Abstract: A recording medium, method and apparatus for managing data are discussed. According to an embodiment, the present invention provides a method of reproducing main data and additional data. The method includes receiving the additional data associated with the main data, the additional data being divided into a plurality of segment units; and reproducing the additional data in a synchronous manner with the main data using time information if indication information indicates a presence of the time information. The time information indicates a presentation time of the additional data with respect to the main data. The main data and the additional data are reproduced according to management data, the management data including link information for linking the main data and the additional data.

Abstract: In an embodiment, a system includes a memory controller, processors and corresponding caches. The system may include sources of uncertainty that prevent the precise scheduling of data forwarding for a load operation that misses in the processor caches. The memory controller may provide an early response that indicates that data should be provided in a subsequent clock cycle. An interface unit between the memory controller and the caches/processors may predict a delay from a currently-received early response to the corresponding data, and may speculatively prepare to forward the data assuming that it will be available as predicted. The interface unit may monitor the delays between the early response and the forwarding of the data, or at least the portion of the delay that may vary. Based on the measured delays, the interface unit may modify the subsequently predicted delays.

Abstract: The invention provides a system and a method for synchronizing cable modems, the method includes the stages of: (i) generating, at a media access control entity, synchronization messages; and (ii) updating the synchronization messages to provide updated synchronization messages, whereas the updating is responsive to delays introduced at least during a stage of multiplexing the updated synchronization messages and additional content. The invention provides a system and a method of encrypting a data stream, the method includes the stages of: (i) receiving, at a multiplexing entity, at least one data stream destined to at least one cable modem; (ii) receiving, at the multiplexing entity, at least one encryption key generated by a cable modem termination system, whereas each encryption key is associated with at least one cable modem; and (iii) encrypting at least one data stream with at least one encryption key associated with the at least one cable modem.

Abstract: A semiconductor device performs operation in synchronization with a certain clock signal. The semiconductor device includes a control unit for outputting operation control information, a storage unit for storing data, a first operation unit for performing operation on first data in accordance with first operation control information, and a second operation unit for performing operation on second data in accordance with second operation control information. The first operation unit includes a plurality of operation circuits. The number of logic gates constituting the entire operation circuits is m. The second operation unit includes at least one operation circuit in which the number of logic gates is n (n>m). Each of the total delay of the operation unit or the total delay of the operation unit is set at a value equal to or less than the cycle of the clock signal.

Abstract: A semiconductor memory device includes a mode register set for establishing information on a delay time, a delay time calculator for calculating an I/O path delay time of a data clock on a basis of a unit period of a system clock, and a delay locked clock generator for reflecting in the data clock a value of subtracting an output of the delay time calculator from the information established in the mode register set.

Abstract: Disclosed herein are solutions for addressing the problem of skew of data within a byte lane by factors caused external to the integrated circuit or module providing the data. To compensate for such skew, an on-chip delay is added to the data out paths of those bits in the byte lane with otherwise would arrive early to their destinations. Such on-chip delay is provided delay circuits preferably positioned directly before the output buffers/bond pads of the integrated circuit or module. By intentionally delaying some of the outputs from the integrated circuit or module, external skew is compensated for so that all data in the byte lane arrives at the destination at substantially the same time. In a preferred embodiment, the delay circuits are programmable to allow the integrated circuit or module to be freely tailored to environments having different skew considerations, such as different styles of connectors.

Abstract: A method is provided in one example embodiment and includes providing a time protocol assistant associated with a time-synchronized domain (TSD). The TSD includes a set of nodes that are synchronized to a same time source. The TSD has defined egress and ingress edge points where bidirectional measurements can be made and the egress and ingress edge points are coupled to the time protocol assistant. The method also includes synchronizing one or more packets flowing through a network that includes the TSD through the same time source. In more specific embodiments, the nodes are synchronized to the same time source via the network and the same time source is a grandmaster clock that synchronizes one or more transparent clocks. In yet other embodiments, the transparent clocks manipulate precision time protocol (PTP) packets sent by the grandmaster clock.

