PLC’s CPU usage briefly goes to 100% and OPC communication breaks down if file is copied using FTP

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1

Hello,

We’re currently experiencing a new, strange behavior with the PLC’s FTP server. When we copy a file to the FTP server using a service we wrote (C# application), the PLC’s CPU usage briefly goes to 100% and OPC communication breaks down. This happened on a CP1584.

Does anyone else have problems with the PLC’s FTP server?

Best regards
Philipp

2

Hi,

I haven’t seen that until now, but maybe it’s really a CPU load topic.
So I have two more questions:.

  • how is the CPU load when not using FTP? Is is already (very) high?
  • Does it also happen when using a different FTP client, for example FileZilla?

Best regards!

3

Yes the CPU load is without using FTP already at around 68%.
It happens with FileZilla also, I always have short peaks to nearly 100% when copy a file to the PLC.

4

Hi,

okay, then unfortunately for me it sounds like a “normal” behavior of a priority based multitasking system like AR.

I assume that the FTP server process has a higher priority inside AR than the OPC UA process, and therefore a running FTP server operation gets/consumes the “remaining processing time that is available for low-priority programs” instead of the OPC UA process (“low-priority” in this context means more or less “everything that runs with lower priority then for example interrupt handlers, IO scheduler, all taskclasses, a.s.o.”).

But as I said, I can’t swear it: because don’t have access to hardware right now, I can’t proof (for example by doing a profiling), if it’s really that context I assume.
I recommend to contact the support team of your local B&R subsidiary to dig a bit more into deep.

Best regards!

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