# Sequential Logic Latches and Flip-Flops. Sequential Logic Circuits The output of sequential logic circuits depends on the past history of the state of.

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Sequential Logic Latches and Flip-Flops

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.

Sequential Logic Circuits Latches Flip-flops

The S-R (SET-RESET) Latch

Negative-OR equivalent of the NAND gate \S-\R latch

The S-R (SET-RESET) Latch

An Application of Latch

The Gated S-R Latch

The Gated D Latch

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 FFs

Edged-Triggered S-R FF

Edge-Triggered D FF

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.

Edge-Triggered JK-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

Flip-Flop Applications Parallel data storage

Flip-Flop Applications Frequency division

Flip-Flop Applications Frequency division

Flip-Flop Applications Counting

Flip-Flop Applications Counting

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