AiVibeOPC Classic (OPC DA, HDA and A&E)
OPC Classic is the original family of OPC Foundation specifications, including Data Access, Historical Data Access and Alarms and Events, built on Microsoft COM and DCOM to let Windows software exchange data with industrial devices.
OPC Data Access (DA) lets client applications browse, read, write and subscribe to current tag values from an OPC server, which in turn communicates with PLCs and devices through native drivers. Historical Data Access (HDA) provides access to archived values, and Alarms and Events (A&E) delivers alarm and event notifications. All rely on Microsoft's Component Object Model and its distributed variant, DCOM, for communication between applications on the same or different Windows computers.
OPC Classic, which emerged in the mid-1990s, solved the problem of every HMI and SCADA package needing its own driver for every device, and it became ubiquitous in Windows-based automation. Many installed SCADA systems, historians and drivers still use OPC DA, so it remains relevant in brownfield integration.
DCOM is difficult to configure across networks and firewalls, is tied to Windows and has been progressively hardened by Microsoft, which has required configuration changes in some installations. For these reasons OPC UA is the recommended successor, and tunnelling products or wrappers can bridge OPC Classic servers to OPC UA clients. Remote DCOM access should be minimised and protected by segmentation following IEC 62443.
Key points
- Original OPC specifications built on Microsoft COM and DCOM
- Includes Data Access, Historical Data Access and Alarms and Events
- Widely installed in Windows-based SCADA, HMI and historian systems
- DCOM is hard to secure and configure across networks
- OPC UA is the platform-independent successor
Where AiVibe comes in
AiAmbA IoT is AiVibe's edge protocol layer: it discovers devices and normalises industrial signals, with supported protocols including Siemens S7, Mitsubishi MC, Delta Modbus, OPC UA and MQTT, and driver availability confirmed per installation. Writes to machines are deny-by-default.