Look at section 15.3 DC Characteristics.  It specifies Input Low Voltage,
Input High Voltage, and also Input Leakage Current.

The input changes state "somewhere" between these two voltages.  If it's not
a Schmitt trigger, then it's likely to flicker back and forth, oscillate, or
do other funny things (also it'll cause the chip to draw more current while
it's doing those things).  The point of the Schmitt trigger is to make the
transition be a clean one.  The spec sheet tells you a range where this will
happen, but the exact point will vary from chip to chip.  (The spec sheet
implies this by the very fact that it gives a range.)

> -----Original Message-----
> From: Jim Dolson [mailto:jdolson@ISERV.NET]
> Sent: Thursday, March 09, 2000 8:49 AM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: At What Voltage Does a Zero Transition to 1 ?
>
>
> I've checked the datasheet for the 16f8xx but can't find the
> answer to a
> question.
>
> Assume that we are running the PIC at 5V.
>
> If we put 0 V on a pin configured for input, it will read as 0.
> If we put 5 V on a pin configured for input, it will read as 1.
>
> (1) If you slowly increase the voltage on the pin, at what
> voltage will
> the pin read as a "1" ?
>
> (2) Does the answer change if it is one of the pins that has a Schmitt
> Trigger built in?
>
> Thanks,
>
> Jim
>