Abstract: An integrated circuit input/output interface with empirically determined delay matching is disclosed. In one embodiment, the integrated circuit input/output interface uses empirical information of signal traces coupled to the integrated circuit to adjust a transmit/receive clock of each pin of the interface so as to compensate for delay mismatches caused by differences in signal trace lengths. In one embodiment, values representative of the empirical information are stored for use by the integrated circuit to generate trace-specific signals so as to compensate for delay differences that are at least partially caused by unmatched signal trace lengths. The empirical information, in one embodiment, includes signal flight time of each signal trace, which can be pre-measured or pre-calculated from known signal trace lengths. The empirical information, in another embodiment, includes trace-specific phase offset values calculated from pre-calculated or pre-measured signal flight times or signal trace lengths.

Abstract: A system that includes a clock tree and multiple variable delay components. The system is characterized by including a first set of fuses indicative of identities of variable delay components that belong to a first set of variable delay components, a second set of fuses indicative of delay values of the variable delay components that belong to the first set of variable delay components, and a second set of variable delay components that are set to at least one default delay value. A method for reducing clock skews, the method includes providing a clock tree that includes a set of variable delay components. The method is characterized by selecting a first set of variable delay components in view of timing violations occurring due clock skews, setting delay values of variable delay components that form a first set of variable delay components by programming fuses, and setting delay values of variable delay components that form a second set of variable delay components to at least one default value.

Abstract: Various embodiments of a control circuit for controlling an address output timing of a semiconductor device are disclosed. In one exemplary embodiment, the circuit may include: a timing signal generation unit configured to decode operation specification information of a semiconductor device and generate a timing signal by delaying a read command or a write command based on a decoding result of the operation specification information; a storage control signal generation unit configured to generate a storage control signal in response to the read command or the write command; an output control signal generation unit configured to generate an output control signal in response to the timing signal; and a storage/output unit configured to store an address in response to the storage control signal, and output the stored address as a timing-adjusted address in response to the output control signal.

Abstract: A DDR memory controller is described wherein a core domain capture clock is created by programmably delaying the core clock of the memory controller. The delay of this capture clock is typically calibrated during a power on the initialization sequence in concert with a DDR memory in a system environment, thereby minimizing the effects of system delays and increasing both device and system yield. An additional embodiment also includes programmably delaying the incoming dqs signal. To compensate for voltage and temperature variations over time during normal operation, a runtime dynamic calibration mechanism and procedure is also provided.

Abstract: One embodiment of the present invention provides a system that augments a circuit design with a mechanism for detecting and correcting timing errors. This system first partitions the circuit into a set of blocks that are clocked by an independent clock source, and integrates an error signal propagation circuit between the set of blocks. For a respective block, the system determines a set of internal registers that are to be implemented as double data sampling registers, and replaces the determined set of internal registers with double data sampling registers, wherein a given double data sampling register is configured to generate an error signal when it detects a timing error. Then, the system integrates a two-phase error correction circuit into the respective block, wherein when notified of a timing error by a double data sampling register, the two-phase error correction circuit is configured to stall registers in the respective block.

Abstract: A delay controller includes an acquiring section that acquires synchronization timings indicating timings when a plurality of controllers, which control via a line a plurality of transmitters that transmit data, synchronously control the transmitters, a determining section that determines a reference synchronization timing serving as a reference for synchronization between the controllers, on the basis of the synchronization timings acquired by the acquiring section, and a synchronization information transmitting section that transmits synchronization information to the controllers, the synchronization information being used when the controllers receive data from each of the transmitters at the reference synchronization timing determined by the determining section.

Abstract: An apparatus and a method for synchronization in a channel card in a mobile communication system are provided. A channel card for synchronizing a Digital Signal Processing (DSP) modem and a system clock in a mobile communication system includes the DSP modem for sending a reference signal, informing of a start of a transmission, to a Field-Programmable Gate Array (FPGA) modem, and the FPGA modem for comparing a reception time of the reference signal with a Global Positioning System (GPS) timer, for recording a GPS timer value corresponding to a start point based on the comparison, and for sending to the DSP modem the recorded GPS timer value corresponding to the start point at a preset GPS timer reference time.

