Maximum frequency count on 16F628/4MHz

[solara]

Whats the maximum physical frequency that can be counted on a 16F628 using a 16F628 (using 16 bit TIMER1 as a pulse counter)?

Is this limited by the minimum rise and fall times for the 16F628.
Anybody know what the practical/theoretical limit is?

[solara]

I should have mentioned this is an external asynchronous clock signal, which is being measured.

[Melanie]

Datasheet, Table 17-7, Parameters 45, 46 & 47. These values are independent of actual Processor Clock Speed.

[solara]

For an asynchronous external clock on a 16F628
45=30ns
46=30ns
47=60ns

This doesnt help me as there is no specified minimimum rise and fall times.
And from the figures above 45+46+rise+fall=47.

[solara]

Is this saying that the maximum external asynchronous clock frequency is 1/60ns =16 MHZ?
Sounds far too low.

[Melanie]

That's what it's telling you. If you don't believe it, take a signal generator and run a test. The PIC isn't exactly a speed demon.