求DDS产生方波verilog代码

一些资料都是任意波形产生需要用到ROM及滤波，我想要一个不用ROM和滤波模块的只产生方波的采用DDS产生方波的verilog代码

http://download.csdn.net/detail/hzh0608/2574136
这个行吗？

你要产生的是50%的方波呢？还是PWM波呢？还是PDM波呢？

module square_wave(
    input clk,
    input rst,

    // control port
    // high_period must be less than period, defined as the length of 1 in one period
    input      [15:0] period,
    input      [15:0] high_period,
    output reg        wave_out
);

reg [15:0] period_count;
always @(posedge clk or posedge rst) begin
    if(rst) begin
        period_count <= 16'd0;
        wave_out <= 1'b1;
    end
    else if(period_count < period) begin
        period_count <= period_count + 16'd1;
        wave_out <= (period_count < high_period) ? 1'b1 : 1'b0;
    end
end

endmodule