Abstract: Methods and apparatus are provided for varying the bandwidth of a loop filter in a loop circuit (e.g., a phase-locked loop circuit). The loop filter can include first and second resistor circuitries coupled to a capacitor. One of the resistor circuitries can be coupled to an output of the loop circuit in response to selection of a mode of operation. The resistor circuitries can each include a plurality of resistors that can be selectively coupled in series to the capacitor or bypassed. In addition, the output of the loop circuit can be coupled to a second capacitor. Either or both of the capacitors can be programmable.

Abstract: A system and method of reducing skew between a plurality of signals transmitted with a transmit clock is described. Skew is detected between the received transmit clock and each of received data signals. Delay is added to the clock or to one or more of the plurality of data signals to compensate for the detected skew. The delay added to each of the plurality of delayed signals is updated to adapt to changes in detected skew.

Abstract: A plurality of improved memory systems employing a phase detection system in conjunction with either a synchronous mirror delay or a delay-locked loop, and related methods of operation, are disclosed. The memory systems determine timing characteristics among multiple signals and, based upon those timing characteristics, vary which clock-related signal is output. The improvement relates in part to the incorporation of a clock divider that reduces the frequency of the clock signals utilized by the system. Due to the incorporation of the clock divider and an edge recovery device, attenuation, power dissipation and duty cycle distortion associated with propagation of the clock signal(s) are reduced. Further, the reduction in frequency of the clock signals allows for numerous differently-phased clock signals to be generated within the system, which allows for finer timing comparisons to be performed, thus allowing for finer selections to be made in relation to which clock-related signal is output.

Abstract: An external clock round-trips a round-trip delay block configured by a selector and a short delay array, and is made capable of corresponding to a wide frequency by generating a long delay time required for synchronization at the time of a low frequency operation. Further, when a plurality of phase comparators are disposed, in both cases where comparing phases all at once and comparing phases one after another, it is possible to complete the phase synchronization within a short time by making a delay amount variable.

Abstract: Circuits and methods for aligning two or more signals including a first and second signal. In one embodiment, a shift register generates two or more shifted copies of the second signal, and each of a plurality of phase detectors receives the first signal and one of the shifted copies of the second signal, each phase detector providing an output indicating whether the first signal is substantially aligned with the shifted copy of the second signal. A multiplexer may also be provided for receiving each of the shifted copies of the second signal, the multiplexer having a plurality of select lines coupled with the output signals of the phase detectors. Some embodiments may include a power saving mode.

Abstract: A microcontroller integrated circuit with a clock controller and a processor automatically switches the source of the clock signal that clocks the processor from a failed fast external precision oscillator to a slow internal backup oscillator, then enables a fast internal precision oscillator, and finally switches to the fast internal precision oscillator. A failure detection circuit within the clock controller detects a failure of the external precision oscillator and sends an associated interrupt signal to the processor. The clock controller decouples the external oscillator from the processor and couples the backup oscillator to the processor. The microcontroller integrated circuit then enables the fast internal precision oscillator, decouples the backup oscillator, and couples the fast internal precision oscillator to the processor.

Abstract: A 40-Gb/s clock and data recovery (CDR) circuit incorporates a quarter-rate phase detector and a multi-phase voltage controlled oscillator to re-time and de-multiplex a 40-Gb/s input data signal into four 10-Gb/s output data signals. The circuit is fabricated in 0.18 ?m CMOS technology.

Abstract: In one embodiment, a method for balancing clock signals in a clock tree includes, at a register, receiving a divided input clock signal and a non-divided input clock signal and generating a first output clock signal based on the received divided input clock signal and the received non-divided input clock signal, the first output signal being associated with a first delay. The method further includes, at a delay line, receiving the non-divided input signal, delaying the non-divided input signal for a time substantially equivalent to the first delay, and generating a second output clock signal associated with a second delay substantially equal to the first delay.

Abstract: A clock signal generator and method thereof are provided for a system to generate an output signal. The apparatus comprises: a delay circuit for generating a delayed clock with a first time, a delay module for generating delayed signal(s), and a decision circuit for comparing the delayed signal(s) with the delayed clock to obtain the relative relation between the delay time and the first time and controlling a delay time of an input signal according to the relative relation to generate the output signal.

