OPC requirements

This document is intended to be used as a guide for developers of OPC-compliant clients for DeltaV software. It is assumed that the reader is familiar with Microsoft Component Object Model (COM) technology and the OPC specifications. For the tutorial example, Barcode, it is also assumed that the reader is familiar with Visual Basic.

System requirements

The DeltaV OPC Data Access (OPC DA) server runs on an Application Station. OPC clients can run on this workstation or on another Windows workstation connected by a network. The network option requires the use of Microsoft Distributed Component Object Model (DCOM) technology.

OPC client programs may be written in either Visual C++ or a higher level business application such as Excel, Visual Basic, and so on. All OPC clients written using Visual Basic must use the OPCDaAuto.dll in their project references. Do not use the OPCDisp.tlb type library as it is not fully functional with DeltaV software.

Important

A client program that is compatible with version 1.0 of the OPC DA server may not run without error on the v2.05A-compliant DeltaV OPC DA server. Clients written for a v1.0 OPC DA server should be updated for compatibility with a v2.05A OPC DA server.

Note

To reduce excessive, repetitive error messages in the Windows Event Log, adjust the limit of the number of OPC client connections available to the DeltaV OPC DA server, by creating one of the following DWORD values in the Windows registry:

  • 64-bit operating system –

    HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\FRSI\DeltaV\CurrentVersion\OPCDAMaximumClients

  • 32-bit operating system –

    HKEY_LOCAL_MACHINE\SOFTWARE\FRSI\DeltaV\CurrentVersion\OPCDAMaximumClients

Set the value of OPCDAMaximumClients to between 3 and 500, inclusive (settings outside of this range default to the nearest of 3 or 500).

References

Kraig Brockschmidt, Inside OLE, Second Edition, Microsoft Press, Redmond, WA, 1995

Microsoft COM Specification, version 0.9 (available from Microsoft's FTP site), October 24, 1995

Microsoft Systems Journal, Q&A, pp. 89-101, April, 1996

OLE Automation Programming Reference, Microsoft Press, Redmond, WA, 1996

OLE 2 Programming Reference, Vol. 1, Microsoft Press, Redmond, WA, 1994

OLE for Process Control, OPC Overview, OPC Foundation (available at http://www.opcfoundation.org/)

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