Please tell us where you read or heard it including the quote, if possible. Test Your Knowledge - and learn some interesting things along the way. Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free! What origins we bring to you and your kin. A word with surprisingly literal origins. Do you feel lucky? How we chose 'justice'. And is one way more correct than the others? How to use a word that literally drives some people nuts. The awkward case of 'his or her'. Identify the word pairs with a common ancestor. Can you spell these 10 commonly misspelled words?
Flip-flop (electronics)
Build a city of skyscrapers—one synonym at a time. Other Words from flip-flop Synonyms Learn More about flip-flop. Other Words from flip - flop flip-flop intransitive verb. Synonyms for flip-flop Synonyms about-face , about-turn [ British ] , reversal , turnabout , turnaround , U-turn , volte-face Visit the Thesaurus for More. First Known Use of flip - flop , in the meaning defined at sense 1. Learn More about flip - flop. Share flip - flop. Resources for flip - flop Time Traveler!
- Diary of a Painted Lady.
- SR Flip-Flop?
- Nutritional Disorders in Poultry farms (Poultry And Rabbit Medicine Book 1)!
- Modern Electro-Plating!
- Voices Behind Closed Doors - Baghdad.
- How to Hold in Pee when You Cant Use the Bathroom.
Explore the year a word first appeared. Dictionary Entries near flip - flop flip coil flipe flip-flap flip-flop flip-flop circuit flip glass flip jump. Statistics for flip - flop Look-up Popularity. Otherwise, operation is identical to that of the SR latch. Historically, SR -latches have been predominant despite the notational inconvenience of active-low inputs. From the teaching point of view, SR latches realised as a pair of cross-coupled components transistors, gates, tubes, etc.
A didactically easier to understand model uses a single feedback loop instead of the cross-coupling. The JK latch is much less frequently used than the JK flip-flop. The JK latch follows the following state table:. Hence, the JK latch is an SR latch that is made to toggle its output oscillate between 0 and 1 when passed the input combination of Latches are designed to be transparent. That is, input signal changes cause immediate changes in output. Additional logic can be added to a simple transparent latch to make it non-transparent or opaque when another input an "enable" input is not asserted.
When several transparent latches follow each other, using the same enable signal, signals can propagate through all of them at once. However, by following a transparent-high latch with a transparent-low or opaque-high latch, a master—slave flip-flop is implemented. With E low enable false the latch is closed opaque and remains in the state it was left the last time E was high.
The enable input is sometimes a clock signal , but more often a read or write strobe. When the enable input is a clock signal, the latch is said to be level-sensitive to the level of the clock signal , as opposed to edge-sensitive like flip-flops below. This latch exploits the fact that, in the two active input combinations 01 and 10 of a gated SR latch, R is the complement of S.
The input NAND stage converts the two D input states 0 and 1 to these two input combinations for the next SR latch by inverting the data input signal.
Flip Flop | Basics, Overview, Truth Table & Various Types
The low state of the enable signal produces the inactive "11" combination. Thus a gated D-latch may be considered as a one-input synchronous SR latch. This configuration prevents application of the restricted input combination. It is also known as transparent latch , data latch , or simply gated latch. It has a data input and an enable signal sometimes named clock , or control. The word transparent comes from the fact that, when the enable input is on, the signal propagates directly through the circuit, from the input D to the output Q.
Gated D-latches are also level-sensitive with respect to the level of the clock or enable signal.
Latches are available as integrated circuits , usually with multiple latches per chip. For example, 74HC75 is a quadruple transparent latch in the series. The classic gated latch designs have some undesirable characteristics.
The input-to-output propagation may take up to three gate delays. The input-to-output propagation is not constant — some outputs take two gate delays while others take three. Designers looked for alternatives. It requires only a single data input, and its output takes a constant two gate delays. In addition, the two gate levels of the Earle latch can, in some cases, be merged with the last two gate levels of the circuits driving the latch because many common computational circuits have an OR layer followed by an AND layer as their last two levels.
