Circuit Path Delay Determination Using Database Lookup
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Solution Overview
Problem
Static timing analysis in circuit design often produces overly conservative delay values due to the use of standard delay libraries, which fail to account for the specific instances of components on an integrated circuit, leading to difficulties in closing the timing of the circuit design.
Innovation Solution
A method and system that utilize a path database and an element database to determine signal path delays, where matching paths retrieve path delay values from the path database and non-matching paths compute delays using element delay values, improving accuracy and reducing analysis time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard delay library with worst-case values is used, then reliability of timing analysis is improved, but manufacturing precision of delay values deteriorates
Solution Approach 1:
The patent segments the delay calculation process into two parts: (1) using pre-characterized path delay values from a path database for matching paths, and (2) computing delay values from element databases for non-matching paths. This segmentation allows the system to use precise measured values where available while maintaining reliability through worst-case element-based computation where necessary.
Solution Approach 2:
The patent performs preliminary characterization of specific signal paths through measurement and stores these path delay values in a path database before actual timing analysis. This preliminary action captures precise delay values for commonly occurring paths, which are then retrieved during timing analysis to improve precision without sacrificing reliability.
2Ease of operation
If standard delay library is used, then ease of operation is improved, but measurement precision of path delays deteriorates
Solution Approach 1:
The system performs preliminary measurement and characterization of path delays through actual measurement of signal paths on the integrated circuit. These measured values are stored in a path database and retrieved during timing analysis, providing precise measurements while maintaining ease of operation through automated lookup.
Solution Approach 2:
The patent creates a copy of actual measured path delay values from physical measurements and stores them in a path database. During timing analysis, these copied measured values are used instead of computing delays from first principles, providing precise measurements while simplifying the analysis process.
3Productivity
If path database with pre-determined values is used, then productivity of timing analysis is improved, but device complexity increases
Solution Approach 1:
The patent segments the delay data into two separate databases: a path database containing pre-measured path delay values and an element database containing element delay values. This segmentation allows the system to use the path database for quick lookup (improving productivity) while maintaining the element database as a fallback for computing complex paths, thereby managing overall system complexity.
Data Source
AI summary
Determining delays of paths in a circuit design includes determining whether or not each path of the plurality of paths matches a path definition of a plurality of path definitions in a path database. For each path that matches a path definition, a first path delay value associated with the matching path definition is read from the path database and associated with the matching path of the circuit design. For each path that does not match any of the path definitions, respective element delay values of elements of the path are read from an element database. A second path delay value of the non-matching path is computed as a function of the respective element delay values, and the second path delay value is associated with the path. The first and second path delay values are output along with information indicating the associated paths.