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[/] [ethmac/] [trunk/] [rtl/] [verilog/] [eth_fifo.v] - Blame information for rev 352

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//////////////////////////////////////////////////////////////////////
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////                                                              ////
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////  eth_fifo.v                                                  ////
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////                                                              ////
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////  This file is part of the Ethernet IP core project           ////
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////  http://www.opencores.org/project,ethmac                     ////
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////                                                              ////
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////  Author(s):                                                  ////
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////      - Igor Mohor (igorM@opencores.org)                      ////
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////                                                              ////
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////  All additional information is avaliable in the Readme.txt   ////
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////  file.                                                       ////
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////                                                              ////
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//////////////////////////////////////////////////////////////////////
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////                                                              ////
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//// Copyright (C) 2001 Authors                                   ////
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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 1.3  2002/04/22 13:45:52  mohor
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// Generic ram or Xilinx ram can be used in fifo (selectable by setting
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// ETH_FIFO_XILINX in eth_defines.v).
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//
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// Revision 1.2  2002/03/25 13:33:04  mohor
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// When clear and read/write are active at the same time, cnt and pointers are
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// set to 1.
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//
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// Revision 1.1  2002/02/05 16:44:39  mohor
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// Both rx and tx part are finished. Tested with wb_clk_i between 10 and 200
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// MHz. Statuses, overrun, control frame transmission and reception still  need
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// to be fixed.
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//
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//
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`include "eth_defines.v"
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`include "timescale.v"
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module eth_fifo (data_in, data_out, clk, reset, write, read, clear, almost_full, full, almost_empty, empty, cnt);
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parameter DATA_WIDTH    = 32;
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parameter DEPTH         = 8;
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parameter CNT_WIDTH     = 4;
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input                     clk;
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input                     reset;
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input                     write;
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input                     read;
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input                     clear;
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input   [DATA_WIDTH-1:0]  data_in;
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output  [DATA_WIDTH-1:0]  data_out;
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output                    almost_full;
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output                    full;
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output                    almost_empty;
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output                    empty;
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output  [CNT_WIDTH-1:0]   cnt;
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`ifdef ETH_FIFO_XILINX
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`else
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  `ifdef ETH_ALTERA_ALTSYNCRAM
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  `else
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    reg     [DATA_WIDTH-1:0]  fifo  [0:DEPTH-1];
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    reg     [DATA_WIDTH-1:0]  data_out;
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  `endif
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`endif
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reg     [CNT_WIDTH-1:0]   cnt;
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reg     [CNT_WIDTH-2:0]   read_pointer;
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reg     [CNT_WIDTH-2:0]   write_pointer;
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always @ (posedge clk or posedge reset)
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begin
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  if(reset)
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    cnt <= 0;
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  else
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  if(clear)
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    cnt <= { {(CNT_WIDTH-1){1'b0}}, read^write};
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  else
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  if(read ^ write)
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    if(read)
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      cnt <= cnt - 1'b1;
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    else
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      cnt <= cnt + 1'b1;
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end
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always @ (posedge clk or posedge reset)
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begin
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  if(reset)
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    read_pointer <= 0;
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  else
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  if(clear)
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    read_pointer <= { {(CNT_WIDTH-2){1'b0}}, read};
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  else
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  if(read & ~empty)
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    read_pointer <= read_pointer + 1'b1;
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end
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always @ (posedge clk or posedge reset)
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begin
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  if(reset)
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    write_pointer <= 0;
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  else
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  if(clear)
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    write_pointer <= { {(CNT_WIDTH-2){1'b0}}, write};
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  else
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  if(write & ~full)
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    write_pointer <= write_pointer + 1'b1;
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end
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assign empty = ~(|cnt);
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assign almost_empty = cnt == 1;
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assign full  = cnt == DEPTH;
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assign almost_full  = &cnt[CNT_WIDTH-2:0];
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`ifdef ETH_FIFO_XILINX
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  xilinx_dist_ram_16x32 fifo
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  ( .data_out(data_out),
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    .we(write & ~full),
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    .data_in(data_in),
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    .read_address( clear ? {CNT_WIDTH-1{1'b0}} : read_pointer),
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    .write_address(clear ? {CNT_WIDTH-1{1'b0}} : write_pointer),
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    .wclk(clk)
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  );
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`else   // !ETH_FIFO_XILINX
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`ifdef ETH_ALTERA_ALTSYNCRAM
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  altera_dpram_16x32    altera_dpram_16x32_inst
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  (
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        .data             (data_in),
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        .wren             (write & ~full),
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        .wraddress        (clear ? {CNT_WIDTH-1{1'b0}} : write_pointer),
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        .rdaddress        (clear ? {CNT_WIDTH-1{1'b0}} : read_pointer ),
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        .clock            (clk),
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        .q                (data_out)
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  );  //exemplar attribute altera_dpram_16x32_inst NOOPT TRUE
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`else   // !ETH_ALTERA_ALTSYNCRAM
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  always @ (posedge clk)
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  begin
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    if(write & clear)
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      fifo[0] <= data_in;
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    else
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   if(write & ~full)
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      fifo[write_pointer] <= data_in;
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  end
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  always @ (posedge clk)
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  begin
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    if(clear)
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      data_out <= fifo[0];
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    else
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      data_out <= fifo[read_pointer];
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  end
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`endif  // !ETH_ALTERA_ALTSYNCRAM
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`endif  // !ETH_FIFO_XILINX
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endmodule

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