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  1. Oleksandr Guminskiy
  2. PLCnext Engineer
  3. Wednesday, 28 July 2021
Dear All!
I have the question about order of variable values processing.
There is a variable, that can be changed inside of plcnext controller program and by eHMI button click.
My question is when PlcNext controller will process eHMI variable change command, on the start of new program cycle, at the end of current program cycle, or it can be change by eHMI command in the middle of current cycle?
Where can I find information about behavior of controller in that case?

Thank you
Accepted Answer
Martin PLCnext Team Accepted Answer Pending Moderation
Data is transmitted between the Runtime and the web page via GDS Port variables in the PLCnext Runtime. This should ensure data consistency, i.e. the value of GDS port variables should not change unexpectedly during program execution. This concept is described in the Info Center, here:
So, the data in the GDS port written from the HMI page should not change in the middle of program execution. It will change "between" program executions.
Hope this helps.
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