MSP430-TIMER

Timer A in continuous mode

— high speed blinking—0.059577273 seconds
Time  = (0xffff+1)/1.1MHz = 0.059578182

.include "msp430g2x31.inc"
org 0xf800
    mov.w #(WDTPW|WDTHOLD), &WDTCTL
    mov.w #0x280, SP
    mov.b #0x41,&P1DIR
    clr.b P1OUT
    mov.w #(TASSEL_2|MC_2|ID_0|TAIE), &TACTL ;ID_0     eint
jimmy:  jmp jimmy
TAISR:
    xor.b #0x41,&P1OUT
    bic.w #1,&TACTL                 reti
ORG     0FFF0h
DW      TAISR
ORG     0FFFEh
DW      0xf800

1 second timer in continuous mode

—using internal DCO (1.012829091 seconds)Time  = ((0xffff+1)/1.1MHz)*17 = 1.012829091  seconds…!!!
Here calculations are done assuming DCO = 1.1MHz

.include "msp430g2x31.inc"
org 0xf800
    mov #(WDTPW|WDTHOLD), &WDTCTL
    mov #0x280, SP
    mov.b #0x41,&P1DIR
    clr.b P1OUT
    clr R5
    mov #(TASSEL_2|MC_2|ID_0|TAIE), &TACTL
    eint
jimmy:  jmp jimmy
TAISR:
    inc R5
    cmp #17,R5
    jne exit
    xor.b #0x41,&P1OUT
    clr R5
exit:
    bic #1, &TACTL
    reti
ORG     0FFF0h
DW      TAISR
ORG     0FFFEh
DW      0xf800

Timer A — using up mode

high speed blinking
Time  = 51001/1.1MHz = 0.046364545

.include "msp430g2x31.inc"
org 0xf800
    mov #(WDTPW|WDTHOLD), &WDTCTL
    mov #0x280, SP
    mov.b #0x41,&P1DIR
    clr.b P1OUT
    mov #(TASSEL_2|MC_1|ID_0|TAIE), &TACTL
    mov #51000, &TACCR0
    eint
jimmy:  jmp jimmy
TAISR:
    xor.b #0x41,&P1OUT
    bic #1, &TACTL
    reti
org    0FFF0h
dw     TAISR
org    0FFFEh
dw     0xf800