A Logic Design Theory for VLSI

Abstract

Classical switching theory fails to account for some key structural and logical properties of the transistor circuits used in VLSI design. This paper proposes a new logic design methodology called CSA theory which is suitable for VLSI. Three kinds of primitive logic devices are defined: connectors (C), switches (S), and attenuators (A); the latter have the characteristics of pullup/pulldown components. It is shown that four new logic values are required, in addition to the usual Boolean 0 and 1 values. These values introduce a concept of gain or drive capability into logic design; they also account for the high-impedance state of tri-state devices. The elements of CSA theory and its application to some basic VLSI design problems are described. It is demonstrated that CSA theory provides a more powerful and more rigorous replacement for the mixed logic/electronic methods currently used in VLSI design.