Abstract: The present disclosure provides a spread spectrum clock generation system having a digitally controlled phase locked loop (PLL) and a digital frequency profile generator to create a near optimal frequency modulation profile for the purpose of achieving spectral flatness in the output frequency modulated clock. The circuit is combined with a multilevel error feedback noise shaping structure that provides the required noise transfer function for the quantization noise but maintains a unity gain all pass signal transfer function. This arrangement offers minimal degradation of the in-band signal-to-noise ratio (SNR) at the cost of higher out-of-band noise.

Abstract: An analog-to-digital-converter (ADC) timing engine may simplify the use of Delta-Sigma ADCs by compensating for the group-delay of the ADC. The compensation may render the group-delay corresponding to the ADC largely transparent to the end-user of the ADC. Therefore, multiple ADCs may be easily synchronized with each other, even if they have different group-delays, and they may further be synchronized with other types of ADCs that do not have group-delays. The data from the ADCs may also be synchronized with external events. The ADC timing engine (ATE) may be programmed with a number of parameters to set proper delays taking into account not only the group-delays corresponding to the various ADC, but delays stemming from a variety of other sources. Multiple ATEs may be synchronized with each other to ensure that data acquisition by the participating ADCs is started and/or stopped at the same point in time.

Abstract: A system and method for digital communication wherein a host provides a host clock and a clockless device transmits to the host a bit stream synchronized according to the clock at a data rate that is an integer multiple of the clock rate. A training mechanism using training data detects time skew between host clock and bit stream, and a digital skew compensation mechanism compensates, substantially in real time, for the skew and for variations in the skew that may occur with the passage of time, in accordance with a vote among at least three samples of a bit of the bit stream, subsequent sampling being retarded or advanced if, respectively, an early or late sample is in disagreement with the vote. Preferably, the compensation value is selected from at least four possible compensation values, and can be stored in a memory to hasten subsequent restarts of the system.

Abstract: A memory control circuit has a write leveling function and controls read/write operations by supplying a clock signal to a plurality of memories through a clock signal line which is wired to the plurality of memories through daisy chain connection. For each of the plurality of memories, a first variable delay unit delays, in a write operation, a data strobe signal output to the memory by a first delay time that is set by utilizing the write leveling function and a second variable delay unit delays, in a read operation, a data signal input from the memory by a second delay time that is set based on the first delay time.

Abstract: Apparatus for synchronizing signals. For memory devices, such as SDRAMs, implementing a synchronization device to synchronize one signal, such as an external clock signal with a second signal, such as a data signal, tuning elements may be provided at various points in the signal path of the synchronization device. The tuning elements are designed to be identical, such that a single design may be used to a signal mismatch that is produced in either direction, using a single design. The tuning elements may be implemented to provide uniformity in the access time through a range of conditions, such as drain voltages and temperatures.

Abstract: A data processing apparatus and method for handling interrupts is provided, the apparatus having an interrupt controller operable to receive interrupts generated by a number of interrupt sources, and to determine based on predetermined criteria whether to output an interrupt request signal. A processing unit is provided which is operable upon receipt of the interrupt request signal to perform an interrupt service routine for a selected one of the received interrupts in order to generate an interrupt response for the corresponding interrupt source. Timer logic is also provided which is operable upon receipt of an interrupt generated by an associated interrupt source to produce a timing indication.

Abstract: An apparatus includes a delay line having multiple delay cells coupled in series. The delay line is configured to receive an input signal and to propagate the input signal through the delay cells. The apparatus also includes multiple sampling circuits configured to sample the input signal at different taps in the delay line and to output sampled values. The delay line has (i) a finer resolution closer to a target tap and (ii) a coarser resolution farther away from the target tap on each side of the target tap. For example, taps nearer the target tap can be closer to each other in order to support the finer resolution, and taps farther from the target tap can be farther apart from each other in order to support the coarser resolution. The apparatus can further include an encoder configured to encode the sampled values in order to generate an encoded value.

Abstract: A data processing circuitry for processing data is disclosed.

Abstract: An interface alignment pattern for de-skewing data bits received on an elastic interface is disclosed. The interface alignment pattern is “busy” in that it has a high number of logic state transitions. The busy interface alignment pattern can be used for scrambling and unscrambling operational data. The interface alignment pattern has a unique timing sequence for determining the location of a data bit's first data beat.

