Data highway needs PMCK Cable not to fault??

I have ran into something this morning I have never seen before. I took over a problem from the 3rd shift guys. We have a line with 9 AB Slick 500 5/04 processors. We are getting a cycle time over on one of the functions on one of the plc's. It seems to only do it if you disconnect my laptop from the DH. Midnights had the same results. Connected through PCMK at 57.6. Think it must be effecting the scan time but not sure. Anyone else ever saw anything like this?

yes ive seen weird stuff on dh+. I actually had my error bits trigger with timeouts. I eventually got fed up with it and wrote a routine that reinits the MSG after it fails.

These types of "weird" problems have been discussed many times here. About 90 % of the time the problem is the same.

Check every phoenix connector on the line, every one of them. Look for things like a shield hair touching one of the conductors, loose terminals, etc. Secondly make sure your terminating resistors are in the right spot and are the right size.

DH+ connections can definately be affected by plugging in/unplugging devices... especially if the device has the token at the time. Then the network has to time out and cycle around to restart the token sequencing.

cycle time over on one of the functions on one of the plc's

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What does this mean, exactly ? My guess is that you mean a watchdog fault, but you might mean a machine cycle.

Does the problem occur immediately when you unplug your laptop, or does it happen only during time periods when your laptop is unplugged ? Is your laptop online with the controller when you get the fault ? Are you performing edits ?

Maybe the DH+ signal is marginal and the addition of the 1784-PCMK stabilizes it. Maybe there's something going on with the memory of the SLC. You need to investigate and post more information.

Are you "Online" with any of the processors when you unplug? How about browsing the network in RSLinx?