This method (as part of the OPC UA Mapper) is provided for each SafetyProvider serving as a diagnostic interface. For time series observation, this interface can be polled, e.g. by the diagnostic device. For details, refer to the OPC UA information model described, see Clause 6.1.2.
The diagnostic interface method does not take any input parameters and returns both the input- and output parameters of the last call of the method ReadSafetyData.
Additionally, a 2-byte sequence number is added to the diagnostic interface, allowing for a detection of missed calls due to polling. The sequence number counts the number of accesses to ReadSafetyData.
A best practice recommendation is to store all input- and output parameters if SComErr_diag is <> 0.