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 Nicklaus Thompson
 * SPDX-License-Identifier: Apache-2.0
 */

`default_nettype none

module tt_um_NicklausThompson_SkyKing (
    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;

	// BNC signals
	wire [7:0] BNC_x;
	wire [6:0] BNC_y;
	wire BNC_trig;

	// PMODs
	wire [7:0] VGA_out, BNC1_out, BNC2Y_out, BNC2X_out;
	assign VGA_out = {hsync, B[0], G[0], R[0], vsync, B[1], G[1], R[1]};
	assign BNC1_out = {BNC_x[4], BNC_x[6], BNC_y[4], BNC_y[6], BNC_x[5], BNC_x[7], BNC_y[5], BNC_trig};
	assign BNC2Y_out = {BNC_trig, BNC_y[5], BNC_y[3], BNC_y[1], BNC_y[6], BNC_y[4], BNC_y[2], BNC_y[0]};
	assign BNC2X_out = {BNC_x[7], BNC_x[5], BNC_x[3], BNC_x[1], BNC_x[6], BNC_x[4], BNC_x[2], BNC_x[0]};
	assign uio_oe  = 8'hFF;

	// 2'b00: VGA
	// 2'b01: XY1
	// 2'b11: XY2
	assign uo_out = ui_in[0] ? (ui_in[1] ? BNC2Y_out : BNC1_out) : VGA_out;
	assign uio_out = ui_in[1] ? BNC2X_out : 8'h00;

	// Sync generator and VGA XY coordinate reference
	hvsync_generator hvsync_gen(
		.clk(clk),
		.reset(~rst_n),
		.hsync(hsync),
		.vsync(vsync),
		.display_on(video_active),
		.hpos(pix_x),
		.vpos(pix_y)
	);

	// Suppress unused signals warning
	wire _unused_ok = &{ena, ui_in, uio_in};

	// VGA image generator
	skyking_generator vga_image_generator(clk, rst_n, hsync, vsync, video_active, pix_x, pix_y, ui_in[3], R, G, B);

	// BNC image generator
	bnc_demo bnc_image_generator(clk, rst_n, BNC_x, BNC_y, BNC_trig);

endmodule // tt_um_NicklausThompson_SkyKing

module bnc_demo(
	input wire clk, 
	input wire rst_n, 
	output reg [7:0] BNC_x,
	output reg [6:0] BNC_y, 
	output wire BNC_trig
);
// >>> Module Implementation Begin

// <<< Module Implementation End
endmodule



module skyking_generator(
	input wire clk, 
	input wire rst_n,
	input wire hsync, 
	input wire vsync, 
	input wire video_active, 
	input wire [9:0] pix_x, 
	input wire [9:0] pix_y,
	input wire alt, 
	output wire [1:0] R, 
	output wire [1:0] G, 
	output wire [1:0] B 
);

	// Counter for timing
	reg [28:0] counter;
	always @(posedge clk) begin
		if (~rst_n) begin
			counter <= 0;
		end else begin
			counter <= counter + 1;
		end
	end

	// Sky gradient
	wire [1:0] r_sky, g_sky;
	assign r_sky = {1'b1, ~&pix_y[8:7]};
	assign g_sky = ~pix_y[8:7];

	// Letters
  wire [17:0] do_letter;
  reg [17:0] character_hold;
  
  always @(posedge clk) begin
    if (~rst_n) character_hold <= 18'b0;
    else begin
      case (counter[24:20])
        default: character_hold <= character_hold;
        5'h00: character_hold[00] <= 1'b1;
        5'h01: character_hold[01] <= 1'b1;
        5'h02: character_hold[02] <= 1'b1;
        5'h03: character_hold[03] <= 1'b1;        
        5'h04: character_hold[04] <= 1'b1;
        5'h05: character_hold[05] <= 1'b1;
        5'h06: character_hold[06] <= 1'b1;
        5'h07: character_hold[07] <= 1'b1;
        5'h08: character_hold[08] <= 1'b1;
        5'h09: character_hold[09] <= 1'b1;
        5'h0A: character_hold[10] <= 1'b1;        
        5'h0B: character_hold[11] <= 1'b1;
        5'h0C: character_hold[12] <= 1'b1;
        5'h0D: character_hold[13] <= 1'b1;
        5'h0E: character_hold[14] <= 1'b1;
        5'h0F: character_hold[15] <= 1'b1;
        5'h11: character_hold[16] <= 1'b1;
        5'h12: character_hold[17] <= 1'b1;
      endcase
    end
  end

	wire [4:0] do_alt_letter;
  wire display_letter = |({do_letter[17:6], (alt ? do_letter[5:1] : do_alt_letter), do_letter[0]} & character_hold);
  
