Omron CX-SUPERVISOR - V2.0, User Manual

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CHAPTER 14 – Using CX-Supervisor as an OPC Client OMRON
Page 230 Release 2.0
A Brief History of OPC Data Access
In the early 1990s a group of people from several important companies involved in the creation of
SCADA (Supervisory Control and Data Acquisition) systems began meeting at Microsoft’s
headquarters in Redmond. Their interests focused on the use of the Windows operating system within
the factory automation environment, in particular for the acquisition of real time 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.
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.