Reduced dead-cycle, adaptive phase tracking method and apparatus
First Claim
1. A method for identifying a sequence of best sampling positions for sampling a data signal having a data eye and a variable bit rate, from samples of the data signal generated using an oversampling clock having sampling positions, where the data eye has a center, said method including the steps of:
- (a) generating, from the samples, relative phase data indicative of the phase of each of at least one of the sampling positions relative to the center of the data eye, for each of a number of tracking periods of the data signal; and
(b) determining from the relative phase data which of the sampling positions is best aligned with the center of the data eye during each of at least some of the tracking periods, thereby identifying the sequence of best sampling positions, wherein step (b) includes the steps of;
(c) applying a first low-pass filter to the relative phase data for at least one of the tracking periods in response to determining that the data signal'"'"'s bit rate is in a first frequency range; and
(d) applying one of a second low-pass filter and no low-pass filter to the relative phase data for at least another one of the tracking periods in response to determining that the data signal'"'"'s bit rate is in a second frequency range, where the second frequency range is different than the first frequency range and the second low-pass filter is different than the first low-pass filter.
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0 Petitions
Accused Products
Abstract
A data sampling method and circuit employing an oversampling clock to oversample a data signal, a phase tracker for use with or in a data sampling circuit, and a method for identifying a sequence of best sampling positions for sampling a data signal from signal samples generated using an oversampling clock. In some embodiments, data indicative of the phase of at least one of the oversampling clock'"'"'s sampling positions relative to the center of the data eye are low-pass filtered in a manner determined by the data signal'"'"'s bit rate. In other embodiments, the number of dead cycles of the phase tracker decision loop is reduced by generating possible solutions in parallel and moving the feedback point so as to occur as late as practical, or the phase tracker ignores a sample set when updating its determination of the best sampling position when the sample set indicates that the data signal has less than a predetermined number of transitions during a corresponding tracking period.
18 Citations
54 Claims
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1. A method for identifying a sequence of best sampling positions for sampling a data signal having a data eye and a variable bit rate, from samples of the data signal generated using an oversampling clock having sampling positions, where the data eye has a center, said method including the steps of:
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(a) generating, from the samples, relative phase data indicative of the phase of each of at least one of the sampling positions relative to the center of the data eye, for each of a number of tracking periods of the data signal; and (b) determining from the relative phase data which of the sampling positions is best aligned with the center of the data eye during each of at least some of the tracking periods, thereby identifying the sequence of best sampling positions, wherein step (b) includes the steps of; (c) applying a first low-pass filter to the relative phase data for at least one of the tracking periods in response to determining that the data signal'"'"'s bit rate is in a first frequency range; and (d) applying one of a second low-pass filter and no low-pass filter to the relative phase data for at least another one of the tracking periods in response to determining that the data signal'"'"'s bit rate is in a second frequency range, where the second frequency range is different than the first frequency range and the second low-pass filter is different than the first low-pass filter. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for selecting samples of a data signal having a data eye, where the data eye has a center and the samples have been generated by oversampling the data signal using an oversampling clock, said method including the steps of:
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(a) generating sampling position control data in response to relative phase data, where the relative phase data are indicative of the phase of a selected sampling position of the oversampling clock relative to the center of the data eye during at least one tracking period of said data signal; (b) generating additional relative phase data such that the additional relative phase data are indicative of the phase of each of multiple sampling positions of the oversampling clock relative to the center of the data eye during a subsequent tracking period of the data signal; (c) after step (b), selecting a subset of a set of the samples and a subset of the additional relative phase data in response to the sampling position control data, wherein the set of the samples has been generated by oversampling the data signal during the subsequent tracking period, the subset of the set of the samples has been generated at the selected sampling position, and the subset of the additional relative phase data is indicative of the phase of the selected sampling position relative to the center of the data eye during the subsequent tracking period; and (d) after step (c), generating updated sampling position control data in response to the subset of the additional relative phase data selected during step (c). - View Dependent Claims (9, 10)
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11. A method for selecting samples of a data signal having a data eye, where the data eye has a center and the samples have been generated by oversampling the data signal using an oversampling clock, said method including the steps of:
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(a) generating sampling position control data in response to relative phase data, where the relative phase data are indicative of the phase of a selected sampling position of the oversampling clock relative to the center of the data eye during at least one tracking period of said data signal; (b) generating additional relative phase data, wherein the additional relative phase data are indicative of the phase of each of multiple sampling positions of the oversampling clock relative to the center of the data eye during a subsequent tracking period of said data signal; (c) after step (b), selecting a subset of a set of the samples and a subset of the additional relative phase data in response to the sampling position control data, wherein the set of the samples has been generated by oversampling the data signal during one tracking period of said at least one tracking period, the subset of the set of the samples has been generated at the selected sampling position, and the subset of the additional relative phase data is indicative of the phase of the selected sampling position relative to the center of the data eye during the subsequent tracking period; and (d) after step (c), generating updated sampling position control data in response to the subset of the additional relative phase data selected during step (c). - View Dependent Claims (12, 13)
