Very Slow Getting Online to SLC 5/05 Over Ethernet

[queenslandpommie 0]

We have an SLC 5/05 on our automation network, one of several SLC 5/05 processors on site.  It functions perfectly well and no ethernet messaging issues or SCADA drop outs.  The difficulty I am experiencing with it is when I am required to fault diagnose it takes a very long time to get online to it with our laptop running RSLogix500.  It sometimes takes as long as 10 minutes.  It makes no difference whether I use the Ethernet devices or the EtherNet/IP Driver in RSLinx, it nearly always takes an age which is frustrating in a breakdown situation.  I don't ever experience these long wait times connecting to any other of the SLC 5/05 controllers or any other controllers for that matter.  Once I am connected to the problematic controller I don't experience any issues, it's just the initial time getting online.  I try to leave the laptop permanently connected to it to avoid the long wait time to connect.  When I open RSLogix500, select Comms, Who Active Go Online, Ethernet devices driver, I can see that the problematic 5/05 has Active as its Status whereas the other 5/05 processors have Remote Run as their status.  Please can anyone advise as to any possible program parameters, RSLinx settings or hardware faults I should be looking for?  I have considered it could be a network problem but I'm unsure about this given how the processor performs well in every other regard.

Neil

Edited 23 Feb 2022 by queenslandpommie
grammar and spelling

[pturmel 157]

Bad cable is quite possible.  Packet dropouts due to a bad cable will cause extreme delays due to TCP retries.  Similar behavior if the SLC's ethernet port itself has become flaky.  No fix for the latter, naturally.

Another possibility is that your SLC has been set to throttle external messages.  See this:

https://forum.inductiveautomation.com/t/typical-performance-between-ignition-and-ab-slc-5-05/17262/3?u=pturmel

[queenslandpommie 0]

Thank you pturmel, I can see that S:/15 is set so I have written it to zero.  I'll see how it goes.  Before changing it I actually got online to it really quickly - Murphy's law.  Time will tell.  I'll be honest, I have considered a bad cable but it is such difficult cable run through several difficult to navigate ceiling spaces that pulling in a new one is the last thing I want to try.  Thanks again.

[BobLfoot 301]

@queenslandpommie Before replacing the cable you might want to run a simple cable test on it.

Fluke Corp and others make Ethernet Cable Testers that will measure the cable length, locate the "bad" spot and a bunch of other parameters about an existing cable.

Of course this means unplugging it at both ends and have a minor amount of downtime.

IF you don't own a cable tester you might find a vendor or electrician with one they would loan for a modest gratuity.

[pcmccartney1 141]

Might I also add for SLC and MLX, you should always have at least one service interrupt (SVC).  Usually, second to last rung.  This always for outside devices to have a time slice to talk to the SLC for devices like the SCADA, other PLCs and your PC.

My last rung was always an unlatch of the math overflow error.  This gives you a chance of diagnosing the offending logic that's causing the processor to fault.