Abstract: In a semiconductor device of the present invention, a clock is not changed instantaneously but it is changed over maximum N+1/M clocks (N: integer not less than 2) by shifting delay cells in a step by step manner to make the phase state of a previous reference signal and the phase state of a present reference signal coincide with each other, whereby the clock is synchronized with the reference signal with accuracy, and the duty of the output clock is kept constant. With this semiconductor device, it is possible to prevent the duty of the clock from being discontinuous when a signal whose reference signal does not coincide with the clock is inputted and reset is made to a rising edge of this reference signal.

Abstract: A phase synchronization circuit comprises: a measurement delay line which includes a plurality of delay elements having different delay times and to which a first clock signal is inputted; a phase comparator line which includes a plurality of phase comparators in accordance with the measurement delay line and to which a signal from the measurement delay line and a second clock signal are inputted so as to measure a transition timing difference between the first clock signal and the second clock signal; and a generation delay line which includes a plurality of delay elements having different delay times in accordance with the measurement delay line and to which a signal from the phase comparator line and a third clock signal are inputted. The delay time of the respective delay elements is fixed.

Abstract: A clock regeneration scheme for a digital communication receiver has a first-in, first-out (FIFO) storage buffer into which received data is clocked in accordance with an input clock signal and a data valid signal. A fixed fractional delay line is coupled to provide respectively different phase delayed versions of the input clock signal and feeds a multiplexer that is controllably operative to couple one of the outputs of the fixed fractional delay line to a regenerated clock output port. A control loop, which includes the FIFO storage buffer, the output port and a steering control input of the multiplexer circuit, is operative to selectively change which output of the fixed fractional delay line is coupled by the multiplexer to the output port, so as to controllably cause the output clock signal to track the effective frequency of the valid data signal.

Abstract: The present invention demonstrates a method and circuit where a plurality of phase clocks from a “frequency lock only” PLL are used to sample an input clock CLKIN. This results in a series of signals from which the phase clock most in synchronization with CLKIN can be determined and presented to the output CLKOUT. If used for data sampling, a phase clock that lags the phase clock most in synchronization may be selected to appear at CLKOUT. This guarantees that sampled data are static during sampling. This system is less complex and consumes minimal power over systems using variable delay circuits.

Abstract: A delay locked loop circuit (200) in which multiple outputs are produced. A single delay line (24) is shared among multiple tap selection circuits (256A, 265B, 265C). Fixed phase shifts (412) can be introduced between multiple outputs. A modulating signal can be used in the tap selection processing to produce digital amplitude, frequency and/or phase modulation.

Abstract: Phase locked loop circuitry operates digitally, to at least a large extent, to select from a plurality of phase-distributed candidate clock signals the signal that is closest in phase to transitions in another signal such as a clock data recovery (“CDR”) signal. The circuitry is constructed and operated to avoid glitches in the output clock signal that might otherwise result from changes in selection of the candidate clock signal.

Abstract: Disclosed is a clock distribution device and method in a compact PCI system based multi-processing system. A compact PCI based multi-processing system preferably includes processing signals upon mounting various circuit boards on multiple slots, even if the location of the system slot is varied, the skew of clocks transmitted to the other slots may be minimized. Accordingly, the system may be configured in a flexible manner because of such variability of the system slot's location. Further, the system may be efficiently repaired and maintained because it is possible to easily and quickly take measures in response to any failure occurring on the board mounted on the system slot.

Abstract: A register controlled delay locked loop includes a clock generation unit which receives an external clock signal for generating a source clock signal by buffering the external clock signal and for generating a delay monitoring clock signal and a reference clock signal by diving the source clock signal by a natural number; a delay line control unit which receives the reference clock signal and a feed-backed clock signal for generating a normal shift control signal and an acceleration shift control signal based on a result of a comparison between phases of the reference clock signal and the feed-backed clock signal; a delay line unit which receives the source clock signal for generating a delay locked clock signal by delaying the source clock signal according to a delay amount of the delay line unit determined by the normal shift control signal and the acceleration shift control signal; and a delay model unit for estimating a delay amount generated while the external clock signal is passed to a data output pin

Abstract: A monitoring device for an electrical machining tool, in particular for temperature monitoring with an accumulator-driven machine, includes a switch element (12) for separating an electrical consumer (14) from a current supply device (10). For detection of a first operating parameter (TMOTOR) of the consumer (14) and/or the current supply device (10), a first sensor (16) is provided, whereby the first sensor (16) is connected with a display unit and/or with the control input of the switch element, in order to control the switching process as a function of the first operating parameter (TMOTOR). Furthermore, the present invention relates to an electrical machining tool as well as a current supply device with the inventive monitoring device and a corresponding method of operation.

