MSP 430 has 16 registers of which 3 are dedicated function registers and remaining are general purpose registers.

R0 – R3 are Dedicated functions registers.

R4 – R15 are General Purpose registers.

i) PC- program counter:

It can be addressed instructions in address mode.

ii) SP- stack pointer:

Always aligned to even addresses.

Operation of Stack Pointer can be explained as follows:

iii) Status register- SR/ R2

It stores status of result of arithmetic or logical operation.

The status register has following fields.

• C - carry bit:
  Set -Carry is generated; Clear- no carry

• Z - zero bit:
  Set- result is zero; Clear- result is not zero

• N - negative:
  Set- result is negative; Clear- result is non-negative

• GIE - general interrupt enable
  Set- enables maskable interrupt; Clear- all maskable interrupts are disabled

• CPU off - set when CPU turns off

• OSC OFF- oscillator off; Set- turns of LFXT1 crystal oscillator when LFXT1 CLK is not used for MCLK or SMCLK.

• SCG0 - system clock generator 0; Set- turns of the FLL+ loop control

• SCG1- system clock generator 1; Set- turns off DCO DC generator, if DCO CLK is not used for MCLK or SMCLK.

iv) Constant generator CG1/ CG2 (R2/R3)

• Depending on source register addressing mode (As) new value, 6 commonly used constants can be generated without a code word or code memory access to retrieve them.
• Powerful feature allows the implementation of emulated instruction.

v) General purpose registers: R4-R15

• To store data values, address pointers, or index values.

• They can be accessed by byte or Word instruction.