Not to disbelieve you Bob but just did a test with the help of my Mathias,
typed in the following:

 bsf           STATUS,Z                   ;Set zero bit
 movf        STATUS,W                 ;Move STATUS into W register
 movwf     STATUS                      ;Move W back into STATUS register
 bcf           STATUS,Z                  ;Clear zero bit
 movf        STATUS,W                 ;Move STATUS into W register
 movwf      STATUS                     ;Move W back into STATUS register

What I saw was the following:

          STATUS = 1A,   W = xx
 bsf           STATUS,Z                   ;Set zero bit
          STATUS = 1E,    W = xx
 movf        STATUS,W                 ;Move STATUS into W register
          STATUS = 1A,   W = 1E
 movwf     STATUS                      ;Move W back into STATUS register
          STATUS = 1E,    W = 1E
 bcf          STATUS,Z                   ;Clear zero bit
          STATUS = 1A,   W = 1E
 movf        STATUS,W                 ;Move STATUS into W register
          STATUS = 1A,    W = 1A
 movwf      STATUS                     ;Move W back into STATUS register
          STATUS = 1A,    W = 1A

Back to the drawing board.

Bob Ammerman wrote:

> > >  org     4
> > >int
> > >   movwf  W_TEMP              ;  "W_TEMP" in Banks 0 and 1
> > >   movf   STATUS, w
> > >   bcf    STATUS, RP0         ;  Set to Bank 0
> > >   movwf  STATUS_TEMP         ;  "STATUS_TEMP" in Bank 0
> > >
> > >    :
> > >
> > >   movf   STATUS_TEMP, w      ;  Restore "STATUS"
> > >   movwf  STATUS
> > >   swapf  W_TEMP, f           ;  Restore "w" without
> > >   swapf  W_TEMP, w           ;   affecting STATUS
> > >   retfie
> >
> > Ouch, Myke.  I just realized that this is wrong.
> >
> > You can't use "movf STATUS, W" because it can (and will) change the Zero
> bit
> > and affect the initial STATUS value.  To move it into a temp location
> > without affecting the original STATUS register, you have to use "swapf
> > STATUS, W" and "movwf status_temp".  Then to restore it, you just "swapf
> > status_temp, W" and then use "movwf STATUS".
>
> Yeah, I think you _can_ use movf STATUS,W because the value it moves to W is
> the value BEFORE the Z bit gets tweaked.
>
> Bob Ammerman
> RAm Systems
> (contract development of high performance, high function, low-level
> software)
>
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