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//////////////////////////////////////////////////////////////////////

////                                                              ////

////  eth_rxcounters.v                                            ////

////                                                              ////

////  This file is part of the Ethernet IP core project           ////

////  http://www.opencores.org/project,ethmac                     ////

////                                                              ////

////  Author(s):                                                  ////

////      - Igor Mohor (igorM@opencores.org)                      ////

////      - Novan Hartadi (novan@vlsi.itb.ac.id)                  ////

////      - Mahmud Galela (mgalela@vlsi.itb.ac.id)                ////

////                                                              ////

////  All additional information is avaliable in the Readme.txt   ////

////  file.                                                       ////

////                                                              ////

//////////////////////////////////////////////////////////////////////

////                                                              ////

//// Copyright (C) 2001 Authors                                   ////

////                                                              ////

//// This source file may be used and distributed without         ////

//// restriction provided that this copyright statement is not    ////

//// removed from the file and that any derivative work contains  ////

//// the original copyright notice and the associated disclaimer. ////

////                                                              ////

//// This source file is free software; you can redistribute it   ////

//// and/or modify it under the terms of the GNU Lesser General   ////

//// Public License as published by the Free Software Foundation; ////

//// either version 2.1 of the License, or (at your option) any   ////

//// later version.                                               ////

////                                                              ////

//// This source is distributed in the hope that it will be       ////

//// useful, but WITHOUT ANY WARRANTY; without even the implied   ////

//// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR      ////

//// PURPOSE.  See the GNU Lesser General Public License for more ////

//// details.                                                     ////

////                                                              ////

//// You should have received a copy of the GNU Lesser General    ////

//// Public License along with this source; if not, download it   ////

//// from http://www.opencores.org/lgpl.shtml                     ////

////                                                              ////

//////////////////////////////////////////////////////////////////////

`include "timescale.v"

module eth_rxcounters

  (

   MRxClk, Reset, MRxDV, StateIdle, StateSFD, StateData, StateDrop, StatePreamble,

   MRxDEqD, DlyCrcEn, DlyCrcCnt, Transmitting, MaxFL, r_IFG, HugEn, IFGCounterEq24,

   ByteCntEq0, ByteCntEq1, ByteCntEq2,ByteCntEq3,ByteCntEq4,ByteCntEq5, ByteCntEq6,

   ByteCntEq7, ByteCntGreat2, ByteCntSmall7, ByteCntMaxFrame, ByteCntOut

   );

input         MRxClk;

input         Reset;

input         MRxDV;

input         StateSFD;

input [1:0]   StateData;

input         MRxDEqD;

input         StateIdle;

input         StateDrop;

input         DlyCrcEn;

input         StatePreamble;

input         Transmitting;

input         HugEn;

input [15:0]  MaxFL;

input         r_IFG;

output        IFGCounterEq24;           // IFG counter reaches 9600 ns (960 ns)

output [3:0]  DlyCrcCnt;                // Delayed CRC counter

output        ByteCntEq0;               // Byte counter = 0

output        ByteCntEq1;               // Byte counter = 1

output        ByteCntEq2;               // Byte counter = 2  

output        ByteCntEq3;               // Byte counter = 3  

output        ByteCntEq4;               // Byte counter = 4  

output        ByteCntEq5;               // Byte counter = 5  

output        ByteCntEq6;               // Byte counter = 6

output        ByteCntEq7;               // Byte counter = 7

output        ByteCntGreat2;            // Byte counter > 2

output        ByteCntSmall7;            // Byte counter < 7

output        ByteCntMaxFrame;          // Byte counter = MaxFL

output [15:0] ByteCntOut;               // Byte counter

wire          ResetByteCounter;

wire          IncrementByteCounter;

wire          ResetIFGCounter;

wire          IncrementIFGCounter;

wire          ByteCntMax;

reg   [15:0]  ByteCnt;

reg   [3:0]   DlyCrcCnt;

reg   [4:0]   IFGCounter;

wire  [15:0]  ByteCntDelayed;

assign ResetByteCounter = MRxDV & (StateSFD & MRxDEqD | StateData[0] & ByteCntMaxFrame);

assign IncrementByteCounter = ~ResetByteCounter & MRxDV &

                              (StatePreamble | StateSFD | StateIdle & ~Transmitting |

                               StateData[1] & ~ByteCntMax & ~(DlyCrcEn & |DlyCrcCnt)

                              );

always @ (posedge MRxClk or posedge Reset)

begin

  if(Reset)

    ByteCnt[15:0] <=  16'd0;

  else

    begin

      if(ResetByteCounter)

        ByteCnt[15:0] <=  16'd0;

      else

      if(IncrementByteCounter)

        ByteCnt[15:0] <=  ByteCnt[15:0] + 16'd1;

     end

end

assign ByteCntDelayed = ByteCnt + 16'd4;

assign ByteCntOut = DlyCrcEn ? ByteCntDelayed : ByteCnt;

assign ByteCntEq0       = ByteCnt == 16'd0;

assign ByteCntEq1       = ByteCnt == 16'd1;

assign ByteCntEq2       = ByteCnt == 16'd2;

assign ByteCntEq3       = ByteCnt == 16'd3;

assign ByteCntEq4       = ByteCnt == 16'd4;

assign ByteCntEq5       = ByteCnt == 16'd5;

assign ByteCntEq6       = ByteCnt == 16'd6;

assign ByteCntEq7       = ByteCnt == 16'd7;

assign ByteCntGreat2    = ByteCnt >  16'd2;

assign ByteCntSmall7    = ByteCnt <  16'd7;

assign ByteCntMax       = ByteCnt == 16'hffff;

assign ByteCntMaxFrame  = ByteCnt == MaxFL[15:0] & ~HugEn;

assign ResetIFGCounter = StateSFD  &  MRxDV & MRxDEqD | StateDrop;

assign IncrementIFGCounter = ~ResetIFGCounter & (StateDrop | StateIdle | StatePreamble | StateSFD) & ~IFGCounterEq24;

always @ (posedge MRxClk or posedge Reset)

begin

  if(Reset)

    IFGCounter[4:0] <=  5'h0;

  else

    begin

      if(ResetIFGCounter)

        IFGCounter[4:0] <=  5'h0;

      else

      if(IncrementIFGCounter)

        IFGCounter[4:0] <=  IFGCounter[4:0] + 5'd1;

    end

end

assign IFGCounterEq24 = (IFGCounter[4:0] == 5'h18) | r_IFG; // 24*400 = 9600 ns or r_IFG is set to 1

always @ (posedge MRxClk or posedge Reset)

begin

  if(Reset)

    DlyCrcCnt[3:0] <=  4'h0;

  else

    begin

      if(DlyCrcCnt[3:0] == 4'h9)

        DlyCrcCnt[3:0] <=  4'h0;

      else

      if(DlyCrcEn & StateSFD)

        DlyCrcCnt[3:0] <=  4'h1;

      else

      if(DlyCrcEn & (|DlyCrcCnt[3:0]))

        DlyCrcCnt[3:0] <=  DlyCrcCnt[3:0] + 4'd1;

    end

end

endmodule