	// S
  assign do_letter[00] = (pix_y[8:2] == 7'b1101000) & (pix_x[8:4] == 5'b00000)   & ~pix_x[9]
                       | (pix_y[8:3] == 6'b110100)  & (pix_x[8:2] == 7'b0000000) & ~pix_x[9]
                       | (pix_y[8:2] == 7'b1101010) & (pix_x[8:4] == 5'b00000)   & ~pix_x[9]
                       | (pix_y[8:3] == 6'b110101)  & (pix_x[8:2] == 7'b0000011) & ~pix_x[9]
                       | (pix_y[8:2] == 7'b1101100) & (pix_x[8:4] == 5'b00000)   & ~pix_x[9];
  // E
  assign do_letter[01] = (pix_y[8:2] == 7'b1101000) & (pix_x[8:3] == 6'b000100)  & ~pix_x[9]
                       | (pix_y[8:2] == 7'b1101000) & (pix_x[8:3] == 6'b000011)  & ~pix_x[9]
                       | (pix_y[8:2] == 7'b1101010) & (pix_x[8:3] == 6'b000100)  & ~pix_x[9]
                       | (pix_y[8:2] == 7'b1101010) & (pix_x[8:3] == 6'b000011)  & ~pix_x[9]
                       | (pix_y[8:2] == 7'b1101100) & (pix_x[8:3] == 6'b000100)  & ~pix_x[9]
                       | (pix_y[8:2] == 7'b1101100) & (pix_x[8:3] == 6'b000011)  & ~pix_x[9]
                       | (pix_y[8:4] == 5'b11010)   & (pix_x[8:2] == 7'b0000110) & ~pix_x[9];
  // E
  assign do_letter[02] = (pix_y[8:2] == 7'b1101000) & (pix_x[8:4] == 5'b000011)  & ~pix_x[9]
                       | (pix_y[8:2] == 7'b1101010) & (pix_x[8:4] == 5'b000011)  & ~pix_x[9]
                       | (pix_y[8:2] == 7'b1101100) & (pix_x[8:4] == 5'b000011)  & ~pix_x[9]
                       | (pix_y[8:4] == 5'b11010)   & (pix_x[8:2] == 7'b0001100) & ~pix_x[9];
  // Y
  assign do_letter[03] = (pix_y[8:3] == 6'b110100)  & (pix_x[8:2] == 7'b0010110) & ~pix_x[9]
                       | (pix_y[8:3] == 6'b110100)  & (pix_x[8:2] == 7'b0011001) & ~pix_x[9]
                       | (pix_y[8:2] == 7'b1101010) & (pix_x[8:3] == 6'b001100)  & ~pix_x[9]
                       | (pix_y[8:2] == 7'b1101010) & (pix_x[8:3] == 6'b001011)  & ~pix_x[9]
                       | (pix_y[8:3] == 6'b110101)  & (pix_x[8:2] == 7'b0010111) & ~pix_x[9]
                       | (pix_y[8:3] == 6'b110101)  & (pix_x[8:2] == 7'b0011000) & ~pix_x[9]
                       | (pix_y[8:2] == 7'b1101100) & (pix_x[8:2] == 7'b0010111) & ~pix_x[9]
                       | (pix_y[8:2] == 7'b1101100) & (pix_x[8:2] == 7'b0011000) & ~pix_x[9];
  // O
  assign do_letter[04] = (pix_y[8:2] == 7'b1101000) & (pix_x[8:4] == 5'b00111)   & ~pix_x[9]
                       | (pix_y[8:2] == 7'b1101100) & (pix_x[8:4] == 5'b00111)   & ~pix_x[9]
                       | (pix_y[8:4] == 5'b11010)   & (pix_x[8:2] == 7'b0011100) & ~pix_x[9]
                       | (pix_y[8:4] == 5'b11010)   & (pix_x[8:2] == 7'b0011111) & ~pix_x[9];
  // U
  assign do_letter[05] = (pix_y[8:2] == 7'b1101100) & (pix_x[8:3] == 6'b010001)
                       | (pix_y[8:2] == 7'b1101100) & (pix_x[8:3] == 6'b010010)
                       | (pix_y[8:4] == 5'b11010)   & (pix_x[8:2] == 7'b0100101)
                       | (pix_y[8:4] == 5'b11010)   & (pix_x[8:2] == 7'b0100010);
  // S
  assign do_letter[06] = (pix_y[8:2] == 7'b1101000) & (pix_x[8:4] == 5'b01011)
                      | (pix_y[8:3] == 6'b110100)  & (pix_x[8:2] == 7'b0101100)
                      | (pix_y[8:2] == 7'b1101010) & (pix_x[8:4] == 5'b01011)
                      | (pix_y[8:3] == 6'b110101)  & (pix_x[8:2] == 7'b0101111)
                      | (pix_y[8:2] == 7'b1101100) & (pix_x[8:4] == 5'b01011);
	// P
  assign do_letter[07] = (pix_y[8:4] == 5'b11010)   & (pix_x[8:2] == 7'b0110010)
                       | (pix_y[8:2] == 7'b1101100) & (pix_x[8:2] == 7'b0110010)
                       | (pix_y[8:3] == 6'b110100)  & (pix_x[8:2] == 7'b0110101)
                       | (pix_y[8:2] == 7'b1101000) & (pix_x[8:3] == 6'b011001)
                       | (pix_y[8:2] == 7'b1101000) & (pix_x[8:3] == 6'b011010)
                       | (pix_y[8:2] == 7'b1101010) & (pix_x[8:3] == 6'b011001)
                       | (pix_y[8:2] == 7'b1101010) & (pix_x[8:3] == 6'b011010);
  // A
  assign do_letter[08] = (pix_y[8:2] == 7'b1101000) & (pix_x[8:4] == 5'b01110)
