Embedded cognitive network card PHY self negotiation

What is self negotiation ？

Self negotiation is through a kind of pulse called fast connection （Fast Link Pulse） Signal implementation of , abbreviation FLP. Both parties of self negotiation passed FLP To exchange data .

There is no Link Under the circumstances , The port keeps sending FLP, stay FLP It contains its own connection ability information , Including supported rate capabilities 、 Duplex capability 、 Flow control capability, etc . This connection capability is obtained from the self negotiation capability register （Auto-Negotiation Advertisement Register ,PHY Standard register address 4 ）.

Rely on pulse position coding to carry data . One FLP Burst contains 33 Pulse positions .17 Odd position pulses are clock pulses , Clock pulses always exist ;16 An even number of position pulses are used to represent data ： This position is indicated by a pulse 1, There is no pulse at this position 0. such 1 individual FPL The burst of can be transmitted 16bit The data of . Self negotiation interactive data is thus transmitted through physical lines

If both sides support self negotiation , Will receive each other's FLP, And the FLP Decode the information in . Get the connection ability of the other party . And record the self negotiation capability value of the opposite end in the self negotiation opposite end capability register （Auto-Negotiation Link Partner Ability Register , PHY Standard register address 5 ）