Abstract: A processor (400) includes a clock source (402), a central processing unit (CPU) (408), and a clock generator (404). The clock source (402) includes an output for providing a periodic clock signal. The CPU (408) includes an input for receiving a CPU clock signal. The clock generator (404) includes a first input coupled to the output of the clock source (402), a second input for receiving a mode signal that indicates an output frequency, and an output coupled to the input of the CPU (408). The clock generator (404) provides the CPU clock signal using periodic pulse skipping such that the CPU clock signal has a number of transitions over a unit of time corresponding to the output frequency.

Abstract: A methodology is disclosed that enables the delay stages of an analog delay locked loop (DLL) or phase locked loop (PLL) to be programmed according to the operating condition, which may depend on the frequency of the input reference clock. The resulting optimized delay stages allow for a broad frequency range of operation, fast locking time over a wide range of input clock frequencies, and a lower current consumption at high clock frequencies. Better performance is achieved by allowing the number of analog delay stages active during a given operation to be flexibly set. The deactivation or turning off of unused delay stages conserves power at higher frequencies. The high frequency range of operation is increased by using a flexible number of delay stages for various input clock frequencies. Because of the rules governing abstracts, this abstract should not be used to construe the claims.

Abstract: Data synchronization is achieved in devices which transmit and/or receive audio and/or video data through the staged locking of phase locked loops. According to an exemplary embodiment, a transmitter includes a serial data source. An encoder provides encoded data and includes a first PLL. A controller includes a second PLL which enables generation of a clock signal. The controller is coupled between the serial data source and the encoder for providing the clock signal to the encoder. The first PLL of the encoder locks to the clock signal.

Abstract: A system and method for generating a clock signal having spread spectrum modulation. The method involves generating a clock signal by generating edge positions for edges of the clock signal from a digital representation of a timing for each edge to impart spread spectrum modulation to the clock signal. A programmable modulator is provided that generates digital values representing edge positions for edges of a clock signal based on at least one of a time-varying period value and a time-varying duty-cycle value. The programmable modulator may comprise a first circuit, called a period modulation circuit, that generates a time-varying digital period value, and a second circuit, called a duty-cycle modulation circuit, that generates a time-varying digital duty-cycle value. The time-varying period values and time-varying duty cycle values are processed to produce a digital edge position value that specifies an edge position for a clock signal.

Abstract: A multimedia processing system and method thereof are provided. The system and method provide for synchronizing a first clock of a multimedia decoder of a first multimedia processing device to a second clock of a multimedia encoder of a second multimedia processing device, synchronizing a first timing reference of the multimedia decoder to a second timing reference of the multimedia encoder, receiving, at a network interface of the first multimedia processing device, an encoded multimedia data stream from a network interface of the second multimedia processing device, wherein the encoded multimedia data stream is encoded by the multimedia encoder based on the second clock and the second timing reference, and decoding the encoded multimedia data stream at the multimedia decoder based on the first clock and the first timing reference.

Abstract: An Automatic System Clock Detection System (ASCDS) may provide integrated circuits (ICs) with the capability to detect the frequency of an external crystal oscillator or clock source, and adjust the IC's internal PLL accordingly for proper IC operation. The frequency detection and PLL adjustment may be performed without any additional pins on the IC, and/or without requiring any additional external information. The ASCDS may be configured with an internal ring oscillator, which may be generated from standard logic elements, a watchdog counter, and an input clock counter. When the IC comes out of power on reset (POR), the ASCDS may compare the input clock counter with the watchdog counter, and determine the clock frequency of the input clock. It may then set the PLL parameters to ensure correct IC operation.

Abstract: An improved HE LINAC-based ion implantation system is disclosed utilizing direct digital synthesis (DDS) techniques to obtain precise frequency and phase control and automated electrode voltage phase calibration. The DDS controller may be used on a multi-stage linear accelerator based implanter to digitally synchronize the frequency and phase of the electric fields to each electrode within each stage of the accelerator. The DDS controller includes digital phase synthesis (DPS) circuits for modulating the phase of the electric field to the electrodes, and a master oscillator that uses digital frequency synthesis or DFS to digitally synthesize a master frequency and phase applied to each of the DPS circuits. Also disclosed are methods for automatically phase and amplitude calibrating the RF electrode voltages of the stages.

