144 results about "Clock domain crossing" patented technology

An apparatus, for use in a semiconductor device, for providing a domain crossing operation. The apparatus includes a domain crossing sensing block, in response to an operation mode signal, first and second delay locked loop (DLL) clock signals and a CAS latency, generates a plurality of selection signals. An output enable signal generator, in response to the plurality of selection signals, generates a plurality of output enable signals. A data control block, in response to the output enable signals and the CAS latency, controls a data output operation in the semiconductor device. Each of a plurality of data align block, in response to the selection signals, the first and second DLL clock signals and an address signal, aligns data corresponding to the address signal in the data output operation.

A method of snap-shot data training to determine the optimum timing of the DQS enable signal in a single read operation is provided. This is accomplished by first writing a Gray code count sequence into the memory and then reading it back in a single burst. The controller samples the read burst at a fixed interval from the time the command was issued to determine the loop-around delay. A simple truth table lookup determines the optimum DQS enable timing for normal reads. Advantageously, during normal read operations, the first positive edge of the enabled DQS signal is used to sample a counter that is enabled every time a command is issued. If the counter sample changes, indicating timing drift has occurred, the DQS enable signal can be adjusted to compensate for the drift and maintain a position centered in the DQS preamble. This technique can also be applied to a system that uses the iterative approach to determining DQS enable timing on power up. Another embodiment of the invention is a simple, low latency clock domain crossing circuit based on the DQS latched sample of the counter.

The invention provides for the hierarchical verification of clock domain crossings. In various implementations of the invention, a device design is partitioned into blocks. Subsequently, a block level clock domain crossing verification process is performed on selected ones of the blocks. Verification interface files are generated by the block level clock domain crossing process. After which, a top level clock domain crossing verification process is performed over the entire design. In various implementations, the top level clock domain crossing verification process utilizes the verification interface files to verify clock domain crossing signals between blocks. Additionally, in some implementations, blocks not verified during block level verification are verified during top level verification. With some implementations of the invention, the device design is partitioned based input from a user of the implementation. Furthermore, in various implementations, the specific clock domain crossing verification checks employed during block level verification and top level verification are specified by a user of the implementation.

A design tool inserts randomized delays into synchronizers for signals crossing from one clock domain to another. Rather than having a wide range of random delays to select from, each synchronizer's randomized delay is selected from only two possibilities. An added delay of either zero or one clock period of the new domain's clock is added as the randomized delay. The randomized delay causes the re-synchronized domain-crossing signal to become available either in the expected cycle or in the cycle following the expected cycle. Logic hazards caused by the domain-crossing signal can be detected and the possible results simulated. The synchronizer can be a series of two flip-flops, with the random delay added to the first flip-flop. Randomized delays of either one or none added periods of the clock can also be added to multi-cycle signals within one clock domain that have two or more clock cycles to propagate.

Provided is a write circuit of a DDR SDRAM, in which a clock domain crossing is generated from a writing driver during a data write operation and a proper data is always transferred to a gio bus line by using the delay of an internal data strobe signal's falling for a certain amount of time as an input data strobe bar signal. Moreover, by using a skew detection circuit, it is possible to detect a skew tDQSS between a clock and a data strobe, and the skew tDQSS is automatically compensated by the skew compensation circuit. From the perspective of a timing error between the clock and the data strobe, therefore, the write operation of the DDR SDRAM has twice the timing margin (0.5tCK) compared to that of the related art. This means that a stable, high-speed write operation of the DDR SDRAM can be made possible.

Methods and apparatus for performing automated formal clock domain crossing verification on a device are detailed. In various implementations of the invention, a device may be analyzed, wherein the clock domain crossing boundaries are identified. Subsequently, a formal clock domain crossing verification method may be applied to the identified clock domain crossing boundaries, resulting in clock domain crossing assertions being identified. After which the identified assertions may be promoted for post clock domain crossing analysis. With various implementations of the invention, a formal clock domain crossing method is provided, wherein the device components near an identified clock domain crossing are extracted. Assertions may then be synthesized and verified based upon the extracted components. Various implementations of the invention provide for clock domain crossing verification to be performed iteratively, wherein a larger and larger selection of the device is extracted during formal verification. Additionally, various implementations of the present invention provide that the clock domain crossing verification operate on the fly during a device verification procedure. With further implementations, a bit-blasted approach to clock domain crossing verification may be provided during formal verification.

Methods and apparatus are provided for allowing efficient clock domain crossing management in programmable chip systems. Components associated with different clock domains can be analyzed. Clock domain crossing components are automatically selected from a library of clock domain crossing components to allow connection between disparate clock domains. Clock domain crossing components can be shared, chained, and intelligently selected for increased efficiency.

A method and arrangement of passing data from a source clock domain to a non-synchronous receive clock domain are provided. A first processing circuit, located in the source clock domain, links write-address information with the data, and a clock generator generates a transmit clock signal in the source clock domain synchronous with a source clock. The first processing circuit transmits the clock signal and the data with the linked write-address information to a second processing circuit in the receive clock domain. In the receive clock domain, the second processing circuit writes the data at an address designating a storage element corresponding to the linked write-address information. The second processing circuit clocks the data into the storage element synchronous with the accompanying transmit clock signal responsive to a write enable signal from the source clock domain, and reads the data out of the storage element synchronous with a receive domain clock.

Unsynchronized clock-domain crossings in the design of integrated circuit are detected by searching for clock-crossing domains. For each clock-crossing that does not include an explicit synchronization cell, an analysis determines if the clock is stable crossing the domains.

