Vlsi Technology, Inc.

Other

Cadence Design Systems, Inc.

Robert D Shur

Thomas J Schaefer

Mark R Hartoog

Arnold Ginetti

Christopher H Kingsley

James Allely Rowson

Steve G Bush

Andrew Robert Wilmot

Tuay-Ling Kathy Lang

Stuart C Rae

Edwin A Harcourt

Doug Dunlop

Bishnupriya Bhattacharya

Koushik Roy

Kenneth D Van Egmond

A method for simulation of mixed-language circuit designs is disclosed. In one embodiment, an object-oriented language module is natively instantiated within a hardware description language based design. In another embodiment, a hardware description language module is natively instantiated within an object-oriented language based design. A system for simulation of mixed-language circuit designs is also disclosed. In one embodiment, a simulator is configured to natively manipulate an object-oriented language module within a hardware description language based design. In another embodiment, a simulator is configured to natively manipulate a hardware description language module within an object-oriented language based design.

Method and system for simulation of mixed-language circuit designs

A method of automatically optimizing a hierarchical netlist of integrated circuit cells comprising at least one upper-level cell containing a multiplicity of subsidiary cells of lower hierachical level includes receiving data defining said netlist and timing constraints for it, and establishing abstract timing models for all the subsidiary cells. Timing constraints are propagated to at least one selected subsidiary cell and this cell is optimized by means of a flat optimizer to produced an optimized version of the selected subsidiary cell. The optimized version of the selected cell is inserted into the netlist. The timing constraints denote arrival times for signals at inputs of a cell and required times for signals at outputs of a cell and each abstract timing model of a cell comprises timing parameters which enable a delay time between a specified input of a cell to a specified output of a cell to be computed.

Automated optimization of hierarchical netlists

A circuit optimization method in which a set of cost functions are stored for each node that indicate the cost of getting signals to that node and the cost of a gate at that node. By 'cost', is meant some figure of merit, such as: the maximal delay for a signal to arrive at a node G; or the area of the elements needed to produce the signal at node G. These cost functions enable the circuit to be optimized without the need for a pattern library and the pattern matching process that is typical of other optimization processes, such as the DAGON Node Tiling Procedure.

Enhanced dynamic programming method for technology mapping of

Vector-specific test circuitry is added to an existing circuit design to enable improved fault test coverage by an existing fault test. Each vector-specific test circuit is designed to produce a single output indicative of whether any faults were detected in a plurality of previously unobservable node states produced in response to an associated test vector.

Vector-specific testability circuitry

A buffer circuit for fanning out a source signal to a plurality of terminals of specified polarities in accordance with specified time constraints is designed by an automated method in which a circuit template is specified in terms of a tree structure. The terminals are ordered in increasing order of required arrival times of the source signal at each of the terminals. A first terminal in a resulting order is assigned to a highest-level potential terminal site of a same polarity as said first terminal, and buffers on a signal path between said first terminal and the source signal are sized so as to satisfy, if possible, a required arrival time of the source signal at said first terminal. So long as required times of arrival are met, additional terminals are placed in like manner. The method proceeds as far as possible using a straight forward assignment procedure of terminals to potential terminal sites, then backtracks, undoing so much of the previous assignments as necessary and making incremental adjustments to allow the method to proceed further if possible. The method is completed when either all terminals have been successfully assigned or all of the previous assignments have been undone.

Buffer circuit design using back track searching of site trees

In a computer aided design system, a netlist specifies the integrated circuit's components and a set of interconnecting nodes. Also provided are a set of timing constraints for propagation of signals from specified input nodes to specified output nodes, and a set of signal delays associated with the circuit's components. The automatic circuit layout synthesis process begins by assigning an initial capacitance value to each node. Next, a routing difficulty value is computed, this value comprises a sum of routing difficulty values associated with each of the nodes in the integrated circuit. Capacitance values for the integrated circuit are then adjusted so as to reduce the computed routing difficulty. Finally, the netlist and adjusted capacitance values are passed to a silicon compiler for automatic placement and routing of a circuit having capacitance values not exceeding the adjusted capacitance values.

