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

////                                                              ////

////  dbg_top.v                                                   ////

////                                                              ////

////                                                              ////

////  This file is part of the SoC/OpenRISC Development Interface ////

////  http://www.opencores.org/projects/DebugInterface/           ////

////                                                              ////

////                                                              ////

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

////       Igor Mohor                                             ////

////       igorm@opencores.org                                    ////

////                                                              ////

////                                                              ////

////  All additional information is available in the README.txt   ////

////  file.                                                       ////

////                                                              ////

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

////                                                              ////

//// Copyright (C) 2000,2001, 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                     ////

////                                                              ////

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

//

// CVS Revision History

//

// $Log: not supported by cvs2svn $

// Revision 1.28  2002/11/06 14:22:41  mohor

// Trst signal is not inverted here any more. Inverted on higher layer !!!.

//

// Revision 1.27  2002/10/10 02:42:55  mohor

// WISHBONE Scan Chain is changed to reflect state of the WISHBONE access (WBInProgress bit added). Internal counter is used (counts 256 wb_clk cycles) and when counter exceeds that value, wb_cyc_o is negated.

//

// Revision 1.26  2002/05/07 14:43:59  mohor

// mon_cntl_o signals that controls monitor mux added.

//

// Revision 1.25  2002/04/22 12:54:11  mohor

// Signal names changed to lower case.

//

// Revision 1.24  2002/04/17 13:17:01  mohor

// Intentional error removed.

//

// Revision 1.23  2002/04/17 11:16:33  mohor

// A block for checking possible simulation/synthesis missmatch added.

//

// Revision 1.22  2002/03/12 10:31:53  mohor

// tap_top and dbg_top modules are put into two separate modules. tap_top

// contains only tap state machine and related logic. dbg_top contains all

// logic necessery for debugging.

//

// Revision 1.21  2002/03/08 15:28:16  mohor

// Structure changed. Hooks for jtag chain added.

//

// Revision 1.20  2002/02/06 12:23:09  mohor

// LatchedJTAG_IR used when muxing TDO instead of JTAG_IR.

//

// Revision 1.19  2002/02/05 13:34:51  mohor

// Stupid bug that was entered by previous update fixed.

//

// Revision 1.18  2002/02/05 12:41:01  mohor

// trst synchronization is not needed and was removed.

//

// Revision 1.17  2002/01/25 07:58:35  mohor

// IDCODE bug fixed, chains reused to decreas size of core. Data is shifted-in

// not filled-in. Tested in hw.

//

// Revision 1.16  2001/12/20 11:17:26  mohor

// TDO and TDO Enable signal are separated into two signals.

//

// Revision 1.15  2001/12/05 13:28:21  mohor

// trst signal is synchronized to wb_clk_i.

//

// Revision 1.14  2001/11/28 09:36:15  mohor

// Register length fixed.

//

// Revision 1.13  2001/11/27 13:37:43  mohor

// CRC is returned when chain selection data is transmitted.

//

// Revision 1.12  2001/11/26 10:47:09  mohor

// Crc generation is different for read or write commands. Small synthesys fixes.

//

// Revision 1.11  2001/11/14 10:10:41  mohor

// Wishbone data latched on wb_clk_i instead of risc_clk.

//

// Revision 1.10  2001/11/12 01:11:27  mohor

// Reset signals are not combined any more.

//

// Revision 1.9  2001/10/19 11:40:01  mohor

// dbg_timescale.v changed to timescale.v This is done for the simulation of

// few different cores in a single project.

//

// Revision 1.8  2001/10/17 10:39:03  mohor

// bs_chain_o added.

//

// Revision 1.7  2001/10/16 10:09:56  mohor

// Signal names changed to lowercase.

//

//

// Revision 1.6  2001/10/15 09:55:47  mohor

// Wishbone interface added, few fixes for better performance,

// hooks for boundary scan testing added.

//

// Revision 1.5  2001/09/24 14:06:42  mohor

// Changes connected to the OpenRISC access (SPR read, SPR write).

//

// Revision 1.4  2001/09/20 10:11:25  mohor

// Working version. Few bugs fixed, comments added.

//

// Revision 1.3  2001/09/19 11:55:13  mohor

// Asynchronous set/reset not used in trace any more.

