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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.