System and method for synthesizing logic circuits with timing constraints

A method estimates the interconnect capacitance of a first net in an integrated circuit. The first step of the method includes the generation of a value which indicates how tightly connected to one another are components connected to the first net. The second step of the method includes the prediction of interconnect capacitance of the first net based on the value generated in the first step and a number representing how many components are connected to the first net.

Method for predicting capacitance of connection nets on an integrated

An event-driven logic simulator provides for future evaluation events. Evaluation latencies are assigned to respective inputs of components based on component type. At least some of these latencies are positive and finite. When a signal status event specifies a change at an input associated with a positive latency, the function for the component is not evaluated at the present time. Instead, the evaluation is postponed to a future time equal to the present time plus the assigned latency. The evaluation is thus latent until the scheduled time becomes present. When multiple evaluation events are indicated for a common component output, a queue manager resolves the conflicts by discarding all but one of the evaluation events for that output. This approach minimizes redundant and superfluous evaluations during circuit simulation.

Circuit simulation system with wake-up latency

In a computer aided design system, capacitative constraints are defined for the nodes of an integrated circuit. A netlist specifies the integrated circuit's components and a set of interconnecting nodes. Also provided are a set of timing constraints for propagation of signals from specified input nodes to specified output nodes, and a set of signal delays associated with the circuit's components. The process begins by assigning a time delay value and a corresponding initial maximum capacitance value to each circuit node, consistent with the specified timing constraints. Next, a routing difficulty value for the entire circuit, equal to a sum of routing difficulty values associated with the circuits's nodes is computed. Each routing difficulty value is a predefined function of the maximum capacitance value for a corresponding node and the number of circuit components coupled to that node. Then, the following steps are repeated until changes in the computed routing difficulty value for the entire circuit meet predefined criteria. Beginning with components coupled to output nodes and progressing toward components adjacent input nodes, the time delay associated with a component's output node is decreased by decreasing its maximum capacitance value and the time delay associated with each of component's input node is increased by a corresponding amount. Then the routing difficulty value is recomputed and the changed time delays are retained only when the change has caused the computed routing difficulty to decrease.

System and method for setting capacitive constraints on synthesized

An integrated circuit includes parity chains which serve as test logic. Each parity chain has a series of XOR gates, where one input to each succeeding XOR gate in a chain is tied to the output of the preceding XOR gate. The remaining inputs are tied to nodes of the main logic, thus defining test points. An error at any one of the test points is reflected in the output of the parity chain. The outputs of the parity chains are arranged as parallel inputs to a linear feedback shift register which provides a serial signature which can be analyzed to detect integrated circuit defects.

Integrated parity-based testing for integrated circuits

A method for simulating a levelized logic circuit including an event-controlled feature for marking components to be reevaluated. An evaluation list is formed which lists signals and corresponding components of the logic circuit which are to be reevaluated. A second list is formed of each component and its corresponding output signals. The external input signals are also listed. Each external input signal is tested for change from a previous evaluation and, if so, the corresponding components in the re-evaluation list are marked for reevaluation. Each component, in levelized order, is then tested to determine whether that component is marked for re-evaluation and, if so, that component is re-evaluated and unmarked, and each signal in the component output signal list which has a non-empty re-evaluation list is tested to determine if the value of the signal has changed since the previous evaluation and, if so, all of the components in that signal's reevaluation list are marked for re-evaluation. Evaluation marks are stored as a marking bit in a memory location associated with a component. The components associated with frequently changing input signals are evaluated without setting or testing their evaluation marks. All reevaluation marks are cleared at the beginning of the execution of the simulation.

Event-controlled LCC stimulation

A simulator for a levelized logic circuit reduces the number of evaluations required. The simulator associates certain lists of signals, called fences, with each component of a logic circuit. A fence is evaluated to determine whether it is active or inactive. Active fences contain signals which have charged since a previous evaluation. Components for active fences are then evaluated by the simulator. Fences are formed by starting with a seed set of signals. If all of the input signals to a component are in one or more fences, a final fence for a component is formed which is the union of the one or more fences. Only signals which can cause an output change on a component are included in fences.

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Los Altos, CA, United States of America

Robert D Shur