WO2014138640A1 - Clock recovery circuit for multiple wire data signals - Google Patents

Clock recovery circuit for multiple wire data signals Download PDF

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Publication number
WO2014138640A1
WO2014138640A1 PCT/US2014/021958 US2014021958W WO2014138640A1 WO 2014138640 A1 WO2014138640 A1 WO 2014138640A1 US 2014021958 W US2014021958 W US 2014021958W WO 2014138640 A1 WO2014138640 A1 WO 2014138640A1
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WO
WIPO (PCT)
Prior art keywords
signal
state transition
instance
comparison signal
filtered version
Prior art date
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Ceased
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PCT/US2014/021958
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English (en)
French (fr)
Inventor
Shoichiro Sengoku
Chulkyu Lee
George Alan Wiley
Joseph Cheung
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Qualcomm Inc
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Qualcomm Inc
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Publication date
Application filed by Qualcomm Inc filed Critical Qualcomm Inc
Priority to CN201480012389.XA priority Critical patent/CN105027490B/zh
Priority to EP14712537.1A priority patent/EP2965459B1/en
Priority to KR1020157026568A priority patent/KR102205823B1/ko
Priority to ES14712537T priority patent/ES2705045T3/es
Priority to JP2015561728A priority patent/JP6461018B2/ja
Publication of WO2014138640A1 publication Critical patent/WO2014138640A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L7/00—Arrangements for synchronising receiver with transmitter
    • H04L7/02—Speed or phase control by the received code signals, the signals containing no special synchronisation information
    • H04L7/033—Speed or phase control by the received code signals, the signals containing no special synchronisation information using the transitions of the received signal to control the phase of the synchronising-signal-generating means, e.g. using a phase-locked loop
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K5/00—Manipulating of pulses not covered by one of the other main groups of this subclass
    • H03K5/125—Discriminating pulses
    • H03K5/1252—Suppression or limitation of noise or interference
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K5/00—Manipulating of pulses not covered by one of the other main groups of this subclass
    • H03K5/153—Arrangements in which a pulse is delivered at the instant when a predetermined characteristic of an input signal is present or at a fixed time interval after this instant
    • H03K5/1534—Transition or edge detectors
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0264—Arrangements for coupling to transmission lines
    • H04L25/0272—Arrangements for coupling to multiple lines, e.g. for differential transmission
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/14—Channel dividing arrangements, i.e. in which a single bit stream is divided between several baseband channels and reassembled at the receiver
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/38—Synchronous or start-stop systems, e.g. for Baudot code
    • H04L25/40—Transmitting circuits; Receiving circuits
    • H04L25/49—Transmitting circuits; Receiving circuits 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
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/38—Synchronous or start-stop systems, e.g. for Baudot code
    • H04L25/40—Transmitting circuits; Receiving circuits
    • H04L25/49—Transmitting circuits; Receiving circuits 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
    • H04L25/4906—Transmitting circuits; Receiving circuits 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 using binary codes
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/38—Synchronous or start-stop systems, e.g. for Baudot code
    • H04L25/40—Transmitting circuits; Receiving circuits
    • H04L25/49—Transmitting circuits; Receiving circuits 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
    • H04L25/493—Transmitting circuits; Receiving circuits 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 by transition coding, i.e. the time-position or direction of a transition being encoded before transmission
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L7/00—Arrangements for synchronising receiver with transmitter
    • H04L7/0054—Detection of the synchronisation error by features other than the received signal transition
    • H04L7/0066—Detection of the synchronisation error by features other than the received signal transition detection of error based on transmission code rule
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L7/00—Arrangements for synchronising receiver with transmitter
    • H04L7/02—Speed or phase control by the received code signals, the signals containing no special synchronisation information
    • H04L7/027—Speed or phase control by the received code signals, the signals containing no special synchronisation information extracting the synchronising or clock signal from the received signal spectrum, e.g. by using a resonant or bandpass circuit

Definitions

  • the present disclosure pertains to transmitting a clock signal within cycles of a multi-wire data signal transfer.
  • multi-wire differential signaling such as 3 -phase or N-factorial low- voltage differential signaling (LVDS)
  • transcoding e.g., the digital-to-digital data conversion of one encoding type to another
  • Embedding clock information by such transcoding is an effective way to minimize skew between clock and data signals, as well as to eliminate the necessity of a phase-locked loop (PLL) to recover the clock information from the data signals.
  • PLL phase-locked loop
  • Clock and data recovery (CDR) circuits are decoder circuits that extract data signals as well as a clock signals from multiple data signals.
  • clock recovery from multiple data signals whose state transitions represent clock events often suffers unintended spike pulses on its recovered clock signal due to inter-lane skew of the data signals or glitch signals by intermediate or undeterminable data signal states at data transition times.
  • a clock recovery circuit comprising a receiver circuit and a clock extraction circuit.
  • the receiver circuit may be adapted to decode a differentially encoded signal on a plurality of data lines, where at least one data symbol is differentially encoded in state transitions of the differentially encoded signal.
  • the plurality of data lines is three or more lines.
  • the clock extraction circuit may obtain a clock signal from state transition signals derived from the state transitions while compensating for skew in the different data lines, and masking data state transition glitches.
  • the clock extraction circuit may include a feedback delayed instance of a first state transition signal (SDRCLK) that is used to obtain the clock signal.
  • SDRCLK first state transition signal
  • the clock extraction circuit may include a comparator, a set-reset latch, and an analog delay device.
  • the comparator may compare a first instance of the first state transition signal (SI) and a level-latched instance of the first state transition signal (S) and outputs a comparison signal (NE).
  • the set-reset latch may receive the comparison signal (NE) from the comparator and outputs a filtered version of the comparison signal (NEFLT).
  • the analog delay device may receive the filtered version of the comparison signal (NEFLT) and outputs a delayed instance of the first state transition signal (SDRCLK), where the delayed instance of the first state transition signal (SDRCLK) is used to obtain the clock signal (DDRCLK).
  • the set-reset latch may be reset based on the delayed instance of the first state transition signal (SDRCLK).
  • the clock extraction circuit may further include a level latch that receives the first state transition signal (SI) and outputs the level-latched instance of the first state Attorney Docket No.130645WO
  • the clock extraction circuit may include a comparator, a set-reset latch, a first analog delay device, a one-shot logic, and a second analog delay device.
