> The 16F628 can do it too - if it's run off the internal RC oscilator.
> Now, what I need is a way to keep the RTC running while the chip is
> running at 32kHz, then the PIC speeds up (on the fly BTW), calculates
> the hash code, displays it, then drops back down to 32kHz. What I don't
> want this thing to do is lose any RTC accuracy. The RTC needs to be
> accurate to within a few seconds per year if possible.

Use a 32KHz watch crystal to run the timer 1 oscillator all the time.
This will be the accurate time base.  Then you can use one of the newer
PICs with on the fly oscillator switching to switch into high gear only
when computation is required.  The exact instruction frequency won't
matter since it won't be used to measure time.


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