I have an old toolchanger that uses an array of relays as a logic board. The process of tool changing is done in stages and the following stage can only be achieved once a reset has been received by the controller to continue. The programming for this is done in M code and uses the redundant sets in the M-20 series. My question is: is it possible to programme this series of M commands (M20,  21, 22.... .... 28 etc.) to I/O's in Mach 3?

You could but it would be better to use macros of 101 and over. Under 100 is meant to be reserved for Machs internal use and even though you may not have conflicts at the moment you may in the future.
Hood

Thanks Hood. I'll do some research into Macros.

Normally you would do a toolchange from within the M6Start macro rather than having multiple macros.
Hood