Abstract: A verification support system for supporting logic verification of a circuit including a transmitter clock domain and a receiver clock domain, the transmitter clock domain, the system includes a detector for receiving data to be transmitted from the transmitter clock domain, and for detecting a fluctuation of the received data due to any timing fluctuation responsive to the transmitter clock. The system includes an identification unit to identify whether or not any fluctuation of the data determined by the detector is propagated to the output of the combinational logic on the basis of propagation of the received data through at least one of logic gates of the receiver clock domain to combinational logic so as to determine any fluctuation of data that is to be inputted to the combinational logic.

Abstract: Mechanisms for performing sequential equivalence checking for asynchronous verification are provided. A first model of the integrated circuit design is provided that has additional logic in it to reflect the possible variance in behavior of the asynchronous crossings. A second model of the integrated circuit design is provided that does not have this asynchronous behavior logic but instead correlates to the simplest synchronous model that is usually used for non-asynchronous functional verification tasks. Sequential equivalence checking is performed to verify that the two models are input/output equivalent. In order to address non-uniform arrival times of bus strands, logic is provided for identifying bus strands that have transitioning bits, determining a representative delay for these strands, comparing the representative delays for all of the bus strands to determine the maximum delay for the entire bus, and applying this maximum delay to one of the models.

Abstract: A logic circuit latch including an input stage for receiving a logical input signal and a pair of differential amplifiers, each having an input operatively coupled to the input stage, and at least one of them having an output arranged to supply the logical output of the latch. Each of the differential amplifiers includes a transistor connected as a load, and an output of each of the differential amplifiers is coupled to bias the load transistor of the other differential amplifier. If the latch switches from the transparent state to the closed state while the logical input signal is transitioning between logical levels, the differential amplifiers drive up the logical output of the latch if the logical input signal transitions from a first to a second logical level, and drive down the logical output of the latch if the input signal transitions from the second to the first logical level.

Abstract: The even-number-stage pulse delay includes a ring delay line constituted of an even number of inverter circuits connected in a ring around which main edge and a reset edge circulate together. The even-number-stage pulse delay is provided with an operation monitoring section configured to detect whether or not the main and reset edges are circulating around the ring delay line.

Abstract: A semiconductor integrated circuit includes a sampling unit, a delay unit, a first operating unit and a second operating unit. The sampling unit samples an input signal supplied from an external circuit in synchronization with a clock signal, and outputs the sampled input signal as a first signal. The delay unit delays the first signal in synchronization with the clock signal, and outputs the delayed first signal as a second signal. The first operating unit operates whether a signal level of the input signal is sustained equal to or longer than a predetermined period based on the first and second signals, and outputs an output signal in synchronization with the clock signal when the signal level of the input signal is sustained equal to or longer than the predetermined period. A signal level of the output signal is sustained equal to or longer than the predetermined period. The second operating unit asynchronously controls the sampling unit based on the input signal and the output signal.

Abstract: A verification support system for supporting logic verification of a circuit including a transmitter clock domain and a receiver clock domain, the transmitter clock domain, the system includes a detector for receiving data to be transmitted from the transmitter clock domain, and for detecting a fluctuation of the received data due to any timing fluctuation responsive to the transmitter clock. The system includes an identification unit to identify whether or not any fluctuation of the data determined by the detector is propagated to the output of the combinational logic on the basis of propagation of the received data through at least one of logic gates of the receiver clock domain to combinational logic so as to determine any fluctuation of data that is to be inputted to the combinational logic.

Abstract: One aspect of the invention relates to a device including a first storage element and a first clock gating element, wherein a data input of the first storage element is coupled to an output of a combinatorial logic (CL) element, wherein the first storage element is clock-gated with the first clock gating element using a first clock enable signal to generate a clock signal for the first storage element, wherein the first clock enable signal is generated to suppress the clock signal in the first clock gating element when each of the at least one data input of the CL element is in a second quiescence inducing condition with respect to the clock signal at the same time as when each of the at least one control input of the CL element is in the first quiescence inducing condition.

