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//////////////////////////////////////////////////////////////////////
////                                                              ////
////  can_testbench.v                                             ////
////                                                              ////
////                                                              ////
////  This file is part of the CAN Protocol Controller            ////
////  http://www.opencores.org/projects/can/                      ////
////                                                              ////
////                                                              ////
////  Author(s):                                                  ////
////       Igor Mohor                                             ////
////       igorm@opencores.org                                    ////
////                                                              ////
////                                                              ////
////  All additional information is available in the README.txt   ////
////  file.                                                       ////
////                                                              ////
//////////////////////////////////////////////////////////////////////
////                                                              ////
//// Copyright (C) 2002, 2003 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                     ////
////                                                              ////
//// The CAN protocol is developed by Robert Bosch GmbH and       ////
//// protected by patents. Anybody who wants to implement this    ////
//// CAN IP core on silicon has to obtain a CAN protocol license  ////
//// from Bosch.                                                  ////
////                                                              ////
//////////////////////////////////////////////////////////////////////
//
// CVS Revision History
//
// $Log: not supported by cvs2svn $
// Revision 1.23  2003/02/12 14:28:30  mohor
// Errors monitoring improved. arbitration_lost improved.
//
// Revision 1.22  2003/02/11 00:57:19  mohor
// Wishbone interface added.
//
// Revision 1.21  2003/02/09 18:40:23  mohor
// Overload fixed. Hard synchronization also enabled at the last bit of
// interframe.
//
// Revision 1.20  2003/02/09 02:24:11  mohor
// Bosch license warning added. Error counters finished. Overload frames
// still need to be fixed.
//
// Revision 1.19  2003/02/04 17:24:33  mohor
// Backup.
//
// Revision 1.18  2003/02/04 14:34:45  mohor
// *** empty log message ***
//
// Revision 1.17  2003/01/31 01:13:31  mohor
// backup.
//
// Revision 1.16  2003/01/16 13:36:14  mohor
// Form error supported. When receiving messages, last bit of the end-of-frame
// does not generate form error. Receiver goes to the idle mode one bit sooner.
// (CAN specification ver 2.0, part B, page 57).
//
// Revision 1.15  2003/01/15 21:05:06  mohor
// CRC checking fixed (when bitstuff occurs at the end of a CRC sequence).
//
// Revision 1.14  2003/01/15 14:40:16  mohor
// RX state machine fixed to receive "remote request" frames correctly. No
// data bytes are written to fifo when such frames are received.
//
// Revision 1.13  2003/01/15 13:16:42  mohor
// When a frame with "remote request" is received, no data is stored to
// fifo, just the frame information (identifier, ...). Data length that
// is stored is the received data length and not the actual data length
// that is stored to fifo.
//
// Revision 1.12  2003/01/14 17:25:03  mohor
// Addresses corrected to decimal values (previously hex).
//
// Revision 1.11  2003/01/14 12:19:29  mohor
// rx_fifo is now working.
//
// Revision 1.10  2003/01/10 17:51:28  mohor
// Temporary version (backup).
//
// Revision 1.9  2003/01/09 21:54:39  mohor
// rx fifo added. Not 100 % verified, yet.
//
// Revision 1.8  2003/01/08 02:09:43  mohor
// Acceptance filter added.
//
// Revision 1.7  2002/12/28 04:13:53  mohor
// Backup version.
//
// Revision 1.6  2002/12/27 00:12:48  mohor
// Header changed, testbench improved to send a frame (crc still missing).
//
// Revision 1.5  2002/12/26 16:00:29  mohor
// Testbench define file added. Clock divider register added.
//
// Revision 1.4  2002/12/26 01:33:01  mohor
// Tripple sampling supported.
//
// Revision 1.3  2002/12/25 23:44:12  mohor
// Commented lines removed.
//
// Revision 1.2  2002/12/25 14:16:54  mohor
// Synchronization working.
//
// Revision 1.1.1.1  2002/12/20 16:39:21  mohor
// Initial
//
//
//
 
// synopsys translate_off
`include "timescale.v"
// synopsys translate_on
`include "can_defines.v"
`include "can_testbench_defines.v"
 
module can_testbench();
 
 
 
parameter Tp = 1;
parameter BRP = 2*(`CAN_TIMING0_BRP + 1);
 
 
 
reg         wb_clk_i;
reg         wb_rst_i;
reg   [7:0] wb_dat_i;
wire  [7:0] wb_dat_o;
reg         wb_cyc_i;
reg         wb_stb_i;
 
reg         wb_we_i;
reg   [7:0] wb_adr_i;
reg         clk;
reg         rx;
wire        tx;
wire        tx_oen;
wire        wb_ack_o;
wire        irq;
 
wire        tx_3st;
wire        rx_and_tx;
 
integer     start_tb;
reg   [7:0] tmp_data;
reg         delayed_tx;
reg         tx_bypassed;
reg         wb_free;
 
 
// Instantiate can_top module
can_top i_can_top
( 
  .wb_clk_i(wb_clk_i),
  .wb_rst_i(wb_rst_i),
  .wb_dat_i(wb_dat_i),
  .wb_dat_o(wb_dat_o),
  .wb_cyc_i(wb_cyc_i),
  .wb_stb_i(wb_stb_i),
  .wb_we_i(wb_we_i),
  .wb_adr_i(wb_adr_i),
  .wb_ack_o(wb_ack_o),
  .clk(clk),
  .rx(rx_and_tx),
  .tx(tx),
  .tx_oen(tx_oen),
  .irq(irq)
);
 
assign tx_3st = tx_oen? 1'bz : tx;
 
 
// Generate wishbone clock signal 10 MHz  FIX ME
initial
begin
  wb_clk_i=0;
  forever #20 wb_clk_i = ~wb_clk_i;
end
 
 
// Generate clock signal 24 MHz FIX ME
initial
begin
  clk=0;
  forever #20 clk = ~clk;
end
 
 
initial
begin
  start_tb = 0;
  wb_dat_i = 'hz;
  wb_cyc_i = 0;
  wb_stb_i = 0;
  wb_we_i = 'hz;
  wb_adr_i = 'hz;
  wb_free = 1;
  rx = 1;
  wb_rst_i = 1;
  #200 wb_rst_i = 0;
  #200 initialize_fifo;
  #200 start_tb = 1;
  tx_bypassed = 0;
end
 
