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

//

//                             UART2BUS VERIFICATION

//

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

// CREATOR    : HANY SALAH

// PROJECT    : UART2BUS UVM TEST BENCH

// UNIT       : INTERFACE

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

// TITLE      : UART BFM

// DESCRIPTION: THIS FILE ACT AS UART MASTER DEVICE APPLY REQUESTS TO THE DUT ACROSS THE STANDARD

//              INTERFACES. IT ALSO INCLUDES ALL THE USER AND STANDARD ROUTINES THAT ARE NEED TO

//              APPLY, RECEIVE AND MONITOR UART DIFFERENT ACTIVITIES.

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

// LOG DETAILS

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

// VERSION      NAME        DATE        DESCRIPTION

//    1       HANY SALAH    25122015    FILE CREATION

//    2       HANY SALAH    07012016    ADD USER ROUTINE, TEXT MODE ROUTINES.

//    3       HANY SALAH    21012016    REPLACE PUSH BYTE WITH PUSH FIELD

//    4       HANY SALAH    31012016    ADD FAULT AND INVALID COMMAND INDICATORS

//    5       HANY SALAH    13022016    IMPROVE BLOCK DESCRIPTION & ADD COMMENTS.

//    6       HANY SALAH    15022016    ENHANCE BLOCK COMMENTS

//    7       HANY SALAH    16022016    ENHANCE BLOCK COMMENTS

//    8       HANY SALAH    17022016    FINALIZE BLOCK COMMENTS

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

// ALL COPYRIGHTS ARE RESERVED FOR THE PRODUCER ONLY .THIS FILE IS PRODUCED FOR OPENCORES MEMBERS

// ONLY AND IT IS PROHIBTED TO USE THIS MATERIAL WITHOUT THE CREATOR'S PERMISSION

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

`include "defin_lib.svh"

interface uart_interface (input bit clock,        // UART Clock Signal

                          input bit reset);       // Global Asynchronous Reset Signal

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

//

//                                       BFM PARAMETERS

//

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

  // BFM Paramenters are the ones which are set in the test file and are propagated in the whole

  // test-bench. They are defined indetails through test file and specifications document.

  // The range of possible values for all the BFM paramters is stated beside each one

  //

  // Define the active clock edge

  int                 act_edge;     // 2: negative edge   1: positive edge

  // Define the first transferred bit from the byte.

  int                 start_bit;    // 2: LSB first       1: MSB first

  // Define the number of stop bits of each UART field

  int                 num_stop_bits;// 2: two stop bits   1: one stop bits

  // Define the number of actual bits inbetween the start and stop bits.

  int                 num_bits;     // 7: seven bits data 8: eight bits data

  // Define the representation of data through the text mode.

  int                 data_rep;     // 2: binarry         1: ASCII

  // Define the parity mode used.

  int                 parity;       // 3: parity odd      2: parity even        1: parity off

  // Define the maximum allowable time between the UART request and the DUT response.

  time                response_time;

  // Define the authorization of false data usage.

  int                 falsedata_gen_en;

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

//

//                                      UART SIGNLAS

//

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

  logic               ser_in;         // Serial Data Input

  logic               ser_out;        // Serial Data Ouptut

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

//

//                                 USER VARIABLES DECLARATIONS

//

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

  // The user variables are those ones which facilitate the usage of BFM and they aren't mentioned

  // in the standard.

  //

  // Start_trans event is triggered by the driver at the start of each transaction. it would let

  // the other components wake up and poll the UART bus.

  // By triggereing this event, other connected components would know that some UART transaction

  // would be forced on the UART busses.

  event start_trans;

  // The following two bits are used only in case of apply wrong modes or wrong commands as the

  // following:

  // wrong_data_ctrl is drived by the driver to state that whether the wrong applied command

  // is read or write.

  // Actuall BFM shouldn't discriminate between both of types. Its response should be nothing!!.