//

// Revision 1.2  2001/09/18 14:13:47  mohor

// Trace fixed. Some registers changed, trace simplified.

//

// Revision 1.1.1.1  2001/09/13 13:49:19  mohor

// Initial official release.

//

// Revision 1.3  2001/06/01 22:22:35  mohor

// This is a backup. It is not a fully working version. Not for use, yet.

//

// Revision 1.2  2001/05/18 13:10:00  mohor

// Headers changed. All additional information is now avaliable in the README.txt file.

//

// Revision 1.1.1.1  2001/05/18 06:35:02  mohor

// Initial release

//

//

// synopsys translate_off

`include "timescale.v"

// synopsys translate_on

`include "dbg_defines.v"

// Top module

module dbg_top(

                // RISC signals

                risc_clk_i, risc_addr_o, risc_data_i, risc_data_o, wp_i,

                bp_i, opselect_o, lsstatus_i, istatus_i,

                risc_stall_o, risc_stall_all_o, risc_sel_o, reset_o,

                // WISHBONE common signals

                wb_rst_i, wb_clk_i,

                // WISHBONE master interface

                wb_adr_o, wb_dat_o, wb_dat_i, wb_cyc_o, wb_stb_o, wb_sel_o,

                wb_we_o, wb_ack_i, wb_cab_o, wb_err_i,

                // TAP states

                ShiftDR, Exit1DR, UpdateDR, UpdateDR_q,

                // Instructions

                IDCODESelected, CHAIN_SELECTSelected, DEBUGSelected,

                // TAP signals

                trst_in, tck, tdi, TDOData,

                BypassRegister,

                // Monitor mux control

                mon_cntl_o

              );

parameter Tp = 1;

// RISC signals

input         risc_clk_i;                 // Master clock (RISC clock)

input  [31:0] risc_data_i;                // RISC data inputs (data that is written to the RISC registers)

input  [10:0] wp_i;                       // Watchpoint inputs

input         bp_i;                       // Breakpoint input

input  [3:0]  lsstatus_i;                 // Load/store status inputs

input  [1:0]  istatus_i;                  // Instruction status inputs

output [31:0] risc_addr_o;                // RISC address output (for adressing registers within RISC)

output [31:0] risc_data_o;                // RISC data output (data read from risc registers)

output [`OPSELECTWIDTH-1:0] opselect_o;   // Operation selection (selecting what kind of data is set to the risc_data_i)

output         risc_stall_o;              // Stalls the selected RISC

output         risc_stall_all_o;          // Stalls all the rest RISCs

output [`RISC_NUM-1:0] risc_sel_o;        // Stalls all the rest RISCs

output         reset_o;                   // Resets the RISC

// WISHBONE common signals

input         wb_rst_i;                   // WISHBONE reset

input         wb_clk_i;                   // WISHBONE clock

// WISHBONE master interface

output [31:0] wb_adr_o;

output [31:0] wb_dat_o;

input  [31:0] wb_dat_i;

output        wb_cyc_o;

output        wb_stb_o;

output  [3:0] wb_sel_o;

output        wb_we_o;

input         wb_ack_i;

output        wb_cab_o;

input         wb_err_i;

// TAP states

input         ShiftDR;

input         Exit1DR;

input         UpdateDR;

input         UpdateDR_q;

input trst_in;

input tck;

input tdi;

input BypassRegister;

output TDOData;

output [3:0] mon_cntl_o;

// Defining which instruction is selected

input         IDCODESelected;

input         CHAIN_SELECTSelected;

input         DEBUGSelected;

reg           wb_cyc_o;

reg [31:0]    ADDR;

reg [31:0]    DataOut;

reg [`OPSELECTWIDTH-1:0] opselect_o;        // Operation selection (selecting what kind of data is set to the risc_data_i)

reg [`CHAIN_ID_LENGTH-1:0] Chain;           // Selected chain

reg [31:0]    DataReadLatch;                // Data when reading register or RISC is latched one risc_clk_i clock after the data is read.