 
 
 
// Generating delayed tx signal (CAN transciever delay)
always
begin
  wait (tx_3st);
  repeat (4*BRP) @ (posedge clk);   // 4 time quants delay
  #1 delayed_tx = tx_3st;
  wait (~tx_3st);
  repeat (4*BRP) @ (posedge clk);   // 4 time quants delay
  #1 delayed_tx = tx_3st;
end
 
//assign rx_and_tx = rx & delayed_tx;   FIX ME !!!
assign rx_and_tx = rx & (delayed_tx | tx_bypassed);
 
 
// Main testbench
initial
begin
  wait(start_tb);
 
  // Set bus timing register 0
  write_register(8'd6, {`CAN_TIMING0_SJW, `CAN_TIMING0_BRP});
 
  // Set bus timing register 1
  write_register(8'd7, {`CAN_TIMING1_SAM, `CAN_TIMING1_TSEG2, `CAN_TIMING1_TSEG1});
 
 
  // Set Clock Divider register
  write_register(8'd31, {`CAN_CLOCK_DIVIDER_MODE, 7'h0});    // Setting the normal mode (not extended)
 
  // Set Acceptance Code and Acceptance Mask registers (their address differs for basic and extended mode
  if(`CAN_CLOCK_DIVIDER_MODE)   // Extended mode
    begin
      // Set Acceptance Code and Acceptance Mask registers
      write_register(8'd16, 8'ha6); // acceptance code 0
      write_register(8'd17, 8'hb0); // acceptance code 1
      write_register(8'd18, 8'h12); // acceptance code 2
      write_register(8'd19, 8'h30); // acceptance code 3
      write_register(8'd20, 8'h0); // acceptance mask 0
      write_register(8'd21, 8'h0); // acceptance mask 1
      write_register(8'd22, 8'h00); // acceptance mask 2
      write_register(8'd23, 8'h00); // acceptance mask 3
    end
  else
    begin
      // Set Acceptance Code and Acceptance Mask registers
//      write_register(8'd4, 8'ha6); // acceptance code
      write_register(8'd4, 8'he8); // acceptance code
      write_register(8'd5, 8'h0f); // acceptance mask
    end
 
  #10;
  repeat (1000) @ (posedge clk);
 
  // Switch-off reset mode
  write_register(8'd0, {7'h0, ~(`CAN_MODE_RESET)});
 
  repeat (BRP) @ (posedge clk);   // At least BRP clocks needed before bus goes to dominant level. Otherwise 1 quant difference is possible
                                  // This difference is resynchronized later.
 
  // After exiting the reset mode
  repeat (7) send_bit(1);         // Sending EOF
  repeat (3) send_bit(1);         // Sending Interframe
 
//  test_synchronization;
 
 
 
  if(`CAN_CLOCK_DIVIDER_MODE)   // Extended mode
    begin
//      test_empty_fifo_ext;    // test currently switched off
      test_full_fifo_ext;     // test currently switched on
//      send_frame_ext;         // test currently switched off
    end
  else
    begin
//      test_empty_fifo;    // test currently switched off
//      test_full_fifo;     // test currently switched off
      send_frame;         // test currently switched off
//      bus_off_test;       // test currently switched off
//      manual_frame;       // test currently switched off
//      forced_bus_off;       // test currently switched on
    end
 
 
  $display("CAN Testbench finished !");
  $stop;
end
 
 
task forced_bus_off;    // Forcing bus-off by writinf to tx_err_cnt register
  begin
 
    // Switch-on reset mode
    write_register(8'd0, {7'h0, `CAN_MODE_RESET});
 
    // Set Clock Divider register
    write_register(8'd31, {1'b1, 7'h0});    // Setting the extended mode (not normal)
 
    // Write 255 to tx_err_cnt register - Forcing bus-off
    write_register(8'd15, 255);
 
    // Switch-off reset mode
    write_register(8'd0, {7'h0, ~(`CAN_MODE_RESET)});
 
//    #1000000;
    #2500000;
 
 
    // Switch-on reset mode
    write_register(8'd0, {7'h0, `CAN_MODE_RESET});
 
    // Write 245 to tx_err_cnt register
    write_register(8'd15, 245);
 
    // Switch-off reset mode
    write_register(8'd0, {7'h0, ~(`CAN_MODE_RESET)});
 
    #1000000;
 
 
  end
endtask   // forced_bus_off
 
 
task manual_frame;    // Testbench sends a frame
  begin
 
    write_register(8'd10, 8'he8); // Writing ID[10:3] = 0xe8
    write_register(8'd11, 8'hb7); // Writing ID[2:0] = 0x5, rtr = 1, length = 7
    write_register(8'd12, 8'h00); // data byte 1
    write_register(8'd13, 8'h00); // data byte 2
    write_register(8'd14, 8'h00); // data byte 3
    write_register(8'd15, 8'h00); // data byte 4
    write_register(8'd16, 8'h00); // data byte 5
    write_register(8'd17, 8'h00); // data byte 6
    write_register(8'd18, 8'h00); // data byte 7
    write_register(8'd19, 8'h00); // data byte 8
 
    fork
      begin
        tx_request;
      end
 
      begin
        #2000;
 
