OPC Classic Server

Introduction

The OPC Classic Specification is a software interface standard that allows programs to communicate with industrial hardware devices. You can connect OPC Classic aware client applications directly to Fernhill SCADA without needing any custom interface software:

Diagram showing Fernhill SCADA relationship with OPC clients

Fernhill SCADA supports these OPC Classic interfaces:

OPC Data Access (OPC DA) Version 1.0a
OPC Data Access (OPC DA) Version 2.0
OPC Data Access (OPC DA) Version 3.0
OPC Alarms and Events (OPC AE) Version 1.0
OPC Historic Data Access (OPC HDA) Version 1.2
OPC Security Version 1.0
OPC Common Version 1.1

OPC Use Cases

Using the OPC Classic Server and a suitable client application you can:

Discover the tags in Fernhill SCADA
Read and write tag values (synchronously or asynchronously)
Set up a subscription to receive notifications when tag values change
Discover the alarms in Fernhill SCADA
Read the current active alarms
Set up a subscription to receive alarm status updates as these occur
Acknowledge alarms in Fernhill SCADA
Manage which alarms are enabled
Discover which tags support historic data
Read raw historic data values from historic enabled tags
Perform simple processing on historic data values, for example Minimum, Maximum and Average

Supported Interfaces

The OPC Classic Server in Fernhill SCADA supports these interfaces:

OPC Server
IOPCCommon
IOPCSecurityNT
IOPCServer
IOPCItemProperties
IOPCItemIO
IOPCBrowseServerAddressSpace
IOPCBrowse
IOPCEventServer
IOPCHDA_Server
IOPCHDA_SyncRead
IConnectionPointContainer

OPC Data Access groups support these interfaces:

OPC Data Access Group
IOPCItemMgt
IOPCGroupStateMgt
IOPCGroupStateMgt2
IOPCSyncIO
IOPCSyncIO2
IOPCAsyncIO
IOPCAsyncIO2
IOPCAsyncIO3
IOPCItemDeadbandMgt
IDataObject
IConnectionPointContainer

OPC Alarms and Events subscriptions support these interfaces:

OPC Event Subscription
IOPCEventSubscriptionMgt
IConnectionPointContainer

The specification of these interfaces is defined by the OPC foundation.

OPC Foundation

The OPC foundation is a non-profit organization that defines and promotes OPC standards for data exchange in Industrial Automation and other related domains.

DCOM

The OPC Classic Server in Fernhill SCADA is an in-process COM server, which avoids any need to set up DCOM.

When the OPC Client application is not on the same computer as Fernhill SCADA, install the OPC Classic Server on the client computer. The Fernhill SCADA Setup program provides the install option Data Access Interfaces for this. In this scenario, the OPC Client application loads the in-process OPC Classic Server, which in turn communicates with Fernhill SCADA using TCP/IP.

The OPC Classic Server in Fernhill SCADA also supports out-of-process activation using the standard Windows DLL Surrogate DLLHost.exe.

Further Information

Diagnosing Connection Problems

To learn how to solve problems connecting to a Fernhill SCADA Server.

OPC Classic Server Administration Tool

To learn how to connect OPC Clients to different computers running Fernhill SCADA.

Using C/C++ to access an OPC Classic Server

For a guide to writing C/C++ code to access an OPC Classic Server.

opcfoundation.org

For information about the OPC standards.

Glossary

For the meaning of terms used in Fernhill SCADA.