO, offset 0x810, reset 0x0000.0000 DATARIS I2CSMIS, type RO, offset 0x814, reset 0x0000.0000 DATAMIS 576 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 I2CSICR, type WO, offset 0x818, reset 0x0000.0000 DATAIC Analog Comparator Base 0x4003.C000 ACMIS, type R/W1C, offset 0x000, reset 0x0000.0000 (see page 488) IN0 ACRIS, type RO, offset 0x004, reset 0x0000.0000 (see page 489) IN0 ACINTEN, type R/W, offset 0x008, reset 0x0000.0000 (see page 490) IN0 ACREFCTL, type R/W, offset 0x010, reset 0x0000.0000 (see page 491) EN RNG VREF ACSTAT0, type RO, offset 0x020, reset 0x0000.0000 (see page 492) OVAL ACCTL0, type R/W, offset 0x024, reset 0x0000.0000 (see page 493) TOEN ASRCP TSLVAL TSEN ISLVAL ISEN CINV Pulse Width Modulator (PWM) Base 0x4002.8000 GlobalSync0 PWMCTL, type R/W, offset 0x000, reset 0x0000.0000 (see page 504) PWMSYNC, type R/W, offset 0x004, reset 0x0000.0000 (see page 505) Sync0 PWMENABLE, type R/W, offset 0x008, reset 0x0000.0000 (see page 506) PWM1En PWM0En PWMINVERT, type R/W, offset 0x00C, reset 0x0000.0000 (see page 507) PWM1Inv PWM0Inv PWMFAULT, type R/W, offset 0x010, reset 0x0000.0000 (see page 508) Fault1 Fault0 PWMINTEN, type R/W, offset 0x014, reset 0x0000.0000 (see page 509) IntFault IntPWM0 PWMRIS, type RO, offset 0x018, reset 0x0000.0000 (see page 510) IntFault IntPWM0 PWMISC, type R/W1C, offset 0x01C, reset 0x0000.0000 (see page 511) IntFault IntPWM0 July 14, 2014 577 Texas Instruments-Production Data Register Quick Reference 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 PWMSTATUS, type RO, offset 0x020, reset 0x0000.0000 (see page 512) Fault PWM0CTL, type R/W, offset 0x040, reset 0x0000.0000 (see page 513) CmpBUpd CmpAUpd LoadUpd Debug Mode Enable PWM0INTEN, type R/W, offset 0x044, reset 0x0000.0000 (see page 515) TrCmpBD TrCmpBU TrCmpAD TrCmpAU TrCntLoad TrCntZero IntCmpBD IntCmpBU IntCmpAD IntCmpAU IntCntLoad IntCntZero IntCmpBD IntCmpBU IntCmpAD IntCmpAU IntCntLoad IntCntZero IntCmpBD IntCmpBU IntCmpAD IntCmpAU IntCntLoad IntCntZero PWM0RIS, type RO, offset 0x048, reset 0x0000.0000 (see page 518) PWM0ISC, type R/W1C, offset 0x04C, reset 0x0000.0000 (see page 519) PWM0LOAD, type R/W, offset 0x050, reset 0x0000.0000 (see page 520) Load PWM0COUNT, type RO, offset 0x054, reset 0x0000.0000 (see page 521) Count PWM0CMPA, type R/W, offset 0x058, reset 0x0000.0000 (see page 522) CompA PWM0CMPB, type R/W, offset 0x05C, reset 0x0000.0000 (see page 523) CompB PWM0GENA, type R/W, offset 0x060, reset 0x0000.0000 (see page 524) ActCmpBD ActCmpBU ActCmpAD ActCmpAU ActLoad ActZero ActCmpAD ActCmpAU ActLoad ActZero PWM0GENB, type R/W, offset 0x064, reset 0x0000.0000 (see page 527) ActCmpBD ActCmpBU PWM0DBCTL, type R/W, offset 0x068, reset 0x0000.0000 (see page 530) Enable PWM0DBRISE, type R/W, offset 0x06C, reset 0x0000.0000 (see page 531) RiseDelay PWM0DBFALL, type R/W, offset 0x070, reset 0x0000.0000 (see page 532) FallDelay 578 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller C Ordering and Contact Information C.1 Ordering Information ® The figure below defines the full set of potential orderable part numbers for all the Stellaris LM3S microcontrollers. See the Package Option Addendum for the valid orderable part numbers for the LM3S812 microcontroller. LM3Snnnn–gppss–rrm Part Number nnn = Sandstorm-class parts nnnn = All other Stellaris® parts Temperature E = –40°C to +105°C I = –40°C to +85°C Revision Speed 20 = 20 MHz 25 = 25 MHz 50 = 50 MHz 80 = 80 MHz