Merging the latch function can implement the latch with no additional gate delays. The Earle latch is hazard free. Intentionally skewing the clock signal can avoid the hazard. The D flip-flop captures the value of the D-input at a definite portion of the clock cycle such as the rising edge of the clock. That captured value becomes the Q output. At other times, the output Q does not change. Most D-type flip-flops in ICs have the capability to be forced to the set or reset state which ignores the D and clock inputs , much like an SR flip-flop.
Here is the truth table for the others S and R possible configurations:. These flip-flops are very useful, as they form the basis for shift registers , which are an essential part of many electronic devices. The advantage of the D flip-flop over the D-type "transparent latch" is that the signal on the D input pin is captured the moment the flip-flop is clocked, and subsequent changes on the D input will be ignored until the next clock event. An exception is that some flip-flops have a "reset" signal input, which will reset Q to zero , and may be either asynchronous or synchronous with the clock.
The above circuit shifts the contents of the register to the right, one bit position on each active transition of the clock. The input X is shifted into the leftmost bit position. The input stage the two latches on the left processes the clock and data signals to ensure correct input signals for the output stage the single latch on the right.
If the clock is low, both the output signals of the input stage are high regardless of the data input; the output latch is unaffected and it stores the previous state. If the clock signal continues staying high, the outputs keep their states regardless of the data input and force the output latch to stay in the corresponding state as the input logical zero of the output stage remains active while the clock is high.
Hence the role of the output latch is to store the data only while the clock is low. The circuit is closely related to the gated D latch as both the circuits convert the two D input states 0 and 1 to two input combinations 01 and 10 for the output SR latch by inverting the data input signal both the circuits split the single D signal in two complementary S and R signals. The role of these latches is to "lock" the active output producing low voltage a logical zero ; thus the positive-edge-triggered D flip-flop can also be thought of as a gated D latch with latched input gates.
A master—slave D flip-flop is created by connecting two gated D latches in series, and inverting the enable input to one of them. It is called master—slave because the second latch in the series only changes in response to a change in the first master latch. For a positive-edge triggered master—slave D flip-flop, when the clock signal is low logical 0 the "enable" seen by the first or "master" D latch the inverted clock signal is high logical 1. This allows the "master" latch to store the input value when the clock signal transitions from low to high. As the clock signal goes high 0 to 1 the inverted "enable" of the first latch goes low 1 to 0 and the value seen at the input to the master latch is "locked".
Nearly simultaneously, the twice inverted "enable" of the second or "slave" D latch transitions from low to high 0 to 1 with the clock signal. This allows the signal captured at the rising edge of the clock by the now "locked" master latch to pass through the "slave" latch. When the clock signal returns to low 1 to 0 , the output of the "slave" latch is "locked", and the value seen at the last rising edge of the clock is held while the "master" latch begins to accept new values in preparation for the next rising clock edge.
By removing the leftmost inverter in the circuit at side, a D-type flip-flop that strobes on the falling edge of a clock signal can be obtained. This has a truth table like this:. Flip-Flops that read in a new value on the rising and the falling edge of the clock are called dual-edge-triggered flip-flops. Such a flip-flop may be built using two single-edge -triggered D-type flip-flops and a multiplexer as shown in the image. An efficient functional alternative to a D flip-flop can be made with dynamic circuits where information is stored in a capacitance as long as it is clocked often enough; while not a true flip-flop, it is still called a flip-flop for its functional role.
While the master—slave D element is triggered on the edge of a clock, its components are each triggered by clock levels. The "edge-triggered D flip-flop", as it is called even though it is not a true flip-flop, does not have the master—slave properties. Edge-triggered D flip-flops are often implemented in integrated high-speed operations using dynamic logic. This means that the digital output is stored on parasitic device capacitance while the device is not transitioning. This design of dynamic flip flops also enables simple resetting since the reset operation can be performed by simply discharging one or more internal nodes.
