@shaneh, you are right about M92 and M350. However, M18 and M84 can still be used to turn off current to external drivers, if you have connected the Enable signals to them.
Hnnn H1 = forbid movement of axes that have not been homed, H0 = allow movement of axes that have not been homed (firmware 1.21 and later)
Snnn S1 = limit movement within axis boundaries, S0 = allow movement outside boundaries
