Generating masking control circuits for test response compactors
First Claim
1. A method of testing a circuit-under-test, comprising:
- during a first interval, providing test pattern data to inputs of a circuit-under-test; and
during a second interval, providing masking instructions for a masking circuit to the inputs of the circuit-under-test.
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Abstract
Disclosed herein are exemplary embodiments of a so-called “X-press” test response compactor. Certain embodiments of the disclosed compactor comprise an overdrive section and scan chain selection logic. Certain embodiments of the disclosed technology offer compaction ratios on the order of 1000×. Exemplary embodiments of the disclosed compactor can maintain about the same coverage and about the same diagnostic resolution as that of conventional scan-based test scenarios. Some embodiments of a scan chain selection scheme can significantly reduce or entirely eliminate unknown states occurring in test responses that enter the compactor. Also disclosed herein are embodiments of on-chip comparator circuits and methods for generating control circuitry for masking selection circuits.
87 Citations
37 Claims
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1. A method of testing a circuit-under-test, comprising:
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during a first interval, providing test pattern data to inputs of a circuit-under-test; and
during a second interval, providing masking instructions for a masking circuit to the inputs of the circuit-under-test. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of generating selection logic for a selection circuit used to control the masking of unknown states during test response compaction, the method comprising:
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generating a candidate polynomial for possible inclusion in a set of accepted polynomials, the candidate polynomial and the accepted polynomials describing connections of two or more inputs of the selection logic to a respective output of the selection circuit;
selecting one or more test sets of polynomials, the test sets respectively comprising at least the candidate polynomial and one or more polynomials from the set of accepted polynomials;
computing rank values for the one or more test sets;
selecting the candidate polynomial for inclusion in the set of accepted polynomials based at least in part on the rank values; and
storing the set of accepted polynomials including the candidate polynomial on one or more computer-readable media. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17)
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18. A method of generating masking instructions for a selection circuit operable to mask test response bits during testing of a circuit-under-test, the method comprising:
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simulating a test pattern being applied to the circuit-under-test to produce a test response;
identifying one or more unknown states in the test response;
selecting one or more test response bits for masking based at least in part on the one or more identified unknown states; and
storing one or more indications of the selected test response bits on one or more computer-readable media. - View Dependent Claims (19, 20, 21, 22, 23, 24)
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25. A method of generating masking instructions for a selection circuit operable to mask test response bits during testing of a circuit, the method comprising:
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assigning weights to one or more scan cells of a selected scan chain;
aggregating the weights for one or more groups of scan cells within the selected scan chain;
computing one or more scores for the selected scan chain based at least in part on the aggregated weights;
determining whether to mask test response bits from the selected scan chain based at least in part on the scores; and
storing an indication of the determination on one or more computer-readable media. - View Dependent Claims (26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37)
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Specification