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 Your Name
 * SPDX-License-Identifier: Apache-2.0
 */

`default_nettype none

parameter D_WIDTH = 4;
parameter A_WIDTH = 3;

module tt_um_TT16 (
    input  wire [7:0] ui_in,    // Dedicated inputs
    output reg  [7:0] uo_out,   // Changed to reg for reset assignment
    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
);

    wire wclk, rclk;
    assign uio_out[0] = wclk;
    assign uio_out[1] = rclk;
    wire [A_WIDTH:0] wptr, rptr;
    wire [A_WIDTH-1:0] waddr, raddr;
    wire [A_WIDTH:0] rptr_sync, wptr_sync;
    
    wire winc = ui_in[4];
    wire rinc = ui_in[5];
    reg [3:0] wdata;
    wire [3:0] rdata;
    wire full, empty;

    // Assign wdata combinationally
    always @(*) begin
        wdata[0] = ui_in[0];
        wdata[1] = ui_in[1];
        wdata[2] = ui_in[2];
        wdata[3] = ui_in[3];
    end

    // Synchronous reset logic for uo_out
    always @(posedge clk or negedge rst_n) begin
        if (!rst_n) begin
            uo_out <= 8'b0; // All output bits to zero
        end else begin
            uo_out <= {2'b00, empty, full, rdata[3:0]};
        end
    end

    assign uio_out[7:2] = 0;
    assign uio_oe  = 8'b0;

    clock_div clk_div_inst (
        .clk(clk),
        .rst_n(rst_n),
        .wclk(wclk),
        .rclk(rclk)
    );
    
    fifo_memory #(.DATA_WIDTH(D_WIDTH), .ADDR_WIDTH(A_WIDTH)) fifo_inst (
        .wclk(wclk),
        .rclk(rclk),
        .waddr(waddr),
        .raddr(raddr),
        .wdata(wdata),
        .wen(winc & ~full),
        .ren(rinc & ~empty),
        .rdata(rdata)
    );

    wptr_full #(.ADDR_WIDTH(A_WIDTH)) wptr_inst (
        .wclk(wclk),
        .rst_n(rst_n),
        .winc(winc),
        .rptr_sync(rptr_sync),
        .full(full),
        .wptr(wptr),
        .waddr(waddr)
    );

    rptr_empty #(.ADDR_WIDTH(A_WIDTH)) rptr_inst (
        .rclk(rclk),
        .rst_n(rst_n),
        .rinc(rinc),
        .wptr_sync(wptr_sync),
        .empty(empty),
        .rptr(rptr),
        .raddr(raddr)
    );

    two_ff_sync #(.PTR_WIDTH(A_WIDTH)) sync_r2w (
        .clk(wclk),
        .rst_n(rst_n),
        .d(rptr),
        .q(rptr_sync)
    );

    two_ff_sync #(.PTR_WIDTH(A_WIDTH)) sync_w2r (
        .clk(rclk),
        .rst_n(rst_n),
        .d(wptr),
        .q(wptr_sync)
    );

    // List all unused inputs to prevent warnings
    wire _unused = &{ena, ui_in[6], ui_in[7], uio_in[7:0]};
endmodule


module fifo_memory #(parameter DATA_WIDTH = 4, ADDR_WIDTH = 3)(
    input wire wclk, rclk,
    input wire [ADDR_WIDTH-1:0] waddr, raddr,
    input wire [DATA_WIDTH-1:0] wdata,
    input wire wen, ren,
    output reg [DATA_WIDTH-1:0] rdata
);
    reg [3:0] mem [(2**ADDR_WIDTH)-1:0];

    // Write with reset: clear memory on rst_n

    always @(posedge wclk) begin
        if (wen) begin
            mem[waddr] <= wdata;
        end
    end

    // Read with reset: clear rdata on rst_n
    always @(posedge rclk) begin
        if (ren) begin
            rdata <= mem[raddr];
        end 
    end
endmodule


module wptr_full #(parameter ADDR_WIDTH = 3)(
    input wclk, rst_n, winc,
    input [ADDR_WIDTH:0] rptr_sync,
    output reg full,
    output reg [ADDR_WIDTH:0] wptr,
    output  [ADDR_WIDTH-1:0] waddr
);
    reg [ADDR_WIDTH:0] wbin;
    wire [ADDR_WIDTH:0] wbin_next, wgray_next;

    assign waddr = wbin_next[ADDR_WIDTH-1:0];
    assign wbin_next = wbin + ((winc & ~full) ? 1 : 0);
    assign wgray_next = (wbin_next >> 1) ^ wbin_next;

    always @(posedge wclk or negedge rst_n) begin
        if (!rst_n) begin
            wbin  <= 0;
            full  <= 1'b0;
            wptr  <= 0;
            
        end else begin
            wbin  <= wbin_next;
            full  <= (wgray_next == {~rptr_sync[ADDR_WIDTH:ADDR_WIDTH-1], rptr_sync[ADDR_WIDTH-2:0]});
            wptr  <= wgray_next;
            
        end
    end
endmodule


module rptr_empty #(parameter ADDR_WIDTH = 3)(
    input rclk, rst_n, rinc,
    input [ADDR_WIDTH:0] wptr_sync,
    output reg empty,
    output reg [ADDR_WIDTH:0] rptr,
    output  [ADDR_WIDTH-1:0] raddr
);
    reg [ADDR_WIDTH:0] rbin;
    wire [ADDR_WIDTH:0] rbin_next, rgray_next;

    assign raddr = rbin_next[ADDR_WIDTH-1:0];
    assign rbin_next = rbin + ((rinc & ~empty) ? 1 : 0);
    assign rgray_next = (rbin_next >> 1) ^ rbin_next;
 
    always @(posedge rclk or negedge rst_n) begin
        if (!rst_n) begin
            rbin  <= 0;
            empty <= 1'b1;
            rptr  <= 0;
            
        end else begin
            rbin  <= rbin_next;
            empty <= (rgray_next == wptr_sync);
            rptr  <= rgray_next;
        end
    end
endmodule




module two_ff_sync #(parameter PTR_WIDTH = 3)(
    input clk, rst_n,
    input [PTR_WIDTH:0] d,
    output reg [PTR_WIDTH:0] q
);
    reg [PTR_WIDTH:0] sync1;

    always @(posedge clk or negedge rst_n) begin
        if (!rst_n) begin
            sync1 <= 0;
            q     <= 0;
        end else begin
            sync1 <= d;
            q     <= sync1;
        end
    end
endmodule





module clock_div(
    input  wire clk,   // 100 MHz
    input  wire rst_n,
    output reg  wclk,     // 50 MHz
    output reg  rclk      // ~33.3 MHz
);
// >>> Module Implementation Begin

// <<< Module Implementation End
endmodule





Reference solution:
rtl/generated.v: 
    // ----------- wclk ÷2 (50 MHz) -----------
    always @(posedge clk or negedge rst_n) begin
        if(!rst_n)
            wclk <= 0;
        else
            wclk <= ~wclk;   // toggle every cycle ? ÷2
    end

    // ----------- rclk ÷3 (33.3 MHz) -----------
    reg [1:0] cnt;
    always @(posedge clk or negedge rst_n) begin
        if(!rst_n) begin
            cnt <= 0;
            rclk   <= 0;
        end else if(cnt == 2) begin
            cnt <= 0;
            rclk   <= ~rclk;  // toggle every 3 cycles ? ÷6 overall
        end else
            cnt <= cnt + 1;
    end