写一个 xilinx AXI4-lite 接口控制SPI接口的控制器

以下是一个简单的 Xilinx AXI4-lite 接口控制 SPI 接口的控制器的代码示例：

module spi_controller (
    input aclk,
    input aresetn,
    input [7:0] tx_data,
    output reg [7:0] rx_data,
    input cs_n,
    input sclk,
    input mosi,
    output reg miso
);

// AXI4-lite slave interface
reg [31:0] axi_awaddr;
reg [2:0] axi_awprot;
reg axi_awvalid, axi_awready;

reg [31:0] axi_araddr;
reg [2:0] axi_arprot;
reg axi_arvalid, axi_arready;

reg [31:0] axi_wdata;
reg [3:0] axi_wstrb;
reg axi_wvalid, axi_wready;

reg [31:0] axi_rdata;
reg axi_rvalid, axi_rready;

// Control signals for the SPI interface
reg [7:0] tx_reg;
reg [7:0] rx_reg;
reg [3:0] bit_count;
reg spi_busy;

// State machine states
localparam IDLE = 2'b00;
localparam WRITE = 2'b01;
localparam READ = 2'b10;

reg [1:0] state;
always @ (posedge aclk) begin
    if (!aresetn) begin
        state <= IDLE;
        axi_awready <= 1'b0;
        axi_arready <= 1'b0;
        axi_wready <= 1'b0;
        axi_rvalid <= 1'b0;
        spi_busy <= 1'b0;
        bit_count <= 0;
    end else begin
        case (state)
            IDLE: begin
                if (axi_awvalid && !spi_busy) begin
                    axi_awready <= 1'b1;
                    axi_arready <= 1'b1;
                    state <= WRITE;
                    tx_reg <= tx_data;
                    rx_reg <= 8'h00;
                    bit_count <= 8;
                    spi_busy <= 1'b1;
                end else if (axi_arvalid && !spi_busy) begin
                    axi_awready <= 1'b1;
                    axi_arready <= 1'b1;
                    state <= READ;
                    tx_reg <= 8'h00;
                    rx_reg <= 8'h00;
                    bit_count <= 8;
                    spi_busy <= 1'b1;
                end else begin
                    axi_awready <= 1'b0;
                    axi_arready <= 1'b0;
                    spi_busy <= 1'b0;
                end
            end
            WRITE: begin
                if (bit_count > 0) begin
                    mosi <= tx_reg[bit_count-1];
                    sclk <= 1'b0;
                    bit_count <= bit_count - 1;
                end else begin
                    sclk <= 1'b1;
                    rx_reg <= {rx_reg[6:0], miso};
                    state <= IDLE;
                    axi_rdata <= rx_reg;
                    axi_rvalid <= 1'b1;
                    spi_busy <= 1'b0;
                end
            end
            READ: begin
                if (bit_count > 0) begin
                    mosi <= 1'b0;
                    sclk <= 1'b0;
                    bit_count <= bit_count - 1;
                end else begin
                    sclk <= 1'b1;
                    rx_reg <= {rx_reg[6:0], miso};
                    state <= IDLE;
                    axi_rdata <= rx_reg;
                    axi_rvalid <= 1'b1;
                    spi_busy <= 1'b0;
                end
            end
            default: state <= IDLE;
        endcase
    end
end

// AXI4-lite slave interface logic
assign axi_awready = (state == IDLE) && !spi_busy;
assign axi_arready = (state == IDLE) && !spi_busy;
assign axi_wready = (state == IDLE) && !spi_busy;
assign axi_rdata = axi_awaddr;

always @ (posedge aclk) begin
    if (!aresetn) begin
        axi_awready <= 1'b0;
        axi_arready <= 1'b0;
        axi_wready <= 1'b0;
        axi_rvalid <= 1'b0;
    end else begin
        if (axi_awvalid && !spi_busy) begin
            axi_awready <= 1'b0;
            axi_awaddr <= axi_awaddr;
            axi_awprot <= axi_awprot;
        end
        if (axi_arvalid && !spi_busy) begin
            axi_arready <= 1'b0;
            axi_araddr <= axi_araddr;
            axi_arprot <= axi_arprot;
        end
        if (axi_wvalid && !spi_busy) begin
            axi_wready <= 1'b0;
            axi_wdata <= axi_wdata;
            axi_wstrb <= axi_wstrb;
        end
        if (axi_rready) begin
            axi_rvalid <= 1'b0;
        end
    end
end

// SPI interface logic
always @ (posedge sclk) begin
    if (cs_n == 1'b0) begin
        miso <= 1'b0;
    end else if (spi_busy) begin
        miso <= rx_reg[7];
    end else begin
        miso <= 1'b1;
    end
end

endmodule

此代码使用 AXI4-lite 接口控制 SPI 接口，支持写入和读取操作。在 IDLE 状态下，如果 AXI4-lite 接收到写入请求，则将状态切换到 WRITE 状态，并在 SPI 接口上发送数据，然后将状态切换回 IDLE 状态，并将数据返回到 AXI4-lite 接口。如果接收到读取请求，则将状态切换到 READ 状态，并从 SPI 接口读取数据，然后将状态切换回 IDLE 状态，并将数据返回到 AXI4-lite 接口。SPI 接口的 MOSI 和 MISO 信号由时钟信号 SCLK 控制。注意，此代码仅供参考，并且可能需要根据您的具体要求进行修改。