Skew detection and correction for orthogonal differential vector signaling codes

Patent metadata

Field	Value
Publication number	US-11716190-B2
Application number	US-202217845641-A
Country	US
Kind code	B2
Filing date	Jun 21, 2022
Priority date	Jun 11, 2018
Publication date	Aug 1, 2023
Grant date	Aug 1, 2023

Abstract

Methods and systems are described for receiving a plurality of signals corresponding to symbols of a codeword on a plurality of wires of a multi-wire bus, and responsively generating a plurality of sub-channel outputs using a plurality of multi-input comparators (MICs) connected to the plurality of wires of the multi-wire bus, generating a plurality of wire-specific skew control signals, each wire-specific skew control signal of the plurality of wire-specific skew control signals generated by combining (i) one or more sub-channel specific skew measurement signals associated with corresponding sub-channel outputs undergoing a transition and (ii) a corresponding wire-specific transition delta, and providing the plurality of wire-specific skew control signals to respective wire-skew control elements to adjust wire-specific skew.

First claim

I claim:

1. A method comprising:
generating a set of data outputs, each data output formed via a respective linear transformation of a plurality of signals received on a plurality of wires of a multi-wire bus, each respective linear transformation associated with a respective sub-channel of a plurality of mutually-orthogonal sub-channels;
generating respective sub-channel specific skew measurement signals for each data output undergoing a transition in consecutive signaling intervals responsive to two or more wires of the multi-wire bus undergoing wire signal level transitions between two of at least four possible wire signal levels;
determining wire-specific transition deltas indicative of a sign and a magnitude of the wire signal level transitions of each wire of the multi-wire bus;
generating a wire-specific skew control signal for each wire of the multi-wire bus, each wire-specific skew control signal generated based on the sub-channel specific skew measurement signals combined with the wire-specific transition delta; and
providing each wire-specific skew control signal to a respective wire-skew adjustment element to adjust wire-specific skew.

2. The method of claim 1 , wherein generating the wire-specific skew control signal for each wire of the multi-wire bus comprises applying a respective input weighting coefficient to each sub-channel specific skew measurement signal, the respective input weighting coefficient corresponding to a weighting factor applied to the respective wire during the respective linear transformation.

3. The method of claim 2 , wherein the respective input weighting coefficients applied to at least two sub-channel specific skew measurement signals are different.

4. The method of claim 1 , wherein the wire transition deltas for at least two wires have equal magnitude and opposite sign.

5. The method of claim 1 , wherein the wire transition delta for at least one wire is zero.

6. The method of claim 1 , wherein determining the wire transition deltas for each wire comprises identifying a codeword sequence based on consecutively-generated sets of data outputs.

7. The method of claim 1 , wherein providing each wire-specific skew control signal to a respective wire-skew control element comprises conveying each wire-specific skew control signal to a transmitter generating the plurality of signals on the multi-wire bus.

8. The method of claim 1 , wherein each wire-skew adjustment element corresponds to a plurality of capacitive elements connected in parallel to a respective wire.

9. The method of claim 1 , wherein the at least four possible wire signal levels correspond to symbol values selected from the group consisting of: [±1, ±⅓].

10. The method of claim 1 , wherein each sub-channel specific skew measurement is generated at an output of a sampler applying a speculative decision feedback equalization (DFE) factor to the data output.

11. An apparatus comprising:
a set of multi-input comparators configured to generate a set of data outputs, each data output formed via a respective linear transformation of a plurality of signals received on a plurality of wires of a multi-wire bus, each respective linear transformation associated with a respective sub-channel of a plurality of mutually-orthogonal sub-channels;
a set of clock data recovery (CDR) samplers configured to generate respective sub-channel specific skew measurement signals for each data output undergoing a transition in consecutive signaling intervals responsive to two or more signals of the plurality of signals undergoing wire signal level transitions between two of at least four possible wire signal levels; and
a skew control circuit configured to:
determine wire-specific transition deltas indicative of a sign and a magnitude of the wire signal level transitions of each wire of the multi-wire bus;
generate wire-specific skew control signals for each wire of the multi-wire bus, each wire-specific skew control signal generated based on the sub-channel specific skew measurement signals combined with the wire-specific transition delta; and
provide each wire-specific skew control signal to a respective wire-skew adjustment element to adjust wire-specific skew.

12. The apparatus of claim 11 , wherein the skew control circuit is configured to apply a respective input weighting coefficient to each sub-channel specific skew measurement signal for a given wire-specific skew control signal, the respective input weighting coefficient corresponding to a weighting factor applied to the respective wire during the respective linear transformation.

13. The apparatus of claim 12 , wherein the respective input weighting coefficients applied to at least two sub-channel specific skew measurement signals are different.

14. The apparatus of claim 11 , wherein the wire transition deltas for at least two wires have equal magnitude and opposite sign.

15. The apparatus of claim 11 , wherein the wire transition delta for at least one wire is zero.

16. The apparatus of claim 11 , wherein the skew control circuit comprises a state change lookup table configured to determine the wire transition deltas for each wire by identifying a codeword sequence based on consecutively-generated sets of data outputs.

17. The apparatus of claim 11 , wherein the skew control circuit is configured to convey each wire-specific skew control signal to a transmitter generating the plurality of signals on the multi-wire bus.

18. The apparatus of claim 11 , wherein each wire-skew adjustment element corresponds to a plurality of capacitive elements connected in parallel to a respective wire.

19. The apparatus of claim 11 , wherein the at least four possible wire signal levels correspond to symbol values selected from the group consisting of: [±1, ±⅓].

20. The apparatus of claim 11 , wherein each CDR sampler corresponds to one of a pair of samplers configured to apply speculative decision feedback equalization (DFE) factors to the data output, the CDR sampler selected from the pair of samplers based on a prior data output.

Assignees

• Kandou Labs SA

Inventors

• Hormati Ali

Classifications

• H04L7/02 Primary

  Speed or phase control by the received code signals, the signals containing no special synchronisation information {(H04L7/0075 takes precedence)} · CPC title

• H04L7/0087

  Preprocessing of received signal for synchronisation, e.g. by code conversion, pulse generation or edge detection · CPC title

• H04L25/0292 Primary

  Arrangements specific to the receiver end · CPC title

• H04L25/0272 Primary

  Arrangements for coupling to multiple lines, e.g. for differential transmission · CPC title

• H03M5/14

  Code representation, e.g. transition, for a given bit cell depending on the information in one or more adjacent bit cells, e.g. delay modulation code, double density code · CPC title