Method for measuring and correcting multi-wire skew

Patent metadata

Field	Value
Publication number	US-10686583-B2
Application number	US-201715641313-A
Country	US
Kind code	B2
Filing date	Jul 4, 2017
Priority date	Jul 4, 2017
Publication date	Jun 16, 2020
Grant date	Jun 16, 2020

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.

First claim

The invention claimed is:

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.

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.

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.

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.

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.

Assignees

• Kandou Labs SA

Inventors

• Ulrich roger
• Tajalli Armin
• Hormati Ali
• Simpson Richard

Classifications

• H04L25/03012

  operating in the time domain (H04L25/03165, H04L25/03178 take precedence) · CPC title

• H04L7/0016 Primary

  correction of synchronization errors · CPC title

• H04L2025/03356

  Baseband transmission · CPC title

• H04L25/4904 Primary

  using self-synchronising codes, e.g. split-phase codes · CPC title

• H04L25/14

  Channel dividing arrangements {, i.e. in which a single bit stream is divided between several baseband channels and reassembled at the receiver} · CPC title