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

////                                                              ////

////  eth_miim.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 1.6  2005/02/21 12:48:07  igorm

// Warning fixes.

//

// Revision 1.5  2003/05/16 10:08:27  mohor

// Busy was set 2 cycles too late. Reported by Dennis Scott.

//

// Revision 1.4  2002/08/14 18:32:10  mohor

// - Busy signal was not set on time when scan status operation was performed

// and clock was divided with more than 2.

// - Nvalid remains valid two more clocks (was previously cleared too soon).

//

// 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 1.2  2001/08/02 09:25:31  mohor

// Unconnected signals are now connected.

//

// Revision 1.1  2001/07/30 21:23:42  mohor

// Directory structure changed. Files checked and joind together.

//

// Revision 1.3  2001/06/01 22:28:56  mohor

// This files (MIIM) are fully working. They were thoroughly tested. The testbench is not updated.

//

//

`include "timescale.v"

module eth_miim

(

  Clk,

  Reset,

  Divider,

  NoPre,

  CtrlData,

  Rgad,

  Fiad,

  WCtrlData,

  RStat,

  ScanStat,

  Mdi,

  Mdo,

  MdoEn,

  Mdc,

  Busy,

  Prsd,

  LinkFail,

  Nvalid,

  WCtrlDataStart,

  RStatStart,

  UpdateMIIRX_DATAReg

);

input         Clk;                // Host Clock

input         Reset;              // General Reset

input   [7:0] Divider;            // Divider for the host clock

input  [15:0] CtrlData;           // Control Data (to be written to the PHY reg.)

input   [4:0] Rgad;               // Register Address (within the PHY)

input   [4:0] Fiad;               // PHY Address

input         NoPre;              // No Preamble (no 32-bit preamble)

input         WCtrlData;          // Write Control Data operation

input         RStat;              // Read Status operation

input         ScanStat;           // Scan Status operation

input         Mdi;                // MII Management Data In

output        Mdc;                // MII Management Data Clock

output        Mdo;                // MII Management Data Output

output        MdoEn;              // MII Management Data Output Enable

output        Busy;               // Busy Signal

output        LinkFail;           // Link Integrity Signal

output        Nvalid;             // Invalid Status (qualifier for the valid scan result)

output [15:0] Prsd;               // Read Status Data (data read from the PHY)

output        WCtrlDataStart;     // This signals resets the WCTRLDATA bit in the MIIM Command register

output        RStatStart;         // This signal resets the RSTAT BIT in the MIIM Command register

output        UpdateMIIRX_DATAReg;// Updates MII RX_DATA register with read data

parameter Tp = 1;

reg           Nvalid;

reg           EndBusy_d;          // Pre-end Busy signal

reg           EndBusy;            // End Busy signal (stops the operation in progress)

reg           WCtrlData_q1;       // Write Control Data operation delayed 1 Clk cycle

reg           WCtrlData_q2;       // Write Control Data operation delayed 2 Clk cycles

reg           WCtrlData_q3;       // Write Control Data operation delayed 3 Clk cycles

reg           WCtrlDataStart;     // Start Write Control Data Command (positive edge detected)

reg           WCtrlDataStart_q;

reg           WCtrlDataStart_q1;  // Start Write Control Data Command delayed 1 Mdc cycle

reg           WCtrlDataStart_q2;  // Start Write Control Data Command delayed 2 Mdc cycles

reg           RStat_q1;           // Read Status operation delayed 1 Clk cycle

reg           RStat_q2;           // Read Status operation delayed 2 Clk cycles

reg           RStat_q3;           // Read Status operation delayed 3 Clk cycles

reg           RStatStart;         // Start Read Status Command (positive edge detected)

reg           RStatStart_q1;      // Start Read Status Command delayed 1 Mdc cycle

reg           RStatStart_q2;      // Start Read Status Command delayed 2 Mdc cycles

reg           ScanStat_q1;        // Scan Status operation delayed 1 cycle

reg           ScanStat_q2;        // Scan Status operation delayed 2 cycles

reg           SyncStatMdcEn;      // Scan Status operation delayed at least cycles and synchronized to MdcEn

wire          WriteDataOp;        // Write Data Operation (positive edge detected)

wire          ReadStatusOp;       // Read Status Operation (positive edge detected)

wire          ScanStatusOp;       // Scan Status Operation (positive edge detected)

wire          StartOp;            // Start Operation (start of any of the preceding operations)

wire          EndOp;              // End of Operation

reg           InProgress;         // Operation in progress

reg           InProgress_q1;      // Operation in progress delayed 1 Mdc cycle

reg           InProgress_q2;      // Operation in progress delayed 2 Mdc cycles

reg           InProgress_q3;      // Operation in progress delayed 3 Mdc cycles

reg           WriteOp;            // Write Operation Latch (When asserted, write operation is in progress)

reg     [6:0] BitCounter;         // Bit Counter

wire    [3:0] ByteSelect;         // Byte Select defines which byte (preamble, data, operation, etc.) is loaded and shifted through the shift register.

