Abstract: An integrated circuit includes a physical layer interface having a control timing domain and a data timing domain, and circuits that enable the control timing domain during a change in power conservation mode in response to a first event, and that enable the data timing domain in response to a second event. The control timing domain can include interface circuits coupled to a command and address path, and the data timing domain can include interface circuits coupled to a data path.

Abstract: A nonvolatile storage or memory device is accessed over a memory bus. The memory bus has an electrical interface typically used for volatile memory devices. A controller coupled to the bus sends synchronous data access commands to the nonvolatile memory device, and reads the response from the device bus based on an expected timing of a reply from the nonvolatile memory device. The controller determines the expected timing based on when the command was sent, and characteristics of the nonvolatile memory device. The controller may not need all the electrical signal lines available on the memory bus, and could issue data access commands to different groups of nonvolatile memory devices over different groups of electrical signal lines. The memory bus may be available and configured for either use with a memory controller and volatile memory devices, or a storage controller and nonvolatile memory devices.

Abstract: An asynchronously pipelined SDRAM has separate pipeline stages that are controlled by asynchronous signals. Rather than using a clock signal to synchronize data at each stage, an asynchronous signal is used to latch data at every stage. The asynchronous control signals are generated within the chip and are optimized to the different latency stages. Longer latency stages require larger delays elements, while shorter latency states require shorter delay elements. The data is synchronized to the clock at the end of the read data path before being read out of the chip. Because the data has been latched at each pipeline stage, it suffers from less skew than would be seen in a conventional wave pipeline architecture. Furthermore, since the stages are independent of the system clock, the read data path can be run at any CAS latency as long as the re-synchronizing output is built to support it.

Abstract: A method of loading configuration data within an integrated circuit that includes multiple dies is disclosed. The method can include receiving configuration data in encrypted form within a first die of the multiple dies of the integrated circuit and decrypting the configuration data within the first die to generate configuration data in unencrypted form. A portion of the configuration data in unencrypted form can be distributed from the first die to each other die of the multiple dies through an interposer to which each die is attached.

Abstract: Methods for controlling read data buffering are disclosed. In one of the methods core operations are performed in response to a receipt of a read command from a master controller and an internal or external communication buffer of a data storage node is selected to forward information to the master controller. The data storage node is selected based upon constraints and contents of one or more communication buffers. Information is forwarded from the selected internal or external communication buffer to the master controller.

Abstract: Systems, methods, and other embodiments associated with clock generation are provided. In one embodiment, an apparatus comprises a digital clock circuit. Receive logic is configured to receive a timing message from a network device, where the timing message includes timing information associated with a stream of content. Content logic is configured to process the stream of content. A frequency and a phase are determined from the timing information. The digital clock circuit is configured to generate a digital clock with the frequency and the phase, where the digital clock is used to control the content logic to process the stream of content.

Abstract: A technique for rate verification of an incoming serial alignment sequence includes receiving an incoming serial stream. A determination is then made as to whether an align sequence is recognized in the incoming serial stream. When an align sequence is recognized, a check is made to determine if an appropriate number of align primitives are received during a predetermined number of clock periods. If the number of received align primitives matches the predetermined number, then a rate-verified align detect signal is asserted.

Abstract: A clock divider circuit has a plurality of dividers for which dividing ratios are settable, a preset register group that stores the dividing ratios set for the plurality of dividers, and a selector that selects a single preset register within the preset register group, and imparts the dividing ratios stored in the selected preset register to the plurality of dividers.

Abstract: A circuit and method for trimming an internal oscillator of a USB device that generates a clock signal as a frequency source of the USB device detect an end of packet from an input data stream to initialize a counter, identify a token packet in the data stream to detect a start of frame token packet for the counter to carry out clock counting on the clock signal to thereby obtain a count value, and compare the count value with a reference value to determine a trimming code for trimming a clock frequency of the internal oscillator.

Abstract: The display apparatus includes an AD converter converting an analog video signal into a digital video signal, a phase adjuster and a horizontal start position detector. The detector detects a horizontal start position where an output value of the AD converter becomes a minimum value that exceeds a threshold level in a video horizontal direction. The phase adjuster acquires a start position change phase where the horizontal start position is changed. The phase adjuster calculates a first phase period where the analog video signal starts its transition from a first level to a second (higher) level and then ends the transition. The phase adjuster sets a phase not included in the first phase period as an adjusted phase of the quantization clock.

