Abstract: The oscillator 40 with cycle time correction includes a low accuracy oscillator 30A generating a clock CLK3, a counter 41 counting the clock CLK3 and cleared by activation of a clear signal CLR1, a register 42 storing a count CN of the counter 41 as a reference value RV in response to activation of a capture signal CAP; a comparator 43 activating a coincidence signal EQ when CN=RV, a control register 44 including a bit outputting a clear signal CLR2, a bit outputting an enable signal EN and a bit outputting a capture signal CAP, and logic circuits 45 and 46 activating the clear signal CLR1 when the clear signal CLR2 is active or when the enable signal EN and the coincidence signal EQ are both active.

Abstract: A semiconductor device for generating first and second internal clocks complementary with each other from an external clock and usable for both a system of a type using a complementary clock and a system of a type generating a 180° phase clock internally, is disclosed. A first clock input circuit (buffer) is supplied with a first external clock and outputs a first internal clock. A second clock input circuit (buffer) is supplied with a second external clock complementary with the first external clock and outputs a second clock. A ½ phase clock generating circuit generates a ½ phase shift signal 180° out of phase with the first internal clock. A second external clock state detection circuit judges whether the second external clock is input to the second clock input buffer.

Abstract: A semiconductor integrated circuit device for minimizing clock skew over clock wiring shortened for reduced wiring delays. A plurality of stages of clock drivers are provided on clock wiring paths ranging from a clock generator to flip-flops. Clock lines connecting upper stage clock drivers are equalized in length in the form of a tree structure, and clock lines connecting lower stage clock drivers are made as short as possible.

Abstract: An integrated circuit interconnection comprising a transmission line having a low characteristic impedance, and including a first end and a second end. A driver is coupled to the first end of the transmission line, and the transmission line is terminated with a current sense amplifier having an input impedance corresponding to the characteristic impedance of the transmission line. A plurality of components selected from the group consisting of capacitive elements, inductive elements and a combination of capacitive and inductive elements are connected at spaced intervals to the transmission line between the first and second ends.

Abstract: Disclosed herein are a clock driver circuit and a method of routing clock interconnect lines, which control the lengths of adjacent interconnect lines and ununiformity of conductive line capacitance due to the intersection of interlayer interconnect lines, thereby reducing clock skews.

Abstract: A field programmable gate array includes a programmable interconnect structure and plurality of logic cells. The logic cells each include a number of combinatorial logic circuits, which have direct interconnections with the programmable interconnect structure, and a plurality of sequential logic element, such as D type flip-flops that acts as registers. The combinatorial logic circuits may be directly connected to the programmable interconnect structure as well as connected to the input terminals of the sequential logic elements. Consequently, the logic cells include both combinatorial and registered connections with the programmable interconnect structure. Moreover, one of the sequential elements may selectively receive a dedicated input from the programmable interconnect structure. The output leads of the logic cell is connected to the programmable interconnect structure through a driver that includes a protection transistor.

Abstract: A semiconductor device for generating first and second internal clocks complementary with each other from an external clock and usable for both a system of a type using a complementary clock and a system of a type generating a 180° phase clock internally, is disclosed. A first clock input circuit (buffer) is supplied with a first external clock and outputs a first internal clock. A second clock input circuit (buffer) is supplied with a second external clock complementary with the first external clock and outputs a second clock. A ½ phase clock generating circuit generates a ½ phase shift signal 180° out of phase with the first internal clock. A second external clock state detection circuit judges whether the second external clock is input to the second clock input buffer.

Abstract: A clock interruption detection circuit comprises a frequency divider circuit for outputting a plurality of frequency divided clocks by dividing an input clock with different division values, an AND circuit for ANDing the Input clock and the plurality of frequency divided clocks, an Inverter for inverting one of the frequency divided clocks with the largest division value, another AND circuit for ANDing the input clock, the rest of the frequency divided clocks and the output of the inverter, a first and a second switch with a control terminal supplied with the output of each of the AND circuits for controlling the on/off of a discharge path of a first and a second capacitor, a first and a second waveform-shaping buffer circuit supplied with a terminal voltage of the first and the second capacitor, and a selection circuit for selecting one of the outputs of the first and second waveform-shaping buffer circuits In accordance with a selection control signal obtained by delaying the output of the inverter by a pre

Abstract: In a clock modulator for modulating a basic clock signal to form a system clock signal for a digital system containing at least one microprocessor and/or other digital module, the system clock signal generating an interference spectrum with interference spikes in the digital system, it is provided that the clock modulator (11) can be adapted as a function of the interference spectrum of the system clock signal (4) in the digital system (5) in such a way that the amplitudes of the interference spikes are reduced.

