IBM BSC CRC?
bobsmithofd at gmail.com
Sun Jan 26 17:12:43 CST 2020
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
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.
On Sun, Jan 26, 2020 at 2:59 PM Mattis Lind via cctalk
<cctalk at classiccmp.org> wrote:
> Hello IBM BSC Experts!
> I am trying to figure out the CRC algorithm used by IBM BSC. I have tried a
> lot of different settings in crcreveng but not getting a match.
> I am pretty convinced that the CRC-16 used by IBM was
> 16 15 2
> x + x + x + 1
> This would give the polynomial 8005.
> Anyone against this statement?
> But what was the initial value?
> I have two actual messages from equipment employing IBM BSC:
> From this document (
> I get that the CRC calculation is reset on SOH (01h) or STX (02h) and
> accumulates until and including the ETX (03h). (excluding any SYN (32h)
> I have tried crcreveng back and forth and I am not getting the CRC bytes
> I think I have tried most things, different bit order, different initial
> values. But nothing.
> I also tried the mode in crcreveng where it searches for matches but it
> always says "no models found". Maybe I am doing something wrong when using
> Any clues? Surely there are someone out there that has been around for some
> time and knows this, right?
> On the topic of crc reveng I tried to verify how it works by using some
> kind of known value: This article
> has a specific example where a certain data in (75h) with initial value
> 90f1h gives output 6390h. I tried to get crc reveng to do the same, but
> failed. There has to be some option I simply do not understand. I tried
> most combinations.
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