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我的程序，只有在片上内部，用接地和接电源来产生捕捉信号，才能成功。引脚外面的信号却捕捉不到

1. //***********************************************************************
   // MSP-FET430P140 Demo - Timer_A0, Capture of ACLK/8 using SMCLK
   //
   // Description: Input capture of ACLK/8 on P1.1(TA0)
   // Run to breakpoint at the _NOP() instruction to see 16 capture
   // values and the differences.
   // ACLK = 32768Hz, MCLK = SMCLK = default ~800kHz
   // //* An external watch crystal on XIN XOUT is required for ACLK *//
   //
   // MSP430F149
   // -----------------
   // /|| XIN|-
   // | | | 32kHz
   // --|RST XOUT|-
   // | |
   // | P2.0/ACLK|---+
   // | | |
   // | P1.1/TA0|<--+
   // | |
   // | P1.0|--->LED
   
   //
   // H. Grewal
   // Texas Instruments Inc.
   // Feb 2005
   // Built with CCE Version: 3.2.0 and IAR Embedded Workbench Version: 3.21A
   //******************************************************************************
   
   #include <msp430x14x.h>
   
   unsigned int new_cap=0;
   unsigned int old_cap=0;
   unsigned int cap_diff=0;
   
   unsigned int diff_array[16]; // RAM array for differences
   unsigned int capture_array[16]; // RAM array for captures
   unsigned char index=0;
   unsigned char count = 0;
   
   void main(void)
   {
   volatile unsigned int i;
   WDTCTL = WDTPW + WDTHOLD; // Stop watchdog timer
   for (i=0; i<20000; i++) // Delay for crystal stabilization
   {
   }
   P1DIR = 0x01; // Set P1.0 out,1.1 input dir
   P1OUT &= ~0x01; // LED off
   P1SEL = 0x02; // Set P1.1 to TA0
   P2DIR = 0x01; // P2.0-ACLK
   P2SEL |= 0x01;
   BCSCTL1 |= DIVA_3; // ACLK/8
   
   CCTL0 = CM_1 + SCS + CCIS_0 + CAP + CCIE; // Rising edge + CCI0A (P1.1)
   // + Capture Mode + Interrupt
   
   TACTL = TASSEL_2 + MC_2; // SMCLK + Continuous Mode
   
   _BIS_SR(LPM0_bits + GIE); // LPM0 + Enable global ints
   }
   
   #pragma vector=TIMERA0_VECTOR
   __interrupt void TimerA0(void)
   {
   new_cap = TACCR0;
   cap_diff = new_cap - old_cap;
   
   diff_array[index] = cap_diff; // record difference to RAM array
   capture_array[index++] = new_cap;
   if (index == 16)
   {
   index = 0;
   P1OUT ^= 0x01; // Toggle P1.0 using exclusive-OR
   }
   old_cap = new_cap; // store this capture value
   count ++;
   if (count == 32)
   {
   count = 0;
   _NOP(); // SET BREAKPOINT HERE
   }
   
   }

复制代码

#include "MSp430G2553.h"unsigned int start,end;unsigned char overflow;
void main( void ){   WDTCTL = WDTPW + WDTHOLD;  P1DIR|=BIT0+BIT6;//P1.6LED，  P1SEL|=BIT0+BIT2;//P1.0->ACLK输出，P1.2->捕获输入  P1OUT&=~BIT6;//关闭LED  BCSCTL1 =DIVA_3;//ACLK8分频（vlo=12Khz）  CCTL1=CM_1+SCS+CCIS_0+CAP+CCIE;//上升沿+同步+CCI0A(p1.2)+捕获功能+捕获中断  TACTL=TASSEL_2+MC_2+ID_3+TAIE+TACLR;//SCLK（DCO=1.1Mhz）8分频，连续计数模式  _BIS_SR(LPM0_bits+GIE);}#pragma vector=TIMER0_A1_VECTOR__interrupt void Timer_A (void){  switch(TAIV)  {    case 2:      if(CCTL1&CM_1)      {        CCTL1=(CCTL1&(~CM_1))|CM_2;        start=TAR;        overflow=0;      }     if(CCTL1&CM_2)//else if与if区别要注意      {          CCTL1=(CCTL1&(~CM_2))|CM_1;          end=TAR;      }      P1OUT|=BIT6;      break;    case 10:      overflow++;      break;    default:      break;   }}