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//----------------------------------------------------------------------------

// Copyright (C) 2001 Authors

//

// This source file may be used and distributed without restriction provided

// that this copyright statement is not removed from the file and that any

// derivative work contains the original copyright notice and the associated

// disclaimer.

//

// This source file is free software; you can redistribute it and/or modify

// it under the terms of the GNU Lesser General Public License as published

// by the Free Software Foundation; either version 2.1 of the License, or

// (at your option) any later version.

//

// This source is distributed in the hope that it will be useful, but WITHOUT

// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

// FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public

// License for more details.

//

// You should have received a copy of the GNU Lesser General Public License

// along with this source; if not, write to the Free Software Foundation,

// Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA

//

//----------------------------------------------------------------------------

//

// *File Name: omsp_dbg.v

// 

// *Module Description:

//                       Debug interface

//

// *Author(s):

//              - Olivier Girard,    olgirard@gmail.com

//

//----------------------------------------------------------------------------

// $Rev: 85 $

// $LastChangedBy: olivier.girard $

// $LastChangedDate: 2011-01-28 22:05:37 +0100 (Fri, 28 Jan 2011) $

//----------------------------------------------------------------------------

`include "timescale.v"

`include "openMSP430_defines.v"

module  omsp_dbg (

// OUTPUTs

    dbg_freeze,                     // Freeze peripherals

    dbg_halt_cmd,                   // Halt CPU command

    dbg_mem_addr,                   // Debug address for rd/wr access

    dbg_mem_dout,                   // Debug unit data output

    dbg_mem_en,                     // Debug unit memory enable

    dbg_mem_wr,                     // Debug unit memory write

    dbg_reg_wr,                     // Debug unit CPU register write

    dbg_reset,                      // Reset CPU from debug interface

    dbg_uart_txd,                   // Debug interface: UART TXD

// INPUTs

    dbg_halt_st,                    // Halt/Run status from CPU

    dbg_mem_din,                    // Debug unit Memory data input

    dbg_reg_din,                    // Debug unit CPU register data input

    dbg_uart_rxd,                   // Debug interface: UART RXD

    decode_noirq,                   // Frontend decode instruction

    eu_mab,                         // Execution-Unit Memory address bus

    eu_mb_en,                       // Execution-Unit Memory bus enable

    eu_mb_wr,                       // Execution-Unit Memory bus write transfer

    eu_mdb_in,                      // Memory data bus input

    eu_mdb_out,                     // Memory data bus output

    exec_done,                      // Execution completed

    fe_mb_en,                       // Frontend Memory bus enable

    fe_mdb_in,                      // Frontend Memory data bus input

    mclk,                           // Main system clock

    pc,                             // Program counter

    por,                            // Power on reset

    puc                             // Main system reset

);

// OUTPUTs

//=========

output              dbg_freeze;     // Freeze peripherals

output              dbg_halt_cmd;   // Halt CPU command

output       [15:0] dbg_mem_addr;   // Debug address for rd/wr access

output       [15:0] dbg_mem_dout;   // Debug unit data output

output              dbg_mem_en;     // Debug unit memory enable

output        [1:0] dbg_mem_wr;     // Debug unit memory write

output              dbg_reg_wr;     // Debug unit CPU register write

output              dbg_reset;      // Reset CPU from debug interface

output              dbg_uart_txd;   // Debug interface: UART TXD

// INPUTs

//=========

input               dbg_halt_st;    // Halt/Run status from CPU

input        [15:0] dbg_mem_din;    // Debug unit Memory data input

input        [15:0] dbg_reg_din;    // Debug unit CPU register data input

input               dbg_uart_rxd;   // Debug interface: UART RXD

input               decode_noirq;   // Frontend decode instruction

input        [15:0] eu_mab;         // Execution-Unit Memory address bus

input               eu_mb_en;       // Execution-Unit Memory bus enable

input         [1:0] eu_mb_wr;       // Execution-Unit Memory bus write transfer

input        [15:0] eu_mdb_in;      // Memory data bus input

input        [15:0] eu_mdb_out;     // Memory data bus output

input               exec_done;      // Execution completed

input               fe_mb_en;       // Frontend Memory bus enable

input        [15:0] fe_mdb_in;      // Frontend Memory data bus input

input               mclk;           // Main system clock

input        [15:0] pc;             // Program counter

input               por;            // Power on reset

input               puc;            // Main system reset

//=============================================================================

// 1)  WIRE & PARAMETER DECLARATION

//=============================================================================

// Diverse wires and registers

wire  [5:0] dbg_addr;

