You are an expert Verilog hardware designer working on a complete FPGA or ASIC project. You are given the full source code of a Verilog project. One of the modules in the project is incomplete — its implementation is missing and marked with:

// >>> Module Implementation Begin

// <<< Module Implementation End

Your task is to complete the missing implementation so that the entire project functions correctly. You must infer what the missing module or logic is supposed to do by analyzing the rest of the codebase: module names, signal connections, instantiations, comments, and usage patterns.

Follow these rules:

1. Only generate Verilog code to go between the `// >>> Module Implementation Begin` and `// <<< Module Implementation End` comments.
2. Use Verilog-2001 syntax. Ensure the code is synthesizable.
3. Assume the goal is a working, integrated hardware design — your code must make the whole system function as intended.
4. Analyze the naming, I/O ports, and how the module is instantiated or used in other parts of the project.
5. Implement correct behavior based on design context. Do not guess randomly — reason it out.
6. Avoid vendor-specific features unless explicitly required.
7. Do not output comments, explanation, or anything outside the required code region unless explicitly asked.

Your output should contain **only the Verilog code** that fits inside the marked region.

/*
 * Copyright (c) 2024 Rebecca G. Bettencourt
 * SPDX-License-Identifier: Apache-2.0
 */

`default_nettype none

parameter Y_5_12 = 200;
parameter Y_7_12 = 280;
parameter Y_8_12 = 320;
parameter Y_9_12 = 360;

parameter X_1_7 = 90;
parameter X_2_7 = 182;
parameter X_3_7 = 274;
parameter X_4_7 = 366;
parameter X_5_7 = 458;
parameter X_6_7 = 550;

parameter X_05_28 = 113;
parameter X_10_28 = 228;
parameter X_15_28 = 343;
parameter X_20_28 = 458;
parameter X_16_21 = 489;
parameter X_17_21 = 519;
parameter X_18_21 = 550;

parameter SUPERBLACK = 4'd1;
parameter BLACK      = 4'd2;
parameter PLUGE      = 4'd3;
parameter I          = 4'd4;
parameter Q          = 4'd6;
parameter BLUE       = 4'd8;
parameter RED        = 4'd9;
parameter MAGENTA    = 4'd10;
parameter GREEN      = 4'd11;
parameter CYAN       = 4'd12;
parameter YELLOW     = 4'd13;
parameter WHITE      = 4'd14;
parameter SUPERWHITE = 4'd15;

module tt_um_rebeccargb_colorbars (
    input  wire [7:0] ui_in,    // Dedicated inputs
    output wire [7:0] uo_out,   // Dedicated outputs
    input  wire [7:0] uio_in,   // IOs: Input path
    output wire [7:0] uio_out,  // IOs: Output path
    output wire [7:0] uio_oe,   // IOs: Enable path (active high: 0=input, 1=output)
    input  wire       ena,      // always 1 when the design is powered, so you can ignore it
    input  wire       clk,      // clock
    input  wire       rst_n     // reset_n - low to reset
);

  // VGA signals
  wire hsync;
  wire vsync;
  wire [1:0] R;
  wire [1:0] G;
  wire [1:0] B;
  wire video_active;
  wire [9:0] pix_x;
  wire [9:0] pix_y;

  // TinyVGA PMOD
  assign uo_out = {hsync, B[0], G[0], R[0], vsync, B[1], G[1], R[1]};

  // ID ROM address
  wire [9:0] id_x = (ui_in[2] ? ((pix_x + counter) % 640) : pix_x) / ((640 / 4) / 16);
  wire [9:0] id_y = (pix_y - Y_5_12) / ((Y_7_12 - Y_5_12) / 16);
  assign uio_out = {id_y[3:0], id_x[5:2]};
  assign uio_oe  = 8'hFF;

