KEYPAD and Interrupt on Changing PORTB

[Mostafa]

hi

i want to implement a keypad using PicBasic PRO, and i want to use the interrupt on change of PORTB. i am using 16F877 and i can't use "polling routine" in this project with , also i can't use any Keypad IC (like 74C922).

i wrote a program and i attach its PROTEUS file its schematic.

'****************************************************************
'*  Name    : PORTB_CHANGE.BAS                                  *
'*  Author  : Mostafa Taghavi Kani                              *
'*  Notice  : Copyright (c) 2006 Embedded Technology            *
'*          : All Rights Reserved                               *
'*  Date    : 2006/12/14                                        *
'*  Version : 1.0                                               *
'*  Notes   :                                                   *
'****************************************************************

define  OSC 4
'PIC 16F877

DEFINE LCD_DREG PORTA
DEFINE LCD_DBIT 0
DEFINE LCD_RSREG PORTA
DEFINE LCD_RSBIT 4
DEFINE LCD_EREG PORTE
DEFINE LCD_EBIT 0
DEFINE LCD_BITS 4
DEFINE LCD_LINES 2

GIE     VAR  INTCON.7
PEIE    VAR  INTCON.6
T0IE    VAR  INTCON.5
INTE    VAR  INTCON.4
RBIE    VAR  INTCON.3
T0IF    VAR  INTCON.2
INTF    VAR  INTCON.1
RBIF    VAR  INTCON.0

RBPU    VAR  OPTION_REG.7
INTEDG  VAR  OPTION_REG.6
T0CS    VAR  OPTION_REG.5
T0SE    VAR  OPTION_REG.7
PSA     VAR  OPTION_REG.3
PS2     VAR  OPTION_REG.2
PS1     VAR  OPTION_REG.1
PS0     VAR  OPTION_REG.0

i       VAR  BYTE
x       VAR  BYTE
ROW     VAR  BYTE
COL     VAR  BYTE
J       VAR  BYTE
R       VAR  BIT
C       VAR  BIT

TRISB=%11110000 : 'PORTB=%11111111
TRISD=%00000000
i=0

INTCON = %10001000
RBPU=0

ON INTERRUPT GOTO TEST

MAIN:
    IF I==0 THEN
        LCDOUT $FE,1,"PRESS ANY KEY!"
    ELSE
        LCDOUT $FE,1,"(ROW,COLUMN)=","(",#R,",",#C,")"
    ENDIF

    PORTB=(PORTB & %11110010)
    PAUSE 20
    PORTB=(PORTB & %11110100)
    PAUSE 20
    PORTB=(PORTB & %11111000)
    PAUSE 20
    GOTO MAIN

DISABLE
TEST:
    @ MOVF PORTB,W  'IMPORTANT:reads PORTB and moves the value to W register!!! 
    ROW=(PORTB & %11110000)
    COL=(PORTB & %00001110)
    SELECT CASE ROW
           CASE %00010000
                R=1
           CASE %00100000
                R=2
           CASE %01000000
                R=3
           CASE %10000000                
                R=4
    END SELECT
    
    SELECT CASE COL
           CASE %00000010
                C=1
           CASE %00000100
                C=2
           CASE %00001000
                C=3
    END SELECT
    i=i+1
    RBIF=0
    RESUME
ENABLE
END

thanks in advance,
with best regards.