Re: [foxboro] CP-60 Fieldbus Communication Errors
- From: tom.vandewater@xxxxxxxxxxxxxx
- To: foxboro@xxxxxxxxxxxxx
- Date: Tue, 22 Mar 2005 15:21:13 -0500
Shelby,
Thanks for the suggestions. We have paid a lot of attention to
proper grounding and our DCM's and 100 series FBM's are mounted in IE-32's
connected to ground in the manner specified by the document you referenced.
Our twinax runs are of minimal length, < 50ft, and just jump from between
one or two additional IE-32's in the same room. The twinax cable we use is
a "Foxboro approved" Belden cable. In fact most of it is the same cable we
used between the old CP-10/30/40's and the old style FBI's and we didn't
have communication issues until we hooked them up to CP-60's.
I am curious to clear up one thing you mention. You said:
"Unless you are running ladder logic in your FBMs, the fallback to rev. 1.11
will provide only marginal relief."
What relationship is there between running ladder logic in FBM's and
receiving intermittent fieldbus errors? I've heard similar statements
before but never heard an explanation.
I'm also interested to see if anyone can explain why all of the
intermittent fieldbus communication errors cease to report whenever you run
the CP fieldbus in "Bus A Disable Switching" or "Bus B Disable Switching".
Does the CP quit reporting fieldbus communication errors when bus switching
is disabled or could the bus switching strategy actually be the cause of the
communication errors? Nobody from Foxboro has ever explained what is going
on with that.
Even though the errors are a lot less frequent, we also get
intermittent errors on CP 60's that have only a short thinnet cable run to
the 3Com SuperStack 6 port fiber optic hubs and all fieldbus segments
communicate via FCM10EF's and fiber. Given that fact, I doubt that
grounding is an issue and it is more likely to be a fieldbus communication
timing issue.
I appreciate all of the feedback from Troy, Teresa, Ted, Robert, and
Dirk. To me, it still sounds like there may be more issues here than just
proper grounding or software/EEprom levels, and I look forward to any light
that could be shed on my questions about ladder logic or fieldbus switching.
Cheers,
Tom VandeWater
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