ABSTRACT
This chapter analyzes and synthesizes both synchronous and asynchronous sequential machines. The synthesis procedure for asynchronous sequential machines is similar in many respects to that described for synchronous sequential machines. A sequential logic circuit consists of combinational logic and storage elements. The storage elements in synchronous sequential machines are bistable multivibrators such as, D flip-flops and JK flip-flops. The storage elements in asynchronous sequential machines are set/reset (SR) latches. Each machine consists of at least one of the following three logical units: input combinational logic; synchronous storage elements; and output combinational logic. The concept of pulse-mode asynchronous sequential machines is frequently encountered in a variety of common applications such as vending machines and traffic control for demand-access intersections. Because of the stringent timing requirements on input pulse duration associated with pulse-mode machines, only the SR latches with edge-triggered D flip-flops offer a high degree of reliability.
