Method and apparatus for efficient fast retraining of ethernet transceivers

1. A method of operation for an Ethernet transceiver, the method comprising:

entering a fast retrain sequence of steps, the fast retrain sequence of steps including

transferring two-level symbols to a link partner without transferring Tomlinson-Harashima Precoder (THP) coefficient information; and

directly following transferring of the two-level symbols, transferring multi-level symbols to the link partner, the multi-level symbols having greater than two symbol levels.

2. The method according to claim 1 , wherein the transferring two-level symbols to a link partner comprises:

selectively transferring uncoded two-level symbols to a link partner; and

selectively transferring coded two-level symbols to the link partner.

3. The method according to claim 2 , wherein the coded two-level symbols are encoded in accordance with Tomlinson-Harashima Precoder (THP) coefficients.

4. The method according to claim 1 , further comprising:

informing the link partner to proceed directly to transferring the multi-level symbols following the transferring of the two-level symbols.

5. The method according to claim 4 , wherein the informing is carried out via an InfoField protocol.

6. The method according to claim 1 , wherein:

the two-level symbols comprise PAM-2 symbols; and

the multi-level symbols comprise PAM-16 symbols.

7. The method according to claim 1 , further comprising:

during the fast retrain sequence of steps, cancelling correlated noise received by a receiver with a correlated noise canceller.

8. An integrated circuit (IC) Ethernet transceiver chip comprising:

receiver circuitry including correlated noise canceller circuitry; and

training logic to control a fast retrain sequence, the fast retrain sequence including

a transfer of uncoded two-level symbols to a link partner;

a transfer of coded two-level symbols to the link partner following the transfer of the uncoded two-level symbols without transferring Tomlinson-Harashima Precoder (THP) coefficient information; and

directly following the transfer of the coded two-level symbols, the training logic to control a transfer of multi-level symbols to the link partner, the multi-level symbols having greater than two symbol levels.

9. The IC Ethernet transceiver chip of claim 8 , wherein the transfer of two-level symbols comprises:

a transfer of uncoded two-level symbols to a link partner; and

a transfer of coded two-level symbols to the link partner.

10. The IC Ethernet transceiver chip according to claim 9 , wherein:

the coded two-level and multi-level symbols are encoded in accordance with a Tomlinson-Harashima Precoder (THP) encoding.

11. The IC Ethernet transceiver chip according to claim 8 , wherein:

the two-level symbols comprise PAM-2 symbols; and

the multi-level symbols comprise PAM-16 symbols.

12. The IC Ethernet transceiver chip according to claim 8 , realized as an NGBASE-T IC Ethernet transceiver chip.

13. A method of operation for an Ethernet transceiver, the method comprising:

for a first mode of operation, performing a training sequence by

transferring two-level symbols to a link partner; and

directly following transferring of the two-level symbols, transferring multi-level symbols to the link partner, the multi-level symbols having greater than two symbol levels; and

for a second mode of operation, performing the training sequence by

transferring uncoded two-level symbols to a link partner;

exchanging updated precoder coefficients with the link partner,

transferring coded two-level symbols to the link partner, the coding consistent with the updated precoder coefficients, and

transferring multi-level symbols to the link partner, the multi-level symbols encoded consistent with the exchanged updated precoder coefficients and having greater than two symbol levels.

14. The method according to claim 13 , wherein for the first mode of operation, the transferring two-level symbols to a link partner comprises:

selectively transferring uncoded two-level symbols to a link partner; and

selectively transferring coded two-level symbols to the link partner.

15. The method according to claim 13 , wherein a selection between using the first mode of operation or the second mode of operation is based on a signal quality parameter.

16. The method according to claim 13 , wherein the precoder encoding comprises:

a Tomlinson-Harashima Precoder (THP) encoding.

17. The method according to claim 13 , wherein the first mode of operation further comprises:

informing the link partner to proceed directly to transferring the multi-level symbols following the transferring of the coded two-level symbols to the link partner.

18. The method according to claim 17 , wherein the informing is carried out via an InfoField protocol.