  // But this indication facilitates the scoreboard work.

  bit wrong_data_ctrl;           //0:read      1: write

  // wrong_mode_ctrl is also drived by the driver to state whether the wrong applied mode is

  // text or binary.

  // Actuall BFM also shouldn't discriminate between both of types. Its response should be

  // nothing. But this indication facilitates the scoreboard work.

  bit wrong_mode_ctrl;           //0:text      1: binary

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

//

//                                       USER ROUTINES

//

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

  // Through This routine, the uart bfm initializes its configuration parameters described above.

  function void set_configuration ( int _edge,

                                    int first_bit,

                                    int _numstopbits,

                                    int _numbits,

                                    int _datarep,

                                    int _paritymode,

                                    time _resp,

                                    int _flse_en);

    act_edge        = _edge;

    start_bit       = first_bit;

    num_stop_bits   = _numstopbits;

    num_bits        = _numbits;

    data_rep        = _datarep;

    parity          = _paritymode;

    response_time   = _resp;

    falsedata_gen_en= _flse_en;

  endfunction: set_configuration

  // Through the following routine, the UART BFM makes an event that some transaction would be

  // forced on UART signals

  function void set_event ();

    -> start_trans ;

  endfunction:set_event

  // This routine is used to force data directly on serial out bus. This routine transform one

  // bit only to the form of uart. This form is defined in the definition library.

  // High value is defined by the macro `one.

  // Low value is defined by the macro `zero.

  function void force_sout(bit x);

    case (x)

      1'b1:

        begin

        ser_out = `one;

        end

      1'b0:

        begin

        ser_out = `zero;

        end

    endcase

  endfunction:force_sout

  // Through this routine, the uart bfm push bit on the serial ouptut port ser_out based on the

  // configured active edge field, UART will push bit on data. BFM will assign testbench error in

  // case of un-configured active edge.

  task push_bit_serout (input bit data);

    case (act_edge)

      `_negedge:

        begin

        @(negedge clock)

          begin

          force_sout(data);

          end

        end

      `_posedge:

        begin

        @(posedge clock)

          begin

          force_sout(data);

          end

        end

      default:

        begin

        $error("Non-configured active edge");

        end

    endcase

  endtask:push_bit_serout

  // The following task will catch single bit from serial output port ser_out based on the config-

  // ured active edge field, UART will capture data bit. Based on the configured active edge, this

  // method block the execution till the correct clock edge and then make delay of a quarter of

  // clock period to guarnttee the stability of data on the serial output port.

  // BFM will assign testbench error in case of un-configured active edge.

  task catch_bit_serout (output bit data);

    case (act_edge)

      `_negedge:

        begin

        @(negedge clock)

          begin

          #(`buad_clk_period/4) data = ser_out;

          end

        end

      `_posedge:

        begin

        @(posedge clock)

          begin

          #(`buad_clk_period/4) data = ser_out;

          end

        end

      default:

        begin

        $error("Non-configured active edge");

        end

    endcase

  endtask:catch_bit_serout

  // The following task will catch single bit from serial input port ser_in based on the config-

  // ured active edge field, UART will capture data bit. Based on the configured active edge, this

  // method block the execution till the correct clock edge and then make delay of a quarter of

  // clock period to guarnttee the stability of data on the serial input port.

  // BFM will assign testbench error in case of un-configured active edge.

  task catch_bit_serin (output bit data);

    case (act_edge)

      `_negedge:

        begin

        @(negedge clock)

          begin

          #(`buad_clk_period/4) data = ser_in;

          end

        end

      `_posedge:

        begin

        @(posedge clock)

          begin

          #(`buad_clk_period/4)data = ser_in;

          end

        end

      default:

        begin

        $error("Non-configured active edge");

        end

    endcase

  endtask:catch_bit_serin

  // Through the following task, UART BFM will force data byte on serial output port based on the

  // configured start_bit field. This mode encapsulate the data byte inbetween start,stop and even

  // parity bits. The sequence would be the following:

  // 1- Force zero bit on the serial output port as start bit.

