A Structural Method for Output Compaction of Sequential Automata Implemented as Circuits
In this paper output space compaction for sequential circuits is considered for the first time. Based on simple estimates for the probabilities of the existence of sensitized paths from the signal lines to the circuit outputs, optimal output partitions can be determined without fault simulation. The outputs are partitioned in such a way that internal stuck-at faults influence at most one of the outputs of a group with high probability. The proposed method is primarily developed for concurrent checking. On average with less than 4 compacted groups of outputs an error detection probability of 98% can be achieved. As the experimental results show, the method is also effectively applicable in pseudo-random test mode. On average for three groups of compacted outputs there is no reduction of the fault coverage for a pseudo-random off-line test. Since the proposed algorithm is of linear complexity with respect to the number of circuit lines and of quadratic complexity with respect to the number of primary circuit outputs large automata can be efficiently processed.
KeywordsSignal Line Fault Coverage Fault Simulation Primary Output Circuit Output
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