  • the comparator may compare a first instance of the first state transition signal (SI) and a level-latched instance of the first state transition signal (S) and outputs a comparison signal (NE).
  • the set-reset latch may receive the comparison signal (NE) from the comparator and outputs a filtered version of the comparison signal ( EFLT).
  • the first analog delay device may receive the filtered version of the comparison signal (NEFLT) and outputs a delayed instance of the filtered version of the comparison signal (NEDEL).
  • the one-shot logic may receive the filtered comparison signal (NEFLT) and the delayed instance of the filtered version of the comparison signal (NEDEL) and outputs a second filtered version of the comparison signal (NE1 SHOT).
  • the second analog delay device may receive the second filtered version of the comparison signal (NE1 SHOT ) and outputs a delayed instance of the first state transition signal (SDRCLK), where the delayed instance of the first state transition signal (SDRCLK) is used to obtain the clock signal (DDRCLK).
  • the set-reset latch may be reset based on the delayed instance of the first state transition signal (SDRCLK).
  • the clock extraction circuit may further include a level latch that receives the first state transition signal (SI) and outputs the level-latched instance of the first state transition signal (S), where the level latch is triggered based on the delayed instance of the first state transition signal (SDRCLK).
  • SI first state transition signal
  • SDRCLK delayed instance of the first state transition signal
  • the clock extraction circuit may include a comparator, a set-reset latch, a first analog delay device, a one-shot logic, a second analog delay device, and a third analog delay device.
  • the comparator may compare a first instance of the first state transition signal (SI) and a level-latched instance of the first state transition signal (S) and outputs a comparison signal (NE).
  • the set-reset latch may receive the comparison signal (NE) from the comparator and outputs a filtered version of the comparison signal (NEFLT).
  • a first analog delay device that receives the filtered version of the comparison signal (NEFLT) and outputs a delayed instance of the filtered version of the comparison signal (NEDEL).
  • the one-shot logic may receive the filtered comparison signal (NEFLT) and the delayed instance of the filtered version of the comparison signal (NEDEL) and outputs a second filtered version of the comparison signal (NE1SHOT).
  • the second analog delay device may receive the second filtered Attorney Docket No.130645WO
  • the third analog delay device may receive the first delayed instance of the first state transition signal (SDRCLKO) and outputs a second delayed instance of the first state transition signal (SDRCLK).
  • SDRCLK second delayed instance of the first state transition signal
  • the set-reset latch may be reset based on the second delayed instance of the first state transition signal (SDRCLK).
  • the clock extraction circuit may further include a level latch that receives the first state transition signal (SI) and outputs the level- latched instance of the first state transition signal (S), where the level latch is triggered based on the second delayed instance of the first state transition signal (SDRCLK).
  • SI first state transition signal
  • SDRCLK second delayed instance of the first state transition signal
  • the clock extraction circuit may include a comparator, a set-reset latch, a first analog delay device, a one-shot logic, a second analog delay device, a third analog delay device, and a flip-flop.
  • the comparator may compare a first instance of the first state transition signal (SI) and a level-latched instance of the first state transition signal (S) and outputs a comparison signal (NE).
  • the set-reset latch may receive the comparison signal (NE) from the comparator (1304) and outputs a filtered version of the comparison signal (NEFLT).
  • the first analog delay device may receive the filtered version of the comparison signal (NEFLT) and outputs a delayed instance of the filtered version of the comparison signal (NEDEL).
  • the one-shot logic may receive the filtered comparison signal (NEFLT) and the delayed instance of the filtered version of the comparison signal (NEDEL) and outputs a second filtered version of the comparison signal (NE1SHOT).
  • the second analog delay device may receive the second filtered version of the comparison signal (NE1 SHOT) and outputs a first delayed instance of the first state transition signal (SDRCLK1), where the first delayed instance of the first state transition signal (SDRCLK1) is used to obtain the clock signal.
  • the third analog delay device may receive the first delayed instance of the first state transition signal (SDRCLK1) and outputs a second delayed instance of the first state transition signal (SDRCLK2).
  • the flip flop may receive the first state transition signal (SI) and outputs the level-latched instance of the first state transition signal (S), where the level latch is triggered based on the first delayed instance of the first state transition signal (SDRCLK2).
  • the set-reset latch may be reset based on the second delayed instance of the first state transition signal (SDRCLK2).
  • a method for recovering a clock signal is also provided.
  • a differentially encoded signal on a plurality of data lines is decoded, where at least one data symbol is Attorney Docket No.130645WO
  • a clock signal is obtained from state transition signals derived from the state transitions while compensating for skew in the different data lines, and masking data state transition glitches. Data is extracted from the decoded differentially encoded signal.
  • the clock signal is a feedback delayed instance of a first state transition signal (SDRCLK) that is used to obtain the clock signal.
  • SDRCLK first state transition signal
  • the clock signal may be obtained by: (a) comparing a first instance of the first state transition signal (SI) and an instance of the first state transition signal (S) to provide a comparison signal (NE); (b) filtering the comparison signal (NE) to provide a filtered version of the comparison signal (NEFLT); and/or (c) delaying the filtered version of the comparison signal (NEFLT) to provide a delayed instance of the first state transition signal (SDRCLK), where the delayed instance of the first state transition signal (SDRCLK) is used to obtain the clock signal (DDRCLK).
  • the clock signal may be obtained by: (a) comparing a first instance of the first state transition signal (SI) and a level-latched instance of the first state transition signal (S) to provide a comparison signal (NE); (b) filtering the comparison signal (NE) to provide a filtered version of the comparison signal (NEFLT); (c) delaying the filtered version of the comparison signal (NEFLT) to provide a delayed instance of the filtered version of the comparison signal (NEDEL); (d) logically combining the filtered comparison signal (NEFLT) and the delayed instance of the filtered version of the comparison signal (NEDEL) to obtain a second filtered version of the comparison signal (NEI SHOT); and/or (d) delaying the second filtered version of the comparison signal (NEI SHOT ) to provide a delayed instance of the first state transition signal (SDRCLK), where the delayed instance of the first state transition signal (SDRCLK) is used to generate the clock signal (DDRCLK).
