Subversion Repositories turbo8051

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

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////  Tubo 8051 cores MAC Interface Module                        ////

////                                                              ////

////  This file is part of the Turbo 8051 cores project           ////

////  http://www.opencores.org/cores/turbo8051/                   ////

////                                                              ////

////  Description                                                 ////

////  Turbo 8051 definitions.                                     ////

////                                                              ////

////  To Do:                                                      ////

////    nothing                                                   ////

////                                                              ////

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

////      - Dinesh Annayya, dinesha@opencores.org                 ////

////                                                              ////

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////                                                              ////

//// Copyright (C) 2000 Authors and OPENCORES.ORG                 ////

////                                                              ////

//// 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                     ////

////                                                              ////

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/***************************************************************

  Description:

        Synchronizes the pulse from one clock to another

 * clock domain

***********************************************************************/

//`timescale 1ns/100ps

module s2f_sync (

                   //outputs

                   sync_out_pulse,

                   //inputs

                   in_pulse,

                   dest_clk,

                   reset_n);

  output sync_out_pulse; //output synchronised to slow clock

  input  in_pulse;       //input based on fast clock, pulse

  input  dest_clk;           //slow clock

  input  reset_n;

  reg    sync1_out, sync2_out, sync3_out;

  always @(posedge dest_clk or negedge reset_n)

    begin

      if (!reset_n)

        begin

          sync1_out <= 0;

          sync2_out <= 0;

          sync3_out <= 0;

        end // if (!reset_n)

      else

        begin

          sync1_out <= in_pulse;

          sync2_out <= sync1_out;

          sync3_out <= sync2_out;

        end // else: !if(reset_n)

    end // always @ (posedge dest_clk or negedge reset_n)

  assign sync_out_pulse = sync2_out && !sync3_out;

endmodule // s2f_sync