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14. A method for identifying a sequence of selected sampling positions for sampling a data signal by processing a sequence of sample sets, where each of the sample sets consists of samples of the data signal that have been generated by oversampling said data signal during a different tracking period, said method including the steps of:
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(a) for each of the sample sets, determining whether said each of the sample sets indicates that the data signal has less than a predetermined number of transitions during the tracking period in which said each of the sample sets was generated; and (b) identifying the sequence of selected sampling positions by processing the sequence of sample sets, including by selecting a different sampling position to replace a previously selected sampling position only in response to each of the sample sets that indicates that the data signal has at least the predetermined number of transitions during the tracking period in which said each of the sample sets was generated, but not in response to any of the sample sets that indicates that the data signal has less than the predetermined number of transitions during the tracking period in which said any one of the sample sets was generated. - View Dependent Claims (15, 16)
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17. A phase tracker for receiving samples of a data signal having a variable bit rate, said samples having been generated by oversampling the data signal at each of at least two sampling positions, said phase tracker including:
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sampling position control circuitry configured to generate, in response to the samples, sampling position control data indicative of a selected one of the sampling positions for each of a sequence of tracking periods of the data signal; and frequency zone detection logic configured to generate a frequency range signal indicative of a frequency range that contains the data signal'"'"'s bit rate, wherein the sampling position control circuitry includes low-pass filter circuitry coupled to receive the frequency range signal and configured to operate in a first mode when the frequency range signal indicates that the bit rate exceeds a first threshold frequency, wherein the low-pass filter circuitry generates filtered data in the first mode, and the sampling position control circuitry is configured to generate the sampling position control data in response to the filtered data when the low-pass filter circuitry operates in the first mode. - View Dependent Claims (18, 19)
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20. A phase tracker configured to receive samples of a data signal having a data eye and a variable bit rate, said samples having been generated by oversampling the data signal at each of at least two sampling positions, where the data eye has a center, said phase tracker including:
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sampling position control data generation circuitry configured to generate relative phase data in response to the samples, and to generate intermediate data and sampling position control data in response to the relative phase data, wherein the relative phase data are indicative of the phase of each of the sampling positions relative to the center of the data eye for each of at least two tracking periods of the data signal, and the sampling position control data are indicative of which of the sampling positions is best aligned with the center of the data eye during each of the tracking periods; and frequency zone detection logic configured to generate a frequency range signal indicative of a frequency range that contains the data signal'"'"'s bit rate, wherein the sampling position control data generation circuitry includes low-pass filter circuitry coupled to receive the frequency range signal and configured to operate in a first mode when the frequency range signal indicates that the bit rate exceeds a first threshold frequency, wherein the low-pass filter circuitry in the first mode applies a first low pass filter to the intermediate data, thereby generating filtered data, and the sampling position control data generation circuitry is configured to generate the sampling position control data in response to the filtered data when the low-pass filter circuitry operates in the first mode. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28)
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29. A circuit for oversampling a data signal having a data eye and a variable bit rate, where the data eye has a center, said circuit including:
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sampling circuitry configured to oversample the data signal, thereby generating samples of the data signal at each of at least two sampling positions; a phase tracker coupled and configured to generate relative phase data in response to the samples and to generate intermediate data and sampling position control data in response to the relative phase data, wherein the relative phase data are indicative of the phase of each of the sampling positions relative to the center of the data eye for each of at least two tracking periods of the data signal, and the sampling position control data are indicative of which of the sampling positions is best aligned with the center of the data eye during each of the tracking periods; and sample selection circuitry coupled and configured to select a subset of the samples for each of the tracking periods in response to the sampling position control data, wherein the phase tracker includes; frequency zone detection logic configured to generate a frequency range signal indicative of a frequency range that contains the data signal'"'"'s bit rate; and low-pass filter circuitry coupled to receive the frequency range signal and configured to operate in a first mode when the frequency range signal indicates that the bit rate exceeds a first threshold frequency, wherein the low-pass filter circuitry in the first mode applies a first low pass filter to the intermediate data, thereby generating filtered data, and the phase tracker is configured to generate the sampling position control data in response to the filtered data when the low-pass filter circuitry operates in the first mode. - View Dependent Claims (30, 31, 32, 33, 34, 35, 36, 37)
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38. A circuit for oversampling a data signal having a data eye, where the data eye has a center, said circuit including:
