Mike Keitz wrote:

> > PICs make good frequency counters.  Without external components (other
> > than amplifying the signal up to TTL levels), any PIC can count a 50 MHz
> > signal to a single cycle.

and Peter Cousens <peter@cousens.her.forthnet.gr> replied:

> How ? a prescaler is out of the question if your counting "to a
> single cycle"
>
> You must mean 5MHz

    No, Peter, he meant 50 MHz.

    The trick is to wire an I/O pin to the TMR0 input, in parallel
    with the incoming signal... You make the I/O pin a hi-impedance
    input while TMR0 and its prescaler are counting incoming pulses,
    then you make it an output and use it to manually clock "extra"
    pulses into the TMR0 input until the TMR0 register increments.

    At that point, you subtract the number of extra pulses that you
    generated from 256 (or whatever divide-by ratio your prescaler
    is set to)... The result is the value of the prescaler when you
    stopped counting incoming pulses.

    -Andy

=== Andrew Warren - fastfwd@ix.netcom.com
=== Fast Forward Engineering - Vista, California
=== http://www.geocities.com/SiliconValley/2499