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         unneback | 
         //////////////////////////////////////////////////////////////////////
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         ////                                                              ////
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         ////  OR1200's Store Buffer FIFO                                  ////
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         ////                                                              ////
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         ////  This file is part of the OpenRISC 1200 project              ////
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         ////  http://www.opencores.org/cores/or1k/                        ////
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         ////                                                              ////
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         ////  Description                                                 ////
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         ////  Implementation of store buffer FIFO.                        ////
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         ////                                                              ////
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         ////  To Do:                                                      ////
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         ////   - N/A                                                      ////
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         ////                                                              ////
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         ////  Author(s):                                                  ////
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         ////      - Damjan Lampret, lampret@opencores.org                 ////
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         ////                                                              ////
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         //////////////////////////////////////////////////////////////////////
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         ////                                                              ////
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         //// Copyright (C) 2002 Authors and OPENCORES.ORG                 ////
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         ////                                                              ////
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         //// This source file may be used and distributed without         ////
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         //// restriction provided that this copyright statement is not    ////
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         //// removed from the file and that any derivative work contains  ////
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         //// the original copyright notice and the associated disclaimer. ////
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         ////                                                              ////
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         //// This source file is free software; you can redistribute it   ////
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         //// and/or modify it under the terms of the GNU Lesser General   ////
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         //// Public License as published by the Free Software Foundation; ////
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         //// either version 2.1 of the License, or (at your option) any   ////
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         //// later version.                                               ////
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         ////                                                              ////
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         //// This source is distributed in the hope that it will be       ////
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         //// useful, but WITHOUT ANY WARRANTY; without even the implied   ////
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         //// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR      ////
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         //// PURPOSE.  See the GNU Lesser General Public License for more ////
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         //// details.                                                     ////
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         ////                                                              ////
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         //// You should have received a copy of the GNU Lesser General    ////
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         //// Public License along with this source; if not, download it   ////
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         //// from http://www.opencores.org/lgpl.shtml                     ////
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         ////                                                              ////
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         //////////////////////////////////////////////////////////////////////
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         //
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         // CVS Revision History
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         //
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         // $Log: not supported by cvs2svn $
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         // Revision 1.2  2002/08/22 02:18:55  lampret
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         // Store buffer has been tested and it works. BY default it is still disabled until uClinux confirms correct operation on FPGA board.
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         //
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         // Revision 1.1  2002/08/18 19:53:08  lampret
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         // Added store buffer.
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         //
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         //
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         // synopsys translate_off
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         `include "timescale.v"
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         // synopsys translate_on
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         `include "or1200_defines.v"
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         module or1200_sb_fifo(
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                 clk_i, rst_i, dat_i, wr_i, rd_i, dat_o, full_o, empty_o
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         );
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         parameter dw = 68;
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         parameter fw = `OR1200_SB_LOG;
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         parameter fl = `OR1200_SB_ENTRIES;
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         //
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         // FIFO signals
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         //
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         input                   clk_i;  // Clock
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         input                   rst_i;  // Reset
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         input   [dw-1:0] dat_i;  // Input data bus
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         input                   wr_i;   // Write request
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         input                   rd_i;   // Read request
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         output [dw-1:0]  dat_o;  // Output data bus
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         output                  full_o; // FIFO full
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         output                  empty_o;// FIFO empty
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         //
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         // Internal regs
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         //
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         reg     [dw-1:0] mem [fl-1:0];
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         reg     [dw-1:0] dat_o;
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         reg     [fw+1:0] cntr;
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         reg     [fw-1:0] wr_pntr;
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         reg     [fw-1:0] rd_pntr;
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         reg                     empty_o;
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         reg                     full_o;
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         always @(posedge clk_i or posedge rst_i)
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                 if (rst_i) begin
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                         full_o <= #1 1'b0;
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                         empty_o <= #1 1'b1;
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                         wr_pntr <= #1 {fw{1'b0}};
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                         rd_pntr <= #1 {fw{1'b0}};
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                         cntr <= #1 {fw+2{1'b0}};
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                         dat_o <= #1 {dw{1'b0}};
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                 end
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                 else if (wr_i && rd_i) begin            // FIFO Read and Write
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                         mem[wr_pntr] <= #1 dat_i;
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                         if (wr_pntr >= fl-1)
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                                 wr_pntr <= #1 {fw{1'b0}};
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                         else
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                                 wr_pntr <= #1 wr_pntr + 1'b1;
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                         if (empty_o) begin
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                                 dat_o <= #1 dat_i;
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                         end
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                         else begin
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                                 dat_o <= #1 mem[rd_pntr];
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                         end
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                         if (rd_pntr >= fl-1)
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                                 rd_pntr <= #1 {fw{1'b0}};
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                         else
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                                 rd_pntr <= #1 rd_pntr + 1'b1;
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                 end
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                 else if (wr_i && !full_o) begin         // FIFO Write
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                         mem[wr_pntr] <= #1 dat_i;
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                         cntr <= #1 cntr + 1'b1;
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                         empty_o <= #1 1'b0;
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                         if (cntr >= (fl-1)) begin
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                                 full_o <= #1 1'b1;
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                                 cntr <= #1 fl;
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                         end
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                         if (wr_pntr >= fl-1)
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                                 wr_pntr <= #1 {fw{1'b0}};
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                         else
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                                 wr_pntr <= #1 wr_pntr + 1'b1;
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                 end
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                 else if (rd_i && !empty_o) begin        // FIFO Read
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                         dat_o <= #1 mem[rd_pntr];
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                         cntr <= #1 cntr - 1'b1;
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                         full_o <= #1 1'b0;
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                         if (cntr <= 1) begin
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                                 empty_o <= #1 1'b1;
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                                 cntr <= #1 {fw+2{1'b0}};
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                         end
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                         if (rd_pntr >= fl-1)
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                                 rd_pntr <= #1 {fw{1'b0}};
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                         else
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                                 rd_pntr <= #1 rd_pntr + 1'b1;
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                 end
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         endmodule
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