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Homework Help: Help with Counter Wiring

  1. Nov 18, 2013 #1
    Problem Statement .

    I am trying to create a 12 bit counter with a combination of 4 bit counters (74191 Spec Sheet: http://pdf1.alldatasheet.com/datasheet-pdf/view/7831/NSC/74191.html)

    I cannot figure this out for he life of me. I'm honestly not understanding many of the circuits we have to build in my course. It's one of those situations where I don't know, for instance, what a "flip flop" is, and then I look it up on the net or in my text, and after reading, I still don't know what a flip flop is.

    I was able to assemble and test the counter (4 bits) but I do not know how to wire three to have a 12 bit counter.

    Attempt at a Solution

    I know that the RCO pin (13) should be connected to the enabler pin (4) of the next counter to signal it to start... In my diagram I have switches (S1, S2, etc....) connected to the pins 15, 1, 10, and 9 (the "inputs" )... the connection them are represented by the red wires...

    I am not sure how to deal with the input pins (A,B,C,D @ pins 15, 1, 10, and 9) of the next counter...should I just connect them all to the output pins QA, QB, QC, QD?

    I don't have a breadboard at the moment so I cannot test this, but I am trying to plan my circuit now and I'll assemble it in class.

    Attached Files:

  2. jcsd
  3. Nov 18, 2013 #2


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    Staff: Mentor

    It would be a lot easier to help if you could show us schematically what you are trying to do. Instead of linking to a datasheet, can you please upload a PDF of the part so we can see what all of its hooks and handles are?

    And what do you think you would normally need to link one 4-bit counter to another to make an 8-bit counter? Are these counters synchronous or ripple? What is the difference?
  4. Nov 18, 2013 #3
    They are synchronous counters. I attached a drawing of the setup, or the wiring I am attempting...I linked the sheet because it has the connection diagram, but here is the PDF attached....

    EDIT: in my original post the breadboard layout you see shows the switches (S1, S2, ....) which are high or low (5 volts or 0 volts)....I have them connected with Red wires to the input pins of the counter, if you compare to the connection diagram in the data sheet (PDF) you'll see what I did. The black wires are shown connecting the counters to each other, from pin (13) on one counter connected to pin (4) on the adjacent counter...

    Attached Files:

  5. Nov 18, 2013 #4

    Simon Bridge

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    Science Advisor
    Homework Helper

    You should get used to thinking through these ... it's usually a matter of going step-by-step: start by describing basically what the component does.

    i.e. "The 4-bit counter basically outputs a binary number that is one more than the last one it outputted - the output is triggered by a pulse at an input" ... is that correct? (check)

    Does it trigger on the leading or trailing edge of the pulse?
    What does it do when it has reached 1111 and it gets another pulse?
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