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//////////////////////////////////////////////////////////////////////
////                                                              ////
////  eth_wishbone.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 available in the Readme.txt   ////
////  file.                                                       ////
////                                                              ////
//////////////////////////////////////////////////////////////////////
////                                                              ////
//// Copyright (C) 2001, 2002 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 "ethmac_defines.v"
`include "timescale.v"
 
 
module eth_wishbone
  (
 
   // WISHBONE common
   WB_CLK_I, WB_DAT_I, WB_DAT_O,
 
   // WISHBONE slave
   WB_ADR_I, WB_WE_I, WB_ACK_O,
   BDCs,
 
   Reset,
 
   // WISHBONE master
   m_wb_adr_o, m_wb_sel_o, m_wb_we_o,
   m_wb_dat_o, m_wb_dat_i, m_wb_cyc_o,
   m_wb_stb_o, m_wb_ack_i, m_wb_err_i,
 
`ifdef ETH_WISHBONE_B3
   m_wb_cti_o, m_wb_bte_o,
`endif
 
   //TX
   MTxClk, TxStartFrm, TxEndFrm, TxUsedData, TxData,
   TxRetry, TxAbort, TxUnderRun, TxDone, PerPacketCrcEn,
   PerPacketPad,
 
   //RX
   MRxClk, RxData, RxValid, RxStartFrm, RxEndFrm, RxAbort,
   RxStatusWriteLatched_sync2,
 
   // Register
   r_TxEn, r_RxEn, r_TxBDNum, r_RxFlow, r_PassAll,
 
   // Interrupts
   TxB_IRQ, TxE_IRQ, RxB_IRQ, RxE_IRQ, Busy_IRQ,
 
   // Rx Status
   InvalidSymbol, LatchedCrcError, RxLateCollision, ShortFrame, DribbleNibble,
   ReceivedPacketTooBig, RxLength, LoadRxStatus, ReceivedPacketGood,
   AddressMiss,
   ReceivedPauseFrm,
 
   // Tx Status
   RetryCntLatched, RetryLimit, LateCollLatched, DeferLatched, RstDeferLatched,
   CarrierSenseLost
 
   // Bist
`ifdef ETH_BIST
   ,
   // debug chain signals
   mbist_si_i,       // bist scan serial in
   mbist_so_o,       // bist scan serial out
   mbist_ctrl_i        // bist chain shift control
`endif
 
`ifdef WISHBONE_DEBUG
   ,
   dbg_dat0
`endif
 
 
   );
 
 
   // WISHBONE common
   input           WB_CLK_I;       // WISHBONE clock
   input [31:0]    WB_DAT_I;       // WISHBONE data input
   output [31:0]   WB_DAT_O;       // WISHBONE data output
 
   // WISHBONE slave
   input [9:2]     WB_ADR_I;       // WISHBONE address input
   input           WB_WE_I;        // WISHBONE write enable input
   input [3:0]      BDCs;           // Buffer descriptors are selected
   output          WB_ACK_O;       // WISHBONE acknowledge output
 
   // WISHBONE master
   output [29:0]   m_wb_adr_o;     // 
   output [3:0]    m_wb_sel_o;     // 
   output          m_wb_we_o;      // 
   output [31:0]   m_wb_dat_o;     // 
   output          m_wb_cyc_o;     // 
   output          m_wb_stb_o;     // 
   input [31:0]    m_wb_dat_i;     // 
   input           m_wb_ack_i;     // 
   input           m_wb_err_i;     // 
 
`ifdef ETH_WISHBONE_B3
   output [2:0]    m_wb_cti_o;     // Cycle Type Identifier
 `ifdef BURST_4BEAT
   output reg [1:0] m_wb_bte_o;     // Burst Type Extension
 `else
   output [1:0]     m_wb_bte_o;     // Burst Type Extension
 `endif
   reg [2:0]         m_wb_cti_o;     // Cycle Type Identifier
`endif
 
   input            Reset;       // Reset signal
 
   // Rx Status signals
   input            InvalidSymbol;    // Invalid symbol was received during 
                                      // reception in 100 Mbps mode
   input            LatchedCrcError;  // CRC error
   input            RxLateCollision;  // Late collision occured while receiving
                                      // frame
   input            ShortFrame;       // Frame shorter then the minimum size 
                                      // (r_MinFL) was received while small 
                                      // packets are enabled (r_RecSmall)
   input            DribbleNibble;    // Extra nibble received
   input            ReceivedPacketTooBig;// Received packet is bigger than 
                                         // r_MaxFL
   input [15:0]     RxLength;         // Length of the incoming frame
   input            LoadRxStatus;     // Rx status was loaded
   input            ReceivedPacketGood;// Received packet's length and CRC are 
                                       // good
   input            AddressMiss;      // When a packet is received AddressMiss 
                                      // status is written to the Rx BD
   input            r_RxFlow;
   input            r_PassAll;
   input            ReceivedPauseFrm;
 
   // Tx Status signals
   input [3:0]       RetryCntLatched;  // Latched Retry Counter
   input            RetryLimit;       // Retry limit reached (Retry Max value +
                                      //  1 attempts were made)
   input            LateCollLatched;  // Late collision occured
   input            DeferLatched;     // Defer indication (Frame was defered 
                                      // before sucessfully sent)
   output           RstDeferLatched;
   input            CarrierSenseLost; // Carrier Sense was lost during the 
                                      // frame transmission
 
   // Tx
   input            MTxClk;         // Transmit clock (from PHY)
   input            TxUsedData;     // Transmit packet used data
   input            TxRetry;        // Transmit packet retry
   input            TxAbort;        // Transmit packet abort
   input            TxDone;         // Transmission ended
   output           TxStartFrm;     // Transmit packet start frame
   output           TxEndFrm;       // Transmit packet end frame
   output [7:0]     TxData;         // Transmit packet data byte
   output           TxUnderRun;     // Transmit packet under-run
   output           PerPacketCrcEn; // Per packet crc enable
   output           PerPacketPad;   // Per packet pading
 
   // Rx
   input            MRxClk;         // Receive clock (from PHY)
   input [7:0]       RxData;         // Received data byte (from PHY)
   input            RxValid;        // 
   input            RxStartFrm;     // 
   input            RxEndFrm;       // 
   input            RxAbort;        // This signal is set when address doesn't
                                    // match.
   output           RxStatusWriteLatched_sync2;
 
   //Register
   input            r_TxEn;         // Transmit enable
   input            r_RxEn;         // Receive enable
   input [7:0]       r_TxBDNum;      // Receive buffer descriptor number
 
   // Interrupts
   output           TxB_IRQ;
   output           TxE_IRQ;
   output           RxB_IRQ;
   output           RxE_IRQ;
   output           Busy_IRQ;
 
 
   // Bist
`ifdef ETH_BIST
   input            mbist_si_i;       // bist scan serial in
   output           mbist_so_o;       // bist scan serial out
   input [`ETH_MBIST_CTRL_WIDTH - 1:0] mbist_ctrl_i; // bist chain shift control
`endif
 
`ifdef WISHBONE_DEBUG
   output [31:0]                        dbg_dat0;
`endif
 
 
 
   reg                                 TxB_IRQ;
   reg                                 TxE_IRQ;
   reg                                 RxB_IRQ;
   reg                                 RxE_IRQ;
 
   reg                                 TxStartFrm;
   reg                                 TxEndFrm;
   reg [7:0]                            TxData;
 
   reg                                 TxUnderRun;
   reg                                 TxUnderRun_wb;
 
   reg                                 TxBDRead;
   wire                                TxStatusWrite;
 
   reg [1:0]                            TxValidBytesLatched;
 
   reg [15:0]                           TxLength;
   reg [15:0]                           LatchedTxLength;
   reg [14:11]                         TxStatus;
 
   reg [14:13]                         RxStatus;
 
   reg                                 TxStartFrm_wb;
   reg                                 TxRetry_wb;
   reg                                 TxAbort_wb;
   reg                                 TxDone_wb;
 
   reg                                 TxDone_wb_q;
   reg                                 TxAbort_wb_q;
   reg                                 TxRetry_wb_q;
   reg                                 TxRetryPacket;
   reg                                 TxRetryPacket_NotCleared;
   reg                                 TxDonePacket;
   reg                                 TxDonePacket_NotCleared;
   reg                                 TxAbortPacket;
   reg                                 TxAbortPacket_NotCleared;
   reg                                 RxBDReady;
   reg                                 RxBDOK/* synthesis syn_allow_retiming=0*/;
   reg                                 TxBDReady;
 
   reg                                 RxBDRead ;
 
   reg [31:0]                           TxDataLatched;
   reg [1:0]                            TxByteCnt;
   reg                                 LastWord;
   reg                                 ReadTxDataFromFifo_tck;
 
   reg                                 BlockingTxStatusWrite;
   reg                                 BlockingTxBDRead;
 
   reg                                 Flop;
 
   reg [7:1]                           TxBDAddress;
   reg [7:1]                           RxBDAddress;
 
   reg                                 TxRetrySync1;
   reg                                 TxAbortSync1;
   reg                                 TxDoneSync1;
 
   reg                                 TxAbort_q;
   reg                                 TxRetry_q;
   reg                                 TxUsedData_q;
 
   reg [31:0]                           RxDataLatched2;
 
   reg [31:8]                          RxDataLatched1;     // Big Endian Byte Ordering
 
   reg [1:0]                            RxValidBytes;
   reg [1:0]                            RxByteCnt;
   reg                                 LastByteIn;
   reg                                 ShiftWillEnd;
 
   reg                                 WriteRxDataToFifo;
   reg [15:0]                           LatchedRxLength;
   reg                                 RxAbortLatched;
 
   reg                                 ShiftEnded;
   reg                                 RxOverrun;
 
   reg [3:0]                            BDWrite;                    // BD Write Enable for access from WISHBONE side
   reg                                 BDRead;                     // BD Read access from WISHBONE side
   wire [31:0]                          RxBDDataIn;                 // Rx BD data in
   wire [31:0]                          TxBDDataIn;                 // Tx BD data in
 
   reg                                 TxEndFrm_wb;
 
   wire                                TxRetryPulse;
   wire                                TxDonePulse;
   wire                                TxAbortPulse;
 
   wire                                StartRxBDRead;
 
   wire                                StartTxBDRead;
 
   wire                                TxIRQEn;
   wire                                WrapTxStatusBit;
 
   wire                                RxIRQEn;
   wire                                WrapRxStatusBit;
 
   wire [1:0]                           TxValidBytes;
 
   wire [7:1]                          TempTxBDAddress;
   wire [7:1]                          TempRxBDAddress;
 
   wire                                RxStatusWrite;
   wire                                RxBufferFull;
   wire                                RxBufferAlmostEmpty;
   wire                                RxBufferEmpty;
 
   reg                                 WB_ACK_O;
 
   wire [8:0]                           RxStatusIn;
   reg [8:0]                            RxStatusInLatched;
 
   reg                                 WbEn, WbEn_q;
   reg                                 RxEn, RxEn_q /* synthesis syn_allow_retiming=0; syn_noprune=1; syn_keep=1 */;
   reg                                 TxEn, TxEn_q /* synthesis syn_allow_retiming=0; syn_noprune=1; syn_keep=1 */;
   reg                                 r_TxEn_q;
   reg                                 r_RxEn_q;
 
   wire                                ram_ce;
   wire [3:0]                           ram_we;
   wire                                ram_oe;
   reg [7:0]                            ram_addr;
   reg [31:0]                           ram_di;
   wire [31:0]                          ram_do;
 
   wire                                StartTxPointerRead;
   reg                                 TxPointerRead;
   reg                                 TxEn_needed;
   reg                                 RxEn_needed;
 
   wire                                StartRxPointerRead;
   reg                                 RxPointerRead/* synthesis syn_allow_retiming=0*/;
 
   // RX shift ending signals
   reg ShiftEnded_rck;
   reg ShiftEndedSync1;
   reg ShiftEndedSync2;
   reg ShiftEndedSync3;
   reg ShiftEndedSync_c1;
   reg ShiftEndedSync_c2;
 
   wire StartShiftWillEnd;
 
   // Pulse for wishbone side having finished writing back
   reg  rx_wb_writeback_finished;
   // Indicator of last set of writes from the Wishbone master coming up
   reg  rx_wb_last_writes;
 
 
   reg  StartOccured;
   reg  TxStartFrm_sync1;
   reg  TxStartFrm_sync2;
   reg  TxStartFrm_syncb1;
   reg  TxStartFrm_syncb2;
 
 
   wire TxFifoClear;
   wire TxBufferAlmostFull;
   wire TxBufferFull;
   wire TxBufferEmpty;
   wire TxBufferAlmostEmpty;
   wire SetReadTxDataFromMemory;
   reg  BlockReadTxDataFromMemory/* synthesis syn_allow_retiming=0*/;
 
   reg tx_burst_en;
   reg rx_burst_en;
   reg [`ETH_BURST_CNT_WIDTH-1:0] tx_burst_cnt;
 
   wire                           ReadTxDataFromMemory_2;
   wire                           tx_burst;
 
   wire [31:0]                     TxData_wb;
   wire                           ReadTxDataFromFifo_wb;
 
   wire [`ETH_TX_FIFO_CNT_WIDTH-1:0] txfifo_cnt;
   wire [`ETH_RX_FIFO_CNT_WIDTH-1:0] rxfifo_cnt;
 
   reg [`ETH_BURST_CNT_WIDTH-1:0]    rx_burst_cnt;
 
   wire                              rx_burst;
   wire                              enough_data_in_rxfifo_for_burst;
   wire                              enough_data_in_rxfifo_for_burst_plus1;
 
   reg ReadTxDataFromMemory/* synthesis syn_allow_retiming=0*/;
   wire WriteRxDataToMemory;
   reg WriteRxDataToMemory_r ;
 
   reg  MasterWbTX;
   reg  MasterWbRX;
 
   reg [29:0] m_wb_adr_o;
   reg        m_wb_cyc_o;
   reg [3:0]  m_wb_sel_o;
   reg        m_wb_we_o;
 
   wire       TxLengthEq0;
   wire       TxLengthLt4;
 
   reg        BlockingIncrementTxPointer;
   reg [31:2] TxPointerMSB;
   reg [1:0]  TxPointerLSB;
   reg [1:0]  TxPointerLSB_rst;
   reg [31:2] RxPointerMSB;
   reg [1:0]  RxPointerLSB_rst;
 
   wire       RxBurstAcc;
   wire       RxWordAcc;
   wire       RxHalfAcc;
   wire       RxByteAcc;
 
