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WO2007000060A2 - Synthetiseur d'horloge commande par logiciel - Google Patents

Synthetiseur d'horloge commande par logiciel Download PDF

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Publication number
WO2007000060A2
WO2007000060A2 PCT/CA2006/001120 CA2006001120W WO2007000060A2 WO 2007000060 A2 WO2007000060 A2 WO 2007000060A2 CA 2006001120 W CA2006001120 W CA 2006001120W WO 2007000060 A2 WO2007000060 A2 WO 2007000060A2
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WO
WIPO (PCT)
Prior art keywords
phase
clock
frame
clocks
wave
Prior art date
Application number
PCT/CA2006/001120
Other languages
English (en)
Other versions
WO2007000060A3 (fr
Inventor
John W. Bogdan
Original Assignee
Bogdan John W
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Bogdan John W filed Critical Bogdan John W
Publication of WO2007000060A2 publication Critical patent/WO2007000060A2/fr
Publication of WO2007000060A3 publication Critical patent/WO2007000060A3/fr
Priority to US11/931,026 priority Critical patent/US8374075B2/en
Priority to US12/351,824 priority patent/US9794096B2/en
Priority to US13/323,820 priority patent/US9077315B2/en
Priority to US13/763,729 priority patent/US8982974B2/en
Priority to US13/844,722 priority patent/US9100165B2/en
Priority to US14/656,264 priority patent/US9641315B2/en
Priority to US14/738,920 priority patent/US9838236B2/en
Priority to US15/582,747 priority patent/US10057047B2/en

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Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
    • H03L7/00—Automatic control of frequency or phase; Synchronisation
    • H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
    • H03L7/07—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop using several loops, e.g. for redundant clock signal generation
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
    • H03L7/00—Automatic control of frequency or phase; Synchronisation
    • H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
    • H03L7/08—Details of the phase-locked loop
    • H03L7/099—Details of the phase-locked loop concerning mainly the controlled oscillator of the loop
    • H03L7/0995—Details of the phase-locked loop concerning mainly the controlled oscillator of the loop the oscillator comprising a ring oscillator
    • H03L7/0996—Selecting a signal among the plurality of phase-shifted signals produced by the ring oscillator
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
    • H03L7/00—Automatic control of frequency or phase; Synchronisation
    • H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
    • H03L7/16—Indirect frequency synthesis, i.e. generating a desired one of a number of predetermined frequencies using a frequency- or phase-locked loop
    • H03L7/22—Indirect frequency synthesis, i.e. generating a desired one of a number of predetermined frequencies using a frequency- or phase-locked loop using more than one loop
    • 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

