assembly - PIC16F84_A Interrupt not working -

just started learning pic microcontrollers. reason, portb remains 0x00 , interrupt never occurs.

;*** counter interrupt *** ;***** pic16fa4_a *************  org     0h  status  equ 03h porta   equ 05h portb   equ 06h trisa   equ 85h trisb   equ 86h intcon  equ 0bh count   equ 0ch count1  equ 08h count2  equ 09h  goto main  ;** interrup routine **  org     04h incf    count,1 clrf    portb ; clear rbo movlw   0ah subwf   count btfss   status,0 ;test carry flag goto    go_on goto    clear  go_on    bcf     intcon,1 retfie  clear    clrf    count bcf     intcon,1 retfie ;** end of inerrupt routine **  main  bsf     intcon,7; global interrupt enable bsf     intcon,4; rb0 interrupt enable bcf     intcon,1; clear interrupt flag in case on  bsf     status,5 movlw   00h     ;all ra pins output pins movwf   trisa movlw   01h     ;rb0 pin input pin movwf   trisb  bcf     status,5  loop movfw   count movwf   porta   ;put count in porta call    delay   ;delay movlw   01h      movwf   portb   ;set rb0 ;expect program control go 04h (org) doesn't ;also, using watch option in debugger, portb stays 0h ;can help?  goto    loop  delay loop1    decfsz  count1,1 goto    loop1  loop2 decfsz  count2 goto    loop2 return        end 

circuit:

it seems want programatically trigger external interrupt on pin rb0/int. this, need set rb0 pin output.

if @ figure 4-4 in page 17 of pic16f84a datasheet, can see block diagram pins rb3:rb0. rb0/int signal connected directly hardware pin via schmitt trigger buffer. means whatever signal present on pin going drive interrupt.

when set trisb0 bit 1, 3-state buffer output in high impedance, meaning thing can drive rb0/int signal external electrical signal connected pin.

if set trisb0 bit 0, logic level write rb0 should able trigger interrupt.