 
`ifdef ETH_WISHBONE_B3
 `ifndef BURST_4BEAT
   assign m_wb_bte_o = 2'b00;    // Linear burst
 `endif
`endif
 
   assign m_wb_stb_o = m_wb_cyc_o;
 
   always @ (posedge WB_CLK_I)
     begin
        WB_ACK_O <= (|BDWrite) & WbEn & WbEn_q | BDRead & WbEn & ~WbEn_q;
     end
 
   assign WB_DAT_O = ram_do;
 
   // Generic synchronous single-port RAM interface
   eth_spram_256x32
     #(1) // Write enable width
     bd_ram
     (
      .clk     (WB_CLK_I),
      .rst     (Reset),
      .ce      (ram_ce),
      .we      (ram_we[0]),
      .oe      (ram_oe),
      .addr    (ram_addr),
      .di      (ram_di),
      .dato    (ram_do)
`ifdef ETH_BIST
      ,
      .mbist_si_i       (mbist_si_i),
      .mbist_so_o       (mbist_so_o),
      .mbist_ctrl_i       (mbist_ctrl_i)
`endif
      );
 
   assign ram_ce = 1'b1;
   assign ram_we = (BDWrite & {4{(WbEn & WbEn_q)}}) |
                   {4{(TxStatusWrite | RxStatusWrite)}};
   assign ram_oe = BDRead & WbEn & WbEn_q | TxEn & TxEn_q &
                   (TxBDRead | TxPointerRead) | RxEn & RxEn_q &
                   (RxBDRead | RxPointerRead);
 
 
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          TxEn_needed <= 1'b0;
        else
          if(~TxBDReady & r_TxEn & WbEn & ~WbEn_q)
            TxEn_needed <= 1'b1;
          else
            if(TxPointerRead & TxEn & TxEn_q)
              TxEn_needed <= 1'b0;
     end
 
   // Enabling access to the RAM for three devices.
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          begin
             WbEn <= 1'b1;
             RxEn <= 1'b0;
             TxEn <= 1'b0;
             ram_addr <= 8'h0;
             ram_di <= 32'h0;
             BDRead <= 1'b0;
             BDWrite <= 0;
          end
        else
          begin
             // Switching between three stages depends on enable signals
             /* verilator lint_off CASEINCOMPLETE */ // JB
             case ({WbEn_q, RxEn_q, TxEn_q, RxEn_needed, TxEn_needed})  // synopsys parallel_case
               5'b100_10, 5'b100_11 :
                 begin
                    WbEn <= 1'b0;
                    RxEn <= 1'b1;  // wb access stage and r_RxEn is enabled
                    TxEn <= 1'b0;
                    ram_addr <= {RxBDAddress, RxPointerRead};
                    ram_di <= RxBDDataIn;
                 end
               5'b100_01 :
                 begin
                    WbEn <= 1'b0;
                    RxEn <= 1'b0;
                    TxEn <= 1'b1;  // wb access stage, r_RxEn is disabled but 
                                   // r_TxEn is enabled
                    ram_addr <= {TxBDAddress, TxPointerRead};
                    ram_di <= TxBDDataIn;
                 end
               5'b010_00, 5'b010_10 :
                 begin
                    WbEn <= 1'b1;  // RxEn access stage and r_TxEn is disabled
                    RxEn <= 1'b0;
                    TxEn <= 1'b0;
                    ram_addr <= WB_ADR_I[9:2];
                    ram_di <= WB_DAT_I;
                    BDWrite <= BDCs[3:0] & {4{WB_WE_I}};
                    BDRead <= (|BDCs) & ~WB_WE_I;
                 end
               5'b010_01, 5'b010_11 :
                 begin
                    WbEn <= 1'b0;
                    RxEn <= 1'b0;
                    TxEn <= 1'b1;  // RxEn access stage and r_TxEn is enabled
                    ram_addr <= {TxBDAddress, TxPointerRead};
                    ram_di <= TxBDDataIn;
                 end
               5'b001_00, 5'b001_01, 5'b001_10, 5'b001_11 :
                 begin
                    WbEn <= 1'b1;  // TxEn access stage (we always go to wb 
                                   // access stage)
                    RxEn <= 1'b0;
                    TxEn <= 1'b0;
                    ram_addr <= WB_ADR_I[9:2];
                    ram_di <= WB_DAT_I;
                    BDWrite <= BDCs[3:0] & {4{WB_WE_I}};
                    BDRead <= (|BDCs) & ~WB_WE_I;
                 end
               5'b100_00 :
                 begin
                    WbEn <= 1'b0;  // WbEn access stage and there is no need 
                                   // for other stages. WbEn needs to be 
                                   // switched off for a bit
                 end
               5'b000_00 :
                 begin
                    WbEn <= 1'b1;  // Idle state. We go to WbEn access stage.
                    RxEn <= 1'b0;
                    TxEn <= 1'b0;
                    ram_addr <= WB_ADR_I[9:2];
                    ram_di <= WB_DAT_I;
                    BDWrite <= BDCs[3:0] & {4{WB_WE_I}};
                    BDRead <= (|BDCs) & ~WB_WE_I;
                 end
             endcase //case ({WbEn_q, RxEn_q, TxEn_q, RxEn_needed, TxEn_needed})
             /* verilator lint_on CASEINCOMPLETE */
          end
     end
 
 
   // Delayed stage signals
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          begin
             WbEn_q <= 1'b0;
             RxEn_q <= 1'b0;
             TxEn_q <= 1'b0;
             r_TxEn_q <= 1'b0;
             r_RxEn_q <= 1'b0;
          end
        else
          begin
             WbEn_q <= WbEn;
             RxEn_q <= RxEn;
             TxEn_q <= TxEn;
             r_TxEn_q <= r_TxEn;
             r_RxEn_q <= r_RxEn;
          end
     end
 
   // Changes for tx occur every second clock. Flop is used for this manner.
   always @ (posedge MTxClk or posedge Reset)
     begin
        if(Reset)
          Flop <= 1'b0;
        else
          if(TxDone | TxAbort | TxRetry_q)
            Flop <= 1'b0;
          else
            if(TxUsedData)
              Flop <= ~Flop;
     end
 
   wire ResetTxBDReady;
   assign ResetTxBDReady = TxDonePulse | TxAbortPulse | TxRetryPulse;
 
   // Latching READY status of the Tx buffer descriptor
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          TxBDReady <= 1'b0;
        else
          if(TxEn & TxEn_q & TxBDRead)
            // TxBDReady is sampled only once at the beginning.
            TxBDReady <= ram_do[15] & (ram_do[31:16] > 4);
          else
            // Only packets larger then 4 bytes are transmitted.
            if(ResetTxBDReady)
              TxBDReady <= 1'b0;
     end
 
   // Reading the Tx buffer descriptor
   assign StartTxBDRead = (TxRetryPacket_NotCleared | TxStatusWrite) &
                          ~BlockingTxBDRead & ~TxBDReady;
 
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          TxBDRead <= 1'b1;
        else
          if(StartTxBDRead)
            TxBDRead <= 1'b1;
          else
            if(TxBDReady)
              TxBDRead <= 1'b0;
     end
 
 
   // Reading Tx BD pointer
   assign StartTxPointerRead = TxBDRead & TxBDReady;
 
   // Reading Tx BD Pointer
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          TxPointerRead <= 1'b0;
        else
          if(StartTxPointerRead)
            TxPointerRead <= 1'b1;
          else
            if(TxEn_q)
              TxPointerRead <= 1'b0;
     end
 
 
   // Writing status back to the Tx buffer descriptor
   assign TxStatusWrite = (TxDonePacket_NotCleared | TxAbortPacket_NotCleared)&
                          TxEn & TxEn_q & ~BlockingTxStatusWrite;
 
 
 
   // Status writing must occur only once. Meanwhile it is blocked.
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          BlockingTxStatusWrite <= 1'b0;
        else
          if(~TxDone_wb & ~TxAbort_wb)
            BlockingTxStatusWrite <= 1'b0;
          else
            if(TxStatusWrite)
              BlockingTxStatusWrite <= 1'b1;
     end
 
 
   reg BlockingTxStatusWrite_sync1;
   reg BlockingTxStatusWrite_sync2;
   reg BlockingTxStatusWrite_sync3;
 
   // Synchronizing BlockingTxStatusWrite to MTxClk
   always @ (posedge MTxClk or posedge Reset)
     begin
        if(Reset)
          BlockingTxStatusWrite_sync1 <= 1'b0;
        else
          BlockingTxStatusWrite_sync1 <= BlockingTxStatusWrite;
     end
 
   // Synchronizing BlockingTxStatusWrite to MTxClk
   always @ (posedge MTxClk or posedge Reset)
     begin
        if(Reset)
          BlockingTxStatusWrite_sync2 <= 1'b0;
        else
          BlockingTxStatusWrite_sync2 <= BlockingTxStatusWrite_sync1;
     end
 
   // Synchronizing BlockingTxStatusWrite to MTxClk
   always @ (posedge MTxClk or posedge Reset)
     begin
        if(Reset)
          BlockingTxStatusWrite_sync3 <= 1'b0;
        else
          BlockingTxStatusWrite_sync3 <= BlockingTxStatusWrite_sync2;
     end
 
   assign RstDeferLatched = BlockingTxStatusWrite_sync2 &
                            ~BlockingTxStatusWrite_sync3;
 
   // TxBDRead state is activated only once. 
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          BlockingTxBDRead <= 1'b0;
        else
          if(StartTxBDRead)
            BlockingTxBDRead <= 1'b1;
          else
            if(~StartTxBDRead & ~TxBDReady)
              BlockingTxBDRead <= 1'b0;
     end
 
 
   // Latching status from the tx buffer descriptor
   // Data is avaliable one cycle after the access is started (at that time 
   // signal TxEn is not active)
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          TxStatus <= 4'h0;
        else
          if(TxEn & TxEn_q & TxBDRead)
            TxStatus <= ram_do[14:11];
     end
 
 
   // Register WriteRxDataToMemory in Wishbone clock domain
   // so it doesn't get out of sync with burst capability indication signals
   always @(posedge WB_CLK_I or posedge Reset)
     if (Reset)
       WriteRxDataToMemory_r <= 0;
     else
       WriteRxDataToMemory_r <= WriteRxDataToMemory;
 
 
   //Latching length from the buffer descriptor;
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          TxLength <= 16'h0;
        else
          if(TxEn & TxEn_q & TxBDRead)
            TxLength <= ram_do[31:16];
          else
            if(MasterWbTX & m_wb_ack_i)
              begin
                 if(TxLengthLt4)
                   TxLength <= 16'h0;
                 else
                   if(TxPointerLSB_rst==2'h0)
                     TxLength <= TxLength - 16'd4;    // Length is subtracted at
                                                     // the data request
                   else
                     if(TxPointerLSB_rst==2'h1)
                       TxLength <= TxLength - 16'd3;    // Length is subtracted 
                                                       // at the data request
                     else
                       if(TxPointerLSB_rst==2'h2)
                         TxLength <= TxLength - 16'd2;   // Length is subtracted
                                                         // at the data request
                       else
                         if(TxPointerLSB_rst==2'h3)
                           TxLength <= TxLength - 16'd1; // Length is subtracted
                                                         // at the data request
              end
     end
 
 
 
   //Latching length from the buffer descriptor;
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          LatchedTxLength <= 16'h0;
        else
          if(TxEn & TxEn_q & TxBDRead)
            LatchedTxLength <= ram_do[31:16];
     end
 
   assign TxLengthEq0 = TxLength == 0;
   assign TxLengthLt4 = TxLength < 4;
 
   reg cyc_cleared;
   reg IncrTxPointer;
 
 
   // Latching Tx buffer pointer from buffer descriptor. Only 30 MSB bits are 
   // latched because TxPointerMSB is only used for word-aligned accesses.
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          TxPointerMSB <= 30'h0;
        else
          if(TxEn & TxEn_q & TxPointerRead)
            TxPointerMSB <= ram_do[31:2];
          else
            if(IncrTxPointer & ~BlockingIncrementTxPointer)
              // TxPointer is word-aligned
              TxPointerMSB <= TxPointerMSB + 1;
     end
 
 
   // Latching 2 MSB bits of the buffer descriptor. Since word accesses are 
   // performed, valid data does not necesserly start at byte 0 (could be byte 
   // 0, 1, 2 or 3). This signals are used for proper selection of the start 
   // byte (TxData and TxByteCnt) are set by this two bits.
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          TxPointerLSB[1:0] <= 0;
        else
          if(TxEn & TxEn_q & TxPointerRead)
            TxPointerLSB[1:0] <= ram_do[1:0];
     end
 
 
   // Latching 2 MSB bits of the buffer descriptor. 
   // After the read access, TxLength needs to be decremented for the number of
   // the valid bytes (1 to 4 bytes are valid in the first word). After the 
   // first read all bytes are valid so this two bits are reset to zero. 
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          TxPointerLSB_rst[1:0] <= 0;
        else
          if(TxEn & TxEn_q & TxPointerRead)
            TxPointerLSB_rst[1:0] <= ram_do[1:0];
          else
            // After first access pointer is word alligned
            if(MasterWbTX & m_wb_ack_i)
              TxPointerLSB_rst[1:0] <= 0;
     end
 
 
   reg  [3:0] RxByteSel;
   wire       MasterAccessFinished;
 
 
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          BlockingIncrementTxPointer <= 0;
        else
          if(MasterAccessFinished)
            BlockingIncrementTxPointer <= 0;
          else
            if(IncrTxPointer)
              BlockingIncrementTxPointer <= 1'b1;
     end
 
 
   assign SetReadTxDataFromMemory = TxEn & TxEn_q & TxPointerRead;
 
