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`timescale 1ns/100ps

module axi_dacfifo_wr (

  // dma fifo interface

  dma_clk,
  dma_data,
  dma_ready,
  dma_valid,

  // request and syncronizaiton

  dma_xfer_req,
  dma_xfer_last,

  // syncronization for the read side

  axi_last_raddr,
  dma_last_addr,
  axi_xfer_out,

  // axi write address, write data and write response channels

  axi_clk,
  axi_resetn,
  axi_awvalid,
  axi_awid,
  axi_awburst,
  axi_awlock,
  axi_awcache,
  axi_awprot,
  axi_awqos,
  axi_awuser,
  axi_awlen,
  axi_awsize,
  axi_awaddr,
  axi_awready,
  axi_wvalid,
  axi_wdata,
  axi_wstrb,
  axi_wlast,
  axi_wuser,
  axi_wready,
  axi_bvalid,
  axi_bid,
  axi_bresp,
  axi_buser,
  axi_bready,

  axi_werror);

  // parameters

  parameter       AXI_DATA_WIDTH = 512;
  parameter       DMA_DATA_WIDTH = 64;
  parameter       AXI_SIZE = 2;
  parameter       AXI_LENGTH = 15;
  parameter       AXI_ADDRESS = 32'h00000000;
  parameter       AXI_ADDRESS_LIMIT = 32'h00000000;

  // for the syncronization buffer

  localparam      MEM_RATIO = AXI_DATA_WIDTH/DMA_DATA_WIDTH;
  localparam      DMA_MADDRESS_WIDTH = 8;
  localparam      AXI_MADDRESS_WIDTH = (MEM_RATIO == 1) ? DMA_MADDRESS_WIDTH :
                                       (MEM_RATIO == 2) ? (DMA_MADDRESS_WIDTH - 1) :
                                       (MEM_RATIO == 4) ? (DMA_MADDRESS_WIDTH - 2) :
                                       (DMA_MADDRESS_WIDTH - 3);

  // for the AXI interface

  localparam      AXI_BYTE_WIDTH = AXI_DATA_WIDTH/8;
  localparam      AXI_AWINCR = (AXI_LENGTH + 1) * AXI_BYTE_WIDTH;

  // dma fifo interface

  input                                     dma_clk;
  input   [(DMA_DATA_WIDTH-1):0]            dma_data;
  output                                    dma_ready;
  input                                     dma_valid;

  input                                     dma_xfer_req;
  input                                     dma_xfer_last;

  output  [31:0]                            axi_last_raddr;
  output  [31:0]                            dma_last_addr;
  output                                    axi_xfer_out;

  // axi interface

  input                                     axi_clk;
  input                                     axi_resetn;
  output                                    axi_awvalid;
  output  [ 3:0]                            axi_awid;
  output  [ 1:0]                            axi_awburst;
  output                                    axi_awlock;
  output  [ 3:0]                            axi_awcache;
  output  [ 2:0]                            axi_awprot;
  output  [ 3:0]                            axi_awqos;
  output  [ 3:0]                            axi_awuser;
  output  [ 7:0]                            axi_awlen;
  output  [ 2:0]                            axi_awsize;
  output  [31:0]                            axi_awaddr;
  input                                     axi_awready;
  output                                    axi_wvalid;
  output  [(AXI_DATA_WIDTH-1):0]            axi_wdata;
  output  [(AXI_BYTE_WIDTH-1):0]            axi_wstrb;
  output                                    axi_wlast;
  output  [ 3:0]                            axi_wuser;
  input                                     axi_wready;
  input                                     axi_bvalid;
  input   [ 3:0]                            axi_bid;
  input   [ 1:0]                            axi_bresp;
  input   [ 3:0]                            axi_buser;
  output                                    axi_bready;

  output                                    axi_werror;

