Origin and Uses
The OPC Specification was based on the OLE, COM, and DCOM technologies developed by Microsoft for the Microsoft Windows operating system family. The specification defined a standard set of objects, interfaces and methods for use in process control and manufacturing automation applications to facilitate interoperability. The most common OPC specification is OPC Data Access, which is used to read and write real-time data. When vendors refer to OPC generically, they typically mean OPC Data Access (AKA OPC DA). OPC DA itself has gone through 3 major revisions since its inception. Versions are backwards compatible, in that a version 3 OPC Server can still be accessed by a version 1 OPC Client, since the specifications add functionality but still require the older version to be implemented as well. However, a Client could be written that does not support the older functions since everything can be done using the newer ones, so a DA 3 compatible Client will not necessarily work with a DA 1.0 Server.
Read more about this topic: OLE For Process Control
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