Abstract: A parallel data interface and method is provided herein, which adjusts a timing relationship of a clock signal to not only minimize clock skew, but to also compensate for noise components that may affect one or more paths of a parallel data bus. In some embodiments, the parallel data interface includes a first phase generator coupled to generate a first plurality of time delay pulses, and a first phase selector adapted to select one of the first plurality of time delay pulses to adjust the timing of a clock signal to sample each and every one of the plurality of data signals between minimum setup and hold time thresholds. In some embodiments, the parallel data interface includes a second phase generator coupled to generate a second plurality of time delay pulses, and a second phase selector adapted to select one of the second plurality of time delay pulses to adjust the timing of the clock signal to output the plurality of data signals from the data interface at least an amount of time (i.e.

Abstract: A clock architecture employing redundant clock synthesizers is disclosed. In one embodiment, a computer system includes first and second clock boards. The first clock board may act as a master, generating a system clock signal, while the second clock board acts as a slave. The first clock board may monitor a phase difference between a first crystal clock signal and a feedback clock signal. If the phase difference exceeds a limit, the first crystal clock signal may be inhibited, preventing the first clock board from generating the system clock signal. The second clock board may monitor the system clock board in reference to a feedback clock signal. If the second clock board detects a predetermined number of consecutive missing clock edges, it may enable a second crystal clock signal, which may be used to generate a system clock signal.

Abstract: A system and method of reducing skew between a plurality of signals transmitted with a transmit clock is described. Skew is detected between the received transmit clock and each of received data signals. Delay is added to the clock or to one or more of the plurality of data signals to compensate for the detected skew. Each of the plurality of delayed signals is compared to a reference signal to detect changes in the skew. The delay added to each of the plurality of delayed signals is updated to adapt to changes in the detected skew.

Abstract: An interleaved delay line for use in phase locked and delay locked loops is comprised of a first portion providing a variable amount of delay substantially independently of process, temperature and voltage (PVT) variations while a second portion, in series with the first portion, provides a variable amount of delay that substantially tracks changes in process, temperature, and voltage variations. By combining, or interleaving, the two types of delay, single and dual locked loops constructed using the present invention achieve a desired jitter performance under PVT variations, dynamically track the delay variations of one coarse tap without a large number of delay taps, and provide for quick and tight locking. Methods of operating delay lines and locked loops are also disclosed.

Abstract: A modular Digital Locked Loop (DLL) architecture capable of generating a plurality of multiple phase clock signals, having particular applicability to synchronization of embedded DRAM systems with on chip timing. The architecture comprises a single core frequency locking circuit that includes a delay element with control logic and locking circuitry capable of locking the DLL system clock frequency to an external reference clock, and a plurality of secondary phase locking circuits capable of synchronizing a plurality of internal clock signals to any phase of the external reference clock.

Abstract: A clock signal recovery circuit that is implemented in a receiver of a universal serial bus (USB) and a method for recovering a clock signal. The clock signal recovery circuit comprises a phase detector, a bidirectional shift register, a multiphase clock signal generator, and a phase selector. The phase detector detects a difference in phases between received data and a predetermined recovery clock signal and generates a first control signal indicative of the detected phase difference. The shift register is shifted in response to the detected signal and outputs a second control signal.

Abstract: Disclosed is a virtual dual-port synchronous RAM device, system, and method, wherein the design requires minimal hardware cost compared with a dual-port RAM architecture or the traditional architecture used with a single-port RAM. Disclosed is a read/write memory device including means to accept signals from a first host and a second host, the first host having a first clock and the second host having a second clock, the signals including a first clock signal and a second clock, a clock switching means for switching between the first clock signal and the second clock signal, a single-port random access memory (RAM) module for storing data, and a RAM clock for synchronizing the clock signals with the RAM module.

Abstract: Method and apparatus for determining delay of a circuit. A clock signal is provided to a variable delay and then to the circuit. The clock signal obtained from the circuit is provided to a data register, such as a flip-flop, as a clock input. The clock signal is provided to the flip-flop as a data input. Output of the data register is provided to a controller to incrementally adjust phase shift until the data input and clock input are substantially aligned in phase. All incremental adjustments in phase shift are counted to provide an indication of delay of the circuit.

