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Flip Flops

The document discusses different types of flip-flops that are used as memory elements in sequential circuits. The basic unit for storing information in a sequential system is the flip-flop, which has two stable output states of either 0V or 5V. Common types of flip-flops include the RS, D, JK, and T flip-flops, which differ in the number of inputs and how the inputs affect the output state. Flip-flops are used to retain information from previous states in a sequential system.

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439 views18 pages

Flip Flops

The document discusses different types of flip-flops that are used as memory elements in sequential circuits. The basic unit for storing information in a sequential system is the flip-flop, which has two stable output states of either 0V or 5V. Common types of flip-flops include the RS, D, JK, and T flip-flops, which differ in the number of inputs and how the inputs affect the output state. Flip-flops are used to retain information from previous states in a sequential system.

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© © All Rights Reserved
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Flip-Flops

To have a sequential system, we must know what


has happened in the past. Therefore, we must have
storage device to retain this information until we
are ready to use it.
The basic unit for this storage is the flip-flop it is the
device with tow stable states, i.e. its output is either
0 V dc (logic 0) or +5V dc (logic 1)
Flip-Flops

Inputs
Combinational outputs
circuit

Memory element

Sequential circuit
Flop-Flips

There are many types of flip-flops. the major


differences various types of flip-flops are in the
number of inputs they process and manner in
which the inputs affect their output state.

The most common types of flip-flops are :


RS flip-flop

The simplest type of flip-flop is the reset-set (RS)


flip-flop. It can be constructed form either two
NAND gates or two NOR gates.
R-S Flip-Flop

R (Reset)
1 Q

2 Q
S (Set)
R-S Truth Table

R S Q Q State
0 0 NC NC No change
0 1 1 0 Set
1 0 0 1 Reset
1 1 invalid invalid

R Q

S Q

Symbol
S (Set)
1

2
R (Reset)
RS Truth table

R S Qn+1 Q
1 1 NC (Qn ) NC
1 0 1 0
0 1 0 1
0 0 invalid
High Edge Clocked RS Flip-Flop

R
Q

Clock

Q
S
High Edge

Low Edge
Clocked RS

CLK S R Q Q---
0 0 0 NC NC
0 1 0 NC NC
1 0 1 0 1
1 1 1 invalid
1 1 0 1 0
1 0 1 0 1
1 0 0 NC NC
Low Edge RS Flip-Flop

Clock
D Flip-Flop
D
Q
D
Clock Flip-Flop
Q

D F.F Truth Table


Logic Symbol
CLK D Qn+1 Q
0 1 On Qn
1 1 1 0
1 0 0 1
JK Flip-Flop

K
Q

Clock

Q
J
J JK Q
Flip-Flop
CLK
K Q
Truth Table
Logic Symbol
CLK J K Qn+1
0 1 0 Qn
1 1 0 1
1 0 1 0
1 1 1 Toggle
T Flip-Flop

Logic 1 (VCC)

Clock
Preset

Clear

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