This document discusses different types of latches used in computing and data storage. It describes latches as basic bistable elements that use feedback to retain information. The document outlines several types of latches including SR latches, D latches, JK latches, and T latches. It explains their circuit designs and behaviors. Examples are provided of how latches are used to encode binary data and in synchronous and asynchronous systems. Advantages of latches like flexibility and power efficiency are contrasted with disadvantages like potential race conditions and metastability issues.

1. LATCHES
Presented by
MD.SAYED HASAN
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2. CONTENT
 What is latches
 Label sensitive device
 MUX based Latches
 Types of latches
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3. WHAT IS LATCHES
 One Bit memory cell
 Basic Bistable element
 Feedback path to retain the information
Figure 1(a) & (b): Bistable element and analog analysis
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4. LABEL SENSITIVE DEVICE
Latch
D
CLK
Q
D Q
CLK
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5. MUX BASED LATCHES
CLK CLK
D D
QQ 0
1
1
0
Figure 2(a): Negative static latches
Negative latch input D is
selected when the CLK is 0
Figure 2(b):Positive static latch
CLK is 1, positive latch
transparent
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6. TYPES OF LATCHES
SR Latches
D Latches
T Latch
J-K Latch
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7. S-R LATCH
S R Q Not Q
0 0 1
0
0
1
0 1 0 1
1 0 1 0
1 1 0 0
A set/reset latches is an offbeat circuit,
which depends on the condition of the S&R inputs
Figure 3: SR latch 7

8. D LATCHES
Enable D (Data) Next State Qn+1 State
1 0 0 Reset
1 1 1 Set
0 X Qn No change
 Simple extension of the
gated SR latch
 Removes the possibility
of invalid input states
Figure 4: D latch
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9. JK LATCH & T LATCH
Enable
 JK latch, as well as RS latch, is
similar.
 Unclear state has been removed
 The output feedback toward inputs,
which is not present in the RS-latch
 The T latch can be formed
whenever the JK latch inputs are
shorted
 If input of the latch is high, the
output will be toggled.
Figure 6(a) & 9(b): JK latch and T latch
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10. APPLICATION
 Keep the conditions of the bits to encode binary
 Widely used in computing as well as data storage
 D latches are applicable for asynchronous systems
 Data latches are used in synchronous two-phase systems for
reducing the transit count.
These are the building blocks for sequential circuit.
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11. ADVANTAGES & DISADVANTAGES
 Very flexible compare Flip Flop
 Latches utilize less power
 Small and occupies less area
 High-speed circuit because asynchronous design no CLK
 Chance to affect to
race conditions.
 Chance of meta-stability
 Difficult for testing and analyzing
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