Help with an error on a Modicon M340

[bigorno]

Hi everyone,

I am quite new to PLC programming and I'm facing an issue I haven't been able to solve on my own. After a ladder logic update from Unity Pro S, the PLC entered error mode.

The processor M340 - BMXP3420302 has :
- its "err" led on (red)
- its "can err" led on (red), even though I'm not using CanBus.
The adjacent IO module (BMXDDM16022) has its "err" led flashing (in red).

According to Schneider documentation, this correspond to a processor, system or configuration error (https://www.schneider-electric.com/en/faqs/FA221750/).

* I cannot connect to the PLC anymore, I can't even ping it. I reset the IP to the default one using the rotary switch (set on clear IP), but I still can't join the PLC. The PLC does not even send any gatuitious ARP request on reset.

* I used Unity SD Card writer to set the ladder logic back to a previous version (which I know does not bring any issue), but the PLC state did not change.

Thanks in advance for your help.

 

[Saffa]

Have you tried connecting via USB? I've always found this pretty reliable if there's a messed up configuration.

What version of Unity and what firmware is the processor? There are compatibility rules but I'm not sure what happens if you ignore them.

 

[bigorno]

Hi Saffa, thanks for your answer

Yes I tried connecting via USB but the device is not detected. I never used the USB connection before, so this may be an independant issue.
I'm using Unity Pro S V8.0.
For the processor firmware version, I don't know how to check it as I can not connect to the PLC.
What I can tell is that this version of Unity Pro should work with the firmware, as I updated the ladder logic several times without any issue.

 

[Lare]

When you used Card writer, are you absolute sure that you didn't format SD card to Windows format. If you formatted SD card to FAT-format, then card is useless.
Also did card writer recognize SD card and writed program to SD card.

https://www.schneider-electric.com.hk/en/download/document/SD+Card+WriterTool/

Try USB and properly shielded USB 2.0 cable. USB is 1st method

 

[bigorno]

Yes I'm absolutely sure, I had already read that I shouldn't do it.

The card writter did recognize the SD card, and writted program to the card without any error. I just did it a second time to be sure.

Windows does not detect any device when I connect the PLC via USB. (it does not appear on device manager).
On reason could be that the cable is broken, I will try with another one tomorrow (I don't have any other right now), and I will tell you whether it works.

 

[Lare]

So, when you resetted IP back to default you tried this IP?
https://www.schneider-electric.co.uk/en/faqs/FA22767/


And when you tried transfer with SD card you tryed as described page86 and step3 forward?

http://www2.schneider-electric.com/...00/FA289478/en_US/M340_CPU_CPS_RACKS_2015.pdf

also

https://www.schneider-electric.co.in/en/faqs/FA166251/

 

[bigorno]

* Yes, I used this page to get the IP address. The MAC address is 00-80-F4-11-97-66, so I used the IP 84.17.151.102. I also changed the IP of my host to 84.17.151.105 with mask 255.255.0.0 so that they be on the same subnetwork. I'm using a tested RJ45 cable to connect the CPU directly to my laptop.

* I did not exactly follow the procedure with your link, as I have only one SD card, but from my understanding it is equivalent, appart from the fact I could not set bit %65 to 1 for obvious reason. What I did :
- I removed the SD card, the CARDAC led was off.
- I used the SD writter to write the new application
- I put it back in the CPU
- I push reset
It has to be noted that the CPU is not in STOP mode (run led flashing), but in OFF mode (run led off : PLC is not configured (application is invalid, incompatible or absent)).

* I tried this morning to connect via USB with another cable (which I tested), but the result is still the same, the device is not even detected (tested with two different OS on two different workstations).

* One point that may be interresting : according to the discrete input/output module on page 61 :
eshop.schneider-electric.com/Download.aspx?infos=H513816_2.pdf;3
The flashing err led means that the communication is lost between the discrete module and the CPU. Furthermore, I can hear a light whistle coming from this module, which I am sure was not present before. Could it be that the problem comes from this module?
One hypothesis could be that the connection between the two modules is broken. As the project was built with such a module, the actual configuration does not correspond to the project, hence the error. However I guess the PLC should still be accessible...

I am going to load a blank project to the SD card with no discrete IO module, physically remove this module and see what happens. I don't have any other idea...

 

[Lare]

Unity CPU stays at run, even if there is faulty modules on rack.
You can remove io-module and chack if it makes difference for situation.

If your CPU don't run with blank program, then there is some fault. CPU, Memory card, rack or power supply is faulty.

Have you spare CPU for testing?

 

[bigorno]

So I removed the IO module and tried with a blank program, loaded directly on the SD card. The result is still the same.

I'm wondering what is the use of the %65 bit : is it just to end any ongoing action with the memory card, or is it putting the CPU in some state before update? Is there a way to check that the blank program is indeed loaded in the CPU unit?

If I remove the SD card and push on reset, the 'err' led is flashing (equivalent to 'application is absent', which is normal, , 'ethlk' is green and "eth sts" is flashing. And, more interresting, I can ping the device (though still not being able to connect through Unity).

Concerning the USB connection, I had confirmation with someone who worked on this PLC before that it was already not working (but I don't know what was the issue).

Unfortunately I don't have any spare CPU...

 

[tragically1969]

Unfortunately I don't have any spare CPU...

Probably not much use to you but sounds like you need one....