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          ReadTxDataFromMemory <= 1'b0;
        else
          if(TxLengthEq0 | TxAbortPulse | TxRetryPulse)
            ReadTxDataFromMemory <= 1'b0;
          else
            if(SetReadTxDataFromMemory)
              ReadTxDataFromMemory <= 1'b1;
     end
 
   assign ReadTxDataFromMemory_2 = ReadTxDataFromMemory &
                                   ~BlockReadTxDataFromMemory | (|tx_burst_cnt);
 
   assign tx_burst = ReadTxDataFromMemory_2 & tx_burst_en;
 
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          BlockReadTxDataFromMemory <= 1'b0;
        else
          if((TxBufferAlmostFull | TxLength <= 4)& MasterWbTX &
             (~cyc_cleared) & (!(TxAbortPacket_NotCleared |
                                 TxRetryPacket_NotCleared)))
            BlockReadTxDataFromMemory <= 1'b1;
          else
            if(ReadTxDataFromFifo_wb | TxDonePacket | TxAbortPacket |
               TxRetryPacket)
              BlockReadTxDataFromMemory <= 1'b0;
     end
 
`define TX_BURST_EN_CONDITION ({1'b0,txfifo_cnt}<(`ETH_TX_FIFO_DEPTH-`ETH_BURST_LENGTH) & (TxLength>(`ETH_BURST_LENGTH*4+4)))
 
   assign MasterAccessFinished = m_wb_ack_i | m_wb_err_i;
 
   // Enabling master wishbone access to the memory for two devices TX and RX.
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          begin
             MasterWbTX <= 1'b0;
             MasterWbRX <= 1'b0;
             m_wb_adr_o <= 30'h0;
             m_wb_cyc_o <= 1'b0;
             m_wb_we_o  <= 1'b0;
             m_wb_sel_o <= 4'h0;
             cyc_cleared<= 1'b0;
             tx_burst_cnt<= 0;
             rx_burst_cnt<= 0;
             IncrTxPointer<= 1'b0;
             tx_burst_en<= 1'b1;
             rx_burst_en<= 1'b0;
`ifdef ETH_WISHBONE_B3
             m_wb_cti_o <= 3'b0;
 `ifdef BURST_4BEAT
             m_wb_bte_o <= 2'b00;
 `endif
`endif
          end
        else
          begin
             // Switching between two stages depends on enable signals
             casez ({MasterWbTX,
                     MasterWbRX,
                     ReadTxDataFromMemory_2,
                     WriteRxDataToMemory_r,
                     MasterAccessFinished,
                     cyc_cleared,
                     tx_burst,
                     rx_burst})  // synopsys parallel_case
 
               8'b00_10_00_10, // Idle and MRB needed
               8'b10_1?_10_1?, // MRB continues
               8'b10_10_01_10, // Clear (previously MR) and MRB needed
               8'b01_1?_01_1?: // Clear (previously MW) and MRB needed
                   begin
                      MasterWbTX <= 1'b1;  // tx burst
                      MasterWbRX <= 1'b0;
                      m_wb_cyc_o <= 1'b1;
                      m_wb_we_o  <= 1'b0;
                      m_wb_sel_o <= 4'hf;
                      cyc_cleared<= 1'b0;
                      IncrTxPointer<= 1'b1;
                      tx_burst_cnt <= tx_burst_cnt+3'h1;
                      if(tx_burst_cnt==0)
                        m_wb_adr_o <= TxPointerMSB;
                      else
                        m_wb_adr_o <= m_wb_adr_o + 1;
 
                      if(tx_burst_cnt==(`ETH_BURST_LENGTH-1))
                        begin
                           tx_burst_en<= 1'b0;
`ifdef ETH_WISHBONE_B3
                           m_wb_cti_o <= 3'b111;
`endif
                        end
                      else
                        begin
`ifdef ETH_WISHBONE_B3
                           m_wb_cti_o <= 3'b010;
 `ifdef BURST_4BEAT
                           m_wb_bte_o <= 2'b01;
 `endif
`endif
                        end
                   end // case: 8'b00_10_00_10,...
`ifdef ETH_RX_BURST_EN
         8'b00_?1_00_?1,             // Idle and MWB needed
         8'b01_?1_10_?1,             // MWB continues
         8'b01_01_01_01,             // Clear (previously MW) and MWB needed
         8'b10_?1_01_?1 :            // Clear (previously MR) and MWB needed
           begin
              MasterWbTX <= 1'b0;  // rx burst
              MasterWbRX <= 1'b1;
              m_wb_cyc_o <= 1'b1;
              m_wb_we_o  <= 1'b1;
              m_wb_sel_o <= RxByteSel;
              IncrTxPointer<= 1'b0;
              cyc_cleared<= 1'b0;
              rx_burst_cnt <= rx_burst_cnt+3'd1;
 
              if(rx_burst_cnt==0)
                m_wb_adr_o <= RxPointerMSB;
              else
                m_wb_adr_o <= m_wb_adr_o + 1;
 
              if(rx_burst_cnt==(`ETH_BURST_LENGTH-1))
                begin
                   rx_burst_en<= 1'b0;
 `ifdef ETH_WISHBONE_B3
                   m_wb_cti_o <= 3'b111;
 `endif
                end
              else
                begin
 `ifdef ETH_WISHBONE_B3
  `ifdef BURST_4BEAT
                   m_wb_cti_o <= 3'b010;
                   m_wb_bte_o <= 2'b01;
  `endif
 `endif
                end
           end // case: 8'b00_x1_00_x1,...
`endif //  `ifdef ETH_RX_BURST_EN
               8'b00_?1_00_?0 ,//idle and MW is needed (data write to rx buffer)
               8'b01_?1_00_?0 :// Sometimes gets caught changing states - JB
                   begin
                      MasterWbTX <= 1'b0;
                      MasterWbRX <= !RxBufferEmpty;
                      m_wb_adr_o <= RxPointerMSB;
                      m_wb_cyc_o <= !RxBufferEmpty;
                      m_wb_we_o  <= !RxBufferEmpty;
                      m_wb_sel_o <= RxByteSel;
                      IncrTxPointer<= 1'b0;
`ifdef ETH_WISHBONE_B3
 `ifdef ETH_RX_BURST_EN
  `ifdef BURST_4BEAT
                      if ((RxPointerMSB[3:2]==2'b00) & !RxBufferEmpty &
                          enough_data_in_rxfifo_for_burst & !m_wb_cyc_o)
                        // Added "& !_m_wb_cyc_o" here to stop burst signals
                        // going high during a transfer
                        begin
                           rx_burst_en<= 1'b1;
                           m_wb_cti_o <= 3'b010;
                           m_wb_bte_o <= 2'b01;
                           rx_burst_cnt<= 1;
                        end
  `endif
 `endif
`endif //  `ifdef ETH_WISHBONE_B3
 
                   end
               8'b00_10_00_00 : // idle and MR is needed (data read from tx 
                                // buffer)
                 begin
                    MasterWbTX <= 1'b1;
                    MasterWbRX <= 1'b0;
                    m_wb_adr_o <= TxPointerMSB;
                    m_wb_cyc_o <= 1'b1;
                    m_wb_we_o  <= 1'b0;
                    m_wb_sel_o <= 4'hf;
                    IncrTxPointer<= 1'b1;
`ifdef BURST_4BEAT
 
                    // Attempt ethernet bugfix, start bursts later
                    if ((TxPointerMSB[3:2]==2'b00) && `TX_BURST_EN_CONDITION)
                      begin
 `ifdef TX_BURST_EN_VERBOSE
                         $display("(%t)(%m): %b enabling tx_burst_en",$time,
                                  {MasterWbTX,MasterWbRX,ReadTxDataFromMemory_2,
                                   WriteRxDataToMemory,MasterAccessFinished,
                                   cyc_cleared,tx_burst,rx_burst});
 `endif
                         tx_burst_en<= 1'b1;
                         tx_burst_cnt <= 3'h1;
 
 `ifdef ETH_WISHBONE_B3
                         m_wb_cti_o <= 3'b010;
                         m_wb_bte_o <= 2'b01;
 `endif
                      end
`endif
                 end
               8'b10_10_01_00,// MR and MR is needed (data read from tx buffer)
               8'b01_1?_01_0?  :// MW and MR is needed (data read from tx 
                                  // buffer)
                   begin
                      MasterWbTX <= 1'b1; // Only switch to TX here
                                          // when not end of RX
                      MasterWbRX <= 1'b0;
                      m_wb_adr_o <= TxPointerMSB;
                      m_wb_cyc_o <= 1'b1;
                      m_wb_we_o  <= 1'b0;
                      m_wb_sel_o <= 4'hf;
                      cyc_cleared<= 1'b0;
                      IncrTxPointer<= 1'b1;
`ifdef BURST_4BEAT
                      if ((TxPointerMSB[3:2]==2'b00) & `TX_BURST_EN_CONDITION)
                        begin
 `ifdef TX_BURST_EN_VERBOSE
                           $display("(%t)(%m): %b enabling tx_burst_en",$time,
                                    {MasterWbTX,MasterWbRX,
                                     ReadTxDataFromMemory_2,
                                     WriteRxDataToMemory,
                                     MasterAccessFinished,
                                     cyc_cleared,
                                     tx_burst,
                                     rx_burst});
 `endif
                           tx_burst_en<= 1'b1;
                           tx_burst_cnt <= 3'h1;
 `ifdef ETH_WISHBONE_B3
                           m_wb_cti_o <= 3'b010;
                           m_wb_bte_o <= 2'b01;
 `endif
                        end
`endif
 
                   end
               8'b01_01_01_00,// MW and MW needed (data write to rx buffer)
               8'b10_?1_01_?0 ://MR and MW is needed (data write to rx buffer)
                   begin
                      MasterWbTX <= 1'b0;
                      MasterWbRX <= !RxBufferEmpty;
                      rx_burst_cnt<= 0;
                      m_wb_adr_o <= RxPointerMSB;
                      m_wb_cyc_o <= !RxBufferEmpty;
                      m_wb_we_o  <= !RxBufferEmpty;
                      m_wb_sel_o <= RxByteSel;
`ifdef ETH_WISHBONE_B3
 `ifdef ETH_RX_BURST_EN
  `ifdef BURST_4BEAT
                      if ((RxPointerMSB[3:2]==2'b00) &
                          enough_data_in_rxfifo_for_burst & !RxBufferEmpty)
                          //enough_data_in_rxfifo_for_burst_plus1)
 
 
                        begin
                           rx_burst_en<= 1'b1;
                           m_wb_cti_o <= 3'b010;
                           m_wb_bte_o <= 2'b01;
                           rx_burst_cnt<= 1;
                        end
  `endif
 `endif //  `ifdef ETH_RX_BURST_EN           
`endif //  `ifdef ETH_WISHBONE_B3            
                      cyc_cleared<= 1'b0;
                      IncrTxPointer<= 1'b0;
                   end
               8'b01_01_10_00,// MW and MW needed (cycle is cleared between 
                              // previous and next access)
               8'b01_1?_10_?0,// MW and MW or MR or MRB needed (cycle is 
                              // cleared between previous and next access)
               8'b10_10_10_00,// MR and MR needed (cycle is cleared between 
                              // previous  and next access)
               8'b10_?1_10_0? :// MR and MR or MW or MWB (cycle is cleared 
                               // between previous and next access)
                   begin
                      m_wb_cyc_o <= 1'b0;// whatever and master read or write is
                                         // needed. We need to clear m_wb_cyc_o
                                         //  before next access is started
                      cyc_cleared<= 1'b1;
                      IncrTxPointer<= 1'b0;
                      tx_burst_cnt<= 0;
`ifdef BURST_4BEAT
                      // Caused a bug!
                      // if (TxPointerMSB[3:2]==2'b00)       
                      //tx_burst_en<= `TX_BURST_EN_CONDITION;        
                      // Set this to 0 here
                      tx_burst_en<= 0;
 
`endif
                      rx_burst_cnt<= 0;
`ifdef ETH_WISHBONE_B3
                      m_wb_bte_o <= 2'b00;
                      m_wb_cti_o <= 3'b0;
`endif
                   end
               8'b??_00_10_00,// whatever and no master read or write is needed
                              // (ack or err comes finishing previous access)
                 8'b??_00_01_00 : // Between cyc_cleared request was cleared
                   begin
                      MasterWbTX <= 1'b0;
                      MasterWbRX <= 1'b0;
                      m_wb_cyc_o <= 1'b0;
                      cyc_cleared<= 1'b0;
                      IncrTxPointer<= 1'b0;
                      rx_burst_cnt<= 0;
                      m_wb_bte_o <= 2'b00;
                      m_wb_cti_o <= 3'b0;
                   end
               8'b00_00_00_00:  // whatever and no master read or write is 
                                // needed (ack or err comes finishing previous 
                                // access)
                 begin
                    tx_burst_cnt<= 0;
`ifdef BURST_4BEAT
 
                    // This caused tx_burst to remain set between
                    // transmits, and sometimes we would burst immediately
                    // and maybe get the wrong data because the offset of
                    // the buffer pointer wasn't 16-byte aligned.
                    //if (TxPointerMSB[3:2]==2'b00)
                    //  tx_burst_en<= `TX_BURST_EN_CONDITION;
 
                    // Fix for transmit problems... maybe - jb
                    if(TxEn & TxEn_q & TxPointerRead & (ram_do[3:0]===4'h0))
                      begin
 `ifdef TX_BURST_EN_VERBOSE
                         $display("(%t)(%m): %b enabling tx_burst_en",$time,
                                  {MasterWbTX,MasterWbRX,ReadTxDataFromMemory_2,
                                   WriteRxDataToMemory,MasterAccessFinished,
                                   cyc_cleared,tx_burst,rx_burst});
 `endif
                         tx_burst_en<= `TX_BURST_EN_CONDITION;
                      end
                    else
                      tx_burst_en<= 0;
`endif
                 end
               default:                    // Don't touch
                 begin
                    MasterWbTX <= MasterWbTX;
                    MasterWbRX <= MasterWbRX;
                    m_wb_cyc_o <= m_wb_cyc_o;
                    m_wb_sel_o <= m_wb_sel_o;
                    IncrTxPointer<= IncrTxPointer;
                 end
             endcase
          end
     end
 
   assign TxFifoClear = (TxAbortPacket | TxRetryPacket | StartTxPointerRead);
 
   eth_fifo
     #(
       `ETH_TX_FIFO_DATA_WIDTH,
       `ETH_TX_FIFO_DEPTH,
       `ETH_TX_FIFO_CNT_WIDTH
       )
   tx_fifo
     (
       .data_in(m_wb_dat_i),
       .data_out(TxData_wb),
       .clk(WB_CLK_I),
       .reset(Reset),
       .write(MasterWbTX & m_wb_ack_i),
       .read(ReadTxDataFromFifo_wb & ~TxBufferEmpty),
       .clear(TxFifoClear),
       .full(TxBufferFull),
       .almost_full(TxBufferAlmostFull),
       .almost_empty(TxBufferAlmostEmpty),
       .empty(TxBufferEmpty),
       .cnt(txfifo_cnt)
       );
 