  • SDRCLK delayed instance of the first state transition signal
  • the clock signal is obtained by: (a) comparing a first instance of the first state transition signal (SI) and a level-latched instance of the first state transition signal (S) to provide a comparison signal (NE); (b) filtering the comparison signal (NE) to provide a filtered version of the comparison signal (NEFLT); (c) delaying the filtered version of the comparison signal (NEFLT) to provide a delayed instance of the filtered version of the comparison signal (NEDEL); (d) logically combining the filtered comparison signal (NEFLT) and the delayed instance of the filtered version of the comparison signal (NEDEL) to provide a second filtered version of the comparison signal (NEI SHOT); (e) delaying the second filtered version of the Attorney Docket No.130645WO
  • NE1SHOT to provide a first delayed instance of the first state transition signal (SDRCLKO), where the first delayed instance of the first state transition signal (SDRCLKO) is used to generate the clock signal; and/or (f) delaying the first delayed instance of the first state transition signal (SDRCLKO) to provide a second delayed instance of the first state transition signal (SDRCLK).
  • the clock signal is obtained by: (a) comparing a first instance of the first state transition signal (SI) and a level-latched instance of the first state transition signal (S) to provide a comparison signal (NE); (b) filtering the comparison signal (NE) to provide a filtered version of the comparison signal (NEFLT); (c) delaying the filtered version of the comparison signal (NEFLT) to provide a delayed instance of the filtered version of the comparison signal (NEDEL); (d) logically combining the filtered comparison signal (NEFLT) and the delayed instance of the filtered version of the comparison signal (NEDEL) to provide a second filtered version of the comparison signal (NE1 SHOT); (e) delaying the second filtered version of the comparison signal (NE1SHOT) to provide a first delayed instance of the first state transition signal (SDRCLKl), where the first delayed instance of the first state transition signal (SDRCLKl) is used to generate the clock signal; and/or (f) delaying the
  • FIG. 1 illustrates a 3-wire differential signaling scheme between a transmitter device and a receiver device based on a circular state diagram.
  • FIG. 2 illustrates an example clock recovery circuit (e.g., decoder) which can be used to decode data transmitted according to a 3-wire differential signaling scheme.
  • decoder e.g., decoder
  • FIG. 3 is a timing diagram for the clock recovery circuit of FIG. 2.
  • FIG. 4 illustrates a solution to the inter-lane skew of FIG. 3 in which a delay is introduced in the clock recovery circuit (decoder) so that the unintended state is delayed sufficiently that it no longer causes a glitch on the recovered clock RXCLK.
  • FIG. 5 is a timing diagram illustrating a timing diagram in which a glitch occurs in the AB transition that cannot be masked out by the delay.
  • FIG. 6 is an alternate clock recovery circuit in which a one-shot circuit is used after the data receiver circuit to remove the inter-lane skew.
  • FIG. 7 illustrates that a glitches transition periods may cause incorrect or erroneous DDRCLK toggles in the clock recovery circuit shown in FIG 6.
  • FIG. 8 illustrates a clock and data transmission scheme for a 4-wire differential signaling system with embedded clock information.
  • FIG. 9 illustrates a clock and data transmission scheme for a 4-wire differential signaling system with embedded clock information.
  • FIG. 10 is a timing diagram for the signals in the CDR circuit in FIG. 9.
  • FIG. 1 1 illustrates exemplary implementations of various circuit components for the CDR circuit of FIG. 9.
  • FIG. 12 illustrates another data transmission scheme for a 4-wire system with embedded clock information.
  • FIG. 13 illustrates yet another data transmission scheme for a 4-wire system with embedded clock information.
  • FIG. 14 is a method operational in a device to recover a clock signal.
  • FIG. 15 illustrates a first method for extracting a clock signal.
  • FIG. 16 illustrates a second method for extracting a clock signal.
  • FIG. 17 illustrates a third method for extracting a clock signal.
  • FIG. 18 illustrates a fourth method for extracting a clock signal.
  • a receiver circuit is adapted to decode a differentially encoded signal on a plurality of data lines, where at least one data symbol is differentially encoded in state transitions of the differentially encoded signal.
  • a clock extraction circuit obtains a clock signal from state transition signals derived from the state transitions while compensating for skew in the different data lines, and masking data state transition glitches.
  • clock recovery circuits descripted herein may be implemented with many different types of multi-wire transmission system.
  • FIG. 1 illustrates a 3 -wire differential signaling scheme between a transmitter device 100 and a receiver device 101 based the states defined by differential signals among conductors A, B, and C.
  • the transmitter device 100 and receiver device 101 may communicate over a multi-line bus 108.
  • three lines A, B, and C are used for the bus 108.
  • the receiver device 101 may include a three-port receiver 1 10 to couple the receiver device 101 to the bus 108.
  • differential signal encoding may be used to transmit signals from the transmitter device 100 the receiver device 101. Consequently, each of a plurality of receivers 1 12 may be configured to take two of the three lines A, B, and C and provide a different signal. For instance, a first line A and a second line B may serve to provide a first differential signal RX AB 114, the second line B and a third line C may serve to provide a second differential signal RX BC 1 16, and the first line A and the third line C may serve to provide a third differential signal RX CA 118 RX. These differential signals 114, 1 16, and 118 may serve as inputs to a decoder circuit 120. The decoder circuit 120 decodes the three differential signals RX AB 114, RX BC 116, and RX_CA 1 18 and outputs the six states XM, YM, ZM, ZP, YP, and XP.
  • a state diagram 103 illustrates the six (6) states XM, YM, ZM, ZP, YP, and XP that may be defined by the differential signals 114, 1 16, and 118 carried by the three conductors A, B, and C 108. As can be observed, the voltage levels across the three differential signals 114, 1 16, and 1 18 may be mapped to different combinations of ones Attorney Docket No.130645WO
  • state XM may be associated with "Oi l”
  • state YM may be associated with "101”
  • state ZP may be associated with "001”
  • state ZM may be associated with "110”
  • state YP may associated with "010”
  • state XP may be associated with "100”.
  • informationen in the states may also be encoded based on transitions between the states. Note that transition between any two states (XM, YM, ZM, ZP, YP, and XP) occurs in a single step without traversing intermediate states. As such, differential data transmission schemes based on the state diagram 103 would be free of state transition decoding problems.
  • Each of the conductors of the bus 108 may be driven High, driven Low, or undriven, with only one conductor being undriven in any single cycle.
  • three differential signals, RX AB 1 14, RX BC 116, and RX CA 118 (e.g., received by a decoder 120 within receiver device 101), are defined as positive differential voltage to logic 1 and negative differential voltage to logic 0 between conductor A relative to conductor B, conductor B relative to conductor C, and conductor C relative to conductor A respectively.
