SPDU

PDU transferred through the safety communication channel

Note 1 to entry: The SPDU may include more than one copy of the SafetyData using differing coding structures and hash functions together with explicit parts of additional protections such as a key, a sequence count, or a time stamp mechanism.

Note 2 to entry: Redundant SCLs may provide two different versions of the SPDU for insertion into separate fields of the OPC UA frame.

[SOURCE: IEC 61784-3:2021, 3.1.47]