Chapter 2 - Combinational logic design

Abstract

A digital circuit is a module with discrete-valued inputs and outputs and a specification describing the function and timing of the module. This chapter focuses on combinational circuits—circuits whose outputs depend only on the current values of the inputs. The function of a combinational circuit can be given by a truth table or a Boolean equation. The Boolean equation for any truth table can be obtained systematically using sum-of-products or product-of-sums form. In sum-of-products form, the function is written as the sum of one or more implicants. Implicants are the product of literals. Literals are the true or complementary forms of the input variables. Boolean equations can be simplified using the rules of Boolean algebra. Computer-aided design tools are used for more complicated functions; such methods and tools are also discussed in this chapter.