CPU 317 goes to stop mode and SF enable.

Hello umayb;

Reading your diagnostic buffer, we can see these problems immediately:

"Requested OB: Rack failure OB (OB86)

and

"Requested OB: Diagnostic interrupt OB (OB82)

To recognize and respond to a specific type of fault, Step 7 uses diagnostic organization blocks specifically designed to gather information from these faults, You can find a list of such diagnostic OBs, for S7-300 in the screenshot below, take from this document:

- Which organization blocks do you need for error handling in STEP 7 V5.5?

https://support.industry.siemens.com/cs/ww/en/view/11499205

In your case, you are experiencing I/O rack failure on your Profibus or Profinet networks, for which OB86 is needed, and hardware interrupt faut on specific modules in the CPU rack or the network, for which OB82 is required.

If the CPU cannot find OB86 and OB82 in the user program, the CPU will go to fault with SF and BF (for communication fault) LEDs active.

To obtain more details on the faults in the diagnostic buffer and possibly keep the CPU running even in the prsence of a single fault, introduce OB86 and OB82 in your program: create 2 New Blocks (in the Step 5 Block forlder), name them OB86 and OB82, compile and dwnload them to the CPU. For the moment empty blocks will do the job, no need for any program inside them.

When the SF and BF LEDs appear again (but the CPU is still running) open the diagnostic buffer once again, you should have enough information to identify the faulty modules by their addresses in HWConfig, so you can examine why they are at fault.

Hope this helps,

Daniel Chartier