Definitions

  • This invention is directed to providing low cost high precision software controlled clock synthesizer (SCCS) offering significantly better stability and precision when used in conventional synchronization systems or in newly emerging precision timing protocols such as IEFE 1 *>88
  • the SCCS can be used in distributed control sy stems and in communication networks for wireless or wireline or optical transmissions w ith very w ide ranges of data rates
  • the SCCS invention defines software controlled clock sy nchronization system based on novel components such as programmable phase synthesizers (PS) precision frame phase detectors (FPD) of an incoming wave-form and noise filtering edge detectors (NFED) for precise recovering of wave-form edges from noisy signals
  • PS programmable phase synthesizers
  • FPD precision frame phase detectors
  • NFED noise filtering edge detectors
  • FPD and NFED define cii cuits and methods enabling ⁇ 10 times faster and more accurate location sy stems than prior art solutions they allow reliable location services for mobile and traffic control a
  • DPLL s for implementing software algot ithm minimizing phase erroi s and providing programmed transfer function between a DPI I output clock and a timing reference
  • said timing reference can be provided as a coin entional external clock connected to a digital phase detector which compares it with the local clock in order to produce the digital phase error or w ith time stamp messages sent by an external source initiating a capture of local clock time and communicating external clock timing corresponding to the captured local timing wherein software is used for pi oducing said digital phase errors b ⁇ comparing the captured local timing with the communicated external timing
  • timing reference comprises components having frequencies highei than I 5 of the DPLL bandw idth
  • time stamp messages are sent over regular communication links they are subjected to highly unpredictable time delay variations (TDVs) resulting from collisions between different packet streams shai ing a common communication line
  • TDVs time delay variations
  • Such unpredictable TDVs are bound to introduce timing reference components having unknow n frequency specti ums when said timing reference is provided by exchanging time stamp packages sent over shared communication link
  • Resulting stability problems cause such puor art DPPI configurations to be highly unreliaole in many applications
  • phase digitization e ⁇ ors Conventional digital phase detectors and said software algorithms minimizing phase errors involve accumulation of phase digitization e ⁇ ors Such accumulation causes an uncontrolled phase drift of the output clock when a software error minimization procedure is unable to recognize and eliminate persistent existence of an digitization error corresponding to a lasting unknown frequency error of the output clock
  • Prior art digital phase detectors offer resolutions worse than that of phase steps limited by maximum clock frequency of IC technology and they require complex processing for calculating precise phase skews when highly irregular edges of a reference timing are defined in newly emerging timing protocols such as IEEE 1588 Similai ly prior art clock synthesizers have phase steps resolutions bounded b ⁇ maximum clock frequency of IC technology and furthermore they use frequency synthesis method unable to provide high precision control of phase transients of s>nthesized clock
  • Prior art s ⁇ nchronization systems use digital phase detectors which are >5 times less accurate than this inventions I PD, and frequency synthesizers producing uncontrolled phase transients during any frequency switching and i itroducing I O times less accurate phase steps than this inventions phase synthesizer PS
  • Such prior art frequency synthesizers are based on direct digital fi equency synthesis (DDFS) method modifying average frequency of an output clock by periodical removal of a clock pulse from a continues stream of pulses Since said frequency synthesizers use over 10 times slower phase processing and introduce unknown numbers of 10 times less accurate phase steps than this inventions PS, they are unable to perform any phase synthesis and produce uncontrolled phase transients during frequenc ⁇ switching and inti oduce much more jitter than the PS C onsequentlv , in order to limit phase ti ansients to acceptable levels, said prior art synchronization systems aie bound to work in closed loop configurations wherein output clock phase is subtracted from reference clock phase and resulting phase error is minimized b ⁇ a programmable control unit driving frequenc> synthesizer producing said output clock
  • SCCS system Since the SCCS system is using said veiy accurate FPD and said very accurate PS free of any uncontrolled phase t ansients it can implement an inherently stable open loop configuration wherein a programmable control unit (PCU) provides signals producing totalK predictable output clock phase implementing precisely defined phase transfer function between an external timing reference and the output clock
  • PCU programmable control unit
  • SCCS system allows -10 times better control of output clock phase transients and much lower phase jittei b ⁇ synthesizing output phase with - 10 times smaller and more accurate phase steps than prior art solutions
  • the SCCS defines digital frame phase detector (FPD) which eliminates said accumulation of digitization eirors during phase tracking ot highly irregular waveforms communicated w ith stamp messages of IEFE 1588 protocol i
  • FPD digital frame phase detector
  • the FPD part of the SCCS invention offers > 5 times more accurate measurements of time e ⁇ ors between the local clock and an external clock occumng during variable lengths time intervals communicated by the externa! source
  • the SCCS defines digital phase synthesizer (PS) enabling direct precise control of phase transfer function between PSs input and output clocks, and the PS allows - 10 times lowerjitter of output clock phase
  • the SCCS significantly reduces system manufacturing costs by enabling use of inexpensive lower frequenc> oscillators including all oscillators alreadv used by potential customers and by enabling use of inexpensive standard CMOS technologies for synthesizing high precision synchronization clocks
  • the SCCS includes invention of a Hybrid PLL (HPLL ) which can multiply crystal frequencies as low as 3OkHz into a stable low litter clock in GHz frequency range
  • the HPLL comprises a DPLL driving an analog PI L (APLL) using an analog phase detector (APD) w ith return input connected to an APLL output clock and w ith ieference input connected to said PS receiving the APLL output clock
  • the DPLL minimizes digital phase error between said crystal oscillator clock and the APLL output clock by introducing phase steps into a transfer function of said PS which produce appropuate phase e ⁇ ois on an output of said APD Since the DPLL is progiammable it can convert any oscillator frequenc ⁇ into any
  • HPLL solution is unique as it allows multiplication of said very low frequency clocks by factors which can be made as high as 50 000 without increasing jitter or causing stability problems combined with indefinite flexibility and precision in setting frequency of generated high frequencv clocks
  • the SCCS offers unique ability of precise recovering of even single edge of incoming noisv wave-form with adaptive time-domain noise filtering edge detector (NFED)
  • NFED adaptive time-domain noise filtering edge detector
  • the SCCS is not limited to discrete sets of input/output frequencies oi local oscillator frequencies but accepts a local oscillator (LocOsc) of any frequencv, and accepts an external reference clock (Fxt_RefClk) of any frequency or an external reference waveform (Ext RefWfm) carrying anv reference frequencv while providing any required frequency of an SCCS output clock (OutClk)
  • the first part is said Hybrid PLL (HPLI ) tor multiplying said local oscillator frequency provided by a crystal producing frequencies as low, 3OkHz b> a programmed b> PCU factor which can exceed 50 000 without any increase ofjitter levels and without any stability problems
  • the HPLL provides practically indefinite flexibility and precision in setting frequency of generated high frequency clocks Resulting frequency can rise as far as is it supported b> a voltage controlled crystal oscillator (VCXO) as long as it i emains lower than maximum clock frequency which exceeds GHz ranges in present IC technologies
  • the HPLL comprises a DPLL (DPLL) driving an analog PLI (APLI ) using an analog phase detector (APD) w ith return input connected to an APLL output clock (LocClk) and w ith refei ence input connected to a local phase synthesizer (L OC PS) receiving the APLL output clock
  • the DPLL minimizes digital phase error 2 (PhaErr2) between said local oscillator (LocOsc) and the LocClk b ⁇ i troducing phase steps into an output phase of said LOC PS which are converted the APD into analog phase e rors controlling phase locking between the LocClk and the OscClk
  • he DPLL uses a frequency phase detectoi 2 (FPD2) for measuring said PhaErr2 which is read by a programmable control unit (PCU) using it for producing said phase steps introduced into said LOC PS output phase wherein amount of introduced phase steps is controlled using an MC- I INT signal received by the PCU from the LOC PS
  • the MC-MNT signals a request from the LOC PS demanding the PCU to send the next series of said phase steps when the last series is applied already
  • the FPD2 receives PCU control signals programming expected i elation betw een phase of the OutClk and phase ot a sampling clock (SampClk) derived from the LocClk through a simple multiplication b> a factor ⁇ 8
  • OE SCS softwaie controlled synthesizer
  • PCU software sub-routines for providing a progtammable phase transfer function (PTF) between the Ext_RefWfm and the OutClk
  • the OE SCS offers unique ability to piogram very precisely synchionized phase free of any uncontrolled transients Therefore the OE SCS provides 10 times better precision in frequency and phase control than prior ait
  • Said PCU controls operations of the OUT PS by defining series of phase steps inserted by the OUT PS into a i hase of the OUTCLK. i he PCU calculates said phase steps by processing a phase error 1 (PhaErrl ) received form a frame phase detector I (FPDl ) measuring phase error between the sampling clock and a filtered reference wave-form (Hlt RefWfm), time stamp messages received from a Time Stamp Decoder (TSD) recovering such messages from the FILT RefWfm ptoduced by a noise filtering edge detector (NFED)
  • PhaErrl phase error 1
  • FPDl frame phase detector
  • Hlt RefWfm filtered reference wave-form
  • TSD Time Stamp Decoder
  • the PCU controls operations of the NFED providing adaptive time domain filtering of the E ⁇ t_RefWfm carry ing synchronization signals which can be encoded into time stamp messages or can be conventional BITS references
  • the PCU receives unfiltered wave-form samples from the NFED and calculates most suitable noise filtering masks and algorithms which the PCU communicates back to the NFED (see section NOISE FILTERING EDGE DETECTORS)
  • an exact c ⁇ nc edge of the FILT RefWfm destined to capture said time stamp can be displaced in time by a known number of i essage symbols (edge displacement)
  • edge displacement is detei mined by a messaging protocol used ⁇ ince FPDl keeps capturing time stamps of all received edges of the FILT_RefWfm the FPD l or the PCU shall be equipped with an edge selection circuit (ESC)
  • ESC provides selection of time stamps captured by said sy nc edge and is synchronized by the time stamp messages produced by the Time Stamp Decoder
  • the OEC ESM comprises the previously explained OEC and is further extended by adding an output clock analog PLL (OutClk_APLL)
  • OutClk_APLL output clock analog PLL
  • the OutClk APL L filters out litter from a synthesized clock from the OUT PS (SynOutClk) c nd produces SCCS output clocks (OutClk(T I )) which are phase aligned with a reference clock selected by the PCU from a set of timing references including the Sy nOutClk, external reference clocks (Ext RefClk) and a clock signal form a mate SCCS unit (f mate)
  • Said external reference clocks are used in the external synchronization mode wherein they are produced by a master synchronization unit and are used to synchronize multiple other units located in a back-plane of a netwoi k element
  • said other units can alternatively use other synchronization references available in other synchronization modes and may be sy nchronized by the Ext_RefWfm carrying a message based piotocol or BITS D clocks v jch plurality of synchronization references and modes allows switching to one of alternative references when an active reference fails
  • he output clock analog PLL comprises a reference selector (RFS) connected to the SynOutClk from the OUT PS and to the external reference clocks and to the f mate clock and to the PCU.
  • RFS reference selector
  • the PCU controls selections of made by the RFS producing a ieference clock (RefClk) for the OutClk_APLL a return clock divider (RCD) connected to a filtered output clock (FiI OutClk) of the OutClk_ APLL and to the
  • OutClk APLL with a frequency of the RefClk an analog phase detector OutClk APD connected to the reference clock and to the return clock and producing an analog phase error (PhaDet lJP DN) driving an output clock loop filtei (OutLoopFil) which drives a VCXO producing the filtered output clock an output PLL (OUT PLL) tor multiplying one selected OutClk(T 1 ) clock and for providing phase alignment t 'tween all the OutClk APLL and the Fil OutClk, wheiein the OUT PLL is connected to the selected OutClk(T 1 ) clock and to the Fil OutClk an output clocks generator (OCG) connected to the output of the OUT PLL and to the PCU, wherein the OCG produces the OutClk(T I ) which are phase aligned but have different frequencies wherein the PCU controls OCG operations by programming said frequencies of the SCCS output clocks
