Flip Flop Apps [PDF Library]

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    Flip-Flop Applications

    Registers

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    Registers

    a register is a collection of flip-flops

    basic function is to hold information

    a shift register is a register thatmoves information on the clock signal

    serial-in/serial-out

    serial-in/parallel-out

    parallel-in/serial-out

    parallel-in/parallel-out

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    Serial-in, serial-out unidirectional shift register.

    Figure 6.26

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    Parallel-in unidirectional shift register.

    Figure 6.28

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    Universal shift register. (a) Logic diagram. (b) Mode control.(c) Symbol.

    Figure 6.29

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    Flip-Flop Applications

    Counters

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    Counters

    Also called pattern generators

    Function: produce a specified outputpattern sequence

    Types of counters Binary ripple counters (asynchronous counters)

    Synchronous counters

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    State diagram of a counter.

    Figure 6.30

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    Binary Ripple Counters

    also called asynchronous binarycounters

    the LSB flip-flop recieves clock input

    from a clock source

    the ithflip-flop recieves clock inputfrom output of the ith-1 flip-flop

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    Four-bit binary ripple counter. (a) Logic diagram. (b) Timingdiagram. (c) Counting sequence.

    Figure 6.31

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    Synchronous Binary Counters

    Solve the settling time problem of theripple counters

    Every flip-flop changes on clock input

    simultaneously

    Large number of flip-flops can causeloading complications

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    Four-bit synchronous binary counter.

    Figure 6.32

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    Four-bit synchronous binary counter variation.

    Figure 6.33

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    Four-bit synchronous binary counter with parallel loadinputs. (a) Logic diagram. (b) Symbol.

    Figure 6.34

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    Synchronous mod-10 counter. (a) Connections. (b) Countingsequence.

    Figure 6.35

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    8-bit synchronous binary counter constructed from two 4-bitsynchronous binary counters.

    Figure 6.36

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    Counters Based on Shift Registers

    Nonbinary counters

    a ring counter: a circular shift registerwhere only one flip-flop is in 1-state and

    the rest are in 0-state a switch-tail counter (twisted-ring

    counter or Johnson counter):complement of the rightmost flip-flopbecomes input of the leftmost flip-flop

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    Mod-4 ring counter. (a) Logic diagram. (b) Countingsequence.

    Figure 6.37

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    Mod-8 twisted-ring counter. (a) Logic diagram. (b) Countingsequence.

    Figure 6.38

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    Mod-7 twisted-ring counter. (a) Logic diagram. (b) Countingsequence.

    Figure 6.39

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    Synchronous Counter Design

    To design a synchronous counter,perform the following steps

    Decide the counting sequence

    Draw an excitation table, whichconsists of 3 parts

    Present state| Next state| flip-flop inputs

    (flip-flop inputs can be obtained from an application

    table of the selected flip-flop)

    Determine inputs of each flip-flop

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    General structure of a synchronous mod-6 counter usingpositive-edge-triggered JK flip-flops.

    Figure 6.40

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    Determination of the minimal-sum expressions for asynchronous mod-6 counter using clocked JK flip-flops.

    Figure 6.41

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    Logic diagram of a synchronous mod-6 counter.

    Figure 6.42

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    Determination of the minimal-sum expressions for asynchronous mod-6 counter using clocked D flip-flops.

    Figure 6.43

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    Determination of the minimal-sum expressions for asynchronous mod-6 counter using clocked T flip-flops.

    Figure 6.44

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    Determination of the minimal-sum expressions for asynchronous mod-6 counter using clocked SR flip-flops.

    Figure 6.45

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