Method and apparatus for identifying faults within a system
First Claim
1. A method for identifying elements of a faulty system, that are likely to contain the faults of the system, based on a set of test vectors output from the system wherein each test vector contains a set of test values, the method comprising the steps of:
- comparing the output test vectors with an expected set of output test vectors to identify faulty test values, with any differences between the output test vectors and corresponding expected test vectors indicating a failure of the test and indicating that at least one element of the system is faulty;
identifying a set of candidate faulty elements for each of the faulty test values; and
identifying elements of the system that are likely to contain the faults of the system by performing a partial intersection on the sets of candidate faulty elements wherein only elements associated with at least a predetermined number of faulty test values are selected.
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Accused Products
Abstract
Lists of candidate faults within an integrated circuit are generated, for the purpose of fault diagnosis, by performing a partial intersection of fault lists output from a full-scan test such as a JTAG test. The fault lists represent all candidate faults which may be responsible for producing a mismatched bit between an output test vector and an expected test vector provided by the full-scan test. The partial intersection is performed by first determining the number of occurrences of each candidate fault within all lists associated with each mismatched bit. Then, only faults which occur at least a pre-selected number of times are selected. In this manner, lists of candidate faulty gates are generated based on the relative degree of intersection between fault sets. The lists of candidate faulty gates are input to an X-Y location tool which determines the physical location on the integrated circuit of each of the candidate faulty gates to facilitate the efficient examination of each of the candidate faulty gates by test personnel.
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Citations
30 Claims
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1. A method for identifying elements of a faulty system, that are likely to contain the faults of the system, based on a set of test vectors output from the system wherein each test vector contains a set of test values, the method comprising the steps of:
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comparing the output test vectors with an expected set of output test vectors to identify faulty test values, with any differences between the output test vectors and corresponding expected test vectors indicating a failure of the test and indicating that at least one element of the system is faulty; identifying a set of candidate faulty elements for each of the faulty test values; and identifying elements of the system that are likely to contain the faults of the system by performing a partial intersection on the sets of candidate faulty elements wherein only elements associated with at least a predetermined number of faulty test values are selected. - View Dependent Claims (2, 3, 4, 5)
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6. An apparatus for identifying elements of a faulty system, that are likely to contain the faults of the system, based on a set of test vectors output from the system wherein each test vector contains a set of test values, the apparatus comprising:
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a device for comparing the output test vectors with an expected set of output test vectors to identify faulty test values, with any differences between the output test vectors and corresponding expected test vectors indicating a failure of the test and indicating that at least one element of the system is faulty; a device for identifying a set of candidate faulty elements for each of the faulty test values; and a device for identifying elements of the system that are likely to contain faults by performing a partial intersection on the sets of candidate faulty elements wherein only elements associated with at least a predetermined number of faulty test values are selected. - View Dependent Claims (7, 8, 9, 10)
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11. A method for identifying elements of a faulty system, that are likely to contain the faults of the system, based on a set of test vectors output from the system wherein each test vector contains a set of test values, the method comprising the steps of:
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providing a device for comparing the output test vectors with an expected set of output test vectors to identify faulty test values, with any differences between the output test vectors and corresponding expected test vectors indicating a failure of the test and indicating that at least one element of the system is faulty; providing a device for identifying a set of candidate faulty elements for each of the faulty test values; and providing a device for identifying elements of the system that are likely to contain faults by performing a partial intersection on the sets of candidate faulty elements wherein only elements associated with at least a predetermined number of faulty test values are selected. - View Dependent Claims (12, 13, 14, 15)
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16. A test method for testing an electronic system provided on a chip and having a plurality of elements, said method comprising the steps of:
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receiving a set of test vectors output from the system; comparing the output test vectors with an expected set of output test vectors to identify faulty test values, with any differences between the output test vectors and corresponding expected test vectors indicating a failure of the test and indicating that at least one element of the system is faulty; identifying a set of candidate faulty elements for each of the faulty test values; and identifying elements of the system that are likely to contain faults based on the sets of candidate faulty elements by performing a partial intersection on the sets of candidate faulty element associated with faulty test values wherein only elements which are associated with at least a predetermined number of faulty values are selected; and determining the physical location of the elements likely to contain faults within the chip by employing a software tool capable of identifying the location on a chip of one or more elements. - View Dependent Claims (17, 18, 19, 20)
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21. A test apparatus for testing an electronic system provided on a chip and having a plurality of elements, said apparatus comprising:
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a device for receiving a set of test vectors output from the system; a device for comparing the output test vectors with an expected set of output test vectors to identify faulty test values, with any differences between the output test vectors and corresponding expected test vectors indicating a failure of the test and indicating that at least one element of the system is faulty; a device for identifying a set of candidate faulty elements for each of the faulty test values; and a device for identifying elements of the system that are likely to contain faults based on the sets of candidate faulty elements by performing a partial intersection on the sets of candidate faulty elements associate with faulty test values wherein only elements which are associated with at least a predetermined number of faulty values are selected; and a device for determining the physical location of the elements likely to contain faults within the chip by employing a software tool capable of identifying the location on a chip of one or more elements. - View Dependent Claims (22, 23, 24, 25)
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26. A method for testing an electronic system provided on a chip and having a plurality of elements, said method comprising the steps of:
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providing a device for receiving a set of test vectors output from the system; providing a device for comparing the output test vectors with an expected set of output test vectors to identify faulty test values, with any differences between the output test vectors and corresponding expected test vectors indicating a failure of the test and indicating that at least one element of the system is faulty; providing a device for identifying a set of candidate faulty elements for each of the faulty test values; and providing a device for identifying elements of the system that are likely to contain faults based on the sets of candidate faulty elements by performing a partial intersection on the sets of candidate faulty elements associated with faulty test values wherein only elements which are associated with at least a predetermined number of faulty values are selected; and providing a device for determining the physical location of the elements likely to contain faults within the chip by employing a software tool capable of identifying the location on a chip of one or more elements. - View Dependent Claims (27, 28, 29, 30)
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Specification