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

////                                                              ////

////  File name "sync_module.v"                                   ////

////                                                              ////

////  This file is part of the "PCI bridge" project               ////

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

////                                                              ////

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

////      - Tadej Markovic, tadej@opencores.org                   ////

////                                                              ////

////  All additional information is avaliable in the README.txt   ////

////  file.                                                       ////

////                                                              ////

////                                                              ////

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

////                                                              ////

//// Copyright (C) 2000 Tadej Markovic, tadej@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                     ////

////                                                              ////

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

//

// CVS Revision History

//

// $Log: not supported by cvs2svn $

// Revision 1.2  2003/03/26 13:16:18  mihad

// Added the reset value parameter to the synchronizer flop module.

// Added resets to all synchronizer flop instances.

// Repaired initial sync value in fifos.

//

// Revision 1.1  2003/01/27 16:49:31  mihad

// Changed module and file names. Updated scripts accordingly. FIFO synchronizations changed.

//

// Revision 1.1  2002/02/01 14:43:31  mihad

// *** empty log message ***

//

//

//

// synopsys translate_off

`include "timescale.v"

// synopsys translate_on

module pci_sync_module

(

                                        set_clk_in,

                                        delete_clk_in,

                                        reset_in,

                                        delete_set_out,

                                        block_set_out,

                                        delete_in

);

// system inputs from two clock domains

input   set_clk_in;

input   delete_clk_in;

input   reset_in;

// control outputs

output  delete_set_out;

output  block_set_out;

// control input

input   delete_in;

// internal signals

reg             del_bit;

wire    meta_del_bit;

reg             sync_del_bit;

reg             delayed_del_bit;

wire    meta_bckp_bit;

reg             sync_bckp_bit;

reg             delayed_bckp_bit;

// DELETE_IN input FF - when set must be active, until it is sinchronously cleared

always@(posedge delete_clk_in or posedge reset_in)

begin

        if (reset_in)

                del_bit <= 1'b0;

        else

        begin

                if (!delayed_bckp_bit && sync_bckp_bit)

                        del_bit <= 1'b0;

                else if (delete_in)

                        del_bit <= 1'b1;

        end

end

assign  block_set_out = del_bit;

// interemediate stage to clk synchronization flip - flops - this ones are prone to metastability

pci_synchronizer_flop   #(1, 0) delete_sync

(

    .data_in        (del_bit),

    .clk_out        (set_clk_in),

    .sync_data_out  (meta_del_bit),

    .async_reset    (reset_in)

) ;

// Final synchronization of del_bit signal to the set clock domain

always@(posedge set_clk_in or posedge reset_in)

begin

        if (reset_in)

                sync_del_bit <= 1'b0;

        else

                sync_del_bit <= meta_del_bit;

end

// Delayed sync_del_bit signal for one clock period pulse generation

always@(posedge set_clk_in or posedge reset_in)

begin

        if (reset_in)

                delayed_del_bit <= 1'b0;

        else

                delayed_del_bit <= sync_del_bit;

end

assign  delete_set_out = !delayed_del_bit && sync_del_bit;

// interemediate stage to clk synchronization flip - flops - this ones are prone to metastability

pci_synchronizer_flop   #(1, 0) clear_delete_sync

(

    .data_in        (sync_del_bit),

    .clk_out        (delete_clk_in),

    .sync_data_out  (meta_bckp_bit),

    .async_reset    (reset_in)

) ;

// Final synchronization of sync_del_bit signal to the delete clock domain

always@(posedge delete_clk_in or posedge reset_in)

begin

        if (reset_in)

                sync_bckp_bit <= 1'b0;

        else

                sync_bckp_bit <= meta_bckp_bit;

end

// Delayed sync_bckp_bit signal for one clock period pulse generation

always@(posedge delete_clk_in or posedge reset_in)

begin

        if (reset_in)

                delayed_bckp_bit <= 1'b0;

        else

                delayed_bckp_bit <= sync_bckp_bit;

end

endmodule