Subversion Repositories sd_card_controller

//////////////////////////////////////////////////////////////////////
////                                                              ////
//// WISHBONE SD Card Controller IP Core                          ////
////                                                              ////
//// edge_detect.v                                                ////
////                                                              ////
//// This file is part of the WISHBONE SD Card                    ////
//// Controller IP Core project                                   ////
//// http://opencores.org/project,sd_card_controller              ////
////                                                              ////
//// Description                                                  ////
//// Signal edge detection. If input signal transitions between   ////
//// two states, output signal is generated for one clock cycle.  ////
////                                                              ////
//// Author(s):                                                   ////
////     - Marek Czerski, ma.czerski@gmail.com                    ////
////                                                              ////
//////////////////////////////////////////////////////////////////////
////                                                              ////
//// Copyright (C) 2013 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                     ////
////                                                              ////
//////////////////////////////////////////////////////////////////////
 
module edge_detect (
    input rst,
    input clk, 
    input sig,
    output rise,
    output fall
);
 
reg [1:0] sig_reg;
 
always @(posedge clk or posedge rst)
    if (rst == 1'b1)
        sig_reg <= 2'b00;
    else
        sig_reg <= {sig_reg[0], sig};
 
assign rise = sig_reg[0] == 1'b1 && sig_reg[1] == 1'b0 ? 1'b1 : 1'b0;
assign fall = sig_reg[0] == 1'b0 && sig_reg[1] == 1'b1 ? 1'b1 : 1'b0;
 
endmodule