6.2.2 Object and ObjectType Definitions

6.2.2.1 SafetyACSet Object

[RQ6.1] Each Server shall have a singleton Folder called SafetyACSet with a fixed NodeID in the Namespace of this document. Because all SafetyProviders and SafetyConsumers on this Server contain a hierarchical Reference from this Object to themselves, it can be used to directly access all SafetyProviders and SafetyConsumers. SafetyACSet is intended for safety-related purposes only. It should not reference non-safety-related items.

See Table 3 for the definition of the SafetyACSet.

[RQ6.2] In addition, a Server shall comprise one OPC UA Object derived from DataType SafetyProviderType for each SafetyProvider it implements, and one OPC UA Object derived from DataType SafetyConsumerType for each SafetyConsumer it implements. The corresponding Information Models shown in Figure 3 and Figure 4 shall be used.

A description of the graphical notation for the different types of Nodes and References (shown in Figure 3, Figure 4, and Figure 6) can be found in OPC UA 10000-3.

Figure 3 describes the SafetyProvider and the SafetyConsumer.

[RQ6.3a] For implementations supporting OPC UA Client/Server, the Call Service of the Method Service Set (see OPC UA 10000-4) shall be used. The Method ReadSafetyData has a set of input arguments that make up the RequestSPDU and a set of output arguments that make up the ResponseSPDU. The SafetyConsumer uses the OPC UA Client with the OPC UA Service Call.

[RQ6.3b] For implementations supporting OPC UA PubSub, the OPC UA Object SafetyPDUs with its Properties RequestSPDU and ResponseSPDU shall be used. RequestSPDU is published by the SafetyConsumer and subscribed by the SafetyProvider. ResponseSPDU is published by the SafetyProvider and subscribed by the SafetyConsumer.

[RQ6.4] For diagnostic purposes, the SPDUs received and sent shall be accessible by calling the Method ReadSafetyDiagnostics.

Figure 4 shows the instances of Server Objects for this document. The ObjectType for the SafetyProviderType contains Methods having outputs of the abstract DataType Structure. Each instance of a SafetyProvider requires its own copy of the Methods which contain the concrete DataTypes for OutSafetyData and OutNonSafetyData.

6.2.2.2 Safety ObjectType definitions

[RQ6.5] To reduce the number of variations and to alleviate validation testing, the following restrictions apply to instances of SafetyProviderType and SafetyConsumerType (or instances of DataTypes derived from SafetyProviderType or SafetyConsumerType):

1. The references shown in Figure 4 originating at SafetyProviderType or SafetyConsumerType and below shall be of ReferenceType HasComponent (and shall not be derived from ReferenceType HasComponent) for Object References or ReferenceType HasProperty (and shall not be derived from ReferenceType HasProperty) for Property References.

2. As BrowseNames (i.e. name and Namespace) are used to find Methods, the names of Objects and Properties shall be locally unique.

3. The DataType of both Properties and MethodArguments shall be used as specified, and no derived DataTypes shall be used (exception: OutSafetyData and OutNonSafetyData).

4. In IEC 62541, the order of Method arguments is relevant.

See Table 4 for the definition of the SafetyObjectsType.

See Table 5 for the definition of the SafetyProviderType.

[RQ6.6] Instances of SafetyProviderType shall use non-abstract DataTypes for the arguments OutSafetyData and OutNonSafetyData.

See Table 6 for the definition of the SafetyConsumerType.

6.2.2.3 Method ReadSafetyData

This Method is mandatory for the Facet SafetyProviderServerMapper. It is used to read SafetyData from the SafetyProvider. It is in the responsibility of the safety application that this Method is not concurrently called by multiple SafetyConsumers. Otherwise, the SafetyConsumer can receive invalid responses resulting in a safe reaction which can lead to either spurious trips or system unavailability, or both.

See Table 7 for Method ReadSafetyData’s arguments and Table 8 for its AdressSpace definition.

The Method argument OutSafetyData has an application-specific DataType derived from Structure. This DateType (including the DataTypeID) is expected to be the same in both the SafetyProvider and the SafetyConsumer. Otherwise, the SafetyConsumer will not accept the transferred data and switch to fail-safe substitute values instead (see state S16 in Table 34 as well as 7.2.3.2 and 7.2.3.5). The Method argument OutNonSafetyData has an application-specific DataType derived from Structure.

