Date   : Mon, 25 Jun 1984 20:27:11-MDT
From   : Ron Fowler <RFOWLER@SIMTEL20.ARPA>
Subject: Zilog SIO as a network controller

I'm involved in a project that involves the interconnection of several
Micro's as a local area network under TurboDOS.  I had planned to use
one of the (very expensive, as it turns out) various new network
controller chips, such as the WD2840 or COMM-9026.  Recently, however
I found out that the Zilog SIO is capable of 800KHz operation (in fact,
I've heard that Televideo's TurboDOS implementation employs the SIO as
the network controller).  Since all of the computers I'm working with
already have at least one SIO, I'd prefer to abandon the "fancy" net
controller in favor of an SIO.

Problem is, it seems that to get this kind of speed, you have to run
in one of the synchronous modes (SDLC or Bisync).  Does anyone know
if this is true?  Programming examples would be very helpful also
(I don't suppose anyone has a TurboDOS driver already written for a
high-speed SIO??? )

Another thing I'm not too sure of is the RS-422 interface itself
(I'm considering a bus topology).  When one station is transmitting
on the RS-422, do all other transmitters have to be tri-stated? If
so, what kind of turn-around is required for a station to become a
transmitter?

Any help will be much appreciated.                     --Ron Fowler