用Verilog写一个双向传输的i2c2mdio模块

以下是一个用Verilog编写的双向传输的I2C2MDIO模块的示例代码：

module i2c2mdio (
    input wire clk,
    input wire rst,
    input wire sda_in,
    input wire scl_in,
    output wire sda_out,
    output wire scl_out,
    inout wire mdio_io,
    inout wire mdc_io
);

    // 状态定义
    reg [2:0] state;
    parameter IDLE = 3'b000;
    parameter START = 3'b001;
    parameter WRITE = 3'b010;
    parameter READ = 3'b011;
    parameter STOP = 3'b100;
    
    // 计数器和寄存器
    reg [7:0] i;
    reg [7:0] data_reg;
    reg [3:0] addr_reg;
    reg [3:0] ack_bit;
    
    // 输出寄存器
    reg sda_reg;
    reg scl_reg;
    
    // 初始化
    initial begin
        state = IDLE;
        i = 0;
        data_reg = 0;
        addr_reg = 0;
        ack_bit = 0;
        sda_reg = 1;
        scl_reg = 1;
    end
    
    // 状态机
    always @(posedge clk or posedge rst) begin
        if (rst) begin
            state <= IDLE;
            i <= 0;
            data_reg <= 0;
            addr_reg <= 0;
            ack_bit <= 0;
            sda_reg <= 1;
            scl_reg <= 1;
        end else begin
            case (state)
                IDLE:
                    if (scl_in == 0 && sda_in == 0) begin
                        state <= START;
                        i <= 0;
                    end else if (mdc_io == 0 && mdio_io == 1) begin
                        state <= READ;
                        i <= 0;
                    end else if (mdc_io == 0 && mdio_io == 0) begin
                        state <= WRITE;
                        i <= 0;
                    end
                START:
                    if (i < 7) begin
                        sda_reg <= 0;
                        scl_reg <= 0;
                        i <= i + 1;
                    end else begin
                        sda_reg <= 0;
                        scl_reg <= 1;
                        state <= WRITE;
                        i <= 0;
                    end
                WRITE:
                    if (i < 8) begin
                        sda_reg <= data_reg[7-i];
                        scl_reg <= 0;
                        i <= i + 1;
                    end else if (i == 8) begin
                        sda_reg <= ack_bit;
                        scl_reg <= 0;
                        i <= i + 1;
                    end else if (i == 9) begin
                        sda_reg <= 1;
                        scl_reg <= 1;
                        i <= 0;
                        state <= STOP;
                    end
                READ:
                    if (i < 8) begin
                        data_reg[7-i] <= sda_in;
                        scl_reg <= 0;
                        i <= i + 1;
                    end else if (i == 8) begin
                        ack_bit <= sda_in;
                        scl_reg <= 0;
                        i <= i + 1;
                    end else if (i == 9) begin
                        scl_reg <= 1;
                        i <= 0;
                        state <= STOP;
                    end
                STOP:
                    if (i < 7) begin
                        sda_reg <= 1;
                        scl_reg <= 0;
                        i <= i + 1;
                    end else if (i == 7) begin
                        sda_reg <= 0;
                        scl_reg <= 0;
                        i <= i + 1;
                    end else if (i == 8) begin
                        sda_reg <= 0;
                        scl_reg <= 1;
                        i <= 0;
                        state <= IDLE;
                    end
            endcase
        end
    end
    
    // 输出信号
    assign sda_out = sda_reg;
    assign scl_out = scl_reg;
    assign mdio_io = sda_reg;
    assign mdc_io = scl_reg;
    
endmodule

这个模块实现了一个简单的I2C2MDIO接口，包括START、WRITE、READ和STOP等状态。它使用了一个状态机来控制数据的传输，并根据输入的时钟和复位信号进行状态转换。输出信号sda_out和scl_out用于控制外部设备的SDA和SCL线，mdio_io和mdc_io用于控制MDIO和MDC线。