  // 2- Send the data byte serially bit by bit.

  // 3- Accoriding to configured parity, force parity bit (optional).

  // 4- Insert one or two stop bits according to BFM configuration.

  // BFM will assign testbench error in case of un-configured parameters.

  task push_field_serout (input byte data);

    bit temp;

    // start bit

    push_bit_serout(1'b0);

    // data fields

    case (start_bit)

      `lsb_first:

        begin

        for (int index=0;index<8;index++)

          begin

          push_bit_serout(data[index]);

          end

        end

      `msb_first:

        begin

        for (int index=7;index>=0;index--)

          begin

          push_bit_serout(data[index]);

          end

        end

      default:

        begin

        $error("Undefined serial mode");

        end

    endcase

    // parity bits

    if(parity == `_parityeven)

      begin

      temp=1'b1;

      for (int index=0;index <8;index++)

        begin

        temp = temp ^ data [index];

        end

      end

    else if(parity == `_parityodd)

      begin

      temp=1'b0;

      for (int index=0;index <8;index++)

        begin

        temp = temp ^ data [index];

        end

      end

    else if (parity != `_parityoff)

      begin

      $error("un-configured parity");

      end

    // Stop bit(s)

    repeat (num_stop_bits)

      begin

      push_bit_serout(1'b1);

      end

  endtask:push_field_serout

  // Through the following task, UART BFM will catpure UART field from serial output port based on

  // the configured start_bit field. The following sequence is carried out :

  // 1- Wait start bit.

  // 2- Catpure the following eight bits in packed byte depending on the configured start bit.

  // 3- Depending on the configured number of stop bits, the stop bit(s) are captured.

  //    - In case that stop bit(s) is zero, the testbench will assign testbench error.

  // BFM will assign testbench error in case of un-configured start_bit field.

  task catch_field_serout (output byte data);

    bit end_bit;

    // wait start bit

    wait(ser_out == 1'b0);

    case(start_bit)

      `lsb_first:

        begin

        for (int index=0;index<8;index++)

          begin

          catch_bit_serout(data[index]);

          end

        end

      `msb_first:

        begin

        for (int index=7;index>=0;index--)

          begin

          catch_bit_serout(data[index]);

          end

        end

      default:

        begin

        $error("Undefined serial mode");

        end

    endcase

    catch_bit_serout(end_bit);

    if(end_bit != 1'b1)

      begin

      $error("at time =%0t ,, the first end bit = %0b",$time,end_bit);

      end

    if (num_stop_bits == 2)

      begin

      catch_bit_serout(end_bit);

      if(end_bit != 1'b1)

        begin

        $error("at time =%0t ,, the first end bit = %0b",$time,end_bit);

        end

      end

  endtask:catch_field_serout

  // Through the following task, UART BFM will catpure UART field from serial input port based on

  // the configured start_bit field. The applied sequence here differs from the one applied on

  // capture field from serial output port since wrong and unknown commands are forced to the DUT

  // on the UART interface. The DUT is supposed to make no response to such commands.

  // This routine pays concern to this issue by initiating two parallel threads at the beginning;

  // 1- The first one run in the background to wait response time and triggered some internal

  //    event (terminate event). It also set internal bit (path_select) to zero to make an

  // indication that no response has been made.

  // 2- The second one includes two parallel sub-threads:

  //    a- The first one wait start bit.

  //    b- The other one wait terminate event triggering.

  //    Whenever one of those sub-threads is terminated, The main thread is joined.

  // The following sequence is carried out in case that start bit is captured:

  // 1- Wait start bit.

  // 2- Catpure the following eight bits in packed byte depending on the configured start bit.

  // 3- Depending on the configured number of stop bits, the stop bit(s) are captured.

  //    - In case that stop bit(s) is zero, the testbench will assign testbench error.

