module ad_mem_asym #(

  parameter   A_ADDRESS_WIDTH =  8,
  parameter   A_DATA_WIDTH = 256,
  parameter   B_ADDRESS_WIDTH =   10,
  parameter   B_DATA_WIDTH =  64) (

  input                             clka,
  input                             wea,
  input       [A_ADDRESS_WIDTH-1:0] addra,
  input       [A_DATA_WIDTH-1:0]    dina,

  input                             clkb,
  input                             reb,
  input       [B_ADDRESS_WIDTH-1:0] addrb,
  output  reg [B_DATA_WIDTH-1:0]    doutb);


  `define max(a,b) {(a) > (b) ? (a) : (b)}
  `define min(a,b) {(a) < (b) ? (a) : (b)}

  function integer clog2;
    input integer value;
    begin
      if (value < 2)
        clog2 = value;
      else begin
        value = value - 1;
        for (clog2 = 0; value > 0; clog2 = clog2 + 1)
          value = value >> 1;
      end
    end
  endfunction

  localparam  MEM_ADDRESS_WIDTH = `max(A_ADDRESS_WIDTH, B_ADDRESS_WIDTH);
  localparam  MIN_WIDTH = `min(A_DATA_WIDTH, B_DATA_WIDTH);
  localparam  MAX_WIDTH = `max(A_DATA_WIDTH, B_DATA_WIDTH);
  localparam  MEM_DATA_WIDTH = MIN_WIDTH;
  localparam  MEM_SIZE = 2 ** MEM_ADDRESS_WIDTH;
  localparam  MEM_RATIO = MAX_WIDTH / MIN_WIDTH;
  localparam  MEM_RATIO_LOG2 = clog2(MEM_RATIO);

  // internal registers

  (* ram_style = "block" *)
  reg      [MEM_DATA_WIDTH-1:0]    m_ram[0:MEM_SIZE-1];

  //---------------------------------------------------------------------------
  // write interface
  //---------------------------------------------------------------------------

  // write data width is narrower than read data width
  generate if (A_DATA_WIDTH <= B_DATA_WIDTH) begin
    always @(posedge clka) begin
      if (wea == 1'b1) begin
        m_ram[addra] <= dina;
      end
    end
  end
  endgenerate

  // write data width is wider than read data width
  generate if (A_DATA_WIDTH > B_DATA_WIDTH) begin
    always @(posedge clka) begin : memwrite
      integer i;
      reg [MEM_RATIO_LOG2-1:0] lsb;
      for (i = 0; i < MEM_RATIO; i = i + 1) begin : awrite
        lsb = i;
        if (wea) begin
          m_ram[{addra, lsb}] <= dina[i * MIN_WIDTH +: MIN_WIDTH];
        end
      end
    end
  end
  endgenerate

  //---------------------------------------------------------------------------
  // read interface
  //---------------------------------------------------------------------------

  // read data width is narrower than write data width
  generate if (A_DATA_WIDTH >= B_DATA_WIDTH) begin
    always @(posedge clkb) begin
      if (reb == 1'b1) begin
        doutb <= m_ram[addrb];
      end
    end
  end
  endgenerate

  // read data width is wider than write data width
  generate if (A_DATA_WIDTH < B_DATA_WIDTH) begin
    always @(posedge clkb) begin : memread
      integer i;
      reg [MEM_RATIO_LOG2-1:0] lsb;
      for (i = 0; i < MEM_RATIO; i = i + 1) begin : aread
        lsb = i;
        if (reb == 1'b1) begin
          doutb[i*MIN_WIDTH +: MIN_WIDTH] <= m_ram[{addrb, lsb}];
        end
      end
    end
  end
  endgenerate

endmodule