Abstract: An integrated circuit interconnection comprising a transmission line having a low characteristic impedance, and including a first end and a second end. A driver is coupled to the first end of the transmission line, and the transmission line is terminated with a current sense amplifier having an input impedance corresponding to the characteristic impedance of the transmission line. A plurality of components selected from the group consisting of capacitive elements, inductive elements and a combination of capacitive and inductive elements are connected at spaced intervals to the transmission line between the first and second ends.

Abstract: A frequency correction circuit includes a temperature sensor (100) disposed to measure temperature and produce temperature signals representing sensed temperatures. A data supplier (110) stores information items, receives digital input signals representing and produces a digital output information signal representing an item selected in accordance with the digital input signal. A control circuit (120) receives the temperature signals and receives the digital output information signal. The control circuit (120) produces control signals based on the temperature signals. A clock circuit (150) is disposed to generate a reference frequency signal. A digital synthesizer (130) receives the reference frequency signal and the control signals. The digital synthesizer produces an output frequency signal as directed by the control signals received from the control circuit (120).

Abstract: Methods and systems are disclosed for eliminating a phase transient of a controlled frequency oscillator, caused by replacing a first reference signal by a second reference signal when the first reference signal becomes corrupted or otherwise unavailable, and for running a controlled frequency oscillator in a frequency-controlled holdover mode. The contradictory requirements of using a relatively low-cost controlled frequency oscillator tunable over a relatively wide frequency range and achieving high stability of its frequency in holdover mode are satisfied.

Abstract: A semiconductor device for generating first and second internal clocks complementary with each other from an external clock and usable for both a system of a type using a complementary clock and a system of a type generating a 180° phase clock internally, is disclosed. A first clock input circuit (buffer) is supplied with a first external clock and outputs a first internal clock. A second clock input circuit (buffer) is supplied with a second external clock complementary with the first external clock and outputs a second clock. A ½ phase clock generating circuit generates a ½ phase shift signal 180° out of phase with the first internal clock. A second external clock state detection circuit judges whether the second external clock is input to the second clock input buffer.

Abstract: A clock control system in a network switching node including an internal reference clock of a low level Stratum and receiving a plurality of high level Stratum clocks (CLOCK 1, CLOCK 2, CLOCK n) from connection lines, one of these high level Stratum clocks being currently used to generate a Master Clock; the device selecting another high level Stratum clock when the clock currently used to generate the Master Clock fails and comprising for each high level Stratum clock, means (12, 16, 20) for phase locking the reference clock on the selected high level Stratum clock and obtaining a plurality of phase locked (PLL) reference clocks (SOURCE 1, SOURCE 2, SOURCE n).

Abstract: A semiconductor device for generating first and second internal clocks complementary with each other from an external clock and usable for both a system of a type using a complementary clock and a system of a type generating a 180° phase clock internally, is disclosed. A first clock input circuit (buffer) is supplied with a first external clock and outputs a first internal clock. A second clock input circuit (buffer) is supplied with a second external clock complementary with the first external clock and outputs a second clock. A ½ phase clock generating circuit generates a ½ phase shift signal 180° out of phase with the first internal clock. A second external clock state detection circuit judges whether the second external clock is input to the second clock input buffer.

Abstract: CMOS integrated circuitry responsive to a clock source having an approximately 50% duty cycle includes a one shot having an input terminal connected to be responsive to the clock wave source. The one shot derives a pulse train in response to cycles of the clock. Each pulse in the pulse train has a duration substantially less than one-half cycle of the clock wave, is initiated in response to and during a clock wave transition, and persists for a period after the transition has been completed. Latches respond to plural data signals and the pulse train so each latch is activated to be responsive to its associated data signal only during the pulses.

Abstract: A balanced dual-edge triggered bit shifting circuit includes a clock circuit to generate low skew, or edge-aligned, complementary clock signals, and a shift register that shifts a data bit in response to the complementary clock signals. The clock circuit is formed from two clock generators, each of which generates the edge-aligned complementary clock signals by alternatively coupling the input terminals of two buffer circuits to a voltage supply terminal and a ground terminal. Transfer gates coordinate the coupling of the input terminals of the buffer circuits so that the resulting output clock signals generated by each clock generator have clock transitions that are substantially simultaneous. The shift register is formed from at least one shift register stage that receives the edge-aligned complementary clock signals. The shift register stage includes two latching stages, each latching stage having an inverter with an output coupled to a latch circuit.

