Thhank you Melanie,

Iīt's working fine now.

As the manual says, I had to disable the interrupts to get it working fine.
With the interrupts enabled sometimes I just read 65535 as a result.

May I ask something else ?

I'm using Timer0 and Timer1 to count my pulses in this same project.
I would like to move to a 16F877 and get access to some analog ports.

My doubt is : Can I use ADCIN with interrupts or should I disable them to read the analog port ?
The PBP manual donīt say I need to disable interrupts on 16F87x series. Is it right ?

Thank you again .

Sérgio