Ethan Dicks ethan.dicks at
Mon Jan 27 13:36:51 CST 2020

On Sun, Jan 26, 2020 at 2:59 PM Mattis Lind via cctalk
<cctalk at> wrote:
> Hello IBM BSC Experts!

I used to be one 25 years ago, but it's been that long since I've even
set up a BSC line.

> I am trying to figure out the CRC algorithm used by 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)
> characters).

That's a good document.

What we used as our "gold standard" in the 80s was a "Data 100" manual
for a 3rd party BSC workstation.  The documentation went way beyond
CRC-16 and message formats.  It delved deeply into the whole protocol.
I don't remember the vendor, and I know I don't have a scan of it.  I
was not able to quickly find a copy online but I admit I didn't search
more than a few minutes.  It would be a good resource to locate.


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