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