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.

module machine (
    input wire clk,
    input wire reset,
    input wire changes,
    input wire finished,
    output reg [1:0] state
);

parameter state_data_IN = 2'b00;
parameter state_data_BUFF = 2'b01;
parameter state_data_OUT = 2'b10;


//Definir current_state y next_state
reg [1:0] current_state, next_state;

always@(posedge clk) begin 
    if (reset)
        current_state <= state_data_IN;
    else
        current_state <= next_state;
end 

always @(*) begin
    next_state = current_state;
    case (current_state)
        state_data_IN: if (changes) begin
                        next_state = state_data_BUFF;
                        end
        state_data_BUFF: if (changes) begin
                        next_state = state_data_OUT;
                        end
        state_data_OUT: if (changes) begin
                        next_state = state_data_BUFF;
                        end else if (finished) begin
                        next_state = state_data_IN; //show the results
                        end
        default: if (changes) begin
                next_state=current_state;
                end
    endcase
end

always@(posedge clk) begin 
    if (reset)
        state <= state_data_IN;
    else
        state <= current_state;
end 
endmodule


module perceptron(
    input [7:0] in0,
    input [7:0] in1,
    input [7:0] in2,
    input [7:0] in3,

    input [7:0] weight0, //aaa
    input [7:0] weight1,
    input [7:0] weight2,
    input [7:0] weight3,
    input [7:0] bias,
    input [7:0] threshold,

    output reg [7:0] out
);
// >>> Module Implementation Begin

// <<< Module Implementation End
endmodule




module register_parameters(
    input wire clk,
    input wire reset,
    input wire [7:0] data_in,
    input [1:0] selector,

    //output reg [7:0] th3,
    output reg [7:0] b3,
    output reg [7:0] w33,
    output reg [7:0] w32,
    output reg [7:0] w31,
    output reg [7:0] w30,
    //output reg [7:0] th2,
    output reg [7:0] b2,
    output reg [7:0] w23,
    output reg [7:0] w22,
    output reg [7:0] w21,
    output reg [7:0] w20,
    //output reg [7:0] th1,
    output reg [7:0] b1,
    output reg [7:0] w13,
    output reg [7:0] w12,
    output reg [7:0] w11,
    output reg [7:0] w10,
    //output reg [7:0] th0,
    output reg [7:0] b0,
    output reg [7:0] w03,
    output reg [7:0] w02,
    output reg [7:0] w01,
    output reg [7:0] w00
);

always @(posedge clk)
begin
    if (reset) begin
    w00<=8'd0;
    w01<=8'd0;
    w02<=8'd0;
    w03<=8'd0;
    b0<=8'd0;
    //th0<=8'd0;
    w10<=8'd0;
    w11<=8'd0;
    w12<=8'd0;
    w13<=8'd0;
    b1<=8'd0;
    //th1<=8'd0;
    w20<=8'd0;
    w21<=8'd0;
    w22<=8'd0;
    w23<=8'd0;
    b2<=8'd0;
    //th2<=8'd0;
    w30<=8'd0;
    w31<=8'd0;
    w32<=8'd0;
    w33<=8'd0;
    b3<=8'd0;
    //th3<=8'd0;
    end

