27 Jan
2020
27 Jan
'20
12:20 a.m.
Den m?n 27 jan. 2020 kl 02:07 skrev Chuck Guzis via cctalk <
cctalk at classiccmp.org>:
On 1/26/20 3:12 PM, Bob Smith via cctalk wrote:
Yes, there are the crc reveng for example. But I cannot get it to generate
the CRC digits that matches. Neither does it give me anything when I ask it
to search for algorithm used.
Of course it is probably just me that don't understand it well enough.
It is slightly worrying though that I cannot recreate known examples that I
find online using crc reveng:
https://stackoverflow.com/questions/23638939/crc-16-ibm-reverse-lookup-in-c
The first answer by Mark Adler involves a pretty simple CRC algorithm that
given the data buffer and initiial crc value in the Maxim example generates
the mentioned output. But I cannot gat the same output using crc reveng. So
I just have to do something wrong when using it. But cannot figure out what.
/Mattis
I ma rusty on this, been almost 50 years since I
worked on the DP8EP
aka the KG83. then the KG11, and the Autodin 2 CRC32 designs in
hardware.
I don't recall whether bisync, aka bsc used LRC8, 12, 16, or crc16 as
the error detection algorithm.
I don't think it used VRC. I did find a refresher that might help, but
I don't think the polynomial you have for crc 16 has enough terms.
BUT I could be misremembering.
If you've got the message and the checksum, however computed, there are
free tools to grind through the usual suspects. I've used it on alien
disk formats very successfully.
--Chuck