Freescale Semiconductor TWR-MCF52259-Ethenet User Manual page 19

Auto-Negotiation is the exchange of information about each stations
abilities over a link segment allows the stations to achieve the best
possible mode of operation.
The highest performance mode of operation that Auto-Negotiation can
achieve is based on a priority table.
The Auto-Negotiation protocol contains a set of priorities which result
in the devices selecting their highest common set of abilities.
If the devices at both ends of the link can support full duplex
operation, and if they also both support Auto-Negotiation of this
capability, then they will automatically configure for full duplex.
The priorities are listed in the table below...
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Auto-Negotiation priority Resolution Table
A 100 Base-TX Full Duplex
B
100 Base-T4
C 100 Base-TX
D 10 Base-T Full Duplex
E
10 Base-T Half Duplex
*Autonegotiation
Full duplex is given a
higher priority than
half duplex, since it
can send more data.
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