  // BFM will assign testbench error in case of un-configured start_bit field.

  task catch_field_serin (output byte data);

    bit end_bit;

    bit path_select;

    event terminate;

    path_select = 1'b1;

    fork

      begin

      #response_time;

      -> terminate;

      path_select = 1'b0;

      end

    join_none

    fork

      wait (ser_in == 1'b0);

      wait (terminate);

    join_any

    if (path_select)

      begin

      #(`buad_clk_period/2);

      case(start_bit)

        `lsb_first:

          begin

          for (int index=0;index<8;index++)

            begin

            catch_bit_serin(data[index]);

            end

          end

        `msb_first:

          begin

          for (int index=7;index>=0;index--)

            begin

            catch_bit_serin(data[index]);

            end

          end

        default:

          begin

          $error("Undefined serial mode");

          end

      endcase

      catch_bit_serin(end_bit);

      if(end_bit != 1'b1)

        begin

        $error("at time =%0t ,, the first end bit = %0b",$time,end_bit);

        end

      if (num_stop_bits == 2)

        begin

        catch_bit_serin(end_bit);

        if(end_bit != 1'b1)

          begin

          $error("at time =%0t ,, the first end bit = %0b",$time,end_bit);

          end

        end

      end

  endtask:catch_field_serin

  // Through the following function, the byte is reversed in the manner where the byte is merrored

  function byte reverse_byte (byte data);

    byte tmp;

    for (int index=0;index<8;index++)

      begin

      tmp[index] = data[7-index];

      end

    return tmp;

  endfunction:reverse_byte

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

//

//                                      UART ROUTINES

//

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

  // This method is provided to initiate write request in UART text mode. This task is accomplis-

  // hed through the following sequence:

  // 1- The first field :(Prefix Character)

  //    Depending on whether the mode type is text or wrong text and whether the prefix is small

  //    or capital character, the BFM force the prefix field. In case of wrong text type, the init-

  //    ial field is the provided wrong_prefix input. also internal wrong_mode_ctrl bit is cleared.

  //    - In case of undefined type, testbench assign testbench error.

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

  // 2- The second field:(White Space Character)

  //    Depending on whether the used white space type is a single space, a tab space or provided

  //    wrong space character is forced on the serial output port.

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

  // 3- The third field:(Data Character)

  //    - In case of the data representation is binary, the data input character is encapsulated

  //      in UART field and forced in single field.

  //    - In case of the data representation is ASCII, the data input character is divided into

  //      two nipples. Each one is converted to ASCII character and sent separately in UART field.

  //      The most significant nipple is sent first.

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

  // 4- The forth field:(White Space Character)

  //    Depending on whether the used white space type is a single space, a tab space or provided

  //    wrong space character is forced on the serial output port.

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

  // 5- The fifth field:(Address Two-Character)

  //    - In case of the data representation is binary, the address input two-character is divided

  //      into two characters. They are encapsulated into two successive UART fields.

  //    - In case of the data representation is ASCII, the address input two-character is divided

  //      into four nipples. Each one is converted to ASCII character and sent separately in UART

  //      field. The ASCII characters are sent where the most significant nipple is sent first.

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

  // 6- The sixth field:(End-Of-Line Character):

  //    Depending on whether the used EOL type is CR, LF or provided wrong space character is

  //    forced on the serial output port.

