Abstract: Methods and apparatus for generating a delayed output signal from an input signal applied to an RC delay circuit of a semiconductor device during an active mode. The RC delay circuit is configured to pull up a voltage level on a node responsive to a reset signal during a stand-by mode.

Abstract: An acoustic fingerprint imaging system is disclosed. In one embodiment, a controller can be coupled to a plurality of delay lines, each associated with a particular transducer. The controller can determine an interrogation point to focus acoustic energy. The controller can direct each of the plurality of delay lines to apply a delayed activation pulse to each transducer based, at least in part, on the transducer's distance from the interrogation point.

Abstract: There is provided a continuous time cross-correlator comprising: a quantizer for quantizing the incoming signal into discrete levels; a delay line comprising one or more delay units separating a plurality of delay line taps; for each of said delay line taps, a comparator for comparing the signal level of the delay line tap with a correlation value; a continuous time counter for taking the outputs of the plurality of comparators as its inputs, counting the results of the comparisons and outputting the results of the comparisons; and an output comparator for comparing the counter output with a threshold value. The cross-correlator provides for high speed continuous time cross-correlation with low power consumption and a small chip area. Methods of continuous time cross correlation are also provided.

Abstract: A circuit is disclosed that provides a programmable hold time for a bus signal without running a system clock and without a frequency requirement between the system clock and a bus clock.

Abstract: Examples of analog delay lines and analog delay systems, such as DLLs incorporating analog delay lines are described, as are circuits and methods for adaptive biasing. Embodiments of adaptive biasing are described and may generate a bias signal for an analog delay line during start-up. The bias signal may be based in part on the frequency of operation of the analog delay line.

Abstract: A tunable delay line is calibrated to maintain the delay of the delay line at a desired value or within a desired range of values. In some aspects a signal is passed through a delay line multiple times so that the cumulative delay of the signal through the delay line (e.g., as indicated by a count) may be calculated over a period of time. The count is compared with an expected count and, based on this comparison, the delay of the delay line is adjusted as necessary. In some aspects the signal may comprise a digital signal. In some aspects a delay through a delay line may be calculated based on analysis of amplitude changes in a signal caused by a phase shift imparted on the signal by the delay line. In some aspects a delay line is incorporated into a transmitted reference system to generate and/or process transmitted reference signals.

Abstract: The present invention relates to a threshold voltage and delay time setting circuit, and a battery management system including the same. The setting circuit is connected to a set resistor and a set capacitor through a pin. The setting circuit includes a threshold voltage setter for setting a threshold voltage according to resistance of the set resistor, and a delay setter for determining a count frequency according to capacitance of the set capacitor and setting a delay time according to the determined count frequency.

Abstract: A system and method for efficiently performing timing characterization of regions of an integrated circuit. An integrated circuit has monitors distributed in different physical regions across its die. Each monitor includes timing characterization and self-test circuitry. This circuitry includes one or more tunable delay lines used during timing measurements. The circuitry verifies the tunable delay lines are defect free prior to the timing measurements. If defects are detected, but tunable delay lines may still be used, a scaling factor may be generated for a failing tunable delay line. The scaling factor may be used during subsequent timing measurements to maintain a high accuracy for the measurements. The timing measurements may determine a particular physical region of the die provides fast or slow timing values. The resulting statistics of the timing measurements may be used to change an operational mode of the IC in at least the particular region.

Abstract: In certain arrangements and methods, a reset-able counter (100) produces multiple delay times as required by, for example, a finite state machine. The counter (100) counts a stored value by a configurable amount. That configurable amount is determined based upon the period of a clock cycle divided by a desired time unit. The value held by the counter does not represent a count of clock cycles, but rather a count of time units. In other aspects, a device generates fixed delays derived from a variable frequency input clock. The device includes a count circuit (100) and a comparator (114, 116). The number of time-units between consecutive clock edges of the input clock is stored, and the count circuit changes a current-count value by a corresponding amount, with the change being responsive to a clock edge of the input clock. The comparator (114, 116) compares the current-count value to a fixed value that represents a fixed delay time.

