Modem emulation undocumented commands such as AT*MAC?

I am reverse engineering a legacy product that uses a Digi Connect ME. The Connect ME is running in “modem emulation” mode.

The connected system sends a few commands like:
ATDHCP?
AT
MAC?

which appear to work, but I can’t see these documented anywhere.

Is there a better document than the “Digi Connect® Family Command Reference”?

http://ftp1.digi.com/support/documentation/90000566_N.pdf