#include "AT89C51SND1_REG.H"

#define LED	     P3_5

unsigned char Counter=0;


void Timer0_ISR() interrupt	1  //Vector addr 0x002b
{
 	TR0 = 0;   //停止T0
	TH0 = 0x5d;
    TL0 = 0x3d;
	Counter++;
	if(Counter==40)	  
		{
			Counter=0;
			LED=~LED;
		}
	TR0 = 1; //重啟T0
}

main()
{
	CKCON|= 0x02;
	TMOD &= 0xf0;
	TMOD |= 0x01; //設(shè)置T0為模式1定時(shí)器
	TH0 = 0x5d;
	TL0 = 0x3d;
	ET0 =1;//打開T0中斷
	EA = 1;//打開中斷
	TR0=1; //啟動(dòng)定時(shí)器T0
	while(1); 
}