//Crystal 4MHz //speed of sound 340m/s //1 TMR0 cycle = (340/1000000)*256*0.5*100 = 4.352 in cm 
#define TRIG PORTA.F0 
#define ECHO PORTA.F1 
double distance; 
unsigned int cont=0; 
//Timer0 //Prescaler 1:1; TMR0 Preload = 197; Actual Interrupt Time : 58 us 
//Place/Copy this part in declaration section 
void InitTimer0()
{ OPTION_REG	 = 0x88; 
TMR0	 = 197; 
INTCON	 = 0xA0; 
} 

void Interrupt()
{ 
if (TMR0IF_bit)
             { TMR0IF_bit= 0; 
              TMR0 = 197; 
              //Enter your code here 
              cont++; 
              }
} 

void main() 
{ 
 CMCON = 0x07; 
 InitTimer0(); 
 TRISa.F0 = 0; 
 TRISa.F1 = 1; 
 TRISb=0x00; 
 while(1)
       { 
        TRIG= 0;
        delay_us(10); 
        TRIG = 1; 
        delay_us(10); 
        TRIG= 0; 
        while(ECHO==0); 
        TMR0=0; 
        cont=0; 
        while(ECHO==1); 
        distance = cont;
        if(distance <6) // less from 6cm
                      {
                      portb.f0=1 ;
                       delay_ms(1000);
                       portb=0;
                      }
       }

 }