Color counting and its application to path delay fault coverage

We propose a new technique for computing exact fault coverage for any fault model. It consists of appropriate formation and counting of colors. Each color represents a set of faults, and the definition of colors varies according to the fault model. The technique utilizes the two aspects on which the fault coverage for any model depends, the circuit lines and the patterns applied to the circuit. Depending upon the sample space of faults for a given model, the representation of faults as colors differs. Colors are generated in a greedy and on demand manner ensuring they are unique. Even though the technique is simple in nature, it has never been used to calculate fault coverage for any fault model before. In this paper we apply it to calculate the fault coverage for the path delay fault model. Our experimental results show improvement over the existent techniques for the above mentioned model.