Sinus Input

Sine wave...huhhh.. :P

If you're putting a sine wave at a digital input (within the digital input range) then the PIC will see a digital high or low depending on the sine voltage level. See the pic datasheet for the logic voltage levels. D from BC

lol! Sorry!! Sine wave, that's it :-P

Thank you a lot!!!

Did I understand well?

We know that RA4 pin from PIC16F84 works (in input mode) as a Schmitt trigger (ST): if VDD=5V, VSS=0V and the input signal in RA4 is a sine wave (2V p-p,

The result of this will be a damaged PIC input pin. You should not pull the input pin below Vss. See section 9.0 of the data sheet, absoloute maximum rating for voltage on any pin with respect to VSS is -0.3V to Vdd+0.3V

Bob

yes and clamping with a silicon diode will still result in a broken PIc as (IMS) they don't like -.4v... so if you insist on doing it like this, clamp with a germanium diode (0.2V) which is starting to get expensive - pass the signal into the pic thru a silicon diode?