Communication by OPC interface
The OPC (
Open Platform Communications) is the standardized specification of the communication interface for applications that are addressed to controlling and monitoring processes. This specification is defined and updated by the unprofitable organization
OPC Foundation (see:
https://www.opcfoundation.org). The specification has the client-server architecture.
There are two specifications for data transfers in the OPC:
-
OPC UA (
Unified Architecture): This specification is built on standard Ethernet communication.
For this OPC specification there is no communication driver in the PROMOTIC system so far (under development). However it is possible to use OPC UA to OPC DA converter and then use the PmaOpcClient object.
More details see Communication by the OPC UA interface.
-
OPC DA (
Data Access): This older specification is built on Microsoft standards
COM and
DCOM.
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).
For this OPC specification there us the PmaOpcClient object in the PROMOTIC system.
More details see Communication by OPC DA interface.
The older 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 functions are not supported in the PROMOTIC system.