  • the heterodyne timing configuration simplifies SCCS by integrating both the APLL and the OC APLL from the OEC ESM into a single APPL. and both the REF PS and OUT PS from the OEC ESM into a single RET PS
  • the HTC may still be used as a less costly alternative, if timing refeience is not provided by a message based protocol, or if a message-based protocol is used in simple networks with stable TDVs
  • Resulting HTC comprises a programmable control unit (PCU) for implementing a programmable phase transfer function (PTF) between the PCU and PCU.
  • PCU programmable control unit
  • PPF phase transfer function
  • the reference selector connected to a filtered local clock (Fil OutClk) and to the external reference clocks
  • the RFT PS introduces such phase steps into the thus synthesizing a return clock (RetClk) for the APD, the APD connected to the RefClk and to the RetClk the APD producing an analog phase error (PhaDet UP DN) driving an output clock loop filter (OutLoopFil) which drives a VCXO producing the filtered output clock the output PLL (OUT PLL) for multiplying one selected OutClk(T 1 ) clock and for providing phase alignment between all the OutClk APLL and the Fil OutClk wherein the OUT PLL is connected to the selected
  • RetClk return clock
  • OutLoopFil output clock loop filter
  • the OUT PLL produces an output reference clock (OutRef) connected to the OCG and to the FPD2, f l >e output clocks generator (OCG) connected to the output of the OUT PLL and to the PCU.
  • OCG output clocks generator
  • OCG operations by programming said frequencies of the SCCS output clocks the NFED and the TSD and the FPD l and the FPD2 having the same connectivity and performing the same operations as defined in the sub-section 1 vvith the exception of the FPD2 which is connected to the OutRef and to the LocOsc and to the PCU, wherein the PCU uses its internal micro-operations for implementing filter functions of an on chip digital PLL
  • said prior art frequency synthesizers produce unpredictable transient during frequency sw itching, they requ ⁇ e second digital phase detector for providing feedback about a phase of synthesizers output clock in order to reduce said phase transients with a DPLL
  • a Software Controlled Clock Sy nthesizer for implementing a programmable phase transfer function (PTF) between an SCCS output clock (OutClk) and external reference clocks (Ext RefClk) or an external reference carrying wave-form (Ext RefWfm) such as BITS references or line references or time stamp messages
  • the SCCS comprises a programmable control unit (PCU) using software subroutines for controlling SCCS status and for said implementation of the PTF, wheiein the PCU controls operations of a i eturn clock phase synthesizer (RET PS) the PCU has terminals for interrupts from other SCCS circuits and for a first phase error (PhaErrl ) and for a second phase error (PhaErr2) and for a time stamp message and a for a waveform sample the RET PS for synthesizing a return clock (RetClk) the RET PS connected to the PCU and to the SCCS output clock (OutClk).
  • PCU programmable
  • a reference input of the APLL is connected to the OutClk or to the Ext RefClk while the return input of the APLL is connected to the synthesized RetClk, a first frame phase detector (FPD l ) receiving a local reference clock (LocClk) and the Ext RefWfm or receiv ing the LocClk and the OutClk or receiving the Ext RefClk and the OutClk wherein the FPD l produces the PhaErrl connected back to the PCU.
  • FPD l first frame phase detector
  • said PCU uses said software subroutines for implementing a digital PLL (DPLL) by processing said first phase error and the second phase erroi into the PCU output driving the RET PS into synthesizing the RetClk providing compliance of the API L output clock w ith the phase transfer function defined by the PTF
  • DPLL digital PLL
  • the SCCS invention includes reference selection means for alternative use of one of multiple connected external timing references, such as reference clocks or external wa ⁇ eforms for producing the SCCS output clock, the
  • SCCS further comprises a reference selector connected to multiple external timing references and controlled by the PCU wherein the PCU selects one of the multiple timing references for being connected to the FPD I which is read by the PCU and used by PCU subroutines for controlling the SCCS output clock activity monitors for the external timing references for producing status signals indicating active non-active conditions wherein said status signals are connected to the PCU, wherein the output signals of the activity monitors are read and processed by the microprocessor which is producing reference selection signals connected to the reference selectois
  • the SCCS further comprises an output phase locked loop (OUT-PLL) referenced by the APLL output clock and producing a fundamental output clock, wherein the OUT-PI L has a return input connected to one SCCS output clock, an output clock generator (OCG) connected to the fundamental output clock, the OCG produces a plurality of the OUT-PLL referenced by the APLL output clock and producing a fundamental output clock, wherein the OUT-PI L has a return input connected to one SCCS output clock, an output clock generator (OCG) connected to the fundamental output clock, the OCG produces a plurality of the OUT-PLL referenced by the APLL output clock and producing a fundamental output clock, wherein the OUT-PI L has a return input connected to one SCCS output clock, an output clock generator (OCG) connected to the fundamental output clock, the OCG produces a plurality of the OUT-PLL referenced by the APLL output clock and producing a fundamental output clock, wherein the OUT-PI L has a return input connected to one SC
  • SCCS output clocks (OutClk) T he SCCS further comprises interface circuits for communication w ith an external control processor connected to the external control processor and to the PCU (see the Parallel Intel face and the Serial Interface in the FIG I and FIG 2 and FIG 3) wherein the interface circuits and the PCU enable the external control processor to read information about statuses of the activitv monitors and to select an external reference clock or the local reference clock for ieferencing the
  • interface circuits and the PCU enable the external control processor to perform switching ot mode of operation of the SCCS between the APLL mode and the DPLL mode
  • the SCCS PCU is provisioned to perform operations listed below reading information about statuses of the activitv monitoi s and selecting an external timing reference or the local reference clock for referencing the SCCS output clock vitching mode of operation of the SCCS between the APLL mode and the DPLL mode
  • the SCCS is provisioned to perform a master slave mode sw itching for maintaining phase alignment between an active SCCS unit and a backup SCCS unit installed in a back-plane for protection switching
  • the SCCS comprises a master slave subroutine reading activity monitor of a reference clock provided by a mate SCCS unit and reading internal status of the own SCCS unit wherein the master/slave subroutine performs switching to the master mode bv selecting other referencf clock than the mate s reference clock when the mate s reference clock becomes inactive or performs switching to the slave mode by selecting the mate's reference clock when the mate s reference clock is detected active during a power- up initialization of the own SCCS unit
  • the SCCS invention comprises using a progtammable phase s ⁇ nthes ⁇ zer to produce an Analog PLL return clock which can be reprogrammed to match a frequencv of a reference clock of said Analog PLl
  • APLL output clock and other SCCS reference clocks implementing digital PLL (DPLL) algorithms for providing the required phase and frequenc ⁇ transfer functions
  • the SCCS invention comprises lining frequency phase detectors (FPDs) for measuring phase errors between the APLl output clock and said other
  • SCCS reference clocks using the PCU for processing the measured phase errors and pi oducing control codes for the return clock synthesizer which implement pre-programmed phase and frequency transfer functions between the APLL output clock and said other SCCS reference clocks
  • the SCCS comprises
  • Said DPLL can provide locking to the Ext RefWfm (which can be a GPS clock) or to a local oscillator
  • the SCCS invention further comprises programmable frequency dividers for a reference signal and foi return signal of said APLL for providing j ogrammable bandwidth adjustments of the APLL p rogrammable frequency dividers in the output clock generator (OCG) which can be reprogrammed b> the PCU in order to allow utilizing a single pin of the OutClk(T 1 ) for providing multiple different output clock fiequencies, activity monitoring circuits for synchronizer input clocks and output clocks frequency monitoring circuits for synchi omzer reference clocks, status control circuits for switching synchronizer modes of operation and active reference clocks, based on an analysis of said activity and frequency monitoring circuits phase transfer control circuits foi providing a required phase transfer function between an active reference clock and synchronizer output clocks, a serial interface which allows the status control circuits and the phase transfer control circuits to be monitored and reprogrammed by an external controller (see the Senal Interface in the Fig 1 FIG 2 and FIG 3) a parallel interface which allows the status control circuits and
  • Ci master'slave switching circuit which allows a pair of integrated s> nchi onizers to work in a master slave configuration hav ing a slave synchronizer being phase locked to a mate clock which is generated by a mate master synchronizer
  • phase transfer conti ol circuits can be implemented as separate on-chip control units or with a single on-chip PCU
  • Ext RefClk One of the external reference clocks (Ext RefClk) is selected to be applied to the APLL reference input and the return phase synthesizer (RET PS) is sw itched by the PCU into producing the APLL return clock which is matching said selected external reference clock
  • the APLL output clock Fil OutClk is applied to the APLL reference input and the return phase synthesizer
  • RET PS is switched b ⁇ the PCU into producing the APLL return clock which is matching said output clock
  • FiI OutClk i he FPDl measures a phase error between the output clock multiplication SampCIk and the Ext RefWfm, and the
  • T he PCU reads the above phase erroi s and uses them to calculate new contents of the RET PS's periodical adjustment buffers and the fiactional adjustment buffers needed for inserting phase deviations requiied for providing a phase transfer function (PTF) between the output clock FiI OutClk and the Ext RefWfm, which is c iready preprogrammed in the PCU
  • PTF phase transfer function
  • he invention includes providing slave mode implementation which ieplaces the external reference clock with the mate SCCS output clock f mate, in order to drive the above described APLL configuration
  • the slave mode allows maintaining phase alignment between active and reserve SCCS units for the purpose of avoiding phase hits when protection switching reverts to using clocks from the reserve SCCS unit
  • the invention includes using the above mentioned method ot slave SCCS phase alignment for all 3 configurations shown in the Fig 1 , Fig 2 and Fig 3)
  • the invention defines the digital wave synthesis from multi-sub-clocks (DWS MSC) as a new timing method and circuit for programming and selecting a phase and a frequency of a synthesized clock
  • DWS MSC comprises programmable phase modifications which are defined below
  • Phase increases of the synthesized clock are provided by adding whole clock periods and/or fractional sub-clock c ela> s, obtained from serially connected delay elements which the reference clock is propagated through to a p resent phase obtained from a counter of reference clock periods and or a present fractional sub-clock dela>
  • Phase decreases of the synthesized clock are provided by subtracting whole clock periods and'or fractional sub- clock delays, obtained from serially connected delay elements which the reference clock is propagated through from a present phase obtained from a counter of clock periods and/or a present fractional sub-clock delay
  • the DWS MSC invention provides an implementation of programmable algorithms for synthesizing a very wide range of low and high frequency wave-forms
  • the DWS MSC invention comprises, a I -P phase generator a synchronous sequential phase processor (SSPP) for r°al time processing and selection of a phase of out-coming wave-form and a programmable computing unit (PCU) 1 >r controlling SSPP operations and supporting signal sy nthesis algorithms
  • SSPP synchronous sequential phase processor
  • PCU programmable computing unit
  • Said 1 -P phase generator is an extension of a 1 bit odd/even phase generator to p bits enabling 2 P ⁇ P phases to be generated from every reference sub-clock, as it is defined below
  • the odd'even phase generator provides splitting of i eference sub-clocks generated by outputs of a reference propagation circuit built with se ⁇ all> connected gates which a reference clock is propagated through, into odd phase sub-clocks which begin during odd cycles of the reference clock and even phase sub-clocks which begin during odd cycles of the reference clock, wheiein the odd even phase selector comprises said reference propagation circuit connected to the reference clock serially connected flip-flops wherein a clock input of a first flip-flop is connected to the reference clock and a data input of a first flip-flop is connected to an inverted output of the first flip-flop while a clock input of any other Nth flip-flop is connected to an (N- I ) output of the reference propagation circuit and a data input of the N flip- flop is connected to an output of the (N-I ) flip-flop connected to the serially connected flip-flops an odd/even selector generating the odd sub-clocks which begin during every odd reference clock cy cle and the even sub-clocks which
