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-- $Id: crc8.vhd 410 2011-09-18 11:23:09Z mueller $ -- -- Copyright 2007-2011 by Walter F.J. Mueller <W.F.J.Mueller@gsi.de> -- -- This program is free software; you may redistribute and/or modify it under -- the terms of the GNU General Public License as published by the Free -- Software Foundation, either version 2, 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 complete details. -- ------------------------------------------------------------------------------ -- Module Name: crc8 - syn -- Description: 8bit CRC generator, use 'A6' polynomial of Koopman and -- Chakravarty. Has HD=3 for up to 247 bits and optimal HD=2 -- error detection for longer messages: -- -- x^8 + x^6 + x^3 + x^2 + 1 (0xa6) -- -- It is irreducible, and can be implemented with <= 37 xor's -- This polynomial is described in -- http://dx.doi.org/10.1109%2FDSN.2004.1311885 -- -- Dependencies: - -- Test bench: - -- Target Devices: generic -- Tool versions: xst 8.2, 9.1, 9.2,.., 13.1; ghdl 0.18-0.29 -- -- Synthesized (xst): -- Date Rev ise Target flop lutl lutm slic t peri -- 2011-09-17 410 13.1 O40d xc3s1200e-4 8 25 - 13 (A6 polynom) -- 2011-09-17 409 13.1 O40d xc3s1200e-4 8 18 - 10 (SAE J1850) -- -- Revision History: -- Date Rev Version Comment -- 2011-09-17 409 1.1 use now 'A6' polynomial of Koopman et al. -- 2011-08-14 406 1.0.1 remove superfluous variable r -- 2007-07-08 65 1.0 Initial version ------------------------------------------------------------------------------ library ieee; use ieee.std_logic_1164.all; use work.slvtypes.all; use work.comlib.all; entity crc8 is -- crc-8 generator, checker generic ( INIT: slv8 := "00000000"); -- initial state of crc register port ( CLK : in slbit; -- clock RESET : in slbit; -- reset ENA : in slbit; -- update enable DI : in slv8; -- input data CRC : out slv8 -- crc code ); end crc8; architecture syn of crc8 is signal R_CRC : slv8 := INIT; -- state registers begin proc_regs: process (CLK) begin if rising_edge(CLK) then if RESET = '1' then R_CRC <= INIT; else if ENA = '1' then R_CRC <= crc8_update(R_CRC, DI); end if; end if; end if; end process proc_regs; CRC <= R_CRC; end syn;
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