#include <io8535.h>
#include <intrinsics.h>

unsigned  int timecount=0;        //定義全局計(jì)時(shí)器

//計(jì)時(shí)器0溢出中斷服務(wù)程序
#pragma vector=0x12
__interrupt void timer0_ovf_isr(void)
{
  TCNT0=6;                         //重新加載500us的間隔
  if(++timecount==1000)
  {
    PORTA=PORTA^0x80;
    timecount=0;                  //清零，等待下一個(gè)500ms的到來
  }
}

void  main(void)
{
  DDRA=0x80;                      //設(shè)置 A 端口最低位為輸出
  TCCR0=0x02;                     //設(shè)置計(jì)數(shù)器的時(shí)鐘為clock/8
  TCNT0=0x00;                     //計(jì)時(shí)器啟動(dòng)時(shí)間為0時(shí)刻
  
  //計(jì)時(shí)器0中斷初始化
  TIMSK=0x01;                     //設(shè)置計(jì)時(shí)器0溢出中斷
  
  //全局中斷使能
  __enable_interrupt();
  while(1)
  ;
}