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

////                                                              ////

////  File name "encoder_10b_rx_model.v"                          ////

////                                                              ////

////  This file is part of the :                                  ////

////                                                              ////

//// "1000BASE-X IEEE 802.3-2008 Clause 36 - PCS project"         ////

////                                                              ////

////  http://opencores.org/project,1000base-x                     ////

////                                                              ////

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

////      - D.W.Pegler Cambridge Broadband Networks Ltd           ////

////                                                              ////

////      { peglerd@gmail.com, dwp@cambridgebroadand.com }        ////

////                                                              ////

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

////                                                              ////

//// Copyright (C) 2009 AUTHORS. All rights reserved.             ////

////                                                              ////

//// 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                     ////

////                                                              ////

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

////                                                              ////

//// This module is based on the coding method described in       ////

//// IEEE Std 802.3-2008 Clause 36 "Physical Coding Sublayer(PCS) ////

//// and Physical Medium Attachment (PMA) sublayer, type          ////

//// 1000BASE-X"; see :                                           ////

////                                                              ////

//// http://standards.ieee.org/about/get/802/802.3.html           ////

//// and                                                          ////

//// doc/802.3-2008_section3.pdf, Clause/Section 36.              ////

////                                                              ////

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

`include "timescale_tb.v"

module encoder_10b_rx_model #(

  parameter DEBUG       = 0,

  parameter out_delay   = 5,

  parameter in_delay    = 2

)(

  interface check_intf,

   // --- Clocks

   input SBYTECLK,

   input reset,

   // --- Ten bit input bus       

   input [9:0] tbi_rx

);

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

  // Checker interface functions

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

   function automatic string check_intf.whoami();

      string buffer;

      $sformat(buffer, "%m");

      return buffer.substr(0, buffer.len()-17);

   endfunction

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

   // 10B symbol, disparity and coding checker 

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

   integer     iteration = 0;

   reg [9:0]   checker_10b_symbol = 10'b0; reg [7:0] checker_8B_symbol = 8'b0;

   reg         null_rd, checker_rd, checker_k, checker_rd_err, checker_code_err;

   integer     checker_x, checker_y, checker_errors;

   task automatic encoder_10b_checker();

      // Pull the next byte

      checker_10b_symbol = tbi_rx;

      // Decode the 10b symbol from the checker model

      encoder_8b10b_threads::decode(checker_10b_symbol, checker_rd, checker_rd, checker_k,

                                    checker_8B_symbol, checker_rd_err, checker_code_err);

      // Split the 8b symbol into 5b/6b and 3b/4b components x and y - Dx.y and Kx.y 

      encoder_8b10b_threads::split(checker_8B_symbol, checker_x, checker_y);

      // Only check for errors after the first symbol

      //if (DEBUG | (iteration & (checker_rd_err | checker_code_err)))

      if (DEBUG)

        begin

           $display("Checker 10b %08d: [10b_symbol = %010b, RD = %01b, 8B_symbol = %08b, K = %01b, RD_err = %01b, CODE_err = %01b] : %s : %s%02d.%01d",

                    iteration, checker_10b_symbol,

                    checker_rd,  checker_8B_symbol, checker_k,

                    checker_rd_err, checker_code_err,

                    ((checker_rd_err | checker_code_err) ? "FAIL" : "PASSED"),

                    ((checker_k) ? "K" : "D"), checker_x, checker_y);

           // Halt if disparity or coding errors

           if (!DEBUG) $stop;

        end

      iteration++;

   endtask // automatic

  initial

    begin

       // Intlialise disparity and coding errors

       checker_k = 0; checker_rd_err = 0; checker_code_err = 0;

       // Initialise checker 8B/10b generation

       encoder_8b10b_threads::init(null_rd, checker_rd, checker_errors);

       // On startup, the receiver (decoder) should assume +ve or -ve disparity

       // See IEEE 802.3-2005 Clause 35 - 36.2.4.4

       // I'm overiding the statup disparity set in encoder_8b10b_threads::init

       // so that it starts as -ve.

       checker_rd = 0;

       // Obtain initial sync...

       @(posedge SBYTECLK);

       while (~reset)

         begin

            // Handle receive from TBI interface

            encoder_10b_checker();

            @(posedge SBYTECLK);

         end

    end

endmodule