In message  <199702040222.UAA14939@Jupiter.Mcs.Net> PICLIST@MITVMA.MIT.EDU
 writes:
> > This points to a powerup problem, at least in my mind.  Also, notice that to
> > make this woek, you need to KNOW the calibration constant, so it won't work
> > well for mass-programming OTP's.  Why would the value stay in OSCCAL when
> > written with instructions several cycles after powerup, but not when written
> > on the first two instructions?
>
> Hmm... others have suggested a problem with old initialization code intended
> for other parts which may clear the calibration register incorrectly; it may
> also be a power-up problem as you suggest.  For fun, however, what if you try
> something like this:
>
> 0FFF:   movlw   $C0     ; Or whatever constant
> 0000:   movwf   $1F     ; Not the calibration port!
> ...
> 00xx:   movf    $1F,w   ; Read back the value above
> 00xx:   movwf   $05     ; ...and store it to the speed register
>
> Does something like that work any better?
>

Did anyone try this?  I'm interested to know if this is a
good work around.

(I'd try it myself, but my PC has been taken away for repair.)


Regards,



Mike Watson
--
Mayes uk