  • Example waveforms of the three differential signals 1 14, 116, and 1 18 are illustrated in the diagram 104.
  • State signals corresponding to the six possible states XM, YM, ZP, ZM, YP, XP, and XM are generated from the differential signals RX AB 1 14, RX BC 116, and RX_CA 118 by a decoder block 120 (DEC), in the receiver device 101, and examplary waveforms of the state signals are shown in the diagram 105.
  • DEC decoder block 120
  • a state transition from a state, XM, YM, ZP, ZM, YP, XP, or XM, to a different state always occurs at any single cycle in a way that a state transition represents data to be transmitted from the transmitter device 100 to the receiver device 101.
  • FIG. 2 illustrates an example clock recovery circuit 200 (e.g., decoder) which can be used to recover a clock signal from the data signals transmitted according to a 3 -wire differential signaling scheme.
  • Other clock recovery circuit implementations Attorney Docket No.130645WO
  • Clock recovery circuit 200 receives input signals XP 202, YP 204, ZP 206, XM 208, YM 210, and ZM 212 from preceding analog circuits (e.g., from decoder 120 in FIG. 1). At any time, only one of the signals XP 202, YP 204, ZP 206, XM 208, YM 210, and ZM 212 can have a value of one (as illustrated inl05), depending on which of the data states just occurred.
  • Inputs signals XP 202, YP 204, ZP 206, XM 208, YM 210, and ZM 212 are respectively coupled to the clock inputs of D flip flops 1 1-16.
  • Each of D flip flops 11-16 has its D data input coupled to a logic one, which causes its Q output to have a value of one whenever its respective clock input experiences a rising edge transition.
  • D flip flop 1 1 will have a Q output of one whenever input signal 202 experiences a rising edge transition, or equivalently, whenever state A-to-B positive occurs.
  • D flip flops 11-16 capture which of the six states has just occurred, as indicated by their respective Q outputs.
  • OR gates 1- 6, which generate reset signals for respective D flip flops 11-16.
  • OR gates 1-6 each receives as inputs pulses caused by rising edges on the Q outputs of D flip flops 11-16 except for the Q output of its respective D flip-flop and a Reset signal 214.
  • OR gate 1 receives pulses caused by rising edges on the Q outputs 224, 226, 228, 230, and 232 (but not Q output 222 of its respective D flip flop 1 1) of D flip-flops 12-16 and Reset signal 214.
  • OR gate 1 will be one whenever any state other than A-to-B positive occurs or if Reset signal 214 is asserted.
  • OR gate 1 will output a value of zero.
  • the Q outputs of D flip-flops 1 1-16 are coupled to OR gates 1-6 through a circuitry, which ensures that OR gates 1-6 are only provided with a pulse and not a continuous signal of value one.
  • Q output 222 of D flip-flop 1 1 is coupled to OR gates 2-6 through an AND gate 71.
  • D flip-flops 21-26 are used to generate a double data rate clock signal Rx_clk 216, which transitions whenever a new input is presented.
  • D flip-flops 21-26 respectively receive as clock inputs input signals 202, 204, 206, 208, 210, and 212.
  • D flip-flops 21-26 also receive Reset signal 214. As shown in FIG. 2, each of D flip flops 21-26 has its Q bar output fed back to its D data input. As such, for each of D flip- flops 21-26, whenever its respective input clock signal experiences a rising edge transition, its Q bar output will toggle from one to zero or from zero to one.
  • the Q bar outputs of D flip-flops 21-26 are input together through XOR gates 35 and 36, as illustrated in FIG. 2.
  • the outputs of XOR gates 35 and 36 are, in turn, input together through XOR gate 37.
  • XOR gate 37 will output a value of one whenever an odd number of the Q bar outputs of D flip-flops 21-26 have a value of one. Since only one of the Q_bar outputs of D flip-flops 21-26 will toggle at any one time while the others will maintain the same value, the output of XOR 37 will toggle for each change in inputs 202, 204, 206, 208, 210, and 212. This generates double data rate clock signal Rx Clk 216.
  • a delay element 62 is used to ensure that Rx Clk signal is in sync with the other signals that are output by clock recovery circuit 200.
  • FIG. 3 is a timing diagram for the clock recovery circuit 200 of FIG. 2.
  • this timing diagram illustrates that inter-lane skew 300, (e.g., timing difference between the AB lane 301 and BC lane 303) may cause an unintended state 302 to be sensed. This may result in an extra toggle 304 in the RXCLK recovered double data rate clock 308 (RXCLK) which is fatal in data communications.
  • RXCLK recovered double data rate clock
  • FIG. 4 illustrates a decoder circuit 420 that may serve to eliminate the inter- lane skew of FIG. 3.
  • the decoder circuit 420 may be the decoder circuit Attorney Docket No.130645WO
  • a delay 402, 404, 406, 408, 410, 412 is introduced in the decoder circuit 420 (decoder) to cause the unintended state 414 to be delayed 416 sufficiently so that it no longer causes a glitch on the recovered clock RXCLK.
  • the ZM line 412 in FIG. 4 no longer has a glitch.
  • additional delays are needed as more wires added. For instance, in an N-factorial (N!) system, for a four- wire system, twenty-four (24) delays would be needed, for a five-wire system, one-hundred twenty (120) delays would be needed. Additionally, such delays must be sufficiently long to accommodate to remove glitches caused by inter-lane skew, but this is wasteful and can degrade decoder performance.
  • FIG. 5 is a timing diagram illustrating a timing diagram in which a glitch 502 occurs in the AB transition that cannot be masked out by the delay 402 (FIG. 4). Consequently, such glitch is propagated 504 despite the delay 402 being used in the decoder 420.
  • FIG. 6 is an alternate clock recovery circuit in which a one-shot circuit 602 is used after the data receiver circuit to remove the inter-lane skew.
  • This one-shot circuit 602 (which includes delays 604, 606, 608, XOR gates 610, 612, and 614, and an OR gate 616) triggers off the falling edge of the SDRCLK line 618 to recover a DDRCLK 620.
  • One advantage with this circuit 602 is that only as many delays as lines are used (i.e., three lines A, B, C, and three delays 604, 606, and 608), so it scales better than the circuit in FIGS. 4 and 5 (which require more delays for the same three lines). However, this circuit does not address the problem of glitches, due to inter-lane skew, within transition periods illustrated in FIG. 5.