Abstract: A apparatus and method are disclosed for generating one or more clock signals. A clock signal is generated based on pattern signals and a reference clock signal. When the reference clock signal transitions high, the state of a first pattern signal is output, and when the reference clock signal transitions low, the state of a second pattern signal is output. Successive states of the first and second pattern signals, selected according to the reference clock signal, provide the generated clock signal.

Abstract: Systems and techniques for producing a signal with a known phase relationship to a source clock at an output of an indeterminate circuit element such as a clock divider. The systems and techniques may be used to allow circuit test data to be accurately compared with simulation data.

Abstract: An apparatus that reduces sampling errors for data communicated between devices uses phase information acquired from a timing reference signal such as a strobe signal to align a data-sampling signal for sampling a data signal that was sent along with the timing reference signal. The data-sampling signal may be provided by adjustably delaying a clock signal according to the phase information acquired from the strobe signal. The data-sampling signal may also have an improved waveform compared to the timing reference signal, including a fifty percent duty cycle and sharp transitions. The phase information acquired from the timing reference signal may also be used for other purposes, such as aligning received data with a local clock domain, or transmitting data so that it arrives at a remote device in synchronism with a reference clock signal at the remote device.

Abstract: A duty cycle corrector includes a first controllable delay, a second controllable delay, a phase detector, and a compensation circuit. The first controllable delay is configured to delay a first signal to provide a second signal. The second controllable delay is configured to delay the second signal to provide a third signal. The phase detector is configured to adjust the first controllable delay and the second controllable delay to phase lock the third signal to the first signal. The compensation circuit is configured to compensate for a mismatch between the first controllable delay and the second controllable delay to provide a fourth signal in response to the first signal and a fifth signal approximately 180 degrees out of phase with the fourth signal in response to the second signal.

Abstract: A delay-locked loop (DLL) circuit comprises a voltage controlled delay line (VCDL) including a plurality of identical delay stages connected in series, and a feedback loop including a phase comparator for controlling the VCDL such that the total delay over a number of stages matches the period of the periodic reference signal. Signal outputs are connected to derive their respective output signals from respective nodes within the delay line. The phase comparator compares the phase of first and second differently delayed versions of the reference signal from respective nodes within the variable delay line separated only by a plurality of identical delay stages.

Abstract: A precise downhole clock that compensates for drift includes a prescaler configured to receive electrical pulses from an oscillator. The prescaler is configured to output a series of clock pulses. The prescaler outputs each clock pulse after counting a preloaded number of electrical pulses from the oscillator. The prescaler is operably connected to a compensator module for adjusting the number loaded into the prescaler. By adjusting the number that is loaded into the prescaler, the timing may be advanced or retarded to more accurately synchronize the clock pulses with a reference time source. The compensator module is controlled by a counter-based trigger module configured to trigger the compensator module to load a value into the prescaler. Finally, a time-base logic module is configured to calculate the drift of the downhole clock by comparing the time of the downhole clock with a reference time source.

Abstract: An integrated circuit arrangement clocked by a single clock having variable delays to different regions of said arrangement such that said regions are partially synchronized to each other, the arrangement comprising: a data transfer buffer for buffering a data stream for transfer between respective first and second ones of said regions, and a data transfer controller, associated with said data transfer buffer and said respective regions, configured to control transfer of said data stream by: initially synchronizing between said respective regions at a start of said data stream, receiving data, in said buffer, from said first region, at a predetermined rate, and outputting said data stream to said second region at said predetermined rate in accordance with said initial synchronization. The arrangement allows deterministic data patterns to arrive at the receiving domain at minimal hardware cost.

Abstract: A method and apparatus for clock generation have been disclosed having a selector logic block that controls operation based upon inputs such as analog input(s), digital input(s), a lookup table, and preset values(s), and combinations of such.

Abstract: An integrated circuit is provided comprising a processor, an onboard system clock having a ring oscillator for generating a clock signal, a memory, and clock trim circuitry. The processor is arranged to, in response to receiving an external signal, determine the number of cycles of the clock signal during a predetermined number of cycles of the external signal or the number of cycles of the external signal during a predetermined number of cycles of the clock signal and to output the determined number of cycles to an external circuit. The processor is also arranged to, in response to receiving a trim value based on the determined number of cycles from the external circuit, store the trim value in the memory and control the clock trim circuitry to trim the frequency of the clock signal generated by the ring oscillator using the trim value.