wire [15:0] dbg_din;

wire        dbg_wr;

reg         mem_burst;

wire        dbg_reg_rd;

wire        dbg_mem_rd;

reg         dbg_mem_rd_dly;

wire        dbg_swbrk;

wire        dbg_rd;

reg         dbg_rd_rdy;

wire        mem_burst_rd;

wire        mem_burst_wr;

wire        brk0_halt;

wire        brk0_pnd;

wire [15:0] brk0_dout;

wire        brk1_halt;

wire        brk1_pnd;

wire [15:0] brk1_dout;

wire        brk2_halt;

wire        brk2_pnd;

wire [15:0] brk2_dout;

wire        brk3_halt;

wire        brk3_pnd;

wire [15:0] brk3_dout;

// Register addresses

parameter           CPU_ID_LO    = 6'h00;

parameter           CPU_ID_HI    = 6'h01;

parameter           CPU_CTL      = 6'h02;

parameter           CPU_STAT     = 6'h03;

parameter           MEM_CTL      = 6'h04;

parameter           MEM_ADDR     = 6'h05;

parameter           MEM_DATA     = 6'h06;

parameter           MEM_CNT      = 6'h07;

`ifdef DBG_HWBRK_0

parameter           BRK0_CTL     = 6'h08;

parameter           BRK0_STAT    = 6'h09;

parameter           BRK0_ADDR0   = 6'h0A;

parameter           BRK0_ADDR1   = 6'h0B;

`endif

`ifdef DBG_HWBRK_1

parameter           BRK1_CTL     = 6'h0C;

parameter           BRK1_STAT    = 6'h0D;

parameter           BRK1_ADDR0   = 6'h0E;

parameter           BRK1_ADDR1   = 6'h0F;

`endif

`ifdef DBG_HWBRK_2

parameter           BRK2_CTL     = 6'h10;

parameter           BRK2_STAT    = 6'h11;

parameter           BRK2_ADDR0   = 6'h12;

parameter           BRK2_ADDR1   = 6'h13;

`endif

`ifdef DBG_HWBRK_3

parameter           BRK3_CTL     = 6'h14;

parameter           BRK3_STAT    = 6'h15;

parameter           BRK3_ADDR0   = 6'h16;

parameter           BRK3_ADDR1   = 6'h17;

`endif

// Register one-hot decoder

parameter           CPU_ID_LO_D  = (64'h1 << CPU_ID_LO);

parameter           CPU_ID_HI_D  = (64'h1 << CPU_ID_HI);

parameter           CPU_CTL_D    = (64'h1 << CPU_CTL);

parameter           CPU_STAT_D   = (64'h1 << CPU_STAT);

parameter           MEM_CTL_D    = (64'h1 << MEM_CTL);

parameter           MEM_ADDR_D   = (64'h1 << MEM_ADDR);

parameter           MEM_DATA_D   = (64'h1 << MEM_DATA);

parameter           MEM_CNT_D    = (64'h1 << MEM_CNT);

`ifdef DBG_HWBRK_0

parameter           BRK0_CTL_D   = (64'h1 << BRK0_CTL);

parameter           BRK0_STAT_D  = (64'h1 << BRK0_STAT);

parameter           BRK0_ADDR0_D = (64'h1 << BRK0_ADDR0);

parameter           BRK0_ADDR1_D = (64'h1 << BRK0_ADDR1);

`endif

`ifdef DBG_HWBRK_1

parameter           BRK1_CTL_D   = (64'h1 << BRK1_CTL);

parameter           BRK1_STAT_D  = (64'h1 << BRK1_STAT);

parameter           BRK1_ADDR0_D = (64'h1 << BRK1_ADDR0);

parameter           BRK1_ADDR1_D = (64'h1 << BRK1_ADDR1);

