title: Ring Oscillator Verilog code
body: <p>I Want to write a code in verilog, for Ring Oscillator. I'm new in Verilog. <br/>
  Here is my code:<br/></p>
  
  <pre><code>module RingOsci(enable, w1, w2, w3);
      input enable;
      output w1, w2, w3;
      wire w4;
  
      and (w4, enable, w3);
      not #2(w2, w1);
      not #2(w3, w2);
      not #2(w1, w4);
  endmodule
  </code></pre>
  
  <p>But Always, W_i is Z.<br/>
  Here is my Test Bench: <br/></p>
  
  <pre><code>module RingOsciTB();
      reg en;
      wire out1, out2, out3;
  
      initial begin
          en = 1'b0;
          #20
          en = 1'b1;
      end
  endmodule
  </code></pre>
  
  <p>How can I change the Z value for enable the Oscillator?<br/></p>