Abstract: In an embodiment of the present invention, a clock generator circuit is disclosed to include a phase locked loop (PLL) that is responsive to a reference frequency and operative to generate a single clock frequency and a clock signal quadrature output frequency and a clock signal in-phase output with the frequency of the clock signal quadrature output frequency and the clock signal in-phase output frequency being a fraction of the frequency of the single clock frequency. The PLL includes a single voltage controlled oscillator (VCO) that generates the single clock frequency. A plurality of dividers is included in the clock generator circuit and is responsive to the clock signal quadrature output frequency and the clock signal in-phase output frequency and generates multiple clock frequencies, each clock frequency being a unique frequency, each of the plurality of dividers generating an output, the final output of the plurality of dividers being synchronized to the reference frequency.

Abstract: Implementations of the present disclosure involve an apparatus and/or method for providing a constant frequency timer signal for a microprocessor that operates with varying core clock signals. The apparatus and/or method utilizes a code generator, such as a gray code generator, operating on a reference clock signal that allows the constant frequency timer signal to be either faster or slower than the core clock frequency. More particularly, the apparatus and/or method may compute a difference between previous gray code samples and add the calculated difference to a software visible reference clock signal such that constant frequency timer signal may be faster or slower than the core clock signal. Through the use of the apparatus and/or method, a core clock signal may be reduced as needed to provide operational power savings to the microprocessor and the computing system employing the techniques described herein, while maintaining synchronization between the executing programs of the computing system.

Abstract: In one embodiment, the present invention includes a method for receiving utilization data from thread units of one or more processor cores, determining an operating frequency for a core clock signal based on the utilization data, a target utilization value, and an operating mode of the processor, and generating the core clock signal based on the determined operating frequency. Other embodiments are described and claimed.

Abstract: A timing recovery controller capable of performing timing recovery for a data sequence at twice a symbol rate includes a sampler, a timing base device, a timing error detector and a timing lock detector. The timing error detector includes a first delay unit and a second delay unit, for delaying a data sequence to output a first delay data sequence and a second delay data sequence, respectively, and a timing error calculating module, for generating a timing error value, to adjust a time base. The timing lock detector includes a third delay unit, for delaying the data sequence to output a third delay data sequence, and a timing lock determination module, for generating a timing lock determination result.

Abstract: For an integrated circuit (IC) that retrieves data from a memory device external to the IC, a novel memory interface module that generates a sampling clock to the memory device and samples the retrieved data is described. The memory interface module adjusts the frequency of the sampling clock and selects a sampling time for sampling the retrieved data. The memory interface includes a training module that monitors a data pin of the memory device for transitions. The training module searches and records the earliest transition and the latest transition with respect to the period of the sampling clock. The memory interface module uses the earliest transition and the latest transition to determine an interval of data uncertainty (uncertainty interval) for the data pin. The memory interface module facilitates determining a new sampling time and a new sampling clock frequency based on the uncertainty intervals.

Abstract: A performance scaling device, a processor having the same, and a performance scaling method thereof are provided. The performance scaling device includes an adaptive voltage scaling unit, a latency prediction unit, and a variable-latency datapath. The adaptive voltage scaling unit generates a plurality of operation voltages and transmits the operation voltages to the variable-latency datapath. The variable-latency datapath operates with different latencies according to the operation voltages and generates an operation latency. The latency prediction unit receives the operation latency and a system latency tolerance and generates a voltage scaling signal for the adaptive voltage scaling unit according to the operation latency and the system latency tolerance. The adaptive voltage scaling unit outputs and scales the operation voltages thereof according to the voltage scaling signal.

Abstract: A transceiver comprises a transmitter that converts a plurality of data components into serial data in response to a first clock signal and transmits the serial data, and a receiver that receives the serial data and converts the serial data into the plurality of data components in response to a second clock signal generated from the serial data. The transmitter adds at least one dummy bit to the serial data at predetermined intervals. The at least one dummy bit includes information regarding a data type of the plurality of data components.

Abstract: The clock circuit of an integrated circuit operates with variations such as temperature, ground noise, and power noise. Various aspects of an improved clock integrated circuit address one or more of the variations in temperature, ground noise, and power noise.