  // internal register

  reg     [(DMA_MADDRESS_WIDTH-1):0]        dma_mem_waddr = 'd0;
  reg     [(DMA_MADDRESS_WIDTH-1):0]        dma_mem_waddr_g = 'd0;
  reg     [(DMA_MADDRESS_WIDTH-1):0]        dma_mem_addr_diff = 'd0;
  reg     [(AXI_MADDRESS_WIDTH-1):0]        dma_mem_raddr_m1 = 'd0;
  reg     [(AXI_MADDRESS_WIDTH-1):0]        dma_mem_raddr_m2 = 'd0;
  reg     [(AXI_MADDRESS_WIDTH-1):0]        dma_mem_raddr = 'd0;
  reg                                       dma_ready = 'd0;
  reg                                       dma_rst_m1 = 1'b0;
  reg                                       dma_rst_m2 = 1'b0;
  reg     [31:0]                            dma_last_addr = 32'b0;
  reg     [31:0]                            dma_addr_cnt = 32'b0;

  reg     [ 2:0]                            axi_xfer_req_m = 3'b0;
  reg     [ 2:0]                            axi_xfer_last_m = 3'b0;
  reg     [(DMA_MADDRESS_WIDTH-1):0]        axi_mem_waddr_m1 = 'b0;
  reg     [(DMA_MADDRESS_WIDTH-1):0]        axi_mem_waddr_m2 = 'b0;
  reg     [(DMA_MADDRESS_WIDTH-1):0]        axi_mem_waddr = 'b0;
  reg                                       axi_mem_ready = 'b0;
  reg                                       axi_mem_ready_d = 'b0;
  reg     [(AXI_DATA_WIDTH-1):0]            axi_mem_rdata_d = 'b0;
  reg     [(AXI_MADDRESS_WIDTH-1):0]        axi_mem_raddr = 'd0;
  reg     [(AXI_MADDRESS_WIDTH-1):0]        axi_mem_raddr_g = 'd0;

  reg                                       axi_reset = 1'b0;
  reg                                       axi_xfer_out = 1'b0;
  reg     [31:0]                            axi_last_raddr = 'b0;
  reg                                       axi_awvalid = 1'b0;
  reg     [31:0]                            axi_awaddr = 32'b0;
  reg                                       axi_xfer_init = 1'b0;
  reg                                       axi_werror = 1'b0;
  reg                                       axi_mem_last = 1'b0;
  reg                                       axi_mem_last_d = 1'b0;
  reg     [ 3:0]                            axi_wvalid_cntr = 4'b0;


  // internal signal

  wire    [(DMA_MADDRESS_WIDTH-1):0]        dma_mem_addr_diff_s;
  wire    [(DMA_MADDRESS_WIDTH-1):0]        dma_mem_raddr_s;
  wire                                      dma_rst_s;

  wire    [(DMA_MADDRESS_WIDTH-1):0]        axi_mem_waddr_s;
  wire                                      axi_req_s;
  wire    [(AXI_DATA_WIDTH-1):0]            axi_mem_rdata_s;
  wire                                      axi_wready_s;
  wire                                      axi_mem_last_s;

  // binary to grey conversion

  function [7:0] b2g;
    input [7:0] b;
    reg   [7:0] g;
    begin
      g[7] = b[7];
      g[6] = b[7] ^ b[6];
      g[5] = b[6] ^ b[5];
      g[4] = b[5] ^ b[4];
      g[3] = b[4] ^ b[3];
      g[2] = b[3] ^ b[2];
      g[1] = b[2] ^ b[1];
      g[0] = b[1] ^ b[0];
      b2g = g;
    end
  endfunction

  // grey to binary conversion

  function [7:0] g2b;
    input [7:0] g;
    reg   [7:0] b;
    begin
      b[7] = g[7];
      b[6] = b[7] ^ g[6];
      b[5] = b[6] ^ g[5];
      b[4] = b[5] ^ g[4];
      b[3] = b[4] ^ g[3];
      b[2] = b[3] ^ g[2];
      b[1] = b[2] ^ g[1];
      b[0] = b[1] ^ g[0];
      g2b = b;
    end
  endfunction


  // syncronize the AXI interface reset

  always @(posedge dma_clk) begin
    dma_rst_m1 <= ~axi_resetn;
    dma_rst_m2 <= dma_rst_m1;
  end
  assign dma_rst_s = dma_rst_m2;

