# Sinus Input

Discussion in 'Electronic Design' started by [email protected], Jun 3, 2007.

1. ### Guest

Hi everyone!

I would like to know what happens when the signal input in a PIC16F84
is a sinus wave. How does this micro see that input if there is not a
comparator? How is it modified then?

Thank you!

2. ### EeyoreGuest

What signal input ?

Graham

3. ### D from BCGuest

Sine wave...huhhh..

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

4. ### Guest

lol! Sorry!! Sine wave, that's it

Thank you a lot!!!

5. ### Guest

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,
0 offset)... The result is a 0V signal all the time?
Or due to the 0V in VSS the signal would be a squared wave with +5V
when sine>0 and 0V when sine<0?

Thank you a lot again!

6. ### BobGuest

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

7. ### feeboGuest

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?