Deterministic Loop Breaking in Multi-Mode Static Timing Analysis

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Solution Overview

Problem

Existing static timing analysis (STA) tools face inconsistencies in breaking point selection across different views and runs, leading to varying timing characteristics and potential engineering change orders, as they typically select breaking points independently for single-mode-single-corner (SMSC) and multi-mode-multi-corner (MMMC) views, which can result in different timing paths and increased design complexity.

Innovation Solution

The method involves identifying structural loops in the design independently of constraints, determining hard breaking points for each view, and merging timing constraints to generate a merged set of timing constraints for a multi-mode-multi-corner (MMMC) view, which includes determining a soft breaking point that does not break timing paths in any single-mode-single-corner (SMSC) views, allowing for consistent breaking points across SMSC and concurrent MMMC STA runs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If breaking points are selected independently for SMSC and MMMC views, then the STA analysis can be performed for each view separately, but the timing characteristics vary across different views and runs

Engineering Contradiction:

ImproveSTA analysis execution efficiencyVSAvoidtiming characteristics consistency

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent segments the breaking point selection into two distinct types: hard breaking points for structural loop breaking in SMSC views, and soft breaking points for phase propagation in MMMC views. This segmentation allows each type to serve its specific function while maintaining overall consistency across views.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent creates a universal soft breaking point selection methodology that serves multiple functions: it breaks combinational loops in MMMC views, enables phase propagation, and ensures consistent timing characteristics across all SMSC and MMMC views simultaneously.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Ease of manufacture

If different breaking points are used for SMSC and MMMC views, then each view can be optimized independently, but the number of engineering change orders increases

Engineering Contradiction:

Improveview-specific optimizationVSAvoiddesign change management

Core Design Contradiction:

Ease of manufactureVSDevice complexity

Solution Approach 1:

The patent performs preliminary identification of structural loops and determines hard breaking points for SMSC views before conducting the MMMC analysis. This preliminary action establishes a consistent foundation that reduces the need for later design changes.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The soft breaking point acts as an intermediary that connects the hard breaking points from SMSC views with the MMMC view analysis. It mediates between the structural constraints of individual views and the merged constraints of the multi-mode multi-corner analysis.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Measurement precision

If breaking point determination is performed separately for each view, then the analysis can be more detailed, but the time required for breaking point determination increases

Engineering Contradiction:

Improvebreaking point determination accuracyVSAvoidbreaking point determination time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent merges the breaking point determination process by identifying structural loops once and reusing this information across all SMSC and MMMC views. The soft breaking point is determined based on merged timing constraints from all views, eliminating redundant analysis while maintaining precision.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent changes the approach from determining breaking points independently for each view to determining a unified soft breaking point based on merged parameters from all views. This parameter change reduces computational complexity while maintaining the precision needed for accurate timing analysis.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11003821B1Deterministic loop breaking in multi-mode multi-corner static timing analysis of integrated circuits

Publication Date: 2021.05.11 CADENCE DESIGN SYST INC

AI summary

The present embodiments relate to static timing analysis (STA) of circuits. The STA can be carried out concurrently for multiple-mode-multiple-corners (MMMC) for circuits including combinational loops. The STA includes determining hard breaking points in the loop associated with each single-mode-single-corner (SMSC) view. The STA also includes merging constraints of all SMSC views to generate a merged set of constraints. The STA includes running MMMC STA for the circuit based on the merged set of constraints. The STA also includes determining a soft breaking point for the loop in the MMMC view for timing propagation and settling. The STA maintains consistency of breaking points across SMSC and MMMC views.