Texas Instruments MSP430x1xx User Manual
User’s Guide
2005 Mixed Signal Products
SLAU049E
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About This Manual
Related Documentation From Texas Instruments
Preface
This manual discusses modules and peripherals of the MSP430x1xx family of
devices. Each discussion presents the module or peripheral in a general
sense. Not all features and functions of all modules or peripherals are present
on all devices. In addition, modules or peripherals may differ in their exact
implementation between device families, or may not be fully implemented on
an individual device or device family.
Pin functions, internal signal connections and operational paramenters differ
from device-to-device. The user should consult the device-specific datasheet
for these details.
Related Documentation From Texas Instruments
For related documentation see the web site http://www.ti.com/msp430.
FCC Warning
This equipment is intended for use in a laboratory test environment only. It generates, uses, and can radiate radio frequency energy and has not been tested
for compliance with the limits of computing devices pursuant to subpart J of
part 15 of FCC rules, which are designed to provide reasonable protection
against radio frequency interference. Operation of this equipment in other environments may cause interference with radio communications, in which case
the user at his own expense will be required to take whatever measures may
be required to correct this interference.
Notational Conventions
Program examples, are shown in a special typeface.
iii
Glossary
Glossary
ACLK Auxiliary Clock See Basic Clock Module
ADC Analog-to-Digital Converter
BOR Brown-Out Reset See System Resets, Interrupts, and Operating Modes
BSL Bootstrap Loader See www.ti.com/msp430 for application reports
CPU Central Processing Unit See RISC 16-Bit CPU
DAC Digital-to-Analog Converter
DCO Digitally Controlled Oscillator See Basic Clock Module
dst Destination See RISC 16-Bit CPU
FLL Frequency Locked Loop See FLL+ in MSP430x4xx Family User’s Guide
GIE General Interrupt Enable See System Resets Interrupts and Operating Modes
INT(N/2) Integer portion of N/2
I/O Input/Output See Digital I/O
ISR Interrupt Service Routine
LSB Least-Significant Bit
LSD Least-Significant Digit
LPM Low-Power Mode See System Resets Interrupts and Operating Modes
MAB Memory Address Bus
MCLK Master Clock See Basic Clock Module
MDB Memory Data Bus
MSB Most-Significant Bit
MSD Most-Significant Digit
NMI (Non)-Maskable Interrupt See System Resets Interrupts and Operating Modes
PC Program Counter See RISC 16-Bit CPU
POR Power-On Reset See System Resets Interrupts and Operating Modes
PUC Power-Up Clear See System Resets Interrupts and Operating Modes
RAM Random Access Memory
SCG System Clock Generator See System Resets Interrupts and Operating Modes
SFR Special Function Register
SMCLK Sub-System Master Clock See Basic Clock Module
SP Stack Pointer See RISC 16-Bit CPU
SR Status Register See RISC 16-Bit CPU
src Source See RISC 16-Bit CPU
TOS Top-of-Stack See RISC 16-Bit CPU
WDT Watchdog Timer See Watchdog Timer
iv
Register Bit Conventions
Each register is shown with a key indicating the accessibility of the each
individual bit, and the initial condition:
Register Bit Accessibility and Initial Condition
Key Bit Accessibility
rw Read/write
r Read only
r0 Read as 0
r1 Read as 1
w Write only
w0 Write as 0
w1 Write as 1
(w) No register bit implemented; writing a 1 results in a pulse.
The register bit is always read as 0.
