In article <o15uta$3ca$
1@panix3.panix.com>, Jeff Jonas <
jeffj@panix.com> wrote: >>> Mainframes don't use serial communications historically.
Async serial: too cheap, simple and standardized for mainframes.
Mainframes did SDLC sync-serial for remote terminals / RJE (remote job entry). >Zilog's serial chips handled that in hardware.
Which was a smart thing, since handling error correction and block stuff
at the data link layer then became possible. Much more reliable than just opening up a port and jamming data through and hoping for the best when it appeared on some screen halfway across the country.
The mini folks first started using async serial so they could take advantage
of cheap teletype consoles.
There used to be many makers of protocol converters
from mainframe SNA to plain RS232 terminals and modems.
Similar to terminal servers to Token Ring, Ethernet, Decnet, etc.
I believe that a bisync-to-async box was the first actual product that an
8051 was used in. Later ones got even smarter and many were available
that supported IBM and Burroughs block terminal protocols and translated
to vt100 sequences.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
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