Inverter Oscillator?

Ed Vogel
2009-02-13
2013-05-23
  • Ed Vogel
    Ed Vogel
    2009-02-13

    Hi,
      I was happy to see your NOR gates could be configured to make RS Latches.  I have tried that with other simulators and it doesn't work, "Logic Friday" for instance.  I would also like to be able to simulate oscillators made from odd number rings of NOR gates. 

    My reason for wanting this is to simulate the behavior an array of optically coupled two input NOR Gates constructed from neon lamps and photoresistors.

    You can read the abstract of one of my conference papers here:

    http://adsabs.harvard.edu/abs/1996SPIE.2863..407V

    "Tic tac toe game using an optically routed gate array"
    Vogel, Edward P.

    Proc. SPIE Vol. 2863, p. 407-412, Current Developments in Optical Design and Engineering VI, Robert E. Fischer; Warren J. Smith; Eds.

    Thank you for a great simulator!  I am looking forward to seeing how many NOR gates it takes to make one Von Neuman Cellular Automata Cell.  I will use you provided clock input instead of rings of NOR Gates.

    Sincerely yours,
                   Ed Vogel

     
    • What does CEDAR Logic do when you attempt to make a NOR gate oscillator ring?

       
    • Ed Vogel
      Ed Vogel
      2009-02-21

      The attached LEDs turn blue which is what I believe an indication of an undefined state.  An oscilloscope trace sweeps but shows a solid blue bar.

      Thanks for getting back with me on this.

      I have used Cedar Logic to construct a single Von Neumann automata cell.  It takes 20 NOR gates.  Nice to finally figure this out.  

      Ed V.

       
      • Yes. That is an undefined state. All gates start out "undefined" until they are given an input which will force the output to a defined state. The trick is to force them to a "defined" state, since the simulator does not simulate random analog circuit noise. (The tool was built for teaching digital logic, and it is generally a good idea to not rely on random circuit noise to make a design work - so we added an "unknown" state to show students that the circuit was not guaranteed to initialize the way they expected.)

        Try the following loop:
        A NOR gate looping back into ONE of it's inputs, with the second input connected to a switch. Drive the switch LOW to force the NOR gate output to a known HIGH state, and then drive the switch HIGH. The NOR gate should start oscillating.

        Let me know how it goes...

         
    • Ed Vogel
      Ed Vogel
      2009-03-06

      Thanks!  It works great.