On Sun, 22 Jul 2001, Byron A Jeff wrote:

>
> Take a look back earlier in this thread when I proposed a secondary slot that
> comes after all of the primary slots. Each node moves to that slot after
> transmitting from the primary slot. These secondary nodes remain in that mode
> until no primary wants to transmit. Then all of the secondaries can move back
> to their primary slot. This enforces fairness when all the nodes want to
> transmit and is more efficient than token ring when nodes do not need to
> transmit.

When this last came up a year or two ago, this is a solution that you
and I both suggested. I've implemented this and it does work. However,
instead of having every node operate at a secondary arbitration slot,
I had only a few assume this role. This was because a few devices were
dedicated masters. In my case, the Baud rate was 38.4 and the
arbitration slot was one bit time ~26 uS. This worked fine for 100m
runs. When the network was extended with fiber (fiber was used for
isolation and not speed), it was necessary to extend the arbitration
slot time to two bit times when the distance was greater than 100m.
This worked well for 300m, after which I had no more fiber available.

Incidently, an IC pin proved invaluable for this project.

Scott

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