Hello all. I try to explain the context of the application where I’m having the issue. I have a large amount of OPC tags that represents machine parameters: those tags should not be read if not on the HMI, so I decided to use a leased tag group with a leased/driven rate of 1000 ms and a rate of 0. The application has many views that allows to acces to those parameters in a structured manner: those view are basically composed by one or more flex repeaters with a bunch of components that are bind to the parameters tags: when I load one of those views the related tags are loaded and start polling their values at the rate of 1 sec, while all the other parameters tags are idle.
The problems is with the initial state of the tags. When I restart the gateway, or simply when I do a tags restart, all the tags are in a state of “uncertain initial value”, that means the tags values have not yet been read frmo PLC: and this is ok. What is not ok is that loading a view, I get a not really beautiful black “overlay unknown” on all the components that are bind to those tags, that disappears after 2-3 seconds, when the tag has been successfully read (problem 1). I thought it could be a graphic latency issue, so I tried with a simple page with just one native component bind to a parameter tag, and I get the same problem.
Also, during those 2-3 seconds of “idle” state, the tag is set to it’s default value, and this value is written to the PLC: so all the parameters values are overwritten on the PLC (problem 2).
Does anyone have any idea regarding the two problems?
Here are the tag group’s settings:
If you disable the Read After Write and Optimistic Write do you still have the issue of the PLC value being overwritten?
Thanks for replying: I cannot make tests right now, don’t really remember but maybe we already did some test changing those parameters. Also, the value was not always overwritten, so it could possibly be a bug.
After this post I also opened a ticket for the two problems, I’ll write here as soon as I get info.