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what is flip flop in digital electronics

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Flip-flop (electronics)

For other uses, see Flip-flop.

An animated interactive SR latch ( = 1 kΩ; = 10 kΩ).

In electronics, a flip-flop or latch is a circuit that has two stable states and can be used to store state information – a bistable multivibrator. The circuit can be made to change state by signals applied to one or more control inputs and will have one or two outputs. It is the basic storage element in sequential logic. Flip-flops and latches are fundamental building blocks of digital electronics systems used in computers, communications, and many other types of systems.

Flip-flops and latches are used as data storage elements. A flip-flop is a device which stores a single (binary digit) of data; one of its two states represents a "one" and the other represents a "zero". Such data storage can be used for storage of , and such a circuit is described as sequential logic in electronics. When used in a finite-state machine, the output and next state depend not only on its current input, but also on its current state (and hence, previous inputs). It can also be used for counting of pulses, and for synchronizing variably-timed input signals to some reference timing signal.

Flip-flops can be either level-triggered (asynchronous, transparent or opaque) or edge-triggered (synchronous, or clocked). The term flip-flop has historically referred generically to both level-triggered and edge-triggered circuits that store a single bit of data using gates. Recently, some authors reserve the term exclusively for discussing clocked circuits; the simple ones are commonly called .[1][2] Using this terminology, a level-sensitive flip-flop is called a transparent latch, whereas an edge-triggered flip-flop is simply called a flip-flop. Using either terminology, the term "flip-flop" refers to a device that stores a single bit of data, but the term "latch" may also refer to a device that stores any number of bits of data using a single trigger. The terms "edge-triggered", and "level-triggered" may be used to avoid ambiguity.[3]

When a level-triggered latch is enabled it becomes transparent, but an edge-triggered flip-flop's output only changes on a single type (positive going or negative going) of clock edge.

Contents

1 History 2 Implementation 3 Flip-flop types

3.1 Simple set-reset latches

3.1.1 SR NOR latch 3.1.2 SR NAND latch

3.1.3 SR AND-OR latch

3.1.4 JK latch

3.2 Gated latches and conditional transparency

3.2.1 Gated SR latch

3.2.2 Gated D latch 3.2.3 Earle latch 3.3 D flip-flop

3.3.1 Classical positive-edge-triggered D flip-flop

3.3.2 Master–slave edge-triggered D flip-flop

3.3.3 Dual-edge-triggered D flip-flop

3.3.4 Edge-triggered dynamic D storage element

3.4 T flip-flop 3.5 JK flip-flop

4 Timing considerations

4.1 Timing parameters

4.2 Metastability

4.3 Propagation delay

History

Flip-flop schematics from the Eccles and Jordan patent filed 1918, one drawn as a cascade of amplifiers with a positive feedback path, and the other as a symmetric cross-coupled pair

The first electronic flip-flop was invented in 1918 by the British physicists William Eccles and F. W. Jordan.[4][5] It was initially called the and consisted of two active elements (vacuum tubes).[6] The design was used in the 1943 British Colossus codebreaking computer[7] and such circuits and their transistorized versions were common in computers even after the introduction of integrated circuits, though flip-flops made from logic gates are also common now.[8][9] Early flip-flops were known variously as trigger circuits or multivibrators.

According to P. L. Lindley, an engineer at the US Jet Propulsion Laboratory, the flip-flop types detailed below (SR, D, T, JK) were first discussed in a 1954 UCLA course on computer design by Montgomery Phister, and then appeared in his book [10][11] Lindley was at the time working at Hughes Aircraft under Eldred Nelson, who had coined the term JK for a flip-flop which changed states when both inputs were on (a logical "one"). The other names were coined by Phister. They differ slightly from some of the definitions given below. Lindley explains that he heard the story of the JK flip-flop from Eldred Nelson, who is responsible for coining the term while working at Hughes Aircraft. Flip-flops in use at Hughes at the time were all of the type that came to be known as J-K. In designing a logical system, Nelson assigned letters to flip-flop inputs as follows: #1: A & B, #2: C & D, #3: E & F, #4: G & H, #5: J & K. Nelson used the notations "-input" and "-input" in a patent application filed in 1953.[12]

Implementation

A traditional (simple) flip-flop circuit based on bipolar junction transistors

Flip-flops can be either simple (transparent or asynchronous) or clocked (synchronous). In the context of hardware description languages, the simple ones are commonly described as ,[1] while the clocked ones are described as .[2]

स्रोत : en.wikipedia.org

Master The Basics Of Flip

Flip Flop in electronics is a circuit with two stable states, used to store binary data. We discussed its 4 types, truth table, and uses.

A flip-flop in digital electronics is a circuit with two stable states that can be used to store binary data. The stored data can be changed by applying varying inputs. Flip-flops and latches are fundamental building blocks of digital electronics systems used in computers, communications, and many other types of systems. Both are used as data storage elements.

It is the basic storage element in sequential logic. But first, let’s clarify the difference between a latch and flip-flops.

Flip-Flop v/s Latch

The primary difference between a latch and a flip-flop is a gating or clocking mechanism.

In Simple words. Flip Flops are edge-triggered and a latch is level-triggered.

If you are confused between latch and flip-flop, then you should check this detailed article where we discussed the difference between Latch and Flip Flop.

