//////////////////////////////////////////////////////////////////////
////                                                              ////
////  eth_receivecontrol.v                                        ////
////                                                              ////
////  This file is part of the Ethernet IP core project           ////
////  http://www.opencores.org/project,ethmac                   ////
////                                                              ////
////  Author(s):                                                  ////
////      - Igor Mohor (igorM@opencores.org)                      ////
////                                                              ////
////  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                     ////
////                                                              ////
//////////////////////////////////////////////////////////////////////
//
// CVS Revision History
//
// $Log: not supported by cvs2svn $
// Revision 1.4  2002/11/22 01:57:06  mohor
// Rx Flow control fixed. CF flag added to the RX buffer descriptor. RxAbort
// synchronized.
//
// Revision 1.3  2002/01/23 10:28:16  mohor
// Link in the header changed.
//
// Revision 1.2  2001/10/19 08:43:51  mohor
// eth_timescale.v changed to timescale.v This is done because of the
// simulation of the few cores in a one joined project.
//
// Revision 1.1  2001/08/06 14:44:29  mohor
// A define FPGA added to select between Artisan RAM (for ASIC) and Block Ram (For Virtex).
// Include files fixed to contain no path.
// File names and module names changed ta have a eth_ prologue in the name.
// File eth_timescale.v is used to define timescale
// All pin names on the top module are changed to contain _I, _O or _OE at the end.
// Bidirectional signal MDIO is changed to three signals (Mdc_O, Mdi_I, Mdo_O
// and Mdo_OE. The bidirectional signal must be created on the top level. This
// is done due to the ASIC tools.
//
// Revision 1.1  2001/07/30 21:23:42  mohor
// Directory structure changed. Files checked and joind together.
//
// Revision 1.1  2001/07/03 12:51:54  mohor
// Initial release of the MAC Control module.
//
//
//
//
//


`include "timescale.v"


module eth_receivecontrol (MTxClk, MRxClk, TxReset, RxReset, RxData, RxValid, RxStartFrm, 
                           RxEndFrm, RxFlow, ReceiveEnd, MAC, DlyCrcEn, TxDoneIn, 
                           TxAbortIn, TxStartFrmOut, ReceivedLengthOK, ReceivedPacketGood, 
                           TxUsedDataOutDetected, Pause, ReceivedPauseFrm, AddressOK, 
                           RxStatusWriteLatched_sync2, r_PassAll, SetPauseTimer
                          );

parameter Tp = 1;


input       MTxClk;
input       MRxClk;
input       TxReset; 
input       RxReset; 
input [7:0] RxData;
input       RxValid;
input       RxStartFrm;
input       RxEndFrm;
input       RxFlow;
input       ReceiveEnd;
input [47:0]MAC;
input       DlyCrcEn;
input       TxDoneIn;
input       TxAbortIn;
input       TxStartFrmOut;
input       ReceivedLengthOK;
input       ReceivedPacketGood;
input       TxUsedDataOutDetected;
input       RxStatusWriteLatched_sync2;
input       r_PassAll;

output      Pause;
output      ReceivedPauseFrm;
output      AddressOK;
output      SetPauseTimer;


reg         Pause;
reg         AddressOK;                // Multicast or unicast address detected
reg         TypeLengthOK;             // Type/Length field contains 0x8808
reg         DetectionWindow;          // Detection of the PAUSE frame is possible within this window
reg         OpCodeOK;                 // PAUSE opcode detected (0x0001)
reg  [2:0]  DlyCrcCnt;
reg  [4:0]  ByteCnt;
reg [15:0]  AssembledTimerValue;
reg [15:0]  LatchedTimerValue;
reg         ReceivedPauseFrm;
reg         ReceivedPauseFrmWAddr;
reg         PauseTimerEq0_sync1;
reg         PauseTimerEq0_sync2;
reg [15:0]  PauseTimer;
reg         Divider2;
reg  [5:0]  SlotTimer;

wire [47:0] ReservedMulticast;        // 0x0180C2000001
wire [15:0] TypeLength;               // 0x8808
wire        ResetByteCnt;             // 
wire        IncrementByteCnt;         // 
wire        ByteCntEq0;               // ByteCnt = 0
wire        ByteCntEq1;               // ByteCnt = 1
wire        ByteCntEq2;               // ByteCnt = 2
wire        ByteCntEq3;               // ByteCnt = 3
wire        ByteCntEq4;               // ByteCnt = 4
wire        ByteCntEq5;               // ByteCnt = 5
wire        ByteCntEq12;              // ByteCnt = 12
wire        ByteCntEq13;              // ByteCnt = 13
wire        ByteCntEq14;              // ByteCnt = 14
wire        ByteCntEq15;              // ByteCnt = 15
wire        ByteCntEq16;              // ByteCnt = 16
wire        ByteCntEq17;              // ByteCnt = 17
wire        ByteCntEq18;              // ByteCnt = 18
wire        DecrementPauseTimer;      // 
wire        PauseTimerEq0;            // 
wire        ResetSlotTimer;           // 
wire        IncrementSlotTimer;       // 
wire        SlotFinished;             // 



