The OPC Data Access Specification (OPC DA) is the first in a group of specifications known as the Classic OPC Specifications. It is a group of client-server standards that enables communicating real-time data from devices such as programmable logic controller (PLCs), Human-Machine Interfaces (HMI), SCADA systems, and ERP/MES systems.
The OPC DA source service is a client that collects data from OPC servers. Data points in OPC are tags that represent data from devices and provide real-time access to data. When you configure the OPC DA source service, specify the details of the OPC server and list of tags.
To connect to the OPC DA server, configure one of the following identifiers:
ProgID. The Programmatic Identifier of the OPC DA server. The ProgID is a registry entry that can be associated with a CLSID. You can find it in the registry under
CLSID. The CLSID of the COM class object of the OPC DA server. A CLSID is a globally unique identifier that identifies a COM class object. If your server or container allows linking to its embedded objects, you need to register a CLSID for each supported class of objects. You can find it in the registry under
The OPC DA source service creates a subscription client to monitor the list of tags that you provide. The source service converts the OPC data, including the tag name, value, timestamp and quality, to PIPE format.