#include <reg51.h>
#define  uint unsigned  int
sbit P1_0=P1^0;
uint count,period;
bit  rflag=0;

void control(void)
{
   TMOD=0x09;
   EX0=1;IT0=1;
   TH0=0;TL0=0;
   P1_0=0;P1_0=1;
   TR0=1;ET0=1;EA=1;
}

void int_0(void) interrupt 0 using 1
{
  EA=0;TR0=0;
  count=TL0+TH0*256;
  rflag=1;
  EA=1;
}

void main(void)
{
  control();
  while(rflag==0);
  period=count*2; /* fosc=6M, unit us */
}