I think you need to reread the explanation of subwf.
You are subtracting W from a file register (or is it the other way
around? i forget. doesn't matter here anyway).
        movf rcreg,W
        subwf 'X',w
Uses file register #(ASCII code for 'X') and W and does absolutely
nothing with rcreg.
Try
        movlw 'X'
        subwf rcreg,W
Then test Z.

Olden A (SApS) wrote:
>
> Hello Everybody,
> <snip>
> I thought that if I took the letter that received (the hex equilanant off
> anyway) and then checking the set/clear status of the Z bit, then I could
> find out which letter was received, ie. H'42' - H'42' would equal Z bit set.
> But that doesn't seem to be happening, can anybody suggest a problem with
> that, either logically (ie I'm being stupid) or from the code below.
>
> Please Help.
> Andrew.
> <snip>
> doconverstion
>
>         bcf     pir1,rcif               ; Here We Clear The Received
> Characters Flag,
>                                         ; Only because we have to do it
> sometime, and
>                                         ; to get this far we have to have
> received a char.
>
>         movf    rcreg,w                 ; move the received char into the w
> register
>
>         subwf   'A',w                   ; subtract the char received from
> the contents
>                                         ; if we received a 'A' zero flag of
> the status
>                                         ; register. If we didn;t then it
> should have skipped
>
>         btfsc   status,Z
>         call    do_A_Converstion

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