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

  task write_text_mode(input int _type,

                       input byte wrong_prefix,

                       input int alph,

                       input int scp_type1,

                       input byte space_wrong1,

                       input int scp_type2,

                       input byte space_wrong2,

                       input int eol,

                       input byte eol_wrong,

                       input bit [`size-1:0] address,

                       input byte data);

    // Write procedures

    // First Field

    case (_type)

      `text_mode:

        begin

        if (alph == `small_let)

          begin

          push_field_serout(`w);

          end

        else if (alph == `capital_let)

          begin

          push_field_serout(`W);

          end

        else

          $error("Testbench error .. No capitar or small letter is choosed");

        end

      `wrong_mode_txt:

        begin

        push_field_serout(wrong_prefix);

        wrong_mode_ctrl = 1'b0;

        end

      default:

        begin

        $error("Undefined communication mode ..");

        end

    endcase

    // Second Field

    if (scp_type1 == `single_space)

      begin

      push_field_serout(`space);

      end

    else if (scp_type1 == `tab_space)

      begin

      push_field_serout(`tab);

      end

    else if (scp_type1 == `space_wrong)

      begin

      push_field_serout(space_wrong1);

      end

    else

      $error("Testbench error .. No single space or multiple space is choosed");

    // third field

    case (data_rep)

      `binary_rep:

        begin

        push_field_serout(data);

        end

      `ascii_rep:

        begin

        push_field_serout(bin_asci_conv(data[7:4]));

        push_field_serout(bin_asci_conv(data[3:0]));

        end

      default:$error("undefined data representation");

    endcase

    // forth field

    if (scp_type2 == `single_space)

      begin

      push_field_serout(`space);

      end

    else if (scp_type2 == `tab_space)

      begin

      push_field_serout(`tab);

      end

    else if (scp_type2 == `space_wrong)

      begin

      push_field_serout(space_wrong2);

      end

    else

      $error("Testbench error .. No single or multiple space is choosed");

    // fivth field

    case (data_rep)

      `binary_rep:

        begin

        push_field_serout(address[15:08]);

        push_field_serout(address[07:00]);

        end

      `ascii_rep:

        begin

        push_field_serout(bin_asci_conv(address[15:12]));

        push_field_serout(bin_asci_conv(address[11:08]));

        push_field_serout(bin_asci_conv(address[07:04]));

        push_field_serout(bin_asci_conv(address[03:00]));

        end

      default:$error("undefined data representation");

    endcase

    // sixth Field

    if (eol == `cr_eol)

      begin

      push_field_serout(`CR);

      end

    else if (eol == `lf_eol)

      begin

      push_field_serout(`LF);

      end

    else if (eol == `eol_wrong)

      begin

      push_field_serout(eol_wrong);

      end

    else

      $error("Testbench error .. either CR or LF isn't choosed as eol");

  endtask:write_text_mode

  // This method is provided to initiate read request in UART text mode. This task is accomplis-

  // hed through the following sequence:

  // 1- The first field :(Prefix Character)

  //    Depending on whether the mode type is text or wrong text and whether the prefix is small

  //    or capital character, the BFM force the prefix field. In case of wrong text type, the init-

  //    ial field is the provided wrong_prefix input. also internal wrong_mode_ctrl bit is cleared.

  //    - In case of undefined type, testbench assign testbench error.

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

  // 2- The second field:(White Space Character)

  //    Depending on whether the used white space type is a single space, a tab space or provided

  //    wrong space character is forced on the serial output port.

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

  // 3- The third field:(Address Two-Character)

  //    - In case of the data representation is binary, the address input two-character is divided

  //      into two characters. They are encapsulated into two successive UART fields.

  //    - In case of the data representation is ASCII, the address input two-character is divided

  //      into four nipples. Each one is converted to ASCII character and sent separately in UART

  //      field. The ASCII characters are sent where the most significant nipple is sent first.

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

  // 4- The forth field:(End-Of-Line Character):

  //    Depending on whether the used EOL type is CR, LF or provided wrong space character is

  //    forced on the serial output port.

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

  // GETTING RESPONSE :

  //    Since we may have no response due to either DUT internal bug or the forced request is

  //    wrong (wrong mode, wrong white space, wrong eol), two parallel threads are initiated; The

  //    first one is to wait for response time and the other one waits start bit on the serial

  //    input port. Both the two threads are terminated by meeting only one of the two events.

  //    In case of the start bit is captured and according to the configured the data representa-

  //    tion.

