Multiple-Valued Logic

All circuits considered so far have been Boolean circuits, i.e. all signals and gates can assume one of the Boolean values 0 or 1. However, to use SAT-based ATPG in an industrial environment it is insufficient to consider only Boolean values. Since industrial circuits contain elements that have non-Boolean behavior, ATPG tools for these circuits have to handle these kinds of gates as well. In this chapter,¹ a brief overview of particular properties of industrial circuits, especially for elements that assume states which cannot be modeled by Boolean values is given. To apply ATPG to those circuits, a four-valued logic is presented in Section 6.1. Furthermore, it is explained in detail how to find an efficient Boolean encoding for this logic. This is done by comparing possible encodings with respect to their sizes in order to find the most suitable one.