Abstract: A methodology is disclosed that enables the delay stages of an analog delay locked loop (DLL) or phase locked loop (PLL) to be programmed according to the operating condition, which may depend on the frequency of the input reference clock. The resulting optimized delay stages allow for a broad frequency range of operation, fast locking time over a wide range of input clock frequencies, and a lower current consumption at high clock frequencies. Better performance is achieved by allowing the number of analog delay stages active during a given operation to be flexibly set. The deactivation or turning off of unused delay stages conserves power at higher frequencies. The high frequency range of operation is increased by using a flexible number of delay stages for various input clock frequencies. Because of the rules governing abstracts, this abstract should not be used to construe the claims.

Abstract: A system for controlling bias of a delay-locked loop includes a peak detector and a comparator in the form of a differential amplifier. The peak detector detects the amplitude of a signal output from the DLL, and the comparator compares the DLL output signal amplitude to a reference signal. The comparator then generates a tail current control signal for the DLL based on a result of the comparison. In one embodiment, the reference signal is indicative of a predetermined tail current value for the DLL, and the tail current control signal adjusts delay of the DLL to equal the predetermined tail current value. Preferably, the tail current control signal maintains the DLL signal output at a substantially constant amplitude in spite of frequency variations and may also be used to set the voltage swing for the DLL.

Abstract: An adjustment and calibration system for post-fabrication treatment of a phase locked loop input receiver is provided. The adjustment and calibration system includes at least one adjustment circuit, to which the phase locked loop input receiver is responsive, and a storage device that selectively stores control information (1) associated with a state of the adjustment circuit and/or (2) from a tester that writes such control information to the storage device, where the control information stored in the storage device is subsequently selectively read out in order to adjust the adjustment circuit to a state corresponding to the control information.

Abstract: An integrated circuit, comprising a processor, an onboard system clock for generating a clock signal, and clock trim circuitry, the integrated circuit being configured to: (a) receive an external signal; (b) determine either the number of cycles of the clock signal during a predetermined number of cycles of the external signal, or the number of cycles of the external signal during a predetermined number of cycles of the clock signal; (c) store a trim value in the integrated circuit, the trim value having been determined on the basis of the determined number of cycles; and (d) use the trim value to control the internal clock frequency.

Abstract: A frequency locked loop in a microcontroller integrated circuit has a precision digital feedback control loop. The frequency locked loop performs a clock multiplication function such that an inexpensive and low frequency external crystal is usable both to clock a processor of the microcontroller with a higher frequency and low-jitter clock signal and to clock a real time clock of the microcontroller with a low frequency time base that is a power of two multiple of one hertz. In one embodiment, the digital feedback control loop includes a ramp generator, a digital filter, and a loop divider. The ramp generator is controlled to output steeper and steeper ramps as the frequency locking process proceeds toward frequency lock. Ramp slope dithering is used to increase resolution. A preset value that presets the loop divider is changed to adjust the phase of a feedback signal with respect to a reference input signal.

Abstract: A system and method for accurately detecting an asynchronous frequency within a synchronous digital system. The improved system and method preconditions the asynchronous frequency so that it does not introduce additional phase noise at low frequencies within a digital PLL. The system comprises a digitally controlled oscillator, having a preconditioner and a digital phase locked loop. The preconditioner receives an input clock signal and outputs a modified clock signal that is synchronized to a master clock signal. The digital phase locked loop receives the modified clock signal output from the preconditioner and outputs an output clock signal that is a version of the input clock signal synchronized to the master clock signal. The preconditioner preferably has a higher bandwidth than the digital PLL, and the preconditioner operates to noise shape phase noise of the synchronization to higher frequencies. The digital phase locked loop may then operate to remove the phase noise at the higher frequencies.

Abstract: A digital-to-phase or digital-to-time-shift converter (100) includes a delay line (106), a multiplexor (108) and synchronization circuit (110). In the converter (100) the clock edges of a reference signal are shifted in response to the value of a multi-bit digital word, IN (104). The synchronization circuit (110) gates the output of the multiplexor (108) such that a pulse appears at the synchronization circuit's (110) output port (114) only when the circuit is gated by a signal at input TRIG (112). The synchronization circuit (110) creates a time aperture for the multiplexor output.

