简化版的AXI-LITE4和配合使用的RTL

//////////////////////////////////////////////////////////////////////////////////
// 
// The ZYNQ FIFO slave settings:
//  - implements write state machine for 32-bit addressable AXI slave
//  - provides settings for state of per-stream fifo pointers
//  - implements configuration of FIFO‘s physical DDR addresses
//////////////////////////////////////////////////////////////////////////////////


module zf_slave_settings
#(
    parameter CONFIG_BASE = 32‘h40000000
)
(
    input clk,
    input rst,

    //------------------------------------------------------------------
    //-- control write signals - slave
    //------------------------------------------------------------------
    input [31:0] AXI_AWADDR,
    input AXI_AWVALID,
    output AXI_AWREADY,
    input [31:0] AXI_WDATA,
    input [3:0] AXI_WSTRB,
    input AXI_WVALID,
    output AXI_WREADY,
    output [1:0] AXI_BRESP,
    output AXI_BVALID,
    input AXI_BREADY,

    //------------------------------------------------------------------
    // settings interface
    //------------------------------------------------------------------
    output reg [31:0] addr,
    output reg [31:0] data,
    output strobe,

    output [31:0] debug
);

////////////////////////////////////////////////////////////////////////
///////////////////////////// Begin R T L //////////////////////////////
////////////////////////////////////////////////////////////////////////

    //------------------------------------------------------------------
    // Control write state machine responds to AXI control writes
    // Used for setting the state of the various FIFOs
    //------------------------------------------------------------------
    localparam STATE_ADDR = 0;
    localparam STATE_DATA = 1;
    localparam STATE_WRITE = 2;

    reg [1:0] state;

    always @(posedge clk) begin
        if (rst) begin
            state <= STATE_ADDR;
            addr <= 0;
            data <= 0;
        end
        else case (state)

        STATE_ADDR: begin
            if (AXI_AWVALID && AXI_AWREADY) begin
                addr <= (AXI_AWADDR - CONFIG_BASE);
                state <= STATE_DATA;
            end
        end

        STATE_DATA: begin
            if (AXI_WVALID && AXI_WREADY) begin
                data <= AXI_WDATA;
                state <= STATE_WRITE;
            end
        end

        STATE_WRITE: begin
            state <= STATE_ADDR;
        end

        default: state <= STATE_ADDR;

        endcase //state
    end

    assign strobe = (state == STATE_WRITE);

    //assign to slave write
    assign AXI_AWREADY = (state == STATE_ADDR);
    assign AXI_WREADY = (state == STATE_DATA);
    assign AXI_BRESP = 0;
    assign AXI_BVALID = AXI_BREADY; //FIXME - we can choose not to assert valid

endmodule //zf_slave_settings

//----------------------------------------------------------------------
//-- A settings register is a peripheral for the settings register bus.
//-- When the settings register sees strobe abd a matching address,
//-- the outputs will be become registered to the given input bus.
//----------------------------------------------------------------------

module setting_reg
  #(parameter my_addr = 0, 
    parameter awidth = 8,
    parameter width = 32,
    parameter rst_idel=0)
    (input clk, input rst, input strobe, input wire [awidth-1:0] addr,
     input wire [31:0] in_data, 
     output reg [width-1:0] out_data, output reg changed);
   
   always @(posedge clk)
     if(rst)
       begin
      out_data <= rst_idel;
      changed <= 1‘b0;
       end
     else
       if(strobe & (my_addr==addr))
     begin
        out_data <= in_data[width-1:0];
        changed <= 1‘b1;
     end
       else
     changed <= 1‘b0;
   
endmodule // setting_reg