OPC (OLE for Process Control) is a set of communication standards maintained by the OPC Foundation for the industrial automation industry. OPC provides a common platform for applications to share data from typically disparate sources, such as PLCs and databases, without the need to comprehend native protocols.
The OPC Data Access solution (OPC DA) provides specifications for client and server applications that are focused on the continuous communication of real-time data. To this end, Citect SCADA supports a runtime OPC DA server that implements the mandatory OPC DA v2.05 and OPC DA v3 interface specifications.
This allows Citect SCADA to provide real-time data to any compliant OPC DA clients, including applications such as AMPLA, OSI-PI and Historian.
In order to allow OPC DA Server to be accessed by the OPC DA Clients, the OPC DA Server process must be configured in the SCADA project. This behavior is different to releases 7.20 and earlier where no configuration step was required.
Note:
• The OPC DA Server does not fully support WriteVQT functionality, as a Citect SCADA I/O server does not allow quality and timestamp changes that are generated from an external source.
• Connecting a Citect SCADA OPC DA client to an Citect SCADA OPC DA server is not recommended, as the client was not designed to be used in this way. This mode of operation has not been validated.
• The OPC DA server uses regular expressions. For example, if retrieving tags with 'bit' in the name, you need to define "bit.*" instead of "bit*".
To determine which OPC DA interfaces are supported by the Citect SCADA OPC DA Server, see the topic Supported OPC DA Server Interfaces in the reference section of this chapter.
See Also
Published June 2018