8bitworkshop/presets/verilog/binary_counter.v

/*
A clock divider in Verilog, using both the cascading
flip-flop method and the binary counter method.
*/

module clock_divider(
  input clk,
  input reset,
  output reg clk_div2,
  output reg clk_div4,
  output reg clk_div8,
  output reg clk_div16,
  output reg [3:0] counter,
  output cntr_div2,
  output cntr_div4,
  output cntr_div8,
  output cntr_div16
);

  // simple ripple clock divider
  
  always @(posedge clk)
    clk_div2 <= ~clk_div2;

  always @(posedge clk_div2)
    clk_div4 <= ~clk_div4;

  always @(posedge clk_div4)
    clk_div8 <= ~clk_div8;

  always @(posedge clk_div8)
    clk_div16 <= ~clk_div16;

  // use bits of (4-bit) counter to divide clocks
  
  always @(posedge clk or posedge reset)
  begin
    if (reset)
      counter <= 0;
    else
      counter <= counter + 1;
  end

  assign cntr_div2 = counter[0];
  assign cntr_div4 = counter[1];
  assign cntr_div8 = counter[2];
  assign cntr_div16 = counter[3];

endmodule