  //    - If it is binary, the following UART field is captured and its data is considered to be

  //      the requested data.

  //    - If it is ASCII, the two successive UART fields is captured and each byte is converted to

  //      binary nipple.

  //    The following character is captured and it must be CR.

  //    The following character is captured and it must be LF.

  //    - If the last two characters aren't as indicated above, the testbench will assign testbench

  //      error.

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

  task read_text_mode (input int _type,

                       input byte wrong_prefix,

                       input int alph,

                       input int scp_type,

                       input byte space_wrong,

                       input int eol,

                       input byte eol_wrong,

                       input bit [`size-1:0] address,

                       input byte false_data,

                       input int false_data_en);

    byte data;

    byte temp;

    byte char1,char2;

    bit miss;

    // Read Request

    // First Field

    case (_type)

      `text_mode:

        begin

        if (alph == `small_let)

          begin

          push_field_serout(`r);

          end

        else if (alph == `capital_let)

          begin

          push_field_serout(`R);

          end

        else

          $error("Testbench error .. No capitar or small letter is choosed");

        end

      `wrong_mode_txt:

        begin

        push_field_serout(wrong_prefix);

        wrong_mode_ctrl = 1'b0;

        end

      default:

        begin

        $error("Undefined communication mode ..");

        end

    endcase

    // Second Field

    if (scp_type == `single_space)

      begin

      push_field_serout(`space);

      end

    else if (scp_type == `tab_space)

      begin

      push_field_serout(`tab);

      end

    else if (scp_type == `space_wrong)

      begin

      push_field_serout(space_wrong);

      end

    else

      $error("Testbench error .. No single or multiple white space is choosed");

    // Third Field

    case (data_rep)

      `binary_rep:

        begin

        push_field_serout(address[15:08]);

        push_field_serout(address[07:00]);

        end

      `ascii_rep:

        begin

        push_field_serout(bin_asci_conv(address[15:12]));

        push_field_serout(bin_asci_conv(address[11:08]));

        push_field_serout(bin_asci_conv(address[07:04]));

        push_field_serout(bin_asci_conv(address[03:00]));

        end

      default:$error("undefined data representation");

    endcase

    // Forth Field

    if (eol == `cr_eol)

      begin

      push_field_serout(`CR);

      end

    else if (eol == `lf_eol)

      begin

      push_field_serout(`LF);

      end

    else if (eol == `eol_wrong)

      begin

      push_field_serout(eol_wrong);

      end

    else

      $error("Testbench error .. No CR or LF is choosed");

    miss = 1'b0;

    fork

      begin: miss_response_thread

      # response_time;

      disable capture_response_thread;

      miss = 1'b1;

      end

      begin: capture_response_thread

      wait(ser_in == 1'b0);

      disable miss_response_thread;

      end

    join

    // Capture Response

    if (miss == 1'b0)

      begin

      if (false_data_en ==`_yes && falsedata_gen_en == `_yes)

        begin

        fork

        push_field_serout(false_data);

        join_none

        end

      case (data_rep)

        `binary_rep:

          begin

          catch_field_serin(data);

          end

        `ascii_rep:

          begin

          catch_field_serin(temp);

          data[7:4] = asci_bin_conv(temp);

          catch_field_serin(temp);

          data[3:0] = asci_bin_conv(temp);

          end

        default:

          begin

          $error("Undefined data representation");

          $stop;

          end

      endcase

      catch_field_serin(char1);

      catch_field_serin(char2);

      if (char1 != `CR || char2 != `LF)

        begin

        $error("EOL is refuesed");

        end

      end

  endtask:read_text_mode

  // This method is provided to initiate write request in UART binary mode. This task is accompli-

  // shed through the following sequence:

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

  //          NOTE :: ALL THE FOLLOWING BYTES ARE ENCAPSULATED INTO DEFINED UART FIELD FORM

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

  // 1- The first byte :(Prefix byte)

  //    Depending on whether the mode type is binary or wrong binary the BFM force the prefix field

  //    In case of wrong binary type, the initial field is the provided wrong_prefix input. also

  //    internal wrong_mode_ctrl bit is set.

