[QUOTEIf you are trying to do what I asked in my first paragraph of this post, then the internal comparators will not work without additional "efforts" because the internal reference voltage for the comparator is based on the Vdd supplied to the PIC.

Hi, Paul

Just compare a 2.5v ref ( or a Zener !!! ) to Vdd ( through a res. divider ...) and comparators will work fine here !!!

That's also how you can detect voltages w/ Logic CMOS, connecting a Zener to an input. ( input "level" changes at VDD/2 ... )

More difficult ( just a little ) is to play with Pics TTL inputs trip point that is a function of VDD ...
Experience shows the trip point is precise enough.

Alain