Hi to All Pic Engineers.

I am using two 4 bit encoder connected to portb.
I am trying to add switch diagnostic mode just to make sure that
encoders are
working ok.
I am using table to subtract if resolute is 0 that is good much. if
resolute is
1 checking status,c bit then it is an error.
the problem is that when the switch is ok it works ok but when the
switch is bad
still indicates it is ok. I realized that I should not load portb in w
register.
my next problem is that how can i do this with higher neebles. what do
you think
about this method.


Andre Abelian                                   thank you for your help.


      LIST    P=16C62A
        #INCLUDE        C:\MPLAB\P16C62A.INC

;------------------------- EQUATIONS ----------------------

RB0             EQU     0
RB1             EQU     1
RB2             EQU     2
RB3             EQU     3
RB7             EQU     7
SWITCHES        EQU     0X10
COUNT1          EQU     0X01
COUNT2          EQU     0X11
SENDREG         EQU     0X0C
A9              EQU     0X0F
COUNT           EQU     0X0D
BIT_COUNT       EQU     0XEH

;------------------------------------------------------------
        ORG     0X000           ; ORIGIN
;------------------------------------------------------------

        CLRF    PORTA           ; CLEAR PORTA
        CLRF    PORTB           ; CLEAR PORTB
        CLRF    PORTC           ; CLEAR PORTC
        BSF     STATUS,RP0      ; SWITCH TO BANK 1
        MOVLW   B'00000100'     ; EXSEPT RA3 ALL OUTPUT
        MOVWF   PORTA           ; DO IT
        MOVLW   B'11111111'     ; INPUTS
        MOVWF   PORTB           ; MAKE PORTB INPUT FOR SWITCHES
        MOVLW   B'00000011'     ; EXSEPT RC0 AND RC1 ALL OUTPUT
        MOVWF   PORTC           ; DO IT
        BCF     STATUS,RP0      ; SWITCH BACK TO BANK 0
        CLRF    PORTA           ; CLEAR PORTA
        CLRF    PORTB           ; CLEAR PORTB
        CLRF    PORTC           ; CLEAR PORTC
;------------------------------------------------------------
        MOVLW   .10             ; LOAD DECIMAL 10 IN W
        MOVWF   BIT_COUNT       ; SAVE IT THERE

;------------------- DIAGNOSTIC MODE -----------------------

START
        CLRW                    ; CLEAR W REGITER
        MOVF    PORTB,W         ; LOAD PORTB
        MOVWF   SWITCHES        ; SAVE IT THERE
        CALL    SW1             ; CALL SWITCH TABLE
        SUBWF   SWITCHES,W      ; SUBTRACK TABLE FROM W
        BTFSS   STATUS,C        ; SKIP IF RESOLT IS 0
        GOTO    BAD             ; IF 1 THEN "ERROR" JUMP
        BCF     PORTA,0         ; MAKE RED LED LOW
        GOTO    START           ; JUMP TO START OVER

BAD     BCF     PORTA,1         ; TURN OFF GREEN LED
        BSF     PORTA,0         ; TURN ON RED ERROR LED
NOTYET  DECFSZ  BIT_COUNT,F     ; COUNT DOWN FOR 10
        GOTO    NOTYET          ; IF NOT
        BCF     PORTA,0         ; TURN OFF RED LED
        BSF     PORTA,1         ; TURN BACK GREEN LED
        GOTO    START           ; JUMP TO START

;--------------------- SWITCH1  TABLE ------------------------

SW1     ADDWF   PCL,F           ; ADD OFFSET TO PCLATH
        RETLW   B'00000000'     ; '0'
        RETLW   B'00000001'     ; '1'
        RETLW   B'00000010'     ; '2'
        RETLW   B'00000011'     ; '3'
        RETLW   B'00000100'     ; '4'
        RETLW   B'00000101'     ; '5'   SWITCH 1
        RETLW   B'00000110'     ; '6'
        RETLW   B'00000111'     ; '7'
        RETLW   B'00001000'     ; '8'
        RETLW   B'00001001'     ; '9'
        RETLW   B'00001010'     ; 'A'
        RETLW   B'00001011'     ; 'B'
        RETLW   B'00001100'     ; 'C'
        RETLW   B'00001101'     ; 'D'
        RETLW   B'00001110'     ; 'E'
        RETLW   B'00001111'     ; 'F'



;------------------- DELAY SUBROUTINE -----------------------

DELAY
        MOVLW   .200            ; LOAD DECIMAL 200 TO COUNT
        MOVWF   COUNT1          ; SAVE IT THERE
D1      MOVLW   .200            ; LOAD AN OTHER 200
        MOVWF   COUNT2          ; SAVE IT THERE
D2      DECFSZ  COUNT2,F        ; DECRIMENT COUNT2
        GOTO    D2              ; IF NOT JUMP
        DECFSZ  COUNT1,F        ; DECRIMENT COUNT1
        GOTO    D1              ; IF NOT JUMP
        RETURN

        END