Abstract: A frequency locked loop in a microcontroller integrated circuit has a precision digital feedback control loop. The frequency locked loop performs a clock multiplication function such that an inexpensive and low frequency external crystal is usable to both clock a processor of the microcontroller with a higher frequency and low-jitter clock signal and to clock a real time clock of the microcontroller with a low frequency time base that is a power of two multiple of one hertz. In one embodiment, the digital feedback control loop includes a ramp generator, a digital filter, and a loop divider. The ramp generator is controlled to output steeper and steeper ramps as the frequency locking process proceeds toward frequency lock. A preset value that presets the loop divider is changed to adjust the phase of a feedback signal with respect to a reference input signal.

Abstract: A closed loop delay line system (700) includes a phase lock loop that provides a phase lock output signal (715). A delay line (702) includes a clock input, a delay line output, and a delay line bias input. A bias signal provided to the delay line bias input (727) adjusts the speed of the delay line (702). A phase detector (720) compares phase between a first timing signal input (704) and the delay line output (706). A bias adjust circuit (726) mixes the phase compare output signal (725) and the phase lock output signal (715) to provide a combination bias signal (727) to the delay line (702). Additionally, the relative timing position of strobe outputs (734) from the delay line (702) can be individually adjusted.

Abstract: Fine tuned signal phase adjustments are provided by multiple cascaded phase mixers. Each phase mixer outputs a signal having a phase between the phases of its two input signals. With each subsequent stage of phase mixers, the signals generated by the phase mixers have a smaller phase difference, thereby providing finer delay adjustments. Multiple stages of phase mixers can be provided in digital delay-locked loop circuitry to provide additional hierarchical delay adjustment.

Abstract: A system and method for initializing and resetting a clocking subsystem having a phased locked loop (PLL) within an input/output interface of a data processing system. A first timer generates signals in response to receiving clock signals from a clock source. A second timer detects the presence or absence of signals from the first timer and in response to an absence outputs a circuit reset signal to a circuit. The circuit in turn issues a reset signal to the PLL and to other systems.

Abstract: An apparatus comprising a first circuit and a second circuit. The first circuit may comprise a control circuit and an oscillator. The control circuit may be configured to generate a control signal in response to a first reference signal and a second reference signal. The oscillator may be configured to generate the second reference signal in response to the control signal and a timing signal. The control signal is generally held when the first reference signal is lost. The second circuit may be configured to generate one or more output signals in response to the second reference signal and one of the one or more output signals. The one or more output signals may have a controlled delay with respect to the first reference signal.

Abstract: An integrated circuit is provided, which includes a phase-locked loop (PLL) that is fabricated on the integrated circuit and has a selectable loop filter capacitance and a selectable output frequency range.

Abstract: A phase-locked loop (PLL) circuit includes a voltage-controlled oscillator (VCO) having a first input to receive a control voltage, one or more second inputs to receive one or more tuning range control signals, and an output to provide an oscillation output signal, a phase detector having inputs to receive the oscillation output signal and a reference signal, a charge pump having an input coupled to the output of the phase detector and having an output to generate the control voltage, a loop filter having an input to receive the control voltage and having a control terminal, and a controller having inputs to receive the control voltage, a high reference voltage, a low reference voltage, and one or more mode signals, and having a first output connected to the control terminal of the loop filter and second outputs to generate the tuning range signals.

Abstract: A semiconductor arrangement is provided for generating a predetermined time delay. Two clocks are connected to two parallel, redundant semi-conductor circuits emitting clock signals from multiplexers. The redundant circuits receive delayed clock signals from one of the clocks, and from the other clock, clock signals that are delayed in adjustable delay circuits to be phased in with the clock signals from the first clock. A number of delay elements and a first reference number of delay elements, providing a predetermined delay time, are connected in a reference delay circuit. A quotient of the two numbers is stored. One of the semi-conductor circuits is replaced by an alternative semi-conductor circuit, the reference delay circuit of which is set on the predetermined delay time, corresponding to a second reference number of delay elements. An adjustable delay circuit is set on the same delay time as the replaced semi-conductor circuit by means of the second reference number and the quotient.

