In firmware version 1.0.0 for the MAC III, port 2 is used for RDM communication and port 1 is used for DMX signals by default (see page 26 of the MAC III user manual).

In future firmware versions, port 1 will be used for RDM, in line with the RDM standard.

In anticipation of the change and at some convenient time, MAC III users running firmware v.1.0.0 are recommended to change the RDM port settings in the control panel (PERSONALITY -> RDM PORT) and modify their systems so that port 1 is used for both RDM and DMX signals.