`endif

`ifdef DBG_HWBRK_2

parameter           BRK2_CTL_D   = (64'h1 << BRK2_CTL);

parameter           BRK2_STAT_D  = (64'h1 << BRK2_STAT);

parameter           BRK2_ADDR0_D = (64'h1 << BRK2_ADDR0);

parameter           BRK2_ADDR1_D = (64'h1 << BRK2_ADDR1);

`endif

`ifdef DBG_HWBRK_3

parameter           BRK3_CTL_D   = (64'h1 << BRK3_CTL);

parameter           BRK3_STAT_D  = (64'h1 << BRK3_STAT);

parameter           BRK3_ADDR0_D = (64'h1 << BRK3_ADDR0);

parameter           BRK3_ADDR1_D = (64'h1 << BRK3_ADDR1);

`endif

// PUC is localy used as a data.

reg  [1:0] puc_sync;

always @ (posedge mclk or posedge por)

  if (por) puc_sync <=  2'b11;

  else     puc_sync <=  {puc_sync[0] , puc};

wire       puc_s     =  puc_sync[1];

//============================================================================

// 2)  REGISTER DECODER

//============================================================================

// Select Data register during a burst

wire  [5:0] dbg_addr_in = mem_burst ? MEM_DATA : dbg_addr;

// Register address decode

reg  [63:0]  reg_dec;

always @(dbg_addr_in)

  case (dbg_addr_in)

    CPU_ID_LO :  reg_dec  =  CPU_ID_LO_D;

    CPU_ID_HI :  reg_dec  =  CPU_ID_HI_D;

    CPU_CTL   :  reg_dec  =  CPU_CTL_D;

    CPU_STAT  :  reg_dec  =  CPU_STAT_D;

    MEM_CTL   :  reg_dec  =  MEM_CTL_D;

    MEM_ADDR  :  reg_dec  =  MEM_ADDR_D;

    MEM_DATA  :  reg_dec  =  MEM_DATA_D;

    MEM_CNT   :  reg_dec  =  MEM_CNT_D;

`ifdef DBG_HWBRK_0

    BRK0_CTL  :  reg_dec  =  BRK0_CTL_D;

    BRK0_STAT :  reg_dec  =  BRK0_STAT_D;

    BRK0_ADDR0:  reg_dec  =  BRK0_ADDR0_D;

    BRK0_ADDR1:  reg_dec  =  BRK0_ADDR1_D;

`endif

`ifdef DBG_HWBRK_1

    BRK1_CTL  :  reg_dec  =  BRK1_CTL_D;

    BRK1_STAT :  reg_dec  =  BRK1_STAT_D;

    BRK1_ADDR0:  reg_dec  =  BRK1_ADDR0_D;

    BRK1_ADDR1:  reg_dec  =  BRK1_ADDR1_D;

`endif

`ifdef DBG_HWBRK_2

    BRK2_CTL  :  reg_dec  =  BRK2_CTL_D;

    BRK2_STAT :  reg_dec  =  BRK2_STAT_D;

    BRK2_ADDR0:  reg_dec  =  BRK2_ADDR0_D;

    BRK2_ADDR1:  reg_dec  =  BRK2_ADDR1_D;

`endif

`ifdef DBG_HWBRK_3

    BRK3_CTL  :  reg_dec  =  BRK3_CTL_D;

    BRK3_STAT :  reg_dec  =  BRK3_STAT_D;

    BRK3_ADDR0:  reg_dec  =  BRK3_ADDR0_D;

    BRK3_ADDR1:  reg_dec  =  BRK3_ADDR1_D;

`endif

    default:     reg_dec  =  {64{1'b0}};

  endcase

// Read/Write probes

wire         reg_write =  dbg_wr;

wire         reg_read  =  1'b1;

// Read/Write vectors

wire  [63:0] reg_wr    = reg_dec & {64{reg_write}};

wire  [63:0] reg_rd    = reg_dec & {64{reg_read}};

