Comms error help please

I am after some advice please. I have a plastic labeller which frequently goes to comms error just after it has been switched on.

The PLC (315-2DP) goes to stop and the comms error Led on the Lauer HMI comes on.

I have interrogated the PLC in the diagnostic buffer and it would seem that the reason for going to stop changes every time.

I get messages saying:-
STOP caused by diagnostic interrupt (OB not loaded or not possible, or no FRB)
FC number 101

Distributed I/O's: station return
Address of the affected DP slave: station number 4

The next time it stops, the message is the same but a but a different station number.

I was wondering if maybe this might be a timing issue. i'm not very clued up on the profibus side of things and thought that perhaps all the nodes ( 7 of them) have to synchronize and start up.

All the profibus cables have been changed and the grounding re-made.

Any ideas would be most welcome.

kevbloke said:

I was wondering if maybe this might be a timing issue. i'm not very clued up on the profibus side of things and thought that perhaps all the nodes ( 7 of them) have to synchronize and start up.

Click to expand...

It's possible I suppose, if you're powering everthing up simultaneously, that your PLC is finishing it's startup routine and starting to solve logic before your DP slave network is completely up so you have a race.

You could add the error OB's to your program so that the CPU would continue running through this fault - probably OB82, OB86, OB121, OB122 in this case.

I would suggest that you add some code to identify DP errors etc that would be masked out by the addition of these OB's, once the system is fully started. For example it's pretty easy to configure SFC51 to monitor your DP slaves and generate an alarm on failure.


Kevin H
(the other kevbloke from Kent)

Thanks for your reply Kevin, i will try to put that into action as soon as the ops release the machine to me.

Kevin H