How can I start tag update from VBS?

I am using TIA Portal 13.

I need to force a tag reading from the PLC. The tag is declared with "On demand" acquisition mode.

Is it possible to trigger that "demand" from the script? All the documentation seems outdated.

There is no "Tags" property of "HmiRuntime" object and "SmartTag" objects don't have "Read"/"Write"/"Update" methods. And I also don't see "UpdateTag" system function available from VBS.

I found several questions of the same topic on the forum but all of them don't have any replies.

Is possible to trigger  a tag's update from a VBS script?

Hello Sap_ru,

you can't use the system function "UpdateTag" in a script, but you can still use it:

• You need a tag ("UpdateTags") in the tag table. (Can be an internal tag).
• Add an "Update ID" to the tag(s) you want to update.
• Now you add the system function "UpdateTag" on an event of the tag "UpdateTags" for every tag you want to update and fill in the "Update ID(s)"
• In the script you change the value of the tag "UpdateTags" according to the event you chose before.
• --> This triggers the event which starts the system function(s) which is/are updating the tag(s). 
  

Hello Sap_ru,

first I thought about a solution as H.J. But according to the description in the WinCC help it is not necessary. Using the tag in a script should update it.

In topic "Updating the Tag Value in Runtime" you find:

• On demand

If you select the "On demand" acquisition mode, the tag is not updated cyclically. It will only be updated on demand using the "UpdateTag" system function, for example, or by ascript.

Regards,

Frink

It's the same description in the WinCC Advanced manual, but I thought it's too vague.

I think I would try to just use the tag in a script like Prof. Frink suggested.

And in if it fails to update by being called in the script you have an alternative to fall back to.

Hi

I had a problem after writing SmartTags of type UDT / Multiplex to the CPU with an index tag

The reading after that just gave the last wrote value no matter what the index was

I solved this by adding "ControlSmartServer hmiStart" after I wrote several values to the CPU

So this is an example of the code:

If more than 100 tags must be updated on demand, it can't be done using UpdateTag, since the IDs have a permissible range of 1 to 100.  In this case, animations must be placed on a screen to trigger the cyclic-on-demand functionality.