System and method for correlated process pessimism removal for static timing analysis
First Claim
1. A method for performing static timing analysis of a digital system in the presence of a plurality of global sources of delay variation comprising the steps of:
- a) selecting, for at least one timing test, at least one pair of an early path and a late path leading to said timing test;
b) identifying at least one global parameter which the delays of said early and late paths depend on, and identifying parameters in which delay functions are separable;
c) determining for at least one of said global parameters at least one consistent value assignment, and setting independently each of said parameters in which delay function are separable from a value that results in a worst slack value at said timing test; and
d) computing for each said consistent assignment a slack value for said path pair.
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Abstract
A method of removing pessimism in static timing analysis is described. Delays are expressed as a function of discrete parameter settings allowing for both local and global variation to be taken in to account. Based on a specified target slack, each failing timing test is examined to determine a consistent set of parameter settings which produces the worst possible slack. The analysis is performed on a path basis. By considering only parameters which are in common to a particular data/clock path-pair, the number of process combinations that need to be explored is reduced when compared to analyzing all combinations of the global parameter settings. Further, if parameters are separable and linear, worst-case variable assignments for a particular clock/data path pair can be computed in linear time by independently assigning each parameter value. In addition, if available, the incremental delay change with respect to each physically realizable process variable may be used to project the worst-case variable assignment on a per-path basis without the need for performing explicit corner enumeration.
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Citations
28 Claims
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1. A method for performing static timing analysis of a digital system in the presence of a plurality of global sources of delay variation comprising the steps of:
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a) selecting, for at least one timing test, at least one pair of an early path and a late path leading to said timing test; b) identifying at least one global parameter which the delays of said early and late paths depend on, and identifying parameters in which delay functions are separable; c) determining for at least one of said global parameters at least one consistent value assignment, and setting independently each of said parameters in which delay function are separable from a value that results in a worst slack value at said timing test; and d) computing for each said consistent assignment a slack value for said path pair. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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25. A system for performing static timing analysis of a digital system in the presence of a plurality of global sources of delay variation comprising:
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a) means for selecting, for at least one timing test, at least one pair of an early path and a late path leading to said timing test; b) means for identifying at least one global parameter which the delays of said early and late paths depend on, and mean for identifying parameters in which delay functions are separable; c) means for determining for at least one of said global parameters at least one consistent value assignment and means for setting dependently each of said parameters in which delay functions are separable to value that results in a worst slack value at said timing test; and d) means for computing for each said consistent assignment a slack value for said path pair. - View Dependent Claims (26, 27)
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28. A program storage device readable by a machine, tangibly, embodying a program of instructions executable by the machine to perform method steps for performing static timing analysis of a digital system in the presence of a plurality of global sources of delay variation, said method steps comprising:
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a) selecting, for at least one timing test, at least one pair of an early path and a late path leading to said timing test; b) identifying at least one global parameter which the delays of said early and late paths depend on, and identifying parameters which delay functions are separable; c) determining for at least one of said global parameters at least one consistent value assignment, and setting independently each of said parameters in which delay functions are separable to a value that results in a worst slack value at timing test d) computing for each said consistent assignment a slack value for said path pair.
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Specification