Modbus: permanent connection???

[Amelie]

I have a question about the modbus-connection (TCP) in LM.

When I add a new device (see screenshot), I can select: permanent connection. (Forgive me if the translation is not 100% correct, but I have a dutch version). What does it do?

I have looked in the manual, but I didn't really find an answer to my question.

When I check the option, the CPU of the LM goes sometimes in red. But, when I uncheck it, the CPU sty's blue. So, I wondering what is the real cause of it, and if there is something else wrong.

[Daniel]

Some TCP devices have limited amount of connections and they go offline after a while. Whit persistent mode the connection is never closed. Normally this is not needed, only on some devices.