Servo controlling program

I've written this program for AT89S52 to control a servo.The signal pin of the servo is connected to the P1_0 of the chips and a LED is connected to the P2_7 of the chip.When I turned the circuit on the servo had no response and only the LED have lit up.Please help me to check if there is any mistake in my program.

#include<AT89X52.h>
unsigned int PWMHIGH;
sbit PWM=P1^0;
void timer0 () interrupt 1
{
   TL0 = (65536- 20000) & 0xFF;                                       //20ms
   TH0 = ((65536-20000) & 0xFF00) >> 8;
   TL1 = (65536-PWMHIGH) & 0xFF;                              //1.5ms
   TH1 = ((65536-PWMHIGH) & 0xFF00)>>8;
   PWM = 1;
   TR1 = 1;
}
void timer1 () interrupt 3
{
   PWM = 0;  TR1 = 0;
}

void main()
{
P2_7=0;
   IE = 0x8A; // EA, Timer0, Timer 1
   // Timer0 , Timer1 Mode1
   TMOD= 0x11;
   PWMHIGH = 1000; // on time
   //timer turn on
   TR0 = 1;
   TF0 = 1;
   while(1);
}