Chapter 6 register

CHAPTER 6 : REGISTER
By:
Siti Sabariah Hj. Salihin
Electrical Engineering Department

EE 202 : DIGITAL ELECTRONICS

1

CHAPTER 202 ::DIGITAL ELECTRONICS
6 REGISTER
EE
Course Learning Outcomes, CLO
Upon completion of the course, students should be able to:
� CLO 3 : Draw logics diagrams, truth tables and timing diagrams for

all common flip flops and use these to implement sequential logic
circuits correctly.


CHAPTER 6 : REGISTER

Upon completion of this Chapter, students should be able to
to:
6.1 Understand the concepts and applications of registers and shift
Registers.
6.1.1 Classify the Shift Register according to the methods of data
input/output: SISO, PIPO, SIPO, PISO.
6.1.2 State the applications of Shift registers listed in 6.1.1
6.1.3 Interpret the Operation and circuit of Shift Register listed in 6.1.1
6.1.4 Interpret the Operation and application of an integrated circuits
Shift Register listed in 6.1.1
6.1.5 Explain the application of Shift Register as arithmetic circuits:
6.1.6 Explain the operations and application of Ring Counters and
Johnson Counter

Introduction – Shift Register
� Shift registers are constructed using several flipflop, connected in such a way to STORE and
TRANSFER/ Shift digital data.
� Basically, D flip-flop is used. The input data
(either ‘0’ or ‘1’) is applied to the D terminal and
the data will be stored at Q during
positive/negative-edge transition of the clock
pulse.
D Q

Q

4

Shift Register
� One D FF is used to store 1-bit of data. Thus, the
number of flip-flops used is the same with the
number of bit stored.
� Shift register mean that the data in each FF can be
transferred/move to other FF upon edge triggering
of the clock signal.
� Four types of data movement in shift register are:� Parallel in / parallel out (PIPO)
� Serial in / serial out (SISO)
� Parallel in / serial out (PISO)
� Serial in / parallel out (SIPO)

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� Serial Data VS Parallel Data movement

Serial

Parallel

•Movement of N-bit data
require N number of CLK
pulses. Thus, the operation is
slow.
•Only one FF is required to be
connected at the output
terminal, thus only one wire is
required.

•Require only one CLK pulse
to transfer all N-bit of data.
Thus, operation is faster than
serial.
•Required N number of
connection to the output
terminal, which is proportional
to the number of bit. Thus, too
many connection is required.


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� Flip-flop configuration for PIPO register.
D3

D2

D Q3

D1

D Q2

CP

D0

D Q1

CP

D Q0

CP

CP

CLK
Q3

Q2


Q1

Q0

7

Parallel in / parallel out (PIPO)
PIPO data movement.
CLK
D3

0

1

1

1

1

D2

0

1

0

1

0

D1

1

1

1

0

1

D0

0

0

1

0

0

Q3

0

1

0

Q2

0

0

1

1

1

0

0

Q1
Q0

0

0

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� Flip-flop connection for SISO.

1st CLK

DIN
CLK

D Q0

2nd CLK

D Q1

3rd CLK

4th CLK

D Q2

D Q3

CP

CP

CP

CP

FF0

FF1

FF2

FF3


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Serial in / serial out (SISO)
SISO data movement. Binary data 10111 is transferred!
1st

2nd

3rd

4th

5th

CLK
DATA-IN

1

0

1

1

1

Q0
Q1

Q2

Q3

10

Flip-flop connection for PISO
SHIFT/LOADD0

D1

D2

D3

Serial
data
out

D Q0
CLK

D Q1

D Q2

D Q3

CP

CP

CP

CP

FF0

FF1

FF2

FF3
11

Parallel in / serial out (PISO)
� PISO data movement.
CLK
D0

0

0

1

1

1

D1

0

1

0

1

0

D2

1

1

1

0

1

D3

1

0

0

1

1

SHIFT/
LOAD
Q3

0

1

1

0

0

1
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Integrated circuits Shift Register

Chips for shift registers
� 74164 is a 8-bit SIPO shift register

A
B
CLR

74164

CLK

Q0 Q 1 Q 2 Q3 Q 4 Q5 Q6 Q 7


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� 74165 is a 8-bit PISO register
D0 D1 D2 D3 D4 D5 D6 D7

SH/LD
SER
CLK INH

Q7
74165

Q7

CLK


14


� 74195 can be used as a 4-bit PIPO register
D0 D1 D2 D3

J
K
SH/LD

74195

CLR
CLK

Q0 Q 1 Q 2 Q 3

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Shift Register as arithmetic circuits:
� Shift Register as Divider 2 circuits

Example :
14 = 1 1 1 0
7 =0111
3.5= 3 = 00 1 1
1.5 = 1 = 0 0 0 1
Notes : Shift to RIGHT as divider 2.


Shift Register as arithmetic circuits:
� Shift Register as Multiplier 2 circuits

Example :
8
16
32
64

= 1100
= 10000
= 100000
= 1000000

Notes : Shift to LEFT as Multiplier 2.


Shift Register Counters
� A shift register counter is a shift register whose
output being fed back (connected back) to the
serial input. This shift register would count the
state in a unique sequence!
� Two types of shift register counter:� The ring counter
� The Johnson counter


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Ring Counter (continue)
�Ring counters are used to
construct “One-Hot”
counters
�It can be constructed for any
desired MOD number
�A MOD-N ring counter uses
N flip-flops connected in the
arrangement as shown in fig.
a)
�In general ring-counter will
require more flip-flops than a
binary counter for the same
MOD number

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Ring Counter
Q3

Q2

Q1


Q0

20



21

0

0

0

1

1

0

0

0

0

1

0

0

0

0

1

0


22

� Exercise: Draw a 3 Bit Ring Counter Circuit with

initial input

010 . show a True Table until 8 clock

pulse/number sequence and draw the output waveform.
� Answer:

Discuss with Your lecturer


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Johnson Counter
Or Twisted-ring counter

�Johnson counter constructed exactly like a normal ring counter
except that the inverted output of the last flip-flop is fed back to
first flip-flop


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Johnson Counter
(Continue)


25

Johnson Counter
(Continue)

0

1

1

1

0

0

1

1

C 0

0

0

1

A

B


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REFERENCES:
1. "Digital Systems Principles And Application"
Sixth Editon, Ronald J. Tocci.
2. "Digital Systems Fundamentals"
P.W Chandana Prasad, Lau Siong Hoe,
Dr. Ashutosh Kumar Singh, Muhammad Suryanata.

Download Tutorials Chapter 6: Register
@ CIDOS
http://www.cidos.edu.my
http://www.sabariahsalihin.com


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