Guo, Ruifeng; Huang, Yu; Cheng, Wu-Tung

A dictionary-based scan chain fault detector includes a dictionary with fault signatures computed for scan cells in the scan chain. Entries in the fault dictionary are compared with failures in the failure log to identify a faulty scan cell. In one embodiment a single fault in a scan chain is identified. In another embodiment, a last fault and a first fault in a scan chain are identified.

Zou, Wei; Tang, Huaxing; Cheng, Wu-Tung

Fault diagnosis techniques (e.g., effect-cause diagnosis techniques) can be speeded up by, for example, using a relatively small dictionary. Examples described herein exhibit a speed up of effect-cause diagnosis by up to about 160 times. The technologies can be used to diagnose defects using compacted fail data produced by test response compactors. A dictionary of small size can be used to reduce the size of a fault candidate list and also to facilitate procedures to select a subset of passing patterns for simulation. Critical path tracing can be used to handle failing patterns with a larger number of failing bits, and a pre-computed small dictionary can be used to quickly find the initial candidates for failing patterns with a smaller number of failing bits. Also described herein are exemplary techniques for selecting passing patterns for fault simulation to identify faults in an electronic circuit.

Guo, Ruifeng; Huang, Yu; Cheng, Wu-Tung

A dictionary-based scan chain fault detector includes a dictionary with fault signatures computed for scan cells in the scan chain. Entries in the fault dictionary are compared with failures in the failure log to identify a faulty scan cell. In one embodiment a single fault in a scan chain is identified. In another embodiment, a last fault and a first fault in a scan chain are identified.

Cheng, Wu-Tung; Tsai, Kun-Han; Huang, Yu; Tamarapalli, Nagesh; Rajski, Janusz

Methods, apparatus, and systems for performing fault diagnosis are disclosed herein. In certain disclosed embodiments, methods for diagnosing faults from compressed test responses are provided. For example, in one exemplary embodiment, a circuit description of an at least partially scan-based circuit-under-test and a compactor for compacting test responses captured in the circuit-under-test is received. A transformation function performed by the compactor to the test responses captured in the circuit-under-test is determined. A diagnostic procedure for evaluating uncompressed test responses is modified into a modified diagnostic procedure that incorporates the transformation function therein. Computer-readable media comprising computer-executable instructions for causing a computer to perform any of the disclosed methods are also provided. Likewise, computer-readable media comprising lists of fault candidates identified by any of the disclosed methods or circuit descriptions created or modified by the disclosed methods are provided.

Cheng, Wu-Tung; Sharma, Manish; Rinderknecht, Thomas Hans

In embodiments of the disclosed technology, diagnosis of a circuit is performed using compactor signatures (a technique referred to herein as "signature-based diagnosis"). Signature-based diagnosis typically does not require a test step that bypasses the compactor. Compactor signatures can be read from a compactor on a per-pattern basis, and an expected signature can be loaded into a compactor while an actual signature is being read from the compactor. Error functions can be used to describe relationships between errors in scan cell values and per-pattern compactor signatures, and the functions can be used to help generate a list of fault candidates in a circuit design.

Huang, Yu; Cheng, Wu-Tung; Rajski, Janusz

Methods, apparatus, and systems for performing fault diagnosis are disclosed herein. In one exemplary embodiment, a failure log is received comprising entries indicative of compressed test responses to chain patterns and compressed test responses to scan patterns. A faulty scan chain in the circuit-under-test is identified based at least in part on one or more of the entries indicative of the compressed test responses to chain patterns. One or more faulty scan cell candidates in the faulty scan chain are identified based at least in part on one or more of the entries indicative of the compressed test responses to scan patterns. The one or more identified scan cell candidates can be reported. Computer-readable media comprising computer-executable instructions for causing a computer to perform any of the disclosed methods are also provided. Likewise, computer-readable media storing lists of fault candidates identified by any of the disclosed methods are also provided.

Huang, Yu; Cheng, Wu-Tung; Rajski, Janusz

Methods, apparatus, and systems for performing fault diagnosis are disclosed herein. In one exemplary embodiment, a failure log is received including entries indicative of compressed test responses to chain patterns and compressed test responses to scan patterns. A faulty scan chain in the circuit-under-test is identified based at least in part on one or more of the entries indicative of the compressed test responses to chain patterns. One or more faulty scan cell candidates in the faulty scan chain are identified based at least in part on one or more of the entries indicative of the compressed test responses to scan patterns. The one or more identified scan cell candidates can be reported. Computer-readable media comprising computer-executable instructions for causing a computer to perform any of the disclosed methods are also provided. Likewise, computer-readable media storing lists of fault candidates identified by any of the disclosed methods are also provided.

Cheng, Wu-Tung; Tsai, Kun-Han; Huang, Yu; Tamarapalli, Nagesh; Rajski, Janusz

Methods, apparatus, and systems for performing fault diagnosis are disclosed herein. In certain disclosed embodiments, methods for diagnosing faults from compressed test responses are provided. For example, in one exemplary embodiment, a circuit description of an at least partially scan-based circuit-under-test and a compactor for compacting test responses captured in the circuit-under-test is received. A transformation function performed by the compactor to the test responses captured in the circuit-under-test is determined. A diagnostic procedure for evaluating uncompressed test responses is modified into a modified diagnostic procedure that incorporates the transformation function therein. Computer-readable media comprising computer-executable instructions for causing a computer to perform any of the disclosed methods are also provided. Likewise, computer-readable media comprising lists of fault candidates identified by any of the disclosed methods or circuit descriptions created or modified by the disclosed methods are provided.