This Object is mandatory for the Facet SafetyProviderPubSubMapper and the Facet SafetyConsumerPubSubMapper It is used by the SafetyProvider to subscribe to the RequestSPDU and to publish the ResponseSPDU. The DataType of RequestSPDU is structured in the same way as the input arguments of ReadSafetyData. The DataType of ResponseSPDU is structured in the same way as the output arguments of ReadSafetyData.

See Table 11 for the definition of the SafetyPDUsType.

Both variables in the SafetyPDUsType have a counterpart within the Information Model of the SafetyConsumer. The SafetyConsumer publishes the RequestSPDU and subscribes to the ResponseSPDU.

Table 11 – SafetyPDUsType definition

Attribute	Value
BrowseName	SafetyPDUsType
IsAbstract	False
References	Node class	BrowseName	DataType	TypeDefinition	Modelling rule
Subtype of BaseObjectType
HasComponent	Variable	<RequestSPDU>	RequestSPDUDataType	BaseDataVariableType	Mandatory Placeholder
HasComponent	Variable	<ResponseSPDU>	ResponseSPDUDataType	BaseDataVariableType	Mandatory Placeholder
Conformance units
SafetyPDUs

The Object SafetyPDUs shall contain exactly one Reference to a Variable of DataType RequestSPDUDataType and exactly one Reference to a Variable of a subtype of DataType ResponseSPDUDataType.

For example, Figure 5 shows a distributed safety application with four SafetyAutomationComponents. It is assumed that SafetyAutomationComponent 1 sends a value to the other three SafetyAutomationComponents using three SafetyProviders, each comprising a pair of SPDUs. For each recipient, there is an individual pair of SPDUs.

Figure 5 – Safety multicast with three recipients using IEC 62541 PubSub