Synopsys, Inc.

Peivand Tehrani

Li Ding

Jiayong Le

Nahmsuk Oh

Alireza Kasnavi

Ayhan Mutlu

Duc Huynh

Ahmed M Shebaita

Rupesh Nayak

Hushrav Mogal

Song Chen

Xin Wang

William Chiu-Ting Shu

Jindrich Zejda

Rachid Helaihel

Narender Hanchate

Christopher Papademetrious

Yazdan Aghaghiri

Ravikishore Gandikota

An equivalent input characterization waveform (EICW) is determined for a channel-connected block (CCB) located on a boundary of a cell, for a specific waveform of interest. The EICW and the specific waveform of interest produce a same timing characteristic of the CCB, but the EICW belongs to a set of waveforms on which a behavioral timing model for the multi-stage cell is based whereas the specific waveform of interest is not so limited. A timing response of the multi-stage cell is then estimated based on applying the EICW.

Timing modeling of multi-stage cells using both behavioral and structural models

A system receives a circuit description and measures of intrinsic delay, intrinsic delay variation, transition time and transition time variation for each stage and determines stage delay variation of each stage. The system receives a circuit description and derate factors and determines an intrinsic delay standard deviation and a correlation coefficient. The system determines a stage delay variation of each stage based on the determined factors. The system receives parameters describing an asymmetric distribution of delay values and generates a normal distribution of delay values. The system receives measures of nominal transition time at an output and input of a wire, and transition time variation at the input of the wire and determines a transition time variation at the output of the wire. The system receives measures of an Elmore delay and a nominal delay of the wire and determines a delay variation at the output of the wire.

Analyzing delay variations and transition time variations for electronic circuits

Disclosed is a method and apparatus that takes timing information associated with a plurality of inputs to a cell, such as an AND-gate, within an integrated circuit (IC) design, store the timing information in a timing information register (TIR) associated with an index identifying the source of the timing information and track the source of the timing information for a predetermined number of cells through the index. The timing information in the TIRs is merged upon the index indicating that the timing information has been tracked through a predetermined number of cells.

Method and apparatus for reducing pessimism of graph based static timing analysis

A system and a method are disclosed for performing static timing analysis. Information describing a distorted input waveform is received by a static timing analyzer. A transition time of the distorted input waveform is determined. Based on the determined input transition time a nominal input waveform and a corresponding nominal output waveform are received. An input waveform distortion is computed based on the nominal input waveform and the distorted input waveform. An output waveform distortion is computed based on an augmented circuit and the input waveform distortion. A distorted output waveform is computed based on the nominal output waveform and the output waveform distortion. The waveforms are represented using the distortion values which are smaller than the actual waveform values, thereby allowing for compact representation. A time-shifted version of an uncoupled input waveform is used to perform conservative timing analysis of circuits that accounts for crosstalk in the circuit.

Augmented simulation method for waveform propagation in delay calculation

A logic design is analyzed using static timing analysis and timing edge tracking for various nets within the logic design. Crosstalk analysis is performed on the logic design to evaluate timing impacts. To reduce pessimism of crosstalk analysis for a victim net, arrival edges are tracked for the victim net. The switching times of the aggressor net are compared to the edges of the victim net during crosstalk analysis.

Arrival edge usage in timing analysis

A method and apparatus to provide a hierarchical timing model with crosstalk consideration is provided. In one embodiment, the method comprises performing block level analysis of a circuit, in one or a plurality of iterations, and storing per iteration data. The method further comprises, in one embodiment, utilizing the per iteration data in performing top level analysis of the circuit.

Consistent hierarchical timing model with crosstalk consideration

Embodiments of a computer system, a method, an integrated circuit and a computer-program product (i.e., software) for use with the computer system are described. These devices and techniques may be used to calculate the total time delay in a signal path due to crosstalk from a group of crosstalk aggressors that are associated with a group of signal paths. In order to properly account for statistical behaviors in the switching times and directions of the switching patterns in the group of signal paths, the time-delay contribution from each of these crosstalk aggressors may be modeled as a corresponding statistical random variable. Because the number of crosstalk aggressors are usually much larger than the number of stages in the signal path, the calculated total path delay may be less pessimistic. Furthermore, in order to detect potential timing violations, the time-delay contributions from additional dominant crosstalk aggressors can be modeled using non-statistical worst-case deterministic values.

Crosstalk time-delay analysis using random variables

Some embodiments of the present invention provide techniques and systems for determining an order for visiting circuit blocks of a circuit design for fixing design requirement violations. Fixing design requirement violations by visiting circuit blocks in this order can improve performance and quality of results. During operation, a system can determine a set of equal value segments in the circuit design. In some embodiments, the system determines equal value segments for multiple corners and combines the equal value segments to obtain the set of equal value segments. Next, the system can determine an order for visiting circuit blocks of the circuit design for fixing design requirement violations based at least on the set of equal value segments. Note that circuit block pins in an equal value segment are associated with the same parameter value, and parameter values indicate an amount or degree of a design requirement violation.

Determining an order for visiting circuit blocks in a circuit design for fixing design requirement violations

A computer is programmed to identify a number of groups of timing windows, each group including a victim timing window and one (or more) aggressor timing window(s), respectively for a victim net and one (or more) aggressor nets in an IC design. The computer automatically slides (i.e. shifts in time) the victim and aggressor timing windows as a group for each die, i.e. by a specific amount that is identical for all timing windows of an instance of a coupled stage in a die, but differs for other instances of the same coupled stage in other dies. Crosstalk analysis is then performed, using time-shifted timing windows which result from sliding, to identify overlapping victim and aggressor nets, followed by variation aware delay calculations to identify timing violations and timing critical nets, followed by revision of the IC design, which is eventually fabricated in a wafer of semiconductor material.

Variation aware victim and aggressor timing overlap detection by pessimism reduction based on relative positions of timing windows

A method to perform timing analysis for a complex logic cell with distorted input waveform and coupled load networks is presented. Timing arc based models are used in conjunction with CCB based current models of portions of the logic cell to compute the output signal of the logic cell. For example, an intermediary signal is generated using a first timing arc based model and an equivalent coupled network output signal is generated using a channel connected block (CCB) based current model.

Distorted waveform propagation and crosstalk delay analysis using multiple cell models

An equivalent waveform for a distorted waveform used in timing and signal integrity analysis in the design of an integrated circuit is automatically generated. The equivalent waveform is produced by calculating the transition quantity of a first non-distorted waveform. The transition quantity is the amount of transition of the first non-distorted waveform that is required for the cell to produce an output waveform with a predetermined end voltage. The end point of the transition period for the distorted waveform is then determined based on when the distorted waveform has accumulated the same transition quantity. The equivalent waveform can then be formed by computing a second non-distorted waveform such that the end point of the transition period for the second non-distorted waveform coincides with the end point of the transition period for the distorted waveform.

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Campbell, CA, United States of America

Peivand Tehrani