//=============================================================================

// 3)  REGISTER: CORE INTERFACE

//=============================================================================

// CPU_ID Register

//-----------------   

wire [15:0] cpu_id_pmem = `PMEM_SIZE;

wire [15:0] cpu_id_dmem = `DMEM_SIZE;

wire [31:0] cpu_id      = {cpu_id_pmem, cpu_id_dmem};

// CPU_CTL Register

//-----------------------------------------------------------------------------

//       7         6          5          4           3        2     1    0

//   Reserved   CPU_RST  RST_BRK_EN  FRZ_BRK_EN  SW_BRK_EN  ISTEP  RUN  HALT

//-----------------------------------------------------------------------------

reg   [6:3] cpu_ctl;

wire        cpu_ctl_wr = reg_wr[CPU_CTL];

always @ (posedge mclk or posedge por)

  if (por)             cpu_ctl <=  4'h0;

  else if (cpu_ctl_wr) cpu_ctl <=  dbg_din[6:3];

wire  [7:0] cpu_ctl_full = {1'b0, cpu_ctl, 3'b000};

wire        halt_cpu = cpu_ctl_wr & dbg_din[`HALT]  & ~dbg_halt_st;

wire        run_cpu  = cpu_ctl_wr & dbg_din[`RUN]   &  dbg_halt_st;

wire        istep    = cpu_ctl_wr & dbg_din[`ISTEP] &  dbg_halt_st;

// CPU_STAT Register

//------------------------------------------------------------------------------------

//      7           6          5           4           3         2      1       0

// HWBRK3_PND  HWBRK2_PND  HWBRK1_PND  HWBRK0_PND  SWBRK_PND  PUC_PND  Res.  HALT_RUN

//------------------------------------------------------------------------------------

reg   [3:2] cpu_stat;

wire        cpu_stat_wr  = reg_wr[CPU_STAT];

wire  [3:2] cpu_stat_set = {dbg_swbrk, puc_s};

wire  [3:2] cpu_stat_clr = ~dbg_din[3:2];

always @ (posedge mclk or posedge por)

  if (por)              cpu_stat <=  2'b00;

  else if (cpu_stat_wr) cpu_stat <= ((cpu_stat & cpu_stat_clr) | cpu_stat_set);

  else                  cpu_stat <=  (cpu_stat                 | cpu_stat_set);

wire  [7:0] cpu_stat_full = {brk3_pnd, brk2_pnd, brk1_pnd, brk0_pnd,

                             cpu_stat, 1'b0, dbg_halt_st};

//=============================================================================

// 4)  REGISTER: MEMORY INTERFACE

//=============================================================================

// MEM_CTL Register

//-----------------------------------------------------------------------------

//       7     6     5     4          3        2         1       0

//            Reserved               B/W    MEM/REG    RD/WR   START

//

// START  :  -  0 : Do nothing.

//           -  1 : Initiate memory transfer.

//

// RD/WR  :  -  0 : Read access.

//           -  1 : Write access.

//

// MEM/REG:  -  0 : Memory access.

//           -  1 : CPU Register access.

//

// B/W    :  -  0 : 16 bit access.

//           -  1 :  8 bit access (not valid for CPU Registers).

//

//-----------------------------------------------------------------------------

reg   [3:1] mem_ctl;

wire        mem_ctl_wr = reg_wr[MEM_CTL];

always @ (posedge mclk or posedge por)

  if (por)             mem_ctl <=  3'h0;

  else if (mem_ctl_wr) mem_ctl <=  dbg_din[3:1];

wire  [7:0] mem_ctl_full  = {4'b0000, mem_ctl, 1'b0};

reg         mem_start;

always @ (posedge mclk or posedge por)

  if (por)  mem_start <=  1'b0;

  else      mem_start <=  mem_ctl_wr & dbg_din[0];

wire        mem_bw    = mem_ctl[3];

// MEM_DATA Register

//------------------   

reg  [15:0] mem_data;

reg  [15:0] mem_addr;

wire        mem_access;

wire        mem_data_wr = reg_wr[MEM_DATA];

wire [15:0] dbg_mem_din_bw = ~mem_bw      ? dbg_mem_din                :

