I am confuse with the following code, because it didn't work as expected.
Perhaps I am missing something. Can somebody on the list please correct my
mistake.

Thanks in advance.

WH Tan


PAGE0_START
        ORG     0x0000  ; RESET vector location
        GOTO    START

        ORG     0x0004
        MOVWF   W_TEMP
        SWAPF   STATUS, W
        MOVWF   STATUS_TEMP

        BCF     INTCON, GIE     ;Is this code is a must, or
                                ;PIC will do it for me?

        BTFSC   INTCON, RBIF    ; Check is RB change ISR?
        GOTO    ISR_RBIF                ; Yes
        GOTO    END_ISR         ; No

ISR_RBIF
        BTFSC PORTB, 7
        GOTO    BIT_7
        BTFSC PORTB, 6
        GOTO    BIT_6
        BTFSC PORTB, 5
        GOTO    BIT_5
        BTFSC PORTB, 4
        GOTO    BIT_4
        GOTO END_ISR

END_ISR
        SWAPF   STATUS_TEMP, W
        MOVWF   STATUS
        SWAPF   W_TEMP, F
        SWAPF   W_TEMP, W

        BCF     INTCON, RBIF
        BSF     INTCON, GIE             ; Again, is this code necessary?
        RETFIE

BIT_7
        ; Send send some character to LCD
        ; to indicate a change on RB7
        ....
        GOTO END_ISR

BIT_6 ~ BIT_4
        ; Do exactly same as BIT_7

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