Teknik Digital

Zulhelman

Encoding, Decoding, andSeven-Segment Displays

Encoder/Decoder Vocabulary

ENCODER- a digital circuit that produces a 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.

ENCODERS AND DECODERSA 0A 1A 2A 3A 4A 5A 6A 7

ENCODER

O 0O 1O 2

A 0A 1A 2

O 0O 1O 2O 3O 4O 5O 6O 7

DECODER

ONLY ONE INPUT ACTIVATED AT A TIMEBINARY CODE OUTPUT

BINARY CODE INPUTONLY ONE OUTPUT ACTIVATED AT A TIME

THE 8421 BCD CODE• BCD stands for Binary-Coded Decimal.

• A BCD number is a four-bit binary group that represents 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

ELECTRONIC ENCODER - DECIMAL TO BCD

0

DecimaltoBCD

Encoder

BCD outputDecimal input 0 0 0 0

5

0 1 0 17

0 1 1 1

3

0 0 1 1

• Encoders are available in IC form.

• This encoder translates from decimal input to BCD output.

10 line to 4 line Encoder

ENCODER1248

DECIMAL BINARY (BCD)

9 5V8 5V7 5V6 5V5 5V4 5V3 5V2 5V1 5V

74147I9I8I7I6I5I4I3I2I1

A0A1A2A3

10 line to 4 line Encoder

01

23

45

6

78

9

DECODER

BINARY (BCD)

DECIMAL

1 0V2 0V4 0V8 0V

74LS42

A3A2A1A0

9876543210

4 line to 10 line Decoder

BCD-to-7-SegmentDecoder/Driver

DECODERS: BCD TO 7-SEGMENT DECODER/DRIVERBCD input

0 0 0 0

Decimal outputLED

0 0 0 10 0 1 00 0 1 10 1 0 0

• Electronic decoders are available in IC form.• This decoder translates from BCD to decimal.• Decimals are shown on an 7-segment LED display.• This IC also drives the 7-segment LED display.

BCD-to-7-SegmentDecoder/Driver

BCD input Decimal output0 0 1 1

?

Q #1- What is the decimal output from the decoder that appears on the 7-segment display?

Answer: 3 Q #2- What is the decimal output from the decoder that

appears on the 7-segment display?

0 0 0 0

Answer: 0 Q #3- What is the decimal output from the decoder that

appears on the 7-segment display?

1 0 0 1

Answer: 9 Q #4- What is the decimal output from the decoder that

appears on the 7-segment display?Answer: 7

0 1 1 1

Q #5- What is the decimal output from the decoder that appears on the 7-segment display?

Answer: 6

0 1 1 0

TEST

BCD-TO-SEVEN SEGMENT DECODER DRIVER

5V

abcdefg.

V+

74LS47A3A2A1A0

testRBI

gfedcba

RBO

TEST

A 0A 1A 2A 3A 4A 5A 6A 7

ENCODER

O 0O 1O 2O 3

A 8A 9

INPUT O3O2O1O0A1=1A4=1A6=1A8=1

TEST

A 0A 1A 2

O 0O 1O 2O 3O 4O 5O 6O 7

DECODER

O 8O 9

A 3

A3 A2 A1 A0 OUTPUT0 0 0 00 1 0 10 1 1 11 0 0 1

TESTANSWER THE FOLLOWING QUESTIONS WITH ONE OR MORE OF THESE WORDS: MUX, DEMUX, ENCODER, DECODER.A. Has more inputs than outputs.

ENCODER, MUXB. Uses select inputs.MUX, DEMUX

C. Can be used in parallel-to-serial conversion.MUXD. Produces a binary code at its output.ENCODER

E. Only one of its outputs is activated at one time.DEMUX, DECODER

F. Used to route input signals to one of several outputs.MUXG. Used to generate arbitrary logic functions. MUX, DEMUXH. 3 line-to-8 line or binary to octal.DECODER

I. Data Selectors are alsoMUX.