                       | (pix_y[8:2] == 7'b1101010) & (pix_x[8:4] == 5'b01110)
                       | (pix_y[8:4] == 5'b11010)   & (pix_x[8:2] == 7'b0111000)
                       | (pix_y[8:4] == 5'b11010)   & (pix_x[8:2] == 7'b0111011)
                       | (pix_y[8:2] == 7'b1101100) & (pix_x[8:2] == 7'b0111000)
                       | (pix_y[8:2] == 7'b1101100) & (pix_x[8:2] == 7'b0111011);
  // C
  assign do_letter[09] = (pix_y[8:4] == 5'b11010)   & (pix_x[8:2] == 7'b0111110)
                       | (pix_y[8:2] == 7'b1101000) & (pix_x[8:3] == 6'b011111)
                       | (pix_y[8:2] == 7'b1101000) & (pix_x[8:3] == 6'b100000)
                       | (pix_y[8:2] == 7'b1101100) & (pix_x[8:3] == 6'b011111)
                       | (pix_y[8:2] == 7'b1101100) & (pix_x[8:3] == 6'b100000);
  // E
  assign do_letter[10] = (pix_y[8:2] == 7'b1101000) & (pix_x[8:4] == 5'b10001)
                       | (pix_y[8:2] == 7'b1101010) & (pix_x[8:4] == 5'b10001)
                       | (pix_y[8:2] == 7'b1101100) & (pix_x[8:4] == 5'b10001)
                       | (pix_y[8:4] == 5'b11010)  & (pix_x[8:2] == 7'b1000100);
  // C
  assign do_letter[11] = (pix_y[8:4] == 5'b11010)   & (pix_x[8:2] == 7'b1001110)
                       | (pix_y[8:2] == 7'b1101000) & (pix_x[8:3] == 6'b100111)
                       | (pix_y[8:2] == 7'b1101000) & (pix_x[8:3] == 6'b101000)
                       | (pix_y[8:2] == 7'b1101100) & (pix_x[8:3] == 6'b100111)
                       | (pix_y[8:2] == 7'b1101100) & (pix_x[8:3] == 6'b101000);
  // O
  assign do_letter[12] = (pix_y[8:2] == 7'b1101000) & (pix_x[8:4] == 5'b10101)
                       | (pix_y[8:2] == 7'b1101100) & (pix_x[8:4] == 5'b10101)
                       | (pix_y[8:4] == 5'b11010)   & (pix_x[8:2] == 7'b1010100)
                       | (pix_y[8:4] == 5'b11010)   & (pix_x[8:2] == 7'b1010111);
	// W
  assign do_letter[13] = (pix_y[8:3] == 6'b110101) & (pix_x[8:3] == 6'b101101)
                       | (pix_y[8:3] == 6'b110101) & (pix_x[8:3] == 6'b101110)
                       | (pix_y[8:2] == 7'b1101100) & (pix_x[8:2] == 7'b1011010)
                       | (pix_y[8:2] == 7'b1101100) & (pix_x[8:2] == 7'b1011101)
                       | (pix_y[8:4] == 5'b11010)  & (pix_x[8:2] == 7'b1011010)
                       | (pix_y[8:4] == 5'b11010)  & (pix_x[8:2] == 7'b1011101);
  // B
  assign do_letter[14] = (pix_y[8:2] == 7'b1101000) & (pix_x[8:4] == 5'b11000)
                       | (pix_y[8:2] == 7'b1101100) & (pix_x[8:4] == 5'b11000)
                       | (pix_y[8:2] == 7'b1101010) & (pix_x[8:4] == 5'b11000)
                       | (pix_y[8:4] == 5'b11010)   & (pix_x[8:2] == 7'b1100000)
                       | (pix_y[8:4] == 5'b11010)   & (pix_x[8:2] == 7'b1100011);
  // O
  assign do_letter[15] = (pix_y[8:4] == 5'b11010)   & (pix_x[8:2] == 7'b1100110)
                       | (pix_y[8:4] == 5'b11010)   & (pix_x[8:2] == 7'b1101001)
                       | (pix_y[8:2] == 7'b1101000) & (pix_x[8:3] == 6'b110011)
                       | (pix_y[8:2] == 7'b1101000) & (pix_x[8:3] == 6'b110100)
                       | (pix_y[8:2] == 7'b1101100) & (pix_x[8:3] == 6'b110011)
                       | (pix_y[8:2] == 7'b1101100) & (pix_x[8:3] == 6'b110100);
  // Y
  assign do_letter[16] = (pix_y[8:3] == 6'b110100)  & (pix_x[8:2] == 7'b1101100)
                       | (pix_y[8:3] == 6'b110100)  & (pix_x[8:2] == 7'b1101111)
                       | (pix_y[8:2] == 7'b1101010) & (pix_x[8:4] == 5'b11011)
                       | (pix_y[8:3] == 6'b110101)  & (pix_x[8:2] == 7'b1101101)
                       | (pix_y[8:3] == 6'b110101)  & (pix_x[8:2] == 7'b1101110)
                       | (pix_y[8:2] == 7'b1101100) & (pix_x[8:2] == 7'b1101101)
                       | (pix_y[8:2] == 7'b1101100) & (pix_x[8:2] == 7'b1101110);
  // Cursor
  assign do_letter[17] = ((pix_y[8:2] == 7'b1101100) & (pix_x[8:3] == 6'b111001)
                       |  (pix_y[8:2] == 7'b1101100) & (pix_x[8:3] == 6'b111010))
                       & counter[22];

