ABSTRACT
Bistable circuits exhibit two stable states that can represent logic 1 and logic 0. These include latches and flip-flops, which are useful in a number of applications that require the temporary retention of one or more bits. There are two requirements for the realization of bistable operation. In contrast, practical bistable circuits provide inputs so the state can be written as well as read. This chapter considers latches, flip-flops, and Schmitt triggers. Latches are simple bistable circuits that have input connections to set their logic states. Flip-flops are similar but are clocked. Schmitt triggers exhibit hysteresis, that is, the VIL and VIH are dependent on the output state. An RS latch may also be constructed using two cross-coupled NAND gates. As a matter of nomenclature, a clocked bistable circuit is called a flip-flop, whereas unclocked bistable circuits are called latches.
