Hi all. I'm new to pics so please excuse this relatively basic question.

PIC:    16f648a with 20MHz xtal
Aim:    To measure the charge time of an RC pair using the
        comparator and timer1 modules.
Issue:  What is the relationship between ticks and uC frequency? Or
        more simply, how do I convert the tmr1 value to seconds?

These are my ponderings :)

Assuming no prescaling does one tick occur for every cycle?

        t(s) = 1 / xtal

Which with prescaling would lead to something like...

        t(s) = prescaler / xtal

So with prescaler 1:8...

        t(s) = ( 8 / 20 * 10^6 ) = 0.4us

Am I somewhere over the plate or stuck out in the carpark?

Rob

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