Truthtables, Karnaughdiagram, PSPICE and a pulsating code.

Discussion in 'Homework Help' started by Digifan, Oct 25, 2012.

  1. Digifan

    Thread Starter New Member

    Oct 25, 2012
    So im trying to create a circuit that pulsates a code in binary.
    I've done a truthtable and done some karnaugh diagrams so I know what kinds of gates etc. to use.
    The circuit consists of five 7474's and alot of gates.

    Things are working out just fine but for some reason the PSPICE simulator gives me some wierd output, everyhing starts out fine, the five signals are low but when they are supposed to change they are unknown(they become double red lines in the simulator).

    Im adding pictures of the error aswell as the circuit.

    Any help at all will be greatly appretiated, cause I have no idea what's wrong.

    Best regards
  2. JoeJester

    AAC Fanatic!

    Apr 26, 2005
    Your diagram is difficult to read.

    Q0 is always low and will never change state. Is that your intention?
  3. takao21203

    Distinguished Member

    Apr 28, 2012
    Maybe you did not consider propagation delays, setup time, dynamic behaviour etc.

    Not knowing what your circuit is supposed to do, as well the schematic is incomplete.

    Did it work before you optimized it using Karnaugh table?

    You have to slice it into independent pieces and make them work correctly step by step.