Problem with communication Siemsns S7 - HMI

bm1209

Member
Join Date
Nov 2012
Location
warsaw
Posts
1
Hello,

I have an annoying problem with communication between Siemens S7 PLC and HMI panel. Here it how it looks like:

I am using Siemens S7-315 with 343 Lean ethernet port. This port is used to communication with HMI terminal. Communication is realized through S7-TCP communication protocol.

When I was testing the communication in the office everything worked fine and nothing wrong happened. The problem occururs only on the installation.

After turning the PLC and HMI on everyting works fine, data is transferred correctly and variables are displyed on HMI. After a few hours the communication is suddenly lost.
This is a direct connection between PLC and HMI and there are no other devices in this network. So it is not possible that suddenly there is an address confilct.

I made a wireshark analysis (I connected a notebook and hub into the network) and I found out that when the communication is lost HMI terminal is trying to get data from the PLC but it is not responding. It looks like PLC ethernet port is broken. You cannot ping PLC from notebook and HMI. On the other hand you can exchange pings between HMI and notebook.

The communication is back again only if you'll restart the PLC.

The strangest thing is that I did not have any problem with the communication when I was testing it in the office. The configuration and project of PLC and HMI is excactly the same. The only difference is that on the installation PLC is realizing also a communication throguh Profibus and MPI.

I've tried to use different ethernet cables (crossed, non-crossed) but in all cases the situation is the same.

Do you know waht can be the cause of such behavoiur? Maybe someone had similar situaion?
 
Hello,

Maybe there are some distributions on site, that's why in office everything is OK, but on site - not. Check Ethernet cable, check grounding.

Best regards
 
Hi,

Do you have extra HMI or SCADA connecting to the PLC. In the hardware configuration CPU Properties, there is an adjustment of how many HMI communications is the CPU going to have.


Best regards,
Kelkoon
 
Sounds like there might be a duplicate IP? Do you have the PLC connected to a larger network?

I have run into the same issue with an iX HMI. Those screens will disable the port if it detects a IP conflict.
 
Some more informations about this issue:

1. We have 315-2AG10-0AB0 with firmware in version 2.6.11

2. When we switch to online mode we can see the same number of occupied and reserved OP Communication (4. Communication.bmp)
https://drive.google.com/file/d/0BwM-cxgAb3LPUDRWY3BCcW5mWkk/view?usp=sharing

3. After 7-12 hours communication is lost and we can't ping CP (343-Lean). In online mode it's like CPU doesn't see this module. (6. online.bmp)
https://drive.google.com/file/d/0BwM-cxgAb3LPMjdCb21fTG9BMFk/view?usp=sharing

4. Is not possible to diagnose CP343 (7. CP343.bmp)
https://drive.google.com/file/d/0BwM-cxgAb3LPUEJmUVNlTXBJOVk/view?usp=sharing

5. Next we change number of OP Communication to 4, but problem is still occurring. (8. newOPcomm.bmp)
https://drive.google.com/file/d/0BwM-cxgAb3LPS2hXZEMzdHQ4WWs/view?usp=sharing

Diagnostic buffer from PLC:
https://drive.google.com/file/d/0BwM-cxgAb3LPcDlYWkdHNE12bW8/view?usp=sharing
 

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