wlk@raider.MFEE.TN.US (Wolf Kozel) (12/23/89)
Greetings Again!
I asked Robert Lipe of our support department (Arnet) about how to
get our Smartports to work with Telebit modems. Here is his reply.
If you'd like to reply to him directly our uunet address is:
uunet!sco!arnet!robertl or call us at (800) 366-8844
>From support!robertl Thu Dec 21 20:46:26 1989
There has been a lot of grief and confusion reported about Telebit modems, such
as the Trailblazer. Here is some information on getting your Telebit to
work with your Arnet Smartport.
Telebit dialers: Telebit modems do a trick they call 'autobaud' they take
incoming characters from the computer and put inter-character spacing in to
simulate different baud rates. The Smartport, of course, doesn't keep these
spaces and pumps the data out the ports as quickly as it can. This is what
a Smartport is supposed to do.
Solution: SLSxnx072 is available from SCO that replaces the dialers and
the uucico binaries. The diskette is known as the "Telebit Utilities"
Telebit Handshaking: Telebit modems, because they run at high speeds, use
hardware handshake as a default. On our full handshake cards, (Smarport-8 and
Smartport-16) this is fine and supported by the cards, drivers, and dialers.
On the limited handshake Arnet cards, this presents a problem. There are only
6 active signals on the Smarport/2, or the Modular Smartport. Two are grounds,
two are transmit and recieve, and there is an incoming and an outgoing
handshake. The incoming handshake defaults (through signal remapping) to CTS
on a lower case device to insure compatibility with terminals requiring
hardware flow control. This same pin becomes DCD on an upper case invocation.
The problem becomes the modem raises DCD when it is connected to the other modem, but uses CTS for flow control. Not enough handshake lines.
Solution: The dialers may be modified, as per their manuals, to set the modems
for XON/XOFF. By altering status registers 58 and 68, our incoming handshake
is used for DCD to allow Unix to hang up on loss of DCD. The other possible
solution is to use the lower case port. This will allow the board to use
CTS as a handshake line, but will not hangup the port on an abnormal disconnect.For detail on this, see the section on "Enhanced Command Mode" in the Telebit
Manuals.
We have many field reports of people successfully using Telebit modems with
our boards. Contrary to many rumors lately, we are compatible with Telebit.
The problems mentioned above have workarounds and are likely true with any
intelligent i/o card. The Telebit modems, like any other high end communicationdevice, will take some efforts to setup.
Robert Lipe
Arnet Technical Support