AB 1756-ENBT stops

GreyVlad

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Join Date
Sep 2022
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Kursk
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My company has an AB 1756 PLC set including one 1756-ENBT module with static IP address. About two weeks ago the module began to stop working after an unpredictable amount of time with "Stop OS" or "EXCP 300" message on its display. Other modules (and a CPU module) are all in OK state. There is no major nor minor fault messages in a CPU.


After power cycling the 1756-ENBT is in OK state. Firmware version is 4.008. After an amount of time from 1 hour to 1 week it stops again.
(After second or third power cycling it forgot its IP address. I gave an address to the module using the AB BOOTP server.)


What spells or manipulations could make the module work a long time? Or maybe i just should throw away the module and search a way to buy the new ENBT?
 
Thank you, dmroeder. For me your answer is just like a daylight at the end of a tunnel.
ENBT firmware upgrading via its ethernet interface should not affect a program running in a 1756 CPU? May I leave a CPU key in a RUN position when upgrading?
 
You can upgrade the firmware of the ENBT with the CPU in place and powered on. Of course, the ENBT will be out of commission during the upgrade, so anything being controlled by it will not function. I would stop whatever process this controller is controlling during the firmware upgrade. To be extra sure nothing will happen with the equipment, you may consider having the controller in PGM mode during the upgrade.
 
Thank you, dmroeder. For me your answer is just like a daylight at the end of a tunnel.
ENBT firmware upgrading via its ethernet interface should not affect a program running in a 1756 CPU? May I leave a CPU key in a RUN position when upgrading?

Hi and welcome to the forum.
If I recall, one needs to be offline and then one may upgrade the firmware. After the new firmware has been installed, you will more than likely need to change the version using the dropdown for the main version from the "change" button on the general tab from the "module properties" page while you are still offline. You won't need to power down. Hope this helps.

Not typing fast enough lol!
 
Thank you for your answers and words of welcome, gentlemen.
I'll try to do upgrading next week when I get to that site, because on Friday the ENBT stopped again, so I got no remote access to the PLC.

I will write here about my success or failure or my questions.
 
I upgraded the ENBT yesterday to 6.006. I registered the EDS file and the module passed the test and began to work, but today it stopped communications again.


The ENBT is connected to the small ethernet switch. And just one PC with RSLinx and RSView32 is connected to the switch. There is no another devices connected.

I am going to change the switch to another one and the ethernet cable to another one. If no results, I am going to search another ENBT module.


The question is: may I pull the module out from the rack and push it back into its place when the PLC power is turned on?
 
This time the displayed message was just "Stop OS".


Is it possible to downgrade the ENBT firmware rev 6.006 to 4.003?
 
...

The question is: may I pull the module out from the rack and push it back into its place when the PLC power is turned on?


Yes you can. ControlLogix is the only platform I know of that allows hot-swapping modules.


This time the displayed message was just "Stop OS".


Is it possible to downgrade the ENBT firmware rev 6.006 to 4.003?


Yes, you can.

The only tech note I can find regarding the "Stop OS" message says that it can occur in older models when there are a lot of safety I/O modules connected to it. That anomaly was fixed at v4.006, so it's probably not related to your issue at all.


When it's locked up, can you ping it locally? If so, try to open the diagnostics web page (type its IP address into your browser) and see if there's any useful info there.



Do you have another -ENBT module to test?



I don't have any ControlLogix parts available to test with any more, so I can't give a lot more insight. Hopefully someone with more expertise can chime in.
 
The ENBT module disconnects itself totally. Its small rightmost LED is steady red, other two small LEDs are not lighted. The message "Stop OS" is steady green.
I can't ping it. And RSView32 HMI screen displayed just empty places, no data.


May the module be too old and incompatible to firmware rev. 6.006?


Or may be, our program (.acd) that running in the PLC was downloaded from very old and incompatible Logix5000 version?
 
I would definitely not expect either of those to cause the symptom you're seeing. I've had 1756-ENBT modules working great with I/O connected to old 1756-L55 controllers at v15-16, so I doubt your project version is an issue. According to Rockwell's download site, FW v6.006 is the latest and should run fine in your ENBT.

One of the things that AB does sometimes is take down manuals for older models. It's horrible and one reason I've kept all of the manuals I ever download to make sure I can access them. The 1756-ENBT was covered by the "EtherNet Modules Installation Instructions" I have from June 2011 (publication ENET-IN002A), which covers the status indicators. Solid red OK light means:
The module detected an unrecoverable major fault. Cycle power to the module. If this does not clear the fault, replace the module.

When trying to get to that manual from their website, it says it's been replaced by others based on catalog numbers. It says the latest installation instructions for the 1756-ENBT is pub 1756-IN019D, which doesn't cover the status indicators. It has a note referring you back to ENET-IN002, which doesn't exist any more. I tried uploading my copy here, but it's too big.
 
Now I have found a laptop with RSLogix v15 installed, the one and only RSLogix that I can find now.
When I connect to the PLC via the ENBT and go online, I can see that there is no ENBT module in the I/O Configuration folder in the Controller Organizer window. Other I/O modules are there.


May be, it is the reason why the ENBT stops working?


When I try to add the ENBT module in the I/O Configuration folder, there is no revisions above revision 3 (no 4, nor 5 nor 6).


Is it absolutely necessary to place the ENBT module to I/O Configuration folder?


Is it possible to add more ENBT revisions to RSLogix v15?
(If not, then I will try to downgrade its firmware to rev.3)
 
What is the probability of the same problem occurring if I obtain another ENBT module with firmware rev.4.003 and just put it into the PLC rack instead of my (probably) broken one?


Is RSLinx able to automatically switch to relevant lesser revision of the EDS file?


Gentlemen, what do you think?
 

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