Nothing Special   »   [go: up one dir, main page]
Scribd Logo
Upload

Welcome to Scribd!

  • 49 views

    Unit V - 3BCD Ripple Counter

    Uploaded by

    Thiriveedhi Subbarayudu
    This document describes a BCD ripple counter circuit. It consists of four JK flip-flops that represent the four binary digits of a decimal number. The output of each flip-flop triggers the next in sequence. It counts from 0 to 9 in decimal before resetting to 0. The state transitions of each flip-flop are described to show how the circuit implements a BCD counter.

    Copyright:

    © All Rights Reserved
    Download as PPTX, PDF, TXT or read online from Scribd

    Unit V - 3BCD Ripple Counter

    Uploaded by

    Thiriveedhi Subbarayudu
    49 views13 pages
    This document describes a BCD ripple counter circuit. It consists of four JK flip-flops that represent the four binary digits of a decimal number. The output of each flip-flop triggers the next in sequence. It counts from 0 to 9 in decimal before resetting to 0. The state transitions of each flip-flop are described to show how the circuit implements a BCD counter.

    Copyright

    © © All Rights Reserved

    Available Formats

    PPTX, PDF, TXT or read online from Scribd

    Did you find this document useful?

    Is this content inappropriate?

    This document describes a BCD ripple counter circuit. It consists of four JK flip-flops that represent the four binary digits of a decimal number. The output of each flip-flop triggers the next in sequence. It counts from 0 to 9 in decimal before resetting to 0. The state transitions of each flip-flop are described to show how the circuit implements a BCD counter.

    Copyright:

    © All Rights Reserved
    Download as PPTX, PDF, TXT or read online from Scribd
    Download as pptx, pdf, or txt
    49 views13 pages

    Unit V - 3BCD Ripple Counter

    Uploaded by

    Thiriveedhi Subbarayudu
    This document describes a BCD ripple counter circuit. It consists of four JK flip-flops that represent the four binary digits of a decimal number. The output of each flip-flop triggers the next in sequence. It counts from 0 to 9 in decimal before resetting to 0. The state transitions of each flip-flop are described to show how the circuit implements a BCD counter.

    Copyright:

    © All Rights Reserved
    Download as PPTX, PDF, TXT or read online from Scribd
    Download as pptx, pdf, or txt
    You are on page 1of 13

    BCD Ripple Counter

    A decimal counter follows a sequence of


    ten states and returns to 0 after the count
    of 9.
    Such a counter must have at least four
    flip-flops to represent each decimal digit,
    since a decimal digit is represented by a
    binary code with at least four bits.
    The sequence of states in a decimal
    counter is dictated by the binary code
    used to represent a decimal digit.
    BCD Ripple Counter
    If BCD is used, the sequence of states is
    shown below in the state diagram.
    This is similar to a binary counter, except
    that the state after 1001 is 0000.
    BCD Ripple Counter
    The logic diagram of a BCD ripple
    counter is shown below.
    The four outputs are designated by the
    letter symbol Q with a numeric subscript
    equal to the binary weight of the
    corresponding bit in the BCD code.
    The flip-flops trigger on the negative
    edge, i.e., when the CP signal goes from 1
    to 0.
    BCD Ripple Counter
    BCD Ripple Counter
    Note that the output of Q1 is applied to the
    CP inputs of both Q2 and Q8 and the output
    of Q2 is applied to the CP input of Q4.
    The J and K inputs are connected either to a
    permanent 1 signals or to outputs of flip-
    flops, as shown in the diagram.
    A ripple counter is an asynchronous
    sequential circuit and cannot be described by
    Boolean equations developed for describing
    clocked sequential circuits.
    BCD Ripple Counter
    Signals that affect the flip-flop transition
    depend on the order in which they change
    from 1 to 0.
    The operation of the counter can be
    explained by a list of conditions for flip-
    flop transitions.
    These conditions are derived from the
    logic diagram and from knowledge of
    how a JK flip-flop operates.
    BCD Ripple Counter
    Remember that when the CP input goes from
    1 to 0, the flip-flop is set if J=1, is cleared if
    K=1, is complemented if J=K=1, and is left
    unchanged if J=K=0.
    The following are the conditions for each
    flip-flop state transition.
    ◦ Q1 is complemented on the negative edge of every
    count pulse.
    ◦ Q2 is complemented if Q8=0 and Q1 goes from 1 to
    0. Q2 is cleared if Q8=1 and Q1 goes from 1 to 0.
    BCD Ripple Counter
    ◦ Q4 is complemented when Q2 goes from 1 to 0.
    ◦ Q8 is complemented when Q4Q2=11 and Q1
    goes from 1 to 0. Q8 is cleared if either Q4 or
    Q2 is 0 and Q1 goes from 1 to 0.
    To verify that these conditions result in
    the sequence required by a BCD ripple
    counter, it is necessary to verify that the
    flip-flop transitions indeed follow a
    sequence of states as specified by the state
    diagram.
    BCD Ripple Counter
    Another way to verify the operation of the
    counter is to derive the timing diagram for
    each flip-flop from the conditions just
    listed.
    The timing diagram is shown below with
    the binary states listed after each clock
    pulse.
    BCD Ripple Counter
    BCD Ripple Counter
    The BCD counter discussed till now is a
    decade counter, since it counts from 0 to 9.
    To count in decimal from 0 to 99, we need
    a two-decade counter.
    To count from 0 to 999, we need a three-
    decade counter.
    Multiple-decade counters can be
    constructed by connecting BCD counters
    in cascade one for each decade.
    BCD Ripple Counter
    A three-decade counter is shown below.

    The inputs to the second and third


    decades come from Q8 of the previous
    decade
    BCD Ripple Counter
    When Q8 in one decade goes from 1 to 0,
    it triggers the count for the next higher-
    order decade while its own decade goes
    from 9 to 0.
    For instance, the count after 399 will be
    400.

    You might also like