Package BZ = 108-ball BGA QC = 100-pin LQFP QN = 48-pin LQFP QR = 64-pin LQFP C.2 Shipping Medium T = Tape-and-reel Omitted = Default shipping (tray or tube) Part Markings The Stellaris microcontrollers are marked with an identifying number. This code contains the following information: ■ The first line indicates the part number, for example, LM3S9B90. ■ In the second line, the first eight characters indicate the temperature, package, speed, revision, and product status. For example in the figure below, IQC80C0X indicates an Industrial temperature (I), 100-pin LQFP package (QC), 80-MHz (80), revision C0 (C0) device. The letter immediately following the revision indicates product status. An X indicates experimental and requires a waiver; an S indicates the part is fully qualified and released to production. ■ The remaining characters contain internal tracking numbers. C.3 Kits The Stellaris Family provides the hardware and software tools that engineers need to begin development quickly. July 14, 2014 579 Texas Instruments-Production Data Ordering and Contact Information ■ Reference Design Kits accelerate product development by providing ready-to-run hardware and comprehensive documentation including hardware design files ■ Evaluation Kits provide a low-cost and effective means of evaluating Stellaris microcontrollers before purchase ■ Development Kits provide you with all the tools you need to develop and prototype embedded applications right out of the box See the website at www.ti.com/stellaris for the latest tools available, or ask your distributor. C.4 Support Information For support on Stellaris products, contact the TI Worldwide Product Information Center nearest you: http://www-k.ext.ti.com/sc/technical-support/product-information-centers.htm. 580 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller D Package Information D.1 48-Pin LQFP Package D.1.1 Package Dimensions Figure D-1. Stellaris LM3S812 48-Pin LQFP Package Note: The following notes apply to the package drawing. July 14, 2014 581 Texas Instruments-Production Data Package Information 1. All dimensions are in mm. 2. Dimensions shown are nominal with tolerances indicated. 3. Foot length "L" is measured at gage plane 0.25 mm above seating plane. 4. L/F: Eftec 64T Cu or equivalent, 0.127 mm (0.005") thick. Package Type Symbol 48LD LQFP Note MIN MAX A - 1.60 A1 0.05 0.15 A2 - 1.40 D 9.00 D1 7.00 E 9.00 E1 7.00 L 0.60 e 0.50 b 0.22 theta 0° - 7° ddd 0.08 ccc 0.08 JEDEC Reference Drawing MS-026 Variation Designator BBC 582 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller D.1.2 Tray Dimensions Figure D-2. 48-Pin LQFP Tray Dimensions July 14, 2014 583 Texas Instruments-Production Data Package Information 584 July 14, 2014 Texas Instruments-Production Data ® Stellaris LM3S812 Microcontroller D.1.3 Tape and Reel Dimensions Figure D-3. 48-Pin LQFP Tape and Reel Dimensions July 14, 2014 585 Texas Instruments-Production Data PACKAGE OPTION ADDENDUM www.ti.com 3-Dec-2021 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan (2) Lead finish/ Ball material MSL Peak Temp Op Temp (°C) Device Marking (3) (4/5) (6) LM3S812-IQN50-C2 NRND LQFP PT 48 250 RoHS & Green NIPDAU Level-3-260C-168 HR -40 to 85 LM3S812 IQN50 PT (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may reference these types of products as "Pb-Free". RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption. Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of