Janusz Rajski

The detection of small size multiple faults by single fault test sets n programmable logic arrays

In this paper we present a method to quantitively predict the multiple fault coverage capability of a single fault detection test set in a PLA. The method enables to determine the coverage ratio defined as the ratio of the number of multiple contact faults detected by a single fault test Tc to the total number of all multiple faults. The analysis is divided into two parts. First we consider multiple faults which do not contain any four-way masking cycle. Next, the masking relations are studied in detail and it is shown that Tc detects significant percentage of faults with four-way masking cycle. Based on these results the bounds of coverage capability of Tc are determined. It is shown that the multiple fault coverage ratio dr increases with increasing number of rows of a PLA and the ratio drops with increasing size of faults.