digital input using the P1.3 (pull down resistor required)
.include "msp430g2x31.inc"
.include "msp430g2x31.inc"
org 0xf800
mov.w #(WDTPW|WDTHOLD), &WDTCTL
CLR.B P1OUT
CLR R5
mov.b #0x41, &P1DIR
L1: MOV.b &P1IN, r5
AND.b #0x8,r5
tst r5
JZ L1
mov.b #0x41, &P1OUT
L3: jmp L3
org 0xfffe
dw 0xf800