///////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2005 Xilinx, Inc.
// This design is confidential and proprietary of Xilinx, All Rights Reserved.
///////////////////////////////////////////////////////////////////////////////
//   ____  ____
//  /   /\/   /
// /___/  \  /   Vendor             : Xilinx
// \   \   \/    Version            : $Name: mig_v1_7 $
//  \   \        Application        : MIG
//  /   /        Filename           : mem_interface_top_rd_data_fifo_0.v
// /___/   /\    Date Last Modified : $Date: 2007/02/15 12:06:16 $
// \   \  /  \   Date Created       : Mon May 2 2005
//  \___\/\___\
//
// Device      : Virtex-4
// Design Name : DDR SDRAM
// Description: Instantiates the distributed RAM which stores the read data
//              from the memory.
///////////////////////////////////////////////////////////////////////////////

`timescale 1ns / 1ps
`include "../rtl/mem_interface_top_parameters_0.v"

module mem_interface_top_rd_data_fifo_0
  (
   input                        CLK,
   input                        RESET,
   input                        READ_EN_DELAYED_RISE,
   input                        READ_EN_DELAYED_FALL,
   input                        FIRST_RISING,
   input [`memory_width-1:0]    READ_DATA_RISE,
   input [`memory_width-1:0]    READ_DATA_FALL,
   input                        fifo_rd_enable,

   output                       READ_DATA_VALID,
   output [`memory_width-1:0]   READ_DATA_FIFO_RISE,
   output [`memory_width-1:0]   READ_DATA_FIFO_FALL
   );




   reg [`memory_width*2-1:0]    fifos_data_out1;
   reg [3:0]                    fifo_rd_addr;
   reg [3:0]                    rise0_wr_addr;
   reg [3:0]                    fall0_wr_addr;
   reg                          fifo_rd_en;
   reg                          fifo_rd_en_r1;
   reg                          fifo_rd_en_r2;
   reg [`memory_width-1:0]      rise_fifo_data;
   reg [`memory_width-1:0]      fall_fifo_data;
   reg                          rd_en_delayed_rise_r;
   reg                          rd_en_delayed_rise_2r;
   reg                          rst_r;

   wire [`memory_width-1:0]     rise_fifo_out;
   wire [`memory_width-1:0]     fall_fifo_out;
   wire                         rd_en_delayed_rise_mux;

   assign READ_DATA_VALID                         = fifo_rd_en_r2;
   assign READ_DATA_FIFO_FALL[`memory_width-1:0]  = fifos_data_out1[`memory_width-1:0];
   assign READ_DATA_FIFO_RISE[`memory_width-1:0]  = fifos_data_out1[`memory_width*2-1 :
                                                                    `memory_width];
   assign rd_en_delayed_rise_mux = (FIRST_RISING) ? rd_en_delayed_rise_r :
                                                    rd_en_delayed_rise_2r;

   always @ (posedge CLK) begin
      rst_r <= RESET;
   end

   // Read Pointer and fifo data output sequencing

   // Read Enable generation for fifos based on write enable

   always @ (posedge CLK) begin
      if (rst_r == 1'b1) begin
         rd_en_delayed_rise_r   <= 1'b0;
         rd_en_delayed_rise_2r  <= 1'b0;
         fifo_rd_en             <= 1'b0;
         fifo_rd_en_r1          <= 1'b0;
         fifo_rd_en_r2          <= 1'b0;
      end
      else begin
         rd_en_delayed_rise_r   <= READ_EN_DELAYED_RISE;
         rd_en_delayed_rise_2r  <= rd_en_delayed_rise_r;
         fifo_rd_en             <= fifo_rd_enable; 
         fifo_rd_en_r1          <= fifo_rd_en;
         fifo_rd_en_r2          <= fifo_rd_en_r1;
      end
   end

   // Write Pointer increment for FIFOs

   always @ (posedge CLK) begin
      if (rst_r == 1'b1)
        rise0_wr_addr[3:0] <= 4'h0;
      else if (READ_EN_DELAYED_RISE == 1'b1)
        rise0_wr_addr[3:0] <= rise0_wr_addr[3:0] + 1'b1;
   end

   always @ (posedge CLK) begin
      if (rst_r == 1'b1)
        fall0_wr_addr[3:0] <= 4'h0;
      else if (READ_EN_DELAYED_FALL == 1'b1)
        fall0_wr_addr[3:0] <= fall0_wr_addr[3:0] + 1'b1;
   end

   ///////////////////////////////// FIFO Data Output Sequencing ///////////////

   always @ (posedge CLK) begin
      if (rst_r == 1'b1) begin
         rise_fifo_data[`memory_width-1:0] <= `memory_width'd0;
         fall_fifo_data[`memory_width-1:0] <= `memory_width'd0;
         fifo_rd_addr[3:0]   <= 4'h0;
      end
      else if (fifo_rd_en == 1'b1) begin
         rise_fifo_data[`memory_width-1:0] <= rise_fifo_out[`memory_width-1:0];
         fall_fifo_data[`memory_width-1:0] <= fall_fifo_out[`memory_width-1:0];
         fifo_rd_addr[3:0]    <= fifo_rd_addr[3:0] + 1'b1;
      end
   end

   always @ (posedge CLK) begin
      if (rst_r == 1'b1)
        fifos_data_out1[`memory_width*2-1:0] <= 16'h0000;
      else if (fifo_rd_en_r1 == 1'b1) begin
         if (FIRST_RISING == 1'b1)
           fifos_data_out1[`memory_width*2-1:0] <= {fall_fifo_data[`memory_width-1:0],
                                                    rise_fifo_data[`memory_width-1:0]};
         else
           fifos_data_out1[`memory_width*2-1:0] <= {rise_fifo_data[`memory_width-1:0],
                                                    fall_fifo_data[`memory_width-1:0]};
      end
   end



   //***************************************************************************
   // Distributed RAM 4 bit wide FIFO instantiations (2 FIFOs per strobe, rising
   //  edge data fifo and falling edge data fifo)
   //***************************************************************************
   // FIFOs associated with DQS(0)

     mem_interface_top_RAM_D_0 ram_rise0
       (
        .DPO    (rise_fifo_out[`memory_width-1:0]),
        .A0     (rise0_wr_addr[0]),
        .A1     (rise0_wr_addr[1]),
        .A2     (rise0_wr_addr[2]),
        .A3     (rise0_wr_addr[3]),
        .D      (READ_DATA_RISE[`memory_width-1:0]),
        .DPRA0  (fifo_rd_addr[0]),
        .DPRA1  (fifo_rd_addr[1]),
        .DPRA2  (fifo_rd_addr[2]),
        .DPRA3  (fifo_rd_addr[3]),
        .WCLK   (CLK),
        .WE     (READ_EN_DELAYED_RISE)
        );

   mem_interface_top_RAM_D_0 ram_fall0
     (
      .DPO      (fall_fifo_out[`memory_width-1:0]),
      .A0       (fall0_wr_addr[0]),
      .A1       (fall0_wr_addr[1]),
      .A2       (fall0_wr_addr[2]),
      .A3       (fall0_wr_addr[3]),
      .D        (READ_DATA_FALL[`memory_width-1:0]),
      .DPRA0    (fifo_rd_addr[0]),
      .DPRA1    (fifo_rd_addr[1]),
      .DPRA2    (fifo_rd_addr[2]),
      .DPRA3    (fifo_rd_addr[3]),
      .WCLK     (CLK),
      .WE       (READ_EN_DELAYED_FALL)
      );


endmodule