ETC LM3S101

P RE L I M I NA R Y
LM3S101 Microcontroller
D ATA SHE E T
DS -LM3S 101- 05
C opyr ight © 2006 Lumi nary Micro , Inc.
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sales office or your distributor to obtain the latest specifications before placing your product order.
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reserves these for future definition and shall have no responsibility whatsoever for conflicts or incompatibilities arising from future changes to
them.
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subsidiaries in the United States and other countries. ARM and Thumb are registered trademarks, and Cortex is a trademark of ARM Limited.
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Luminary Micro, Inc.
2499 South Capital of Texas Hwy, Suite A-100
Austin, TX 78746
Main: +1-512-279-8800
Fax: +1-512-279-8879
http://www.luminarymicro.com
2
October 5, 2006
Preliminary
LM3S101 Data Sheet
Table of Contents
Legal Disclaimers and Trademark Information.............................................................................. 2
Revision History ............................................................................................................................. 14
About This Document..................................................................................................................... 15
Audience........................................................................................................................................................... 15
About This Manual............................................................................................................................................ 15
Related Documents .......................................................................................................................................... 15
Documentation Conventions............................................................................................................................. 15
1.
Architectural Overview ....................................................................................................... 18
1.1
1.2
1.3
1.4
1.4.1
1.4.2
1.4.3
1.4.4
1.4.5
1.4.6
1.4.7
1.4.8
1.5
Product Features ................................................................................................................................. 18
Target Applications .............................................................................................................................. 20
High-Level Block Diagram ................................................................................................................... 21
Functional Overview ............................................................................................................................ 22
ARM Cortex™-M3 ............................................................................................................................... 22
Motor Control Peripherals .................................................................................................................... 22
Analog Peripherals .............................................................................................................................. 22
Serial Communications Peripherals..................................................................................................... 23
System Peripherals.............................................................................................................................. 23
Memory Peripherals............................................................................................................................. 24
Additional Features .............................................................................................................................. 25
Hardware Details ................................................................................................................................. 25
System Block Diagram ........................................................................................................................ 26
2.
ARM Cortex-M3 Processor Core........................................................................................ 27
2.1
2.2
2.2.1
2.2.2
2.2.3
2.2.4
2.2.5
2.2.6
Block Diagram ..................................................................................................................................... 28
Functional Description ......................................................................................................................... 28
Serial Wire and JTAG Debug .............................................................................................................. 28
Embedded Trace Macrocell (ETM) ...................................................................................................... 29
Trace Port Interface Unit (TPIU) .......................................................................................................... 29
ROM Table .......................................................................................................................................... 29
Memory Protection Unit (MPU) ............................................................................................................ 29
Nested Vectored Interrupt Controller (NVIC) ....................................................................................... 29
3.
Memory Map ........................................................................................................................ 30
4.
Interrupts ............................................................................................................................. 32
5.
JTAG Interface .................................................................................................................... 35
5.1
5.2
5.2.1
5.2.2
5.2.3
5.2.4
5.3
5.4
5.4.1
5.4.2
Block Diagram ..................................................................................................................................... 36
Functional Description ......................................................................................................................... 36
JTAG Interface Pins............................................................................................................................. 37
JTAG TAP Controller ........................................................................................................................... 38
Shift Registers ..................................................................................................................................... 39
Operational Considerations ................................................................................................................. 39
Initialization and Configuration............................................................................................................. 40
Register Descriptions........................................................................................................................... 41
Instruction Register (IR) ....................................................................................................................... 41
Data Registers ..................................................................................................................................... 43
6.
System Control.................................................................................................................... 45
6.1
6.1.1
Functional Description ......................................................................................................................... 45
Device Identification............................................................................................................................. 45
October 5, 2006
3
Preliminary
Table of Contents
6.1.2
6.1.3
6.1.4
6.1.5
6.2
6.3
6.4
Reset Control ....................................................................................................................................... 45
Power Control ...................................................................................................................................... 48
Clock Control ....................................................................................................................................... 48
System Control .................................................................................................................................... 50
Initialization and Configuration............................................................................................................. 51
Register Map ....................................................................................................................................... 51
Register Descriptions........................................................................................................................... 52
7.
Internal Memory .................................................................................................................. 83
7.1
7.2
7.2.1
7.2.2
7.3
7.3.1
7.3.2
7.4
7.5
Block Diagram ..................................................................................................................................... 83
Functional Description ......................................................................................................................... 83
SRAM Memory .................................................................................................................................... 83
Flash Memory ...................................................................................................................................... 84
Initialization and Configuration............................................................................................................. 85
Changing Flash Protection Bits ........................................................................................................... 85
Flash Programming ............................................................................................................................. 86
Register Map ....................................................................................................................................... 86
Register Descriptions........................................................................................................................... 87
8.
General-Purpose Input/Outputs (GPIOs) .......................................................................... 97
8.1
8.2
8.2.1
8.2.2
8.2.3
8.2.4
8.2.5
8.2.6
8.3
8.4
8.5
Block Diagram ..................................................................................................................................... 98
Functional Description ......................................................................................................................... 98
Data Register Operation ...................................................................................................................... 99
Data Direction .................................................................................................................................... 100
Interrupt Operation............................................................................................................................. 100
Mode Control ..................................................................................................................................... 101
Pad Configuration .............................................................................................................................. 101
Identification....................................................................................................................................... 101
Initialization and Configuration........................................................................................................... 101
Register Map ..................................................................................................................................... 103
Register Descriptions......................................................................................................................... 104
9.
General-Purpose Timers .................................................................................................. 135
9.1
9.2
9.2.1
9.2.2
9.2.3
9.3
9.3.1
9.3.2
9.3.3
9.3.4
9.3.5
9.3.6
9.4
9.5
Block Diagram ................................................................................................................................... 136
Functional Description ....................................................................................................................... 136
GPTM Reset Conditions .................................................................................................................... 136
32-Bit Timer Operating Modes........................................................................................................... 137
16-Bit Timer Operating Modes........................................................................................................... 138
Initialization and Configuration........................................................................................................... 142
32-Bit One-Shot/Periodic Timer Mode ............................................................................................... 142
32-Bit Real-Time Clock (RTC) Mode ................................................................................................. 143
16-Bit One-Shot/Periodic Timer Mode ............................................................................................... 143
16-Bit Input Edge Count Mode .......................................................................................................... 143
16-Bit Input Edge Timing Mode ......................................................................................................... 144
16-Bit PWM Mode.............................................................................................................................. 144
Register Map ..................................................................................................................................... 145
Register Descriptions......................................................................................................................... 146
10.
Watchdog Timer ................................................................................................................ 167
10.1
10.2
10.3
10.4
Block Diagram ................................................................................................................................... 167
Functional Description ....................................................................................................................... 168
Initialization and Configuration........................................................................................................... 168
Register Map ..................................................................................................................................... 168
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October 5, 2006
Preliminary
LM3S101 Data Sheet
10.5
Register Descriptions......................................................................................................................... 169
11.
Universal Asynchronous Receiver/Transmitter (UART)................................................ 190
11.1
11.2
11.2.1
11.2.2
11.2.3
11.2.4
11.2.5
11.2.6
11.3
11.4
11.5
Block Diagram ................................................................................................................................... 191
Functional Description ....................................................................................................................... 191
Transmit/Receive Logic ..................................................................................................................... 191
Baud-Rate Generation ....................................................................................................................... 192
Data Transmission ............................................................................................................................. 193
FIFO Operation .................................................................................................................................. 193
Interrupts............................................................................................................................................ 193
Loopback Operation .......................................................................................................................... 194
Initialization and Configuration........................................................................................................... 194
Register Map ..................................................................................................................................... 195
Register Descriptions......................................................................................................................... 196
12.
Synchronous Serial Interface (SSI) ................................................................................. 226
12.1
12.2
12.2.1
12.2.2
12.2.3
12.2.4
12.3
12.4
12.5
Block Diagram ................................................................................................................................... 226
Functional Description ....................................................................................................................... 227
Bit Rate Generation ........................................................................................................................... 227
FIFO Operation .................................................................................................................................. 227
Interrupts............................................................................................................................................ 227
Frame Formats .................................................................................................................................. 228
Initialization and Configuration........................................................................................................... 235
Register Map ..................................................................................................................................... 236
Register Descriptions......................................................................................................................... 237
13.
Analog Comparators......................................................................................................... 261
13.1
13.2
13.2.1
13.3
13.4
13.5
Block Diagram ................................................................................................................................... 261
Functional Description ....................................................................................................................... 261
Internal Reference Programming....................................................................................................... 263
Initialization and Configuration........................................................................................................... 264
Register Map ..................................................................................................................................... 265
Register Descriptions......................................................................................................................... 265
14.
Pin Diagram ....................................................................................................................... 273
15.
Signal Tables ..................................................................................................................... 274
16.
Operating Characteristics ................................................................................................ 281
17.
Electrical Characteristics ................................................................................................. 282
17.1
17.1.1
17.1.2
17.1.3
17.1.4
17.1.5
17.2
17.2.1
17.2.2
17.2.3
17.2.4
17.2.5
17.2.6
17.2.7
DC Characteristics ............................................................................................................................. 282
Maximum Ratings .............................................................................................................................. 282
Recommended DC Operating Conditions ......................................................................................... 282
On-Chip Low Drop-Out (LDO) Regulator Characteristics .................................................................. 283
Power Specifications ......................................................................................................................... 284
Flash Memory Characteristics ........................................................................................................... 284
AC Characteristics ............................................................................................................................. 285
Load Conditions ................................................................................................................................. 285
Clocks ................................................................................................................................................ 285
Analog Comparator............................................................................................................................ 286
Synchronous Serial Interface (SSI) ................................................................................................... 287
JTAG and Boundary Scan ................................................................................................................. 289
General-Purpose I/O.......................................................................................................................... 291
Reset ................................................................................................................................................. 291
October 5, 2006
5
Preliminary
Table of Contents
18.
Package Information......................................................................................................... 294
Appendix A. Serial Flash Loader ................................................................................................. 295
A.1
A.1.1
A.1.2
A.2
A.2.1
A.2.2
A.2.3
A.3
A.3.1
A.3.2
A.3.3
A.3.4
A.3.5
A.3.6
Interfaces ........................................................................................................................................... 295
UART ................................................................................................................................................. 295
SSI ..................................................................................................................................................... 295
Packet Handling................................................................................................................................. 295
Packet Format ................................................................................................................................... 296
Sending Packets ................................................................................................................................ 296
Receiving Packets ............................................................................................................................. 296
Commands ........................................................................................................................................ 296
COMMAND_PING (0x20) .................................................................................................................. 297
COMMAND_GET_STATUS (0x23) ................................................................................................... 297
COMMAND_DOWNLOAD (0x21)...................................................................................................... 297
COMMAND_SEND_DATA (0x24) ..................................................................................................... 297
COMMAND_RUN (0x22) ................................................................................................................... 298
COMMAND_RESET (0x25)............................................................................................................... 298
Ordering and Contact Information .............................................................................................. 299
Ordering Information ....................................................................................................................................... 299
Development Kit ............................................................................................................................................. 299
Company Information ..................................................................................................................................... 299
Support Information ........................................................................................................................................ 300
6
October 5, 2006
Preliminary
LM3S101 Data Sheet
List of Figures
Figure 1-1.
Figure 1-2.
Figure 2-1.
Figure 2-2.
Figure 5-1.
Figure 5-2.
Figure 5-3.
Figure 5-4.
Figure 5-5.
Figure 6-1.
Figure 6-2.
Figure 7-1.
Figure 8-1.
Figure 8-2.
Figure 8-3.
Figure 8-4.
Figure 9-1.
Figure 9-2.
Figure 9-3.
Figure 9-4.
Figure 10-1.
Figure 11-1.
Figure 11-2.
Figure 12-1.
Figure 12-2.
Figure 12-3.
Figure 12-4.
Figure 12-5.
Figure 12-6.
Figure 12-7.
Figure 12-8.
Figure 12-9.
Figure 12-10.
Figure 12-11.
Figure 12-12.
Figure 13-1.
Figure 13-2.
Figure 13-3.
Figure 14-1.
Figure 17-1.
Figure 17-2.
Figure 17-3.
Figure 17-4.
Figure 17-5.
Figure 17-6.
Figure 17-7.
Stellaris High-Level Block Diagram ........................................................................................... 21
LM3S101 Controller System-Level Block Diagram ................................................................... 26
CPU Block Diagram .................................................................................................................. 28
TPIU Block Diagram .................................................................................................................. 29
JTAG Module Block Diagram .................................................................................................... 36
Test Access Port State Machine ............................................................................................... 39
IDCODE Register Format.......................................................................................................... 43
BYPASS Register Format ......................................................................................................... 43
Boundary Scan Register Format ............................................................................................... 44
External Circuitry to Extend Reset............................................................................................. 46
Main Clock Tree ........................................................................................................................ 49
Flash Block Diagram ................................................................................................................. 83
GPIO Module Block Diagram .................................................................................................... 98
GPIO Port Block Diagram.......................................................................................................... 99
GPIODATA Write Example...................................................................................................... 100
GPIODATA Read Example ..................................................................................................... 100
GPTM Module Block Diagram ................................................................................................. 136
16-Bit Input Edge Count Mode Example ................................................................................. 140
16-Bit Input Edge Time Mode Example................................................................................... 141
16-Bit PWM Mode Example .................................................................................................... 142
WDT Module Block Diagram ................................................................................................... 167
UART Module Block Diagram.................................................................................................. 191
UART Character Frame........................................................................................................... 192
SSI Module Block Diagram...................................................................................................... 226
TI Synchronous Serial Frame Format (Single Transfer).......................................................... 228
TI Synchronous Serial Frame Format (Continuous Transfer) ................................................. 229
Freescale SPI Format (Single Transfer) with SPO=0 and SPH=0 .......................................... 230
Freescale SPI Format (Continuous Transfer) with SPO=0 and SPH=0 .................................. 230
Freescale SPI Frame Format with SPO=0 and SPH=1........................................................... 231
Freescale SPI Frame Format (Single Transfer) with SPO=1 and SPH=0............................... 231
Freescale SPI Frame Format (Continuous Transfer) with SPO=1 and SPH=0....................... 232
Freescale SPI Frame Format with SPO=1 and SPH=1........................................................... 232
MICROWIRE Frame Format (Single Frame)........................................................................... 233
MICROWIRE Frame Format (Continuous Transfer) ............................................................... 234
MICROWIRE Frame Format, SSIFss Input Setup and Hold Requirements............................ 235
Analog Comparator Module Block Diagram ............................................................................ 261
Structure of Comparator Unit................................................................................................... 262
Comparator Internal Reference Structure ............................................................................... 263
Pin Connection Diagram.......................................................................................................... 273
Load Conditions....................................................................................................................... 285
SSI Timing for TI Frame Format (FRF=01), Single Transfer Timing Measurement ................ 287
SSI Timing for MICROWIRE Frame Format (FRF=10), Single Transfer................................. 288
SSI Timing for SPI Frame Format (FRF=00), with SPH=1...................................................... 288
JTAG Test Clock Input Timing................................................................................................. 290
JTAG Test Access Port (TAP) Timing ..................................................................................... 290
JTAG TRST Timing ................................................................................................................. 290
October 5, 2006
7
Preliminary
List of Figures
Figure 17-8.
Figure 17-9.
Figure 17-10.
Figure 17-11.
Figure 17-12.
Figure 17-13.
Figure 18-1.
External Reset Timing (RST)................................................................................................... 292
Power-On Reset Timing .......................................................................................................... 292
Brown-Out Reset Timing ......................................................................................................... 292
Software Reset Timing ............................................................................................................ 292
Watchdog Reset Timing .......................................................................................................... 293
LDO Reset Timing ................................................................................................................... 293
28-Pin SOIC Package ............................................................................................................. 294
8
October 5, 2006
Preliminary
LM3S101 Data Sheet
List of Tables
Table 0-1.
Table 3-1.
Table 4-1.
Table 4-2.
Table 5-1.
Table 5-2.
Table 6-1.
Table 6-2.
Table 6-3.
Table 6-4.
Table 7-1.
Table 7-2.
Table 8-1.
Table 8-2.
Table 8-3.
Table 9-1.
Table 9-2.
Table 10-1.
Table 11-1.
Table 12-1.
Table 13-1.
Table 13-2.
Table 13-3.
Table 13-4.
Table 15-1.
Table 15-2.
Table 15-3.
Table 15-4.
Table 16-1.
Table 16-2.
Table 17-1.
Table 17-2.
Table 17-3.
Table 17-4.
Table 17-5.
Table 17-6.
Table 17-7.
Table 17-8.
Table 17-9.
Table 17-10.
Table 17-11.
Table 17-12.
Table 17-13.
Documentation Conventions ..................................................................................................... 15
Memory Map.............................................................................................................................. 30
Exception Types ........................................................................................................................ 32
Interrupts ................................................................................................................................... 33
JTAG Port Pins Reset State ...................................................................................................... 37
JTAG Instruction Register Commands ...................................................................................... 41
System Control Register Map.................................................................................................... 51
VADJ to VOUT .......................................................................................................................... 62
PLL Mode Control...................................................................................................................... 73
Default Crystal Field Values and PLL Programming ................................................................. 74
Flash Protection Policy Combinations ....................................................................................... 85
Flash Register Map ................................................................................................................... 86
GPIO Pad Configuration Examples ........................................................................................ 101
GPIO Interrupt Configuration Example ................................................................................... 102
GPIO Register Map ................................................................................................................. 103
16-Bit Timer With Prescaler Configurations ............................................................................ 139
GPTM Register Map................................................................................................................ 145
WDT Register Map .................................................................................................................. 168
UART Register Map ................................................................................................................ 195
SSI Register Map .................................................................................................................... 236
Comparator 0 Operating Modes .............................................................................................. 262
Comparator 1 Operating Modes .............................................................................................. 262
Internal Reference Voltage and ACREFCTL Field Values ...................................................... 263
Analog Comparator Register Map ........................................................................................... 265
Signals by Pin Number ............................................................................................................ 274
Signals by Signal Name .......................................................................................................... 276
Signals by Function, Except for GPIO ..................................................................................... 278
GPIO Pins and Alternate Functions......................................................................................... 279
Temperature Characteristics ................................................................................................... 281
Thermal Characteristics........................................................................................................... 281
Maximum Ratings.................................................................................................................... 282
Recommended DC Operating Conditions ............................................................................... 282
LDO Regulator Characteristics................................................................................................ 283
Power Specifications ............................................................................................................... 284
Flash Memory Characteristics ................................................................................................. 284
Phase Locked Loop (PLL) Characteristics .............................................................................. 285
Clock Characteristics............................................................................................................... 285
Analog Comparator Characteristics......................................................................................... 286
Analog Comparator Voltage Reference Characteristics.......................................................... 286
SSI Characteristics .................................................................................................................. 287
JTAG Characteristics............................................................................................................... 289
GPIO Characteristics............................................................................................................... 291
Reset Characteristics .............................................................................................................. 291
October 5, 2006
9
Preliminary
List of Registers
List of Registers
System Control ............................................................................................................................... 45
Register 1:
Register 2:
Register 3:
Register 4:
Register 5:
Register 6:
Register 7:
Register 8:
Register 9:
Register 10:
Register 11:
Register 12:
Register 13:
Register 14:
Register 15:
Register 16:
Register 17:
Register 18:
Register 19:
Register 20:
Register 21:
Register 22:
Register 23:
Register 24:
Register 25:
Register 26:
Register 27:
Register 28:
Register 29:
Register 30:
Device Identification 0 (DID0), offset 0x000 .............................................................................. 53
Device Identification 1 (DID1), offset 0x004 .............................................................................. 54
Device Capabilities 0 (DC0), offset 0x008................................................................................. 56
Device Capabilities 1 (DC1), offset 0x010................................................................................. 57
Device Capabilities 2 (DC2), offset 0x014................................................................................. 58
Device Capabilities 3 (DC3), offset 0x018................................................................................. 59
Device Capabilities 4 (DC4), offset 0x01C ................................................................................ 60
Power-On and Brown-Out Reset Control (PBORCTL), offset 0x030 ........................................ 61
LDO Power Control (LDOPCTL), offset 0x034.......................................................................... 62
Software Reset Control 0 (SRCR0), offset 0x040 ..................................................................... 63
Software Reset Control 1 (SRCR1), offset 0x044 ..................................................................... 64
Software Reset Control 2 (SRCR2), offset 0x048 ..................................................................... 65
Raw Interrupt Status (RIS), offset 0x050................................................................................... 66
Interrupt Mask Control (IMC), offset 0x054 ............................................................................... 67
Masked Interrupt Status and Clear (MISC), offset 0x058.......................................................... 69
Reset Cause (RESC), offset 0x05C .......................................................................................... 70
Run-Mode Clock Configuration (RCC), offset 0x060................................................................. 71
XTAL to PLL Translation (PLLCFG), offset 0x064 .................................................................... 75
Run-Mode Clock Gating Control 0 (RCGC0), offset 0x100 ....................................................... 76
Sleep-Mode Clock Gating Control 0 (SCGC0), offset 0x110..................................................... 76
Deep-Sleep-Mode Clock Gating Control 0 (DCGC0), offset 0x120........................................... 76
Run-Mode Clock Gating Control 1 (RCGC1), offset 0x104 ....................................................... 77
Sleep-Mode Clock Gating Control 1 (SCGC1), offset 0x114..................................................... 77
Deep-Sleep-Mode Clock Gating Control 1 (DCGC1), offset 0x124........................................... 77
Run-Mode Clock Gating Control 2 (RCGC2), offset 0x108 ....................................................... 79
Sleep-Mode Clock Gating Control 2 (SCGC2), offset 0x118..................................................... 79
Deep-Sleep-Mode Clock Gating Control 2 (DCGC2), offset 0x128........................................... 79
Deep-Sleep Clock Configuration (DSLPCLKCFG), offset 0x144 .............................................. 80
Clock Verification Clear (CLKVCLR), offset 0x150.................................................................... 81
Allow Unregulated LDO to Reset the Part (LDOARST), offset 0x160 ....................................... 82
Internal Memory .............................................................................................................................. 83
Register 1:
Register 2:
Register 3:
Register 4:
Register 5:
Register 6:
Register 7:
Register 8:
Register 9:
Flash Memory Protection Read Enable (FMPRE), offset 0x130 ............................................... 88
Flash Memory Protection Program Enable (FMPPE), offset 0x134 .......................................... 88
USec Reload (USECRL), offset 0x140...................................................................................... 89
Flash Memory Address (FMA), offset 0x000 ............................................................................. 90
Flash Memory Data (FMD), offset 0x004 .................................................................................. 91
Flash Memory Control (FMC), offset 0x008 .............................................................................. 92
Flash Controller Raw Interrupt Status (FCRIS), offset 0x00C ................................................... 94
Flash Controller Interrupt Mask (FCIM), offset 0x010 ............................................................... 95
Flash Controller Masked Interrupt Status and Clear (FCMISC), offset 0x014........................... 96
General-Purpose Input/Outputs (GPIOs) ...................................................................................... 97
Register 1:
Register 2:
Register 3:
Register 4:
GPIO Data (GPIODATA), offset 0x000 ................................................................................... 105
GPIO Direction (GPIODIR), offset 0x400 ................................................................................ 106
GPIO Interrupt Sense (GPIOIS), offset 0x404......................................................................... 107
GPIO Interrupt Both Edges (GPIOIBE), offset 0x408.............................................................. 108
10
October 5, 2006
Preliminary
LM3S101 Data Sheet
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 Interrupt Event (GPIOIEV), offset 0x40C....................................................................... 109
GPIO Interrupt Mask (GPIOIM), offset 0x410.......................................................................... 110
GPIO Raw Interrupt Status (GPIORIS), offset 0x414.............................................................. 111
GPIO Masked Interrupt Status (GPIOMIS), offset 0x418 ........................................................ 112
GPIO Interrupt Clear (GPIOICR), offset 0x41C....................................................................... 113
GPIO Alternate Function Select (GPIOAFSEL), offset 0x420 ................................................. 114
GPIO 2-mA Drive Select (GPIODR2R), offset 0x500.............................................................. 115
GPIO 4-mA Drive Select (GPIODR4R), offset 0x504.............................................................. 116
GPIO 8-mA Drive Select (GPIODR8R), offset 0x508.............................................................. 117
GPIO Open Drain Select (GPIOODR), offset 0x50C............................................................... 118
GPIO Pull-Up Select (GPIOPUR), offset 0x510 ...................................................................... 119
GPIO Pull-Down Select (GPIOPDR), offset 0x514.................................................................. 120
GPIO Slew Rate Control Select (GPIOSLR), offset 0x518...................................................... 121
GPIO Digital Input Enable (GPIODEN), offset 0x51C ............................................................. 122
GPIO Peripheral Identification 4 (GPIOPeriphID4), offset 0xFD0 ........................................... 123
GPIO Peripheral Identification 5 (GPIOPeriphID5), offset 0xFD4 ........................................... 124
GPIO Peripheral Identification 6 (GPIOPeriphID6), offset 0xFD8 ........................................... 125
GPIO Peripheral Identification 7 (GPIOPeriphID7), offset 0xFDC........................................... 126
GPIO Peripheral Identification 0 (GPIOPeriphID0), offset 0xFE0 ........................................... 127
GPIO Peripheral Identification 1(GPIOPeriphID1), offset 0xFE4 ............................................ 128
GPIO Peripheral Identification 2 (GPIOPeriphID2), offset 0xFE8 ........................................... 129
GPIO Peripheral Identification 3 (GPIOPeriphID3), offset 0xFEC........................................... 130
GPIO PrimeCell Identification 0 (GPIOPCellID0), offset 0xFF0 .............................................. 131
GPIO PrimeCell Identification 1 (GPIOPCellID1), offset 0xFF4 .............................................. 132
GPIO PrimeCell Identification 2 (GPIOPCellID2), offset 0xFF8 .............................................. 133
GPIO PrimeCell Identification 3 (GPIOPCellID3), offset 0xFFC.............................................. 134
General-Purpose Timers .............................................................................................................. 135
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:
GPTM Configuration (GPTMCFG), offset 0x000..................................................................... 147
GPTM TimerA Mode (GPTMTAMR), offset 0x004 .................................................................. 148
GPTM TimerB Mode (GPTMTBMR), offset 0x008 .................................................................. 149
GPTM Control (GPTMCTL), offset 0x00C............................................................................... 150
GPTM Interrupt Mask (GPTMIMR), offset 0x018 .................................................................... 152
GPTM Raw Interrupt Status (GPTMRIS), offset 0x01C .......................................................... 154
GPTM Masked Interrupt Status (GPTMMIS), offset 0x020 ..................................................... 155
GPTM Interrupt Clear (GPTMICR), offset 0x024..................................................................... 156
GPTM TimerA Interval Load (GPTMTAILR), offset 0x028 ...................................................... 157
GPTM TimerB Interval Load (GPTMTBILR), offset 0x02C...................................................... 158
GPTM TimerA Match (GPTMTAMATCHR), offset 0x030 ....................................................... 159
GPTM TimerB Match (GPTMTBMATCHR), offset 0x034 ....................................................... 160
GPTM TimerA Prescale (GPTMTAPR), offset 0x038.............................................................. 161
GPTM TimerB Prescale (GPTMTBPR), offset 0x03C ............................................................. 162
GPTM TimerA Prescale Match (GPTMTAPMR), offset 0x040................................................ 163
GPTM TimerB Prescale Match (GPTMTBPMR), offset 0x044................................................ 164
GPTM TimerA (GPTMTAR), offset 0x048 ............................................................................... 165
GPTM TimerB (GPTMTBR), offset 0x04C .............................................................................. 166
Watchdog Timer............................................................................................................................ 167
Register 1:
Register 2:
Watchdog Load (WDTLOAD), offset 0x000 ............................................................................ 170
Watchdog Value (WDTVALUE), offset 0x004 ......................................................................... 171
October 5, 2006
11
Preliminary
List of Registers
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 Control (WDTCTL), offset 0x008............................................................................ 172
Watchdog Interrupt Clear (WDTICR), offset 0x00C ................................................................ 173
Watchdog Raw Interrupt Status (WDTRIS), offset 0x010 ....................................................... 174
Watchdog Masked Interrupt Status (WDTMIS), offset 0x014.................................................. 175
Watchdog Lock (WDTLOCK), offset 0xC00 ............................................................................ 176
Watchdog Test (WDTTEST), offset 0x418 .............................................................................. 177
Watchdog Peripheral Identification 4 (WDTPeriphID4), offset 0xFD0..................................... 178
Watchdog Peripheral Identification 5 (WDTPeriphID5), offset 0xFD4..................................... 179
Watchdog Peripheral Identification 6 (WDTPeriphID6), offset 0xFD8..................................... 180
Watchdog Peripheral Identification 7 (WDTPeriphID7), offset 0xFDC .................................... 181
Watchdog Peripheral Identification 0 (WDTPeriphID0), offset 0xFE0 ..................................... 182
Watchdog Peripheral Identification 1 (WDTPeriphID1), offset 0xFE4 ..................................... 183
Watchdog Peripheral Identification 2 (WDTPeriphID2), offset 0xFE8 ..................................... 184
Watchdog Peripheral Identification 3 (WDTPeriphID3), offset 0xFEC .................................... 185
Watchdog PrimeCell Identification 0 (WDTPCellID0), offset 0xFF0........................................ 186
Watchdog PrimeCell Identification 1 (WDTPCellID1), offset 0xFF4........................................ 187
Watchdog PrimeCell Identification 2 (WDTPCellID2), offset 0xFF8........................................ 188
Watchdog PrimeCell Identification 3 (WDTPCellID3 ), offset 0xFFC ...................................... 189
Universal Asynchronous Receiver/Transmitter (UART) ........................................................... 190
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 ...................................................................................... 197
UART Receive Status/Error Clear (UARTRSR/UARTECR), offset 0x004 .............................. 199
UART Flag (UARTFR), offset 0x018 ....................................................................................... 201
UART Integer Baud-Rate Divisor (UARTIBRD), offset 0x024 ................................................. 203
UART Fractional Baud-Rate Divisor (UARTFBRD), offset 0x028 ........................................... 204
UART Line Control (UARTLCRH), offset 0x02C ..................................................................... 205
UART Control (UARTCTL), offset 0x030................................................................................. 207
UART Interrupt FIFO Level Select (UARTIFLS), offset 0x034 ................................................ 208
UART Interrupt Mask (UARTIM), offset 0x038 ........................................................................ 209
UART Raw Interrupt Status (UARTRIS), offset 0x03C............................................................ 211
UART Masked Interrupt Status (UARTMIS), offset 0x040 ...................................................... 212
UART Interrupt Clear (UARTICR), offset 0x044...................................................................... 213
UART Peripheral Identification 4 (UARTPeriphID4), offset 0xFD0.......................................... 214
UART Peripheral Identification 5 (UARTPeriphID5), offset 0xFD4.......................................... 215
UART Peripheral Identification 6 (UARTPeriphID6), offset 0xFD8.......................................... 216
UART Peripheral Identification 7 (UARTPeriphID7), offset 0xFDC ......................................... 217
UART Peripheral Identification 0 (UARTPeriphID0), offset 0xFE0.......................................... 218
UART Peripheral Identification 1 (UARTPeriphID1), offset 0xFE4.......................................... 219
UART Peripheral Identification 2 (UARTPeriphID2), offset 0xFE8.......................................... 220
UART Peripheral Identification 3 (UARTPeriphID3), offset 0xFEC ......................................... 221
UART PrimeCell Identification 0 (UARTPCellID0), offset 0xFF0............................................. 222
UART PrimeCell Identification 1 (UARTPCellID1), offset 0xFF4............................................. 223
UART PrimeCell Identification 2 (UARTPCellID2), offset 0xFF8............................................. 224
UART PrimeCell Identification 3 (UARTPCellID3), offset 0xFFC ............................................ 225
Synchronous Serial Interface (SSI) ............................................................................................. 226
Register 1:
Register 2:
Register 3:
Register 4:
SSI Control 0 (SSICR0), offset 0x000 ..................................................................................... 238
SSI Control 1 (SSICR1), offset 0x004 ..................................................................................... 240
SSI Data (SSIDR), offset 0x008 .............................................................................................. 242
SSI Status (SSISR), offset 0x00C ........................................................................................... 243
12
October 5, 2006
Preliminary
LM3S101 Data Sheet
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:
SSI Clock Prescale (SSICPSR), offset 0x010 ......................................................................... 244
SSI Interrupt Mask (SSIIM), offset 0x014 ................................................................................ 245
SSI Raw Interrupt Status (SSIRIS), offset 0x018 .................................................................... 246
SSI Masked Interrupt Status (SSIMIS), offset 0x01C.............................................................. 247
SSI Interrupt Clear (SSIICR), offset 0x020.............................................................................. 248
SSI Peripheral Identification 4 (SSIPeriphID4), offset 0xFD0.................................................. 249
SSI Peripheral Identification 5 (SSIPeriphID5), offset 0xFD4.................................................. 250
SSI Peripheral Identification 6 (SSIPeriphID6), offset 0xFD8.................................................. 251
SSI Peripheral Identification 7 (SSIPeriphID7), offset 0xFDC ................................................. 252
SSI Peripheral Identification 0 (SSIPeriphID0), offset 0xFE0.................................................. 253
SSI Peripheral Identification 1 (SSIPeriphID1), offset 0xFE4.................................................. 254
SSI Peripheral Identification 2 (SSIPeriphID2), offset 0xFE8.................................................. 255
SSI Peripheral Identification 3 (SSIPeriphID3), offset 0xFEC ................................................. 256
SSI PrimeCell Identification 0 (SSIPCellID0), offset 0xFF0..................................................... 257
SSI PrimeCell Identification 1 (SSIPCellID1), offset 0xFF4..................................................... 258
SSI PrimeCell Identification 2 (SSIPCellID2), offset 0xFF8..................................................... 259
SSI PrimeCell Identification 3 (SSIPCellID3), offset 0xFFC .................................................... 260
Analog Comparators .................................................................................................................... 261
Register 1:
Register 2:
Register 3:
Register 4:
Register 5:
Register 6:
Register 7:
Register 8:
Analog Comparator Masked Interrupt Status (ACMIS), offset 0x00........................................ 266
Analog Comparator Raw Interrupt Status (ACRIS), offset 0x04.............................................. 267
Analog Comparator Interrupt Enable (ACINTEN), offset 0x08 ................................................ 268
Analog Comparator Reference Voltage Control (ACREFCTL), offset 0x10 ............................ 269
Analog Comparator Status 0 (ACSTAT0), offset 0x20 ............................................................ 270
Analog Comparator Status 1 (ACSTAT1), offset 0x40 ............................................................ 270
Analog Comparator Control 0 (ACCTL0), offset 0x24 ............................................................. 271
Analog Comparator Control 1 (ACCTL1), offset 0x44 ............................................................. 271
October 5, 2006
13
Preliminary
Revision History
Revision History
This table provides a summary of the document revisions.
Date
Revision
Description
March 27, 2006
00
Initial public release of LM3S101 and LM3S102 data sheets.
March 30, 2006
01
Second release of LM3S101 and LM3S102 data sheets. Includes the following
changes:
• Added timing data.
May 2006
02
Third release of LM3S101 and LM3S102 data sheets. Includes the following
changes:
• Added Initialization and Configuration section to System Control chapter
• Renamed boot oscillator to internal oscillator
• Corrected reset value of DC1 in System Control Register Map (was correct on
register reference page)
• Corrected description of bits to set to enable PWM mode in timer
• Corrected WDTICR register offset (was correct in Register Map but not on
register reference page)
• Added Watchdog Test (WDTTEST) register
• Changed some bit and register names for consistency with DriverLib:
- Changed USESYS bit in RCC register to USESYSDIV
- Changed name of Capture bit fields in GPTMIMR, GPTMRIS, GPTMMIS,
and GPTMICR registers from C1bitname and C2bitname to CAbitname and
CBbitname
• Fixed minor style and edit issues
July 2006
03
Fourth release of LM3S101 and LM3S102 data sheets. Includes the following
changes:
• Added initialization and configuration content into PWM, Comparators, and
JTAG chapters.
• Clarified that peripheral clock must be set before enabling peripherals in
“Initialization and Configuration” sections.
September 2006
04
Fifth release of LM3S101 data sheet. Includes the following changes:
• Updated the clocking examples in the I2C chapter.
• Added “5-V-tolerant” description for GPIOs to feature list, GPIO chapter, and
Electrical chapter.
• Added maximum values for 20 MHz and 25 MHz parts to Table 9-1, “16-Bit
Timer With Prescaler Configurations” in the Timers chapter.
• Made the following changes in the System Control chapter:
- Updated field descriptions in the Run-Mode Clock Configuration
(RCC) register.
- Updated the internal oscillator clock speed.
- Added the Deep-Sleep Clock Configuration (DSLPCFG) register.
- Added bus fault information to the clock gating registers.
October 2006
05
Sixth release of LM3S101 data sheet. Includes the following changes:
• Added Serial Flash Loader usage information.
14
October 5, 2006
Preliminary
LM3S101 Data Sheet
About This Document
This data sheet provides reference information for the LM3S101 microcontroller, describing the
functional blocks of the system-on-chip (SoC) device designed around the ARM® Cortex™-M3
core.
Audience
This manual is intended for system software developers, hardware designers, and application
developers.
About This Manual
This document is organized into sections that correspond to each major feature.
Related Documents
The following documents are referenced by the data sheet, and available on the documentation
CD or from the Luminary Micro web site at www.luminarymicro.com:

ARM® Cortex™-M3 Technical Reference Manual

CoreSight™ Design Kit Technical Reference Manual

ARM® v7-M Architecture Application Level Reference Manual
The following related documents are also referenced:

IEEE Standard 1149.1-Test Access Port and Boundary-Scan Architecture
This documentation list was current as of publication date. Please check the Luminary Micro web
site for additional documentation, including application notes and white papers.
Documentation Conventions
This document uses the conventions shown in Table 0-1.
Table 0-1. Documentation Conventions
Notation
Meaning
General Register Notation
REGISTER
APB registers are indicated in uppercase bold. For example,
PBORCTL is the Power-On and Brown-Out Reset Control register. If
a register name contains a lowercase n, it represents more than one
register. For example, SRCRn represents any (or all) of the three
Software Reset Control registers: SRCR0, SRCR1, and SRCR2.
bit
A single bit in a register.
bit field
Two or more consecutive and related bits.
offset 0xnnn
A hexadecimal increment to a register’s address, relative to that
module’s base address as specified in Table 3-1, "Memory Map," on
page 30.
October 5, 2006
15
Preliminary
About This Document
Table 0-1. Documentation Conventions
Notation
Meaning
Register N
Registers are numbered consecutively throughout the document to
aid in referencing them. The register number has no meaning to
software.
reserved
Register bits marked reserved are reserved for future use. Reserved
bits return an indeterminate value, and should never be changed.
Only write a reserved bit with its current value.
yy:xx
The range of register bits inclusive from xx to yy. For example, 31:15
means bits 15 through 31 in that register.
Register Bit/Field Types
This value in the register bit diagram indicates whether software
running on the controller can change the value of the bit field.
RO
Software can read this field. Always write the chip reset value.
R/W
Software can read or write this field.
R/W1C
Software can read or write this field. A write of a 0 to a W1C bit does
not affect the bit value in the register. A write of a 1 clears the value
of the bit in the register; the remaining bits remain unchanged.
This register type is primarily used for clearing interrupt status bits
where the read operation provides the interrupt status and the write
of the read value clears only the interrupts being reported at the time
the register was read.
W1C
Software can write this field. A write of a 0 to a W1C bit does not
affect the bit value in the register. A write of a 1 clears the value of
the bit in the register; the remaining bits remain unchanged. A read
of the register returns no meaningful data.
This register is typically used to clear the corresponding bit in an
interrupt register.
WO
Only a write by software is valid; a read of the register returns no
meaningful data.
Register Bit/Field Reset Value
This value in the register bit diagram shows the bit/field value after
any reset, unless noted.
0
Bit cleared to 0 on chip reset.
1
Bit set to 1 on chip reset.
–
Nondeterministic.
Pin/Signal Notation
[]
Pin alternate function; a pin defaults to the signal without the
brackets.
pin
Refers to the physical connection on the package.
signal
Refers to the electrical signal encoding of a pin.
16
October 5, 2006
Preliminary
LM3S101 Data Sheet
Table 0-1. Documentation Conventions
Notation
Meaning
assert a signal
Change the value of the signal from the logically False state to the
logically True state. For active High signals, the asserted signal
value is 1 (High); for active Low signals, the asserted signal value is
0 (Low). The active polarity (High or Low) is defined by the signal
name (see SIGNAL and SIGNAL below).
deassert a signal
Change the value of the signal from the logically True state to the
logically False state.
SIGNAL
Signal names are in uppercase and in the Courier font. An overbar
on a signal name indicates that it is active Low. To assert SIGNAL is
to drive it Low; to deassert SIGNAL is to drive it High.
SIGNAL
Signal names are in uppercase and in the Courier font. An active
High signal has no overbar. To assert SIGNAL is to drive it High; to
deassert SIGNAL is to drive it Low.
Numbers
X
An uppercase X indicates any of several values is allowed, where X
can be any legal pattern. For example, a binary value of 0X00 can be
either 0100 or 0000, a hex value of 0xX is 0x0 or 0x1, and so on.
0x
Hexadecimal numbers have a prefix of 0x. For example, 0x00FF is
the hexadecimal number FF. Binary numbers are indicated with a b
suffix, for example, 1011b. Decimal numbers are written without a
prefix or suffix.
October 5, 2006
17
Preliminary
Architectural Overview
1
Architectural Overview
The Luminary Micro Stellaris™ family of microcontrollers—the first ARM® Cortex™-M3 based
controllers—brings high-performance 32-bit computing to cost-sensitive embedded microcontroller
applications. These pioneering parts deliver customers 32-bit performance at a cost equivalent to
legacy 8- and 16-bit devices, all in a package with a small footprint.
The LM3S101 controller in the Stellaris family offers the advantages of ARM’s widely available
development tools, System-on-Chip (SoC) infrastructure IP applications, and a large user
community. Additionally, the controller uses ARM’s Thumb®-compatible Thumb-2 instruction set to
reduce memory requirements and, thereby, cost.
Luminary Micro offers a complete solution to get to market quickly, with a customer development
board, white papers and application notes, and a strong support, sales, and distributor network.
1.1
Product Features
The LM3S101 microcontroller includes the following product features:

32-Bit RISC Performance
– 32-bit ARM® Cortex™-M3 v7M architecture optimized for small-footprint embedded
applications
– Thumb®-compatible Thumb-2-only instruction set processor core for high code density
– 20-MHz operation
– Hardware-division and single-cycle-multiplication
– Integrated Nested Vectored Interrupt Controller (NVIC) providing deterministic interrupt
handling
– 14 interrupts with eight priority levels
– Unaligned data access, enabling data to be efficiently packed into memory
– Atomic bit manipulation (bit-banding) delivers maximum memory utilization and
streamlined peripheral control

Internal Memory
– 8 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
– 2 KB single-cycle SRAM

General-Purpose Timers
– Two timers, each of which can be configured as a single 32-bit timer or as two 16-bit timers
– 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 in periodic and one-shot mode when the controller asserts the
CPU Halt flag during debug
– 16-bit Timer modes:
18
October 5, 2006
Preliminary
LM3S101 Data Sheet
•
General-purpose timer function with an 8-bit prescaler
•
Programmable one-shot timer
•
Programmable periodic timer
•
User-enabled stalling when the controller asserts CPU Halt flag during debug
– 16-bit Input Capture modes:
•
Input edge count capture
•
Input edge time capture
– 16-bit PWM mode:
•

Simple PWM mode with software-programmable output inversion of the PWM signal
ARM FiRM-compliant Watchdog Timer
– 32-bit down counter with a programmable load register
– Separate watchdog clock with an enable
– Programmable interrupt generation logic with interrupt masking
– Lock register protection from runaway software
– Reset generation logic with an enable/disable
– User-enabled stalling when the controller asserts the CPU Halt flag during debug

Synchronous Serial Interface (SSI)
– Master or slave operation
– Programmable clock bit rate and prescale
– Separate transmit and receive FIFOs, 16 bits wide, 8 locations deep
– Programmable interface operation for Freescale SPI, MICROWIRE, or Texas Instruments
synchronous serial interfaces
– Programmable data frame size from 4 to 16 bits
– Internal loopback test mode for diagnostic/debug testing

UART
– Fully programmable 16C550-type UART
– Separate 16x8 transmit (TX) and 16x12 receive (RX) FIFOs to reduce CPU interrupt
service loading
– Programmable baud-rate generator with fractional divider
– Programmable FIFO length, including 1-byte deep operation providing conventional
double-buffered interface
– FIFO trigger levels of 1/8, 1/4, 1/2, 3/4, and 7/8
– Standard asynchronous communication bits for start, stop, and parity
– False-start-bit detection
– Line-break generation and detection

Analog Comparators
– Two independent integrated analog comparators
– Configurable for output to drive an output pin or generate an interrupt
October 5, 2006
19
Preliminary
Architectural Overview
– Compare external pin input to external pin input or to internal programmable voltage
reference

GPIOs
– 2 to 18 GPIOs, depending on configuration
– 5-V-tolerant input/outputs
– Programmable interrupt generation as either edge-triggered or level-sensitive
– Bit masking in both read and write operations through address lines
– Programmable control for GPIO pad configuration:

•
Weak pull-up or pull-down resistors
•
2-mA, 4-mA, and 8-mA pad drive
•
Slew rate control for the 8-mA drive
•
Open drain enables
•
Digital input enables
Power
– On-chip Low Drop-Out (LDO) voltage regulator, with programmable output user-adjustable
from 2.25 V to 2.75 V
– Low-power options on controller: Sleep and Deep-sleep modes
– Low-power options for peripherals: software controls shutdown of individual peripherals
– User-enabled LDO unregulated voltage detection and automatic reset
– 3.3-V supply brownout detection and reporting via interrupt or reset

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

Additional Features
– Six reset sources
– Programmable clock source control
– Clock gating to individual peripherals for power savings
– IEEE 1149.1-1990 compliant Test Access Port (TAP) controller
– Debug access via JTAG and Serial Wire interfaces
– Full JTAG boundary scan

1.2
Industrial-range 28-pin RoHS-compliant SOIC package
Target Applications

Factory automation and control
20
October 5, 2006
Preliminary
LM3S101 Data Sheet
1.3

Industrial control power devices

Building and home automation
High-Level Block Diagram
Figure 1-1.
Stellaris High-Level Block Diagram
ARM Cortex-M3
(including Nested DCode bus
Flash
Vectored Interrupt
Controller (NVIC)) ICode bus
System
Control
& Clocks
LMI JTAG
Test Access Port
(TAP)
Controller
APB Bridge
Memory
Peripherals
SRAM
General-Purpose
Timers
General-Purpose
Input/Outputs
(GPIOs)
System
Peripherals
Universal
Asynchronous
Receiver/
Transmitter
(UART)
Peripheral Bus
Watchdog
Timer
Synchronous
Serial
Serial
Communications
Interface
Peripherals
(SSI)
Analog
Comparators
Analog
Peripherals
LM3S101
October 5, 2006
21
Preliminary
Architectural Overview
1.4
Functional Overview
The following sections provide an overview of the features of the LM3S101 microcontroller. The
chapter number in parenthesis indicates where that feature is discussed in detail. Ordering and
support information can be found in “Ordering and Contact Information” on page 299.
1.4.1
ARM Cortex™-M3
1.4.1.1
Processor Core (Section 2 on page 27)
All members of the Stellaris product family, including the LM3S101 microcontroller, are designed
around an ARM Cortex™-M3 processor core. The ARM Cortex-M3 processor provides the core
for a high-performance, low-cost platform that meets the needs of minimal memory
implementation, reduced pin count, and low power consumption, while delivering outstanding
computational performance and exceptional system response to interrupts.
Section 2, “ARM Cortex-M3 Processor Core,” on page 27 provides an overview of the ARM core;
the core is detailed in the ARM® Cortex™-M3 Technical Reference Manual.
1.4.1.2
Nested Vectored Interrupt Controller (NVIC)
The LM3S101 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 14 interrupts.
Section 4, “Interrupts,” on page 32 provides an overview of the NVIC controller and the interrupt
map. Exceptions and interrupts are detailed in the ARM® Cortex™-M3 Technical Reference
Manual.
1.4.2
Motor Control Peripherals
To enhance motor control, the LM3S101 controller features Pulse Width Modulation (PWM)
outputs.
1.4.2.1
PWM (“16-Bit PWM Mode” on page 144)
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 LM3S101, PWM motion control functionality can be achieved through the motion control
features of the general-purpose timers (using the CCP pins).
The General-Purpose Timer Module’s CCP (Capture Compare PWM) pins are software
programmable to support a simple PWM mode with a software-programmable output inversion of
the PWM signal.
1.4.3
Analog Peripherals
To handle analog signals, the LM3S101 controller offers two analog comparators.
1.4.3.1
Analog Comparators (Section 13 on page 261)
An analog comparator is a peripheral that compares two analog voltages, and provides a logical
output that signals the comparison result.
22
October 5, 2006
Preliminary
LM3S101 Data Sheet
The LM3S101 controller provides two independent integrated analog comparators that can be
configured to drive an output or generate an interrupt.
A comparator can compare a test voltage against any one of these voltages:

An individual external reference voltage

A shared single external reference voltage

Section 14, “Pin Diagram,” on page 273

Section 15, “Signal Tables,” on page 274

Section 16, “Operating Characteristics,” on page 281

Section 17, “Electrical Characteristics,” on page 282

Section 18, “Package Information,” on page 294
October 5, 2006
25
Preliminary
Architectural Overview
1.5
System Block Diagram
Figure 1-2. LM3S101 Controller System-Level Block Diagram
VDD_3.3V
LDO
VDD_2.5V
LDO
GND
ARM Cortex-M3
(20 MHz)
CM3Core
DCode
Debug
OSC0
Flash
(8 KB)
ICode
NVIC
Bus
PLL
IOSC
APB Bridge
OSC1
SRAM
(2 KB)
POR
BOR
RST
Peripheral Bus
GPIO Port A
PA5/SSITx
PA4/SSIRx
PA3/SSIFss
PA2/SSIClk
SSI
PA1/U0Tx
PA0/U0Rx
UART0
GPIO Port C
PC3/TDO/SWO
PC2/TDI
PC1/TMS/SWDIO
PC0/TCK/SWCLK
Watchdog
Timer
System
Control
& Clocks
GPIO Port B
PB7/TRST
Analog
Comparators
PB6/C0+
PB5/C0o/C1PB4/C0PB3
PB2
GP Timer1
PB1/32KHz
GP Timer0
PB0/CCP0
JTAG
SWD/SWO
LM3S101
26
October 5, 2006
Preliminary
LM3S101 Data Sheet
2
ARM Cortex-M3 Processor Core
The ARM Cortex-M3 processor provides the core for a high-performance, low-cost platform that
meets the needs of minimal memory implementation, reduced pin count, and low power
consumption, while delivering outstanding computational performance and exceptional system
response to interrupts. Features include:

Compact core.