Abstract: An all digital power supply system provides a supply voltage to semiconductor circuits. The power supply system utilizes an up/down counter and a pulse width modulator to output a signal into a LC network that generates the supply voltage. The width of the pulses output by the pulse width modulator are defined by an encoder that generates width information in response to a propagation delay detector that measures the propagation delay of a first clock signal when clocked by a second clock signal. The system supplies the optimum or minimum required voltage to insure that a critical path through a digital chip is met over process, voltage, and temperature (PVT) variations without the use of a band gap reference voltage source. A state machine is also used to counteract oscillations introduced by start up and load transients, thereby eliminating the need for a proportional integrator differentiator (PID).

Abstract: A digital PLL (phase locked loop) circuit includes a sampling circuit, a plurality of internal circuits and an output switching circuit. The sampling circuit samples a burst data signal in response to a multi-phase clock signal to produce N (N is a positive integer larger than one) sampled data signals. The multi-phase clock signal includes N clock signals, each of which has substantially the same frequency as the data signal and which have phases different by a predetermined component from one after another. Each of the plurality of internal circuits is selected in response to a first selection signal, and outputs a set of a selected one of the N clock signals and an identified data signal from the N sampled data signals, which corresponds to the selected clock signal, in response to the selected clock signal, when the internal circuit is selected.

Abstract: A standard clock 34 is input to a phase comparator 52 and a phase controller 56. The ring oscillator 50 oscillates a shift clock 70 having a same cycle as the standard clock 34. The phase comparator 52 matches the downward shift of the shift clock 70 with the downward shift of the standard clock 34 to output a shift clock 72. The shift clock 72 is supplied to the pulse inserter 54. The phase controller 56 receives the standard clock 34 and generates a phase control signal 74 indicating cycles of the shift clock 72 to which the insert-pulses are inserted among a plurality of cycles of the shift clock 72. The pulse inserter 54 inserts the insert-pulses to the cycles of the shift clock indicated by the phase control signal 74. The phase-lock unit 58 generates a delay clock 82 by delaying the phase of the shift clock 70 oscillated by the ring oscillator 50 with respect to the phase of the standard clock, based on the standard clock and the shift clock 76 including the insert-pulses.

Abstract: A precision signal delay apparatus and method for introducing time delay to a signal. Precision delay is introduced by a pair of delay locked loops (DLLs) connected in series each with selected delay (i.e., a Vernier-type circuit). Nonuniformity in the precision delay is compensated with a delay compensation circuit. The apparatus and method may be used for phase shifting, data delay, precision pulse width modulation, and precision time windowing.

Abstract: A phase locked loop that includes a receiver that is adjustable to substantially match delay of a system clock and a feedback clock at an input of the phase locked loop is provided. The receiver employs system clock path circuitry to input the system clock and feedback clock path circuitry to input the feedback clock, where current flow and load resistances associated with the system clock path circuitry and current flow and load resistances associated with the feedback clock path circuitry are responsive to one or more bias signals that are adjustable using one or more adjustment circuits that are operatively connected to the receiver. The control of the one or more bias signals via the one or more adjustment circuits facilitates the generation of substantially delay matched system and feedback clocks.

Abstract: A method of synchronizing a clock signal to a data signal, comprising the steps of (A) detecting a first edge of the data signal, (B) determining a first value indicating a position of the first edge, (C) adding the first value to a second value, wherein the second value indicates a position of a second edge of the data signal and (D) adjusting the clock signal, based on the result of step (C), if the result is greater than a predetermined value.

Abstract: A high speed zero phase restart for a multiphase clock for a PRML read/write channel design. The zero phase restart includes an input for receiving a plurality of clock pulse waves, each having substantially equal period and each being out of phase with respect to other clock pulse waves; an output including at least one output terminal corresponding to one of the clock pulse waves; and a zero phase circuit configured to sequentially couple the plurality of clock pulse waves to the corresponding output terminals.

Abstract: Various systems and methods providing clock delay compensation for circuits such as a multi-pair gigabit Ethernet transceiver are disclosed. In an analog implementation a buffer with an adjustable delay may be used to minimize the delay mismatch between clock trees. The delay of the adjustable-delay buffer is controlled by bias voltages that determine the charging and discharging current to the adjustable buffer. A phase detector circuit is used to compare the clock phases for rising and falling edges, and to adjust the bias voltages that control these edges. In a digital implementation a selector switch, responsive to a phase detector, may be used to route clock signals through circuit elements to delay clock signals.

