Hello,

I'm running a 1513-1 PN CPU, Firmware V2.1.0. Randomly the PLC started losing connection to its Profinet devices (mainly remote IO and Siemens VFDs). The diagnostic buffer shows error messages for around 10 seconds, after which it appears communication is restored. After this first occurred it happened 1-2 times per day for a couple days 12+ hours apart from one another, then nothing for two weeks, and then it happened again today.

Because it happens so randomly we're not sure how best to troubleshoot - we're logging pings to the PLC from a PC on the same network but when the dropout occurs the pings still go through fine. Attached is the PLC's diagnostic buffer, though it's mostly full of "I/O read access error" from devices it's losing communications with.

Any ideas are appreciated and let me know if you need more info. Thanks!

Hi,

are there any switches between the CPU and the affected IO devices?
If yes, are these PROFINET (which prioritizing PN protocol) certified switches, or standard ethernet switches?
Is a line topology used and are devices affected at the end of the line? If yes, rework topology to optimize the distribution of communication load.

According PN standard, the communication load should be at 20% max. Even with a communication load of 20% or more, the PROFINET standard recommends thinking about better distribution.

regards

sancruz

Hi LucasFWB,

can I ask some very basic questions?  Any recent modifications / installations of power cables in the near vicinity of the profinet cabling?  Is the installation of the copper cabling sound, devoid of possible interference?

Hi fritz, thank you very much for the reply. I'm glad you find this problem "wonderful"; I wish our operators felt the same way ;-) I'll try to answer your questions as best as possible:

- Attached is an overview of the Profinet network

- Send clock is set at 1ms

- Update times for all IO and VFDs is set to 2ms (average PLC cycle time is ~50ms so doesn't seem like this needs to be so quick?)

- We have an HMI PC, the Scalence switches mentioned above, as well as several other pieces of equipment with their own controllers that we're communicating with via Modbus with the "MB_CLIENT" instruction

- I hadn't done a netload calculation (didn't know what it was before you mentioned it). I entered it in a calculator I found online and looks like it thinks the packet rate is overloaded. See attached

- The PLC is on a gateway making it accessible to outside networks. Next troubleshooting attempt I will be disconnecting it from any external networks

Once again, thank you for the detailed questions!