This may have been touched on by the previous post... Although we say a '0' is 0V and we say the supply voltage is a '1', real circuits may have signals which do not go all the way down to zero, or all the way up to the supply level.Any other reason ???
True, ambiguity is less likely for logic '0' signals. Nevertheless real circuitry does not always perform to ideal specs. A signal conceivably might not go all the way down to 0 volts. It might happen due to noise on the line, mistakes in design, mistakes in component usage, fan-out to too great a load, etc.BradtheRad,
If you are worried about the 0v, level shifter would not solve the problem.