Hello cila.petr;

For your first case, understand that a configured IO Device will always generate a diagnostic message( that you cannot override or bypass) if it loses its connection to the IO Controller that sent it its name and IP address. As long as it is defined as a IO Device, the diagnostic LED will remain active if it loses the IO Controller. For more details, download the Profinet System Description below, look at information in sections 2.3-2.7 and Ch.3. The attached screenshot was taken from Ch.3.

https://www.profibus.com/download/profinet-technology-and-application-system-description

Your second question discusses the opposite problem, an IO Controller losing one or more IO Devices. Of course, when these IO Devices do not reply when polled, the IO Controller will generate a fault and the diagnostic LEDs will become active. However, it is possible to remove a faulty or missing IO Device from the IO Controller's polling list, using the instruction D_ACT_DP in TIA Portal:

This article will describe the basics of using D_ACT_DP, check out your Step 7 and WinCC v1x manual and the step 7 Online help for more details:

https://support.industry.siemens.com/cs/ca/en/view/105020938

Hope this helps,

Daniel Chartier