  • the odd even phase generator is extended into the 1 -P phase generator splitting the reference sub-clocks into 1 -P phase sub-clocks which begin during the corresponding 1 -P cy cles of the reference clock
  • the 1 -P phase selector further comprises a parallel 1 -P sub-clock counter built as an extension to the first flip-flop working as 1 -2 counter wherein the whole 1 -P sub-clock counter is clocked by the first reference sub-clock wherein an output of the 1 -P sub-clock counter represents a 1 -P phase number of the first sub-clock
  • 1 -P phase selectoi s built as extensions to the co ⁇ esponding odd'even selectors
  • a first 1 -P selector is connected to the I -P sub-clock counter and selects a phase of the first reference sub-clock, defined by the 1 -P sub-clock counter w hile every next N-K* 1 phase selector is connected to its N-K buffer and to its W-K+ 1 reference sub-clock (0 ⁇ K ⁇ N) wherein every next N-K+ 1 phase selector generates phases, of its N-K- I sub- clock defined by its buffer content plus (N-K)
  • the 1 -P phase generator can use both solutions defined below using rising edges of the reference sub-clocks for clocking the 1 -P sub-clock counter and the 2-P buffers while negative pulses of the reference sub-clocks are used for activating outputs of the 1 -P selectors generating the 1 -P phase sub-clocks, i using rising edges of the reference sub-clocks for clocking the 1 -P sub-clock counter and the 2-P buffers while r egative pulses of the reference sub-clocks are used for activating outputs of the 1 -P selectors generating the 1 -P p hase sub-clocks
  • the 1 -P phase generator can use the serially connected gates of the reference propagation circuit, which are connected into a ring oscillator controlled by a PLL circuit oi are connected into a delay line control by a delay locked loop (DLL) circuit or are connected into an open ended dela ⁇ line
  • this 1 -P phase generator invention includes extending the remaining 2 -N flip-flops w ith parallel sub- clock counters, the same as the parallel sub-clock counter extending the 1 st flip-flop, instead of using the defined hove 2-P multi-bit buffers
  • the use of the 2-P parallel counters requires adding preset means for all the 1 -P counters in order to maintain the same or predictably shifted content in all the 1 -N parallel counters Continues maintaining of said predictability of all the parallel counters content is necessary for generating predictable sequences of multiphase sub-clocks
  • Said SSPP invention comprises a selection of one of multi sub-clocks for providing an edge of out-coming synthesized signal, where said sub-clocks are generated by the outputs of serially connected gates which an SSPP reference clock is propagated through
  • the SSPP comprises calculating a binar ⁇ positioning of a next edge of the out-coming wave-form versus a previous wave edge, which represents a number of reference clock cycles combined with a number of reference clock fractional delays which correspond to a particular sub-clock phase delay versus the reference clock Furthermore the SSPP comprises selective enabling of a particular sub-clock, which provides the calculated phase step between the previous and the current wave-form edges
  • the SSPP further comprises a synchronous sequential processing (SSP) of incoming signal by using multiple ⁇ ally connected processing stages with ever ⁇ stage being fed b> data from the previous stage which ate clocked- 1 1 by a clock which is synchronous with the reference clock
  • SSP synchronous sequential processing
  • the synchronous sequential processor multiplies processing speed by splitting complex signal processing operation into a sequence of singular micro-cycles, wherein ever> consecutive micro-c> cle of the complex operation is performed by a separate logical or arithmetical processing stage during a corresponding consecutive time slot s ⁇ nchronous with a reference clock providing a fundamental timing for a synthesized wave-form, se ⁇ a!l> connected sequential stages are connected to a programmable control unit (PCU), wherein the sequential stages are clocked by reference sub-clocks generated by a reference propagation circuit built with serially connected gates which the reference clock is propagated through whereby inputs from the PCU are processed into a phase delay between a next edge of the synthesized wave-form versus a previous edge and a position of the next edge is calculated by adding the phase delay to a position of the previous edge wherein the positions of wave-form edges are provided by a last of the sequential stages and said positions are expressed as numbers identifying reference sub-clocks needed for generating said wave-form
  • the above defined SSP can be implemented by processing said inputs from the PCU into a phase modification step which is added to a period of the reference clock in order to calculate the phase delay
  • this invention includes the SSP circuit upgraded into a parallel multiphase processor (PMP) by extending the time slot allowed for the micro-cycles of the s>nchronous sequential processor by a factor of P wherein
  • PMP parallel multiphase processor
  • l he parallel multiphase processor further comprises a parallel processing phase 2-P built w ith plurality of 2-P parallel multiphase stages which are connected serially and are driven b ⁇ the phase sub-clocks belonging to the same 2-P phase
  • the SSPP invention comprises the use of the parallel multiphase processing for sy nthesizing a target wave-form by assigning consecutive parallel phases for the processing of a synthesized signal phase using signal modulation data provided by a programmable control unit (PCU) or bv any other source
  • PCU programmable control unit
  • the SSPP invention comprises using 1 to N parallel phases which are assigned for processing incoming signal data with clocks corresponding to reference clock periods number 1 to N as it is further described below
  • circuits of phase 1 process edge skews or phase skews or other incoming signal data with a clock which corresponds to the reterence clock period number 1
  • the above mentioned sub-clock selecting methods further include
  • the SSPP invention includes using said serially connected gates
  • Every said sub-clock phase delay versus the reference clock phase amounts to a fraction of a reference clock period which is defined by a content of a fraction selection register which is assigned for a particular processing phase and is driven by the SSPP
  • the SSPP invention includes a parallel stage pi ocessing of an incoming signal providing multiple processing stages which are driven by the same clock which is applied simultaneously to inputs of output registers of all the parallel stages
  • the SSPP further comprises
  • the SSPP invention includes using the 1 -P phase generator defined above to generate SSPP clocks which drive said parallel phases and said sequential stages and to generate selector sw itching signals for said merging and splitting of processing phases
  • the SSPP invention includes time sharing of said parallel phases which is based on assigning a task of processing of a next wave-form edge timing to a next available parallel processing phase
  • the SSPP comprises a timing control (TC) cii cuit which uses decoding of reference clock counters and oi other ⁇ ave edge decoding and said SSPP clocks for performing said time sharing phase assignments and for further c ontrol of operations of an already assigned phase
  • TC timing control
  • 1 he SSPP comprises passing outputs of a one parallel phase to a next parallel phase, in order to use said passed outputs for processing conducted b ⁇ a follow ing stage of the next parallel phase
  • the outputs passing is performed b ⁇ l e-timing output register bits of the one phase b> clocking them into an output register of the next parallel phase simultaneously with processing results of the next parallel phase
  • 1 he SSPP further comprises all the possible combinations of the above defined parallel multiphase processing parallel stage pi ocessing synchronous sequential processing, merging of processing phases, splitting of processing phases and outputs passing
  • the SSPP invention includes processing stage configurations using selectors arithmometers and output registei s which are arranged as it is defined below
  • 1 he SSPP invention comprises: using switching signals of said input selectors for producing pulses which clock data into output registers of previous stages; using switching signals of said output selectors for producing pulses which clock data into output registers of previous stages;
  • the SSPP invention also comprises: using results obtained in earlier stages for controlling later stages operations, and using results obtained in the later stages for controlling the earlier stages operations.
  • Proper arrangements of said parallel and sequential combinations and said stages configurations provide real time processing capabilities for very wide ranges of signal frequencies and enable a wide coverage of very diversified application areas.
  • 1 he DWS MSC invention comprises two different methods for accommodating a phase skew between the reference clock and a required carrier clock frequency of the transmitted signal, and both methods allow elimination of ambiguities and errors in encoding of output signal data patterns. Said two methods are further defined below:
  • a source of the reference clock provides frequency or phase alignment with the timing of the data which are being encoded and sent out in the synthesized output wave-form
  • phase skews between the reference clock and the timing of the destined for transmission data are digitally measured and translated into implemented by the SSPP phase adjustments of the synthesized signal which provide required carrier frequency of the transmitted output signal;
  • both above mentioned methods include measurements of phase or frequency deviations of the destined for transmission data versus the reference clock, and using said measurements results to assure required carrier frequency of the synthesized signal.
  • the DWS MSC method comprises phase modulations of the synthesized wave-form by adding or subtracting a number of reference clock periods and/or a number of fractional delays to a phase of any edge of the
  • Said adding or subtracting of a number of reference clock periods is further referred to as a periodical adjustment, and said adding or subtracting of fractional delays is further called a fractional adjustment.
  • the DWS MSC method allows synthesizing of any waveform by modulating a phase of the reference clock with periodical and/or fractional adjustments of any size.
  • the invention also includes the Phase Synthesizer (PS) for carrying out the DWS MSC method; as it is further explained below and is shown in FlG.4, FlG.4A, FIG.5. and FIG.6.
  • the Timing Diagram of the PS is shown in the FIG.7.
  • phase synthesizer provides programmable modifications of a phase of a synthesized clock by unlimited number of gate delays per a modification step with step resolution matching single gate delay at steps frequencies ranging from 0 to 1 /2 of maximum clock frequency
  • delay control circuit is connected to a programmable control unit (PCU) wherein the delay control circuit defines size and frequency of phase delay modifications of the synthesized clock versus a reference clock, the delay control circuit also having a terminal connected to reference sub-clocks generated by a reference propagation circuit or connected to odd/even sub-clocks generated by an odd/even phase selector
  • the reference clock is connected to the reference propagation circuit consisting of serially connected gates wherein outputs of the gates generate the reference sub-clocks providing variety of phase delays versus the reference clock
  • the reference sub-clocks are connected to an odd/even phase selector which splits the reference sub-clocks by generating separate odd sub-clocks and even sub-clocks, wherein the odd sub-clocks begin during odd cycles of the reference clock and the even sub-clock
  • !t ⁇ output selector is connected to the output of the clock selection register and to the outputs of the odd/even phase selector, wherein the output selector uses inputs from the clock selection register for selecting output of the odd/even phase selector which is passed through the output selector for providing the synthesized clock.
  • the above defined PS can use the odd/even phase generator or the 1 -P phase generator, which have been already defined above.
  • the PS can use the delay control circuit implemented with the parallel multiphase processor (PMP) which has been already defined above.
  • PMP parallel multiphase processor
  • the PS invention comprises 2 different implementation methods, which are explained below.
  • the first PS implementation method is based on moving a synthesized clock selection point from a delay line which propagates a reference clock (see the FIG.4); wherein: said phase increases are provided by moving said selection point of the synthesized clock from the reference clock i •Opagation circuit, in a way which adds gate delays to a present delay obtained from the propagation circuit; s iid phase decreases are provided by moving said selection point of the synthesized clock from the reference clock propagation circuit, in a way which subtracts gate delays from a present delay obtained from the propagation circuit;
  • the first PS implementation method is conceptually presented in FIG.4 & FIG.6, and its principles of operations are explained below.
