Subversion Repositories ssp_uart

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

//

//  Copyright 2006-2013 by Michael A. Morris, dba M. A. Morris & Associates

//

//  All rights reserved. The source code contained herein is publicly released

//  under the terms and conditions of the GNU Lesser Public License. No part of

//  this source code may be reproduced or transmitted in any form or by any

//  means, electronic or mechanical, including photocopying, recording, or any

//  information storage and retrieval system in violation of the license under

//  which the source code is released.

//

//  The source code contained herein is free; it may be redistributed and/or

//  modified in accordance with the terms of the GNU Lesser General Public

//  License as published by the Free Software Foundation; either version 2.1 of

//  the GNU Lesser General Public License, or any later version.

//

//  The source code contained herein is freely released WITHOUT ANY WARRANTY;

//  without even the implied warranty of MERCHANTABILITY or FITNESS FOR A

//  PARTICULAR PURPOSE. (Refer to the GNU Lesser General Public License for

//  more details.)

//

//  A copy of the GNU Lesser General Public License should have been received

//  along with the source code contained herein; if not, a copy can be obtained

//  by writing to:

//

//  Free Software Foundation, Inc.

//  51 Franklin Street, Fifth Floor

//  Boston, MA  02110-1301 USA

//

//  Further, no use of this source code is permitted in any form or means

//  without inclusion of this banner prominently in any derived works.

//

//  Michael A. Morris

//  Huntsville, AL

//

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

`timescale 1ns / 1ps

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

// Company:         Alpha Beta Technologies, Inc.

// Engineer:        Michael A. Morris 

// 

// Create Date:     11:45:29 12/31/2006 

// Design Name:     USB MBP HDL 

// Module Name:     re1ce 

// Project Name:    USBMBP_HDL

// Target Devices:  XC2S15-5TQ144

// Tool versions:   ISE Webpack 8.2i

// Description:     Multi-stage synchronizer with rising edge detection

//

// Dependencies:    None

//

// Revision History:

//

//  0.01    06L31   MAM     File Created

//

//  1.00    13G06   MAM     Added initial values for the sync FFs

//

// Additional Comments: 

//

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

module re1ce(den, din, clk, rst, trg, pls);

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

//

//  Module Port Declarations

//

input   den;

input   din;

input   clk;

input   rst;

output  trg;

output  pls;

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

//

//  Module Level Declarations

//

reg     QIn;

reg     [2:0] QSync;

wire    Rst_QIn;

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

//

//  Implementation

//

assign Rst_QIn = (rst | pls);

always @(posedge din or posedge Rst_QIn) begin

    if(Rst_QIn)

        #1 QIn <= 1'b0;

    else if(den)

        #1 QIn <= den;

end

assign trg = QIn;

always @(posedge clk or posedge rst) begin

    if(rst)

        #1 QSync <= 3'b0;

    else

        #1 QSync <= {QSync[0] & ~QSync[1], QSync[0], QIn};

end

assign pls = QSync[2];

endmodule