On Sat, Jul 21, 2001 at 05:35:54AM +0200, Patrick J wrote:
> OK, I might be totally off but how about _avoiding_ collision instead of
> detecting it ?
>
> Say all pics on the bus have ID:s #1..#5, and that also represent their priority
> on the bus.
> Now, for a pic to be allowed to send it must wait the number of mS that is equal
> to its
> ID number (2mS for pic with ID=2 in this example) AFTER the LAST detected
> transmission
> on the bus, before it starts to send.
>
> This would mean that pics w high priority (low ID and therefor short wait time)
> can
> 'sneak' in before a low priorty pic which is still waiting before send.
> In principle a low priority pic can be 'starved' (no data) but if one can asume
> the
> high priority pics can behave and not take up all of the bus it should work.

It's always better if the protocol guarantees that starvation won't occur
instead of making it voluntary for high priority nodes behave.

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.

But I agree that collision advoidance is a good idea.

BAJ

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