fpga实现spi接口代码

以下是FPGA实现SPI接口的代码示例：

module spi_interface (
    input clk,
    input reset,
    input [7:0] spi_data_in,
    output [7:0] spi_data_out,
    output spi_cs,
    output spi_clk,
    output spi_mosi,
    input spi_miso
);

reg [7:0] spi_data_out_reg;
reg spi_cs_reg;
reg spi_clk_reg;
reg spi_mosi_reg;

assign spi_data_out = spi_data_out_reg;
assign spi_cs = spi_cs_reg;
assign spi_clk = spi_clk_reg;
assign spi_mosi = spi_mosi_reg;

parameter IDLE = 2'b00;
parameter READ = 2'b01;
parameter WRITE = 2'b10;
parameter DONE = 2'b11;

reg [1:0] spi_state;
reg [7:0] spi_data_in_reg;
reg [7:0] spi_data_out_reg;
reg [3:0] spi_count;

always @(posedge clk) begin
    if (reset) begin
        spi_state <= IDLE;
        spi_data_out_reg <= 8'h00;
        spi_cs_reg <= 1'b1;
        spi_clk_reg <= 1'b0;
        spi_mosi_reg <= 1'b0;
        spi_data_in_reg <= 8'h00;
        spi_count <= 4'd0;
    end else begin
        case (spi_state)
            IDLE: begin
                spi_cs_reg <= 1'b1;
                spi_clk_reg <= 1'b0;
                spi_mosi_reg <= 1'b0;
                spi_data_out_reg <= 8'h00;
                spi_data_in_reg <= 8'h00;
                spi_count <= 4'd0;
                if (spi_data_in != 8'h00) begin
                    spi_state <= WRITE;
                end else if (spi_miso == 1'b0) begin
                    spi_state <= READ;
                end
            end
            READ: begin
                spi_cs_reg <= 1'b0;
                spi_clk_reg <= 1'b1;
                spi_mosi_reg <= 1'b0;
                spi_data_out_reg <= 8'h00;
                spi_data_in_reg <= {spi_data_in_reg[6:0], spi_miso};
                spi_count <= spi_count + 1;
                if (spi_count == 4'd7) begin
                    spi_state <= DONE;
                end
            end
            WRITE: begin
                spi_cs_reg <= 1'b0;
                spi_clk_reg <= 1'b1;
                spi_mosi_reg <= spi_data_in[7-spi_count];
                spi_data_out_reg <= 8'h00;
                spi_data_in_reg <= spi_data_in;
                spi_count <= spi_count + 1;
                if (spi_count == 4'd7) begin
                    spi_state <= DONE;
                end
            end
            DONE: begin
                spi_cs_reg <= 1'b1;
                spi_clk_reg <= 1'b0;
                spi_mosi_reg <= 1'b0;
                spi_data_out_reg <= spi_data_in_reg;
                spi_data_in_reg <= 8'h00;
                spi_count <= 4'd0;
                spi_state <= IDLE;
            end
        endcase
    end
end

endmodule

这个模块实现了一个简单的SPI接口，可用于与外部设备进行通信。它包括一个状态机，用于控制数据的读取和写入。在IDLE状态下，它等待输入数据或检测到来自外部设备的数据。在READ和WRITE状态下，它生成时钟和数据信号以进行数据传输。在DONE状态下，它等待下一个传输。