Wagner Lipnharski wrote:
>
> Hi, there is a friend that needs a special circuit to attach
> to a PIC, but I can't find a single chip solution for him.
>
> He needs a 2^8 bits counter, 8 stages, easy solution,
> but it needs to have a serial output, not parallel, so
> he could read the actual counter 8 bits using a 2 wire
> serial transfer.
>
> He can not use a microcontroller to count it because the
> signal high frequency involved, around 15MHz.

Using the internal prescaler, a PIC can count up to 50MHz.
The only drawback is that the prescaler can't be read directly.
It can be read indirectly with a trick, used by many PIC based
frequency meters (another PIC pin sends pulses to the counter
input until the prescaler overflows and TMR0 changes).

This implies that the PIC can't counts external pulses when
you are reading the prescaler. In case this is not a problem
for your friend, this solution requires no external chip!

Adriano