A common dynamic flip-flop variety is the true single-phase clock TSPC type which performs the flip-flop operation with little power and at high speeds. However, dynamic flip-flops will typically not work at static or low clock speeds: If the T input is high, the T flip-flop changes state "toggles" whenever the clock input is strobed. If the T input is low, the flip-flop holds the previous value. This behavior is described by the characteristic equation:. This "divide by" feature has application in various types of digital counters. To synthesize a D flip-flop, simply set K equal to the complement of J.
Similarly, to synthesize a T flip-flop, set K equal to J.
SR Flip Flop
The JK flip-flop is therefore a universal flip-flop, because it can be configured to work as an SR flip-flop, a D flip-flop, or a T flip-flop. The input must be held steady in a period around the rising edge of the clock known as the aperture. Imagine taking a picture of a frog on a lily-pad. If you take a picture of the frog as it jumps into the water, you will get a blurry picture of the frog jumping into the water—it's not clear which state the frog was in.
But if you take a picture while the frog sits steadily on the pad or is steadily in the water , you will get a clear picture. In the same way, the input to a flip-flop must be held steady during the aperture of the flip-flop. Setup time is the minimum amount of time the data input should be held steady before the clock event, so that the data is reliably sampled by the clock. Hold time is the minimum amount of time the data input should be held steady after the clock event, so that the data is reliably sampled by the clock. Aperture is the sum of setup and hold time.
The data input should be held steady throughout this time period. Recovery time is the minimum amount of time the asynchronous set or reset input should be inactive before the clock event, so that the data is reliably sampled by the clock. The recovery time for the asynchronous set or reset input is thereby similar to the setup time for the data input.
Removal time is the minimum amount of time the asynchronous set or reset input should be inactive after the clock event, so that the data is reliably sampled by the clock. The removal time for the asynchronous set or reset input is thereby similar to the hold time for the data input. Short impulses applied to asynchronous inputs set, reset should not be applied completely within the recovery-removal period, or else it becomes entirely indeterminable whether the flip-flop will transition to the appropriate state.
This second situation may or may not have significance to a circuit design. The differentiation offers circuit designers the ability to define the verification conditions for these types of signals independently. Flip-flops are subject to a problem called metastability , which can happen when two inputs, such as data and clock or clock and reset, are changing at about the same time. When the order is not clear, within appropriate timing constraints, the result is that the output may behave unpredictably, taking many times longer than normal to settle to one state or the other, or even oscillating several times before settling.
Flip flop v/s Latch
Theoretically, the time to settle down is not bounded. In a computer system, this metastability can cause corruption of data or a program crash if the state is not stable before another circuit uses its value; in particular, if two different logical paths use the output of a flip-flop, one path can interpret it as a 0 and the other as a 1 when it has not resolved to stable state, putting the machine into an inconsistent state. The metastability in flip-flops can be avoided by ensuring that the data and control inputs are held valid and constant for specified periods before and after the clock pulse, called the setup time t su and the hold time t h respectively.
These times are specified in the data sheet for the device, and are typically between a few nanoseconds and a few hundred picoseconds for modern devices. Depending upon the flip-flop's internal organization, it is possible to build a device with a zero or even negative setup or hold time requirement but not both simultaneously. Unfortunately, it is not always possible to meet the setup and hold criteria, because the flip-flop may be connected to a real-time signal that could change at any time, outside the control of the designer.
In this case, the best the designer can do is to reduce the probability of error to a certain level, depending on the required reliability of the circuit. One technique for suppressing metastability is to connect two or more flip-flops in a chain, so that the output of each one feeds the data input of the next, and all devices share a common clock. With this method, the probability of a metastable event can be reduced to a negligible value, but never to zero.
The probability of metastability gets closer and closer to zero as the number of flip-flops connected in series is increased.