Abstract: A circuit comprising a single-wire serial interface (SWSI), a delay module coupled to the SWSI and operable to introduce a delay during a data transmission, the delay being dependent on a local clock (LC) associated with the circuit, wherein the delay enables the circuit to synchronize the data transmission with a device coupled to the SWSI based on the LC.

Abstract: A time synchronization method and system for a multi-core system are provided.

Abstract: One inventive aspect relates to a digital sub-circuit suitable for embedding in an at least partially digital circuit for minimizing the influence of another digital sub-circuit on the at least partially digital circuit, the other digital sub-circuit being part of the at least partially digital circuit. The influence of the other digital sub-circuit may, for example, be the introduction of ground bounce by switching of the other digital sub-circuit. Another inventive aspect relates to an at least partially digital circuit comprising such a digital sub-circuit for minimizing the influence of another digital sub-circuit to the at least partially digital circuit and to a method for reducing the influence of another digital sub-circuit to an at least partially digital circuit.

Abstract: A method of synchronizing cyclemasters over a distributed bridge is disclosed. The method comprises: a local portal sending a synchronization signal to a peer portal through a bridge fabric upon occurrence of a cycle synchronization event on the local portal; the peer portal sampling its local cycle timer to obtain a sample value when the peer portal receives the synchronization signal; a bridge manager at an upstream portal communicating the sample value to a bridge manager at an alpha portal; the bridge manager at the alpha portal using the sampled time value to compensate for delays through a bridge fabric, calculate the correction to be applied to a cycle timer associated with the alpha portal, and correct the cycle timer.

Abstract: The invention concerns a method for controlling access to encrypted data (CT) by control words (CW), said control words being received by a security module in control messages (ECM) and returned to a unit operating on the encrypted data. Said control messages (ECM) contain at least one first control word (CW1) and a second control word (CW2), said control words each allowing access to the encrypted data (CT) during a predetermined period called cryptoperiod (CP). Said method includes the following steps: sending said encrypted data to at least one operating unit; and sending control messages (ECM) to said control unit, such a control message (ECM) containing at least two specific control words (CW1, CW2) being sent to the operating unit after sending the data encrypted by said first control word (CW1) and before sending the data encrypted by said second control word (CW2).

Abstract: Receiver architectures and bias circuits for a data processor are provided. A receiver architecture includes a linear receiver having a first input node for a data (DQ) signal, a second input node for a reference voltage, and output nodes for a differential output signal. The linear receiver compares the DQ signal to the reference voltage, and generates the differential output signal in response to the comparison. A sense amplifier is coupled to the linear receiver. The sense amplifier has input nodes connected to the output nodes of the linear receiver, and an output node for a binary output signal having voltage characteristics compatible with the processor. The sense amplifier transforms the differential output signal into the binary output signal. The receiver architecture also includes a programming architecture coupled to the linear receiver to set operating characteristics of the linear receiver.

Abstract: In a data bus with asynchronous data transmission via a clock and a data line, the transmitted data are ascertained by sampling with a multiple of the data rate of the data bus. Sampling is done in this case with a clock which is not synchronous with the asynchronous clock of the data bus. For avoiding interferences which develop due to the unnecessary operation of the interface circuit with a high frequency clock when no data are currently transmitted, a control circuit is provided for detecting the beginning and the end of a data transmission. Only at the beginning of a data transmission, the interface circuit will be supplied with the required clock. After the end of the data transmission, the clock for the interface circuit will be switched off again. The control circuit is preferably designed as a state machine which reacts, without the need for clock signals, to the states on the data and clock line of the data bus.

Abstract: Routing circuitry for automatically routing either a first set of USB signals derived from an Ethernet local area network (LAN) at an Ethernet connector or a second set of USB signals derived from a USB host at a USB connector to an output connector which can interface with a data processing device.

Abstract: A method, system, and computer program product are provided for achieving timing closure in a clocked logic circuit. For each local clock buffer in a set of local clock buffers, a logic synthesis tool determines a clock control signal input from a set of clock control signal inputs that will drive a clock control signal to the local clock buffer at a target frequency such that a first timing constraint may be met. The operation performed by the logic synthesis tool forms a determined clock control signal input. Responsive to the logic synthesis tool determining the determined clock control signal input, the logic synthesis tool couples the local clock buffer to the determined clock control signal input that drives the clock control signal to the local clock buffer at the target frequency to achieve timing closure in the clocked logic circuit.

