Notes

#include <msp430g2553.h>

#define RTC_STATE_SECONDS 0
#define RTC_STATE_MINUTES 1
#define RTC_STATE_HOURS 2

volatile unsigned long timerCount = 0;
volatile unsigned long rtcState[3] = {0, 0, 0};


void timerInit(void){
// Enable Timer Interrupts
TACCTL0 = CCIE;

// SMCLK, Count to CCR0 Value, Divide by 8
TA0CTL = TASSEL_2 + MC_1 + ID_3;

// 1,000,000 / 8 / 25 = 5000
TACCR0 = 5000;
}


int main(void){
//Disable Watchdog
WDTCTL = WDTPW + WDTHOLD;

// Set clock to 1 MHz
BCSCTL1 = CALBC1_1MHZ;
DCOCTL = CALDCO_1MHZ;

timerInit();




}

// Timer Interrupt

#pragma vector=TIMER0_A0_VECTOR
__interrupt void Timer_A (void) {
timerCount++;
if (timerCount >= 25){
timerCount = 0;
rtcState[RTC_STATE_SECONDS]++;
if (rtcState[RTC_STATE_SECONDS] >= 60){
rtcState[RTC_STATE_SECONDS] = 0;
rtcState[RTC_STATE_MINUTES]++;
if (rtcState[RTC_STATE_MINUTES] >= 60){
rtcState[RTC_STATE_MINUTES] = 0;
rtcState[RTC_STATE_HOURS]++;
if (rtcState[RTC_STATE_HOURS] >= 24) {
rtcState[RTC_STATE_HOURS] = 0;
}
}
}
}
}