Motor using Encoder as Limit Switch?

[Mark McLeod]

I probably wouldn't do that if it's a critical mechanical stop involving multiple revolutions.

An incremental encoder will tell you how far you've moved, but it won't know where the device was when it started.
An absolute encoder will tell you where in a single rotation you are, but for multiple rotation devices it also won't know where it started.

Both of them forget where they are when the robot is turned off.

A true limit switch is really absolute. It knows exactly where the mechanical thingy is when a mechanical limit switch is engaged.