// Reserved multicast address and Type/Length for PAUSE control
assign ReservedMulticast = 48'h0180C2000001;
assign TypeLength = 16'h8808;


// Address Detection (Multicast or unicast)
always @ (posedge MRxClk or posedge RxReset)
begin
  if(RxReset)
    AddressOK <=  1'b0;
  else
  if(DetectionWindow & ByteCntEq0)
    AddressOK <=   RxData[7:0] == ReservedMulticast[47:40] | RxData[7:0] == MAC[47:40];
  else
  if(DetectionWindow & ByteCntEq1)
    AddressOK <=  (RxData[7:0] == ReservedMulticast[39:32] | RxData[7:0] == MAC[39:32]) & AddressOK;
  else
  if(DetectionWindow & ByteCntEq2)
    AddressOK <=  (RxData[7:0] == ReservedMulticast[31:24] | RxData[7:0] == MAC[31:24]) & AddressOK;
  else
  if(DetectionWindow & ByteCntEq3)
    AddressOK <=  (RxData[7:0] == ReservedMulticast[23:16] | RxData[7:0] == MAC[23:16]) & AddressOK;
  else
  if(DetectionWindow & ByteCntEq4)
    AddressOK <=  (RxData[7:0] == ReservedMulticast[15:8]  | RxData[7:0] == MAC[15:8])  & AddressOK;
  else
  if(DetectionWindow & ByteCntEq5)
    AddressOK <=  (RxData[7:0] == ReservedMulticast[7:0]   | RxData[7:0] == MAC[7:0])   & AddressOK;
  else
  if(ReceiveEnd)
    AddressOK <=  1'b0;
end



// TypeLengthOK (Type/Length Control frame detected)
always @ (posedge MRxClk or posedge RxReset )
begin
  if(RxReset)
    TypeLengthOK <=  1'b0;
  else
  if(DetectionWindow & ByteCntEq12)
    TypeLengthOK <=  ByteCntEq12 & (RxData[7:0] == TypeLength[15:8]);
  else
  if(DetectionWindow & ByteCntEq13)
    TypeLengthOK <=  ByteCntEq13 & (RxData[7:0] == TypeLength[7:0]) & TypeLengthOK;
  else
  if(ReceiveEnd)
    TypeLengthOK <=  1'b0;
end



// Latch Control Frame Opcode
always @ (posedge MRxClk or posedge RxReset )
begin
  if(RxReset)
    OpCodeOK <=  1'b0;
  else
  if(ByteCntEq16)
    OpCodeOK <=  1'b0;
  else
    begin
      if(DetectionWindow & ByteCntEq14)
        OpCodeOK <=  ByteCntEq14 & RxData[7:0] == 8'h00;
    
      if(DetectionWindow & ByteCntEq15)
        OpCodeOK <=  ByteCntEq15 & RxData[7:0] == 8'h01 & OpCodeOK;
    end
end


// ReceivedPauseFrmWAddr (+Address Check)
always @ (posedge MRxClk or posedge RxReset )
begin
  if(RxReset)
    ReceivedPauseFrmWAddr <=  1'b0;
  else
  if(ReceiveEnd)
    ReceivedPauseFrmWAddr <=  1'b0;
  else
  if(ByteCntEq16 & TypeLengthOK & OpCodeOK & AddressOK)
    ReceivedPauseFrmWAddr <=  1'b1;        
end



// Assembling 16-bit timer value from two 8-bit data
always @ (posedge MRxClk or posedge RxReset )
begin
  if(RxReset)
    AssembledTimerValue[15:0] <=  16'h0;
  else
  if(RxStartFrm)
    AssembledTimerValue[15:0] <=  16'h0;
  else
    begin
      if(DetectionWindow & ByteCntEq16)
        AssembledTimerValue[15:8] <=  RxData[7:0];
      if(DetectionWindow & ByteCntEq17)
        AssembledTimerValue[7:0] <=  RxData[7:0];
    end
end


// Detection window (while PAUSE detection is possible)
always @ (posedge MRxClk or posedge RxReset )
begin
  if(RxReset)
    DetectionWindow <=  1'b1;
  else
  if(ByteCntEq18)
    DetectionWindow <=  1'b0;
  else
  if(ReceiveEnd)
    DetectionWindow <=  1'b1;
end



// Latching Timer Value
always @ (posedge MRxClk or posedge RxReset )
begin
  if(RxReset)
    LatchedTimerValue[15:0] <=  16'h0;
  else
  if(DetectionWindow &  ReceivedPauseFrmWAddr &  ByteCntEq18)
    LatchedTimerValue[15:0] <=  AssembledTimerValue[15:0];
  else
  if(ReceiveEnd)
    LatchedTimerValue[15:0] <=  16'h0;
end



