At 19:07 02/27/99 -0500, Wagner Lipnharski wrote:
>So, or I understood it wrong, or some previous post is not correct,
>when somebody said the PIC could read external frequencies 8 times
>its own clock.
>
>Now, using prescaler, the min time for a complete external cycle
>at that pin is 60ns (for VDD between 3 and 6 Volts), it also means
>a maximum external frequency of 16MHz.
>
>Again, somebody also said about 50MHz to be easy to read.

timer0 with prescaler has a min period of "the greater of 20ns or
((Tcy+40ns)/N)" with Tcy the instruction cycle and N the prescale value
(param. no. 42). selecting a prescale value of 256 gives the 50MHz
previously mentioned, since the second term is then much smaller than 20ns
with any reasonable clock frequency. (assuming approx. 50% duty cycle in
the signal to satisfy param. 40 and 41.) these timer0 specs seem to be
valid for most models.

ge