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 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:

1. OPC UA (UA = Unified Architecture)

This specification is built on standard Ethernet communication.

For this communication in the PROMOTIC system can be used: PmOpcUaClient - Driver for communication with OPC UA server.

More details see Communication by the OPC UA interface.

It is also possible to use OPC UA to OPC DA converter and then to use the PmaOpcDaClient object.

See Communication OPC UA in the PROMOTIC system using the converter to OPC DA.

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 functions are not supported in the PROMOTIC system.

Promotic

Communication by OPC interface

1. OPC UA (UA = Unified Architecture)

2. OPC DA (DA = Data Access)

See also: