You can create a simple priority scheme with the priorities in any order by programming a different priority value for each slave interface, where 0 is the highest priority. See Fixed priority operation.

You can create a round-robin style scheme by assigning the same value to each slave interface priority, and any value has the same effect.

This does not achieve a strict round-robin scheme because the priority group achieves fair provision by the least recently used mechanism, but it does provide the fairness of access and prevention of denial of service properties of a true round-robin scheme. See Round-robin priority operation.