How about:

        btfss My_Flags, Complement_Carry
        goto done
        btfsc STATUS, CARRY
        goto clear_carry
        bsf STATUS, CARRY
        goto done
clear_carry:
        bcf STATUS, CARRY
done:

It takes a few more locations and cycles, but it doesn't require a register.


HTH - Martin R. Green
elimar@bigfoot.com

----------
From:   N STEENKAMP [M.ING E&E][SMTP:STEENKMP@FIRGA.SUN.AC.ZA]
Sent:   Friday, September 26, 1997 11:14 PM
To:     PICLIST@mitvma.mit.edu
Subject:        Complementing Carry

Hi all,

I have been stuck now for at least 1/2 hour trying to figure out a way to
conditionally complement the carry flag on an '84.  The best I could come
up with was:

   comf  STATUS, W
   movwf Temp
   btfsc My_Flags, Complement_Carry
    rrf  Temp, W

This just doesn't feel like the right way!

I also tried:
   movlw 01h
   btfsc MyFlags, Complement_Carry
    xorwf STATUS, F

but it didn't work.  I was hoping that the xorwf instruction would
operate as normal and change the carry flag and afterwards set the Z flag
if the result was 0, but C is totally protected from being modified.

Has anyone got a better approach (preferably one that does not need a
file register)?  Maybe its staring me in the face, but right now I'm
staring at the insides of my eyelids :-O

G'night (to all on this side of the globe)
Niki