	// Alt letters
  // O
  assign do_alt_letter[00] = (pix_y[8:2] == 7'b1101000) & (pix_x[8:3] == 6'b000100)  & ~pix_x[9]
                           | (pix_y[8:2] == 7'b1101000) & (pix_x[8:3] == 6'b000011)  & ~pix_x[9]
                           | (pix_y[8:2] == 7'b1101100) & (pix_x[8:3] == 6'b000100)  & ~pix_x[9]
                           | (pix_y[8:2] == 7'b1101100) & (pix_x[8:3] == 6'b000011)  & ~pix_x[9]
                           | (pix_y[8:4] == 5'b11010)   & (pix_x[8:2] == 7'b0000110) & ~pix_x[9]
                           | (pix_y[8:4] == 5'b11010)   & (pix_x[8:2] == 7'b0001001) & ~pix_x[9];
  // L
  assign do_alt_letter[01] = (pix_y[8:4] == 5'b11010)   & (pix_x[8:2] == 7'b0010000) & ~pix_x[9]
                           | (pix_y[8:2] == 7'b1101100) & (pix_x[8:4] == 5'b00100)& ~pix_x[9];
  // O
  assign do_alt_letter[02] = (pix_y[8:2] == 7'b1101000) & (pix_x[8:3] == 6'b001011)  & ~pix_x[9]
                           | (pix_y[8:2] == 7'b1101000) & (pix_x[8:3] == 6'b001100)  & ~pix_x[9]
                           | (pix_y[8:2] == 7'b1101100) & (pix_x[8:3] == 6'b001011)  & ~pix_x[9]
                           | (pix_y[8:2] == 7'b1101100) & (pix_x[8:3] == 6'b001100)  & ~pix_x[9]
                           | (pix_y[8:4] == 5'b11010)   & (pix_x[8:2] == 7'b0010110) & ~pix_x[9]
                           | (pix_y[8:4] == 5'b11010)   & (pix_x[8:2] == 7'b0011001) & ~pix_x[9];
  // N
  assign do_alt_letter[03] = (pix_y[8:4] == 5'b11010)   & (pix_x[8:2] == 7'b0011100) & ~pix_x[9]
                           | (pix_y[8:4] == 5'b11010)   & (pix_x[8:2] == 7'b0011111) & ~pix_x[9]
                           | (pix_y[8:2] == 7'b1101100) & (pix_x[8:2] == 7'b0011100) & ~pix_x[9]
                           | (pix_y[8:2] == 7'b1101100) & (pix_x[8:2] == 7'b0011111) & ~pix_x[9]
                           | (pix_y[8:2] == 7'b1101010) & (pix_x[8:4] == 5'b00111)   & ~pix_x[9]
                           | (pix_y[8:2] == 7'b1101001) & (pix_x[8:3] == 6'b001110)   & ~pix_x[9]
                           | (pix_y[8:2] == 7'b1101011) & (pix_x[8:3] == 6'b001111)   & ~pix_x[9];
  // G
  assign do_alt_letter[04] = (pix_y[8:4] == 5'b11010)   & (pix_x[8:2] == 7'b0100010) & ~pix_x[9]
                           | (pix_y[8:3] == 6'b110101)  & (pix_x[8:2] == 7'b0100101) & ~pix_x[9]
                           | (pix_y[8:2] == 7'b1101000) & (pix_x[8:3] == 6'b010001)  & ~pix_x[9]
                           | (pix_y[8:2] == 7'b1101000) & (pix_x[8:3] == 6'b010010)  & ~pix_x[9]
                           | (pix_y[8:2] == 7'b1101010) & (pix_x[8:3] == 6'b010010)  & ~pix_x[9]
                           | (pix_y[8:2] == 7'b1101100) & (pix_x[8:3] == 6'b010001)  & ~pix_x[9]
                           | (pix_y[8:2] == 7'b1101100) & (pix_x[8:3] == 6'b010010)  & ~pix_x[9];

