21-M Ladder editing enable

Hi all,

I recently acquired a mill with a 21-M control, and I need to edit the ladder program to enable g127.5 for DNC. Unfortunately the manufacturer did not provide a tape or remote switch, and the memory on this machine is very limited.

This machine unfortunately did not come with the ladder edit option, and I have verified that the PMC module on the main card is the one without the edit option (A20B-2900-0143). I do have an edit-capable PMC module on hand from a prior retrofit (A20B-2900-0142). I have a couple questions regarding this swap:

1.) Can this swap happen without consequence to the ladder program? My understanding is that the ladder program is in the UV EPROM (socketed), and thus is non-volatile. This leads me to believe that the PMC card is only for processing.

2.) If I swap these cards to enable editing, does this mean I will have to enable a parameter? I am assuming that I would, but I am unsure (and I do not want to test until I find an answer to question 1!)

Thank you for any help. This looks like a great machine, but sadly is in retrofit territory if I can't run a decent sized program.

-Tim

Another question would be whether the G127.5 register could be written to directly? I know that the CNC communicates with the PMC via "F" registers (which could be an M code, for example), and then the PMC communicates back to the CNC via "G" registers.

Is there a possibility that the G127.5 could be operated without the interaction of the PMC? I guess this might be a diagnostic bit? I have no official training here, so I'm just trying to figure out something that will make the machine usable.

Thanks!
-Tim

Ohhhh boy. I just started digging through the diagnostics pages, and it looks like G127.5 is not even present. So I guess a super-secret parameter must be enabled in order to even have DNC capability?

EDIT: Maybe that's not as big an issue as I thought. It seems that the Diagnostics pages will only contain the information that is in ladder currently; if G127.5 is not in ladder, it will not be in diagnostics either.

Try G43.5