Theoretic analysis and enhanced x-tolerance of test response compact based on convolutional code

This paper addresses the problem of test response compaction. In order to maximize compaction ratio, a single-output encoder based on check matrix of a (n, n-1, m, 3) convolutional code is proposed. Theoretic analysis for this encoder is presented to avoid two and any odd erroneous bit cancellations, handle one unknown bit (X bit) and diagnose one erroneous bit. The X-bits tolerance capacity can be enhanced by choosing a proper memory size and weight of check matrix, which can also be obtained by an optimized input assignment algorithm. The theoretic analysis and experimental results on aliasing shows the efficiency of the proposed encoder.