The circuit utilized to do such an operation is referred to as a "latch circuit." It is a self-maintaining circuit in the sense that it maintains its electrified state until another input is received. The three most common types of latch circuits are the magnetic latch, electric latch, and thermal latch.
In a magnetic latch, the action of a magnet is used to maintain power on or off. Magnetic latches are usually found in power supplies where the output can be maintained even when power is removed from the supply itself. Magnetic latches are also used in programmable logic devices (PLDs) to hold their configuration bits after power down.
Electric latches use a solid-state switch to maintain power on or off. They are commonly used in applications where there is a need for a fast-acting signal line to which both voltage and ground are given. For example, this type of latch could be used to control power to a load such as an LED array when the master device does not give a strong positive or negative pulse.
Thermal latches work on the basis of resistance changing states due to heat. The most common form of thermal latch uses a bistable alloy wire whose resistance changes depending on whether it is hot or cold.
Latches also add memory to capture and store the input value at some point in time (memory). A third signal, control, causes this latching behavior. When control goes high, the output becomes stable and will not change unless control comes back low. This is called "latch mode". When control stays low, the output remains unstable and can change any time it wants.
In addition to capturing values, latches can be used to provide synchronizing signals. If control is already high when data in comes available on data out, then data out will immediately contain the most recent data from memory. Otherwise it would have to wait until control went down before writing its value to data out.
Finally, latches can be used as registers. Data out will contain the same value as data in whenever control is high. If control needs to store something for later use, then it must go down once so that other circuits can use data out while it's being stored.
Latches can be simple or complex. Simple latches have only two states: latch or non-latch. They cannot retain information other than whether or not control is high at a given moment. To capture the value of data inputs you need a more complex latch called a flip-flop.
A latch is a type of logic circuit in digital electronics that is also known as a bistable-multivibrator. Because it has two stable modes, active high and active low, it functions as a storage device by storing data via a feedback lane. The term "latch" comes from the fact that it has two stable states, like a door or gate latch.
Latch circuits are used where memory retention is not critical, such as for internal state machines. They can be simple to implement, for example using cross-coupled CMOS inverters, or more complex, such as ECL gates with current steering. Since only two possible states exist, there is no need for multiplexers or other control circuitry to determine which one of several stored values should be output.
Latches are commonly used to store data in devices such as microprocessors where memory elements must hold their value after being set once. Other uses include holding audio signals while keyed transistors switch them into another path, such as holding the left channel of a stereo signal off while the right channel is switched on, and then holding that signal level until the next time the speaker is turned on. This is useful for preventing distortion when changing signal levels rapidly.
Digital cameras use similar technology to retain images captured during exposure periods even when the power is removed.
When the clock signal is high, a latch allows data to flow from input to output and then recalls the data when the clock signal is low. This action occurs repeatedly until either input data is sent or reset is called.
A latch is a subset of a logical circuit. The latches have two stable states: low and high. Because of these states, latches are also known as bistable-multivibrators. A latch is a data storage device that uses the feedback lane to store data. Locks and keys depend on latches for their operation. For example, a car lock depends on a latch to keep its engine turned off even when the key is removed.
Latches are widely used in hardware design because they can be easily implemented in silicon technology. There are several types of latches depending on how they are initialized and what type of information they retain.
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A flip-flop or latch is a circuit in electronics that has two stable states and may be used to store state information as a bistable multivibrator. Signals provided to one or more control inputs can cause the circuit to change state, and it will have one or two outputs. The term is applied to any device which has this property.
Latches are commonly used to implement memory elements such as registers and memory buffers. They may also be used to synchronize two processes or signals. For example, one process may lock itself in a particular state by setting the control input to high, while another process uses the output signal as a clock to determine when to start its own operation. Locks are often used in security systems to prevent multiple processes from running simultaneously.
The ability of a latch to retain its current state as power is removed from the circuit is useful for battery-powered devices such as microcontrollers. If a latch's power source fails, then it will retain its last state which could potentially be a valid state for the system.
In digital logic circuits, the term "latch" is also used to describe a specific type of logic gate which has three stable states: 0, 1, and X. The state X cannot appear on output pins unless it is the result of a prior transition (i.e., not loaded from an external signal). Thus, latches can hold their previous state during standby conditions.