        repeat (16)
        begin
          send_bit(0);  // SOF
          send_bit(1);  // ID
          send_bit(1);  // ID
          send_bit(1);  // ID
          send_bit(0);  // ID
          send_bit(1);  // ID
          send_bit(0);  // ID
          send_bit(0);  // ID
          send_bit(0);  // ID
          send_bit(1);  // ID
          send_bit(0);  // ID
          send_bit(1);  // ID
          send_bit(1);  // RTR
          send_bit(0);  // IDE
          send_bit(0);  // r0
          send_bit(0);  // DLC
          send_bit(1);  // DLC
          send_bit(1);  // DLC
          send_bit(1);  // DLC
          send_bit(1);  // CRC
          send_bit(0);  // CRC
          send_bit(0);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC
          send_bit(0);  // CRC
          send_bit(1);  // CRC
          send_bit(0);  // CRC
          send_bit(0);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC DELIM
          send_bit(1);  // ACK            ack error
          send_bit(0);  // ERROR
          send_bit(0);  // ERROR
          send_bit(0);  // ERROR
          send_bit(0);  // ERROR
          send_bit(0);  // ERROR
          send_bit(0);  // ERROR
          send_bit(1);  // ERROR DELIM
          send_bit(1);  // ERROR DELIM
          send_bit(1);  // ERROR DELIM
          send_bit(1);  // ERROR DELIM
          send_bit(1);  // ERROR DELIM
          send_bit(1);  // ERROR DELIM
          send_bit(1);  // ERROR DELIM
          send_bit(1);  // ERROR DELIM
          send_bit(1);  // INTER
          send_bit(1);  // INTER
          send_bit(1);  // INTER
        end // repeat
 
        // Node is error passive now.
        repeat (20)
 
        begin
          send_bit(0);  // SOF
          send_bit(1);  // ID
          send_bit(1);  // ID
          send_bit(1);  // ID
          send_bit(0);  // ID
          send_bit(1);  // ID
          send_bit(0);  // ID
          send_bit(0);  // ID
          send_bit(0);  // ID
          send_bit(1);  // ID
          send_bit(0);  // ID
          send_bit(1);  // ID
          send_bit(1);  // RTR
          send_bit(0);  // IDE
          send_bit(0);  // r0
          send_bit(0);  // DLC
          send_bit(1);  // DLC
          send_bit(1);  // DLC
          send_bit(1);  // DLC
          send_bit(1);  // CRC
          send_bit(0);  // CRC
          send_bit(0);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC
          send_bit(0);  // CRC
          send_bit(1);  // CRC
          send_bit(0);  // CRC
          send_bit(0);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC DELIM
          send_bit(1);  // ACK            ack error
          send_bit(0);  // ERROR
          send_bit(0);  // ERROR
          send_bit(0);  // ERROR
          send_bit(0);  // ERROR
          send_bit(0);  // ERROR
          send_bit(0);  // ERROR
          send_bit(1);  // ERROR DELIM
          send_bit(1);  // ERROR DELIM
          send_bit(1);  // ERROR DELIM
          send_bit(1);  // ERROR DELIM
          send_bit(1);  // ERROR DELIM
          send_bit(1);  // ERROR DELIM
          send_bit(1);  // ERROR DELIM
          send_bit(1);  // ERROR DELIM
          send_bit(1);  // INTER
          send_bit(1);  // INTER
          send_bit(1);  // INTER
          send_bit(1);  // SUSPEND
          send_bit(1);  // SUSPEND
          send_bit(1);  // SUSPEND
          send_bit(1);  // SUSPEND
          send_bit(1);  // SUSPEND
          send_bit(1);  // SUSPEND
          send_bit(1);  // SUSPEND
          send_bit(1);  // SUSPEND
        end // repeat
 
        // Node is bus-off now
 
        #100000;
 
        // Switch-off reset mode
        write_register(8'd0, {7'h0, ~(`CAN_MODE_RESET)});
 
        repeat (128 * 11)
        begin
          send_bit(1);
        end // repeat
 
      end
 
 
    join
 
 
 
    fork
      begin
        tx_request;
      end
 
      begin
        #1100;
 
        send_bit(1);    // To spend some time before transmitter is ready.
 
        repeat (1)
        begin
          send_bit(0);  // SOF
          send_bit(1);  // ID
          send_bit(1);  // ID
          send_bit(1);  // ID
          send_bit(0);  // ID
          send_bit(1);  // ID
          send_bit(0);  // ID
          send_bit(0);  // ID
          send_bit(0);  // ID
          send_bit(1);  // ID
          send_bit(0);  // ID
          send_bit(1);  // ID
          send_bit(1);  // RTR
          send_bit(0);  // IDE
          send_bit(0);  // r0
          send_bit(0);  // DLC
          send_bit(1);  // DLC
          send_bit(1);  // DLC
          send_bit(1);  // DLC
          send_bit(1);  // CRC
          send_bit(0);  // CRC
          send_bit(0);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC
          send_bit(0);  // CRC
          send_bit(1);  // CRC
          send_bit(0);  // CRC
          send_bit(0);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC DELIM
          send_bit(0);  // ACK
          send_bit(1);  // ACK DELIM
          send_bit(1);  // EOF
          send_bit(1);  // EOF
          send_bit(1);  // EOF
          send_bit(1);  // EOF
          send_bit(1);  // EOF
          send_bit(1);  // EOF
          send_bit(1);  // EOF
          send_bit(1);  // INTER
          send_bit(1);  // INTER
          send_bit(1);  // INTER
        end // repeat
      end
 
    join
 
 
 
 
 
    read_receive_buffer;
    release_rx_buffer;
 
    read_receive_buffer;
    release_rx_buffer;
    read_receive_buffer;
 
    #4000000;
 
  end
endtask
 
 
 
task bus_off_test;    // Testbench sends a frame
  begin
 
    write_register(8'd10, 8'he8); // Writing ID[10:3] = 0xe8
    write_register(8'd11, 8'hb7); // Writing ID[2:0] = 0x5, rtr = 1, length = 7
    write_register(8'd12, 8'h00); // data byte 1
    write_register(8'd13, 8'h00); // data byte 2
    write_register(8'd14, 8'h00); // data byte 3
    write_register(8'd15, 8'h00); // data byte 4
    write_register(8'd16, 8'h00); // data byte 5
    write_register(8'd17, 8'h00); // data byte 6
    write_register(8'd18, 8'h00); // data byte 7
    write_register(8'd19, 8'h00); // data byte 8
 
    fork
      begin
        tx_request;
      end
 
      begin
        #2000;
 