h0 Cleared by hardware
Register Bit Conventions
h1 Set by hardware
−0,−1 Condition after PUC
−(0),−(1)
Condition after POR
v
vi
Contents
1 Introduction 1-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.1 Architecture 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2 Flexible Clock System 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.3 Embedded Emulation 1-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.4 Address Space 1-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.4.1 Flash/ROM 1-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.4.2 RAM 1-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.4.3 Peripheral Modules 1-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.4.4 Special Function Registers (SFRs) 1-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.4.5 Memory Organization 1-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2 System Resets, Interrupts, and Operating Modes 2-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.1 System Reset and Initialization 2-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.1.1 Power-On Reset (POR) 2-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.1.2 Brownout Reset (BOR) 2-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.1.3 Device Initial Conditions After System Reset 2-5. . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2 Interrupts 2-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2.1 (Non)-Maskable Interrupts (NMI) 2-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2.2 Maskable Interrupts 2-10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2.3 Interrupt Processing 2-11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2.4 Interrupt Vectors 2-13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3 Operating Modes 2-14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3.1 Entering and Exiting Low-Power Modes 2-16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.4 Principles for Low-Power Applications 2-17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.5 Connection of Unused Pins 2-17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
vii
Contents
3 RISC 16-Bit CPU 3-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1 CPU Introduction 3-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2 CPU Registers 3-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2.1 Program Counter (PC) 3-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2.2 Stack Pointer (SP) 3-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2.3 Status Register (SR) 3-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2.4 Constant Generator Registers CG1 and CG2 3-7. . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2.5 General−Purpose Registers R4 - R15 3-8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3 Addressing Modes 3-9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3.1 Register Mode 3-10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3.2 Indexed Mode 3-11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3.3 Symbolic Mode 3-12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3.4 Absolute Mode 3-13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3.5 Indirect Register Mode 3-14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3.6 Indirect Autoincrement Mode 3-15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3.7 Immediate Mode 3-16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4 Instruction Set 3-17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4.1 Double-Operand (Format I) Instructions 3-18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4.2 Single-Operand (Format II) Instructions 3-19. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4.3 Jumps 3-20. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4.4 Instruction Cycles and Lengths 3-72. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4.5 Instruction Set Description 3-74. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4 Basic Clock Module 4-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.1 Basic Clock Module Introduction 4-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2 Basic Clock Module Operation 4-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2.1 Basic Clock Module Features for Low-Power Applications 4-4. . . . . . . . . . . . . . . .
4.2.2 LFXT1 Oscillator 4-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2.3 XT2 Oscillator 4-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2.4 Digitally-Controlled Oscillator (DCO) 4-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2.5 DCO Modulator 4-9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2.6 Basic Clock Module Fail-Safe Operation 4-10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2.7 Synchronization of Clock Signals 4-13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.3 Basic Clock Module Registers 4-14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5 Flash Memory Controller 5-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.1 Flash Memory Introduction 5-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2 Flash Memory Segmentation 5-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.3 Flash Memory Operation 5-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.3.1 Flash Memory Timing Generator 5-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.3.2 Erasing Flash Memory 5-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.3.3 Writing Flash Memory 5-8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.3.4 Flash Memory Access During Write or Erase 5-14. . . . . . . . . . . . . . . . . . . . . . . . . . .
5.3.5 Stopping a Write or Erase Cycle 5-15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.3.6 Configuring and Accessing the Flash Memory Controller 5-15. . . . . . . . . . . . . . . . .
5.3.7 Flash Memory Controller Interrupts 5-15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.3.8 Programming Flash Memory Devices 5-15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.4 Flash Memory Registers 5-17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
viii
Contents
6 Supply Voltage Supervisor 6-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.1 SVS Introduction 6-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.2 SVS Operation 6-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.2.1 Configuring the SVS 6-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.2.2 SVS Comparator Operation 6-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.2.3 Changing the VLDx Bits 6-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.2.4 SVS Operating Range 6-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.3 SVS Registers 6-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7 Hardware Multiplier 7-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.1 Hardware Multiplier Introduction 7-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.2 Hardware Multiplier Operation 7-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.2.1 Operand Registers 7-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.2.2 Result Registers 7-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.2.3 Software Examples 7-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.2.4 Indirect Addressing of RESLO 7-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.2.5 Using Interrupts 7-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.3 Hardware Multiplier Registers 7-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8 DMA Controller 8-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.1 DMA Introduction 8-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.2 DMA Operation 8-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.2.1 DMA Addressing Modes 8-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.2.2 DMA Transfer Modes 8-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.2.3 Initiating DMA Transfers 8-12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.2.4 Stopping DMA Transfers 8-14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.2.5 DMA Channel Priorities 8-14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.2.6 DMA Transfer Cycle Time 8-15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.2.7 Using DMA with System Interrupts 8-16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.2.8 DMA Controller Interrupts 8-16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2
8.2.9 Using the I
C Module with the DMA Controller 8-17. . . . . . . . . . . . . . . . . . . . . . . . .
