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[/] [openrisc/] [trunk/] [orpsocv2/] [rtl/] [verilog/] [uart16550/] [uart_sync_flops.v] - Diff between revs 6 and 360

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//////////////////////////////////////////////////////////////////////
 
////                                                              ////
 
////  uart_sync_flops.v                                             ////
 
////                                                              ////
 
////                                                              ////
 
////  This file is part of the "UART 16550 compatible" project    ////
 
////  http://www.opencores.org/cores/uart16550/                   ////
 
////                                                              ////
 
////  Documentation related to this project:                      ////
 
////  - http://www.opencores.org/cores/uart16550/                 ////
 
////                                                              ////
 
////  Projects compatibility:                                     ////
 
////  - WISHBONE                                                  ////
 
////  RS232 Protocol                                              ////
 
////  16550D uart (mostly supported)                              ////
 
////                                                              ////
 
////  Overview (main Features):                                   ////
 
////  UART core receiver logic                                    ////
 
////                                                              ////
 
////  Known problems (limits):                                    ////
 
////  None known                                                  ////
 
////                                                              ////
 
////  To Do:                                                      ////
 
////  Thourough testing.                                          ////
 
////                                                              ////
 
////  Author(s):                                                  ////
 
////      - Andrej Erzen (andreje@flextronics.si)                 ////
 
////      - Tadej Markovic (tadejm@flextronics.si)                ////
 
////                                                              ////
 
////  Created:        2004/05/20                                  ////
 
////  Last Updated:   2004/05/20                                  ////
 
////                  (See log for the revision history)          ////
 
////                                                              ////
 
////                                                              ////
 
//////////////////////////////////////////////////////////////////////
 
////                                                              ////
 
//// Copyright (C) 2000, 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 $
 
//
 
 
 
 
 
`include "timescale.v"
 
 
 
 
 
module uart_sync_flops
 
(
 
  // internal signals
 
  rst_i,
 
  clk_i,
 
  stage1_rst_i,
 
  stage1_clk_en_i,
 
  async_dat_i,
 
  sync_dat_o
 
);
 
 
 
parameter Tp            = 1;
 
parameter width         = 1;
 
parameter init_value    = 1'b0;
 
 
 
input                           rst_i;                  // reset input
 
input                           clk_i;                  // clock input
 
input                           stage1_rst_i;           // synchronous reset for stage 1 FF
 
input                           stage1_clk_en_i;        // synchronous clock enable for stage 1 FF
 
input   [width-1:0]             async_dat_i;            // asynchronous data input
 
output  [width-1:0]             sync_dat_o;             // synchronous data output
 
 
 
 
 
//
 
// Interal signal declarations
 
//
 
 
 
reg     [width-1:0]             sync_dat_o;
 
reg     [width-1:0]             flop_0;
 
 
 
 
 
// first stage
 
always @ (posedge clk_i or posedge rst_i)
 
begin
 
    if (rst_i)
 
        flop_0 <= #Tp {width{init_value}};
 
    else
 
        flop_0 <= #Tp async_dat_i;
 
end
 
 
 
// second stage
 
always @ (posedge clk_i or posedge rst_i)
 
begin
 
    if (rst_i)
 
        sync_dat_o <= #Tp {width{init_value}};
 
    else if (stage1_rst_i)
 
        sync_dat_o <= #Tp {width{init_value}};
 
    else if (stage1_clk_en_i)
 
        sync_dat_o <= #Tp flop_0;
 
end
 
 
 
endmodule
 
 
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