Hi Henrik & Alain;

I'm amazed with both excelent solutions you gave me . I'll use them in other projects I have in mind.
Nevertheless, Alain's solution can't fit in this particular project, because it is a motor controller. (sorry, but I didn't tell it before to focus the thread on the specific part of the problem)

Why can't fit in my project?

Alain's CCP1 solution can't be possible, because as motor controller, I use the unique CCP module in PWM mode to drive motor's H-bridge. (remember it's a PIC16F68A)
Well, of course Alain (Acetronics) couldn't guess that CCP was unavailable: I had not told it.

To Henrik's solution, I'll add TMR0 in timer mode, as time reference, for speed calculation. A little bit uncomfortable (8-bit variable), but factible (I hope).

Thank you Alain and Henrick.

PD: I would be still more gratefull if any of you give me an opinion on my Post#3.

Regards!
Rodrigo