Abstract: A data processing system, comprising: a PLL configured to receive a reference clock and to generate a common clock; a processing unit configured to output an operation condition data based on one of temperature, voltage, or process information; and at least two data processing circuits, each comprising: a first clock signal generator configured to receive the common clock signal, the first clock signal generator having a first clock latency adjusting circuit configured to adjust clock signal propagation delay based on the operation condition data; and a second clock signal generator configured to receive the common clock signal, the second clock signal generator having a second clock latency adjusting circuit configured to adjust clock signal propagation delay based on the operation condition data.

Abstract: A clock generator is provided. The clock generator includes a crystal oscillator, an inverter coupled to the crystal oscillator in parallel, a first circuit and a second circuit. The crystal oscillator has a first terminal and a second terminal The inverter generates a first signal and a second signal at the first and second terminals of the crystal oscillator, respectively. The first circuit coupled to the first terminal of the crystal oscillator generates a first clock signal with a constant frequency according to the first signal. The second circuit coupled to the second terminal of the crystal oscillator generates a second clock signal with a variable frequency according to the second signal.

Abstract: A clock circuit is suitable for use in a timing circuit which provides time information according to a reference clock. The clock circuit includes a clock detector to detect whether or not an interruption of the reference clock occurs. When the interruption of the reference clock occurs, a clock interruption signal is issued as a reference whether or not to reset the timing circuit.

Abstract: Method, apparatus and system are described for converting received timestamps to a time-recording standard recognized by the receiving computing system. Embodiments of the invention generally include receiving data from an external device that includes a timestamp. If the received data is the first communication from the external device, creating a time base used for converting subsequently received timestamps to a recognized standard. Moreover, the system updates the time base if a counter failure at the external device is detected. When the external device transmits subsequent data, the time base is added to the subsequently received timestamps to convert the subsequent timestamps to a time-recording standard recognized by the computing system.

Abstract: Method is described for converting received timestamps to a time-recording standard recognized by the receiving computing system. Embodiments of the invention generally include receiving data from an external device that includes a timestamp. If the received data is the first communication from the external device, creating a time base used for converting subsequently received timestamps to a recognized standard. Moreover, the system updates the time base if a counter failure at the external device is detected. When the external device transmits subsequent data, the time base is added to the subsequently received timestamps to convert the subsequent timestamps to a time-recording standard recognized by the computing system.

Abstract: A mechanism is provided for monitoring and verifying a clock state of a chip that does not write out clock state information. Responsive to identifying an access to the chip, the access is scanned to identify a chip register and a clock domain that will be accessed. A determination is made as to whether a bit of a clock trust unit associated with the chip register and the clock domain indicates whether to trust a clock state associated with the bit in a logical clock state unit. Responsive to the bit of the clock trust unit indicating that the clock state associated with the bit in the logical clock state unit is trusted, the clock state from the logical clock state unit is identified. Responsive to the clock state matching the clock state required by the access, the access is forwarded to the chip for execution.

Abstract: A microcomputer is provided having a memory card interface capable of correctly latching data even when a card such as an MMC card is connected thereto. In the microcomputer having an interface with an external device such as a memory card, the interface unit is provided with an output driver connected to an external terminal for outputting a clock signal to output the clock signal and with an equivalent load circuit capable of imparting, to the clock signal extracted from an arbitrary position in a stage previous to the output driver in a clock signal path, delay equivalent to delay resulting from an external load connected to the external terminal in order to generate a clock signal for latching data inputted from the memory card.

Abstract: An apparatus includes a delay line having at least two parallel branches, where each branch includes multiple delay cells coupled in series. The delay line is configured to receive an input signal and to propagate the input signal in parallel through the delay cells in the branches. The apparatus also includes multiple sampling circuits configured to sample the input signal at different taps in the branches of the delay line and to output sampled values. The taps in a first of the branches are associated with different amounts of delay compared to the taps in a second of the branches. At least some of the delay cells in the branches of the delay line could have a minimum delay, and a difference in delay between at least one tap in the first branch and at least one tap in the second branch could be less than a smallest of the minimum delays.

