S7-1200 loses ET200s after restart

Hello all,

I am facing a strange issue I never came across before. I have a S7-1200 (1215 latest firmware) connected to an ET200s station (6ES7-151-3BA23-0AB0).
It worked ok for a couple of months, until the following issue appeared:

I there is a power cycle for the S7-1200 then when the PLC restarts it cannot establish communication with the ET200s. I can see it connect and disconnect probably every 10s. The problem is resolved by downloading the hardware configuration and the system is ok until the next restart.

I use S7 with ET200s & ET200sp extensively but I never came across a problem like that.

Any thoughts?

Regards Nik.

Diagnostic buffer ?

You have loaded the Device Name on the ET200S ? Is there a flashcard in the ET200S ?

The name is assigned and there is a MMC installed.

Do you see anything in the diagnostics of the IO device? You should be able to do "online and diagnostics" for the interface module as well.

You wrote that you could see that the ET200S connects and disconnects every 10 sec.
What do you base this observation on ?
If I interpret the diagnostic buffer correct, then the ET200S never succesfully connects.

Can you see the ET200S, when you use the "Assign Device Name" in STEP7 ?
If so, does it have the correct Device Name already.
You havent by accidence turned topology on ?
Is there anything else on the network, apart from you PG, the S7-1200 and the ET200S ?
How is the ET200S connected to the S7-1200, directly, wia a switch, or how ?

@mk42
When the fault occurs the online and diagnostics for the RIO reports that there is no Data exchange with the IO-controller. I don't remember the exact wording but that is the content of the message.

@Jesper
I say that the ET200s connects and disconnects because I see in the Network view the ET200s station coming online and then disconnected and that repeats. In the diagnostic buffer you can see with the green tick when the station returns. Also when I look at the HMI when the station returns I can see that some values are updating.

Can you see the ET200S, when you use the "Assign Device Name" in STEP7 ?
Yes I can.

If so, does it have the correct Device Name already.
Yes it has the correct name even if the PLC is switched off.

You havent by accidence turned topology on ?
What do you mean?

Is there anything else on the network, apart from you PG, the S7-1200 and the ET200S ?
There are a lot of other devices in the network. 4xS7-1200, 1xS7-1500, 3xET200s, 4xBasic panels, 3xcomfort panels.

How is the ET200S connected to the S7-1200, directly, wia a switch, or how ?
It was connected via the plant network with switches but I 've setup a direct ethernet cable from the ET200s to a switch next to the S7-1200 (inside the same panel).

I didn't mention that the S7-1200 is an I-Device to the S7-1500. I don't see that being an issue as I used this setup a lot in the past. The PN update times are set to 8ms (from 2ms) just to make sure that update times are not an issue.

I say that the ET200s connects and disconnects because I see in the Network view the ET200s station coming online and then disconnected and that repeats. In the diagnostic buffer you can see with the green tick when the station returns. Also when I look at the HMI when the station returns I can see that some values are updating.

Click to expand...

OK, I am used to STEP7 Classic that there are separate entries for Stations "disappearing" and "reappearing".

You havent by accidence turned topology on ?
What do you mean?

Click to expand...

Not sure if S7-1200 supports this, but with S7-300 and S7-1500, you can configure exactly how the network is interconnected in real life. That gives better diagnostics, but maybe it also make it more finicky.
You can see the topology-view tab next to the network-view tab in TIA (if it exists).

Is there anything else on the network, apart from you PG, the S7-1200 and the ET200S ?
There are a lot of other devices in the network. 4xS7-1200, 1xS7-1500, 3xET200s, 4xBasic panels, 3xcomfort panels.

Click to expand...

If you have the possibility to do so, try to connect the ET200S directly to the S7-1200, and remove evrything else. Just to see if makes a difference.

I see what you mean by topology. If you set up the HW in the topology view you tie the ports to their partners exclusively. I am aware of that but it is not the case here.
I dont think the other devices cause the issue. There is a cable from the ET200s to a switch which is next to the CPU. The CPU is connected to that switch with a 30cm patch cord. The switch is unmanaged.

A simple unmanaged switch can definitely cause problems.
Just try out my suggestion about disconnecting everything except the S7-1200 and the ET200S.
Am I right that there are 2 ports on the S7-1200 ? If so, I am guessing that the 2 ports are via an integral switch that is proper Profinet rated. If you connect one port to the ET200S, and the other port to the rest via the switch, does it make a difference ?

I don't know if this is applicable or not . . .
We have some CPU 416-2 Siemens PLC's. There is, in the 'panel application' for them an archive function and we archive them to a hard drive file then, on a power cycle, the PLC is supposed to reload itself from the archive file.

The vendor which set up the system sent us an update letting us know that the archive program does not capture the entire program inside the PLC, and gave us another procedure to use to make the archive file to reload the PLC from.

The new procedure works very well. (I don't think we ever tested the original archive function - the computer and PLC's are all on UPS.)

Any chance your PLC does the same thing on a power cycle - tries to reload off something that does not have all the program . . .
MadPoet.

I've definitely seen plenty of cases where there was a wierd network issue, and swapping the unmanaged switch for a managed one made all the issues go away. Other times, it works just fine, it depends what the unmanaged switch supports.

I second the option to try to connect the PLC directly to just the one IO drop, and see if the problem continues.