Thumb-2 instruction set, delivering the high-performance expected of an ARM core in the
memory size usually associated with 8- and 16-bit devices; typically in the range of a few
kilobytes of memory for microcontroller class applications.

Exceptional interrupt handling, by implementing the register manipulations required for
handling an interrupt in hardware.

Full-featured debug solution with a:
– Serial Wire JTAG Debug Port (SWJ-DP)
– Flash Patch and Breakpoint (FPB) unit for implementing breakpoints
– Data Watchpoint and Trigger (DWT) unit for implementing watchpoints, trigger resources,
and system profiling
– Instrumentation Trace Macrocell (ITM) for support of printf style debugging
– Trace Port Interface Unit (TPIU) for bridging to a Trace Port Analyzer
The Stellaris family of microcontrollers builds on this core to bring high-performance 32-bit
computing to cost-sensitive embedded microcontroller applications, such as factory automation
and control, industrial control power devices, and building and home automation.
For more information on the ARM Cortex-M3 processor core, see the ARM® Cortex™-M3
Technical Reference Manual. For information on SWJ-DP, see the CoreSight™ Design Kit
Technical Reference Manual.
October 5, 2006
27
Preliminary
ARM Cortex-M3 Processor Core
2.1
Block Diagram
Figure 2-1. CPU Block Diagram
Nested
Vectored
Interrupt
Controller
Interrupts
Sleep
ARM
Cortex-M3
CM3 Core
Debug
Instructions
Data
Trace
Port
Interface
Unit
Flash
Patch and
Breakpoint
Data
Watchpoint
and Trace
2.2
Adv. HighPerf. Bus
Access Port
Private
Peripheral
Bus
(external)
ROM
Table
Private Peripheral
Bus
(internal )
Serial Wire JTAG
Debug Port
Instrumentation
Trace Macrocell
Serial
Wire
Output
Trace
Port
(SWO)
Adv. Peripheral
Bus
Bus
Matrix
I-code bus
D-code bus
System bus
Functional Description
Important: The ARM® Cortex™-M3 Technical Reference Manual describes all the features of
an ARM Cortex-M3 in detail. However, these features differ based on the
implementation. This section describes the Stellaris implementation.
Luminary Micro has implemented the ARM Cortex-M3 core as shown in Figure 2-1. As noted in
the ARM® Cortex™-M3 Technical Reference Manual, several Cortex-M3 components are flexible
in their implementation: SW/JTAG-DP, ETM, TPIU, the ROM table, the MPU, and the Nested
Vectored Interrupt Controller (NVIC). Each of these is addressed in the sections that follow.
2.2.1
Serial Wire and JTAG Debug
Luminary Micro has replaced the ARM SW-DP and JTAG-DP with the ARM
CoreSight™-compliant Serial Wire JTAG Debug Port (SWJ-DP) interface. This means Chapter 12,
“Debug Port,” of the ARM® Cortex™-M3 Technical Reference Manual does not apply to Stellaris
devices.
The SWJ-DP interface combines the SWD and JTAG debug ports into one module. See the
CoreSight™ Design Kit Technical Reference Manual for details on SWJ-DP.
28
October 5, 2006
Preliminary
LM3S101 Data Sheet
2.2.2
Embedded Trace Macrocell (ETM)
ETM was not implemented in the Stellaris devices. This means Chapters 15 and 16 of the ARM®
Cortex™-M3 Technical Reference Manual can be ignored.
2.2.3
Trace Port Interface Unit (TPIU)
The TPIU acts as a bridge between the Cortex-M3 trace data from the ITM, and an off-chip Trace
Port Analyzer. The Stellaris devices have implemented TPIU as shown in Figure 2-2. This is
similar to the non-ETM version described in the ARM® Cortex™-M3 Technical Reference Manual,
however, SWJ-DP only provides SWV output for the TPIU.
Figure 2-2. 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)
ROM Table
The default ROM table was implemented as described in the ARM® Cortex™-M3 Technical
Reference Manual.
2.2.5
Memory Protection Unit (MPU)
The LM3S101 controller does not include the memory protection unit (MPU) of the ARM CortexM3.
2.2.6
Nested Vectored Interrupt Controller (NVIC)
2.2.6.1
Interrupts
The ARM® Cortex™-M3 Technical Reference Manual describes the maximum number of
interrupts and interrupt priorities. The LM3S101 microcontroller supports 14 interrupts with eight
priority levels.
2.2.6.2
SysTick Calibration Value Registers
The SysTick Calibration Value register is not implemented.
October 5, 2006
29
Preliminary
Memory Map
3
Memory Map
The memory map for the LM3S101 is provided in Table 3-1. In this manual, register addresses are
given as a hexadecimal increment, relative to the module’s base address as shown in the memory
map. See also Chapter 4, “Memory Map” in the ARM® Cortex™-M3 Technical Reference Manual.
Table 3-1. Memory Map (Sheet 1 of 2)
Start
End
Description
For details on
registers, see ...
page 87
Memory
0x00000000
0x00001FFF
On-chip flash
0x00002000
0x1FFFFFFF
Reserveda
0x20000000
0x200003FF
Bit-banded on-chip SRAM
-
0x20000400
0x200FFFFF
Reserveda
-
0x22000000
0x2200FFFF
Bit-band alias of 0x20000000 through 0x200003FF
-
0x22010000
0x23FFFFFF
Reserveda
-
0x40000000
0x40000FFF
Watchdog timer
page 169
0x40001000
0x40003FFF
Reserved for three additional watchdog timers (per FiRM
specification)a
-
0x40004000
0x40004FFF
GPIO Port A
page 104
0x40005000
0x40005FFF
GPIO Port B
page 104
0x40006000
0x40006FFF
GPIO Port C
page 104
0x40007000
0x40007FFF
Reserved for additional GPIO port (per FiRM
specification)a
-
0x40008000
0x40008FFF
SSI
page 237
0x40009000
0x4000BFFF
Reserved for three additional SSIs (per FiRM
specification)a
-
0x4000C000
0x4000CFFF
UART0
page 196
0x4000D000
0x4000FFFF
Reserved for additional UART (per FiRM specification)a
-
0x40010000
0x4001FFFF
Reserved for future FiRM peripheralsa
-
0x40020000
0x40023FFF
Reserveda
-
0x40024000
0x40027FFF
Reserveda
-
0x40028000
0x4002BFFF
Reserveda
-
0x4002C000
0x4002FFFF
Reserveda
-
FiRM Peripherals
Peripherals
30
October 5, 2006
Preliminary
LM3S101 Data Sheet
Table 3-1. Memory Map (Sheet 2 of 2)
Start
End
Description
For details on
registers, see ...
0x40030000
0x40030FFF
Timer0
page 146
0x40031000
0x40031FFF
Timer1
page 146
0x40032000
0x40037FFF
Reserveda
-
0x40038000
0x4003BFFF
Reserveda
-
0x4003C000
0x4003CFFF
Analog comparators
page 265
0x4003D000
0x400FCFFF
Reserveda
-
0x400FD000
0x400FDFFF
Flash control
page 87
0x400FE000
0x400FFFFF
System control
page 52
0x40100000
0x41FFFFFF
Reserveda
-
0x42000000
0x43FFFFFF
Bit-band alias of 0x40000000 through 0x400FFFFF
-
0x44000000
0xDFFFFFFF
Reserveda
-
ARM® Cortex™-M3
Technical Reference
Manual
Private Peripheral Bus
0xE0000000
0xE0000FFF
Instrumentation Trace Macrocell (ITM)
0xE0001000
0xE0001FFF
Data Watchpoint and Trace (DWT)
0xE0002000
0xE0002FFF
Flash Patch and Breakpoint (FPB)
0xE0003000
0xE000DFFF
Reserveda
0xE000E000
0xE000EFFF
Nested Vectored Interrupt Controller (NVIC)
0xE000F000
0xE003FFFF
Reserveda
0xE0040000
0xE0040FFF
Trace Port Interface Unit (TPIU)
0xE0041000
0xE0041FFF
Reserveda
-
0xE0042000
0xE00FFFFF
Reserveda
-
0xE0100000
0xFFFFFFFF
Reserved for vendor peripheralsa
-
a. All reserved space returns a bus fault when read or written.
October 5, 2006
31
Preliminary
Interrupts
4
Interrupts
The ARM Cortex-M3 processor and the Nested Vectored Interrupt Controller (NVIC) prioritize and
handle all exceptions. All exceptions are handled in Handler Mode. The processor state is
automatically stored to the stack on an exception, and automatically restored from the stack at the
end of the Interrupt Service Routine (ISR). The vector is fetched in parallel to the state saving,
which enables efficient interrupt entry. The processor supports tail-chaining, which enables
back-to-back interrupts to be performed without the overhead of state saving and restoration.
Table 4-1 lists all the exceptions. Software can set eight priority levels on seven of these
exceptions (system handlers) as well as on 14 interrupts (listed in Table 4-2). Priorities on the
system handlers are set with the NVIC System Handler Priority registers. Interrupts are enabled
through the NVIC Interrupt Set Enable register and prioritized with the NVIC Interrupt Priority
registers. You can also group priorities by splitting priority levels into pre-emption priorities and
subpriorities. All the interrupt registers are described in Chapter 8, “Nested Vectored Interrupt
Controller” in the ARM® Cortex™-M3 Technical Reference Manual.
Internally, the highest user-settable priority (0) is treated as fourth priority, after a Reset, NMI, and
a Hard Fault. Note that 0 is the default priority for all the settable priorities.
If you assign the same priority level to two or more interrupts, their hardware priority (the lower the
position number) determines the order in which the processor activates them. For example, if both
GPIO Port A and GPIO Port B are priority level 1, then GPIO Port A has higher priority.
See Chapter 5, “Exceptions” and Chapter 8, “Nested Vectored Interrupt Controller” in the ARM®
Cortex™-M3 Technical Reference Manual for more information on exceptions and interrupts.
Table 4-1. Exception Types
Position
Prioritya
-
0
-
Reset
1
-3 (highest)
Non-Maskable
Interrupt (NMI)
2
-2
Exception Type
Description
Stack top is loaded from first entry of vector table on
reset.
Invoked on power up and warm reset. On first
instruction, drops to lowest priority (and then is
called the base level of activation). This is
asynchronous.
Cannot be stopped or preempted by any exception
but reset. This is asynchronous.
An NMI is only producible by software, using the
NVIC Interrupt Control State register.
Hard Fault
3
-1
All classes of Fault, when the fault cannot activate
due to priority or the configurable fault handler has
been disabled. This is synchronous.
Memory
Management
4
settable
MPU mismatch, including access violation and no
match. This is synchronous.
The priority of this exception can be changed.
Bus Fault
5
settable
Pre-fetch fault, memory access fault, and other
address/memory related faults. This is synchronous
when precise and asynchronous when imprecise.
You can enable or disable this fault.
32
October 5, 2006
Preliminary
LM3S101 Data Sheet
Table 4-1. Exception Types (Continued)
Position
Prioritya
Description
6
settable
Usage fault, such as undefined instruction executed
or illegal state transition attempt. This is
synchronous.
7-10
-
SVCall
11
settable
System service call with SVC instruction. This is
synchronous.
Debug Monitor
12
settable
Debug monitor (when not halting). This is
synchronous, but only active when enabled. It does
not activate if lower priority than the current
activation.
-
13
-
PendSV
14
settable
Pendable request for system service. This is
asynchronous and only pended by software.
SysTick
15
settable
System tick timer has fired. This is asynchronous.
16 and
above
settable
Asserted from outside the ARM Cortex-M3 core and
fed through the NVIC (prioritized). These are all
asynchronous. Table 4-2 lists the interrupts on the
LM3S101 controller.
Exception Type
Usage Fault
-
Interrupts
Reserved.
Reserved.
a. 0 is the default priority for all the settable priorities.
Table 4-2. Interrupts
Interrupt
(Bit in Interrupt Registers)
Description
0
GPIO Port A
1
GPIO Port B
2
GPIO Port C
3-4
Reserved
5
UART0
6
Reserved
7
SSI
8-17
Reserved
18
Watchdog timer
19
Timer0a
20
Timer0b
21
Timer1a
22
Timer1b
October 5, 2006
33
Preliminary
Interrupts
Table 4-2. Interrupts (Continued)
Interrupt
(Bit in Interrupt Registers)
23-24
Description
Reserved
25
Analog Comparator 0
26
Analog Comparator 1
27
Reserved
28
System Control
29
Flash Control
30-31
Reserved
34
October 5, 2006
Preliminary
LM3S101 Data Sheet
5
JTAG Interface
The Joint Test Action Group (JTAG) port is an IEEE standard that defines a Test Access Port and
Boundary Scan Architecture for digital integrated circuits and provides a standardized serial
interface for controlling the associated test logic. The TAP, Instruction Register (IR), and Data
Registers (DR) can be used to test the interconnections of assembled printed circuit boards and
obtain manufacturing information on the components. The JTAG Port also provides a means of
accessing and controlling design-for-test features such as I/O pin observation and control, scan
testing, and debugging.
The JTAG port is comprised of the standard five pins: TRST, TCK, TMS, TDI, and TDO. Data is
transmitted serially into the controller on TDI and out of the controller on TDO. The interpretation of
this data is dependent on the current state of the TAP controller. For detailed information on the
operation of the JTAG port and TAP controller, please refer to the IEEE Standard 1149.1-Test
Access Port and Boundary-Scan Architecture.
The LMI JTAG controller works with the ARM JTAG controller built into the Cortex-M3 core. This is
implemented by multiplexing the TDO outputs from both JTAG controllers. ARM JTAG instructions
select the ARM TDO output while LMI JTAG instructions select the LMI TDO outputs. The
multiplexer is controlled by the LMI JTAG controller, which has comprehensive programming for
the ARM, LMI, and unimplemented JTAG instructions.
The JTAG module has the following features:

IEEE 1149.1-1990 compatible Test Access Port (TAP) controller

Four-bit Instruction Register (IR) chain for storing JTAG instructions

IEEE standard instructions:
– BYPASS instruction
– IDCODE instruction
– SAMPLE/PRELOAD instruction
– EXTEST instruction
– INTEST instruction

ARM additional instructions:
– APACC instruction
– DPACC instruction
– ABORT instruction

Integrated ARM Serial Wire Debug (SWD)
See the ARM® Cortex™-M3 Technical Reference Manual for more information on the ARM JTAG
controller.
October 5, 2006
35
Preliminary
JTAG Interface
5.1
Block Diagram
Figure 5-1. JTAG Module Block Diagram
TRST
TCK
TMS
TDI
TAP Controller
Instruction Register (IR)
BYPASS Data Register
TDO
Boundary Scan Data Register
IDCODE Data Register
ABORT Data Register
DPACC Data Register
APACC Data Register
Cortex-M3
Debug
Port
5.2
Functional Description
A high-level conceptual drawing of the JTAG module is shown in Figure 5-1. The JTAG module is
composed of the Test Access Port (TAP) controller and serial shift chains with parallel update
registers. The TAP controller is a simple state machine controlled by the TRST, TCK and TMS
inputs. The current state of the TAP controller depends on the current value of TRST and the
sequence of values captured on TMS at the rising edge of TCK. The TAP controller determines
when the serial shift chains capture new data, shift data from TDI towards TDO, and update the
parallel load registers. The current state of the TAP controller also determines whether the
Instruction Register (IR) chain or one of the Data Register (DR) chains is being accessed.
The serial shift chains with parallel load registers are comprised of a single Instruction Register
(IR) chain and multiple Data Register (DR) chains. The current instruction loaded in the parallel
load register determines which DR chain is captured, shifted, or updated during the sequencing of
the TAP controller.
Some instructions, like EXTEST and INTEST, operate on data currently in a DR chain and do not
capture, shift, or update any of the chains. Instructions that are not implemented decode to the
BYPASS instruction to ensure that the serial path between TDI and TDO is always connected (see
Table 5-2 on page 41 for a list of implemented instructions).
See “JTAG and Boundary Scan” on page 289 for JTAG timing diagrams.
36
October 5, 2006
Preliminary
LM3S101 Data Sheet
5.2.1
JTAG Interface Pins
The JTAG interface consists of five standard pins: TRST, TCK, TMS, TDI, and TDO. These pins and
their associated reset state are given in Table 5-1. Detailed information on each pin follows.
Table 5-1. JTAG Port Pins Reset State
5.2.1.1
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.
5.2.1.2
Test Clock Input (TCK)
The TCK pin is the clock for the JTAG module. This clock is provided so the test logic can operate
independently of any other system clocks. In addition, it ensures that multiple JTAG TAP
controllers that are daisy-chained together can synchronously communicate serial test data
between components. During normal operation, TCK is driven by a free-running clock with a
nominal 50% duty cycle. When necessary, TCK can be stopped at 0 or 1 for extended periods of
time. While TCK is stopped at 0 or 1, the state of the TAP controller does not change and data in
the JTAG Instruction and Data Registers is not lost.
By default, the internal pull-up resistor on the TCK pin is enabled after reset. This assures that no
clocking occurs if the pin is not driven from an external source. The internal pull-up and pull-down
resistors can be turned off to save internal power as long as the TCK pin is constantly being driven
by an external source.
5.2.1.3
Test Mode Select (TMS)
The TMS pin selects the next state of the JTAG TAP controller. TMS is sampled on the rising edge
of TCK. Depending on the current TAP state and the sampled value of TMS, the next state is
entered. Because the TMS pin is sampled on the rising edge of TCK, the IEEE Standard 1149.1
expects the value on TMS to change on the falling edge of TCK.
Holding TMS high for five consecutive TCK cycles drives the TAP controller state machine to the
Test-Logic-Reset state. When the TAP controller enters the Test-Logic-Reset state, the JTAG
Instruction Register (IR) resets to the default instruction, IDCODE. Therefore, this sequence can
be used as a reset mechanism, similar to asserting TRST. The JTAG Test Access Port state
machine can be seen in its entirety in Figure 5-2 on page 39.
October 5, 2006
37
Preliminary
JTAG Interface
By default, the internal pull-up resistor on the TMS pin is enabled after reset. Changes to the
pull-up resistor settings on GPIO Port C should ensure that the internal pull-up resistor remains
enabled on PC1/TMS; otherwise JTAG communication could be lost.
5.2.1.4
Test Data Input (TDI)
The TDI pin provides a stream of serial information to the IR chain and the DR chains. TDI is
sampled on the rising edge of TCK and, depending on the current TAP state and the current
instruction, presents this data to the proper shift register chain. Because the TDI pin is sampled on
the rising edge of TCK, the IEEE Standard 1149.1 expects the value on TDI to change on the
falling edge of TCK.
By default, the internal pull-up resistor on the TDI pin is enabled after reset. Changes to the
pull-up resistor settings on GPIO Port C should ensure that the internal pull-up resistor remains
enabled on PC2/TDI; otherwise JTAG communication could be lost.
5.2.1.5
Test Data Output (TDO)
The TDO pin provides an output stream of serial information from the IR chain or the DR chains.
The value of TDO depends on the current TAP state, the current instruction, and the data in the
chain being accessed. In order to save power when the JTAG port is not being used, the TDO pin is
placed in an inactive drive state when not actively shifting out data. Because TDO can be
connected to the TDI of another controller in a daisy-chain configuration, the IEEE Standard
1149.1 expects the value on TDO to change on the falling edge of TCK.
By default, the internal pull-up resistor on the TDO pin is enabled after reset. This assures that the
pin remains at a constant logic level when the JTAG port is not being used. The internal pull-up
and pull-down resistors can be turned off to save internal power if a High-Z output value is
acceptable during certain TAP controller states.
5.2.2
JTAG TAP Controller
The JTAG TAP controller state machine is shown in Figure 5-2 on page 39. The TAP controller
state machine is reset to the Test-Logic-Reset state on the assertion of a Power-On-Reset (POR)
or the assertion of TRST. Asserting the correct sequence on the TMS pin allows the JTAG module
to shift in new instructions, shift in data, or idle during extended testing sequences. For detailed
information on the function of the TAP controller and the operations that occur in each state,
please refer to IEEE Standard 1149.1.
38
October 5, 2006
Preliminary
LM3S101 Data Sheet
Figure 5-2. Test Access Port State Machine
Test Logic
1
0
Run Test Idle
0
Select DR Scan
1
Select IR Scan
1
0
1
Capture DR
1
Capture IR
0
0
Shift DR
Shift IR
0
1
Exit 1 DR
Exit 1 IR
1
Pause IR
0
1
Exit 2 DR
0
1
0
Exit 2 IR
1
1
Update DR
5.2.3
1
0
Pause DR
1
0
1
0
0
1
0
0
Update IR
1
0
Shift Registers
The Shift Registers consist of a serial shift register chain and a parallel load register. The serial
shift register chain samples specific information during the TAP controller’s CAPTURE states and
allows this information to be shifted out of TDO during the TAP controller’s SHIFT states. While the
sampled data is being shifted out of the chain on TDO, new data is being shifted into the serial shift
register on TDI. This new data is stored in the parallel load register during the TAP controller’s
UPDATE states. Each of the shift registers is discussed in detail in “Shift Registers” on page 39.
5.2.4
Operational Considerations
There are certain operational considerations when using the JTAG module. Because the JTAG
pins can be programmed to be GPIOs, board configuration and reset conditions on these pins
must be considered. In addition, because the JTAG module has integrated ARM Serial Wire
Debug, the method for switching between these two operational modes requires clarification.
5.2.4.1
GPIO Functionality
When the controller is reset with either a POR or RST, the JTAG port pins default to their JTAG
configurations. The default configuration includes enabling the pull-up resistors (setting GPIOPUR
October 5, 2006
39
Preliminary
JTAG Interface
to 1 for PB7 and PC[3:0]) and enabling the alternate hardware function (setting GPIOAFSEL to 1
for PB7 and PC[3:0]) on the JTAG pins.
It is possible for software to configure these pins as GPIOs after reset by writing 0s to PB7 and
PC[3:0]in the GPIOAFSEL register. If the user does not require the JTAG port for debugging or
board-level testing, this provides five more GPIOs for use in the design.
Caution – If the JTAG pins are used as GPIOs in a design, PB7 and PC2 cannot have external
pull-down resistors connected to both of them at the same time. If both pins are pulled Low during
reset, the controller has unpredictable behavior. If this happens, remove one or both of the
pull-down resistors, and apply RST or power-cycle the part
In addition, it is possible to create a software sequence that prevents the debugger from connecting
to the Stellaris microcontroller. If the program code loaded into flash immediately changes the
JTAG pins to their GPIO functionality, the debugger does not have enough time to connect and
halt the controller before the JTAG pin functionality switches. This locks the debugger out of the
part. This can be avoided with a software routine that restores JTAG functionality using an
external trigger.
5.2.4.2
ARM Serial Wire Debug (SWD)
In order to seamlessly integrate the ARM Serial Wire Debug (SWD) functionality, a serial-wire
debugger must be able to connect to the Cortex-M3 core without having to perform, or have any
knowledge of, JTAG cycles. This is accomplished with a SWD preamble that is issued before the
SWD session begins.
The preamble used to enable the SWD interface of the SWJ-DP module starts with the TAP
controller in the Test-Logic-Reset state. From here, the preamble sequences the TAP controller
through the following states: Run Test Idle, Select DR, Select IR, Capture IR, Exit1 IR, Update IR,
Run Test Idle, Select DR, Select IR, Capture IR, Exit1 IR, Update IR, Run Test Idle, Select DR,
Select IR, and Test-Logic-Reset states.
Stepping through the JTAG TAP Instruction Register (IR) load sequences of the TAP state
machine twice without shifting in a new instruction enables the SWD interface and disables the
JTAG interface. For more information on this operation and the SWD interface, see the ARM®
Cortex™-M3 Technical Reference Manual and the ARM® CoreSight Technical Reference Manual.
Because this sequence is a valid series of JTAG operations that could be issued, the ARM JTAG
TAP controller is not fully compliant to the IEEE Standard 1149.1. This is the only instance where
the ARM JTAG TAP controller does not meet full compliance with the specification. Due to the low
probability of this sequence occuring during normal operation of the TAP controller, it should not
affect normal performance of the JTAG interface.
5.3
Initialization and Configuration
After a Power-On-Reset or an external reset (RST), the JTAG pins are automatically configured for
JTAG communication. No user-defined initialization or configuration is needed. However, if the
user application changes these pins to their GPIO function, they must be configured back to their
JTAG functionality before JTAG communication can be restored. This is done by enabling the five
JTAG pins (PB7 and PC[3:0]) for their alternate function using the GPIOAFSEL register.
40
October 5, 2006
Preliminary
LM3S101 Data Sheet
5.4
Register Descriptions
There are no APB-accessible registers in the JTAG TAP Controller or Shift Register chains. The
registers within the JTAG controller are all accessed serially through the TAP Controller. The
registers can be broken down into two main categories: Instruction Registers and Data Registers.
5.4.1
Instruction Register (IR)
The JTAG TAP Instruction Register (IR) is a four-bit serial scan chain with a parallel load register
connected between the JTAG TDI and TDO pins. When the TAP Controller is placed in the correct
states, bits can be shifted into the Instruction Register. Once these bits have been shifted into the
chain and updated, they are interpreted as the current instruction. The decode of the Instruction
Register bits is shown in Table 5-2. A detailed explanation of each instruction, along with its
associated Data Register, follows.
Table 5-2. JTAG Instruction Register Commands
IR[3:0]
Instruction
0000
EXTEST
Drives the values preloaded into the Boundary Scan Chain by the
SAMPLE/PRELOAD instruction onto the pads.
0001
INTEST
Drives the values preloaded into the Boundary Scan Chain by the
SAMPLE/PRELOAD instruction into the controller.
0010
SAMPLE / PRELOAD
1000
ABORT
Shifts data into the ARM Debug Port Abort Register.
1010
DPACC
Shifts data into and out of the ARM DP Access Register.
1011
APACC
Shifts data into and out of the ARM AC Access Register.
1110
IDCODE
Loads manufacturing information defined by the IEEE Standard 1149.1
into the IDCODE chain and shifts it out.
1111
BYPASS
Connects TDI to TDO through a single Shift Register chain.
All Others
Reserved
Defaults to the BYPASS instruction to ensure that TDI is always
connected to TDO.
5.4.1.1
Description
Captures the current I/O values and shifts the sampled values out of the
Boundary Scan Chain while new preload data is shifted in.
EXTEST Instruction
The EXTEST instruction does not have an associated Data Register chain. The EXTEST
instruction uses the data that has been preloaded into the Boundary Scan Data Register using the
SAMPLE/PRELOAD instruction. When the EXTEST instruction is present in the Instruction
Register, the preloaded data in the Boundary Scan Data Register associated with the outputs and
output enables are used to drive the GPIO pads rather than the signals coming from the core. This
allows tests to be developed that drive known values out of the controller, which can be used to
verify connectivity.
5.4.1.2
INTEST Instruction
The INTEST instruction does not have an associated Data Register chain. The INTEST instruction
uses the data that has been preloaded into the Boundary Scan Data Register using the SAMPLE/
PRELOAD instruction. When the INTEST instruction is present in the Instruction Register, the
preloaded data in the Boundary Scan Data Register associated with the inputs are used to drive
the signals going into the core rather than the signals coming from the GPIO pads. This allows
October 5, 2006
41
Preliminary
JTAG Interface
tests to be developed that drive known values into the controller, which can be used for testing. It
is important to note that although the RST input pin is on the Boundary Scan Data Register chain,
it is only observable.
5.4.1.3
SAMPLE/PRELOAD Instruction
The SAMPLE/PRELOAD instruction connects the Boundary Scan Data Register chain between
TDI and TDO. This instruction samples the current state of the pad pins for observation and
preloads new test data. Each GPIO pad has an associated input, output, and output enable signal.
When the TAP controller enters the Capture DR state during this instruction, the input, output, and
output-enable signals to each of the GPIO pads are captured. These samples are serially shifted
out of TDO while the TAP controller is in the Shift DR state and can be used for observation or
comparison in various tests.
While these samples of the inputs, outputs, and output enables are being shifted out of the
Boundary Scan Data Register, new data is being shifted into the Boundary Scan Data Register
from TDI. Once the new data has been shifted into the Boundary Scan Data Register, the data is
saved in the parallel load registers when the TAP controller enters the Update DR state. This
update of the parallel load register preloads data into the Boundary Scan Data Register that is
associated with each input, output, and output enable. This preloaded data can be used with the
EXTEST and INTEST instructions to drive data into or out of the controller. Please see “Boundary
Scan Data Register” on page 43 for more information.
5.4.1.4
ABORT Instruction
The ABORT instruction connects the associated ABORT Data Register chain between TDI and
TDO. This instruction provides read and write access to the ABORT Register of the ARM Debug
Access Port (DAP). Shifting the proper data into this Data Register clears various error bits or
initiates a DAP abort of a previous request. Please see the “ABORT Data Register” on page 44 for
more information.
5.4.1.5
DPACC Instruction
The DPACC instruction connects the associated DPACC Data Register chain between TDI and
TDO. This instruction provides read and write access to the DPACC Register of the ARM Debug
Access Port (DAP). Shifting the proper data into this register and reading the data output from this
register allows read and write access to the ARM debug and status registers. Please see “DPACC
Data Register” on page 44 for more information.
5.4.1.6
APACC Instruction
The APACC instruction connects the associated APACC Data Register chain between TDI and
TDO. This instruction provides read and write access to the APACC Register of the ARM Debug
Access Port (DAP). Shifting the proper data into this register and reading the data output from this
register allows read and write access to internal components and buses through the Debug Port.
Please see “APACC Data Register” on page 44 for more information.
5.4.1.7
IDCODE Instruction
The IDCODE instruction connects the associated IDCODE Data Register chain between TDI and
TDO. This instruction provides information on the manufacturer, part number, and version of the
ARM core. This information can be used by testing equipment and debuggers to automatically
configure their input and output data streams. IDCODE is the default instruction that is loaded into
the JTAG Instruction Register when a power-on-reset (POR) is asserted, TRST is asserted, or the
Test-Logic-Reset state is entered. Please see “IDCODE Data Register” on page 43 for more
information.
42
October 5, 2006
Preliminary
LM3S101 Data Sheet
5.4.1.8
BYPASS Instruction
The BYPASS instruction connects the associated BYPASS Data Register chain between TDI and
TDO. This instruction is used to create a minimum length serial path between the TDI and TDO
ports. The BYPASS Data Register is a single-bit shift register. This instruction improves test
efficiency by allowing components that are not needed for a specific test to be bypassed in the
JTAG scan chain by loading them with the BYPASS instruction. Please see “BYPASS Data
Register” on page 43 for more information.
5.4.2
Data Registers
The JTAG module contains six Data Registers. These include: IDCODE, BYPASS, Boundary
Scan, APACC, DPACC, and ABORT serial Data Register chains. Each of these Data Registers is
discussed in the following sections.
5.4.2.1
IDCODE Data Register
The format for the 32-bit IDCODE Data Register defined by the IEEE Standard 1149.1 is shown in
Figure 5-3. The standard requires that every JTAG-compliant device implement either the
IDCODE instruction or the BYPASS instruction as the default instruction. The LSB of the IDCODE
Data Register is defined to be a 1 to distinguish it from the BYPASS instruction, which has an LSB
of 0. This allows auto configuration test tools to determine which instruction is the default
instruction.
The major uses of the JTAG port are for manufacturer testing of component assembly, and
program development and debug. To facilitate the use of auto-configuration debug tools, the
IDCODE instruction outputs a value of 0x1BA00477. This value indicates an ARM Cortex-M3,
Version 1 processor. This allows the debuggers to automatically configure themselves to work
correctly with the Cortex-M3 during debug.
Figure 5-3. IDCODE Register Format
31
TDI
5.4.2.2
28 27
Version
12 11
Part Number
1 0
Manufacturer ID
1
TDO
BYPASS Data Register
The format for the 1-bit BYPASS Data Register defined by the IEEE Standard 1149.1 is shown in
Figure 5-4. The standard requires that every JTAG-compliant device implement either the
BYPASS instruction or the IDCODE instruction as the default instruction. The LSB of the BYPASS
Data Register is defined to be a 0 to distinguish it from the IDCODE instruction, which has an LSB
of 1. This allows auto configuration test tools to determine which instruction is the default
instruction.
Figure 5-4. BYPASS Register Format
0
TDI
5.4.2.3
0 TDO
Boundary Scan Data Register
The format of the Boundary Scan Data Register is shown in Figure 5-5. Each GPIO pin, in a
counter-clockwise direction from the JTAG port pins, is included in the Boundary Scan Data
Register. Each GPIO pin has three associated digital signals that are included in the chain. These
October 5, 2006
43
Preliminary
JTAG Interface
signals are input, output, and output enable, and are arranged in that order as can be seen in the
figure. In addition to the GPIO pins, the controller reset pin, RST, is included in the chain. Because
the reset pin is always an input, only the input signal is included in the Data Register chain.
When the Boundary Scan Data Register is accessed with the SAMPLE/PRELOAD instruction, the
input, output, and output enable from each digital pad are sampled and then shifted out of the
chain to be verified. The sampling of these values occurs on the rising edge of TCK in the Capture
DR state of the TAP controller. While the sampled data is being shifted out of the Boundary Scan
chain in the Shift DR state of the TAP controller, new data can be preloaded into the chain for use
with the EXTEST and INTEST instructions. These instructions either force data out of the
controller, with the EXTEST instruction, or into the controller, with the INTEST instruction.
Figure 5-5. Boundary Scan Register Format
TDI
I
N
O
U
T
O
E
...
GPIO PB6
I
N
O
U
T
GPIO m
O
E
I
N
RST
I
N
O
U
T
GPIO m+1
O
E
...
I
N
O
U
T
O TDO
E
GPIO n
For detailed information on the order of the input, output, and output enable bits for each of the
GPIO ports, please refer to the Stellaris Family Boundary Scan Description Language (BSDL)
files, downloadable from www.luminarymicro.com.
5.4.2.4
APACC Data Register
The format for the 35-bit APACC Data Register defined by ARM is described in the ARM®
Cortex™-M3 Technical Reference Manual.
5.4.2.5
DPACC Data Register
The format for the 35-bit DPACC Data Register defined by ARM is described in the ARM®
Cortex™-M3 Technical Reference Manual.
5.4.2.6
ABORT Data Register
The format for the 35-bit ABORT Data Register defined by ARM is described in the ARM®
Cortex™-M3 Technical Reference Manual.
44
October 5, 2006
Preliminary
LM3S101 Data Sheet
6
System Control
System control determines the overall operation of the device. It provides information about the
device, controls the clocking of the device and individual peripherals, and handles reset detection
and reporting.
6.1
Functional Description
The System Control module provides the following capabilities:
6.1.1

Device identification, see page 45

Local control, such as reset (see page 45), power (see page 48) and clock control (see
page 48)

System control (Run, Sleep, and Deep-Sleep modes), see page 50
Device Identification
Seven read-only registers provide software with information on the microcontroller, such as
version, part number, SRAM size, Flash size, and other features. See the DID0, DID1 and
DC0-DC4 registers starting on page 53.
6.1.2
Reset Control
This section discusses aspects of hardware functions during reset as well as system software
requirements following the reset sequence.
6.1.2.1
Reset Sources
The controller has six sources of reset:
1. External reset input pin (RST) assertion, see page 45.
2. Power-on reset (POR), see page 46.
3. Internal brown-out (BOR) detector, see page 46.
4. Software-initiated reset (with the software reset registers), see page 47.
5. A watchdog timer reset condition violation, see page 47.
6. Internal low drop-out (LDO) regulator output, see page 48.
After a reset, the Reset Cause (RESC) register (see page 70) is set with the reset cause. The bits
in this register are sticky and maintain their state across multiple reset sequences, except when an
external reset is the cause, and then all the other bits in the RESC register are cleared.
Note:
6.1.2.2
The main oscillator is used for external resets and power-on resets; the internal oscillator
is used during the internal process by internal reset and clock verification circuitry.
RST Pin Assertion
The external reset pin (RST) resets the controller. This resets the core and all the peripherals
except the JTAG TAP controller (see “JTAG Interface” on page 35). The external reset sequence is
as follows:
1. The external reset pin (RST) is asserted and then de-asserted.
2. After RST is de-assserted, the main crystal oscillator must be allowed to settle and there is an
internal main oscillator counter that takes from 15-30 ms to account for this. During this time,
internal reset to the rest of the controller is held active.
October 5, 2006
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Preliminary
System Control
3. The internal reset is released and the controller fetches and loads the initial stack pointer, the
initial program counter, and the first instruction designated by the program counter, and then
begins execution.
The external reset timing is shown in Figure 17-8 on page 292.
6.1.2.3
Power-On Reset (POR)
The Power-On Reset (POR) circuitry detects a rise in power-supply voltage and generates an
on-chip reset pulse. To use the on-chip circuitry, the RST input needs a pull-up resistor (1K to
10K Ω).
The device must be operating within the specified operating parameters at the point when the
on-chip power-on reset pulse is complete. The specified operating parameters include supply
voltage, frequency, temperature, and so on. If the operating conditions are not met at the point of
POR end, the Stellaris controller does not operate correctly. In this case, the reset must be
extended using external circuitry. The RST input may be used with the circuit as shown in
Figure 6-1.
Figure 6-1. External Circuitry to Extend Reset
Stellaris
D1
R1
RST
C1
R2
The R1 and C1 components define the power-on delay. The R2 resistor mitigates any leakage from
the RST input. The diode discharges C1 rapidly when the power supply is turned off.
The Power-On Reset sequence is as follows:
1. The controller waits for the later of external reset (RST) or internal POR to go inactive.
2. After the resets are inactive, the main crystal oscillator must be allowed to settle and there is
an internal main oscillator counter that takes from 15-30 ms to account for this. During this
time, internal reset to the rest of the controller is held active.
3. The internal reset is released and the controller fetches and loads the initial stack pointer, the
initial program counter, and the first instruction designated by the program counter, and then
begins execution.
The internal POR is only active on the initial power-up of the controller. The Power-On Reset
timing is shown in Figure 17-9 on page 292.
6.1.2.4
Brown-Out Reset (BOR)
A drop in the input voltage resulting in the assertion of the internal brown-out detector can be used
to reset the controller. This is initially disabled and may be enabled by software.
The system provides a brown-out detection circuit that triggers if VDD drops below VBTH. The
circuit is provided to guard against improper operation of logic and peripherals that operate off VDD
and not the LDO voltage. If a brown-out condition is detected, the system may generate a
controller interrupt or a system reset. The BOR circuit has a digital filter that protects against
noise-related detection. This feature may be optionally enabled.
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October 5, 2006
Preliminary
LM3S101 Data Sheet
Brown-out resets are controlled with the Power-On and Brown-Out Reset Control (PBORCTL)
register (see page 61). The BORIOR bit in the PBORCTL register must be set for a brown-out to
trigger a reset. The brown-out reset sequence is as follows:
1. When VDD drops below VBTH, an internal BOR condition is set.
2. If the BORWT bit in the PBORCTL register is set, the BOR condition is resampled sometime
later (specified by BORTIM) to determine if the original condition was caused by noise. If the
BOR condition is not met the second time, then no action is taken.
3. If the BOR condition exists, an internal reset is asserted.
4. The internal reset is released and the controller fetches and loads the initial stack pointer, the
initial program counter, and the first instruction designated by the program counter, and then
begins execution.
5. The internal BOR signal is released after 500 μs to prevent another BOR condition from being
set before software has a chance to investigate the original cause.
The internal Brown-Out Reset timing is shown in Figure 17-10 on page 292.
6.1.2.5
Software Reset
Each peripheral can be reset by software. There are three registers that control this function (see
the SRCRn registers, starting on page 63). If the bit position corresponding to a peripheral is set,
the peripheral is reset. The encoding of the reset registers is consistent with the encoding of the
clock gating control for peripherals and on-chip functions (see “System Control” on page 50).
Writing a bit lane with a value of 1 initiates a reset of the corresponding unit. Note that all reset
signals for all clocks of the specified unit are asserted as a result of a software-initiated reset.
The entire system can be reset by software also. Setting the SYSRESETREQ bit in the Cortex-M3
Application Interrupt and Reset Control register resets the entire system including the core. The
software-initiated system reset sequence is as follows:
1. A software system reset in initiated by writing the SYSRESETREQ bit in the ARM Cortex-M3
Application Interrupt and Reset Control register.
2. An internal reset is asserted.
3. The internal reset is released and the controller fetches and loads the initial stack pointer, the
initial program counter, and the first instruction designated by the program counter, and then
begins execution.
The software-initiated system reset timing is shown in Figure 17-11 on page 292.
6.1.2.6
Watchdog Timer Reset
The watchdog timer module's function is to prevent system hangs. The watchdog timer can be
configured to generate an interrupt to the controller on its first time-out, and to generate a reset
signal on its second time-out.
After the first time-out event, the 32-bit counter is reloaded with the value of the Watchdog Timer
Load (WDTLOAD) register (see page 170), 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.
October 5, 2006
47
Preliminary
System Control
3. The internal reset is released and the controller fetches and loads the initial stack pointer, the
initial program counter, and the first instruction designated by the program counter, and then
begins execution.
The watchdog reset timing is shown in Figure 17-12 on page 293.
6.1.2.7
Low Drop-Out
A reset can be made when the internal low drop-out (LDO) regulator output goes unregulated. This
is initially disabled and may be enabled by software. LDO is controlled with the LDO Power
Control (LDOPCTL) register (see page 62). The LDO reset sequence is as follows:
1. LDO goes unregulated and the LDOARST bit in the LDOARST register is set.
2. An internal reset is asserted.
3. The internal reset is released and the controller fetches and loads the initial stack pointer, the
initial program counter, and the first instruction designated by the program counter, and then
begins execution.
The LDO reset timing is shown in Figure 17-13 on page 293.
6.1.3
Power Control
The LDO regulator permits the adjustment of the on-chip output voltage (VOUT). The output may
be adjusted in 50 mV increments between the range of 2.25 V through 2.75 V. The adjustment is
made through the VADJ field of the LDO Power Control (LDOPCTL) register (see page 62).
6.1.4
Clock Control
System control determines the clocking and control of clocks in this part.
6.1.4.1
Fundamental Clock Sources
There are two fundamental clock sources for use in the device:

The main oscillator, driven from either an external crystal or a single-ended source. As a
crystal, the main oscillator source is specified to run from 1-8 MHz. However, when the crystal
is being used as the PLL source, it must be from 3.579545–8.192 MHz to meet PLL
requirements. As a single-ended source, the range is from DC to the specified speed of the
device.

The internal oscillator, which is an on-chip free running clock. The internal oscillator is
specified to run at 12 MHz ± 50%. It can be used to clock the system, but the tolerance of
frequency range must be met.
The internal system clock may be driven by either of the above two reference sources as well as
the internal PLL, provided that the PLL input is connected to a clock source that meets its AC
requirements.
Nearly all of the control for the clocks is provided by the Run-Mode Clock Configuration (RCC)
register (see page 71).
Figure 6-2 shows the logic for the main clock tree. The peripheral blocks are driven by the System
Clock signal and can be programmatically enabled/disabled.
48
October 5, 2006
Preliminary
LM3S101 Data Sheet
Figure 6-2. Main Clock Tree
USESYSDIVa
OSC1
OSC2
Main
Osc
1-8 MHz
SYSDIVa
Internal
Osc
15 MHz
System Clock
PLL
(200 MHz
output )
÷4
a
OSCSRC
OEN
a
a
BYPASS
a
XTAL
PWRDNa
a. These are bit fields within the Run-Mode Clock Configuration(RCC) register.
6.1.4.2
PLL Frequency Configuration
The user does not have direct control over the PLL frequency, but is required to match the external
crystal used to an internal PLL-Crystal table. This table is used to create the best fit for PLL
parameters to the crystal chosen. Not all crystals result in the PLL operating at exactly 200 MHz,
though the frequency is within ±1%. The result of the lookup is kept in the XTAL to PLL
Translation (PLLCTL) register (see page 75).
Table 6-4 on page 74 describes the available crystal choices and default programming of the
PLLCTL register. The crystal number is written into the XTAL field of the Run-Mode Clock
Configuration (RCC) register (see page 71). Any time the XTAL field changes, a read of the
internal table is performed to get the correct value. Table 6-4 on page 74 describes the available
crystal choices and default programming values.
6.1.4.3
PLL Modes
The PLL has two modes of operation: Normal and Power-Down

Normal: The PLL multiplies the input clock reference and drives the output.

