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.

//=========================================================
// Author   : Emrys Leowhel Oling
// Date     : 2025-09-07
// Design   : Tiny Tapeout Wrapper for 4-bit ALU
// License  : Apache-2.0
//=========================================================

`default_nettype none
`timescale 1ns/1ns

module tt_um_alu_4bit_wrapper (
    input  wire [7:0] ui_in,    // [3:0] = A, [7:4] = B
    output wire [7:0] uo_out,   // {Flags[3:0], ALU_Out[3:0]}
    input  wire [7:0] uio_in,   // [3:0] = ALU_Sel
    output wire [7:0] uio_out,  // Not used
    output wire [7:0] uio_oe,   // Not used
    input  wire ena,            // enable (unused)
    input  wire clk,            // clock (unused)
    input  wire rst_n           // reset (unused)
);
// >>> Module Implementation Begin

// <<< Module Implementation End
endmodule




//=========================================================
// Author   : Emrys Leowhel Oling
// Date     : 2025-09-07
// Design   : 4-bit ALU with Flags (Clocked Version)
// Purpose  : For TTsky25a ALU (Tiny Tapeout project)
// License  : APACHE-2.0
//=========================================================

`default_nettype none
`timescale 1ns/1ns

module alu_4bit (
    input  wire       clk,       // Clock
    input  wire       rst_n,     // Active-low reset (optional)
    input  wire [3:0] A,         // First operand
    input  wire [3:0] B,         // Second operand
    input  wire [3:0] ALU_Sel,   // Operation select
    output reg  [3:0] ALU_Out,   // ALU result

    // Status flags
    output reg Carry,
    output reg Zero,
    output reg Negative,
    output reg Overflow
);
     /*    ALU Operations:  0000=ADD, 
                        0001=SUB, 
                        0010=MUL, 
                        0011=DIV, 
                        0100=SHL, 
                        0101=SHR, 
                        0110=ROL, 
                        0111=ROR, 
                        1000=AND, 
                        1001=OR, 
                        1010=XOR, 
                        1011=NOR, 
                        1100=NAND, 
                        1101=XNOR, 
                        1110=GT, 
                        1111=EQ */
    reg [4:0] tmp;   

    always @(posedge clk or negedge rst_n) begin
        if (!rst_n) begin
            // Reset all outputs
            ALU_Out  <= 4'h0;
            Carry    <= 1'b0;
            Zero     <= 1'b0;
            Negative <= 1'b0;
            Overflow <= 1'b0;
        end else begin
            // Default values
            ALU_Out  <= 4'h0;
            Carry    <= 1'b0;
            Zero     <= 1'b0;
            Negative <= 1'b0;
            Overflow <= 1'b0;

            case (ALU_Sel)
                // Arithmetic
                4'b0000: begin // ADD
                    tmp      = A + B;
                    ALU_Out  <= tmp[3:0];
                    Carry    <= tmp[4];
                    Overflow <= (A[3] == B[3]) && (ALU_Out[3] != A[3]);
                end
                4'b0001: begin // SUB
                    tmp      = A - B;
                    ALU_Out  <= tmp[3:0];
                    Carry    <= tmp[4];
                    Overflow <= (A[3] != B[3]) && (ALU_Out[3] != A[3]);
                end
                4'b0010: ALU_Out <= A * B;                      // MUL (truncated)
                4'b0011: ALU_Out <= (B != 0) ? (A / B) : 4'hF;  // DIV safe

                // Shifts / rotates
                4'b0100: begin ALU_Out <= A << 1; Carry <= A[3]; end
                4'b0101: begin ALU_Out <= A >> 1; Carry <= A[0]; end
                4'b0110: ALU_Out <= {A[2:0], A[3]}; // rotate left
                4'b0111: ALU_Out <= {A[0], A[3:1]}; // rotate right

                // Logical
                4'b1000: ALU_Out <= A & B;
                4'b1001: ALU_Out <= A | B;
                4'b1010: ALU_Out <= A ^ B;
                4'b1011: ALU_Out <= ~(A | B);
                4'b1100: ALU_Out <= ~(A & B);
                4'b1101: ALU_Out <= ~(A ^ B);

                // Comparisons
                4'b1110: ALU_Out <= (A > B)  ? 4'd1 : 4'd0;
                4'b1111: ALU_Out <= (A == B) ? 4'd1 : 4'd0;
            endcase

            // Common flags
            Zero     <= (ALU_Out == 4'h0);
            Negative <= ALU_Out[3];
        end
    end

endmodule


Reference solution:
rtl/generated.v: 
    assign uio_out = 8'h00;
    assign uio_oe  = 8'h00;

    // Internal wires
    wire [3:0] alu_out;
    wire carry, zero, negative, overflow;

    // Explicit operand split
    wire [3:0] a_in   = ui_in[3:0]; // Operand A
    wire [3:0] b_in   = ui_in[7:4]; // Operand B
    wire [3:0] sel_in = uio_in[3:0];// ALU select

    // Instantiate ALU
    alu_4bit alu_inst (
        .clk(clk),
        .rst_n(rst_n),
        .A(a_in),
        .B(b_in),
        .ALU_Sel(sel_in),
        .ALU_Out(alu_out),
        .Carry(carry),
        .Zero(zero),
        .Negative(negative),
        .Overflow(overflow)
    );

    // Pack outputs: upper 4 bits = flags, lower 4 bits = ALU result
    assign uo_out = {carry, zero, negative, overflow, alu_out};