Flip flops help!

Discussion in 'Homework Help' started by maxxface, Jun 27, 2014.

  1. maxxface

    Thread Starter New Member

    May 26, 2014
    6
    0
    I am currently designing a circuit that uses a T Flip Flop and has inputs x, down and load. It's purpose is either to store or to downcount depending on the input. I'm not even sure how to ask the question, so I'll add photos. The first one is decrementing mod 8 counter with a t flip flip, and the second is a counter with a load, the behavioural description as follows:

    ld dn FUNCTION
    0 0 No change
    0 1 Q <-- Q minus 1
    1 0 Q <--- x
    1 1 Q <----x
    The circuit i need to design takes an input x and either downcounts or loads, depending on the inputs.

    NOW what I have to do is use 4 instances of the counter w/ load to design a circuit that can downcount from whatever you push on a hex keyboard since it has load capabilities. I can only use one other gate if necessary and those four instances. On the entity definition, there is inputs for clk, Reset, dn, ld, x and outputs of c and q, where c is the communication line, like used in the mod 8 downcounter.

    So I don't really know at all how to do this, I got the design for the counter w/ load Using a T Flip Flop excitation table and drawing k maps... I'm pretty sure it's right because it works all by itself. If anyone can help me out that would be much appreciated! This is my first course in circuits and i'll try my best to clarify anything I can. Thank you!
     
  2. MrCarlos

    Active Member

    Jan 2, 2010
    400
    134
    Hello maxxface

    First of all:
    How did you make the attached image ?
    Have you any simulator for electronic circuits which you develop your projects ?

    second:
    I do not clearly understand the approach you describe in your message

    For example here:
    The circuit I need to design takes an input x and either down counts or loads, depending on the inputs.
    Which ones did you mean inputs ?

    Could you explain a little more what you want to do ?.
     
  3. maxxface

    Thread Starter New Member

    May 26, 2014
    6
    0
    I am using Logicworks 5 to design the circuits.
    Here's the problem from the work sheet

    When i say downcounter I mean decrementing counter, for instance, if you input 4 it will display 4,3,2,1,0,4,3.......

    Hope this cleared it up a little.
     
  4. Brownout

    Well-Known Member

    Jan 10, 2012
    2,375
    998
    First of all, 'x' isn't an input. The 'x' is used to denote 'don't care' Your inputs should be 'ld' and 'dn'. Maybe it would be helpful if you posted the questions for the previous parts. Second, which of the two schematics is your answer to the first part? You have one which looks like a 3-bit counter and another which looks like a single bit module. Which do you intend to use for the n-counter.

    The secret to the question is the 'load' function. If you want to have an arbitrary n-counter, use the load function to accomplish that.
     
  5. MrCarlos

    Active Member

    Jan 2, 2010
    400
    134

    Well maxxface

    One of the things I need to be able to help you, is to touch your CCT file.
    This file type is generated by your simulator LogicWorks 5.
    An image like the one that upload in your post #1 does not serve me because the problem you may have in your design not transferred to the image file.

    Pack your xyxyx.CCT file. With WinZip or WinRar and upload it here.

    I do not have that "LogicWorks 5" computer program but I have a friend who has it and I can go with him to see what is happening with your design.
     
  6. maxxface

    Thread Starter New Member

    May 26, 2014
    6
    0
    I actually spent a bit of time tinkering with it and ended up using the c (or Q') to trigger the other downs, so that they would decrement properly. Then i ended up using a AND-4 gate with 4 inverters to trigger the load when the output = 0000 to restart the counting.

    Apologies for the messy post, I'll get better I promise. I'm just really stoked that I figured it all out! Thank you all for your time with this!
     
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