CPU 317-2PN/DP Bus Faults

Hello All,

Recently we had a power surge on one of our machines that wiped out the SCADA PC.  After replacing the PC we rebooted the machine and now have bus faults on some of our field components (connected via Profibus).

 I can see the field buses blinking/triggering while they attempt to make a connection.  Not ALL of the field buses are showing this error.  I uploaded the diagnostic buffer file with this post.  I noticed that the "bad" components change every time i update the diagnostic. 

Can anyone provide some advice on where to begin troubleshooting with this.  I have already checked all of the ProfiBus connections and they are secure. I suspect the PLC might have issues due to the power surge but then I would also expect all of the field buses to show communication errors which is not the case here.

Thanks for your time and help!

If stations that fall out are changing, they are not constantly the same then I would say that bad connection or profibus cable broken/shorted to gnd  is the cause.

It has no big importance the position of the disconnected station, you can be easely fooled.  The signal reflects from problematic connection and then collides with new sent signal (sent for the station that dissapears) which it doesn't reach the station.

By the way, have you checked the terminating resistors?

Hello james r,

where did the power surge come in? Via 24V supply? Or is it possible it coupled on Profibus?

It would be helpful if you can post your HW-configuration with Profibus nodes and addresses for CPU.

Regards

Ah Marko,

I feel so silly for not checking the terminating resistors first.  My mind did not point to that way but I'm glad yours did.  There terminating resistor to the SCADA PC workstation was not switched ON.  Of course, when I switched it on everything was right with the machine.  Thanks for your help.

-James