  // Suppress unused signals warning
  wire _unused_ok = &{ena, ui_in, uio_in, id_x[9:6], id_y[9:4]};

  reg [9:0] counter;

  hvsync_generator hvsync_gen(
    .clk(clk),
    .reset(~rst_n),
    .hsync(hsync),
    .vsync(vsync),
    .display_on(video_active),
    .hpos(pix_x),
    .vpos(pix_y)
  );

  wire [9:0] bar_x = (ui_in[3] ? ((pix_x + (640 - counter)) % 640) : pix_x);

  wire [3:0] bar_color = (
    bar_x < X_1_7 ? WHITE :
    bar_x < X_2_7 ? YELLOW :
    bar_x < X_3_7 ? CYAN :
    bar_x < X_4_7 ? GREEN :
    bar_x < X_5_7 ? MAGENTA :
    bar_x < X_6_7 ? RED :
    BLUE
  );

  wire [3:0] rom_in;
  id_rom id(uio_out, rom_in);

  wire id_ui_in = ui_in[4 + id_x[1:0]];
  wire id_rom_in = rom_in[3 - id_x[1:0]];
  wire id_pixel = ui_in[1] ? id_ui_in : id_rom_in;
  wire [3:0] id_color = id_pixel ? WHITE : BLACK;

  wire [3:0] cas_color = (
    bar_x < X_1_7 ? BLUE :
    bar_x < X_2_7 ? BLACK :
    bar_x < X_3_7 ? MAGENTA :
    bar_x < X_4_7 ? BLACK :
    bar_x < X_5_7 ? CYAN :
    bar_x < X_6_7 ? BLACK :
    WHITE
  );

  wire [3:0] bot_color = (
    pix_x < X_05_28 ? I :
    pix_x < X_10_28 ? SUPERWHITE :
    pix_x < X_15_28 ? Q :
    pix_x < X_20_28 ? BLACK :
    pix_x < X_16_21 ? SUPERBLACK :
    pix_x < X_17_21 ? BLACK :
    pix_x < X_18_21 ? PLUGE :
    BLACK
  );

  wire [3:0] color_index = (
    pix_y < Y_5_12 ? bar_color :
    (pix_y < Y_7_12 && ui_in[0]) ? id_color :
    pix_y < Y_8_12 ? bar_color :
    pix_y < Y_9_12 ? cas_color :
    bot_color
  );

  wire [5:0] color;
  palette pal(color_index, color);

  assign R = video_active ? color[5:4] : 2'b00;
  assign G = video_active ? color[3:2] : 2'b00;
  assign B = video_active ? color[1:0] : 2'b00;

  always @(posedge vsync) begin
    if (~rst_n) begin
      counter <= 0;
    end else begin
      counter <= (counter + 5) % 640;
    end
  end

endmodule


module palette (
  input wire [3:0] color_index,
  output wire [5:0] rrggbb
);

  reg [5:0] palette[15:0];
  initial begin
    palette[0]  = 6'b000000; // sync            (rgb(0%, 0%, 0%))
    palette[1]  = 6'b000000; // NTSC superblack (rgb(3.5%, 3.5%, 3.5%))
    palette[2]  = 6'b000000; // NTSC black      (rgb(7.5%, 7.5%, 7.5%))
    palette[3]  = 6'b000000; // NTSC PLUGE      (rgb(11.5%, 11.5%, 11.5%))
    palette[4]  = 6'b000001; // NTSC -I         (rgb(0%, 12%, 30%))
    palette[5]  = 6'b010000; // NTSC +I
    palette[6]  = 6'b010010; // NTSC +Q         (rgb(20%, 0%, 42%))
    palette[7]  = 6'b000100; // NTSC -Q
    palette[8]  = 6'b000010; // NTSC blue       (rgb(0%, 0%, 75%))
    palette[9]  = 6'b100000; // NTSC red        (rgb(75%, 0%, 0%))
    palette[10] = 6'b100010; // NTSC magenta    (rgb(75%, 0%, 75%))
    palette[11] = 6'b001000; // NTSC green      (rgb(0%, 75%, 0%))
    palette[12] = 6'b001010; // NTSC cyan       (rgb(0%, 75%, 75%))
    palette[13] = 6'b101000; // NTSC yellow     (rgb(75%, 75%, 0%))
    palette[14] = 6'b101010; // NTSC white      (rgb(75%, 75%, 75%))
    palette[15] = 6'b111111; // NTSC superwhite (rgb(100%, 100%, 100%))
  end

  assign rrggbb = palette[color_index];

endmodule


module id_rom (
  input wire [7:0] addr,
  output wire [3:0] data
);
// >>> Module Implementation Begin

