#include "msp430x24x.h"

volatile unsigned int i;

void main(void)
{
    // interval: [VLO_freq/(2*32768)] ~ 1/6Hz ~ 6 second interval
    WDTCTL = WDT_ADLY_1000;                   // WDT 1s*4 interval timer
    BCSCTL1 |= DIVA_1;                        // ACLK/2
    BCSCTL3 |= LFXT1S_2;                      // ACLK = VLO
    IE1 |= WDTIE;                             // Enable WDT interrupt
    P1DIR = 0xFF;                             // All P1.x outputs
    P1OUT = 0;                                // All P1.x reset
    P2SEL = 0;                                // All P2.x GPIO function
    P2DIR = 0xFF;                             // All P2.x outputs
    P2OUT = 0;                                // All P2.x reset
    P3DIR = 0xFF;                             // All P3.x outputs
    P3OUT = 0;                                // All P3.x reset
    P4DIR = 0xFF;                             // All P4.x outputs
    P4OUT = 0;                                // All P4.x reset
    P5DIR = 0xFF;                             // All P5.x outputs
    P5OUT = 0;                                // All P5.x reset
    P6DIR = 0xFF;                             // All P6.x outputs
    P6OUT = 0;                                // All P6.x reset
    
    while(1)
    {
        __bis_SR_register(LPM3_bits + GIE);     // Enter LPM3, enable interrupts
        P1OUT |= 0x01;                          // Set P1.0 LED on
        for (i = 20000; i > 0; i--);            // Delay
        P1OUT &= ~0x01;                         // Clear P1.0 LED off
    }
}

#pragma vector=WDT_VECTOR
__interrupt void watchdog_timer (void)
{
    __bic_SR_register_on_exit(LPM3_bits);     // Clear LPM3 bits from 0(SR)
}