                              mem_addr[0] ? {8'h00, dbg_mem_din[15:8]} :

                                            {8'h00, dbg_mem_din[7:0]};

always @ (posedge mclk or posedge por)

  if (por)                 mem_data <=  16'h0000;

  else if (mem_data_wr)    mem_data <=  dbg_din;

  else if (dbg_reg_rd)     mem_data <=  dbg_reg_din;

  else if (dbg_mem_rd_dly) mem_data <=  dbg_mem_din_bw;

// MEM_ADDR Register

//------------------   

reg  [15:0] mem_cnt;

wire        mem_addr_wr  = reg_wr[MEM_ADDR];

wire        dbg_mem_acc  = (|dbg_mem_wr | (dbg_rd_rdy & ~mem_ctl[2]));

wire        dbg_reg_acc  = ( dbg_reg_wr | (dbg_rd_rdy &  mem_ctl[2]));

wire [15:0] mem_addr_inc = (mem_cnt==16'h0000)         ? 16'h0000 :

                           (dbg_mem_acc & ~mem_bw)     ? 16'h0002 :

                           (dbg_mem_acc | dbg_reg_acc) ? 16'h0001 : 16'h0000;

always @ (posedge mclk or posedge por)

  if (por)              mem_addr <=  16'h0000;

  else if (mem_addr_wr) mem_addr <=  dbg_din;

  else                  mem_addr <=  mem_addr + mem_addr_inc;

// MEM_CNT Register

//------------------   

wire        mem_cnt_wr  = reg_wr[MEM_CNT];

wire [15:0] mem_cnt_dec = (mem_cnt==16'h0000)         ? 16'h0000 :

                          (dbg_mem_acc | dbg_reg_acc) ? 16'hffff : 16'h0000;

always @ (posedge mclk or posedge por)

  if (por)             mem_cnt <=  16'h0000;

  else if (mem_cnt_wr) mem_cnt <=  dbg_din;

  else                 mem_cnt <=  mem_cnt + mem_cnt_dec;

//=============================================================================

// 5)  BREAKPOINTS / WATCHPOINTS

//=============================================================================

`ifdef DBG_HWBRK_0

// Hardware Breakpoint/Watchpoint Register read select

wire [3:0] brk0_reg_rd = {reg_rd[BRK0_ADDR1],

                          reg_rd[BRK0_ADDR0],

                          reg_rd[BRK0_STAT],

                          reg_rd[BRK0_CTL]};

// Hardware Breakpoint/Watchpoint Register write select

wire [3:0] brk0_reg_wr = {reg_wr[BRK0_ADDR1],

                          reg_wr[BRK0_ADDR0],

                          reg_wr[BRK0_STAT],

                          reg_wr[BRK0_CTL]};

omsp_dbg_hwbrk dbg_hwbr_0 (

// OUTPUTs

    .brk_halt   (brk0_halt),   // Hardware breakpoint command

    .brk_pnd    (brk0_pnd),    // Hardware break/watch-point pending

    .brk_dout   (brk0_dout),   // Hardware break/watch-point register data input

// INPUTs

    .brk_reg_rd (brk0_reg_rd), // Hardware break/watch-point register read select

    .brk_reg_wr (brk0_reg_wr), // Hardware break/watch-point register write select

    .dbg_din    (dbg_din),     // Debug register data input

    .eu_mab     (eu_mab),      // Execution-Unit Memory address bus

    .eu_mb_en   (eu_mb_en),    // Execution-Unit Memory bus enable

    .eu_mb_wr   (eu_mb_wr),    // Execution-Unit Memory bus write transfer

    .eu_mdb_in  (eu_mdb_in),   // Memory data bus input

    .eu_mdb_out (eu_mdb_out),  // Memory data bus output

    .exec_done  (exec_done),   // Execution completed

    .fe_mb_en   (fe_mb_en),    // Frontend Memory bus enable

    .mclk       (mclk),        // Main system clock

    .pc         (pc),          // Program counter

    .por        (por)          // Power on reset

);

`else

assign brk0_halt =  1'b0;

assign brk0_pnd  =  1'b0;

assign brk0_dout = 16'h0000;

