SIMATIC WinCC Open Architecture Forum

Hi,

I'd like to check my undestanding of how the UI works.

We have a late customer request for a screen refresh icon to prove that the screen is not frozen. We already have a clock display on the navigation panel and we would prefer not to add an icon to every panel in our system. My understanding is that as WinCC OA is event based each panel does not 'refresh' but each symbol responds to its dpConnects. Does the clock or another symbol changing prove that the UI is running and healthy? Is it even possible for the UI to freeze and appear healthy without crashing?

Thank you

You are right. When the clock widget (or any other widget) changes, it means the UI is still running the main loop correctly and is not "frozen".
Would the UI for whatever reason not being able to come back to the main loop, e.g. you are using any code which could block doing an operating system function call, e.g. assume there is somewhere code which does a write() on e.g. the network but is wrongly implemented to be using a blocking write until the other end reads, the UI would not be able to redraw anything, appearing to be frozen.

Great, thank you!