  • FIG. 7 illustrates that a glitches 702 and 704 transition periods may cause incorrect or erroneous DDRCLK toggles 706 and 708.
  • a clock recovery circuit including a receiver circuit and a clock extraction circuit.
  • the receiver circuit may be adapted to decode a differentially encoded signal on a plurality of data lines, where at least one data symbol is differentially encoded in state transitions of the differentially encoded signal.
  • the clock extraction circuit may obtain a clock signal from state transition signals derived from the state transitions while compensating for skew in the different data lines, and masking data state transition glitches.
  • the plurality of data lines may be three or more lines.
  • the clock extraction circuit may include a Attorney Docket No.130645WO
  • SDRCLK first state transition signal
  • FIG. 14 is a method operational in a device to recover a clock signal.
  • a differentially encoded signal on a plurality of data lines may be decoded, where at least one data symbol is differentially encoded in state transitions of the differentially encoded signal 1402.
  • a clock signal may be obtained from state transition signals derived from the state transitions while compensating for skew in the different data lines, and masking data state transition glitches 1404. Additionally, data may be extracted from the decoded differentially encoded signal 1406.
  • the clock signal may be a feedback delayed instance of a first state transition signal (SDRCLK) that is used to obtain the clock signal.
  • SDRCLK first state transition signal
  • FIG. 8 illustrates a clock and data transmission scheme for a 4-wire system 800 with embedded clock information.
  • the present 4-wire system 800 uses a level latch 810, a comparator 804, and latch 806, and an analog delay 808 to generate a signal S on a delay which serves to reset the signal S itself.
  • This clock extraction circuit includes a comparator 804, a set-reset latch 806, an analog delay device 808, and a (bused) level latch 810.
  • the comparator 804 may compare a first instance of the first state transition signal (SI) and a level-latched instance of the first state transition signal (S) and outputs a comparison signal (NE).
  • the set-reset latch 806 may receive the comparison signal (NE) from the comparator 804 and outputs a filtered version of the comparison signal (NEFLT).
  • the analog delay device 808 may receive the filtered version of the comparison signal (NEFLT) and outputs a delayed instance of the first state transition signal (SDRCLK), where the delayed instance of the first state transition signal (SDRCLK) is used to generate the clock signal (DDRCLK).
  • NEFLT filtered version of the comparison signal
  • SDRCLK delayed instance of the first state transition signal
  • the level latch 810 may receive the first state transition signal (SI) and outputs the level-latched instance of the first state transition signal (S), where the level latch 810 is triggered based on the delayed instance of the first state transition signal (SDRCLK).
  • SI first state transition signal
  • SDRCLK delayed instance of the first state transition signal
  • the comparator 804 may compare the SI signal and a signal S (output from the level latch 810) and generates a not equal NE signal that serves as input into the latch 806.
  • the comparator 804 outputs a High when signals SI and S are not equal (i.e., they are different symbols) and a Low when signals SI and S are equal (i.e., they are the same symbol).
  • signal S is just a delayed and filtered version of signal SI where the glitches have been removed due to the delay 808.
  • the comparator 804 and delay of the signal S causes the setup glitches in the signal NE to be masked in the NEFLT signal.
  • the feedback and delays in this circuit, the SDRCLK 816 and DDRCLK 814 are resistant to line skew and glitches in the symbol transitions.
  • tdRsi- reset time of the set-reset latch 806 from the rising (leading) edge of SDRCLK 816.
  • signals SI and S hold the previous symbol value SO 822.
  • Signals NE, NEFLT, and SDRCLK are zero.
  • the DDRCLK 814 is stable but can be either high or low.
  • SI 824 When a new symbol value SI 824 is being received, it causes signal SI to start changing its value.
  • the SI value may be different from S 1 824 (valid data) due to the possibility of receiving intermediate or indeterminate states 826 of the signal transition (from SO to S I) that may be caused, for example, by inter-wire skew, over/under shoot, cross-talk, etc.
  • the NE signal becomes high as soon as the comparator 804 detects different value between SI and S, and that asynchronously sets the set-reset latch 806 output, NEFLT signal, high after tdNE, which hold its high state until it is reset by a high state of SDRCLK 816 which will arrive approximately a Delay period (caused by analog delay 808) after rising of NEFLT signal.
  • NEFLT signal high after tdNE, which hold its high state until it is reset by a high state of SDRCLK 816 which will arrive approximately a Delay period (caused by analog delay 808) after rising of NEFLT signal.
  • the intermediate states at SI may contain a short period of symbol value SO 822 causing the comparator 804 output NE signal to turn back low for short period (spikes 828 in the NE signal).
  • the low state of the NE signal will not affect the set-reset latch 806 output, NEFLT signal, since the set-reset latch 806 effectively filters out spikes on the NE signal before outputting the NEFLT signal.
  • the high state of NEFLT signal propagates to the SDRCLK signal 816 after a Delay period 830 caused by the analog delay 808.
  • NEFLT signal to low after tdRST.
  • the high state of SDRCLK signal 816 also enables the level latch 810 for the SI signal value to be output to S signal.
  • the comparator 804 detects that the S signal (symbol SI 832) matches the symbol S I 824 of the SI signal, and turns its output, the NE signal, to low.
  • the falling (trailing) edge 836 of the SDRCLK signal 816 causes DDRCLK signal to toggle 838 after propagation delay of its clock tree network.
  • the timing constraint for the symbol cycle period t S YM may be as follows: tdNE + Delayx2 + t dRS T + t HD ⁇ t S YM.
  • the symbol cycle time tsYM must be greater than total of: two Delay periods, tHD, tdNE, and tdRST. If the total of these four time periods exceeds the t S YM period, the trailing edge of SDRCLK overlaps the next symbol cycle, disabling the NEFLT signal from being set for the overlapping period. Note that the amount of overlapping accumulates from cycle to cycle and eventually result in a loss (skip) of a whole symbol.
  • the timing constraint for the setup time tSU may be as follows:
  • the setup time tsu must be greater than total of: one Delay period and tdNE. Failing to satisfy this condition causes the level latch 810 to propagate an invalid intermediate state of the SI input signal to the S signal.
  • FIG. 15 illustrates a first method for extracting a clock signal.
  • this method may be implemented by the circuit illustrated in FIG. 8.
  • 16 instance of the first state transition signal (SI) is compared to a level-latched instance of the first state transition signal (S) to provide a comparison signal (NE) 1502.