Power-Down: Most of the PLL internal circuitry is disabled and the PLL does not drive the
output.
The modes are programmed using the RCC register fields as shown in Table 6-4 on page 74.
6.1.4.4
PLL Operation
If the PLL configuration is changed, the PLL output is not stable for a period of time (PLL
TREADY=0.5 ms) and during this time, the PLL is not usable as a clock reference.
The PLL is changed by one of the following:

Change to the XTAL value in the RCC register (see page 71)—writes of the same value do not
cause a relock.

Change in the PLL from Power-Down to Normal mode.
A counter is defined to measure the TREADY requirement. The counter is clocked by the main
oscillator. The range of the main oscillator has been taken into account and the down counter is
set to 0x1200 (that is, ~600 μs at a 8.192-MHz external oscillator clock). Hardware is provided to
keep the PLL from being used as a system clock until the TREADY condition is met after one of the
October 5, 2006
49
Preliminary
System Control
two changes above. It is the user's responsibility to have a stable clock source (like the main
oscillator) before the RCC register is switched to use the PLL.
6.1.4.5
Clock Verification Timers
There are three identical clock verification circuits that can be enabled though software. The circuit
checks the faster clock by a slower clock using timers:

The main oscillator checks the PLL.

The main oscillator checks the internal oscillator.

The internal oscillator divided by 64 checks the main oscillator.
If the verification timer function is enabled and a failure is detected, the main clock tree is
immediately switched to a working clock and an interrupt is generated to the controller. Software
can then determine the course of action to take. The actual failure indication and clock switching
does not clear without a write to the CLKVCLR register, an external reset, or a POR reset. The
clock verification timers are controlled by the PLLVER, IOSCVER, and MOSCVER bits in the RCC
register (see page 71).
6.1.5
System Control
For power-savings purposes, the RCGCn, SCGCn, and DCGCn registers control the clock gating
logic for each peripheral or block in the system while the controller is in Run, Sleep, and
Deep-Sleep mode, respectively. The DC1, DC2 and DC4 registers act as a write mask for the
RCGCn, SCGCn, and DCGCn registers.
In Run mode, the controller is actively executing code. In Sleep mode, the clocking of the device is
unchanged but the controller no longer executes code (and is no longer clocked). In Deep-Sleep
mode, the clocking of the device may change (depending on the Run mode clock configuration)
and the controller no longer executes code (and is no longer clocked). An interrupt returns the
device to Run mode from one of the sleep modes; the sleep modes are entered on request from
the code. Each mode is described in more detail in this section.
6.1.5.1
Run Mode
Run mode provides normal operation of the processor and all of the peripherals that are currently
enabled by the RCGCn registers. The system clock can be any of the available clock sources
including the PLL.
6.1.5.2
Sleep Mode
In Sleep mode, the Cortex-M3 processor core and the memory subsystem are not clocked.
Peripherals are clocked that are enabled in the SCGCn register when Auto Clock Gating is
enabled (see RCC register on page 71) or the RCGCn register when the Auto Clock Gating is
disabled. The System Clock has the same source and frequency as that during Run mode.
6.1.5.3
Deep-Sleep Mode
The Cortex-M3 processor core and the memory subsystem are not clocked. Peripherals are
clocked that are enabled in the DCGCn register when Auto Clock Gating is enabled (see RCC
register) or the RCGCn register when the Auto Clock Gating is disabled. The system clock source
is the main oscillator by default or the internal oscillator specified in the DSLPCLKCFG register if
one is enabled (see page 80). When the DSLPCLKCFG register is used, the internal oscillator is
powered up, if necessary, and the main oscillator is powered down. If the PLL is running at the
time of the WFI instruction, hardware powers the PLL down and overrides the SYSDIV field of the
active RCC register to be /16 or /64 respectively. When the Deep-Sleep exit event occurs,
hardware brings the system clock back to the source and frequency it had at the onset of
Deep-Sleep mode before enabling the clocks that were stopped during the Deep-Sleep duration.
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October 5, 2006
Preliminary
LM3S101 Data Sheet
6.2
Initialization and Configuration
The PLL is configured using direct register writes to the Run-Mode Clock Configuration (RCC)
register. The steps required to successfully change the PLL-based system clock are:
1. Bypass the PLL and system clock divider by setting the BYPASS bit and clearing the USESYS
bit in the RCC register. This configures the system to run off a “raw” clock source (using the
main oscillator or internal oscillator) and allows for the new PLL configuration to be validated
before switching the system clock to the PLL.
2. Select the crystal value (XTAL) and oscillator source (OSCSRC), and clear the PWRDN and OE
bits in RCC. Setting the XTAL field automatically pulls valid PLL configuration data for the
appropriate crystal, and clearing the PWRDN and OE bits powers and enables the PLL and its
output.
3. Select the desired system divider (SYSDIV) and set the USESYS bit in RCC. The SYSDIV field
determines the system frequency for the microcontroller.
4. Wait for the PLL to lock by polling the PLLLRIS bit in the Raw Interrupt Status (RIS) register.
If the PLL doesn’t lock, the configuration is invalid.
5. Enable use of the PLL by clearing the BYPASS bit in RCC.
Important: If the BYPASS bit is cleared before the PLL locks, it is possible to render the device
unusable.
6.3
Register Map
Table 6-1 lists the System Control registers, grouped by function. The offset listed is a
hexadecimal increment to the register’s address, relative to the System Control base address of
0x400FE000.
Table 6-1. System Control Register Map (Sheet 1 of 2)
Offset
Name
Reset
Type
Description
See
page
Device Identification and Capabilities
0x000
DID0
-
RO
Device identification 0
53
0x004
DID1
-
RO
Device identification 1
54
0x008
DC0
0x00070003
RO
Device capabilities 0
56
0x010
DC1
0x00000009
RO
Device capabilities 1
57
0x014
DC2
0x03030011
RO
Device capabilities 2
58
0x018
DC3
0x810003C0
RO
Device Capabilities 3
59
0x01C
DC4
0x00000007
RO
Device Capabilities 4
60
Local Control
October 5, 2006
51
Preliminary
System Control
Table 6-1. System Control Register Map (Sheet 2 of 2)
Offset
Name
0x030
See
page
Reset
Type
Description
PBORCTL
0x00007FFD
R/W
Power-On and Brown-Out Reset Control
61
0x034
LDOPCTL
0x00000000
R/W
LDO Power Control
62
0x040
SRCR0
0x00000000
R/W
Software Reset Control 0
63
0x044
SRCR1
0x00000000
R/W
Software Reset Control 1
64
0x048
SRCR2
0x00000000
R/W
Software Reset Control 2
65
0x050
RIS
0x00000000
RO
Raw Interrupt Status
66
0x054
IMC
0x00000000
R/W
Interrupt Mask Control
67
0x058
MISC
0x00000000
R/W1C
Masked Interrupt Status and Clear
69
0x05C
RESC
-
R/W
Reset Cause
70
0x060
RCC
0x07803AC0
R/W
Run-Mode Clock Configuration
71
0x064
PLLCFG
-
RO
XTAL to PLL translation
75
System Control
0x100
RCGC0
0x00000001
R/W
Run-Mode Clock Gating Control 0
76
0x104
RCGC1
0x00000000
R/W
Run-Mode Clock Gating Control 1
77
0x108
RCGC2
0x00000000
R/W
Run-Mode Clock Gating Control 2
79
0x110
SCGC0
0x00000001
R/W
Sleep-Mode Clock Gating Control 0
76
0x114
SCGC1
0x00000000
R/W
Sleep-Mode Clock Gating Control 1
77
0x118
SCGC2
0x00000000
R/W
Sleep-Mode Clock Gating Control 2
79
0x120
DCGC0
0x00000001
R/W
Deep-Sleep-Mode Clock Gating Control 0
76
0x124
DCGC1
0x00000000
R/W
Deep-Sleep-Mode Clock Gating Control 1
77
0x128
DCGC2
0x00000000
R/W
Deep-Sleep-Mode Clock Gating Control 2
79
0X144
DSLPCLKCFG
0x07800000
R/W
Deep-Sleep Clock Configuration
80
0x150
CLKVCLR
0x00000000
R/W
Clock verification clear
81
0x160
LDOARST
0x00000000
R/W
Allow unregulated LDO to reset the part
82
6.4
Register Descriptions
The remainder of this section lists and describes the System Control registers, in numerical order
by address offset.
52
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 1: Device Identification 0 (DID0), offset 0x000
This register identifies the version of the device.
Device Identification 0 (DID0)
Offset 0x000
31
30
reserved
Type
Reset
29
28
27
26
25
24
23
22
21
20
19
18
17
16
reserved
VER
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
MINOR
MAJOR
Type
Reset
Bit/Field
Name
Type
Reset
Description
31
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
30:28
VER
RO
0
This field defines the version of the DID0 register format:
0=Register version for the Stellaris microcontrollers
27:16
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
15:8
MAJOR
RO
-
This field specifies the major revision number of the device.
The major revision number is indicated in the part number
as a letter (A for first revision, B for second, and so on).
This field is encoded as follows:
0: Revision A (initial device)
1: Revision B (first revision)
and so on.
7:0
MINOR
RO
-
This field specifies the minor revision number of the device.
This field is numeric and is encoded as follows:
0: No changes. Major revision was most recent update.
1: One interconnect change made since last major revision
update.
2: Two interconnect changes made since last major revision
update.
and so on.
October 5, 2006
53
Preliminary
System Control
Register 2: Device Identification 1 (DID1), offset 0x004
This register identifies the device family, part number, temperature range, and package type.
Device Identification 1 (DID1)
Offset 0x004
31
30
29
28
27
26
RO
0
25
24
23
22
21
20
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
-
RO
-
RO
0
FAM
VER
Type
Reset
18
17
16
RO
0
RO
0
RO
0
RO
1
3
2
1
0
PARTNO
reserved
Type
Reset
19
TEMP
Bit/Field
Name
Type
Reset
31:28
VER
RO
0x0
RO
-
RoHS
PKG
RO
0
RO
1
QUAL
RO
-
RO
-
Description
This field defines the version of the DID1 register format:
0=Register version for the Stellaris microcontrollers
27:24
FAM
RO
0x0
Family
This field provides the family identification of the device
within the Luminary Micro product portfolio.
The 0x0 value indicates the Stellaris family of
microcontrollers.
23:16
PARTNO
RO
0x01
Part Number
This field provides the part number of the device within the
family.
The 0x01 value indicates the LM3S101 microcontroller.
15:8
reserved
RO
0
7:5
TEMP
RO
see table
Reserved bits return an indeterminate value, and should
never be changed.
Temperature Range
This field specifies the temperature rating of the device.
This field is encoded as follows:
TEMP
000
Commercial temperature range (0°C to
70°C)
001
Industrial temperature range (-40°C to
85°C)
010-111
4:3
PKG
RO
0x0
2
RoHS
RO
1
Description
Reserved
This field specifies the package type. A value of 0 indicates
a 28-pin SOIC package.
RoHS-Compliance
A 1 in this bit specifies the device is RoHS-compliant.
54
October 5, 2006
Preliminary
LM3S101 Data Sheet
Bit/Field
Name
Type
Reset
1:0
QUAL
RO
see table
Description
This field specifies the qualification status of the device.
This field is encoded as follows:
QUAL
October 5, 2006
Description
00
Engineering Sample (unqualified)
01
Pilot Production (unqualified)
10
Fully Qualified
11
Reserved
55
Preliminary
System Control
Register 3: Device Capabilities 0 (DC0), offset 0x008
This register is predefined by the part and can be used to verify features.
Device Capabilities Register 0 (DC0)
Offset 0x008
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
1
RO
1
RO
1
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
1
SRAMSZ
Type
Reset
FLSHSZ
Type
Reset
Bit/Field
Name
Type
Reset
Description
31:16
SRAMSZ
RO
0x0007
Indicates the size of the on-chip SRAM. A value of 0x0007
indicates 2 KB of SRAM.
15:0
FLSHSZ
RO
0x0003
Indicates the size of the on-chip flash memory. A value of
0x03 indicates 8 KB of Flash.
56
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 4: Device Capabilities 1 (DC1), offset 0x010
This register is predefined by the part and can be used to verify features.
Device Capabilities 1 (DC1)
Offset 0x010
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
1
RO
0
RO
0
PLL
WDT
SWO
SWD
JTAG
RO
0
RO
0
RO
1
RO
1
RO
1
RO
1
RO
1
reserved
Type
Reset
MINSYSDIV
Type
Reset
RO
1
RO
0
RO
0
reserved
MPU
RO
0
reserved
RO
0
RO
0
Bit/Field
Name
Type
Reset
Description
31:16
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
15:12
MINSYSDIV
RO
0x09
The reset value is hardware-dependent. A value of 0x09
specifies a 20-MHz CPU clock with a PLL divider of 10.
See the RCC register (page 71) for how to change the
system clock divisor using the SYSDIV bit.
11:8
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
7
MPU
RO
0
This bit indicates whether the Memory Protection Unit
(MPU) in the Cortex-M3 is available. A 0 in this bit indicates
the MPU is not available; a 1 indicates the MPU is
available.
See the ARM® Cortex™-M3 Technical Reference Manual
for details on the MPU.
6:5
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
4
PLL
RO
1
A 1 in this bit indicates the presence of an implemented
PLL in the device.
3
WDTa
RO
1
A 1 in this bit indicates a watchdog timer on the device.
2
SWOa
RO
1
A 1 in this bit indicates the presence of the ARM Serial Wire
Output (SWO) trace port capabilities.
1
SWDa
RO
1
A 1 in this bit indicates the presence of the ARM Serial Wire
Debug (SWD) capabilities.
0
JTAGa
RO
1
A 1 in this bit indicates the presence of a JTAG port.
a. These bits mask the Run-Mode Clock Gating Control 0 (RCGC0) register (see page 113), Sleep-Mode Clock Gating Control 0
(SCGC0) register (see page 113), and Deep-Sleep-Mode Clock Gating Control 0 (DCGC0) register (see page 113). Bits that are
not noted are passed as 0.
October 5, 2006
57
Preliminary
System Control
Register 5: Device Capabilities 2 (DC2), offset 0x014
This register is predefined by the part and can be used to verify features.
Device Capabilities 2 (DC2)
Offset 0x014
31
30
29
28
27
26
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
15
14
13
12
11
10
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
25
24
23
22
21
20
19
18
RO
1
RO
0
RO
0
9
8
7
RO
0
RO
0
RO
0
RO
0
RO
1
RO
1
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
COMP1 COMP0
reserved
Type
Reset
RO
0
17
16
GPTM1 GPTM0
reserved
SSI
RO
1
RO
0
RO
0
UART0
RO
0
RO
1
Bit/Field
Name
Type
Reset
Description
31:26
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
25
COMP1
RO
1
A 1 in this bit indicates the presence of analog
comparator 1.
24
COMP0
RO
1
A 1 in this bit indicates the presence of analog
comparator 0.
23:18
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
17
GPTM1
RO
1
A 1 in this bit indicates the presence of General-Purpose
Timer module 1.
16
GPTM0
RO
1
A 1 in this bit indicates the presence of General-Purpose
Timer module 0.
15:5
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
4
SSI
RO
1
A 1 in this bit indicates the presence of the SSI module.
3:1
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
0
UART0
RO
1
A 1 in this bit indicates the presence of the UART0 module.
58
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 6: Device Capabilities 3 (DC3), offset 0x018
This register is predefined by the part and can be used to verify features.
Device Capabilities 3 (DC3)
Offset 0x018
31
30
29
28
27
26
25
RO
1
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
32KHz
Type
Reset
23
22
21
20
19
18
17
16
RO
1
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
9
8
7
6
5
4
3
2
1
0
C1-
C0o
C0+
C0-
RO
1
RO
1
RO
1
RO
1
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
CCP0
reserved
reserved
Type
Reset
24
reserved
reserved
Bit/Field
Name
Type
Reset
Description
31
32KHz
RO
1
A 1 in this bit indicates the presence of a 32.768-KHz input
pin.
30:25
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
24
CCP0
RO
1
A 1 in this bit indicates the presence of the Capture/
Compare/PWM pin 0.
23:10
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
9
C1-
RO
1
A 1 in this bit indicates the presence of the C1- pin.
8
C0o
RO
1
A 1 in this bit indicates the presence of the C0o pin.
7
C0+
RO
1
A 1 in this bit indicates the presence of the C0+ pin.
6
C0-
RO
1
A 1 in this bit indicates the presence of the C0- pin.
5:0
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
October 5, 2006
59
Preliminary
System Control
Register 7: Device Capabilities 4 (DC4), offset 0x01C
This register is predefined by the part and can be used to verify features.
Device Capabilities 4 (DC4)
Offset 0x01C
31
30
29
28
27
26
25
24
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
PORTC PORTB PORTA
RO
1
RO
1
RO
1
Bit/Field
Name
Type
Reset
Description
31:3
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
2
PORTC
RO
1
A 1 in this bit indicates the presence of GPIO Port C.
1
PORTB
RO
1
A 1 in this bit indicates the presence of GPIO Port B.
0
PORTA
RO
1
A 1 in this bit indicates the presence of GPIO Port A.
60
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 8: Power-On and Brown-Out Reset Control (PBORCTL), offset 0x030
This register is responsible for controlling reset conditions after initial power-on reset.
Power-On and Brown-Out Reset Control (PBORCTL)
Offset 0x030
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R/W
0
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
reserved
Type
Reset
BORTIM
Type
Reset
Bit/Field
Name
Type
Reset
31:16
reserved
RO
0
15:2
BORTIM
R/W
0x1FFF
BORIOR BORWT
R/W
1
R/W
0
R/W
1
Description
Reserved bits return an indeterminate value, and should
never be changed.
This field specifies the number of internal oscillator clocks
delayed before the BOR output is resampled if the BORWT
bit is set.
The width of this field is derived by the tBOR width of 500 μs
and the internal oscillator (IOSC) frequency of 15 MHz ±
50%. At +50%, the counter value has to exceed 10,000.
1
BORIOR
R/W
0
BOR Interrupt or Reset
This bit controls how a BOR event is signaled to the
controller. If set, a reset is signaled. Otherwise, an interrupt
is signaled.
0
BORWT
R/W
1
BOR Wait and Check for Noise
This bit specifies the response to a brown-out signal
assertion. If BORWT is set to 1, the controller waits BORTIM
IOSC periods before resampling the BOR output, and if
asserted, it signals a BOR condition interrupt or reset. If the
BOR resample is deasserted, the cause of the initial
assertion was likely noise and the interrupt or reset is
suppressed. If BORWT is 0, BOR assertions do not resample
the output and any condition is reported immediately if
enabled.
October 5, 2006
61
Preliminary
System Control
Register 9: LDO Power Control (LDOPCTL), offset 0x034
The VADJ field in this register adjusts the on-chip output voltage (VOUT).
LDO Power Control (LDOPCTL)
Offset 0x034
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
VADJ
Bit/Field
Name
Type
Reset
31:6
reserved
RO
0
5:0
VADJ
R/W
0x0
Description
Reserved bits return an indeterminate value, and should
never be changed.
This field sets the on-chip output voltage. The programming
values for the VADJ field are provided in Table 6-2.
Table 6-2. VADJ to VOUT
VADJ Value
VOUT (V)
VADJ Value
VOUT (V)
VADJ Value
VOUT (V)
0x1B
2.75
0x1F
2.55
0x03
2.35
0x1C
2.70
0x00
2.50
0x04
2.30
0x1D
2.65
0x01
2.45
0x05
2.25
0x1E
2.60
0x02
2.40
0x06-0x3F
Reserved
62
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 10: Software Reset Control 0 (SRCR0), offset 0x040
Writes to this register are masked by the bits in the Device Capabilities 1 (DC1) register (see
page 57).
Software Reset Control 0 (SRCR0)
Offset 0x040
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
WDT
reserved
Type
Reset
R/W
0
reserved
RO
0
RO
0
RO
0
Bit/Field
Name
Type
Reset
Description
31:4
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
3
WDT
R/W
0
Reset control for the Watchdog unit.
2:0
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
October 5, 2006
63
Preliminary
System Control
Register 11: Software Reset Control 1 (SRCR1), offset 0x044
Writes to this register are masked by the bits in the Device Capabilities 2 (DC2) register (see
page 58).
Software Reset Control 1 (SRCR1)
Offset 0x044
31
30
29
28
27
26
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
15
14
13
12
11
10
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
25
24
23
22
21
20
19
18
R/W
0
RO
0
RO
0
9
8
7
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
COMP1 COMP0
reserved
Type
Reset
RO
0
17
16
GPTM1 GPTM0
reserved
SSI
R/W
0
RO
0
RO
0
UART0
RO
0
R/W
0
Bit/Field
Name
Type
Reset
Description
31:26
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
25
COMP1
R/W
0
Reset control for analog comparator 1.
24
COMP0
R/W
0
Reset control for analog comparator 0.
23:18
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
17
GPTM1
R/W
0
Reset control for General-Purpose Timer module 1.
16
GPTM0
R/W
0
Reset control for General-Purpose Timer module 0.
15:5
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
4
SSI
R/W
0
Reset control for the SSI units.
3:1
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
0
UART0
R/W
0
Reset control for the UART0 module.
64
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 12: Software Reset Control 2 (SRCR2), offset 0x048
Writes to this register are masked by the bits in the Device Capabilities 4 (DC4) register (see
page 60).
Software Reset Control (SRCR2)
Offset 0x048
31
30
29
28
27
26
25
24
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
PORTC PORTB PORTA
R/W
0
R/W
0
R/W
0
Bit/Field
Name
Type
Reset
Description
31:3
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
2
PORTC
R/W
0
Reset control for GPIO Port C.
1
PORTB
R/W
0
Reset control for GPIO Port B.
0
PORTA
R/W
0
Reset control for GPIO Port A.
October 5, 2006
65
Preliminary
System Control
Register 13: Raw Interrupt Status (RIS), offset 0x050
Central location for system control raw interrupts. These are set and cleared by hardware.
Raw Interrupt Status (RIS)
Offset 0x050
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
PLLLRIS CLRIS
RO
0
RO
0
IOFRIS MOFRIS LDORIS BORRIS PLLFRIS
RO
0
RO
0
RO
0
RO
0
RO
0
Bit/Field
Name
Type
Reset
Description
31:7
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
6
PLLLRIS
RO
0
PLL Lock Raw Interrupt Status
This bit is set when the PLL TREADY Timer asserts.
5
CLRIS
RO
0
Current Limit Raw Interrupt Status
This bit is set if the LDO’s CLE output asserts.
4
IOFRIS
RO
0
Internal Oscillator Fault Raw Interrupt Status
This bit is set if an internal oscillator fault is detected.
3
MOFRIS
RO
0
Main Oscillator Fault Raw Interrupt Status
This bit is set if a main oscillator fault is detected.
2
LDORIS
RO
0
LDO Power Unregulated Raw Interrupt Status
This bit is set if a LDO voltage is unregulated.
1
BORRIS
RO
0
Brown-Out Reset Raw Interrupt Status
This bit is the raw interrupt status for any brown-out
conditions. If set, a brown-out condition was detected. An
interrupt is reported if the BORIM bit in the IMC register is
set and the BORIOR bit in the PBORCTL register is cleared.
0
PLLFRIS
RO
0
PLL Fault Raw Interrupt Status
This bit is set if a PLL fault is detected (stops oscillating).
66
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 14: Interrupt Mask Control (IMC), offset 0x054
Central location for system control interrupt masks.
Interrupt Mask Control (IMC)
Offset 0x054
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
PLLLIM
CLIM
IOFIM
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
MOFIM LDOIM BORIM PLLFIM
R/W
0
R/W
0
R/W
0
R/W
0
Bit/Field
Name
Type
Reset
Description
31:7
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
6
PLLLIM
R/W
0
PLL Lock Interrupt Mask
This bit specifies whether a current limit detection is
promoted to a controller interrupt. If set, an interrupt is
generated if PLLLRIS in RIS is set; otherwise, an interrupt
is not generated.
5
CLIM
R/W
0
Current Limit Interrupt Mask
This bit specifies whether a current limit detection is
promoted to a controller interrupt. If set, an interrupt is
generated if CLRIS is set; otherwise, an interrupt is not
generated.
4
IOFIM
R/W
0
Internal Oscillator Fault Interrupt Mask
This bit specifies whether an internal oscillator fault
detection is promoted to a controller interrupt. If set, an
interrupt is generated if IOFRIS is set; otherwise, an
interrupt is not generated.
3
MOFIM
R/W
0
Main Oscillator Fault Interrupt Mask
This bit specifies whether a main oscillator fault detection is
promoted to a controller interrupt. If set, an interrupt is
generated if MOFRIS is set; otherwise, an interrupt is not
generated.
2
LDOIM
R/W
0
LDO Power Unregulated Interrupt Mask
This bit specifies whether an LDO unregulated power
situation is promoted to a controller interrupt. If set, an
interrupt is generated if LDORIS is set; otherwise, an
interrupt is not generated.
October 5, 2006
67
Preliminary
System Control
Bit/Field
Name
Type
Reset
1
BORIM
R/W
0
Description
Brown-Out Reset Interrupt Mask
This bit specifies whether a brown-out condition is
promoted to a controller interrupt. If set, an interrupt is
generated if BORRIS is set; otherwise, an interrupt is not
generated.
0
PLLFIM
R/W
0
PLL Fault Interrupt Mask
This bit specifies whether a PLL fault detection is promoted
to a controller interrupt. If set, an interrupt is generated if
PLLFRIS is set; otherwise, an interrupt is not generated.
68
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 15: Masked Interrupt Status and Clear (MISC), offset 0x058
Central location for system control result of RIS AND IMC to generate an interrupt to the controller.
All of the bits are R/W1C and this action also clears the corresponding raw interrupt bit in the RIS
register (see page 66).
Masked Interrupt Status and Clear (MISC)
Offset 0x058
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
PLLLMIS CLMIS IOFMIS MOFMIS LDOMIS BORMIS PLLFMIS
R/W1C
0
R/W1C
0
R/W1C
0
R/W1C
0
R/W1C
0
R/W1C
0
R/W1C
0
Bit/Field
Name
Type
Reset
Description
31:7
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
6
PLLLMIS
R/W1C
0
PLL Lock Masked Interrupt Status
This bit is set when the PLL TREADY timer asserts. The
interrupt is cleared by writing a 1 to this bit.
5
CLMIS
R/W1C
0
Current Limit Masked Interrupt Status
This bit is set if the LDO’s CLE output asserts. The interrupt
is cleared by writing a 1 to this bit.
4
IOFMIS
R/W1C
0
Internal Oscillator Fault Masked Interrupt Status
This bit is set if an internal oscillator fault is detected. The
interrupt is cleared by writing a 1 to this bit.
3
MOFMIS
R/W1C
0
Main Oscillator Fault Masked Interrupt Status
This bit is set if a main oscillator fault is detected. The
interrupt is cleared by writing a 1 to this bit.
2
LDOMIS
R/W1C
0
LDO Power Unregulated Masked Interrupt Status
This bit is set if LDO power is unregulated. The interrupt is
cleared by writing a 1 to this bit.
1
BORMIS
R/W1C
0
Brown-Out Reset Masked Interrupt Status
This bit is the masked interrupt status for any brown-out
conditions. If set, a brown-out condition was detected. An
interrupt is reported if the BORIM bit in the IMC register is
set and the BORIOR bit in the PBORCTL register is cleared.
The interrupt is cleared by writing a 1 to this bit.
0
PLLFMIS
R/W1C
0
PLL Fault Masked Interrupt Status
This bit is set if a PLL fault is detected (stops oscillating).
The interrupt is cleared by writing a 1 to this bit.
October 5, 2006
69
Preliminary
System Control
Register 16: Reset Cause (RESC), offset 0x05C
This field specifies the cause of the reset event to software. The reset value is determined by the
cause of the reset. When an external reset is the cause (EXT is set), all other reset bits are
cleared. However, if the reset is due to any other cause, the remaining bits are sticky, allowing
software to see all causes.
Reset Cause (RESC)
Offset 0x05C
31
30
29
28
27
26
25
24
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
8
7
6
5
4
3
2
1
0
LDO
SW
WDT
BOR
POR
EXT
RO
0
RO
0
RO
0
R/W
-
R/W
-
R/W
-
R/W
-
R/W
-
R/W
-
reserved
Type
Reset
reserved
Type
Reset
RO
0
Bit/Field
Name
Type
Reset
Description
31:6
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
5
LDO
R/W
-
When set to 1, LDO power OK lost is the cause of the reset
event.
4
SW
R/W
-
When set to 1, a software reset is the cause of the reset
event.
3
WDT
R/W
-
When set to 1, a watchdog reset is the cause of the reset
event.
2
BOR
R/W
-
When set to 1, a brown-out reset is the cause of the reset
event.
1
POR
R/W
-
When set to 1, a power-on reset is the cause of the reset
event.
0
EXT
R/W
-
When set to 1, an external reset (RST assertion) is the
cause of the reset event.
70
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 17: Run-Mode Clock Configuration (RCC), offset 0x060
This register is defined to provide source control and frequency speed.
Run-Mode Clock Configuration (RCC)
Offset 0x060
31
30
29
28
RO
0
15
26
25
RO
0
RO
0
RO
0
R/W
0
R/W
1
R/W
1
R/W
1
R/W
1
14
13
12
11
10
9
8
PWRDN
OEN
BYPASS
PLLVER
R/W
1
R/W
1
R/W
1
R/W
0
R/W
1
R/W
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
RO
0
27
ACG
24
23
21
20
19
R/W
0
RO
0
RO
0
7
6
5
4
R/W
1
R/W
1
R/W
0
SYSDIV
22
18
17
16
RO
0
RO
0
RO
0
RO
0
3
2
1
0
reserved
USESYSDIV
XTAL
OSCSRC
R/W
0
IOSCVER MOSCVER IOSCDIS MOSCDIS
R/W
0
R/W
0
R/W
0
R/W
0
Bit/Field
Name
Type
Reset
Description
31:28
Reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
27
ACG
R/W
0
Auto Clock Gating
This bit specifies whether the system uses the Sleep-Mode
Clock Gating Control (SCGCn) registers (see page 76)
and Deep-Sleep-Mode Clock Gating Control (DCGCn)
registers (see page 76) if the controller enters a Sleep or
Deep-Sleep mode (respectively). If set, the SCGCn or
DCGCn registers are used to control the clocks distributed
to the peripherals when the controller is in a sleep mode.
Otherwise, the Run-Mode Clock Gating Control (RCGCn)
registers (see page 76) 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.
October 5, 2006
71
Preliminary
System Control
Bit/Field
Name
Type
Reset
26:23
SYSDIV
R/W
0xF
Description
System Clock Divisor
Specifies which divisor is used to generate the system clock
from the PLL output (200 MHz).
Binary
Value
Divisor
(BYPASS=1)
Frequency
(BYPASS=0)
00001000
reserved
reserved
1001
/10
20 MHz
1010
/11
18.18 MHz
1011
/12
16.67 MHz
1100
/13
15.38 MHz
1101
/14
14.29 MHz
1110
/15
13.33 MHz
1111
/16
12.5 MHz (default)
When reading the Run-Mode Clock Configuration (RCC)
register (see page 71), the SYSDIV value is MINSYSDIV if
a lower divider was requested and the PLL is being used.
This lower value is allowed to divide a non-PLL source.
22
USESYSDIV
R/W
0
Use the system clock divider as the source for the system
clock. The system clock divider is forced to be used when
the PLL is selected as the source.
21:14
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
13
PWRDN
R/W
1
PLL Power Down
This bit connects to the PLL PWRDN input. The reset value
of 1 powers down the PLL. See Table 6-4 on page 74 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.
72
October 5, 2006
Preliminary
LM3S101 Data Sheet
Bit/Field
Name
Type
Reset
10
PLLVER
R/W
0
Description
PLL Verification
This bit controls the PLL verification timer function. If set,
the verification timer is enabled and an interrupt is
generated if the PLL becomes inoperative. Otherwise, the
verification timer is not enabled.
9:6
XTAL
R/W
0xB
This field specifies the crystal value attached to the main
oscillator. The encoding for this field is provided in Table 6-4
on page 74.
Oscillator-Related Bits
5:4
OSCSRC
R/W
0x0
Picks among the four input sources for the OSC. The
values are:
Value
Input Source
00
Main oscillator (default)
01
Internal oscillator
10
Internal oscillator / 4 (this is necessary if used
as input to PLL)
11
reserved
3
IOSCVER
R/W
0
This bit controls the internal oscillator verification timer
function. If set, the verification timer is enabled and an
interrupt is generated if the timer becomes inoperative.
Otherwise, the verification timer is not enabled.
2
MOSCVER
R/W
0
This bit controls the main oscillator verification timer
function. If set, the verification timer is enabled and an
interrupt is generated if the timer becomes inoperative.
Otherwise, the verification timer is not enabled.
1
IOSCDIS
R/W
0
Internal Oscillator Disable
0: Internal oscillator is enabled.
1: Internal oscillator is disabled.
0
MOSCDIS
R/W
0
Main Oscillator Disable
0: Main oscillator is enabled.
1: Main oscillator is disabled.
Table 6-3. PLL Mode Control
PWRDN
OEN
Mode
1
X
Power down
0
0
Normal
October 5, 2006
73
Preliminary
System Control
Table 6-4. Default Crystal Field Values and PLL Programming
Crystal Number
(XTAL Binary Value)
0000-0011
Crystal Frequency (MHz)
reserved
0100
3.579545 MHz
0101
3.6864 MHz
0110
4 MHz
0111
4.096 MHz
1000
4.9152 MHz
1001
5 MHz
1010
5.12 MHz
1011
6 MHz (reset value)
1100
6.144 MHz
1101
7.3728 MHz
1110
8 MHz
1111
8.192 MHz
74
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 18: XTAL to PLL Translation (PLLCFG), offset 0x064
This register provides a means of translating external crystal frequencies into the appropriate PLL
settings. This register is initialized during the reset sequence and updated anytime that the XTAL
field changes in the Run-Mode Clock Configuration (RCC) register (see page 71).
XTAL to PLL Translation (PLLCFG)
Offset 0x064
31
30
29
28
27
26
25
24
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
8
7
6
5
4
3
2
1
0
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
RO
-
reserved
Type
Reset
OD
Type
Reset
RO
-
F
R
Bit/Field
Name
Type
Reset
Description
31:16
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
15:14
OD
RO
-
This field specifies the value supplied to the PLL’s OD input.
13:5
F
RO
-
This field specifies the value supplied to the PLL’s F input.
4:0
R
RO
-
This field specifies the value supplied to the PLL’s R input.
October 5, 2006
75
Preliminary
System Control
Register 19: Run-Mode Clock Gating Control 0 (RCGC0), offset 0x100
Register 20: Sleep-Mode Clock Gating Control 0 (SCGC0), offset 0x110
Register 21: Deep-Sleep-Mode Clock Gating Control 0 (DCGC0), offset 0x120
These registers control the clock gating logic. Each bit controls a clock enable for a given
interface, function, or unit. If set, the unit receives a clock and functions. Otherwise, the unit is
unclocked and disabled (saving power). If the unit is unclocked, reads or writes to the unit will
generate a bus fault. The reset state of these bits is 0 (unclocked) unless otherwise noted, so that
all functional units are disabled. It is the responsibility of software to enable the ports necessary for
the application. Note that these registers may contain more bits than there are interfaces,
functions, or units to control. This is to assure reasonable code compatibility with other family and
future parts.
RCGC0 is the clock configuration register for running operation, SCGC0 for Sleep operation, and
DCGC0 for Deep-Sleep operation. Setting the ACG bit in the Run-Mode Clock Configuration
(RCC) register (see page 71) specifies that the system uses sleep modes.
Run-Mode, Sleep-Mode and Deep-Sleep-Mode Clock Gating Control 0 (RCGC0, SCGC0, and DCGC0)
Offset 0x100, 0x110, 0x120
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
WDT
SWO
SWD
JTAG
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
1
reserved
Type
Reset
reserved
Type
Reset
a.
Bit/Field
Name
Type
Reset
Description
31:4
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
3
WDT
R/W
0
This bit controls the clock gating for the WDT module. If
set, the unit receives a clock and functions. Otherwise, the
unit is unclocked and disabled.a
2
SWO
R/W
0
This bit controls the clock gating for the SWO module. If
set, the unit receives a clock and functions. Otherwise, the
unit is unclocked and disabled.a
1
SWD
R/W
0
This bit controls the clock gating for the SWD module. If
set, the unit receives a clock and functions. Otherwise, the
unit is unclocked and disabled.a
0
JTAG
R/W
1
This bit controls the clock gating for the JTAG module.
The reset state for this bit is 1. At reset, the unit receives a
clock and functions. Setting this bit to 0 leaves the unit
unclocked and disabled.a
If the unit is unclocked, reads or writes to the unit will generate a bus fault.
76
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 22: Run-Mode Clock Gating Control 1 (RCGC1), offset 0x104
Register 23: Sleep-Mode Clock Gating Control 1 (SCGC1), offset 0x114
Register 24: Deep-Sleep-Mode Clock Gating Control 1 (DCGC1), offset 0x124
These registers control the clock gating logic. Each bit controls a clock enable for a given
interface, function, or unit. If set, the unit receives a clock and functions. Otherwise, the unit is
unclocked and disabled (saving power). If the unit is unclocked, reads or writes to the unit will
generate a bus fault. The reset state of these bits is 0 (unclocked) unless otherwise noted, so that
all functional units are disabled. It is the responsibility of software to enable the ports necessary for
the application. Note that these registers may contain more bits than there are interfaces,
functions, or units to control. This is to assure reasonable code compatibility with other family and
future parts.
RCGC1 is the clock configuration register for running operation, SCGC1 for Sleep operation, and
DCGC1 for Deep-Sleep operation. Setting the ACG bit in the Run-Mode Clock Configuration
(RCC) register (see page 71) specifies that the system uses sleep modes.
Run-Mode, Sleep-Mode, and Deep-Sleep-Mode Clock Gating Control 1 (RCGC1, SCGC1, and DCGC1)
Offset 0x104, 0x114, and 0x124
31
30
29
28
27
26
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
15
14
13
12
11
10
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
25
24
23
22
21
20
19
18
R/W
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
COMP1 COMP0
reserved
Type
Reset
RO
0
17
16
GPTM1 GPTM0
reserved
SSI
R/W
0
RO
0
RO
0
UART0
RO
0
R/W
0
Bit/Field
Name
Type
Reset
Description
31:26
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
25
COMP1
R/W
0
This bit controls the clock gating for the Comparator 1
module. If set, the unit receives a clock and functions.
Otherwise, the unit is unclocked and disabled.a
24
COMP0
R/W
0
This bit controls the clock gating for the Comparator 0
module. If set, the unit receives a clock and functions.
Otherwise, the unit is unclocked and disabled.a
23:18
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
17
GPTM1
R/W
0
This bit controls the clock gating for the General Purpose
Timer 1 module. If set, the unit receives a clock and
functions. Otherwise, the unit is unclocked and disabled.a
16
GPTM0
R/W
0
This bit controls the clock gating for the General Purpose
Timer 0 module. If set, the unit receives a clock and
functions. Otherwise, the unit is unclocked and disabled.a
October 5, 2006
77
Preliminary
System Control
a.
Bit/Field
Name
Type
Reset
Description
15:5
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
4
SSI
R/W
0
This bit controls the clock gating for the SSI module. If set,
the unit receives a clock and functions. Otherwise, the unit
is unclocked and disabled.a
3:1
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
0
UART0
R/W
0
This bit controls the clock gating for the UART0 module. If
set, the unit receives a clock and functions. Otherwise, the
unit is unclocked and disabled.a
If the unit is unclocked, reads or writes to the unit will generate a bus fault.
78
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 25: Run-Mode Clock Gating Control 2 (RCGC2), offset 0x108
Register 26: Sleep-Mode Clock Gating Control 2 (SCGC2), offset 0x118
Register 27: Deep-Sleep-Mode Clock Gating Control 2 (DCGC2), offset 0x128
These registers control the clock gating logic. Each bit controls a clock enable for a given
interface, function, or unit. If set, the unit receives a clock and functions. Otherwise, the unit is
unclocked and disabled (saving power). If the unit is unclocked, reads or writes to the unit will
generate a bus fault. The reset state of these bits is 0 (unclocked) unless otherwise noted, so that
all functional units are disabled. It is the responsibility of software to enable the ports necessary for
the application. Note that these registers may contain more bits than there are interfaces,
functions, or units to control. This is to assure reasonable code compatibility with other family and
future parts.
RCGC2 is the clock configuration register for running operation, SCGC2 for Sleep operation, and
DCGC2 for Deep-Sleep operation. Setting the ACG bit in the Run-Mode Clock Configuration
(RCC) register (see page 71) specifies that the system uses sleep modes.
Run-Mode, Sleep-Mode, and Deep-Sleep-Mode Clock Gating Control 2 (RCGC2, SCGC2, and DCGC2)
Offset 0x108, 0x118, and 0x128
31
30
29
28
27
26
25
24
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
a.
RO
0
PORTC PORTB PORTA
R/W
0
R/W
0
R/W
0
Bit/Field
Name
Type
Reset
Description
31:3
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
2
PORTC
R/W
0
This bit controls the clock gating for the GPIO Port C
module. If set, the unit receives a clock and functions.
Otherwise, the unit is unclocked and disabled.a
1
PORTB
R/W
0
This bit controls the clock gating for the GPIO Port B
module. If set, the unit receives a clock and functions.
Otherwise, the unit is unclocked and disabled.a
0
PORTA
R/W
0
This bit controls the clock gating for the GPIO Port A
module. If set, the unit receives a clock and functions.
Otherwise, the unit is unclocked and disabled.a
If the unit is unclocked, reads or writes to the unit will generate a bus fault.
October 5, 2006
79
Preliminary
System Control
Register 28: Deep-Sleep Clock Configuration (DSLPCLKCFG), offset 0x144
This register is used to automatically switch from the main oscillator to the internal oscillator when
entering Deep-Sleep mode. The system clock source is the main oscillator by default. When this
register is set, the internal oscillator is powered up and the main oscillator is powered down. When
the Deep-Sleep exit event occurs, hardware brings the system clock back to the source and
frequency it had at the onset of Deep-Sleep mode.
Deep-Sleep Clock Configuration (DSLPCLKCFG)
Offset 0x144
31
30
29
28
27
26
25
24
23
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
IOSC
R/W
0
Bit/Field
Name
Type
Reset
Description
31:1
Reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
0
IOSC
R/W
0
This field allows an override of the main oscillator when
Deep-Sleep mode is running. When set, this field forces the
internal oscillator to be the clock source during Deep-Sleep
mode. Otherwise, the main oscillator remains as the default
system clock source.
80
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 29: Clock Verification Clear (CLKVCLR), offset 0x150
This register is provided as a means of clearing the clock verification circuits by software. Since
the clock verification circuits force a known good clock to control the process, the controller is
allowed the opportunity to solve the problem and clear the verification fault. This register clears all
clock verification faults. To clear a clock verification fault, the VERCLR bit must be set and then
cleared by software. This bit is not self-clearing.
Clock Verification Clear (CLKVCLR)
Offset 0x150
31
30
29
28
27
26
25
24
23
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
VERCLR
R/W
0
Bit/Field
Name
Type
Reset
Description
31:1
Reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
0
VERCLR
R/W
0
Clear clock verification faults.
October 5, 2006
81
Preliminary
System Control
Register 30: Allow Unregulated LDO to Reset the Part (LDOARST), offset 0x160
This register is provided as a means of allowing the LDO to reset the part if the voltage goes
unregulated. Use this register to choose whether to automatically reset the part if the LDO goes
unregulated, based on the design tolerance for LDO fluctuation.
Allow Unregulated LDO to Reset the Part (LDOARST)
Offset 0x160
31
30
29
28
27
26
25
24
23
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
LDOARST
R/W
0
Bit/Field
Name
Type
Reset
Description
31:1
Reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
0
LDOARST
R/W
0
Set to 1 to allow unregulated LDO output to reset the part.
82
October 5, 2006
Preliminary
LM3S101 Data Sheet
7
Internal Memory
The LM3S101 microcontroller comes with 2 KB of bit-banded SRAM and 8 KB of flash memory.
The flash controller provides a user-friendly interface, making flash programming a simple task.
Flash protection can be applied to the flash memory on a 2-KB block basis.
7.1
Block Diagram
Figure 7-1. Flash Block Diagram
Flash Timing
USECRL
Flash Control
ICode
Cortex-M3
DCode
FMA
FMD
Flash Array
FMC
System Bus
FCRIS
FCIM
FCMISC
Bridge
APB
Flash Protection
FMPRE
SRAM Array
7.2
FMPPE
Functional Description
This section describes the functionality of both memories.
7.2.1
SRAM Memory
The internal SRAM of the Stellaris devices is located at address 0x20000000 of the device
memory map. To reduce the number of time consuming read-modify-write (RMW) operations,
ARM has introduced bit-banding technology in the new Cortex-M3 processor. With a
bit-band-enabled processor, certain regions in the memory map (SRAM and peripheral space) can
use address aliases to access individual bits in a single, atomic operation.
October 5, 2006
83
Preliminary
Internal Memory
The bit-band alias is calculated by using the formula:
bit-band alias = bit-band base + (byte offset * 32) + (bit number * 4)
For example, if bit 3 at address 0x20001000 is to be modified, the bit-band alias is calculated as:
0x22000000 + (0x1000 * 32) + (3 * 4) = 0x2202000C
With the alias address calculated, an instruction performing a read/write to address 0x2202000C
allows direct access to only bit 3 of the byte at address 0x20001000.
For details about bit-banding, please refer to Chapter 4, “Memory Map” in the ARM® Cortex™-M3
Technical Reference Manual.
7.2.2
Flash Memory
The flash is organized as a set of 1-KB blocks that can be individually erased. Erasing a block
causes the entire contents of the block to be reset to all 1s. These blocks are paired into a set of
2-KB blocks that can be individually protected. The blocks can be marked as read-only or
execute-only, providing different levels of code protection. Read-only blocks cannot be erased or
programmed, protecting the contents of those blocks from being modified. Execute-only blocks
cannot be erased or programmed, and can only be read by the controller instruction fetch
mechanism, protecting the contents of those blocks from being read by either the controller or by a
debugger.
7.2.2.1
Flash Memory Timing
The timing for the flash is automatically handled by the flash controller. However, in order to do so,
it must know the clock rate of the system in order to time its internal signals properly. The number
of clock cycles per microsecond must be provided to the flash controller for it to accomplish this
timing. It is software's responsibility to keep the flash controller updated with this information via
the USec Reload (USECRL) register (see page 89).
On reset, USECRL is loaded with a value that configures the flash timing so that it works with the
selected crystal value. If software changes the system operating frequency, the new operating
frequency must be loaded into USECRL before any flash modifications are attempted. For
example, if the device is operating at a speed of 20 MHz, a value of 0x13 must be written to the
USECRL register.
7.2.2.2
Flash Memory Protection
The user is provided two forms of flash protection per 2-KB flash blocks in two 32-bit wide
registers. The protection policy for each form is controlled by individual bits (per policy per block) in
the FMPPE and FMPRE registers (see page 88).