Abstract: 3An optimal delay value, usually the mid-delay in the operational window, for the data signal may be retained as a way of shifting the skew of the clock on all data lines at the same time. That delay value may be stored in a memory and converted to a control voltage for controlling a digitally controlled voltage variable delay to adjust the delay for data in a bus. The digitally controlled voltage variable delay contains a number of individual delay units which are selectively activated by the control voltage from the value stored in memory. A phase locked loop is employed to ensure that variations due to voltage, temperature, and processing are minimized.

Abstract: The present invention comprises a master global clock distributed in a low-skew manner over a relevant clock domain area coupled with a plurality of locally generated clocks in said clock domain area. The plurality of locally generated clocks are tuned to allow for skew and jitter tolerance. The present invention further comprises embodiments with 3, 4, 5, and 6 locally generated clocks.

Abstract: Methods and systems are disclosed for eliminating a phase transient of a controlled frequency oscillator. caused by replacing a first reference signal by a second reference signal when the first reference signal becomes corrupted or otherwise unavailable, and for running a controlled frequency oscillator in a frequency-controlled holdover mode. The contradictory requirements of using a relatively low-cost controlled frequency oscillator tunable over a relatively wide frequency range and achieving high stability of its frequency in holdover mode are satisfied.

Abstract: Methods and systems are disclosed for eliminating a phase transient of a controlled frequency oscillator caused by replacing a first reference signal by a second reference signal when the first reference signal becomes corrupted or otherwise unavailable, and for running a controlled frequency oscillator in a frequency-controlled holdover mode. The contradictory requirements of using a relatively low-cost controlled frequency oscillator tunable over a relatively wide frequency range and achieving high stability of its frequency in holdover mode are satisfied.

Abstract: A frequency correction circuit includes a temperature sensor (100) disposed to measure temperature and produce temperature signals representing sensed temperatures. A data supplier (110) stores information items, receives digital input signals representing and produces a digital output information signal representing an item selected in accordance with the digital input signal. A control circuit (120) receives the temperature signals and receives the digital output information signal. The control circuit (120) produces control signals based on the temperature signals. A clock circuit (150) is disposed to generate a reference frequency signal. A digital synthesizer (130) receives the reference frequency signal and the control signals. The digital synthesizer produces an output frequency signal as directed by the control signals received from the control circuit (120).

Abstract: A device which reduces jitter and narrows the frequency spectrum of a jitter-ridden clock signal includes a basic unit having a plurality of series connected delay elements outputs from each delay element are all connected to an AND/NAND gate. A front end of the device locates missing clock pulses and ensures regular clock pulses are relayed to the remainder of the device. A succeeding section including plural basic units hones the signal such that jitter elements are removed. By the output of this section time duty cycles are uneven, a positive edge triggered flip-flop is then used to obtain 50% duty cycles at the expense of halving the clock signal's frequency. Optionally a frequency doubler can be employed to regain the clock signal's original frequency.

Abstract: A semiconductor integrated circuit device for minimizing clock skew over clock wiring shortened for reduced wiring delays. A plurality of stages of clock drivers are provided on clock wiring paths ranging from a clock generator to flip-flops. Clock lines connecting upper stage clock drivers are equalized in length in the form of a tree structure, and clock lines connecting lower stage clock drivers are made as short as possible.

Abstract: There is provided a method of controlling a clock, including the steps of (a) receiving an external clock signal, (b) calculating a first period of time defined as (T1−T2) wherein T1 is a cycle of the external clock signal, and T2 is a period of time during which the external clock signal is transmitted through devices generating skew to the external clock signal, (c) stopping the external clock signal to be transmitted by the first period of time, and (d) driving the external clock signal to thereby turn the external clock signal into an internal clock signal. The method makes it possible to detect delay in a clock signal, and generate no delay error inherent to a digital circuit.

Abstract: A clock control circuit for reducing jitter has at least one averaging circuit for generating, and outputting from an output terminal, a signal having a time difference obtained by internally dividing a time difference between first and second signals input respectively from first and second input terminals. First and second clock signals are supplied respectively to the first and second input terminals of the timing averaging circuit, and a clock in which a time difference between pulses of the first and second clock signals is averaged is generated.

