Programmed with the 8051 pins P1.0 and P1.1, respectively, and the output period of 1ms square wave 500us

#include<reg51.h>

unsigned char k;

Pl = 0 ^ Gate1 the sbit;
the sbit Gate2 Pl ^ = 1;
main ()
{
  n-= 0;
  TH1 = 0xFF;
  TL1 = 0x06; // 250us timer generates an interrupt
  TMOD = 0x10; // Timer 1 operating in Mode . 1
  TR1 =. 1; // enable the timer
  ET0 = 1; // open interrupt 
  EA = 1; // open global interrupt
  while (1) {;}

}

void Timer(void) interrupt 1
{  

  TH1=0xff; 

  TL1 = 0x05; // 250us timer interrupt is generated 

  ! Gate2 = Gate2; // 500us square wave generating  
  K ++;   
  IF (K == 2) 
  { 

         k=0; 

         ! Gate1 = Gate1; // square wave generated 1ms

  }
}