Abstract: A clock generator has a clock generating circuit, a phase difference detection circuit, and a control signal generating circuit. The clock generating circuit has a function for varying a clock phase in accordance with a control signal, the phase difference detection circuit compars the clock phase output from the clock generating circuit with a phase of a reference waveform, and detecting a phase difference therebetween, and the control signal generating circuit generates a control signal for controlling the clock phase of the clock generating circuit, based on phase difference information obtained from the phase difference detection circuit.

Abstract: Circuits and methods align an internal signal with an external signal. A phase lock loop network receives the external signal to generate phase lock loop signals. A programmable ratio decoder provides a code. An alignment unit generates the internal signal based on at least one of the phase lock loop signals. The alignment unit aligns internal signal with the external signal based on the code.

Abstract: A clock compensation circuit is provided. The circuit comprises a clock synchronization circuit coupled to receive an input clock signal, wherein the clock synchronization circuit generates a master clock signal and produces a plurality of internal logic clock signals. The circuit further comprises a phase comparator coupled to receive one of the plurality of internal logic clock signals and a sample clock from an associated receiver, wherein the phase comparator generates a control signal based on a phase comparison between the sample clock and the one of the plurality of internal logic clock signals and a down converter channel coupled to receive each of the plurality of internal logic clock signals and the control signal and to pass data in phase with the sample clock using the internal logic clock signal based on the control signal.

Abstract: A master clock signal source (10) generates a master clock signal having a frequency equal to N times the bit rate of received data, where N is a positive integer. A modulo-N counter (12) counts the master clock signal. An edge detecting circuit (4) detects a transition of the received data from a H level to a L level. A counter (8) counts the master clock signal and resets the modulo-N counter (12) if the count counted during a time period in which three edge representative signals occur is 2N. In accordance with the count in the modulo-N counter 12, a clock generating unit 14 generates a clock signal.

Abstract: A phase locked loop that may use UP and/or DN signals having programmable active state durations to control the speed of a clock signal.

Abstract: The embodiment of the present invention provides a joint clock source coupling architecture of a time division duplex (TDD) transceiver to minimize a circuit element interference and stabilize a performance of a circuit element within the TDD transceiver. Thereby, a communication link of the TDD transceiver is ensured, and a throughput of the TDD transceiver is increased.

Abstract: The present invention includes an integrated circuit that can use a high-frequency timing reference generator from a high-speed serial interface to provide the clocking and timing requirements for the integrated circuit. The timing mechanism in the present invention obviates the need for phase locked loop (PLL) macrocells to provide timing reference and timing signals in the IC. The ICs of the present invention are preferably used as disk drive integrated circuits that include DSP, memory, data path controllers, data interfaces, custom macrocells, and DSP peripherals. The high-speed serial interface is preferably a Serial ATA (SATA), Universal Serial Bus (USB), Fiber Channel, or Serial Attached SCSI (SAS), among others.

Abstract: The invention relates to a processing device for digital data which is capable of processing data which have been sampled with a sampling clock which may have any value whatsoever with respect to the basic clock of the device. To achieve this, the device is provided with means for generating from its basic clock an operational clock which is a function of the sampling clock of the data to be processed. This operational clock has a constant integer number of active periods during one cycle of the sampling clock. Application: Digital communication systems, especially demodulation.

Abstract: The present invention discloses a universal clock generator, which comprises a high frequency clock region for generating high frequency clocks and a low frequency clock region for generating high frequency clocks. The low frequency clock region includes at least one delay lock loop for increasing the number of high frequency clocks of the high frequency clock region. When the number of high frequency clocks (such as a CPU clock, SDRAM clock, AGP clock and PCI clock) is not enough, the delay lock loop of the low frequency clock region can be cascaded to support insufficient clocks.

Abstract: An apparatus comprising a first circuit and a second circuit. The first circuit may be configured to receive a first reference signal and generate a second reference signal. A frequency and a phase of the second reference signal may be (i) adjusted in response to the first reference signal and (ii) held when the first reference signal is lost. The second circuit may be configured to generate one or more output signals in response to the second reference signal and one of the one or more output signals. The one or more output signals may have a controlled and/or substantially zero delay with respect to the first reference signal.