Flash Memory Protection Program Enable (FMPPE): If set, the block may be programmed
(written) or erased. If cleared, the block may not be changed.

Flash Memory Protection Read Enable (FMPRE): If set, the block may be executed or read
by software or debuggers. If cleared, the block may only be executed. The contents of the
memory block are prohibited from being accessed as data and traversing the DCode bus.
84
October 5, 2006
Preliminary
LM3S101 Data Sheet
The policies may be combined as shown in Table 7-1.
Table 7-1. Flash Protection Policy Combinations
FMPPE
FMPRE
Protection
0
0
Execute-only protection. The block may only be executed and may not be
written or erased. This mode is used to protect code.
1
0
The block may be written, erased or executed, but not read. This combination
is unlikely to be used.
0
1
Read-only protection. The block may be read or executed but may not be
written or erased. This mode is used to lock the block from further modification
while allowing any read or execute access.
1
1
No protection. The block may be written, erased, executed or read.
An access that attempts to program or erase a PE-protected block is prohibited. A controller
interrupt may be optionally generated (by setting the AMASK bit in the FIM register) to alert
software developers of poorly behaving software during the development and debug phases.
An access that attempts to read an RE-protected block is prohibited. Such accesses return data
filled with all 0s. A controller interrupt may be optionally generated to alert software developers of
poorly behaving software during the development and debug phases.
The factory settings for the FMPRE and FMPPE registers are a value of 1 for all implemented
banks. This implements a policy of open access and programmability. The register bits may be
changed by writing the specific register bit. The changes are not permanent until the register is
committed (saved), at which point the bit change is permanent. If a bit is changed from a 1 to a 0
and not committed, it may be restored by executing a power-on reset sequence.
7.2.2.3
Flash Memory Programming
Writing the flash memory requires that the code be executed out of SRAM to avoid corrupting or
interrupting the bus timing. Flash pages can be erased on a page basis (1 KB in size), or by
performing a mass erase of the entire flash.
All erase and program operations are performed using the Flash Memory Address (FMA), Flash
Memory Data (FMD) and Flash Memory Control (FMC) registers. See section 7.3 for examples.
7.3
Initialization and Configuration
This section shows examples for using the flash controller to perform various operations on the
contents of the flash memory.
7.3.1
Changing Flash Protection Bits
As discussed in Section 7.2.2.2, changes to the protection bits must be committed before they
take effect. The sequence 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 90) 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 92) is written with the COMT bit set. This
initiates a write sequence and commits the changes.
October 5, 2006
85
Preliminary
Internal Memory
7.3.2
Flash Programming
The Stellaris devices provide a user-friendly interface for flash programming. All erase/program
operations are handled via three registers: FMA, FMD and FMC.
The flash is programmed using the following sequence:
1. Write source data to the FMD register.
2. Write the target address to the FMA register.
3. Write the flash write key and the WRITE bit (a value of 0xA4420001) to the FMC register.
4. Poll the FMC register until the WRITE bit is cleared.
To perform an erase of a 1-KB page:
1. Write the page address to the FMA register.
2. Write the flash write key and the ERASE bit (a value of 0xA4420002) to the FMC register.
3. Poll the FMC register until the ERASE bit is cleared.
To perform a mass erase of the flash:
1. Write the flash write key and the MERASE bit (a value of 0xA4420004) to the FMC register.
2. Poll the FMC register until the MERASE bit is cleared.
7.4
Register Map
Table 7-2 lists the Flash memory and control registers. The offset listed is a hexadecimal
increment to the register’s address, relative to the Flash control base address of 0x400FD000,
except for FMPRE and FMPPE, which are relative to the System Control base address of
0x400FE000.
Table 7-2. Flash Register Map
See
page
Offset
Name
Reset
Type
Description
0x130a
FMPRE
0x0F
R/W0
Flash memory read protect
88
a
FMPPE
0x0F
R/W0
Flash memory program protect
88
USECRL
0x13
R/W
USec reload
89
0x134
0X140a
0x000
FMA
0x00000000
R/W
Flash memory address
90
0x004
FMD
0x00000000
R/W
Flash memory data
91
0x008
FMC
0x00000000
R/W
Flash memory control
92
0x00C
FCRIS
0x00000000
RO
Flash controller raw interrupt status
94
0x010
FCIM
0x00000000
R/W
Flash controller interrupt mask
95
0x014
FCMISC
0x00000000
R/W1C
Flash controller masked interrupt status and clear
96
a. Relative to System Control base address of 0x400FE000.
86
October 5, 2006
Preliminary
LM3S101 Data Sheet
7.5
Register Descriptions
The remainder of this section lists and describes the Flash Memory registers, in numerical order
by address offset.
October 5, 2006
87
Preliminary
Internal Memory
Register 1: Flash Memory Protection Read Enable (FMPRE), offset 0x130
Register 2: Flash Memory Protection Program Enable (FMPPE), offset 0x134
Note:
Offset is relative to System Control base address of 0x400FE000
These registers store the read-only (FMPRE) and execute-only (FMPPE) protection bits for each
2 KB flash block. This register is loaded during the power-on reset sequence.
The factory settings for the FMPRE and FMPPE registers are a value of 1 for all implemented
banks. This implements a policy of open access and programmability. The register bits may be
changed by writing the specific register bit. However, this register is R/W0; the user can only
change the protection bit from a 1 to a 0 (and may NOT change a 0 to a 1).
The changes are not permanent until the register is committed (saved), at which point the bit
change is permanent. If a bit is changed from a 1 to a 0 and not committed, it may be restored by
executing a power-on reset sequence.
For additional information, see “Flash Memory Protection” on page 84.
Flash Memory Protection Read Enable and Program Enable (FMPRE and FMPPE)
Offset 0x130 and 0x134
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
Block3
Block2
Block1
Block0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W0
1
R/W0
1
R/W0
1
R/W0
1
reserved
Type
Reset
reserved
Type
Reset
Bit/Field
Name
Type
Reset
31:4
reserved
RO
0
3:0
Block3Block0
R/W0
0x0F
88
Description
Reserved bits return an indeterminate value, and
should never be changed.
Enable 2-KB flash blocks to be written or erased
(FMPPE register), or executed or read (FMPRE
register). The policies may be combined as shown
in Table 7-1 on page 85.
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 3: USec Reload (USECRL), offset 0x140
Note:
Offset is relative to System Control base address of 0x400FE000
This register is provided as a means of creating a 1 μs tick divider reload value for the flash
controller. The internal flash has specific minimum and maximum requirements on the length of
time the high voltage write pulse can be applied. It is required that this register contain the
operating frequency (in MHz -1) whenever the flash is being erased or programmed. The user is
required to change this value if the clocking conditions are changed for a flash erase/program
operation.
Usec Reload (USECRL)
Offset 0x140
31
30
29
28
27
26
25
24
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
8
7
6
5
4
3
2
1
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
1
R/W
0
R/W
0
R/W
1
R/W
1
reserved
Type
Reset
reserved
Type
Reset
RO
0
USEC
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
USEC
R/W
0x13
Description
Reserved bits return an indeterminate value, and should
never be changed.
MHz -1 of the controller clock when the flash is being
erased or programmed.
USEC should be set to 0x13 (19 MHz) whenever the flash is
being erased or programmed.
October 5, 2006
89
Preliminary
Internal Memory
Register 4: Flash Memory Address (FMA), offset 0x000
During a write operation, this register contains a 4-byte-aligned address and specifies where the
data is written. During erase operations, this register contains a 1 KB-aligned address and
specifies which page is erased. Note that the alignment requirements must be met by software or
the results of the operation are unpredictable.
Flash Memory Address (FMA)
Offset 0x000
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
RO
0
OFFSET
R/W
0
Bit/Field
Name
Type
Reset
Description
31:13
reserved
RO
0x0
Reserved bits return an indeterminate value, and should
never be changed.
12:0
OFFSET
R/W
0x0
Address offset in flash where operation is performed.
90
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 5: Flash Memory Data (FMD), offset 0x004
This register contains the data to be written during the programming cycle or read during the read
cycle. Note that the contents of this register are undefined for a read access of an execute-only
block. This register is not used during the erase cycles.
Flash Memory Data (FMD)
Offset 0x004
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
DATA
Type
Reset
DATA
Type
Reset
Bit/Field
Name
Type
Reset
31:0
DATA
R/W
0x0
Description
Data value for write operation.
October 5, 2006
91
Preliminary
Internal Memory
Register 6: Flash Memory Control (FMC), offset 0x008
When this register is written, the flash controller initiates the appropriate access cycle for the
location specified by the Flash Memory Address (FMA) register (see page 90). If the access is a
write access, the data contained in the Flash Memory Data (FMD) register (see page 91) is
written.
This is the final register written and initiates the memory operation. There are four control bits in
the lower byte of this register that, when set, initiate the memory operation. The most used of
these register bits are the ERASE and WRITE bits.
It is a programming error to write multiple control bits and the results of such an operation are
unpredictable.
Flash Memory Control (FMC)
Offset 0x008
31
30
29
28
27
26
25
24
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
15
14
13
12
11
10
9
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
23
22
21
20
19
18
17
16
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
WRKEY
Type
Reset
COMT MERASE ERASE WRITE
reserved
Type
Reset
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
Bit/Field
Name
Type
Reset
Description
31:16
WRKEY
WO
0x0
15:4
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
3
COMT
R/W
0
Commit (write) of register value to nonvolatile storage. A
write of 0 has no effect on the state of this bit.
This field contains a write key, which is used to minimize the
incidence of accidental flash writes. The value 0xA442 must
be written into this field for a write to occur. Writes to the
FMC register without this WRKEY value are ignored. A
read of this field returns the value 0.
If read, the state of the previous commit access is provided.
If the previous commit access is complete, a 0 is returned;
otherwise, if the commit access is not complete, a 1 is
returned.
This can take up to 50 μs.
2
MERASE
R/W
0
Mass erase flash memory
If this bit is set, the flash main memory of the device is all
erased. A write of 0 has no effect on the state of this bit.
If read, the state of the previous mass erase access is
provided. If the previous mass erase access is complete, a
0 is returned; otherwise, if the previous mass erase access
is not complete, a 1 is returned.
This can take up to 250 ms.
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October 5, 2006
Preliminary
LM3S101 Data Sheet
Bit/Field
Name
Type
Reset
1
ERASE
R/W
0
Description
Erase a page of flash memory
If this bit is set, the page of flash main memory as specified
by the contents of FMA is erased. A write of 0 has no effect
on the state of this bit.
If read, the state of the previous erase access is provided. If
the previous erase access is complete, a 0 is returned;
otherwise, if the previous erase access is not complete, a 1
is returned.
This can take up to 25 ms.
0
WRITE
R/W
0
Write a word into flash memory
If this bit is set, the data stored in FMD is written into the
location as specified by the contents of FMA. A write of 0
has no effect on the state of this bit.
If read, the state of the previous write update is provided. If
the previous write access is complete, a 0 is returned;
otherwise, if the write access is not complete, a 1 is
returned.
This can take up to 50 μs.
October 5, 2006
93
Preliminary
Internal Memory
Register 7: Flash Controller Raw Interrupt Status (FCRIS), offset 0x00C
This register indicates that the flash controller has an interrupt condition. An interrupt is only
signaled if the corresponding FCIM register bit is set.
Flash Controller Raw Interrupt Status (FCRIS)
Offset 0x00C
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
PRIS
ARIS
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
Bit/Field
Name
Type
Reset
Description
31:2
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
1
PRIS
RO
0
Programming Raw Interrupt Status
This bit indicates the current state of the programming
cycle. If set, the programming cycle completed; if cleared,
the programming cycle has not completed. Programming
cycles are either write or erase actions generated through
the Flash Memory Control (FMC) register bits (see
page 92).
0
ARIS
RO
0
Access Raw Interrupt Status
This bit indicates if the flash was improperly accessed. If
set, the program tried to access the flash counter to the
policy as set in the Flash Memory Protection Read
Enable (FMPRE) and Flash Memory Protection Program
Enable (FMPPE) registers (see page 88). Otherwise, no
access has tried to improperly access the flash.
94
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 8: Flash Controller Interrupt Mask (FCIM), offset 0x010
This register controls whether the flash controller generates interrupts to the controller.
Flash Controller Interrupt Mask (FCIM)
Offset 0x010
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
PMASK AMASK
reserved
Type
Reset
RO
0
R/W
0
R/W
0
Bit/Field
Name
Type
Reset
Description
31:2
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
1
PMASK
R/W
0
Programming Interrupt Mask
This bit controls the reporting of the programming raw
interrupt status to the controller. If set, a
programming-generated interrupt is promoted to the
controller. Otherwise, interrupts are recorded but
suppressed from the controller.
0
AMASK
R/W
0
Access Interrupt Mask
This bit controls the reporting of the access raw interrupt
status to the controller. If set, an access-generated interrupt
is promoted to the controller. Otherwise, interrupts are
recorded but suppressed from the controller.
October 5, 2006
95
Preliminary
Internal Memory
Register 9: Flash Controller Masked Interrupt Status and Clear (FCMISC), offset 0x014
This register provides two functions. First, it reports the cause of an interrupt by indicating which
interrupt source or sources are signalling the interrupt. Second, it serves as the method to clear
the interrupt reporting.
Flash Controller Masked Interrupt Status and Clear (FCMISC)
Offset 0x014
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
PMISC
AMISC
R/W1C
0
R/W1C
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
Bit/Field
Name
Type
Reset
Description
31:2
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
1
PMISC
R/W1C
0
Programming Masked Interrupt Status and Clear
This bit indicates whether an interrupt was signaled
because a programming cycle completed and was not
masked. This bit is cleared by writing a 1. The PRIS bit in
the FCRIS register (see page 94) is also cleared when the
PMISC bit is cleared.
0
AMISC
R/W1C
0
Access Masked Interrupt Status and Clear
This bit indicates whether an interrupt was signaled
because an improper access was attempted and was not
masked. This bit is cleared by writing a 1. The ARIS bit in
the FCRIS register is also cleared when the AMISC bit is
cleared.
96
October 5, 2006
Preliminary
LM3S101 Data Sheet
8
General-Purpose Input/Outputs (GPIOs)
The GPIO module is composed of three physical GPIO blocks, each corresponding to an
individual GPIO port (Port A, Port B, and Port C). The GPIO module is FiRM-compliant and
supports 2 to 18 programmable input/output pins, depending on the peripherals being used.
The GPIO module has the following features:

Programmable control for GPIO interrupts:
– Interrupt generation masking
– Edge-triggered on rising, falling, or both
– Level-sensitive on High or Low values

5-V-tolerant input/outputs

Bit masking in both read and write operations through address lines

Programmable control for GPIO pad configuration:
– Weak pull-up or pull-down resistors
– 2-mA, 4-mA, and 8-mA pad drive
– Slew rate control for the 8-mA drive
– Open drain enables
– Digital input enables
October 5, 2006
97
Preliminary
General-Purpose Input/Outputs (GPIOs)
8.1
Block Diagram
Figure 8-1. GPIO Module Block Diagram
U0Rx
PA1
U0Tx
PA2
PA3
PA4
GPIO Port A
PA0
UART0
SSIClk
SSIFss
SSIRx
SSI
SSITx
PB0
CCP0
Timer 0
PB1
32KHz
Timer 1
PB2
PB3
PB4
PB5
GPIO Port B
PA5
C0C0o/C1-
Analog
Comparators
C0+
PB6
PC0
PC1
PC2
PC3
8.2
GPIO Port C
PB7
TCK/SWCLK
TRST
TMS/SWDIO
JTAG
TDI
TDO/SWO
Functional Description
Important: All GPIO pins are inputs by default (GPIODIR=0 and GPIOAFSEL=0), with the
exception of the five JTAG pins (PB7 and PC[3:0]. The JTAG pins default to their
JTAG functionality (GPIOAFSEL=1). Asserting a Power-On-Reset (POR) or an
external reset (RST) puts both groups of pins back to their default state.
Each GPIO port is a separate hardware instantiation of the same physical block (see Figure 8-2).
The LM3S101 microcontroller contains three ports and thus three of these physical GPIO blocks.
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October 5, 2006
Preliminary
LM3S101 Data Sheet
Figure 8-2. GPIO Port Block Diagram
Function
Selection
GPIOAFSEL
D
E
M
U
X
Alternate Input
Alternate Output
Alternate Output Enable
GPIO Input
I/O
Data
M
U
X
Pad Output
M
U
X
Pad Output Enable
I/O
Pad
Package I/O Pin
GPIO Output
GPIODATA
GPIODIR
Interrupt
Pad Input
GPIO Output Enable
Interrupt
Control
I/O Pad
Control
GPIOIS
GPIOIBE
GPIOIEV
GPIOIM
GPIORIS
GPIOMIS
GPIOICR
GPIODR2R
GPIODR4R
GPIODR8R
GPIOSLR
GPIOPUR
GPIOPDR
GPIOODR
GPIODEN
Identification Registers
GPIOPeriphID0
GPIOPeriphID1
GPIOPeriphID2
GPIOPeriphID3
8.2.1
GPIOPeriphID4
GPIOPeriphID5
GPIOPeriphID6
GPIOPeriphID7
GPIOPCellID0
GPIOPCellID1
GPIOPCellID2
GPIOPCellID3
Data Register Operation
To aid in the efficiency of software, the GPIO ports allow for the modification of individual bits in the
GPIO Data (GPIODATA) register (see page 105) by using bits [9:2] of the address bus as a mask.
This allows software drivers to modify individual GPIO pins in a single instruction, without affecting
the state of the other pins. This is in contrast to the "typical" method of doing a read-modify-write
operation to set or clear an individual GPIO pin. To accommodate this feature, the GPIODATA
register covers 256 locations in the memory map.
During a write, if the address bit associated with that data bit is set to 1, the value of the
GPIODATA register is altered. If it is cleared to 0, it is left unchanged.
For example, writing a value of 0xEB to the address GPIODATA + 0x098 would yield as shown in
Figure 8-3, where u is data unchanged by the write.
October 5, 2006
99
Preliminary
General-Purpose Input/Outputs (GPIOs)
Figure 8-3. GPIODATA Write Example
ADDR[9:2]
9
8
7
6
5
4
3
2
1
0
0x098
0
0
1
0
0
1
1
0
0
0
0xEB
1
1
1
0
1
0
1
1
GPIODATA
u
u
1
u
u
0
1
u
7
6
5
4
3
2
1
0
During a read, if the address bit associated with the data bit is set to 1, the value is read. If the
address bit associated with the data bit is set to 0, it is read as a zero, regardless of its actual
value. For example, reading address GPIODATA + 0x0C4 yields as shown in Figure 8-4.
Figure 8-4. GPIODATA Read Example
8.2.2
ADDR[9:2]
9
8
7
6
5
4
3
2
1
0
0x0C4
0
0
1
1
0
0
0
1
0
0
GPIODATA
1
0
1
1
1
1
1
0
Returned Value
0
0
1
1
0
0
0
0
7
6
5
4
3
2
1
0
Data Direction
The GPIO Direction (GPIODIR) register (see page 106) is used to configure each individual pin
as an input or output.
8.2.3
Interrupt Operation
The interrupt capabilities of each GPIO port are controlled by a set of seven registers. With these
registers, it is possible to select the source of the interrupt, its polarity, and the edge properties.
When one or more GPIO inputs cause an interrupt, a single interrupt output is sent to the interrupt
controller for the entire GPIO port. For edge-triggered interrupts, software must clear the interrupt
to enable any further interrupts. For a level-sensitive interrupt, it is assumed that the external
source holds the level constant for the interrupt to be recognized by the controller.
Three registers are required to define the edge or sense that causes interrupts:

GPIO Interrupt Sense (GPIOIS) register (see page 107)

GPIO Interrupt Both Edges (GPIOIBE) register (see page 108)

GPIO Interrupt Event (GPIOIEV) register (see page 109)
Interrupts are enabled/disabled via the GPIO Interrupt Mask (GPIOIM) register (see page 110).
When an interrupt condition occurs, the state of the interrupt signal can be viewed in two locations:
the GPIO Raw Interrupt Status (GPIORIS) and GPIO Masked Interrupt Status (GPIOMIS)
registers (see pages 111 and 112). As the name implies, the GPIOMIS register only shows
interrupt conditions that are allowed to be passed to the controller. The GPIORIS register indicates
that a GPIO pin meets the conditions for an interrupt, but has not necessarily been sent to the
controller.
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October 5, 2006
Preliminary
LM3S101 Data Sheet
Interrupts are cleared by writing a 1 to the GPIO Interrupt Clear (GPIOICR) register (see
page 113).
When programming interrupts, the interrupts should be masked (GPIOIM set to 0). Writing any
value to an interrupt control register (GPIOIS, GPIOIBE, or GPIOIEV) can generate a spurious
interrupt if the corresponding bits are enabled.
8.2.4
Mode Control
The GPIO pins can be controlled by either hardware or software. When hardware control is
enabled via the GPIO Alternate Function Select (GPIOAFSEL) register (see page 114), the pin
state is controlled by its alternate function (that is, the peripheral). Software control corresponds to
GPIO mode, where the GPIODATA register is used to read/write the corresponding pins.
8.2.5
Pad Configuration
The pad configuration registers allow for GPIO pad configuration by software based on the
application requirements. The pad configuration registers include the GPIODR2R, GPIODR4R,
GPIODR8R, GPIOODR, GPIOPUR, GPIOPDR, GPIOSLR, and GPIODEN registers.
8.2.6
Identification
The identification registers configured at reset allow software to detect and identify the module as
a GPIO block. The identification registers include the GPIOPeriphID0-GPIOPeriphID7 registers
as well as the GPIOPCellID0-GPIOPCellID3 registers.
8.3
Initialization and Configuration
To use the GPIO, the peripheral clock must be enabled by setting PORTA, PORTB, and PORTC in
the RCGC2 register.
On reset, all GPIO pins (except for the five JTAG pins) default to general-purpose input mode
(GPIODIR and GPIOAFSEL both set to 0). Table 8-1 shows all possible configurations of the
GPIO pads and the control register settings required to achieve them. Table 8-2 shows how a
rising edge interrupt would be configured for pin 2 of a GPIO port.
Table 8-1. GPIO Pad Configuration Examples
GPIOAFSEL
GPIODIR
GPIOODR
GPIODEN
GPIOPUR
GPIOPDR
GPIODR2R
GPIODR4R
GPIODR8R
GPIOSLR
Register Bit Valuea
Digital Input (GPIO)
0
0
0
1
?
?
X
X
X
X
Digital Output (GPIO)
0
1
0
1
?
?
?
?
?
?
Open Drain Input (GPIO)
0
0
1
1
X
X
X
X
X
X
Open Drain Output (GPIO)
0
1
1
1
X
X
?
?
?
?
Digital Input (Timer CCP)
1
X
0
1
?
?
X
X
X
X
Digital Output (Timer PWM)
1
X
0
1
?
?
?
?
?
?
Digital Input/Output (SSI)
1
X
0
1
?
?
?
?
?
?
Configuration
October 5, 2006
101
Preliminary
General-Purpose Input/Outputs (GPIOs)
Table 8-1. GPIO Pad Configuration Examples (Continued)
GPIOAFSEL
GPIODIR
GPIOODR
GPIODEN
GPIOPUR
GPIOPDR
GPIODR2R
GPIODR4R
GPIODR8R
GPIOSLR
Register Bit Valuea
Digital Input/Output (UART)
1
X
0
1
?
?
?
?
?
?
Analog Input (Comparator)
0
0
0
0
0
0
X
X
X
X
Digital Output (Comparator)
1
X
0
1
?
?
?
?
?
?
Configuration
a. X=Ignored (don’t care bit)
?=Can be either 0 or 1, depending on the configuration
Table 8-2. GPIO Interrupt Configuration Example
Register
Desired Interrupt
Event Trigger
Pin 2 Bit Valuea
7
6
5
4
3
2
1
0
0=edge
1=level
X
X
X
X
X
0
X
X
GPIOIBE
0=single edge
1=both edges
X
X
X
X
X
0
X
X
GPIOIEV
0=Low level, or
negative edge
1=High level, or
positive edge
X
X
X
X
X
1
X
X
0=masked
1=not masked
0
0
0
0
0
1
0
0
GPIOIS
GPIOIM
a. X=Ignored (don’t care bit)
102
October 5, 2006
Preliminary
LM3S101 Data Sheet
8.4
Register Map
Table 8-2 lists the GPIO registers. The offset listed is a hexadecimal increment to the register’s
address, relative to that GPIO port’s base address:

GPIO Port A: 0x40004000

GPIO Port B: 0x40005000

GPIO Port C: 0x40006000
Important: The GPIO registers in this chapter are duplicated in each GPIO block, however,
depending on the block, all eight bits may not be connected to a GPIO pad (see
Figure 8-1 on page 98). In those cases, writing to those unconnected bits has no
effect and reading those unconnected bits returns no meaningful data.
Table 8-3. GPIO Register Map
Offset
Name
0x000
See
page
Reset
Type
Description
GPIODATA
0x00000000
R/W
Data
105
0x400
GPIODIR
0x00000000
R/W
Data direction
106
0x404
GPIOIS
0x00000000
R/W
Interrupt sense
107
0x408
GPIOIBE
0x00000000
R/W
Interrupt both edges
108
0x40C
GPIOIEV
0x00000000
R/W
Interrupt event
109
0x410
GPIOIM
0x00000000
R/W
Interrupt mask enable
110
0x414
GPIORIS
0x00000000
RO
Raw interrupt status
111
0x418
GPIOMIS
0x00000000
RO
Masked interrupt status
112
0x41C
GPIOICR
0x00000000
W1C
Interrupt clear
113
0x420
GPIOAFSEL
see notea
R/W
Alternate function select
114
0x500
GPIODR2R
0x000000FF
R/W
2-mA drive select
115
0x504
GPIODR4R
0x00000000
R/W
4-mA drive select
116
0x508
GPIODR8R
0x00000000
R/W
8-mA drive select
117
0x50C
GPIOODR
0x00000000
R/W
Open drain select
118
0x510
GPIOPUR
0x000000FF
R/W
Pull-up select
119
0x514
GPIOPDR
0x00000000
R/W
Pull-down select
120
0x518
GPIOSLR
0x00000000
R/W
Slew rate control select
121
0x51C
GPIODEN
0x000000FF
R/W
Digital input enable
122
0xFD0
GPIOPeriphID4
0x00000000
RO
Peripheral identification 4
123
0xFD4
GPIOPeriphID5
0x00000000
RO
Peripheral identification 5
124
0xFD8
GPIOPeriphID6
0x00000000
RO
Peripheral identification 6
125
October 5, 2006
103
Preliminary
General-Purpose Input/Outputs (GPIOs)
Table 8-3. GPIO Register Map (Continued)
Offset
Name
0xFDC
See
page
Reset
Type
Description
GPIOPeriphID7
0x00000000
RO
Peripheral identification 7
126
0xFE0
GPIOPeriphID0
0x00000061
RO
Peripheral identification 0
127
0xFE4
GPIOPeriphID1
0x00000000
RO
Peripheral identification 1
128
0xFE8
GPIOPeriphID2
0x00000018
RO
Peripheral identification 2
129
0xFEC
GPIOPeriphID3
0x00000001
RO
Peripheral identification 3
130
0xFF0
GPIOPCellID0
0x0000000D
RO
GPIO PrimeCell identification 0
131
0xFF4
GPIOPCellID1
0x000000F0
RO
GPIO PrimeCell identification 1
132
0xFF8
GPIOPCellID2
0x00000005
RO
GPIO PrimeCell identification 2
133
0xFFC
GPIOPCellID3
0x000000B1
RO
GPIO PrimeCell identification 3
134
a. The default reset value for the GPIOAFSEL register is 0x00000000 for all GPIO pins, with the exception of the five JTAG pins
(PB7 and PC[3:0]. These five pins default to JTAG functionality. Because of this, the default reset value of GPIOAFSEL for
GPIO Port B is 0x00000080 while the default reset value of GPIOAFSEL for Port C is 0x0000000F.
8.5
Register Descriptions
The remainder of this section lists and describes the GPIO registers, in numerical order by
address offset.
104
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 1: GPIO Data (GPIODATA), offset 0x000
The GPIODATA register is the data register. In software control mode, values written in the
GPIODATA register are transferred onto the GPIO port pins if the respective pins have been
configured as outputs through the GPIO Direction (GPIODIR) register (see page 106).
In order to write to GPIODATA, the corresponding bits in the mask, resulting from the address bus
bits [9:2], must be High. Otherwise, the bit values remain unchanged by the write.
Similarly, the values read from this register are determined for each bit by the mask bit derived
from the address used to access the data register, bits [9:2]. Bits that are 1 in the address mask
cause the corresponding bits in GPIODATA to be read, and bits that are 0 in the address mask
cause the corresponding bits in GPIODATA to be read as 0, regardless of their value.
A read from GPIODATA returns the last bit value written if the respective pins are configured as
outputs, or it returns the value on the corresponding input pin when these are configured as inputs.
All bits are cleared by a reset.
GPIO Data (GPIODATA)
Offset 0x000
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
DATA
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
DATA
R/W
0
Description
Reserved bits return an indeterminate value, and should never
be changed.
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 99 for examples of reads and
writes.
October 5, 2006
105
Preliminary
General-Purpose Input/Outputs (GPIOs)
Register 2: GPIO Direction (GPIODIR), offset 0x400
The GPIODIR register is the data direction register. Bits set to 1 in the GPIODIR register configure
the corresponding pin to be an output, while bits set to 0 configure the pins to be inputs. All bits are
cleared by a reset, meaning all GPIO pins are inputs by default.
GPIO Direction (GPIODIR)
Offset 0x400
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
DIR
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
DIR
R/W
0x00
Description
Reserved bits return an indeterminate value, and should never
be changed.
GPIO Data Direction
0: Pins are inputs.
1: Pins are outputs.
106
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 3: GPIO Interrupt Sense (GPIOIS), offset 0x404
The GPIOIS register is the interrupt sense register. Bits set to 1 in GPIOIS configure the
corresponding pins to detect levels, while bits set to 0 configure the pins to detect edges. All bits
are cleared by a reset.
GPIO Interrupt Sense (GPIOIS)
Offset 0x404
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
IS
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
IS
R/W
0x00
Description
Reserved bits return an indeterminate value, and should never
be changed.
GPIO Interrupt Sense
0: Edge on corresponding pin is detected (edge-sensitive).
1: Level on corresponding pin is detected (level-sensitive).
October 5, 2006
107
Preliminary
General-Purpose Input/Outputs (GPIOs)
Register 4: GPIO Interrupt Both Edges (GPIOIBE), offset 0x408
The GPIOIBE register is the interrupt both-edges register. When the corresponding bit in the GPIO
Interrupt Sense (GPIOIS) register (see page 107) 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 109). Clearing a bit
configures the pin to be controlled by GPIOIEV. All bits are cleared by a reset.
GPIO Interrupt Both Edges (GPIOIBE)
Offset 0x408
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
IBE
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
IBE
R/W
0x00
Description
Reserved bits return an indeterminate value, and should never
be changed.
GPIO Interrupt Both Edges
0: Interrupt generation is controlled by the GPIO Interrupt Event
(GPIOIEV) register (see page 142).
1: Both edges on the corresponding pin trigger an interrupt.
Note:
108
Single edge is determined by the corresponding bit in
GPIOIEV.
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 5: GPIO Interrupt Event (GPIOIEV), offset 0x40C
The GPIOIEV register is the interrupt event register. Bits set to High in GPIOIEV configure the
corresponding pin to detect rising edges or high levels, depending on the corresponding bit value
in the GPIO Interrupt Sense (GPIOIS) register (see page 107). Clearing a bit configures the pin to
detect falling edges or low levels, depending on the corresponding bit value in GPIOIS. All bits are
cleared by a reset.
GPIO Interrupt Event (GPIOIEV)
Offset 0x40C
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
IEV
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
IEV
R/W
0x00
Description
Reserved bits return an indeterminate value, and should never
be changed.
GPIO Interrupt Event
0: Falling edge or Low levels on corresponding pins trigger
interrupts.
1: Rising edge or High levels on corresponding pins trigger
interrupts.
October 5, 2006
109
Preliminary
General-Purpose Input/Outputs (GPIOs)
Register 6: GPIO Interrupt Mask (GPIOIM), offset 0x410
The GPIOIM register is the interrupt mask register. Bits set to High in GPIOIM allow the
corresponding pins to trigger their individual interrupts and the combined GPIOINTR line. Clearing
a bit disables interrupt triggering on that pin. All bits are cleared by a reset.
GPIO Interrupt Mask (GPIOIM)
Offset 0x410
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
IME
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
IME
R/W
0x00
Description
Reserved bits return an indeterminate value, and should never
be changed.
GPIO Interrupt Mask Enable
0: Corresponding pin interrupt is masked.
1: Corresponding pin interrupt is not masked.
110
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 7: GPIO Raw Interrupt Status (GPIORIS), offset 0x414
The GPIORIS register is the raw interrupt status register. Bits read High in GPIORIS reflect the
status of interrupt trigger conditions detected (raw, prior to masking), indicating that all the
requirements have been met, before they are finally allowed to trigger by the GPIO Interrupt
Mask (GPIOIM) register (see page 110). Bits read as zero indicate that corresponding input pins
have not initiated an interrupt. All bits are cleared by a reset.
GPIO Raw Interrupt Status (GPIORIS)
Offset 0x414
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RIS
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
RIS
RO
0x00
Description
Reserved bits return an indeterminate value, and should never
be changed.
GPIO Interrupt Raw Status
Reflect the status of interrupt trigger condition detection on pins
(raw, prior to masking).
0: Corresponding pin interrupt requirements not met.
1: Corresponding pin interrupt has met requirements.
October 5, 2006
111
Preliminary
General-Purpose Input/Outputs (GPIOs)
Register 8: GPIO Masked Interrupt Status (GPIOMIS), offset 0x418
The GPIOMIS register is the masked interrupt status register. Bits read High in GPIOMIS reflect
the status of input lines triggering an interrupt. Bits read as Low indicate that either no interrupt has
been generated, or the interrupt is masked.
GPIOMIS is the state of the interrupt after masking.
GPIO Masked Interrupt Status (GPIOMIS)
Offset 0x418
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
MIS
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
MIS
RO
0x00
Description
Reserved bits return an indeterminate value, and should never
be changed.
GPIO Masked Interrupt Status
Masked value of interrupt due to corresponding pin.
0: Corresponding GPIO line interrupt not active.
1: Corresponding GPIO line asserting interrupt.
112
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 9: GPIO Interrupt Clear (GPIOICR), offset 0x41C
The GPIOICR register is the interrupt clear register. Writing a 1 to a bit in this register clears the
corresponding interrupt edge detection logic register. Writing a 0 has no effect.
GPIO Interrupt Clear (GPIOICR)
Offset 0x41C
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
W1C
0
W1C
0
W1C
0
W1C
0
W1C
0
W1C
0
W1C
0
W1C
0
reserved
Type
Reset
reserved
Type
Reset
IC
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
IC
W1C
0x00
Description
Reserved bits return an indeterminate value, and should never
be changed.
GPIO Interrupt Clear
0: Corresponding interrupt is unaffected.
1: Corresponding interrupt is cleared.
October 5, 2006
113
Preliminary
General-Purpose Input/Outputs (GPIOs)
Register 10: GPIO Alternate Function Select (GPIOAFSEL), offset 0x420
The GPIOAFSEL register is the mode control select register. Writing a 1 to any bit in this register
selects the hardware control for the corresponding GPIO line. All bits are cleared by a reset,
therefore no GPIO line is set to hardware control by default.
Caution – All GPIO pins are inputs by default (GPIODIR=0 and GPIOAFSEL=0), with the
exception of the five JTAG pins (PB7 and PC[3:0]). The JTAG pins default to their JTAG
functionality (GPIOAFSEL=1). Asserting a Power-On-Reset (POR) or an external reset (RST)
puts both groups of pins back to their default state.
If the JTAG pins are used as GPIOs in a design, PB7 and PC2 cannot have external pull-down
resistors connected to both of them at the same time. If both pins are pulled Low during reset, the
controller has unpredictable behavior. If this happens, remove one or both of the pull-down
resistors, and apply RST or power-cycle the part.
In addition, it is possible to create a software sequence that prevents the debugger from connecting
to the Stellaris microcontroller. If the program code loaded into flash immediately changes the
JTAG pins to their GPIO functionality, the debugger may not have enough time to connect and
halt the controller before the JTAG pin functionality switches. This may lock the debugger out of
the part. This can be avoided with a software routine that restores JTAG functionality based on an
external or software trigger.
GPIO Alternate Function Select (GPIOAFSEL)
Offset 0x420
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
-
R/W
-
R/W
-
R/W
-
R/W
-
R/W
-
R/W
-
R/W
-
reserved
Type
Reset
reserved
Type
Reset
AFSEL
Bit/Field
Name
Type
Reset
Description
31:8
reserved
RO
0
7:0
AFSEL
R/W
see note
Reserved bits return an indeterminate value, and should never
be changed.
GPIO Alternate Function Select
0: Software control of corresponding GPIO line (GPIO mode).
1: Hardware control of corresponding GPIO line (alternate
hardware function).
Note:
114
The default reset value for the GPIOAFSEL register is
0x00 for all GPIO pins, with the exception of the five
JTAG pins (PB7 and PC[3:0]). These five pins
default to JTAG functionality. Because of this, the
default reset value of GPIOAFSEL for GPIO Port B is
0x80 while the default reset value of GPIOAFSEL for
Port C is 0x0F.
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 11: GPIO 2-mA Drive Select (GPIODR2R), offset 0x500
The GPIODR2R register is the 2-mA drive control register. It allows for each GPIO signal in the
port to be individually configured without affecting the other pads. When writing a DRV2 bit for a
GPIO signal, the corresponding DRV4 bit in the GPIODR4R register and the DRV8 bit in the
GPIODR8R register are automatically cleared by hardware.
GPIO 2-mA Drive Select (GPIODR2R)
Offset 0x500
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
reserved
Type
Reset
reserved
Type
Reset
DRV2
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
DRV2
R/W
0xFF
Description
Reserved bits return an indeterminate value, and should never
be changed.
Output Pad 2-mA Drive Enable
A write of 1 to either GPIODR4[n] or GPIODR8[n] clears the
corresponding 2-mA enable bit. The change is effective on the
second clock cycle after the write.
October 5, 2006
115
Preliminary
General-Purpose Input/Outputs (GPIOs)
Register 12: GPIO 4-mA Drive Select (GPIODR4R), offset 0x504
The GPIODR4R register is the 4-mA drive control register. It allows for each GPIO signal in the
port to be individually configured without affecting the other pads. When writing the DRV4 bit for a
GPIO signal, the corresponding DRV2 bit in the GPIODR2R register and the DRV8 bit in the
GPIODR8R register are automatically cleared by hardware.
GPIO 4-mA Drive Select (GPIODR4R)
Offset 0x504
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
DRV4
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
DRV4
R/W
0x00
Description
Reserved bits return an indeterminate value, and should never
be changed.
Output Pad 4-mA Drive Enable
A write of 1 to either GPIODR2[n] or GPIODR8[n] clears the
corresponding 4-mA enable bit. The change is effective on the
second clock cycle after the write.
116
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 13: GPIO 8-mA Drive Select (GPIODR8R), offset 0x508
The GPIODR8R register is the 8-mA drive control register. It allows for each GPIO signal in the
port to be individually configured without affecting the other pads. When writing the DRV8 bit for a
GPIO signal, the corresponding DRV2 bit in the GPIODR2R register and the DRV4 bit in the
GPIODR4R register are automatically cleared by hardware.
GPIO 8-mA Drive Select (GPIODR8R)
Offset 0x508
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
DRV8
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
DRV8
R/W
0x00
Description
Reserved bits return an indeterminate value, and should never
be changed.
Output Pad 8-mA Drive Enable
A write of 1 to either GPIODR2[n] or GPIODR4[n] clears the
corresponding 8-mA enable bit. The change is effective on the
second clock cycle after the write.
October 5, 2006
117
Preliminary
General-Purpose Input/Outputs (GPIOs)
Register 14: GPIO Open Drain Select (GPIOODR), offset 0x50C
The GPIOODR register is the open drain control register. Setting a bit in this register enables the
open drain configuration of the corresponding GPIO pad. When open drain mode is enabled, the
corresponding bit should also be set in the GPIO Digital Input Enable (GPIODEN) register (see
page 122). Corresponding bits in the drive strength registers (GPIODR2R, GPIODR4R,
GPIODR8R, and GPIOSLR) can be set to achieve the desired rise and fall times. The GPIO acts
as an open drain input if the corresponding bit in the GPIODIR register is set to 0; and as an open
drain output when set to 1.
GPIO Open Drain Select (GPIOODR)
Offset 0x50C
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
ODE
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
ODE
R/W
0x00
Description
Reserved bits return an indeterminate value, and should never
be changed.
Output Pad Open Drain Enable
0: Open drain configuration is disabled.
1: Open drain configuration is enabled.
118
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 15: GPIO Pull-Up Select (GPIOPUR), offset 0x510
The GPIOPUR register is the pull-up control register. When a bit is set to 1, it enables a weak
pull-up resistor on the corresponding GPIO signal. Setting a bit in GPIOPUR automatically clears
the corresponding bit in the GPIO Pull-Down Select (GPIOPDR) register (see page 120).
GPIO Pull-Up Select (GPIOPUR)
Offset 0x510
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
reserved
Type
Reset
reserved
Type
Reset
PUE
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PUE
R/W
0xFF
Description
Reserved bits return an indeterminate value, and should never
be changed.
Pad Weak Pull-Up Enable
A write of 1 to GPIOPDR[n] clears the corresponding
GPIOPUR[n] enables. The change is effective on the second
clock cycle after the write.
October 5, 2006
119
Preliminary
General-Purpose Input/Outputs (GPIOs)
Register 16: GPIO Pull-Down Select (GPIOPDR), offset 0x514
The GPIOPDR register is the pull-down control register. When a bit is set to 1, it enables a weak
pull-down resistor on the corresponding GPIO signal. Setting a bit in GPIOPDR automatically
clears the corresponding bit in the GPIO Pull-Up Select (GPIOPUR) register (see page 119).
GPIO Pull-Down Select (GPIOPDR)
Offset 0x514
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
PDE
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PDE
R/W
0x00
Description
Reserved bits return an indeterminate value, and should never
be changed.
Pad Weak Pull-Down Enable
A write of 1 to GPIOPUR[n] clears the corresponding
GPIOPDR[n] enables. The change is effective on the second
clock cycle after the write.
120
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 17: GPIO Slew Rate Control Select (GPIOSLR), offset 0x518
The GPIOSLR register is the slew rate control register. Slew rate control is only available when
using the 8-mA drive strength option via the GPIO 8-mA Drive Select (GPIODR8R) register (see
page 117).
GPIO Slew Rate Control Select (GPIOSLR)
Offset 0x518
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
SRL
Bit/Field
Name
Type
Reset
Description
31:8
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
7:0
SRL
R/W
0
Slew Rate Limit Enable (8-mA drive only)
0: Slew rate control disabled.
1: Slew rate control enabled.
October 5, 2006
121
Preliminary
General-Purpose Input/Outputs (GPIOs)
Register 18: GPIO Digital Input Enable (GPIODEN), offset 0x51C
The GPIODEN register is the digital input enable register. By default, all GPIO signals are
configured as digital inputs at reset. The only time that a pin should not be configured as a digital
input is when the GPIO pin is configured to be one of the analog input signals for the analog
comparators.
GPIO Digital Input Enable (GPIODEN)
Offset 0x51C
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
reserved
Type
Reset
reserved
Type
Reset
DEN
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
DEN
R/W
0xFF
Description
Reserved bits return an indeterminate value, and should never
be changed.
Digital-Input Enable
0: Digital input disabled
1: Digital input enabled
122
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 19: GPIO Peripheral Identification 4 (GPIOPeriphID4), offset 0xFD0
The GPIOPeriphID4, GPIOPeriphID5, GPIOPeriphID6, and GPIOPeriphID7 registers can
conceptually be treated as one 32-bit register; each register contains eight bits of the 32-bit
register, used by software to identify the peripheral.
GPIO Peripheral Identification 4 (GPIOPeriphID4)
Offset 0xFD0
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID4
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID4
RO
0x00
Description
Reserved bits return an indeterminate value, and should
never be changed.
GPIO Peripheral ID Register[7:0]
October 5, 2006
123
Preliminary
General-Purpose Input/Outputs (GPIOs)
Register 20: GPIO Peripheral Identification 5 (GPIOPeriphID5), offset 0xFD4
The GPIOPeriphID4, GPIOPeriphID5, GPIOPeriphID6, and GPIOPeriphID7 registers can
conceptually be treated as one 32-bit register; each register contains eight bits of the 32-bit
register, used by software to identify the peripheral.
GPIO Peripheral Identification 5 (GPIOPeriphID5)
Offset 0xFD4
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID5
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID5
RO
0x00
Description
Reserved bits return an indeterminate value, and should
never be changed.
GPIO Peripheral ID Register[15:8]
124
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 21: GPIO Peripheral Identification 6 (GPIOPeriphID6), offset 0xFD8
The GPIOPeriphID4, GPIOPeriphID5, GPIOPeriphID6, and GPIOPeriphID7 registers can
conceptually be treated as one 32-bit register; each register contains eight bits of the 32-bit
register, used by software to identify the peripheral.
GPIO Peripheral Identification 6 (GPIOPeriphID6)
Offset 0xFD8
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID6
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID6
RO
0x00
Description
Reserved bits return an indeterminate value, and should
never be changed.
GPIO Peripheral ID Register[23:16]
October 5, 2006
125
Preliminary
General-Purpose Input/Outputs (GPIOs)
Register 22: GPIO Peripheral Identification 7 (GPIOPeriphID7), offset 0xFDC
The GPIOPeriphID4, GPIOPeriphID5, GPIOPeriphID6, and GPIOPeriphID7 registers can
conceptually be treated as one 32-bit register; each register contains eight bits of the 32-bit
register, used by software to identify the peripheral.
GPIO Peripheral Identification 7 (GPIOPeriphID7)
Offset 0xFDC
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID7
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID7
RO
0x00
Description
Reserved bits return an indeterminate value, and should
never be changed.
GPIO Peripheral ID Register[31:24]
126
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 23: GPIO Peripheral Identification 0 (GPIOPeriphID0), offset 0xFE0
The GPIOPeriphID0, GPIOPeriphID1, GPIOPeriphID2, and GPIOPeriphID3 registers can
conceptually be treated as one 32-bit register; each register contains eight bits of the 32-bit
register, used by software to identify the peripheral.
GPIO Peripheral Identification 0 (GPIOPeriphID0)
Offset 0xFE0
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
1
RO
0
RO
0
RO
0
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
PID0
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID0
RO
0x61
Description
Reserved bits return an indeterminate value, and should never
be changed.
GPIO Peripheral ID Register[7:0]
Can be used by software to identify the presence of this
peripheral.
October 5, 2006
127
Preliminary
General-Purpose Input/Outputs (GPIOs)
Register 24: GPIO Peripheral Identification 1(GPIOPeriphID1), offset 0xFE4
The GPIOPeriphID0, GPIOPeriphID1, GPIOPeriphID2, and GPIOPeriphID3 registers can
conceptually be treated as one 32-bit register; each register contains eight bits of the 32-bit
register, used by software to identify the peripheral.
GPIO Peripheral Identification 1 (GPIOPeriphID1)
Offset 0xFE4
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID1
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID1
RO
0x00
Description
Reserved bits return an indeterminate value, and should never
be changed.
GPIO Peripheral ID Register[15:8]
Can be used by software to identify the presence of this
peripheral.
128
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 25: GPIO Peripheral Identification 2 (GPIOPeriphID2), offset 0xFE8
The GPIOPeriphID0, GPIOPeriphID1, GPIOPeriphID2, and GPIOPeriphID3 registers can
conceptually be treated as one 32-bit register; each register contains eight bits of the 32-bit
register, used by software to identify the peripheral.
GPIO Peripheral Identification 2 (GPIOPeriphID2)
Offset 0xFE8
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
1
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID2
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID2
RO
0x18
Description
Reserved bits return an indeterminate value, and should never
be changed.
GPIO Peripheral ID Register[23:16]
Can be used by software to identify the presence of this
peripheral.
October 5, 2006
129
Preliminary
General-Purpose Input/Outputs (GPIOs)
Register 26: GPIO Peripheral Identification 3 (GPIOPeriphID3), offset 0xFEC
The GPIOPeriphID0, GPIOPeriphID1, GPIOPeriphID2, and GPIOPeriphID3 registers can
conceptually be treated as one 32-bit register; each register contains eight bits of the 32-bit
register, used by software to identify the peripheral.
GPIO Peripheral Identification 3 (GPIOPeriphID3)
Offset 0xFEC
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
PID3
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID3
RO
0x01
Description
Reserved bits return an indeterminate value, and should never
be changed.
GPIO Peripheral ID Register[31:24]
Can be used by software to identify the presence of this
peripheral.
130
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 27: GPIO PrimeCell Identification 0 (GPIOPCellID0), offset 0xFF0
The GPIOPCellID0, GPIOPCellID1, GPIOPCellID2, and GPIOPCellID3 registers are four 8-bit
wide registers, that can conceptually be treated as one 32-bit register. The register is used as a
standard cross-peripheral identification system.
GPIO Primecell Identification 0 (GPIOPCellID0)
Offset 0xFF0
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
1
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
CID0
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
CID0
RO
0x0D
Description
Reserved bits return an indeterminate value, and should never
be changed.
GPIO PrimeCell ID Register[7:0]
Provides software a standard cross-peripheral identification
system.
October 5, 2006
131
Preliminary
General-Purpose Input/Outputs (GPIOs)
Register 28: GPIO PrimeCell Identification 1 (GPIOPCellID1), offset 0xFF4
The GPIOPCellID0, GPIOPCellID1, GPIOPCellID2, and GPIOPCellID3 registers are four 8-bit
wide registers, that can conceptually be treated as one 32-bit register. The register is used as a
standard cross-peripheral identification system.
GPIO Primecell Identification 1 (GPIOPCellID1)
Offset 0xFF4
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
1
RO
1
RO
1
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
CID1
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
CID1
RO
0xF0
Description
Reserved bits return an indeterminate value, and should never
be changed.
GPIO PrimeCell ID Register[15:8]
Provides software a standard cross-peripheral identification
system.
132
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 29: GPIO PrimeCell Identification 2 (GPIOPCellID2), offset 0xFF8
The GPIOPCellID0, GPIOPCellID1, GPIOPCellID2, and GPIOPCellID3 registers are four 8-bit
wide registers, that can conceptually be treated as one 32-bit register. The register is used as a
standard cross-peripheral identification system.
GPIO Primecell Identification 2 (GPIOPCellID2)
Offset 0xFF8
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
CID2
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
CID2
RO
0x05
Description
Reserved bits return an indeterminate value, and should never
be changed.
GPIO PrimeCell ID Register[23:16]
Provides software a standard cross-peripheral identification
system.
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General-Purpose Input/Outputs (GPIOs)
Register 30: GPIO PrimeCell Identification 3 (GPIOPCellID3), offset 0xFFC
The GPIOPCellID0, GPIOPCellID1, GPIOPCellID2, and GPIOPCellID3 registers are four 8-bit
wide registers, that can conceptually be treated as one 32-bit register. The register is used as a
standard cross-peripheral identification system.
GPIO Primecell Identification 3 (GPIOPCellID3)
Offset 0xFFC
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
0
RO
1
RO
1
RO
0
RO
0
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
CID3
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
CID3
RO
0xB1
Description
Reserved bits return an indeterminate value, and should never
be changed.
GPIO PrimeCell ID Register[31:24]
Provides software a standard cross-peripheral identification
system.
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LM3S101 Data Sheet
9
General-Purpose Timers
Programmable timers can be used to count or time external events that drive the Timer input pins.
The LM3S101 controller General-Purpose Timer Module (GPTM) contains two GPTM blocks
(Timer0 and Timer1). Each GPTM block provides two 16-bit timer/counters (referred to as TimerA
and TimerB) that can be configured to operate independently as timers or event counters, or
configured to operate as one 32-bit timer or one 32-bit Real-Time Clock (RTC).
The following modes are supported:

32-bit Timer modes:
– Programmable one-shot timer
– Programmable periodic timer
– Real-Time Clock using 32.768-KHz input clock
– Software-controlled event stalling (excluding RTC mode)

16-bit Timer modes:
– General-purpose timer function with an 8-bit prescaler
– Programmable one-shot timer
– Programmable periodic timer
– Software-controlled event stalling

16-bit Input Capture modes:
– Input edge count capture
– Input edge time capture

16-bit PWM mode:
– Simple PWM mode with software-programmable output inversion of the PWM signal
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9.1
Block Diagram
Figure 9-1. GPTM Module Block Diagram
0x0000 (Down Counter Modes )
TimerA Control
GPTMTAPMR
TA Comparator
GPTMTAPR
Clock / Edge
Detect
GPTMTAMATCHR
Interrupt / Config
TimerA
Interrupt
GPTMCFG
GPTMTAILR
GPTMAR
En
GPTMCTL
GPTMIMR
TimerB
Interrupt
32KHz
GPTMTAMR
RTC Divider
GPTMRIS
GPTMMIS
TimerB Control
GPTMICR
GPTMTBR
GPTMTBPMR
En
Clock / Edge
Detect
GPTMTBPR
GPTMTBMATCHR
CCP1
TB Comparator
GPTMTBILR
GPTMTBMR
0x0000 (Down Counter Modes )
System
Clock
9.2
Functional Description
The main components of each GPTM block are two free-running 16-bit up/down counters (referred
to as TimerA and TimerB), two 16-bit match registers, two prescaler match registers, and two
16-bit load/initialization registers and their associated control functions. The exact functionality of
each GPTM is controlled by software and configured through the register interface.
Software configures the GPTM using the GPTM Configuration (GPTMCFG) register (see
page 147), the GPTM TimerA Mode (GPTMTAMR) register (see page 148), and the GPTM
TimerB Mode (GPTMTBMR) register (see page 149). When in one of the 32-bit modes, the timer
can only act as a 32-bit timer. However, when configured in 16-bit mode, the GPTM can have its
two 16-bit timers configured in any combination of the 16-bit modes.
9.2.1
GPTM Reset Conditions
After reset has been applied to the GPTM module, the module is in an inactive state, and all
control registers are cleared and in their default states. Counters TimerA and TimerB are initialized
to 0xFFFF, along with their corresponding load registers: the GPTM TimerA Interval Load
(GPTMTAILR) register (see page 157) and the GPTM TimerB Interval Load (GPTMTBILR)
register (see page 158). The prescale counters are initialized to 0x00: the GPTM TimerA
Prescale (GPTMTAPR) register (see page 161) and the GPTM TimerB Prescale (GPTMTBPR)
register (see page 162).
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9.2.2
32-Bit Timer Operating Modes
Note:
Both the odd- and even-numbered CCP pins are used for 16-bit mode. Only the
even-numbered CCP pins are used for 32-bit mode.
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 157

GPTM TimerB Interval Load (GPTMTBILR) register [15:0], see page 158

GPTM TimerA (GPTMTAR) register [15:0], see page 165

GPTM TimerB (GPTMTBR) register [15:0], see page 166
In the 32-bit modes, the GPTM translates a 32-bit write access to GPTMTAILR into a write access
to both GPTMTAILR and GPTMTBILR. The resulting word ordering for such a write operation is:
GPTMTBILR[15:0]:GPTMTAILR[15:0]. Likewise, a read access to GPTMTAR returns the
value: GPTMTBR[15:0]:GPTMTAR[15:0].
9.2.2.1
32-Bit One-Shot/Periodic Timer Mode
In 32-bit one-shot and periodic timer modes, the concatenated versions of the TimerA and TimerB
registers are configured as a 32-bit down-counter. The selection of one-shot or periodic mode is
determined by the value written to the TAMR field of the GPTM TimerA Mode (GPTMTAMR)
register (see page 148), 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 150), the
timer begins counting down from its preloaded value. Once the 0x00000000 state is reached, the
timer reloads its start value from the concatenated GPTMTAILR on the next cycle. If configured to
be a one-shot timer, the timer stops counting and clears the TAEN bit in the GPTMCTL register. If
configured as a periodic timer, it continues counting.
In addition to reloading the count value, the GPTM generates interrupts and output triggers when it
reaches the 0x0000000 state. The GPTM sets the TATORIS bit in the GPTM Raw Interrupt
Status (GPTMRIS) register (see page 154), and holds it until it is cleared by writing the GPTM
Interrupt Clear (GPTMICR) register (see page 156). If the time-out interrupt is enabled in the
GPTM Interrupt Mask (GPTIMR) register (see page 152), the GPTM also sets the TATOMIS bit in
the GPTM Masked Interrupt Status (GPTMISR) register (see page 155).
The output trigger is a one-clock-cycle pulse that is asserted when the counter hits the
0x00000000 state, and deasserted on the following clock cycle. It is enabled by setting the TAOTE
bit in GPTMCTL.
If software reloads the GPTMTAILR register while the counter is running, the counter loads the
new value on the next clock cycle and continues counting from the new value.
If the TASTALL bit in the GPTMCTL register is asserted, the timer freezes counting until the signal
is deasserted.
9.2.2.2
32-Bit Real-Time Clock Timer Mode
In Real-Time Clock (RTC) mode, the concatenated versions of the TimerA and TimerB registers
are configured as a 32-bit up-counter. When RTC mode is selected for the first time, the counter is
loaded with a value of 0x00000001. All subsequent load values must be written to the GPTM
TimerA Match (GPTMTAMATCHR) register (see page 159) by the controller.
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General-Purpose Timers
The 32KHZ pin is dedicated to the 32-bit RTC function, and the input clock is 32.768 KHz.
When software writes the TAEN bit in GPTMCTL, the counter starts counting up from its preloaded
value of 0x00000001. When the current count value matches the preloaded value in
GPTMTAMATCHR, it rolls over to a value of 0x00000000 and continues counting until either a
hardware reset, or it is disabled by software (clearing the TAEN bit). When a match occurs, the
GPTM asserts the RTCRIS bit in GPTMRIS. If the RTC interrupt is enabled in GPTIMR, the GPTM
also sets the RTCMIS bit in GPTMISR and generates a controller interrupt. The status flags are
cleared by writing the RTCCINT bit in GPTMICR.
If the TASTALL and/or TBSTALL bits in the GPTMCTL register are set, the timer does not freeze if
the RTCEN bit is set in GPTMCTL.
9.2.3
16-Bit Timer Operating Modes
The GPTM is placed into global 16-bit mode by writing a value of 0x4 to the GPTM Configuration
(GPTMCFG) register (see page 147). This section describes each of the GPTM 16-bit modes of
operation. Timer A and Timer B have identical modes, so a single description is given using an n
to reference both.
9.2.3.1
16-Bit One-Shot/Periodic Timer Mode
In 16-bit one-shot and periodic timer modes, the timer is configured as a 16-bit down-counter with
an optional 8-bit prescaler that effectively extends the counting range of the timer to 24 bits. The
selection of one-shot or periodic mode is determined by the value written to the TnMR field of the
GPTMTnMR register. The optional prescaler is loaded into the GPTM Timern Prescale
(GPTMTnPR) register.
When software writes the TnEN bit in the GPTMCTL register, the timer begins counting down from
its preloaded value. Once the 0x0000 state is reached, the timer reloads its start value from
GPTMTnILR and GPTMTnPR on the next cycle. If configured to be a one-shot timer, the timer
stops counting and clears the TnEN bit in the GPTMCTL register. If configured as a periodic timer,
it continues counting.
In addition to reloading the count value, the timer generates interrupts and output triggers when it
reaches the 0x0000 state. The GPTM sets the TnTORIS bit in the GPTMRIS register, and holds it
until it is cleared by writing the GPTMICR register. If the time-out interrupt is enabled in GPTIMR,
the GPTM also sets the TnTOMIS bit in GPTMISR and generates a controller interrupt.
The output trigger is a one-clock-cycle pulse that is asserted when the counter hits the 0x0000
state, and deasserted on the following clock cycle. It is enabled by setting the TnOTE bit in the
GPTMCTL register, and can trigger SoC-level events.
If software reloads the GPTMTAILR register while the counter is running, the counter loads the
new value on the next clock cycle and continues counting from the new value.
If the TnSTALL bit in the GPTMCTL register is enabled, the timer freezes counting until the signal
is deasserted.
The following example shows a variety of configurations for a 16-bit free running timer while using
the prescaler. All values assume a 20-MHz clock with Tc=20 ns (clock period).
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Table 9-1. 16-Bit Timer With Prescaler Configurations
Prescale
#Clock (TC)a
Max Time
Units
00000000
1
3.2768
mS
00000001
2
6.554
mS
00000010
3
9.8302
mS
------------
--
11111100
254
832.3073
mS
11111110
255
835.584
mS
11111111
256
838.8608
mS
a. TC is the clock period.
9.2.3.2
16-Bit Input Edge Count Mode
In Edge Count mode, the timer is configured as a down-counter capable of capturing three types
of events: rising edge, falling edge, or both. To place the timer in Edge Count mode, the TnCMR bit
of the GPTMTnMR register must be set to 0. The type of edge that the timer counts is determined
by the TnEVENT fields of the GPTMCTL register. During initialization, the GPTM Timern Match
(GPTMTnMATCHR) register is configured so that the difference between the value in the
GPTMTnILR register and the GPTMTnMATCHR register equals the number of edge events that
must be counted.
When software writes the TnEN bit in the GPTM Control (GPTMCTL) register, the timer is enabled
for event capture. Each input event on the CCP pin decrements the counter by 1 until the event
count matches GPTMTnMATCHR. When the counts match, the GPTM asserts the CnMRIS bit in
the GPTMRIS register (and the CnMMIS bit, if the interrupt is not masked). The counter is then
reloaded using the value in GPTMTnILR, and stopped since the GPTM automatically clears the
TnEN bit in the GPTMCTL register. Once the event count has been reached, all further events are
ignored until TnEN is re-enabled by software.
Figure 9-2 shows how input edge count mode works. In this case, the timer start value is set to
GPTMnILR=0x000A and the match value is set to GPTMnMATCHR=0x0006 so that four edge
events are counted. The counter is configured to detect both edges of the input signal.
Note that the last two edges are not counted since the timer automatically clears the TnEN bit after
the current count matches the value in the GPTMnMR register.
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General-Purpose Timers
Figure 9-2. 16-Bit Input Edge Count Mode Example
Timer reload
on next cycle
Count
Ignored
Ignored
0x000A
0x0009
0x0008
0x0007
0x0006
Timer stops,
flags
asserted
Input Signal
9.2.3.3
16-Bit Input Edge Time Mode
In Edge Time mode, the timer is configured as a free-running down-counter initialized to the value
loaded in the GPTMTnILR register (or 0xFFFF at reset). This mode allows for event capture of
both rising and falling edges. The timer is placed into Edge Time mode by setting the TnCMR bit in
the GPTMTnMR register, and the type of event that the timer captures is determined by the
TnEVENT fields of the GPTMCTL register.
When software writes the TnEN bit in the GPTMCTL register, the timer is enabled for event
capture. When the selected input event is detected, the current Tn counter value is captured in the
GPTMTnR register and is available to be read by the controller. The GPTM then asserts the
CnERIS bit (and the CnEMIS bit, if the interrupt is not masked).
After an event has been captured, the timer does not stop counting. It continues to count until the
TnEN bit is cleared. When the timer reaches the 0x0000 state, it is reloaded with the value from the
GPTMnILR register.
Figure 9-3 shows how input edge timing mode works. In the diagram, it is assumed that the start
value of the timer is the default value of 0xFFFF, and the timer is configured to capture rising edge
events.
Each time a rising edge event is detected, the current count value is loaded into the GPTMTnR
register, and is held there until another rising edge is detected (at which point the new count value
is loaded into GPTMTnR).
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Figure 9-3. 16-Bit Input Edge Time Mode Example
Count
0xFFFF
GPTMTnR=X
GPTMTnR=Y
GPTMTnR=Z
Z
X
Y
Time
Input Signal
9.2.3.4
16-Bit PWM Mode
The GPTM supports a simple PWM generation mode. In PWM mode, the timer is configured as a
down-counter with a start value (and thus period) defined by GPTMTnILR. PWM mode is enabled
with the GPTMTnMR register by setting the TnAMS bit to 0x1, the TNCMR bit to 0x0, and the TnMR
field to 0x2.
PWM mode can take advantage of the 8-bit prescaler by using the GPTM Timern Prescale
Register (GPTMTnPR) and the GPTM Timern Prescale Match Register (GPTMTnPMR). This
effectively extends the range of the timer to 24 bits.
When software writes the TnEN bit in the GPTMCTL register, the counter begins counting down
until it reaches the 0x0000 state. On the next counter cycle, the counter reloads its start value from
GPTMTnILR (and GPTMTnPR if using a prescaler) and continues counting until disabled by
software clearing the TnEN bit in the GPTMCTL register. No interrupts or status bits are asserted
in PWM mode.
The output PWM signal asserts when the counter is at the value of the GPTMTnILR register (its
start state), and is deasserted when the counter value equals the value in the GPTM Timern
Match Register (GPTMnMATCHR). Software has the capability of inverting the output PWM
signal by setting the TnPWML bit in the GPTMCTL register.
Figure 9-4 shows how to generate an output PWM with a 1-ms period and a 66% duty cycle
assuming a 50-MHz input clock and TnPWML=0 (duty cycle would be 33% for the TnPWML=1
configuration). For this example, the start value is GPTMnIRL=0xC350 and the match value is
GPTMnMR=0x411A.
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General-Purpose Timers
Figure 9-4. 16-Bit PWM Mode Example
Count
GPTMTnR=GPTMnMR
GPTMTnR=GPTMnMR
0xC350
0x411A
Time
TnEN set
TnPWML = 0
Output
Signal
TnPWML = 1
9.3
Initialization and Configuration
To use the general-purpose timers, the peripheral clock must be enabled by setting the GPTM0 and
GPTM1 bits in the RCGC1 register.
This section shows module initialization and configuration examples for each of the supported
timer modes.
9.3.1
32-Bit One-Shot/Periodic Timer Mode
The GPTM is configured for 32-bit One-Shot and Periodic modes by the following sequence:
1. Ensure the timer is disabled (the TAEN bit in the GPTMCTL register is cleared) before making
any changes.
2. Write the GPTM Configuration Register (GPTMCFG) with a value of 0x0.
3. Set the TAMR field in the GPTM TimerA Mode Register (GPTMTAMR):
a. Write a value of 0x1 for One-Shot mode.
b. Write a value of 0x2 for Periodic mode.
4. Load the start value into the GPTM TimerA Interval Load Register (GPTMTAILR).
5. If interrupts are required, set the TATOIM bit in the GPTM Interrupt Mask Register
(GPTMIMR).
6. Set the TAEN bit in the GPTMCTL register to enable the timer and start counting.
7. Poll the TATORIS bit in the GPTMRIS register or wait for the interrupt to be generated (if
enabled). In both cases, the status flags are cleared by writing a 1 to the TATOCINT bit of the
GPTM Interrupt Clear Register (GPTMICR).
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In One-Shot mode, the timer stops counting after step 7. To re-enable the timer, repeat the
sequence. A timer configured in Periodic mode does not stop counting after it times out.
9.3.2
32-Bit Real-Time Clock (RTC) Mode
To use the RTC mode, the timer must have a 32.768-KHz input signal on its 32KHz pin. To enable
the RTC feature, follow these steps:
1. Ensure the timer is disabled (the TAEN bit is cleared) before making any changes.
2. Write the GPTM Configuration Register (GPTMCFG) with a value of 0x1.
3. Write the desired match value to the GPTM TimerA Match Register (GPTMTAMATCHR).
4. Set/clear the RTCEN bit in the GPTM Control Register (GPTMCTL) as desired.
5. If interrupts are required, set the RTCIM bit in the GPTM Interrupt Mask Register
(GPTMIMR).
6. Set the TAEN bit in the GPTMCTL register to enable the timer and start counting.
When the timer count equals the value in the GPTMTAMATCHR register, the counter is re-loaded
with 0x00000000 and begins counting. If an interrupt is enabled, it does not have to be cleared.
9.3.3
16-Bit One-Shot/Periodic Timer Mode
A timer is configured for 16-bit One-Shot and Periodic modes by the following sequence:
1. Ensure the timer is disabled (the TnEN bit is cleared) before making any changes.
2. Write the GPTM Configuration Register (GPTMCFG) with a value of 0x4.
3. Set the TnMR field in the GPTM Timer Mode (GPTMTnMR) register:
a. Write a value of 0x1 for One-Shot mode.
b. Write a value of 0x2 for Periodic mode.
4. If a prescaler is to be used, write the prescale value to the GPTM Timern Prescale Register
(GPTMTnPR).
5. Load the start value into the GPTM Timer Interval Load Register (GPTMTnILR).
6. If interrupts are required, set the TnTOIM bit in the GPTM Interrupt Mask Register
(GPTMIMR).
7. Set the TnEN bit in the GPTM Control Register (GPTMCTL) to enable the timer and start
counting.
8. Poll the TnTORIS bit in the GPTMRIS register or wait for the interrupt to be generated (if
enabled). In both cases, the status flags are cleared by writing a 1 to the TnTOCINT bit of the
GPTM Interrupt Clear Register (GPTMICR).
In One-Shot mode, the timer stops counting after step 8. To re-enable the timer, repeat the
sequence. A timer configured in Periodic mode does not stop counting after it times out.
9.3.4
16-Bit Input Edge Count Mode
A timer is configured to Input Edge Count mode by the following sequence:
1. Ensure the timer is disabled (the TnEN bit is cleared) before making any changes.
2. Write the GPTM Configuration (GPTMCFG) register with a value of 0x4.
3. In the GPTM Timer Mode (GPTMTnMR) register, write the TnCMR field to 0x0 and the TnMR
field to 0x3.
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4. Configure the type of event(s) that the timer captures by writing the TnEVENT field of the
GPTM Control (GPTMCTL) register.
5. Load the timer start value into the GPTM Timern Interval Load (GPTMTnILR) register.
6. Load the desired event count into the GPTM Timern Match (GPTMTnMATCHR) register.
7. If interrupts are required, set the CnMIM bit in the GPTM Interrupt Mask (GPTMIMR) register.
8. Set the TnEN bit in the GPTMCTL register to enable the timer and begin waiting for edge
events.
9. Poll the CnMRIS bit in the GPTMRIS register or wait for the interrupt to be generated (if
enabled). In both cases, the status flags are cleared by writing a 1 to the CnMCINT bit of the
GPTM Interrupt Clear (GPTMICR) register.
In Input Edge Count Mode, the timer stops after the desired number of edge events has been
detected. To re-enable the timer, ensure that the TnEN bit is cleared and repeat steps 4-9.
9.3.5
16-Bit Input Edge Timing Mode
A timer is configured to Input Edge Timing mode by the following sequence:
1. Ensure the timer is disabled (the TnEN bit is cleared) before making any changes.
2. Write the GPTM Configuration (GPTMCFG) register with a value of 0x4.
3. In the GPTM Timer Mode (GPTMTnMR) register, write the TnCMR field to 0x1 and the TnMR
field to 0x3.
4. Configure the type of event that the timer captures by writing the TnEVENT field of the GPTM
Control (GPTMCTL) register.
5. Load the timer start value into the GPTM Timern Interval Load (GPTMTnILR) register.
6. If interrupts are required, set the CnEIM bit in the GPTM Interrupt Mask (GPTMIMR) register.
7. Set the TnEN bit in the GPTM Control (GPTMCTL) register to enable the timer and start
counting.
8. Poll the CnERIS bit in the GPTMRIS register or wait for the interrupt to be generated (if
enabled). In both cases, the status flags are cleared by writing a 1 to the CnECINT bit of the
GPTM Interrupt Clear (GPTMICR) register. The time at which the event happened can be
obtained by reading the GPTM Timern (GPTMTnR) register.
In Input Edge Timing mode, the timer continues running after an edge event has been detected,
but the timer interval can be changed at any time by writing the GPTMTnILR register. The change
takes effect at the next cycle after the write.
9.3.6
16-Bit PWM Mode
A timer is configured to PWM mode using the following sequence:
1. Ensure the timer is disabled (the TnEN bit is cleared) before making any changes.
2. Write the GPTM Configuration (GPTMCFG) register with a value of 0x4.
3. In the GPTM Timer Mode (GPTMTnMR) register, set the TnAMS bit to 0x1, the TNCMR bit to
0x0, and the TnMR field to 0x2.
4. Configure the output state of the PWM signal (whether or not it is inverted) in the TnEVENT
field of the GPTM Control (GPTMCTL) register.
5. Load the timer start value into the GPTM Timern Interval Load (GPTMTnILR) register.
6. Load the GPTM Timern Match (GPTMTnMATCHR) register with the desired value.
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7. If a prescaler is going to be used, configure the GPTM Timern Prescale (GPTMTnPR)
register and the GPTM Timern Prescale Match (GPTMTnPMR) register.
8. Set the TnEN bit in the GPTM Control (GPTMCTL) register to enable the timer and begin
generation of the output PWM signal.
In PWM Timing mode, the timer continues running after the PWM signal has been generated. The
PWM period can be adjusted at any time by writing the GPTMTnILR register, and the change
takes effect at the next cycle after the write.
9.4
Register Map
Table 9-1 lists the GPTM registers. The offset listed is a hexadecimal increment to the register’s
address, relative to that timer’s base address:

Timer0: 0x40030000

Timer1: 0x40031000
Table 9-2. GPTM Register Map
Type
Description
See
page
0x00000000
R/W
Configuration
147
GPTMTAMR
0x00000000
R/W
TimerA mode
148
0x008
GPTMTBMR
0x00000000
R/W
TimerB mode
149
0x00C
GPTMCTL
0x00000000
R/W
Control
150
0x018
GPTMIMR
0x00000000
R/W
Interrupt mask
152
0x01C
GPTMRIS
0x00000000
RO
Interrupt status
154
0x020
GPTMMIS
0x00000000
RO
Masked interrupt status
155
0x024
GPTMICR
0x00000000
W1C
Interrupt clear
156
0x028
GPTMTAILR
0x0000FFFFa
0xFFFFFFFF
R/W
TimerA interval load
157
0x02C
GPTMTBILR
0x0000FFFF
R/W
TimerB interval load
158
Offset
Name
0x000
GPTMCFG
0x004
Reset
a
0x030
GPTMTAMATCHR
0x0000FFFF
0xFFFFFFFF
R/W
TimerA match
159
0x034
GPTMTBMATCHR
0x0000FFFF
R/W
TimerB match
160
0x038
GPTMTAPR
0x00000000
R/W
TimerA prescale
161
0x03C
GPTMTBPR
0x00000000
R/W
TimerB prescale
162
0x040
GPTMTAPMR
0x00000000
R/W
TimerA prescale match
163
0x044
GPTMTBPMR
0x00000000
R/W
TimerB prescale match
164
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Preliminary
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Table 9-2. GPTM Register Map (Continued)
Offset
Name
0x048
0x04C
See
page
Reset
Type
Description
GPTMTAR
0x0000FFFFa
0xFFFFFFFF
RO
TimerA
165
GPTMTBR
0x0000FFFF
RO
TimerB
166
a. The default reset value for the GPTMTAILR, GPTMTAMATCHR, and GPTMTAR registers is 0x0000FFFF when in 16-bit mode
and 0xFFFFFFFF when in 32-bit mode.
9.5
Register Descriptions
The remainder of this section lists and describes the GPTM registers, in numerical order by
address offset.
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October 5, 2006
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LM3S101 Data Sheet
Register 1: GPTM Configuration (GPTMCFG), offset 0x000
This register configures the global operation of the GPTM module. The value written to this
register determines whether the GPTM is in 32- or 16-bit mode.
GPTM Configuration (GPTMCFG)
Offset 0x000
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
GPTMCFG
R/W
0
R/W
0
Bit/Field
Name
Type
Reset
Description
31:3
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
2:0
GPTMCFG
R/W
0
GPTM Configuration
0x0: 32-bit timer configuration.
0x1: 32-bit real-time clock (RTC) counter configuration.
0x2: Reserved.
0x3: Reserved.
0x4-0x7: 16-bit timer configuration, function is controlled by bits
1:0 of GPTMTAMR and GPTMTBMR.
October 5, 2006
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Preliminary
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Register 2: GPTM TimerA Mode (GPTMTAMR), offset 0x004
This register configures the GPTM based on the configuration selected in the GPTMCFG register.
When in 16-bit PWM mode, set the TAAMS bit to 0x1, the TACMR bit to 0x0, and the TAMR field to
0x2.
GPTM TimerA Mode (GPTMTAMR)
Offset 0x004
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
TAAMS TACMR
reserved
Type
Reset
R/W
0
R/W
0
TAMR
R/W
0
R/W
0
Bit/Field
Name
Type
Reset
Description
31:4
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
3
TAAMS
R/W
0
GPTM TimerA Alternate Mode Select
0: Capture mode is enabled.
1: PWM mode is enabled.
Note:
2
TACMR
R/W
0
To enable PWM mode, you must also clear the TACMR
bit and set the TAMR field to 0x2.
GPTM TimerA Capture Mode
0: Edge-Count mode.
1: Edge-Time mode.
1:0
TAMR
R/W
0
GPTM TimerA Mode
0x0: Reserved.
0x1: One-Shot Timer mode.
0x2: Periodic Timer mode.
0x3: Capture mode.
The Timer mode is based on the timer configuration defined by
bits 2:0 in the GPTMCFG register (16-or 32-bit).
In 16-bit timer configuration, TAMR controls the 16-bit timer
modes for TimerA.
In 32-bit timer configuration, this register controls the mode and
the contents of GPTMTBMR are ignored.
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LM3S101 Data Sheet
Register 3: GPTM TimerB Mode (GPTMTBMR), offset 0x008
This register configures the GPTM based on the configuration selected in the GPTMCFG register.
When in 16-bit PWM mode, set the TBAMS bit to 0x1, the TBCMR bit to 0x0, and the TBMR field to
0x2.
GPTM TimerB Mode (GPTMTBMR)
Offset 0x008
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
TBAMS TBCMR
reserved
Type
Reset
R/W
0
R/W
0
TBMR
R/W
0
R/W
0
Bit/Field
Name
Type
Reset
Description
31:4
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
3
TBAMS
R/W
0
GPTM TimerB Alternate Mode Select
0: Capture mode is enabled.
1: PWM mode is enabled.
Note:
2
TBCMR
R/W
0
To enable PWM mode, you must also clear the TBCMR
bit and set the TBMR field to 0x2.
GPTM TimerB Capture Mode
0: Edge-Count mode.
1: Edge-Time mode.
1:0
TBMR
R/W
0
GPTM TimerB Mode
0x0: Reserved.
0x1: One-Shot Timer mode.
0x2: Periodic Timer mode.
0x3: Capture mode.
The timer mode is based on the timer configuration defined by
bits 2:0 in the GPTMCFG register.
In 16-bit timer configuration, these bits control the 16-bit timer
modes for TimerB.
In 32-bit timer configuration, this register’s contents are ignored
and GPTMTAMR is used.
October 5, 2006
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Preliminary
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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.
GPTM Control (GPTMCTL)
Offset 0x00C
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
res
TBPWML
TBOTE
res
RO
0
R/W
0
R/W
0
RO
0
TBSTALL
TBEN
res
TASTALL
TAEN
R/W
0
R/W
0
RO
0
R/W
0
R/W
0
reserved
Type
Reset
Type
Reset
TBEVENT
R/W
0
R/W
0
TAPWML TAOTE
R/W
0
R/W
0
RTCEN
R/W
0
TAEVENT
R/W
0
R/W
0
Bit/Field
Name
Type
Reset
Description
31:15
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
14
TBPWML
R/W
0
GPTM TimerB PWM Output Level
0: Output is unaffected.
1: Output is inverted.
13
TBOTE
R/W
0
GPTM TimerB Output Trigger Enable
0: The output TimerB trigger is disabled.
1: The output TimerB trigger is enabled.
12
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
11:10
TBEVENT
R/W
0
GPTM TimerB Event Mode
00: Positive edge.
01: Negative edge.
10: Reserved.
11: Both edges.
9
TBSTALL
R/W
0
GPTM TimerB Stall Enable
0: TimerB stalling is disabled.
1: TimerB stalling is enabled.
8
TBEN
R/W
0
GPTM TimerB Enable
0: TimerB is disabled.
1: TimerB is enabled and begins counting or the capture logic is
enabled based on the GPTMCFG register.
7
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
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LM3S101 Data Sheet
Bit/Field
Name
Type
Reset
6
TAPWML
R/W
0
Description
GPTM TimerA PWM Output Level
0: Output is unaffected.
1: Output is inverted.
5
TAOTE
R/W
0
GPTM TimerA Output Trigger Enable
0: The output TimerA trigger is disabled.
1: The output TimerA trigger is enabled.
4
RTCEN
R/W
0
GPTM RTC Enable
0: RTC counting is disabled.
1: RTC counting is enabled.
3:2
TAEVENT
R/W
0
GPTM TimerA Event Mode
00: Positive edge.
01: Negative edge.
10: Reserved.
11: Both edges.
1
TASTALL
R/W
0
GPTM TimerA Stall Enable
0: TimerA stalling is disabled.
1: TimerA stalling is enabled.
0
TAEN
R/W
0
GPTM TimerA Enable
0: TimerA is disabled.
1: TimerA is enabled and begins counting or the capture logic is
enabled based on the GPTMCFG register.
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Register 5: GPTM Interrupt Mask (GPTMIMR), offset 0x018
This register allows software to enable/disable GPTM controller-level interrupts. Writing a 1
enables the interrupt, while writing a 0 disables it.
GPTM Interrupt Mask (GPTMIMR)
Offset 0x018
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
CBEIM CBMIM TBTOIM
reserved
Type
Reset
RO
0
R/W
0
R/W
0
R/W
0
reserved
RTCIM
R/W
0
CAEIM CAMIM TATOIM
R/W
0
R/W
0
R/W
0
Bit/Field
Name
Type
Reset
Description
31:11
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
10
CBEIM
R/W
0
GPTM CaptureB Event Interrupt Mask
0: Interrupt is disabled.
1: Interrupt is enabled.
9
CBMIM
R/W
0
GPTM CaptureB Match Interrupt Mask
0: Interrupt is disabled.
1: Interrupt is enabled.
8
TBTOIM
R/W
0
GPTM TimerB Time-Out Interrupt Mask
0: Interrupt is disabled.
1: Interrupt is enabled.
7:4
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
3
RTCIM
R/W
0
GPTM RTC Interrupt Mask
0: Interrupt is disabled.
1: Interrupt is enabled.
2
CAEIM
R/W
0
GPTM CaptureA Event Interrupt Mask
0: Interrupt is disabled.
1: Interrupt is enabled.
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LM3S101 Data Sheet
Bit/Field
Name
Type
Reset
1
CAMIM
R/W
0
Description
GPTM CaptureA Match Interrupt Mask
0: Interrupt is disabled.
1: Interrupt is enabled.
0
TATOIM
R/W
0
GPTM TimerA Time-Out Interrupt Mask
0: Interrupt is disabled.
1: Interrupt is enabled.
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Preliminary
General-Purpose Timers
Register 6: GPTM Raw Interrupt Status (GPTMRIS), offset 0x01C
This register shows the state of the GPTM's internal interrupt signal. These bits are set whether or
not the interrupt is masked in the GPTMIMR register. Each bit can be cleared by writing a 1 to its
corresponding bit in GPTMICR.
GPTM Raw Interrupt Status (GPTMRIS)
Offset 0x01C
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RTCRIS
CAERIS
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
CBERIS
reserved
CBMRIS TBTORIS
RO
0
RO
0
RO
0
CAMRIS TATORIS
RO
0
RO
0
Bit/Field
Name
Type
Reset
Description
31:11
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
10
CBERIS
RO
0
GPTM CaptureB Event Raw Interrupt
This is the CaptureB Event interrupt status prior to masking.
9
CBMRIS
RO
0
GPTM CaptureB Match Raw Interrupt
This is the CaptureB Match interrupt status prior to masking.
8
TBTORIS
RO
0
GPTM TimerB Time-Out Raw Interrupt
This is the TimerB time-out interrupt status prior to masking.
7:4
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
3
RTCRIS
RO
0
GPTM RTC Raw Interrupt
This is the RTC Event interrupt status prior to masking.
2
CAERIS
RO
0
GPTM CaptureA Event Raw Interrupt
This is the CaptureA Event interrupt status prior to masking.
1
CAMRIS
RO
0
GPTM CaptureA Match Raw Interrupt
This is the CaptureA Match interrupt status prior to masking.
0
TATORIS
RO
0
GPTM TimerA Time-Out Raw Interrupt
This the TimerA time-out interrupt status prior to masking.
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October 5, 2006
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LM3S101 Data Sheet
Register 7: GPTM Masked Interrupt Status (GPTMMIS), offset 0x020
This register show the state of the GPTM's controller-level interrupt. If an interrupt is unmasked in
GPTMIMR, and there is an event that causes the interrupt to be asserted, the corresponding bit is
set in this register. All bits are cleared by writing a 1 to the corresponding bit in GPTMICR.
GPTM Masked Interrupt Status (GPTMMIS)
Offset 0x020
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
CBEMIS
reserved
CBMMIS TBTOMIS
RO
0
RO
0
RO
0
RTCMIS
RO
0
CAEMIS CAMMIS TATOMIS
RO
0
RO
0
RO
0
Bit/Field
Name
Type
Reset
Description
31:11
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
10
CBEMIS
RO
0
GPTM CaptureB Event Masked Interrupt
This is the CaptureB event interrupt status after masking.
9
CBMMIS
RO
0
GPTM CaptureB Match Masked Interrupt
This is the CaptureB match interrupt status after masking.
8
TBTOMIS
RO
0
GPTM TimerB Time-Out Masked Interrupt
This is the TimerB time-out interrupt status after masking.
7:4
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
3
RTCMIS
RO
0
GPTM RTC Masked Interrupt
This is the RTC event interrupt status after masking.
2
CAEMIS
RO
0
GPTM CaptureA Event Masked Interrupt
This is the CaptureA event interrupt status after masking.
1
CAMMIS
RO
0
GPTM CaptureA Match Masked Interrupt
This is the CaptureA match interrupt status after masking.
0
TATOMIS
RO
0
GPTM TimerA Time-Out Masked Interrupt
This is the TimerA time-out interrupt status after masking.
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Preliminary
General-Purpose Timers
Register 8: GPTM Interrupt Clear (GPTMICR), offset 0x024
This register is used to clear the status bits in the GPTMRIS and GPTMMIS registers. Writing a 1
to a bit clears the corresponding bit in the GPTMRIS and GPTMMIS registers.
GPTM Interrupt Clear (GPTMICR)
Offset 0x024
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
W1C
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
reserved
CBECINT CBMCINT TBTOCINT
W1C
0
W1C
0
W1C
0
RTCCINT CAECINT CAMCINTTATOCINT
W1C
0
W1C
0
W1C
0
W1C
0
Bit/Field
Name
Type
Reset
Description
31:11
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
10
CBECINT
W1C
0
GPTM CaptureB Event Interrupt Clear
0: The interrupt is unaffected.
1: The interrupt is cleared.
9
CBMCINT
W1C
0
GPTM CaptureB Match Interrupt Clear
0: The interrupt is unaffected.
1: The interrupt is cleared.
8
TBTOCINT
W1C
0
GPTM TimerB Time-Out Interrupt Clear
0: The interrupt is unaffected.
1: The interrupt is cleared.
7:4
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
3
RTCCINT
W1C
0
GPTM RTC Interrupt Clear
0: The interrupt is unaffected.
1: The interrupt is cleared.
2
CAECINT
W1C
0
GPTM CaptureA Event Interrupt Clear
0: The interrupt is unaffected.
1: The interrupt is cleared.
1
CAMCINT
W1C
0
GPTM CaptureA Match Raw Interrupt
This is the CaptureA match interrupt status after masking.
0
TATOCINT
W1C
0
GPTM TimerA Time-Out Raw Interrupt
0: The interrupt is unaffected.
1: The interrupt is cleared.
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October 5, 2006
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LM3S101 Data Sheet
Register 9: GPTM TimerA Interval Load (GPTMTAILR), offset 0x028
This register is used to load the starting count value into the timer. When GPTM is configured to
one of the 32-bit modes, GPTMTAILR appears as a 32-bit register (the upper 16-bits correspond
to the contents of the GPTM TimerB Interval Load (GPTMTBILR) register). In 16-bit mode, the
upper 16 bits of this register read as 0s and have no effect on the state of GPTMTBILR.
GPTM TimerA Interval Load (GPTMTAILR)
Offset 0x028
31
30
29
28
27
26
25
24
23
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
15
14
13
12
11
10
9
8
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
22
21
20
19
18
17
16
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
7
6
5
4
3
2
1
0
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
TAILRH
Type
Reset
TAILRL
Type
Reset
R/W
1
1/0 = 1 if timer is configured in 32-bit mode; 0 if timer is configured in 16-bit mode.
Bit/Field
Name
Type
Reset
Description
31:16
TAILRH
R/W
0xFFFF
(32-bit
mode)
0x0000
(16-bit
mode)
15:0
TAILRL
R/W
0xFFFF
GPTM TimerA Interval Load Register High
When configured for 32-bit mode via the GPTMCFG register,
the GPTM TimerB Interval Load (GPTMTBILR) register loads
this value on a write. A read returns the current value of
GPTMTBILR.
In 16-bit mode, this field reads as 0 and does not have an effect
on the state of GPTMTBILR.
GPTM TimerA Interval Load Register Low
For both 16- and 32-bit modes, writing this field loads the
counter for TimerA. A read returns the current value of
GPTMTAILR.
October 5, 2006
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Preliminary
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Register 10: GPTM TimerB Interval Load (GPTMTBILR), offset 0x02C
This register is used to load the starting count value into TimerB. When the GPTM is configured to
a 32-bit mode, GPTMTBILR returns the current value of TimerB and ignores writes.
GPTM TimerB Interval Load (GPTMTBILR)
Offset 0x02C
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
reserved
Type
Reset
TBILRL
Type
Reset
Bit/Field
Name
Type
Reset
Description
31:16
reserved
RO
0
15:0
TBILRL
R/W
0xFFFF
Reserved bits return an indeterminate value, and should never
be changed.
GPTM TimerB Interval Load Register
When the GPTM is not configured as a 32-bit timer, a write to
this field updates GPTMTBILR. In 32-bit mode, writes are
ignored, and reads return the current value of GPTMTBILR.
158
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 11: GPTM TimerA Match (GPTMTAMATCHR), offset 0x030
This register is used in 32-bit Real-Time Clock mode and 16-bit PWM and Input Edge Count
modes.
GPTM TimerA Match (GPTMTAMATCHR)
Offset 0x030
31
30
29
28
27
26
25
24
23
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
15
14
13
12
11
10
9
8
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
22
21
20
19
18
17
16
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
R/W
1/0
7
6
5
4
3
2
1
0
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
TAMRH
Type
Reset
TAMRL
Type
Reset
R/W
1
1/0 = 1 if timer is configured in 32-bit mode; 0 if timer is configured in 16-bit mode.
Bit/Field
Name
Type
Reset
Description
31:16
TAMRH
R/W
0xFFFF
(32-bit
mode)
0x0000
(16-bit
mode)
15:0
TAMRL
R/W
0xFFFF
GPTM TimerA Match Register High
When configured for 32-bit Real-Time Clock (RTC) mode via
the GPTMCFG register, this value is compared to the upper
half of GPTMTAR, to determine match events.
In 16-bit mode, this field reads as 0 and does not have an effect
on the state of GPTMTBMATCHR.
GPTM TimerA Match Register Low
When configured for 32-bit Real-Time Clock (RTC) mode via
the GPTMCFG register, this value is compared to the lower half
of GPTMTAR, to determine match events.
When configured for PWM mode, this value along with
GPTMTAILR, determines the duty cycle of the output PWM
signal.
When configured for Edge Count mode, this value along with
GPTMTAILR, determines how many edge events are counted.
The total number of edge events counted is equal to the value
in GPTMTAILR minus this value.
October 5, 2006
159
Preliminary
General-Purpose Timers
Register 12: GPTM TimerB Match (GPTMTBMATCHR), offset 0x034
This register is used in 32-bit Real-Time Clock mode and 16-bit PWM and Input Edge Count
modes.
GPTM TimerB Match (GPTMTBMATCHR)
Offset 0x034
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
TBMRL
Type
Reset
Bit/Field
Name
Type
Reset
31:16
reserved
RO
0
15:0
TBMRL
R/W
0xFFFF
R/W
0
Description
Reserved bits return an indeterminate value, and should never
be changed.
GPTM TimerB Match Register Low
When configured for PWM mode, this value along with
GPTMTBILR, determines the duty cycle of the output PWM
signal.
When configured for Edge Count mode, this value along with
GPTMTBILR, determines how many edge events are counted.
The total number of edge events counted is equal to the value
in GPTMTBILR minus this value.
160
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 13: GPTM TimerA Prescale (GPTMTAPR), offset 0x038
This register allows software to extend the range of the 16-bit timers.
GPTM TimerA Prescale (GPTMTAPR)
Offset 0x038
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
TAPSR
R/W
0
Bit/Field
Name
Type
Reset
Description
31:8
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
7:0
TAPSR
R/W
0
GPTM TimerA Prescale
The register loads this value on a write. A read returns the
current value of the register.
Refer to Table 9-1 on page 139 for more details and an
example.
October 5, 2006
161
Preliminary
General-Purpose Timers
Register 14: GPTM TimerB Prescale (GPTMTBPR), offset 0x03C
This register allows software to extend the range of the 16-bit timers.
GPTM TimerB Prescale (GPTMTBPR)
Offset 0x03C
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
TBPSR
R/W
0
Bit/Field
Name
Type
Reset
Description
31:8
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
7:0
TBPSR
R/W
0
GPTM TimerB Prescale
The register loads this value on a write. A read returns the
current value of this register.
Refer to Table 9-1 on page 139 for more details and an
example.
162
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 15: GPTM TimerA Prescale Match (GPTMTAPMR), offset 0x040
This register effectively extends the range of GPTMTAMATCHR to 24 bits.
GPTM TimerA Prescale Match (GPTMTAPMR)
Offset 0x040
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
TAPSMR
R/W
0
Bit/Field
Name
Type
Reset
Description
31:8
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
7:0
TAPSMR
R/W
0
GPTM TimerA Prescale Match
This value is used alongside GPTMTAMATCHR to detect timer
match events while using a prescaler.
October 5, 2006
163
Preliminary
General-Purpose Timers
Register 16: GPTM TimerB Prescale Match (GPTMTBPMR), offset 0x044
This register effectively extends the range of GPTMTBMATCHR to 24 bits.
GPTM TimerB Prescale Match (GPTMTBPMR)
Offset 0x044
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
TBPSMR
R/W
0
Bit/Field
Name
Type
Reset
Description
31:8
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
7:0
TBPSMR
R/W
0
GPTM TimerB Prescale Match
This value is used alongside GPTMTBMATCHR to detect timer
match events while using a prescaler.
164
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 17: GPTM TimerA (GPTMTAR), offset 0x048
This register shows the current value of the TimerA counter in all cases except for Input Edge
Count mode. When in this mode, this register contains the time at which the last edge event took
place.
GPTM TimerA (GPTMTAR)
Offset 0x048
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
1/0
RO
1/0
RO
1/0
RO
1/0
RO
1/0
RO
1/0
RO
1/0
RO
1/0
RO
1/0
RO
1/0
RO
1/0
RO
1/0
RO
1/0
RO
1/0
RO
1/0
RO
1/0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
TARH
Type
Reset
TARL
Type
Reset
1/0 = 1 if timer is configured in 32-bit mode; 0 if timer is configured in 16-bit mode.
Bit/Field
Name
Type
Reset
Description
31:16
TARH
RO
0xFFFF
(32-bit
mode)
GPTM TimerA Register High
If the GPTMCFG is in a 32-bit mode, TimerB value is read. If the
GPTMCFG is in a 16-bit mode, this is read as zero.
0x0000
(16-bit
mode)
15:0
TARL
RO
0xFFFF
GPTM TimerA Register Low
A read returns the current value of the GPTM TimerA Count
Register, except in Input Edge Count mode, when it returns the
timestamp from the last edge event.
October 5, 2006
165
Preliminary
General-Purpose Timers
Register 18: GPTM TimerB (GPTMTBR), offset 0x04C
This register shows the current value of the TimerB counter in all cases except for Input Edge
Count mode. When in this mode, this register contains the time at which the last edge event took
place.
GPTM TimerB (GPTMTBR)
Offset 0x04C
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
reserved
Type
Reset
TBRL
Type
Reset
Bit/Field
Name
Type
Reset
Description
31:16
reserved
RO
0
15:0
TBRL
RO
0xFFFF
Reserved bits return an indeterminate value, and should never
be changed.
GPTM TimerB
A read returns the current value of the GPTM TimerB Count
Register, except in Input Edge Count mode, when it returns the
timestamp from the last edge event.
166
October 5, 2006
Preliminary
LM3S101 Data Sheet
10
Watchdog Timer
A watchdog timer can generate nonmaskable interrupts (NMIs) or a reset when a time-out value is
reached. The watchdog timer is used to regain control when a system has failed due to a software
error or due to the failure of an external device to respond in the expected way.
The Stellaris Watchdog Timer module consists of a 32-bit down counter, a programmable load
register, interrupt generation logic, a locking register, and user-enabled stalling.
The Watchdog Timer can be configured to generate an interrupt to the controller on its first
time-out, and to generate a reset signal on its second time-out. Once the Watchdog Timer has
been configured, the lock register can be written to prevent the timer configuration from being
inadvertently altered.
10.1
Block Diagram
Figure 10-1.
WDT Module Block Diagram
WDTLOAD
Control / Clock /
Interrupt
Generation
WDTCTL
WDTICR
Interrupt
WDTRIS
32-Bit Down
Counter
WDTMIS
WDTLOCK
System Clock
0x00000000
WDTTEST
Comparator
WDTVALUE
Identification Registers
WDTPCellID0
WDTPeriphID0
WDTPeriphID4
WDTPCellID1
WDTPeriphID1
WDTPeriphID5
WDTPCellID2
WDTPeriphID2
WDTPeriphID6
WDTPCellID3
WDTPeriphID3
WDTPeriphID7
October 5, 2006
167
Preliminary
Watchdog Timer
10.2
Functional Description
The Watchdog Timer module consists of a 32-bit down counter, a programmable load register,
interrupt generation logic, and a locking register. Once the Watchdog Timer has been configured,
the Watchdog Timer Lock (WDTLOCK) register is written, which prevents the timer configuration
from being inadvertently altered by software.
The Watchdog Timer module generates the first time-out signal when the 32-bit counter reaches
the zero state after being enabled; enabling the counter also enables the watchdog timer interrupt.
After the first time-out event, the 32-bit counter is re-loaded with the value of the Watchdog Timer
Load (WDTLOAD) register, and the timer resumes counting down from that value.
If the timer counts down to its zero state again before the first time-out interrupt is cleared, and the
reset signal has been enabled (via the WatchdogResetEnable function), the Watchdog timer
asserts its reset signal to the system. If the interrupt is cleared before the 32-bit counter reaches its
second time-out, the 32-bit counter is loaded with the value in the WDTLOAD register, and
counting resumes from that value.
If WDTLOAD is written with a new value while the Watchdog Timer counter is counting, then the
counter is loaded with the new value and continues counting.
Writing to WDTLOAD does not clear an active interrupt. An interrupt must be specifically cleared
by writing to the Watchdog Interrupt Clear (WDTICR) register.
The Watchdog module interrupt and reset generation can be enabled or disabled as required.
When the interrupt is re-enabled, the 32-bit counter is preloaded with the load register value and
not its last state.
10.3
Initialization and Configuration
To use the WDT, its peripheral clock must be enabled by setting the WDT bit in the RCGC0 register.
The Watchdog Timer is configured using the following sequence:
1. Load the WDTLOAD register with the desired timer load value.
2. If the Watchdog is configured to trigger system resets, set the RESEN bit in the WDTCTL
register.
3. Set the INTEN bit in the WDTCTL register to enable the Watchdog and lock the control
register.
If software requires that all of the watchdog registers are locked, the Watchdog Timer module can
be fully locked by writing any value to the WDTLOCK register. To unlock the Watchdog Timer,
write a value of 0x1ACCE551.
10.4
Register Map
Table 10-1 lists the Watchdog registers. The offset listed is a hexadecimal increment to the
register’s address, relative to the Watchdog Timer base address of 0x40000000.
Table 10-1. WDT Register Map
Offset
Name
0x000
See
page
Reset
Type
Description
WDTLOAD
0xFFFFFFFF
R/W
Load
170
0x004
WDTVALUE
0xFFFFFFFF
RO
Current value
171
0x008
WDTCTL
0x00000000
R/W
Control
172
168
October 5, 2006
Preliminary
LM3S101 Data Sheet
Table 10-1. WDT Register Map (Continued)
Offset
Name
0x00C
See
page
Reset
Type
Description
WDTICR
-
WO
Interrupt clear
173
0x010
WDTRIS
0x00000000
RO
Raw interrupt status
174
0x014
WDTMIS
0x00000000
RO
Masked interrupt status
175
0x418
WDTTEST
0x00000000
R/W
Watchdog stall enable
177
0xC00
WDTLOCK
0x00000000
R/W
Lock
176
0xFD0
WDTPeriphID4
0x00000000
RO
Peripheral identification 4
178
0xFD4
WDTPeriphID5
0x00000000
RO
Peripheral identification 5
179
0xFD8
WDTPeriphID6
0x00000000
RO
Peripheral identification 6
180
0xFDC
WDTPeriphID7
0x00000000
RO
Peripheral identification 7
181
0xFE0
WDTPeriphID0
0x00000005
RO
Peripheral identification 0
182
0xFE4
WDTPeriphID1
0x00000018
RO
Peripheral identification 1
183
0xFE8
WDTPeriphID2
0x00000018
RO
Peripheral identification 2
184
0xFEC
WDTPeriphID3
0x00000001
RO
Peripheral identification 3
185
0xFF0
WDTPCellID0
0x0000000D
RO
PrimeCell identification 0
186
0xFF4
WDTPCellID1
0x000000F0
RO
PrimeCell identification 1
187
0xFF8
WDTPCellID2
0x00000005
RO
PrimeCell identification 2
188
0xFFC
WDTPCellID3
0x000000B1
RO
PrimeCell identification 3
189
10.5
Register Descriptions
The remainder of this section lists and describes the WDT registers, in numerical order by address
offset.
October 5, 2006
169
Preliminary
Watchdog Timer
Register 1: Watchdog Load (WDTLOAD), offset 0x000
This register is the 32-bit interval value used by the 32-bit counter. When this register is written, the
value is immediately loaded and the counter restarts counting down from the new value. If the
WDTLOAD register is loaded with 0x00000000, an interrupt is immediately generated.
Watchdog Load (WDTLOAD)
Offset 0x000
31
30
29
28
27
26
25
24
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
15
14
13
12
11
10
9
8
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
23
22
21
20
19
18
17
16
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
7
6
5
4
3
2
1
0
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
R/W
1
WDTLoad
Type
Reset
WDTLoad
Type
Reset
Bit/Field
Name
Type
Reset
31:0
WDTLoad
R/W
0xFFFFFFFF
R/W
1
Description
Watchdog Load Value
170
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 2: Watchdog Value (WDTVALUE), offset 0x004
This register contains the current count value of the timer.
Watchdog Value (WDTVALUE)
Offset 0x004
31
30
29
28
27
26
25
24
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
15
14
13
12
11
10
9
8
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
23
22
21
20
19
18
17
16
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
7
6
5
4
3
2
1
0
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
RO
1
WDTValue
Type
Reset
WDTValue
Type
Reset
Bit/Field
Name
Type
Reset
31:0
WDTValue
RO
0xFFFFFFFF
RO
1
Description
Watchdog Value
Current value of the 32-bit down counter.
October 5, 2006
171
Preliminary
Watchdog Timer
Register 3: Watchdog Control (WDTCTL), offset 0x008
This register is the watchdog control register. The watchdog timer can be configured to generate a
reset signal (upon second time-out) or an interrupt on time-out.
When the watchdog interrupt has been enabled, all subsequent writes to the control register are
ignored. The only mechanism that can re-enable writes is a hardware reset.
Watchdog Control (WDTCTL)
Offset 0x008
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RESEN
INTEN
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
Bit/Field
Name
Type
Reset
Description
31:2
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
1
RESEN
R/W
0
Watchdog Reset Enable
0: Disabled.
1: Enable the Watchdog module reset output.
0
INTEN
R/W
0
Watchdog Interrupt Enable
0: Interrupt event disabled (once this bit is set, it can only
be cleared by a hardware reset)
1: Interrupt event enabled. Once enabled, all writes are
ignored.
172
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 4: Watchdog Interrupt Clear (WDTICR), offset 0x00C
This register is the interrupt clear register. A write of any value to this register clears the Watchdog
interrupt and reloads the 32-bit counter from the WDTLOAD register. Value for a read or reset is
indeterminate.
Watchdog Interrupt Clear (WDTICR)
Offset 0x00C
31
30
29
28
27
26
25
24
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
15
14
13
12
11
10
9
8
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
23
22
21
20
19
18
17
16
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
7
6
5
4
3
2
1
0
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
WO
-
WDTIntClr
Type
Reset
WDTIntClr
Type
Reset
Bit/Field
Name
Type
Reset
31:0
WDTIntClr
WO
-
WO
-
Description
Watchdog Interrupt Clear
October 5, 2006
173
Preliminary
Watchdog Timer
Register 5: Watchdog Raw Interrupt Status (WDTRIS), offset 0x010
This register is the raw interrupt status register. Watchdog interrupt events can be monitored via
this register if the controller interrupt is masked.
Watchdog Raw Interrupt Status (WDTRIS)
Offset 0x010
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
WDTRIS
RO
0
Bit/Field
Name
Type
Reset
Description
31:1
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
0
WDTRIS
RO
0
Watchdog Raw Interrupt Status
Gives the raw interrupt state (prior to masking) of
WDTINTR.
174
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 6: Watchdog Masked Interrupt Status (WDTMIS), offset 0x014
This register is the masked interrupt status register. The value of this register is the logical AND of
the raw interrupt bit and the Watchdog interrupt enable bit.
Watchdog Masked Interrupt Status (WDTMIS)
Offset 0x014
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
WDTMIS
reserved
Type
Reset
RO
0
RO
0
Bit/Field
Name
Type
Reset
Description
31:1
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
0
WDTMIS
RO
0
Watchdog Masked Interrupt Status
Gives the masked interrupt state (after masking) of the
WDTINTR interrupt.
October 5, 2006
175
Preliminary
Watchdog Timer
Register 7: Watchdog Lock (WDTLOCK), offset 0xC00
Writing 0x1ACCE551 to the WDTLOCK register enables write access to all other registers. Writing
any other value to the WDTLOCK register re-enables the locked state for register writes to all the
other registers. Reading the WDTLOCK register returns the lock status rather than the 32-bit
value written. Therefore, when write accesses are disabled, reading the WDTLOCK register
returns 0x00000001 (when locked; otherwise, the returned value is 0x00000000 (unlocked)).
Watchdog Lock (WDTLOCK)
Offset 0xC00
31
30
29
28
27
26
25
24
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
15
14
13
12
11
10
9
8
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
23
22
21
20
19
18
17
16
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
7
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
WDTLock
Type
Reset
WDTLock
Type
Reset
Bit/Field
Name
Type
Reset
31:0
WDTLock
R/W
0x0000
R/W
0
Description
Watchdog Lock
A write of the value 0x1ACCE551 unlocks the watchdog
registers for write access. A write of any other value
reapplies the lock, preventing any register updates.
A read of this register returns the following values:
Locked: 0x00000001
Unlocked: 0x00000000
176
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 8: Watchdog Test (WDTTEST), offset 0x418
This register provides user-enabled stalling when the microcontroller asserts the CPU halt flag
during debug.
Watchdog Test (WDTTEST)
Offset 0x418
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
reserved
STALL
R/W
0
Bit/Field
Name
Type
Reset
Description
31:9
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
8
STALL
R/W
0
Watchdog Stall Enable
When set to 1, if the Stellaris microcontroller is stopped
with a debugger, the watchdog timer stops counting. Once
the microcontroller is restarted, the watchdog timer
resumes counting.
7:0
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
October 5, 2006
177
Preliminary
Watchdog Timer
Register 9: Watchdog Peripheral Identification 4 (WDTPeriphID4), offset 0xFD0
The WDTPeriphIDn registers are hard-coded and the fields within the register determine the reset
value.
Watchdog Peripheral Identification 4 (WDTPeriphID4)
Offset 0xFD0
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID4
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID4
RO
0x00
Description
Reserved bits return an indeterminate value, and should
never be changed.
WDT Peripheral ID Register[7:0]
178
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 10: Watchdog Peripheral Identification 5 (WDTPeriphID5), offset 0xFD4
The WDTPeriphIDn registers are hard-coded and the fields within the register determine the reset
value.
Watchdog Peripheral Identification 5 (WDTPeriphID5)
Offset 0xFD4
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID5
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID5
RO
0x00
Description
Reserved bits return an indeterminate value, and should
never be changed.
WDT Peripheral ID Register[15:8]
October 5, 2006
179
Preliminary
Watchdog Timer
Register 11: Watchdog Peripheral Identification 6 (WDTPeriphID6), offset 0xFD8
The WDTPeriphIDn registers are hard-coded and the fields within the register determine the reset
value.
Watchdog Peripheral Identification 6 (WDTPeriphID6)
Offset 0xFD8
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID6
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID6
RO
0x00
Description
Reserved bits return an indeterminate value, and should
never be changed.
WDT Peripheral ID Register[23:16]
180
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 12: Watchdog Peripheral Identification 7 (WDTPeriphID7), offset 0xFDC
The WDTPeriphIDn registers are hard-coded and the fields within the register determine the reset
value.
Watchdog Peripheral Identification 7 (WDTPeriphID7)
Offset 0xFDC
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID7
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID7
RO
0x00
Description
Reserved bits return an indeterminate value, and should
never be changed.
WDT Peripheral ID Register[31:24]
October 5, 2006
181
Preliminary
Watchdog Timer
Register 13: Watchdog Peripheral Identification 0 (WDTPeriphID0), offset 0xFE0
The WDTPeriphIDn registers are hard-coded and the fields within the register determine the reset
value.
Watchdog Peripheral Identification 0 (WDTPeriphID0)
Offset 0xFE0
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
PID0
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID0
RO
0x05
Description
Reserved bits return an indeterminate value, and should
never be changed.
Watchdog Peripheral ID Register[7:0]
182
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 14: Watchdog Peripheral Identification 1 (WDTPeriphID1), offset 0xFE4
The WDTPeriphIDn registers are hard-coded and the fields within the register determine the reset
value.
Watchdog Peripheral Identification 1 (WDTPeriphID1)
Offset 0xFE4
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
1
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID1
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID1
RO
0x18
Description
Reserved bits return an indeterminate value, and should
never be changed.
Watchdog Peripheral ID Register[15:8]
October 5, 2006
183
Preliminary
Watchdog Timer
Register 15: Watchdog Peripheral Identification 2 (WDTPeriphID2), offset 0xFE8
The WDTPeriphIDn registers are hard-coded and the fields within the register determine the reset
value.
Watchdog Peripheral Identification 2 (WDTPeriphID2)
Offset 0xFE8
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
1
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID2
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID2
RO
0x18
Description
Reserved bits return an indeterminate value, and should
never be changed.
Watchdog Peripheral ID Register[23:16]
184
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 16: Watchdog Peripheral Identification 3 (WDTPeriphID3), offset 0xFEC
The WDTPeriphIDn registers are hard-coded and the fields within the register determine the reset
value.
Watchdog Peripheral Identification 3 (WDTPeriphID3)
Offset 0xFEC
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
PID3
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID3
RO
0x01
Description
Reserved bits return an indeterminate value, and should
never be changed.
Watchdog Peripheral ID Register[31:24]
October 5, 2006
185
Preliminary
Watchdog Timer
Register 17: Watchdog PrimeCell Identification 0 (WDTPCellID0), offset 0xFF0
The WDTPCellIDn registers are hard-coded and the fields within the register determine the reset
value.
Watchdog Primecell Identification 0 (WDTPCellID0)
Offset 0xFF0
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
1
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
CID0
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
CID0
RO
0x0D
Description
Reserved bits return an indeterminate value, and should
never be changed.
Watchdog PrimeCell ID Register[7:0]
186
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 18: Watchdog PrimeCell Identification 1 (WDTPCellID1), offset 0xFF4
The WDTPCellIDn registers are hard-coded and the fields within the register determine the reset
value.
Watchdog Primecell Identification 1 (WDTPCellID1)
Offset 0xFF4
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
1
RO
1
RO
1
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
CID1
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
CID1
RO
0xF0
Description
Reserved bits return an indeterminate value, and should
never be changed.
Watchdog PrimeCell ID Register[15:8]
October 5, 2006
187
Preliminary
Watchdog Timer
Register 19: Watchdog PrimeCell Identification 2 (WDTPCellID2), offset 0xFF8
The WDTPCellIDn registers are hard-coded and the fields within the register determine the reset
value.
Watchdog Primecell Identification 2 (WDTPCellID2)
Offset 0xFF8
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
CID2
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
CID2
RO
0x05
Description
Reserved bits return an indeterminate value, and should
never be changed.
Watchdog PrimeCell ID Register[23:16]
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LM3S101 Data Sheet
Register 20: Watchdog PrimeCell Identification 3 (WDTPCellID3 ), offset 0xFFC
The WDTPCellIDn registers are hard-coded and the fields within the register determine the reset
value.
Watchdog Primecell Identification 3 (WDTPCellID3)
Offset 0xFFC
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
0
RO
1
RO
1
RO
0
RO
0
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
CID3
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
CID3
RO
0xB1
Description
Reserved bits return an indeterminate value, and should
never be changed.
Watchdog PrimeCell ID Register[31:24]
October 5, 2006
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Preliminary
Universal Asynchronous Receiver/Transmitter (UART)
11
Universal Asynchronous Receiver/Transmitter
(UART)
The Universal Asynchronous Receiver/Transmitter (UART) provides fully programmable,
16C550-type serial interface characteristics. The LM3S101 controller is equipped with one UART
module.
The UART has the following features:

Separate transmit and receive FIFOs

Programmable FIFO length, including 1-byte deep operation providing conventional
double-buffered interface

FIFO trigger levels of 1/8, 1/4, 1/2, 3/4, and 7/8

Programmable baud-rate generator allowing rates up to 460.8 Kbps

Standard asynchronous communication bits for start, stop and parity

False start bit detection

Line-break generation and detection

Fully programmable serial interface characteristics:
– 5, 6, 7, or 8 data bits
– Even, odd, stick, or no-parity bit generation/detection
– 1 or 2 stop bit generation
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LM3S101 Data Sheet
11.1
Block Diagram
Figure 11-1. UART Module Block Diagram
System Clock
TXFIFO
16x8
Interrupt Control
Interrupt
UARTIFLS
.
.
.
UARTIM
UARTMIS
Identification
Registers
UARTRIS
UARTICR
Transmitter
UnTx
Receiver
UnRx
UARTPCellID0
UARTPCellID1
Baud Rate
Generator
UARTDR
UARTPCellID2
UARTIBRD
UARTPCellID3
UARTFBRD
UARTPeriphID0
UARTPeriphID1
UARTPeriphID2
UARTPeriphID3
UART PeriphID4
RXFIFO
16x8
Control / Status
UARTPeriphID5
UARTPeriphID6
UARTPeriphID7
UARTRSR/ECR
.
.
.
UARTFR
UARTLCRH
UARTCTL
11.2
Functional Description
The Stellaris UART performs the functions of parallel-to-serial and serial-to-parallel conversions. It
is similar in functionality to a 16C550 UART, but is not register compatible.
The UART is configured for transmit and/or receive via the TXE and RXE bits of the UART Control
(UARTCTL) register (see page 207). 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.
11.2.1
Transmit/Receive Logic
The transmit logic performs parallel-to-serial conversion on the data read from the transmit FIFO.
The control logic outputs the serial bit stream beginning with a start bit, and followed by the data
October 5, 2006
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Preliminary
Universal Asynchronous Receiver/Transmitter (UART)
bits (LSB first), parity bit, and the stop bits according to the programmed configuration in the
control registers. See Figure 11-2 for details.
The receive logic performs serial-to-parallel conversion on the received bit stream after a valid
start pulse has been detected. Overrun, parity, frame error checking, and line-break detection are
also performed, and their status accompanies the data that is written to the receive FIFO.
Figure 11-2. UART Character Frame
UnTX
LSB
1
5-8 data bits
0
n
Parity bit
if enabled
Start
11.2.2
1-2
stop bits
MSB
Baud-Rate Generation
The baud-rate divisor is a 22-bit number consisting of a 16-bit integer and a 6-bit fractional part.
The number formed by these two values is used by the baud-rate generator to determine the bit
period. Having a fractional baud-rate divider allows the UART to generate all the standard baud
rates.
The 16-bit integer is loaded through the UART Integer Baud-Rate Divisor (UARTIBRD) register
(see page 203) and the 6-bit fractional part is loaded with the UART Fractional Baud-Rate
Divisor (UARTFBRD) register (see page 204). The baud-rate divisor (BRD) has the following
relationship to the system clock (where BRDI is the integer part of the BRD and BRDF is the
fractional part, separated by a decimal place.):
BRD = BRDI + BRDF = SysClk / (16 * Baud Rate)
The 6-bit fractional number (that is to be loaded into the DIVFRAC bit field in the UARTFBRD
register) can be calculated by taking the fractional part of the baud-rate divisor, multiplying it by 64,
and adding 0.5 to account for rounding errors:
UARTFBRD[DIVFRAC] = integer(BRDF * 64 + 0.5)
The UART generates an internal baud-rate reference clock at 16x the baud-rate (referred to as
Baud16). This reference clock is divided by 16 to generate the transmit clock, and is used for
error detection during receive operations.
Along with the UART Line Control, High Byte (UARTLCRH) register (see page 205), 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
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LM3S101 Data Sheet
11.2.3
Data Transmission
Data received or transmitted is stored in two 16-byte FIFOs, though the receive FIFO has an extra
four bits per character for status information. For transmission, data is written into the transmit
FIFO. If the UART is enabled, it causes a data frame to start transmitting with the parameters
indicated in the UARTLCRH register. Data continues to be transmitted until there is no data left in
the transmit FIFO. The BUSY bit in the UART Flag (UARTFR) register (see page 201) 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 U0Rx 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 191).
The start bit is valid if U0Rx is still low on the eighth cycle of Baud16, otherwise a false start bit is
detected and it is ignored. Start bit errors can be viewed in the UART Receive Status (UARTRSR)
register (see page 199). If the start bit was valid, successive data bits are sampled on every 16th
cycle of Baud16 (that is, one bit period later) according to the programmed length of the data
characters. The parity bit is then checked if parity mode was enabled. Data length and parity are
defined in the UARTLCRH register.
Lastly, a valid stop bit is confirmed if U0Rx 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.
11.2.4
FIFO Operation
The UART has two 16-entry FIFOs; one for transmit and one for receive. Both FIFOs are accessed
via the UART Data (UARTDR) register (see page 197). 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 205).
FIFO status can be monitored via the UART Flag (UARTFR) register (see page 201) and the
UART Receive Status (UARTRSR) register. Hardware monitors empty, full and overrun
conditions. The UARTFR register contains empty and full flags (TXFE, TXFF, RXFE and RXFF bits)
and the UARTRSR register shows overrun status via the OE bit.
The trigger points at which the FIFOs generate interrupts is controlled via the UART Interrupt
FIFO Level Select (UARTIFLS) register (see page 208). Both FIFOs can be individually
configured to trigger interrupts at different levels. Available configurations include 1/8, 1/4, 1/2, 3/4
and 7/8. For example, if the 1/4 option is selected for the receive FIFO, the UART generates a
receive interrupt after 4 data bytes are received. Out of reset, both FIFOs are configured to trigger
an interrupt at the 1/2 mark.
11.2.5
Interrupts
The UART can generate interrupts when the following conditions are observed:

Overrun Error

Break Error

Parity Error

Framing Error
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Universal Asynchronous Receiver/Transmitter (UART)

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 212).
The interrupt events that can trigger a controller-level interrupt are defined in the UART Interrupt
Mask (UARTIM) register (see page 209) 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 211).
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 213).
11.2.6
Loopback Operation
The UART can be placed into an internal loopback mode for diagnostic or debug work. This is
accomplished by setting the LBE bit in the UARTCTL register (see page 207). In loopback mode,
data transmitted on U0Tx is received on the U0Rx input.
11.3
Initialization and Configuration
To use the UART, the peripheral clock must be enabled by setting the UART0 bit in the RCGC1
register.
This section discusses the steps that are required for using a UART module. For this example, the
system clock is assumed to be 20 MHz and the desired UART configuration is:

115200 baud rate

Data length of 8 bits

One stop bit

No parity

FIFOs disabled

No interrupts
The first thing to consider when programming the UART is the baud-rate divisor (BRD), since the
UARTIBRD and UARTFBRD registers must be written before the UARTLCRH register. Using the
equation described in “Baud-Rate Generation” on page 192, 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 203) should be set to 10.
The value to be loaded into the UARTFBRD register (see page 204) is calculated by the equation:
UARTFBRD[DIVFRAC] = integer(0.8507 * 64 + 0.5) = 54
With the BRD values in hand, the UART configuration is written to the module in the following
order:
1. Disable the UART by clearing the UARTEN bit in the UARTCTL register.
2. Write the integer portion of the BRD to the UARTIBRD register.
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LM3S101 Data Sheet
3. Write the fractional portion of the BRD to the UARTFBRD register.
4. Write the desired serial parameters to the UARTLCRH register (in this case, a value of
0x00000060).
5. Enable the UART by setting the UARTEN bit in the UARTCTL register.
11.4
Register Map
Table 11-1 lists the UART registers. The offset listed is a hexadecimal increment to the register’s
address, relative to that UART’s base address:

UART0: 0x4000C000
Note:
The UART must be disabled (see the UARTEN bit in the UARTCTL register on page 207)
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 11-1. UART Register Map
Offset
Name
0x000
0x004
See
page
Reset
Type
Description
UARTDR
0x00000000
R/W
Data
197
UARTRSR
0x00000000
R/W
Receive Status (read)
199
UARTECR
Error Clear (write)
0x018
UARTFR
0x00000090
RO
Flag Register (read only)
201
0x024
UARTIBRD
0x00000000
R/W
Integer Baud-Rate Divisor
203
0x028
UARTFBRD
0x00000000
R/W
Fractional Baud-Rate Divisor
204
0x02C
UARTLCRH
0x00000000
R/W
Line Control Register, High byte
205
0x030
UARTCTL
0x00000300
R/W
Control Register
207
0x034
UARTIFLS
0x00000012
R/W
Interrupt FIFO Level Select
208
0x038
UARTIM
0x00000000
R/W
Interrupt Mask
209
0x03C
UARTRIS
0x0000000F
RO
Raw Interrupt Status
211
0x040
UARTMIS
0x00000000
RO
Masked Interrupt Status
212
0x044
UARTICR
0x00000000
W1C
Interrupt Clear
213
0xFD0
UARTPeriphID4
0x00000000
RO
Peripheral identification 4
214
0xFD4
UARTPeriphID5
0x00000000
RO
Peripheral identification 5
215
0xFD8
UARTPeriphID6
0x00000000
RO
Peripheral identification 6
216
0xFDC
UARTPeriphID7
0x00000000
RO
Peripheral identification 7
217
0xFE0
UARTPeriphID0
0x00000011
RO
Peripheral identification 0
218
0xFE4
UARTPeriphID1
0x00000000
RO
Peripheral identification 1
219
0xFE8
UARTPeriphID2
0x00000018
RO
Peripheral identification 2
220
0xFEC
UARTPeriphID3
0x00000001
RO
Peripheral identification 3
221
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Preliminary
Universal Asynchronous Receiver/Transmitter (UART)
Table 11-1. UART Register Map (Continued)
Offset
Name
0xFF0
See
page
Reset
Type
UARTPCellID0
0x0000000D
RO
PrimeCell identification 0
222
0xFF4
UARTPCellID1
0x000000F0
RO
PrimeCell identification 1
223
0xFF8
UARTPCellID2
0x00000005
RO
PrimeCell identification 2
224
0xFFC
UARTPCellID3
0x000000B1
RO
PrimeCell identification 3
225
11.5
Description
Register Descriptions
The remainder of this section lists and describes the UART registers, in numerical order by
address offset.
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LM3S101 Data Sheet
Register 1: UART Data (UARTDR), offset 0x000
This register is the data register (the interface to the FIFOs).
When FIFOs are enabled, data written to this location is pushed onto the transmit FIFO. If FIFOs
are disabled, data is stored in the transmitter holding register (the bottom word of the transmit
FIFO). A write to this register initiates a transmission from the UART.
For received data, if the FIFO is enabled, the data byte and the 4-bit status (break, frame, parity
and overrun) is pushed onto the 12-bit wide receive FIFO. If FIFOs are disabled, the data byte and
status are stored in the receiving holding register (the bottom word of the receive FIFO). The
received data can be retrieved by reading this register.
UART Data (UARTDR)
Offset 0x000
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
OE
RO
0
RO
0
RO
0
RO
0
RO
0
BE
PE
FE
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
DATA
Bit/Field
Name
Type
Reset
Description
31:12
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
11
OE
RO
0
UART Overrun Error
1=New data was received when the FIFO was full, resulting in
data loss.
0=There has been no data loss due to a FIFO overrun.
10
BE
RO
0
UART Break Error
This bit is set to 1 when a break condition is detected, indicating
that the receive data input was held Low for longer than a fullword transmission time (defined as start, data, parity, and stop
bits).
In FIFO mode, this error is associated with the character at the
top of the FIFO. When a break occurs, only one 0 character is
loaded into the FIFO. The next character is only enabled after
the received data input goes to a 1 (marking state) and the next
valid start bit is received.
9
PE
RO
0
UART Parity Error
This bit is set to 1 when the parity of the received data character
does not match the parity defined by bits 2 and 7 of the
UARTLCRH register.
In FIFO mode, this error is associated with the character at the
top of the FIFO.
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Universal Asynchronous Receiver/Transmitter (UART)
Bit/Field
Name
Type
Reset
8
FE
RO
0
Description
UART Framing Error
This bit is set to 1 when the received character does not have a
valid stop bit (a valid stop bit is 1).
7:0
DATA
R/W
0
When written, the data that is to be transmitted via the UART.
When read, the data that was received by the UART.
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October 5, 2006
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LM3S101 Data Sheet
Register 2: UART Receive Status/Error Clear (UARTRSR/UARTECR), offset 0x004
The UARTRSR/UARTECR register is the receive status register/error clear register.
In addition to the UARTDR register, receive status can also be read from the UARTRSR register. If
the status is read from this register, then the status information corresponds to the entry read from
UARTDR prior to reading UARTRSR. The status information for overrun is set immediately when
an overrun condition occurs.
A write of any value to the UARTECR register clears the framing, parity, break, and overrun errors.
All the bits are cleared to 0 on reset.
UART Receive Status (UARTRSR): Read
Offset 0x004
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
OE
BE
PE
FE
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
23
22
21
20
19
18
17
16
reserved
Type
Reset
reserved
Type
Reset
UART Error Clear (UARTECR): Write
Offset 0x004
31
30
29
28
27
26
25
24
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
WO
0
reserved
Type
Reset
reserved
Type
Reset
Bit/Field
Name
WO
0
Type
DATA
Reset
Description
Read-Only Receive Status (UARTRSR) Register
31:4
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed. The UARTRSR register cannot be written.
3
OE
RO
0
UART Overrun Error
When this bit is set to 1, data is received and the FIFO is already
full. This bit is cleared to 0 by a write to UARTECR.
The FIFO contents remain valid since no further data is written
when the FIFO is full, only the contents of the shift register are
overwritten. The CPU must now read the data in order to empty
the FIFO.
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Preliminary
Universal Asynchronous Receiver/Transmitter (UART)
Bit/Field
Name
Type
Reset
2
BE
RO
0
Description
UART Break Error
This bit is set to 1 when a break condition is detected, indicating
that the received data input was held Low for longer than a fullword transmission time (defined as start, data, parity, and stop
bits).
This bit is cleared to 0 by a write to UARTECR.
In FIFO mode, this error is associated with the character at the
top of the FIFO. When a break occurs, only one 0 character is
loaded into the FIFO. The next character is only enabled after
the receive data input goes to a 1 (marking state) and the next
valid start bit is received.
1
PE
RO
0
UART Parity Error
This bit is set to 1 when the parity of the received data character
does not match the parity defined by bits 2 and 7 of the
UARTLCRH register.
This bit is cleared to 0 by a write to UARTECR.
0
FE
RO
0
UART Framing Error
This bit is set to 1 when the received character does not have a
valid stop bit (a valid stop bit is 1).
This bit is cleared to 0 by a write to UARTECR.
In FIFO mode, this error is associated with the character at the
top of the FIFO.
Write-Only Error Clear (UARTECR) Register
31:8
reserved
WO
0
Reserved bits return an indeterminate value, and should never
be changed.
7:0
DATA
WO
0
A write to this register of any data clears the framing, parity,
break and overrun flags.
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October 5, 2006
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LM3S101 Data Sheet
Register 3: UART Flag (UARTFR), offset 0x018
The UARTFR register is the flag register. After reset, the TXFF, RXFF, and BUSY bits are 0, and
TXFE and RXFE bits are 1.
UART Flag (UARTFR)
Offset 0x018
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
TXFE
RXFF
TXFF
RXFE
BUSY
RO
0
RO
0
RO
1
RO
0
RO
0
RO
1
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
reserved
RO
0
RO
0
RO
0
Bit/Field
Name
Type
Reset
Description
31:8
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
7
TXFE
RO
1
UART Transmit FIFO Empty
The meaning of this bit depends on the state of the FEN bit in the
UARTLCRH register.
If the FIFO is disabled (FEN is 0), this bit is set when the transmit
holding register is empty.
If the FIFO is enabled (FEN is 1), this bit is set when the transmit
FIFO is empty.
6
RXFF
RO
0
UART Receive FIFO Full
The meaning of this bit depends on the state of the FEN bit in the
UARTLCRH register.
If the FIFO is disabled, this bit is set when the receive holding
register is full.
If the FIFO is enabled, this bit is set when the receive FIFO is
full.
5
TXFF
RO
0
UART Transmit FIFO Full
The meaning of this bit depends on the state of the FEN bit in the
UARTLCRH register.
If the FIFO is disabled, this bit is set when the transmit holding
register is full.
If the FIFO is enabled, this bit is set when the transmit FIFO is
full.
October 5, 2006
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Preliminary
Universal Asynchronous Receiver/Transmitter (UART)
Bit/Field
Name
Type
Reset
4
RXFE
RO
1
Description
UART Receive FIFO Empty
The meaning of this bit depends on the state of the FEN bit in the
UARTLCRH register.
If the FIFO is disabled, this bit is set when the receive holding
register is empty.
If the FIFO is enabled, this bit is set when the receive FIFO is
empty.
3
BUSY
RO
0
UART Busy
When this bit is 1, the UART is busy transmitting data. This bit
remains set until the complete byte, including all stop bits, has
been sent from the shift register.
This bit is set as soon as the transmit FIFO becomes non-empty
(regardless of whether UART is enabled).
2:0
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
202
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 4: UART Integer Baud-Rate Divisor (UARTIBRD), offset 0x024
The UARTIBRD register is the integer part of the baud-rate divisor value. All the bits are cleared
on reset. The minimum possible divide ratio is 1 (when UARTIBRD=0), in which case the
UARTFBRD register is ignored. When changing the UARTIBRD register, the new value does not
take effect until transmission/reception of the current character is complete. Any changes to the
baud-rate divisor must be followed by a write to the UARTLCRH register. See “Baud-Rate
Generation” on page 192 for configuration details.
UART Integer Baud-Rate Divisor
Offset 0x024
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
DIVINT
Type
Reset
Bit/Field
Name
Type
Reset
Description
31:16
reserved
RO
0
15:0
DIVINT
R/W
0x0000
Reserved bits return an indeterminate value, and should never
be changed.
Integer Baud-Rate Divisor
October 5, 2006
203
Preliminary
Universal Asynchronous Receiver/Transmitter (UART)
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 192
for configuration details.
UART Fractional Baud-Rate Divisor (UARTFBRD)
Offset 0x028
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
DIVFRAC
Bit/Field
Name
Type
Reset
31:6
reserved
RO
0
5:0
DIVFRAC
R/W
0x00
R/W
0
Description
Reserved bits return an indeterminate value, and should never
be changed.
Fractional Baud-Rate Divisor
204
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 6: UART Line Control (UARTLCRH), offset 0x02C
The UARTLCRH register is the line control register. Serial parameters such as data length, parity
and stop bit selection are implemented in this register.
When updating the baud-rate divisor (UARTIBRD and/or UARTIFRD), the UARTLCRH register
must also be written. The write strobe for the baud-rate divisor registers is tied to the UARTLCRH
register.
UART Line Control (UARTLCRH)
Offset 0x02C
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
FEN
STP2
EPS
PEN
BRK
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
SPS
reserved
Type
Reset
R/W
0
WLEN
R/W
0
R/W
0
Bit/Field
Name
Type
Reset
Description
31:8
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
7
SPS
R/W
0
UART Stick Parity Select
When bits 1, 2 and 7 of UARTLCRH are set, the parity bit is
transmitted and checked as a 0. When bits 1 and 7 are set and 2
is cleared, the parity bit is transmitted and checked as a 1.
When this bit is cleared, stick parity is disabled.
6:5
WLEN
R/W
0
UART Word Length
The bits indicate the number of data bits transmitted or received
in a frame as follows:
0x3: 8 bits
0x2: 7 bits
0x1: 6 bits
0x0: 5 bits (default)
4
FEN
R/W
0
UART Enable FIFOs
If this bit is set to 1, transmit and receive FIFO buffers are
enabled (FIFO mode).
When cleared to 0, FIFOs are disabled (Character mode). The
FIFOs become 1-byte-deep holding registers.
3
STP2
R/W
0
UART Two Stop Bits Select
If this bit is set to 1, two stop bits are transmitted at the end of a
frame. The receive logic does not check for two stop bits being
received.
October 5, 2006
205
Preliminary
Universal Asynchronous Receiver/Transmitter (UART)
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.
206
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 7: UART Control (UARTCTL), offset 0x030
The UARTCTL register is the control register. All the bits are cleared on reset except for the
Transmit Enable (TXE) and Receive Enable (RXE) bits, which are set to 1.
To enable the UART module, the UARTEN bit must be set to 1. If software requires a configuration
change in the module, the UARTEN bit must be cleared before the configuration changes are
written. If the UART is disabled during a transmit or receive operation, the current transaction is
completed prior to the UART stopping.
UART Control (UARTCR)
Offset 0x030
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RXE
TXE
LBE
R/W
1
R/W
1
R/W
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
reserved
RO
0
UARTEN
R/W
0
Bit/Field
Name
Type
Reset
Description
31:10
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
9
RXE
R/W
1
UART Receive Enable
If this bit is set to 1, the receive section of the UART is enabled.
When the UART is disabled in the middle of a receive, it
completes the current character before stopping.
8
TXE
R/W
1
UART Transmit Enable
If this bit is set to 1, the transmit section of the UART is enabled.
When the UART is disabled in the middle of a transmission, it
completes the current character before stopping.
7
LBE
R/W
0
UART Loop Back Enable
If this bit is set to 1, the UnTX path is fed through the UnRX path.
6:1
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
0
UARTEN
R/W
0
UART Enable
If this bit is set to 1, the UART is enabled. When the UART is
disabled in the middle of transmission or reception, it completes
the current character before stopping.
October 5, 2006
207
Preliminary
Universal Asynchronous Receiver/Transmitter (UART)
Register 8: UART Interrupt FIFO Level Select (UARTIFLS), offset 0x034
The UARTIFLS register is the interrupt FIFO level select register. You can use this register to
define the FIFO level at which the TXRIS and RXRIS bits in the UARTRIS register are triggered.
The interrupts are generated based on a transition through a level rather than being based on the
level. That is, the interrupts are generated when the fill level progresses through the trigger level.
For example, if the receive trigger level is set to the half-way mark, the interrupt is triggered as the
module is receiving the 9th character.
Out of reset, the TXIFLSEL and RXIFLSEL bits are configured so that the FIFOs trigger an
interrupt at the half-way mark.
UART Interrupt FIFO Level Select (UARTIFLS)
Offset 0x034
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
TXIFLSEL
RXIFLSEL
Bit/Field
Name
Type
Reset
31:6
reserved
RO
0
5:3
RXIFLSEL
R/W
0X2
R/W
1
R/W
1
R/W
0
Description
Reserved bits return an indeterminate value, and should never
be changed.
UART Receive Interrupt FIFO Level Select
The trigger points for the receive interrupt are as follows:
000: RX FIFO ≥ 1/8 full
001: RX FIFO ≥ 1/4 full
010: RX FIFO ≥ 1/2 full (default)
011: RX FIFO ≥ 3/4 full
100: RX FIFO ≥ 7/8 full
101-111: Reserved
2:0
TXIFLSEL
R/W
0X2
UART Transmit Interrupt FIFO Level Select
The trigger points for the transmit interrupt are as follows:
000: TX FIFO ≤ 1/8 full
001: TX FIFO ≤ 1/4 full
010: TX FIFO ≤ 1/2 full (default)
011: TX FIFO ≤ 3/4 full
100: TX FIFO ≤ 7/8 full
101-111: Reserved
208
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 9: UART Interrupt Mask (UARTIM), offset 0x038
The UARTIM register is the interrupt mask set/clear register.
On a read, this register gives the current value of the mask on the relevant interrupt. Writing a 1 to
a bit allows the corresponding raw interrupt signal to be routed to the interrupt controller. Writing a
0 prevents the raw interrupt signal from being sent to the interrupt controller.
UART Interrupt Mask (UARTIM)
Offset 0x038
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
OEIM
BEIM
PEIM
FEIM
RTIM
TXIM
RXIM
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
reserved
Bit/Field
Name
Type
Reset
Description
31:11
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
10
OEIM
R/W
0
UART Overrun Error Interrupt Mask
On a read, the current mask for the OEIM interrupt is returned.
Setting this bit to 1 promotes the OEIM interrupt to the interrupt
controller.
9
BEIM
R/W
0
UART Break Error Interrupt Mask
On a read, the current mask for the BEIM interrupt is returned.
Setting this bit to 1 promotes the BEIM interrupt to the interrupt
controller.
8
PEIM
R/W
0
UART Parity Error Interrupt Mask
On a read, the current mask for the PEIM interrupt is returned.
Setting this bit to 1 promotes the PEIM interrupt to the interrupt
controller.
7
FEIM
R/W
0
UART Framing Error Interrupt Mask
On a read, the current mask for the FEIM interrupt is returned.
Setting this bit to 1 promotes the FEIM interrupt to the interrupt
controller.
6
RTIM
R/W
0
UART Receive Time-Out Interrupt Mask
On a read, the current mask for the RTIM interrupt is returned.
Setting this bit to 1 promotes the RTIM interrupt to the interrupt
controller.
October 5, 2006
209
Preliminary
Universal Asynchronous Receiver/Transmitter (UART)
Bit/Field
Name
Type
Reset
5
TXIM
R/W
0
Description
UART Transmit Interrupt Mask
On a read, the current mask for the TXIM interrupt is returned.
Setting this bit to 1 promotes the TXIM interrupt to the interrupt
controller.
4
RXIM
R/W
0
UART Receive Interrupt Mask
On a read, the current mask for the RXIM interrupt is returned.
Setting this bit to 1 promotes the RXIM interrupt to the interrupt
controller.
3:0
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
210
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 10: UART Raw Interrupt Status (UARTRIS), offset 0x03C
The UARTRIS register is the raw interrupt status register. On a read, this register gives the current
raw status value of the corresponding interrupt. A write has no effect.
UART Raw Interrupt Status (UARTRIS)
Offset 0x03C
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
OERIS
BERIS
PERIS
FERIS
RTRIS
TXRIS
RXRIS
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
1
RO
1
RO
1
reserved
Type
Reset
reserved
Type
Reset
RO
0
reserved
Bit/Field
Name
Type
Reset
Description
31:11
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
10
OERIS
RO
0
UART Overrun Error Raw Interrupt Status
Gives the raw interrupt state (prior to masking) of this interrupt.
9
BERIS
RO
0
UART Break Error Raw Interrupt Status
Gives the raw interrupt state (prior to masking) of this interrupt.
8
PERIS
RO
0
UART Parity Error Raw Interrupt Status
Gives the raw interrupt state (prior to masking) of this interrupt.
7
FERIS
RO
0
UART Framing Error Raw Interrupt Status
Gives the raw interrupt state (prior to masking) of this interrupt.
6
RTRIS
RO
0
UART Receive Time-Out Raw Interrupt Status
Gives the raw interrupt state (prior to masking) of this interrupt.
5
TXRIS
RO
0
UART Transmit Raw Interrupt Status
Gives the raw interrupt state (prior to masking) of this interrupt.
4
RXRIS
RO
0
UART Receive Raw Interrupt Status
Gives the raw interrupt state (prior to masking) of this interrupt.
3:0
reserved
RO
0xF
This reserved bit is read-only and has a reset value of 0xF.
October 5, 2006
211
Preliminary
Universal Asynchronous Receiver/Transmitter (UART)
Register 11: UART Masked Interrupt Status (UARTMIS), offset 0x040
The UARTMIS register is the masked interrupt status register. On a read, this register gives the
current masked status value of the corresponding interrupt. A write has no effect.
UART Masked Interrupt Status (UARTMIS)
Offset 0x040
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
OEMIS
BEMIS
PEMIS
FEMIS
RTMIS
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
reserved
TXMIS RXMIS
RO
0
RO
0
RO
0
RO
0
Bit/Field
Name
Type
Reset
Description
31:11
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
10
OEMIS
RO
0
UART Overrun Error Masked Interrupt Status
Gives the masked interrupt state of this interrupt.
9
BEMIS
RO
0
UART Break Error Masked Interrupt Status
Gives the masked interrupt state of this interrupt.
8
PEMIS
RO
0
UART Parity Error Masked Interrupt Status
Gives the masked interrupt state of this interrupt.
7
FEMIS
RO
0
UART Framing Error Masked Interrupt Status
Gives the masked interrupt state of this interrupt.
6
RTMIS
RO
0
UART Receive Time-Out Masked Interrupt Status
Gives the masked interrupt state of this interrupt.
5
TXMIS
RO
0
UART Transmit Masked Interrupt Status
Gives the masked interrupt state of this interrupt.
4
RXMIS
RO
0
UART Receive Masked Interrupt Status
Gives the masked interrupt state of this interrupt.
3:0
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
212
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 12: UART Interrupt Clear (UARTICR), offset 0x044
The UARTICR register is the interrupt clear register. On a write of 1, the corresponding interrupt
(both raw interrupt and masked interrupt, if enabled) is cleared. A write of 0 has no effect.
UART Interrupt Clear (UARTICR)
Offset 0x044
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
OEIC
BEIC
PEIC
FEIC
RTIC
TXIC
RXIC
W1C
0
W1C
0
W1C
0
W1C
0
W1C
0
W1C
0
W1C
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
reserved
Bit/Field
Name
Type
Reset
Description
31:11
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
10
OEIC
W1C
0
Overrun Error Interrupt Clear
0: No effect on the interrupt.
1: Clears interrupt.
9
BEIC
W1C
0
Break Error Interrupt Clear
0: No effect on the interrupt.
1: Clears interrupt.
8
PEIC
W1C
0
Parity Error Interrupt Clear
0: No effect on the interrupt.
1: Clears interrupt.
7
FEIC
W1C
0
Framing Error Interrupt Clear
0: No effect on the interrupt.
1: Clears interrupt.
6
RTIC
W1C
0
Receive Time-Out Interrupt Clear
0: No effect on the interrupt.
1: Clears interrupt.
5
TXIC
W1C
0
Transmit Interrupt Clear
0: No effect on the interrupt.
1: Clears interrupt.
4
RXIC
W1C
0
Receive Interrupt Clear
0: No effect on the interrupt.
1: Clears interrupt.
3:0
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
October 5, 2006
213
Preliminary
Universal Asynchronous Receiver/Transmitter (UART)
Register 13: UART Peripheral Identification 4 (UARTPeriphID4), offset 0xFD0
The UARTPeriphIDn registers are hard-coded and the fields within the registers determine the
reset values.
UART Peripheral Identification 4 (UARTPeriphID4)
Offset 0xFD0
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID4
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID4
RO
0x00
Description
Reserved bits return an indeterminate value, and should
never be changed.
UART Peripheral ID Register[7:0]
214
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 14: UART Peripheral Identification 5 (UARTPeriphID5), offset 0xFD4
The UARTPeriphIDn registers are hard-coded and the fields within the registers determine the
reset values.
UART Peripheral Identification 5 (UARTPeriphID5)
Offset 0xFD4
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID5
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID5
RO
0x00
Description
Reserved bits return an indeterminate value, and should
never be changed.
UART Peripheral ID Register[15:8]
October 5, 2006
215
Preliminary
Universal Asynchronous Receiver/Transmitter (UART)
Register 15: UART Peripheral Identification 6 (UARTPeriphID6), offset 0xFD8
The UARTPeriphIDn registers are hard-coded and the fields within the registers determine the
reset values.
UART Peripheral Identification 6 (UARTPeriphID6)
Offset 0xFD8
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID6
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID6
RO
0x00
Description
Reserved bits return an indeterminate value, and should
never be changed.
UART Peripheral ID Register[23:16]
216
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 16: UART Peripheral Identification 7 (UARTPeriphID7), offset 0xFDC
The UARTPeriphIDn registers are hard-coded and the fields within the registers determine the
reset values.
UART Peripheral Identification 7 (UARTPeriphID7)
Offset 0xFDC
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID7
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID7
RO
0x00
Description
Reserved bits return an indeterminate value, and should
never be changed.
UART Peripheral ID Register[31:24]
October 5, 2006
217
Preliminary
Universal Asynchronous Receiver/Transmitter (UART)
Register 17: UART Peripheral Identification 0 (UARTPeriphID0), offset 0xFE0
The UARTPeriphIDn registers are hard-coded and the fields within the registers determine the
reset values.
UART Peripheral Identification 0 (UARTPeriphID0)
Offset 0xFE0
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
0
RO
0
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
PID0
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID0
RO
0x11
Description
Reserved bits return an indeterminate value, and should never
be changed.
UART Peripheral ID Register[7:0]
Can be used by software to identify the presence of this
peripheral.
218
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 18: UART Peripheral Identification 1 (UARTPeriphID1), offset 0xFE4
The UARTPeriphIDn registers are hard-coded and the fields within the registers determine the
reset values.
UART Peripheral Identification 1 (UARTPeriphID1)
Offset 0xFE4
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID1
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID1
RO
0x00
Description
Reserved bits return an indeterminate value, and should never
be changed.
UART Peripheral ID Register[15:8]
Can be used by software to identify the presence of this
peripheral.
October 5, 2006
219
Preliminary
Universal Asynchronous Receiver/Transmitter (UART)
Register 19: UART Peripheral Identification 2 (UARTPeriphID2), offset 0xFE8
The UARTPeriphIDn registers are hard-coded and the fields within the registers determine the
reset values.
UART Peripheral Identification 2 (UARTPeriphID2)
Offset 0xFE8
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
1
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID2
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID2
RO
0x18
Description
Reserved bits return an indeterminate value, and should never
be changed.
UART Peripheral ID Register[23:16]
Can be used by software to identify the presence of this
peripheral.
220
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 20: UART Peripheral Identification 3 (UARTPeriphID3), offset 0xFEC
The UARTPeriphIDn registers are hard-coded and the fields within the registers determine the
reset values.
UART Peripheral Identification 3 (UARTPeriphID3)
Offset 0xFEC
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
PID3
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID3
RO
0x01
Description
Reserved bits return an indeterminate value, and should never
be changed.
UART Peripheral ID Register[31:24]
Can be used by software to identify the presence of this
peripheral.
October 5, 2006
221
Preliminary
Universal Asynchronous Receiver/Transmitter (UART)
Register 21: UART PrimeCell Identification 0 (UARTPCellID0), offset 0xFF0
The UARTPCellIDn registers are hard-coded and the fields within the registers determine the
reset values.
UART Primecell Identification 0 (UARTPCellID0)
Offset 0xFF0
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
1
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
CID0
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
CID0
RO
0x0D
Description
Reserved bits return an indeterminate value, and should never
be changed.
UART PrimeCell ID Register[7:0]
Provides software a standard cross-peripheral identification
system.
222
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 22: UART PrimeCell Identification 1 (UARTPCellID1), offset 0xFF4
The UARTPCellIDn registers are hard-coded and the fields within the registers determine the
reset values.
UART Primecell Identification 1 (UARTPCellID1)
Offset 0xFF4
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
1
RO
1
RO
1
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
CID1
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
CID1
RO
0xF0
Description
Reserved bits return an indeterminate value, and should never
be changed.
UART PrimeCell ID Register[15:8]
Provides software a standard cross-peripheral identification
system.
October 5, 2006
223
Preliminary
Universal Asynchronous Receiver/Transmitter (UART)
Register 23: UART PrimeCell Identification 2 (UARTPCellID2), offset 0xFF8
The UARTPCellIDn registers are hard-coded and the fields within the registers determine the
reset values.
UART Primecell Identification 2 (UARTPCellID2)
Offset 0xFF8
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
CID2
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
CID2
RO
0x05
Description
Reserved bits return an indeterminate value, and should never
be changed.
UART PrimeCell ID Register[23:16]
Provides software a standard cross-peripheral identification
system.
224
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 24: UART PrimeCell Identification 3 (UARTPCellID3), offset 0xFFC
The UARTPCellIDn registers are hard-coded and the fields within the registers determine the
reset values.
UART Primecell Identification 3 (UARTPCellID3)
Offset 0xFFC
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
0
RO
1
RO
1
RO
0
RO
0
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
CID3
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
CID3
RO
0xB1
Description
Reserved bits return an indeterminate value, and should never
be changed.
UART PrimeCell ID Register[31:24]
Provides software a standard cross-peripheral identification
system.
October 5, 2006
225
Preliminary
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 has the following features:
12.1