wire          MdcEn;              // MII Management Data Clock Enable signal is asserted for one Clk period before Mdc rises.

wire          ShiftedBit;         // This bit is output of the shift register and is connected to the Mdo signal

wire          MdcEn_n;

wire          LatchByte1_d2;

wire          LatchByte0_d2;

reg           LatchByte1_d;

reg           LatchByte0_d;

reg     [1:0] LatchByte;          // Latch Byte selects which part of Read Status Data is updated from the shift register

reg           UpdateMIIRX_DATAReg;// Updates MII RX_DATA register with read data

// Generation of the EndBusy signal. It is used for ending the MII Management operation.

always @ (posedge Clk or posedge Reset)

begin

  if(Reset)

    begin

      EndBusy_d <= #Tp 1'b0;

      EndBusy <= #Tp 1'b0;

    end

  else

    begin

      EndBusy_d <= #Tp ~InProgress_q2 & InProgress_q3;

      EndBusy   <= #Tp EndBusy_d;

    end

end

// Update MII RX_DATA register

always @ (posedge Clk or posedge Reset)

begin

  if(Reset)

    UpdateMIIRX_DATAReg <= #Tp 0;

  else

  if(EndBusy & ~WCtrlDataStart_q)

    UpdateMIIRX_DATAReg <= #Tp 1;

  else

    UpdateMIIRX_DATAReg <= #Tp 0;

end

// Generation of the delayed signals used for positive edge triggering.

always @ (posedge Clk or posedge Reset)

begin

  if(Reset)

    begin

      WCtrlData_q1 <= #Tp 1'b0;

      WCtrlData_q2 <= #Tp 1'b0;

      WCtrlData_q3 <= #Tp 1'b0;

      RStat_q1 <= #Tp 1'b0;

      RStat_q2 <= #Tp 1'b0;

      RStat_q3 <= #Tp 1'b0;

      ScanStat_q1  <= #Tp 1'b0;

      ScanStat_q2  <= #Tp 1'b0;

      SyncStatMdcEn <= #Tp 1'b0;

    end

  else

    begin

      WCtrlData_q1 <= #Tp WCtrlData;

      WCtrlData_q2 <= #Tp WCtrlData_q1;

      WCtrlData_q3 <= #Tp WCtrlData_q2;

      RStat_q1 <= #Tp RStat;

      RStat_q2 <= #Tp RStat_q1;

      RStat_q3 <= #Tp RStat_q2;

      ScanStat_q1  <= #Tp ScanStat;

      ScanStat_q2  <= #Tp ScanStat_q1;

      if(MdcEn)

        SyncStatMdcEn  <= #Tp ScanStat_q2;

    end

end

// Generation of the Start Commands (Write Control Data or Read Status)

always @ (posedge Clk or posedge Reset)

begin

  if(Reset)

    begin

      WCtrlDataStart <= #Tp 1'b0;

      WCtrlDataStart_q <= #Tp 1'b0;

      RStatStart <= #Tp 1'b0;

    end

  else

    begin

      if(EndBusy)

        begin

          WCtrlDataStart <= #Tp 1'b0;

          RStatStart <= #Tp 1'b0;

        end

      else

        begin

          if(WCtrlData_q2 & ~WCtrlData_q3)

            WCtrlDataStart <= #Tp 1'b1;

          if(RStat_q2 & ~RStat_q3)

            RStatStart <= #Tp 1'b1;

          WCtrlDataStart_q <= #Tp WCtrlDataStart;

        end

    end

end

// Generation of the Nvalid signal (indicates when the status is invalid)

always @ (posedge Clk or posedge Reset)

begin

  if(Reset)

    Nvalid <= #Tp 1'b0;

  else

    begin

      if(~InProgress_q2 & InProgress_q3)

        begin

          Nvalid <= #Tp 1'b0;

        end

      else

        begin

          if(ScanStat_q2  & ~SyncStatMdcEn)

            Nvalid <= #Tp 1'b1;

        end

    end

end

// Signals used for the generation of the Operation signals (positive edge)

always @ (posedge Clk or posedge Reset)

begin

  if(Reset)

    begin

      WCtrlDataStart_q1 <= #Tp 1'b0;

      WCtrlDataStart_q2 <= #Tp 1'b0;

      RStatStart_q1 <= #Tp 1'b0;

      RStatStart_q2 <= #Tp 1'b0;

      InProgress_q1 <= #Tp 1'b0;

      InProgress_q2 <= #Tp 1'b0;

      InProgress_q3 <= #Tp 1'b0;

          LatchByte0_d <= #Tp 1'b0;

          LatchByte1_d <= #Tp 1'b0;