   // Start: Generation of the TxStartFrm_wb which is then synchronized to the 
   // MTxClk
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          TxStartFrm_wb <= 1'b0;
        else
          if(TxBDReady & ~StartOccured & (TxBufferFull | TxLengthEq0))
            TxStartFrm_wb <= 1'b1;
          else
            if(TxStartFrm_syncb2)
              TxStartFrm_wb <= 1'b0;
     end
 
   // StartOccured: TxStartFrm_wb occurs only ones at the beginning. Then it's 
   // blocked.
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          StartOccured <= 1'b0;
        else
          if(TxStartFrm_wb)
            StartOccured <= 1'b1;
          else
            if(ResetTxBDReady)
              StartOccured <= 1'b0;
     end
 
   // Synchronizing TxStartFrm_wb to MTxClk
   always @ (posedge MTxClk or posedge Reset)
     begin
        if(Reset)
          TxStartFrm_sync1 <= 1'b0;
        else
          TxStartFrm_sync1 <= TxStartFrm_wb;
     end
 
   always @ (posedge MTxClk or posedge Reset)
     begin
        if(Reset)
          TxStartFrm_sync2 <= 1'b0;
        else
          TxStartFrm_sync2 <= TxStartFrm_sync1;
     end
 
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          TxStartFrm_syncb1 <= 1'b0;
        else
          TxStartFrm_syncb1 <= TxStartFrm_sync2;
     end
 
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          TxStartFrm_syncb2 <= 1'b0;
        else
          TxStartFrm_syncb2 <= TxStartFrm_syncb1;
     end
 
   always @ (posedge MTxClk or posedge Reset)
     begin
        if(Reset)
          TxStartFrm <= 1'b0;
        else
          if(TxStartFrm_sync2)
            TxStartFrm <= 1'b1;
          else
            if(TxUsedData_q | ~TxStartFrm_sync2 &
               (TxRetry & (~TxRetry_q) | TxAbort & (~TxAbort_q)))
              TxStartFrm <= 1'b0;
     end
   // End: Generation of the TxStartFrm_wb which is then synchronized to the 
   // MTxClk
 
 
   // TxEndFrm_wb: indicator of the end of frame
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          TxEndFrm_wb <= 1'b0;
        else
          if(TxLengthEq0 & TxBufferAlmostEmpty & TxUsedData)
            TxEndFrm_wb <= 1'b1;
          else
            if(TxRetryPulse | TxDonePulse | TxAbortPulse)
              TxEndFrm_wb <= 1'b0;
     end
 
 
   // Marks which bytes are valid within the word.
   assign TxValidBytes = TxLengthLt4 ? TxLength[1:0] : 2'b0;
 
   reg LatchValidBytes;
   reg LatchValidBytes_q;
 
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          LatchValidBytes <= 1'b0;
        else
          if(TxLengthLt4 & TxBDReady)
            LatchValidBytes <= 1'b1;
          else
            LatchValidBytes <= 1'b0;
     end
 
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          LatchValidBytes_q <= 1'b0;
        else
          LatchValidBytes_q <= LatchValidBytes;
     end
 
 
   // Latching valid bytes
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          TxValidBytesLatched <= 2'h0;
        else
          if(LatchValidBytes & ~LatchValidBytes_q)
            TxValidBytesLatched <= TxValidBytes;
          else
            if(TxRetryPulse | TxDonePulse | TxAbortPulse)
              TxValidBytesLatched <= 2'h0;
     end
 
 
   assign TxIRQEn          = TxStatus[14];
   assign WrapTxStatusBit  = TxStatus[13];
   assign PerPacketPad     = TxStatus[12];
   assign PerPacketCrcEn   = TxStatus[11];
 
 
   assign RxIRQEn         = RxStatus[14];
   assign WrapRxStatusBit = RxStatus[13];
 
 
   // Temporary Tx and Rx buffer descriptor address
   assign TempTxBDAddress[7:1] = {7{ TxStatusWrite     & ~WrapTxStatusBit}}   & (TxBDAddress + 1) ; // Tx BD increment or wrap (last BD)
 
   assign TempRxBDAddress[7:1] = {7{ WrapRxStatusBit}} & (r_TxBDNum[6:0])     | // Using first Rx BD
                                 {7{~WrapRxStatusBit}} & (RxBDAddress + 1) ; // Using next Rx BD (incremenrement address)
 
 
   // Latching Tx buffer descriptor address
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          TxBDAddress <= 7'h0;
        else if (r_TxEn & (~r_TxEn_q))
          TxBDAddress <= 7'h0;
        else if (TxStatusWrite)
          TxBDAddress <= TempTxBDAddress;
     end
 
 
   // Latching Rx buffer descriptor address
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          RxBDAddress <= 7'h0;
        else if(r_RxEn & (~r_RxEn_q))
          RxBDAddress <= r_TxBDNum[6:0];
        else if(RxStatusWrite)
          RxBDAddress <= TempRxBDAddress;
     end
 
   wire [8:0] TxStatusInLatched = {TxUnderRun, RetryCntLatched[3:0],
                                   RetryLimit, LateCollLatched, DeferLatched,
                                   CarrierSenseLost};
 
   assign RxBDDataIn = {LatchedRxLength, 1'b0, RxStatus, 4'h0,
                        RxStatusInLatched};
   assign TxBDDataIn = {LatchedTxLength, 1'b0, TxStatus, 2'h0,
                        TxStatusInLatched};
 
 
   // Signals used for various purposes
   assign TxRetryPulse   = TxRetry_wb   & ~TxRetry_wb_q;
   assign TxDonePulse    = TxDone_wb    & ~TxDone_wb_q;
   assign TxAbortPulse   = TxAbort_wb   & ~TxAbort_wb_q;
 
 
 
   // Generating delayed signals
   always @ (posedge MTxClk or posedge Reset)
     begin
        if(Reset)
          begin
             TxAbort_q      <= 1'b0;
             TxRetry_q      <= 1'b0;
             TxUsedData_q   <= 1'b0;
          end
        else
          begin
             TxAbort_q      <= TxAbort;
             TxRetry_q      <= TxRetry;
             TxUsedData_q   <= TxUsedData;
          end
     end
 
   // Generating delayed signals
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          begin
             TxDone_wb_q   <= 1'b0;
             TxAbort_wb_q  <= 1'b0;
             TxRetry_wb_q  <= 1'b0;
          end
        else
          begin
             TxDone_wb_q   <= TxDone_wb;
             TxAbort_wb_q  <= TxAbort_wb;
             TxRetry_wb_q  <= TxRetry_wb;
          end
     end
 
 
   reg TxAbortPacketBlocked;
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          TxAbortPacket <= 1'b0;
        else
          if(TxAbort_wb & (~tx_burst_en) & MasterWbTX & MasterAccessFinished &
             (~TxAbortPacketBlocked) | TxAbort_wb & (~MasterWbTX) &
             (~TxAbortPacketBlocked))
            TxAbortPacket <= 1'b1;
          else
            TxAbortPacket <= 1'b0;
     end
 
 
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          TxAbortPacket_NotCleared <= 1'b0;
        else
          if(TxEn & TxEn_q & TxAbortPacket_NotCleared)
            TxAbortPacket_NotCleared <= 1'b0;
          else
            if(TxAbort_wb & (~tx_burst_en) & MasterWbTX &
               MasterAccessFinished & (~TxAbortPacketBlocked) | TxAbort_wb &
               (~MasterWbTX) & (~TxAbortPacketBlocked))
              TxAbortPacket_NotCleared <= 1'b1;
     end
 
 
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          TxAbortPacketBlocked <= 1'b0;
        else
          if(!TxAbort_wb & TxAbort_wb_q)
            TxAbortPacketBlocked <= 1'b0;
          else
            if(TxAbortPacket)
              TxAbortPacketBlocked <= 1'b1;
     end
 
 
   reg TxRetryPacketBlocked;
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          TxRetryPacket <= 1'b0;
        else
          if(TxRetry_wb & !tx_burst_en & MasterWbTX & MasterAccessFinished &
             !TxRetryPacketBlocked | TxRetry_wb & !MasterWbTX &
             !TxRetryPacketBlocked)
            TxRetryPacket <= 1'b1;
          else
            TxRetryPacket <= 1'b0;
     end
 
 
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          TxRetryPacket_NotCleared <= 1'b0;
        else
          if(StartTxBDRead)
            TxRetryPacket_NotCleared <= 1'b0;
          else
            if(TxRetry_wb & !tx_burst_en & MasterWbTX & MasterAccessFinished &
               !TxRetryPacketBlocked | TxRetry_wb & !MasterWbTX &
               !TxRetryPacketBlocked)
              TxRetryPacket_NotCleared <= 1'b1;
     end
 
 
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          TxRetryPacketBlocked <= 1'b0;
        else
          if(!TxRetry_wb & TxRetry_wb_q)
            TxRetryPacketBlocked <= 1'b0;
          else
            if(TxRetryPacket)
              TxRetryPacketBlocked <= 1'b1;
     end
 
 
   reg TxDonePacketBlocked;
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          TxDonePacket <= 1'b0;
        else
          if(TxDone_wb & !tx_burst_en & MasterWbTX & MasterAccessFinished &
             !TxDonePacketBlocked | TxDone_wb & !MasterWbTX &
             !TxDonePacketBlocked)
            TxDonePacket <= 1'b1;
          else
            TxDonePacket <= 1'b0;
     end
 
 
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          TxDonePacket_NotCleared <= 1'b0;
        else
          if(TxEn & TxEn_q & TxDonePacket_NotCleared)
            TxDonePacket_NotCleared <= 1'b0;
          else
            if(TxDone_wb & !tx_burst_en & MasterWbTX & MasterAccessFinished
               & (~TxDonePacketBlocked) | TxDone_wb & !MasterWbTX
               & (~TxDonePacketBlocked))
              TxDonePacket_NotCleared <= 1'b1;
     end
 
 
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          TxDonePacketBlocked <= 1'b0;
        else
          if(!TxDone_wb & TxDone_wb_q)
            TxDonePacketBlocked <= 1'b0;
          else
            if(TxDonePacket)
              TxDonePacketBlocked <= 1'b1;
     end
 
 
   // Indication of the last word
   always @ (posedge MTxClk or posedge Reset)
     begin
        if(Reset)
          LastWord <= 1'b0;
        else
          if((TxEndFrm | TxAbort | TxRetry) & Flop)
            LastWord <= 1'b0;
          else
            if(TxUsedData & Flop & TxByteCnt == 2'h3)
              LastWord <= TxEndFrm_wb;
     end
 
 
   // Tx end frame generation
   always @ (posedge MTxClk or posedge Reset)
     begin
        if(Reset)
          TxEndFrm <= 1'b0;
        else
          if(Flop & TxEndFrm | TxAbort | TxRetry_q)
            TxEndFrm <= 1'b0;
          else
            if(Flop & LastWord)
              begin
                 case (TxValidBytesLatched)  // synopsys parallel_case
                   1 : TxEndFrm <= TxByteCnt == 2'h0;
                   2 : TxEndFrm <= TxByteCnt == 2'h1;
                   3 : TxEndFrm <= TxByteCnt == 2'h2;
 
                   default : TxEndFrm <= 1'b0;
                 endcase
              end
     end
 
 
   // Tx data selection (latching)
   always @ (posedge MTxClk or posedge Reset)
     begin
        if(Reset)
          TxData <= 0;
        else
          if(TxStartFrm_sync2 & ~TxStartFrm)
            case(TxPointerLSB)  // synopsys parallel_case
              2'h0 : TxData <= TxData_wb[31:24];// Big Endian Byte Ordering
              2'h1 : TxData <= TxData_wb[23:16];// Big Endian Byte Ordering
              2'h2 : TxData <= TxData_wb[15:08];// Big Endian Byte Ordering
              2'h3 : TxData <= TxData_wb[07:00];// Big Endian Byte Ordering
            endcase
          else
            if(TxStartFrm & TxUsedData & TxPointerLSB==2'h3)
              TxData <= TxData_wb[31:24];// Big Endian Byte Ordering
            else
              if(TxUsedData & Flop)
                begin
                   case(TxByteCnt)  // synopsys parallel_case
                     // Big Endian Byte Ordering
 
                     1 : TxData <= TxDataLatched[23:16];
                     2 : TxData <= TxDataLatched[15:8];
                     3 : TxData <= TxDataLatched[7:0];
                   endcase
                end
     end
 
 
   // Latching tx data
   always @ (posedge MTxClk or posedge Reset)
     begin
        if(Reset)
          TxDataLatched[31:0] <= 32'h0;
        else
          if(TxStartFrm_sync2 & ~TxStartFrm | TxUsedData & Flop &
             TxByteCnt == 2'h3 | TxStartFrm & TxUsedData & Flop &
             TxByteCnt == 2'h0)
            TxDataLatched[31:0] <= TxData_wb[31:0];
     end
 
 
   // Tx under run
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          TxUnderRun_wb <= 1'b0;
        else
          if(TxAbortPulse)
            TxUnderRun_wb <= 1'b0;
          else
            if(TxBufferEmpty & ReadTxDataFromFifo_wb)
              TxUnderRun_wb <= 1'b1;
     end
 
 
   reg TxUnderRun_sync1;
 
   // Tx under run
   always @ (posedge MTxClk or posedge Reset)
     begin
        if(Reset)
          TxUnderRun_sync1 <= 1'b0;
        else
          if(TxUnderRun_wb)
            TxUnderRun_sync1 <= 1'b1;
          else
            if(BlockingTxStatusWrite_sync2)
              TxUnderRun_sync1 <= 1'b0;
     end
 
