Alice,

I've really really done this.  But there are two seperate
oscillators.  One runs timer 1 (usually 32 kHz) and the other runs
the PIC core (regular OSC).  The Timer 1 osc when enabled is
approximately like the main osc when set to LP mode, so the same
crystal and cap selection and wiring apply.

BUT this only helps is you can run a while on main osc freq, then go
to sleep until woken by Timer 1.  I used it with T1 as a RTC tick,
and the PIC slept most of the time to save power.  I gather that's
the most common use for the T1 osc.  But it DOESN'T give you
selectable core osc frequency, which was the original question, but
it might work in the same application?

It occurs to me that you might be able to add some scary external
logic to drive the OSC1 from the T1OSO OR the main crystal under
program control, to give a "drowse mode" where the main clock was
slowed to save power.  I'd have to think about that more another
time...

Regards,

Barry.
------------
Barry King, KA1NLH
NRG Systems "Measuring the Wind's Energy"
http://www.nrgsystems.com
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