#Latch is a logic circuit and a fundamental building block of #digitalelectronics. Latches are sequential logic circuits that are used to store Binary information. Latches have two states, are High and Low states. As the Latches have two states they are also referred to as #Multivibrators.
Latches are level-sensitive which operate with enable signal. Latches store single-bit data until the device is set to one (1). Latches are widely used in computing as well as data storage.
Types of latches:
There are different types of Latches like SR Latch, Gated SR Latch, D Latch, Gated D Latch, JK Latch, and T Latch.
SR Latch:
SR Latch is a Set- Reset Latch. It is an #asynchronous device i.e., it works separately for control signals depending upon the S and R states. SR latch can be made using either two #NAND or two #NOR gates.
Circuit Diagram:
The circuit diagram of SR Latch is given below
Truth Table of SR Latch:
The truth table of SR Latch is given below
Set(S) Reset(R) Q (Q)'
0 0 Latch Latch
0 1 0 1
1 0 1 0
1 1 0 0
Gated SR Latch:
Gated SR Latch is a special type of SR Latch with three inputs Set, Reset and Enable. The Operation of this latch is enabled by the enable input. As it requires enable signal for its operation it is sometimes referred to as #synchronous SR latch.
Circuit Diagram:
The circuit diagram of the Gated SR Latch is given below
Truth Table of Gated SR Latch:
The truth table of Gated SR Latch is given below
E or CLK Set(S) Reset(R) Q (Q)'
0 0 0 Latch Latch
0 0 1 Latch Latch
0 1 0 Latch Latch
0 1 1 Latch Latch
1 0 0 Latch Latch
1 0 1 0 1
1 1 0 1 0
1 1 1 0 0
D Latch:
D Latch is a Data Latch that has only one input. The output of the D latch is the same as the Data input.
Circuit Diagram:
The circuit diagram of D Latch is given below
Truth Table of D Latch:
The Truth table of D Latch is given below
Data(D) Q (Q)'
0 0 1
1 1 0Gated D Latch:
The gated D Latch has two inputs, they are data and enable. The output of the Gated D Latch is the same as data input if the enable is set to one else there is no change in the output.
The circuit diagram of Gated D Latch is given below
Circuit Diagram:
Truth Table of Gated D Latch:
D latch truth table is given below
Enable(E) Data(D) Q (Q)'
0 0 Latch Latch
0 1 Latch Latch
1 0 0 1
1 1 1 0 JK Latch:
JK Latch is similar to RS latch which has two inputs, J and K. The difference between RS latch and JK Latch is that JK Latch has feedback from output to input while there is no feedback in the RS Latch.
Circuit Diagram:
The output of the JK Latch Toggles when both the inputs are high
T Latch:
T Latch is designed by shorting the inputs J and K of JK Latch. When the input of T Latch is high, the output toggles.
Circuit Diagram:
The circuit diagram of T Latch is given below
Advantages of Latches
The advantages of latches are
Latches are flexible to design compared to flipflops.
Latches are small and occupy less area.
Latches use less power.
Latches don't require a clock signal.
Disadvantages of Latches
The disadvantages of latches are:
There is a chance to affect to race around conditions.
Analysis of Latches is difficult as they are level sensitive.
Applications of Latches
Latches are used in digital circuits. Some of the applications of Latches are
They are memory elements that are used to store information in the form of bits.
They are used in computing.
They are used in circuits like power gating and the clock as storage devices.
See Also:
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Written By: Nagapuri Swathi