OPC Servers provide real-time data by firing events whenever the value (or quality) of an item added by the OPC client changes. This OnDataChange event is defined by the OPC specification. An OPC Client can subscribe to this event and provide a handler function that gathers the new item values whenever the OPC Server fires the OnDataChange event.
The event handlers for gathering incoming unsolicited point updates in the CIMPLICITY OPC Client are compliant with the Data Access 3 and Data Access 2 specifications. The OPC Client tests to see if it has connected to a 3 or 2 compliant OPC Server and sets up the proper event handler for optimum performance.
Review data access specification documentation for the most current details about valid interfaces and methods.
Note: CIMPLICITY does not support Data Access 1 specification.
About OPC Servers
About OPC Client.