	// Plane
  wire do_plane;
  assign do_plane = (pix_x >= 310) & (pix_x <= 330) & (pix_y >= 180) & (pix_y <= 300) // Fuselage
                  | (pix_x >= 260) & (pix_x <= 380) & (pix_y >= 230) & (pix_y <= 240) // Wing main
                  | (pix_x >= 270) & (pix_x <= 370) & (pix_y >= 240) & (pix_y <= 244) // Wing taper
                  | (pix_x >= 290) & (pix_x <= 350) & (pix_y >= 295) & (pix_y <= 300) // Tail main
                  | (pix_x >= 300) & (pix_x <= 340) & (pix_y >= 293) & (pix_y <= 295) // Tail taper
                  | (pix_x >= 287) & (pix_x <= 293) & (pix_y >= 210) & (pix_y <= 255) // Engine L
                  | (pix_x >= 347) & (pix_x <= 353) & (pix_y >= 210) & (pix_y <= 255) // Engine R
                  | (pix_x >= 280) & (pix_x <= 300) & (pix_y >= 215) & (pix_y <= 216) // Prop L
                  | (pix_x >= 340) & (pix_x <= 360) & (pix_y >= 215) & (pix_y <= 216) // Prop R
                  | (pix_x >= 315) & (pix_x <= 325) & (pix_y >= 175) & (pix_y <= 180); // Nose

