digital works counter

Discussion in 'Homework Help' started by DG7, Nov 25, 2012.

  1. DG7

    Thread Starter New Member

    Nov 25, 2012
    4
    0
    Hello everybody!
    I'm just starting on digital circuits and also on this forum. This is my fisrt post. I found this forum when I was trying to find an answer for me question about building a counter on digital works.
    As I said, I'm using digital works. The ideia is to make a counter using two 7 segment leds, that goes like: 00, 01, 02,...29, 00, 01, etc.
    I've reached that point. I had no major problems with that.
    But now, I'm suppost to add 2 " buttons":
    One start/pause button.
    And a reset button, that only works when the counter is paused.
    I'm not sure how can I add those buttons. Can any one help me on that, please?
    I hope I can keep learning, and soon I can help other users too.
    Thanks!

    Edit: I've seen some post about similar counters on this forum. But I can't find any about those specific buttons.
     
    Last edited: Nov 25, 2012
  2. DG7

    Thread Starter New Member

    Nov 25, 2012
    4
    0
    Should I add some images from the circuit?
     
  3. WBahn

    Moderator

    Mar 31, 2012
    17,715
    4,788
    You implemented a counter that free-runs through a cycle of 30 states. What would it take to reset the counter to zero? What would it take to stop the counting action in such a way that it can be continued?
     
    DG7 likes this.
  4. DG7

    Thread Starter New Member

    Nov 25, 2012
    4
    0
    Hello WBahn.
    First of all, thank you for your answer. That's exacty what I'm trying to find out. I'm following a book, and making some web search about this question. My guess is that I'll need some Multiplexers on the counter. And the " start/pause" and the " reset" button will be the multiplexer select lines. I think this is right. I just can't find a way to build it. As I said on my 1st post, I'm just starting with digital circuits.
    Thanks again, WBahn.
     
  5. DG7

    Thread Starter New Member

    Nov 25, 2012
    4
    0
    q
    As I wrote on my other post, I think I'll need a MUX on my counter with 2 selectors. eg.

    s0= 1 - allows clock signal to the circuit (START) --- s0=0 " cuts" the signal.(PAUSE)
    s1=1 sends 0 to all flip flops( RESET)

    I'm not sure if this is right. But I guess it should be something near that. I've read a lot about how MUX works. I now have a solid idea about that. I'm just having some problems on gluing all together. Well, I'm still learning. So, I guess that's normal. :)

    By the way, I've changed the circuit to something more "useful". To 4 7 segments leds.
    00 00 ... 59 59 , 00 00 etc

    Thanks again.
     
    Last edited: Nov 26, 2012
  6. WBahn

    Moderator

    Mar 31, 2012
    17,715
    4,788
    How about getting one digit working, first. Say have it count 0,1,2,3,4,5,0,1,... and get your pause and reset working on it. Expanding to more digits is then pretty trvial.

    We can't begin to guess at the best way for you to do it with your circuit unless you post a schematic of your circuit.
     
    DG7 likes this.
  7. WBahn

    Moderator

    Mar 31, 2012
    17,715
    4,788
    I have no idea what an "iterative input" to an AND gate is.

    What is the output of this AND gate going to? An asynchronous reset?

    Your AND gate is going to be HI whenever you are in any state covered by x11x, so states 6, 7, 14, and 15. Since you are using an asynchronous ripple counter, this is not an unreasonable approach. But a much better approach is to design a synchronous counter. You need to decide which is more appropriate for what you are trying to accomplish.

    What happens if you gate your clock, meaning to pass your input clock through a logic gate whose output is held at a logic LO if the other input is LO but follows the clock input if the other input is HI. What gate exhibits this behavior?
     
Loading...