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Digital ElectronicsDigital ElectronicsElectronics TechnologyElectronics Technology
Landon Johnson
Encoding, Decoding, and
Seven-Segment Displays
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Encoder/Decoder CompetenciesEncoder/Decoder Competencies
52. Given four different input combinations to a 10 line to 4 lineencoder, the student will state the output combinations with100% accuracy.
53. Given four different input combinations for a 4 line to 10line decoder, the student will state the output combinations
with 100% accuracy.
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Encoder/Decoder VocabularyEncoder/Decoder Vocabulary
ENCODER- a digital circuit that produces abinary output code depending on which of itsinputs are activated.
DECODER- a digital circuit that converts aninput binary code into a single numericoutput.
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ENCODERS AND DECODERSENCODERS AND DECODERS
A0
A1
A2
A3
A4A
5
A6
A7
ENCODER
O0
O1
O2
A0
A1
A2
O0
O1
O2
O3
O4O
5
O6
O7
DECODER
ONLY ONE INPUTONLY ONE INPUT
ACTIVATED AT A TIMEACTIVATED AT A TIME
BINARY CODE OUTPUTBINARY CODE OUTPUT
BINARY CODE INPUTBINARY CODE INPUT
ONLY ONE OUTPUTONLY ONE OUTPUT
ACTIVATED AT A TIMEACTIVATED AT A TIME
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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
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ELECTRONIC ENCODER -
DECIMALTO 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.
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10 line to 4 line Encoder10 line to 4 line Encoder
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ENCODER
1248
DECIMAL BINARY (BCD)
9 5V
8 5V
7 5V
6 5V
5 5V
4 5V3 5V
2 5V
1 5V
74147I9I8I7I6I5I4
I3I2I1
A0A1A2A3
10 line to 4 line Encoder10 line to 4 line Encoder
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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 Decoder4 line to 10 line Decoder
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BCD-to-
7-Segment
Decoder/
Driver
DECODERS: BCD TO
7-SEGMENT DECODER/DRIVER
BCD 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.
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BCD-to-
7-Segment
Decoder/Driver
BCD inputDecimal output
0011
?
Q #1- What is the decimal output from the decoder thatappears on the 7-segment display?
Answer: 3
Q #2- What is the decimal output from the decoder thatappears on the 7-segment display?
0000
Answer: 0
Q #3- What is the decimal output from the decoder thatappears on the 7-segment display?
1 0 0 1
Answer: 9
Q #4- What is the decimal output from the decoder thatappears on the 7-segment display?
Answer: 7
0 1 1 1
Q #5- What is the decimal output from the decoder thatappears on the 7-segment display?
Answer: 6
0 1 1 0
TEST
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BCD-TO-SEVEN SEGMENT DECODER DRIVER
5V
abcdef g .
V+
74LS47A3A2A1A0
testRBI
gfedcba
RBO
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TEST
A0
A1
A2
A3
A4
A5
A6
A7
ENCODER
O0
O1
O2
O3
A8
A9
I PUT 3
A1=1
A4=1
A6=1
A8=1
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TEST
A0
A1
A2
O0
O1
O2
O3
O4
O5
O6
O7
DECODER
O8
O9
A3
A3 A2 A1 A0
0 0 0 00 1 0 1
0 1 1 1
1 0 0 1
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TEST
ANSWERTHE FOLLOWING QUESTIONS WITH ONE ORMOREOF THESE WORDS: M X, DEM X, 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. 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. 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.