Encoder and Decoder Encoding, Decoding
Jan 19, 2015
Encoder and Decoder
Encoding, Decoding
Encoder
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.
Decoder
ENCODERS AND DECODERS
A 0
A 1
A 2
A 3
A 4
A 5
A 6
A 7
ENCODER
O 0
O 1
O 2
A 0
A 1
A 2
O 0
O 1
O 2
O 3
O 4
O 5
O 6
O 7
DECODER
ONLY ONE INPUT ACTIVATED AT A TIME
BINARY CODE OUTPUT
BINARY CODE INPUT
ONLY 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
Decimalto
BCDEncoder
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.
10 line to 4 line Encoder
ENCODER1248
DECIMAL BINARY (BCD)
9 5V
8 5V
7 5V
6 5V5 5V
4 5V3 5V
2 5V1 5V
74147I9I8I7I6I5I4I3I2I1
A0A1A2A3
10 line to 4 line Encoder
0
1
2
3
4
5
6
7
8
9
DECODER
BINARY (BCD)
DECIMAL
1 0V
2 0V
4 0V
8 0V
74LS42
A3A2A1A0
9876543210
4 line to 10 line Decoder
BCD-to-7-SegmentDecoder/
Driver
DECODERS: BCD TO 7-SEGMENT DECODER/DRIVER
BCD input
0 0 0 00 0 0 0
Decimal outputLED
0 0 0 10 0 0 10 0 1 00 0 1 00 0 1 10 0 1 10 1 0 00 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 inputDecimal output
0 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
abcdef g .
V+
74LS47A3A2A1A0
testRBI
gfedcba
RBO
TEST
A 0
A 1
A 2
A 3
A 4
A 5
A 6
A 7
ENCODER
O 0
O 1
O 2
O 3
A 8
A 9
INPUT O3 O2 O1 O0A1=1A4=1A6=1A8=1
TEST
A 0
A 1
A 2
O 0
O 1
O 2
O 3
O 4
O 5
O 6
O 7
DECODER
O 8
O 9
A 3
A3 A2 A1 A0 OUTPUT0 0 0 00 1 0 10 1 1 11 0 0 1
TEST
ANSWER THE FOLLOWING QUESTIONS WITH ONE OR MORE OF
THESE WORDS: MUX, DEMUX, ENCODER, DECODER.
A. Has more inputs than outputs. ENCODER, MUX
B. Uses select inputs. MUX, DEMUX
C. Can be used in parallel-to-serial conversion. MUX
D. 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. MUX
G. Used to generate arbitrary logic functions. MUX, DEMUX
H. 3 line-to-8 line or binary to octal. DECODER
I. Data Selectors are also MUX.
The End
….. Thank you ….