Re: Opinions on 16-bit checksums.

From: CBFalconer (cbfalconer_at_yahoo.com)
Date: 08/26/04 

Date: Thu, 26 Aug 2004 04:15:59 GMT

Neil Bradley wrote:
>
... snip ...
>
> In 20 years of embedded systems development when 16 bit (or bigger)
> CRCs are used, I've witnessed no failures or oddities. During that
> period I've had about a dozen failures with checksums. Simple
> experience dictates it as such.
>
> Plus, I'm not a math whiz, but IIRC, CRC is significantly better
> than checksum because it also has data position order and sequence
> dependencies, and checksum doesn't.

I can't prove it, but I contend that no single bit error can
possibly result in an unchanged CRC checksum. I suspect that this
applies to some possible maximum number of bit errors. There are
other methods optimized to detect burst errors. 

-- 
Chuck F (cbfalconer@yahoo.com) (cbfalconer@worldnet.att.net)
   Available for consulting/temporary embedded and systems.
   <http://cbfalconer.home.att.net>  USE worldnet address!

Relevant Pages

  • Re: CRC versus CheckSum
    ... I have a situation where I have a byte in which to place either a checksum ... Our packets cannot have bytes in a packet swapped in order (the transport ... jsut as good as the CRC. ... Neither detect all errors (there are after all the same number of states for the sum in either case). ...
    (comp.arch.embedded)
  • Re: Opinions on 16-bit checksums.
    ... it's no longer a checksum, ... >> cancel themselves out, but a CRC would. ... I've witnessed no failures or oddities. ... I don't think it can be assumed that ROMs ...
    (comp.arch.embedded)
  • Re: Opinions on 16-bit checksums.
    ... >> possibly result in an unchanged CRC checksum. ... > There are two big reasons CRCs are used in serial communications: ... algorithms that consider the order of the data as well as the value - a ...
    (comp.arch.embedded)
  • Re: Crc16 on power failure
    ... a checksum is faster to calculate than a CRC by software. ... True, they are faster, but they are not nearly as good at detecting ... coonsider running an EEC on each parameter instead of a block check. ...
    (comp.arch.embedded)
  • Re: Opinions on 16-bit checksums.
    ... out there besides CRC and "add up the bytes". ... There are other checksum ... I don't think it can be assumed that ROMs ... ROMs do have the same error characteristics as a serial data ...
    (comp.arch.embedded)