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//
// Copyright 2011 Ettus Research LLC
//
// This program is free software: 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
// 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/>.
//
module crc
(input clk,
input reset,
input clear,
input [7:0] data,
input calc,
output [31:0] crc_out,
output match);
function[31:0] NextCRC;
input[7:0] D;
input[31:0] C;
reg[31:0] NewCRC;
begin
NewCRC[0] = C[24]^C[30]^D[1]^D[7];
NewCRC[1] = C[25]^C[31]^D[0]^D[6]^C[24]^C[30]^D[1]^D[7];
NewCRC[2] = C[26]^D[5]^C[25]^C[31]^D[0]^D[6]^C[24]^C[30]^D[1]^D[7];
NewCRC[3] = C[27]^D[4]^C[26]^D[5]^C[25]^C[31]^D[0]^D[6];
NewCRC[4] = C[28]^D[3]^C[27]^D[4]^C[26]^D[5]^C[24]^C[30]^D[1]^D[7];
NewCRC[5] = C[29]^D[2]^C[28]^D[3]^C[27]^D[4]^C[25]^C[31]^D[0]^D[6]^C[24]^C[30]^D[1]^D[7];
NewCRC[6] = C[30]^D[1]^C[29]^D[2]^C[28]^D[3]^C[26]^D[5]^C[25]^C[31]^D[0]^D[6];
NewCRC[7] = C[31]^D[0]^C[29]^D[2]^C[27]^D[4]^C[26]^D[5]^C[24]^D[7];
NewCRC[8] = C[0]^C[28]^D[3]^C[27]^D[4]^C[25]^D[6]^C[24]^D[7];
NewCRC[9] = C[1]^C[29]^D[2]^C[28]^D[3]^C[26]^D[5]^C[25]^D[6];
NewCRC[10] = C[2]^C[29]^D[2]^C[27]^D[4]^C[26]^D[5]^C[24]^D[7];
NewCRC[11] = C[3]^C[28]^D[3]^C[27]^D[4]^C[25]^D[6]^C[24]^D[7];
NewCRC[12] = C[4]^C[29]^D[2]^C[28]^D[3]^C[26]^D[5]^C[25]^D[6]^C[24]^C[30]^D[1]^D[7];
NewCRC[13] = C[5]^C[30]^D[1]^C[29]^D[2]^C[27]^D[4]^C[26]^D[5]^C[25]^C[31]^D[0]^D[6];
NewCRC[14] = C[6]^C[31]^D[0]^C[30]^D[1]^C[28]^D[3]^C[27]^D[4]^C[26]^D[5];
NewCRC[15] = C[7]^C[31]^D[0]^C[29]^D[2]^C[28]^D[3]^C[27]^D[4];
NewCRC[16] = C[8]^C[29]^D[2]^C[28]^D[3]^C[24]^D[7];
NewCRC[17] = C[9]^C[30]^D[1]^C[29]^D[2]^C[25]^D[6];
NewCRC[18] = C[10]^C[31]^D[0]^C[30]^D[1]^C[26]^D[5];
NewCRC[19] = C[11]^C[31]^D[0]^C[27]^D[4];
NewCRC[20] = C[12]^C[28]^D[3];
NewCRC[21] = C[13]^C[29]^D[2];
NewCRC[22] = C[14]^C[24]^D[7];
NewCRC[23] = C[15]^C[25]^D[6]^C[24]^C[30]^D[1]^D[7];
NewCRC[24] = C[16]^C[26]^D[5]^C[25]^C[31]^D[0]^D[6];
NewCRC[25] = C[17]^C[27]^D[4]^C[26]^D[5];
NewCRC[26] = C[18]^C[28]^D[3]^C[27]^D[4]^C[24]^C[30]^D[1]^D[7];
NewCRC[27] = C[19]^C[29]^D[2]^C[28]^D[3]^C[25]^C[31]^D[0]^D[6];
NewCRC[28] = C[20]^C[30]^D[1]^C[29]^D[2]^C[26]^D[5];
NewCRC[29] = C[21]^C[31]^D[0]^C[30]^D[1]^C[27]^D[4];
NewCRC[30] = C[22]^C[31]^D[0]^C[28]^D[3];
NewCRC[31] = C[23]^C[29]^D[2];
NextCRC = NewCRC;
end
endfunction
reg [31:0] crc_reg;
always @ (posedge clk)
if (reset | clear)
crc_reg <= 32'hffffffff;
else if (calc)
crc_reg <= NextCRC(data,crc_reg);
assign crc_out = ~{crc_reg[24],crc_reg[25],crc_reg[26],crc_reg[27],crc_reg[28],crc_reg[29],crc_reg[30],crc_reg[31],
crc_reg[16],crc_reg[17],crc_reg[18],crc_reg[19],crc_reg[20],crc_reg[21],crc_reg[22],crc_reg[23],
crc_reg[8],crc_reg[9],crc_reg[10],crc_reg[11],crc_reg[12],crc_reg[13],crc_reg[14],crc_reg[15],
crc_reg[0],crc_reg[1],crc_reg[2],crc_reg[3],crc_reg[4],crc_reg[5],crc_reg[6],crc_reg[7] };
assign match = (crc_reg == 32'hc704_dd7b);
endmodule // crc
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