        repeat (16)
        begin
          send_bit(0);  // SOF
          send_bit(1);  // ID
          send_bit(1);  // ID
          send_bit(1);  // ID
          send_bit(0);  // ID
          send_bit(1);  // ID
          send_bit(0);  // ID
          send_bit(0);  // ID
          send_bit(0);  // ID
          send_bit(1);  // ID
          send_bit(0);  // ID
          send_bit(1);  // ID
          send_bit(1);  // RTR
          send_bit(0);  // IDE
          send_bit(0);  // r0
          send_bit(0);  // DLC
          send_bit(1);  // DLC
          send_bit(1);  // DLC
          send_bit(1);  // DLC
          send_bit(1);  // CRC
          send_bit(0);  // CRC
          send_bit(0);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC
          send_bit(0);  // CRC
          send_bit(1);  // CRC
          send_bit(0);  // CRC
          send_bit(0);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC DELIM
          send_bit(1);  // ACK            ack error
          send_bit(0);  // ERROR
          send_bit(0);  // ERROR
          send_bit(0);  // ERROR
          send_bit(0);  // ERROR
          send_bit(0);  // ERROR
          send_bit(0);  // ERROR
          send_bit(1);  // ERROR DELIM
          send_bit(1);  // ERROR DELIM
          send_bit(1);  // ERROR DELIM
          send_bit(1);  // ERROR DELIM
          send_bit(1);  // ERROR DELIM
          send_bit(1);  // ERROR DELIM
          send_bit(1);  // ERROR DELIM
          send_bit(1);  // ERROR DELIM
          send_bit(1);  // INTER
          send_bit(1);  // INTER
          send_bit(1);  // INTER
        end // repeat
 
        // Node is error passive now.
        repeat (20)
 
        begin
          send_bit(0);  // SOF
          send_bit(1);  // ID
          send_bit(1);  // ID
          send_bit(1);  // ID
          send_bit(0);  // ID
          send_bit(1);  // ID
          send_bit(0);  // ID
          send_bit(0);  // ID
          send_bit(0);  // ID
          send_bit(1);  // ID
          send_bit(0);  // ID
          send_bit(1);  // ID
          send_bit(1);  // RTR
          send_bit(0);  // IDE
          send_bit(0);  // r0
          send_bit(0);  // DLC
          send_bit(1);  // DLC
          send_bit(1);  // DLC
          send_bit(1);  // DLC
          send_bit(1);  // CRC
          send_bit(0);  // CRC
          send_bit(0);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC
          send_bit(0);  // CRC
          send_bit(1);  // CRC
          send_bit(0);  // CRC
          send_bit(0);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC DELIM
          send_bit(1);  // ACK            ack error
          send_bit(0);  // ERROR
          send_bit(0);  // ERROR
          send_bit(0);  // ERROR
          send_bit(0);  // ERROR
          send_bit(0);  // ERROR
          send_bit(0);  // ERROR
          send_bit(1);  // ERROR DELIM
          send_bit(1);  // ERROR DELIM
          send_bit(1);  // ERROR DELIM
          send_bit(1);  // ERROR DELIM
          send_bit(1);  // ERROR DELIM
          send_bit(1);  // ERROR DELIM
          send_bit(1);  // ERROR DELIM
          send_bit(1);  // ERROR DELIM
          send_bit(1);  // INTER
          send_bit(1);  // INTER
          send_bit(1);  // INTER
          send_bit(1);  // SUSPEND
          send_bit(1);  // SUSPEND
          send_bit(1);  // SUSPEND
          send_bit(1);  // SUSPEND
          send_bit(1);  // SUSPEND
          send_bit(1);  // SUSPEND
          send_bit(1);  // SUSPEND
          send_bit(1);  // SUSPEND
        end // repeat
 
        // Node is bus-off now
 
        #100000;
 
        // Switch-off reset mode
        write_register(8'd0, {7'h0, ~(`CAN_MODE_RESET)});
 
        repeat (128 * 11)
        begin
          send_bit(1);
        end // repeat
 
      end
 
 
    join
 
 
 
    fork
      begin
        tx_request;
      end
 
      begin
        #1100;
 
        send_bit(1);    // To spend some time before transmitter is ready.
 
        repeat (1)
        begin
          send_bit(0);  // SOF
          send_bit(1);  // ID
          send_bit(1);  // ID
          send_bit(1);  // ID
          send_bit(0);  // ID
          send_bit(1);  // ID
          send_bit(0);  // ID
          send_bit(0);  // ID
          send_bit(0);  // ID
          send_bit(1);  // ID
          send_bit(0);  // ID
          send_bit(1);  // ID
          send_bit(1);  // RTR
          send_bit(0);  // IDE
          send_bit(0);  // r0
          send_bit(0);  // DLC
          send_bit(1);  // DLC
          send_bit(1);  // DLC
          send_bit(1);  // DLC
          send_bit(1);  // CRC
          send_bit(0);  // CRC
          send_bit(0);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC
          send_bit(0);  // CRC
          send_bit(1);  // CRC
          send_bit(0);  // CRC
          send_bit(0);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC
          send_bit(1);  // CRC DELIM
          send_bit(0);  // ACK
          send_bit(1);  // ACK DELIM
          send_bit(1);  // EOF
          send_bit(1);  // EOF
          send_bit(1);  // EOF
          send_bit(1);  // EOF
          send_bit(1);  // EOF
          send_bit(1);  // EOF
          send_bit(1);  // EOF
          send_bit(1);  // INTER
          send_bit(1);  // INTER
          send_bit(1);  // INTER
        end // repeat
      end
 
    join
 
    read_receive_buffer;
    release_rx_buffer;
    read_receive_buffer;
    release_rx_buffer;
    read_receive_buffer;
 
    #4000000;
 
    receive_frame(0, 0, {26'h00000e8, 3'h1}, 4'h1, 15'h30bb); // mode, rtr, id, length, crc
 
