Nec Usa, Inc.

Surendra K Bommu

Srimat T Chakradhar

Kiran B Doreswamy

Xijiang Lin

A method of generating a vector set, said vector set being used for testing sequential circuits. The method comprises selecting a plurality of fault models, identifying a fault list each for each of said plurality of fault models, identifying a vector set each for each of said fault lists, selecting a tolerance limit each for each of said fault lists, thereby each fault model having an associated fault list, an associated vector set and an associated tolerance limit, compacting each of said vector set such that the compacted vector set identifies all the faults in the associated fault list or a drop in fault list coverage is within the associated tolerance limit; and creating a vector set by combining all vector sets compacted. A system and a computer program product for testing circuits with a compacted vector set where the compacted vector set is created by dropping faults based on a tolerance limit.

Segmented compaction with pruning and critical fault elimination

A method of solving a test generation problem for sequential circuits is disclosed. The method comprises recursively dividing an original test generation problem into smaller problems, wherein said sub-problems may be dependent while one or more of said dependent sub-problems may have solution-specific independence, finding solutions for said sub-problems, reusing solutions for dependent sub-problems, whenever the dependent sub-problems enjoy solution-specific independence; and identifying a minimal subset of conflicting objectives if a sub-problem that has to be solved to achieve multiple objectives has no solution. A test generation system comprising a computer, said computer having a cpu and memory, said memory comprising instructions capable of implementing components of said system. The components comprise a test generation problem solver that recursively solves test generation problems wherein solutions for sub-problems are reused, a problem partitioner that receives test generation problems and partitions said test generation problems into sub-problems wherein said sub-problems may be dependent and wherein said sub-problems may have solution-specific dependence, a consistent label checker that receives the test generation problem from the problem solver and determined if there is consistent labeling, a partition merger that merges a subset of sub-problems if no solution exists for said subset of sub-problems and if said subset of sub-problems are dependent and a conflict set generator that generates a conflict set of objectives that prevents a specific sub-problem from having a solution.

On-line partitioning for sequential circuit test generation

A two phase vector restoration technique which extracts a minimal subsequence from a sequence that detects a chosen set of faults is provided. The disclosed vector restoration technique is useful in static compaction of test sequences and in fault diagnosis. An accelerated two phase vector restoration that provides further improvement is also provided. The present invention is a significant improvement over the state of the art in the following ways: (1) a sequence of length n can be restored with only O(n log,n) simulations while known approaches require simulation of O(n,) vectors, (2) a two-step restoration process is used that makes vector restoration practical for large designs, and (3) restoration process for several faults is overlapped to provide significant acceleration in vector restoration. The described vector restoration technique has been integrated into a static test sequence compaction system.

Vector restoration using accelerated validation and refinement

A technique for static compaction of test sequences is described. The method for static compaction according to the present invention includes two key features: (1) two-phase vector restoration, and (2) identification, pruning, and re-ordering of segments. Segments partition the compaction problem into sub-problems. Segments are identified, dynamically pruned and re-ordered to achieve further compaction and speed up.

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Marlboro, MA, United States of America

Surendra K Bommu