//******************************************************************************
//  MSP430F21x2 Demo - Timer0_A3, Toggle P1.0, Overflow ISR, 32kHz ACLK
//
//  Description: Toggle P1.0 using software and the Timer0_A1 overflow ISR.
//  In this example an ISR triggers when TA overflows. Inside the ISR P1.0
//  is toggled. Toggle rate is exactly 0.5Hz.
//  Proper use of the TA0IV interrupt vector generator is demonstrated.
//  ACLK = TA0CLK = LFXT1 = 32768Hz, MCLK = SMCLK = default DCO ~1.2MHz
//  //* An external watch crystal on XIN XOUT is required for ACLK *//
//
//              MSP430F21x2
//            -----------------
//        /|\|              XIN|-
//         | |                 | 32kHz
//         --|RST          XOUT|-
//           |                 |
//           |             P1.0|-->LED
//
//  A. Dannenberg
//  Texas Instruments Inc.
//  April 2006
//  Built with CCE Version: 3.2.0 and IAR Embedded Workbench Version: 3.41A
//******************************************************************************
#include "msp430x21x2.h"

void main(void)
{
  WDTCTL = WDTPW + WDTHOLD;                 // Stop WDT
  P1DIR |= 0x01;                            // P1.0 output
  TACTL = TASSEL_1 + MC_2 + TAIE;           // ACLK, contmode, interrupt

  __bis_SR_register(LPM3_bits + GIE);       // Enter LPM3 w/ interrupt
}

// Timer0_A1 Interrupt Vector (TA0IV) handler
#pragma vector=TIMER0_A1_VECTOR
__interrupt void Timer0_A1(void)
{
  switch (__even_in_range(TAIV, 10))        // Efficient switch-implementation
  {
    case  2:  break;                        // TACCR1 not used
    case  4:  break;                        // TACCR2 not used
    case 10:  P1OUT ^= 0x01;                // overflow
              break;
  }
}