    #1000000;
 
  end
endtask   // bus_off_test
 
 
 
task send_frame;    // CAN IP core sends frames
  begin
 
    if(`CAN_CLOCK_DIVIDER_MODE)   // Extended mode
      begin
 
        // Writing TX frame information + identifier + data
        write_register(8'd16, 8'h12);
        write_register(8'd17, 8'h34);
        write_register(8'd18, 8'h56);
        write_register(8'd19, 8'h78);
        write_register(8'd20, 8'h9a);
        write_register(8'd21, 8'hbc);
        write_register(8'd22, 8'hde);
        write_register(8'd23, 8'hf0);
        write_register(8'd24, 8'h0f);
        write_register(8'd25, 8'hed);
        write_register(8'd26, 8'hcb);
        write_register(8'd27, 8'ha9);
        write_register(8'd28, 8'h87);
      end
    else
      begin
        write_register(8'd10, 8'hea); // Writing ID[10:3] = 0xea
        write_register(8'd11, 8'h28); // Writing ID[2:0] = 0x1, rtr = 0, length = 8
        write_register(8'd12, 8'h56); // data byte 1
        write_register(8'd13, 8'h78); // data byte 2
        write_register(8'd14, 8'h9a); // data byte 3
        write_register(8'd15, 8'hbc); // data byte 4
        write_register(8'd16, 8'hde); // data byte 5
        write_register(8'd17, 8'hf0); // data byte 6
        write_register(8'd18, 8'h0f); // data byte 7
        write_register(8'd19, 8'hed); // data byte 8
      end
 
 
    // Enable irqs (basic mode)
    write_register(8'd0, 8'h1e);
 
 
 
    fork
      begin
        $display("\n\nStart receiving data from CAN bus");
        receive_frame(0, 0, {26'h00000e8, 3'h1}, 4'h1, 15'h30bb); // mode, rtr, id, length, crc
        receive_frame(0, 0, {26'h00000e8, 3'h1}, 4'h2, 15'h2da1); // mode, rtr, id, length, crc
        receive_frame(0, 0, {26'h00000ee, 3'h1}, 4'h0, 15'h6cea); // mode, rtr, id, length, crc
        receive_frame(0, 0, {26'h00000ee, 3'h1}, 4'h1, 15'h00c5); // mode, rtr, id, length, crc
        receive_frame(0, 0, {26'h00000ee, 3'h1}, 4'h2, 15'h7b4a); // mode, rtr, id, length, crc
 
      end
 
      begin
        tx_request;
      end
 
      begin
        // Transmitting acknowledge
        wait (can_testbench.i_can_top.i_can_bsp.tx_state & can_testbench.i_can_top.i_can_bsp.rx_ack);
        #1 rx = 0;
        wait (can_testbench.i_can_top.i_can_bsp.rx_ack_lim);
        #1 rx = 1;
      end
 
 
    join
 
    read_receive_buffer;
    release_rx_buffer;
    release_rx_buffer;
    read_receive_buffer;
    release_rx_buffer;
    read_receive_buffer;
    release_rx_buffer;
    read_receive_buffer;
    release_rx_buffer;
    read_receive_buffer;
 
    #200000;
 
    read_receive_buffer;
 
    // Read irq register
    read_register(8'd3);
    #1000;
 
  end
endtask   // send_frame
 
 
 
task test_empty_fifo;
  begin
    receive_frame(0, 0, {26'h0000008, 3'h1}, 4'h3, 15'h7bcb); // mode, rtr, id, length, crc
    receive_frame(0, 0, {26'h0000008, 3'h1}, 4'h7, 15'h085c); // mode, rtr, id, length, crc
 
    read_receive_buffer;
    fifo_info;
 
    release_rx_buffer;
    $display("\n\n");
    read_receive_buffer;
    fifo_info;
 
    release_rx_buffer;
    $display("\n\n");
    read_receive_buffer;
    fifo_info;
 
    release_rx_buffer;
    $display("\n\n");
    read_receive_buffer;
    fifo_info;
 
    receive_frame(0, 0, {26'h0000008, 3'h1}, 4'h8, 15'h57a0); // mode, rtr, id, length, crc
 
    $display("\n\n");
    read_receive_buffer;
    fifo_info;
 
    release_rx_buffer;
    $display("\n\n");
    read_receive_buffer;
    fifo_info;
 
    release_rx_buffer;
    $display("\n\n");
    read_receive_buffer;
    fifo_info;
  end
endtask
 
 
 
task test_empty_fifo_ext;
  begin
    receive_frame(1, 0, 29'h14d60246, 4'h3, 15'h5262); // mode, rtr, id, length, crc
    receive_frame(1, 0, 29'h14d60246, 4'h7, 15'h1730); // mode, rtr, id, length, crc
 
    read_receive_buffer;
    fifo_info;
 
    release_rx_buffer;
    $display("\n\n");
    read_receive_buffer;
    fifo_info;
 
    release_rx_buffer;
    $display("\n\n");
    read_receive_buffer;
    fifo_info;
 
    release_rx_buffer;
    $display("\n\n");
    read_receive_buffer;
    fifo_info;
 
    receive_frame(1, 0, 29'h14d60246, 4'h8, 15'h2f7a); // mode, rtr, id, length, crc
 
    $display("\n\n");
    read_receive_buffer;
    fifo_info;
 
    release_rx_buffer;
    $display("\n\n");
    read_receive_buffer;
    fifo_info;
 
    release_rx_buffer;
    $display("\n\n");
    read_receive_buffer;
    fifo_info;
  end
endtask
 
 
 
task test_full_fifo;
  begin
 
    // Enable irqs (basic mode)
    write_register(8'd0, 8'h1e);
 
    release_rx_buffer;
    $display("\n\n");
    read_receive_buffer;
    fifo_info;
 
    receive_frame(0, 0, {26'h0000008, 3'h1}, 4'h0, 15'h4edd); // mode, rtr, id, length, crc
    fifo_info;
    receive_frame(0, 0, {26'h0000008, 3'h1}, 4'h1, 15'h1ccf); // mode, rtr, id, length, crc
    fifo_info;
    receive_frame(0, 0, {26'h0000008, 3'h1}, 4'h2, 15'h73f4); // mode, rtr, id, length, crc
    fifo_info;
    receive_frame(0, 0, {26'h0000008, 3'h1}, 4'h3, 15'h7bcb); // mode, rtr, id, length, crc
    fifo_info;
    receive_frame(0, 0, {26'h0000008, 3'h1}, 4'h4, 15'h37da); // mode, rtr, id, length, crc
    fifo_info;
    receive_frame(0, 0, {26'h0000008, 3'h1}, 4'h5, 15'h7e15); // mode, rtr, id, length, crc
    fifo_info;
    receive_frame(0, 0, {26'h0000008, 3'h1}, 4'h6, 15'h39cf); // mode, rtr, id, length, crc
    fifo_info;
    receive_frame(0, 0, {26'h0000008, 3'h1}, 4'h7, 15'h085c); // mode, rtr, id, length, crc
    fifo_info;
    receive_frame(0, 0, {26'h0000008, 3'h1}, 4'h8, 15'h57a0); // mode, rtr, id, length, crc
    fifo_info;
    receive_frame(0, 0, {26'h0000008, 3'h1}, 4'h8, 15'h57a0); // mode, rtr, id, length, crc
    fifo_info;
$display("FIFO should be full now");
 
    // Following one is accepted with overrun
    receive_frame(0, 0, {26'h0000008, 3'h1}, 4'h8, 15'h57a0); // mode, rtr, id, length, crc
    fifo_info;
 
    release_rx_buffer;
    fifo_info;
 
    // Space just enough for the following frame.
    receive_frame(0, 0, {26'h0000008, 3'h1}, 4'h0, 15'h4edd); // mode, rtr, id, length, crc
    fifo_info;
 
    // Following accepted with overrun
    receive_frame(0, 0, {26'h0000008, 3'h1}, 4'h8, 15'h57a0); // mode, rtr, id, length, crc
    fifo_info;
    read_overrun_info(0, 15);
 
    release_rx_buffer;
    release_rx_buffer;
 
    release_rx_buffer;
    read_receive_buffer;
    fifo_info;
    receive_frame(0, 0, {26'h0000008, 3'h1}, 4'h8, 15'h57a0); // mode, rtr, id, length, crc
    fifo_info;
    read_overrun_info(0, 15);
    $display("\n\n");
 
    release_rx_buffer;
    read_receive_buffer;
    fifo_info;
 
    release_rx_buffer;
    read_receive_buffer;
    fifo_info;
 
    release_rx_buffer;
    read_receive_buffer;
    fifo_info;
 
    release_rx_buffer;
    read_receive_buffer;
    fifo_info;
 
    release_rx_buffer;
    read_receive_buffer;
    fifo_info;
 
    release_rx_buffer;
    read_receive_buffer;
    fifo_info;
 
    clear_data_overrun;
 
    release_rx_buffer;
    read_receive_buffer;
    fifo_info;
 
    release_rx_buffer;
    read_receive_buffer;
    fifo_info;
 
    clear_data_overrun;
 
    release_rx_buffer;
    read_receive_buffer;
    fifo_info;
 
    release_rx_buffer;
    read_receive_buffer;
    fifo_info;
 
    release_rx_buffer;
    read_receive_buffer;
    fifo_info;
 
    release_rx_buffer;
    read_receive_buffer;
    fifo_info;
 
    release_rx_buffer;
    read_receive_buffer;
    fifo_info;
 
    // Read irq register
    read_register(8'd3);
 
    // Read irq register
    read_register(8'd3);
    #1000;
 
  end
endtask
 
 
 
task test_full_fifo_ext;
  begin
    release_rx_buffer;
    $display("\n\n");
    read_receive_buffer;
    fifo_info;
 
    receive_frame(1, 0, 29'h14d60246, 4'h0, 15'h6f54); // mode, rtr, id, length, crc
    read_receive_buffer;
    fifo_info;
    receive_frame(1, 0, 29'h14d60246, 4'h1, 15'h6d38); // mode, rtr, id, length, crc
    read_receive_buffer;
    fifo_info;
    receive_frame(1, 0, 29'h14d60246, 4'h2, 15'h053e); // mode, rtr, id, length, crc
    fifo_info;
    read_receive_buffer;
    receive_frame(1, 0, 29'h14d60246, 4'h3, 15'h5262); // mode, rtr, id, length, crc
    fifo_info;
    receive_frame(1, 0, 29'h14d60246, 4'h4, 15'h4bba); // mode, rtr, id, length, crc
    fifo_info;
    receive_frame(1, 0, 29'h14d60246, 4'h5, 15'h4d7d); // mode, rtr, id, length, crc
    fifo_info;
    receive_frame(1, 0, 29'h14d60246, 4'h6, 15'h6f40); // mode, rtr, id, length, crc
    fifo_info;
    receive_frame(1, 0, 29'h14d60246, 4'h7, 15'h1730); // mode, rtr, id, length, crc
    fifo_info;
    read_overrun_info(0, 10);
 
    release_rx_buffer;
    release_rx_buffer;
    fifo_info;
    receive_frame(1, 0, 29'h14d60246, 4'h8, 15'h2f7a); // mode, rtr, id, length, crc
    fifo_info;
    read_overrun_info(0, 15);
    $display("\n\n");
 
    release_rx_buffer;
    read_receive_buffer;
    fifo_info;
 
    release_rx_buffer;
    read_receive_buffer;
    fifo_info;
 
    release_rx_buffer;
    read_receive_buffer;
    fifo_info;
 
    release_rx_buffer;
    read_receive_buffer;
    fifo_info;
 
    release_rx_buffer;
    read_receive_buffer;
    fifo_info;
 
    release_rx_buffer;
    read_receive_buffer;
    fifo_info;
 
    release_rx_buffer;
    read_receive_buffer;
    fifo_info;
 
  end
endtask
 
 
 
task initialize_fifo;
  integer i;
  begin
    for (i=0; i<32; i=i+1)
      begin
        can_testbench.i_can_top.i_can_bsp.i_can_fifo.length_info[i] = 0;
        can_testbench.i_can_top.i_can_bsp.i_can_fifo.overrun_info[i] = 0;
      end
 
    for (i=0; i<64; i=i+1)
      begin
        can_testbench.i_can_top.i_can_bsp.i_can_fifo.fifo[i] = 0;
      end
 
    $display("(%0t) Fifo initialized", $time);
  end
endtask
 
 
task read_overrun_info;
  input [4:0] start_addr;
  input [4:0] end_addr;
  integer i;
  begin
    for (i=start_addr; i<=end_addr; i=i+1)
      begin
        $display("len[0x%0x]=0x%0x", i, can_testbench.i_can_top.i_can_bsp.i_can_fifo.length_info[i]);
        $display("overrun[0x%0x]=0x%0x\n", i, can_testbench.i_can_top.i_can_bsp.i_can_fifo.overrun_info[i]);
      end
  end
endtask
 
 
task fifo_info;   // Displaying how many packets and how many bytes are in fifo. Not working when wr_info_pointer is smaller than rd_info_pointer.
  begin
      $display("(%0t) Currently %0d bytes in fifo (%0d packets)", $time, can_testbench.i_can_top.i_can_bsp.i_can_fifo.fifo_cnt, 
      (can_testbench.i_can_top.i_can_bsp.i_can_fifo.wr_info_pointer - can_testbench.i_can_top.i_can_bsp.i_can_fifo.rd_info_pointer));
end
endtask
 
 
task read_register;
  input [7:0] reg_addr;
 
  begin
    wait (wb_free);
    wb_free = 0;
    @ (posedge wb_clk_i);
    #1; 
    wb_adr_i = reg_addr;
    wb_cyc_i = 1;
    wb_stb_i = 1;
    wb_we_i = 0;
    wait (wb_ack_o);
    $display("(%0t) Reading register [%0d] = 0x%0x", $time, wb_adr_i, wb_dat_o);
    @ (posedge wb_clk_i);
    #1; 
    wb_adr_i = 'hz;
    wb_cyc_i = 0;
    wb_stb_i = 0;
    wb_we_i = 'hz;
    wb_free = 1;
  end
endtask
 
 
task write_register;
  input [7:0] reg_addr;
  input [7:0] reg_data;
 
  begin
    wait (wb_free);
    wb_free = 0;
    @ (posedge wb_clk_i);
    #1; 
    wb_adr_i = reg_addr;
    wb_dat_i = reg_data;
    wb_cyc_i = 1;
    wb_stb_i = 1;
    wb_we_i = 1;
    wait (wb_ack_o);
    @ (posedge wb_clk_i);
    #1; 
    wb_adr_i = 'hz;
    wb_dat_i = 'hz;
    wb_cyc_i = 0;
    wb_stb_i = 0;
    wb_we_i = 'hz;
    wb_free = 1;
  end
endtask
 
 
task read_receive_buffer;
  integer i;
  begin
    if(`CAN_CLOCK_DIVIDER_MODE)   // Extended mode
      begin
        for (i=8'd16; i<=8'd28; i=i+1)
          read_register(i);
        if (can_testbench.i_can_top.i_can_bsp.i_can_fifo.overrun_info[can_testbench.i_can_top.i_can_bsp.i_can_fifo.rd_info_pointer])
          $display("\nWARNING: This packet was received with overrun.");
      end
    else
      begin
        for (i=8'd20; i<=8'd29; i=i+1)
          read_register(i);
        if (can_testbench.i_can_top.i_can_bsp.i_can_fifo.overrun_info[can_testbench.i_can_top.i_can_bsp.i_can_fifo.rd_info_pointer])
          $display("\nWARNING: This packet was received with overrun.");
      end
  end
endtask
 
 
task release_rx_buffer;
  begin
    write_register(8'd1, 8'h4);
    $display("(%0t) Rx buffer released.", $time);
  end
endtask
 
 
task tx_request;
  begin
    write_register(8'd1, 8'h1);
    $display("(%0t) Tx requested.", $time);
  end
endtask
 
 
task tx_abort;
  begin
    write_register(8'd1, 8'h2);
    $display("(%0t) Tx abort requested.", $time);
  end
endtask
 
 
task clear_data_overrun;
  begin
    write_register(8'd1, 8'h8);
    $display("(%0t) Data overrun cleared.", $time);
  end
endtask
 
 
task test_synchronization;
  begin
    // Hard synchronization
    #1 rx=0;
    repeat (2*BRP) @ (posedge clk);
    repeat (8*BRP) @ (posedge clk);
    #1 rx=1;
    repeat (10*BRP) @ (posedge clk);
 
    // Resynchronization on time
    #1 rx=0;
    repeat (10*BRP) @ (posedge clk);
    #1 rx=1;
    repeat (10*BRP) @ (posedge clk);
 
    // Resynchronization late
    repeat (BRP) @ (posedge clk);
    repeat (BRP) @ (posedge clk);
    #1 rx=0;
    repeat (10*BRP) @ (posedge clk);
    #1 rx=1;
 
    // Resynchronization early
    repeat (8*BRP) @ (posedge clk);   // two frames too early
    #1 rx=0;
    repeat (10*BRP) @ (posedge clk);
    #1 rx=1;
    repeat (10*BRP) @ (posedge clk);
  end
endtask
 
 
task send_bit;
  input bit;
  integer cnt;
  begin
    #1 rx=bit;
    repeat ((`CAN_TIMING1_TSEG1 + `CAN_TIMING1_TSEG2 + 3)*BRP) @ (posedge clk);
  end
endtask
 
 
task receive_frame;           // CAN IP core receives frames
  input mode;
  input remote_trans_req;
  input [28:0] id;
  input  [3:0] length;
  input [14:0] crc;
 
  reg [117:0] data;
  reg         previous_bit;
  reg         stuff;
  reg         tmp;
  reg         arbitration_lost;
  integer     pointer;
  integer     cnt;
  integer     total_bits;
  integer     stuff_cnt;
 
  begin
 
    stuff_cnt = 1;
    stuff = 0;
 
    if(mode)          // Extended format
      data = {id[28:18], 1'b1, 1'b1, id[17:0], remote_trans_req, 2'h0, length};
    else              // Standard format
      data = {id[10:0], remote_trans_req, 1'b0, 1'b0, length};
 
    if (~remote_trans_req)
      begin
        if(length)    // Send data if length is > 0
          begin
            for (cnt=1; cnt<=(2*length); cnt=cnt+1)  // data   (we are sending nibbles)
              data = {data[113:0], cnt[3:0]};
          end
      end
 
