Panel 800 PP8866r certain tags from a PLC froze after removing power to the display!
I have a PP886r panel and a PM856. Access variables over control net. About 50 tags being read every 0.5 seconds.
I removed power to the display. When the display powered up, some of the tags had frozen. Ie., they were TRUE in the PLC but false in the dispay. Other tags were not frozen. I only solved the problem by downloading to the panel. I was unable to replicate the problem a second time.
How could this happen? Is there any way of preventing this from happening again? It is a serious issue, because there was no way to tell that the values had in fact frozen.
Panel 800 controller and tag settings: The controller is marked as "active". No tags are marked as "non-volatile". No tags are "always active". In the "data exchange" setting, "direction" is left blank and "When" is set to "value change" for all tags.