[SI-LIST] Re: Circle bus topology; Circular Firing Squad?
- From: "Salkow, Steven" <steven.salkow@xxxxxxxx>
- To: David.Carney@xxxxxxxxxx, si-list@xxxxxxxxxxxxx
- Date: Thu, 26 Jul 2007 14:21:57 -0700
Mr Townsend et All made good points.
DFM software would flag this as an error.
Electrically, I think the idea is that the propagating standing magnetic
wave of each arc path would exactly cancel each other when the waves met
and no reflections would reflect back to the source. If one side of a
path was not exactly equal, the point at which the waves cancel would
not be at an physical midpoint rather at an electrical midpoint which
may fall on a driven node. The point made by others already is better
schemes exist already such as star distribution where end point
termination may be used to easily terminate a line with quite
predictable results.
ss
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Townsend, Fred
Sent: Thursday, July 26, 2007 9:05 AM
To: David.Carney@xxxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Circle bus topology; Circular Firing Squad?
David:
I have to ask what would be gained from such a topology? Ron and Scott
both make some very good points. In the case of the Mux bus (1553)the
ring encompasses the airplane and the double ring structure gives
increased reliability. Microwave can make use of some structures like
directional couplers to help reduce reflections. If rings are good why
aren't we still using the token ring? Again the token ring was over an
area much bigger than a PCB. A ring in a PCB would have all of the
problems with no apparent gain. Think about your PCB router. Rings would
drive the router nuts?
Fred Townsend
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of David Carney (Neenah)
Sent: Thursday, July 26, 2007 6:47 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Circle bus topology
Has anyone ever experimented with a circle bus topology. The basic
concept would be a bus with several devices attached. They would be
routed in a daisy chain topology, and then the two ends of the daisy
chain would be connected together. The PCB routing would look like a
circle or a loop for each net on the bus. Pointers to references such
as papers or application notes would be greatly appreciated. I'm
particularly interested in signal integrity and EMC implications of this
topology.
=20
Thanks.
=20
=20
----------
David Carney
Senior Hardware Engineer
Plexus Corp.
Phone - 920-751-5646
=20
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=20
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