    else begin
        case(selector)
            2'b00   :   begin 
                        w00<=w00;
                        w01<=w01;
                        w02<=w02;
                        w03<=w03;
                        b0<=b0;
                        //th0<=th0;
                        w10<=w11;
                        w11<=w11;
                        w12<=w12;
                        w13<=w13;
                        b1<=b1;
                        //th1<=th1;
                        w20<=w21;
                        w21<=w21;
                        w22<=w22;
                        w23<=w23;
                        b2<=b2;
                        //th2<=th2;
                        w30<=w31;
                        w31<=w31;
                        w32<=w32;
                        w33<=w33;
                        b3<=b3;
                        //th3<=th3;
                        end
            2'b01   :   begin 
                        w00<=w01;
                        w01<=w02;
                        w02<=w03;
                        w03<=b0;
                        //b0<=th0;
                        b0<=w10;
                        //th0<=w10;
                        w10<=w11;
                        w11<=w12;
                        w12<=w13;
                        w13<=b1;
                        //b1<=th1;
                        b1<=w20;
                        //th1<=w20;
                        w20<=w21;
                        w21<=w22;
                        w22<=w23;
                        w23<=b2;
                        //b2<=th2;
                        b2<=w30;
                        //th2<=w30;
                        w30<=w31;
                        w31<=w32;
                        w32<=w33;
                        w33<=b3;
                        //b3<=th3;
                        b3<=data_in;
                        //th3<=data_in;
                        end
            2'b10   :   begin 
                        w00<=w00;
                        w01<=w01;
                        w02<=w02;
                        w03<=w03;
                        b0<=b0;
                        //th0<=th0;
                        w10<=w11;
                        w11<=w11;
                        w12<=w12;
                        w13<=w13;
                        b1<=b1;
                        //th1<=th1;
                        w20<=w21;
                        w21<=w21;
                        w22<=w22;
                        w23<=w23;
                        b2<=b2;
                        //th2<=th2;
                        w30<=w31;
                        w31<=w31;
                        w32<=w32;
                        w33<=w33;
                        b3<=b3;
                        //th3<=th3;
                        end
            default :   begin 
                        w00<=w00;
                        w01<=w01;
                        w02<=w02;
                        w03<=w03;
                        b0<=b0;
                        //th0<=th0;
                        w10<=w11;
                        w11<=w11;
                        w12<=w12;
                        w13<=w13;
                        b1<=b1;
                        //th1<=th1;
                        w20<=w21;
                        w21<=w21;
                        w22<=w22;
                        w23<=w23;
                        b2<=b2;
                        //th2<=th2;
                        w30<=w31;
                        w31<=w31;
                        w32<=w32;
                        w33<=w33;
                        b3<=b3;
                        //th3<=th3;
                        end
            endcase
    end
end
    
endmodule


module shift_register_inputs(
    input clk,rstn,
    input [7:0] data_in,
    input [1:0] selector,  // From the state machine. Determines where do the neuron inputs come From
    //input [1:0] selector_output,
    
    // The outputs of the neurons0..3 are inputs to the shift register, so it can use them as inputs to the next layer
    input [7:0] neuron0_output, // The output of the neuron0, is an input to the shift register 
    input [7:0] neuron1_output, // The output of the neuron1, is an input to the shift register
    input [7:0] neuron2_output, // The output of the neuron2, is an input to the shift register
    input [7:0] neuron3_output, // The output of the neuron3, is an input to the shift register

    // These 4 outputs are the inputs0..3 to each neuron.
    output reg [7:0] neuron_input0, // Input 0 for all neurons on the current layer
    output reg [7:0] neuron_input1, // Input 1 for all neurons on the current layer
    output reg [7:0] neuron_input2, // Input 2 for all neurons on the current layer
    output reg [7:0] neuron_input3, // Input 3 for all neurons on the current layer

    // Once all layers have passed, when we feed 4 new inputs to the network, the outputs of the network
    // will appear here, from neuron3_output to neuron0_output
    output reg [7:0] network_outputs
);




always@(posedge clk)
begin

    if(rstn) 
    begin
        neuron_input0 <= 8'b00000000;
        neuron_input1 <= 8'b00000000;
        neuron_input2 <= 8'b00000000;
        neuron_input3 <= 8'b00000000;
        network_outputs <= 8'b00000000;
    end

    else
    begin
        case(selector)
            2'b00   :   begin                                   // Receives new data
                            neuron_input0 <= data_in;           // and pases it thorugh the neurons.
                            neuron_input1 <= neuron_input0;
                            neuron_input2 <= neuron_input1;
                            neuron_input3 <= neuron_input2;
                            network_outputs <= neuron_input3;

                        end
            2'b01   :   begin
                            neuron_input0 <= neuron_input0;
                            neuron_input1 <= neuron_input1;
                            neuron_input2 <= neuron_input2;
                            neuron_input3 <= neuron_input3;
                            network_outputs <= network_outputs;
                        end
            2'b10   :   begin
                            neuron_input0 <= neuron0_output;
                            neuron_input1 <= neuron1_output;
                            neuron_input2 <= neuron2_output;
                            network_outputs <= network_outputs;
                        end
            default :   begin                               // The default state keeps everything as it was
                            neuron_input0 <= neuron_input0;
                            neuron_input1 <= neuron_input1;
                            neuron_input2 <= neuron_input2;
                            neuron_input3 <= neuron_input3;
                            network_outputs <= network_outputs;
                        end