`endif

`ifdef DBG_HWBRK_1

// Hardware Breakpoint/Watchpoint Register read select

wire [3:0] brk1_reg_rd = {reg_rd[BRK1_ADDR1],

                          reg_rd[BRK1_ADDR0],

                          reg_rd[BRK1_STAT],

                          reg_rd[BRK1_CTL]};

// Hardware Breakpoint/Watchpoint Register write select

wire [3:0] brk1_reg_wr = {reg_wr[BRK1_ADDR1],

                          reg_wr[BRK1_ADDR0],

                          reg_wr[BRK1_STAT],

                          reg_wr[BRK1_CTL]};

omsp_dbg_hwbrk dbg_hwbr_1 (

// OUTPUTs

    .brk_halt   (brk1_halt),   // Hardware breakpoint command

    .brk_pnd    (brk1_pnd),    // Hardware break/watch-point pending

    .brk_dout   (brk1_dout),   // Hardware break/watch-point register data input

// INPUTs

    .brk_reg_rd (brk1_reg_rd), // Hardware break/watch-point register read select

    .brk_reg_wr (brk1_reg_wr), // Hardware break/watch-point register write select

    .dbg_din    (dbg_din),     // Debug register data input

    .eu_mab     (eu_mab),      // Execution-Unit Memory address bus

    .eu_mb_en   (eu_mb_en),    // Execution-Unit Memory bus enable

    .eu_mb_wr   (eu_mb_wr),    // Execution-Unit Memory bus write transfer

    .eu_mdb_in  (eu_mdb_in),   // Memory data bus input

    .eu_mdb_out (eu_mdb_out),  // Memory data bus output

    .exec_done  (exec_done),   // Execution completed

    .fe_mb_en   (fe_mb_en),    // Frontend Memory bus enable

    .mclk       (mclk),        // Main system clock

    .pc         (pc),          // Program counter

    .por        (por)          // Power on reset

);

`else

assign brk1_halt =  1'b0;

assign brk1_pnd  =  1'b0;

assign brk1_dout = 16'h0000;

`endif

 `ifdef DBG_HWBRK_2

// Hardware Breakpoint/Watchpoint Register read select

wire [3:0] brk2_reg_rd = {reg_rd[BRK2_ADDR1],

                          reg_rd[BRK2_ADDR0],

                          reg_rd[BRK2_STAT],

                          reg_rd[BRK2_CTL]};

// Hardware Breakpoint/Watchpoint Register write select

wire [3:0] brk2_reg_wr = {reg_wr[BRK2_ADDR1],

                          reg_wr[BRK2_ADDR0],

                          reg_wr[BRK2_STAT],

                          reg_wr[BRK2_CTL]};

omsp_dbg_hwbrk dbg_hwbr_2 (

// OUTPUTs

    .brk_halt   (brk2_halt),   // Hardware breakpoint command

    .brk_pnd    (brk2_pnd),    // Hardware break/watch-point pending

    .brk_dout   (brk2_dout),   // Hardware break/watch-point register data input

// INPUTs

    .brk_reg_rd (brk2_reg_rd), // Hardware break/watch-point register read select

    .brk_reg_wr (brk2_reg_wr), // Hardware break/watch-point register write select

    .dbg_din    (dbg_din),     // Debug register data input

    .eu_mab     (eu_mab),      // Execution-Unit Memory address bus

    .eu_mb_en   (eu_mb_en),    // Execution-Unit Memory bus enable

    .eu_mb_wr   (eu_mb_wr),    // Execution-Unit Memory bus write transfer

    .eu_mdb_in  (eu_mdb_in),   // Memory data bus input

    .eu_mdb_out (eu_mdb_out),  // Memory data bus output

    .exec_done  (exec_done),   // Execution completed

    .fe_mb_en   (fe_mb_en),    // Frontend Memory bus enable

    .mclk       (mclk),        // Main system clock

    .pc         (pc),          // Program counter

    .por        (por)          // Power on reset

);

`else

assign brk2_halt =  1'b0;

assign brk2_pnd  =  1'b0;

assign brk2_dout = 16'h0000;