reg           RegAccessTck;                 // Indicates access to the registers (read or write)

reg           RISCAccessTck;                // Indicates access to the RISC (read or write)

reg [7:0]     BitCounter;                   // Counting bits in the ShiftDR and Exit1DR stages

reg           RW;                           // Read/Write bit

reg           CrcMatch;                     // The crc that is shifted in and the internaly calculated crc are equal

reg           RegAccess_q;                  // Delayed signals used for accessing the registers

reg           RegAccess_q2;                 // Delayed signals used for accessing the registers

reg           RISCAccess_q;                 // Delayed signals used for accessing the RISC

reg           RISCAccess_q2;                // Delayed signals used for accessing the RISC

reg           RISCAccess_q3;                // Delayed signals used for accessing the RISC

reg           wb_AccessTck;                 // Indicates access to the WISHBONE

reg [31:0]    WBReadLatch;                  // Data latched during WISHBONE read

reg           WBErrorLatch;                 // Error latched during WISHBONE read

reg           WBInProgress;                 // WISHBONE access is in progress

reg [7:0]     WBAccessCounter;              // Counting access cycles. WBInProgress is cleared to 0 after counter exceeds 0xff

wire          WBAccessCounterExceed;        // Marks when the WBAccessCounter exceeds max value (oxff)

reg           WBInProgress_sync1;           // Synchronizing WBInProgress

reg           WBInProgress_tck;             // Synchronizing WBInProgress to tck clock signal

wire trst;

wire [31:0]             RegDataIn;        // Data from registers (read data)

wire [`CRC_LENGTH-1:0]  CalculatedCrcOut; // CRC calculated in this module. This CRC is apended at the end of the TDO.

wire RiscStall_reg;                       // RISC is stalled by setting the register bit

wire RiscReset_reg;                       // RISC is reset by setting the register bit

wire RiscStall_trace;                     // RISC is stalled by trace module

wire RegisterScanChain;                   // Register Scan chain selected

wire RiscDebugScanChain;                  // Risc Debug Scan chain selected

wire WishboneScanChain;                   // WISHBONE Scan chain selected

wire RiscStall_read_access;               // Stalling RISC because of the read access (SPR read)

wire RiscStall_write_access;              // Stalling RISC because of the write access (SPR write)

wire RiscStall_access;                    // Stalling RISC because of the read or write access

wire BitCounter_Lt4;

wire BitCounter_Eq5;

wire BitCounter_Eq32;

wire BitCounter_Lt38;

wire BitCounter_Lt65;

// This signals are used only when TRACE is used in the design

`ifdef TRACE_ENABLED

  wire [39:0] TraceChain;                 // Chain that comes from trace module

  reg  ReadBuffer_Tck;                    // Command for incrementing the trace read pointer (synchr with tck)

  wire ReadTraceBuffer;                   // Command for incrementing the trace read pointer (synchr with MClk)

  reg  ReadTraceBuffer_q;                 // Delayed command for incrementing the trace read pointer (synchr with MClk)

  wire ReadTraceBufferPulse;              // Pulse for reading the trace buffer (valid for only one Mclk command)

  // Outputs from registers

  wire ContinMode;                        // Trace working in continous mode

  wire TraceEnable;                       // Trace enabled

  wire [10:0] WpTrigger;                  // Watchpoint starts trigger

  wire        BpTrigger;                  // Breakpoint starts trigger

  wire [3:0]  LSSTrigger;                 // Load/store status starts trigger

  wire [1:0]  ITrigger;                   // Instruction status starts trigger

  wire [1:0]  TriggerOper;                // Trigger operation

  wire        WpTriggerValid;             // Watchpoint trigger is valid

  wire        BpTriggerValid;             // Breakpoint trigger is valid

  wire        LSSTriggerValid;            // Load/store status trigger is valid

  wire        ITriggerValid;              // Instruction status trigger is valid

  wire [10:0] WpQualif;                   // Watchpoint starts qualifier

  wire        BpQualif;                   // Breakpoint starts qualifier

  wire [3:0]  LSSQualif;                  // Load/store status starts qualifier

  wire [1:0]  IQualif;                    // Instruction status starts qualifier

  wire [1:0]  QualifOper;                 // Qualifier operation

  wire        WpQualifValid;              // Watchpoint qualifier is valid

  wire        BpQualifValid;              // Breakpoint qualifier is valid

  wire        LSSQualifValid;             // Load/store status qualifier is valid

  wire        IQualifValid;               // Instruction status qualifier is valid

  wire [10:0] WpStop;                     // Watchpoint stops recording of the trace