  //    - In case of undefined type, testbench assign testbench error.

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

  // 2- The second byte:(Command byte)

  //    Depending on whether the command is valid or invalid command, the two bits of the command

  //    are assigned. Also the auto increment bit and acknowledge request bit are assigned

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

  // 3- The third byte:(Address highest byte)

  //    - The address bits [15:08] .

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

  // 4- The forth field:(Address lowest byte)

  //    - The address bits [07:00] .

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

  // 5- The fifth field:(Length Of Data byte)

  //    - The number of data bytes inclosed into this stimulus.

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

  // 6- The rest fields:(Data):

  //    Data Bytes are sent one by one.

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

  // GETTING RESPONSE:

  //    In case that the command includes acknowledge request, UART BFM will wait for the ackno-

  //    wledge unified character.

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

  task automatic write_binary_mode (input int _type,

                                    input byte wrong_prefix,

                                    input int command,

                                    input int reqack,

                                    input int reqinc,

                                    input int unsigned data_length,

                                    input bit [`size-1:0] address,

                                    ref byte data []);

    byte tmp;

    int unsigned index;

    // first byte : binary prefix

    case(_type)

    `binary_mode:

      begin

      push_field_serout(`bin_prfx);

      end

    `wrong_mode_binry:

      begin

      push_field_serout(wrong_prefix);

      wrong_mode_ctrl = 1'b1;

      end

    default:

      begin

      $error("Undefined Communication Mode");

      end

    endcase

    // second byte : command

    case(command)

      `write_comm:

        begin

        tmp[5:4] = `write_ctrl;

        end

      `wrong_comm_write:

        begin

        tmp[5:4] = `invalid_ctrl;

        wrong_data_ctrl = 1'b1;

        end

      default:

        begin

        $error("Undefined Command");

        end

    endcase

    tmp[5:4] = 2'b10;

    if(reqinc==`_yes)

      begin

      tmp[1] = 1'b0;

      end

    else if (reqinc == `_no)

      begin

      tmp[1] = 1'b1;

      end

    else

      begin

      $error("undefined increment request");

      end

    if(reqack==`_yes)

      begin

      tmp[0] = 1'b1;

      end

    else if (reqack == `_no)

      begin

      tmp[0] = 1'b0;

      end

    else

      begin

      $error("undefined acknowledge request");

      end

    push_field_serout(tmp);

    // Third byte : higher byte of address

    push_field_serout(address[15:08]);

    // Forth byte : Lower byte of address

    push_field_serout(address[07:00]);

    // Fifth byte : data length

    push_field_serout(data_length);

    index = 0;

    while(index

      begin

      push_field_serout(data[index]);

      index++;

      end

    if (reqack == `_yes)

      begin

      catch_field_serin(tmp);

      if (tmp != `ACK)

        begin

        $error("The captured acknowledge isn't as unified character");

        end

      end

  endtask:write_binary_mode

  // This method is provided to initiate read request in UART binary mode. This task is accompli-

  // shed through the following sequence:

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

  //          NOTE :: ALL THE FOLLOWING BYTES ARE ENCAPSULATED INTO UART DEFINED FIELD FORM

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

  // 1- The first byte :(Prefix byte)

  //    Depending on whether the mode type is binary or wrong binary the BFM force the prefix field

  //    In case of wrong binary type, the initial field is the provided wrong_prefix input. also

  //    internal wrong_mode_ctrl bit is set.

  //    - In case of undefined type, testbench assign testbench error.

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

  // 2- The second byte:(Command byte)

  //    Depending on whether the command is valid or invalid command, the two bits of the command

  //    are assigned. Also the auto increment bit and acknowledge request bit are assigned