i would be so grateful if you could explain exactly how the OPC DA server performs when enabling it in the workstationST:
- In the OPC DA server tab, does the "Client Driven variable" means the variable of the workstation which are held by the OPC?
- does it copy directly the EGD data?
- if a variable is shared from an other device through the OPC, it would be copied directly in the EGD?
- how data is provided to other OPC clients or external servers?
Thanks in advance.
I'm not sure I fully understand what you are asking, but I'll give it a try. The OPC DA server in Workstation is primarily used to aggregate data from multiple sources (EGD, Modbus, legacy protocols like GSM) and normalize it to OPC DA, typically so it can be consumed by an HMI or SCADA system.
EGD is the simplest--all you have to do is reference the device (Consumed Devices on the General tab) and all of the EGD variables from that device will show up on your OPC DA server.
The "Client-driven Variables" are for defining new variables that "live" in the WorkstationST server. Why would you create variables? Typically to consume Modbus or another protocol; on the Modbus tab you set the Connected Variable for a register to a Workstation variable. This gives you an opportunity to create a real name and rich metadata for signals brought in by 30-year old protocols that don't support modern concepts like... names. :)
Later versions of WorkstationST added OPC UA support and move these variable declarations to a dedicated "Variables" tab, because it is common between the two servers.
Thank you for you response.
Building on what you said and about EGD data, can i choose which EGD data that would show up on the OPC server? in other words, prevent some variables from being copied to OPC server!
All the variables which are present in EGD configuration server will be present in WorkstationST OPC DA server. You cannot choose this from WorkstationST. In any case, a client who is connecting to the GE OPC DA server can choose on its end the variables from the server. The complete list of EGD signals will be visible to the client and they can choose the variables needed.