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sampling circuitry configured to oversample the data signal using an oversampling clock having multiple sampling positions, thereby generating samples of the data signal at each of the sampling positions; and a pipelined phase tracker coupled and configured to generate relative phase data in response to the samples and to generate sampling position control data in response to the relative phase data, wherein the phase tracker includes; first circuitry coupled and configured to receive those of the samples generated during a tracking period of the data signal and to generate a first quantity of the relative phase data in response to the received samples, wherein the first quantity of the relative phase data is indicative of the phase of each the sampling positions relative to the center of the data eye during the tracking period; second circuitry coupled to receive the first quantity of the relative phase data, a set of the samples, and a first quantity of the sampling position control data generated in response to a second quantity of the relative phase data indicative of the phase of at least one the sampling positions relative to the center of the data eye during at least one other tracking period of the data signal, wherein the second circuitry is configured to select a subset of the first quantity of the relative phase data and a subset of the set of the samples in response to the first quantity of the sampling position control data, such that the subset of the first quantity of the relative phase data is indicative of the phase of a selected one of the sampling positions relative to the center of the data eye, and such that the subset of the set of the samples was generated at the selected one of the sampling positions; and third circuitry, coupled to receive the subset of the first quantity of the relative phase data and configured to generate a second quantity of the sampling position control data in response thereto. - View Dependent Claims (39, 40)
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41. A pipelined phase tracker configured to receive samples of a data signal having a data eye, where the data eye has a center and the samples have been generated by oversampling the data signal at each of at least two sampling positions, said phase tracker including:
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first circuitry configured to receive those of the samples generated during a tracking period of the data signal and to generate a first quantity of relative phase data in response to said samples, wherein the first quantity of relative phase data is indicative of the phase of each the sampling positions relative to the center of the data eye during the tracking period; second circuitry coupled to receive the first quantity of relative phase data, a set of the samples, and a first quantity of sampling position control data generated in response to a second quantity of relative phase data, wherein the second quantity of relative phase data is indicative of the phase of at least one the sampling positions relative to the center of the data eye during at least one other tracking period, and the second circuitry is configured to select a subset of the first quantity of relative phase data and a subset of the set of the samples in response to the first quantity of sampling position control data, such that the subset of the first quantity of relative phase data is indicative of the phase of a selected one of the sampling positions relative to the center of the data eye, and such that the subset of the set of the samples was generated at the selected one of the sampling positions; and third circuitry, coupled to receive the subset of the first quantity of relative phase data and configured to generate a second quantity of sampling position control data in response thereto. - View Dependent Claims (42, 43)
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44. A circuit for oversampling a data signal, said circuit including:
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sampling circuitry configured to oversample the data signal using an oversampling clock having multiple sampling positions, thereby generating samples of the data signal at each of the sampling positions during each tracking period of a sequence of tracking periods; and a phase tracker coupled and configured to receive a sequence of sample sets and to determine a sequence of selected sampling positions for sampling the data signal in response to the sample sets, wherein each of the sample sets is a set of the samples generated during a different one of the tracking periods and each of the selected sampling positions is for a different one of the tracking periods, wherein the phase tracker includes; logic circuitry coupled and configured to generate transition data in response to the sample sets, wherein the transition data include transition data for each of the tracking periods indicating whether the data signal has less than a predetermined number of transitions during said each of the tracking periods; and additional logic circuitry coupled and configured to determine the sequence of selected sampling positions in response to the transition data and the sample sets, including by selecting an updated sampling position to replace a previously selected sampling position only in response to each of the sample sets for which the transition data indicate that the data signal has at least the predetermined number of transitions during the tracking period in which said each of the sample sets was generated, but not in response to any of the sample sets for which the transition data indicate that the data signal has less than the predetermined number of transitions during the tracking period in which said any of the sample sets was generated. - View Dependent Claims (45)
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46. A phase tracker configured to receive a sequence of sample sets, wherein each of the sample sets is a subset of a sequence of samples of a data signal, the samples in the sequence have been generated using an oversampling clock having multiple sampling positions and include samples of the data signal at each of the sampling positions during each tracking period of a sequence of tracking periods, and each of the sample sets consists of samples generated during a different one of the tracking periods, said phase tracker including:
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logic circuitry configured to generate transition data in response to the sample sets, wherein the transition data include transition data for each of the tracking periods indicating whether the data signal has less than a predetermined number of transitions during said each of the tracking periods; and additional logic circuitry coupled and configured to determine a sequence of selected sampling positions for sampling the data signal in response to the transition data and the sample sets, including by selecting an updated sampling position to replace a previously selected sampling position only in response to each of the sample sets for which the transition data indicate that the data signal has at least the predetermined number of transitions during the tracking period in which said each of the sample sets was generated, but not in response to any of the sample sets for which the transition data indicate that the data signal has less than the predetermined number of transitions during the tracking period in which said any of the sample sets was generated, wherein each of the selected sampling positions is for a different one of the tracking periods. - View Dependent Claims (47)
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48. A receiver configured to receive at least one data signal that has been transmitted over a serial link, said data signal having a data eye and a variable bit rate, where the data eye has a center, said receiver including:
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sampling circuitry configured to oversample the data signal; and a phase tracker coupled to receive samples of the data signal from the sampling circuitry, said samples having been generated by oversampling said data signal at each of at least two sampling positions, wherein the phase tracker includes; sampling position control data generation circuitry coupled and configured to generate relative phase data in response to the samples, and to generate intermediate data and sampling position control data in response to the relative phase data, wherein the relative phase data are indicative of the phase of each of the sampling positions relative to the center of the data eye for each of at least two tracking periods of the data signal, and the sampling position control data are indicative of which of the sampling positions is best aligned with the center of the data eye during each of the tracking periods; and frequency zone detection logic configured to generate a frequency range signal indicative of a frequency range that contains the data signal'"'"'s bit rate, wherein the sampling position control data generation circuitry includes low-pass filter circuitry coupled to receive the frequency range signal and configured to operate in a first mode when the frequency range signal indicates that the bit rate exceeds a first threshold frequency, wherein the low-pass filter circuitry in the first mode applies a first low pass filter to the intermediate data, thereby generating filtered data, and the sampling position control data generation circuitry is configured to generate the sampling position control data in response to the filtered data when the low-pass filter circuitry operates in the first mode. - View Dependent Claims (49, 50, 51)
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52. A receiver configured to receive at least one data signal that has been transmitted over a serial link, said data signal having a data eye, where the data eye has a center, said receiver including:
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sampling circuitry configured to oversample the data signal; and a pipelined phase tracker coupled to receive samples of the data signal from the sampling circuitry, said samples having been generated by oversampling said data signal at each of at least two sampling positions, wherein the phase tracker includes; first circuitry coupled and configured to receive those of the samples generated during a tracking period of the data signal and to generate a first quantity of relative phase data in response to said samples, wherein the first quantity of relative phase data is indicative of the phase of each the sampling positions relative to the center of the data eye during the tracking period; second circuitry coupled to receive the first quantity of relative phase data, a set of the samples, and a first quantity of sampling position control data generated in response to a second quantity of relative phase data, wherein the second quantity of relative phase data is indicative of the phase of at least one the sampling positions relative to the center of the data eye during at least one other tracking period, and the second circuitry is configured to select a subset of the first quantity of relative phase data and a subset of the set of the samples in response to the first quantity of sampling position control data, such that the subset of the first quantity of relative phase data is indicative of the phase of a selected one of the sampling positions relative to the center of the data eye, and such that the subset of the set of the samples was generated at the selected one of the sampling positions; and third circuitry, coupled to receive the subset of the first quantity of relative phase data and configured to generate a second quantity of sampling position control data in response thereto. - View Dependent Claims (53)
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54. A receiver configured to receive at least one data signal that has been transmitted over a serial link, said data signal having a data eye, where the data eye has a center, said receiver including:
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sampling circuitry configured to generate a sequence of samples of the data signal using an oversampling clock having multiple sampling positions, so that the samples in the sequence include samples of the data signal at each of the sampling positions during each tracking period of a sequence of tracking periods; and a phase tracker coupled to receive a sequence of sample sets, wherein each of the sample sets is a subset of the sequence of samples of the data signal, each of the sample sets consists of samples generated during a different one of the tracking periods, and the phase tracker includes; logic circuitry coupled and configured to generate transition data in response to the sample sets, wherein the transition data include transition data for each of the tracking periods indicating whether the data signal has less than a predetermined number of transitions during said each of the tracking periods; and additional logic circuitry coupled and configured to determine a sequence of selected sampling positions for sampling the data signal in response to the transition data and the sample sets, including by selecting an updated sampling position to replace a previously selected sampling position only in response to each of the sample sets for which the transition data indicate that the data signal has at least the predetermined number of transitions during the tracking period in which said each of the sample sets was generated, but not in response to any of the sample sets for which the transition data indicate that the data signal has less than the predetermined number of transitions during the tracking period in which said any of the sample sets was generated, wherein each of the selected sampling positions is for a different one of the tracking periods.
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Specification