There are two types of circuit namely combinational circuit ( no memory elements to store past or future values which may affect the output ,only present input changes the output ) and sequential circuit ( memory element like flip-flop are involves which store data and changes the output ).
Latches and flip-flops are the basic elements for storing information. They 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. One latch or flip-flop can store one bit of information.
The interconnection of digital logic gates to produce a memory device leads to applications such as switch debounce circuits, shift registers and counters, etc. Also, memory elements made from bistable latches form the basis of accumulators and registers on which a computer, or micro-controller, does its complex arithmetic.
The main difference between latches and flip-flops is that for latches, their outputs are constantly affected by their inputs as long as the enable signal is asserted. In other words, when they are enabled, their content changes immediately when their inputs change. Flip-flops, on the other hand, have their content change only either at the rising or falling edge of the enable signal. This enable signal is usually the controlling clock signal. After the rising or falling edge of the clock, the flip-flop content remains constant even if the input changes.
What is a Flip-flop?
A flip-flop is a device which stores a single bit (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 state, 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.
Types of Flip-flops
There are basically four different types of flip flops and these are:
- Set-Reset (SR) flip-flop or Latch
- JK flip-flop
- D (Data or Delay) flip-flop
- T (Toggle) flip-flop
What You Need To Know About Flip-Flop
- A flip flop is a combination of latches and a clock signal which changes its output on the triggering edge of the clock pulse. If clock pulse is not applied even though if we change any input in the flip flop there will be no change in output unlike latches.
- Flip flops are also building blocks of sequential circuits. But, these can be built from the latches.
- Flip flop continuously checks its inputs and changes its output correspondingly only at times determined by clocking signal.
- A flip flop is edge triggered circuit which means it changes its state either on the positive triggered edge or on the negative triggered edge of clock pulse.
- A Flip flop requires more power consumption in the circuit.
- A flip flop is synchronous which means change of output depends on the enable signal(more often a clock signal)
- There are no problems of glitches in flip flop since it is synchronous in nature.
- The transistor count in latch is less as compared to Flip flop.
- Flip flop is sensitive to a single change, they can transfer data only at the single instant and data cannot be changed until next signal change. Flip flops are used as a register.
- Flip flop uses more number of gates as compared to latch.
- It works on the basis of clock pulses.
- Flip flops are known as series logic circuitry since their current output depend on the applied input, applying input and obtained output.
- Due to clock signal, operation of the Flip-flops is comparatively slower to that of the latches.
- Flip-flops are complex to design because they have a clock signal and it has to be carefully routed.
- Register circuit can be made using Flip Flop circuits.
- The working flip flop depends on the binary input as well as a clock signal.
- The different types of Flip flops are, SR-Flip Flop, JK-Flip Flop, D-Flip Flop, T-Flip Flop.
What is a Latch?
A Latch is a special type of logical circuit. The latches have low and high two stable states. Due to these states, latches also refer to as bistable-multivibrators. A latch is a storage device that holds the data using the feedback lane. The latch stores 1 -bit until the device set to 1. The latch changes the stored data and constantly trials the inputs when the enable input set to 1. Based on the enable signal, the circuit works in two states. When the enable input is high, then both the inputs are low, and when the enable input is low, both the inputs are high.
Types of Latches
There are various types of latches used in digital circuits which are as follows:
- SR Latch
- Gated S-R Latch
- D latch
- Gated D Latch
- JK Latch
- T Latch.
What You Need To Know About Latch
- A latch is a circuit which changes its output as soon as there is any change in the input.
- Latches are building blocks of sequential circuits and these can be built from logic gates.
- Latch continuously checks its inputs and changes its output correspondingly.
- A latch is level triggered circuit which means that the output of the present state and input of the next state depends on the level that is binary input 1 or 0.
- A latch uses less power consumption for the circuit.
- A latch is asynchronous in nature which means output changes spontaneously.
- A latch is more prone to problems of glitches due to instantaneous change in input.
