AVR-Chat

> The convention of using logic 0 for 0 volts and logic 1 for a high...

Actually, there are several nested conventions.  One is positive logic 
vs negative logic.  In the former, the most positive voltage is a 
logic 1 while in the latter the most negative voltage is a logic 1.

Once you adopt one of those major conventions you move on to 
establishing what voltage ranges will be recognized for each level as 
well as possibly an "indeterminate" region.

One logic family that used positive logic but negative voltages was 
ECL.  The thresholds were something like -0.9V for a logic 1 and -
2.75V for a logic 0.  I have a faint recollection of some Digital 
Equipment Corp. logic cards that were implemented using DTL or RTL 
technology  that were negative logic but I can't recall the details.

Don