Abstract: A tunable delay line is calibrated to maintain the delay of the delay line at a desired value or within a desired range of values. In some aspects a signal is passed through a delay line multiple times so that the cumulative delay of the signal through the delay line (e.g., as indicated by a count) may be calculated over a period of time. The count is compared with an expected count and, based on this comparison, the delay of the delay line is adjusted as necessary. In some aspects the signal may comprise a digital signal. In some aspects a delay through a delay line may be calculated based on analysis of amplitude changes in a signal caused by a phase shift imparted on the signal by the delay line. In some aspects a delay line is incorporated into a transmitted reference system to generate and/or process transmitted reference signals.

Abstract: A trimming system for determining a trim solution for a semiconductor device includes an internal value generating circuit for generating an internal value based upon a counter value. The relationship between the internal delay value and an external reference is compared to determine if the counter value is a possible trim solution, while predetermined counter values are excluded as a trim solution.

Abstract: A programmable delay line includes a first oscillator that is enabled and generates a plurality of clock cycles of a clock signal in response to a transition of the input signal. A first programmable ripple counter is coupled to the first oscillator, counts with each successive clock cycle to a programmed count, and generates a first signal in response to reaching the programmed count. A control circuit is coupled to the first oscillator and to the first programmable ripple counter. The control circuit transitions the output signal and disables the first oscillator in response to the first signal.

Abstract: Delay lock loop circuits are described, which may include two or more delay stages that each includes a plurality of selectable delay elements. A reference signal drives an input of the first delay stage, which provides a first output. The first output drives an input of the second delay stage, which provides a second output. The circuits further include a first selector register that is associated with the first delay stage. A value maintained in the first selector register determines a number of the selectable delay elements utilized in the first delay stage. The circuits further include a second selector register associated with the second delay stage. A value maintained in the second selector register determines a number of the selectable delay elements utilized in the second delay stage. Modification of the values maintained in the first and second selector registers are synchronized to the first and second outputs, respectively.

Abstract: A timing generator that needs no analog circuit for adding jitters and allows the circuit scale and power consumption to be reduced.

Abstract: An apparatus, includes a counter which counts a frequency of input of a first signal, a delay controller which generates a second signal by adding a delay to the first signal, the delay corresponding to the frequency, and a control circuit which halts the counter counting the frequency, when a phase difference between the first signal and the second signal is a predetermined value.

Abstract: A master-slave device communication circuit includes a master device, a bus, and a slave device having a bus switch connected to the master device via the bus, and a status detecting circuit. The status detecting circuit includes a power input terminal and a detecting signal output terminal. A power terminal of the master device is connected to the power input terminal of the status detecting circuit. The detecting signal output terminal is connected to the bus switch and a trigger pin of the master device. When the master device supplies power to the slave device via the power terminal thereof, the detecting signal output terminal transmits a control signal to control the bus switch to turn on the bus and trigger the master device to communicate with the slave device after a delay time.

Abstract: A phase interpolator receives an input clock signal and varies the phase of an output clock signal in accordance with a phase control signal.

Abstract: When certain digital circuit devices receive data bus signals, I/O interfaces need to sample the data signals during a time when these signals are both valid and stable. Typically, the data signals are sampled at a time corresponding to a point halfway between rising and falling edges of a reference clock signal associated with the data bus, which sampling time corresponds to a 90-degree phase shift of the reference clock signal. In one embodiment of the invention, a delay count generator determines a delay value corresponding to a quarter cycle (i.e., 90 degrees) of the reference clock signal. In making this determination, a counter counts the number of clock cycles of an internally generated, relatively high-frequency clock signal, where the number corresponds to a specified portion (e.g., one half) of a period of a divided-down version of the reference clock signal. That number can then be used to generate the 90-degree delay value.

Abstract: A delay line is periodically configured into a delay-locked loop for calibration purposes. That is, the delay line is operated in an open loop mode during a first time period in which a signal, such as an aperiodic signal, is the input signal into the delay line. Periodically, the delay line is configured into a delay-locked loop and the delay line is recalibrated based on a periodic signal supplied to the delay-locked loop.

Abstract: The self correcting scheme to match pull up and pull down devices includes: a first comparator for comparing a common mode signal to a high reference limit; a second comparator for comparing the common mode signal to a low reference limit; a first flip flop having an input coupled to an output of the first comparator; a second flip flop having an input coupled to an output of the second comparator; a counter having inputs coupled to the first and second flip flops; and a delay device controlled by an output of the counter, wherein the delay device provides a pull down control signal that is delayed relative to a pull up control signal.

