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// ============================================================================

//        __

//   \\__/ o\    (C) 2016-2021  Robert Finch, Waterloo

//    \  __ /    All rights reserved.

//     \/_//     robfinch<remove>@finitron.ca

//       ||

//

// 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 3 of the License, or     

// (at your option) any later version.                                      

//                                                                          

// This source file 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 General Public License for more details.                             

//                                                                          

// You should have received a copy of the GNU General Public License        

// along with this program.  If not, see <http://www.gnu.org/licenses/>.    

//

//

// Button / switch debounce circuit.

// Assumes 25MHz clock

// Approximately 10ms of debounce is provided.

// ============================================================================

//

module BtnDebounce(clk, btn_i, o);

input clk;

input btn_i;

output reg o;

reg [18:0] counter;

reg val1, val2;

always @(posedge clk)

begin

  val1 <= btn_i;

  val2 <= val1;

end

always @(posedge clk)

if (val1 != val2)

  counter <= 19'h0;

else if (counter[18])

  counter <= 19'h0;

else

  counter <= counter + 19'd1;

always @(posedge clk)

if (counter[18])

  o <= val2;

endmodule