Bonsoir Rich,
Sorry, I don't explain correctly.
Suppose I connect a MDI to a MDI-X through a crossover cable instead of a straight cable. We have an emitter face to an emitter, and a receiver face to a receiver. In this case, it's not a polarity issue, but a question of pair inversion.
It's the same thing if we connect a MDI to a MDI through a straight cable. I heard that some devices detect that and try to invert the pairs. Have you seen that?
Regards, Michelot
(snip)
Yes, they can put drivers and receivers on both sides, with an enable on the drivers. Once it detects which one is in use, it can enable the appropriate drivers.
On devices that support 1000baseT, which sends and receives on all four pairs at the same time, it is easy to do, and many do it. Otherwise it is relatively rare, but I have known some to do it.
-- glen
Bonjour Glen,
The optional function is named autoswitching MDI/MDI-X or automatic MDI/MDI-X configuration, it implies to have the auto-negociation enable. Today, this solution exists also for 100 Mbit/s. The physical level try to detect a link activity (frame ou pulses) during 80 to 100 ms. If no activity is detected, the MDI pairs are switched in the other configuration, and another listen slot time is taken, randomly, greater than 80 ms. Thus, the probability that both sides take the same duration is low. Both ends can implement the autoswitching.
Regards, Michelot
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