  wire        BpStop;                     // Breakpoint stops recording of the trace

  wire [3:0]  LSSStop;                    // Load/store status stops recording of the trace

  wire [1:0]  IStop;                      // Instruction status stops recording of the trace

  wire [1:0]  StopOper;                   // Stop operation

  wire WpStopValid;                       // Watchpoint stop is valid

  wire BpStopValid;                       // Breakpoint stop is valid

  wire LSSStopValid;                      // Load/store status stop is valid

  wire IStopValid;                        // Instruction status stop is valid

  wire RecordPC;                          // Recording program counter

  wire RecordLSEA;                        // Recording load/store effective address

  wire RecordLDATA;                       // Recording load data

  wire RecordSDATA;                       // Recording store data

  wire RecordReadSPR;                     // Recording read SPR

  wire RecordWriteSPR;                    // Recording write SPR

  wire RecordINSTR;                       // Recording instruction

  // End: Outputs from registers

  wire TraceTestScanChain;                // Trace Test Scan chain selected

  wire [47:0] Trace_Data;                 // Trace data

  wire [`OPSELECTWIDTH-1:0]opselect_trace;// Operation selection (trace selecting what kind of

                                          // data is set to the risc_data_i)

  wire BitCounter_Lt40;

`endif

assign trst = trst_in;                   // trst_pad_i is active high !!! Inverted on higher layer.

/**********************************************************************************

*                                                                                 *

*   JTAG_DR:  JTAG Data Register                                                  *

*                                                                                 *

**********************************************************************************/

reg [`DR_LENGTH-1:0]JTAG_DR_IN;    // Data register

reg TDOData;

always @ (posedge tck or posedge trst)

begin

  if(trst)

    JTAG_DR_IN[`DR_LENGTH-1:0]<=#Tp 0;

  else

  if(IDCODESelected)                          // To save space JTAG_DR_IN is also used for shifting out IDCODE

    begin

      if(ShiftDR)

        JTAG_DR_IN[31:0] <= #Tp {tdi, JTAG_DR_IN[31:1]};

      else

        JTAG_DR_IN[31:0] <= #Tp `IDCODE_VALUE;

    end

  else

  if(CHAIN_SELECTSelected & ShiftDR)

    JTAG_DR_IN[12:0] <= #Tp {tdi, JTAG_DR_IN[12:1]};

  else

  if(DEBUGSelected & ShiftDR)

    begin

      if(RiscDebugScanChain | WishboneScanChain)

        JTAG_DR_IN[73:0] <= #Tp {tdi, JTAG_DR_IN[73:1]};

      else

      if(RegisterScanChain)

        JTAG_DR_IN[46:0] <= #Tp {tdi, JTAG_DR_IN[46:1]};

    end

end

wire [73:0] RISC_Data;

wire [46:0] Register_Data;

wire [73:0] WISHBONE_Data;

wire [12:0] chain_sel_data;

wire wb_Access_wbClk;

reg select_crc_out;

always @ (posedge tck or posedge trst)

begin

  if(trst)

    select_crc_out <= 0;

  else

  if( RegisterScanChain  & BitCounter_Eq5  |

      RiscDebugScanChain & BitCounter_Eq32 |

      WishboneScanChain  & BitCounter_Eq32 )

    select_crc_out <=#Tp tdi;

  else

  if(CHAIN_SELECTSelected)

    select_crc_out <=#Tp 1;

  else

  if(UpdateDR)

    select_crc_out <=#Tp 0;

end

wire [8:0] send_crc;

assign send_crc = select_crc_out? {9{BypassRegister}}    :    // Calculated CRC is returned when read operation is

                                  {CalculatedCrcOut, 1'b0} ;  // performed, else received crc is returned (loopback).

assign RISC_Data      = {send_crc, DataReadLatch, 33'h0};

assign Register_Data  = {send_crc, DataReadLatch, 6'h0};

assign WISHBONE_Data  = {send_crc, WBReadLatch, 31'h0, WBInProgress, WBErrorLatch};

assign chain_sel_data = {send_crc, 4'h0};