Abstract: An integrated circuit which generates a plurality of local clock signals with substantially no phase difference from an internal clock signal and a stable internal clock generating circuit that generates an internal clock having with reduced sensitivity to variations in a manufacturing process, temperature, supply voltage and noise are provided. The local clock signal generating circuit includes a plurality of phase blenders, each which receives the signals at two points on a clock signal line which transmits the internal clock signals, blends the received signals, and generates a local clock signal having a phase intermediate the phases of the signals at the two points. The internal clock signal generating circuit includes a feedback circuit and a delay lock loop (DLL) circuit.

Abstract: A method and apparatus for drastically reducing timing uncertainties in clocked digital circuits simply, at virtually no cost, and using only standard clock drivers and simple, inexpensive electrical components is described. The method includes the steps of minimizing timing uncertainties by controlling both clock skew and clock jitter. Intrinsic clock skew is eliminated by ganging the outputs of a multi-line clock together onto a capacitive metal island disposed on a printed circuit board (PCB). Extrinsic clock skew is controlled through the use of wide, relatively high-capacitance traces of matched length and disposed on a single, common signal layer of the PCB, each leading to a respective receiver circuit and terminated identically. Clock jitter is controlled by electrically isolating a region of the PCB, disposing the clock driver in the region in such a way as to minimize noise, and providing quiet local power and ground to the region.

Abstract: An integrated circuit having an apparatus for automatically adjusting noise immunity is disclosed. The integrated circuit includes multiple functional logic circuits, a clock generator, a group of noise monitor circuits, and a control logic circuit. The clock generator generates a clock signal to all these circuits. The noise monitor circuits are utilized to detect noise occurring in the integrated circuit. In response to any noise detected by the noise monitor circuits, the control logic circuit decreases the speed of the clock signal sent to all the circuits, especially the functional logic circuits, via a slow down signal to the clock generator. Alternatively, the control logic circuit can inform the functional logic circuits via a noise alert signal to increase the noise immunity of certain noise sensitive circuits within the functional logic circuits.

Abstract: The circuit configuration produces complementary signals. An input signal is routed from an input terminal via a first path, through a pass element, and to a first output terminal. The input signal is also routed on a second path, connected in parallel with the first path, via an inverter, and to a second output terminal. The first and the second output terminal are connected to a first and a second output node, respectively, via a compensation device. The compensation device compensates for the different time delays in the signals on the first and on the second path.

Abstract: A system and method for providing master and slave phase-aligned clocks. Upon a failure of a master clock signal, the system switches over to a slave clock signal in phase alignment with the master clock signal. The master clock signal is from a first clock source, while the slave clock signal is from a second clock source. The second clock source comprises a phase locked loop (PLL) including a switch, which is coupled to selectively provide a control signal to a voltage controlled oscillator (VCO). The switch may also provide a reference control voltage to the VCO. The first clock source may be on a first clock board, and the second clock source may be on a second clock board. The clock boards are preferably hot swappable. The first clock board may be removed from the system, such as upon a failure, and a third clock board placed in the system.

Abstract: This invention relates generally to Fibre Channel Loop topology in a computer system and more particularly to structure and method for by-passing a failed controller connected in a dual-active mode Fibre Channel Loop.

Abstract: A method and apparatus for drastically reducing timing uncertainties in clocked digital circuits simply, at virtually no cost, and using only standard clock drivers and simple, inexpensive electrical components is described. The method includes the steps of minimizing timing uncertainties by controlling both clock skew and clock jitter. Intrinsic clock skew is eliminated by ganging the outputs of a multi-line clock together onto a capacitive metal island disposed on a printed circuit board (PCB). Extrinsic clock skew is controlled through the use of wide, relatively high-capacitance traces of matched length and disposed on a single, common signal layer of the PCB, each leading to a respective receiver circuit and terminated identically. Clock jitter is controlled by electrically isolating a region of the PCB, disposing the clock driver in the region in such a way as to minimize noise, and providing quiet local power and ground to the region.