Abstract: The present invention switches between a first clock signal (CLK0) and a second clock signal (CLK1). Each input signal is buffered by a corresponding tristate buffer (TBUF0, TBUF1). A multiplexer (MUX) receives the tristate buffer outputs and selects one clock signal in response to a multiplexer control signal (MUX_SEL). A control stage (CONTROL) received a clock selection signal (SEL) and provides multiplexer control signal (MUX_SEL). A change in multiplexer control signal (MUX_SEL) is triggered by a next edge of target clock (CLK1) following a delay. This prevents glitches in the output signal.

Abstract: A voltage regulator and method of voltage regulation for a power-on reset condition are described. Voltage regulation control signals responsive to the power-on reset condition are obtained. The control signals are generated with a first voltage to be associated with a second voltage to provide a first power-on-reset signal and a second power-on-reset signal which are opposite in state to one another. A portion of driver logic is tri-stated responsive to the control signals, and the second power-on-reset signal to at least impede supply to supply current leakage. Voltage is pulled up on a first output port and a second output port of the driver logic responsive to the first power-on-reset signal. A portion of a semiconductor substrate is electrically coupled to a higher one of a first voltage and a second voltage responsive to the pulling up to at least further impede the supply to supply current leakage.

Abstract: An arbiter module receives two or more closely occurring asynchronous requests and provides an output with a low metastability failure probability. The arbiter module includes a request resolving module that receives multiple asynchronous requests for providing a final output. The request resolving module includes one or more arbiter stages cascaded with each other and operatively coupled with logic units.

Abstract: An apparatus, system, and method are described for synchronously resetting logic circuits. A synchronous reset signal is coupled to at least one asynchronous reset input for synchronously resetting sequential logic. In one embodiment, reset logic generates a signal coupled to the at least one asynchronous reset input of the sequential logic to synchronously reset the sequential logic.

Abstract: A DFLOP circuit for an EAIC system includes a resolver. The resolver includes a signal transmission controller that is activated under the control of an internal clock signal to receive and transmit an input signal, and a precharge unit that is activated in response to the internal clock signal to precharge an output node of the signal transmission controller.

Abstract: A computer system apparatus for asynchronous data transfer between a source and sink without the use of an asynchronous control signal. includes metastability circuits, data change detection logic, a stability window delay counter, and a mux/register pair to allow for the holding of previous stable data during the transition. While the processing logic employed specifically applies to asynchronous logic, the logic can be extended to synchronous or untimed interfaces as well. Also disclosed is a programmable means to adjust the window delay.

Abstract: There are provided a buffer circuit buffers data between a synchronous circuit and an asynchronous circuit, and a control method therefor. There are also provided an interface circuit that controls data transfer between a synchronous memory circuit and the asynchronous circuit, and a control method therefor, which are used in the buffer circuit and the control method therefor. A data buffer circuit that is interposed between an image processing system and a main system includes a one-port RAM, a control signal generating section, an subsequent cycle address generating section, and a first selector. The first selector selectively outputs the present cycle address to an address of the one-port RAM when an access to the one-port RAM is a write access, and selectively outputs the subsequent cycle address to the address of the one-port RAM when the access to the one-port RAM is a read access.

Abstract: An arbiter circuit (100) can include a latch circuit (102) that latches competing input signals (MATCH1 and MATCH2) to generate signals on latch output (110-0 and 110-1). A filter section (104) can prevent metastable states of latch output signals from propagating through to output signals (BUSY2 and BUSY1). In addition, filter section (104) can generate output signals (BUSY2 and BUSY1) having one set of values when both inputs are inactive, and a second set of values when latch (102) is in the metastable state.

Abstract: A data synchronizer is provided for synchronizing data across two different clock domains in a manner that avoids additive jitter. The data synchronizer includes a synchronizer inputting a sampling clock and a data clock, and outputting an edge pulse. A synchronizer jitter lockout circuit inputs the edge pulse and the sampling clock and outputs a data sampling enable signal which never coincides with a data transition.

Abstract: A dual-edge-triggered clock-gated logic circuit includes; a delay clock generator operating to generate first, second, third and fourth delay clock signals in response to a clock signal, and a pulse generator operating to generate a pulse signal in response to the clock signal, the first, third, and fourth delay clock signals, and the control signal. The pulse generator operates to generate the pulse signal at the rising and falling edges of the clock signal.

