BIST generators for sequential faults

The authors consider faults with sequential behavior, e.g., delay or stuck-open faults, and discuss the state transition properties of linear-feedback-shift-register (LFSR) and one-dimensional linear-hybrid-cellular-automata (LHCA) test pattern generators. Upper and lower bounds on the transition coverage of any general n-cell generator with a period of 2/sup n/-1 are presented. It is shown that an XLHCA/XLFSR test pattern generator, which is derived from an LHCA/LFSR by grouping the odd and even numbered cell outputs, has superior transition coverage. On the basis of analysis and results of simulating the ISCAS'85 benchmark circuits, it is concluded that the XLHCA and XLFSR are excellent candidates for test pattern generators in BIST to detect faults with sequential behavior.<<ETX>>