  • the comparison signal (NE) is filtered to provide a filtered version of the comparison signal (NEFLT) 1504.
  • the filtered version of the comparison signal (NEFLT) is delayed to provide a delayed instance of the first state transition signal (SDRCLK), where the delayed instance of the first state transition signal (SDRCLK) is used to obtain the clock signal (DDRCLK) 1506.
  • the delayed instance of the first state transition signal (SDRCLK) serves to trigger a level-latch that enables the latch-leveled instance of the first state transition signal (S) 1508.
  • the delayed instance of the first state transition signal (SDRCLK) also serves to reset a set-reset latch that provides the filtered version of the comparison signal (NEFLT) 1510.
  • FIG. 9 illustrates a clock and data transmission scheme for a 4-wire system with embedded clock information.
  • This CDR circuit is similar to that of FIG. 8 but an additional analog delay 902 has been introduced along with a one-shot logic 902/903.
  • This clock extraction circuit includes a comparator 904, a set-reset latch 906, a first analog delay device 902, a one-shot logic 902/903, a second analog delay device 908, and a level latch 910.
  • the comparator 904 may compare a first instance of the first state transition signal (SI) and a level-latched instance of the first state transition signal (S) and outputs a comparison signal (NE).
  • the set-reset latch 906 may receive the comparison signal (NE) from the comparator 904 and outputs a filtered version of the comparison signal (NEFLT).
  • the first analog delay device 902 may receive the filtered version of the comparison signal (NEFLT) and outputs a delayed instance of the filtered version of the comparison signal (NEDEL).
  • the one-shot logic 902/903 may receive the filtered comparison signal (NEFLT) and the delayed instance of the filtered version of the comparison signal (NEDEL) and outputs a second filtered version of the comparison signal (NEISHOT).
  • the second analog delay device 908 may receive the second filtered version of the comparison signal (NEISHOT ) and outputs a delayed instance of the first state transition signal (SDRCLK), where the delayed instance of the first state transition signal (SDRCLK) is used to generate the clock signal (DDRCLK).
  • the set- reset latch 906 may be reset based on the delayed instance of the first state transition signal (SDRCLK).
  • the level latch 910 may receive the first state transition signal (SI) Attorney Docket No.130645WO
  • the small delay P 902 introduced provides more margins for setup time between symbols.
  • tdRsi- reset time of the set-reset latch 906 from the rising (leading) edge of SDRCLK 916
  • tdis propagation delay of the one-shot logic 903.
  • signals SI and S hold the previous symbol value SymO 922.
  • Signals NE, NEFLT, and SDRCLK are zero.
  • the DDRCLK 914 is stable but can be either high or low.
  • Syml 924 When a new symbol value Syml 924 is being received, it causes signal SI to start changing its value.
  • the SI value may be different from Syml 924 (valid data) due to the possibility of receiving intermediate or indeterminate states 926 of the signal transition (from SymO to Syml) that may be caused, for example, by inter-wire skew, over/under shoot, cross-talk, etc.
  • the NE signal becomes high as soon as the comparator 904 detects different value between SI and S, and that asynchronously sets the set-reset latch 906 output, NEFLT signal, high after tdNE, which hold its high state until it is reset by a high state of SDRCLK 916 which will arrive approximately a Delay period S (caused by analog delay 908) after rising of NEFLT signal.
  • the intermediate states at SI may contain a short period of symbol value SymO 922 causing the comparator 904 output NE signal to turn back low for short period (spikes 928 in the NE signal).
  • the low state of the NE signal will not affect the set-reset latch 906 output, NEFLT signal, since the set-reset latch 906 effectively filters out spikes on the NE signal before outputting the NEFLT signal.
  • the one-shot circuit (logic gate 903 with analog delay P 902) generates high state on its output, NEI SHOT signal, after tdl S from rising edge of NEFLT signal, and holds the NEISHOT signal at a high state for the Delay P period 902 before turns it to a low state.
  • the high state of NEISHOT signal propagates to the SDRCLK signal 916 after a Delay S period 930 caused by the analog delay S 908.
  • NEFLT signal to low after tdRST.
  • the high state of SDRCLK signal 916 also enables the level latch 910 for the SI signal value to be output to S signal.
  • the comparator 904 detects when the S signal (symbol Syml 932) and matches the symbol Syml 924 of the SI signal, and turns its output, the NE signal, to low.
  • the low state of NEI SHOT signal propagates to the SDRCLK signal 916 after a Delay period S 930 caused by the analog delay S 908.
  • the falling (trailing) edge 936 of the SDRCLK signal 916 causes DDRCLK signal to toggle 938 after propagation delay of its clock tree network.
  • the timing constraint for the symbol cycle period t S YM may be as follows:
  • the symbol cycle time tsYM must be greater than total of: a Delay period S, a Delay Period P, t H D, tdNE, tais and tdRST- If the total of these six time periods exceeds the t S YM period, the trailing edge of SDRCLK overlaps the next symbol cycle, disabling the NEFLT signal from being set for the overlapping period. Note that the amount of overlapping period accumulates cycle by cycle and eventually results in an extra SDRCLK pulse in one symbol cycle.
  • the timing constraint for the setup time tsu may be as follows:
  • the delay period S must be less than the setup time tsu plus the maximum skew.
  • FIG. 10 is a timing diagram for the signals in the CDR circuit in FIG. 9.
  • the signal NE and then signal NEFLT are set as soon as the circuit detects the received data signal SI change from previously latched received data S regardless of the signal value, Attorney Docket No.130645WO
  • FIG. 1 1 illustrates exemplary implementations of various circuits components for the CDR circuit of FIG. 9.
  • FIG. 16 illustrates a second method for extracting a clock signal.
  • this method may be implemented by the circuit illustrated in FIGS. 9, 10 and 1 1.
  • a first instance of the first state transition signal (SI) is compared to an instance of the first state transition signal (S) to provide a comparison signal (NE) 1602.
  • the comparison signal (NE) is filtered to provide a filtered version of the comparison signal (NEFLT) 1604.
  • the filtered version of the comparison signal (NEFLT) is delayed to provide a delayed instance of the filtered version of the comparison signal (NEDEL) 1606.
  • the filtered comparison signal (NEFLT) and the delayed instance of the filtered version of the comparison signal (NEDEL) are logically combine to obtain a second filtered version of the comparison signal (NE1SHOT) 1608.
