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The concept of OPC ist conceived for the application in the cell and management level. With it the OPC Server delivers process data from the management level.
OPC Clients and OPC Server
Illustration 1. OPC Servers
OPC defines objects, which are described by object interfaces. In the OPC server there are two kinds of object interfaces, which can be addressed by an OPC client (image 2):
- The COM-Custom-Interface
- The OLE-Automation-Interface
Illustration 2. Object interface of the OPC Server
The COM-Interface is used by function pointer orientated languages such as C++. Through the automation interface it is possible to communicate with script languages such as Visual Basic.
An OPC server consists of three hierarchical gradated objects:
- server
- groups and
- items.
Illustration 3. OPC object hierarchy
An OPC server shows the real objects as items (variables). These items are within the OPC server unique. The client organizes the items in one or more OPC groups.