At 03:14 AM 9/27/97 GMT+0200, you wrote:
>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
>
>

to complement any bit you can do the following. note: the carry bit (bit 0)
is in the status register (ram location 3).

        btfsc   3,0     ; status,c
        bcf     3,0
        btfss   3,0
        bsf     3,0

what instruction was used to place the data into 'w'. if it didn't set
the zero flag you could use this

        iorlw   0       ; sets the zero flag if 'w' is zero

michael