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`timescale 1ns/1ps

module util_pulse_gen #(

  parameter   PULSE_WIDTH = 7,
  parameter   PULSE_PERIOD = 100000000)(         // t_period * clk_freq

  input               clk,
  input               rstn,

  input       [31:0]  pulse_period,
  input               pulse_period_en,

  output  reg         pulse
);

  // internal registers

  reg     [(PULSE_WIDTH-1):0]  pulse_width_cnt = {PULSE_WIDTH{1'b1}};
  reg     [31:0]               pulse_period_cnt = 32'h0;
  reg     [31:0]               pulse_period_d = 32'b0;

  wire                         end_of_period_s;

  // flop the desired period

  always @(posedge clk) begin
    pulse_period_d <= (pulse_period_en) ? pulse_period : PULSE_PERIOD;
  end

  // a free running pulse generator

  always @(posedge clk) begin
    if (rstn == 1'b0) begin
      pulse_period_cnt <= 32'h0;
    end else begin
      pulse_period_cnt <= (pulse_period_cnt < pulse_period_d) ? (pulse_period_cnt + 1) : 32'b0;
    end
  end

  assign  end_of_period_s = (pulse_period_cnt == (pulse_period_d - 1)) ? 1'b1 : 1'b0;

  // generate pulse with a specified width

  always @(posedge clk) begin
    if (rstn == 1'b0) begin
      pulse_width_cnt <= 0;
      pulse <= 0;
    end else begin
      pulse_width_cnt <= (pulse == 1'b1) ? pulse_width_cnt + 1 : {PULSE_WIDTH{1'h0}};
      if(end_of_period_s == 1'b1) begin
        pulse <= 1'b1;
      end else if(pulse_width_cnt == {PULSE_WIDTH{1'b1}}) begin
        pulse <= 1'b0;
      end
    end
  end

endmodule