----- Original Message -----
From: William Chops Westfield <billw@CISCO.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Tuesday, November 12, 2002 11:22 PM
Subject: Re: [PIC]: simple 16F877 long call strategy needed


>         Unfortunately, MPASM can't deal with macros that aren't
>         fixed-length.
>
> I still don't get it?  Most macro assemblers have problems with macros
that
> evaluate to different lengths during different assembler passes due to
> unresolved forward references (or values that change) during the first
pass
> (and most assemblers have two passes), but that's a pretty small subset of
> "macros that aren't fixed length"...
>
> I CAN do something like this, right:
>
> mystring macro text
>         dt text
> endm
>
> Isn't that a non-fixed-length macro?
>
> BillW

A variable length macro would by something like

st16    .macro    dst, arg

        .if    (arg & $ff) == 0
        clrf    dst+0
        .else
        movlw    arg & $ff
        movwf    dst+0
        .endif

        .if    (arg & $ff00) == 0
        clrf    dst+1
        .else
        movlw    (arg >> 8) & $ff
        movwf    dst+1
        .endif

        .endm

calling st16 with an undefined label (a forward reference) would result in
zero the first time round (generating two instructions the first time) and
then a non zero the second time round (generating three or four instructions
the second time)

Regards
Sergio Masci
http://www.xcprod.com

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