Method for measuring and correcting multi-wire skew

• US 10,686,583 B2
• Filed: 07/04/2017
• Issued: 06/16/2020
• Est. Priority Date: 07/04/2017
• Status: Active Grant

• Current Assignee: Kandou Labs, SA
• Original Assignee: Kandou Labs, SA
• Inventors: Ulrich, Roger, Tajalli, Armin, Hormati, Ali, Simpson, Richard
• Primary Examiner(s): Payne, David C
• Assistant Examiner(s): Hassan, Sarah
• Application Number:
  US15/641,313
• Publication Number:
  US 20190013927A1
• Time in Patent Office: 1,078 Days
• Field of Search: 375355, 327160
• CPC Class Codes: H04L 2025/03356 Baseband transmission
• CPC Class Codes: H04L 25/03 Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
• CPC Class Codes: H04L 25/03057 with a recursive structure H04L25/03031 takes precedence
• CPC Class Codes: H04L 25/03878 Line equalisers; line build-out devices
• CPC Class Codes: H04L 25/14 Channel dividing arrangements , i.e. in which a single bit stream is divided between several baseband channels and reassembled at the receiver
• CPC Class Codes: H04L 25/49 using code conversion at the transmitter; using predistortion; using insertion of idle bits for obtaining a desired frequency spectrum; using three or more amplitude levels ; Baseband coding techniques specific to data transmission systems spectral shaping H04L25/03828
• CPC Class Codes: H04L 25/4904 using self-synchronising codes, e.g. split-phase codes
• CPC Class Codes: H04L 25/4919 using balanced multilevel codes H04L25/4927 takes precedence
• CPC Class Codes: H04L 7/0016 correction of synchronization errors
• CPC Class Codes: H04L 7/0025 interpolation of clock signal
• CPC Class Codes: H04L 7/0054 Detection of the synchronisation error by features other than the received signal transition by means of signal transition H04L7/033
• CPC Class Codes: H04L 7/0079 Receiver details
• CPC Class Codes: H04L 7/033 using the transitions of the received signal to control the phase of the synchronising-signal-generating means, e.g. using a phase-locked loop

Abstract

Generating, during a first and second signaling interval, an aggregated data signal by forming a linear combination of wire signals received in parallel from wires of a multi-wire bus, wherein at least some of the wire signals undergo a signal level transition during the first and second signaling interval; measuring a signal skew characteristic of the aggregated data signal; and, generating wire-specific skew offset metrics, each wire-specific skew offset metric based on the signal skew characteristic.

Claims

1. A method comprising:

generating, during a first and second signaling interval, an aggregated data signal by forming a linear combination of at least three wire signals received at a multi-input comparator (MIC) in parallel from wires of a multi-wire bus, wherein at least two of the wire signals undergo a signal level transition during the first and second signaling interval, and wherein the aggregated data signal is representative of a sub-channel data signal of an orthogonal differential code;

obtaining a signal skew measurement of the aggregated data signal in response to a transition time of the aggregated data signal at an output of the MIC; and

,

adjusting a signal skew of the aggregated data signal by updating wire-specific skew offset values of the at least two wires undergoing the signal level transition based on the signal skew measurement.

2. The method of claim 1 wherein each wire-specific skew offset value is also updated based on a magnitude of the signal level transition on a specific wire.

3. The method of claim 2 wherein the magnitude of the signal level transition on a specific wire is determined according to an identified codeword transition.

4. The method of claim 1 wherein the wire-specific skew offset values are updated in response to a counter value exceeding a threshold.

5. The method of claim 1 wherein the linear combination is formed in accordance with elements of a row of an orthogonal matrix.

6. The method of claim 1 further comprising generating at least one wire-specific skew control signal.

7. The method of claim 6 wherein the at least one wire-specific skew control signal is used to control a capacitive loading on a corresponding wire at a receiver to update the wire-specific skew offset value of the corresponding wire.

8. The method of claim 6 wherein the at least one wire-specific skew control signal is conveyed to a transmitter.

19. The method of claim 1, wherein the wire-specific skew offset values of the at least two wires undergoing the signal level transition are updated by equal amounts.

9. A method comprising:

receiving a sequence of orthogonal codewords, each codeword having a plurality of codeword signal elements received in parallel over respective wires of a multi-wire bus;

for each codeword in the sequence of codewords;

forming a set of weighted sums of the codeword signal elements, each sum being formed by a corresponding multi-input comparator (MIC);

identifying a codeword data value based on the set of weighted sums;

determining a skew measurement from one or more of the weighted sums in the set of weighted sums;

identifying a predetermined sequence of codewords and responsively determining a set of wire-specific skew offset values based on the predetermined sequence and the skew measurement; and

,

generating one or more wire-specific skew control signals.

10. The method of claim 9 wherein the MIC weights correspond to rows of an orthogonal matrix.

11. The method of claim 9 wherein determining a skew measurement from one or more of the weighted sums in the set of weighted sums is performed via a slicer selected from a prior data value.

12. The method of claim 9 wherein determining a skew measurement from one or more of the weighted sums in the set of weighted sums is performed via oversampling.

13. The method of claim 9 wherein determining a skew measurement from one or more of the weighted sums in the set of weighted sums is performed via regular baud sampling on a ½

rate test pattern.

14. The method of claim 9 wherein the predetermined sequence of codewords includes a plurality of sequences, and different sequences have different wire-specific skew offset values.

20. The method of claim 9, wherein determining the set of wire-specific skew offset values comprises updating each wire-specific skew offset value by an equal amount.

15. An apparatus comprising:

a plurality of multi-wire signal combiners, each configured to form an aggregate data signal from codeword component signals received on a multi-wire bus;

a skew measurement circuit configured to generate a skew measurement signal from one or more of the aggregate data signals;

a codeword sequence detector configured to identify one or more predetermined sequences of codewords and responsively output a set of wire-specific skew offset values; and

,

a skew control signal generator configured to generate one or more wire-specific skew control signals.

16. The apparatus of claim 15 wherein the skew control signal generator comprises a plurality of counters.

17. The apparatus of claim 16 wherein the codeword sequence detector is connected to the plurality of counters to increment or decrement the counters in proportion to a wire-specific transition level.

18. The apparatus of claim 16 wherein the codeword sequence detector is connected to the plurality of counters to increment or decrement the counters in response to an identified transition sequence.