          LatchByte <= #Tp 2'b00;

    end

  else

    begin

      if(MdcEn)

        begin

          WCtrlDataStart_q1 <= #Tp WCtrlDataStart;

          WCtrlDataStart_q2 <= #Tp WCtrlDataStart_q1;

          RStatStart_q1 <= #Tp RStatStart;

          RStatStart_q2 <= #Tp RStatStart_q1;

          LatchByte[0] <= #Tp LatchByte0_d;

          LatchByte[1] <= #Tp LatchByte1_d;

          LatchByte0_d <= #Tp LatchByte0_d2;

          LatchByte1_d <= #Tp LatchByte1_d2;

          InProgress_q1 <= #Tp InProgress;

          InProgress_q2 <= #Tp InProgress_q1;

          InProgress_q3 <= #Tp InProgress_q2;

        end

    end

end

// Generation of the Operation signals

assign WriteDataOp  = WCtrlDataStart_q1 & ~WCtrlDataStart_q2;

assign ReadStatusOp = RStatStart_q1     & ~RStatStart_q2;

assign ScanStatusOp = SyncStatMdcEn     & ~InProgress & ~InProgress_q1 & ~InProgress_q2;

assign StartOp      = WriteDataOp | ReadStatusOp | ScanStatusOp;

// Busy

assign Busy = WCtrlData | WCtrlDataStart | RStat | RStatStart | SyncStatMdcEn | EndBusy | InProgress | InProgress_q3 | Nvalid;

// Generation of the InProgress signal (indicates when an operation is in progress)

// Generation of the WriteOp signal (indicates when a write is in progress)

always @ (posedge Clk or posedge Reset)

begin

  if(Reset)

    begin

      InProgress <= #Tp 1'b0;

      WriteOp <= #Tp 1'b0;

    end

  else

    begin

      if(MdcEn)

        begin

          if(StartOp)

            begin

              if(~InProgress)

                WriteOp <= #Tp WriteDataOp;

              InProgress <= #Tp 1'b1;

            end

          else

            begin

              if(EndOp)

                begin

                  InProgress <= #Tp 1'b0;

                  WriteOp <= #Tp 1'b0;

                end

            end

        end

    end

end

// Bit Counter counts from 0 to 63 (from 32 to 63 when NoPre is asserted)

always @ (posedge Clk or posedge Reset)

begin

  if(Reset)

    BitCounter[6:0] <= #Tp 7'h0;

  else

    begin

      if(MdcEn)

        begin

          if(InProgress)

            begin

              if(NoPre & ( BitCounter == 7'h0 ))

                BitCounter[6:0] <= #Tp 7'h21;

              else

                BitCounter[6:0] <= #Tp BitCounter[6:0] + 1'b1;

            end

          else

            BitCounter[6:0] <= #Tp 7'h0;

        end

    end

end

// Operation ends when the Bit Counter reaches 63

assign EndOp = BitCounter==63;

assign ByteSelect[0] = InProgress & ((NoPre & (BitCounter == 7'h0)) | (~NoPre & (BitCounter == 7'h20)));

assign ByteSelect[1] = InProgress & (BitCounter == 7'h28);

assign ByteSelect[2] = InProgress & WriteOp & (BitCounter == 7'h30);

assign ByteSelect[3] = InProgress & WriteOp & (BitCounter == 7'h38);

// Latch Byte selects which part of Read Status Data is updated from the shift register

assign LatchByte1_d2 = InProgress & ~WriteOp & BitCounter == 7'h37;

assign LatchByte0_d2 = InProgress & ~WriteOp & BitCounter == 7'h3F;

// Connecting the Clock Generator Module

eth_clockgen #(.Tp(Tp))

clkgen(.Clk(Clk), .Reset(Reset), .Divider(Divider[7:0]), .MdcEn(MdcEn), .MdcEn_n(MdcEn_n), .Mdc(Mdc)

                   );

// Connecting the Shift Register Module

eth_shiftreg #(.Tp(Tp))

shftrg(.Clk(Clk), .Reset(Reset), .MdcEn_n(MdcEn_n), .Mdi(Mdi), .Fiad(Fiad), .Rgad(Rgad),

                    .CtrlData(CtrlData), .WriteOp(WriteOp), .ByteSelect(ByteSelect), .LatchByte(LatchByte),

                    .ShiftedBit(ShiftedBit), .Prsd(Prsd), .LinkFail(LinkFail)

                   );

// Connecting the Output Control Module

eth_outputcontrol #(.Tp(Tp))

outctrl(.Clk(Clk), .Reset(Reset), .MdcEn_n(MdcEn_n), .InProgress(InProgress),

                          .ShiftedBit(ShiftedBit), .BitCounter(BitCounter), .WriteOp(WriteOp), .NoPre(NoPre),

                          .Mdo(Mdo), .MdoEn(MdoEn)

                         );

endmodule