// <<< Module Implementation End
endmodule




`ifndef HVSYNC_GENERATOR_H
`define HVSYNC_GENERATOR_H

/*
Video sync generator, used to drive a VGA monitor.
Timing from: https://en.wikipedia.org/wiki/Video_Graphics_Array
To use:
- Wire the hsync and vsync signals to top level outputs
- Add a 3-bit (or more) "rgb" output to the top level
*/

module hvsync_generator(clk, reset, hsync, vsync, display_on, hpos, vpos);

  input clk;
  input reset;
  output reg hsync, vsync;
  output display_on;
  output reg [9:0] hpos;
  output reg [9:0] vpos;

  // declarations for TV-simulator sync parameters
  // horizontal constants
  parameter H_DISPLAY       = 640; // horizontal display width
  parameter H_BACK          =  48; // horizontal left border (back porch)
  parameter H_FRONT         =  16; // horizontal right border (front porch)
  parameter H_SYNC          =  96; // horizontal sync width
  // vertical constants
  parameter V_DISPLAY       = 480; // vertical display height
  parameter V_TOP           =  33; // vertical top border
  parameter V_BOTTOM        =  10; // vertical bottom border
  parameter V_SYNC          =   2; // vertical sync # lines
  // derived constants
  parameter H_SYNC_START    = H_DISPLAY + H_FRONT;
  parameter H_SYNC_END      = H_DISPLAY + H_FRONT + H_SYNC - 1;
  parameter H_MAX           = H_DISPLAY + H_BACK + H_FRONT + H_SYNC - 1;
  parameter V_SYNC_START    = V_DISPLAY + V_BOTTOM;
  parameter V_SYNC_END      = V_DISPLAY + V_BOTTOM + V_SYNC - 1;
  parameter V_MAX           = V_DISPLAY + V_TOP + V_BOTTOM + V_SYNC - 1;

  wire hmaxxed = (hpos == H_MAX) || reset;	// set when hpos is maximum
  wire vmaxxed = (vpos == V_MAX) || reset;	// set when vpos is maximum
  
  // horizontal position counter
  always @(posedge clk)
  begin
    hsync <= (hpos>=H_SYNC_START && hpos<=H_SYNC_END);
    if(hmaxxed)
      hpos <= 0;
    else
      hpos <= hpos + 1;
  end

  // vertical position counter
  always @(posedge clk)
  begin
    vsync <= (vpos>=V_SYNC_START && vpos<=V_SYNC_END);
    if(hmaxxed)
      if (vmaxxed)
        vpos <= 0;
      else
        vpos <= vpos + 1;
  end
  
  // display_on is set when beam is in "safe" visible frame
  assign display_on = (hpos<H_DISPLAY) && (vpos<V_DISPLAY);

