Applicom opc server: comm error not always showing in DSC?

[MichelC]

I am using DSC and a PFB 2000 applicom card + opc server to communicate with PLCs over a profibus/mpi network.
It appears that communication failures between the board and the PLCs are sometimes not showing in DSC. When it happens the DSC read functions return the last valid tag values and timestamps but no error (see attached snapshots). The problem disappears if I restart DSC and the applicom opc server.

It seems to me that DSC fails to read the error status from the opc server...

Is there a way to detect a communication failure at the opc server level from LabView while DSC is running?

Thanks for your help.
Michel.

[Roli]

The DSC OPC Client normally reads the quality information from the OPC Server. I've tested it with the Matrikon Demo OPC Server that has an OPC item which reports randomly a different OPC item quality and with LabVIEW DSC 6.1.

As I see from your snapshots the OPC server reports a status 3997696. If you evaluate this value status with the Get Tag Status Info.vi, we have a "Value exceeded", status 61, as a warning. As I remember, LabVIEW DSC 6.0 was treating warnings similar to an error and would after a warning not update anymore. Therefore, the DSC Engine would never get the Comm Failure error after a "Value exceeded" warning. I guess in LabVIEW DSC 6.1 and later, National Instruments changed this behavior and the OPC Client and the DSC Engine keeps updating v
alues with warnings till you will recieve an error.
Are you using LabVIEW DSC 6.0 or 6.1 (or 7.0 :))?

If you use 6.1, you might verify with Server Explorer and see if the OPC server properly reports the Comm Failure as a OPC quality, there.

If you use 6.0, I recommend an upgrade to the brand new 7.0.

Let us know and I hope it helps
Roland