1769 AENTR comm's on power cycle

John Morris

Lifetime Supporting Member
Join Date
Sep 2015
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San Antonio
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Hello all

Using 1769 L30ER, Studio 5K v29.11.

The unit has 16 modules, 8 local, and 8 remote.

On power cycle the 1769 AENTR is giving a major fault on communications with two 1769 OW16/A and a 1769 IF8/A modules on the remote rack.

The RPI is set to 80 ms, for all remote modules and I dialed down the chassis size from 31 to 11 during install ( no selection for 8 ) the ports are configured for auto negotiate and running full duplex

I do not have specifics on the exact verbiage of Fault or a code, but it basically is says it hasn't had any communication in x amount of time for these modules.

Once the fault is cleared, there is no issue, machine runs perfectly. This is only a power cycle/start up issue.

Please accept my apologies for not provide complete information, but it's being relayed to me from 1800 miles away.

Any and all help with this issue is greatly appreciated.

Thank you for your time.
 
I have heard that some Ethernet switches require more time to boot on power up than do the PLC's Ethernet modules. This could result in the error that you are experiencing.
 
I have heard that some Ethernet switches require more time to boot on power up than do the PLC's Ethernet modules. This could result in the error that you are experiencing.

I agree, but there has to be a way around it. this is a way too common device for this to be the only time it has happened.

Still trolling through the RW manuals.
 
Look into what the fault code is, and exactly how it is cleared.

If it's a fault of the CPU itself, then the issue is probably the "major fault if connection breaks in run mode" selection for the 1769-AENT or one of the modules. You can experiment by simply disconnecting the AENT once the system is up and running.

Are there any managed switches in the system ? It's possible they're going through a startup process that interferes with the 1769-AENT, like if they start up and then apply their IGMP Snooping filters later.
 
Ken,

Its a stand alone unit, the local and remote are in the same cabinet. No managed switches. All of the modules are check boxed for the "Major Fault if connection breaks"

The CPU acknowledges the "Request to Run" but can not because one or more of the modules is not communicating", Basically pointing the finger at the AENTR, who's pointing the finger at the thee cards

That put's us in a Major fault category at the CPU from the AENTR. As soon as it's cleared, there's never a comms problem.

I don't know Ken, I did something wrong, just haven't figured it out yet, The real smack is it's very intermittent too. Cycle power nine out of ten, nothing.

Unit is just south of Alberta. Can't get my hands on it. But my counter parts says just clearing the fault after start up sets it right. I'll try and get him to give me the fault codes tomorrow.

I'll be working this all weekend till I find something.

Thank you for the feed back Ken.
 
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Can you detail the I/O layout, in particular the location of the power supply?

Are you aware that all 1769 modules have a power supply distance rating - i.e. a maximum number of slots that you can have between a power supply and the card? If you have modules too far from a power supply, you can get intermittent issues with the connection to the modules.

Also, does the remote chassis have the end cap (1769-ECR) fitted? That will also usually cause modules to not show up, although it's usually more of a "permanent" problem than an "only at startup" problem.

Can you clarify this statement, as well? I'm not sure what you mean, but my spidey senses are telling me that it might be relevant...

... I dialed down the chassis size from 31 to 11 during install ( no selection for 8 )...
 
ASF

Thank you for your reply.

I/O-- (LOCAL) L30er ,IA16,IA16,1A16,IA16, PS ,IA16, IA16, OW16, OW16, ECR

I/O--(REMOTE) AENTR, OW16, OW16, OW16, OW16, IR6, PS , IF8, HSC, IQ16, IQ16F, IQ32,ECR

On the AENTR, I selected the chassis size as 11 slots.

The underlined modules are the ones that are slow to communicate

Correction: on the original post I stated 8 remote modules. The remote unit has ten modules.
 
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the consequence is not predictable, in my experience
the reality is that the power supply placement is not in compliance with the manufacturer's recommendation.
we really don't know the exact and precise meaning for the recommendation - and it doesn't matter.
.
correct the problem by moving the power supply.
 
Tarik1978, jdbrant,

Thank you for your feed back

Since this was my first time with this platform, I consulted my RW distributor for the set up. This was his recommended configuration.

Now questioning his knowledge, I have checked Rockwell Automation Publication 1769-TD005K-EN-P - January 2017, pg 9, line 5, column 3, Power supply distance rating for the L30ER compact logix controller, " 1769 Compact I/O modules: 4…8, depending on module".