// Delayed CEC counter
always @ (posedge MRxClk or posedge RxReset)
begin
  if(RxReset)
    DlyCrcCnt <=  3'h0;
  else
  if(RxValid & RxEndFrm)
    DlyCrcCnt <=  3'h0;
  else
  if(RxValid & ~RxEndFrm & ~DlyCrcCnt[2])
    DlyCrcCnt <=  DlyCrcCnt + 3'd1;
end

             
assign ResetByteCnt = RxEndFrm;
assign IncrementByteCnt = RxValid & DetectionWindow & ~ByteCntEq18 & 
			  (~DlyCrcEn | DlyCrcEn & DlyCrcCnt[2]);


// Byte counter
always @ (posedge MRxClk or posedge RxReset)
begin
  if(RxReset)
    ByteCnt[4:0] <=  5'h0;
  else
  if(ResetByteCnt)
    ByteCnt[4:0] <=  5'h0;
  else
  if(IncrementByteCnt)
    ByteCnt[4:0] <=  ByteCnt[4:0] + 5'd1;
end


assign ByteCntEq0 = RxValid & ByteCnt[4:0] == 5'h0;
assign ByteCntEq1 = RxValid & ByteCnt[4:0] == 5'h1;
assign ByteCntEq2 = RxValid & ByteCnt[4:0] == 5'h2;
assign ByteCntEq3 = RxValid & ByteCnt[4:0] == 5'h3;
assign ByteCntEq4 = RxValid & ByteCnt[4:0] == 5'h4;
assign ByteCntEq5 = RxValid & ByteCnt[4:0] == 5'h5;
assign ByteCntEq12 = RxValid & ByteCnt[4:0] == 5'h0C;
assign ByteCntEq13 = RxValid & ByteCnt[4:0] == 5'h0D;
assign ByteCntEq14 = RxValid & ByteCnt[4:0] == 5'h0E;
assign ByteCntEq15 = RxValid & ByteCnt[4:0] == 5'h0F;
assign ByteCntEq16 = RxValid & ByteCnt[4:0] == 5'h10;
assign ByteCntEq17 = RxValid & ByteCnt[4:0] == 5'h11;
assign ByteCntEq18 = RxValid & ByteCnt[4:0] == 5'h12 & DetectionWindow;


assign SetPauseTimer = ReceiveEnd & ReceivedPauseFrmWAddr & ReceivedPacketGood & ReceivedLengthOK & RxFlow;
assign DecrementPauseTimer = SlotFinished & |PauseTimer;


// PauseTimer[15:0]
always @ (posedge MRxClk or posedge RxReset)
begin
  if(RxReset)
    PauseTimer[15:0] <=  16'h0;
  else
  if(SetPauseTimer)
    PauseTimer[15:0] <=  LatchedTimerValue[15:0];
  else
  if(DecrementPauseTimer)
    PauseTimer[15:0] <=  PauseTimer[15:0] - 16'd1;
end

assign PauseTimerEq0 = ~(|PauseTimer[15:0]);



// Synchronization of the pause timer
always @ (posedge MTxClk or posedge TxReset)
begin
  if(TxReset)
    begin
      PauseTimerEq0_sync1 <=  1'b1;
      PauseTimerEq0_sync2 <=  1'b1;
    end
  else
    begin
      PauseTimerEq0_sync1 <=  PauseTimerEq0;
      PauseTimerEq0_sync2 <=  PauseTimerEq0_sync1;
    end
end


// Pause signal generation
always @ (posedge MTxClk or posedge TxReset)
begin
  if(TxReset)
    Pause <=  1'b0;
  else
  if((TxDoneIn | TxAbortIn | ~TxUsedDataOutDetected) & ~TxStartFrmOut)
    Pause <=  RxFlow & ~PauseTimerEq0_sync2;
end


// Divider2 is used for incrementing the Slot timer every other clock
always @ (posedge MRxClk or posedge RxReset)
begin
  if(RxReset)
    Divider2 <=  1'b0;
  else
  if(|PauseTimer[15:0] & RxFlow)
    Divider2 <=  ~Divider2;
  else
    Divider2 <=  1'b0;
end


assign ResetSlotTimer = RxReset;
assign IncrementSlotTimer =  Pause & RxFlow & Divider2;


// SlotTimer
always @ (posedge MRxClk or posedge RxReset)
begin
  if(RxReset)
    SlotTimer[5:0] <=  6'h0;
  else
  if(ResetSlotTimer)
    SlotTimer[5:0] <=  6'h0;
  else
  if(IncrementSlotTimer)
    SlotTimer[5:0] <=  SlotTimer[5:0] + 6'd1;
end


assign SlotFinished = &SlotTimer[5:0] & IncrementSlotTimer;  // Slot is 512 bits (64 bytes)



// Pause Frame received
always @ (posedge MRxClk or posedge RxReset)
begin
  if(RxReset)
    ReceivedPauseFrm <= 1'b0;
  else
  if(RxStatusWriteLatched_sync2 & r_PassAll | ReceivedPauseFrm & (~r_PassAll))
    ReceivedPauseFrm <= 1'b0;
  else
  if(ByteCntEq16 & TypeLengthOK & OpCodeOK)
    ReceivedPauseFrm <= 1'b1;        
end


endmodule
