Need help on PI-OPC-Interface

Discussion created by Helmy on Feb 8, 2013
Latest reply on Feb 9, 2013 by Helmy

I have successfully set up and run a PI-OPC interface for a DeltaV OPC Server. The interface is used for both reading from and writing to the OPC Server. The reading part is working nicely, but I have a little problem with the writing part (i.e. output tags).

Suppose I have the following tags:

Tag #1:
Tag name: 05WellTest-001/Target.CV
InstTag: 05WellTest-001/Target.CV
Location1..5: 1, 0, 1, 3, 0
Pointsource: O

Tag #2: (Output tag)
Tag name: 05WellTest-001/Target.CV.OUT
InstTag: 05WellTest-001/Target.CV
Location 1..5: 1, 0, 2, 0, 0
Pointsource: O

I have no trouble reading and writing within the DeltaV OPC Server, all is great. For example, I send a value to the output tag Target.CV.OUT, say 50, the value goes through to the Target.CV. Note that the Target.CV value can be changed by an operator through the DCS, and the current Target.CV value might not be the same as the one previously set by Target.CV.OUT tag.

The problem arises when I restart the interface. If I restart the interface (for whatever reason such as interface machine restarts or for making changes on the interface configurations), ALL current values that are in the output tags are written back to the DCS, and in the example above, the Target.CV value goes back to 50.

Is there a way that the interface can suppress writing to the OPC Server during interface restarts? Is there a switch on the interface that I can set to avoid writing the current values of the output tags to the target InstrumentTags? Or am I missing something? I have tried to configure the output tags using both types of configuration as documented in the manual.

Thanks in advance!