Abstract
Sequential circuit testing has been recognized as one of the most difficult problems in the area of fault detection. Controllability and observability of a sequential circuit is low because of their internal states. Therefore finding suitable sequence of test patterns is becoming increasingly complex. We have proposed a method to estimate an expectation graph by utilizing a mathematical model which exploits probabilistic 4-value system. The expectation graph is used to determine the minimum number of faults detected by a suitable sequence of test patterns. Experimental results show our mathematical model has reduced number of test patterns in specified fault coverage.