John Albers <PICLIST@MITVMA.MIT.EDU> wrote:

> I was wondering what the best way was to compare a file register to
> a number and to compare a file register to another file register.
> This is what I have come up with. Could someone please check the
> validity of the following statements?

    Just an aside, John:  You can check stuff like this YOURSELF by
    simply running the code through the MPLAB simulator and watching
    the C and Z flags.

> Compare a file register to a number.  For example to compare COUNT to
> the number 12.
>
> movf     COUNT,w
> sublw   d'12'
>
> COUNT < 12    , if   C flag <> Z flag
> COUNT = 12    , if   Z flag = 1
> COUNT <= 12  , if   C flag = 1
> COUNT > 12    , if   C flag = 0
> COUNT >= 12  , if   C flag = Z flag

    COUNT <  12:  C=1 and Z=0
    COUNT =  12:  Z=1
    COUNT <= 12:  C=1
    COUNT >  12:  C=0
    COUNT >= 12:  C=0 or Z = 1

    Since it's easier to check just one flag than two, I'd do the
    "COUNT < 12" comparison by replacing it with "COUNT <= 11".

    Similarly, I'd replace the "COUNT >= 12" with "COUNT > 11".

> What is the best way to check [C flag <> Z Flag] and [C flag =  Z
> Flag]

    Fortunately, you don't have to, since those states don't mean
    anything.

    -Andy


=== Andrew Warren - fastfwd@ix.netcom.com
=== Fast Forward Engineering - San Diego, California
=== http://www.geocities.com/SiliconValley/2499