想咨询下MSP430定时器捕获功能，一直进中断，捕获管脚改过之后就消失了

程序（1）

采用P2.3管脚捕获

#include <msp430x43x.h>

void main(void)
{
  WDTCTL = WDTPW + WDTHOLD;       // Stop watchdog timer to prevent time out reset
  _EINT();                                                     //开中断
  P2SEL |= BIT3;                                        // 设置引脚P2.3第二功能定时器捕获
  TACTL |= TASSEL_1 | TACLR | TAIE | TAIFG;          // 定时器寄存器设置，先进中断
  TACCR1 = 0x7fff;
  TACCTL1 |= CCIE;                           
  TACCTL2 |= CCIS_1 | CCIE | CAP | CM_2;           // 选CCIB2捕获，开中断
  TACTL |= MC_2;
  while(1);
}

void Time_Deal(void)
{
  unsigned char flag;
  flag = TAIV;
  switch(flag)
  {
  case 2:
    _NOP();           //不执行
    break;
  case 4:
    _NOP();             //程序一直死在这里
    break;
  case 10:
    _NOP();
    break;
  }
}

#pragma vector= TIMERA1_VECTOR
__interrupt void TIMERA1_IRQ()
{
  Time_Deal();
}

程序（2）

#include <msp430x43x.h>

void main(void)
{
  WDTCTL = WDTPW + WDTHOLD;       // Stop watchdog timer to prevent time out reset
  _EINT();
  P2SEL |= BIT0;
  TACTL |= TASSEL_1 | TACLR | TAIE | TAIFG;
  TACCR1 = 0x7fff;
  TACCTL1 |= CCIE;
  TACCTL2 |= CCIS_0 | CCIE | CAP | CM_2;
  TACTL |= MC_2;
  while(1);
}

void Time_Deal(void)
{
  unsigned char flag;
  flag = TAIV;
  switch(flag)
  {
  case 2:
    _NOP();        
    break;
  case 4:
    _NOP();           
    break;
  case 10:
    _NOP();
    break;
  }
}

#pragma vector= TIMERA1_VECTOR
__interrupt void TIMERA1_IRQ()
{
  Time_Deal();
}

该程序运行起来没有任何问题