A study on Identifying Undetectable Faults Using Uninitializable Flip-Flops
Jae-Hun Lee, Jin-U Jo · The Transactions of the Korea Information Processing Society · 1997
Undetectable faults in a digital circuit are faults that no input patterms can detect.Identifying these faults in test geferation process is very time- consuming especially for sequential circuits .In this paper we present a new algorithm to identify unedtectable faults in sequential cirouits .In the alorithm. we identify uninitializable fip-flops and then, faults that prevent intialization of the fkip-flops(FPIs)are identified, finally propagation path of the FPI is checked. Time complexity of this algorithm is porportional to the product of the number of flip flops with at lest a self loop and the number of gates in the circuit. Experiments were performed on the ISCAS89 benchmark ciruits to show the feadibility of the proposed algorithm.We could identify large amount of undetectable faults(up to 50% of the number of flip-flops)in circuits with uninitializable flip-flops. Consider-ing that most of the time in test generation is cinsumed in identifying undetecatable faults, performance of test generator can be improved by using this algorithm as a pre-processing of test generation