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.

`default_nettype none

module tt_um_alif (
    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
);
// >>> Module Implementation Begin

// <<< Module Implementation End
endmodule



module lif (
    input wire [11:0]    current,
    input wire          clk,
    input wire          reset_n,
    output reg [7:0]    state,
    output wire         spike
);
    reg [7:0]    adapt_threshold;  // Temporarily exposed for testing
    reg [7:0]    spike_counter;     // Temporarily exposed for testing
    wire [7:0] next_state;
    reg [7:0] threshold;

    always @(posedge clk) begin
        if (!reset_n) begin
            state <= 0;
            threshold <= 50;
            adapt_threshold <= 250;  // Start adapt_threshold higher to see decay
            spike_counter <= 0;
        end else begin
            state <= next_state;
            
            // Adapt threshold increase upon spiking
            if (spike) begin
                if (adapt_threshold < 170) begin
                    adapt_threshold <= adapt_threshold + (state >> 2); // Increment proportional to current
                    spike_counter <= 0;  // Reset counter on spike
                end else begin
                    spike_counter <= 0;  // Reset counter on spike
                end
            end else begin
                spike_counter <= spike_counter + 1;  // Increment counter each cycle without spike
            end

            // Decay adapt_threshold over time if it's greater than base threshold
            if (spike_counter > 5 && adapt_threshold > threshold)
                adapt_threshold <= adapt_threshold - (1 + (spike_counter >> 3)); // Decay rate increases over time
        end
    end

    wire [11:0] scaled_state;  // Intermediate 12-bit result for scaling
    assign scaled_state = (state * 14) >> 4;

    wire [11:0] sum = current + scaled_state; // 12-bit addition
    assign next_state = (sum > 12'h0FF) ? 8'hFF : sum[7:0];

    assign spike = (state >= adapt_threshold);

endmodule


// module lif (
//     input wire [7:0]    current,
//     input wire          clk,
//     input wire          reset_n,
//     output reg [7:0]    state,
//     output wire         spike
// );

//     wire [7:0] next_state;
//     reg [7:0] threshold;
//     reg [7:0] adapt_threshold;  // Adaptive threshold

//     always @(posedge clk) begin
//         if (!reset_n) begin
//             state <= 0;
//             threshold <= 200;
//             adapt_threshold <= 250;  // Start adapt_threshold higher to see decay
//         end else begin
//             state <= next_state;
//             // Decay adapt_threshold over time if it's greater than base threshold
//             if (adapt_threshold > threshold)
//                 adapt_threshold <= adapt_threshold - 1;
//         end
//     end

//     // next state logic
//     assign next_state = current + (state >> 1);

//     // spiking logic with adaptive threshold
//     assign spike = (state >= adapt_threshold);

// endmodule




// /*
//  * Copyright (c) 2024 Your Name
//  * SPDX-License-Identifier: Apache-2.0
//  */

// `default_nettype none

// module lif (
//     input wire [7:0]    current,
//     input wire          clk,
//     input wire          reset_n,
//     output reg [7:0]    state,
//     output wire         spike
// );

//     wire [7:0] next_state;
//     reg [7:0] threshold;

//     always @(posedge clk) begin
        
//         if (!reset_n) begin
//             state <= 0;
//             threshold <= 200;
//         end else begin
//             state <= next_state;
//         end
//     end

//     // next state logic
//     assign next_state = current + (state >> 1);

//     // spiking logic
//     assign spike = (state >= threshold);


// endmodule

Reference solution:
rtl/generated.v: 
  // All output pins must be assigned. If not used, assign to 0.
  assign uio_oe  = 1;            // Set all IOs as outputs
  assign uio_out[4:0] = 0;       // Assign unused output pins to 0

  // List all unused inputs to prevent warnings
  wire _unused = &{ena, uio_in, 1'b0};

  // Generate noisy variations of uio_in
  wire [11:0] noisy_input1 = {4'b0000, ui_in} + 12'h001;  // Add a small value as "noise"
  wire [11:0] noisy_input2 = {4'b0000, ui_in} + 12'h002;  // Add a different small value for second "noise"
  wire [11:0] noisy_input3 = {4'b0000, ui_in} + 12'h003;  // Add a different small value for second "noise"

  // Instantiate two LIF neurons with noisy inputs
  wire [7:0] state1, state2, state3;     // Internal states of the neurons
  wire spike1, spike2, spike3;            // Spike outputs from the neurons

  lif lif1 (
      .current(noisy_input1),
      .clk(clk),
      .reset_n(rst_n),
      .state(state1),
      .spike(spike1)
  );

  lif lif2 (
      .current(noisy_input2),
      .clk(clk),
      .reset_n(rst_n),
      .state(state2),
      .spike(spike2)
  );

  lif lif3 (
      .current(noisy_input3),
      .clk(clk),
      .reset_n(rst_n),
      .state(state3),
      .spike(spike3)
  );

  // Route spike outputs to specific bits of uio_out
  assign uio_out[7] = spike1;
  assign uio_out[6] = spike2;
  assign uio_out[5] = spike3;

  // route internal states to `uo_out` for tests
  assign uo_out = state1;