On 17 Sep 97 at 17:32, Clyde Smith-Stubbs wrote:

> On Wed, Sep 17, 1997 at 04:19:31PM +0930, Mike Smith wrote:
> > On 16 Sep 97 at 21:56, Pioneer Microsystems wrote:
>
> > > into a windowed C554. All will fit properly, but I have a problem.
> > > This part has only one bank of user RAM.  Upon interrupting, I might
> > > be in the upper page, and then my W save action will go zinging off
> >
> > How about
> > save RP0 to RP1 (which is unused, but available)
>
> The problem with this solution is that RP1 is marked by Microchip as
> not to be used - they advise that it should be left at zero. While
> in the chip itself RP1 does work, and has no bad side effects, if
> you run the MPLAB simulator for certain chips (not sure if it
> affects the '554, but it does affect the '62x chips) then setting
> RP1 does Bad Things. Specifically, all registers become
> inaccessible, including the STATUS register, so the only way to
> recover is to reset the simulator.

Never used the simulator - use an ICE instead... & it works OK on
that.  - well, it does for the 16c7x series.  I wonder why Microchip
made their simulator different to the chip?  That is bad design (ok
using a non-documented feature is too<g>) - like if they suddenly
started producing an existing chip on which the TRIS *instruction*
(as opposed to registers) didn't work.

make a note of your version....
MikeS
<mikesmith_oz@nosp*m.relaymail.net>
(remove the you know what before replying)