        endcase
    end
/*
    begin
        case(selector_output)
            2'b00   :   begin  
                            network_outputs <= neuron_input0;
            end 
            2'b01   :   begin  
                            network_outputs <= neuron_input1;
            end 
            2'b10   :   begin  
                            network_outputs <= neuron_input2;
            end 
            2'b11   :   begin  
                            network_outputs <= neuron_input3;
            end 
            default: begin
                    network_outputs <= network_outputs;
            end
        endcase
    end
    */
end

endmodule


module tt_um_neural_network (
    input wire clk,
    input wire rst_n,
    input wire [7:0] uio_in,
    input wire [7:0] ui_in,
    
    output wire [7:0] uo_out,
    output wire [7:0] uio_oe,
    output wire [7:0] uio_out,

    input wire ena
);
assign uio_oe = 0;
assign uio_out = 0;    
// Señales internas
wire [1:0] state;
wire [7:0] neuron_input0, neuron_input1, neuron_input2, neuron_input3;
wire [7:0] neuron0_output, neuron1_output, neuron2_output, neuron3_output;
wire [7:0] w00, w01, w02, w03, b0;
wire [7:0] w10, w11, w12, w13, b1;
wire [7:0] w20, w21, w22, w23, b2;
wire [7:0] w30, w31, w32, w33, b3;

// Instanciando los módulos
machine machine_inst (
    .clk(clk),
    .reset(~rst_n),
    .changes(uio_in[1]),
    .state(state),
    .finished(uio_in[0])
);

shift_register_inputs shift_reg_inst (
    .clk(clk),
    .rstn(~rst_n),
    .data_in(ui_in),
    .selector(state),
    //.selector_output(uio_in[1:0]),
    .neuron0_output(neuron0_output),
    .neuron1_output(neuron1_output),
    .neuron2_output(neuron2_output),
    .neuron3_output(neuron3_output),
    .neuron_input0(neuron_input0),
    .neuron_input1(neuron_input1),
    .neuron_input2(neuron_input2),
    .neuron_input3(neuron_input3),
    .network_outputs(uo_out)
);

perceptron perceptron0 (
    .in0(neuron_input0),
    .in1(neuron_input1),
    .in2(neuron_input2),
    .in3(neuron_input3),
    .weight0(w00),
    .weight1(w01),
    .weight2(w02),
    .weight3(w03),
    .bias(b0),
    .threshold(8'd0),
    .out(neuron0_output)
);

perceptron perceptron1 (
    .in0(neuron_input0),
    .in1(neuron_input1),
    .in2(neuron_input2),
    .in3(neuron_input3),
    .weight0(w10),
    .weight1(w11),
    .weight2(w12),
    .weight3(w13),
    .bias(b1),
    .threshold(8'd0),
    .out(neuron1_output)
);

perceptron perceptron2 (
    .in0(neuron_input0),
    .in1(neuron_input1),
    .in2(neuron_input2),
    .in3(neuron_input3),
    .weight0(w20),
    .weight1(w21),
    .weight2(w22),
    .weight3(w23),
    .bias(b2),
    .threshold(8'd0),
    .out(neuron2_output)
);

perceptron perceptron3 (
    .in0(neuron_input0),
    .in1(neuron_input1),
    .in2(neuron_input2),
    .in3(neuron_input3),
    .weight0(w30),
    .weight1(w31),
    .weight2(w32),
    .weight3(w33),
    .bias(b3),
    .threshold(8'd0),
    .out(neuron3_output)
);

register_parameters reg_params_inst (
    .clk(clk),
    .reset(~rst_n),
    .data_in(ui_in),
    .selector(state),
    //.th3(th3),
    .b3(b3),
    .w33(w33),
    .w32(w32),
    .w31(w31),
    .w30(w30),
    //.th2(th2),
    .b2(b2),
    .w23(w23),
    .w22(w22),
    .w21(w21),
    .w20(w20),
    //.th1(th1),
    .b1(b1),
    .w13(w13),
    .w12(w12),
    .w11(w11),
    .w10(w10),
    //.th0(th0),
    .b0(b0),
    .w03(w03),
    .w02(w02),
    .w01(w01),
    .w00(w00)
);

endmodule


Reference solution:
rtl/generated.v: 
reg [7:0] sum_p;
reg [7:0] res;

always@(*)
begin
    
    sum_p=(in0<<weight0)+(in1<<weight1)+(in2<weight2)+(in3<<weight3)+bias;
    res = sum_p - threshold;
    if (res[7])
        out = 8'b00000000;
    else
        out = sum_p;
end