For example, let us talk about SR latch and SR flip-flops. In this circuit when you Set S as active, the output Q will be high and Q’ will be Low. This is irrespective of anything else. (This is an active-low circuit; so active here means low, but for an active high circuit, active would mean high)

SR Latch

A flip-flop, on the other hand, is a synchronous Circuit and is also known as a gated or clocked SR latch.

SR Flip Flop Circuit

In this circuit diagram, the output is changed (i.e. the stored data is changed) only when you give an active clock signal. Otherwise, even if the S or R is active, the data will not change.

Let’s understand the flip-flop in detail with the truth table and circuits.

Types

There are basically 4 types of flip-flops:

SR Flip-Flop JK Flip-Flop D Flip-Flop T Flip-Flop

SR Flip Flop

This is the most common flip-flop among all. This simple flip-flop circuit has a set input (S) and a reset input (R). In this system, when you Set “S” as active, the output “Q” would be high, and “Q” would be low. Once the outputs are established, the wiring of the circuit is maintained until “S” or “R” go high, or power is turned off.

As shown above, it is the simplest and easiest to understand. The two outputs, as shown above, are the inverse of each other. The truth table of SR Flip-Flop is highlighted below.

S R Q Q’

0 0 0 1 0 1 0 1 1 0 1 0 1 1 ∞ ∞

JK Flip-Flop

Due to the undefined state in the SR flip-flops, another flip-flop is required in electronics. The JK flip-flop is an improvement on the SR flip-flop where S=R=1 is not a problem.

JK Flip Flop Circuit

The input condition of J=K=1, gives an output inverting the output state. However, the outputs are the same when one tests the circuit practically.

In simple words, If J and K data input are different (i.e. high and low), then the output Q takes the value of J at the next clock edge. If J and K are both low, then no change occurs. If J and K are both high at the clock edge, then the output will toggle from one state to the other. JK Flip-Flops can function as Set or Reset Flip-flops.

Truth Table:

J K Q Q’

0 0 0 0 0 1 0 0 1 0 0 1 1 1 0 1 0 0 1 1 0 1 1 0 1 0 1 1 1 1 1 0

D Flip-Flop

D flip-flop is a better alternative that is very popular with digital electronics. They are commonly used for counters and shift registers and input synchronization.

D Flip-Flop

In the D flip-flops, the output can only be changed at the clock edge, and if the input changes at other times, the output will be unaffected.

Truth Table:

Clock D Q Q’

↓ » 0 0 0 1 ↑ » 1 0 0 1 ↓ » 0 1 0 1 ↑ » 1 1 1 0

The change of state of the output is dependent on the rising edge of the clock. The output (Q) is the same as the input and can only change at the rising edge of the clock.

T Flip-Flop

A T flip-flop is like a JK flip-flop. These are basically single-input versions of JK flip-flops. This modified form of the JK is obtained by connecting inputs J and K together. It has only one input along with the clock input.

These flip-flops are called T flip-flops because of their ability to complement their state i.e. Toggle, hence they are named Toggle flip-flops.

Truth Table:

T Q Q (t+1)

0 0 0 1 0 1 0 1 1 1 1 0

Applications

These are the various types of flip-flops being used in digital electronic circuits and the applications of Flip-flops are as specified below.

Counters

स्रोत : www.electronicsforu.com

Basics of flip flop

Basics of flip flop with Tutorial, Number System, Gray code, Boolean algebra and logic gates, Canonical and standard form, Simplification of Boolean function etc.

Basics of Flip Flop

A circuit that has two stable states is treated as a flip flop. These stable states are used to store binary data that can be changed by applying varying inputs. The flip flops are the fundamental building blocks of the digital system. Flip flops and latches are examples of data storage elements. In the sequential logical circuit, the flip flop is the basic storage element. The latches and flip flops are the basic storage elements but different in working. There are the following types of flip flops:

SR Flip Flop

The S-R flip flop is the most common flip flop used in the digital system. In SR flip flop, when the set input "S" is true, the output Y will be high, and Y' will be low. It is required that the wiring of the circuit is maintained when the outputs are established. We maintain the wiring until set or reset input goes high, or power is shutdown.

The S-R flip flop is the simplest and easiest circuit to understand.

J-K Flip-flop

The JK flip flop is used to remove the drawback of the S-R flip flop, i.e., undefined states. The JK flip flop is formed by doing modification in the SR flip flop. The S-R flip flop is improved in order to construct the J-K flip flop. When S and R input is set to true, the SR flip flop gives an inaccurate result. But in the case of JK flip flop, it gives the correct output.

In J-K flip flop, if both of its inputs are different, the value of J at the next clock edge is taken by the output Y. If both of its input is low, then no change occurs, and if high at the clock edge, then from one state to the other, the output will be toggled. The JK Flip Flop is a Set or Reset Flip flop in the digital system.

D Flip Flop

D flip flop is a widely used flip flop in digital systems. The D flip flop is mostly used in shift-registers, counters, and input synchronization.

T Flip Flop

Just like JK flip-flop, T flip flop is used. Unlike JK flip flop, in T flip flop, there is only single input with the clock input. The T flip flop is constructed by connecting both of the inputs of JK flip flop together as a single input.

The T flip flop is also known as Toggle flip-flop. These T flip-flops are able to find the complement of its state.

Truth Table:

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स्रोत : www.javatpoint.com

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Mohammed 1 month ago

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