AD usage of MSP430

//
//                    +-----(0.9766us)---------\------------------>+
//    TA0_ISR        TA1      ADC10_ISR             TA0_ISR        TA1
//  -----+------------+------------+-----------\------+------------+----->
//   Enable ADC    Trigger ADC  Disable ADC
//   and Vref                   Compare
//       +-( >30us--->+
//
//
//               MSP430G2x33/G2x53
//            -----------------
//        /||              XIN|-
//         | |                 | 32kHz
//         --|RST          XOUT|-
//           |                 |
//       >---|P1.7/A7     P1.0 |--> LED
//
//  D. Dang
//  Texas Instruments Inc.
//  December 2010
//   Built with CCS Version 4.2.0 and IAR Embedded Workbench Version: 5.10
//******************************************************************************
#include  "msp430g2553.h"

void main(void)
{
  WDTCTL = WDTPW + WDTHOLD;                 // Stop WDT

  ADC10CTL1 = INCH_7 + SHS_1;               // P1.7, TA1 trigger sample start
  ADC10AE0 = 0x80;                          // P1.7 ADC10 option select
  P1DIR |= 0x01;                            // Set P1.0 to output direction
  TACCTL0 = CCIE;                           // Enable interrupt
  TACCR0 = 32-1;                            // PWM Period
  TACCTL1 = OUTMOD_3;                       // TACCR1 set/reset
  TACCR1 = 2;                               // TACCR1 PWM Duty Cycle
  TACTL = TASSEL_1 + MC_1;                  // ACLK, up mode
  __bis_SR_register(LPM3_bits + GIE);       // Enter LPM3, enable interrupts
}

// ADC10 interrupt service routine
#pragma vector=ADC10_VECTOR
__interrupt void ADC10_ISR(void)
{
  ADC10CTL0 &= ~ENC;                        // ADC10 disabled
  ADC10CTL0 = 0;                            // ADC10, Vref disabled completely
  if (ADC10MEM < 0x88)                      // ADC10MEM = A7 > 0.2V?
    P1OUT &= ~0x01;                         // Clear P1.0 LED off
  else
    P1OUT |= 0x01;                          // Set P1.0 LED on
}

// Timer A0 interrupt service routine
#pragma vector=TIMER0_A0_VECTOR
__interrupt void Timer_A(void)
{
  ADC10CTL0 = SREF_1 + ADC10SHT_2 + REFON + ADC10ON + ADC10IE;
  ADC10CTL0 |= ENC;                         // ADC10 enable set
}