Abstract: In accordance with some embodiments, a method for high frequency clock distribution in a VLSI system includes splitting an original master clock signal into one or more pairs of lower-frequency sub-clocks for a destination in the VLSI system, distributing each lower-frequency sub-clock of the one or more pairs of lower-frequency sub-clocks to a corresponding channel coupled to the destination, and reconstructing a reference master clock signal at the destination from the one or more pairs of lower-frequency sub-clocks, wherein the reconstructed reference master clock signal replicates the original master clock signal.

Abstract: A method and a device are described for testing a frequency-modulated clock generator, the device including a cycle counting unit for counting clock cycles of a clock signal of the clock generator in multiple consecutive measuring periods, which are defined, in particular, by a measuring signal having a measuring frequency, and for outputting cycle count values, and including a comparator device for receiving and comparing the cycle count values with each other and for outputting at least one output signal as a function of the comparison. In particular, ascertained maximum and minimum values may be compared with each other.

Abstract: The core chips each include a timing control circuit that outputs a timing signal synchronized with the outputting of parallel data to the interface chip. The interface chip includes a data input circuit that captures parallel data in synchronization with the timing signal. With this arrangement, the timing to output the parallel data and the timing to capture the parallel data are both synchronized with the timing signal generated in the core chips. Therefore, even if there is a difference in operation speed between each core chip and the interface chip, the parallel data can be accurately captured on the interface chip side.

Abstract: An apparatus for clock calibration on a remote device includes a first oscillator, a second oscillator, and a clock calibration module. The first oscillator generates a first clock signal during an active communication mode to facilitate communications between the remote and host devices. The first oscillator is inactive during a sniff mode. The second oscillator generates a second clock signal during both the active communication and sniff modes. The clock calibration module generates an estimated count for the first clock signal approximately at a transition from the sniff mode to the active communication mode. The estimated count is based on a clock ratio of a baseline count of the first clock signal relative to a baseline count of the second clock signal. The clock calibration module also calculates a difference between the estimated count and an actual count from the host device to determine whether to update the clock ratio.

Abstract: A clock divider circuit has a plurality of dividers for which dividing ratios are settable, a preset register group that stores the dividing ratios set for the plurality of dividers, and a selector that selects a single preset register within the preset register group, and imparts the dividing ratios stored in the selected preset register to the plurality of dividers.

Abstract: A digital audio device has a plurality of input ports that are provided with a plurality of digital audio signals. A plurality of extraction parts extract a clock signal from the digital audio signal, when the clock signal is superimposed in the digital audio signal provided to corresponding input ports. A first selection part selects the extracted clock signal as a word clock when the clock signal is extracted by any one of the plurality of the extraction parts. A frequency storage part stores a frequency of the clock signal selected by the first selection part. An internal clock generator outputs a clock signal having a frequency as specified. A second selection part selects the clock signal output from the internal clock generator as a word clock when no clock signal is extracted by the plurality of the extraction parts, the frequency of the clock signal output from the internal clock generator being set to the frequency stored in the frequency storage part.

Abstract: A method for reducing electromagnetic emissions in an electronic device having a multiple micro-controllers includes identifying the number of micro-controllers installed in the electronic device. An operating frequency range of the electronic device is determined based on the operating frequency range of each micro-controller. A frequency spacing for each micro-controller within the operating frequency range of the electronic device is then calculated, and an operating frequency is assigned to each micro-controller. The operating frequency of each micro-controller is separated from the operating frequency of each other micro-controller by at least the frequency spacing. Then, the operating frequency of each micro-controller is set at the assigned operating frequency.

Abstract: A system and method are provided for reducing a latency associated with timestamps in a multi-core, multi threaded processor. A processor capable of simultaneously processing a plurality of threads is provided. The processor includes a plurality of cores, a plurality of network interfaces for network communication, and a timer circuit for reducing a latency associated with timestamps used for synchronization of the network communication utilizing a precision time protocol.

Abstract: A device for adjusting the timing of at least one edge of an output pulse created in response to a reference pulse is disclosed. Such a device may include a first memory circuit having two or more first memory cells and a second memory circuit also having two or more second memory cells. The first memory circuit may be configured to periodically sample the reference pulse at the rising edges of a first sample clock while the second memory circuit may be configured to periodically sample the reference pulse at the falling edges of the first sample clock. A combinatorial logic circuit may also be included to produce the output pulse having at least one adjusted edge based on a set of timing instructions and timing information provided by the first and/or second memory circuits.

