Patent ID: 7477611

Claim:
An auto negotiation state machine for use by auto negotiation circuitry of a wired Ethernet transceiver that supports communications with an Ethernet link partner at a plurality of rates including a lowest rate and a plurality of higher rates, the state machine comprising: a start state that is entered when reset is asserted, when auto negotiation is disabled, or when auto negotiation is restarted; an idle state that is entered from the start state when reset is deasserted and when auto negotiation is enabled, when in the idle state, the auto negotiation circuitry is operable to: access an abilities register to read the information regarding the plurality of higher rates; write a supported rates variable with the information regarding the plurality of higher rates read from the abilities register; write a qualified supported rates variable with the contents of the supported rates variable; access at least one downgrade indication variable; when the at least one downgrade indication variable indicates a higher rates downgrade, alter the qualified supported rates variable based upon the downgrade indication variable; perform auto negotiation with the Ethernet link partner based upon the qualified supported rates variable; negotiate an agreed link rate with the Ethernet link partner of the lowest rate and the plurality of higher rates; and attempt to establish a link with the Ethernet link partner at the agreed link rate; a link pass state that is entered from the idle state when the attempt to establish the link with the Ethernet link partner is successful; and a link fail state that is entered from the idle state when the attempt to establish the link with the Ethernet link partner is unsuccessful.