Abstract: A method for positioning/routing a clock circuit for an integrated circuit compensates for phase differences by adjusting secondary amplifiers having adjustable input delays. The method includes the steps of positioning first conductive lines parallel to a first direction evenly spaced with respect to the second direction. The first conductive lines are connected to outputs of the first amplifiers. A balanced tree-like structure provides each of the first amplifiers a clock signal coming from a single source. The method further includes the steps of positioning functional blocks for forming the integrated circuit, and the positioning of second lines parallel to the second direction. Each secondary amplifier is routed to the closest second line. An equivalent electrical diagram corresponding to the path taken by the clock signal between the input of the tree-like structure device and the input of each secondary amplifier is determined.

Abstract: The present invention provides a semiconductor IC and a method for designing the same which adjusts the clock skews on a chip without additional delay circuit. A decrease in design time is realized when the semiconductor IC includes hard megacells (whose functions have been confirmed) or standard cell blocks. In the case of a semiconductor IC including hard megacells and a standard cell blocks, each megacell and standard cell block according to the present invention has sub-clock buffers on every row, for example, sub-clock buffers on the row and sub-clock buffers on the row in the megacell. The adjustment needed for accommodating clock skews on a chip is determined by calculating a delay time for the various IC chip blocks. Next, sub-clock buffers are chosen based on a result of a calculation for the delay time. Finally, the wiring design is completed which minimizes clock skew.

Abstract: A semiconductor integrated circuit includes: a phase difference reduction circuit for reducing a first phase difference between a clock signal and a data signal; and a circuit for receiving the data signal with a reduced first phase difference between the clock signal and the data signal.

Abstract: A clock buffer circuit includes an amplifier section and a control section. The amplifier section amplifies a clock signal in response to a control signal. The control section generates the control signal based on an amplitude of the clock signal.

Abstract: A timing circuit can be selectively configured to generate output pulses in response to either the falling edges or the rising edges of an input signal. The timing circuit includes a multiplexer, an output pulse width controller (OPWC), a gating circuit (GC) and a latch circuit. The OPWC includes a delay circuit that can be configured to provide a predetermined delay .delta. that can be larger than the pulse width of the input signal pulses. The multiplexer is connected to receive a first input signal and an inverted version of a second input signal. The first input signal is used in a rising edge triggered mode, whereas the second input signal is used in a falling edge triggered mode. The multiplexer receives a mode signal to selectively output one of the input signals to the GC. The GC is also connected to receive the output signal from the OPWC.

Abstract: An integrated circuit chip having improved on-chip circuitry including a phase-locked-loop for providing accurately timed signal having different durations and differently occurring timing edges.

Abstract: A data processing apparatus functions as a timer or counter by counting clock pulses of a system clock signal to generate a timing signal. The system clock signal is generated as one of either a first or a second basic clock signal generated by two respective oscillators. Even if the second basic clock signal which has a lower frequency fluctuates, the data processing apparatus can accurately generate a pulse signal having a desired period. When the first basic clock signal is selected as the system clock signal, the second basic clock signal is measured with the system clock signal. When the second basic clock signal is selected as the system clock signal, a numerical value up to which the clock pulses of the system clock signal are counted is corrected on the basis of the measured second basic clock signal.

Abstract: An apparatus adjusts the duty cycle of a single-ended clock signal. The single-ended clock signal oscillates between first and second voltages. The apparatus includes an error indication circuit, a duty cycle error measurement circuit and a duty cycle adjuster. The error indication circuit includes a reference circuit and a comparison circuit. The reference circuit is coupled to a first node having the first voltage and a second node having the second voltage to generate a reference signal from the first and second voltages. The reference circuit includes at least one instance of a first electrical characteristic cell. The comparison circuit is coupled to receive a feedback clock signal and to generate a comparison signal therefrom. The comparison circuit includes at least one instance of the first electrical characteristic cell. The duty cycle error measurement circuit is coupled to receive the reference signal and the comparison signal.

Abstract: A clock circuit is used in a semiconductor device having a control block and a macroblock in order to provide synchronous clocks. The clock circuit contains a clock source for generating the clocks; a clock tree, coupled between the clock source and the control block and the macroblock, for relaying the clocks to the control block and the macrobock; and programmable delays coupled between the clock source and the clock tree and between the clock tree and the control block and the macroblock in order to reduce overall clock skew.