  • the PLL x L Freq. Multiplier produces the series of sub-clocks CIkO, CIkR - Clkl .
  • the sub-clock CIkO keeps clocking in a reversed output of its own selector PRO.
  • the sub-clocks CLkR-CIkI keep clocking in outputs of the previous selectors PRO, PRR - PR2 into their own selectors PRR-PRl .
  • every selector in the PRO is being reversed by every CIkO, every selector in the PRO, PRR - PRI chain is being reversed as well by a falling edge of its own sub-clock CIkO, CIkR - Clk l . and every selector in the chain represents reversal of its predecessor which is delayed by a single sub-clock fractional delay.
  • PR lN - PRR select sub-clocks CIkO, Clkl - CIkR during any odd processing phase, and their reversals PRON, PRl - PRRN select sub-clocks CIkO, Clkl - CIkR during any even processing phase.
  • phase l The odd/even processing phase has been named phase l /phase2, and their sub-clocks are named 1 CIkO, 1 Clkl -
  • phase l /phase2 sub-clocks are used to run a phase synthesis processing in separate designated for ⁇ hasel/phase2 phase processing stages which work in parallel, a time available for performing single stage operations is doubled (see also the FIG.6 for more comprehensive presentation of said parallel processing).
  • CSRl Clock Selection Register 1
  • the Clock Selection Register 1 can be reloaded at the beginning of the phase2 by the 2CIkO and its decoders shall be ready to select a glitch free phase 1 sub-clock which is defined by any binary content of the
  • the CSR2 is reloaded by the I CIkO, in order to select a single glitch free sub-clock belonging to the phase2.
  • the second PS implementation method is based on adjusting alignment between an exit point of the synthesized clock from the reference propagation circuit versus an input reference clock; in a way which adds gate delays for phase increases, and subtracts gate delays for phase decreases.
  • FIG.4A The second method is presented in FIG.4A. and its differences versus the FIG.4 are explained below.
  • the moving exit point from the driven by Fsync/2Dsel phase locked delay line is used as a return clock for the PLL x 2Dsel multiplier, instead of using a fixed output of the INVO to be the PLL return clock.
  • I he fixed output of the INVO is divided by the programmable frequency divider (PFD) in order to provide the synthesized clock Fsynt, instead of the moving synthesized clock selection point.
  • PFD programmable frequency divider
  • the PS invention comprises using all the listed below reference clock propagation circuits by any of the two methods: an open ended delay line built with serially connected logical gates or other delay elements; a ring oscillator built with serially connected logical gates or other delay elements, which have propagation delays controlled in a PLL configuration; a delay line built with serially connected logical gates or other delay elements, which have propagation delays iy controlled in a Delay Locked Loop (DLL) configuration.
  • DLL Delay Locked Loop
  • Said selection of a sub-clock for synthesized clock timing can be physically implemented in two different ways: by using phase producing gates from 1 invO to 1 invR and from 1 invO to 1 invR, as having 3state outputs with enable inputs EN, one of which is enabled by one of the outputs of the sub-clock selection gates from l selO to l selR and from 2selO to 2selR; or by using the sub-clock selection gates which have all their outputs connected into a common collector configuration (instead of having them followed by the 3state gates), in order to allow a currently active output of one of the sub-clock selection gates to produce a phase of the synthesized clock FselN.
  • 1 he PS invention comprises fractional adjustments of synthesized clock phase for providing high resolution phase modifications by fractional parts of a reference clock period.
  • the PS invention comprises combined periodical and fractional adjustments of synthesized clock phase, which use counters of reference clock periods for generating counter end (CE) signals when a periodical part of a phase adjustment is expired.
  • the PS invention further comprises using said counter end signals for generation of control signals which assign and/or synchronize consecutive parallel processing phases for processing consecutive combined or fractional phase adjustments of the synthesized clock.
  • the PS invention comprises:
  • the Frame Phase Detector operates as follows: r ieasures local clock phase continuously by counting time units signaled by the local clock; uses abstract frame consisting of time intervals defined by software for high resolution measurements of local clock phase error versus an external clock phase defined by it's frame signaled by external events, wherein such time intervals expected by software and expressed in local time units are subtracted from time intervals between said external events measured in local clock units; resulting phase error is read back by software subroutines.
  • Such software defined frame instead of using an equivalent frame produced by hardware is advantageous, as it eliminates circuits and errors associated with using such electrical local frame and allows instant phase adjustments to be applied after the arrival of the external frame thus resulting in more stable DPLL operations. Furthermore such software frame is more suitable for time messaging protocols such as IEEE 1588.
  • the FPD comprises solutions outlined below.
  • a frame phase detector for measuring a frame phase skew between a first frame consisting of a programmable sequence of expected numbers of sampling local clocks, and a second frame defined with a series of time intervals located between second frame edges defined by changes of an external frame signal or by changes of a frame status signal driven with external messages such as time stamps, wherein a frame measurement circuit captures a number of said sampling clocks occurring during an interval of the second frame and a phase processing unit subtracts the captured number from the expected number representing expected duration of the corresponding interval of the first frame; wherein-the frame phase detector comprises: a means for a detection of said second frame edges, by detecting said changes of the external frame signal, or by detecting said changes of the frame status driven by the external messages; the frame measurement circuit using the sampling local clock, which is a higher frequency signal, to measure said time intervals of the second frame having lower frequency, wherein the frame measurement circuit counts said sampling clocks occurring during every interval of the second frame and captures and buffers the counted value until it is read
  • FPD
  • a frame phase detector as described in statement 1 wherein said second frame begins with a numerical first edge, representing initial phase of the second frame, defined as a number of sampling delays between an expected location of such numerical first edge and the first counted sampling clock, wherein the frame measurement circuit is preset to the numerical first edge before any said counting of the sampling clocks takes place; the frame phase detector comprising: a means for presetting the frame measurement circuit to said numerical first edge before said counting of the sampling periods of the first interval of the second frame takes place; a means for supplementing said preset numerical first edge by adding following sampling periods counted until the second edge of the second frame is encountered, and a means for for for capturing and buffering a resulting total number of sampling periods until it is read by a phase processing unit; wherein the resulting total number of the sampling periods represents duration of such first interval of the second frame and is made available for further processing.
  • a frame phase detector as described in statement 1 receiving an incoming wave-form carrying the external frame signal or carrying the external message; the frame phase detector wherein: said detection of the second frame edges from the incoming wave-form, is performed by a circuit synchronized with the local sampling clock and producing a known propagation delay.
  • an FPD as described in statement 1 wherein the frame phase skew is calculated without any accumulation of digitization errors of said intervals phase skews while the single intervals phase skews are still available for intermediate signal processing; the FPD comprising: a means for rounding said counted number of the sampling periods by adding 1 such sampling period to the counted number defining length of said frame interval, wherein 1/2 of the added sampling period approximates a fraction of the sampling period occurring before said counting of the interval sampling periods and another 1/2 of the added sampling period approximates a fraction of the sampling period occurring after said counting; whereby such addition of 1 sampling period to every interval measurement, provides all sampling periods occurring between said counted numbers of sampling periods relating to consecutive intervals of the second frame, and reduces a digitization error of any long frame to a time sampling error of a single interval.
  • a frame phase detector as described in statement 1 including a high resolution circuit for extending resolution of phase measurements below a period of the local clock, wherein the high resolution circuit propagates the local clock through a delay line built with serially connected gates producing different phases of the local clock; the frame phase detector comprising: t ie high resolution circuit using a phase capture register for capturing a state of outputs of the serially connected gates, which the local clock is propagated through, at an edge of the interval of the second frame; or the high resolution circuit using a phase capture register for capturing an edge of the interval of the second frame by using the outputs of the serially connected gates as sampling sub-clocks applied to clocking-in inputs of the phase capture register while said second frame , defined with the frame signal or the frame status, is applied to data inputs of the phase capture register.
  • a frame phase detector as described in statement 1 including a high resolution circuit for extending resolution of phase measurements below the period of the local clock, wherein the high resolution circuit propagates the second frame, defined with the frame signal or the frame status, through a delay line built with serially connected gates producing different phases of the second frame; the frame phase detector comprising: the high resolution circuit using a phase capture register for capturing a phase of an edge of the interval of the second frame by applying the outputs of the serially connected gates which the second frame is propagated through to data inputs of the phase capture register while the local clock is used for clocking the data inputs in; v the high resolution circuit using a phase capture register for capturing a phase of an edge of the interval of the second frame by using the outputs of the serially connected gates-which the second signal frame is propagated through-as clocking in signals while the local clock is applied to data inputs of the phase capture register.
  • a frame phase detector as described in statement 1 including a noise filtering edge detector (NFED) improving reliability and precision of said detection of the second frame edges by removing phase noise from wave-form edges and amplitude glitches from wave-form levels through continues over-sampling and digital filtering of an entire incoming wave-form carrying said external frame signal or said external messages, wherein the incoming wave-form is over-sampled with sampling sub-clocks generated by a delay line built with serially connected gates which the sampling local clock is propagated through, and wave-forms variable length pulses are processed by comparing an edge mask, which provides an expected pattern of wave-form samples corresponding to an edge of the wave-form, with a sequence of wave-form samples surrounding a consecutive analyzed sample; the FPD wherein the NFED further comprises: a wave capturing circuit for capturing results of sampling the incoming wave-form in time instances produced by the outputs of the delay line which the sampling local clock is propagated through; means for performing logical or arithmetic operations on particular samples of the edge mask and
  • the invention of the NFED is directed to signal and data recovery in wireless, optical , or wireline transmission systems and measurement systems.
  • the noise filtering edge detector provides digital filtering of waveform pulses transmitting serial streams of data symbols with data rates reaching ' ⁇ of maximum clock frequency of IC technology.
  • the NFED enables: continues waveform over-sampling with sampling frequencies 5 times higher than the maximum clock 1 equency; elimination of phase jitter from edges of the pulses and elimination of amplitude glitches from insides of the pulses as well; and a system for adaptive noise filtering based on analysis of captured unfiltered portions of the over- sampled waveform.
  • noise filtering edge detectors shall be particularly advantageous in system on chip (SOC) implementations of signal processing systems.
  • the NFED invention provides an implementation of programmable algorithms for noise filtering for a very wide range of low and high frequency wave-forms.
  • the NFED is based on invention of a synchronous sequential processor (SSP) which allows > 10 times faster processing than digital signal processors of prior art.
  • SSP synchronous sequential processor
  • the NFED comprises: the SSP used for capturing and real time processing of an incoming waveform (see the end of this sub-section);
  • WFSC wave-from screening & capturing circuit
  • PCU programmable control unit