Abstract: A bit synchronization device which extracts an output data signal and an output clock signal from an input data signal on the basis of a multi-phase clock signal. The bit synchronization device is provided with a processing circuit which holds a phase corresponding to a change point of an input data signal with a multi-phase clock signal, and while the input data has a phase without change point, carrying out a data identification free from an error by selecting a clock signal corresponds to the phase without change point.

Abstract: An incoming signal's duty cycle is transformed to a known value by a first programmable duty cycle generator, and the output of the first programmable duty cycle generator is applied to a second programmable duty cycle generator which includes multiple stages which provide multiple duty cycle tap point outpoints, each having a different known value of a precise duty cycle, wherein the leading edges or trailing edges of the multiple duty cycle tap point output signals are phase aligned with respect to each other by voltage controlled delay matching elements which are replicas of the stages of the second duty cycle generator.

Abstract: A synchronization circuit for gradually shifting the phase domain of a control signal to permit synchronization of a signal with a clock signal in a different phase domain in a system with a single frequency, but arbitrary phase relationship. The present invention allows a control signal in the phase domain of an internal clock to be synchronized with an external clock, when the phase domain of the external clock differs substantially from that of the internal clock. In synchronizing the control signal to the external clock, the present invention avoids the generation of runt pulses while providing a control signal synchronized to the external clock in the least amount of time feasible (i.e., with the lowest latency time). Because the present invention has no failure modes due to timing relationships, MTBF is infinite for failures caused by such relationships and therefore need not be a concern. This also implies that no risk is posed to the proper operation of the circuits driven thereby.

Abstract: A precision signal delay apparatus and method for introducing time delay to a signal. Precision delay is introduced by a pair of delay locked loops (DLLs) connected in series each with selectable delay (i.e., a Vernier-type circuit). Nonuniformity in the precision delay is compensated with a delay compensation circuit. The apparatus and method may be used for phase shifting, data delay, precision pulse width modulation, and precision time windowing.

Abstract: A clock recovery circuit is provided for use in a memory with a clock synchronized interface, wherein an external clock is temporarily intercepted to shorten lock-in time when an internal clock is to be generated from the external clock. The clock recovery circuit includes a delay circuit array, receiving the external clock, for generating reference clocks, a control circuit comparing phases of the external clock and of the reference clocks and detecting the number of delay stages required for locking in, and a latching circuit for holding the number of delay stages required for locking in. Once synchronism is detected, the generation of internal clock can be resumed in a short period of time even if the supply of the external clock is temporarily suspended.

Abstract: A prescaler (200) includes a first frequency divider (204, 206) configured to receive an input signal at an input frequency. The prescaler further includes a phase rotator (208) coupled to the first frequency divider to produce a plurality of signal phases in response to the input signal. A frequency control circuit (214) is configured as a one-hot decoder to select one signal phase of the plurality of signal phases. The one-hot decoder provides maximum speed of operation of the prescaler by eliminating decoding of the feedback signal.

Abstract: A burst synchronizing circuit synchronizes a received data signal in a burst fashion and sampling phases with which the received data signal is sampled. A first part samples a data pattern with different sampling phases. A second part selects the received data signal sampled with an optimal sampling phase based on sampling phases with which the data pattern is detected.

Abstract: An input data signal is digitally sampled by a data sampling section using an N-phase clock signal including N clock signals whose frequencies are almost the same as the bit rate of the input data signal and whose phases has been successively shifted by 1/N of the clock cycle, and thereby a parallel sample data signal including N sample data signals is obtained. An edge point detection operation section detects edge points in the N sample data signals in one cycle of an extracted clock signal and outputs an edge point operation output signal. A clock signal extraction section selects a clock signal from the N-phase clock signal based on the information of the edge point operation output signal and outputs the selected clock signal as the extracted clock signal. A delay section delays the N sample data signals of the parallel sample data signal and thereby outputs a parallel delayed sample data signal including N delayed sample data signals.

Abstract: In the present invention, an external power source supplied to an integrated circuit device is divided into a first external power source for the DLL circuit and a second external power source for circuits other than the DLL circuit. According to the present invention, it is arranged that power source noise generated in the second external power source cannot be transmitted to the variable delay circuit by utilizing the first external power source preferably for the variable delay circuit of the DLL circuit and even more preferably for its delay unit. Also, preferably, it is arranged that power source noise generated in the second external power source cannot be transmitted to the phase coincidence detection unit by utilizing the first power source for the phase coincidence detection unit in the phase comparison circuit of the DLL circuit.

