Hi,

As form TIA V17, there is the possibility to update tag on demand, i.e., by calling a system function (Update Tag).

Configuration steps:

1. Create a PLC tag on HMI as usual.
2. Go to tag’s properties: settings, settings, acquisition mode, set the value “on demand”.
3. Give a number (arbitrary) for “Update ID” (Properties: settings, Updates, Update ID)
4. In a button event, for example, call the system function “Update Tag” and give the ID set in the step 3 (or the equivalent in Java Script “HMIRuntime.Tags.SysFct.UpdateTag(‘ID number’);”

TIP:

• if you intend to update several tag at the same time/event, use the same Update ID number for them.

Sample program