Quote Originally Posted by irving2008 View Post
Well if that was the case it would be pointless IMHO. I had a quick scan round and can't find the original design writeup for this circuit. I am wondering if the PIC modulates the VREF rather than just shutting it off...
It could do that - it would reduce the holding torque for the motors as a result. It would then provide the "full" VREF when it's being clocked. It might be a very short pulse...