8.2.10 Using ADC12 with the DMA Controller 8-17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.2.11 Using DAC12 With the DMA Controller 8-17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.3 DMA Registers 8-18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9 Digital I/O 9-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.1 Digital I/O Introduction 9-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.2 Digital I/O Operation 9-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.2.1 Input Register PnIN 9-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.2.2 Output Registers PnOUT 9-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.2.3 Direction Registers PnDIR 9-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.2.4 Function Select Registers PnSEL 9-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.2.5 P1 and P2 Interrupts 9-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.2.6 Configuring Unused Port Pins 9-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9.3 Digital I/O Registers 9-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ix
Contents
10 Watchdog Timer 10-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.1 Watchdog Timer Introduction 10-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.2 Watchdog Timer Operation 10-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.2.1 Watchdog Timer Counter 10-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.2.2 Watchdog Mode 10-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.2.3 Interval Timer Mode 10-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.2.4 Watchdog Timer Interrupts 10-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.2.5 Operation in Low-Power Modes 10-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.2.6 Software Examples 10-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.3 Watchdog Timer Registers 10-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11 Timer_A 11-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11.1 Timer_A Introduction 11-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11.2 Timer_A Operation 11-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11.2.1 16-Bit Timer Counter 11-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11.2.2 Starting the Timer 11-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11.2.3 Timer Mode Control 11-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11.2.4 Capture/Compare Blocks 11-11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11.2.5 Output Unit 11-13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11.2.6 Timer_A Interrupts 11-17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11.3 Timer_A Registers 11-19. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12 Timer_B 12-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.1 Timer_B Introduction 12-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.1.1 Similarities and Differences From Timer_A 12-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.2 Timer_B Operation 12-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.2.1 16-Bit Timer Counter 12-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.2.2 Starting the Timer 12-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.2.3 Timer Mode Control 12-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.2.4 Capture/Compare Blocks 12-11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.2.5 Output Unit 12-14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.2.6 Timer_B Interrupts 12-18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.3 Timer_B Registers 12-20. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13 USART Peripheral Interface, UART Mode 13-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.1 USART Introduction: UART Mode 13-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.2 USART Operation: UART Mode 13-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.2.1 USART Initialization and Reset 13-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.2.2 Character Format 13-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.2.3 Asynchronous Communication Formats 13-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.2.4 USART Receive Enable 13-9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.2.5 USART Transmit Enable 13-10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.2.6 UART Baud Rate Generation 13-11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.2.7 USART Interrupts 13-17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3 USART Registers: UART Mode 13-21. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Contents
14 USART Peripheral Interface, SPI Mode 14-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.1 USART Introduction: SPI Mode 14-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.2 USART Operation: SPI Mode 14-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.2.1 USART Initialization and Reset 14-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.2.2 Master Mode 14-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.2.3 Slave Mode 14-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.2.4 SPI Enable 14-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.2.5 Serial Clock Control 14-9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.2.6 SPI Interrupts 14-11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.3 USART Registers: SPI Mode 14-13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2
15 USART Peripheral Interface, I
15.1 I
15.2 I
2
C Module Introduction 15-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2
C Module Operation 15-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2
15.2.1 I
15.2.2 I
15.2.3 I
15.2.4 I
15.2.5 The I
15.2.6 I
15.2.7 Using the I
15.2.8 I
C Module Initialization 15-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2
C Serial Data 15-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2
C Addressing Modes 15-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2
C Module Operating Modes 15-8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2
C Data Register I2CDR 15-15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2
C Clock Generation and Synchronization 15-16. . . . . . . . . . . . . . . . . . . . . . . . . . .
2
2
C Interrupts 15-18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
C Mode 15-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
C Module with Low Power Modes 15-17. . . . . . . . . . . . . . . . . . . . . . . . .
15.3 I2C Module Registers 15-20. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16 Comparator_A 16-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.1 Comparator_A Introduction 16-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.2 Comparator_A Operation 16-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.2.1 Comparator 16-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.2.2 Input Analog Switches 16-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.2.3 Output Filter 16-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.2.4 Voltage Reference Generator 16-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.2.5 Comparator_A, Port Disable Register CAPD 16-6. . . . . . . . . . . . . . . . . . . . . . . . . . .
16.2.6 Comparator_A Interrupts 16-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.2.7 Comparator_A Used to Measure Resistive Elements 16-7. . . . . . . . . . . . . . . . . . . .