Abstract: A system and method for buffering bidirectional digital input/output (I/O) lines. The system (e.g., data acquisition system) may comprise a device including circuitry for buffering bidirectional digital lines. A first integrated circuit (IC) of the device includes a first and a second bidirectional buffer coupled to a first bidirectional digital I/O line, and a second IC of the device includes a third bidirectional buffer. The first IC and the second IC each include a control unit to control the driving direction of the corresponding bidirectional buffers independently to change the direction of the data flow through the first bidirectional digital I/O line from the output direction to the input direction or vice versa. The driving direction of the bidirectional buffers are changed at different times in a particular sequence, and the order depends on whether the direction change is from the output direction to the input direction or vice versa.

Abstract: The invention relates to a method for controlling the reading-in of a data signal at an input of an electrical circuit to an input latch with the aid of a clock signal, with the data item, which is indicated by the data signal, being transferred to the input latch with a clock edge of the clock signal, with the clock edge of the clock signal being shifted in time as a function of a time delay between a signal edge of the input signal at the input and the clock edge, such that the time delay between the signal edge of the data signal and the clock edge is within a predetermined time window.

Abstract: A metastability filtering circuit comprising: a sampling circuit for sampling a first clock signal with a second clock signal to produce a sampled first clock signal, the first clock signal being synchronous to an interface between first and second systems; an edge detection circuit coupled to the sampling circuit for receiving the sampled first clock signal and for producing a rate adapted first clock signal; a delay circuit coupled to the edge detection circuit for receiving the rate adapted first clock signal and for producing first and second clock enable signals, the second clock enable signal being a delayed version of the first clock enable signal; and, a shift register clocked by the second clock signal and having first and second sequential registers enabled by the first and second clock enable signals, respectively, for receiving an input signal from the first system at the first register and providing a filtered output signal to the second system from the second register, wherein the filtered outpu

Abstract: A look-ahead decision feedback equalizing receiver includes an equalizing block for amplifying a high-frequency component of an external data signal fed thereto in response to a first and a second input signal, to provide a first and a second equalized external data signal; a clock synthesizer for outputting sampling clocks, a timing thereof being adjusted by receiving an external clock synchronized with the external data signal; an over-sampler for over-sampling the first and the second equalized external data signal in synchronization with the sampling clocks. A MUX block for multiplexing the outputs of the over-sampler in response to outputs of the MUX block, to thereby attain decision results; and a phase detector for deciding the timing of the sampling clock by analyzing the decision results.

Abstract: An arbiter circuit (100) can include a latch (106) that latches competing input signals (Req_A and Req_B) to generate latch output signals (latn1 and latn2). A filter section (108) can prevent metastable states of latch output signals (latn1 and latn2) from propagating through to output signals (Sel_A and Sel_B). If both input signals (Req_A and Req_B) are activated, a feedback circuit (110) can activate a feedback signal (fb) after a predetermined delay (?), provided both output signals (Sel_A and Sel_B) remain inactive.

Abstract: A method and apparatus for ensuring proper operation of a dynamic circuit is provided. A dynamic circuit instance has a plurality of outputs connected to a respective one of a plurality of leakage detector circuits. An output of each leakage detector circuit is connected with a respective one of a plurality of keeper circuits that reside at the dynamic circuit. Each of the plurality of keeper circuits has a unique size ratio with respect to a logic element size of the dynamic circuit.

Abstract: A clock synchronization circuit for synchronizing a first clock signal and a second clock signal for data transfer from a first function block, which is clocked by the first clock signal, to a second function block which is clocked by the second clock signal, where the clock synchronization circuit has a sampling unit for sampling the second clock signal using the first clock signal in order to generate samples and edge detection values of the sampled second clock signal, a logic circuit for outputting the generated edge detection values as a reconstructed clock signal and generating an Edge-too-Early signal and an Edge-too-Late signal; and a signal delay circuit, which delays the reconstructed second clock signal on the bases of the Edge-too-Early signal or the Edge-too-Late signal.

