I am doing some similar conversions for a C Compiler I am converting that
used to produce a source file for an 8051 style assembler for PIC's.  The
bad news is that there are no direct conversions for the conditional jump
instructions you are looking at.  The good news is all can be simulated on
a PIC, but will require at least two, and sometimes quite a few PIC
instructions.  This isn't as bad as it seems since the 8051 is not a RISC
device, so the number of clock cycles used for a jump is comparable to the
8051 equivalent, it is just a lot cleaner to look at the 8051 versions than
the PIC versions.  If you want to keep the clean look in you ASM files, I
suggest you write macros that convert the old compare instructions into a
sequence of PIC ones that do the same thing.

Oh, one other caveat, many of the PIC equivalents will mess up one or other
of the arguments (W or a register file).

The csxx instruction are basically "compare and skip if true" instructions.
 They can be simulated simply for stuff like "csnz file":

    movf file,1
    btfsc STATUS, ZERO
    skipee  ; this is the instruction that will be skipped.

Of course STATUS and ZERO are defines for your target device.

A cjxx instruction like "cjz file, target" can be written as:

    movf file,1
    btfsc STATUS, ZERO
    goto target   ; this instruction will be skipped if file is NOT zero.

These were simple, but it gets messier when you need to use the carry flag
and the zero flag for comparisons like greater than or below.  In these
cases your code will have a few btfsx instructions and maybe a few local
labels (or relative goto's) too.

This is not intended to explain the whole process (I don't have time for
that), but hopefully it will put you on the right path.


HTH - Martin R. Green
elimar@bigfoot.com

BTW - another gotcha is that other uC's allow direct file to file
comparisons, while with PIC's you must move one register file into W and
perform the comparison from there.  It makes thing messier but it can be
done.

----------
From:   David Bramham[SMTP:d.bramham@QUT.EDU.AU]
Sent:   Wednesday, August 13, 1997 6:33 PM
To:     PICLIST@mitvma.mit.edu
Subject:        Parallax to MPlab

Hi all,
        I have a copy of RCV2LCD.SRC for Parallax PIC Application.I would
like to
convert it to an MPlab ASM file .However,I have problems converting such
statements as 'csne'and 'cjb'. Does anybody have either a this program in
ASM file format or a list of conversions between the 2 codes.

Many thanks

David