Abstract: A DDR memory controller is described wherein a core domain capture clock is created by programmably delaying the core clock of the memory controller. The delay of this capture clock is calibrated during a power on the initialization sequence in concert with a DDR memory in a system environment, thereby minimizing the effects of system delays and increasing both device and system yield. An additional embodiment also includes programmably delaying the incoming dqs signal.

Abstract: A processing system includes a bus and a processor whose core is constrained to have one or more core clock signal frequencies no lower than a predetermined multiple of the lowest of one or more bus clock signal frequencies. In a power-save mode, the processor is able to generate one or more core clock signals at frequencies such that the lowest core clock signal frequency is lower than the predetermined multiple of the lowest of the one or more bus clock signal frequencies in performance mode. The processor is able to achieve this by generating the one or more bus clock signals so that the lowest of the bus clock signal frequencies in power-save mode is lower than the lowest of the bus clock signal frequencies in performance mode.

Abstract: According to the present invention, a phase shift of data received by an external device controller is delayed and corrected, and a control signal used for the data load control on the external device controller side is delayed period-by-period. Further, the phase shift is adjusted and then the control signal is adjusted. The adjustment can beneficially be performed very quickly. Moreover, the present invention is also beneficial for preventing a failure to load data.

Abstract: A variable clock control information generator receives graphics engine activity data relating to the operating level of a graphics engine, and memory activity data relating to an activity level of memory. In response, the variable clock control information generator produces graphics engine clock control information and memory clock control information with respect to each other, such that a relative difference between the graphics engine activity data and the memory activity data is within balance threshold data. Accordingly, the variable clock control information generator adapts to the varying levels of graphics engine activity and memory activity and adjusts the frequency of the graphics engine clock signal and the frequency of the memory clock signal to achieve a balanced relative activity level.

Abstract: A clock skew controller for adjusting a skew between a first clock, which is input to a first clock mesh, and a second clock mesh input to a second clock mesh, includes a pulse generator adapted to output a pulse signal corresponding to a delay time between a first output clock output from the first clock mesh and a second output clock output from the second clock mesh, a pulse width detector adapted to generate a digital signal corresponding to a pulse width of the pulse signal, and a clock delay adjuster adapted to delay one of the first and second clocks by a time corresponding to the digital signal.

Abstract: A speculative transfer mechanism transfers a source synchronous read request from a first clock domain to a second clock domain. The address portion having address information is transferred to the second clock domain in response to detecting a source synchronous address strobe latching signal. A pointer is generated in response to detecting the address strobe latching signal and passed into the second clock domain. In one embodiment, a pointer is retimed to be stable for a timing window for which a crossover of the address portion may be performed in the second clock domain. Request logic in the second clock domain generates a read command based on the address portion and the pointer.

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: A semiconductor device includes: an LCD controller configured to output a plurality of image signals in parallel; a plurality of signal lines respectively corresponding to the plurality of image signals to be outputted in parallel; a plurality of terminal portions respectively connected to the plurality of signal lines; and delay circuits configured to delay a plurality of image signals, which are divided into a plurality of groups to the extent that the sum of each value of a current flowing through each signal line does not exceed a predetermined current value and outputted from a plurality of terminal portions, by a predetermined delay time from each other among the plurality of groups.

Abstract: A latency signal generator and method thereof are provided. The example latency signal generator may include a sampling clock signal generator adjusting a plurality of initial sampling clock signals based on a received clock signal to generate a plurality of adjusted sampling clock signals, a latch enable signal supply unit adjusting a plurality of initial latch enable signals based on a given one of the plurality of initial sampling clock signals to generate a plurality of adjusted latch enable signals and a latch unit including a plurality of latency latches, each of the plurality of latency latches selectively latching a given internal read command based on one of the plurality of adjusted sampling clock signals and one of the plurality of adjusted latch enable signals.

Abstract: A semiconductor device includes an analog circuit with a first delay variation in response to a variation in a power supply potential, and a digital circuit with a second delay variation smaller than the first delay variation. The analog circuit is connected to a first power supply potential. The digital circuit includes a detecting circuit detecting a first delay caused by a first circuit connected to the first power supply potential, and a second circuit generating a control signal to control the analog circuit, the second circuit being connected to a second power supply potential whose potential variation is smaller than the first power supply potential. A second delay caused by the second circuit is controlled in correlation to the first delay.