16.3 Comparator_A Registers 16-9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17 ADC12 17-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.1 ADC12 Introduction 17-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.2 ADC12 Operation 17-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.2.1 12-Bit ADC Core 17-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.2.2 ADC12 Inputs and Multiplexer 17-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.2.3 Voltage Reference Generator 17-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.2.4 Auto Power-Down 17-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.2.5 Sample and Conversion Timing 17-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.2.6 Conversion Memory 17-10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.2.7 ADC12 Conversion Modes 17-10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.2.8 Using the Integrated Temperature Sensor 17-16. . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.2.9 ADC12 Grounding and Noise Considerations 17-17. . . . . . . . . . . . . . . . . . . . . . . . .
17.2.10 ADC12 Interrupts 17-18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.3 ADC12 Registers 17-20. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Contents
18 ADC10 18-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.1 ADC10 Introduction 18-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.2 ADC10 Operation 18-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.2.1 10-Bit ADC Core 18-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.2.2 ADC10 Inputs and Multiplexer 18-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.2.3 Voltage Reference Generator 18-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.2.4 Auto Power-Down 18-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.2.5 Sample and Conversion Timing 18-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.2.6 Conversion Modes 18-9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.2.7 ADC10 Data Transfer Controller 18-15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.2.8 Using the Integrated Temperature Sensor 18-21. . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.2.9 ADC10 Grounding and Noise Considerations 18-22. . . . . . . . . . . . . . . . . . . . . . . . .
18.2.10 ADC10 Interrupts 18-23. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.3 ADC10 Registers 18-24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19 DAC12 19-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.1 DAC12 Introduction 19-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.2 DAC12 Operation 19-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.2.1 DAC12 Core 19-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.2.2 DAC12 Reference 19-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.2.3 Updating the DAC12 Voltage Output 19-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.2.4 DAC12_xDAT Data Format 19-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.2.5 DAC12 Output Amplifier Offset Calibration 19-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.2.6 Grouping Multiple DAC12 Modules 19-8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.2.7 DAC12 Interrupts 19-9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.3 DAC12 Registers 19-10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
xii
Chapter 1
This chapter describes the architecture of the MSP430.
Topic Page
1.1 Architecture 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2 Flexible Clock System 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.3 Embedded Emulation 1-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.4 Address Space 1-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Introduction
1-1
Architecture
1.1 Architecture
The MSP430 incorporates a 16-bit RISC CPU, peripherals, and a flexible clock
system that interconnect using a von-Neumann common memory address
bus (MAB) and memory data bus (MDB). Partnering a modern CPU with
modular memory-mapped analog and digital peripherals, the MSP430 offers
solutions for demanding mixed-signal applications.
Key features of the MSP430x1xx family include:
- Ultralow-power architecture extends battery life
J 0.1-µA RAM retention
J 0.8-µA real-time clock mode
J 250-µA / MIPS active
- High-performance analog ideal for precision measurement
J 12-bit or 10-bit ADC — 200 ksps, temperature sensor, V
12-bit dual-DAC
J
J Comparator-gated timers for measuring resistive elements
J Supply voltage supervisor
- 16-bit RISC CPU enables new applications at a fraction of the code size.
J Large register file eliminates working file bottleneck
J Compact core design reduces power consumption and cost
J Optimized for modern high-level programming
J Only 27 core instructions and seven addressing modes
J Extensive vectored-interrupt capability
- In-system programmable Flash permits flexible code changes, field
upgrades and data logging
1.2 Flexible Clock System
The clock system is designed specifically for battery-powered applications. A
low-frequency auxiliary clock (ACLK) is driven directly from a common 32-kHz
watch crystal. The ACLK can be used for a background real-time clock self
wake-up function. An integrated high-speed digitally controlled oscillator
(DCO) can source the master clock (MCLK) used by the CPU and high-speed
peripherals. By design, the DCO is active and stable in less than 6 µs.
MSP430-based solutions effectively use the high-performance 16-bit RISC
CPU in very short bursts.
Ref
1-2
- Low-frequency auxiliary clock = Ultralow-power stand-by mode
- High-speed master clock = High performance signal processing
Introduction
Figure 1−1.MSP430 Architecture
Embedded Emulation
MCLK
ACLK
SMCLK
ACLK
SMCLK
Flash/
ROM
MAB 16-Bit
JTAG/Debug
MDB 16-Bit
Watchdog
Clock
System
RISC CPU
16-Bit
JTAG
1.3 Embedded Emulation
Dedicated embedded emulation logic resides on the device itself and is
accessed via JTAG using no additional system resources.