   // Tx under run
   always @ (posedge MTxClk or posedge Reset)
     begin
        if(Reset)
          TxUnderRun <= 1'b0;
        else
          if(BlockingTxStatusWrite_sync2)
            TxUnderRun <= 1'b0;
          else
            if(TxUnderRun_sync1)
              TxUnderRun <= 1'b1;
     end
 
 
   // Tx Byte counter
   always @ (posedge MTxClk or posedge Reset)
     begin
        if(Reset)
          TxByteCnt <= 2'h0;
        else
          if(TxAbort_q | TxRetry_q)
            TxByteCnt <= 2'h0;
          else
            if(TxStartFrm & ~TxUsedData)
              case(TxPointerLSB)  // synopsys parallel_case
                2'h0 : TxByteCnt <= 2'h1;
                2'h1 : TxByteCnt <= 2'h2;
                2'h2 : TxByteCnt <= 2'h3;
                2'h3 : TxByteCnt <= 2'h0;
              endcase
            else
              if(TxUsedData & Flop)
                TxByteCnt <= TxByteCnt + 1'b1;
     end
 
 
   // Start: Generation of the ReadTxDataFromFifo_tck signal and synchronization to the WB_CLK_I
   reg ReadTxDataFromFifo_sync1;
   reg ReadTxDataFromFifo_sync2;
   reg ReadTxDataFromFifo_sync3;
   reg ReadTxDataFromFifo_syncb1;
   reg ReadTxDataFromFifo_syncb2;
   reg ReadTxDataFromFifo_syncb3;
 
 
   always @ (posedge MTxClk or posedge Reset)
     begin
        if(Reset)
          ReadTxDataFromFifo_tck <= 1'b0;
        else
          if(TxStartFrm_sync2 & ~TxStartFrm | TxUsedData & Flop &
             TxByteCnt == 2'h3 & ~LastWord | TxStartFrm & TxUsedData & Flop &
             TxByteCnt == 2'h0)
            ReadTxDataFromFifo_tck <= 1'b1;
          else
            if(ReadTxDataFromFifo_syncb2 & ~ReadTxDataFromFifo_syncb3)
              ReadTxDataFromFifo_tck <= 1'b0;
     end
 
   // Synchronizing TxStartFrm_wb to MTxClk
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          ReadTxDataFromFifo_sync1 <= 1'b0;
        else
          ReadTxDataFromFifo_sync1 <= ReadTxDataFromFifo_tck;
     end
 
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          ReadTxDataFromFifo_sync2 <= 1'b0;
        else
          ReadTxDataFromFifo_sync2 <= ReadTxDataFromFifo_sync1;
     end
 
   always @ (posedge MTxClk or posedge Reset)
     begin
        if(Reset)
          ReadTxDataFromFifo_syncb1 <= 1'b0;
        else
          ReadTxDataFromFifo_syncb1 <= ReadTxDataFromFifo_sync2;
     end
 
   always @ (posedge MTxClk or posedge Reset)
     begin
        if(Reset)
          ReadTxDataFromFifo_syncb2 <= 1'b0;
        else
          ReadTxDataFromFifo_syncb2 <= ReadTxDataFromFifo_syncb1;
     end
 
   always @ (posedge MTxClk or posedge Reset)
     begin
        if(Reset)
          ReadTxDataFromFifo_syncb3 <= 1'b0;
        else
          ReadTxDataFromFifo_syncb3 <= ReadTxDataFromFifo_syncb2;
     end
 
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          ReadTxDataFromFifo_sync3 <= 1'b0;
        else
          ReadTxDataFromFifo_sync3 <= ReadTxDataFromFifo_sync2;
     end
 
   assign ReadTxDataFromFifo_wb = ReadTxDataFromFifo_sync2 &
                                  ~ReadTxDataFromFifo_sync3;
   // End: Generation of the ReadTxDataFromFifo_tck signal and synchronization 
   // to the WB_CLK_I
 
 
   // Synchronizing TxRetry signal (synchronized to WISHBONE clock)
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          TxRetrySync1 <= 1'b0;
        else
          TxRetrySync1 <= TxRetry;
     end
 
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          TxRetry_wb <= 1'b0;
        else
          TxRetry_wb <= TxRetrySync1;
     end
 
 
   // Synchronized TxDone_wb signal (synchronized to WISHBONE clock)
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          TxDoneSync1 <= 1'b0;
        else
          TxDoneSync1 <= TxDone;
     end
 
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          TxDone_wb <= 1'b0;
        else
          TxDone_wb <= TxDoneSync1;
     end
 
   // Synchronizing TxAbort signal (synchronized to WISHBONE clock)
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          TxAbortSync1 <= 1'b0;
        else
          TxAbortSync1 <= TxAbort;
     end
 
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          TxAbort_wb <= 1'b0;
        else
          TxAbort_wb <= TxAbortSync1;
     end
 
 
   reg RxAbortSync1;
   reg RxAbortSync2;
   reg RxAbortSync3;
   reg RxAbortSync4;
   reg RxAbortSyncb1;
   reg RxAbortSyncb2;
 
   assign StartRxBDRead = RxStatusWrite | RxAbortSync3 & ~RxAbortSync4 |
                          r_RxEn & ~r_RxEn_q;
 
   // Reading the Rx buffer descriptor
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          RxBDRead <= 1'b0;
        else
          if(StartRxBDRead)
            RxBDRead <= 1'b1;
          else
            if(RxBDReady)
              RxBDRead <= 1'b0;
     end
 
 
   // Reading of the next receive buffer descriptor starts after reception 
   // status is written to the previous one.
 
   // Latching READY status of the Rx buffer descriptor
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          RxBDReady <= 1'b0;
        else
          if(RxPointerRead)
            RxBDReady <= 1'b0;
          else
            if(RxEn & RxEn_q & RxBDRead)
              // RxBDReady is sampled only once at the beginning
              RxBDReady <= ram_do[15];
     end // always @ (posedge WB_CLK_I or posedge Reset)
 
   // Indicate we just read the RX buffer descriptor and that RxBDReady is 
   // valid.
   reg rx_just_read_bd;
   always @ (posedge WB_CLK_I or posedge Reset)
     if(Reset)
       rx_just_read_bd <= 0;
     else if (rx_just_read_bd)
       rx_just_read_bd <= 0;
     else
       rx_just_read_bd <= (RxEn & RxEn_q & RxBDRead);
 
   // Signal to indicate we've checked and the RxBD we want to use is not free
   reg rx_waiting_for_bd_to_become_free/*syn_allow_retiming=0; syn_keep=1; syn_preserve=1*/;
   always @ (posedge WB_CLK_I or posedge Reset)
     if(Reset)
       rx_waiting_for_bd_to_become_free <= 0;
     else if (rx_just_read_bd & !RxBDReady)
       // Assert if we read the BD and it's not cool
       rx_waiting_for_bd_to_become_free <= 1;
     else if (RxBDOK)
       rx_waiting_for_bd_to_become_free <= 0;
 
 
 
   // Latching Rx buffer descriptor status
   // Data is avaliable one cycle after the access is started (at that time 
   // signal RxEn is not active)
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          RxStatus <= 2'h0;
        else
          if(RxEn & RxEn_q & RxBDRead)
            RxStatus <= ram_do[14:13];
     end
 
 
   // RxBDOK generation
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          RxBDOK <= 1'b0;
        else
          if(rx_wb_writeback_finished | RxAbortSync2 & ~RxAbortSync3 |
             ~r_RxEn & r_RxEn_q)
            RxBDOK <= 1'b0;
          else
            if(RxBDReady)
              RxBDOK <= 1'b1;
     end
 
   // Reading Rx BD pointer
   assign StartRxPointerRead = RxBDRead & RxBDReady;
 
   // Reading Tx BD Pointer
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          RxPointerRead <= 1'b0;
        else
          if(StartRxPointerRead)
            RxPointerRead <= 1'b1;
          else
            if(RxEn & RxEn_q)
              RxPointerRead <= 1'b0;
     end
 
 
   //Latching Rx buffer pointer from buffer descriptor;
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          RxPointerMSB <= 30'h0;
        else
          if(RxEn & RxEn_q & RxPointerRead)
            RxPointerMSB <= ram_do[31:2];
          else
            if(MasterWbRX & m_wb_ack_i)
              // Word access  (always word access. m_wb_sel_o are used for 
              // selecting bytes)
              RxPointerMSB <= RxPointerMSB + 1;
     end
 
 
   //Latching last addresses from buffer descriptor (used as byte-half-word 
   // indicator);
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          RxPointerLSB_rst[1:0] <= 0;
        else
          if(MasterWbRX & m_wb_ack_i)
            // After first write all RxByteSel are active
            RxPointerLSB_rst[1:0] <= 0;
          else
            if(RxEn & RxEn_q & RxPointerRead)
              RxPointerLSB_rst[1:0] <= ram_do[1:0];
     end
 
 
   always @ (RxPointerLSB_rst)
     begin
        case(RxPointerLSB_rst[1:0])  // synopsys parallel_case
          2'h0 : RxByteSel[3:0] = 4'hf;
          2'h1 : RxByteSel[3:0] = 4'h7;
          2'h2 : RxByteSel[3:0] = 4'h3;
          2'h3 : RxByteSel[3:0] = 4'h1;
        endcase
     end
 
 
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          RxEn_needed <= 1'b0;
        else
          if(/*~RxReady &*/ r_RxEn & WbEn & ~WbEn_q)
            RxEn_needed <= 1'b1;
          else
            if(RxPointerRead & RxEn & RxEn_q)
              RxEn_needed <= 1'b0;
     end
 
 
   // Reception status is written back to the buffer descriptor after the end 
   // of frame is detected.
   assign RxStatusWrite = rx_wb_writeback_finished & RxEn & RxEn_q;
 
   reg RxEnableWindow;
 
   // Indicating that last byte is being reveived
   always @ (posedge MRxClk or posedge Reset)
     begin
        if(Reset)
          LastByteIn <= 1'b0;
        else
          if(ShiftWillEnd & (&RxByteCnt) | RxAbort)
            LastByteIn <= 1'b0;
          else
            if(RxValid /*& RxReady*/& RxEndFrm & ~(&RxByteCnt) & RxEnableWindow)
              LastByteIn <= 1'b1;
     end
 
   assign StartShiftWillEnd = LastByteIn  | RxValid & RxEndFrm & (&RxByteCnt) &
                              RxEnableWindow;
 
   // Indicating that data reception will end
   always @ (posedge MRxClk or posedge Reset)
     begin
        if(Reset)
          ShiftWillEnd <= 1'b0;
        else
          if(ShiftEnded_rck | RxAbort)
            ShiftWillEnd <= 1'b0;
          else
            if(StartShiftWillEnd)
              ShiftWillEnd <= 1'b1;
     end
 
   // Receive byte counter
   always @ (posedge MRxClk or posedge Reset)
     begin
        if(Reset)
          RxByteCnt <= 2'h0;
        else
          if(ShiftEnded_rck | RxAbort)
            RxByteCnt <= 2'h0;
          else
            if(RxValid & RxStartFrm /*& RxReady*/)
              case(RxPointerLSB_rst)  // synopsys parallel_case
                2'h0 : RxByteCnt <= 2'h1;
                2'h1 : RxByteCnt <= 2'h2;
                2'h2 : RxByteCnt <= 2'h3;
                2'h3 : RxByteCnt <= 2'h0;
              endcase
            else
              if(RxValid & RxEnableWindow /*& RxReady*/ | LastByteIn)
                RxByteCnt <= RxByteCnt + 1;
     end
 
 
   // Indicates how many bytes are valid within the last word
   always @ (posedge MRxClk or posedge Reset)
     begin
        if(Reset)
          RxValidBytes <= 2'h1;
        else
          if(RxValid & RxStartFrm)
            case(RxPointerLSB_rst)  // synopsys parallel_case
              2'h0 : RxValidBytes <= 2'h1;
              2'h1 : RxValidBytes <= 2'h2;
              2'h2 : RxValidBytes <= 2'h3;
              2'h3 : RxValidBytes <= 2'h0;
            endcase
          else
            if(RxValid & ~LastByteIn & ~RxStartFrm & RxEnableWindow)
              RxValidBytes <= RxValidBytes + 1;
     end
 
 
   always @ (posedge MRxClk or posedge Reset)
     begin
        if(Reset)
          RxDataLatched1       <= 24'h0;
        else
          if(RxValid /*& RxReady*/ & ~LastByteIn)
            if(RxStartFrm)
              begin
                 case(RxPointerLSB_rst)     // synopsys parallel_case
                   // Big Endian Byte Ordering
                   2'h0:        RxDataLatched1[31:24] <= RxData;
                   2'h1:        RxDataLatched1[23:16] <= RxData;
                   2'h2:        RxDataLatched1[15:8]  <= RxData;
                   2'h3:        RxDataLatched1        <= RxDataLatched1;
                 endcase
              end
            else if (RxEnableWindow)
              begin
                 case(RxByteCnt)     // synopsys parallel_case
                   // Big Endian Byte Ordering
                   2'h0:        RxDataLatched1[31:24] <= RxData;
                   2'h1:        RxDataLatched1[23:16] <= RxData;
                   2'h2:        RxDataLatched1[15:8]  <= RxData;
                   2'h3:        RxDataLatched1        <= RxDataLatched1;
                 endcase
              end
     end
 
   wire SetWriteRxDataToFifo;
 
   // Assembling data that will be written to the rx_fifo
   always @ (posedge MRxClk or posedge Reset)
     begin
        if(Reset)
          RxDataLatched2 <= 32'h0;
        else
          if(SetWriteRxDataToFifo & ~ShiftWillEnd)
            // Big Endian Byte Ordering
            RxDataLatched2 <= {RxDataLatched1[31:8], RxData};
          else
            if(SetWriteRxDataToFifo & ShiftWillEnd)
              case(RxValidBytes)  // synopsys parallel_case
                // Big Endian Byte Ordering
 
