> John Payson wrote:
>
> > > On Thu, Sep 18, 1997 at 07:50:09PM -0500, John Payson wrote:
> > > > It's true that not all PICs have a hardware known-zero.
> > Nonetheless, you
> > > > might want to consider having the compiler allocate one.  You
> > could use
>
> Would someone be so kind as to explain what exactly the significance of
> a known zero is?
> >From what I've seen, I can deduct that you use it as a fixed reference
> point to which you can compare all your arithmic and answers?

A known-zero location is useful for the following two instructions:

        rlf     KZ,w    ; W will be 0 if carry clear, 1 if carry set
        rrf     KZ,w    ; W will be 0 if carry clear, 128 if carry set

If you have a loop counter that's always left at zero when you're not
using it, you can replace:

        movlw   8
        movwf   counter

with

        bsf     counter,3

or likewise for counts of 1, 2, 4, etc. or 255 [use comf or decf]; in
addition, the normal "decfsnz loop" behavior is to loop precisely 256
times if the counter is zero at the start.