Abstract: A logic circuit block and a memory circuit block are provided on a semiconductor chip. A timing adjustment circuit block for adjusting the propagation timing of signals is provided on a line between the circuit blocks. A timing adjustment circuit unit includes: a delay element block including a plurality of delay elements for adding different delay amounts to the inter-block signals; a counter circuit block for receiving a timing adjustment control signal from the timing adjustment circuit block; and a fuse circuit block in which a fuse is melted down based on a fuse information signal held by the counter circuit block after a timing verification and which replaces the function of the counter circuit block.

Abstract: A digital delay line including a first feedback delay line having a first number of interlinked first delay elements, at least one second feedback counter having a second number of second interlinked counting elements, the counting elements being clocked by one of the first delay elements.

Abstract: Described are fast synchronous counters with reduced combinatorial logic. In one embodiment, a four-bit shift register is configured in a ring and preset with a data pattern (e.g., 1000). The register is then rapidly shifted into any of four unique states. Combinatorial logic connected to the shift register converts the four unique states into a two-bit binary signal representative of the four states. In the general case, counters in accordance with this embodiment represent N-bit binary numbers using 2N synchronous storage elements. Two or more counters can be combined to produce larger synchronous counters. An up/down counter in accordance with yet another embodiment is connected to a multi-path delay line to create a variable delay circuit. The switching speed of the delay circuit is independent of the number of delay settings. Also advantageous, the delay circuit scales linearly, in terms of power consumption and area, with changes in delay granularity.

Abstract: A counter has selectable divide factors using multiple multiplexers. The counter includes an inverter and cascading delay stages having selectable stage delays. The inverter connects a stage output of a last one of the delay stages to a stage input of a first one of the delay stages. Each delay stages includes a stage input to receive a quotient signal, at least two paths having different associated path delays each coupled to receive the quotient signal from the stage from the stage input, and a multiplexer. The multiplexer is coupled to selectively communicate the quotient signal from one of the at least two paths to a stage output to select one of the stage delays.

Abstract: Disclosed is a semiconductor device for outputting an output signal with a given phase held relative to an external clock despite a difference in characteristic, a change in temperature, and a fluctuation in supply voltage. The semiconductor device comprises an input circuit for inputting the external clock and outputting a reference signal, an output circuit for receiving an output timing signal and outputting an output signal according to the timing of the output timing signal, and an output timing control circuit for controlling the output timing so that the output signal exhibits a given phase relative to the external clock.

Abstract: A delay compensation circuit that determines the effects of process, voltage, and temperature (PVT) conditions of a chip by measuring the effective delay time of delay components inside the chip. The delay compensation circuit includes a plurality of sampler modules, each of which receives a delayed clock signal from one of a series of delay cells within a tapped delay circuit. The delay compensation circuit generates an output value based on the total number of sampling modules that lock into a fixed input signal using the delayed clock signals. Since the delay time of each delay cell changes based on variations of PVT conditions, the output values generated by the delay compensation circuit are determinate of PVT conditions in the chip. These output values can be used to design components to compensate for variances in PVT conditions or to control a variable delay component based on detected PVT conditions.

Abstract: In a delay circuit, a voltage detecting circuit is additionally provided. This voltage detecting circuit detects such a condition that a voltage appeared at a measuring terminal of the delay circuit is shifted from a predetermined voltage range for a time duration longer than, or equal to a preset time duration. Even when the measuring terminal of the delay circuit is short-circuited to the power supply voltage, or the ground potential, this delay circuit firmly inverts the output signal level based on delay time set by an internal delay circuit.

Abstract: An improved DDLL containing a majority filter counter circuit is disclosed. The majority filter counter circuit is located between the phase detector and the shift register of the DDLL. The majority filter counter circuit receives shifting commands from the phase detector and filters the shift commands from reaching the shift register until a predetermined number (e.g., 16) have been received from the phase detector before transmitting a shift command (either shift right or shift left) to the shift register. Once the shift register receives the shift command, the shift register directs the delay line to shift by one tap in either a shift right or a shift left direction depending upon the phase relationship between CLKIn and CLKOut. By waiting for e.g., 16 shift commands, the majority filter counter circuit ensures that a premature shift command is not delivered to the shift register in the case of a noise event.