  • the second filtered version of the comparison signal (NE1SHOT ) is delayed to provide a delayed instance of the first state transition signal (SDRCLK), where the delayed instance of the first state transition signal (SDRCLK) is used to generate the clock signal (DDRCLK) 1610.
  • the delayed instance of the first state transition signal (SDRCLK) serves to trigger a level-latch that enables the latch-leveled instance of the first state transition signal (S) 1612.
  • the delayed instance of the first state transition signal (SDRCLK) also serves to reset a set-reset latch that provides the filtered version of the comparison signal (NEFLT) 1614.
  • FIG. 12 illustrates another data transmission scheme for a 4-wire system with embedded clock information. This clock recovery circuit is similar to that of FIG. 9 but an additional analog delay 1209 has been introduced.
  • This clock extraction circuit includes a comparator 1204, a set-reset latch 1206, a first analog delay device 1202, a one-shot logic 1202/1203, a second analog delay device 1208, a third analog delay device 1209, and a level latch 1210.
  • the comparator 1204 may compare a first instance of the first state transition signal (SI) and Attorney Docket No.130645WO
  • the set-reset latch 1206 may receive the comparison signal (NE) from the comparator and outputs a filtered version of the comparison signal (NEFLT).
  • the first analog delay device 1202 may receive the filtered version of the comparison signal (NEFLT) and outputs a delayed instance of the filtered version of the comparison signal (NEDEL).
  • the one-shot logic 1202/1203 may receive the filtered comparison signal (NEFLT) and the delayed instance of the filtered version of the comparison signal (NEDEL) and outputs a second filtered version of the comparison signal (NEISHOT).
  • the second analog delay device 1208 may receive the second filtered version of the comparison signal (NEI SHOT) and outputs a first delayed instance of the first state transition signal (SDRCLKO), where the first delayed instance of the first state transition signal (SDRCLKO) is used to generate the clock signal (DDRCLK).
  • the third analog delay device S I 1209 may receive the first delayed instance of the first state transition signal (SDRCLKO) and outputs a second delayed instance of the first state transition signal (SDRCKL).
  • the set-reset latch 1206 may be reset based on the second delayed instance of the first state transition signal.
  • the level latch 1210 may receive the first state transition signal (SI) and outputs the level-latched instance of the first state transition signal (S), where the level latch 1210 is triggered based on the second delayed instance of the first state transition signal (SDRCLK).
  • SI first state transition signal
  • SDRCLK second delayed instance of the first state transition signal
  • the timing diagram 1212 is very similar to the timing diagram 912 (FIG. 9), but the delay S 1208 has been replaced by two equivalent delays SO 1208 and SI 1209. This approach causes the DDRCLK to toggle earlier in FIG. 12 than in FIG. 9.
  • the timing constraint for the symbol cycle period t S YM may be as follows: tdNE + tdis + Delay SO + Delay SI + Delay P + t HD ⁇ t SYM .
  • the symbol cycle time tsYM must be greater than total of: a Delay period SO, a Delay period SI, a Delay Period P, tdNE, tdis, and 1 ⁇ 2> If the total of these six time periods exceeds the t S YM period, the trailing edge of SDRCLK overlaps the next symbol cycle, disabling the NEFLT signal from being set for the overlapping period. Note that the amount of overlapping period accumulates cycle by cycle and eventually results in an extra SDRCLK pulse in one symbol cycle.
  • the timing constraint for the delay P may be as follows:
  • the delay period S must greater than the total of: t S u plus the maximum skew. Failing to satisfy this condition causes the level latch 810 to propagate an invalid intermediate state of the SI input signal to the S signal.
  • FIG. 17 illustrates a third method for extracting a clock signal.
  • this method may be implemented by the circuit illustrated in FIG. 12.
  • a first instance of the first state transition signal (SI) is compared to a level-latched instance of the first state transition signal (S) to provide a comparison signal (NE) 1702.
  • the comparison signal (NE) is filtered to provide a filtered version of the comparison signal (NEFLT) 1704.
  • the filtered version of the comparison signal (NEFLT) is delayed to provide a delayed instance of the filtered version of the comparison signal (NEDEL) 1706.
  • the filtered comparison signal (NEFLT) and the delayed instance of the filtered version of the comparison signal (NEDEL) are logically combined to provide a second filtered version of the comparison signal (NEI SHOT) 1708.
  • the second filtered version of the comparison signal (NEI SHOT) is delayed to provide a first delayed instance of the first state transition signal (SDRCLKO), where the first delayed instance of the first state transition signal (SDRCLKO) is used to generate the clock signal (DDRCLK) 1710.
  • the first delayed instance of the first state transition signal (SDRCLKO) may be further delayed (delay SI 1209 in FIG. 12) to obtain a second delayed instance of the first state transition signal (SDRCLK) 1712.
  • the second delayed instance of the first state transition signal serves to trigger a level-latch that enables the latch- leveled instance of the first state transition signal (S) 1714.
  • the second delayed instance of the first state transition signal also serves to reset a set-reset latch that provides the filtered version of the comparison signal (NEFLT) 1716.
  • FIG. 13 illustrates yet another data transmission scheme for a 4-wire system with embedded clock information.
  • This clock recovery circuit is similar to that of FIG. 12 but a flip flop 1310 instead of the level latchl210 (FIG. 12).
  • This clock extraction circuit includes a comparator 1304, a set-reset latch 1306, a first analog delay device 1302, a one-shot logic 1302/1303, a second analog delay device 1308, a third analog delay device 1309, and a flip flop 1310.
  • the comparator 1304 may compare a first instance of the first state transition signal (SI) and a latched instance of the first state transition signal (S) and outputs a comparison signal (NE).
  • the set-reset latch 1306 Attorney Docket No.130645WO
  • the 22 may receive the comparison signal (NE) from the comparator and outputs a filtered version of the comparison signal (NEFLT).
  • the first analog delay device 1302 may receive the filtered version of the comparison signal (NEFLT) and outputs a delayed instance of the filtered version of the comparison signal (NEDEL).
  • the one-shot logic 1302/1303 may receive the filtered comparison signal (NEFLT) and the delayed instance of the filtered version of the comparison signal (NEDEL) and outputs a second filtered version of the comparison signal (NE1 SHOT).
  • the second analog delay device SI 1308 may receive the second filtered version of the comparison signal (NE1 SHOT) and outputs a first delayed instance of the first state transition signal (SDRCLKl), where the first delayed instance of the first state transition signal (SDRCLKl) is used to generate the clock signal (DDRCLK).