                1 : RxDataLatched2 <= {RxDataLatched1[31:24], 24'h0};
                2 : RxDataLatched2 <= {RxDataLatched1[31:16], 16'h0};
                3 : RxDataLatched2 <= {RxDataLatched1[31:8],   8'h0};
              endcase
     end
 
 
   reg WriteRxDataToFifoSync1;
   reg WriteRxDataToFifoSync2;
   reg WriteRxDataToFifoSync3;
 
 
   // Indicating start of the reception process
   assign SetWriteRxDataToFifo = (RxValid & ~RxStartFrm &
                                  RxEnableWindow & (&RxByteCnt))
                                 /*| (RxValid & RxStartFrm &
                                  (&RxPointerLSB_rst)) */
                                 |(ShiftWillEnd & LastByteIn & (&RxByteCnt));
 
   always @ (posedge MRxClk or posedge Reset)
     begin
        if(Reset)
          WriteRxDataToFifo <= 1'b0;
        else
          if(SetWriteRxDataToFifo & ~RxAbort)
            WriteRxDataToFifo <= 1'b1;
          else
            if(WriteRxDataToFifoSync2 | RxAbort)
              WriteRxDataToFifo <= 1'b0;
     end
 
 
 
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          WriteRxDataToFifoSync1 <= 1'b0;
        else
          if(WriteRxDataToFifo)
            WriteRxDataToFifoSync1 <= 1'b1;
          else
            WriteRxDataToFifoSync1 <= 1'b0;
     end
 
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          WriteRxDataToFifoSync2 <= 1'b0;
        else
          WriteRxDataToFifoSync2 <= WriteRxDataToFifoSync1;
     end
 
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          WriteRxDataToFifoSync3 <= 1'b0;
        else
          WriteRxDataToFifoSync3 <= WriteRxDataToFifoSync2;
     end
 
   wire WriteRxDataToFifo_wb;
   assign WriteRxDataToFifo_wb = WriteRxDataToFifoSync2 &
                                 ~WriteRxDataToFifoSync3;
   // Receive fifo selection register - JB
   reg [3:0] rx_shift_ended_wb_shr;
   reg       rx_ethside_fifo_sel /* synthesis syn_allow_retiming=0; syn_noprune=1; syn_keep=1 */;
   reg       rx_wbside_fifo_sel /* synthesis syn_allow_retiming=0; syn_noprune=1; syn_keep=1 */;
 
   // Shift in this - our detection of end of data RX
   always @(posedge WB_CLK_I)
     rx_shift_ended_wb_shr <= {rx_shift_ended_wb_shr[2:0],
                               ShiftEndedSync1 & ~ShiftEndedSync2};
 
 
   always @ (posedge WB_CLK_I or posedge Reset)
     if(Reset)
       rx_ethside_fifo_sel <= 0;
     else
       if(rx_shift_ended_wb_shr[3:2] == 2'b01)
         // Switch over whenever we've finished receiving last frame's data
         rx_ethside_fifo_sel <= ~rx_ethside_fifo_sel;
 
   // Wishbone side looks at other FIFO when we write back the status of this 
   // received frame
   always @ (posedge WB_CLK_I or posedge Reset)
     if(Reset)
       rx_wbside_fifo_sel <= 0;
     else
       if(rx_wb_writeback_finished & RxEn & RxEn_q)
         // Switch over whenever we've finished receiving last frame's data
         rx_wbside_fifo_sel <= ~rx_wbside_fifo_sel;
 
   reg  LatchedRxStartFrm;
   reg  SyncRxStartFrm;
   reg  SyncRxStartFrm_q;
   reg  SyncRxStartFrm_q2;
   wire RxFifoReset;
 
   always @ (posedge MRxClk or posedge Reset)
     begin
        if(Reset)
          LatchedRxStartFrm <= 0;
        else
          if(RxStartFrm & ~SyncRxStartFrm_q)
            LatchedRxStartFrm <= 1;
          else
            if(SyncRxStartFrm_q)
              LatchedRxStartFrm <= 0;
     end
 
 
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          SyncRxStartFrm <= 0;
        else
          if(LatchedRxStartFrm)
            SyncRxStartFrm <= 1;
          else
            SyncRxStartFrm <= 0;
     end
 
 
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          SyncRxStartFrm_q <= 0;
        else
          SyncRxStartFrm_q <= SyncRxStartFrm;
     end
 
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          SyncRxStartFrm_q2 <= 0;
        else
          SyncRxStartFrm_q2 <= SyncRxStartFrm_q;
     end
   wire rx_startfrm_wb;
   assign rx_startfrm_wb = SyncRxStartFrm_q & ~SyncRxStartFrm_q2;
 
 
   assign RxFifoReset = rx_startfrm_wb;
 
 
   wire [31:0] rx_fifo0_data_out;
   wire        rx_fifo0_write;
   wire        rx_fifo0_read;
   wire        rx_fifo0_clear;
   wire        rx_fifo0_full;
   wire        rx_fifo0_afull;
   wire        rx_fifo0_empty;
   wire        rx_fifo0_aempty;
 
 
   wire [31:0] rx_fifo1_data_out;
   wire        rx_fifo1_write;
   wire        rx_fifo1_read;
   wire        rx_fifo1_clear;
   wire        rx_fifo1_full;
   wire        rx_fifo1_afull;
   wire        rx_fifo1_empty;
   wire        rx_fifo1_aempty;
 
   wire [`ETH_RX_FIFO_CNT_WIDTH-1:0] rx_fifo0_cnt;
   wire [`ETH_RX_FIFO_CNT_WIDTH-1:0] rx_fifo1_cnt;
 
   // RX FIFO buffer 0 controls
   assign rx_fifo0_write = (!rx_ethside_fifo_sel) & WriteRxDataToFifo_wb &
                           ~rx_fifo0_full;
 
   assign rx_fifo0_read = (!rx_wbside_fifo_sel) & MasterWbRX & m_wb_ack_i &
                          ~rx_fifo0_empty;
 
   assign rx_fifo0_clear = (!rx_ethside_fifo_sel) & RxFifoReset;
 
   // RX FIFO buffer 1 controls
   assign rx_fifo1_write = (rx_ethside_fifo_sel) & WriteRxDataToFifo_wb &
                           ~rx_fifo1_full;
 
   assign rx_fifo1_read = (rx_wbside_fifo_sel) & MasterWbRX & m_wb_ack_i &
                           ~rx_fifo1_empty;
 
   assign rx_fifo1_clear = (rx_ethside_fifo_sel) & RxFifoReset;
 
   eth_fifo #(
              `ETH_RX_FIFO_DATA_WIDTH,
              `ETH_RX_FIFO_DEPTH,
              `ETH_RX_FIFO_CNT_WIDTH
              )
   rx_fifo0 (
             .clk            (WB_CLK_I         ),
             .reset          (Reset            ),
             // Inputs
             .data_in        (RxDataLatched2   ),
             .write          (rx_fifo0_write   ),
             .read           (rx_fifo0_read    ),
             .clear          (rx_fifo0_clear   ),
             // Outputs
             .data_out       (rx_fifo0_data_out),
             .full           (rx_fifo0_full    ),
             .almost_full    (),
             .almost_empty   (rx_fifo0_aempty  ),
             .empty          (rx_fifo0_empty   ),
             .cnt            (rx_fifo0_cnt     )
             );
 
   eth_fifo #(
              `ETH_RX_FIFO_DATA_WIDTH,
              `ETH_RX_FIFO_DEPTH,
              `ETH_RX_FIFO_CNT_WIDTH
              )
   rx_fifo1 (
             .clk            (WB_CLK_I         ),
             .reset          (Reset            ),
             // Inputs
             .data_in        (RxDataLatched2   ),
             .write          (rx_fifo1_write   ),
             .read           (rx_fifo1_read    ),
             .clear          (rx_fifo1_clear   ),
             // Outputs
             .data_out       (rx_fifo1_data_out),
             .full           (rx_fifo1_full    ),
             .almost_full    (),
             .almost_empty   (rx_fifo1_aempty  ),
             .empty          (rx_fifo1_empty   ),
             .cnt            (rx_fifo1_cnt     )
             );
 
   assign m_wb_dat_o = rx_wbside_fifo_sel ?
                       rx_fifo1_data_out : rx_fifo0_data_out;
   assign rxfifo_cnt = rx_wbside_fifo_sel ?
                       rx_fifo1_cnt : rx_fifo0_cnt;
 
   assign RxBufferAlmostEmpty = rx_wbside_fifo_sel ?
                                rx_fifo1_aempty : rx_fifo0_aempty;
 
   assign RxBufferEmpty = rx_wbside_fifo_sel ?
                          rx_fifo1_empty : rx_fifo0_empty;
 
   assign RxBufferFull = rx_wbside_fifo_sel ?
                         rx_fifo1_full : rx_fifo0_full;
 
 
 
 
 
   wire                              write_rx_data_to_memory_wait;
   assign write_rx_data_to_memory_wait = !RxBDOK | RxPointerRead;
   wire                              write_rx_data_to_memory_go;
 
`ifdef ETH_RX_BURST_EN
   assign enough_data_in_rxfifo_for_burst = rxfifo_cnt>=(`ETH_BURST_LENGTH);
   assign enough_data_in_rxfifo_for_burst_plus1 = rxfifo_cnt>(`ETH_BURST_LENGTH - 1);
   // While receiving, don't flog the bus too hard, only write out when
   // we can burst. But when finishing keep going until we've emptied the fifo
   assign write_rx_data_to_memory_go
     = RxEnableWindow & (rx_wbside_fifo_sel == rx_ethside_fifo_sel) ?
       (rxfifo_cnt>(`ETH_BURST_LENGTH) + 2) | (|rx_burst_cnt) : ~RxBufferEmpty;
 
`else
   assign enough_data_in_rxfifo_for_burst = rxfifo_cnt>=`ETH_BURST_LENGTH;
   assign enough_data_in_rxfifo_for_burst_plus1 = rxfifo_cnt>`ETH_BURST_LENGTH;
   assign write_rx_data_to_memory_go = ~RxBufferEmpty;
`endif // !`ifdef ETH_RX_BURST_EN
 
   assign WriteRxDataToMemory = write_rx_data_to_memory_go &
                                !write_rx_data_to_memory_wait;
 
   assign rx_burst = rx_burst_en & WriteRxDataToMemory;
 
 
   // Generation of the end-of-frame signal
   always @ (posedge MRxClk or posedge Reset)
     begin
        if(Reset)
          ShiftEnded_rck <= 1'b0;
        else
          if(~RxAbort & SetWriteRxDataToFifo & StartShiftWillEnd)
            ShiftEnded_rck <= 1'b1;
          else
            if(RxAbort | ShiftEndedSync_c1 & ShiftEndedSync_c2)
              ShiftEnded_rck <= 1'b0;
     end
 
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          ShiftEndedSync1 <= 1'b0;
        else
          ShiftEndedSync1 <= ShiftEnded_rck;
     end
 
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          ShiftEndedSync2 <= 1'b0;
        else
          ShiftEndedSync2 <= ShiftEndedSync1;
     end
 
   // indicate end of wishbone RX is coming up
   always @ (posedge WB_CLK_I or posedge Reset)
     if(Reset)
       rx_wb_last_writes <= 1'b0;
     else if (!rx_wb_last_writes)
       rx_wb_last_writes <= ShiftEndedSync1 & ~ShiftEndedSync2;
     else if (rx_wb_writeback_finished & RxEn & RxEn_q)
       rx_wb_last_writes <= 0;
 
   // Pulse indicating last of RX data has been written out
   always @ (posedge WB_CLK_I or posedge Reset)
     if(Reset)
       rx_wb_writeback_finished <= 0;
     else if (rx_wb_writeback_finished & RxEn & RxEn_q)
       rx_wb_writeback_finished <= 0;
     else
       rx_wb_writeback_finished <= rx_wb_last_writes & RxBufferEmpty &
                                   !WriteRxDataToFifo_wb;
 
 
   always @ (posedge MRxClk or posedge Reset)
     begin
        if(Reset)
          ShiftEndedSync_c1 <= 1'b0;
        else
          ShiftEndedSync_c1 <= ShiftEndedSync2;
     end
 
   always @ (posedge MRxClk or posedge Reset)
     begin
        if(Reset)
          ShiftEndedSync_c2 <= 1'b0;
        else
          ShiftEndedSync_c2 <= ShiftEndedSync_c1;
     end
 
   // Generation of the end-of-frame signal
   always @ (posedge MRxClk or posedge Reset)
     begin
        if(Reset)
          RxEnableWindow <= 1'b0;
        else
          if(RxStartFrm)
            RxEnableWindow <= 1'b1;
          else
            if(RxEndFrm | RxAbort)
              RxEnableWindow <= 1'b0;
     end
 
 
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          RxAbortSync1 <= 1'b0;
        else
          RxAbortSync1 <= RxAbortLatched;
     end
 
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          RxAbortSync2 <= 1'b0;
        else
          RxAbortSync2 <= RxAbortSync1;
     end
 
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          RxAbortSync3 <= 1'b0;
        else
          RxAbortSync3 <= RxAbortSync2;
     end
 
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          RxAbortSync4 <= 1'b0;
        else
          RxAbortSync4 <= RxAbortSync3;
     end
 
   always @ (posedge MRxClk or posedge Reset)
     begin
        if(Reset)
          RxAbortSyncb1 <= 1'b0;
        else
          RxAbortSyncb1 <= RxAbortSync2;
     end
 
   always @ (posedge MRxClk or posedge Reset)
     begin
        if(Reset)
          RxAbortSyncb2 <= 1'b0;
        else
          RxAbortSyncb2 <= RxAbortSyncb1;
     end
 
 
   always @ (posedge MRxClk or posedge Reset)
     begin
        if(Reset)
          RxAbortLatched <= 1'b0;
        else
          if(RxAbortSyncb2)
            RxAbortLatched <= 1'b0;
          else
            if(RxAbort)
              RxAbortLatched <= 1'b1;
     end
 
 
   always @ (posedge MRxClk or posedge Reset)
     begin
        if(Reset)
          LatchedRxLength[15:0] <= 16'h0;
        else
          if(LoadRxStatus)
            LatchedRxLength[15:0] <= RxLength[15:0];
     end
 
 
   assign RxStatusIn = {ReceivedPauseFrm, AddressMiss, RxOverrun, InvalidSymbol, DribbleNibble, ReceivedPacketTooBig, ShortFrame, LatchedCrcError, RxLateCollision};
 
   always @ (posedge MRxClk or posedge Reset)
     begin
        if(Reset)
          RxStatusInLatched <= 'h0;
        else
          if(LoadRxStatus)
            RxStatusInLatched <= RxStatusIn;
     end
 
