Presentation on theme: "Sequential Logic Latches and Flip-Flops. Sequential Logic Circuits The output of sequential logic circuits depends on the past history of the state of."— Presentation transcript:
Sequential Logic Circuits The output of sequential logic circuits depends on the past history of the state of the outputs. Therefore, it incorporate a memory element (circuits must remember the past states of their outputs). Main characteristic of these circuits feedback An output logic level is treated just like another input to the circuit.
Flip-Flops Flip-flops are synchronous bistable devices. Synchronous means that the output changes state only at a specified point on the triggering input called the clock (CLK). Changes in the output occur in synchronization with the clock.
Edge-Triggered JK-FF JK-FF is versatile and is a widely used type of flip-flop. The functioning of the JK-FF is identical to that of the SR-FF in the SET, RESET, and NC. The difference is that the JK-FF has NO invalid state as does the SR-FF.
Asynchronous Preset and Clear Inputs Most IC flip-flops have asynchronous inputs. These are inputs that affect the state of the FF independent of the clock. Preset (PRE) or direct set (S D ) Clear (CLR) or direct reset (R D ) Logic symbol for a J-K flip-flop active-LOW preset and clear inputs.
Edge-triggered JK-FF with PRE and CLR Toggle mode example