Test length for random testing of sequential machines application to RAMs

Abstract

For a combinational fault, the probability of nondetection decreases exponentially with the test length L: /spl epsiv/=(1-p/sub f/)/sup L/, where p/sub f/ is the probability of detecting the fault f by a random test vector. For a sequential fault, the problem is more complex because of the memory effect (the probability of detection at time l depends on the vectors previously applied) and the exact solution requires the analysis of a Markov chain modeling the detection process. This paper shows that there is a value, obtained from the transition matrix of the Markov chain, which can take the place of p/sub f/ when the test length is relatively long (this value is different from the average detection probability). From this result and taking into account a particular property of bounded faults in RAMs, several results concerning these faults, already observed by several authors, are shown.