This code blinks on and off an LED on my MSP430 from TI. I've marked teh number of cycles used for each instruction, but I'm not sure where the actual 'timing' factor comes in, as the RED led blinks on and off about every half second. To me, it looks like it should just be beignn toggled as fast as the processor can go. I'm trying to get the delayloop to be 1/10 of a second so the main loop can run it 100 times, thus blinking the LED very quickly, once every 10 seconds.
;*******************************************************************************
.cdecls C,LIST, "msp430.h" ; MSP430
;------------------------------------------------------------------------------
.text ; beginning of executable code
;------------------------------------------------------------------------------
RESET: mov.w #0x0280,SP ; init stack pointer, 5 CYCLES
mov.w #WDTPW+WDTHOLD,&WDTCTL ; stop WDT, 5 CYCLES
bis.b #0x01,&P1DIR ; set P1.0 as output, 5 CYCLES
; Total 15 Cycles
mainloop: xor.b #0x01,&P1OUT ; toggle P1.0. 5 CYLCES
mov.w #0,r15 ; use R15 as delay counter, 2 CYCLES execute 100 delayloop times
; Total 7 Cycles
delayloop: sub.w #1,r15 ; delay over? 2 CYCLES
jnz delayloop ; n 2 CYCLES go for 1/10 of a second
jmp mainloop ; y, toggle led 2 CYCLES
; Total 6 Cycles
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; Interrupt Vectors
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.sect ".reset" ; MSP430 RESET Vector
.word RESET ; start address
.end