 
   // Rx overrun
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          RxOverrun <= 1'b0;
        else
          if(RxStatusWrite)
            RxOverrun <= 1'b0;
          else
            if(RxBufferFull & WriteRxDataToFifo_wb)
              RxOverrun <= 1'b1;
     end
 
 
 
   wire TxError;
   assign TxError = TxUnderRun | RetryLimit | LateCollLatched | CarrierSenseLost;
 
   wire RxError;
 
   // ShortFrame (RxStatusInLatched[2]) can not set an error because short 
   // frames are aborted when signal r_RecSmall is set to 0 in MODER register. 
   // AddressMiss is identifying that a frame was received because of the 
   // promiscous mode and is not an error
   assign RxError = (|RxStatusInLatched[6:3]) | (|RxStatusInLatched[1:0]);
 
 
 
   reg  RxStatusWriteLatched;
   reg  RxStatusWriteLatched_sync1;
   reg  RxStatusWriteLatched_sync2;
   reg  RxStatusWriteLatched_syncb1;
   reg  RxStatusWriteLatched_syncb2;
 
 
   // Latching and synchronizing RxStatusWrite signal. This signal is used for 
   // clearing the ReceivedPauseFrm signal
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          RxStatusWriteLatched <= 1'b0;
        else
          if(RxStatusWriteLatched_syncb2)
            RxStatusWriteLatched <= 1'b0;
          else
            if(RxStatusWrite)
              RxStatusWriteLatched <= 1'b1;
     end
 
 
   always @ (posedge MRxClk or posedge Reset)
     begin
        if(Reset)
          begin
             RxStatusWriteLatched_sync1 <= 1'b0;
             RxStatusWriteLatched_sync2 <= 1'b0;
          end
        else
          begin
             RxStatusWriteLatched_sync1 <= RxStatusWriteLatched;
             RxStatusWriteLatched_sync2 <= RxStatusWriteLatched_sync1;
          end
     end
 
 
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          begin
             RxStatusWriteLatched_syncb1 <= 1'b0;
             RxStatusWriteLatched_syncb2 <= 1'b0;
          end
        else
          begin
             RxStatusWriteLatched_syncb1 <= RxStatusWriteLatched_sync2;
             RxStatusWriteLatched_syncb2 <= RxStatusWriteLatched_syncb1;
          end
     end
 
 
 
   // Tx Done Interrupt
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          TxB_IRQ <= 1'b0;
        else
          if(TxStatusWrite & TxIRQEn)
            TxB_IRQ <= ~TxError;
          else
            TxB_IRQ <= 1'b0;
     end
 
 
   // Tx Error Interrupt
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          TxE_IRQ <= 1'b0;
        else
          if(TxStatusWrite & TxIRQEn)
            TxE_IRQ <= TxError;
          else
            TxE_IRQ <= 1'b0;
     end
 
 
   // Rx Done Interrupt
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          RxB_IRQ <= 1'b0;
        else
          if(RxStatusWrite & RxIRQEn & ReceivedPacketGood &
             (~ReceivedPauseFrm | ReceivedPauseFrm & r_PassAll & (~r_RxFlow)))
            RxB_IRQ <= (~RxError);
          else
            RxB_IRQ <= 1'b0;
     end
 
 
   // Rx Error Interrupt
   always @ (posedge WB_CLK_I or posedge Reset)
     begin
        if(Reset)
          RxE_IRQ <= 1'b0;
        else
          if(RxStatusWrite & RxIRQEn & (~ReceivedPauseFrm | ReceivedPauseFrm
                                        & r_PassAll & (~r_RxFlow)))
            RxE_IRQ <= RxError;
          else
            RxE_IRQ <= 1'b0;
     end
 
   // Set this high when we started receiving another packet while the wishbone
   // side was still writing out the last one. This makes sure we check at the
   // right time if the next buffer descriptor is free.
   reg rxstartfrm_occurred;
   always @ (posedge WB_CLK_I)
     if (Reset)
       rxstartfrm_occurred <= 0;
     else if (rx_just_read_bd)
       rxstartfrm_occurred <= 0;
     else if (((rx_ethside_fifo_sel != rx_wbside_fifo_sel) | StartRxBDRead |
               RxBDRead) & rx_startfrm_wb)
       rxstartfrm_occurred <= 1;
 
 
 
   reg busy_wb;
   always @ (posedge WB_CLK_I or posedge Reset)
     if(Reset)
       busy_wb <= 0;
     else if (busy_wb)
       busy_wb <= 0;
     else if
       // Indicate busy if either:
       // a) RX is idle and we get a start frame and current BD indicates not
       //    ready.
       // b) RX is already receiving another packet and we got a startframe,
       //    indicated by rx_startfrm_occurred, and we then read the BD and
       //    it says it's not ready.
       // This actually may not work since it's in the MII RX clock domain.
       ((rx_ethside_fifo_sel == rx_wbside_fifo_sel) &
        ((rxstartfrm_occurred & rx_just_read_bd & ~RxBDReady) |
         (!rxstartfrm_occurred & !StartRxBDRead & !RxBDRead & rx_startfrm_wb &
          rx_waiting_for_bd_to_become_free))
        )
       busy_wb <= 1;
 
 
   assign Busy_IRQ = busy_wb;
 
   always @(posedge Busy_IRQ)
     $display("(%t)(%m) Ethernet MAC BUSY signal asserted", $time);
 
 
   // Assign the debug output
`ifdef WISHBONE_DEBUG
   // Top byte, burst progress counters
   assign dbg_dat0[31] = 0;
   assign dbg_dat0[30:28] = rx_burst_cnt;
   assign dbg_dat0[27] = 0;
   assign dbg_dat0[26:24] = tx_burst_cnt;
 
   // Third byte
   assign dbg_dat0[23] = 0;
   assign dbg_dat0[22] = 0;
   assign dbg_dat0[21] = rx_burst;
   assign dbg_dat0[20] = rx_burst_en;
   assign dbg_dat0[19] = 0;
   assign dbg_dat0[18] = 0;
   assign dbg_dat0[17] = tx_burst;
   assign dbg_dat0[16] = tx_burst_en;
   // Second byte - TxBDAddress - or TX BD address pointer
   assign dbg_dat0[15:8] = { 1'b0, TxBDAddress};
   // Bottom byte - FSM controlling vector
   assign dbg_dat0[7:0] = {MasterWbTX,MasterWbRX,
                           ReadTxDataFromMemory_2,WriteRxDataToMemory,
                           MasterAccessFinished,cyc_cleared,
                           tx_burst,rx_burst};
 
`endif
 
 
 