Abstract: Synchronous circuitry for processing digital data in which the data are filtered to compensate for expected jitter in time-average frequency clock signals. Time-average frequency synthesis circuitry generates internal clock signals of a desired frequency, for example as based on a recovered clock signal from an input data stream, in a manner in which not all periods of the clock signal are of uniform duration. A jitter precorrection filter is inserted into the data path to apply a variable delay to pre-correct for distortion caused by jitter in the clock cycle. In embodiments of the invention using a flying-adder architecture to generate the clock signal, coefficients of the digital filer realizing the jitter precorrection filter are calculated according to the currently-selected oscillator phase and according to a fractional portion of a digital frequency control word.

Abstract: A method and controller are provided for the compensation of time delays in remote feedback signals in power system control. The method includes converting the time delay into a phase shift and calculating four compensation angles from the phase shift. The optimal compensation angle is determined and applied to the remote feedback signals. A technique of equipping a controller with a global clock is also disclosed.

Abstract: A phase amount added to a clock signal or a plurality of data signals for adjusting a phase relationship therebetween in a reception apparatus is changed, and, a result of the phase adjusting operation is stored when the phase amount added to the clock signal or the plurality of data signals is changed.

Abstract: An apparatus and method is disclosed to compensate for skew and asymmetry of a locally processed system clock used to synchronize an output signal, e.g., a data signal or a timing signal, from a logic circuit, for example a memory device. A first phase detector, array of delay lock loop (DLL) delay elements and accompanying circuitry are disclosed to phase-lock the rising edge of the output signal with the rising edge of the system clock XCLK signal. Additionally, a comparator circuit, a register delay, an array of DLL delay elements and accompanying circuitry are disclosed to add or subtract delay from the falling edge of the DQ signal in order to produce a symmetrical output of the DQ signal.

Abstract: A method for delivering data to first and second processes comprising: identifying a first process communicatively connected to a first data access port; identifying a second process communicatively connected to a second data access port; identifying a data-throughput requirement of the first process via the first data access port; identifying a current data-throughput being delivered to the first process via the first data access port; identifying a data-throughput difference representing a difference between the data-throughput requirement of the first process and the current data-throughput being delivered to the first process; and delivering data to the first process via the first data access port at a rate that meets the data-throughput requirement at an expense, if necessary, of a data rate delivered to the second process via the second data access port.

Abstract: A memory interface circuit is connectable to a DDR-SDRAM which outputs read data in synchronization with a data strobe signal together with the data strobe signal. A clock generator generates internal clock signals and memory clock signals supplied to the DDR-SDRAM. The memory interface circuit determines a delay of arrival of the data strobe signal relative to the corresponding internal clock signal by using a data strobe signal inputted in a read cycle with respect to the DDR-SDRAM, samples the arrived read data, based on a signal obtained by shifting the phase of the arrived data strobe signal, and synchronizes the sampled read data to the corresponding internal clock signal on the basis of the result of determination of the arrival delay.

Abstract: Apparatus for synchronizing signals. For memory devices, such as SDRAMs, implementing a synchronization device to synchronize one signal, such as an external clock signal with a second signal, such as a data signal, tuning elements may be provided at various points in the signal path of the synchronization device. The tuning elements are designed to be identical, such that a single design may be used to a signal mismatch that is produced in either direction, using a single design. The tuning elements may be implemented to provide uniformity in the access time through a range of conditions, such as drain voltages and temperatures.

Abstract: Two data processing units having the same function, one of which is used for a master and the other for comparison, are provided, control of a circuit unit is performed by the master, the master data processing unit and the circuit unit are operated in synchronization with a first clock signal, the second data processing unit is operated in synchronization with a second clock signal having the same cycle and different phase from the first clock signal, and processing results of both the data processing units are compared in a comparison circuit. Flip flops are disposed on a signal path from the circuit unit to the comparison data processing unit and on a signal path from the master data processing unit to the comparator, and both the first and second clock signals are used for latch clocks of the flip flops in accordance with input signals thereof.