Client - Dynamic created DataSets (CreateDataSet, DeleteDataSet)

This sample shows the use of the "CreateDataSetReq" and "DeleteDataSet" methods of the client function block.

Download TwinCAT XAE Project (*.zip): Sample17.zip

The example described here uses the state machine that is described in the "General Client project structure" chapter. The States 0, 1, 11 and 100 are identical to the state machine described there. Other states were modified for the example or new states were also added.

General information about the dynamic DataSets

The instances of the static DataSets, which are always available during runtime, are either configured by the user in TwinCAT Telecontrol Configurator or imported from an ICD file. The PLC project generation later creates the necessary PLC code for the instantiation of these DataSets. This code also includes the configuration of the DataSet members and the assignment of the DataSet to a logical node in the IEC 61850 data model. The configuration of the static DataSets must not be changed at runtime of the PLC program and the DataSets can also not be deleted.

Sometimes, however, you want to create a DataSet dynamically and use it only for a short time (e.g. as long as the communication connection is up). During this time you may want to monitor some measured values with the help of a report and when the connection is no longer present then remove/delete this DataSet from the data model again.

With the help of the client methods: "CreateDataSetReq" and "DeleteDataSetReq" DataSets can be created, configured and deleted dynamically (at runtime). The dynamically created DataSets can be configured as either "persistent" or "non-persistent" DataSets. The "non-persistent" DataSets are permanently assigned to a client-server connection and only exist as long as the connection is not interrupted. The "non-persistent" DataSets of a client-server connection are not visible for another client-server connection. I.e. a client cannot see or delete the "non-persistent" DataSets of another client. A non-persistent DataSet can only be deleted by the client that created it or is automatically deleted when that client is disconnected.

The "persistent" DataSets, on the other hand, are visible to all clients and can also be deleted by another client at a later time. However, this is not recommended as the creator client may not notice and may try to continue accessing this DataSet. The "persistent" DataSets are not automatically deleted when the connection is terminated and remain in the data model until they are explicitly deleted.

A dynamically created "persistent" or "non-persistent" DataSet, which is used, for example, by a report control block, cannot be deleted. I.e. as long as the control block Attribute: "DatSet" references this DataSet, this DataSet cannot be deleted. If you want to delete such a DataSet, then the attribute "DatSet" must reference another DataSet or the "DatSet" reference must be deleted (e.g. an empty string deletes the "DatSet" reference).

In a client project and after a TwinCAT restart or a reset of the TwinCAT PLC, all "persistent" and "non-persistent" DataSets on the client side are automatically deleted. On the server side, however, the "persistent" DataSets may remain because they could not be explicitly deleted.

The static DataSets are basically also "persistent" DataSets. They differ from the dynamically generated DataSets in that they cannot be deleted.

For each DataSet that you want to create dynamically at a later time (at runtime), you need an instance of the function block: "FB_AcsiCommonDataSetClass". These instances are manually added to the PLC project beforehand during PLC programming. However, they are not yet linked to the client data model. The PLC application can then later use these instances at runtime to create the dynamic DataSets on the server side. Only then are these instances also linked to the data model on the client side. The DataSet members can also be preconfigured. The method "CreateDataSetReq" needs as first parameter: "ipDataSet" an interface pointer to such a preconfigured DataSet object. The second parameter: "ipLogicalNode" determines whether a "persistent" or "non-persistent" DataSet should be created. Only the "persistent" DataSets are linked to a logical node. In this case, this parameter must be valid. For a "non-persistent" DataSet this parameter is zero. On success, a dynamic DataSet is created on the server side and the preconfigured DataSet instance is linked to the data model on the client side. The method "DeleteDataSetReq" needs as first parameter: "ipDataSet" an interface pointer to a DataSet object (which was already added to the data model before). If successful, the DataSet is then deleted from the data model on the server side and the link between the DataSet and the data model is also deleted on the client side.

…
fbNonPersistent: FB_AcsiCommonDataSetClass:=(sObjectName:='NonPersistentDataSet');
fbPersistent: FB_AcsiCommonDataSetClass:=(sObjectName:='PersistentDataSet');
…

…
ELSIF bCreateDataSet_NonPersistent THEN
    bCreateDataSet_NonPersistent:= FALSE;
    IF fbNonPersistent.nMembers = 0 THEN
        bSuccess:= fbNonPersistent.AddMember(ipData:=fbIED.IEDLD1.XCBR1.Pos.stVal, eFc:=E_AcsiFc.ST_);
        bSuccess:= fbNonPersistent.AddMember(ipData:=fbIED.IEDLD1.LLN0.Mod_.stVal, eFc:=E_AcsiFc.ST_);
    END_IF
    bSuccess:= fbConnection.CreateDataSetReq(ipDataSet:=fbNonPersistent, ipLogicalNode:=0, hUser:=0, ipSink:=0, nInvokeID=>nInvokeID, ipResult=>ipResult);
    state:= SEL(bSuccess, 100, 11);
ELSIF bCreateDataSet_Persistent THEN
    bCreateDataSet_Persistent:= FALSE;
    IF fbPersistent.nMembers = 0 THEN
        bSuccess:= fbPersistent.AddMember(ipData:=fbIED.IEDLD1.MMXU1.TotW.mag.f, eFc:=E_AcsiFc.MX);
        bSuccess:= fbPersistent.AddMember(ipData:=fbIED.IEDLD1.LLN0.Beh.stVal, eFc:=E_AcsiFc.ST_);
    END_IF
    bSuccess:= fbConnection.CreateDataSetReq(ipDataSet:=fbPersistent, ipLogicalNode:=fbIED.IEDLD1.LLN0, hUser:=0, ipSink:=0, nInvokeID=>nInvokeID, ipResult=>ipResult);
    state:= SEL(bSuccess, 100, 11);
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