运行程序后 new和old都有值可是相减后T值总是0为什么

1万 · 2018-6-13 20:41

#include "MSp430G2553.h"
#include"LCD.h"
unsigned int old=0,new=0,T,zhuangsu;
unsigned char overflow;

void main( void )
{

      WDTCTL = WDTPW + WDTHOLD;
      P1DIR|=BIT6;
      P1SEL|=BIT2;//P1.2->捕获输入
      P1OUT&=~BIT6;//关闭LED
      BCSCTL1 = CALBC1_1MHZ;
      DCOCTL  = CALBC1_1MHZ;
      Port_init();
                                    //delay_ms(100);
                                    LCD_init();
                                    LCD_clear();
      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+TAIE+TACLR;
      _EINT();
      while(1){_BIS_SR(GIE);
      xianshi();
      }
}
void xianshi(void)
{

         T=2*T/1000000;
         zhuangsu=60/T;
      LCD_write_str(0,0,"zhuangsu:");
                                                            LCD_write_char(0,1,num_char_table[zhuangsu/10000]);
                                                            LCD_write_char(1,1,num_char_table[zhuangsu%10000/1000]);
                                    //LCD_write_char(3,1,'.');
                                                            LCD_write_char(2,1,num_char_table[zhuangsu%1000/100]);
                                                      LCD_write_char(3,1,num_char_table[zhuangsu%100/10]);
                                             LCD_write_char(4,1,num_char_table[zhuangsu%10]);
                                                               //LCD_write_char(4,1,num_char_table[0]);
                                                               LCD_write_str(5,1,"zhuang/min");
}
#pragma vector=TIMER0_A1_VECTOR
__interrupt void Timer_A (void)
{
  switch(TAIV)
  {
case 2:
   if(CCTL1&CM_1)
   {

      new=TAR;
      T=new-old;
      overflow=0;
   }
   old=new;
   P1OUT^=BIT6;
   break;
case 10:
   overflow++;
   break;
default:
   break;
}
}