  • the NFED compares: a captured set of binary values surrounding a particular bit of a captured waveform, with an edge mask comprising a programmed set of binary values. Such comparison produces an indicator of proximity between the surrounded bit and an expected edge of the waveform.
  • the indicator is named edge proximity figure (EPF). Said comparison comprises:
  • NFED further comprises: modulating locations of detected rising and/or falling waveform edges by an edge modulating factor (EMF) used to modify edge thresholds which are subtracted from the EPFs. wherein such reduced EPFs are used for finding edge location: using an edge modulation control register (EMCR) programmed by the PCU, for defining function transforming said EMFs into said modifications of edge thresholds.
  • EMF edge modulating factor
  • EMCR edge modulation control register
  • the NFED still further comprises displacing detected edges by a preset number of bits, in order to compensate for inter-symbol interference ISI or other duty cycle distortions.
  • the NFED invention further includes:
  • edge mask registers for providing said edge masks used for detecting rising and/or falling waveform edges
  • edge threshold registers for providing said edge thresholds used for detecting rising and/or falling waveform edges
  • edge displacement registers for providing said edge displacement numbers used for shifting detected rising and/or falling edges by a programmable number of bits of waveform processing registers
  • filter control registers which control; said logical and/or arithmetic operations conducting the comparison of captured waveform bits with the edge mask, and said edge displacements in the processed waveforms;
  • the NFED invention comprises: a wave capturing circuit for capturing an incoming wave-form sampled by sub-clocks produced by the outputs of the delay line which the sampling clock is propagated through; a circuit performing logical or arithmetic operations on particular samples of the edge mask and their counterparts from the wave-form samples surrounding the consecutive analyzed sample of the captured wave-form; using the results of said operations for defining a filtered location of an edge of the waveform.
  • Such NFED further comprises: a filter arithmometer for comparing the edge mask with the captured wave-form in order to introduce noise filtering corrections of the edges of the filtered wave-form; a filter mask register providing the edge mask which is compared with the captured wave-form of an input signal and/or filter control register which provides code for controlling operations of said filter arithmometer in order to provide said corrections of the filtered wave-form.
  • the NFED compares said edge mask samples of the expected edge pattern with samples from a consecutive processed region of the captured wave-form. Consequently the NFED comprises: accessing any said consecutive processed region of the captured wave-form and using such region as comprising samples corresponding to the edge mask samples; selection of a consecutive sample from the edge mask and simultaneous selection of a corresponding consecutive sample from the processed region of the captured wave-form; calculating a correlation component between such selected samples by performing an arithmetical or logical operation on said selected samples; calculating a digital correlation integral by adding said correlation components calculated for single samples of the edge mask.
  • the NFED includes calculating correlation integrals for said consecutive processed regions uniformly spread over all the captured wave-form, wherein the calculated correlation integrals are further analyzed and locations of their maximums or minimums are used to produce said filtered locations of said edges of the filtered wave-form; ; uch NFED operations comprise; moving said processed region by a programmable number of samples positions of the captured wave-form; sloring and comparison of said correlation integrals calculated for different processed regions, in order to identify said maximums or minimums and their locations; using said locations of said maximums or minimums for producing the filtered locations of the edges of the filtered wave-from.
  • the NFED includes compensation of inter-symbol interference (ISI) or other predictable noise by adding a programmable displacement to said filtered location of the edge of the wave-form.
  • ISI inter-symbol interference
  • the NFED comprises: programmable amendment of the filtered location of the wave-form edge by presetting said programmable displacement with a new content; using such newly preset displacement for shifting the filtered location of the next detected edge.
  • the NFED includes compensation of periodical predictable noise with programmable modulations of said filtered locations of the wave-form edges by using an edge modulating factor (EMF) for a periodical diversification of said edge thresholds corresponding to different said regions of the wave-form; wherein the NFED comprises: modulation of the filtered locations of the wave-form edges by using the edge modulating factor (EMF) for modulating said edge thresholds; subtracting such modulated thresholds from the correlation integrals calculated in said different wave-form regions; using such reduced correlation integrals for locating said maximums defining locations of filtered edges.
  • EMF edge modulating factor
  • the NFED further includes: using an edge modulation control register (EMCR) programmed by the PCU, for said modulation of the edge thresholds.
  • EMCR edge modulation control register
  • the NFED comprises: sequential processing stages configured into a sequential synchronous pipeline processor driven synchronously with said sampling clock. I he NFED further comprises parallel processing phases implemented with said synchronous sequential p+f processors; wherein: said parallel processing phases are driven by clocks having two or more times lower frequencies than said sampling clock; consecutive parallel phases are driven by clocks which are shifted in time by one or more periods of said sampling clock;
  • the NFED comprises using multiple noise filtering sequential stages in every parallel processing phase for extending said wave-form filtering beyond a boundary of a single phase.
  • Such NFED further includes an over-sampled capturing of consecutive wave-form phases in corresponding phases wave registers which are further rewritten to wave buffers with overlaps which are sufficient for providing all wave samples needed for a uniform filtering of any edge detection despite crossing boundaries of the wave buffers which are loaded and used during different said phases; wherein the NFED comprises: rewriting the entire wave register belonging to one phase into the wave buffer of the same phase and rewriting an end part of said wave register into a front part of the next phase wave buffer, while the remaining part of the next wave buffer is loaded from the wave register belonging to the next phase; whereby every wave buffer contains entire said wave-form regions needed for calculating said EPF's corresponding to the samples belonging to the phase covered by this buffer.
  • the NFED includes: merging of said parallel processing phases, wherein multiple said parallel processing phases are merged into a smaller number of parallel phases or into a single processing phase, when passing from one said sequential processing stage to the- next sequential stage, splitting of said parallel processing phases, wherein one said processing phase is split into multiple parallel processing phases or multiple parallel processing phases are split into even more parallel phases, when passing from one said sequential processing stage to the next sequential stage.
  • the NFED includes said PCU for analyzing results of said real time signal processing form the SSP and for controlling operations of the SSP; wherein the PCU comprises: means for reading results of captured signal processing from the SSP;
  • the NFED includes a wave-form screening and capturing circuit (WFSC) for capturing pre-selected intervals of unfiltered over-sampled wave-form; wherein the WFSC comprises: using programmable screening masks and/or programmable control codes for verifying incoming wave-form captures for compliance with said programmable screening masks, buffering captured wave-form for which the pre-programmed compliance or non-compliance has been detected, or for counting a number of said detections; communicating said buffered wave-form and a detections counter to the PCU.
  • WFSC wave-form screening and capturing circuit
  • the PCU reads resulting captured signals from the WFSC and controls operations of the WFSC; wherein the PCU comprises: programming the screening masks and/or the control codes for performing said verification of captured wave-forms compliance or non-compliance with said screening patterns; reading verification results and/or reading captured wave-forms which correspond to the preprogrammed verification criteria.
  • the NFED includes using said PCU for adaptive noise filtering; wherein the PCU comprises: means for programmable waveform analysis: means for loading edge mask registers which provide said edge masks used for detecting rising and/or falling waveform edges; or means for loading edge threshold registers which provide said edge thresholds used for detecting rising and/or falling waveform edges; or means for loading edge displacement registers which provide said edge displacements used for shifting detected rising and/or falling edges by a programmable number of samples positions of the captured wave-form; or means for loading filter control registers which control said logical and/or arithmetic operations conducting the comparison of captured wave-form samples with the edge mask, and said edge displacements in the processed wave-forms; i 1 means for controlling said EMF by presetting the EMCR in accordance with adaptive noise filtering algorithms.
  • the SSP includes real time capturing and processing of in-coming wave-form and a programmable computing unit (PCU) for controlling SSP operations and supporting adaptive signal analysis algorithms.
  • PCU programmable computing unit
  • Said SSP comprises an over-sampling of incoming wave-form level by using a locally generated sampling clock and its sub-clocks generated by. the outputs of serially connected gates which the sampling clock is propaga f ed through. If an active edge of the wave-form is detected by capturing a change in a wave-form level, the position of the captured signal change represents an edge skew between the wave-form edge and an edge of the sampling clock.
  • the SSP includes 3 other methods of the edge skew capturing which are defined below:
  • the above mentioned edge skew capturing methods further include:
  • the SSP invention includes using said serially connected gates:
  • Every said edge skew amounts to a fraction of a sampling clock period.
  • t he SSP invention comprises measuring time intervals between active wave form edges, as being composed of said tdge skew of a front edge of the incoming waveform, an integer number of sampling clock periods between the front edge and an end edge, and said edge skew of the end edge of the wave-form.
  • the SSP invention further comprises a parallel multiphase processing of incoming signal by assigning consecutive parallel phases for the capturing of edge skews and/or processing of other incoming wave-form data with clocks which correspond to consecutive sampling clocks.
  • the SSP invention comprises using 1 to N parallel phases which are assigned for processing incoming signal data with clocks corresponding to sampling clock periods numbered from 1 to N, as it is further described below:
  • circuits of phase 1 process edge skews or phase skews or other incoming signal data with a clock which corresponds to the sampling clock period number 1 ;
  • circuits of phase N process edge skews or phase skews or other incoming signal data with a clock which corresponds to the sampling clock period number N.
  • Said parallel multiphase processing allows N times longer capturing and/or processing times for said multiphase stages, compared with a single phase solution.
  • the SSP invention includes parallel stage processing of incoming signal by providing multiple processing stages which are driven by the same clock which is applied simultaneously to inputs of output registers of all the parallel stages.
  • the SSP further comprises a synchronous sequential processing of incoming signal by using multiple serially connected processing stages with every stage being fed by data from the previous stage which are clocked-in by a clock which is synchronous with the sampling clock.
  • SSP further comprises:
  • SSP invention includes a sequential clock generation (SCG) circuit which uses said clock selectors and said sub-clocks: to generate SSP clocks which drive said parallel phases and said sequential stages, and to generate selector switching signals for said merging and splitting of processing phases.
  • SCG sequential clock generation
  • the SSP invention includes time sharing of said parallel phases: which is based on assigning a task of processing of a newly began wave-form pulse to a next available parallel processing phase.
  • the SSP comprises a sequential phase control (SPC) circuit, which uses results of a wave edge decoding and said
  • SSP clocks for performing said time sharing phase assignments and for further control of operations of an already assigned phase.
  • SSP comprises passing outputs of a one parallel phase to a next parallel phase, in order to use said passed outputs for processing conducted by a following stage of the next parallel phase.
  • the outputs passing is performed: by re-timing output register bits of the one phase by clocking them into an output register of the next parallel phase simultaneously with processing results of the next parallel phase.
