//-----------------------------------------------------------------------------
// Title         : debounce
// Project       : ECE 491 - Senior Design I
//-----------------------------------------------------------------------------
// File          : debounce.v
// Author        : John Nestor  <johnnest@localhost>
// Created       : 19.08.2005
// Last modified : 19.08.2005
//-----------------------------------------------------------------------------
// Description :
// This circuit uses a shift register to remove mechanical bounce from a switch
// input.  It uses a 100 Hz clock and assumes an active-high input.
//-----------------------------------------------------------------------------
//------------------------------------------------------------------------------
// Modification history :
// 19.08.2005 : created
//-----------------------------------------------------------------------------

module debounce (pb, clk_100Hz, pb_debounced);
   input    pb;
   input    clk_100Hz;
   output   pb_debounced;
   reg 	    pb_debounced;

   reg [3:0] shift_pb;
   
   always @ (posedge clk_100Hz) begin
      shift_pb [3:0] <= {shift_pb [2:0], pb};
      if (shift_pb == 4'b1111) pb_debounced <= 1;
      else pb_debounced <= 0;
   end

endmodule // debounce