add and subtract

Discussion in 'Homework Help' started by miruku90, Oct 21, 2010.

  1. miruku90

    Thread Starter New Member

    Oct 21, 2010
    [​IMG]Can someone tell me wat gates or which ff shud i use? :(

    Draw a sequential circuit which maintains a two-bit value in two flip-flops (of any
    kind), with two inputs: "add one" and "subtract one"'. The "add one" operation is
    like a normal up counter, the output of the counter increases by one, "Subtract
    one" performs the opposite function; e.g. a 3 will change to 2 (and then if the user
    presses "add one" next, it will go back to 3). These two input will never be 1
    simultaneously, and each time they are 1 they will stay at 1 "long enough" for any
    You can use any desired components such as any kind of flip-flops, etc;
  2. n1ist

    Senior Member

    Mar 8, 2009
    Start by drawing out the state table for what you are trying to do. You can make this counter with almost any kind of flip flop (JK, D, or T should work).

    You can pull up the data sheet for the 74193 up/down counter for some hints.