Publication 1769-TD008A-EN-P - January 2010 for the 1769 PA4, pg 7, line 14, column 3, "8 I/O modules can be connected on either side of the power supply for a maximum of 16 modules"

Rockwell Automation Publication 1769-TD007D-EN-P - May 2014, pg 6 Technical Specifications - 1768 and 1769 EtherNet/IP Modules, the 1769 AENTR doesn't have a distance rating, just a PS recommendation, 1769 PA4

I would ask my rep, but he's MIA till Monday. (twerp)

The controller is not really the problem, the major faults all culminate with the AENTR unit not communicating in a timely manner with the three cards on the remote side.

Things we have tried and checked today, uncheck the “major fault” box on the connections tab of the AENTR, and lower all the RPI’s to 2ms on the remote side, and checked to make sure the port speed on the controller and the AENTR are the same, and lower them if possible. I haven't heard back yet on the impact these changes made, if any.

This is not a high speed machine and it doesn't have to work at warp speed like say a bottling line would, and after the initial start up/power cycle fault is cleared the machine works perfectly.

It's quite the puzzler..

Thank you both for your time and helping me explore all options.
 
Question

On the date/time tab of the CPU properties I have the "Time Synchronization" box checked. Could this have anything to do with this issue.

I haven't found anything in any of the publications or manuals, and the web seems to have next to nothing on the subject.

Any direction would be appreciated.
 
Now questioning his knowledge, I have checked Rockwell Automation Publication 1769-TD005K-EN-P - January 2017, pg 9, line 5, column 3, Power supply distance rating for the L30ER compact logix controller, " 1769 Compact I/O modules: 4…8, depending on module".
This document specifies a distance rating of four for the CPU, ("Controller and 1769-SDN: 4"), clarified in the next column over as "3 I/O modules between controller and power supply". I/O modules have distance ratings varying from 4-8 as noted.

This being the case, your setup is not technically correct - there should be only three modules between CPU and PS on your main chassis. I think it's unlikely that this is related to your problem, but if you get RA tech support involved, that'll likely be the first thing they'll point to. The good news is that moving the power supply does not affect your slot numbering, so if your wiring length allows, you could move it one slot to the left without affecting anything, and at least you can rule that part of the puzzle out. Your OW16's have a distance rating of 8, so no issues with the modules on the right of the PS.
Publication 1769-TD008A-EN-P - January 2010 for the 1769 PA4, pg 7, line 14, column 3, "8 I/O modules can be connected on either side of the power supply for a maximum of 16 modules"
True, although not quite the whole story. You couldn't connect 8x OB32's to one side of a power supply, because they only have a distance rating of 6. You could connect 2x OW16's and 6x OB32's, as long as you put the OB32's closest to the PS and the OW16's at the end. In any case, all of your I/O modules are within their respective power supply distance rating, so it's unlikely that this is the cause of your problem.

Rockwell Automation Publication 1769-TD007D-EN-P - May 2014, pg 6 Technical Specifications - 1768 and 1769 EtherNet/IP Modules, the 1769 AENTR doesn't have a distance rating, just a PS recommendation, 1769 PA4
This document states on page 37: "The adapter has a distance rating of five, therefore the adapter must be within five modules of the power supply." As before, this means only four modules are permitted between the AENTR and the power supply - and you have five. This could quite likely be the cause of your problems - and again, even if it's not, RA will be no help until you make it right either way. Once again, you should be able to move the PS without upsetting anything else - all your modules will still be within their required distance rating.


Things we have tried and checked today, uncheck the “major fault” box on the connections tab of the AENTR, and lower all the RPI’s to 2ms on the remote side, and checked to make sure the port speed on the controller and the AENTR are the same, and lower them if possible. I haven't heard back yet on the impact these changes made, if any.

Unchecking the major fault will stop the PLC from faulting out, but does not address the cause of the problem. It only masks it. What are the consequences of the machine trying to run with three I/O modules out of action?

Lowering the RPI will make things worse if anything - if you're already struggling to communicate with the cards, trying to do it faster won't help at all.

My approach from here would be:
1. Restore all settings to what they were previously to start from a level playing field
2. Move power supply modules to correct locations and monitor
3. If no improvement, make sure all bus connecting plugs/levers are clean, dry, corrosion free, and properly engaged. Unplug and replug a few times and make sure it feel solidly engaged
4. If no improvement, swap some of the suspect modules with known good ones from elsewhere in the chassis, to see if the problem follows the module or the position
5. Go to the pub and drink beer until you come up with another idea that's so crazy it just might work 🍺
 

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