International Business Machines Corporation

Adil Bhanji

Debjit Sinha

Kerim Kalafala

Manish Verma

Naiju K Abdul

Chandramouli Visweswariah

Michael H Wood

Soroush Abbaspour

Hemlata Gupta

Jack DiLullo

Alex Rubin

Natesan Venkateswaran

Gregory M Schaeffer

Peter Feldmann

Nathaniel Douglas Hieter

Albert Thomas Williams

Sean Michael Carey

Ravichander Ledalla

Barry Lee Dorfman

Vern Anthony Victoria

Jeffrey Mark Ritzinger

Jeremy J Leitzen

Chaobo Li

Prashant D Joshi

Don Richard Rozales

Ravi Chander Ledalla

Methods and apparatus for creating an improved VLSI design. In-context timing analysis of a nominal VLSI design is performed and at least one assigned apportionment adjustment is determined for a sub-block of the nominal VLSI design. One or more slack adjustments are derived for at least one port of the sub-block based on the at least one apportionment adjustment and the one or more slack adjustments are applied to the in-context timing analysis to simulate a post optimization version of the sub-block. The in-context timing analysis is repeated using the one or more applied slack adjustments to generate the improved VLSI design.

Apportionment aware hierarchical timing optimization

Efficiency of electronic design automation is increased by accessing a data structure characterizing a hierarchical integrated circuit design including sub-blocks each with a plurality of ports. For each given one of the ports of each of the sub-blocks, obtain a wire specification for a corresponding net connected to the given one of the ports in the design, and based on the wire specification, consult a technology-specific lookup table to determine at least one of a corresponding default driving cell and default electrical model for an external wire coupling one of the default driving cell and an actual driving cell to the given one of the ports. Optimize each of the sub-blocks out-of-context based on the at least one of default driving cells and default electrical models; verify in-context closure for the optimized sub-blocks; and, responsive to the in-context closure, update the data structure to reflect the optimized sub-blocks.

Technology lookup table-based default assertion generation and consumption for timing closure of VLSI designs

A system and method to generate a clock domain-independent abstract of a component in an integrated circuit design. The method includes performing an initial analysis of the component using an initial clock value for each clock domain type, the clock domain types including a functional clock and a test clock, executing an abstractor to obtain a reduced order model of the initial analysis as a clock domain-dependent abstract, and obtaining original constraints associated with one or more circuit elements within the component from the clock domain-dependent abstract. Generating generalized constraints is based on clock domain-dependent constraints among the original constraints, and generating the clock domain-independent abstract is based on the generalized constraints. The method also includes obtaining a physical implementation based on one or more analyses using the clock domain-independent abstract.

Clock domain-independent abstracts

A method, system and computer program product perform timing analysis of an integrated circuit design with callback-based constraint processing for clock domain independence. A timing graph representation of the integrated circuit design includes nodes interconnected by edges. Loading timing abstracts representing the nodes of the timing graph precedes obtaining a timing result based on propagating timing values and associated timing tags from an input to an output of the integrated circuit design and processing timing constraints at one or more of the nodes as callbacks. Each timing tag indicates a clock domain. After applying a design change, one or more modified timing tags that are added or changed as a result of the design change are determined. The timing constraints associated with the modified timing tags are processed as callbacks, and the timing result are re-computed.

Callback based constraint processing for clock domain independence

The timing analysis of an integrated chip component using dynamic load sensitive timing feedback constraints maintaining the timing accuracy for all the boundary paths is achieved by capturing a reduced order representation for parasitic load within a component for each of its primary input and primary output along with sensitivities of the arrival time, the slew and the required arrival time to the load representation at the component parent level of hierarchy as part of generating load sensitive feedback constraints. During the out-of-context timing closure of the component, the base load representation and the sensitivities, and an updated load representation enables the calculation of the updated boundary constraint for an accurate timing analysis. The accuracy improvement increases a chip designer productivity during timing closure resulting in a shortened time to take the chip design through timing closure to manufacturing. The method is applicable for deterministic as well as for statistical timing analyses.

Method of hierarchical timing closure employing dynamic load-sensitive feedback constraints

A modeling system includes a processor with software that performs static timing analysis (STA) on a design model. STA software executes a static timing analysis (STA) run with shortened clock cycles to model full cycle clock variability. Designers or other entities interpret the results of the shortened STA run data by performing modeling on the output data to generate slack data for design model data paths. STA software executes an STA run with an extended clock cycle to automatically separate half cycle data path (HCDP) slack data from full cycle data path (FCDP) slack data. The full and half cycle clock variability method may automatically adjust slack data for all half cycle data paths (HCDP)s to account for the additional half cycle variation (AHCV) and half cycle clock edge variability that may penalize the design model results in a real hardware implementation.

Modeling full and half cycle clock variability

A method for performing a hierarchical statistical timing analysis of an integrated circuit (IC) chip design by abstracting one or more macros of the design. The method includes performing a statistical static timing analysis of at least one macro; performing a statistical abstraction of the macro to obtain a statistical abstract model of the macro timing characteristics; applying the statistical abstract model as the timing model for each occurrence of the macro leading to a simplified IC chip design; and performing a hierarchical statistical timing analysis of the simplified chip design. The method achieves a context aware statistical abstraction, where a generated statistical abstract model is instantiated for each macro of the chip during statistical static timing analysis at the chip level, providing a compressed and pruned statistical timing abstraction and reducing the model-size during the statistical abstraction.

Performing a statistical timing abstraction for a hierarchical timing analysis of VLSI circuits

A method for converting interconnect parasitics of an interconnect network into slew dependent pin capacitances utilizes charge matching between predetermined voltage thresholds. During timing abstraction of a macro, parasitics of interconnects connected to the primary inputs are represented as slew dependent pin capacitances in an abstract model being created. Interconnect model order reduction is employed to speed the process. The generated abstract is subsequently used in place of each occurrence of the macro during chip level hierarchical static timing analysis, leading to an enhanced accuracy of the timing analysis of the logic components driving the abstracts.

Method of employing slew dependent pin capacitances to capture interconnect parasitics during timing abstraction of VLSI circuits

An accurate method to compute the capacitance at a pin whose capacitance is slew dependant. The method uses existing library characterized data and provides an equation based approach which can easily be integrated in static timing analysis without the added resource needs that an iterative approach would require. An RC/RLC network from slew and output load dependent pin capacitance tables is generated. The resulting linear network which models the pin capacitance is then stitched to the original interconnect network and used to calculate the propagation delay across a gate and corresponding interconnect. The method steps include: a) determining a response of the gate pin capacitance to its input slew and output load; b) synthesizing a linear time-invariant filter that matches the response; c) extending the interconnect model to include the synthesized time-invariant filter; and d) inputting the extended interconnect model into a static timing analysis for determining timing behavior between a gate input and each of its fan-out gates.

Method of modeling and employing the CMOS gate slew and output load dependent pin capacitance during timing analysis

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Wappingers Falls, NY, United States of America

Adil Bhanji