I have an older M3 control, so it is a different beast, but a lot of the same concepts still apply. On my machine, it was possible to have PLC in EPROMs that are installed in a "personality cartridge" or, I believe, something that was dynamically loaded through the RS232 port. In the latter
pizza tower case, the personality cartridge would be filled with RAM. You likely have the same setup. If you have EPROMs, you'll need to get the appropriate software and then burn new EPROMs. Oh, and the personality cartridge on my machine doesn't have socketed EPROMs, so you'd have to do a lot of unsoldering too. If you have a RAM based solution, you'd still need the software, but then you'd just upload the new version.
It *MIGHT* be possible to make temporary changes to the PLC in RAM. I've theorized, but not confirmed, that the PC reads the EPROM and copies the data to RAM. That would make sense to me. Once in RAM, you could modify the PLC to your hearts content using the built in editor. The manuals should tell you how to do this.... However, this type of editing will be lost when you reformat the memory (and, again, this is theory... I've not actually tried it.sssssss