1794 Connection Timeout

Greetings everyone,

I have a Compact Logix L35E processor communicating to 2 1794-AENT flex I/O modules. I get a connection timeout on the AENT modules and their I/O. The timeout lasts about 3 seconds and always re-establishes. The cables test good, there are no bent pins on the AENT racks, and all the I/O modules in the AENT work properly. The connection timeout occurs every 5-7 minutes. I ran RSLogix5000 task monitor on the connection and everything looks normal from a traffic standpoint. I'm using an IGMP snooping capable switch to manage the multi-cast groups. All of my RPI's are at 750mS. Any ideas?

TIA,

Greg

Are the FLEX adapters the only devices connected to the CompactLogix over EtherNet/IP, or are they the only ones that are faulting their I/O connections ?

I've seen FLEX adapters have some problems with noise when they aren't well grounded through the DIN rain clip, but that's been very obvious by looking at the Ethernet communication statistics, with lots of FSC checksum and alignment errors.

Check the pins between the AENT & I/O base for any bend or improper connection.

this common problem in flex I/os

Hi guys,

Thanks for the quick response. I did check for bent pins, I've bent a few in the past and verified these are not bent.

Ken,

There are only 2 AENT modules communicating to the L35E. I read one of your posts last year using Ethereal when you triggered it using serial keys. Pretty cool, by the way. At any rate Ethereal shows we have a TON of UDP traffic, all Ethernet/IP. The traffic doesn't look like general broadcasts, but ENBT cards talking to specific IP's. I do know that in our plant there are a few ENBT cards which reside in the I/O configuration of the processor, which I know Rockwell says not to do.

I will verify proper grounding of the AENT modules tomorrow.

Greg

Ken,

Thanks for the message, I sent you an email.

Greg

Greg Dake said:

I have a Compact Logix L35E processor communicating to 2 1794-AENT flex I/O modules. I get a connection timeout on the AENT modules and their I/O. The timeout lasts about 3 seconds and always re-establishes. The cables test good, there are no bent pins on the AENT racks, and all the I/O modules in the AENT work properly. The connection timeout occurs every 5-7 minutes.

Click to expand...

I've been told by Rockwell to use steel din rail, not aluminum.

Greg Dake said:

I ran RSLogix5000 task monitor on the connection and everything looks normal from a traffic standpoint. I'm using an IGMP snooping capable switch to manage the multi-cast groups. All of my RPI's are at 750mS. Any ideas?

Click to expand...

750 ms is really slow
Have you looked at the ethernet statistics for the adapters and the L35E using the built-in http servers?

I had a strange situation with ethernet flex a while back where one adapter started dropping out regularly...on checking the stats on the web pages I found that the adapters were rejecting around 500 packets per second. Turned out the Hirschman switch defaults to IGMP snooping off. Although the switch had been previously configured to turn it on, the config had not been saved to the switch's EEPROM. Consequently, after a power cut the switch went back to default settings. Re-config fixed it.
Curiously, only one adapter was affected and it was the furthest from the switch.

Ken Roach said:

I've seen FLEX adapters have some problems with noise when they aren't well grounded through the DIN rain clip, but that's been very obvious by looking at the Ethernet communication statistics, with lots of FSC checksum and alignment errors.

Click to expand...

I've seen the opposite... We were having a similar issue. Upon recommendation from another engineer that had the same problem, we ripped off the ground clip on the back of the AENT and the problem was fixed. Who knows...

Grounded

I have properly grounded all modules involved per the special grouding practices outlined in the AENT grounding technote from Rockwell. I just did this and it appears the problem still exists. One interesting thing to note the connection timeout counter only increments in the L35E and not the two AENT modules.

Greg