Bob Blick <PICLIST@MITVMA.MIT.EDU> wrote:

> So the idea would be:
>
> If the prescaler is used, never to do any writes to TMR0 if you wish
> to preserve the accuracy of continuous timing(I'm thinking propeller
> clock here, of course), just let the timer free run and keep track
> of your count elsewhere.

    Yes, unless you want to go to the trouble of synchronizing the
    prescaler using code like the example I posted.

> If you are not using the prescaler, use the add-to-TMR0
> method(which is when you'd most likely need it anyway, since you'd
> certainly miss some counts, and not a predictable number of them,
> since interrupt response time varies)?

    Yes, or just let it free-run anyway and handle it as above.

> Does that seem like a useful rule of thumb?

    Yes.

> Or is TMR0 possibly advanced while you are in the process of
> adding to it?

    TMR0 (and/or its prescaler) is DEFINITELY advanced while you're
    writing to it, so you need to make allowances for that.  The
    easiest way, in general, is to just make a rough guess as to the
    reload value, then fine-tune that value by observing the
    program's behavior on a scope.

    -Andy

=== Andrew Warren - fastfwd@ix.netcom.com
=== Fast Forward Engineering - Vista, California
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