Hi,
I find that the polynomial for CRC-8-ATM is 1 + x + x^2 + x^8 and the representations as 0x07 or 0xE0 in the below link
Does it mean that 0x07 and 0xE0 based CRC calculation are inter-operable ?
When/Where should we need to use 0x07 and When/Where should we need to use 0xE0 ?
Why is it mentioned as either 0x07 or 0xE0 ? Any ideas ?
Thx in advans, Karthik Balaguru
Taken as is, the two "polynomials" are equivalent ("reciproqual"), see
Now it's a matter of convention, look if your application works LSB first or MSB first. BTW what is your application ? Are you developing something from scratch or interfacing to something already well defined ?
BTW
yg
-- http://ygdes.com / http://yasep.org
while the entry for CRC-8-ATM is:
0x07 or 0xE0 (0x83)Meaning normal is 0x07 (00000111), reversed is 0xE0 (11100000), reverse of reciprocal is 0x83.
Which to use depends upon whether you enumerate the bits LSB-first or MSB-first.
Depends on the direction you are shifting data in the register.
--
[mail]: Chuck F (cbfalconer at maineline dot net)
[page]:
Try the download section.
results.http://www.ross.net/crc/download/crc_v3.txtcontains more
Working on ROHC. The RFC 4815 states that it uses
0xE0. I was wondering about the reason for opting 0xE0 instead of 0x07 and hence raised these queries to know if there is any specific advantage in using either 0xE0 or 0x07.Agreed,
0xE0 and 0x07 are not inter-operable.But, is the performance same(equivalent) for both
0xE0 and 0x07 based CRC.Thx in advans, Karthik Balaguru
yes, 11100000 and 00000111 are just the same polynomials, in a reverse bit order. Mathematically, in the Galois Field GF(2^8), this is just like 2 facets of the same medal. Please read the "A Painless Guide to CRC Error Detection Algorithms", it's a very good read.
yg
-- http://ygdes.com / http://yasep.org
So, performance(cpu cycles) does not vary for either 0xE0 or 0x07 based CRC.
That's Interesting !
Thx, Karthik Balaguru
Yes, This info was very helpful.
Thx, Karthik Balaguru
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