Omron CX-Supervisor, User Manual

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An Overview of OPC SECTION 17 Using CX-Supervisor as an OPC Client
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data. Microsoft at the time were working on the development of OLE 2.0
(Object Linking and Embedding) and it was apparent that this new technology
would replace that of DDE (Dynamic Data Exchange) which up until that point
had been used extensively for data exchange within SCADA systems
designed for Windows. The new OLE technology was more flexible, robust
and efficient than DDE.
OLE provided an opportunity to create a standard interface between the
SCADA core and the device drivers responsible for reading and writing data to
various automation devices such as PLCs. Such a standard interface would
benefit both the SCADA vendors and equipment suppliers as the SCADA
vendors would not need to invest costly effort in developing software drivers,
while the equipment manufacturers could provide just one driver that would
work with all Windows software - in the same way that printer manufacturers
already could.
The first draft of the OPC (OLE for Process Control) specification v1.0 was
released in December 1995. The following year, the group of companies
involved in the definition of the standard decided that an independent body
must be set up to manage the OPC specification. This decision resulted in the
formation of the OPC Foundation that has continued to develop the philosophy
of standardised interfaces for SCADA.
In 1998 the Data Access 2.0 specification for OPC was released. This
addressed several deficiencies and ambiguities in the original standard and
included specifications for both the Automation interfaces (typically used by
VB programmers) and Custom interfaces (typically used by C++
programmers).
In 2000, using these DA 2.0 specifications Omron created the first version of
CX-Server OPC, which provides Client and Server software for the CX-
Automation Suite software range.
The current version of Omron's CX-Server OPC is compliant with version 2.05
of the Data Access specification.
17-1-2 Other OPC Specifications
Since the first OPC Data Access specification was produced in 1995 the OPC
Foundation have addressed a number of additional areas of control and
automation normally associated with SCADA. The original specification for
Data Access is now just part of a whole series of specifications that include
such areas as Alarms/Events and Batch control, although the DA interface is
still far more commonly supported than the others.
The figure below shows some of the current areas covered by OPC Interface
Specifications: