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

//

//  WISHBONE revB.2 compliant Computer Operating Properly - Test Bench

//

//  Author: Bob Hayes

//          rehayes@opencores.org

//

//  Downloaded from: http://www.opencores.org/projects/cop.....

//

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

// Copyright (c) 2009, Robert Hayes

//

// All rights reserved.

//

// Redistribution and use in source and binary forms, with or without

// modification, are permitted provided that the following conditions are met:

//     * Redistributions of source code must retain the above copyright

//       notice, this list of conditions and the following disclaimer.

//     * Redistributions in binary form must reproduce the above copyright

//       notice, this list of conditions and the following disclaimer in the

//       documentation and/or other materials provided with the distribution.

//     * Neither the name of the <organization> nor the

//       names of its contributors may be used to endorse or promote products

//       derived from this software without specific prior written permission.

//

// THIS SOFTWARE IS PROVIDED BY Robert Hayes ''AS IS'' AND ANY

// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE

// DISCLAIMED. IN NO EVENT SHALL Robert Hayes BE LIABLE FOR ANY

// DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES

// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;

// LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND

// ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS

// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

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

// 45678901234567890123456789012345678901234567890123456789012345678901234567890

`include "timescale.v"

module tst_bench_top();

  //

  // wires && regs

  //

  reg        mstr_test_clk;

  reg [19:0] vector;

  reg [ 7:0] test_num;

  reg [15:0] wb_temp;

  reg        rstn;

  reg        sync_reset;

  reg        por_reset_b;

  reg        startup_osc;

  reg        stop_mode;

  reg        wait_mode;

  reg        debug_mode;

  reg        scantestmode;

  reg [ 8:0] osc_div;

  wire [31:0] adr;

  wire [15:0] dat_i, dat_o, dat0_i, dat1_i, dat2_i, dat3_i;

  wire we;

  wire stb;

  wire cyc;

  wire ack, ack_1, ack_2, ack_3, ack_4;

  wire inta_1, inta_2, inta_3, inta_4;

  wire count_en_1;

  wire count_flag_1;

  reg [15:0] q, qq;

  reg        en_osc_clk;

  wire       osc_clk;

  wire scl, scl0_o, scl0_oen, scl1_o, scl1_oen;

  wire sda, sda0_o, sda0_oen, sda1_o, sda1_oen;

  // Name Address Locations

  parameter COP_CNTRL = 5'b0_0000;

  parameter COP_TOUT  = 5'b0_0001;

  parameter COP_COUNT = 5'b0_0010;

  parameter RD      = 1'b1;

  parameter WR      = 1'b0;

  parameter SADR    = 7'b0010_000;

  parameter COP_CNTRL_COP_EVENT  = 16'h0100;  // COP Enable interrupt request

  parameter COP_CNTRL_IRQ        = 16'h00c0;  // COP Enable interrupt request

  parameter COP_CNTRL_DEBUG_ENA  = 16'h0020;  // COP Enable in system debug mode

  parameter COP_CNTRL_STOP_ENA   = 16'h0010;  // COP Enable in system stop mode

  parameter COP_CNTRL_WAIT_ENA   = 16'h0008;  // COP Enable in system wait mode

  parameter COP_CNTRL_COP_ENA    = 16'h0004;  // COP Enable bit

  parameter COP_CNTRL_CWP        = 16'h0002;  // COP Write Protect

  parameter COP_CNTRL_CLCK       = 16'h0001;  // COP Lock

  parameter COP_COUNT_SVRW0      = 16'h5555;  // Default COP Service word 0

  parameter COP_COUNT_SVRW1      = 16'haaaa;  // Default COP Service word 1

  parameter SLAVE_0_CNTRL = 5'b0_1000;

  parameter SLAVE_0_MOD   = 5'b0_1001;

  parameter SLAVE_0_COUNT = 5'b0_1010;

  parameter SLAVE_1_CNTRL = 5'b1_0000;

  parameter SLAVE_1_MOD   = 5'b1_0001;

  parameter SLAVE_1_COUNT = 5'b1_0010;

  parameter COP_2_CNTRL_0   = 5'b1_1000;

  parameter COP_2_CNTRL_1   = 5'b1_1001;

  parameter COP_2_TOUT_0    = 5'b1_1010;

  parameter COP_2_TOUT_1    = 5'b1_1011;

  parameter COP_2_COUNT_0   = 5'b1_1100;

  parameter COP_2_COUNT_1   = 5'b1_1101;

  // initial values and testbench setup

  initial

    begin

      mstr_test_clk = 0;

      vector = 0;

      test_num = 0;

      por_reset_b = 0;

      startup_osc = 0;

      stop_mode = 0;

      wait_mode = 0;

      debug_mode = 0;

      scantestmode = 0;

      osc_div = 0;

      en_osc_clk = 1'b0;

      `ifdef WAVES

           $shm_open("waves");

           $shm_probe("AS",tst_bench_top,"AS");

           $display("\nINFO: Signal dump enabled ...\n\n");

      `endif

      `ifdef WAVES_V

           $dumpfile ("cop_wave_dump.lxt");

           $dumpvars (0, tst_bench_top);

           $dumpon;

           $display("\nINFO: VCD Signal dump enabled ...\n\n");

      `endif

    end

  // generate clock

  always #20 mstr_test_clk = ~mstr_test_clk;

  always @(posedge mstr_test_clk)

    vector <= vector + 1;

  always @(mstr_test_clk)

    begin

      if (osc_div <= 7)

        osc_div <= osc_div + 1;

      else

        osc_div <= 0;

      if (osc_div == 7)

        startup_osc <= !startup_osc;

    end

  assign osc_clk = startup_osc && en_osc_clk;

  // hookup wishbone master model

  wb_master_model #(.dwidth(16), .awidth(32))

          u0 (

          .clk(mstr_test_clk),

          .rst(rstn),

          .adr(adr),

          .din(dat_i),

          .dout(dat_o),

          .cyc(cyc),

          .stb(stb),

          .we(we),

          .sel(),

          .ack(ack),

          .err(1'b0),

          .rty(1'b0)

  );

  // Address decoding for different COP module instances

  wire stb0 = stb && ~adr[4] && ~adr[3];

  wire stb1 = stb && ~adr[4] &&  adr[3];

  wire stb2 = stb &&  adr[4] && ~adr[3];

  wire stb3 = stb &&  adr[4] &&  adr[3];

  // Create the Read Data Bus

  assign dat_i = ({16{stb0}} & dat0_i) |

                 ({16{stb1}} & dat1_i) |

                 ({16{stb2}} & dat2_i) |

                 ({16{stb3}} & {8'b0, dat3_i[7:0]});

  assign ack = ack_1 || ack_2 || ack_3 || ack_4;

  // hookup wishbone_COP_master core - Parameters take all default values

  //  Async Reset, 16 bit Bus, 16 bit Granularity

  cop_top  #(.SINGLE_CYCLE(1'b0))

          cop_1(

          // wishbone interface

          .wb_clk_i(mstr_test_clk),

          .wb_rst_i(1'b0),         // sync_reset

          .arst_i(rstn),           // rstn

          .wb_adr_i(adr[2:0]),

          .wb_dat_i(dat_o),

          .wb_dat_o(dat0_i),

          .wb_we_i(we),

          .wb_stb_i(stb0),

          .wb_cyc_i(cyc),

          .wb_sel_i( 2'b11 ),

          .wb_ack_o(ack_1),

          .cop_rst_o(cop_1_out),

          .cop_irq_o(cop_1_irq),

          .por_reset_i(por_reset_b),

          .startup_osc_i(osc_clk),

          .stop_mode_i(stop_mode),

          .wait_mode_i(wait_mode),

          .debug_mode_i(debug_mode),

          .scantestmode(scantestmode)

  );

  // hookup wishbone_COP_slave core - Parameters take all default values

  //  Sync Reset, 16 bit Bus, 16 bit Granularity

  cop_top #(.ARST_LVL(1'b1),

            .INIT_ENA(1'b1),

            .SERV_WD_0(16'haa55),

            .SERV_WD_1(16'hc396))

          cop_2(

          // wishbone interface

          .wb_clk_i(mstr_test_clk),

          .wb_rst_i(sync_reset),

          .arst_i(1'b0),

          .wb_adr_i(adr[2:0]),

          .wb_dat_i(dat_o),

          .wb_dat_o(dat1_i),

          .wb_we_i(we),

          .wb_stb_i(stb1),

          .wb_cyc_i(cyc),

          .wb_sel_i( 2'b11 ),

          .wb_ack_o(ack_2),

          .cop_rst_o(cop_2_out),

          .cop_irq_o(cop_2_irq),

          .por_reset_i(por_reset_b),

          .startup_osc_i(osc_clk),

          .stop_mode_i(stop_mode),

          .wait_mode_i(wait_mode),

          .debug_mode_i(debug_mode),

          .scantestmode(scantestmode)

  );

  assign dat2_i = 16'h0000;

  assign ack_3 = 1'b0;

  // hookup wishbone_COP_slave core

  //  8 bit Bus, 8 bit Granularity

  cop_top #(.DWIDTH(8))

          cop_4(

          // wishbone interface

          .wb_clk_i(mstr_test_clk),

          .wb_rst_i(sync_reset),

          .arst_i(1'b1),

          .wb_adr_i(adr[2:0]),

          .wb_dat_i(dat_o[7:0]),

          .wb_dat_o(dat3_i[7:0]),

          .wb_we_i(we),

          .wb_stb_i(stb3),

          .wb_cyc_i(cyc),

          .wb_sel_i( 2'b11 ),

          .wb_ack_o(ack_4),

          .cop_rst_o(cop_4_out),

          .cop_irq_o(cop_4_irq),

          .por_reset_i(por_reset_b),

          .startup_osc_i(osc_clk),

          .stop_mode_i(stop_mode),

          .wait_mode_i(wait_mode),

          .debug_mode_i(debug_mode),

          .scantestmode(scantestmode)

  );

// Test Program

initial

  begin

      $display("\nstatus: %t Testbench started", $time);

      // reset system

      rstn = 1'b1; // negate reset

      repeat(1) @(posedge mstr_test_clk);

      sync_reset = 1'b1;  // Make the sync reset 1 clock cycle long

      #2;          // move the async reset away from the clock edge

      rstn = 1'b0; // assert async reset

      #5;          // Keep the async reset pulse with less than a clock cycle

      rstn = 1'b1; // negate async reset

      por_reset_b = 1'b1;

      repeat(1) @(posedge mstr_test_clk);

      sync_reset = 1'b0;

      $display("\nstatus: %t done reset", $time);

      test_num = test_num + 1;

      repeat(2) @(posedge mstr_test_clk);

      //

      // program core

      //

      reg_test_16;

      reg_test_8;

      cop_count_test;

      cop_count_test_8;

      cop_irq_test;

      repeat(10) @(posedge mstr_test_clk);

      $display("\nTestbench done at vector=%d\n", vector);

      $finish;

  end

// Poll for flag set

task wait_flag_set;

  begin

    u0.wb_read(1, COP_CNTRL, q);

    while(~|(q & COP_CNTRL_COP_EVENT))

      u0.wb_read(1, COP_CNTRL, q); // poll it until it is set

    $display("COP Flag set detected at vector =%d", vector);

  end

endtask

// check register bits - reset, read/write

task reg_test_16;

  begin

      test_num = test_num + 1;

      $display("TEST #%d Starts at vector=%d, reg_test_16", test_num, vector);

      u0.wb_cmp(0, COP_CNTRL, 16'h0004);   // verify reset

      u0.wb_cmp(0, COP_TOUT,  16'hffff);   // verify reset

      u0.wb_cmp(0, COP_COUNT, 16'hffff);   // verify reset

      u0.wb_write(1, COP_CNTRL, 16'h0000); // Clear COP_ENA

      u0.wb_cmp(  0, COP_CNTRL, 16'h0000); // verify clear

      u0.wb_write(1, COP_CNTRL, COP_CNTRL_WAIT_ENA);  //

      u0.wb_cmp(  0, COP_CNTRL, COP_CNTRL_WAIT_ENA);  //

      u0.wb_write(1, COP_CNTRL, COP_CNTRL_STOP_ENA);  //

      u0.wb_cmp(  0, COP_CNTRL, COP_CNTRL_STOP_ENA);  //

      u0.wb_write(1, COP_CNTRL, COP_CNTRL_DEBUG_ENA); //

      u0.wb_cmp(  0, COP_CNTRL, COP_CNTRL_DEBUG_ENA); //

      u0.wb_write(1, COP_CNTRL, 16'h0000); // Clear all bits

      u0.wb_write(1, COP_TOUT, 16'hc639); // Check TOUT reg

      u0.wb_cmp(  0, COP_TOUT, 16'hc639); // verify

      u0.wb_write(1, COP_TOUT, 16'h39c6); // Check TOUT reg

      u0.wb_cmp(  0, COP_TOUT, 16'h39c6); // verify

      // Verify that control bits can not be changed when COP_ENA is set

      u0.wb_write(1, COP_CNTRL, COP_CNTRL_COP_ENA); //

      u0.wb_cmp(  0, COP_CNTRL, COP_CNTRL_COP_ENA); //

      u0.wb_write(1, COP_CNTRL, COP_CNTRL_WAIT_ENA | COP_CNTRL_STOP_ENA | COP_CNTRL_DEBUG_ENA | COP_CNTRL_COP_ENA);

      $display("Debug 1");

      u0.wb_cmp(  0, COP_CNTRL, COP_CNTRL_COP_ENA); // verify that all bits are still clear

      $display("Debug 2");

      u0.wb_write(1, COP_CNTRL, 16'h0000); // Clear COP_ENA

      u0.wb_write(1, COP_CNTRL, COP_CNTRL_WAIT_ENA | COP_CNTRL_STOP_ENA | COP_CNTRL_DEBUG_ENA);

      u0.wb_cmp(  0, COP_CNTRL, COP_CNTRL_WAIT_ENA | COP_CNTRL_STOP_ENA | COP_CNTRL_DEBUG_ENA);

      u0.wb_write(1, COP_CNTRL, COP_CNTRL_WAIT_ENA | COP_CNTRL_STOP_ENA | COP_CNTRL_DEBUG_ENA | COP_CNTRL_COP_ENA); //

      u0.wb_cmp(  0, COP_CNTRL, COP_CNTRL_WAIT_ENA | COP_CNTRL_STOP_ENA | COP_CNTRL_DEBUG_ENA | COP_CNTRL_COP_ENA);

      u0.wb_write(1, COP_CNTRL, COP_CNTRL_COP_ENA); //

      u0.wb_cmp(  0, COP_CNTRL, COP_CNTRL_WAIT_ENA | COP_CNTRL_STOP_ENA | COP_CNTRL_DEBUG_ENA | COP_CNTRL_COP_ENA);

      u0.wb_write(1, COP_CNTRL, 16'h0000); //

      u0.wb_cmp(  0, COP_CNTRL, 16'h0000);

      // Verify TOUT bits are locked when COP_ENA is set

      u0.wb_write(1, COP_TOUT,  16'h5555); // Check TOUT reg

      u0.wb_write(1, COP_CNTRL, COP_CNTRL_COP_ENA); // Lock TOUT reg

      u0.wb_write(1, COP_TOUT,  16'haaaa); // Try to overwrite with new bits

      u0.wb_cmp(  0, COP_TOUT,  16'h5555); // verify old bits are still there

      u0.wb_write(1, COP_CNTRL, 16'h0000); // Enable writes to TOUT reg

      u0.wb_write(1, COP_TOUT,  16'haaaa); // Write new bits

      u0.wb_cmp(  0, COP_TOUT,  16'haaaa); // verify new bits

      u0.wb_write(1, COP_CNTRL, COP_CNTRL_COP_ENA); // Lock TOUT reg

      u0.wb_write(1, COP_TOUT,  16'h5555); // Try to overwrite with new bits

      u0.wb_cmp(  0, COP_TOUT,  16'haaaa); // verify old bits are still there

      u0.wb_write(1, COP_CNTRL, 16'h0000); // Enable writes to TOUT reg

      // Verify COP_EN bit is locked when CWP is set

      u0.wb_write(1, COP_CNTRL, COP_CNTRL_COP_ENA | COP_CNTRL_CWP); // 

      u0.wb_cmp(  0, COP_CNTRL, COP_CNTRL_COP_ENA | COP_CNTRL_CWP);

      u0.wb_write(1, COP_CNTRL, COP_CNTRL_CWP); // 

      u0.wb_cmp(  0, COP_CNTRL, COP_CNTRL_COP_ENA | COP_CNTRL_CWP);

      u0.wb_write(1, COP_CNTRL, 16'h0000);      // 

      u0.wb_cmp(  0, COP_CNTRL, COP_CNTRL_COP_ENA);

      u0.wb_write(1, COP_CNTRL, 16'h0000);      // 

      u0.wb_cmp(  0, COP_CNTRL, 16'h0000);

      u0.wb_write(1, COP_CNTRL, COP_CNTRL_CWP); // 

      u0.wb_write(1, COP_CNTRL, COP_CNTRL_COP_ENA | COP_CNTRL_CWP); // 

      u0.wb_cmp(  0, COP_CNTRL, COP_CNTRL_CWP);

      // Verify CWP bit is locked when CLCK is set

      u0.wb_write(1, COP_CNTRL, COP_CNTRL_CLCK | COP_CNTRL_CWP); // COP Write Protect is ON

      u0.wb_cmp(  0, COP_CNTRL, COP_CNTRL_CLCK | COP_CNTRL_CWP);

      u0.wb_write(1, COP_CNTRL, 16'h0000);  // Try too clear both bits 

      u0.wb_cmp(  0, COP_CNTRL, COP_CNTRL_CLCK | COP_CNTRL_CWP);

      system_reset;  // This is the only way to clear CLCK

      u0.wb_cmp(  0, COP_CNTRL, COP_CNTRL_COP_ENA);

      u0.wb_write(1, COP_CNTRL, COP_CNTRL_CLCK); // COP Write Protect is OFF

      u0.wb_cmp(  0, COP_CNTRL, COP_CNTRL_CLCK);

      u0.wb_write(1, COP_CNTRL, COP_CNTRL_COP_ENA | COP_CNTRL_CWP | COP_CNTRL_WAIT_ENA | COP_CNTRL_STOP_ENA | COP_CNTRL_DEBUG_ENA);

      u0.wb_cmp(  0, COP_CNTRL, COP_CNTRL_CLCK | COP_CNTRL_COP_ENA | COP_CNTRL_WAIT_ENA | COP_CNTRL_STOP_ENA | COP_CNTRL_DEBUG_ENA);

      $display("Debug 3");

      u0.wb_read( 0, COP_COUNT, wb_temp);

      u0.wb_write(0, COP_COUNT, 16'h0000);

      u0.wb_cmp(  0, COP_COUNT, wb_temp); // verify register not writable

      u0.wb_write(0, COP_COUNT, 16'hffff);

      u0.wb_cmp(  0, COP_COUNT, wb_temp); // verify register not writable

      system_reset;  // This is the only way to clear CLCK

  end

endtask

task reg_test_8;

  begin

      test_num = test_num + 1;

      $display("TEST #%d Starts at vector=%d, reg_test_8", test_num, vector);

      u0.wb_cmp(0, COP_2_CNTRL_0, 16'h0004);   // verify reset

      u0.wb_cmp(0, COP_2_CNTRL_1, 16'h0000);   // verify reset

      u0.wb_cmp(0, COP_2_TOUT_0,  16'h00ff);   // verify reset

      u0.wb_cmp(0, COP_2_TOUT_1,  16'h00ff);   // verify reset

      u0.wb_cmp(0, COP_2_COUNT_0, 16'h00ff);   // verify reset

      u0.wb_cmp(0, COP_2_COUNT_1, 16'h00ff);   // verify reset

      u0.wb_write(0, COP_2_CNTRL_0, 16'h0000);  // Remove write prtection

      u0.wb_write(0, COP_2_TOUT_0,  16'haa55);

      u0.wb_cmp(  0, COP_2_TOUT_0,  16'h0055);   // verify write

      u0.wb_cmp(  0, COP_2_TOUT_1,  16'h00ff);   // verify hig byte unchanged

      u0.wb_write(0, COP_2_TOUT_1,  16'h66aa);

      u0.wb_cmp(  0, COP_2_TOUT_1,  16'h00aa);   // verify write

      u0.wb_cmp(  0, COP_2_TOUT_0,  16'h0055);   // verify low byte unchanged

  end

endtask

task cop_count_test;

  begin

      test_num = test_num + 1;

      $display("TEST #%d Starts at vector=%d, cop_count_test",

                test_num, vector);

      // program internal registers

      u0.wb_cmp(  0, COP_COUNT, 16'hffff); // reset value

      u0.wb_write(1, COP_CNTRL, 16'h0000); // Turn off COP_ENA

      u0.wb_write(1, COP_TOUT,  16'h5555); // Write TOUT reg

      u0.wb_write(1, COP_CNTRL, COP_CNTRL_COP_ENA); //

      send_x_osc_clks(1);

      u0.wb_cmp(  0, COP_COUNT, 16'h5555); // verify counter initilized

      send_x_osc_clks(5);

      u0.wb_cmp(  0, COP_COUNT, 16'h5550); // verify counter has decremented

      u0.wb_write(0, COP_COUNT, COP_COUNT_SVRW0); // Send the two Service words

      u0.wb_write(0, COP_COUNT, COP_COUNT_SVRW1);

      send_x_osc_clks(2);

      u0.wb_cmp(  0, COP_COUNT, 16'h5555); // verify counter initilized

      send_x_osc_clks(5);

      u0.wb_cmp(  0, COP_COUNT, 16'h5550); // verify counter has decremented

      u0.wb_write(1, COP_CNTRL, 16'h0000); // Turn off COP_ENA

      u0.wb_write(1, COP_CNTRL, COP_CNTRL_COP_ENA); // Verify toggle of COP_ENA resets COP

      send_x_osc_clks(2);

      u0.wb_cmp(  0, COP_COUNT, 16'h5555); // verify counter initilized

      u0.wb_write(1, COP_CNTRL, 16'h0000); // Turn off COP_ENA

      u0.wb_write(1, COP_TOUT,  16'h0005); // Write TOUT reg

      u0.wb_write(1, COP_CNTRL, COP_CNTRL_COP_ENA); //

      send_x_osc_clks(9);  // Give enough clocks so counter rolls over

      repeat(8) @(posedge mstr_test_clk);

      u0.wb_cmp(  0, COP_CNTRL, COP_CNTRL_COP_EVENT | COP_CNTRL_COP_ENA); // verify Status bit set

      u0.wb_write(1, COP_CNTRL, COP_CNTRL_COP_EVENT | COP_CNTRL_COP_ENA); //

      u0.wb_cmp(  1, COP_CNTRL, COP_CNTRL_COP_ENA); // verify Status bit cleared

      u0.wb_write(1, COP_CNTRL, 16'h0000); // Turn off COP_ENA

      u0.wb_write(1, COP_TOUT,  16'h0005); // Write TOUT reg

      u0.wb_write(1, COP_CNTRL, COP_CNTRL_COP_ENA); //

      send_x_osc_clks(9);  // Give enough clocks so counter rolls over

      repeat(8) @(posedge mstr_test_clk);

      u0.wb_cmp(  0, COP_CNTRL, COP_CNTRL_COP_EVENT | COP_CNTRL_COP_ENA); // verify Status bit set

      u0.wb_write(0, COP_COUNT, COP_COUNT_SVRW0);   // Send the two Service words

      u0.wb_write(0, COP_COUNT, COP_COUNT_SVRW1);

      u0.wb_cmp(  1, COP_CNTRL, COP_CNTRL_COP_ENA); // verify Status bit cleared

   end

endtask

task cop_irq_test;

  begin

      test_num = test_num + 1;

      $display("TEST #%d Starts at vector=%d, cop_irq_test",

                test_num, vector);

      // program internal registers

      u0.wb_write(1, COP_CNTRL, 16'h0000); // Turn off COP_ENA

      u0.wb_write(1, COP_TOUT,  16'h0014); // Write TOUT reg

//      u0.wb_write(1, COP_CNTRL, COP_CNTRL_IRQ | COP_CNTRL_COP_ENA); //

      u0.wb_write(1, COP_CNTRL, 16'h0040 | COP_CNTRL_COP_ENA); //

      send_x_osc_clks(10);

      u0.wb_write(1, COP_CNTRL, 16'h0000); // Turn off COP_ENA

      u0.wb_write(1, COP_TOUT,  16'h0022); // Write TOUT reg

      send_x_osc_clks(1);

//      u0.wb_write(1, COP_CNTRL, COP_CNTRL_IRQ | COP_CNTRL_COP_ENA); //

      u0.wb_write(1, COP_CNTRL, 16'h0080 | COP_CNTRL_COP_ENA); //

      send_x_osc_clks(10);

   end

endtask

task cop_count_test_8;

  begin

      test_num = test_num + 1;

      $display("TEST #%d Starts at vector=%d, cop_count_test_8",

                test_num, vector);

      // program internal registers

      u0.wb_write(0, COP_2_CNTRL_0, 16'h0000);  // Remove write prtection

      u0.wb_write(0, COP_2_TOUT_0,  16'h0005);  // Set timout value

      u0.wb_write(0, COP_2_TOUT_1,  16'h0000);

      u0.wb_write(0, COP_2_CNTRL_0, COP_CNTRL_COP_ENA);  // Enable COP Watchdog Timer

      send_x_osc_clks(9);  // Give enough clocks so counter rolls over

      u0.wb_cmp(0, COP_2_CNTRL_1, 16'h0001);   // verify COP event bit set

      u0.wb_write(0, COP_2_COUNT_0, 16'h0055);   // write 8 bit service words

      u0.wb_write(0, COP_2_COUNT_0, 16'h00aa);   //  to clear event

      send_x_osc_clks(2);  // Give enough clocks so counter rolls over

      u0.wb_cmp(0, COP_2_CNTRL_1, 16'h0000);   // verify COP event bit set

   end

endtask

task system_reset;  // reset system

  begin

      repeat(1) @(posedge mstr_test_clk);

      sync_reset = 1'b1;  // Make the sync reset 1 clock cycle long

      #2;                 // move the async reset away from the clock edge

      rstn = 1'b0;        // assert async reset

      #5;                 // Keep the async reset pulse with less than a clock cycle

      rstn = 1'b1;        // negate async reset

      repeat(1) @(posedge mstr_test_clk);

      sync_reset = 1'b0;

      $display("\nstatus: %t System Reset Task Done", $time);

      test_num = test_num + 1;

      repeat(2) @(posedge mstr_test_clk);

   end

endtask

task send_x_osc_clks;

  input [ 7:0] x_val;

  begin

      $display("Sending %d osc_clks", x_val);

      @(negedge startup_osc);

      #2;                // 

      en_osc_clk = 1'b1; // 

      repeat(x_val) @(posedge startup_osc);

      @(negedge startup_osc);

      #2;                // 

      en_osc_clk = 1'b0; // 

      repeat(1) @(posedge mstr_test_clk);

   end

endtask

endmodule  // tst_bench_top