想用TimerA测频。 可是，高度的时候发现，程序一直在对TAIV进行判断。 而且，进入TAIV的时候，TAR并没有到达溢出值呀。 非常困惑。求大神解答。     void main(void)
{
  WDTCTL = WDTPW + WDTHOLD;                 // Stop WDT
  BoardConfig(0x88);                        //打开数码管，关闭流水灯和电平转换
 
  BCSCTL1 &= ~XT2OFF; // XT2on 打开高频晶体振荡器
  do
  {
    IFG1 &= ~OFIFG;
    for(unsigned int i = 0xFF;i > 0;i--);
  }
  while((IFG1&OFIFG) != 0); // Change the system clock
 
  BCSCTL2 |= SELM_2 + DIVM_0 + SELS + DIVS_0; 
 
 
  CCTL1 |= CCIE + CAP + CM_1 + CCIS_1 + SCS;                // 上升沿捕获
  TACTL |= TASSEL_2 + TACLR  + TAIE;                  // SMCLK, contmode
  TACTL |= MC_2;
 
  P2SEL |= BIT2;
  //P1SEL |= BIT1;
 
  //P3DIR |= BIT4;                            // P3.4 output
  //P3OUT &= ~BIT4;              //P3.4输出1
 
  P4DIR = 0xff;                 //设置P4，P5的IO方向为输出
  P5DIR = 0xff;                 
  P4OUT = 0x00;                 //设置P4，P5的输出初值
  P5OUT = 0xff;   _EINT();                      //打开全局中断
 
  while(1)
  {
    t = 0;
    if(t == 6)
    {
      t = 0;
    }
    //for display
    for(;pos <6;)
    {
     
      display[pos++] = output % 10;
      output /= 10;
    }
     
    P4OUT = scandata[display[t++]];             
    P5OUT = ( 0xff ^ ( BIT5 >>t ) );
   
  }
} // Timer A interrupt service routine
#pragma vector=TIMERA0_VECTOR
__interrupt void Timer_A0 (void)
{
  //P3OUT ^= BIT4;                            // Toggle P3.4
  if (flag == 0)
  {
    flag = 1;
    start = CCR0;
  }
  if (flag == 1)
  {
    flag = 0;
    end = CCR0;
    temp = end - start + 65535 * oft;
    result += temp;
    cnt++;
    oft = 0;;
    if ( cnt == 8 )
    {
      output = result <<3;
      cnt = 0;
      pos = 0;
    }
  }
}
// Timer_A Interrupt Vector (TAIV) handler
#pragma vector=TIMERA1_VECTOR
__interrupt void Timer_A1 (void)
{
 switch( TAIV )
 {
   case  2:
      if (flag == 0)
  {
    flag = 1;
    start = CCR1;
  }
  if (flag == 1)
  {
    flag = 0;
    end = CCR1;
    temp = end - start + 65535 * oft;
    result += temp;
    cnt++;
    oft = 0;;
    if ( cnt == 8 )
    {
      output = result <<3;
      cnt = 0;
      pos = 0;
    }
  }
  break;                          // CCR1 not used
   case  4: break;                          // CCR2 not used
   case 10: oft++;                  // overflow
            break;
 }
}
//
void delay(void)
{
    uint tmp;
   
    for(tmp = 120;tmp > 0;tmp--);
} 此帖出自小平头技术问答