What is 'negated signal' ?
There are no silly questions if you don't know something. A negated signal is always the opposite of the other one, meaning when signal A is HIGH, the negated signal is LOW and when signal A is LOW, the negated signal is HIGH.
From the schematic : Which one is negated by which one ?
Unfortunately this doesn't get clear from the article. I would just try and attach a scope to two pins. The scope output will show you quickly which are the right ones. Probably this changes from one drive manufacturer to the other, so you have to check anyway.