Master or slave operation

Programmable clock bit rate and prescale

Separate transmit and receive FIFOs, 16 bits wide, 8 locations deep

Programmable interface operation for Freescale SPI, MICROWIRE, or Texas Instruments
synchronous serial interfaces

Programmable data frame size from 4 to 16 bits

Internal loopback test mode for diagnostic/debug testing
Block Diagram
Figure 12-1.
SSI Module Block Diagram
Interrupt
Interrupt Control
SSIIM
SSIMIS
Control / Status
SSIRIS
SSIICR
SSICR0
SSICR1
TxFIFO
8 x 16
.
.
.
SSITx
SSISR
SSIDR
RxFIFO
8 x 16
Transmit /
Receive
Logic
SSIRx
SSIClk
SSIFss
System Clock
Clock
Prescaler
Identification Registers
SSIPCellID0
SSIPeriphID 0
SSIPeriphID 4
SSIPCellID1
SSIPeriphID 1
SSIPeriphID 5
SSIPCellID2
SSIPeriphID 2
SSIPeriphID 6
SSIPCellID3
SSIPeriphID 3
SSIPeriphID 7
.
.
.
SSICPSR
226
October 5, 2006
Preliminary
LM3S101 Data Sheet
12.2
Functional Description
The SSI performs serial-to-parallel conversion on data received from a peripheral device. The
CPU accesses data, control, and status information. The transmit and receive paths are buffered
with internal FIFO memories allowing up to eight 16-bit values to be stored independently in both
transmit and receive modes.
12.2.1
Bit Rate Generation
The SSI includes a programmable bit rate clock divider and prescaler to generate the serial output
clock. Bit rates are supported to 1.5 MHz and higher, although maximum bit rate is determined by
peripheral devices.
The serial bit rate is derived by dividing down the 20-MHz input clock. The clock is first divided by
an even prescale value CPSDVSR from 2 to 254, which is programmed in the SSI Clock Prescale
(SSICPSR) register (see page 244). 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 238).
The frequency of the output clock SSIClk is defined by:
FSSIClk = FSysClk / (CPSDVSR * (1 + SCR))
Note that although the SSIClk transmit clock can theoretically be 10 MHz, the module may not be
able to operate at that speed. For transmit operations, the system clock must be at least two times
faster than the SSIClk. For receive operations, the system clock must be at least 12 times faster
than the SSIClk.
See “Electrical Characteristics” on page 282 to view SSI timing parameters.
12.2.2
FIFO Operation
12.2.2.1
Transmit FIFO
The common transmit FIFO is a 16-bit wide, 8-locations deep, first-in, first-out memory buffer. The
CPU writes data to the FIFO by writing the SSI Data (SSIDR) register (see page 242), 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.
12.2.2.2
Receive FIFO
The common receive FIFO is a 16-bit wide, 8-locations deep, first-in, first-out memory buffer.
Received data from the serial interface is stored in the buffer until read out by the CPU, which
accesses the read FIFO by reading the SSIDR register.
When configured as a master or slave, serial data received through the SSIRx pin is registered
prior to parallel loading into the attached slave or master receive FIFO, respectively.
12.2.3
Interrupts
The SSI can generate interrupts when the following conditions are observed:

Transmit FIFO service

Receive FIFO service

Receive FIFO time-out

Receive FIFO overrun
October 5, 2006
227
Preliminary
Synchronous Serial Interface (SSI)
All of the interrupt events are ORed together before being sent to the interrupt controller, so the
SSI can only generate a single interrupt request to the controller at any given time. You can mask
each of the four individual maskable interrupts by setting the appropriate bits in the SSI Interrupt
Mask (SSIIM) register (see page 245). 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 246 and page 247, respectively).
12.2.4
Frame Formats
Each data frame is between 4 and 16 bits long, depending on the size of data programmed, and is
transmitted starting with the MSB. There are three basic frame types that can be selected:

Texas Instruments synchronous serial

Freescale SPI

MICROWIRE
For all three formats, the serial clock (SSIClk) is held inactive while the SSI is idle, and SSIClk
transitions at the programmed frequency only during active transmission or reception of data. The
idle state of SSIClk is utilized to provide a receive timeout indication that occurs when the receive
FIFO still contains data after a timeout period.
For Freescale SPI and MICROWIRE frame formats, the serial frame (SSIFss) pin is active Low,
and is asserted (pulled down) during the entire transmission of the frame.
For Texas Instruments synchronous serial frame format, the SSIFss pin is pulsed for one serial
clock period starting at its rising edge, prior to the transmission of each frame. For this frame
format, both the SSI and the off-chip slave device drive their output data on the rising edge of
SSIClk, and latch data from the other device on the falling edge.
Unlike the full-duplex transmission of the other two frame formats, the MICROWIRE format uses a
special master-slave messaging technique, which operates at half-duplex. In this mode, when a
frame begins, an 8-bit control message is transmitted to the off-chip slave. During this transmit, no
incoming data is received by the SSI. After the message has been sent, the off-chip slave decodes
it and, after waiting one serial clock after the last bit of the 8-bit control message has been sent,
responds with the requested data. The returned data can be 4 to 16 bits in length, making the total
frame length anywhere from 13 to 25 bits.
12.2.4.1
Texas Instruments Synchronous Serial Frame Format
Figure 12-2 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
228
October 5, 2006
Preliminary
LM3S101 Data Sheet
In this mode, SSIClk and SSIFss are forced Low, and the transmit data line SSITx is tristated
whenever the SSI is idle. Once the bottom entry of the transmit FIFO contains data, SSIFss is
pulsed High for one SSIClk period. The value to be transmitted is also transferred from the
transmit FIFO to the serial shift register of the transmit logic. On the next rising edge of SSIClk,
the MSB of the 4 to 16-bit data frame is shifted out on the SSITx pin. Likewise, the MSB of the
received data is shifted onto the SSIRx pin by the off-chip serial slave device.
Both the SSI and the off-chip serial slave device then clock each data bit into their serial shifter on
the falling edge of each SSIClk. The received data is transferred from the serial shifter to the
receive FIFO on the first rising edge of SSIClk after the LSB has been latched.
Figure 12-3 shows the Texas Instruments synchronous serial frame format when back-to-back
frames are transmitted.
Figure 12-3.
TI Synchronous Serial Frame Format (Continuous Transfer)
SSIClk
SSIFss
SSITx/SSIRx
MSB
LSB
4 to 16 bits
12.2.4.2
Freescale SPI Frame Format
The Freescale SPI interface is a four-wire interface where the SSIFss signal behaves as a slave
select. The main feature of the Freescale SPI format is that the inactive state and phase of the
SSIClk signal are programmable through the SPO and SPH bits within the SSISCR0 control
register.
SPO Clock Polarity Bit
When the SPO clock polarity control bit is Low, it produces a steady state Low value on the
SSIClk pin. If the SPO bit is High, a steady state High value is placed on the SSIClk pin when
data is not being transferred.
SPH Phase Control Bit
The SPH phase control bit selects the clock edge that captures data and allows it to change state.
It has the most impact on the first bit transmitted by either allowing or not allowing a clock
transition before the first data capture edge. When the SPH phase control bit is Low, data is
captured on the first clock edge transition. If the SPH bit is High, data is captured on the second
clock edge transition.
12.2.4.3
Freescale SPI Frame Format with SPO=0 and SPH=0
Single and continuous transmission signal sequences for Freescale SPI format with SPO=0 and
SPH=0 are shown in Figure 12-4 and Figure 12-5.
October 5, 2006
229
Preliminary
Synchronous Serial Interface (SSI)
Figure 12-4.
Freescale SPI Format (Single Transfer) with SPO=0 and SPH=0
SSIClk
SSIFss
MSB
SSIRx
LSB
Q
4 to 16 bits
MSB
SSITx
Figure 12-5.
LSB
Freescale SPI Format (Continuous Transfer) with SPO=0 and SPH=0
SSIClk
SSIFss
SSIRx LSB
MSB
LSB
MSB
4 to 16 bits
SSITx LSB
MSB
LSB
MSB
In this configuration, during idle periods:

SSIClk is forced Low

SSIFss is forced High

The transmit data line SSITx is arbitrarily forced Low

When the SSI is configured as a master, it enables the SSIClk pad

When the SSI is configured as a slave, it disables the SSIClk pad
If the SSI is enabled and there is valid data within the transmit FIFO, the start of transmission is
signified by the SSIFss master signal being driven Low. This causes slave data to be enabled
onto the SSIRx input line of the master. The master SSITx output pad is enabled.
One half SSIClk period later, valid master data is transferred to the SSITx pin. Now that both the
master and slave data have been set, the SSIClk master clock pin goes High after one further
half SSIClk period.
The data is now captured on the rising and propagated on the falling edges of the SSIClk signal.
In the case of a single word transmission, after all bits of the data word have been transferred, the
SSIFss line is returned to its idle High state one SSIClk period after the last bit has been
captured.
However, in the case of continuous back-to-back transmissions, the SSIFss signal must be
pulsed High between each data word transfer. This is because the slave select pin freezes the
data in its serial peripheral register and does not allow it to be altered if the SPH bit is logic zero.
Therefore, the master device must raise the SSIFss pin of the slave device between each data
transfer to enable the serial peripheral data write. On completion of the continuous transfer, the
SSIFss pin is returned to its idle state one SSIClk period after the last bit has been captured.
12.2.4.4
Freescale SPI Frame Format with SPO=0 and SPH=1
The transfer signal sequence for Freescale SPI format with SPO=0 and SPH=1 is shown in
Figure 12-6, which covers both single and continuous transfers.
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Figure 12-6.
Freescale SPI Frame Format with SPO=0 and SPH=1
SSIClk
SSIFss
SSIRx
Q
LSB
MSB
Q
4 to 16 bits
SSITx
MSB
LSB
In this configuration, during idle periods:

SSIClk is forced Low

SSIFss is forced High

The transmit data line SSITx is arbitrarily forced Low

When the SSI is configured as a master, it enables the SSIClk pad

When the SSI is configured as a slave, it disables the SSIClk pad
If the SSI is enabled and there is valid data within the transmit FIFO, the start of transmission is
signified by the SSIFss master signal being driven Low. The master SSITx output is enabled.
After a further one half SSIClk period, both master and slave valid data is enabled onto their
respective transmission lines. At the same time, the SSIClk is enabled with a rising edge
transition.
Data is then captured on the falling edges and propagated on the rising edges of the SSIClk
signal.
In the case of a single word transfer, after all bits have been transferred, the SSIFss line is
returned to its idle High state one SSIClk period after the last bit has been captured.
For continuous back-to-back transfers, the SSIFss pin is held Low between successive data
words and termination is the same as that of the single word transfer.
12.2.4.5
Freescale SPI Frame Format with SPO=1 and SPH=0
Single and continuous transmission signal sequences for Freescale SPI format with SPO=1 and
SPH=0 are shown in Figure 12-7 and Figure 12-8.
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
MSB
LSB
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Figure 12-8.
Freescale SPI Frame Format (Continuous Transfer) with SPO=1 and SPH=0
SSIClk
SSIFss
SSITx/SSIRx
LSB
MSB
LSB
MSB
4 to 16 bits
In this configuration, during idle periods:

SSIClk is forced High

SSIFss is forced High

The transmit data line SSITx is arbitrarily forced Low

When the SSI is configured as a master, it enables the SSIClk pad

When the SSI is configured as a slave, it disables the SSIClk pad
If the SSI is enabled and there is valid data within the transmit FIFO, the start of transmission is
signified by the SSIFss master signal being driven Low, which causes slave data to be
immediately transferred onto the SSIRx line of the master. The master SSITx output pad is
enabled.
One half period later, valid master data is transferred to the SSITx line. Now that both the master
and slave data have been set, the SSIClk master clock pin becomes Low after one further half
SSIClk period. This means that data is captured on the falling edges and propagated on the rising
edges of the SSIClk signal.
In the case of a single word transmission, after all bits of the data word are transferred, the
SSIFss line is returned to its idle High state one SSIClk period after the last bit has been
captured.
However, in the case of continuous back-to-back transmissions, the SSIFss signal must be
pulsed High between each data word transfer. This is because the slave select pin freezes the
data in its serial peripheral register and does not allow it to be altered if the SPH bit is logic zero.
Therefore, the master device must raise the SSIFss pin of the slave device between each data
transfer to enable the serial peripheral data write. On completion of the continuous transfer, the
SSIFss pin is returned to its idle state one SSIClk period after the last bit has been captured.
12.2.4.6
Freescale SPI Frame Format with SPO=1 and SPH=1
The transfer signal sequence for Freescale SPI format with SPO=1 and SPH=1 is shown in
Figure 12-9, which covers both single and continuous transfers.
Figure 12-9.
Freescale SPI Frame Format with SPO=1 and SPH=1
SSIClk
SSIFss
SSIRx
Q
LSB
MSB
Q
4 to 16 bits
SSITx
Note:
MSB
LSB
Q is undefined in Figure 12-9.
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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.
12.2.4.7
MICROWIRE Frame Format
Figure 12-10 shows the MICROWIRE frame format, again for a single frame. Figure 12-11 shows
the same format when back-to-back frames are transmitted.
Figure 12-10.
MICROWIRE Frame Format (Single Frame)
SSIClk
SSIFss
SSITx
MSB
LSB
8-bit control
SSIRx
0
MSB
LSB
4 to 16 bits
output data
MICROWIRE format is very similar to SPI format, except that transmission is half-duplex instead
of full-duplex, using a master-slave message passing technique. Each serial transmission begins
with an 8-bit control word that is transmitted from the SSI to the off-chip slave device. During this
transmission, no incoming data is received by the SSI. After the message has been sent, the
off-chip slave decodes it and, after waiting one serial clock after the last bit of the 8-bit control
message has been sent, responds with the required data. The returned data is 4 to 16 bits in
length, making the total frame length anywhere from 13 to 25 bits.
In this configuration, during idle periods:

SSIClk is forced Low

SSIFss is forced High

The transmit data line SSITx is arbitrarily forced Low
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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.
Figure 12-12 illustrates these setup and hold time requirements. With respect to the SSIClk rising
edge on which the first bit of receive data is to be sampled by the SSI slave, SSIFss must have a
setup of at least two times the period of SSIClk on which the SSI operates. With respect to the
SSIClk rising edge previous to this edge, SSIFss must have a hold of at least one SSIClk
period.
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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
12.3
Initialization and Configuration
To use the SSI, its peripheral clock must be enabled by setting the SSI bit in the RCGC1 register.
For each of the frame formats, the SSI is configured using the following steps:
1. Ensure that the SSE bit in the SSICR1 register is disabled before making any configuration
changes.
2. Select whether the SSI is a master or slave:
a. For master operations, set the SSICR1 register to 0x00000000.
b. For slave mode (output enabled), set the SSICR1 register to 0x00000004.
c. For slave mode (output disabled), set the SSICR1 register to 0x0000000C.
3. Configure the clock prescale divisor by writing the SSICPSR register.
4. Write the SSICR0 register with the following configuration:
– Serial clock rate (SCR)
– Desired clock phase/polarity, if using Freescale SPI mode (SPH and SPO)
– The protocol mode: Freescale SPI, TI SSF, MICROWIRE (FRF)
– The data size (DSS)
5. Enable the SSI by setting the SSE bit in the SSICR1 register.
As an example, assume the SSI must be configured to operate with the following parameters:

Master operation

Freescale SPI mode (SPO=1, SPH=1)