  // write address generation for the asymetric memory

  always @(posedge dma_clk) begin
    if (dma_rst_s == 1'b1) begin
      dma_addr_cnt <= 32'b0;
      dma_last_addr <= 32'b0;
    end else begin
      if((dma_valid == 1'b1) && (dma_xfer_req == 1'b1)) begin
        dma_addr_cnt <= (dma_xfer_last == 1'b1) ? 32'b0 : dma_addr_cnt + 1;
        dma_last_addr <= (dma_xfer_last == 1'b1) ? dma_addr_cnt : dma_last_addr;
      end
    end
  end

  always @(posedge dma_clk) begin
    if (dma_rst_s == 1'b1) begin
      dma_mem_waddr <= 8'h0;
      dma_mem_waddr_g <= 8'h0;
    end else begin
      if ((dma_ready == 1'b1) && (dma_valid == 1'b1)) begin
        dma_mem_waddr <= dma_mem_waddr + 1;
      end
      dma_mem_waddr_g <= b2g(dma_mem_waddr);
    end
  end

  assign dma_mem_addr_diff_s = {1'b1, dma_mem_waddr} - dma_mem_raddr_s;
  assign dma_mem_raddr_s = (MEM_RATIO == 1) ?  dma_mem_raddr :
                           (MEM_RATIO == 2) ? {dma_mem_raddr, 1'b0} :
                           (MEM_RATIO == 4) ? {dma_mem_raddr, 2'b0} :
                                              {dma_mem_raddr, 3'b0};

  always @(posedge dma_clk) begin
    if (dma_rst_s == 1'b1) begin
      dma_mem_addr_diff <= 'b0;
      dma_mem_raddr_m1 <= 'b0;
      dma_mem_raddr_m2 <= 'b0;
      dma_mem_raddr <= 'b0;
    end else begin
      dma_mem_raddr_m1 <= g2b(axi_mem_raddr_g);
      dma_mem_raddr_m2 <= dma_mem_raddr_m1;
      dma_mem_raddr <= dma_mem_raddr_m2;
      dma_mem_addr_diff <= dma_mem_addr_diff_s[DMA_MADDRESS_WIDTH-1:0];
      if (dma_mem_addr_diff >= 180) begin
        dma_ready <= 1'b0;
      end else begin
        dma_ready <= 1'b1;
      end
    end
  end

  // read address generation for the asymetric memory

  always @(posedge axi_clk) begin
    if (axi_resetn == 1'b0) begin
      axi_xfer_req_m <= 3'b0;
      axi_xfer_last_m <= 3'b0;
      axi_mem_waddr_m1 <= 'b0;
      axi_mem_waddr_m2 <= 'b0;
      axi_mem_waddr <= 'b0;
      axi_xfer_init <= 1'b0;
    end else begin
      axi_xfer_req_m <= {axi_xfer_req_m[1:0], dma_xfer_req};
      axi_xfer_last_m <= {axi_xfer_last_m[1:0], dma_xfer_last};
      axi_mem_waddr_m1 <= g2b(dma_mem_waddr_g);
      axi_mem_waddr_m2 <= axi_mem_waddr_m1;
      axi_mem_waddr <= axi_mem_waddr_m2;
      axi_xfer_init = ~axi_xfer_req_m[2] & axi_xfer_req_m[1];
    end
  end

  assign axi_wready_s = ~axi_wvalid | axi_wready;
  assign axi_mem_ready_s = (axi_mem_raddr == axi_mem_waddr_s) ? 1'b0 : axi_wready_s;
  assign axi_req_s = (axi_mem_raddr[1:0] == 2'h0) ? axi_mem_ready_s : 1'b0;
  assign axi_mem_last_s = (axi_wvalid_cntr == AXI_LENGTH) ? axi_mem_ready_s : 1'b0;
  assign axi_mem_waddr_s = (MEM_RATIO == 1) ? axi_mem_waddr :
                           (MEM_RATIO == 2) ? axi_mem_waddr[(DMA_MADDRESS_WIDTH-1):1] :
                           (MEM_RATIO == 4) ? axi_mem_waddr[(DMA_MADDRESS_WIDTH-1):2] :
                                              axi_mem_waddr[(DMA_MADDRESS_WIDTH-1):3];

