module ad_dds_2 #(

  // Range = 8-24
  parameter   DDS_DW = 16,
  // Range = 8-24
  parameter   PHASE_DW = 16,
  // Set 1 for CORDIC or 2 for Polynomial
  parameter   DDS_TYPE = 1,
  // Range = 8-24
  parameter   CORDIC_DW = 16,
  // Range = 8-24 ( make sure CORDIC_PHASE_DW < CORDIC_DW)
  parameter   CORDIC_PHASE_DW = 16) (

  // interface

  input                   clk,
  input                   dds_format,
  input   [PHASE_DW-1:0]  dds_phase_0,
  input   [        15:0]  dds_scale_0,
  input   [PHASE_DW-1:0]  dds_phase_1,
  input   [        15:0]  dds_scale_1,
  output  [  DDS_DW-1:0]  dds_data);

 // Local parameters

 localparam CORDIC = 1;
 localparam POLYNOMIAL = 2;

 // The width for Polynomial DDS is fixed (16)
 localparam DDS_D_DW = (DDS_TYPE == CORDIC) ? CORDIC_DW : 16;
 localparam DDS_P_DW = (DDS_TYPE == CORDIC) ? CORDIC_PHASE_DW : 16;
 // concatenation or truncation width
 localparam C_T_WIDTH = (DDS_D_DW > DDS_DW) ? (DDS_D_DW - DDS_DW) : (DDS_DW - DDS_D_DW);

  // internal registers

  reg     [  DDS_DW-1:0]  dds_data_width = 0;
  reg     [DDS_D_DW-1:0]  dds_data_rownd = 0;
  reg     [DDS_D_DW-1:0]  dds_data_int = 0;
  reg     [        15:0]  dds_scale_0_d = 0;
  reg     [        15:0]  dds_scale_1_d = 0;
  reg     [  DDS_DW-1:0]  dds_data_out = 0;

  // internal signals

  wire    [DDS_D_DW-1:0]  dds_data_0_s;
  wire    [DDS_D_DW-1:0]  dds_data_1_s;
  wire    [DDS_P_DW-1:0]  dds_phase_0_s;
  wire    [DDS_P_DW-1:0]  dds_phase_1_s;

  generate
    // dds channel output
    assign dds_data = dds_data_out;

    // output data format
    always @(posedge clk) begin
      dds_data_out[DDS_DW-1] <= dds_data_width[DDS_DW-1] ^ dds_format;
      dds_data_out[DDS_DW-2: 0] <= dds_data_width[DDS_DW-2: 0];
    end

    // set desired data width
    always @(posedge clk) begin
      if (DDS_DW < DDS_D_DW) begin // truncation
        // fair rownding
        dds_data_rownd <= dds_data_int + {(C_T_WIDTH){dds_data_int[DDS_D_DW-1]}};
        dds_data_width <= dds_data_rownd[DDS_D_DW-1:DDS_D_DW-DDS_DW];
      end else begin // concatenation
        dds_data_width <= dds_data_int << C_T_WIDTH;
      end
    end

    // dual tone
    always @(posedge clk) begin
      dds_data_int <= dds_data_0_s + dds_data_1_s;
    end

     always @(posedge clk) begin
       dds_scale_0_d <= dds_scale_0;
       dds_scale_1_d <= dds_scale_1;
     end

     // phase
      if (DDS_P_DW > PHASE_DW) begin
        assign dds_phase_0_s = {dds_phase_0,{DDS_P_DW-PHASE_DW{1'b0}}};
        assign dds_phase_1_s = {dds_phase_1,{DDS_P_DW-PHASE_DW{1'b0}}};
      end else begin
        assign dds_phase_0_s = dds_phase_0[(PHASE_DW-1):PHASE_DW-DDS_P_DW];
        assign dds_phase_1_s = dds_phase_1[(PHASE_DW-1):PHASE_DW-DDS_P_DW];
      end

     // dds-1

     ad_dds_1 #(
       .DDS_TYPE(DDS_TYPE),
       .DDS_D_DW(DDS_D_DW),
       .DDS_P_DW(DDS_P_DW))
     i_dds_1_0 (
       .clk (clk),
       .angle (dds_phase_0_s),
       .scale (dds_scale_0_d),
       .dds_data (dds_data_0_s));

     // dds-2

     ad_dds_1 #(
       .DDS_TYPE(DDS_TYPE),
       .DDS_D_DW(DDS_D_DW),
       .DDS_P_DW(DDS_P_DW))
     i_dds_1_1 (
       .clk (clk),
       .angle (dds_phase_1_s),
       .scale (dds_scale_1_d),
       .dds_data (dds_data_1_s));
  endgenerate

endmodule