Bandwidth control for differential manchester encoding auto-negotiation signaling

A method comprising:

• determining to exchange link capabilities with a link partner that has initially unknown receiver filter characteristics;
• transmitting, through a communication interface, a start delimiter prior to the exchange of link capabilities, the start delimiter comprising:
• a first state comprising a first encoding violation, followed by:
• a transition to a second state opposite that of the first state, the second state comprising a second encoding violation, where:
• the first state followed by the second state defines a start delimiter length adapted to create frequency content for the start delimiter that:
• passes sufficiently through a first predefined receiver filter response possible for the link partner, to allow the link partner to detect the first encoding violation and the second encoding violation when the link partner adheres to the first predefined receiver filter response;
• and
• passes sufficiently through a second predefined receiver filter response possible for the link partner, to allow the link partner to detect the first encoding violation and the second encoding violation when the link partner adheres to the second predefined receiver filter response.

A system comprising:

• a communication interface operable to communicate with a link partner;
• and
• a receiver coupled with the communication interface, the receiver configured to:
• receive, from the link partner, a first signal;
• detect that the first signal comprises a first encoding violation nominally two-thirds through the first signal;
• receive, from the link partner, a second signal immediately following the first signal;
• detect that the second signal comprises a second encoding violation nominally one-third through the second signal;
• and
• determine, responsive to detecting the first encoding violation and the second encoding violation, that the first signal followed by the second signal defines a start delimiter for an auto-negotiation page that will follow the start delimiter.