  • the third analog delay device S2 1309 may receive the first delayed instance of the first state transition signal (SDRCLKl) and outputs a second delayed instance of the first state transition signal (SDRCKL2) 1315.
  • the set-reset latch 1306 may be reset based on the second delayed instance of the first state transition signal (SDRCKL2) 1315.
  • the flip flop 1310 may receive the first state transition signal (SI) and outputs the latched instance of the first state transition signal (S), where the flip flop 1310 is triggered based on the first delayed instance of the first state transition signal (SDRCLKl) 1316.
  • SI first state transition signal
  • SDRCLKl first state transition signal
  • the timing diagram 1312 is very similar to the timing diagram 1212 (FIG. 12).
  • the timing constraint for the symbol cycle period t S YM may be as follows: tdNE + tdis + Delay SI + Delay P ⁇ t SYM .
  • the symbol cycle time tsYM must be greater than total of: a Delay period SI, a Delay period P, tdNE, and tdis- If the total of these four time periods exceeds the t S YM period, the trailing edge of SDRCLKl overlaps the next symbol cycle, disabling the NEFLT signal from being set for the overlapping period. Note that the amount of overlapping period accumulates cycle by cycle and eventually results in an extra SDRCLK pulse in one symbol cycle.
  • the timing constraint for the delay P may be as follows:
  • the delay period P must greater than delay period S2, which must be greater that the total of: tas + tdNE + thRREL- [00110]
  • the timing constraint for the 1 ⁇ 2) may be as follows: Attorney Docket No.130645WO
  • the timing constraint for the delay P and delay SI may be as follows:
  • FIG. 18 illustrates a fourth method for extracting a clock signal.
  • this method may be implemented by the circuit illustrated in FIG. 13.
  • a first instance of the first state transition signal (SI) may be compared to a level-latched instance of the first state transition signal (S) to provide a comparison signal (NE) 1802.
  • the comparison signal (NE) may be filtered to provide a filtered version of the comparison signal (NEFLT) 1804.
  • the filtered version of the comparison signal (NEFLT) may be delayed to provide a delayed instance of the filtered version of the comparison signal (NEDEL) 1806.
  • the filtered comparison signal (NEFLT) and the delayed instance of the filtered version of the comparison signal (NEDEL) may be logically combined to provide a second filtered version of the comparison signal (NE1SHOT) 1808.
  • the second filtered version of the comparison signal (NE1 SHOT) may be delayed to provide a first delayed instance of the first state transition signal (SDRCLK1), where the first delayed instance of the first state transition signal (SDRCLK1) is used to generate the clock signal 1810.
  • the first delayed instance of the first state transition signal (SDRCLK1) may be delayed to provide a second delayed instance of the first state transition signal (SDRCLK2), wherein the level-latched instance of the first state transition signal (S) is obtained from a level latch (1210) that is triggered based on the first delayed instance of the first state transition signal (SDRCLK2) 1812.
  • the first delayed instance of the first state transition signal (SDRCLK1) serves to trigger a flip flop that enables the latch-leveled instance of the first state transition signal (S) 1814.
  • the second delayed instance of the first state transition signal (SDRCLK2) serves to reset a set-reset latch that provides the filtered version of the comparison signal (NEFLT) 1816.
  • the embodiments may be described as a process that is depicted as a flowchart, a flow diagram, a structure diagram, or a block diagram. Although a flowchart may describe the operations as a sequential process, many of the operations can be performed in parallel or concurrently. In addition, the order of the operations may be re-arranged.
  • a process is terminated when its operations are completed.
  • a process may correspond to a method, a function, a procedure, a subroutine, a subprogram, etc. When a process corresponds to a function, its termination corresponds to a return of the function to the calling function or the main function.
  • a storage medium may represent one or more devices for storing data, including read-only memory (ROM), random access memory (RAM), magnetic disk storage mediums, optical storage mediums, flash memory devices and/or other machine readable mediums for storing information.
  • ROM read-only memory
  • RAM random access memory
  • magnetic disk storage mediums magnetic disk storage mediums
  • optical storage mediums flash memory devices and/or other machine readable mediums for storing information.
  • machine readable medium includes, but is not limited to portable or fixed storage devices, optical storage devices, wireless channels and various other mediums capable of storing, containing or carrying instruction(s) and/or data.
  • embodiments may be implemented by hardware, software, firmware, middleware, microcode, or any combination thereof.
  • the program code or code segments to perform the necessary tasks may be stored in a machine-readable medium such as a storage medium or other storage(s).
  • a processor may perform the necessary tasks.
  • a code segment may represent a procedure, a function, a subprogram, a program, a routine, a subroutine, a module, a software package, a class, or any combination of instructions, data structures, or program statements.
  • a code segment may be coupled to another code segment or a hardware circuit by passing and/or receiving information, data, arguments, parameters, or memory contents. Information, arguments, parameters, data, etc. may be passed, forwarded, or transmitted via any suitable means including memory sharing, message passing, token passing, network transmission, etc.
  • DSP digital signal processor
  • ASIC application specific integrated circuit
  • FPGA field programmable gate array
  • a general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine.
  • a processor may also be implemented as a combination of computing components, e.g., a combination of a DSP and a microprocessor, a number of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.
  • a software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.
  • a storage medium may be coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor.

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PCT/US2014/021958 2013-03-07 2014-03-07 Clock recovery circuit for multiple wire data signals Ceased WO2014138640A1 (en)

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CN201480012389.XA CN105027490B (zh) 2013-03-07 2014-03-07 用于多个线数据信号的时钟恢复电路
EP14712537.1A EP2965459B1 (en) 2013-03-07 2014-03-07 Clock recovery circuit for multiple wire data signals
KR1020157026568A KR102205823B1 (ko) 2013-03-07 2014-03-07 다중 와이어 데이터 신호들을 위한 클록 복원 회로
ES14712537T ES2705045T3 (es) 2013-03-07 2014-03-07 Circuito de recuperación de reloj para señales de datos de hilos múltiples
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US201361778768P 2013-03-13 2013-03-13
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US14/199,322 US9363071B2 (en) 2013-03-07 2014-03-06 Circuit to recover a clock signal from multiple wire data signals that changes state every state cycle and is immune to data inter-lane skew as well as data state transition glitches
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