[SI-LIST] Re: Circle bus topology

Just to clarify in 2) I was referring to end terminations.  A perfect 
source termination theoretically  would extinguish after a flight time 
of one full trip around the loop:  incident pulse at V/2 half way 
around, and V/1 half way back.  This assumes no unevenly distributed 
parasitic reactances between any two half circles.

Steve.

steve weir wrote:
> David I think it is a very bad idea.  Let's get down to basics of 
> digital signaling:
>
> We want to send each pulse on its way from source to destination with 
> the following characteristics:
>
> 1. The timing is well controlled.
> 2. Any given pulse extinguishes in such a way that it does not 
> interfere with successive pulses.  Ideally we have no memory in the 
> interconnect and therefore no ISI.
>
> When you close the circle you create two timing paths from each source 
> to each destination violating 1).  You also eliminate your ability to 
> emulate an infinite length IE memoryless transmission line by 
> employing termination, violating 2).  So to my thinking, this is a 
> very bad idea.
>
> Steve.
> David Carney (Neenah) wrote:
>> 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.
>>  
>> Thanks.
>>  
>>  
>> ----------
>> David Carney
>> Senior Hardware Engineer
>> Plexus Corp.
>> Phone - 920-751-5646
>>  
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>
>
>

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