Abstract: The invention provides a phase compensation circuit that can carry out phase compensation grater than the variable delay time range of a variable delay circuit without increasing more than necessary the delay time of the variable delay circuit even in the case that the phase of the reference signal and the phase of the feedback signal change because of changes in the operating environment due to fluctuations in the power source voltage and fluctuations in temperature. The phase compensation circuit that compensates the phase of a clock signal provides a plurality of variable delay circuits, a first phase comparator that compares the phase of a reference signal to the phase of a feedback signal, a second phase comparator that compares the phases of the plurality of variable delay circuits, a switching circuit that switches the outputs of the plurality of variable delay circuits, and a control circuit.

Abstract: A system and method for reducing timing uncertainties in a serial data signal A system may comprise a transmitter configured to transmit serial data to a receiver through a transmission medium, e.g., wireless, wired. The receiver may comprise an oscillator configured to generate multiple phases of a clock. The receiver may further comprise a retiming mechanism configured to reduce the timing uncertainties of the serial data received by the receiver by selecting a particular phase of the clock to be asserted to sample the serial data signal. The particular phase may be selected by selecting the appropriate synchronization state/retiming state. A retiming state indicates which particular phase of the clock should be asserted to sample the serial data signal. A synchronization state indicates which particular phase of the clock is the appropriate one to assert at a given transition of the serial data signal.

Abstract: Method for recovering a clock signal from an input data signal in a telecommunications system, that provides for comparing the input data signal with a recovered clock signal in order to control said recovered clock signal generation and provides for generating a plurality of delayed clock signals, obtained by multi-delaying at least a reference signal, said delayed clock signals being phase-shifted with respect to each other. According to the invention, said delayed clock signals show a phase shift with respect to each other, that is nominally constant in time, and, moreover, it is provided for selecting the recovered clock signal among said delayed clock signals.

Abstract: A digital variable clocking circuit is provided. The variable clocking circuit is configured to receive an input clock signal and to generate an output clock signal having an output clock frequency equal to the frequency of the input clock signal multiplied by a multiplier M and divided by a divisor D. In one embodiment of the present invention, the average frequency of the output clock signal during a concurrence period is equal to the selected frequency because the active edge of the output clock signal is triggered by the rising edge of the reference clock signal during a concurrence. Furthermore, the waveform of the output clock signal is shaped to approximate the waveform of an ideal output clock signal by selectively inserting delays distributed throughout the concurrence period using a Modulo-M delta sigma circuit. The modulo-M delta sigma circuit, which receives modulo value M, a pulse value P, and a clock signal, generates an output signal that includes P pulses spread across M clock periods.

Abstract: A combination delay circuit for use in a frequency multiplier comprises a first delay circuit including a plurality of delay lines each having eight segments each effecting a unit delay time td, a latch array having 8 latch elements, one element disposed for each delay line, each receiving an output from a corresponding one of delay segments, and second through eighth delay circuits each having a single delay element effecting the unit delay time. The corresponding between the latch elements and the second through eighth delay circuits is such that delay times in the outputs of the third, fifth, seventh delay circuits are ¼, ½ and ¾, respectively, of the delay times in the output of the eighth delay circuit. The frequency multiplier having the combinational delay circuit multiplies the reference frequency by double, quadruple, and octuple.

Abstract: A digital phase synchronizing apparatus delays sequentially a clock signal output from an oscillator, generates a plurality of delayed clock signals, selects a delayed clock signal that is synchronized with horizontal synchronizing signal HS from among the delayed clock signals using a change point detection circuit, and selects the output signal. Meanwhile, fine delay circuit further delays sequentially the selected delayed clock signal, generates a plurality of delayed clock signals, and selects a delayed clock signal that corresponds to the setting of a rotary dip switch as the system clock, thereby to efficiently acquire phase synchronization of the clock signal with the input signal without being affected by the signal characteristics of the input signal.

Abstract: A bit synchronization circuit operates at high speed range as high as Gb/s or higher and can establish synchronization within 10 bits with rejecting jitter to permit accurate bit synchronization. The bit synchronization circuit thus generates a plurality of clocks having mutually different phases in synchronism with an input reference clock. A phase relationship between a plurality of clocks and an input data to be decided is discriminated by a phase comparator circuit. The clock having optimal phase relationship, namely clock having level transition timing having at a substantially center portion of mutually adjacent level transition timing of the input data, is determined by a phase determination circuit. An decision circuit and selector are provided for deciding input data at the level transition timing of the determined clock.