    // Adding CRC
    data = {data[104:0], crc[14:0]};
 
 
    // Calculating pointer that points to the bit that will be send
    if (remote_trans_req)
      begin
        if(mode)          // Extended format
          pointer = 52;
        else              // Standard format
          pointer = 32;
      end
    else
      begin
        if(mode)          // Extended format
          pointer = 52 + 8 * length;
        else              // Standard format
          pointer = 32 + 8 * length;
      end
 
    // This is how many bits we need to shift
    total_bits = pointer;
 
    // Waiting until previous msg is finished before sending another one
    if (arbitration_lost)           //  Arbitration lost. Another node is transmitting. We have to wait until it is finished.
      wait ( (~can_testbench.i_can_top.i_can_bsp.error_frame) & 
             (~can_testbench.i_can_top.i_can_bsp.rx_inter   ) & 
             (~can_testbench.i_can_top.i_can_bsp.tx_state   )
           );
    else                            // We were transmitter of the previous frame. No need to wait for another node to finish transmission.
      wait ( (~can_testbench.i_can_top.i_can_bsp.error_frame) & 
             (~can_testbench.i_can_top.i_can_bsp.rx_inter   )
           );
    arbitration_lost = 0;
 
    send_bit(0);                        // SOF
    previous_bit = 0;
 
    fork 
 
    begin
      for (cnt=0; cnt<=total_bits; cnt=cnt+1)
        begin
          if (stuff_cnt == 5)
            begin
              stuff_cnt = 1;
              total_bits = total_bits + 1;
              stuff = 1;
              tmp = ~data[pointer+1];
              send_bit(~data[pointer+1]);
              previous_bit = ~data[pointer+1];
            end
          else
            begin
              if (data[pointer] == previous_bit)
                stuff_cnt <= stuff_cnt + 1;
              else
                stuff_cnt <= 1;
 
              stuff = 0;
              tmp = data[pointer];
              send_bit(data[pointer]);
              previous_bit = data[pointer];
              pointer = pointer - 1;
            end
          if (arbitration_lost)
            cnt=total_bits+1;         // Exit the for loop
        end
 
        // Nothing send after the data (just recessive bit)
        repeat (13) send_bit(1);         // CRC delimiter + ack + ack delimiter + EOF + intermission= 1 + 1 + 1 + 7 + 3
    end
 
    begin
      while (mode ? (cnt<32) : (cnt<12))
        begin
          #1 wait (can_testbench.i_can_top.sample_point);
          if (mode)
            begin
              if (cnt<32 & tmp & (~rx_and_tx))
                begin
                  arbitration_lost = 1;
                  rx = 1;       // Only recessive is send from now on.
                end
            end
          else
            begin
              if (cnt<12 & tmp & (~rx_and_tx))
                begin
                  arbitration_lost = 1;
                  rx = 1;       // Only recessive is send from now on.
                end
            end
        end
    end
 
    join
 
  end
endtask
 
 
 
// State machine monitor (btl)
always @ (posedge clk)
begin
  if(can_testbench.i_can_top.i_can_btl.go_sync & can_testbench.i_can_top.i_can_btl.go_seg1 | can_testbench.i_can_top.i_can_btl.go_sync & can_testbench.i_can_top.i_can_btl.go_seg2 | 
     can_testbench.i_can_top.i_can_btl.go_seg1 & can_testbench.i_can_top.i_can_btl.go_seg2)
    begin
      $display("(%0t) ERROR multiple go_sync, go_seg1 or go_seg2 occurance\n\n", $time);
      #1000;
      $stop;
    end
 
  if(can_testbench.i_can_top.i_can_btl.sync & can_testbench.i_can_top.i_can_btl.seg1 | can_testbench.i_can_top.i_can_btl.sync & can_testbench.i_can_top.i_can_btl.seg2 | 
     can_testbench.i_can_top.i_can_btl.seg1 & can_testbench.i_can_top.i_can_btl.seg2)
    begin
      $display("(%0t) ERROR multiple sync, seg1 or seg2 occurance\n\n", $time);
      #1000;
      $stop;
    end
end
 
/* stuff_error monitor (bsp)
always @ (posedge clk)
begin
  if(can_testbench.i_can_top.i_can_bsp.stuff_error)
    begin
      $display("\n\n(%0t) Stuff error occured in can_bsp.v file\n\n", $time);
      $stop;                                      After everything is finished add another condition (something like & (~idle)) and enable stop
    end
end
*/
 
//
// CRC monitor (used until proper CRC generation is used in testbench
always @ (posedge clk)
begin
  if (can_testbench.i_can_top.i_can_bsp.rx_ack       &
      can_testbench.i_can_top.i_can_bsp.sample_point & 
      can_testbench.i_can_top.i_can_bsp.crc_err
     )
    $display("*E (%0t) ERROR: CRC error (Calculated crc = 0x%0x, crc_in = 0x%0x)", $time, can_testbench.i_can_top.i_can_bsp.calculated_crc, can_testbench.i_can_top.i_can_bsp.crc_in);
end
 
 
 
 
 
/*
// overrun monitor
always @ (posedge clk)
begin
  if (can_testbench.i_can_top.i_can_bsp.i_can_fifo.wr & can_testbench.i_can_top.i_can_bsp.i_can_fifo.fifo_full)
    $display("(%0t)overrun", $time);
end
*/
 
 
// form error monitor
always @ (posedge clk)
begin
  if (can_testbench.i_can_top.i_can_bsp.form_err)
    $display("*E (%0t) ERROR: form_error", $time);
end
 
 
 
// acknowledge error monitor
always @ (posedge clk)
begin
  if (can_testbench.i_can_top.i_can_bsp.ack_err)
    $display("*E (%0t) ERROR: acknowledge_error", $time);
end
 
 
endmodule