keil code

#include <REGX51.H>
 unsigned long ref_speed,read_counter, error, kp, t,dc,Ton;
 sbit outbit=P1^0;
 sbit inbit=P3^4;
 char i;
  main()
 {
  TMOD=0x15;
  IE=0x88;   //Enable timer 1 interrupt
  kp=1;
  t=100;
  ref_speed=800;
  TH1=255;
 TL1=240;
 TR1=1;
 inbit=0; 
while (1)
{
error=0;
TH0=0;
TL0=0;
TR0=1;
for ( i=0;i<10;i++);
TR0=0;
read_counter=TL0;
TR0=1;
error=ref_speed -( read_counter );
read_counter=read_counter*1000/15;
error=kp*error;
dc=50+error;
if (dc>=90)
dc=90;
else if(dc<=10)
dc=10;
else
;
Ton=(dc*100);

}
}

 void t1isr(void) interrupt 3
 {
 TR1=0;
 if (outbit==0)
 {outbit=!outbit;
 TH1=255;
 TL1=255-Ton;
 TR1=1;
 }
 else 
 {outbit=!outbit;
 TH1=255;
 TL1=255-(100-Ton);
 TR1=1;
 }
 }