Cellular automata for weighted random pattern generation

Fault testing random-pattern-resistant circuits requires that BIST (built-in self-test) techniques generate large numbers of pseudorandom patterns. To shorten these long test lengths, this study describes a cellular automata-based method that efficiently generates weighted pseudorandom BIST patterns. This structure, called a weighted cellular automaton (WCA), uses no external weighting logic. The design algorithm MWCARGO combines generation of the necessary weight sets and design of the WCA. In this study, WCA pattern generators designed by MWCARGO achieved 100 percent coverage of testable stuck-at faults for benchmark circuits with random-pattern-resistant faults. The WCA applies complete tests much faster than existing test-per-scan techniques. At the same time, the hardware overhead of WCA proves to be competitive with that of current test-per-clock schemes.