#define ServoPin PORTBbits.RB4
#define ServoTris TRISBbits.TRISB4
#define ServoBit 4

int ServoPos;

void low_isr();                    

#pragma code low_vector=0x18    //setup the ISR vector
void low_interrupt (){
  _asm GOTO low_isr _endasm    //jump to interrupt handler
}
#pragma code

#pragma interruptlow low_isr   //the ISR
void low_isr(){
static unsigned char PortState;
    if((PortState^PORTB)&(1<<ServoBit)){
        if(PORTB&(1<<ServoBit)){
            TMR1L=0;
            TMR1H=0;
            T1CONbits.TMR1ON=1;
        }else{
            T1CONbits.TMR1ON=0;         //stop timer 1
            ServoPos=TMR1H*256+TMR1L;   //16 bit timer value       
        }
    }
    PortState=PORTB;
    INTCONbits.RBIF=0;
}
#pragma code

//and in main I did,

    T1CON=0;
    ServoTris=1;
    INTCONbits.RBIE=1;
    INTCONbits.GIE=1;

#include <p18f1320.h> 

#pragma config WDT = OFF, LVP = OFF, OSC = INTIO2

#define ServoPin PORTBbits.RB4
#define ServoTris TRISBbits.TRISB4
#define ServoBit 4

void low_isr();                    

int isrServoPos;

#pragma code low_vector=0x18                //setup the ISR vector
void low_interrupt (){
  _asm GOTO low_isr _endasm                 //jump to interrupt handler
}
#pragma code

#pragma interruptlow low_isr                //the actual ISR
void low_isr(){
static unsigned char PortState;             //to remember previous state
    if((PortState^PORTB)&(1<<ServoBit)){    //has the servo pin changed?
        if(PORTB&(1<<ServoBit)){            //is it the start of a pulse
            TMR1L=0;
            TMR1H=0;                        //yes, so start timer
            T1CONbits.TMR1ON=1;
        }else{                              //must be end of pulse
            T1CONbits.TMR1ON=0;             //so, stop timer 1
            isrServoPos=TMR1H*256+TMR1L;    //Store 16 bit timer value
        }
    }
    PortState=PORTB;                        //keep copy of previous state
    INTCONbits.RBIF=0;                      //clear interrupt flag
}
#pragma code

void main(void){
int ServoPos;
    OSCCON=0x70;                            //8MHz please
    ADCON1=0x7f;                            //no ADC
    INTCON2bits.NOT_RBPU=0;                 //WPU on
    T1CON=0;                                //init timer 1
    ServoTris=1;                            //servo pin set to input
    INTCONbits.RBIE=1;                      //port B change interrupt enabled
    INTCONbits.GIE=1;                       //Global interrupts enabled

    while(1){
        if(isrServoPos!=ServoPos)
            ServoPos=isrServoPos;

    }
}