The benefits of embedded emulation include:
RAM
Peripheral
Peripheral Peripheral Peripheral
Bus
Conv.
Peripheral
MDB 8-Bit
Peripheral Peripheral
- Unobtrusive development and debug with full-speed execution,
breakpoints, and single-steps in an application are supported.
- Development is in-system subject to the same characteristics as the final
application.
- Mixed-signal integrity is preserved and not subject to cabling interference.
Introduction
1-3
Address Space
1.4 Address Space
The MSP430 von-Neumann architecture has one address space shared with
special function registers (SFRs), peripherals, RAM, and Flash/ROM memory
as shown in Figure 1−2. See the device-specific data sheets for specific
memory maps. Code access are always performed on even addresses. Data
can be accessed as bytes or words.
The addressable memory space is 64 KB with future expansion planned.
Figure 1−2.Memory Map
Access
0FFFFh
0FFE0h
0FFDFh
0200h
01FFh
0100h
0FFh
010h
1.4.1 Flash/ROM
Word/Byte
Word/Byte
Word/Byte
Word
Byte
Byte
0Fh
0h
Interrupt Vector Table
Flash/ROM
RAM
16-Bit Peripheral Modules
8-Bit Peripheral Modules
Special Function Registers
The start address of Flash/ROM depends on the amount of Flash/ROM
present and varies by device. The end address for Flash/ROM is 0FFFFh.
Flash can be used for both code and data. Word or byte tables can be stored
and used in Flash/ROM without the need to copy the tables to RAM before
using them.
1.4.2 RAM
1-4
Introduction
The interrupt vector table is mapped into the upper 16 words of Flash/ROM
address space, with the highest priority interrupt vector at the highest
Flash/ROM word address (0FFFEh).
RAM starts at 0200h. The end address of RAM depends on the amount of RAM
present and varies by device. RAM can be used for both code and data.
1.4.3 Peripheral Modules
Peripheral modules are mapped into the address space. The address space
from 0100 to 01FFh is reserved for 16-bit peripheral modules. These modules
should be accessed with word instructions. If byte instructions are used, only
even addresses are permissible, and the high byte of the result is always 0.
The address space from 010h to 0FFh is reserved for 8-bit peripheral modules.
These modules should be accessed with byte instructions. Read access of
byte modules using word instructions results in unpredictable data in the high
byte. If word data is written to a byte module only the low byte is written into
the peripheral register, ignoring the high byte.
1.4.4 Special Function Registers (SFRs)
Some peripheral functions are configured in the SFRs. The SFRs are located
in the lower 16 bytes of the address space, and are organized by byte. SFRs
must be accessed using byte instructions only. See the device-specific data
sheets for applicable SFR bits.
1.4.5 Memory Organization
Address Space
Bytes are located at even or odd addresses. Words are only located at even
addresses as shown in Figure 1−3. When using word instructions, only even
addresses may be used. The low byte of a word is always an even address.
The high byte is at the next odd address. For example, if a data word is located
at address xxx4h, then the low byte of that data word is located at address
xxx4h, and the high byte of that word is located at address xxx5h.
Figure 1−3.Bits, Bytes, and Words in a Byte-Organized Memory
xxxAh
157146. . Bits . .
. . Bits . .9180
Byte
Byte
Word (High Byte)
Word (Low Byte)
xxx9h
xxx8h
xxx7h
xxx6h
xxx5h
xxx4h
xxx3h
Introduction
1-5
1-6
Introduction
Chapter 2
This chapter describes the MSP430x1xx system resets, interrupts, and
operating modes.
Topic Page
2.1 System Reset and Initialization 2-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2 Interrupts 2-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3 Operating Modes 2-14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.4 Principles for Low-Power Applications 2-17. . . . . . . . . . . . . . . . . . . . . . . .
2.5 Connection of Unused Pins 2-17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
System Resets, Interrupts, and Operating Modes
2-1
System Reset and Initialization
2.1 System Reset and Initialization
The system reset circuitry shown in Figure 2−1 sources both a power-on reset
(POR) and a power-up clear (PUC) signal. Different events trigger these reset
signals and different initial conditions exist depending on which signal was
generated.