  • the SSP further comprises all the possible combinations of the above defined: parallel multiphase processing, parallel stage processing, synchronous sequential processing, merging of processing phases, splitting of processing phases, and outputs passing.
  • the SSP invention includes processing stage configurations using selectors, arithmometers, and output registers, which are arranged as it is defined below:
  • input selectors select constant values or outputs of previous stages or outputs of parallel stages or an output of the same stage to provide arithmometer inputs, and arithmometer output is clocked-in to an output register by a clock which is synchronous to the sampling clock;
  • Proper arrangements of said parallel and sequential combinations and said stages configurations provide real time processing capabilities for very wide ranges of signal frequencies and enable a wide coverage of very diversified application areas.
  • the wave-form screening and capturing circuits comprises:
  • Said PCU comprises implementation of the functions listed below:
  • first PS implementation is selected for the preferred embodiment, and it is shown in the I IG.4, FIG.5, FIG.6 and FIG.7.
  • the PS invention comprises wave timing definition, which includes two major components downloaded to the PS from the PCU: basic less frequently changed phase adjustments, which can include both periodical adjustments and fractional adjustments, define more stable components of wave-form phase; high frequency phase modulations, which can include both the periodical adjustments and the fractional adjustments, allow every leading edge phase and/or every falling edge phase to be modulated with a different modulation factor.
  • phase modulations are downloaded to the PS simultaneously in batches containing multiple different modulation factors, where every said batch refers to a series of consecutive wave edges.
  • the PS has internal selection circuits, which select and use consecutive modulation factors for modulating phases of consecutive edges.
  • modulation factors M l , M2 - M6, M7 are shifted left, by one factor for every new edge, in the Phase Modulation Buffers (PMB 1 /PMB2) for providing consecutive modulation factor needed for a next edge in the left end of the PMB 1/PMB2.
  • Such updated modulation factor is then added to the basic phase adjustments and resulting modulated phase adjustments are downloaded into the Periodical Number Registers (PNR1/PNR2) and into the Fractional Number Registers (FNRl /FNR2).
  • the CSR1/CSR2 registers are loaded by the early sub-clocks of the present Phase2/Phasel cycle of the fsync.
  • the CSR1/CSR2 are loaded: with a current content of the Fractional Selection Register (FSR) (shown in FIG.6), if the LD Cl or LD C2 (Load
  • Timing Control (TC) circuits are shown in FIG.5, the resulting Timing Diagram of Phase Synthesizer (TDPS) is shown in FIG.7, and TC operations are explained below.
  • TC Timing Control
  • the LD_C1 signal enables loading of the Period Counter I (PC l ) with a number of periods which the previous stages of the Synchronous Sequential phase Processor (SSPP) have calculated for the current phase adjustment.
  • Said download deactivates/activates the C l E signal if a downloaded value is (bigger than 1 ) / (equal to 1 ) accordingly.
  • phase 2 control circuit is driven by the Cl E and by the LD C 1 , and controls phase 2 operations with signals LD C2, LD RE2, LD BU2; as it is further explained below:
  • the first Cl E activation period generates the LD C2 signal, and is followed by setting the LDR2 FF which terminates the LD _C2.
  • the LD_C2 signal enables loading of PC2 with a periods number for the next phase adjustment, enables loading of the FSR with a fractional adjustment for the next phase adjustment, and enables a downloading of the FSR to the CSRl or to the CSR2.
  • the LD RE2 signal clocks in: a new modified fractional adjustment to the Fractional Number Register 2 (FNR2), and a new modified periodical adjustment to the Periodical Number Register 2 (PNR2).
  • FNR2 Fractional Number Register 2
  • PNR2 Periodical Number Register 2
  • the C2E signal activates the LD_C 1 similarly as the C l E has activated the LD_C2.
  • phase 1 control circuit is similarly driven by the C2E and by the LD_C2; and similarly generates the LD Cl ,
  • LD REI , LD_BU 1 signals for controlling phase] operations.
  • phase 1 The only differences in the phase 1 versus phase 2 operations, are specified below:
  • the LD BLJ 1 signal clocks in a decreased by 1 value to the MC which is the modulo 4 counter.
  • FIG.3 shows the heterodyne timing configuration (HTC) according to the preferred embodiment.
  • the HTC integrates both Digital PLLs (DPLLs) and Analog PLLs (APLLs) into a single CMOS ASIC, with the exception of the external VCXO which provides a stable clock (Fil LocClk) having very low phase jitter.
  • DPLLs Digital PLLs
  • APLLs Analog PLLs
  • RFS 'I he Reference Selector
  • the FiI OutClk drives the Output PLL (OUT PLL), and is connected to the fsync/L input of the Return Clock
  • RET PS Synthesizer
  • the RET PS synthesizes the RetClk, which is connected to the APD return input.
  • Said OUT_PLL generates the output reference clock (OutRef) which drives the Output Clocks Generator (OCG) which provides all the major HTC output clocks OutClk(T: 1 ).
  • OutRef output reference clock
  • OCG Output Clocks Generator
  • the DPLL mode of the HTC is described below.
  • the Fil OutClk signal is programmed to be selected by the RFS for the APD reference signal, and the RET_PS f rovides the APD return signal which is synthesized from the same Fil_OutClk signal.
  • Ext RefWfm One of the external reference waveforms (Ext RefWfm) is selected by a selector controlled by the PCU for being processed by the NFED providing the filtered reference waveform (Fil RefWfm), which is connected to the Time
  • Both frame phase detectors FPD l / FPD2 shall use the high frequency sampling clock (SampClk) for accurate digital measurements of the PhaErrl and the PhaErr2.
  • Said sampling clock is generated by the frequency multiplier OutRefxR from the OutRef generated by the
  • the PCU reads the measured phase errors and uses the RET PS to introduce digital phase displacements between the APD reference input and the APD return input which will drive the VCXO based PLL for providing required phase transfer functions between the FiI OutClk and the Ext_RefWfm.
  • the Fil OutClk drives the OUT PLL which has much higher BW than the VCXO PLL and the OUT PLL I 'jtermines phase of the OutClk.
  • the OutClk implements the same phase transfer function as the Fil OutClk.
  • the PCU calculates said Periodical Numbers (PN), Fractional Numbers (FN) and Phase Modifications (PM) which need to be provided to the Return Phase Synthesizer (RET PS); in order to achieve a preprogrammed transfer function between the HTC output clocks and the selected DPLL reference clock Ext RefWfm.
  • HTC free-run and hold-over modes use the above described DPLL mode configuration, as it is described below.
  • the PCU uses the phase error measurements for calculating phase differences which need to be inserted via the RET PS for providing said OutClk locking to the local oscillator LocOsc.
  • the PCU inserts phase differences via the RET PS which cause the OutClk to maintain its last frequency displacement versus the LocOsc.
  • the preferred embodiment implements the above defined general components of the NFED and is shown in FIG.8, I lG.9 and FlG.10.
  • 1 he NFED comprises over-sampling and capturing of consecutive wave-form intervals in specifically dedicated consecutive wave registers, wherein odd intervals are written into the wave register 1 WR and even intervals are written into the wave register 2WR. Therefore incoming stream of samples is split into the two parallel processing phases (sometimes named as parallel synchronous pipelines). The first processing phase begins in the wave register I WR and the second begins in the register 2WR. Such splitting into 2 parallel phases obviously doubles cycle time available in the sequential stages following the register 1 WR and in the stages following the 2WR as well.
  • a sequential clock generation circuit shows a method for splitting a steady stream of mutually overlapping sub-clocks spaced by a gate delay only into sub-sets of sub-clocks active during their dedicated phases only and non-active during all other phases. Such subsets are obviously used for providing timing for their dedicated phases.
  • the wave register 1 WR is further split into 2 parallel sub-phases and the 2WR is split into other 2 parallel sub- phases, for the purpose of quadrupling cycle time available in said sub-phases (see the FIG.8 showing the wave registers I WR, 2WR followed by the wave buffers H WB, 12WB, 21 WB, 22WB).
  • the NFED invention includes rewriting:
  • the digital filter arithmometers 21 DFA 1 /22DFA1/1 1 DFA 1/12DFA 1 perform all the comparison functions, between the edge mask registers REM/FEM and the waveform buffers 21 WB/22WB/1 1 WB/ 12 WB involving the edge threshold registers RET/FET. with the 3 basic operations which are further explained below.
  • the first operation is performed on all the waveform bits and involves the edge mask bits as it is specified below:
  • WB 112 , WB 11 are logically compared with the mask bits B 0 , B 1 , B 2 , B 1 . B 4 , B 5 , B 6 , B M and the resulting 8bit binary expression BE k (7:0)is created as equal to;
  • BE k (6) + BE k (7) which shall amount to a 0 - 8 decimal number.
  • every such arithmometer consists of 15 parallel micro-arithmometers, wherein each such micro-arithmometer performs operation on an 8bit edge mask and on 8bit wave region.
  • the third operation performs functions explained below: • In order to carry the same level from the last bit of the previous phase DFRI into the following bits of the present phase digital filter register2 (DFR2), the last bit DFRl (R) of the previous DFRl is always rewritten into the carry bit DFRl(C) of the present DFRl and is used by the digital filter arithmometer (DFRA2) to fill front bits of the DFR2 with the same level as the last bit of the previous phase DFRl . The verification is made if the EPF V indicates a rising edge condition by exceeding the content of the rising edge threshold RET(T:0).
  • the digital filter arithmometers 21 DFA2/22DFA2/1 1 DFA2/12DFA2 perform; the inter-phase continuation of filling front bits of the present phase register in accordance with the level set in the last bit of the previous phase, followed by said edge displacement which compensates for duty cycle distortions due to inter-symbol interference (ISI), etc..
  • ISI inter-symbol interference
  • the edge displacement comprises the 3 basic operations described below.
  • DFR3 digital filter register3
  • DFR3 digital filter arithmometers
  • the wave-form screening and capturing (WFSC) of screened out intervals is performed by the circuits which are shown in FIG. l 1 and the timing diagrams of the WFSC are shown FIG.12.
  • i he WFSC allows the PCU to perform screening and capturing of the incoming signal, for timing intervals which correspond roughly to a period of a single data bit, based on a content of the wave buffers 1 I WB, 12WB, 21 WB and 22WB.
  • 1 he WFSC allows the PCU to screen signal quality of incoming wave form, by applying programmable screening functions using programmable data masks, as it is listed below:
  • the WFSC allows also the PCU to select arbitrarily a content of any of the wave buffers during any particular time slot; for being captured and made available for analysis by the PCU.
  • T he second stage uses the mask detection arithmometers 1 1 MDA/12MDA for identifying wave-forms which are beyond usually acceptable range defined by the PCU.
  • the programmable control unit determines logical and/or arithmetical processing which the 1 1 MDA/12MDA shall perform, by pre-loading the detection control register (DCR) with a control code applied as the DCR(P:0) to the 1 1 MDA/12MDA.
  • DCR detection control register
  • the PCU determines the mask DMR(R:0) which the captured data 1 1 WB(R:0)/12WB(R:0) shall be processed against, by pre-loading the detection mask register (DMR).
  • DMR detection mask register
  • the 1 1 SEL signal equal to 1/0 selects; the 1 1 WB(R:0)/12WB(R:0) to be downloaded to the phase one detected data buffer (I DDB) by the clock l Clk2 (see FIG.1 1 and FIG.12), if the 1 1 DET/12DET indicate detection of a preselected mask by the mask detection arithmometer 1 1 DMA/12DMA.
  • the last captured I DDB content is further downloaded to the phasel data register ( I DDR) by the clock signal l Clk.3/128.
  • the I MCB is downloaded to the phase l mask counter register (I MCR) and the output of the 1 MCB>O decoder (MCB>0 DEC) is downloaded to the I MCR(P) bit, by the I Clk.3/128.
  • Said PCU controlled capturing of a wave buffer content is implemented, as it is explained further below.
  • the sample number register (SNR) is loaded by the PCU: with a phase number defined as phase 1 /phase2 if the
  • SNR(O) is set 0/1 , and with a particular phase cycle number in a time frame defined by SNR(7: 1 ) bits. Since there are 2 phases with 128 cycles per time frame, SNR(7:0) bits define 1 of 256 sampling cycles for having its wave buffer captured and made available for a further analysis by the PCU.
  • ⁇ lid SNR is downloaded into the phase 1 sample number buffer ( I SNB) at the beginning of a time frame by the first t hasel clock of the frame l Clk2/128.
  • phasel sample number counter (I SNC) is set to 0, since the 1 PHA/I28ena selects 0 to be loaded into the 1 SNC by 1 Clk2.
  • the 1 SNC(7: 1 ) and the 1 SNB(7: 1 ) are being compared by the logical comparator (Log.Comp.), which produces the
  • the output of the 3: 1 SEL is additionally captured in the phase 1 sampled data register (1 SDR) by the signal 1 Clk3/ 128.
  • Said 1 SDR is read by the PCU, which is notified about availability of the requested sample by the signal

