Communication Problem busf led on CPU 315-2DP is blinking - how to retrieve error messages from cpu buffer?

2. Open all the stations so that the programmable modules configured in them

are visible.

3. Check to see which CPU is displaying a diagnostics symbol indicating an error

or fault. You can open the help page with an explanation of the diagnostics

symbols using the F1 key.

4. Select the station that you want to examine.

7. Select a faulty module in the quick view.

8. Click the "Module Information" button to obtain the information on this module.

9. Click the "Open Station Online" button in the quick view to display the

diagnostic view. The diagnostic view contains all the modules in the station in

their slot order.

10. Double-click a module in the diagnostic view in order to display its module

information. In this way, you can also obtain information for those modules that

are not faulty and therefore not displayed in the quick view.

You do not necessarily have to carry out all of the steps; you can stop as soon as

you have obtained the diagnostic information you require.


Depending on what OBs have been inserted in your program, you might get this type of message in the buffer: "STOP because programming error OB not loaded", or "Missing or requested OB", followed by an OBxx number. In that case, go to the program folder of your Step 7 projectr, Insert a new block --> OB, select the appropriate OBxx number in the following dialog, save and download it to the CPU (no need to program any logic for the moment). Restart the CPU; if the BusF LED comes back on, the CPU will not go into Stop mode (the error OBxx is taking care of that) and your buffer should have more information on a defective module or Profibuis slave.

Note that in the Diagnostic View any defective slave should also be shown with a red triangle, and they have their own diagnostic buffer, so you can access it by doule-clicking on it.

If you need any help in understanding a diagnostic buffer, there is a button to save the entries as a text file, which can be uploaded to the forum. Many here are experts on this kind of proble, maybe we can give more precise help.

Hope this helps,
Daniel Chartier