`endif

`ifdef DBG_HWBRK_3

// Hardware Breakpoint/Watchpoint Register read select

wire [3:0] brk3_reg_rd = {reg_rd[BRK3_ADDR1],

                          reg_rd[BRK3_ADDR0],

                          reg_rd[BRK3_STAT],

                          reg_rd[BRK3_CTL]};

// Hardware Breakpoint/Watchpoint Register write select

wire [3:0] brk3_reg_wr = {reg_wr[BRK3_ADDR1],

                          reg_wr[BRK3_ADDR0],

                          reg_wr[BRK3_STAT],

                          reg_wr[BRK3_CTL]};

omsp_dbg_hwbrk dbg_hwbr_3 (

// OUTPUTs

    .brk_halt   (brk3_halt),   // Hardware breakpoint command

    .brk_pnd    (brk3_pnd),    // Hardware break/watch-point pending

    .brk_dout   (brk3_dout),   // Hardware break/watch-point register data input

// INPUTs

    .brk_reg_rd (brk3_reg_rd), // Hardware break/watch-point register read select

    .brk_reg_wr (brk3_reg_wr), // Hardware break/watch-point register write select

    .dbg_din    (dbg_din),     // Debug register data input

    .eu_mab     (eu_mab),      // Execution-Unit Memory address bus

    .eu_mb_en   (eu_mb_en),    // Execution-Unit Memory bus enable

    .eu_mb_wr   (eu_mb_wr),    // Execution-Unit Memory bus write transfer

    .eu_mdb_in  (eu_mdb_in),   // Memory data bus input

    .eu_mdb_out (eu_mdb_out),  // Memory data bus output

    .exec_done  (exec_done),   // Execution completed

    .fe_mb_en   (fe_mb_en),    // Frontend Memory bus enable

    .mclk       (mclk),        // Main system clock

    .pc         (pc),          // Program counter

    .por        (por)          // Power on reset

);

`else

assign brk3_halt =  1'b0;

assign brk3_pnd  =  1'b0;

assign brk3_dout = 16'h0000;

`endif

//============================================================================

// 6) DATA OUTPUT GENERATION

//============================================================================

wire [15:0] cpu_id_lo_rd = cpu_id[15:0]           & {16{reg_rd[CPU_ID_LO]}};

wire [15:0] cpu_id_hi_rd = cpu_id[31:16]          & {16{reg_rd[CPU_ID_HI]}};

wire [15:0] cpu_ctl_rd   = {8'h00, cpu_ctl_full}  & {16{reg_rd[CPU_CTL]}};

wire [15:0] cpu_stat_rd  = {8'h00, cpu_stat_full} & {16{reg_rd[CPU_STAT]}};

wire [15:0] mem_ctl_rd   = {8'h00, mem_ctl_full}  & {16{reg_rd[MEM_CTL]}};

wire [15:0] mem_data_rd  = mem_data               & {16{reg_rd[MEM_DATA]}};

wire [15:0] mem_addr_rd  = mem_addr               & {16{reg_rd[MEM_ADDR]}};

wire [15:0] mem_cnt_rd   = mem_cnt                & {16{reg_rd[MEM_CNT]}};

wire [15:0] dbg_dout = cpu_id_lo_rd |

                       cpu_id_hi_rd |

                       cpu_ctl_rd   |

                       cpu_stat_rd  |

                       mem_ctl_rd   |

                       mem_data_rd  |

                       mem_addr_rd  |

                       mem_cnt_rd   |

                       brk0_dout    |

                       brk1_dout    |

                       brk2_dout    |

                       brk3_dout;

// Tell UART/JTAG interface that the data is ready to be read

always @ (posedge mclk or posedge por)

  if (por)                           dbg_rd_rdy  <=  1'b0;

  else if (mem_burst | mem_burst_rd) dbg_rd_rdy  <= (dbg_reg_rd | dbg_mem_rd_dly);

  else                               dbg_rd_rdy  <=  dbg_rd;

//============================================================================

// 7) CPU CONTROL

//============================================================================

// Reset CPU

//--------------------------

wire dbg_reset  = cpu_ctl[`CPU_RST];

// Break after reset