/*****************************************************************
//功能：利用定时器A的捕捉能测量脉冲信号的脉宽
//
//
//                               MSP430F449
//                         -----------------
//                 /|\|                           XIN|-
//                   | |                                 | 32kHz
//                   --|RST                   XOUT|-
//                       |                                 |
//                       |               P1.5/ACLK|---+
//                       |                                 |     |
//                       |                 P2.0/TA2|<--+
//                       |                                 |
//                       |                                 |
//说明：ACLK要进行8分频(4K),并将其作为外部的要捕获的脉冲;
//MCLK=SMCLK=8M;
*****************************************************************/
#include   <msp430x44x.h>
int pwm_start,pwm_end,pwm_wide=0;

void main(void)
{
   WDTCTL = WDTPW + WDTHOLD;                                 // Stop WDT
   P1DIR = 0x20;                                     //   P1.5 输出
   P1SEL = 0x20;                           // P1.5输出ACLK
  
   P2SEL|=BIT0;                                                           //P2.0 CCI2A
  
   SCFI0 |= FN_4;
   SCFQCTL = 121;                                     // (121+1) ×32768 *2= 7.99Mhz
   FLL_CTL0=DCOPLUS+OSCCAP1;             //MCLK=SMCLK=8M
  
   FLL_CTL1 |= FLL_DIV_8;                                                 //ACLK要进行8分频,ACLK=4K
  
  
   TACCTL2 =CAP+CM_3+CCIS_0+SCS+CCIE;   //捕获模式，上升和下降都捕获，选择CCI2A，同步，捕获中断开                
                                                                           //Capture input select: 0 - CCI2A
   TACTL = TASSEL_2 + MC_2 ;       //SMCLK=8M,L连续计数模式
   _EINT();                                 //开总中断
   LPM0;
   _NOP();
   pwm_wide=pwm_end-pwm_start;

   while(1);
}

// Timer_A3 Interrupt Vector (TAIV) handler
#pragma vector=TIMERA1_VECTOR
__interrupt void Timer_A(void)
{
  
   switch(TAIV)
  {case 2:break;
   case 4:
         if(TACCTL2 & CCI)
               pwm_start=CCR2;    
         else
               pwm_end=CCR2;
         //pwm_wide=pwm_end-pwm_start;
         break;
   case 10:
         break;
   }
   LPM0_EXIT;
}