Abstract: A delay system includes a first filter configured for receiving a selected input signal and a first mechanism for activating the first filter to produce a delayed output signal which is a function of a selected input signal. The delay system further includes a second filter configured for receiving a signal from said first filter to apply an additional delay to the signal received by said first filter, and a second mechanism for activating the second filter to produce a delayed signal which is a function of a signal received from the first filter. The delay system further comprises a divider system for tracking times from a clock reference. The delay system implements a method of delaying a received signal by sampling a selected signal with a predetermined clock signal and producing the selected signal at a time delayed to the extent of a comparison of a reduced frequency clock with a predetermined value.

Abstract: A fixed-length delay generation circuit comprises a first variable delay circuit (VDC), a clock generation circuit, a VDC group including one or more second VDCs, and a delay controller. The clock signal is input to a second VDC disposed at the initial stage in the VDC group. The delay controller outputs a signal by which delay amount in the first and second VDCs are made smaller when a difference between phases of a delay clock signal output from the VDC group and of the clock signal generated by the clock generation circuit is greater than a predetermined value. The delay controller outputs a signal by which delay amount in the first and second VDCs are made larger when the difference between phases of a delay clock signal output from the VDC group and of the clock signal generated by the clock generation circuit is smaller than such value.

Abstract: A two step variable length delay circuit, used digital elements being easy to design, and being capable of adjusting the phases of signals in a wide range and also with finer phases, and having low jitters and without considering the timing of switching of a signal, is provided. A first selection circuit selects m pieces of sequential outputs from plural taps of a coarse adjustment delay circuit and inputs the selected m pieces of sequential outputs to a first ring interpolator. The first ring interpolator amplifies the inputted m pieces of sequential outputs, further mixes waveforms of adjacent two inputs and also mixes waveforms of the first input and the last input, and outputs the amplified inputs and the mixed waveforms. Further, the outputs from the first ring interpolator are inputted to a second ring interpolator, and at the second ring interpolator, the same operation at the first ring interpolator is executed.

Abstract: An internal clock generation circuit according to the present invention comprises a phase comparator, a shift register, a filter, a monitor circuit, and a plurality of delay lines such as first and second delay lines. The first delay line has delay steps each larger than that of the second delay line. The first delay line is first used to generate a clock minimized in phase difference with respect to an external clock. The clock signal is inputted to the second delay line to perform fine adjustment to the phase difference.

Abstract: A delay system includes a first filter configured for receiving a selected input signal and a first mechanism for activating the first filter to produce a delayed output signal which is a function of a selected input signal. The delay system filter includes a second filter configured for receiving a signal from said first filter to apply an additional delay to the signal received by said first filter, and a second mechanism for activating the second filter to produce a delayed signal which is a function of a signal received from the first filter. The delay system further comprises a divider system for tracking times from a clock reference. The delay system implements a method of delaying a received signal by sampling a selected signal with a predetermined clock signal and producing the selected signal at a time delayed to the extent of a comparison of a reduced frequency clock with a predetermined value.

Abstract: The semiconductor device for setting a delay time, according to the present invention, comprises: a plurality of serially connected delay circuits into which a reference signal is input; a selector switch for selecting one of delay signals output from connection points between the delay circuits; and an internal selection signal generator for producing a selection signal for switching the selector switch to select one of the connection points.

Abstract: An output delay circuit has a counter which is reset at every input of an input signal of a first signal state thereto and counts input clocks while the input signal of a second signal state is inputted thereto; a comparator for comparing an accumulated number of the input clocks having been counted by the counter with a predetermined clock number set in advance; and a logic circuit for, when it is determined by the comparator that the accumulated number of the input clocks is less than the predetermined clock number, outputting an output signal having a signal state same as the first signal state of the input signal, while for, when it is determined by the comparator that the accumulated number of the input clocks is not less than the predetermined clock number, outputting an output signal having a signal state same as the second signal state of the input signal

Abstract: A circuit and method for performing a delay locked function for correcting phase differences between an input clock signal RCLK and an internally generated clock signal ICLK and for controlling the correcting step to maintain an accurate locking operation when a phase difference is below a threshold valve (the maximum time for which the internal step jitter may occur).

Abstract: A digital pulse delay system comprises: a counter incremented responsive to a succession of input pulses and generating a plurality of successive gating signals; a plurality of gates, each having a first input for receiving said input pulses and a second input the receiving a different one of said gating signals; a plurality of pulse delay circuits providing uniform time delays, each receiving an output pulse from a different one of said gates; and, an output circuit combining said uniformly delayed pulses from all of said delay circuits into a single output signal representing a uniformly delayed version of said succession of input pulses.