A flexible and scalable bi-directional CDC interface is set forth between clock domains in a SoC device. The interface comprises a pulse sync circuit for receiving a pulse synchronized to the source clock domain and in response outputting a busy signal to the source clock domain and outputting the pulse synchronized to said destination clock domain; an input register for latching data from said source clock domain in response to a transition of said source clock in the event said busy signal is not active and preventing said data from being latched in the event said busy signal is active so as not to corrupt previously latched data; and an output register for receiving said pulse from said pulse sync circuit and in response latching said pulse from said input register on a transition of said destination clock.

Names of signals are propagated through a circuit design inside tuples, with each tuple including at least a signal name and a sequential depth. A tuple being propagated is added to a list of zero or more tuples currently identified with a circuit element, unless a tuple of the same signal name is already present in the list. If already present in the list, then propagation of that tuple is stopped. Propagation of tuples may also be stopped depending on user-defined limits, e.g. on sequential depth. Tuple propagation may be used, depending on the embodiment, to identify features of interest in the circuit design, e.g. (a) a point of convergence of differently clocked signals, (b) location of gray coders, and (c) location of synchronizers, by appropriate identification of circuit elements from which tuple propagation is to start, and by appropriate checks on lists of tuples that result from tuple propagation.

The invention provides a device and a method for processing clock-domain-crossing asynchronous data, a chip and an operating method of the chip. The device comprises a first data sampling unit, a second data sampling unit, a logical operation unit and a clock signal synchronization unit, wherein the first data sampling unit acquires data and obtains a first data signal in a first clock domain; the second data sampling unit acquires the data and obtains a second data signal in a second clock domain; the logical operation unit receives the first data signal and the second data signal and performs logical operation; the clock signal synchronization unit samples a first clock signal in the first clock domain and/or a second clock signal in the second clock domain to obtain a first synchronous clock signal and/or a second synchronous clock signal; and at least one of the first data sampling unit and the second data sampling unit acquires the data under the first synchronous clock signal and/or the second synchronous clock signal. The method comprises the following steps of: synchronizing clock signals in other clock domains by using a reference clock signal; and sampling the data. By the invention, data synchronism can be ensured, and the processing accuracy of the data is improved.

A structure, system, and method block clock inputs to clock domains (using a computer). While the clock domain inputs are blocked, the structure, system, and method perform a first timing test only of signals that are transmitted within the clock domains (using the computer) by only observing latches that receive signals from sources within the clock domains. The structure, system, and method also unblock the clock inputs to the clock domains (using the computer). While the clock domain inputs are unblocked, the structure, system, and method perform a second timing test only of signals that are transmitted between the clock domains by only observing latches that receive signals from other clock domains.

Disclosed is a method and system for clock tree construction across clock domains, an integrated circuit and fabrication method thereof. A method for clock tree construction includes acquiring a netlist describing an integrated circuit (IC), comprising data for describing physical locations and logic connections of clock sinks belonging to multiple clock domains on the pattern of the IC, and constructing the clock tree across clock domains based on the netlist, such that clock cells belonging to different clock domains can share more physical locations. Accordingly, clock trees can be constructed across clock domains to improve IC performance.

A method for generating timing exceptions for integrated circuit (IC) designs is disclosed. The method includes synthesizing an input RTL description into a gate-level netlist mapped to a technology library; detecting timing critical paths in the netlist; and determining for each detected timing critical path whether it induces timing exceptions. The timing exceptions generated by the disclosed method include, but are not limited to, multi-cycle paths, clock domain crossing false paths, asynchronous false paths, functional false paths, combinational false paths, sequential false paths, timing false paths, and the like.

The invention discloses a clock domain crossing AHB (advanced high-performance bus) bridging method and device. The device comprises a master control logic module, a slave control logic module, a master clock and slave clock data latching module and an asynchronous pulse and synchronous circuit module. The master control logic module generates a bus control signal of a master clock domain according to a bus signal of a master device; the master control logic module generates a response signal fed back to the master device according to a slave device bus signal sampled in the master clock domain and latched by a slave clock domain; the slave control logic module generates a bus control signal of the slave clock domain according to a response signal of a slave device and a master device bus signal sampled in the slave clock domain and latched by the master clock domain; when the bus control signal is effectively enabled, the master clock and slave clock data latching module latches and samples synchronous data; the asynchronous pulse and synchronous circuit module synchronizes clock domain crossing signals to an opposite-party clock domain. The clock domain crossing AHB bridging method and device have the advantage that the master and slave devices can implement the AHB protocol under any frequency.

A circuit verifier having an input interface configured to receive descriptions of integrated circuits and a processing unit configured to scan through a description of an integrated circuit received through the input interface in order to identify clock domain crossings in the circuit and to provide a numerical score for each of the identified clock domain crossings.

A circuit verifier scans through a description of an integrated circuit to identify black-boxes in the description. The verifier assigns the identified black-boxes to clock domains and identifies clock domain crossings, in which a black-box assigned to a first clock domain is connected to an element belonging to a second clock domain. In some cases the verifier identifies signal reconvergence through black-boxes.

A synchronizer module is provided that may be used to facilitate the simulation of circuitry having clock domain crossing signals. A multiple-stage synchronizer may be used where at least one of the multiple synchronizer stages is dynamically enabled and disabled. The synchronizer module may have a delay unit for selectively applying a variable delay. This may allow for better modelling the real-silicon behaviour for simulation purposes to detect signal synchronization problems earlier in the flow, for instance during RTL (Register Transfer Level) design.