Would reflections then add, acceptably, while the signal is still
transitioning? Or would this lead to too large an amplitude due to multiple
simultaneous reflections from each leg?
*************************************************************
Shayle I. Hirschman, Senior Engineer
Managing Director
Digital Design Solutions
http://www.digital-designs.com
[email protected]
Phone 901/759-1802 Fax 901/759-2324
At 10:58 AM 3/29/99 -0800, you wrote:
>>Chris Bobek wrote:
>
>
>>I have an address bus that is 75ohm, and 19" long. There are 8 loads >that
>>are daisy-chained along the trace. The edge from the driver (which
>>is at one end) is 3ns.
>
>>I was wondering if I would be better off with a star pattern, where >each
leg is short (less than 4"). Would this work and not require
>>any termination?
>
>
>>Thank you very much,
>
>
>Star patterns are a nightmare. There are so many reflections in
>the system that it easily becomes unstable. If the star is not
>perfectly balanced your signal integrity will degrade rapidly.
>Just the process variations for each agent can be enough to degrade
>your signal integrity to an unacceptable level. Furthermore, if
>you have a GTL-like bus a star wont work because it would require
>too many pull-up resistors. Star topologies can be made to work,
>but not without a lot of pain. They should be avoided for a high
>speed bus unless all other options have failed.
>
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