//******************************************************************************
// MSP430F20xx Demo - LFXT1 Oscillator Fault Detection
//
// Description: System runs normally in LPM3 with WDT timer clocked by
// 32kHz ACLK with a 1x4 second interrupt. P1.0 is normally pulsed every
// second inside WDT interrupt. If an LFXT1 oscillator fault occurs,
// NMI is requested forcing exit from LPM3. P1.0 is toggled rapidly by software
// as long as LFXT1 oscillator fault is present. Assumed only LFXT1 as NMI
// source - code does not check for other NMI sources.
// ACLK = LFXT1 = 32768, MCLK = SMCLK = Default DCO
//
// //*External watch crystal on XIN XOUT is required for ACLK*//
//
// M. Buccini / L. Westlund
// Texas Instruments Inc.
// September 2005
// Built with CCE Version: 3.2.0 and IAR Embedded Workbench Version: 3.40A
//******************************************************************************
#include <msp430x20x3.h>
volatile unsigned int i;
void main(void)
    {
        WDTCTL = WDT_ADLY_1000; // WDT 1s interval timer
        IE1 |= WDTIE; // Enable WDT interrupt
        P1DIR = 0xFF; // All P1.x outputs
        P1OUT = 0; // All P1.x reset
        P2DIR = 0xFF; // All P2.x outputs
        P2OUT = 0; // All P2.x reset
        BCSCTL3 = XCAP_3; //12.5pF cap- setting for 32768Hz crystal
        // An immedate Osc Fault will occur next
        IE1 |= OFIE; // Enable Osc Fault
    while(1)
        {
            P1OUT ^= 0x01; // Toggle P1.0 using exclusive-OR
            _BIS_SR(LPM3_bits + GIE); // Enter LPM3 w/interrupt
        }
    }
    #pragma vector=WDT_VECTOR
        __interrupt void watchdog_timer (void)
    {
        _BIC_SR_IRQ(LPM3_bits); // Clear LPM3 bits from 0(SR)
    }
    #pragma vector=NMI_VECTOR
    __interrupt void nmi_ (void)
    {
    do
    {
        IFG1 &= ~OFIFG; // Clear OSCFault flag
        for (i = 0xFFF; i > 0; i--); // Time for flag to set
        P1OUT ^= 0x01; // Toggle P1.0 using exclusive-OR
    }
    while (IFG1 & OFIFG); // OSCFault flag still set?
    IE1 |= OFIE; // Enable Osc Fault
}