Link Training is performed after auto-negotiation converges to a backplane or copper technology. Technology selection can also be the result of a manual entry or parallel detection. Link training might be required due to frequency-dependent losses that can occur as digital signals traverse the backplane or a copper cable. The primary function of the Link Training core is to provide register information and a training sequence over the backplane link which is then analyzed by a receiving circuit which is not part of the core.
The other function of the core is to communicate training feedback from the receiver to the corresponding transmitter so that its equalizer circuit (not part of the core) can be adjusted as required. The two circuits comprising the core are the receive Link Training block and the transmit Link Training block.