8/10/2019 Encoder & Decoder Ppt

1/36

Alpha Breathing

8/10/2019 Encoder & Decoder Ppt

2/36

Evocation

8/10/2019 Encoder & Decoder Ppt

3/36

ENCODER & DECODER

8/10/2019 Encoder & Decoder Ppt

4/36

INTRODUCTION

ENCODER- a digital circuit that producesa binary output code depending on

which of its inputs are activated.

DECODER- a digital circuit that converts

an input binary code into a single

numeric output.

8/10/2019 Encoder & Decoder Ppt

5/36

ENCODERS AND DECODERS

REPRESENTATION

A0

A1

A2

A3

A4

A5

A6

A7

ENCODER

O0

O1

O2

A0

A1

A2

O0

O1

O2

O3

O4

O5

O6

O7

DECODER

8/10/2019 Encoder & Decoder Ppt

6/36

THE 8421 BCD CODE

BCD stands for Binary-Coded Decimal.

A BCD number is a four-bit binary group thatrepresents one of the ten decimal digits 0

through 9.Example:

Decimal number 4926 4 9 2 6

8421 BCD coded number 0100 1001 0010 0110

8/10/2019 Encoder & Decoder Ppt

7/36

ELECTRONIC ENCODER -

DECIMAL TO BCD

0

Decimal

to

BCD

Encoder

BCD output

Decimal input0 0 0 0

5

0 1 0 1

7

0 1 1 1

3

0 0 1 1

Encoders are available in IC form.

This encoder translates from

decimal input to BCD output.

8/10/2019 Encoder & Decoder Ppt

8/36

10 line to 4 line Encoder

8/10/2019 Encoder & Decoder Ppt

9/36

8/10/2019 Encoder & Decoder Ppt

10/36

ENCODER

1248DECIMAL BINARY (BCD)

95V

85V

7 5V

65V

5 5V

4 5V3 5V

2 5V

15V

74147I9I8I7I6I5I4

I3I2I1

A0A1A2A3

10 line to 4 line Encoder

8/10/2019 Encoder & Decoder Ppt

11/36

Decoder

Accepts a value and decodes it

Output corresponds to value of ninputs

Consists of: Inputs (n)

Outputs (2n, numbered from 02n- 1)

Selectors / Enable (active high or active low)

8/10/2019 Encoder & Decoder Ppt

12/36

The truth table of 2-to-4

Decoder

8/10/2019 Encoder & Decoder Ppt

13/36

2-to-4 Decoder

8/10/2019 Encoder & Decoder Ppt

14/36

2-to-4 Decoder

8/10/2019 Encoder & Decoder Ppt

15/36

The truth table of 3-to-8

Decoder

A2 A1 A0 D0 D1 D2 D3 D4 D5 D6 D7

0 0 0 1

0 0 1 1

0 1 0 1

0 1 1 1

1 0 0 1

1 0 1 1

1 1 0 1

1 1 1 1

8/10/2019 Encoder & Decoder Ppt

16/36

3-to-8 Decoder

8/10/2019 Encoder & Decoder Ppt

17/36

3-to-8 Decoder with Enable

8/10/2019 Encoder & Decoder Ppt

18/36

Decoder Expansion

Decoder expansion Combine two or more small decoders with

enable inputs to form a larger decoder

3-to-8-line decoder constructed from two 2-to-4-line decoders The MSB is connected to the enable inputs

if A2=0, upper is enabled; if A2=1, lower is

enabled.

8/10/2019 Encoder & Decoder Ppt

19/36

Decoder Expansion

8/10/2019 Encoder & Decoder Ppt

20/36

Combining two 2-4 decoders to form

one 3-8 decoder using enable switch

The highest bit is used for the enables

8/10/2019 Encoder & Decoder Ppt

21/36

How about 4-16 decoder

Use how many 3-8 decoder?

Use how many 2-4 decoder?

8/10/2019 Encoder & Decoder Ppt

22/36

Encoders

Perform the inverse operation of a

decoder

2n(or less) input lines and n output lines

8/10/2019 Encoder & Decoder Ppt

23/36

Encoders

8/10/2019 Encoder & Decoder Ppt

24/36

Encoders with OR gates

8/10/2019 Encoder & Decoder Ppt

25/36

Encoders

Perform the inverse operation of a decoder

2n(or less) input lines and n output lines

8/10/2019 Encoder & Decoder Ppt

26/36

Accepts multiple values and encodes them

Works when more than one input is active

Consists of:

Inputs (2n)

Outputs

when more than one output is active, setsoutput to correspond to highest input

V (indicates whether any of the inputs areactive)

Selectors / Enable (active high or active low)

Priority Encoder

8/10/2019 Encoder & Decoder Ppt

27/36

D3 D2 D1 D0 A1 A0 V

0 0 0 0 x X 0

0 0 0 1 0 0 1

0 0 1 0 0 1 1

0 0 1 1 0 1 1

0 1 0 0 1 0 1

0 1 0 1 1 0 1

0 1 1 0 1 0 1

0 1 1 1 1 0 1

1 0 0 0 1 1 1

1 0 0 1 1 1 1

1 0 1 0 1 1 1

1 0 1 1 1 1 1

1 1 0 0 1 1 1

1 1 0 1 1 1 1

1 1 1 0 1 1 1

1 1 1 1 1 1 1

8/10/2019 Encoder & Decoder Ppt

28/36

Priority Encoder

8/10/2019 Encoder & Decoder Ppt

29/36

Puzzles

8/10/2019 Encoder & Decoder Ppt

30/36

8/10/2019 Encoder & Decoder Ppt

31/36

8/10/2019 Encoder & Decoder Ppt

32/36

8/10/2019 Encoder & Decoder Ppt

33/36

33

Mind Map Encoder and Decoder

8/10/2019 Encoder & Decoder Ppt

34/36

Encoder Applications

Applications

Priority Encoder

Mind Map Encoder and Decoder

Decoder2 to 4 line

decoder

3 to 8 line

Decoder

Decimal BCD

to encoder

TruthtableBlockdiagram Logicdiagram

Code

conversion

Octal to binary

encoder

Hexadecimal to

binary encoder

Counter system

A to D counter

Display system

Block

diagramTruth

table

Logic

diagram

8/10/2019 Encoder & Decoder Ppt

35/36

Summary

Encoders & Decoders

Truth table

K-Map

Logic Diagram

8/10/2019 Encoder & Decoder Ppt

36/36

36