Figure 2−1.Power-On Reset and Power-Up Clear Schematic
V
V
CC
V
CC
CC
V
CC
Brownout
‡
Reset
0 V
0 V
EQU
KEYV
§
†
†
†
†
†
SVS_POR
RST/NMI
WDTNMI
WDTSSEL
WDTQn
WDTIFG
(from flash module)
† From watchdog timer peripheral module
‡ Devices with BOR only
# Devices without BOR only
§ Devices with SVS only
POR
POR
Detect
Detect
0 V
0 V
#
~ 50us
A POR is a device reset. A POR is only generated by the following three
events:
POR
Delay
0 V
#
Resetwd1
Resetwd2
S
S
R
S
S
S
S
S
R
POR
Latch
Delay
PUC
Latch
MCLK
POR
PUC
2-2
- Powering up the device
- A low signal on the RST/NMI pin when configured in the reset mode
- An SVS low condition when PORON = 1.
A PUC is always generated when a POR is generated, but a POR is not
generated by a PUC. The following events trigger a PUC:
- A POR signal
- Watchdog timer expiration when in watchdog mode only
- Watchdog timer security key violation
- A Flash memory security key violation
System Resets, Interrupts, and Operating Modes
2.1.1 Power-On Reset (POR)
When the VCC rise time is slow, the POR detector holds the POR signal active
until VCC has risen above the V
supply provides a fast rise time the POR delay, t
V
CC
active time on the POR signal to allow the MSP430 to initialize.
System Reset and Initialization
level, as shown in Figure 2−2. When the
POR
(POR_DELAY)
, provides
If power to the MSP430 is cycled, the supply voltage V
to ensure that another POR signal occurs when VCC is powered up again. If
VCC does not fall below V
and power-up conditions do not set correctly. See device-specific datasheet
for parameters.
Figure 2−2.POR Timing
V
V
CC(min)
V
POR
V
min
Set Signal for
POR circuitry
must fall below V
CC
during a cycle or a glitch, a POR is not generated
min
V
CC
PORPOR
min
No POR
t
(POR_DELAY)
System Resets, Interrupts, and Operating Modes
t
(POR_DELAY)
2-3
System Reset and Initialization
2.1.2 Brownout Reset (BOR)
Some devices have a brownout reset circuit (see device-specific datasheet)
that replaces the POR detect and POR delay circuits. The brownout reset
circuit detects low supply voltages such as when a supply voltage is applied
to or removed from the V
device by triggering a POR signal when power is applied or removed. The
operating levels are shown in Figure 2−3.
terminal. The brownout reset circuit resets the
CC
The POR signal becomes active when V
remains active until V
elapses. The delay t
hysteresis V
V
(B_IT−)
Figure 2−3.Brownout Timing
V
V
(B_IT+)
V
(B_IT−)
V
CC(start)
Set Signal for
POR circuitry
hys(B_IT−)
level. It
(BOR)
The
CC.
CC
(BOR)
hys(B_ IT−)
crosses the V
crosses the V
CC
(B_IT+)
threshold and the delay t
CC(start)
is adaptive being longer for a slow ramping V
ensures that the supply voltage must drop below
to generate another POR signal from the brownout reset circuitry.
V
CC
2-4
t
(BOR)
As the V
level is significantly above the V
(B_IT−)
BOR provides a reset for power failures where V
See device-specific datasheet for parameters.
System Resets, Interrupts, and Operating Modes
level of the POR circuit, the
min
does not fall below V
CC
min.
2.1.3 Device Initial Conditions After System Reset
After a POR, the initial MSP430 conditions are:
- The RST/NMI pin is configured in the reset mode.
- I/O pins are switched to input mode as described in the Digital I/O chapter.
- Other peripheral modules and registers are initialized as described in their
respective chapters in this manual.
- Status register (SR) is reset.
- The watchdog timer powers up active in watchdog mode.
- Program counter (PC) is loaded with address contained at reset vector
location (0FFFEh). CPU execution begins at that address.
Software Initialization
After a system reset, user software must initialize the MSP430 for the
application requirements. The following must occur:
System Reset and Initialization
- Initialize the SP, typically to the top of RAM.
- Initialize the watchdog to the requirements of the application.
- Configure peripheral modules to the requirements of the application.
Additionally, the watchdog timer, oscillator fault, and flash memory flags can
be evaluated to determine the source of the reset.
System Resets, Interrupts, and Operating Modes
2-5
System Reset and Initialization
2.2 Interrupts
The interrupt priorities are fixed and defined by the arrangement of the
modules in the connection chain as shown in Figure 2−4. The nearer a module
is to the CPU/NMIRS, the higher the priority. Interrupt priorities determine what
interrupt is taken when more than one interrupt is pending simultaneously.
