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

////                                                              ////

////  flow_ctrl.v                                                 ////

////                                                              ////

////  This file is part of the Ethernet IP core project           ////

////  http://www.opencores.org/projects.cgi/web/ethernet_tri_mode/////

////                                                              ////

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

////      - Jon Gao (gaojon@yahoo.com)                            ////

////                                                              ////

////                                                              ////

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

////                                                              ////

//// Copyright (C) 2001 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                     ////

////                                                              ////

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

//                                                                    

// CVS Revision History                                               

//                                                                    

// $Log: not supported by cvs2svn $

// Revision 1.2  2005/12/16 06:44:19  Administrator

// replaced tab with space.

// passed 9.6k length frame test.

//

// Revision 1.1.1.1  2005/12/13 01:51:45  Administrator

// no message

//                                           

module flow_ctrl

(

Reset               ,

Clk                 ,

//host processor    ,

tx_pause_en         ,

xoff_cpu            ,

xon_cpu             ,

//MAC_rx_flow       ,

pause_quanta        ,

pause_quanta_val    ,

//MAC_tx_ctrl       ,

pause_apply         ,

pause_quanta_sub    ,

xoff_gen            ,

xoff_gen_complete   ,

xon_gen             ,

xon_gen_complete

);

input           Reset               ;

input           Clk                 ;

                //host processor    ;

input           tx_pause_en         ;

input           xoff_cpu            ;

input           xon_cpu             ;

                //MAC_rx_flow       ;

input   [15:0]  pause_quanta        ;

input           pause_quanta_val    ;

                //MAC_tx_ctrl       ;

output          pause_apply         ;

input           pause_quanta_sub    ;

output          xoff_gen            ;

input           xoff_gen_complete   ;

output          xon_gen             ;

input           xon_gen_complete    ;

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

//internal signals                                                              

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

reg             xoff_cpu_dl1            ;

reg             xoff_cpu_dl2            ;

reg             xon_cpu_dl1             ;

reg             xon_cpu_dl2             ;

reg [15:0]      pause_quanta_dl1        ;

reg             pause_quanta_val_dl1    ;

reg             pause_quanta_val_dl2    ;

reg             pause_apply             ;

reg             xoff_gen                ;

reg             xon_gen                 ;

reg [15:0]      pause_quanta_counter    ;

reg             tx_pause_en_dl1         ;

reg             tx_pause_en_dl2         ;

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

//boundery signal processing                                                               

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

always @ (posedge Clk or posedge Reset)

    if (Reset)

        begin

        xoff_cpu_dl1        <=0;

        xoff_cpu_dl2        <=0;

        end

    else

        begin

        xoff_cpu_dl1        <=xoff_cpu;

        xoff_cpu_dl2        <=xoff_cpu_dl1;

        end

always @ (posedge Clk or posedge Reset)

    if (Reset)

        begin

        xon_cpu_dl1     <=0;

        xon_cpu_dl2     <=0;

        end

    else

        begin

        xon_cpu_dl1     <=xon_cpu;

        xon_cpu_dl2     <=xon_cpu_dl1;

        end

always @ (posedge Clk or posedge Reset)

    if (Reset)

        begin

        pause_quanta_dl1        <=0;

        end

    else

        begin

        pause_quanta_dl1        <=pause_quanta;

        end

always @ (posedge Clk or posedge Reset)

    if (Reset)

        begin

        pause_quanta_val_dl1    <=0;

        pause_quanta_val_dl2    <=0;

        end

    else

        begin

        pause_quanta_val_dl1    <=pause_quanta_val;

        pause_quanta_val_dl2    <=pause_quanta_val_dl1;

        end

always @ (posedge Clk or posedge Reset)

    if (Reset)

        begin

        tx_pause_en_dl1     <=0;

        tx_pause_en_dl2     <=0;

        end

    else

        begin

        tx_pause_en_dl1     <=tx_pause_en;

        tx_pause_en_dl2     <=tx_pause_en_dl1;

        end

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

//gen output signals                                                            

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

always @ (posedge Clk or posedge Reset)

    if (Reset)

        xoff_gen        <=0;

    else if (xoff_gen_complete)

        xoff_gen        <=0;

    else if (xoff_cpu_dl1&&!xoff_cpu_dl2)

        xoff_gen        <=1;

always @ (posedge Clk or posedge Reset)

    if (Reset)

        xon_gen     <=0;

    else if (xon_gen_complete)

        xon_gen     <=0;

    else if (xon_cpu_dl1&&!xon_cpu_dl2)

        xon_gen     <=1;

always @ (posedge Clk or posedge Reset)

    if (Reset)

        pause_quanta_counter    <=0;

    else if(pause_quanta_val_dl1&&!pause_quanta_val_dl2)

        pause_quanta_counter    <=pause_quanta_dl1;

    else if(pause_quanta_sub&&pause_quanta_counter!=0)

        pause_quanta_counter    <=pause_quanta_counter-1;

always @ (posedge Clk or posedge Reset)

    if (Reset)

        pause_apply     <=0;

    else if(pause_quanta_counter==0)

        pause_apply     <=0;

    else if (tx_pause_en_dl2)

        pause_apply     <=1;

endmodule