module up_axi (

  // reset and clocks

  up_rstn,
  up_clk,

  // axi4 interface

  up_axi_awvalid,
  up_axi_awaddr,
  up_axi_awready,
  up_axi_wvalid,
  up_axi_wdata,
  up_axi_wstrb,
  up_axi_wready,
  up_axi_bvalid,
  up_axi_bresp,
  up_axi_bready,
  up_axi_arvalid,
  up_axi_araddr,
  up_axi_arready,
  up_axi_rvalid,
  up_axi_rresp,
  up_axi_rdata,
  up_axi_rready,

  // pcore interface

  up_wreq,
  up_waddr,
  up_wdata,
  up_wack,
  up_rreq,
  up_raddr,
  up_rdata,
  up_rack);

  // parameters

  parameter   ADDRESS_WIDTH = 14;
  localparam  AW = ADDRESS_WIDTH - 1;

  // reset and clocks

  input           up_rstn;
  input           up_clk;

  // axi4 interface

  input           up_axi_awvalid;
  input   [31:0]  up_axi_awaddr;
  output          up_axi_awready;
  input           up_axi_wvalid;
  input   [31:0]  up_axi_wdata;
  input   [ 3:0]  up_axi_wstrb;
  output          up_axi_wready;
  output          up_axi_bvalid;
  output  [ 1:0]  up_axi_bresp;
  input           up_axi_bready;
  input           up_axi_arvalid;
  input   [31:0]  up_axi_araddr;
  output          up_axi_arready;
  output          up_axi_rvalid;
  output  [ 1:0]  up_axi_rresp;
  output  [31:0]  up_axi_rdata;
  input           up_axi_rready;

  // pcore interface

  output          up_wreq;
  output  [AW:0]  up_waddr;
  output  [31:0]  up_wdata;
  input           up_wack;
  output          up_rreq;
  output  [AW:0]  up_raddr;
  input   [31:0]  up_rdata;
  input           up_rack;

  // internal registers

  reg             up_axi_awready = 'd0;
  reg             up_axi_wready = 'd0;
  reg             up_axi_bvalid = 'd0;
  reg             up_wack_d = 'd0;
  reg             up_wsel = 'd0;
  reg             up_wreq = 'd0;
  reg     [AW:0]  up_waddr = 'd0;
  reg     [31:0]  up_wdata = 'd0;
  reg     [ 4:0]  up_wcount = 'd0;
  reg             up_axi_arready = 'd0;
  reg             up_axi_rvalid = 'd0;
  reg     [31:0]  up_axi_rdata = 'd0;
  reg             up_rack_d = 'd0;
  reg     [31:0]  up_rdata_d = 'd0;
  reg             up_rsel = 'd0;
  reg             up_rreq = 'd0;
  reg     [AW:0]  up_raddr = 'd0;
  reg     [ 4:0]  up_rcount = 'd0;

  // internal signals

  wire            up_wack_s;
  wire            up_rack_s;
  wire    [31:0]  up_rdata_s;

  // write channel interface

  assign up_axi_bresp = 2'd0;

  always @(negedge up_rstn or posedge up_clk) begin
    if (up_rstn == 1'b0) begin
      up_axi_awready <= 'd0;
      up_axi_wready <= 'd0;
      up_axi_bvalid <= 'd0;
    end else begin
      if (up_axi_awready == 1'b1) begin
        up_axi_awready <= 1'b0;
      end else if (up_wack_s == 1'b1) begin
        up_axi_awready <= 1'b1;
      end
      if (up_axi_wready == 1'b1) begin
        up_axi_wready <= 1'b0;
      end else if (up_wack_s == 1'b1) begin
        up_axi_wready <= 1'b1;
      end
      if ((up_axi_bready == 1'b1) && (up_axi_bvalid == 1'b1)) begin
        up_axi_bvalid <= 1'b0;
      end else if (up_wack_d == 1'b1) begin
        up_axi_bvalid <= 1'b1;
      end
    end
  end

  assign up_wack_s = (up_wcount == 5'h1f) ? 1'b1 : (up_wcount[4] & up_wack);

  always @(negedge up_rstn or posedge up_clk) begin
    if (up_rstn == 1'b0) begin
      up_wack_d <= 'd0;
      up_wsel <= 'd0;
      up_wreq <= 'd0;
      up_waddr <= 'd0;
      up_wdata <= 'd0;
      up_wcount <= 'd0;
    end else begin
      up_wack_d <= up_wack_s;
      if (up_wsel == 1'b1) begin
        if ((up_axi_bready == 1'b1) && (up_axi_bvalid == 1'b1)) begin
          up_wsel <= 1'b0;
        end
        up_wreq <= 1'b0;
        up_waddr <= up_waddr;
        up_wdata <= up_wdata;
      end else begin
        up_wsel <= up_axi_awvalid & up_axi_wvalid;
        up_wreq <= up_axi_awvalid & up_axi_wvalid;
        up_waddr <= up_axi_awaddr[AW+2:2];
        up_wdata <= up_axi_wdata;
      end
      if (up_wack_s == 1'b1) begin
        up_wcount <= 5'h00;
      end else if (up_wcount[4] == 1'b1) begin
        up_wcount <= up_wcount + 1'b1;
      end else if (up_wreq == 1'b1) begin
        up_wcount <= 5'h10;
      end
    end
  end

  // read channel interface

  assign up_axi_rresp = 2'd0;

  always @(negedge up_rstn or posedge up_clk) begin
    if (up_rstn == 1'b0) begin
      up_axi_arready <= 'd0;
      up_axi_rvalid <= 'd0;
      up_axi_rdata <= 'd0;
    end else begin
      if (up_axi_arready == 1'b1) begin
        up_axi_arready <= 1'b0;
      end else if (up_rack_s == 1'b1) begin
        up_axi_arready <= 1'b1;
      end
      if ((up_axi_rready == 1'b1) && (up_axi_rvalid == 1'b1)) begin
        up_axi_rvalid <= 1'b0;
        up_axi_rdata <= 32'd0;
      end else if (up_rack_d == 1'b1) begin
        up_axi_rvalid <= 1'b1;
        up_axi_rdata <= up_rdata_d;
      end
    end
  end

  assign up_rack_s = (up_rcount == 5'h1f) ? 1'b1 : (up_rcount[4] & up_rack);
  assign up_rdata_s = (up_rcount == 5'h1f) ? {2{16'hdead}} : up_rdata;

  always @(negedge up_rstn or posedge up_clk) begin
    if (up_rstn == 1'b0) begin
      up_rack_d <= 'd0;
      up_rdata_d <= 'd0;
      up_rsel <= 'd0;
      up_rreq <= 'd0;
      up_raddr <= 'd0;
      up_rcount <= 'd0;
    end else begin
      up_rack_d <= up_rack_s;
      up_rdata_d <= up_rdata_s;
      if (up_rsel == 1'b1) begin
        if ((up_axi_rready == 1'b1) && (up_axi_rvalid == 1'b1)) begin
          up_rsel <= 1'b0;
        end
        up_rreq <= 1'b0;
        up_raddr <= up_raddr;
      end else begin
        up_rsel <= up_axi_arvalid;
        up_rreq <= up_axi_arvalid;
        up_raddr <= up_axi_araddr[AW+2:2];
      end
      if (up_rack_s == 1'b1) begin
        up_rcount <= 5'h00;
      end else if (up_rcount[4] == 1'b1) begin
        up_rcount <= up_rcount + 1'b1;
      end else if (up_rreq == 1'b1) begin
        up_rcount <= 5'h10;
      end
    end
  end

endmodule