#include<reg51.h>      
sbit P1_0=P1^0;
sbit S1=P3^0;      
bit flag;  

void  mDelay(unsigned int x)    
{
  unsigned int i,j;
  for (i=x;i>0;i--)
  for (j=0;j<114;j++);
}

void timer0() interrupt 1
{
  P1_0=!P1_0; 	
  TH0=(65536-461)/256; 	
  TL0=(65536-461)%256;
}


void main(void) 
{
  TMOD = 0x01;    
  P1_0=0;
  TH0=(65536-461)/256; 	
  TL0=(65536-461)%256;    
  EA=1; 
  ET0=1; 
  TR0=0;
  flag=0;             
  while(1)
 {
   if(S1==0)         
  {
    mDelay(10);   
    if(S1==0)      		 	
    {
      flag=~flag;
      while(S1==0);
      TR0=flag;
     }			
    }		 	
   }
 }