Re: [foxboro] RCNI

The NCNI connects to both the A and B Nodebus because we want the same
module to handle either the A or B bus. We don't want to sell and you don't
want to buy, a "left-handed" and a "right-handed" module. Can you imagine
the confusion?


To avoid such a situation, the NCNI sits on both busses and there is a
switch on the front that specifies either A or B service. Of course, you
could have both NCNI switched to the same network and cause problems, but we
humans don't make mistakes like that. :-)


Anyway, I'm pretty sure that the "internal magic" includes ignoring the
non-selected bus, but I have to admit that I've never asked.




Regards,

Alex Johnson
Invensys
10707 Haddington
Houston, TX 77063
713.722.2859 (office)
713.722.2700 (switchboard)
713.932.0222 (fax)
ajohnson@xxxxxxxxxxx <mailto:ajohnson@xxxxxxxxxxx> 
For the latest information on ArchestrA, go to
www.invensys.com/Archestra.html
<http://www.invensys.com/divisions/Archestra.html> .


        -----Original Message-----
        From:   Corey R Clingo [SMTP:clingoc@xxxxxxxxxxxxx]
        Sent:   Wednesday, January 15, 2003 10:19 AM
        To:     foxboro@xxxxxxxxxxxxx
        Subject:        Re: [foxboro] RCNI



        "The NCNI takes two 10 Mbps Nodebus inputs (bus A and bus B) and
produces
        ONE
        100 Mbps Ethernet output to one of the Control Network switches (A
or B).
        It
        takes two NCNIs per I/A Series Nodebus to build a complete
connection to
        the
        Control Network. There is additional
        internal magic."

        Really?  This stuff gets more interesting all the time.  I wonder
why both
        nodebus segments have to connect to each switch.  Seems to open the
door to
        potential "crossed-cable" type problems.

        Corey


         
         
        
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