Abstract: A multimedia processing system for processing a program stream containing a program clock reference information. The system comprises a clock generator, a timer, a modifier, a processing unit, a parser and a compensator. The clock generator generates a clock signal. The timer receives the clock signal and generates a time information. The modifier incorporates a timing reference information into the program stream, wherein the timing reference information is provided according to the time information and the program clock reference information. The processing unit processes the program stream to generate a data stream incorporated with the timing reference information. The parser extracts the timing reference information from the data stream. And, the compensator generates a control signal according to the timing reference information. Wherein the clock generator receives the control signal and adjusts the clock signal.

Abstract: A multi-use physical (PHY) architecture that includes a PHY connection that includes one or more bit lines and that is communicatively coupled to a first processor. The PHY connection is configurable to carry signals between the first processor and a second processor, or between the first processor and a memory. The one or more bit lines are configured to carry signals bi-directionally at a first voltage when the PHY connection is configured to carry signals between the first processor and the memory. The one or more bit lines are configured to carry signals uni-directionally at a second voltage when the PHY connection is configured to carry signals between the first processor and the second processor. The second voltage is different than the first voltage.

Abstract: A clocking system, comprises a plurality of clocked data processing devices and a clock control circuit controlling a generation of a plurality of clock signals and an application of the clock signals to the plurality of data processing devices, allowing to clock at least one of the data processing devices while freezing all but the at least one of the data processing devices. A method for clocking a plurality of clocked data processing devices comprises controlling a generation of a plurality of clock signals and controlling an application of the clock signals to the plurality of data processing devices, allowing to clock at least one of the data processing devices while freezing all but the at least one of the data processing devices.

Abstract: A clock generator includes a first clock generating unit configured to generate a first clock signal based on a system clock signal, a second clock generating unit configured to generate a second clock signal with a frequency higher than the frequency of the first clock signal based on the system clock signal, a counting unit configured to count the number of clock pulses of the second clock signal in a cycle of the first clock signal, and an adjusting unit configured to adjust a falling edge or a rising edge of the second clock signal to synchronize with a falling edge or a rising edge of the first clock signal based on an assert signal that is output when the number of clock pulses of the second clock signal counted by the counting unit reaches a predetermined value.

Abstract: A single wire serial interface for power ICs and other devices is provided. To use the interface, a device is configured to include an EN/SET input pin. A counter within the device counts clock pulses sent to the EN/SET input pin. The output of the counter is passed to a ROM or other decoder circuit. The ROM selects an operational state for the device that corresponds to the value of the counter. In this way, control states may be selected for the device by sending corresponding clock pulses to the EN/SET pin. Holding the EN/SET pin high causes the device to maintain its operational state. Holding the EN/SET pin low for a predetermined timeout period resets the counter and causes the device to adopt a predetermined configuration (such as off) until new clock pulses are received at the EN/SET pin.

Abstract: Systems and methods are disclosed for precise event time measurement using high-speed deserializer circuitry. The described embodiments utilize high speed deserializer circuitry to achieve a precision based upon a bit period associated with the operation of the high speed operation of the deserializer circuitry rather than upon slower speed clock periods associated with reference clock signals. In certain embodiments, the disclosed systems and methods receive an event occurrence signal and use deserializer circuitry to sample the event occurrence signal and to produce multi-bit parallel data representing the event occurrence signal. Precise timestamps can then be generated based upon the multi-bit parallel data. Advantageously, the precision of these time measurements is associated with the bit period of the high speed operation of the deserializer circuitry and are not limited to lower speeds at which other circuitry within the system may be operating, for example, based upon a slower reference clock signal.

Abstract: In a data processor having a bus controller that performs timing control of access from the CPU operated in synchronization with a high-speed first clock signal to a peripheral circuit operated in synchronization with a low-speed second clock signal, a timing control circuit is provided between the peripheral circuit and the bus controller, and the bus controller causes, in response to a read instruction from the peripheral circuit, the timing control circuit to output data held by the peripheral circuit to the bus controller in synchronization with the cycle of the high-speed clock signal, causes the timing control circuit to start, in response to a write instruction directed to the peripheral circuit, writing into the peripheral circuit in synchronization with the cycle of the high-speed clock signal, and terminates the writing in synchronization with the cycle of the low-speed clock signal.

