Re: [foxboro] FCP's and "remote" I/O

Stan,

In another e-mail, you asked if this would work:

CP-+ -(cu)- FBMs
   |
   + FCM2Fx - (fo) - FCM2Fx - (fo) FCM2Fx - -(cu)- FBMs
------------         ------     -------      -----------
Std 4-port bp       2-port bp    2-port bp   Std 2/4/8 port bp 
                    |
                    | (cu)
                    |


I would say that almost. 

This configuration does what you want:

CP-+ -(cu)- FBMs
   |
   + FCM2Fx - (fo) - FCM2Fx + FCM2Fx - (fo) FCM2Fx -(cu)- FBMs
------------         --------------+-        -------       -----------
Std 4-port bp          4-port bp   |       2-port bp       Std 2/4/8
port bp 
                                   | 
                                  (cu)
                                   |
                                   +--(cu)-- FBMs

That is, you can split the copper fieldbus off at the 4-port baseplate
in the middle I/O drop and make another jump using a 2nd pair of FCM2Fx
devices. This does require a 4-port baseplate and 4 FCM2Fx devices at
that drop to make it work.


One other thought - I've never put a passive star in the -(fo)- line of
a fieldbus, but it really should work:

   + FCM2Fx - (fo) - PS - FCM2Fx       -(cu)- FBMs
------------         |    ----------          -----------------
Std 4-port bp        |    2-port bp           Std 2/4/8 port bp
                     |
                     +--- FCM2Fx       -(cu)- FBMs
                          ----------          -----------------
                          2-port bp           Std 2/4/8 port bp
 
The IEEE 1118 based I/A Series fieldbus is topology blind. So splitting
copper wire into a chicken's foot is fine. The FCM2Fx are really just
wire so that a passive star splitter should work for them as well.

Of course, you have to find one and, of course, I suspect that we
haven't tested it, but like I said it should work. Passive Stars worked
well on CBLANs.

PS. "It should work." is a major entry in the book of famous last words.



Regards,
 
Alex Johnson
Invensys Process Systems
10900 Equity Drive
Houston, TX 77041
713 329 8472 (desk)
713 329 1600 (operator)
713 329 1944 (SSC Fax)
713 329 1700 (Central Fax)
alex.johnson@xxxxxxxxxxxxxxxx


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