PICdude wrote:
> What I'm not clear on, is that if I run the PIC from an external =20
> oscillator (say 12Mhz, 20ppm crystal) instead, can I use that =20
> instruction clock to wake the PIC periodically?
You can but you will have to use "idle" mode rather than "sleep" mode.
Sleep mode disables the main clock while idle mode doesn't. I dunno
if the power consumption in idle mode will be acceptable to you.

> Or is there some simpler method to do this?
>  =20
Have you considered simply using a seperate RTC chip to track the time?
--=20
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.