Ur824 expanding Adat what to get

Not sure exactly but I do have have a Firewire card I could use if that was the case if it’s just for configuration purposes. There is a thread about the scenario here where the UR824 is master and MR 816 is slave:

EDIT: Steinberg has the configuration info here: https://helpcenter.steinberg.de/hc/en-us/articles/206085924-How-to-use-the-MR816X-CSX-as-a-slave-device-via-ADAT