Abstract: A method and computer-usable medium including instructions for performing a method of managing power consumption in a multicore processor comprising a plurality of processor elements with at least one power saving mode. The method includes listing, using at least one distribution queue, a portion of the executable transactions in order of eligibility for execution. A plurality of executable transaction schedulers are provided. The executable transaction schedulers are linked together to provide a multilevel scheduler. The most eligible executable transaction is output from the multilevel scheduler to the at least one distribution queue. One or more of the plurality of processor elements are placed into a first power saving mode when a number of executable transactions allocated to the plurality of processor elements is such that only a portion of available processor elements are used to execute executable transactions.

Abstract: A motherboard with overclocking and overvolting functions is provided. The motherboard with an overvolting function includes a specified component, a voltage regulator and a micro-controller. The specified component receives an operating voltage. The voltage regulator generates the operating voltage according to a reference voltage. The micro-controller is electrically connected to an external input device for receiving a control signal issued by the external input device and adjusting the reference voltage according to the control signal.

Abstract: For use in systems having multiple potential clock sources, circuitry and methods are used for selecting from among multiple clock sources and for preventing switching to an inactive clock source. Such clock switching circuitry and methods are used to detect an activity-status indication of the clock sources, generate a selection based update-enable signal responsive to the detected activity-status indication of the selected clock source, update a clock select input signal in response to a clock switch request for switching to the selected clock source and based on the generated selection based update-enable signal, and control switching to the selected clock source based on the updated clock select input signal.

Abstract: An integrated circuit includes a data signal reception unit that receives a data signal transmitted from a transmission circuit, a timing signal reception unit that receives a timing signal transmitted from the transmission circuit and indicating a reading timing of the data signal, a timing adjustment unit that adjusts an output timing of the timing signal received by the timing signal reception unit, a reading unit that reads the data signal received by the data signal reception unit according to an adjusted timing signal of which the output timing is adjusted by the timing adjustment unit, and a voltage value acquisition unit that acquires a voltage value of the data signal received by the data signal reception unit and a voltage value of the adjusted timing signal of which the output timing is adjusted by the timing adjustment unit.

Abstract: In the present method of implementing functioning of an encryption engine, a plurality of logic blocks are provided, each for running a function. Each function is run based on three variables, each of which may have a first or second value. The function is run with the first variable value selected as having its first value, and with the second and third variables having their actual values. The function is again run with the first variable value selected as having its second value, and again with the second and third variables having their actual values. An actual value of the first variable is determined, and the output of the logic block is determined by the actual value of the first variable.

Abstract: Some embodiments include a graphics processing with thermal management capabilities. The graphics processing unit may include a display controller, a microprocessing engine coupled to the display controller, and a clock circuit coupled to the display controller and the microprocessing engine. The clock circuit may further include a raw clock signal coupled to the display controller, a divider coupled to the raw clock signal, and a multiplexer coupled to the divider. The divider may generate a divided version of the raw clock signal, which may be coupled to the multiplexer along with the raw clock signal. The multiplexer may selectively provide the raw clock signal and/or the divided version of the clock signal to the microprocessing engine such that the microprocessing engine may receive a timing signal that is independent of operations of the graphics processing unit and result in fewer glitches.

Abstract: A system for generating a true random number and implemented within an existing System on Chip (SoC) is provided herein. The system includes one or more sub circuitry synchronous modules configured to operate in a specified nominal clock rate, wherein each sub circuitry synchronous modules yields expected deterministic results when operating in its nominal clock rate; and a control module configured to clock the one or more sub circuitry synchronous modules each in a clock rate higher than its respective the nominal clock rate and beyond a specified value, to yield a non deterministic behavior of the one or more sub circuitry synchronous modules, resulting in one or more random signals, wherein the system is implemented within an existing system on chip (SOC).

Abstract: A processor including a first execution core section clocked to perform execution operations at a first clock frequency, and a second execution core section clocked to perform execution operations at a second clock frequency which is different than the first clock frequency. The second execution core section runs faster and includes a data cache and critical ALU functions, while the first execution core section includes latency-tolerant functions such as instruction fetch and decode units and non-critical ALU functions. The processor may further include an I/O ring which may be still slower than the first execution core section. Optionally, the first execution core section may include a third execution core section whose clock rate is between that of the first and second execution core sections. Clock multipliers/dividers may be used between the various sections to derive their clocks from a single source, such as the I/O clock.