- The transistor count in latch is less as compared to Flip flop.
- The latch is sensitive to the duration of the pulse and can send or receive the data when the switch is on
- A latch uses lesser number of gates.
- It is based on the enable function input.
- The latches are series logic circuitry, also referred to as bistable multi vibrator since it has 2 stable states. It is constructed with the use of logic gates and used for storage of information in the form of binary numbers.
- Operation of the latch is faster as they do not have to wait for any clock signal.
- Latches are simpler to design as there is no clock signal (no careful routing of the clock signal is required).
- Register circuits cannot be made using Latches because latch does not need any clock signal.
- The working of Latches depends on the binary inputs only.
- The different types of latches are, D-Latch, SR-Latch, JK-Latch, T-Latch.
Difference Between Flip-flop And Latch In Tabular Form
| BASIS OF COMPARISON | FLIP-FLOP | LATCH |
| Description | A flip flop is a combination of latches and a clock signal which changes its output on the triggering edge of the clock pulse. | A latch is a circuit which changes its output as soon as there is any change in the input. |
| Construction | Flip flops are also building blocks of sequential circuits. But, these can be built from the latches. | Latches are building blocks of sequential circuits and these can be built from logic gates. |
| Function | Flip flop continuously checks its inputs and changes its output correspondingly only at times determined by clocking signal. | Latch continuously checks its inputs and changes its output correspondingly. |
| Circuit Trigger | A flip flop is an edge triggered circuit which means it changes its state either on the positive triggered edge or on the negative triggered edge of clock pulse. | A latch is a level triggered circuit which means that the output of the present state and input of the next state depends on the level that is binary input 1 or 0. |
| Power Consumption | A Flip flop requires more power consumption in the circuit. | A latch uses less power consumption for the circuit. |
| Nature | A flip flop is synchronous which means change of output depends on the enable signal(more often a clock signal) | A latch is asynchronous in nature which means output changes spontaneously. |
| Glitches | There are no problems of glitches in flip flop since it is synchronous in nature. | A latch is more prone to problems of glitches due to instantaneous change in input. |
| Transition Count | The transistor count in latch is less as compared to Flip flop. | The transistor count in latch is less as compared to Flip flop. |
| Sensitivity | Flip flop is sensitive to a single change, they can transfer data only at the single instant and data cannot be changed until next signal change. | The latch is sensitive to the duration of the pulse and can send or receive the data when the switch is on |
| Number of Logic Gates | Flip flop uses more number of gates as compared to latch. | A latch uses lesser number of gates. |
| Basis | It works on the basis of clock pulses. | It is based on the enable function input. |
| Alternative Name | Flip flops are known as series logic circuitry. | The latches are series logic circuitry, also referred to as bistable multi vibrator since it has 2 stable states. |
| Operation Speed | Due to clock signal, operation of the Flip-flops is comparatively slower to that of the latches. | Operation of the latch is faster as they do not have to wait for any clock signal. |
| Designing | Flip-flops are complex to design because they have a clock signal and it has to be carefully routed. | Latches are simpler to design as there is no clock signal (no careful routing of the clock signal is required). |
| Register | Register circuit can be made using Flip Flop circuits. | Register circuits cannot be made using Latches because latch does not need any clock signal. |
| Working | The working flip flop depends on the binary input as well as a clock signal. | The working of Latches depends on the binary inputs only. |
| Types | The different types of Flip flops are, SR-Flip Flop, JK-Flip Flop, D-Flip Flop, T-Flip Flop. | The different types of latches are, D-Latch, SR-Latch, JK-Latch, T-Latch. |
Summary
Flip-flops can be with clock and without clock. One with clock produces change in the output only when it receives the clock. That is suppose if you make some changes at the input, those changes won’t reflect at the output unless it receives appropriate clock.
Latches are flip flops without clock. They are named so because since there is no clock, suppose you make some changes at the input, the flip-flop quickly Latches to the required output or produces the required output without needing to wait for any other signal.