Description

Function Description

The function block UA_NodeGetHandleList is used to get node handles for multiple nodes.

Passing at NODEIDS input an array [ 0 .. 31 ] of NodeIds Structure Elements, this block returns an array [ 0 .. 31 ] of NodeHdls.

It translates NodeIds to NodeHdls in order to optimize the payload of OPC UA requests from the client to the server.

The NodeIds requests by the client are registered by server that returns to correspondent handles for future requests.

Representation in FBD

Parameter Description

Input parameters:

Name	Type	Comment
EXECUTE	BOOL	FB performs its task on rising edge on this input.
CONNECTIONHDL	DWORD	Connection handle.
NODEIDCOUNT	UINT	Number of NodeIDs In Array of NodeIDs.
NODEIDS	AUANodeID	Array of UANodeID
TIMEOUT	TIME	Time to response.

Output parameters:

Name	Type	Comment
DONE	BOOL	FB has successfully completed its task.
BUSY	BOOL	The FB is not finished and new output values are to be expected.
ERROR	BOOL	Signals that an error has occurred within the FB. Set to true if either ERRORID or any of the NodeErrorIDs indicates an error.
ERRORID	DWORD	Error code.
NODEERRORIDS	ANY_ARRAY_DWORD	Array of NodeErrorIDs. (DWORD)
NODEHDLS	ANY_ARRAY_DWORD	Array of Node Handles. (DWORD)

NOTE: UA_NodeGetHandleList uses the inside register nodes service that is managed on the server side for a session: "Registers one or more nodes for repeated use within a session."

Because the nodes are the same, there is no verification that these nodes have already been registered. So handles are incremented. It is up to the client side to take care to avoid creating a new registration on nodes already registered. PLC applications that use OPCUA Client EFBs could use Release Handle EFB in order to free node registration in the server.

To limit the size of the application variable that is filled for pin NODEIDS, the maximum number of node handles is limited to 32.

If you require more that 32 node handles for future usage for UA_ReadList, UA_WriteList, UA_MonitoredAddItem (up to 251 variables), you need to iterate the call of UA_NodeGetHandleList with the required NodeIds, and concatenate the handle array of the output to fill the handle array of the others blocks.

Runtime Error

Refer to the Appendix for a list of OPC UA detected error codes.