I have s7-400 plc with ET-200M station as a slave..
When the power for ET-200M is reset, then the plc goes to stop mode..
Which organization block (OB?) do i need to prevent it from stopping?
But to be absolutely sure, open up the CPU diagnostics while online and an active DP error (ET200M is shutdown). The diagnostic buffer will tell you exactly which OB you are missing.
It's not obligatory to write any code. You could set a bit in each of them to tell your HMI that there was a Rack Fault in OB86, a Programming Error in OB121, or an I/O Error in OB122.