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97a4f2a Oct 27, 2017
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////////////////////////////////////////////////////////////////////////////////
//
// Filename: lfsr_gal.v
//
// Project: DSP Filtering Example Project
//
// Purpose:
//
// Creator: Dan Gisselquist, Ph.D.
// Gisselquist Technology, LLC
//
////////////////////////////////////////////////////////////////////////////////
//
// Copyright (C) 2017, Gisselquist Technology, LLC
//
// This program is free software (firmware): you can redistribute it and/or
// modify it under the terms of the GNU General Public License as published
// by the Free Software Foundation, either version 3 of the License, or (at
// your option) any later version.
//
// This program is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY 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. (It's in the $(ROOT)/doc directory. Run make with no
// target there if the PDF file isn't present.) If not, see
// <http://www.gnu.org/licenses/> for a copy.
//
// License: GPL, v3, as defined and found on www.gnu.org,
// http://www.gnu.org/licenses/gpl.html
//
//
////////////////////////////////////////////////////////////////////////////////
//
//
`default_nettype none
//
module lfsr_gal(i_clk, i_reset, i_ce, i_in, o_bit);
parameter LN=8; // LFSR Register length/polynomial deg
parameter [(LN-1):0] TAPS = 8'hb4,
INITIAL_FILL = { { (LN-1){1'b0}}, 1'b1 };
//
input wire i_clk, i_reset, i_ce, i_in;
output wire o_bit;
reg [(LN-1):0] sreg;
initial sreg = INITIAL_FILL;
always @(posedge i_clk)
if (i_reset)
sreg <= INITIAL_FILL;
else if (i_ce)
begin
if (sreg[0])
sreg <= { i_in, sreg[(LN-1):1] } ^ TAPS;
else
sreg <= { i_in, sreg[(LN-1):1] };
end
assign o_bit = sreg[0];
endmodule