Landscapes

  • Stabilization Of Oscillater, Synchronisation, Frequency Synthesizers (AREA)

Abstract

La présente invention concerne un synthétiseur d'horloge commandé par logiciel (SCCS) de haute précision et peu coûteux qui permet de produire une horloge synchronisée à faible gigue assurant une précision de la synthèse de phase et de fréquence améliorée d'un ordre, à partir de signaux de référence de temps externe ou de messages de référence temporelle. Le SCCS comprend; une boucle à phase asservie hybride (HPLL) assurant des facteurs de multiplication de la fréquence variant entre 1 et 50 000 tout en maintenant une très faible gigue de sortie indépendamment de la qualité de l'horloge de référence et des détecteurs de contour de filtrage du bruit (NFED) qui assurent une précision améliorée d'un ordre de la détection de la phase des signaux de référence.
PCT/CA2006/001120 2003-06-25 2006-06-27 Synthetiseur d'horloge commande par logiciel WO2007000060A2 (fr)

Priority Applications (8)

Application Number Priority Date Filing Date Title
US11/931,026 US8374075B2 (en) 2006-06-27 2007-10-31 Phase and frequency recovery techniques
US12/351,824 US9794096B2 (en) 2005-06-27 2009-01-10 Direct synchronization of synthesized clock
US13/323,820 US9077315B2 (en) 2003-06-25 2011-12-12 Inverse signal transformation
US13/763,729 US8982974B2 (en) 2005-06-27 2013-02-10 OFDM clock recovery
US13/844,722 US9100165B2 (en) 2005-06-27 2013-03-15 Direct data recovery
US14/656,264 US9641315B2 (en) 2005-06-27 2015-03-12 Clock recovery techniques
US14/738,920 US9838236B2 (en) 2006-06-27 2015-06-14 Direct synthesis of receiver clock
US15/582,747 US10057047B2 (en) 2005-06-27 2017-04-30 Phase synthesis techniques

Applications Claiming Priority (2)

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CA 2510004 CA2510004A1 (fr) 2005-06-27 2005-06-27 Synchroniseur d'horloge commande par logiciel
CA2,510,004 2005-06-27

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CN116301197A (zh) * 2023-04-27 2023-06-23 上海合见工业软件集团有限公司 时钟数据恢复方法、电子设备和介质

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CN108712226B (zh) * 2018-05-28 2020-03-27 中国电子科技集团公司第二十九研究所 一种芯片半自动同步方法及系统
CN112532239B (zh) * 2020-11-24 2024-01-02 珠海泰芯半导体有限公司 一种usb数据恢复系统

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US5485490A (en) * 1992-05-28 1996-01-16 Rambus, Inc. Method and circuitry for clock synchronization
TW525350B (en) * 2001-12-20 2003-03-21 Realtek Semiconductor Co Ltd Hybrid phase locked loop
US6933791B2 (en) * 2003-07-07 2005-08-23 National Central University Frequency synthesizing circuit having a frequency multiplier for an output PLL reference signal

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CN116301197A (zh) * 2023-04-27 2023-06-23 上海合见工业软件集团有限公司 时钟数据恢复方法、电子设备和介质
CN116301197B (zh) * 2023-04-27 2023-08-04 上海合见工业软件集团有限公司 时钟数据恢复方法、电子设备和介质

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