Abstract: An apparatus including a clock generating circuit and a programmable logic circuit. The clock generating circuit may be configured to generate one or more output signals in response to a reference signal and one or more control signals, wherein the output signals each have a frequency and a phase that are dynamically variable. The programmable logic circuit may be configured to generate one or more of the control signals and receive the one or more output signals.

Abstract: A VCO phase lock loop system may include a first voltage controlled oscillator that provides a first oscillation signal relative to a first frequency and a second voltage controlled oscillator that provide a second oscillation signal relative to a second frequency. A loop filter capacitor may be associated with both the first voltage controlled oscillator and the second voltage controlled oscillator. A selection device may enable components associated with the either one of the voltage controlled oscillators while disabling components associated with the other one of the voltage controlled oscillators.

Abstract: Modern portable communications units, and in particular cellular telephones, can contain several frequency bands for receiving and several frequency bands for transmitting signals. Typically these units contain a baseband unit and a frequency synthesizer unit, which may be embodied as VLSI integrated circuits. The baseband unit commonly contains the user interfaces and control signals for controlling other portions of the circuitry. The second unit is sometimes called a frequency synthesizer unit. The second unit is dedicated to producing frequencies that are used by the communications system to create RF signals for broadcast and also to take RF signals and extract the modulated signal from them for decoding. As personal communications units have begun using an increasing number of bands it is often necessary to configure different filters to receive or broadcast the different bands. Typically, the baseband Integrated Circuit or separate circuitry does this filter configuration management.

Abstract: An integrated circuit has a timing circuit with a power source and a capacitor. The timing circuit outputs an output signal whose time can be adjusted and which has a switching time delayed with respect to a reference time. A control signal output by a drive circuit is connected to the timing circuit for adjustment of the output signal with regard to the switching time. The output signal from the timing circuit is connected to the drive circuit for assessment of the output signal with regard to the switching time. The operation of the timing circuit can thus be adjusted independently of process fluctuations during the production of the integrated circuit.

Abstract: A method of detecting a frequency of a digital phase locked loop in an optical disc reproduction and/or recording apparatus, which includes (a) detecting an edge point of an input signal, (b) sampling a previous and following input signal on the basis of the detected edge point into a predetermined frequency, (c) counting a number of reference clock signals between the detected edge point and a sample which is positioned previously, adding a count value and an interval of time corresponding to the count value to obtain a frequency count value at the edge point, and (e) comparing the obtained frequency count value with a predetermined reference value, to enhance the frequency according to the comparison result can detect frequency having high resolution with only a reference clock frequency without heightening a frequency of a reference clock signal, to thereby enhance the quality of data.

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: An apparatus that reduces sampling errors for data communicated between devices uses phase information acquired from a timing reference signal such as a strobe signal to align a data-sampling signal for sampling a data signal that was sent along with the timing reference signal. The data-sampling signal may be provided by adjustably delaying a clock signal according to the phase information acquired from the strobe signal. The data-sampling signal may also have an improved waveform compared to the timing reference signal, including a fifty percent duty cycle and sharp transitions. The phase information acquired from the timing reference signal may also be used for other purposes, such as aligning received data with a local clock domain, or transmitting data so that it arrives at a remote device in synchronism with a reference clock signal at the remote device.

Abstract: A significantly more efficient implementation of a DLL for systems using two separate clock signals, whereby a single DLL circuit is used to provide for locking of both clock signals. According to the present invention, a phase detector circuit comprises: a first compare block coupled to receive a first clock signal and a second clock signal, and configured to generate a first output signal representing a lead or lag condition; a delay cell having an input and an output, the input coupled to receive the second clock signal; a second compare block coupled to receive the first clock signal and the output of the delay cell, and configured to generate a second output signal representing a lead or lag condition; and a logic block coupled to receive the first output signal and the second output signal, and configured to generate a phase detect output signal indicating a lock condition or an out-of-phase condition.

Abstract: An output clock signal is generated from a main clock signal having a predetermined main frequency and from a secondary clock signal generated by a quartz crystal. A frequency synthesizer is preprogrammed to generate two output clock signals whose respective frequencies are slightly greater than and slightly less than the frequency of the main clock signal. The synthesizer switches between the two output clock signals depending on the phase error between the selected output clock signal and the main clock signal.