`ifdef TRACE_ENABLED

  assign Trace_Data     = {CalculatedCrcOut, TraceChain};

`endif

//TDO is changing on the falling edge of tck

always @ (negedge tck or posedge trst)

begin

  if(trst)

    begin

      TDOData <= #Tp 0;

      `ifdef TRACE_ENABLED

      ReadBuffer_Tck<=#Tp 0;

      `endif

    end

  else

  if(UpdateDR)

    begin

      TDOData <= #Tp CrcMatch;

      `ifdef TRACE_ENABLED

      if(DEBUGSelected & TraceTestScanChain & TraceChain[0])  // Sample in the trace buffer is valid

        ReadBuffer_Tck<=#Tp 1;                                // Increment read pointer

      `endif

    end

  else

    begin

      if(ShiftDR)

        begin

          if(IDCODESelected)

            TDOData <= #Tp JTAG_DR_IN[0]; // IDCODE is shifted out 32-bits, then tdi is bypassed

          else

          if(CHAIN_SELECTSelected)

            TDOData <= #Tp chain_sel_data[BitCounter];        // Received crc is sent back

          else

          if(DEBUGSelected)

            begin

              if(RiscDebugScanChain)

                TDOData <= #Tp RISC_Data[BitCounter];         // Data read from RISC in the previous cycle is shifted out

              else

              if(RegisterScanChain)

                TDOData <= #Tp Register_Data[BitCounter];     // Data read from register in the previous cycle is shifted out

              else

              if(WishboneScanChain)

                TDOData <= #Tp WISHBONE_Data[BitCounter];     // Data read from the WISHBONE slave

              `ifdef TRACE_ENABLED

              else

              if(TraceTestScanChain)

                TDOData <= #Tp Trace_Data[BitCounter];        // Data from the trace buffer is shifted out

              `endif

            end

        end

      else

        begin

          TDOData <= #Tp 0;

          `ifdef TRACE_ENABLED

          ReadBuffer_Tck<=#Tp 0;

          `endif

        end

    end

end

//synopsys translate_off

always @ (posedge tck)

begin

  if(ShiftDR & CHAIN_SELECTSelected & BitCounter > 12)

    begin

      $display("\n%m Error: BitCounter is bigger then chain_sel_data bits width[12:0]. BitCounter=%d\n",BitCounter);

      $stop;

    end

  else

  if(ShiftDR & DEBUGSelected)

    begin

      if(RiscDebugScanChain & BitCounter > 73)

        begin

          $display("\n%m Error: BitCounter is bigger then RISC_Data bits width[73:0]. BitCounter=%d\n",BitCounter);

          $stop;

        end

      else

      if(RegisterScanChain & BitCounter > 46)

        begin

          $display("\n%m Error: BitCounter is bigger then RISC_Data bits width[46:0]. BitCounter=%d\n",BitCounter);

          $stop;

        end

      else

      if(WishboneScanChain & BitCounter > 73)

        begin

          $display("\n%m Error: BitCounter is bigger then WISHBONE_Data bits width[73:0]. BitCounter=%d\n",BitCounter);

          $stop;

        end

      `ifdef TRACE_ENABLED

      else

      if(TraceTestScanChain & BitCounter > 47)

        begin

          $display("\n%m Error: BitCounter is bigger then Trace_Data bits width[47:0]. BitCounter=%d\n",BitCounter);

          $stop;

        end

      `endif

    end

end

// synopsys translate_on

/**********************************************************************************

*                                                                                 *

*   End: JTAG_DR                                                                  *

*                                                                                 *

**********************************************************************************/

/**********************************************************************************

*                                                                                 *

*   CHAIN_SELECT logic                                                            *

*                                                                                 *

**********************************************************************************/

always @ (posedge tck or posedge trst)

begin

  if(trst)

    Chain[`CHAIN_ID_LENGTH-1:0]<=#Tp `GLOBAL_BS_CHAIN;  // Global BS chain is selected after reset

  else

  if(UpdateDR & CHAIN_SELECTSelected & CrcMatch)

    Chain[`CHAIN_ID_LENGTH-1:0]<=#Tp JTAG_DR_IN[3:0];   // New chain is selected

end

/**********************************************************************************

*                                                                                 *