There are three types of interrupts:
- System reset
- (Non)-maskable NMI
- Maskable
Figure 2−4.Interrupt Priority
CPU
PUC
PUC
Circuit
WDT Security Key
Flash Security Key
Priority
GMIRS
GIE
NMIRS
OSCfault
Flash ACCV
Reset/NMI
MAB − 5LSBs
High
Module
1
Low
Module
2
12 12 12 12 1
Bus
Grant
WDT
Timer
Module
m
Module
n
2-6
System Resets, Interrupts, and Operating Modes
2.2.1 (Non)-Maskable Interrupts (NMI)
(Non)-maskable NMI interrupts are not masked by the general interrupt enable
bit (GIE), but are enabled by individual interrupt enable bits (NMIIE, ACCVIE,
OFIE). When a NMI interrupt is accepted, all NMI interrupt enable bits are
automatically reset. Program execution begins at the address stored in the
(non)-maskable interrupt vector , 0FFFCh. User software must set the required
NMI interrupt enable bits for the interrupt to be re-enabled. The block diagram
for NMI sources is shown in Figure 2−5.
A (non)-maskable NMI interrupt can be generated by three sources:
- An edge on the RST/NMI pin when configured in NMI mode
- An oscillator fault occurs
- An access violation to the flash memory
Reset/NMI Pin
At power-up, the RST/NMI pin is configured in the reset mode. The function
of the RST/NMI pins is selected in the watchdog control register WDTCTL. If
the RST
as long as the RST
the CPU starts program execution at the word address stored in the reset
vector, 0FFFEh.
/NMI pin is set to the reset function, the CPU is held in the reset state
/NMI pin is held low. After the input changes to a high state,
System Reset and Initialization
If the RST
/NMI pin is configured by user software to the NMI function, a signal
edge selected by the WDTNMIES bit generates an NMI interrupt if the NMIIE
bit is set. The RST
/NMI flag NMIIFG is also set.
Note: Holding RST/NMI Low
When configured in the NMI mode, a signal generating an NMI event should
not hold the RST
/NMI pin low. If a PUC occurs from a dif ferent source while
the NMI signal is low, the device will be held in the reset state because a PUC
changes the RST
/NMI pin to the reset function.
Note: Modifying WDTNMIES
When NMI mode is selected and the WDTNMIES bit is changed, an NMI can
be generated, depending on the actual level at the RST
/NMI pin. When the
NMI edge select bit is changed before selecting the NMI mode, no NMI is
generated.
System Resets, Interrupts, and Operating Modes
2-7
System Reset and Initialization
Figure 2−5.Block Diagram of (Non)-Maskable Interrupt Sources
ACCV
ACCVIFG
S
FCTL1.1
ACCVIE
IE1.5
Clear
PUC
RST/NMI
IFG1.4
PUC
IE1.4
PUC
OSCFault
IFG1.1
IE1.1
PUC
S
Clear
Clear
S
Clear
NMIIFG
NMIIE
OFIFG
OFIE
NMI_IRQA
WDTTMSEL
WDTNMIES
Counter
WDTNMI
WDT
WDTTMSEL
KEYV
WDTQn EQU
S
IFG1.0
Clear
POR
IRQA
IE1.0
Clear
Flash Module
POR PUC
System Reset
Generator
WDTIFG
WDTIE
V
CC
PUC POR
PUC
POR
NMIRS
IRQ
2-8
IRQA: Interrupt Request Accepted
Watchdog Timer Module
System Resets, Interrupts, and Operating Modes
PUC
Flash Access Violation
The flash ACCVIFG flag is set when a flash access violation occurs. The flash
access violation can be enabled to generate an NMI interrupt by setting the
ACCVIE bit. The ACCVIFG flag can then be tested by NMI the interrupt service
routine to determine if the NMI was caused by a flash access violation.
Oscillator Fault
The oscillator fault signal warns of a possible error condition with the crystal
oscillator. The oscillator fault can be enabled to generate an NMI interrupt b y
setting the OFIE bit. The OFIFG flag can then be tested by NMI the interrupt
service routine to determine if the NMI was caused by an oscillator fault.
A PUC signal can trigger an oscillator fault, because the PUC switches the
LFXT1 to LF mode, therefore switching off the HF mode. The PUC signal also
switches off the XT2 oscillator.