Abstract: A system for compensating for thermal drift of an output signal (OUT1) produced by a logic circuit in response to an input CLOCK signal after a temperature dependent delay includes a variable delay circuit, an oscillator and a digital phase lock controller. The delay circuit delays the OUT1signal to produce a compensated output signal (OUT2) with a variable delay controlled by input CONTROL data. The oscillator generates an output signal (OSC.sub.-- OUT) having a period also controlled by the input CONTROL data which is substantially proportional to the sum of the temperature dependent delay of the logic circuit and the delay of the variable delay circuit. The digital phase lock controller continually monitors the period of the OSC.sub.-- OUT signal and adjusts the CONTROL data so that the period of the OSC.sub.-- OUT signal remains substantially constant. This ensures that the delay between the CLOCK signal and OUT2 remains constant despite temperature dependent variations in the delay of the logic circuit.

Abstract: Circuitry for adjusting the phase of an incoming periodic signal, typically a clock signal, throughout the entire period of the periodic signal. Phase adjustment circuitry has high resolution and employs only the number of delay elements in a delay chain necessary to span at least the period of the incoming signal or at least half the period in the case of dual chains receiving complementary clocks. Phase adjustment circuitry includes a delay chain of having a plurality of taps, a boundary detector for indicating when a tap is at a phase boundary of the incoming periodic signal, and selection circuitry for selecting one of the taps from the delay chain based on the boundary detector output and the selection circuitry input such that the selected tap is the desired phase adjustment of the incoming periodic signal and that the delay of the incoming signal is adjustable across its phase boundaries.

Abstract: A programmable delay line. The programmable delay line includes a series of delay cells which are programmably connected in series. The programmable delay line includes a main delay chain and auxiliary delay chains. The main delay chain includes unit delay cells. The auxiliary delay chains include a unit delay cell, and a delay cell which has a delay that is between one and two time greater than the delay through a unit delay cell. The delay resolution of the programmable delay line is less than the delay of a unit delay cell. The programmable delay line further includes a reference oscillator and calibration circuitry. The reference oscillator includes a series of unit delay cells, and generates a reference signal having a period which is an integer multiple of the delay of a unit delay cell. Variations in the delay of a unit delay cell influence the period of the reference signal.

Abstract: A temperature balanced circuit is provided which is capable of, in case a CMOS.cndot.IC is utilized as a delay circuit, giving a constant delay time to an input signal to the delay circuit even if the frequency of the input signal is varied. A delay circuit 11 and a dummy circuit 11 having the same construction as that of the delay circuit are provided in a CMOS.cndot.IC. There are provided a counter counting first pulse signals CP1 supplied to the delay circuit during a fixed time interval and arithmetic unit finding a difference between a count value of this counter and a predetermined value, and the same number of second pulse signals as the difference value found by the arithmetic unit is supplied to the dummy circuit, thereby to define to a constant value both the number of the first pulses and the number of the second pulses supplied to the CMOS.cndot.IC within a unit time interval, which results in uniformity of an amount of heat generated in the CMOS.cndot.IC.

Abstract: An integrated circuit and method produce a first clock signal (CLOCK) from a reference clock (REFCLK) but at a different frequency. A variable delay line (32) produces the first clock signal by introducing a variable delay in the reference clock signal that is controlled by a programming signal generated in a counter (34). The programming signal is incremented by a second clock signal (UP) while transitions of a fixed delay clock signal lead transitions of the first clock signal. When the programming signal reaches the count of a rollover code (ROLLOVER), the programming signal is reset to a zero count to begin a new sequence. A calibration circuit (36, 38, 40, 42) determines the count of the programming signal needed to produce the rollover code when the variable delay is at least as great as one period of the reference clock signal.

Abstract: A digital delay circuit structure includes a digital calibration circuit and a digital delayed signal generator. The digital delay circuit is automatically calibrated when a calibrate signal goes active. Once the auto-calibration process is completed, the circuit switches back to a normal delay mode operation where the digital delay circuit remains until the next transition of the calibrate signal. A calibration control circuit generates a sample gate signal which initiates a feedback signal to the input terminal delay chain circuit that causes the delay chain output signal to oscillate. A calibration counter circuit counts the oscillations and couples this information to a count decoder circuit which in turn generates a signal to select one of a plurality of taps in the delay chain circuit. The digital delay circuit automatically compensates for delay variations caused by process extremes, temperature, and average voltage changes.