endmodule

`endif


Reference solution:
rtl/generated.v: 
  reg [3:0] mem[255:0];
  initial begin
    mem[0] = 4'h0;
    mem[1] = 4'h0;
    mem[2] = 4'h0;
    mem[3] = 4'h0;
    mem[4] = 4'h0;
    mem[5] = 4'h0;
    mem[6] = 4'h0;
    mem[7] = 4'h0;
    mem[8] = 4'h0;
    mem[9] = 4'h0;
    mem[10] = 4'h0;
    mem[11] = 4'h0;
    mem[12] = 4'h0;
    mem[13] = 4'h0;
    mem[14] = 4'h0;
    mem[15] = 4'h0;
    mem[16] = 4'h0;
    mem[17] = 4'h3;
    mem[18] = 4'hC;
    mem[19] = 4'h0;
    mem[20] = 4'h0;
    mem[21] = 4'h0;
    mem[22] = 4'h0;
    mem[23] = 4'h0;
    mem[24] = 4'h0;
    mem[25] = 4'h0;
    mem[26] = 4'h0;
    mem[27] = 4'h0;
    mem[28] = 4'h0;
    mem[29] = 4'h0;
    mem[30] = 4'h0;
    mem[31] = 4'h0;
    mem[32] = 4'h0;
    mem[33] = 4'h4;
    mem[34] = 4'h2;
    mem[35] = 4'h0;
    mem[36] = 4'h0;
    mem[37] = 4'h0;
    mem[38] = 4'h0;
    mem[39] = 4'h0;
    mem[40] = 4'h0;
    mem[41] = 4'h0;
    mem[42] = 4'h0;
    mem[43] = 4'h0;
    mem[44] = 4'h0;
    mem[45] = 4'h0;
    mem[46] = 4'h0;
    mem[47] = 4'h0;
    mem[48] = 4'h0;
    mem[49] = 4'h4;
    mem[50] = 4'h2;
    mem[51] = 4'h0;
    mem[52] = 4'h0;
    mem[53] = 4'h0;
    mem[54] = 4'h0;
    mem[55] = 4'h0;
    mem[56] = 4'h0;
    mem[57] = 4'h0;
    mem[58] = 4'h0;
    mem[59] = 4'h0;
    mem[60] = 4'h0;
    mem[61] = 4'h0;
    mem[62] = 4'h0;
    mem[63] = 4'h0;
    mem[64] = 4'h0;
    mem[65] = 4'h8;
    mem[66] = 4'h1;
    mem[67] = 4'h1;
    mem[68] = 4'hD;
    mem[69] = 4'hD;
    mem[70] = 4'h9;
    mem[71] = 4'h4;
    mem[72] = 4'h7;
    mem[73] = 4'h2;
    mem[74] = 4'h6;
    mem[75] = 4'h7;
    mem[76] = 4'h2;
    mem[77] = 4'h5;
    mem[78] = 4'h7;
    mem[79] = 4'h0;
    mem[80] = 4'h0;
    mem[81] = 4'hF;
    mem[82] = 4'h1;
    mem[83] = 4'h0;
    mem[84] = 4'h8;
    mem[85] = 4'h9;
    mem[86] = 4'h5;
    mem[87] = 4'h4;
    mem[88] = 4'h2;
    mem[89] = 4'h5;
    mem[90] = 4'h5;
    mem[91] = 4'h4;
    mem[92] = 4'h5;
    mem[93] = 4'h5;
    mem[94] = 4'h2;
    mem[95] = 4'h0;
    mem[96] = 4'h0;
    mem[97] = 4'h2;
    mem[98] = 4'h1;
    mem[99] = 4'h0;
    mem[100] = 4'h8;
    mem[101] = 4'h9;
    mem[102] = 4'h5;
    mem[103] = 4'h4;
    mem[104] = 4'h2;
    mem[105] = 4'h5;
    mem[106] = 4'h5;
    mem[107] = 4'h4;
    mem[108] = 4'h5;
    mem[109] = 4'h5;
    mem[110] = 4'h2;
    mem[111] = 4'h0;
    mem[112] = 4'h0;
    mem[113] = 4'hA;
    mem[114] = 4'h1;
    mem[115] = 4'h0;
    mem[116] = 4'h8;
    mem[117] = 4'h9;
    mem[118] = 4'h4;
    mem[119] = 4'h8;
    mem[120] = 4'h2;
    mem[121] = 4'h5;
    mem[122] = 4'h5;
    mem[123] = 4'h6;
    mem[124] = 4'h5;
    mem[125] = 4'h5;
    mem[126] = 4'h2;
    mem[127] = 4'h0;
    mem[128] = 4'h0;