System Reset and Initialization
System Resets, Interrupts, and Operating Modes
2-9
System Reset and Initialization
Example of an NMI Interrupt Handler
The NMI interrupt is a multiple-source interrupt. An NMI interrupt automatically
resets the NMIIE, OFIE and ACCVIE interrupt-enable bits. The user NMI
service routine resets the interrupt flags and re-enables the interrupt-enable
bits according to the application needs as shown in Figure 2−6.
Figure 2−6.NMI Interrupt Handler
Start of NMI Interrupt Handler
Reset by HW:
OFIE, NMIIE, ACCVIE
OFIFG=1
User’s Software,
Oscillator Fault
Handler
Optional
Set NMIIE, OFIE,
ACCVIE Within One
Instruction
RETI
End of NMI Interrupt
Handler
yes
no
ACCVIFG=1
yes
Reset ACCVIFG
User’s Software,
Flash Access
Violation Handler
Example 1:
BIS #(NMIIE+OFIE+ACCVIE), &IE1
Example 2:
BIS Mask,&IE1 ; Mask enables only
no
NMIIFG=1
yes
Reset NMIIFGReset OFIFG
User’s Software,
External NMI
Handler
; interrupt sources
no
Note: Enabling NMI Interrupts with ACCVIE, NMIIE, and OFIE
The ACCVIE, NMIIE, and OFIE enable bits should not be set inside of an NMI
interrupt service routine, unless they are set by the last instruction of the
routine before the RETI instruction. Otherwise, nested NMI interrupts may
occur, causing stack overflow and unpredictable operation.
2.2.2 Maskable Interrupts
Maskable interrupts are caused by peripherals with interrupt capability
including the watchdog timer overflow in interval-timer mode. Each maskable
interrupt source can be disabled individually by an interrupt enable bit, or all
maskable interrupts can be disabled by the general interrupt enable (GIE) bit
in the status register (SR).
2-10
System Resets, Interrupts, and Operating Modes
Each individual peripheral interrupt is discussed in the associated peripheral
Before
After
module chapter in this manual.
2.2.3 Interrupt Processing
When an interrupt is requested from a peripheral and the peripheral interrupt
enable bit and GIE bit are set, the interrupt service routine is requested. Only
the individual enable bit must be set for (non)-maskable interrupts to be
requested.
Interrupt Acceptance
The interrupt latency is 6 cycles, starting with the acceptance of an interrupt
request, and lasting until the start of execution of the first instruction of the
interrupt-service routine, as shown in Figure 2−7. The interrupt logic executes
the following:
1) Any currently executing instruction is completed.
2) The PC, which points to the next instruction, is pushed onto the stack.
3) The SR is pushed onto the stack.
System Reset and Initialization
4) The interrupt with the highest priority is selected if multiple interrupts
occurred during the last instruction and are pending for service.
5) The interrupt request flag resets automatically on single-source flags.
Multiple source flags remain set for servicing by software.
6) The SR is cleared with the exception of SCG0, which is left unchanged.
This terminates any low-power mode. Because the GIE bit is cleared,
further interrupts are disabled.
7) The content of the interrupt vector is loaded into the PC: the program
continues with the interrupt service routine at that address.
Figure 2−7.Interrupt Processing
Interrupt
Item1
SP TOS
Item2
Interrupt
Item1
Item2
PC
SP TOS
SR
System Resets, Interrupts, and Operating Modes
2-11
System Reset and Initialization
Return From Interrupt
The interrupt handling routine terminates with the instruction:
RETI (return from an interrupt service routine)
The return from the interrupt takes 5 cycles to execute the following actions
and is illustrated in Figure 2−8.
1) The SR with all previous settings pops from the stack. All previous settings
of GIE, CPUOFF, etc. are now in effect, regardless of the settings used
during the interrupt service routine.
2) The PC pops from the stack and begins execution at the point where it was
interrupted.
Figure 2−8.Return From Interrupt
Before After
Return From Interrupt
Interrupt Nesting
Item1
Item2
PC
SP TOS
SR
SP TOS
Item1
Item2
PC
SR
Interrupt nesting is enabled if the GIE bit is set inside an interrupt service
routine. When interrupt nesting is enabled, any interrupt occurring during an
interrupt service routine will interrupt the routine, regardless of the interrupt
priorities.
2-12
System Resets, Interrupts, and Operating Modes
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