  always @(posedge axi_clk) begin
    if (axi_resetn == 1'b0) begin
      axi_mem_ready <= 1'b0;
      axi_mem_ready_d <= 1'b0;
      axi_mem_rdata_d <= 'b0;
      axi_mem_raddr <= 'b0;
      axi_wvalid_cntr <= 4'b0;
    end else begin
      axi_mem_ready <= axi_mem_ready_s;
      axi_mem_last <= axi_mem_last_s;
      axi_mem_last_d <= axi_mem_last;
      axi_mem_ready_d <= axi_mem_ready;
      axi_mem_rdata_d <= axi_mem_rdata_s;
      if (axi_mem_ready_s == 1'b1) begin
        axi_mem_raddr <= axi_mem_raddr + 1;
        axi_wvalid_cntr <= (axi_wvalid_cntr == AXI_LENGTH) ? 4'b0 : axi_wvalid_cntr + 1;
      end
      axi_mem_raddr_g <= b2g(axi_mem_raddr);
    end
  end

  // write address generation for AXI MEMORY MAP interface

  // address channel

  assign axi_awid = 4'b0000;
  assign axi_awburst = 2'b01;
  assign axi_awlock = 1'b0;
  assign axi_awcache = 4'b0010;
  assign axi_awprot = 3'b000;
  assign axi_awqos = 4'b0000;
  assign axi_awuser = 4'b0001;
  assign axi_awlen = AXI_LENGTH;
  assign axi_awsize = AXI_SIZE;

  always @(posedge axi_clk) begin
    if (axi_resetn == 1'b0) begin
      axi_awvalid <= 'd0;
      axi_awaddr <= AXI_ADDRESS;
      axi_last_raddr <= AXI_ADDRESS;
      axi_xfer_out <= 1'b0;
    end else begin
      if (axi_awvalid == 1'b1) begin
        if (axi_awready == 1'b1) begin
          axi_awvalid <= 1'b0;
        end
      end else begin
        if (axi_req_s == 1'b1) begin
          axi_awvalid <= 1'b1;
        end
      end
      if (axi_xfer_init == 1'b1) begin
        axi_awaddr <= (axi_xfer_out == 1'b1) ? AXI_ADDRESS : axi_last_raddr;
        axi_xfer_out <= 1'b0;
      end else if ((axi_awvalid == 1'b1) && (axi_awready == 1'b1)) begin
        axi_awaddr <= axi_awaddr + AXI_AWINCR;
      end
      if ((axi_xfer_req_m[2] == 1) && (axi_xfer_last_m[2] == 1)) begin
        axi_last_raddr <= axi_awaddr - AXI_AWINCR;
        axi_xfer_out <= 1'b1;
      end
    end
  end

  // write channel

  assign axi_wstrb = {AXI_BYTE_WIDTH{1'b1}};
  assign axi_wuser = 4'b0000;

  // response channel

  assign axi_bready = 1'b1;

  always @(posedge axi_clk) begin
    if (axi_resetn == 1'b0) begin
      axi_werror <= 'd0;
    end else begin
      axi_werror <= axi_bvalid & axi_bresp[1];
    end
  end

  // fifo needs a reset

  always @(posedge axi_clk) begin
    if (axi_resetn == 1'b0) begin
      axi_reset <= 1'b1;
    end else begin
      axi_reset <= 1'b0;
    end
  end

  // instantiations

  ad_mem_asym #(
    .A_ADDRESS_WIDTH (DMA_MADDRESS_WIDTH),
    .A_DATA_WIDTH (DMA_DATA_WIDTH),
    .B_ADDRESS_WIDTH (AXI_MADDRESS_WIDTH),
    .B_DATA_WIDTH (AXI_DATA_WIDTH))
  i_mem_asym (
    .clka (dma_clk),
    .wea (dma_valid),
    .addra (dma_mem_waddr),
    .dina (dma_data),
    .clkb (axi_clk),
    .addrb (axi_mem_raddr),
    .doutb (axi_mem_rdata_s));

  ad_axis_inf_rx #(.DATA_WIDTH(AXI_DATA_WIDTH)) i_axis_inf (
    .clk (axi_clk),
    .rst (axi_reset),
    .valid (axi_mem_ready_d),
    .last (axi_mem_last_d),
    .data (axi_mem_rdata_d),
    .inf_valid (axi_wvalid),
    .inf_last (axi_wlast),
    .inf_data (axi_wdata),
    .inf_ready (axi_wready));

endmodule