Synthesis of single-output space compactors with application to scan-based IP cores

This paper addresses the problem of space compaction of test responses of combinational and scan-based sequential circuits. It is shown that given a precomputed test set T, the test responses at the functional outputs of the given circuit-under-test (CUT) can be compacted to a single periodic output, with guaranteed zero-aliasing. The method is independent of the fault model and the structure of the CUT, and uses only the knowledge of the test set T and the corresponding fault-free responses|it is particularly suitable for intellectual property (IP) cores. A new concept of distinguishing outputs and characteristic response function is utilized for synthesizing the compactor. Relevant experimental results on hardware overhead for several ISCAS circuits are presented.