Abstract: A low-skew single-ended to differential signal converter includes a conventional single-ended to differential converter that drives a pair of output driver circuits. Each driver circuit is formed from a pair of transfer gates that receive a supply voltage or a reference voltage, respectively. The transfer gates transfer only a portion of the supply or reference voltage in response to the inverted signal from the conventional converter. The portion of the transferred voltage is insufficient to trigger output members in the output drivers and the output voltages from the drivers do not transition in response to the noninverted signal. The inverted signal causes the outputs of the transfer gates to transition fully, triggering the respective output inverters. Because the inverted signal causes transitions of both of the output signals, skew of the output signals is reduced relative to skew of the inverted and noninverted signals.

Abstract: A system for distributing clock signals to multiple locations on a chip with minimal skew is disclosed. A series of FIFO control structures, connected in a ring by signal lines of substantially equal length, generates multiple clock signals of equal phase and frequency. The oscillation frequency of the FIFO control ring may be increased to accommodate higher-speed chips, while maintaining synchronization of clock pulses at each stage of the FIFO control ring.

Abstract: A method and apparatus are described which eliminate the clock skew problems associated with routing clock signals throughout a circuit. Particularly well suited for Very Large Scale Integration ("VLSI") chips, the method and apparatus provide a resonator which is distributed across the circuit. This allows the clock to be accessed at a variety of locations without any propagation delay between the access points. The method for distributing a single, distributed clock signal to a plurality of clock connection points in a circuit comprises two steps. The first step is to generate the clock signal, such that the clock signal is available at a plurality of clock source points without propagation delay. The second step is to couple the plurality of clock source points to the plurality of clock connection points in the circuit.

Abstract: A byte accessible memory interface circuit using a reduced set of memory control signals. The present invention includes an interface circuit having a reduced set of memory control signals for performing word length reads and writes to an external memory module containing a plurality of integrated circuit (IC) memory chips. The interface circuit contains a respective multiplexer and a respective register circuit for each byte of the word length data. The multiplexers select a byte of data from either an on-chip data bus or from a bus carrying data read from the external memory module. To perform a full length word write, the data from the on-chip bus is loaded into the registers (via the multiplexers) and then written to the memory module. To perform a partial length word write, a pre-read operation is performed at the target address and a word length data is loaded into the registers. The new data is then received over the on-chip data bus and routed by the multiplexers into the byte locations to be changed.

Abstract: A method and apparatus for drastically reducing timing uncertainties in clocked digital circuits simply, at virtually no cost, and using only standard clock drivers and simple, inexpensive electrical components is described. The method includes the steps of minimizing timing uncertainties by controlling both clock skew and clock jitter. Intrinsic clock skew is eliminated by ganging the outputs of a multi-line clock together onto a capacitive metal island disposed on a printed circuit board (PCB). Extrinsic clock skew is controlled through the use of wide, relatively high-capacitance traces of matched length and disposed on a single, common signal layer of the PCB, each leading to a respective receiver circuit and terminated identically. Clock jitter is controlled by electrically isolating a region of the PCB, disposing the clock driver in the region in such a way as to minimize noise, and providing quiet local power and ground to the region.

Abstract: An integrated circuit formed within a substrate has a first circuit section and an active noise cancellation section located at least between the first circuit section and a noise source. The active noise cancellation section is coupled to the substrate and injects counter-charge into the substrate to isolate the first circuit section from noise produced by the noise source.

Abstract: A clock distribution circuit reliably reduces clock skew, while preventing the waveform of a clock signal from rounding, which would otherwise occur due to an increase in resistance, and preventing instability of the clock signal, which would otherwise occur due to an increase in inductance, thereby realizing ideal clock distribution. In the clock distribution circuit, a clock wiring pattern for distributing the clock signal is formed on a chip, and a wiring pattern whose resistance is lower than the clock wiring pattern is formed on a substrate, on which the chip is mounted, in such a way as to be connected to the clock wiring pattern at a plurality of locations. The clock distribution circuit is applied to semiconductor integrated circuits such as LSIs built in multichip modules.

Abstract: An external clock signal CK is input to a buffer, which generates an internal clock signal CLK having a skew of D1 with respect to the external clock signal CK. The internal clock signal is input first to a delay circuit which has a delay time A, then to a delay array which provides a delay time D2, and finally to a delay circuit which has a delay time of D2. The delay circuit generates a corrected internal clock signal CK' which is synchronous with the external clock signal CK. The delay array is composed of delay units, each having a state-holding section. The state-holding section of any delay unit that has passed a forward pulse is set in a predetermined state. Once its state-holding section is set in the predetermined state, the delay unit provides a correct delay time of 2.times..DELTA..