pci_par_crit.v

这是用pci-wishbone核和16450串口核在xilinx的fpga上实现的串口程序

//////////////////////////////////////////////////////////////////////
////                                                              ////
////  File name "par_crit.v"                                      ////
////                                                              ////
////  This file is part of the "PCI bridge" project               ////
////  http://www.opencores.org/cores/pci/                         ////
////                                                              ////
////  Author(s):                                                  ////
////      - Miha Dolenc ([e-mail])                     ////
////                                                              ////
////  All additional information is avaliable in the README       ////
////  file.                                                       ////
////                                                              ////
////                                                              ////
//////////////////////////////////////////////////////////////////////
////                                                              ////
//// Copyright (C) 2001 Miha Dolenc, [e-mail]          ////
////                                                              ////
//// 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: pci_par_crit.v,v $
// Revision 1.2  2003/02/13 18:26:33  mihad
// Cleaned up the code. No functional changes.
//
// Revision 1.1  2003/01/27 16:49:31  mihad
// Changed module and file names. Updated scripts accordingly. FIFO synchronizations changed.
//
// Revision 1.3  2002/02/01 15:25:12  mihad
// Repaired a few bugs, updated specification, added test bench files and design document
//
// Revision 1.2  2001/10/05 08:14:28  mihad
// Updated all files with inclusion of timescale file for simulation purposes.
//
// Revision 1.1.1.1  2001/10/02 15:33:46  mihad
// New project directory structure
//
//

// module is used to separate logic which uses criticaly constrained inputs from slower logic.
// It is used to synthesize critical timing logic separately with faster cells or without optimization

// this one is used in parity generator/checker for calculating parity signal

// synopsys translate_off
`include "timescale.v"
// synopsys translate_on

module pci_par_crit
(
    par_out,
    par_out_in,
    pci_cbe_en_in,
    data_par_in,
    pci_cbe_in
) ;

output par_out ;

input   par_out_in,
        pci_cbe_en_in,
        data_par_in ;

input   [3:0] pci_cbe_in ;

assign par_out = pci_cbe_en_in ? par_out_in : ( pci_cbe_in[3] ^ pci_cbe_in[2] ^ pci_cbe_in[1] ^ pci_cbe_in[0] ^ data_par_in) ;

endmodule