What is OPC DA?
OPC DA is a protocol standard developed by OPC Foundation to ease communication between Industrial Devices. DA stands for Data Access which allows the reading and writing of numerical data between devices. OPC DA is a very old standard, it is today referred to as OPC Classic. It is based on Microsoft DCOM technology, which is now superseded by Web Services such as REST.
OPC Itself has now also evolved. The latest version is called OPC UA (Unified Architecture). OPC DA is still used as a lot of manufacturers still support it and has yet to migrate to OPC UA
OPC DA is a Server Client Protocol
When a device says it wants to communicate via OPC, it means that it seeks to communicatie with an OPC Server. The device now becomes the client. Open-Plant is an OPC Client, as it seeks to communicate with OPC Servers.
What are the different OPC DA Versions?
OPC DA has several versions, but generally speaking the most common version are:
- OPC DA 2.05 released in 1998
- OPC DA 3.00 release in 2003
IMPORTANT: These standards are not meant to be backward compatible. Meaning OPCDA 3.00 will not be able to talk to OPCDA 2.05 server and vice versa.
Who actually implements OPC DA?
OPC DA is implemented by device manufacturer or application providers such as Open-Plant. When a manufacturer develops an OPC Server, he will choose which version he intends to implement. Typical manufacturers would want to implement ALL versions so his device can be compatible with all clients. However, there are some major vendors who seeks to implement only one particular version due to his dominance, or in simple terms 'He's the boss!'
Open-Plant as an OPC Client implements all OPC DA versions. This means it can communicate with all OPC Servers whether it be OPC DA 2.05 or OPC DA 3.00