AVR-Chat

On Fri, 2005-10-21 at 17:58 +0100, David Collier wrote:
> > On Wed, 2005-10-05 at 17:43 +0100, David Collier wrote:
> > > If I run this chip off a 32KHz XTAL.. does it multiply up 
> internally, or does it actually RUN at 32KHz???
> >   AVR microprocessors do not contain PLLs in their clock circuitry.
> > They run at whatever frequency the clock is running at, unless you
> > choose to divide that frequency in those chips which support clock
> > division (which I believe includes the entire line of AVR chips).
> So running the CPU on a watch XTAL gives you a pretty slow computer -
> I assume you can run on the internal osc, and use the 32KHz as a
> timing reference to trim it then?

   If I understand what you are asking, I believe the answer is no.
Depending on WHICH AVR processor you are using, the internalk oscillator
is either fixed, or can be trimmed by writing to the OSCCAL register.
So far as I understand it, the 32 Khz oscillator is used strictly for
the watchdog timer, and to start up the processor from a deep sleep
state (someone who knows more correct me if I am wrong, please?).

Tom