Chris McSweeny wrote :

> Thanks for clarifying that. So as I originally suggested, with a 12f683 I
> can rely on the port latches being initialised to low and simply set the
> TRIS as appropriate.

No no no, that's not *generaly* so. It depends on what you "do"
with the other pins on GPIO.

I thought my description of the case where RMW will bite you
was clear enough.

And there is *no* difference between 12F629/675/683 in this case
(besides of some default, but...)

Or *any* other PIC16 or PIC18 (as long as we are talking about
the PORTx registers).

> Jan - when I was suggesting doing a movlw, movwf TRIS, that was to switch
> one pin to low and another pin back to OC at the same time, though I could
> presumably just as well do bcf, bsf on the appropriate bits.

Depends on your timing requirements. I just thought you where changing
*one* bit in TRISIO, and thought there was no need to mess with W in that
case.

> I've not got a good idea what's going on the other end of the resistor - it
> is a current setting resistor in a boost constant current regulator. I guess
> thinking about it, it is more likely to be switched with a very low duty
> cycle when I'm measuring rather than a fixed low voltage - I shan't be
> relying on the value when it's switched anyway (though actually now slightly
> concerned it may go above VDD).

OK, I though it was a "normal" pullup...

Jan-Erik.

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