Abstract: A logic circuit includes an input for one or several input operands, an output for a result and an inverted result, a first circuit branch with a first logic assembly, which is coupled to the input and the output, to calculate the result, as well as a second circuit branch with a second logic assembly, which is coupled to the input and the output, to calculate the inverted result, wherein the first logic assembly and the second logic assembly have different run times for calculating the result and the inverted result, respectively. Further, a delay circuit and a compensation circuit, respectively, are provided in the first and/or second circuit branch to reduce a difference of the run times and the power consumptions, respectively, of the first and the second circuit branch.

Abstract: A circuit configuration for detecting an unwanted attack on an integrated circuit has a signal line to which a clock signal is applied and at least one line pair which is respectively used to code a bit. The signal line and the at least one line pair are connected between a first and a second circuit block in the integrated circuit. The signal line and the at least one line pair are connected to a detector circuit which changes the operating sequence in the integrated circuit on the basis of the signals on the signal line and on the at least one line pair. The detector circuit can be used to the same extent to test for production faults.

Abstract: The present invention relates to dynamic hardware logic of computer processors. In particular, it relates to a method and respective system for operating a dynamic logic circuit implementing some predetermined logic function with reduced charge sharing. In order to further reduce charge sharing it is proposed to provide a predetermined number of pre-engineered switching arrangements (24, 26, 28) implementing the same logic function with a different combinatorial distribution of input variables (A, B, C), wherein each arrangement is connected between said precharged node of higher potential and a lower potential.

Abstract: A static storage element distorts metastable feedback signals in an unbalanced feedback loop with the resulting metastable signals eroding and being suppressed as they circulate in the loop. The element exhibits a predetermined output state subsequent to suppression of the eroded signals.

Abstract: A method and apparatus for creating a modified dynamic flip-flop avoids the power waste created by prior art dynamic flip-flops by including a conditional pre-charge control circuit and method. When the modified dynamic flip-flop is in a holding mode, i.e., in the clock disable state, the modified dynamic flip-flop does not use power pre-charging and discharging the internal dynamic node every cycle.

Abstract: A method for distributing clocks to flip-flop circuits which constitute a logic circuit includes obtaining a timing slack of a first minimum delay time with respect to a minimum delay constraint time and a timing slack of a first maximum delay time with respect to a maximum delay constraint time for a clock in an input path to a flip-flop circuit, obtaining a timing slack of a second minimum delay time with respect to a minimum delay constraint time and a timing slack of a second maximum delay time with respect to a maximum delay constraint time for a clock in an output path from all the flip-flop circuits which receive the clocks from a clock terminal directly and obtaining a delay value which maximizes a minimum value of each of the first and second minimum delay time and maximum delay time of timing slacks.

Abstract: A synchronizer circuit which synchronizes an input clock signal to a sampling clock to generate a synchronized signal. In an embodiment, an adaptive module detects the occurrence of a positive edge in an input clock signal after a logic low corresponding to a prior negative edge is propagated to as a synchronized signal, and provides a logic high as an input to a sampling module. The sampling module propagates the signal led at the input as the synchronized signal. The adaptive module causing the input to remain at logic high at least until the synchronization module provides logic level as the synchronized signal. The negative edges in the input signal may also be processed similarly.

Abstract: A self-timed data transmission system includes a data bit group defined by at least two data bits to be transmitted from a corresponding plurality of transmitting storage elements. A corresponding plurality of data receiving storage elements receives the data transmitted from said transmitting storage elements. Encoding logic is used for encoding the transmitted data from the transmitting storage elements, wherein the encoded transmitted data is coupled to a plurality of data lines. The encoding logic is further configured so as to result in only one of the plurality of data lines being activated during a given data transmission cycle.

Abstract: A latch circuit capable of ensuring race-free staging for signals in dynamic logic circuits is disclosed. The latch circuit includes four separate logic gates. The first inputs of the first and second logic gates are connected to a first and second precharged internal nodes of the dynamic logic circuit, respectively. The second inputs of the first and second gates are connected to a first and second differential outputs of the dynamic logic circuit, respectively. The first inputs of the third and fourth gates are connected to an output of the first and second logic gates, respectively. The second input of the fourth gate is connected to an output of the third logic gate to provide a first output for the latch circuit. Similarly, the second input of the third logic gate is connected to the output of the fourth logic gate to provide a second output for the latch circuit.

