写一个Xilinx 的AXI4-Lite 接口的 SPI控制器

以下是一个简单的基于Xilinx AXI4-Lite接口的SPI控制器的Verilog代码：

module axi_spi_controller (
    input wire clk,
    input wire rst,
    input wire [31:0] axi_awaddr,
    input wire [2:0] axi_awprot,
    input wire axi_awvalid,
    output reg axi_awready,
    input wire [31:0] axi_wdata,
    input wire [3:0] axi_wstrb,
    input wire axi_wvalid,
    output reg axi_wready,
    output reg [31:0] axi_bresp,
    output reg axi_bvalid,
    input wire axi_bready,
    input wire [31:0] axi_araddr,
    input wire [2:0] axi_arprot,
    input wire axi_arvalid,
    output reg axi_arready,
    output reg [31:0] axi_rdata,
    output reg [1:0] axi_rresp,
    output reg axi_rvalid,
    input wire axi_rready,
    output reg spi_cs,
    output reg spi_clk,
    output reg spi_mosi,
    input wire spi_miso
);

// AXI4-Lite read/write registers
reg [31:0] control_reg;
reg [31:0] status_reg;
reg [31:0] data_reg;

// SPI controller state machine
reg [3:0] spi_state;
localparam IDLE = 4'b0000;
localparam WRITE = 4'b0001;
localparam READ = 4'b0010;

// SPI controller shift register
reg [7:0] spi_shift_reg;
reg [3:0] spi_shift_count;

// AXI4-Lite read/write logic
always @(posedge clk) begin
    if (rst) begin
        axi_awready <= 1'b0;
        axi_wready <= 1'b0;
        axi_bresp <= 2'b00;
        axi_bvalid <= 1'b0;
        axi_arready <= 1'b0;
        axi_rdata <= 32'h0;
        axi_rresp <= 2'b00;
        axi_rvalid <= 1'b0;
    end else begin
        // Write address
        if (axi_awvalid && !axi_awready) begin
            axi_awready <= 1'b1;
            axi_wready <= 1'b1;
            control_reg <= axi_wdata;
        end else if (axi_wvalid && !axi_wready) begin
            axi_wready <= 1'b1;
            case (axi_awaddr[1:0])
                2'b00: data_reg[7:0] <= axi_wdata[7:0];
                2'b01: data_reg[15:8] <= axi_wdata[7:0];
                2'b10: data_reg[23:16] <= axi_wdata[7:0];
                2'b11: data_reg[31:24] <= axi_wdata[7:0];
            endcase
        end else if (axi_wvalid && axi_wready) begin
            axi_wready <= 1'b0;
            axi_bresp <= 2'b00;
            axi_bvalid <= 1'b1;
        end else begin
            axi_awready <= 1'b0;
            axi_wready <= 1'b0;
            axi_bresp <= 2'b00;
            axi_bvalid <= 1'b0;
        end
        
        // Read address
        if (axi_arvalid && !axi_arready) begin
            axi_arready <= 1'b1;
            case (axi_araddr[1:0])
                2'b00: axi_rdata <= control_reg;
                2'b01: axi_rdata <= status_reg;
                2'b10: axi_rdata <= data_reg;
                2'b11: axi_rdata <= 32'h0;
            endcase
            axi_rresp <= 2'b00;
            axi_rvalid <= 1'b1;
        end else if (axi_rvalid && !axi_rready) begin
            axi_rvalid <= 1'b0;
        end else if (!axi_arvalid) begin
            axi_arready <= 1'b0;
        end
    end
end

// SPI controller state machine logic
always @(posedge clk) begin
    if (rst) begin
        spi_cs <= 1'b1;
        spi_clk <= 1'b0;
        spi_mosi <= 1'b0;
        spi_state <= IDLE;
        spi_shift_reg <= 8'h0;
        spi_shift_count <= 4'h0;
    end else begin
        case (spi_state)
            IDLE: begin
                spi_cs <= 1'b1;
                spi_clk <= 1'b0;
                if (control_reg[0]) begin
                    spi_state <= WRITE;
                    spi_shift_reg <= data_reg[7:0];
                    spi_shift_count <= 4'h8;
                    spi_cs <= 1'b0;
                end else if (control_reg[1]) begin
                    spi_state <= READ;
                    spi_shift_reg <= 8'h0;
                    spi_shift_count <= 4'h0;
                    spi_cs <= 1'b0;
                end
            end
            WRITE: begin
                spi_cs <= 1'b0;
                spi_clk <= ~spi_clk;
                if (spi_clk) begin
                    spi_mosi <= spi_shift_reg[7];
                    spi_shift_reg <= {spi_shift_reg[6:0], 1'b0};
                    spi_shift_count <= spi_shift_count - 1;
                end
                if (!spi_clk && spi_shift_count == 0) begin
                    spi_state <= IDLE;
                    spi_cs <= 1'b1;
                end
            end
            READ: begin
                spi_cs <= 1'b0;
                spi_clk <= ~spi_clk;
                if (spi_clk) begin
                    spi_shift_reg <= {spi_shift_reg[6:0], spi_miso};
                    spi_shift_count <= spi_shift_count + 1;
                end
                if (!spi_clk && spi_shift_count == 8) begin
                    spi_state <= IDLE;
                    spi_cs <= 1'b1;
                    status_reg <= {24'h0, spi_shift_reg[7:0]};
                end
            end
        endcase
    end
end

endmodule

这个控制器将AXI4-Lite接口与SPI总线接口连接起来，并且支持读写控制寄存器和数据寄存器，可以进行SPI读写操作。在这个实现中，控制器的状态机负责管理SPI操作，包括写操作和读操作。

需要注意的是，这个实现只是一个简单的例子，可能需要根据具体的设计需求进行修改和扩展。在实际的设计中，还需要考虑时序约束、接口协议等方面的细节。