#include <reg51.h>
#define uchar unsigned char
uchar i,time;
uchar period=250;
uchar high=50;
timer0() interrupt 1 using 1 {
  TH0=(65536-8333)/256;
  TL0=(65536-8333)%256;
  if (++time==high) P1=0;
  else if(time==period) {
    time=0;
    P1=1;
  }
}
main () {
  TMOD=0x01;
  TH0=(65536-8333)/256;
  TL0=(65536-8333)%256;
  EA=1;
  ET0=1;
  TR0=1;
  do { } while (1);
}