clock.v

register,原程序及testbench,供初学者参考

// This model of a structural clock simulates very fast.

module clock(clk);
output clk;
  reg  start;

//clock oscillator, period = 20 time units
  nand #10 (clk, clk, start); // changes to start, clk are delayed 10 time units

  initial     //initialize the clock oscillator
    begin
      start = 0;        // After 10 time units, clk will equal 1.
      #10 start = 1;    // After another 10, clk will equal 0.
    end


endmodule