Communication by OPC interface
The
OPC (
Open Platform Communications) is the standardized specification of the communication interface for applications that are addressed to monitoring and control processes.
This specification is defined and updated by the organization
OPC Foundation (see:
https://www.opcfoundation.org).
The specification has the client-server architecture.
There are two specifications for data transfer in the
OPC:
1. OPC UA (UA = Unified Architecture)
This specification is built on standard Ethernet communication.
More details see
Communication by the OPC UA interface.
For this communication in the PROMOTIC system can be used:
2. OPC DA (DA = Data Access)
This older specification is built on standards
COM and
DCOM by the
Microsoft company.
The main disadvantage of this specification is its dependence on the
Microsoft standards and very difficult configuration in situations if the
OPC server is not located on the same computer as the running PROMOTIC application (then it is necessary to configure
DCOM - see
Configuration of the DCOM interface for OPC-DA server).
For this
OPC specification there is
the PmaOpcDaClient object in the PROMOTIC system.
More details see
Communication by OPC DA interface.
The specification includes data sharing (
OPC DA) and also:
- alarms and events sharing (OPC Alarm and Event Handling)
- historic trends sharing (OPC Historical Data Access), etc.
These additional functionalities are not supported in the PROMOTIC system.
