Re: [foxboro] Foxboro CAR# 1003753 Communication Problems on Nodes with Node Bu s Extenders
- From: "Schouten, Frits JF" <Frits.Schouten@xxxxxxxxxxxx>
- To: "'foxboro@xxxxxxxxxxxxx'" <foxboro@xxxxxxxxxxxxx>
- Date: Thu, 10 Oct 2002 13:20:33 +1000
We are having this DNBX problem for years now.
Very slow display updates, often cyan points, regular reboots required
(lockups).
The operators don't complain anymore. They are past the point of blaming me
for the problem. They have just given up......
Foxboro is still looking at it. Must be very complex. A CAR is filed long
time ago.
Just the other day a local rep came around to collect more data.
My 5cts worth.
Cheers,
Frits Schouten.
-----Original Message-----
From: tom.vandewater@xxxxxxxxxxxxxx
[mailto:tom.vandewater@xxxxxxxxxxxxxx]
Sent: Thursday, 10 October 2002 14:42
To: foxboro@xxxxxxxxxxxxx
Subject: [foxboro] Foxboro CAR# 1003753 Communication Problems on Nodes
with Node Bu s Extenders
List,
I have just submitted a CAR regarding Communication Problems on Nodes with
Node Bus Extenders! A description of the problem, symptoms, and work-around
follows. I urge all of you that are experiencing this problem to submit a
CAR also. You are welcome to cut and paste my text directly into the CAR.
This list is a great forum to communicate both the good and the bad about
Fox IA and represents a good cross section of users. The CAR system is the
only "formal" way we have to define problems to Foxboro. Let's use it to
our advantage!
Tom VandeWater
Control Systems Developer/Analyst
Dow Corning Corp.
Carrollton, KY USA
We have been aware of a problem on nodes connected via
NBE's, (Nodebus Extenders), or FONBE's, (Fiber Optic Node
Bus Extenders), since Feb of 2001. Although the potential
for the problem appears to have existed from the early days
of NBE's, it occurs much more frequently on nodes using
newer stations such as CP-60's and AW-51D's. When we
started installing this new equipment on nodes with
NBE's/FONBE's we began having serious nodebus
communication problems!! We worked with Foxboro to
identify the problem so it could be fixed. Craig Ouellette of
Foxboro submitted CAR # 1001833 on our behalf on June
14th, 2001. Because we didn't submit the CAR ourselves it
has been a struggle to get any information on its status.
The nodebus communication problems caused by
NBE/FONBE's are understood by Foxboro and are quite
complex. They can cause individual stations to switch
busses from "A" to "B". This can cause information transfer
between stations to dramatically slow down or even cease
to happen. FT stations cannot stay married and divorce their
partners, (especially noticed with FTCBLAN modules), and
NFD reports intermittent cable failures on the nodebus. We
have seen these symptoms on several nodes that have
NBE's or FONBE's but never on nodes without them. From
discussions with other users, it appears that DNBX's have
caused similar problems to occur and the problems may be
related. We don't use DNBX's so I can't say for sure. I have
forwarded a lengthy document to Foxboro that talks in detail
about the problem and our history with it.
Our work-around solution has been to cause a physical
failure on the "B" nodebus by pulling a terminating resistor
for "B" on each segment that is connected by a set of NBE's
or FONBE's. This insures that the "B" cable test will never
pass and will remain failed. The failed cable is recognized by
all stations and keeps them from switching to it. When all of
the stations communicate only on the "A" nodebus the
problems are masked but if a physical fault in the "A" bus
occurs we have no backup. At this point I feel more
confident in the reliability of the single "A" bus than the
quote/unquote reliability of the dual bus using NBE's or
FONBE's.
We have heard for a year and a half that a solution is being
worked on for this problem but nobody is committing to a
timetable for the fix. In the meantime we have a significant
risk and are not able to utilize the dual nodebus on these
nodes. We fixed the problem on one of our critical nodes by
forcing all of our stations into a single nodebus segment, thus
eliminating the use of "Extenders" on that node. We no longer
have an issue on those stations!! This is not a viable option
for other nodes in our plant. We need a fix NOW!
I can forward another copy of the document in .pdf or .doc format.
It describes in detail the problem if anyone is interested.
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