Abstract: An asynchronous pipeline for high-speed applications uses simple transparent latches in its datapath and small latch controllers for each pipeline stage. The stages communicate with each other using request signals and acknowledgment signals. Each transition on the request signal indicates the arrival of a distinct new data item. Each stage comprises a data latch that is normally enabled to allow data to pass through, and a latch controller that enables and disables the data latch. The request signal and the data are inputs to the data latch. Once the stage has latched the data, a done signal is produced, which is sent to the latch controller, to the previous stage as an acknowledgment signal, and to the next stage as a request signal. The latch controller disables the latch upon receipt of the done signal, and re-enables the data latch upon receipt of the acknowledgment signal from the next stage. For correct operation, the request signal must arrive at the stage after the data inputs have stabilized.

Abstract: A method and apparatus to synchronize signals between different clock domains are described.

Abstract: A first circuit is to generate a data signal containing data. A second circuit is to utilize said data, where the first and second circuits are commonly clocked by a latch signal, further a circuit has a first level sensitive latch to latch the data signal from the first circuit upon receiving by way of a delay circuit the latch signal, and a second level sensitive latch to latch an output signal of the first level sensitive latch to the second circuit upon receiving the latch signal. Other embodiments are also described and claimed.

Abstract: A clock signal selector circuit is disclosed including a synchronizer circuit, two switching circuits, and a multiplexer. The synchronizer circuit synchronizes a first control signal to a first clock signal, thereby producing a second control signal. A first switching circuit produces the first clock signal at a first node when the second control signal is asserted. The multiplexer drives a second node with a signal at the first node when the second control signal is asserted. The second switching circuit forms an electrical connection between the first and second nodes when the second control signal is deasserted. The two switching circuits significantly reduce a probability of error at the second node due to metastability when the second control signal transitions from asserted to deasserted and the first clock signal is deselected. The second switching circuit provides electrical feedback from the second node to the first node.

Abstract: Methods and apparatus are provided for trapping metastability events to provide a metastable-free output signal. Values of an input signal compared to at least three different threshold voltages are latched at a predetermined point in time. A first intermediate signal is activate when all of the at least three corresponding latched values are in a first logic state. A second intermediate signal is activated when all of the at least three corresponding latched values are in second logic state. An output signal is placed in a first predetermined logic state in response to the second intermediate signal and is changed from the first predetermined logic state to a second predetermined logic state in response to the first intermediate signal.

Abstract: Methods and apparatus implementing techniques for prevention of metastability in a bistable circuit. The techniques include detecting a change in a data signal, sampling the detected change in reference to a sampling window of a clock signal input of a bistable circuit to determine if the detected change occurs within the sampling window, and selecting a stable data input to present to an input of the bistable circuit based on whether the detected change occurs within the sampling window. The sampling window represents a time period during which a change in the data signal can cause metastability in a bistable circuit.

Abstract: A method and circuit for transferring multiple bits of data across asynchronous clock domains is provided. The method includes detecting a change in a status bit of a data word being transferred from a source in a source clock domain to a destination register in a destination clock domain, the source clock and destination clock being asynchronous. The method includes sampling the detected change in reference to a change window where the change window is sized to encompass all bits of the data word. A stable input is selected for each bistable circuit of the destination register based on whether the detected change in the status bit is likely to produce metastability in the receiving register.

Abstract: Selector circuits and systems for single and multilevel selection within one clock cycle having a static switching factor on the output of a dynamic logic circuit. A logic device for single and multilevel selection having a dynamic logic circuit portion and a static logic circuit portion is implemented. In this way, an output logic state is maintained so long as the value of the Boolean operation being performed by the logic device does not change. Additionally, static logic elements may perform the inversions necessary to output both logic senses, mitigating the need to provide for dual-rail dynamic logic implementations. An asymmetric clock permits a concomitant decrease in the size of the precharge transistors thus ameliorating the area required by the logic element and obviating a need for keeper device.

