S7 400 PLC freezing


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We have Siemens S7 400 PLC, it is connected via Profibus to S7 300. Suddenly all analog input signals in S7 400 go to freezing value at last value and become red color.
Hello sugger;

Where do you see the analog input values go red? HWConfig, SCADA, HMI? Are these values coming from I/O cards on the S7-400 rack, or over Profibus-DP?

When this happened, did you open the Diagnostic Buffer for the CPU, or the analog input cards (from HWConfig, ONLINE, object properties [CPU or I/O module])? You should find entries there that define the encountered problem, or at least inform you of the correct OBx block that should be loaded on the CPU for further diagnostics.

Hope this helps,
Daniel Chartier