Re: [SI-LIST] : New VME Backplane -- Star Layout

Mike Mayer ([email protected])
Wed, 16 Sep 1998 10:46:18 -0500 (CDT)

=I believe you are correct, it is still a transmission line. The comments in
=the EETimes article sound like they're coming from a marketing type.
=But that said, I do believe that the settling times on this new VME
=backplane could be improved, and the loads could be more consistent. Every
=board would now see the same load. Currently, the board in slot 1 really
=sees a different load than the board in the middle of the backplane. Also,
=if the board in slot 1 was the driver, the board in slot 2 sees a very ugly
=signal compared to the board in slot 21....
=A major drawback on this approach is the huge routing resources needed to do
=a star topology, instead of a daisy-chain, on a 21 slot VME BUS!

Do you think the trace lengths are balanced? i.e., Is the length from
slot 9 tromboned to the same length as the trace from slot 1 to the
star? That would truly make every board see the same load and the
same transmission line. That would eliminate the large slot-to-slot
difference that exists now.

Mike Mayer                               Artesyn Communication Products, Inc
                                         Madison, WI

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