Abstract: An apparatus comprising a first arbiter cell, a second arbiter cell and a selection device. The first arbiter cell may be configured to lock if one or more requests are not resolved within a first predetermined time period. The second arbiter cell may be configured to dominate if the first arbiter cell enters a metastable state. The selection device may be configured to provide arbitration between the first and second arbiter cells within a second predetermined time period.

Abstract: A method and circuit for transferring multiple bits of data across asynchronous clock domains is provided. The method includes detecting a change in a status bit of a data word being transferred from a source in a source clock domain to a destination register in a destination clock domain, the source clock and destination clock being asynchronous. The method includes sampling the detected change in reference to a change window where the change window is sized to encompass all bits of the data word. A stable input is selected for each bistable circuit of the destination register based on whether the detected change in the status bit is likely to produce metastability in the receiving register.

Abstract: A latch is provided which includes: a transparent catch latch having a data input, a data output and a control node arranged to receive a catch signal; a transparent pass latch having a data input connected to the data output of the transparent catch latch at an internal storage node, a data output, and a control node arranged to receive a pass signal; and logic circuitry having an enable input and a clock input connected to provide a gated clock signal to provide one of said catch signal and said pass signal. In another aspect an integrated circuit is provided with input and output guard flops, each including a transparent catch latch and a transparent pass latch, and further including a logic gate with an enable input and a clock input connected to provide a gated clock signal to at least one of the transparent pass latch of the input guard-flop and transparent catch latch of the output guard flop.

Abstract: An apparatus comprising a margin logic circuit, one or more discriminator circuits and a sense circuit. The margin logic circuit may be configured to receive a plurality of requests and present one or more control signals. The one or more discriminators may be configured to (i) present one or more leading access signals and (ii) receive the one or more control signals and the plurality of requests. The sense circuit may be configured to receive the one or more leading access signals and the plurality of requests and present grant access signal. The sense circuit may be configured to reduce the effects of metastable conditions.

Abstract: A clock gating circuit reduces the power dissipation in a digital circuit including at least one functional block by gating the clock signal at an input to a clock tree feeding the functional block. The clock gating circuit includes a logic gate that receives a clock signal and a clock disable signal generated by the functional block, and gates the clock signal at the input to the clock tree feeding the functional block. Further, a global signal generator is provided to transmit a global signal to each of the functional blocks to prevent the generation of clock disable signals, when necessary, such as during testing of chips.

Abstract: A synchronous clocking method and apparatus is disclosed for clocking a plurality of processing units. Each of the plurality of processing units is connected to at least another one using an interblock synchronization signal. Upon receipt of the interblock synchronization signal, data is provided between at least two processing units.

Abstract: A method and apparatus for testing ADC circuitry. The method and apparatus detects infrequently occurring errors by providing a series of waveforms to the ADC that have different amplitude, frequency, or voltage offset from one another. The outputs of the ADC for the waveforms are then analyzed for timing related errors.

Abstract: A flip flop (30) comprising a master stage (34) comprising a first plurality of transistors (54, 56), wherein each of the first plurality of transistors comprises a selective conductive path between a source and drain. The flip flop also comprises a slave stage (42) comprising a second plurality of transistors (60, 62, 64, 66), wherein each of the second plurality of transistors comprises a selective conductive path between a source and drain. For the flip flop, in a low power mode the flip flop is operable to receive a first voltage (VDD) coupled to the selective conductive path for each of the first plurality of transistors. Also in the low power mode, the flip flop is operable to receive a second voltage (VDDL) coupled to the selective conductive path for each of the second plurality of transistors. Lastly, the second voltage is greater than the first voltage in the low power mode.

Abstract: Method and apparatus are provided for trapping metastability events to provide a metastable-free output signal. At least three successive values of an input signal are latched successively over a predetermined period which is less than half of a fundamental period of the input signal to provide at least three corresponding latched values. First and second intermediate signals are activated when outputs of all of the at least three corresponding latched values are in respective first and second logic states. An output signal is placed in a first predetermined logic state in response to the second intermediate signal and is changed from the first predetermined logic state to a second predetermined logic state in response to the first intermediate signal.