    mem[129] = 4'hB;
    mem[130] = 4'hD;
    mem[131] = 4'h0;
    mem[132] = 4'h8;
    mem[133] = 4'h9;
    mem[134] = 4'h4;
    mem[135] = 4'h8;
    mem[136] = 4'h2;
    mem[137] = 4'h7;
    mem[138] = 4'h6;
    mem[139] = 4'h4;
    mem[140] = 4'h5;
    mem[141] = 4'h5;
    mem[142] = 4'h2;
    mem[143] = 4'h0;
    mem[144] = 4'h0;
    mem[145] = 4'hA;
    mem[146] = 4'h9;
    mem[147] = 4'h0;
    mem[148] = 4'h8;
    mem[149] = 4'h9;
    mem[150] = 4'h4;
    mem[151] = 4'h8;
    mem[152] = 4'h2;
    mem[153] = 4'h5;
    mem[154] = 4'h4;
    mem[155] = 4'h4;
    mem[156] = 4'h5;
    mem[157] = 4'h5;
    mem[158] = 4'h2;
    mem[159] = 4'h0;
    mem[160] = 4'h0;
    mem[161] = 4'hA;
    mem[162] = 4'h9;
    mem[163] = 4'h0;
    mem[164] = 4'h8;
    mem[165] = 4'h9;
    mem[166] = 4'h4;
    mem[167] = 4'h8;
    mem[168] = 4'h2;
    mem[169] = 4'h5;
    mem[170] = 4'h4;
    mem[171] = 4'h4;
    mem[172] = 4'h5;
    mem[173] = 4'h5;
    mem[174] = 4'h2;
    mem[175] = 4'h0;
    mem[176] = 4'h0;
    mem[177] = 4'h8;
    mem[178] = 4'h9;
    mem[179] = 4'h0;
    mem[180] = 4'h9;
    mem[181] = 4'hD;
    mem[182] = 4'h4;
    mem[183] = 4'h8;
    mem[184] = 4'h2;
    mem[185] = 4'h5;
    mem[186] = 4'h4;
    mem[187] = 4'h7;
    mem[188] = 4'h2;
    mem[189] = 4'h2;
    mem[190] = 4'h2;
    mem[191] = 4'h0;
    mem[192] = 4'h0;
    mem[193] = 4'h4;
    mem[194] = 4'hA;
    mem[195] = 4'h0;
    mem[196] = 4'h0;
    mem[197] = 4'h0;
    mem[198] = 4'h0;
    mem[199] = 4'h0;
    mem[200] = 4'h0;
    mem[201] = 4'h0;
    mem[202] = 4'h0;
    mem[203] = 4'h0;
    mem[204] = 4'h0;
    mem[205] = 4'h0;
    mem[206] = 4'h0;
    mem[207] = 4'h0;
    mem[208] = 4'h0;
    mem[209] = 4'h4;
    mem[210] = 4'hA;
    mem[211] = 4'h0;
    mem[212] = 4'h0;
    mem[213] = 4'h0;
    mem[214] = 4'h0;
    mem[215] = 4'h0;
    mem[216] = 4'h0;
    mem[217] = 4'h0;
    mem[218] = 4'h0;
    mem[219] = 4'h0;
    mem[220] = 4'h0;
    mem[221] = 4'h0;
    mem[222] = 4'h0;
    mem[223] = 4'h0;
    mem[224] = 4'h0;
    mem[225] = 4'h3;
    mem[226] = 4'h8;
    mem[227] = 4'h0;
    mem[228] = 4'h0;
    mem[229] = 4'h0;
    mem[230] = 4'h0;
    mem[231] = 4'h0;
    mem[232] = 4'h0;
    mem[233] = 4'h0;
    mem[234] = 4'h0;
    mem[235] = 4'h0;
    mem[236] = 4'h0;
    mem[237] = 4'h0;
    mem[238] = 4'h0;
    mem[239] = 4'h0;
    mem[240] = 4'h0;
    mem[241] = 4'h0;
    mem[242] = 4'h0;
    mem[243] = 4'h0;
    mem[244] = 4'h0;
    mem[245] = 4'h0;
    mem[246] = 4'h0;
    mem[247] = 4'h0;
    mem[248] = 4'h0;
    mem[249] = 4'h0;
    mem[250] = 4'h0;
    mem[251] = 4'h0;
    mem[252] = 4'h0;
    mem[253] = 4'h0;
    mem[254] = 4'h0;
    mem[255] = 4'h0;
  end

  assign data = mem[addr];