8-bit asynchronous up/down counter

Discussion in 'Homework Help' started by vikkie, Dec 20, 2008.

  1. vikkie

    Thread Starter New Member

    Dec 20, 2008
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    Hi i want to design a 8-bit asynchronous up/down counter with shift capability with minimum number of transistors.Anyone who have better design option.please let me know.
     
  2. mik3

    Senior Member

    Feb 4, 2008
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    Is this a school or personal project?
     
  3. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Pretty ambitious. No, I think the better design option is that you do it.

    Seriously, there are numerous examples of counters and shift registers in all the logic families. Even if none of those will quite do, we have no indication from you as to very important parameters that would somewhat dictate the design. I suppose this means that this has to be an assignment, and you might not have done a lot of research just yet.

    Once you have got off to a start, please do come back with specific questions.
     
  4. vikkie

    Thread Starter New Member

    Dec 20, 2008
    9
    0
    Its a personal project.

    I have to design a counter with 2 differential inputs.It should count up in +ive clock and count down during -ive clock cycle.Also it should shift the count serially.
    I have designed the circuit.It counts up during +ive cycle.
    1) Now i want to swap the 2 differential inputs so that it can count down.
    2) I don't know how to shift this data serially.

    I need help in these 2 problems.
     
  5. beenthere

    Retired Moderator

    Apr 20, 2004
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    Look up the data sheet for a 7491 - that's an 8 bit shift register.

    Look up the data sheet for a 74191 - that's an up/down counter.

    Never reinvent the wheel - just adopt the design to suit your needs.
     
  6. vikkie

    Thread Starter New Member

    Dec 20, 2008
    9
    0
    I have to design the circuit using CMOS transistors.

    Ok.Can anyone tell me how to swap 2 inputs.I have designed the up counter with differential inputs and outputs.For down counting i have to swap my inputs,but i am unable to design a swap circuit,so that for ist +ive half cycle it counts up and next + ive half cycle it counts down.

    need help!
     
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