Post by thread:] PIC]:during the ISR, what is TMR0 doing?

> So if my end goal was to have the main ISR execute every > second, then an additional counter loaded with 64 should > do the trick You won't be able to make the "main ISR" execute every second with that fast a clock using even the maximum prescaler. Did you mean "main do-something" routine ? The longest timer period is 256 count *256 prescale. A 262,144Hz crystal would give you 1 IRQ/sec ( 262144 / 4 / 256 /256 ) without using an IRQ counter. You can go slower than that, eg 100kHz and 32.768kHz crystals are available, if you use a lower prescaler or reloading for "decimal" crystals -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.