1 Mbps bit rate

8 data bits
Assuming the system clock is 20 MHz, the bit rate calculation would be:
FSSIClk = FSysClk / (CPSDVSR * (1 + SCR)) ' 1x106 = 20x106 / (CPSDVSR * (1 +
SCR))
In this case, if CPSDVSR=2, SCR must be 9.
The configuration sequence would be as follows:
1. Ensure that the SSE bit in the SSICR1 register is disabled.
2. Write the SSICR1 register with a value of 0x00000000.
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3. Write the SSICPSR register with a value of 0x00000002.
4. Write the SSICR0 register with a value of 0x000009C7.
5. The SSI is then enabled by setting the SSE bit in the SSICR1 register to 1.
12.4
Register Map
Table 12-1 lists the SSI registers. The offset listed is a hexadecimal increment to the register’s
address, relative to the SSI base address of 0x40008000.
Note:
The SSI must be disabled (see the SSE bit in the SSICR1 register) before any of the
control registers are reprogrammed.
Table 12-1. SSI Register Map
Offset
Name
0x000
Description
See
page
Reset
Type
SSICR0
0x00000000
RW
Control 0
238
0x004
SSICR1
0x00000000
RW
Control 1
240
0x008
SSIDR
0x00000000
RW
Data
242
0x00C
SSISR
0x00000003
RO
Status
243
0x010
SSICPSR
0x00000000
RW
Clock prescale
244
0x014
SSIIM
0x00000000
RW
Interrupt mask
245
0x018
SSIRIS
0x00000008
RO
Raw interrupt status
246
0x01C
SSIMIS
0x00000000
RO
Masked interrupt status
247
0x020
SSIICR
0x00000000
W1C
Interrupt clear
248
0xFD0
SSIPeriphID4
0x00000000
RO
Peripheral identification 4
249
0xFD4
SSIPeriphID5
0x00000000
RO
Peripheral identification 5
250
0xFD8
SSIPeriphID6
0x00000000
RO
Peripheral identification 6
251
0xFDC
SSIPeriphID7
0x00000000
RO
Peripheral identification 7
252
0xFE0
SSIPeriphID0
0x00000022
RO
Peripheral identification 0
253
0xFE4
SSIPeriphID1
0x00000000
RO
Peripheral identification 1
254
0xFE8
SSIPeriphID2
0x00000018
RO
Peripheral identification 2
255
0xFEC
SSIPeriphID3
0x00000001
RO
Peripheral identification 3
256
0xFF0
SSIPCellID0
0x0000000D
RO
PrimeCell identification 0
257
0xFF4
SSIPCellID1
0x000000F0
RO
PrimeCell identification 1
258
0xFF8
SSIPCellID2
0x00000005
RO
PrimeCell identification 2
259
0xFFC
SSIPCellID3
0x000000B1
RO
PrimeCell identification 3
260
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LM3S101 Data Sheet
12.5
Register Descriptions
The remainder of this section lists and describes the SSI registers, in numerical order by address
offset.
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Synchronous Serial Interface (SSI)
Register 1: SSI Control 0 (SSICR0), offset 0x000
SSICR0 is control register 0 and contains bit fields that control various functions within the SSI
module. Functionality such as protocol mode, clock rate and data size are configured in this
register.
SSI Control 0 (SSICR0)
Offset 0x000
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
SPH
SPO
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
SCR
Type
Reset
DSS
FRF
R/W
0
Bit/Field
Name
Type
Reset
Description
31:16
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
15:8
SCR
R/W
0
SSI Serial Clock Rate
The value SCR is used to generate the transmit and receive bit
rate of the SSI. The bit rate is:
BR= FSSICLK/(CPSDVSR * (1 + SCR))
where CPSDVSR is an even value from 2-254 programmed in the
SSICPSR register, and SCR is a value from 0-255.
7
SPH
R/W
0
SSI Serial Clock Phase
This bit is only applicable to the Freescale SPI Format.
The SPH control bit selects the clock edge that captures data
and allows it to change state. It has the most impact on the first
bit transmitted by either allowing or not allowing a clock
transition before the first data capture edge.
When the SPH bit is 0, data is captured on the first clock edge
transition. If SPH is 1, data is captured on the second clock edge
transition.
6
SPO
R/W
0
SSI Serial Clock Polarity
This bit is only applicable to the Freescale SPI Format.
When the SPO bit is 0, it produces a steady state Low value on
the SSIClk pin. If SPO is 1, a steady state High value is placed
on the SSIClk pin when data is not being transferred.
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Bit/Field
Name
Type
Reset
5:4
FRF
R/W
0
Description
SSI Frame Format Select.
The FRF values are defined as follows:
FRF Value
3:0
DSS
R/W
0
Frame Format
00
Freescale SPI Frame Format
01
Texas Instruments Synchronous
Serial Frame Format
10
MICROWIRE Frame Format
11
Reserved
SSI Data Size Select
The DSS values are defined as follows:
DSS Value
Data Size
0000-0010
Reserved
0011
4-bit data
0100
5-bit data
0101
6-bit data
0110
7-bit data
0111
8-bit data
1000
9-bit data
1001
10-bit data
1010
11-bit data
1011
12-bit data
1100
13-bit data
1101
14-bit data
1110
15-bit data
1111
16-bit data
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Register 2: SSI Control 1 (SSICR1), offset 0x004
SSICR1 is control register 1 and contains bit fields that control various functions within the SSI
module. Master and slave mode functionality is controlled by this register.
SSI Control 1 (SSCR1)
Offset 0x004
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
SOD
MS
SSE
LBM
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
Bit/Field
Name
Type
Reset
Description
31:4
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
3
SOD
R/W
0
SSI Slave Mode Output Disable
This bit is relevant only in the Slave mode (MS=1). In
multiple-slave systems, it is possible for the SSI master to
broadcast a message to all slaves in the system while
ensuring that only one slave drives data onto the serial output
line. In such systems, the TXD lines from multiple slaves
could be tied together. To operate in such a system, the SOD
bit can be configured so that the SSI slave does not drive the
SSITx pin.
0: SSI can drive SSITx output in Slave Output mode.
1: SSI must not drive the SSITx output in Slave mode.
2
MS
R/W
0
SSI Master/Slave Select
This bit selects Master or Slave mode and can be modified
only when SSI is disabled (SSE=0).
0: Device configured as a master.
1: Device configured as a slave.
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LM3S101 Data Sheet
Bit/Field
Name
Type
Reset
1
SSE
R/W
0
Description
SSI Synchronous Serial Port Enable
Setting this bit enables SSI operation.
0: SSI operation disabled.
1: SSI operation enabled.
Note:
0
LBM
R/W
0
This bit must be set to 0 before any control registers
are reprogrammed.
SSI Loopback Mode
Setting this bit enables Loopback Test mode.
0: Normal serial port operation enabled.
1: Output of the transmit serial shift register is connected
internally to the input of the receive serial shift register.
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Register 3: SSI Data (SSIDR), offset 0x008
SSIDR is the data register and is 16-bits wide. When SSIDR is read, the entry in the receive FIFO
(pointed to by the current FIFO read pointer) is accessed. As data values are removed by the SSI
receive logic from the incoming data frame, they are placed into the entry in the receive FIFO
(pointed to by the current FIFO write pointer).
When SSIDR is written to, the entry in the transmit FIFO (pointed to by the write pointer) is written
to. Data values are removed from the transmit FIFO one value at a time by the transmit logic. It is
loaded into the transmit serial shifter, then serially shifted out onto the SSITx pin at the
programmed bit rate.
When a data size of less than 16 bits is selected, the user must right-justify data written to the
transmit FIFO. The transmit logic ignores the unused bits. Received data less than 16 bits is
automatically right-justified in the receive buffer.
When the SSI is programmed for MICROWIRE frame format, the default size for transmit data is
eight bits (the most significant byte is ignored). The receive data size is controlled by the
programmer. The transmit FIFO and the receive FIFO are not cleared even when the SSE bit in the
SSICR1 register is set to zero. This allows the software to fill the transmit FIFO before enabling the
SSI.
SSI Data (SSIDR)
Offset 0x008
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
DATA
Type
Reset
Bit/Field
Name
Type
Reset
Description
31:16
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
15:0
DATA
R/W
0
SSI Receive/Transmit Data
A read operation reads the receive FIFO. A write operation
writes the transmit FIFO.
Software must right-justify data when the SSI is programmed
for a data size that is less than 16 bits. Unused bits at the top
are ignored by the transmit logic. The receive logic
automatically right-justifies the data.
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Register 4: SSI Status (SSISR), offset 0x00C
SSISR is a status register that contains bits that indicate the FIFO fill status and the SSI busy
status.
SSI Status (SSISR)
Offset 0x00C
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
BSY
RFF
RNE
TNF
TFE
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
1
reserved
Type
Reset
reserved
Type
Reset
RO
0
Bit/Field
Name
Type
Reset
Description
31:5
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
4
BSY
RO
0
SSI Busy Bit
0: SSI is idle.
1: SSI is currently transmitting and/or receiving a frame, or the
transmit FIFO is not empty.
3
RFF
RO
0
SSI Receive FIFO Full
0: Receive FIFO is not full.
1: Receive FIFO is full.
2
RNE
RO
0
SSI Receive FIFO Not Empty
0: Receive FIFO is empty.
1: Receive FIFO is not empty.
1
TNF
RO
1
SSI Transmit FIFO Not Full
0: Transmit FIFO is full.
1: Transmit FIFO is not full.
0
TFE
R0
1
SSI Transmit FIFO Empty
0: Transmit FIFO is not empty.
1: Transmit FIFO is empty.
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Synchronous Serial Interface (SSI)
Register 5: SSI Clock Prescale (SSICPSR), offset 0x010
SSICPSR is the clock prescale register and specifies the division factor by which the system clock
must be internally divided before further use.
The value programmed into this register must be an even number between 2 and 254. The
least-significant bit of the programmed number is hard-coded to zero. If an odd number is written
to this register, data read back from this register has the least-significant bit as zero.
SSI Clock Prescale (SSICPSR)
Offset 0x010
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
CPSDVSR
R/W
0
Bit/Field
Name
Type
Reset
Description
31:8
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
7:0
CPSDVSR
R/W
0
SSI Clock Prescale Divisor
This value must be an even number from 2 to 254, depending
on the frequency of SSIClk. The LSB always returns 0 on
reads.
244
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 6: SSI Interrupt Mask (SSIIM), offset 0x014
The SSIIM register is the interrupt mask set or clear register. It is a read/write register and all bits
are cleared to 0 on reset.
On a read, this register gives the current value of the mask on the relevant interrupt. A write of 1 to
the particular bit sets the mask, enabling the interrupt to be read. A write of 0 clears the
corresponding mask.
SSI Interrupt Mask (SSIIM)
Offset 0x014
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
TXIM
RXIM
RTIM
RORIM
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
0
R/W
0
R/W
0
R/W
0
reserved
Type
Reset
reserved
Type
Reset
Bit/Field
Name
Type
Reset
Description
31:4
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
3
TXIM
R/W
0
SSI Transmit FIFO Interrupt Mask
0: TX FIFO half-full or less condition interrupt is masked.
1: TX FIFO half-full or less condition interrupt is not masked.
2
RXIM
R/W
0
SSI Receive FIFO Interrupt Mask
0: RX FIFO half-full or more condition interrupt is masked.
1: RX FIFO half-full or more condition interrupt is not masked.
1
RTIM
R/W
0
SSI Receive Time-Out Interrupt Mask
0: RX FIFO time-out interrupt is masked.
1: RX FIFO time-out interrupt is not masked.
0
RORIM
R/W
0
SSI Receive Overrun Interrupt Mask
0: RX FIFO overrun interrupt is masked.
1: RX FIFO overrun interrupt is not masked.
October 5, 2006
245
Preliminary
Synchronous Serial Interface (SSI)
Register 7: SSI Raw Interrupt Status (SSIRIS), offset 0x018
The SSIRIS register is the raw interrupt status register. On a read, this register gives the current
raw status value of the corresponding interrupt prior to masking. A write has no effect.
SSI Raw Interrupt Status (SSIRIS)
Offset 0x018
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
TXRIS
RXRIS
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
0
reserved
Type
Reset
reserved
Type
Reset
RTRIS RORRIS
RO
0
Bit/Field
Name
Type
Reset
31:4
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
3
TXRIS
RO
1
SSI Transmit FIFO Raw Interrupt Status
RO
0
Description
Indicates that the transmit FIFO is half full or less, when set.
2
RXRIS
RO
0
SSI Receive FIFO Raw Interrupt Status
Indicates that the receive FIFO is half full or more, when set.
1
RTRIS
RO
0
SSI Receive Time-Out Raw Interrupt Status
Indicates that the receive time-out has occurred, when set.
0
RORRIS
RO
0
SSI Receive Overrun Raw Interrupt Status
Indicates that the receive FIFO has overflowed, when set.
246
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 8: SSI Masked Interrupt Status (SSIMIS), offset 0x01C
The SSIMIS register is the masked interrupt status register. On a read, this register gives the
current masked status value of the corresponding interrupt. A write has no effect.
SSI Masked Interrupt Status (SSIMIS)
Offset 0x01C
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
TXMIS RXMIS
reserved
Type
Reset
RO
0
RO
0
RTMIS RORMIS
RO
0
Bit/Field
Name
Type
Reset
31:4
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
3
TXMIS
RO
0
SSI Transmit FIFO Masked Interrupt Status
RO
0
Description
Indicates that the transmit FIFO is half full or less, when set.
2
RXMIS
RO
0
SSI Receive FIFO Masked Interrupt Status
Indicates that the receive FIFO is half full or more, when set.
1
RTMIS
RO
0
SSI Receive Time-Out Masked Interrupt Status
Indicates that the receive time-out has occurred, when set.
0
RORMIS
RO
0
SSI Receive Overrun Masked Interrupt Status
Indicates that the receive FIFO has overflowed, when set.
October 5, 2006
247
Preliminary
Synchronous Serial Interface (SSI)
Register 9: SSI Interrupt Clear (SSIICR), offset 0x020
The SSIICR register is the interrupt clear register. On a write of 1, the corresponding interrupt is
cleared. A write of 0 has no effect.
SSI Interrupt Clear (SSIICR)
Offset 0x020
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RTIC
RORIC
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
W1C
0
W1C
0
reserved
Type
Reset
reserved
Type
Reset
Bit/Field
Name
Type
Reset
Description
31:2
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
1
RTIC
W1C
0
SSI Receive Time-Out Interrupt Clear
0: No effect on interrupt.
1: Clears interrupt.
0
RORIC
W1C
0
SSI Receive Overrun Interrupt Clear
0: No effect on interrupt.
1: Clears interrupt.
248
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 10: SSI Peripheral Identification 4 (SSIPeriphID4), offset 0xFD0
The SSIPeriphIDn registers are hard-coded and the fields within the register determine the reset
value.
SSI Peripheral Identification 4 (SSIPeriphID4)
Offset 0xFD0
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
PID4
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID4
RO
0x00
Description
Reserved bits return an indeterminate value, and should
never be changed.
SSI Peripheral ID Register[7:0]
October 5, 2006
249
Preliminary
Synchronous Serial Interface (SSI)
Register 11: SSI Peripheral Identification 5 (SSIPeriphID5), offset 0xFD4
The SSIPeriphIDn registers are hard-coded and the fields within the register determine the reset
value.
SSI Peripheral Identification 5 (SSIPeriphID5)
Offset 0xFD4
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
PID5
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID5
RO
0x00
Description
Reserved bits return an indeterminate value, and should
never be changed.
SSI Peripheral ID Register[15:8]
250
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 12: SSI Peripheral Identification 6 (SSIPeriphID6), offset 0xFD8
The SSIPeriphIDn registers are hard-coded and the fields within the register determine the reset
value.
SSI Peripheral Identification 6 (SSIPeriphID6)
Offset 0xFD8
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
PID6
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID6
RO
0x00
Description
Reserved bits return an indeterminate value, and should
never be changed.
SSI Peripheral ID Register[23:16]
October 5, 2006
251
Preliminary
Synchronous Serial Interface (SSI)
Register 13: SSI Peripheral Identification 7 (SSIPeriphID7), offset 0xFDC
The SSIPeriphIDn registers are hard-coded and the fields within the register determine the reset
value.
SSI Peripheral Identification 7 (SSIPeriphID7)
Offset 0xFDC
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
RO
0
PID7
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID7
RO
0x00
Description
Reserved bits return an indeterminate value, and should
never be changed.
SSI Peripheral ID Register[31:24]
252
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 14: SSI Peripheral Identification 0 (SSIPeriphID0), offset 0xFE0
The SSIPeriphIDn registers are hard-coded and the fields within the register determine the reset
value.
SSI Peripheral Identification 0 (SSIPeriphID0)
Offset 0xFEO
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
0
RO
0
RO
0
RO
1
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID0
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID0
RO
0x22
Description
Reserved bits return an indeterminate value, and should
never be changed.
SSI Peripheral ID Register[7:0]
Can be used by software to identify the presence of this
peripheral.
October 5, 2006
253
Preliminary
Synchronous Serial Interface (SSI)
Register 15: SSI Peripheral Identification 1 (SSIPeriphID1), offset 0xFE4
The SSIPeriphIDn registers are hard-coded and the fields within the register determine the reset
value.
SSI Peripheral Identification 1 (SSIPeriphID1)
Offset 0xFE4
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID1
RO
0
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID1
RO
0x00
Description
Reserved bits return an indeterminate value, and should
never be changed.
SSI Peripheral ID Register [15:8]
Can be used by software to identify the presence of this
peripheral.
254
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 16: SSI Peripheral Identification 2 (SSIPeriphID2), offset 0xFE8
The SSIPeriphIDn registers are hard-coded and the fields within the register determine the reset
value.
SSI Peripheral Identification 2 (SSIPeriphID2)
Offset 0xFE8
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
1
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
PID2
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID2
RO
0x18
Description
Reserved bits return an indeterminate value, and should
never be changed.
SSI Peripheral ID Register [23:16]
Can be used by software to identify the presence of this
peripheral.
October 5, 2006
255
Preliminary
Synchronous Serial Interface (SSI)
Register 17: SSI Peripheral Identification 3 (SSIPeriphID3), offset 0xFEC
The SSIPeriphIDn registers are hard-coded and the fields within the register determine the reset
value.
SSI Peripheral Identification 3 (SSIPeriphID3)
Offset 0xFEC
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
PID3
RO
0
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
PID3
RO
0x01
Description
Reserved bits return an indeterminate value, and should
never be changed.
SSI Peripheral ID Register [31:24]
Can be used by software to identify the presence of this
peripheral.
256
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 18: SSI PrimeCell Identification 0 (SSIPCellID0), offset 0xFF0
The SSIPCellIDn registers are hard-coded and the fields within the register determine the reset
value.
SSI Primecell Identification 0 (SSIPCellID0)
Offset 0xFF0
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
1
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
CID0
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
CID0
RO
0x0D
Description
Reserved bits return an indeterminate value, and should
never be changed.
SSI PrimeCell ID Register [7:0]
Provides software a standard cross-peripheral identification
system.
October 5, 2006
257
Preliminary
Synchronous Serial Interface (SSI)
Register 19: SSI PrimeCell Identification 1 (SSIPCellID1), offset 0xFF4
The SSIPCellIDn registers are hard-coded and the fields within the register determine the reset
value.
SSI Primecell Identification 1 (SSIPCellID1)
Offset 0xFF4
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
1
RO
1
RO
1
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
CID1
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
CID1
RO
0xF0
Description
Reserved bits return an indeterminate value, and should
never be changed.
SSI PrimeCell ID Register [15:8]
Provides software a standard cross-peripheral identification
system.
258
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 20: SSI PrimeCell Identification 2 (SSIPCellID2), offset 0xFF8
The SSIPCellIDn registers are hard-coded and the fields within the register determine the reset
value.
SSI Primecell Identification 2 (SSIPCellID2)
Offset 0xFF8
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
CID2
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
CID2
RO
0x05
Description
Reserved bits return an indeterminate value, and should
never be changed.
SSI PrimeCell ID Register [23:16]
Provides software a standard cross-peripheral identification
system.
October 5, 2006
259
Preliminary
Synchronous Serial Interface (SSI)
Register 21: SSI PrimeCell Identification 3 (SSIPCellID3), offset 0xFFC
The SSIPCellIDn registers are hard-coded and the fields within the register determine the reset
value.
SSI Primecell Identification 3 (SSIPCellID3)
Offset 0xFFC
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
1
RO
0
RO
1
RO
1
RO
0
RO
0
RO
0
RO
1
reserved
Type
Reset
reserved
Type
Reset
CID3
Bit/Field
Name
Type
Reset
31:8
reserved
RO
0
7:0
CID3
RO
0xB1
Description
Reserved bits return an indeterminate value, and should
never be changed.
SSI PrimeCell ID Register [31:24]
Provides software a standard cross-peripheral identification
system.
260
October 5, 2006
Preliminary
LM3S101 Data Sheet
13
Analog Comparators
An analog comparator is a peripheral that compares two analog voltages, and provides a logical
output that signals the comparison result.
The LM3S101 controller provides two independent integrated analog comparators that can be
configured to drive an output1 or generate an interrupt.
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 to cause it to
start capturing a sample sequence. The interrupt generation logic is separate.
13.1
Block Diagram
Figure 13-1.
Analog Comparator Module Block Diagram
C1-
-ve input
<none>
+ve input
Comparator 1
output
<none>
+ve input (alternate)
ACCTL1
ACSTAT1
interrupt
reference input
C0-
-ve input
C0+
+ve input
interrupt
Comparator 0
output
C0o
+ve input (alternate)
ACCTL0
ACSTAT0
interrupt
reference input
interrupt
Voltage
Ref
internal
bus
13.2
ACREFCTL
Functional Description
Important: It is recommended that the Digital-Input enable (the GPIODEN bit in the GPIO
module) for the analog input pin be disabled to prevent excessive current draw from
the I/O pads.
The comparator compares the VIN- and VIN+ inputs to produce an output, VOUT.
1.Not all comparators have the option to drive an output pin. See Table 13-1 and Table 13-2 for more
information.
October 5, 2006
261
Preliminary
Analog Comparators
As shown in Figure 13-2, the input source for VIN- is an external input. In addition to an external
input, input sources for VIN+ can be the +ve input of comparator 0 or an internal reference.
Figure 13-2.
Structure of Comparator Unit
-ve input
+ve input
output
0
+ve input (alternate)
1
reference input
2
CINV
IntGen
ACCTL
internal
bus
interrupt
ACSTAT
A comparator is configured through two status/control registers (ACCTL and ACSTAT). The
internal reference is configured through one control register (ACREFCTL). Interrupt status and
control is configured through three registers (ACMIS, ACRIS, and ACINTEN). The operating
modes of the comparators are shown in Table 13-1 and Table 13-2.
Typically, the comparator output is used internally to generate controller interrupts. It may also be
used to drive an external pin.
Important: Certain register bit values must be set before using the analog comparators. The
proper pad configuration for the comparator input and output pins are described in
Table 8-1 on page 101.
Table 13-1. Comparator 0 Operating Modes
ACCNTL0
Comparator 0
ASRCP
VIN-
VIN+
Output
Interrupt
00
C0-
C0+
C0o/C1-
yes
01
C0-
C0+
C0o/C1-
yes
10
C0-
Vref
C0o/C1-
yes
11
C0-
reserved
C0o/C1-
yes
Table 13-2. Comparator 1 Operating Modes
ACCNTL1
Comparator 1
ASRCP
VIN-
VIN+
Output
Interrupt
00
C0o/C1-a
n/a
n/a
yes
01
C0o/C1-
C0+
n/a
yes
10
C0o/C1-
Vref
n/a
yes
262
October 5, 2006
Preliminary
LM3S101 Data Sheet
Table 13-2. Comparator 1 Operating Modes
ACCNTL1
Comparator 1
ASRCP
VIN-
VIN+
Output
Interrupt
11
C0o/C1-
reserved
n/a
yes
a. C0o and C1- signals share a single pin and may only be used as one or the other.
13.2.1
Internal Reference Programming
The structure of the internal reference is shown in Figure 13-3. This is controlled by a single
configuration register (ACREFCTL). Table 13-3 shows the programming options to develop
specific internal reference values, to compare an external voltage against a particular voltage
generated internally.
Figure 13-3.
Comparator Internal Reference Structure
8R
AVDD
8R
R
R
R
R
•••
EN
15
14
•••
1
0
Decoder
VREF
internal
reference
RNG
Table 13-3. Internal Reference Voltage and ACREFCTL Field Values
ACREFCTL Register
Output Reference Voltage Based on VREF Field Value
EN Bit Value
RNG Bit Value
EN=0
RNG=X
0 V (GND) for any value of VREF; however, it is recommended that
RNG=1 and VREF=0 for the least noisy ground reference.
October 5, 2006
263
Preliminary
Analog Comparators
Table 13-3. Internal Reference Voltage and ACREFCTL Field Values (Continued)
ACREFCTL Register
Output Reference Voltage Based on VREF Field Value
EN Bit Value
RNG Bit Value
EN=1
RNG=0
Total resistance in ladder is 32 R.
R VREF
V REF = AV DD × ---------------RT
( VREF + 8 )
VREF = AVDD × ----------------------------32
VREF = 0.825 + 0.103 ⋅ VREF
The range of internal reference in this mode is 0.825–2.37 V.
RNG=1
Total resistance in ladder is 24 R.
R VREF
V REF = AV DD × ---------------RT
( VREF )
V REF = AV DD × -------------------24
V REF = 0.1375 ⋅ VREF
The range of internal reference for this mode is 0.0–2.0625 V.
13.3
Initialization and Configuration
The following example shows how to configure analog comparator to read back its output value
from an internal register.
1. Enable the analog comparator 0 clock by writing a value of 0x00100000 to the RCGC1 register
in the System Control module.
2. In the GPIO module, enable the GPIO port/pin associated with C0- as a GPIO input.
3. Configure the internal voltage reference to 1.65 V by writing the ACREFCTL register with the
value 0x0000030C.
4. Configure comparator 0 to use the internal voltage reference and to not output a value on the
C0O pin by writing the ACCTL0 register with the value of 0x0000040C.
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.
264
October 5, 2006
Preliminary
LM3S101 Data Sheet
13.4
Register Map
Table 13-4 lists the comparator registers. The offset listed is a hexadecimal increment to the
register’s address, relative to the Analog Comparator base address of 0x4003C000.
Table 13-4. Analog Comparator Register Map
Name
Reset
Type
0x00
ACMIS
0x00000000
RO
Interrupt status
266
0X04
ACRIS
0x00000000
RO
Raw interrupt status
267
0X08
ACINTEN
0x00000000
R/W
Interrupt enable
268
0x10
ACREFCTL
0x00000000
R/W
Reference voltage control
269
0x20
ACSTAT0
0x00000000
RO
Comparator 0 status
270
0x40
ACSTAT1
0x00000000
RO
Comparator 1 status
270
0x24
ACCTL0
0x00000000
RW
Comparator 0 control
271
0x44
ACCTL1
0x00000000
RW
Comparator 1 control
271
13.5
Description
See
page
Offset
Register Descriptions
The remainder of this section lists and describes the Analog Comparator registers, in numerical
order by address offset.
October 5, 2006
265
Preliminary
Analog Comparators
Register 1: Analog Comparator Masked Interrupt Status (ACMIS), offset 0x00
This register provides a summary of the interrupt status (masked) of the comparators.
Analog Comparator Masked Interrupt Status (ACMIS)
Offset 0x000
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
IN1
IN0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
Bit/Field
Name
Type
Reset
Description
31:2
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
1
IN1
RO
0
Comparator 1 Masked Interrupt Status
Gives the masked interrupt state of this interrupt.
0
IN0
RO
0
Comparator 0 Masked Interrupt Status
Gives the masked interrupt state of this interrupt.
266
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 2: Analog Comparator Raw Interrupt Status (ACRIS), offset 0x04
This register provides a summary of the interrupt status (raw) of the comparators.
Analog Comparator Raw Interrupt Status (ACRIS)
Offset 0x04
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
IN1
IN0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
Bit/Field
Name
Type
Reset
Description
31:2
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
1
IN1
RO
0
When set, indicates that an interrupt has been generated by
comparator 1.
0
IN0
RO
0
When set, indicates that an interrupt has been generated by
comparator 0.
October 5, 2006
267
Preliminary
Analog Comparators
Register 3: Analog Comparator Interrupt Enable (ACINTEN), offset 0x08
This register provides the interrupt enable for the comparators.
Analog Comparator Interrupt Enable (ACINTEN)
Offset 0x08
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
IN1
IN0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
RO
0
RO
R/W
0
reserved
Type
Reset
reserved
Type
Reset
Bit/Field
Name
Type
Reset
Description
31:2
reserved
RO
0
Reserved bits return an indeterminate value, and should never
be changed.
1
IN1
R/W
0
When set, enables the controller interrupt from the comparator 1
output.
0
IN0
R/W
0
When set, enables the controller interrupt from the comparator 0
output.
268
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 4: Analog Comparator Reference Voltage Control (ACREFCTL), offset 0x10
This register specifies whether the resistor ladder is powered on as well as the range and tap.
Analog Comparator Reference Voltage Control (ACREFCTL)
Offset 0x010
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
R/W
RO
0
RO
0
RO
0
RO
0
RO
0
RO
R/W
0
R/W
RO
0
RO
R/W
0
R/W
RO
0
reserved
Type
Reset
VREF
ENreserved
RNG
Type
Reset
RO
R/W
0
Bit/Field
Name
Type
Reset
Description
31:10
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
9
EN
R/W
0
The EN bit specifies whether the resistor ladder is powered
on. If 0, the resistor ladder is unpowered. If 1, the resistor
ladder is connected to the analog VDD.
This bit is reset to 0 so that the internal reference consumes
the least amount of power if not used and programmed.
8
RNG
R/W
0
The RNG bit specifies the range of the resistor ladder. If 0, the
resistor ladder has a total resistance of 32 R. If 1, the resistor
ladder has a total resistance of 24 R.
7:4
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
3:0
VREF
R/W
0
The VREF bit field specifies the resistor ladder tap that is
passed through an analog multiplexer. The voltage
corresponding to the tap position is the internal reference
voltage available for comparison. See Table 13-3 on page 263
for some output reference voltage examples.
October 5, 2006
269
Preliminary
Analog Comparators
Register 5: Analog Comparator Status 0 (ACSTAT0), offset 0x20
Register 6: Analog Comparator Status 1 (ACSTAT1), offset 0x40
These registers specify the current output value of that comparator.
Analog Comparator Status 0 (ACSTAT0)
Offset 0x020
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
OVAL
reserved
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
reserved
Type
Reset
reserved
Type
Reset
Bit/Field
Name
Type
Reset
Description
31:2
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
1
OVAL
RO
0
The OVAL bit specifies the current output value of the
comparator.
0
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
270
October 5, 2006
Preliminary
LM3S101 Data Sheet
Register 7: Analog Comparator Control 0 (ACCTL0), offset 0x24
Register 8: Analog Comparator Control 1 (ACCTL1), offset 0x44
These registers configure that comparator’s input and output.
Analog Comparator Control 0 (ACCTL0)
Offset 0x024
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
RO
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RO
0
RO
0
RO
0
RO
0
RO
R/W
0
CINV
reserved
RO
R/W
0
RO
0
RO
0
RO
0
RO
0
R/W
RO
0
RO
RO
0
reserved
Type
Reset
ASRCP
reserved
Type
Reset
RO
0
reserved
ISEN
ISLVAL
R/W
RO
0
RO
R/W
0
RO
R/W
0
Bit/Field
Name
Type
Reset
Description
31:11
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
10:9
ASRCP
R/W
0
The ASRCP field specifies the source of input voltage to the
VIN+ terminal of the comparator. The encodings for this field
are as follows:
ASRCP
Function
00
Pin value
01
Pin value of C0+
10
Internal voltage reference
11
Reserved
8:5
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
4
ISLVAL
R/W
0
The ISLVAL bit specifies the sense value of the input that
generates an interrupt if in Level Sense mode. If 0, an
interrupt is generated if the comparator output is Low.
Otherwise, an interrupt is generated if the comparator output
is High.
3:2
ISEN
R/W
0
The ISEN field specifies the sense of the comparator output
that generates an interrupt. The sense conditioning is as
follows:
ISEN
October 5, 2006
Function
00
Level sense, see ISLVAL
01
Falling edge
10
Rising edge
11
Either edge
271
Preliminary
Analog Comparators
Bit/Field
Name
Type
Reset
Description
1
CINV
R/W
0
The CINV bit conditionally inverts the output of the
comparator. If 0, the output of the comparator is unchanged. If
1, the output of the comparator is inverted prior to being
processed by hardware.
0
reserved
RO
0
Reserved bits return an indeterminate value, and should
never be changed.
272
October 5, 2006
Preliminary
LM3S101 Data Sheet
14
Pin Diagram
Figure 14-1 shows the pin diagram and pin-to-signal-name mapping.
Figure 14-1.
Pin Connection Diagram
PB7/TRST
PB6/C0+
PB5/C0o/C1PB4/C0RST
LDO
VDD
GND
OSC0
OSC1
PA0/U0Rx
PA1/U0Tx
PA2/SSIClk
PA3/SSIFss
1
2
3
4
5
6
7
8
9
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
15
PC0/TCK/SWCLK
PC1/TMS/SWDIO
PC2/TDI
PC3/TDO/SWO
PB3
PB2
VDD
GND
PB1/32KHz
PB0/CCP0
GND
VDD
PA5/SSITx
PA4/SSIRx
LM3S101
October 5, 2006
273
Preliminary
Signal Tables
15
Signal Tables
The following tables list the signals available for each pin. Functionality is enabled by software with
the GPIOAFSEL register (see page 114).
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.
Table 15-1 shows the pin-to-signal-name mapping, including functional characteristics of the
signals. Table 15-2 lists the signals in alphabetical order by signal name. Table 15-3 groups the
signals by functionality, except for GPIOs. Table 15-4 lists the GPIO pins and their alternate
functionality.
Table 15-1. Signals by Pin Number (Sheet 1 of 2)
Pin
Number
Pin
Type
Buffer
Type
I/O
TTL
GPIO port B bit 7.
I
TTL
JTAG TAP reset input.
PB6
I/O
TTL
GPIO port B bit 6.
C0+
I
Analog
PB5
I/O
TTL
GPIO port B bit 5.
C0o
O
TTL
Analog comparator 0 output.
C1–
I
Analog
PB4
I/O
TTL
C0–
I
Analog
5
RST
I
TTL
6
LDO
-
Power
The low drop-out regulator output voltage. This pin requires an
external capacitor between the pin and GND of 1 μF or greater.
7
VDD
-
Power
Positive supply for logic and I/O pins.
8
GND
-
Power
Ground reference for logic and I/O pins.
9
OSC0
I
Analog
Oscillator crystal input or an external clock reference input.
10
OSC1
O
Analog
Oscillator crystal output.
11
PA0
I/O
TTL
GPIO port A bit 0.
I
TTL
UART0 receive data input.
PA1
I/O
TTL
GPIO port A bit 1.
U0Tx
O
TTL
UART0 transmit data output.
PA2
I/O
TTL
GPIO port A bit 2.
SSIClk
I/O
TTL
SSI clock reference (input when in slave mode and output in
master mode).
1
Signal Name
PB7
TRST
2
3
4
U0Rx
12
13
Description
Analog comparator 0 positive reference input.
Analog comparator 1 negative reference input.
GPIO port B bit 4.
Analog comparator 0 negative reference input.
System reset input.
274
October 5, 2006
Preliminary
LM3S101 Data Sheet
Table 15-1. Signals by Pin Number (Sheet 2 of 2)
Pin
Number
Pin
Type
Buffer
Type
PA3
I/O
TTL
GPIO port A bit 3.
SSIFss
I/O
TTL
SSI frame enable (input for an SSI slave device and output for an
SSI master device).
PA4
I/O
TTL
GPIO port A bit 4.
I
TTL
SSI receive data input.
PA5
I/O
TTL
GPIO port A bit 5.
SSITx
O
TTL
SSI transmit data output.
17
VDD
-
Power
Positive supply for logic and I/O pins.
18
GND
-
Power
Ground reference for logic and I/O pins.
19
PB0
I/O
TTL
GPIO port B bit 0.
CCP0
I/O
TTL
Timer 0 capture input, compare output, or PWM output port 0.
PB1
I/O
TTL
GPIO port B bit 1.
32KHz
I
TTL
Timer clock reference input for real-time clock operation.
21
GND
-
Power
Ground reference for logic and I/O pins.
22
VDD
-
Power
Positive supply for logic and I/O pins.
23
PB2
I/O
TTL
GPIO port B bit 2.
24
PB3
I/O
TTL
GPIO port B bit 3.
25
PC3
I/O
TTL
GPIO port C bit 3.
TDO
O
TTL
JTAG scan test output.
SWO
O
TTL
Serial-wire output.
PC2
I/O
TTL
GPIO port C bit 2.
TDI
I
TTL
JTAG scan data input.
PC1
I/O
TTL
GPIO port C bit 1.
TMS
I
TTL
JTAG mode select input.
SWDIO
I/O
TTL
Serial-wire debug input/output.
PC0
I/O
TTL
GPIO port C bit 0.
TCK
I
TTL
JTAG scan clock reference input.
SWCLK
I
TTL
Serial-wire clock reference input.
14
15
Signal Name
SSIRx
16
20
26
27
28
Description
October 5, 2006
275
Preliminary
Signal Tables
Table 15-2. Signals by Signal Name (Sheet 1 of 2)
Pin
Number
Pin
Type
Buffer
Type
32KHz
20
I
TTL
C0+
2
I
Analog
Analog comparator 0 positive reference input.
C0–
4
I
Analog
Analog comparator 0 negative reference input.
C0o
3
O
TTL
C1–
3
I
Analog
CCP0
19
I/O
TTL
GND
8
-
Power
Ground reference for logic and I/O pins.
GND
18
-
Power
Ground reference for logic and I/O pins.
GND
21
-
Power
Ground reference for logic and I/O pins.
LDO
6
-
Power
The low drop-out regulator output voltage. This pin requires an
external capacitor between the pin and GND of 1 μF or greater.
OSC0
9
I
Analog
Oscillator crystal input or an external clock reference input.
OSC1
10
O
Analog
Oscillator crystal output.
PA0
11
I/O
TTL
GPIO port A bit 0.
PA1
12
I/O
TTL
GPIO port A bit 1.
PA2
13
I/O
TTL
GPIO port A bit 2.
PA3
14
I/O
TTL
GPIO port A bit 3.
PA4
15
I/O
TTL
GPIO port A bit 4.
PA5
16
I/O
TTL
GPIO port A bit 5.
PB0
19
I/O
TTL
GPIO port B bit 0.
PB1
20
I/O
TTL
GPIO port B bit 1.
PB2
23
I/O
TTL
GPIO port B bit 2.
PB3
24
I/O
TTL
GPIO port B bit 3.
PB4
4
I/O
TTL
GPIO port B bit 4.
PB5
3
I/O
TTL
GPIO port B bit 5.
PB6
2
I/O
TTL
GPIO port B bit 6.
PB7
1
I/O
TTL
GPIO port B bit 7.
PC0
28
I/O
TTL
GPIO port C bit 0.
PC1
27
I/O
TTL
GPIO port C bit 1.
Signal Name
Description
Timer clock reference input for real-time clock operation.
Analog comparator 0 output.
Analog comparator 1 negative reference input.
Timer 0 capture input, compare output, or PWM output port 0.
276
October 5, 2006
Preliminary
LM3S101 Data Sheet
Table 15-2. Signals by Signal Name (Sheet 2 of 2)
Pin
Number
Pin
Type
Buffer
Type
PC2
26
I/O
TTL
GPIO port C bit 2.
PC3
25
I/O
TTL
GPIO port C bit 3.
RST
5
I
TTL
System reset input.
SSIClk
13
I/O
TTL
SSI clock reference (input when in slave mode and output in
master mode).
SSIFss
14
I/O
TTL
SSI frame enable (input for an SSI slave device and output for an
SSI master device).
SSIRx
15
I
TTL
SSI receive data input.
SSITx
16
O
TTL
SSI transmit data output.
SWCLK
28
I
TTL
Serial-wire clock reference input.
SWDIO
27
I/O
TTL
Serial-wire debug input/output.
SWO
25
O
TTL
Serial-wire output.
TCK
28
I
TTL
JTAG scan clock reference input.
TDI
26
I
TTL
JTAG scan data input.
TDO
25
O
TTL
JTAG scan test output.
TMS
27
I
TTL
JTAG mode select input.
TRST
1
I
TTL
JTAG TAP reset input.
U0Rx
11
I
TTL
UART0 receive data input.
U0Tx
12
O
TTL
UART0 transmit data output.
VDD
7
-
Power
Positive supply for logic and I/O pins.
VDD
17
-
Power
Positive supply for logic and I/O pins.
VDD
22
-
Power
Positive supply for logic and I/O pins.
Signal Name
Description
October 5, 2006
277
Preliminary
Signal Tables
Table 15-3. Signals by Function, Except for GPIO (Sheet 1 of 2)
Pin
Number
Pin
Type
Buffer
Type
C0+
2
I
Analog
Analog comparator 0 positive reference
input.
C0–
4
I
Analog
Analog comparator 0 negative reference
input.
C0o
3
O
TTL
C1–
3
I
Analog
Analog comparator 1 negative reference
input.
32KHz
20
I
TTL
Timer clock reference input for real-time
clock operation.
CCP0
19
I/O
TTL
Timer 0 capture input, compare output, or
PWM output port 0.
SWCLK
28
I
TTL
Serial wire clock reference input.
SWDIO
27
I/O
TTL
Serial-wire debug input/output.
SWO
25
O
TTL
Serial-wire output.
TCK
28
I
TTL
JTAG scan clock reference input.
TDI
26
I
TTL
JTAG scan data input.
TDO
25
O
TTL
JTAG scan test output.
TMS
27
I
TTL
JTAG mode select input.
TRST
1
I
TTL
JTAG TAP reset input.
GND
8
-
Power
Ground reference for logic and I/O pins.
GND
18
-
Power
Ground reference for logic and I/O pins.
GND
21
-
Power
Ground reference for logic and I/O pins.
LDO
6
-
Power
The low drop-out regulator output voltage.
This pin requires an external capacitor
between the pin and GND of 1 μF or greater.
VDD
7
-
Power
Positive supply for logic and I/O pins.
VDD
17
-
Power
Positive supply for logic and I/O pins.
VDD
22
-
Power
Positive supply for logic and I/O pins.
Function
Signal Name
Analog
Comparator
General-Purpose
Timers
JTAG/SWD/SWO
Power
278
Description
Analog comparator 0 output.
October 5, 2006
Preliminary
LM3S101 Data Sheet
Table 15-3. Signals by Function, Except for GPIO (Sheet 2 of 2)
Pin
Number
Pin
Type
Buffer
Type
SSIClk
13
I/O
TTL
SSI clock reference (input when in slave
mode and output in master mode).
SSIFss
14
I/O
TTL
SSI frame enable (input for an SSI slave
device and output for an SSI master device).
SSIRx
15
I
TTL
SSI receive data input.
SSITx
16
O
TTL
SSI transmit data output.
OSC0
9
I
Analog
Oscillator crystal input or an external clock
reference input.
OSC1
10
O
Analog
Oscillator crystal output.
RST
5
I
TTL
System reset input.
U0Rx
11
I
TTL
UART0 receive data input.
U0Tx
12
O
TTL
UART0 transmit data output.
Function
Signal Name
SSI
System Control &
Clocks
UART
Description
Table 15-4. GPIO Pins and Alternate Functions (Sheet 1 of 2)
GPIO Pin
Pin
Number
Multiplexed
Function
PA0
11
U0Rx
PA1
12
U0Tx
PA2
13
SSIClk
PA3
14
SSIFss
PA4
15
SSIRx
PA5
16
SSITx
PB0
19
CCP0
PB1
20
32KHz
PB2
23
PB3
24
PB4
4
C0-
PB5
3
C0o
PB6
2
C0+
PB7
1
TRST
PC0
28
TCK
Multiplexed
Function
C1-
SWCLK
October 5, 2006
279
Preliminary
Signal Tables
Table 15-4. GPIO Pins and Alternate Functions (Sheet 2 of 2)
GPIO Pin
Pin
Number
Multiplexed
Function
Multiplexed
Function
SWDIO
PC1
27
TMS
PC2
26
TDI
PC3
25
TDO
SWO
280
October 5, 2006
Preliminary
LM3S101 Data Sheet
16
Operating Characteristics
Table 16-1. Temperature Characteristics
Characteristic
Symbol
Value
Unit
Operating temperature rangea
TA
-40 to +85 for industrial
Characteristic
Symbol
Value
Unit
Thermal resistance (junction to ambient)a
θJA
74
°C/W
Average junction temperatureb
TJ
TA + (PAVG • θJA)
°C
Maximum junction temperature
TJMAX
pendingc
°C
°C
a. Maximum storage temperature is 150°C.
Table 16-2. Thermal Characteristics
a. Junction to ambient thermal resistance θJA numbers are determined by a package simulator.
b. Power dissipation is a function of temperature.
c. Pending characterization completion.
October 5, 2006
281
Preliminary
Electrical Characteristics
17
Electrical Characteristics
17.1
DC Characteristics
17.1.1
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 17-1. Maximum Ratings
Characteristica
Symbol
Value
Unit
Supply voltage range (VDD)
VDD
0.0 to +3.6
V
Input voltage
VIN
-0.3 to 5.5
V
Maximum current for pins, excluding pins
operating as GPIOs
I
100
mA
Maximum current for GPIO pins
I
100
mA
a. Voltages are measured with respect to GND.
Important: This device contains circuitry to protect the inputs against damage due to high-static
voltages or electric fields; however, it is advised that normal precautions be taken to
avoid application of any voltage higher than maximum-rated voltages to this
high-impedance circuit. Reliability of operation is enhanced if unused inputs are
connected to an appropriate logic voltage level (for example, either GND or VDD).
17.1.2
Recommended DC Operating Conditions
Table 17-2. Recommended DC Operating Conditions
Parameter
Parameter Name
Min
Nom
Max
Unit
VDD
Supply voltage
3.0
3.3
3.6
V
VIH
High-level input voltage
2.0
-
5.0
V
VIL
Low-level input voltage
-0.3
-
1.3
V
VSIH
High-level input voltage for Schottky inputs
0.8 * VDD
-
VDD
V
VSIL
Low-level input voltage for Schottky inputs
0
-
0.2 * VDD
V
VOH
High-level output voltage
2.4
-
-
V
VOL
Low-level output voltage
-
-
0.4
V
282
October 5, 2006
Preliminary
LM3S101 Data Sheet
Table 17-2. Recommended DC Operating Conditions (Continued)
Parameter
IOH
IOL
17.1.3
Parameter Name
Min
Nom
Max
Unit
2-mA Drive
2.0
-
-
mA
4-mA Drive
4.0
-
-
mA
8-mA Drive
8.0
-
-
mA
2-mA Drive
2.0
-
-
mA
4-mA Drive
4.0
-
-
mA
8-mA Drive
8.0
-
-
mA
High-level source current, VOH=2.4 V
Low-level sink current, VOL=0.4 V
On-Chip Low Drop-Out (LDO) Regulator Characteristics
Table 17-3. 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
-
μF
VLDOOUT
October 5, 2006
283
Preliminary
Electrical Characteristics
17.1.4
Power Specifications
The power measurements specified in Table 17-4 are run on the core processor using SRAM with
the following specifications:

VDD=3.3 V

LDO=2.5

Temperature=25°C

System Clock=20 MHz (with PLL)

Code while(1){} executed from SRAM with no active peripherals
Table 17-4. Power Specifications
Parameter
IDD_RUN
IDD_SLEEP
IDD_DEEPSLEEP
Parameter Name
Min
Nom
Max
Unit
Run mode
-
35a
pendinga
mA
Sleep mode
-
pendinga
pendinga
μA
-
pendinga
pendinga
μA
Deep-Sleep mode
a. Pending characterization completion.
17.1.5
Flash Memory Characteristics
Table 17-5. Flash Memory Characteristics
Parameter
Min
Nom
Max
Unit
10,000
-
-
cycles
Data retention at average operating
temperature of 85°C
10
-
-
years
TPROG
Word program time
20
-
-
μs
TERASE
Page erase time
20
-
-
ms
TME
Mass erase time
200
-
-
ms
PECYC
TRET
Parameter Name
Number of guaranteed program/erase
cyclesa before failure
a. A program/erase cycle is defined as switching the bits from 1-> 0 -> 1.
284
October 5, 2006
Preliminary
LM3S101 Data Sheet
17.2
AC Characteristics
17.2.1
Load Conditions
Unless otherwise specified, the following conditions are true for all timing measurements. Timing
measurements are for 4-mA drive strength.
Figure 17-1.
Load Conditions
pin
CL = 50 pF
GND
17.2.2
Clocks
Table 17-6. Phase Locked Loop (PLL) Characteristics
Parameter
Parameter Name
Min
Nom
Max
Unit
fREF_CRYSTAL
Crystal referencea
3.579545
-
8.192
MHz
fREF_EXT
External clock referencea
3.579545
-
8.192
MHz
fPLL
PLL frequencyb
-
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 (see page 71).
b. PLL frequency is automatically calculated by the hardware based on the XTAL field of the RCC register.
Table 17-7. Clock Characteristics
Parameter
Parameter Name
Min
Nom
Max
Unit
fIOSC
Internal oscillator
frequency
7
15
22
MHz
fMOSC
Main oscillator frequency
1
-
8
MHz
tMOSC_PER
Main oscillator period
125
-
1000
ns
fREF_CRYSTAL_BYPASS
Crystal reference using the
main oscillator (PLL in
BYPASS mode)
1
-
8
MHz
fREF_EXT_BYPASS
External clock reference
(PLL in BYPASS mode)
0
-
20
MHz
fSYSTEM_CLOCK
System clock
0
-
20
MHz
October 5, 2006
285
Preliminary
Electrical Characteristics
17.2.3
Analog Comparator
Table 17-8. Analog Comparator Characteristics
Parameter
Parameter Name
Min
Nom
Max
Unit
VOS
Input offset voltage
-
± 10
± 25
mV
VCM
Input common mode voltage range
0
-
VDD-1.5
V
Common mode rejection ratio
50
-
-
dB
CMRR
TRT
Response time
-
-
1
μs
TMC
Comparator mode change to Output Valid
-
-
10
μs
Min
Nom
Max
Unit
Table 17-9. Analog Comparator Voltage Reference Characteristics
Parameter
Parameter Name
RHR
Resolution high range
-
VDD/32
-
LSB
RLR
Resolution low range
-
VDD/24
-
LSB
AHR
Absolute accuracy high range
-
-
± 1/2
LSB
ALR
Absolute accuracy low range
-
-
± 1/4
LSB
286
October 5, 2006
Preliminary
LM3S101 Data Sheet
17.2.4
Synchronous Serial Interface (SSI)
Table 17-10.
SSI Characteristics
Parameter
No.
Parameter
Parameter Name
Min
Nom
Max
Unit
S1
tCLK_PER
SSIClk cycle time
2
-
65024
system
clocks
S2
tCLK_HIGH
SSIClk high time
-
1/2
-
tCLK_PER
S3
tCLK_LOW
SSIClk low time
-
1/2
-
tCLK_PER
S4
tCLKRF
SSIClk rise/fall time
-
7.4
26
ns
S5
tDMD
Data from master valid delay time
0
-
20
ns
S6
tDMS
Data from master setup time
20
-
-
ns
S7
tDMH
Data from master hold time
40
-
-
ns
S8
tDSS
Data from slave setup time
20
-
-
ns
S9
tDSH
Data from slave hold time
40
-
-
ns
Figure 17-2.
SSI Timing for TI Frame Format (FRF=01), Single Transfer Timing Measurement
S1
S2
S4
SSIClk
S3
SSIFss
SSITx
SSIRx
MSB
LSB
4 to 16 bits
October 5, 2006
287
Preliminary
Electrical Characteristics
Figure 17-3.
SSI Timing for MICROWIRE Frame Format (FRF=10), Single Transfer
S2
S1
SSIClk
S3
SSIFss
SSITx
MSB
LSB
8-bit control
SSIRx
0
MSB
LSB
4 to 16 bits output data
Figure 17-4.
SSI Timing for SPI Frame Format (FRF=00), with SPH=1
S1
S4
S2
SSIClk
(SPO=0)
S3
SSIClk
(SPO=1)
S6
SSITx
(master)
MSB
S5
SSIRx
(slave)
S7
S8
LSB
S9
MSB
LSB
SSIFss
288
October 5, 2006
Preliminary
LM3S101 Data Sheet
17.2.5
JTAG and Boundary Scan
Table 17-11. JTAG Characteristics
Parameter
No.
Parameter
J1
fTCK
TCK operational clock frequency
J2
tTCK
TCK operational clock period
J3
tTCK_LOW
J4
tTCK_HIGH
J5
Min
Nom
Max
Unit
0
-
10
MHz
100
-
-
ns
TCK clock Low time
-
½ tTCK
-
ns
TCK clock High time
-
½ tTCK
-
ns
tTCK_R
TCK rise time
0
-
10
ns
J6
tTCK_F
TCK fall time
0
-
10
ns
J7
tTMS_SU
TMS setup time to TCK rise
20
-
-
ns
J8
tTMS_HLD
TMS hold time from TCK rise
20
-
-
ns
J9
tTDI_SU
TDI setup time to TCK rise
25
-
-
ns
J10
tTDI_HLD
TDI hold time from TCK rise
25
-
-
ns
J11
tTDO_ZDV
TCK fall to
Data Valid
from High-Z
-
23
35
ns
4-mA drive
15
26
ns
8-mA drive
14
25
ns
8-mA drive with slew rate control
18
29
ns
21
35
ns
4-mA drive
14
25
ns
8-mA drive
13
24
ns
8-mA drive with slew rate control
18
28
ns
9
11
ns
4-mA drive
7
9
ns
8-mA drive
6
8
ns
8-mA drive with slew rate control
7
9
ns
TCK fall to
Data Valid
from Data
Valid
J12
tTDO_DV
J13
tTDO_DVZ
TCK fall to
High-Z from
Data Valid
J14
tTRST
J15
tTRST_SU
Parameter Name
2-mA drive
2-mA drive
2-mA drive
-
-
TRST assertion time
100
-
-
ns
TRST setup time to TCK rise
10
-
-
ns
October 5, 2006
289
Preliminary
Electrical Characteristics
Figure 17-5.
JTAG Test Clock Input Timing
J2
J3
J4
TCK
J6
Figure 17-6.
J5
JTAG Test Access Port (TAP) Timing
TCK
J7
TMS
TDI
J8
J7
TMS Input Valid
TMS Input Valid
J9
J9
J10
TDI Input Valid
TDO
J10
TDI Input Valid
J11
Figure 17-7.
J8
J12
J13
TDO Output Valid
TDO Output Valid
JTAG TRST Timing
TCK
J14
J15
TRST
290
October 5, 2006
Preliminary
LM3S101 Data Sheet
17.2.6
General-Purpose I/O
Table 17-12.
GPIO Characteristicsa
Parameter
Parameter Name
Condition
Min
Nom
Max
Unit
tGPIOR
GPO Rise Time
(from 20% to 80%
of VDD)
2-mA drive
-
17
26
ns
4-mA drive
9
13
ns
8-mA drive
6
9
ns
8-mA drive with slew rate control
10
12
ns
17
25
ns
4-mA drive
8
12
ns
8-mA drive
6
10
ns
8-mA drive with slew rate control
11
13
ns
GPO Fall Time
(from 80% to 20%
of VDD)
tGPIOF
2-mA drive
-
a. All GPIOs are 5 V-tolerant.
17.2.7
Reset
Table 17-13.
Reset Characteristics
Parameter
No.
Parameter
R1
VTH
Reset threshold
R2
VBTH
Brown-Out threshold
R3
TPOR
R4
TBOR
R5
TIRPOR
R6
Parameter Name
Min
Nom
Max
Unit
-
2.0
-
V
2.85
2.9
2.95
V
Power-On Reset timeout
-
10
-
ms
Brown-Out timeout
-
500
-
μs
Internal reset timeout after POR
15
-
30
ms
TIRBOR
Internal reset timeout after BORa
2.5
-
20
μs
R7
TIRHWR
Internal reset timeout after hardware
reset (RST pin)
15
-
30
ms
R8
TIRSWR
Internal reset timeout after
software-initiated system reseta
2.5
-
20
μs
R9
TIRWDR
Internal reset timeout after watchdog
reseta
2.5
-
20
μs
R10
TIRLDOR
Internal reset timeout after LDO reseta
2.5
-
20
μs
R11
TVDDRISE
Supply voltage (VDD) rise time (0V-3.3V)
100
ms
a. 20 * tMOSC_PER
October 5, 2006
291
Preliminary
Electrical Characteristics
Figure 17-8.
External Reset Timing (RST)
RST
R7
/Reset
(Internal)
Figure 17-9.
Power-On Reset Timing
R1
VDD
R3
/POR
(Internal)
R5
/Reset
(Internal)
Figure 17-10.
Brown-Out Reset Timing
R2
VDD
R4
/BOR
(Internal)
R6
/Reset
(Internal)
Figure 17-11. Software Reset Timing
SW Reset
R8
/Reset
(Internal)
292
October 5, 2006
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LM3S101 Data Sheet
Figure 17-12.
Watchdog Reset Timing
WDT
Reset
(Internal)
R9
/Reset
(Internal)
Figure 17-13.
LDO Reset Timing
LDO Reset
(Internal)
R10
/Reset
(Internal)
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Preliminary
Package Information
18
Package Information
Figure 18-1.
28-Pin SOIC Package
NOTES:
1.
2.
3.
4.
5.
6.
7.
DIMENSION IN INCH DIMENSION IN MM
Dimension “D” does not include mold flash, protrusions, or gate burrs.
MOld flash, protrusions, and gate burrs shall not exceed .006”
(0.15mm) per side.
Dimension “E” does not include inter-lead flash or protrusions. Interlead flash and protrusion shall not exceed “.010” (0.25 mm) per side.
“L” is the length of terminal for soldering to a substrate.
“N” is the number of terminal positions.
Terminal numbers are shown for reference only.
The lead width “b”, as measured .014” (0.36 mm) or greater above
the seating plane, shall not exceed a maximum value of .024” (0.61
mm).
Reference drawing JEDEC MS013, Variation AE.
294
SYMBOL
A
MIN
MAX
MIN
MAX
.093
.014
2.35
2.65
A1
.004
.012
0.10
0.30
B
.013
.020
0.33
0.51
C
.009
.013
0.23
.032
D
.696
.713
17.70
18.10
E
.291
.299
7.40
7.60
e
0.50 BSC
1.27 BSC
H
.394
.419
10.00
10.65
h
.010
.029
0.25
0.75
L
.016
.050
0.40
1.27
S
.021
.031
0.533
.0787
α
0°
8°
0°
8°
October 5, 2006
Preliminary
LM3S101 Data Sheet
Appendix A. Serial Flash Loader
The Stellaris serial flash loader is used to download code to the flash memory of a device without
the use of a debug interface. The serial flash loader uses a simple packet interface to provide
synchronous communication with the device. The flash loader runs off the crystal and does not
enable the PLL, so its speed is determined by the crystal used. The two serial interfaces that can
be used are the UART0 and SSI interfaces. For simplicity, both the data format and
communication protocol are identical for both serial interfaces.
A.1
Interfaces
Once communication with the flash loader is established via one of the serial interfaces, that
interface is used until the flash loader is reset or new code takes over. For example, once you start
communicating using the SSI port, communications with the flash loader via the UART are
disabled until the device is reset.
A.1.1
UART
The Universal Asynchronous Receivers/Transmitters (UART) communication uses a fixed serial
format of 8 bits of data, no parity, and 1 stop bit. The baud rate used for communication is
automatically detected by the flash loader and can be any valid baud rate supported by the host
and the device. The auto detection sequence requires that the baud rate should be no more than
1/32 the crystal frequency of the board that is running the serial flash loader. This is actually the
same as the hardware limitation for the maximum baud rate for any UART on a Stellaris device.
In order to determine the baud rate, the serial flash loader needs to determine the relationship
between its own crystal frequency and the baud rate. This is enough information for the flash
loader to configure its UART to the same baud rate as the host. This automatic baud rate detection
allows the host to use any valid baud rate that it wants to communicate with the device.
The method used to perform this automatic synchronization relies on the host sending the flash
loader two bytes that are both 0x55. This generates a series of pulses to the flash loader that it can
use to calculate the ratios needed to program the UART to match the host’s baud rate. After the
host sends the pattern, it attempts to read back one byte of data from the UART. The flash loader
returns the value of 0xCC to indicate successful detection of the baud rate. If this byte is not
received after at least twice the time required to transfer the two bytes, the host can resend
another pattern of 0x55, 0x55, and wait for the 0xCC byte again until the flash loader
acknowledges that it has received a synchronization pattern correctly. For example, the time to
wait for data back from the flash loader should be calculated as at least 2*(20(bits/sync)/baud rate
(bits/sec)). For a baud rate of 115200, this time is 2*(20/115200) or 0.35ms.
A.1.2
SSI
The Synchronous Serial Interface (SSI) port also uses a fixed serial format for communications,
with the framing defined as Motorola format with SPH set to 1 and SPO set to 1. See the section
on SSI formats for more details on this transfer protocol. Like the UART, this interface has
hardware requirements that limit the maximum speed that the SSI clock can run. This allows the
SSI clock to be at most 1/12 the crystal frequency of the board running the flash loader. Since the
host device is the master, the SSI on the flash loader device does not need to determine the clock
as it is provided directly by the host.
A.2
Packet Handling
All communications, with the exception of the UART auto-baud, are done via defined packets that
are acknowledged (ACK) or not acknowledged (NAK) by the devices. The packets use the same
October 5, 2006
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Preliminary
format for receiving and sending packets, including the method used to acknowledge successful or
unsuccessful reception of a packet.
A.2.1
Packet Format
All packets sent and received from the device use the following byte-packed format.
struct
{
unsigned char ucSize;
unsigned char ucCheckSum;
unsigned char Data[];
};
ucSize – The first byte received holds the total size of the transfer including the size and checksum
bytes.
ucChecksum – This holds a simple checksum of the bytes in the data buffer only. The algorithm is
Data[0]+Data[1]+…+ Data[ucSize-3].
Data – This is the raw data intended for the device, which is formatted in some form of command
interface. There should be ucSize – 2 bytes of data provided in this buffer to or from the device.
A.2.2
Sending Packets
The actual bytes of the packet can be sent individually or all at once, the only limitation is that
commands that cause flash memory access should limit the download sizes to prevent losing
bytes during flash programming. This limitation is discussed further in the commands that interact
with the flash.
Once the packet has been formatted correctly by the host, it should be sent out over the UART or
SSI interface. Then the host should poll the UART or SSI interface for the first non-zero data
returned from the device. The first non-zero byte will either be an ACK (0xCC) or a NAK (0x33)
byte from the device indicating the packet was received successfully (ACK) or unsuccessfully
(NAK). This does not indicate that the actual contents of the command issued in the data portion of
the packet were valid, just that the packet was received correctly.
A.2.3
Receiving Packets
The flash loader sends a packet of data in the same format that it receives a packet. The flash
loader may transfer leading zero data before the first actual byte of data is sent out. The first
non-zero byte is the size of the packet followed by a checksum byte, and finally followed by the
data itself. There is no break in the data after the first non-zero byte is sent from the flash loader.
Once the device communicating with the flash loader receives all the bytes, it must either ACK or
NAK the packet to indicate that the transmission was successful. The appropriate response after
sending a NAK to the flash loader is to resend the command that failed and request the data again.
If needed, the host may send leading zeros before sending down the ACK/NAK signal to the flash
loader, as the flash loader only accepts the first non-zero data as a valid response. This zero
padding is needed by the SSI interface in order to receive data to or from the flash loader.
A.3
Commands
The next section defines the list of commands that can be sent to the flash loader. The first byte of
the data should always be one of the defined commands, followed by data or parameters as
determined by the command that is sent.
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LM3S101 Data Sheet
A.3.1
COMMAND_PING (0x20)
This command simply accepts the command and sets the global status to success. The format of
the packet is as follows:
Byte[0] = 0x03;
Byte[1] = checksum(Byte[2]);
Byte[2] = COMMAND_PING;
The ping command has 3 bytes and the value for COMMAND_PING is 0x20 and the checksum of
one byte is that same byte, making Byte[1] also 0x20. Since the ping command has no real return
status, the receipt of an ACK can be interpreted as a successful ping to the flash loader.
A.3.2
COMMAND_GET_STATUS (0x23)
This command returns the status of the last command that was issued. Typically, this command
should be sent after every command to ensure that the previous command was successful or to
properly respond to a failure. The command requires one byte in the data of the packet and should
be followed by reading a packet with one byte of data that contains a status code. The last step is
to ACK or NAK the received data so the flash loader knows that the data has been read.
Byte[0] = 0x03
Byte[1] = checksum(Byte[2])
Byte[2] = COMMAND_GET_STATUS
A.3.3
COMMAND_DOWNLOAD (0x21)
This command is sent to the flash loader to indicate where to store data and how many bytes will
be sent by the COMMAND_SEND_DATA commands that follow. The command consists of two
32-bit values that are both transferred MSB first. The first 32-bit value is the address to start
programming data into, while the second is the 32-bit size of the data that will be sent. This
command also triggers an erase of the full area to be programmed so this command takes longer
than other commands. This results in a longer time to receive the ACK/NAK back from the board.
This command should be followed by a COMMAND_GET_STATUS to ensure that the Program
Address and Program size are valid for the device running the flash loader.
The format of the packet to send this command is a follows:
Byte[0] = 11
Byte[1] = checksum(Bytes[2:10])
Byte[2] = COMMAND_DOWNLOAD
Byte[3] = Program Address [31:24]
Byte[4] = Program Address [23:16]
Byte[5] = Program Address [15:8]
Byte[6] = Program Address [7:0]
Byte[7] = Program Size [31:24]
Byte[8] = Program Size [23:16]
Byte[9] = Program Size [15:8]
Byte[10] = Program Size [7:0]
A.3.4
COMMAND_SEND_DATA (0x24)
This command should only follow a COMMAND_DOWNLOAD command or another
COMMAND_SEND_DATA command if more data is needed. Consecutive send data commands
October 5, 2006
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Preliminary
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.3.5
COMMAND_RUN (0x22)
This command is used to tell the flash loader to execute from the address passed as the parameter
in this command. This command consists of a single 32-bit value that is interpreted as the address
to execute. The 32-bit value is transmitted MSB first and the flash loader responds with an ACK
signal back to the host device before actually executing the code at the given address. This allows
the host to know that the command was received successfully and the code is now running.
Byte[0]
Byte[1]
Byte[2]
Byte[3]
Byte[4]
Byte[5]
Byte[6]
A.3.6
=
=
=
=
=
=
=
7
checksum(Bytes[2:6])
COMMAND_RUN
Execute Address[31:24]
Execute Address[23:16]
Execute Address[15:8]
Execute Address[7:0]
COMMAND_RESET (0x25)
This command is used to tell the flash loader device to reset. This is useful when downloading a
new image that overwrote the flash loader and wants to start from a full reset. Unlike the
COMMAND_RUN command, this allows the initial stack pointer to be read by the hardware and
set up for the new code. It can also be used to reset the flash loader if a critical error occurs and
the host device wants to restart communication with the flash loader.
Byte[0] = 3
Byte[1] = checksum(Byte[2])
Byte[2] = COMMAND_RESET
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.
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LM3S101 Data Sheet
Ordering and Contact Information
Ordering Information
Features
a.
b.
c.
d.
e.
f.
√
-
2
-
1
-
I
Speed (Clock
Frequency in MHz)
QEI
1
Packagee
CCP Pins
-
PWM Pins
-
Analog
Comparator(s)
2
I2C
2
to
18
SSI
Timersb
2
UART(s)
GPIOsa
LM3S101-IRN20(T)
f
# of 10-Bit Channels
SRAM (KB)
8
LM3S101-IRN20
Samples Per Second
Flash (KB)
Order Number
Operating
Temperatured
PWMc
ADC
RN
20
Minimum is number of pins dedicated to GPIO; additional pins are available if certain peripherals are not used. See data sheet for
details.
One timer available as RTC.
PWM motion control functionality can be achieved through dedicated motion control hardware (using the PWM pins) or through
the motion control features of the general-purpose timers (using the CCP pins). See data sheet for details.
I=Industrial (–40 to 85°C).
RN=28-pin RoHS-compliant SOIC.
T=Tape and Reel.
Development Kit
The Luminary Micro Stellaris™ Family Development Kit
provides the hardware and software tools that engineers
need to begin development quickly. Ask your Luminary Micro
distributor for part number DK-LM3S101. See the Luminary
Micro website for the latest tools available.
Tools to
begin
development
quickly
Company Information
Luminary Micro, Inc. designs, markets, and sells ARM Cortex-M3 based microcontrollers for use in embedded
applications within the industrial, commercial, and consumer markets. Luminary Micro is ARM's lead partner in
the implementation of the Cortex-M3 core. Please contact us if you are interested in obtaining further
information about our company or our products.
Luminary Micro, Inc.
2499 South Capital of Texas Hwy, Suite A-100
Austin, TX 78746
Main: +1-512-279-8800
Fax: +1-512-279-8879
http://www.luminarymicro.com
[email protected]
October 5, 2006
299
Preliminary
Support Information
For support on Luminary Micro products, contact:
[email protected]
+1-512-279-8800, ext. 3
300
October 5, 2006
Preliminary

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