endmodule

Line No.	Rev	Author	Line
1	6	julius	`//////////////////////////////////////////////////////////////////////`
2			`//// ////`
3			`//// eth_wishbone.v ////`
4			`//// ////`
5			`//// This file is part of the Ethernet IP core project ////`
6	409	julius	`//// http://www.opencores.org/project,ethmac ////`
7	6	julius	`//// ////`
8			`//// Author(s): ////`
9			`//// - Igor Mohor (igorM@opencores.org) ////`
10			`//// ////`
11			`//// All additional information is available in the Readme.txt ////`
12			`//// file. ////`
13			`//// ////`
14			`//////////////////////////////////////////////////////////////////////`
15			`//// ////`
16			`//// Copyright (C) 2001, 2002 Authors ////`
17			`//// ////`
18			`//// This source file may be used and distributed without ////`
19			`//// restriction provided that this copyright statement is not ////`
20			`//// removed from the file and that any derivative work contains ////`
21			`//// the original copyright notice and the associated disclaimer. ////`
22			`//// ////`
23			`//// This source file is free software; you can redistribute it ////`
24			`//// and/or modify it under the terms of the GNU Lesser General ////`
25			`//// Public License as published by the Free Software Foundation; ////`
26			`//// either version 2.1 of the License, or (at your option) any ////`
27			`//// later version. ////`
28			`//// ////`
29			`//// This source is distributed in the hope that it will be ////`
30			`//// useful, but WITHOUT ANY WARRANTY; without even the implied ////`
31			`//// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR ////`
32			`//// PURPOSE. See the GNU Lesser General Public License for more ////`
33			`//// details. ////`
34			`//// ////`
35			`//// You should have received a copy of the GNU Lesser General ////`
36			`//// Public License along with this source; if not, download it ////`
37			`//// from http://www.opencores.org/lgpl.shtml ////`
38			`//// ////`
39			`//////////////////////////////////////////////////////////////////////`
40
41	409	julius	`include "ethmac_defines.v"
42	6	julius	`include "timescale.v"
43
44
45			`module eth_wishbone`
46	403	julius	`(`
47	6	julius
48	403	julius	`// WISHBONE common`
49			`WB_CLK_I, WB_DAT_I, WB_DAT_O,`
50	6	julius
51	403	julius	`// WISHBONE slave`
52			`WB_ADR_I, WB_WE_I, WB_ACK_O,`
53			`BDCs,`
54	6	julius
55	403	julius	`Reset,`
56	6	julius
57	403	julius	`// WISHBONE master`
58			`m_wb_adr_o, m_wb_sel_o, m_wb_we_o,`
59			`m_wb_dat_o, m_wb_dat_i, m_wb_cyc_o,`
60			`m_wb_stb_o, m_wb_ack_i, m_wb_err_i,`
61	6	julius
62			`ifdef ETH_WISHBONE_B3
63	403	julius	`m_wb_cti_o, m_wb_bte_o,`
64	6	julius	`endif
65
66	403	julius	`//TX`
67			`MTxClk, TxStartFrm, TxEndFrm, TxUsedData, TxData,`
68			`TxRetry, TxAbort, TxUnderRun, TxDone, PerPacketCrcEn,`
69			`PerPacketPad,`
70	6	julius
71	403	julius	`//RX`
72	439	julius	`MRxClk, RxData, RxValid, RxStartFrm, RxEndFrm, RxAbort,`
73			`RxStatusWriteLatched_sync2,`
74	403	julius
75			`// Register`
76			`r_TxEn, r_RxEn, r_TxBDNum, r_RxFlow, r_PassAll,`
77	6	julius
78	403	julius	`// Interrupts`
79			`TxB_IRQ, TxE_IRQ, RxB_IRQ, RxE_IRQ, Busy_IRQ,`
80
81			`// Rx Status`
82			`InvalidSymbol, LatchedCrcError, RxLateCollision, ShortFrame, DribbleNibble,`
83	439	julius	`ReceivedPacketTooBig, RxLength, LoadRxStatus, ReceivedPacketGood,`
84			`AddressMiss,`
85	403	julius	`ReceivedPauseFrm,`
86
87			`// Tx Status`
88	439	julius	`RetryCntLatched, RetryLimit, LateCollLatched, DeferLatched, RstDeferLatched,`
89			`CarrierSenseLost`
90	6	julius
91	403	julius	`// Bist`
92	6	julius	`ifdef ETH_BIST
93	403	julius	`,`
94			`// debug chain signals`
95			`mbist_si_i, // bist scan serial in`
96			`mbist_so_o, // bist scan serial out`
97			`mbist_ctrl_i // bist chain shift control`
98	6	julius	`endif
99
100	403	julius	`ifdef WISHBONE_DEBUG
101			`,`
102			`dbg_dat0`
103			`endif
104	6	julius
105
106	403	julius	`);`
107	6	julius
108
109	403	julius	`// WISHBONE common`
110			`input WB_CLK_I; // WISHBONE clock`
111			`input [31:0] WB_DAT_I; // WISHBONE data input`
112			`output [31:0] WB_DAT_O; // WISHBONE data output`
113	6	julius
114	403	julius	`// WISHBONE slave`
115			`input [9:2] WB_ADR_I; // WISHBONE address input`
116			`input WB_WE_I; // WISHBONE write enable input`
117			`input [3:0] BDCs; // Buffer descriptors are selected`
118			`output WB_ACK_O; // WISHBONE acknowledge output`
119	6	julius
120	403	julius	`// WISHBONE master`
121			`output [29:0] m_wb_adr_o; //`
122			`output [3:0] m_wb_sel_o; //`
123			`output m_wb_we_o; //`
124			`output [31:0] m_wb_dat_o; //`
125			`output m_wb_cyc_o; //`
126			`output m_wb_stb_o; //`
127			`input [31:0] m_wb_dat_i; //`
128			`input m_wb_ack_i; //`
129			`input m_wb_err_i; //`
130	69	julius
131	6	julius	`ifdef ETH_WISHBONE_B3
132	403	julius	`output [2:0] m_wb_cti_o; // Cycle Type Identifier`
133			`ifdef BURST_4BEAT
134			`output reg [1:0] m_wb_bte_o; // Burst Type Extension`
135			`else
136			`output [1:0] m_wb_bte_o; // Burst Type Extension`
137			`endif
138			`reg [2:0] m_wb_cti_o; // Cycle Type Identifier`
139	6	julius	`endif
140
141	403	julius	`input Reset; // Reset signal`
142	6	julius
143	403	julius	`// Rx Status signals`
144			`input InvalidSymbol; // Invalid symbol was received during`
145			`// reception in 100 Mbps mode`
146			`input LatchedCrcError; // CRC error`
147			`input RxLateCollision; // Late collision occured while receiving`
148			`// frame`
149			`input ShortFrame; // Frame shorter then the minimum size`
150			`// (r_MinFL) was received while small`
151			`// packets are enabled (r_RecSmall)`
152			`input DribbleNibble; // Extra nibble received`
153			`input ReceivedPacketTooBig;// Received packet is bigger than`
154			`// r_MaxFL`
155			`input [15:0] RxLength; // Length of the incoming frame`
156			`input LoadRxStatus; // Rx status was loaded`
157			`input ReceivedPacketGood;// Received packet's length and CRC are`
158			`// good`
159			`input AddressMiss; // When a packet is received AddressMiss`
160			`// status is written to the Rx BD`
161			`input r_RxFlow;`
162			`input r_PassAll;`
163			`input ReceivedPauseFrm;`
164	6	julius
165	403	julius	`// Tx Status signals`
166			`input [3:0] RetryCntLatched; // Latched Retry Counter`
167			`input RetryLimit; // Retry limit reached (Retry Max value +`
168			`// 1 attempts were made)`
169			`input LateCollLatched; // Late collision occured`
170			`input DeferLatched; // Defer indication (Frame was defered`
171			`// before sucessfully sent)`
172			`output RstDeferLatched;`
173			`input CarrierSenseLost; // Carrier Sense was lost during the`
174			`// frame transmission`
175	6	julius
176	403	julius	`// Tx`
177			`input MTxClk; // Transmit clock (from PHY)`
178			`input TxUsedData; // Transmit packet used data`
179			`input TxRetry; // Transmit packet retry`
180			`input TxAbort; // Transmit packet abort`
181			`input TxDone; // Transmission ended`
182			`output TxStartFrm; // Transmit packet start frame`
183			`output TxEndFrm; // Transmit packet end frame`
184			`output [7:0] TxData; // Transmit packet data byte`
185			`output TxUnderRun; // Transmit packet under-run`
186			`output PerPacketCrcEn; // Per packet crc enable`
187			`output PerPacketPad; // Per packet pading`
188	6	julius
189	403	julius	`// Rx`
190			`input MRxClk; // Receive clock (from PHY)`
191			`input [7:0] RxData; // Received data byte (from PHY)`
192			`input RxValid; //`
193			`input RxStartFrm; //`
194			`input RxEndFrm; //`
195			`input RxAbort; // This signal is set when address doesn't`
196			`// match.`
197			`output RxStatusWriteLatched_sync2;`
198	6	julius
199	403	julius	`//Register`
200			`input r_TxEn; // Transmit enable`
201			`input r_RxEn; // Receive enable`
202			`input [7:0] r_TxBDNum; // Receive buffer descriptor number`
203	6	julius
204	403	julius	`// Interrupts`
205			`output TxB_IRQ;`
206			`output TxE_IRQ;`
207			`output RxB_IRQ;`
208			`output RxE_IRQ;`
209			`output Busy_IRQ;`
210	6	julius
211
212	403	julius	`// Bist`
213	6	julius	`ifdef ETH_BIST
214	403	julius	`input mbist_si_i; // bist scan serial in`
215			`output mbist_so_o; // bist scan serial out`
216			input [`ETH_MBIST_CTRL_WIDTH - 1:0] mbist_ctrl_i; // bist chain shift control
217	6	julius	`endif
218
219	403	julius	`ifdef WISHBONE_DEBUG
220			`output [31:0] dbg_dat0;`
221			`endif
222	6	julius
223
224
225	403	julius	`reg TxB_IRQ;`
226			`reg TxE_IRQ;`
227			`reg RxB_IRQ;`
228			`reg RxE_IRQ;`
229	6	julius
230	403	julius	`reg TxStartFrm;`
231			`reg TxEndFrm;`
232			`reg [7:0] TxData;`
233	6	julius
234	403	julius	`reg TxUnderRun;`
235			`reg TxUnderRun_wb;`
236	6	julius
237	403	julius	`reg TxBDRead;`
238			`wire TxStatusWrite;`
239	6	julius
240	403	julius	`reg [1:0] TxValidBytesLatched;`
241	6	julius
242	403	julius	`reg [15:0] TxLength;`
243			`reg [15:0] LatchedTxLength;`
244			`reg [14:11] TxStatus;`
245	6	julius
246	403	julius	`reg [14:13] RxStatus;`
247	6	julius
248	403	julius	`reg TxStartFrm_wb;`
249			`reg TxRetry_wb;`
250			`reg TxAbort_wb;`
251			`reg TxDone_wb;`
252	6	julius
253	403	julius	`reg TxDone_wb_q;`
254			`reg TxAbort_wb_q;`
255			`reg TxRetry_wb_q;`
256			`reg TxRetryPacket;`
257			`reg TxRetryPacket_NotCleared;`
258			`reg TxDonePacket;`
259			`reg TxDonePacket_NotCleared;`
260			`reg TxAbortPacket;`
261			`reg TxAbortPacket_NotCleared;`
262			`reg RxBDReady;`
263	439	julius	`reg RxBDOK/* synthesis syn_allow_retiming=0*/;`
264	403	julius	`reg TxBDReady;`
265	6	julius
266	439	julius	`reg RxBDRead ;`
267	6	julius
268	403	julius	`reg [31:0] TxDataLatched;`
269			`reg [1:0] TxByteCnt;`
270			`reg LastWord;`
271			`reg ReadTxDataFromFifo_tck;`
272	6	julius
273	403	julius	`reg BlockingTxStatusWrite;`
274			`reg BlockingTxBDRead;`
275	6	julius
276	403	julius	`reg Flop;`
277	6	julius
278	403	julius	`reg [7:1] TxBDAddress;`
279			`reg [7:1] RxBDAddress;`
280	6	julius
281	403	julius	`reg TxRetrySync1;`
282			`reg TxAbortSync1;`
283			`reg TxDoneSync1;`
284	6	julius
285	403	julius	`reg TxAbort_q;`
286			`reg TxRetry_q;`
287			`reg TxUsedData_q;`
288	6	julius
289	403	julius	`reg [31:0] RxDataLatched2;`
290	6	julius
291	403	julius	`reg [31:8] RxDataLatched1; // Big Endian Byte Ordering`
292	6	julius
293	403	julius	`reg [1:0] RxValidBytes;`
294			`reg [1:0] RxByteCnt;`
295			`reg LastByteIn;`
296			`reg ShiftWillEnd;`
297	6	julius
298	403	julius	`reg WriteRxDataToFifo;`
299			`reg [15:0] LatchedRxLength;`
300			`reg RxAbortLatched;`
301	6	julius
302	403	julius	`reg ShiftEnded;`
303			`reg RxOverrun;`
304	6	julius
305	403	julius	`reg [3:0] BDWrite; // BD Write Enable for access from WISHBONE side`
306			`reg BDRead; // BD Read access from WISHBONE side`
307			`wire [31:0] RxBDDataIn; // Rx BD data in`
308			`wire [31:0] TxBDDataIn; // Tx BD data in`
309	6	julius
310	403	julius	`reg TxEndFrm_wb;`
311	6	julius
312	403	julius	`wire TxRetryPulse;`
313			`wire TxDonePulse;`
314			`wire TxAbortPulse;`
315	6	julius
316	403	julius	`wire StartRxBDRead;`
317	6	julius
318	403	julius	`wire StartTxBDRead;`
319	6	julius
320	403	julius	`wire TxIRQEn;`
321			`wire WrapTxStatusBit;`
322	6	julius
323	403	julius	`wire RxIRQEn;`
324			`wire WrapRxStatusBit;`
325	6	julius
326	403	julius	`wire [1:0] TxValidBytes;`
327	6	julius
328	403	julius	`wire [7:1] TempTxBDAddress;`
329			`wire [7:1] TempRxBDAddress;`
330	6	julius
331	403	julius	`wire RxStatusWrite;`
332			`wire RxBufferFull;`
333			`wire RxBufferAlmostEmpty;`
334			`wire RxBufferEmpty;`
335	6	julius
336	403	julius	`reg WB_ACK_O;`
337	6	julius
338	403	julius	`wire [8:0] RxStatusIn;`
339			`reg [8:0] RxStatusInLatched;`
340	6	julius
341	403	julius	`reg WbEn, WbEn_q;`
342	439	julius	`reg RxEn, RxEn_q /* synthesis syn_allow_retiming=0; syn_noprune=1; syn_keep=1 */;`
343			`reg TxEn, TxEn_q /* synthesis syn_allow_retiming=0; syn_noprune=1; syn_keep=1 */;`
344	403	julius	`reg r_TxEn_q;`
345			`reg r_RxEn_q;`
346	6	julius
347	403	julius	`wire ram_ce;`
348			`wire [3:0] ram_we;`
349			`wire ram_oe;`
350			`reg [7:0] ram_addr;`
351			`reg [31:0] ram_di;`
352			`wire [31:0] ram_do;`
353
354			`wire StartTxPointerRead;`
355			`reg TxPointerRead;`
356			`reg TxEn_needed;`
357			`reg RxEn_needed;`
358
359			`wire StartRxPointerRead;`
360	439	julius	`reg RxPointerRead/* synthesis syn_allow_retiming=0*/;`
361	403	julius
362			`// RX shift ending signals`
363			`reg ShiftEnded_rck;`
364			`reg ShiftEndedSync1;`
365			`reg ShiftEndedSync2;`
366			`reg ShiftEndedSync3;`
367			`reg ShiftEndedSync_c1;`
368			`reg ShiftEndedSync_c2;`
369
370			`wire StartShiftWillEnd;`
371
372			`// Pulse for wishbone side having finished writing back`
373			`reg rx_wb_writeback_finished;`
374			`// Indicator of last set of writes from the Wishbone master coming up`
375			`reg rx_wb_last_writes;`
376
377
378	439	julius	`reg StartOccured;`
379			`reg TxStartFrm_sync1;`
380			`reg TxStartFrm_sync2;`
381			`reg TxStartFrm_syncb1;`
382			`reg TxStartFrm_syncb2;`
383	403	julius
384	439	julius
385			`wire TxFifoClear;`
386			`wire TxBufferAlmostFull;`
387			`wire TxBufferFull;`
388			`wire TxBufferEmpty;`
389			`wire TxBufferAlmostEmpty;`
390			`wire SetReadTxDataFromMemory;`
391			`reg BlockReadTxDataFromMemory/* synthesis syn_allow_retiming=0*/;`
392
393			`reg tx_burst_en;`
394			`reg rx_burst_en;`
395			reg [`ETH_BURST_CNT_WIDTH-1:0] tx_burst_cnt;
396
397			`wire ReadTxDataFromMemory_2;`
398			`wire tx_burst;`
399
400			`wire [31:0] TxData_wb;`
401			`wire ReadTxDataFromFifo_wb;`
402
403			wire [`ETH_TX_FIFO_CNT_WIDTH-1:0] txfifo_cnt;
404			wire [`ETH_RX_FIFO_CNT_WIDTH-1:0] rxfifo_cnt;
405
406			reg [`ETH_BURST_CNT_WIDTH-1:0] rx_burst_cnt;
407
408			`wire rx_burst;`
409			`wire enough_data_in_rxfifo_for_burst;`
410			`wire enough_data_in_rxfifo_for_burst_plus1;`
411
412			`reg ReadTxDataFromMemory/* synthesis syn_allow_retiming=0*/;`
413			`wire WriteRxDataToMemory;`
414			`reg WriteRxDataToMemory_r ;`
415
416			`reg MasterWbTX;`
417			`reg MasterWbRX;`
418
419			`reg [29:0] m_wb_adr_o;`
420			`reg m_wb_cyc_o;`
421			`reg [3:0] m_wb_sel_o;`
422			`reg m_wb_we_o;`
423
424			`wire TxLengthEq0;`
425			`wire TxLengthLt4;`
426
427			`reg BlockingIncrementTxPointer;`
428			`reg [31:2] TxPointerMSB;`
429			`reg [1:0] TxPointerLSB;`
430			`reg [1:0] TxPointerLSB_rst;`
431			`reg [31:2] RxPointerMSB;`
432			`reg [1:0] RxPointerLSB_rst;`
433
434			`wire RxBurstAcc;`
435			`wire RxWordAcc;`
436			`wire RxHalfAcc;`
437			`wire RxByteAcc;`
438
439
440	6	julius	`ifdef ETH_WISHBONE_B3
441	403	julius	`ifndef BURST_4BEAT
442			`assign m_wb_bte_o = 2'b00; // Linear burst`
443			`endif
444	6	julius	`endif
445
446	403	julius	`assign m_wb_stb_o = m_wb_cyc_o;`
447	6	julius
448	403	julius	`always @ (posedge WB_CLK_I)`
449			`begin`
450			`WB_ACK_O <= (\|BDWrite) & WbEn & WbEn_q \| BDRead & WbEn & ~WbEn_q;`
451			`end`
452	6	julius
453	403	julius	`assign WB_DAT_O = ram_do;`
454	6	julius
455	403	julius	`// Generic synchronous single-port RAM interface`
456			`eth_spram_256x32`
457			`#(1) // Write enable width`
458			`bd_ram`
459			`(`
460			`.clk (WB_CLK_I),`
461			`.rst (Reset),`
462			`.ce (ram_ce),`
463			`.we (ram_we[0]),`
464			`.oe (ram_oe),`
465			`.addr (ram_addr),`
466			`.di (ram_di),`
467	439	julius	`.dato (ram_do)`
468	6	julius	`ifdef ETH_BIST
469	403	julius	`,`
470			`.mbist_si_i (mbist_si_i),`
471			`.mbist_so_o (mbist_so_o),`
472			`.mbist_ctrl_i (mbist_ctrl_i)`
473	6	julius	`endif
474	403	julius	`);`
475	6	julius
476	403	julius	`assign ram_ce = 1'b1;`
477			`assign ram_we = (BDWrite & {4{(WbEn & WbEn_q)}}) \|`
478			`{4{(TxStatusWrite \| RxStatusWrite)}};`
479			`assign ram_oe = BDRead & WbEn & WbEn_q \| TxEn & TxEn_q &`
480			`(TxBDRead \| TxPointerRead) \| RxEn & RxEn_q &`
481			`(RxBDRead \| RxPointerRead);`
482	6	julius
483
484	403	julius	`always @ (posedge WB_CLK_I or posedge Reset)`
485			`begin`
486			`if(Reset)`
487			`TxEn_needed <= 1'b0;`
488			`else`
489			`if(~TxBDReady & r_TxEn & WbEn & ~WbEn_q)`
490			`TxEn_needed <= 1'b1;`
491			`else`
492			`if(TxPointerRead & TxEn & TxEn_q)`
493			`TxEn_needed <= 1'b0;`
494			`end`
495	6	julius
496	403	julius	`// Enabling access to the RAM for three devices.`
497			`always @ (posedge WB_CLK_I or posedge Reset)`
498			`begin`
499			`if(Reset)`
500			`begin`

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