*   Register read/write logic                                                     *

*   RISC registers read/write logic                                               *

*                                                                                 *

**********************************************************************************/

always @ (posedge tck or posedge trst)

begin

  if(trst)

    begin

      ADDR[31:0]        <=#Tp 32'h0;

      DataOut[31:0]     <=#Tp 32'h0;

      RW                <=#Tp 1'b0;

      RegAccessTck      <=#Tp 1'b0;

      RISCAccessTck     <=#Tp 1'b0;

      wb_AccessTck      <=#Tp 1'h0;

    end

  else

  if(UpdateDR & DEBUGSelected & CrcMatch)

    begin

      if(RegisterScanChain)

        begin

          ADDR[4:0]         <=#Tp JTAG_DR_IN[4:0];    // Latching address for register access

          RW                <=#Tp JTAG_DR_IN[5];      // latch R/W bit

          DataOut[31:0]     <=#Tp JTAG_DR_IN[37:6];   // latch data for write

          RegAccessTck      <=#Tp 1'b1;

        end

      else

      if(RiscDebugScanChain)

        begin

          ADDR[31:0]        <=#Tp JTAG_DR_IN[31:0];   // Latching address for RISC register access

          RW                <=#Tp JTAG_DR_IN[32];     // latch R/W bit

          DataOut[31:0]     <=#Tp JTAG_DR_IN[64:33];  // latch data for write

          RISCAccessTck     <=#Tp 1'b1;

        end

      else

      if(WishboneScanChain & (!WBInProgress_tck))

        begin

          ADDR              <=#Tp JTAG_DR_IN[31:0];   // Latching address for WISHBONE slave access

          RW                <=#Tp JTAG_DR_IN[32];     // latch R/W bit

          DataOut           <=#Tp JTAG_DR_IN[64:33];  // latch data for write

          wb_AccessTck      <=#Tp 1'b1;               // 

        end

    end

  else

    begin

      RegAccessTck      <=#Tp 1'b0;       // This signals are valid for one tck clock period only

      RISCAccessTck     <=#Tp 1'b0;

      wb_AccessTck      <=#Tp 1'b0;

    end

end

assign wb_adr_o = ADDR;

assign wb_we_o  = RW;

assign wb_dat_o = DataOut;

assign wb_sel_o[3:0] = 4'hf;

assign wb_cab_o = 1'b0;

// Synchronizing the RegAccess signal to risc_clk_i clock

dbg_sync_clk1_clk2 syn1 (.clk1(risc_clk_i),   .clk2(tck),           .reset1(wb_rst_i),  .reset2(trst),

                         .set2(RegAccessTck), .sync_out(RegAccess)

                        );

// Synchronizing the RISCAccess signal to risc_clk_i clock

dbg_sync_clk1_clk2 syn2 (.clk1(risc_clk_i),    .clk2(tck),          .reset1(wb_rst_i),  .reset2(trst),

                         .set2(RISCAccessTck), .sync_out(RISCAccess)

                        );

// Synchronizing the wb_Access signal to wishbone clock

dbg_sync_clk1_clk2 syn3 (.clk1(wb_clk_i),     .clk2(tck),           .reset1(wb_rst_i),  .reset2(trst),

                         .set2(wb_AccessTck), .sync_out(wb_Access_wbClk)

                        );

// Delayed signals used for accessing registers and RISC

always @ (posedge risc_clk_i or posedge wb_rst_i)

begin

  if(wb_rst_i)

    begin

      RegAccess_q   <=#Tp 1'b0;

      RegAccess_q2  <=#Tp 1'b0;

      RISCAccess_q  <=#Tp 1'b0;

      RISCAccess_q2 <=#Tp 1'b0;

      RISCAccess_q3 <=#Tp 1'b0;

    end

  else

    begin

      RegAccess_q   <=#Tp RegAccess;

      RegAccess_q2  <=#Tp RegAccess_q;

      RISCAccess_q  <=#Tp RISCAccess;

      RISCAccess_q2 <=#Tp RISCAccess_q;

      RISCAccess_q3 <=#Tp RISCAccess_q2;

    end

end

// Chip select and read/write signals for accessing RISC

assign RiscStall_write_access = RISCAccess & ~RISCAccess_q2 &  RW;