Abstract: A digital signal delay circuit includes a first pair of counters for setting a starting point of a digital output signal by counting an adjustably set number of clock pulses corresponding to an intended time delay from a starting point of a digital input signal. The circuit further includes a second pair of counters for setting an ending point of the digital output signal by counting an adjustably set number of clock pulses corresponding to an intended output pulse width from an ending point of the digital input signal. The state of the digital output signal is only determined by the state of the output signal of the last counter in the first pair of counters. The output signal from the last counter in the first pair of counters controls a count starting point of the first counter in the second pair of counters. The output signal from the second pair of counters controls an initializing point on which the state of the output signal from the last counter in the first pair of counters is inverted.

Abstract: A digital phase shifter phase shifts an input signal by a predetermined phase angle. A length of a cycle of the input signal is determined. Then an output signal is generated which is phase delayed from the input signal by a phase amount. The phase amount is approximately equal to the length of the cycle of the input signal multiplied by the predetermined phase angle.

Abstract: A precision delay circuit in an integrated circuit chip includes a transistor switching circuit in combination with a control circuit and a compensation circuit. The transistor switching circuit receives an input signal; and in response, the transistors switch on and off at an unpredictable speed to generate an output signal with a delay that has a large tolerance. The control circuit estimates the unpredictable speed at which the transistors switch and it generates control signals that identify the estimated speed. The compensation circuit includes a plurality of compensation components for the transistor switching circuit. This compensation circuit receives the control signals from the control circuit; and in response, it selectively couples the compensation components to the transistor switching circuit such that the combination of the transistors and the selectively coupled components generates the output signal with a precise delay that has an insignificant tolerance.

Abstract: Output pulses of a period which is an integral multiple of the fundamental period T are generated by coarse timing generating means 13 in correspondence with an integral part Di of timing set data read out of a memory 11, and the output pulses are distributed by distributing means 17 to set- and reset-side delay means 26s and 26r under the control of a waveform generation control circuit 18. Pieces of data Dr and Ds, which are obtained by adding a fractional part of the timing set data read out of the memory and set-side skew absorbing data and reset-side skew absorbing data, respectively, are provided as delay control signals to the set- and reset-side delay means 26s and 26r. The pulse distributed to the set-side delay means 26s is delayed by logical delay means 27s for any one of delay times 0, 1T and 2T in accordance with the integral value of the data Ds, and the thus delayed pulse is further delayed by fine delay means 28s in accordance with the fractional value of the data Ds.

Abstract: A data conversion circuit receives input data from external sourcing logic and performs a parallel-serial conversion. Likewise, a data conversion circuit performs a serial-parallel conversion and presents output data to external sinking logic. In the parallel-serial conversion (10), the input data is translated (12) and stored in a register (14). A multiplexer (16) rotates through the data to provide the serial output. In the serial-parallel conversion (70), the input data is sequenced into a multiplexer (74) to achieve the parallel data word. The parallel data word is stored in a register (76) before presenting it to external logic. Phase delay logic (22) sets the delay of a transfer data control signal that requests data be read or written.

Abstract: A circuit arrangement for delaying a useful signal which is stored in the form of time-discrete signal samples in a row of storage devices at time intervals which are determined by a clock signal and is read therefrom after expiration of a selectable delay time. Each storage device is connectable, via a respective input circuit to a useful signal input and, via a respective output circuit, to a useful signal output.

Abstract: A timing generator for generating delay timing signals which have delay time up to n-times of a reference clock period is capable of considerably reducing the hardware size. The timing generator is used in a semiconductor testing apparatus. The timing generator can contribute to reduce the total size and cost of the semiconductor testing apparatus. The timing generator includes a counter for counting the reference clock, an adder for adding the output of the counter to delay data, a series of registers for storing the output of the adder and shifting the output of the adder in synchronism with a delay trigger signal, a series of exclusive OR gates for comparing each output of the registers with the output of the counter and generating coincidence signals when the output from the register and the counter coincide with each other, and an OR gate for receiving the outputs of the exclusive OR gates and generating a signal which is combined of the outputs from the exclusive OR gates.