> If you can spare a RAM location then try:
>
> (assume SWITCH has been equated to a spare ram address)
>
>       movf    GPIO,w          ; get switch values
>       movwf   SWITCH  ; store in ram location
>       rlf     SWITCH,f        ; rotate left to put in bits 0 - 3
        movlw   0xf0            ; clear top nibble (may not need this)
        andwf   SWITCH,f        ;
>       swapf   SWITCH,w        ; swap upper and lower nibbles and put back
> in w
>
>
>
Doubtless the asm gurus will scorn this and show an obvious way that dosen't
use w :o)


> I am using a 12C509 to read four switches.  I have /MCLR enabled so that
> GP3 is not
> an input.  I also have GP0 as an output and I am running off of the
> internal R/C
> oscillator (freeing up GP4,5).
>
> Thus I have GP1,2,4,5 as inputs reading the switches.  I want to take the
> four
> inputs and place them in the high nybble of W so that:
>         GP1 = Bit4 = Switch A
>         GP2 = Bit5 = Switch B
>         GP4 = Bit6 = Switch C
>         GP5 = Bit7 = Switch D
>
> Here's what I wrote:
>
>         ; READ THE SWITCHES
>         MOVF    GPIO,W  ; W = 00DC0BA0
> ;
>         ; SHIFT BITS TO ALIGN WITH THE HIGH NYBBLE
>         BTFSC   W,5     ; is GP5 (pin 2) HI?
>         BSF     W,7     ; if it is, then Bit7=HI
>         BTFSC   W,4     ; is GP4 (pin 3) HI?
>         BSF     W,6     ; if it is, then Bit6=HI
>         ANDLW   0x0C6   ; W = DC000BA0
>         BTFSC   W,2     ; is GP2 (pin 5) HI?
>         BSF     W,5     ; if it is, then Bit5=HI
>         BTFSC   W,1     ; is GP1 (pin 6) HI?
>         BSF     W,4     ; if it is, then Bit4=HI
>                         ; W = DCBA0BA0
> ;
>         ; MASK OFF LOW NYBBLE
>         ANDLW   0x0F0   ; W = DCBA0000
>
> It looks right to me but I am getting flakey results and I am suspicious
> of the bit
> manipulation.  It is late Sunday night in California and of course I have
> a demo in
> twelve hours...
>
> Can anyone see a flaw here?  Is there a better way of shifting the bits?
>
> My read of the datasheet says that bits 0,3,6,7 of GPIO (all non-inputs)
> should
> read as 0's right?  I mean I don't need an ANDLW 0x036 after the read of
> GPIO or
> something?
>
> Any help appreciated,
>
> Michael
>
> * TAKE THE '.NOSPAM' OUT OF MY ADDRESS TO REPLY
> **********************************************
> Outside of a dog, a book is man's best friend.
> Inside of a dog, it's too hard to read anyway!
>                                   Groucho Marx
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>