Data Arbitration is the system function that manages the reception and transmission of dual / redundant SPCS data.
If the Subsea system performs this function, only a single process value or operator command is typically passed between the SPCS and DCS system. If the DCS performs this function, both the A and B data values would typically be passed across the interface.
There are multiple types of data that could require arbitration. Instruments can be redundant, SEMs can be redundant and it is possible that the different types of data maybe arbitrated in different locations. I.e. in some projects, sensor data may be arbitrated by the DCS while the SEM may be arbitrated by the SPCS. Data Arbitration choices can also affect redundancy.