Signature

	ReadSafetyData (
		[in]	UInt32	InSafetyConsumerID,
		[in]	UInt32	InMonitoringNumber,
		[in]	InFlagsType	InFlags,
		[out]	Structure	OutSafetyData,
		[out]	OutFlagsType	OutFlags,
		[out]	UInt32	OutSPDU_ID_1,
		[out]	UInt32	OutSPDU_ID_2,
		[out]	UInt32	OutSPDU_ID_3,
		[out]	UInt32	OutSafetyConsumerID,
		[out]	UInt32	OutMonitoringNumber,
		[out]	UInt32	OutCRC,
		[out]	Structure	OutNonSafetyData)
	;

6.2.2.4 Method ReadSafetyDiagnostics

This Method is mandatory for the Facet SafetyProviderServerMapper and optional for the Facet SafetyProviderPubSubMapper. It is provided for each SafetyProvider serving as a Diagnostic Interface, see 6.4.3.

See Table 9 for the arguments of Method ReadSafetyDiagnostics and Table 10 for its AddressSpace definition.

The Method arguments OutSafetyData and OutNonSafetyData are application-specific types derived from Structure.

Signature

	ReadSafetyDiagnostics (
		[out]	UInt32	InSafetyConsumerID,
		[out]	UInt32	InMonitoringNumber,
		[out]	InFlagsType	InFlags,
		[out]	Structure	OutSafetyData,
		[out]	OutFlagsType	OutFlags,
		[out]	UInt32	OutSPDU_ID_1,
		[out]	UInt32	OutSPDU_ID_2,
		[out]	UInt32	OutSPDU_ID_3,
		[out]	UInt32	OutSafetyConsumerID,
		[out]	UInt32	OutMonitoringNumber,
		[out]	UInt32	OutCRC,
		[out]	Structure	OutNonSafetyData)
		;

6.2.2.5 Object SafetyPDUs

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.

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.

6.2.2.6 Objects SafetyProviderParameters and SafetyConsumerParameters

Figure 6 shows the safety parameters for the SafetyProvider and the SafetyConsumer.

Table 12 shows the definition for the SafetyProviderParametersType. Refer to 6.3.3.3 for more details on the Safety Parameter Interface (SPI) of the SafetyProvider.

The parameters for SafetyProviderID and SafetyBaseID exist in pairs for “Configured” and “Active” states:

• SafetyProviderIDConfigured and SafetyProviderIDActive,

• SafetyBaseIDConfigured and SafetyBaseIDActive.

The “[...]Configured” parameters shall always deliver the values as configured via the SPI. The “[...]Active” parameters shall deliver:

• the corresponding “[...]Configured” values if the system is still offline;

• the values which have been set during runtime via the SAPI parameters (SafetyProviderID, SafetyBaseID);

• the corresponding “[...]Configured” values if the active values have been set to zero via the SAPI parameters (SafetyProviderID, SafetyBaseID).

The Property SafetyBaseIDConfigured is shared for all SafetyProviders with the same SafetyBaseIDConfigured value. If multiple instances of SafetyObjectsType are running on the same Node, it is a viable optimization that a Property SafetyBaseIDConfigured is referenced by either multiple SafetyProviders or SafetyConsumers, or both.

For releases up to Release 2.0 of the document, the value for the SafetyStructureSignatureVersion shall be 0x0001 (see RQ7.21 in 7.2.3.5).

Table 13 shows the definition of the SafetyConsumerParametersType. The Properties SafetyStructureIdentifier and SafetyStructureSignatureVersion are optional, because SafetyStructureSignature is typically calculated in an offline engineering tool. For small devices, it could be beneficial to only upload the SafetyStructureSignature to the device, but not SafetyStructureIdentifier and SafetyStructureSignatureVersion in order to save either bandwidth or memory, or both. Refer to 6.3.4.4 for more details on the Safety Parameter Interface (SPI) of the SafetyConsumer.

The parameters for SafetyProviderID, SafetyBaseID and SafetyConsumerID exist in pairs for “Configured” and “Active” states: SafetyProviderIDConfigured and SafetyProviderIDActive, SafetyBaseIDConfigured and SafetyBaseIDActive, and SafetyConsumerIDConfigured and SafetyConsumerIDActive.

The “[...]Configured” parameters shall always deliver the values as configured via the SPI. The “[...]Active” parameters shall deliver:

• the corresponding “[...]Configured” values if the system is still offline;

• the values which have been set during runtime via the SAPI parameters (SafetyProviderID, SafetyBaseID, SafetyConsumerID);

• the corresponding “[...]Configured” values if the active values have been set to zero via the SAPI parameters (SafetyProviderID, SafetyBaseID, SafetyConsumerID).