  // VGA color channels
  assign R = video_active ? (r_sky | {2{display_letter}}) & {2{~do_plane}} : 2'b00;
  assign G = video_active ? (g_sky | {2{display_letter}}) & {2{~do_plane}} : 2'b00;
  assign B = video_active ? {2{display_letter}} & {2{~do_plane}} : 2'b00;
	
	// Suppress unused signals warning
	wire _unused_ok = &{hsync, vsync};

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: 
	// Counter for timing
	reg [28:0] counter;
	always @(posedge clk) begin
		if (~rst_n) begin
			counter <= 0;
		end else begin
			counter <= counter + 1;
		end
	end
	
	always @(posedge clk) begin
		// 8-bit X output
		if (~rst_n) begin
			BNC_x <= 8'd0;
			BNC_y <= 7'd0;
		end
		
		case (counter[4:0])
			0: BNC_x <= 8'd186;
			1: BNC_x <= 8'd207;
			2: BNC_x <= 8'd225;
			3: BNC_x <= 8'd239;
			4: BNC_x <= 8'd249;
			5: BNC_x <= 8'd254;
			6: BNC_x <= 8'd254;
			7: BNC_x <= 8'd249;
			8: BNC_x <= 8'd240;
			9: BNC_x <= 8'd226;
			10: BNC_x <= 8'd209;
			11: BNC_x <= 8'd188;
			12: BNC_x <= 8'd165;
			13: BNC_x <= 8'd140;
			14: BNC_x <= 8'd115;
			15: BNC_x <= 8'd91;
			16: BNC_x <= 8'd68;
			17: BNC_x <= 8'd47;
			18: BNC_x <= 8'd29;
			19: BNC_x <= 8'd15;
			20: BNC_x <= 8'd5;
			21: BNC_x <= 8'd0;
			22: BNC_x <= 8'd0;
			23: BNC_x <= 8'd5;
			24: BNC_x <= 8'd14;
			25: BNC_x <= 8'd28;
			26: BNC_x <= 8'd46;
			27: BNC_x <= 8'd67;
			28: BNC_x <= 8'd90;
			29: BNC_x <= 8'd114;
			30: BNC_x <= 8'd139;
			31: BNC_x <= 8'd164;
			default: BNC_x <= 8'd0;
		endcase // counter[4:0]
		
		// 7-bit Y output
		case (counter[4:0])
			0: BNC_y <= 7'd120;
			1: BNC_y <= 7'd113;
			2: BNC_y <= 7'd104;
			3: BNC_y <= 7'd94;
			4: BNC_y <= 7'd83;
			5: BNC_y <= 7'd71;
			6: BNC_y <= 7'd58;
			7: BNC_y <= 7'd46;
			8: BNC_y <= 7'd34;
			9: BNC_y <= 7'd24;
			10: BNC_y <= 7'd15;
			11: BNC_y <= 7'd7;
			12: BNC_y <= 7'd3;
			13: BNC_y <= 7'd0;
			14: BNC_y <= 7'd0;
			15: BNC_y <= 7'd2;
			16: BNC_y <= 7'd7;
			17: BNC_y <= 7'd13;
			18: BNC_y <= 7'd22;
			19: BNC_y <= 7'd33;
			20: BNC_y <= 7'd44;
			21: BNC_y <= 7'd56;
			22: BNC_y <= 7'd69;
			23: BNC_y <= 7'd81;
			24: BNC_y <= 7'd93;
			25: BNC_y <= 7'd103;
			26: BNC_y <= 7'd112;
			27: BNC_y <= 7'd119;
			28: BNC_y <= 7'd124;
			29: BNC_y <= 7'd126;
			30: BNC_y <= 7'd126;
			31: BNC_y <= 7'd124;
			default: BNC_y <= 7'd0;
		endcase // counter[4:0]
end

	assign BNC_trig = counter[3];