[13069] - Write value to Opc item feature for Expression Tags is no longer available in 8.0

Dear all,
in the 7.9.x releases, I was used to use the “Write value back to OPC item” feature for Expression Tags.

Where do I find this feature in the new tag environment?
Thank you.

Hi Andrea.morando

Unfortunately there is no way to give you an answer on whether or not this feature will be included in 8.0 and is under management review. I Will write a feature ticket request for it and keep you updated on what the decisions have been made about it.


This issue was fixed in the build that was uploaded today (3/29).
Please let us know if you continue to see this behavior after upgrading.

I am currently using the 8.0.1 release. Actually I did not find this feature in the expression tags. Could you clarify me better?

This functionality as it was in 7.9 is not coming back.

Tags that had an OPC write-back defined now get a special “Legacy Value Changed” entry in the Tag Event Scripts:

Tags that you want to add this functionality to should just use the regular Value Changed event to invoke system.opc.writeValue.

1 Like

Ok, that’s clear.
Thank you again.


Hi Kevin,

It seems that the “Legacy Value Changed” is missing. I’m in 8.0.2.
I tried the followin code in “Value changed” but does not work. The opc object is a vector and the value is a 1 column dataset…


Thank you very much


“Legacy Value Change” was something that would only appear on upgrades after the fix was added. Adding a new one to Value Changed is the right place…

You can’t write a dataset to OPC, you’ll need to pull the scalar value you want to write out of the dataset first.

Al working ok now.
Thank you very much for your help!