No sweat making me refresh my memory! I am chasing a few 10 things to play with. Have a great new year, cause we humans can't decide which method to use measure a year. bb
On Sun, Jan 26, 2020 at 6:23 PM Nigel Johnson via cctalk <cctalk@classiccmp.org> wrote: > > Sorry guys, that LTspice stuff was not for this group - my mailer must > have screwed up! > > 73 de Nigel ve3id > > > On 26/01/2020 18:12, Bob Smith via cctalk wrote: > > 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. > > > > https://www.automatas.org/modbus/crc7.html > > bob > > > > On Sun, Jan 26, 2020 at 2:59 PM Mattis Lind via cctalk > > <cctalk@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: > >> 32016CD90240404070032688 > >> and > >> 32016CD90240C84050030D28 > >> > >> From this document ( > >> http://bitsavers.trailing-edge.com/pdf/ibm/datacomm/GA27-3004-2_General_Information_Binary_Synchronous_Communications_Oct70.pdf > >> ) > >> 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) > >> characters). > >> > >> I have tried crcreveng back and forth and I am not getting the CRC bytes > >> right. > >> 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 > >> crcreveng? > >> > >> 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 > >> https://stackoverflow.com/questions/23638939/crc-16-ibm-reverse-lookup-in-c > >> > >> 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. > >> > >> /Mattis > > > > -- > Nigel Johnson > MSc., MIEEE > VE3ID/G4AJQ/VA3MCU > > Amateur Radio, the origin of the open-source concept! > > > You can reach me by voice on Skype: TILBURY2591 > > If time travel ever will be possible, it already is. Ask me again yesterday > > This e-mail is not and cannot, by its nature, be confidential. En route from > me to you, it will pass across the public Internet, easily readable by any > number of system administrators along the way. > Nigel Johnson <nw.john...@ieee.org> > > > Please consider the environment when deciding if you really need to print > this message > > >
