1. This forum section is a read-only archive which contains old newsgroup posts. If you wish to post a query, please do so in one of our main forum sections (here). This way you will get a faster, better response from the members on Motherboard Point.

# 85-bits CRC

Discussion in 'Embedded' started by Ignacio G.T., Jul 23, 2007.

1. ### Ignacio G.T.Guest

Dear all:

I have to compute a long CRC (85 bits). I'm used to compute 16-bits and
32-bits CRCs, using tables or using "brute-force" algorithms (via
software) which make use of the fact that 16 bits or 32 bits makes a
word or half a word.

But 85 bits demands, perhpas, other approaches, to be effective. I
wonder if some of you can point me in the right direction. Is there
any other group more suited to be asked? Books, references?

--
Saludos,
Ignacio G.T.

Ignacio G.T., Jul 23, 2007

"Ignacio G.T." <> wrote in message
news:...
> Dear all:
>
> I have to compute a long CRC (85 bits).

I am curuous what is this for?

> I'm used to compute 16-bits and
> 32-bits CRCs, using tables or using "brute-force" algorithms (via
> software) which make use of the fact that 16 bits or 32 bits makes a
> word or half a word.
>
> But 85 bits demands, perhpas, other approaches, to be effective.
> I wonder if some of you can point me in the right direction. Is there
> any other group more suited to be asked? Books, references?

CRC is a remainder of the polynomial division. Thus you can extend the 85
bit CRC polynomial to 96 bit polynomial, which is a multiple of machine
word. The 96 bit CRC can be computed efficiently, and then you convert the
96 bit CRC to 85 bits.