This page discusses using the ViewStation's serial
ports for connecting to host computers. The mode of serial communication
can be direct, using the ViewStation's local terminal emulators, or it
can use the TCP level interface on the serial line with PPP, CSLIP, or
SLIP protocols.
ViewStation Serial Ports
The
ViewStation has two serial ports, Serial 1 (RJ11) with all ViewStations
and Serial 2 (DB25) with the optional Communications board. These ports
are configured from the Setup Mode Communications menu. The serial ports
are designated /dev/tty1 and /dev/tty2 respectively.
Pin Assignments for Serial Port 1
Pin Assignments for Serial Port 2
ViewStation Serial
Port Window
The Communications Options -
Serial Ports Menu in Setup Mode contains fields for the serial port
settings.
The field Serial 1 Port Use (or Serial
2 Port Use) determines how the particular serial port is used; it
has options Unspecified, Normal SLIP, Compressed SLIP, PPP, or Console.
This is the assignment of the logical port to a connector.
Choose one of these configuration options, such as PPP or
CSLIP (this compressed format uses "Van Jacobsen compression", RFC
1144; the remote host must also use this technique to decompress the
data it receives). CAUTION: Select PPP, or SLIP options only if that
is your only connection. If you have other connections to the host or
Ethernet and use PPP only occasionally, you should select "Unspecified"
as your serial port use and use the "Start PPP" option on the pull-down
menu. The reason for this "Unspecified" selection is that if "PPP" is
your Serial Port Use selection, the ViewStation will send repeated
requests to the host to start the PPP daemon, even if you aren't
currently using a PPP session.
Now set the communications settings as required by the remote
host connection, things like baud rate, parity, etc. When you have
made all your selections, click on Apply Settings, (Save in NVM if you
wish) and exit Setup Mode. When you try to log onto the remote host you
specified for CSLIP (using Telnet), the ViewStation opens the CSLIP
communications port using the settings you specified. (Note that the
communications interface is forced to 8 data bits and no XON/XOFF when
using SLIP or CSLIP. Most Unix systems use 7 data bits and Even parity
with their serial connections; the parity bit is required but ignored on
input. SLIP and CSLIP require 8 data bits to communicate. The
ViewStation automatically sets its serial ports to 8 data bits, and no
XON/XOFF when the SLIP or CSLIP mode is active. The previous
communications setting is restored when the SLIP mode is terminated.
You shouldn't save settings in NVM while the SLIP interface is active
unless you want these SLIP communication values saved for that port.)
You can log onto another host, using either Serial Port or
Ethernet, with another Telnet session if you wish. The ViewStation
looks at the host address you use in your Telnet session and then
selects the appropriate interface as its connection, either the Serial
Port 1 or Port 2 remote host, or some other host on your Ethernet
network. The Default Telnet host field in Setup Mode lets you select
one host as your Default connection.
Your remote host addresses for the serial ports should be
different; if you use the same remote host address, the last one you
set (with Apply settings) will be used. Note also that some things,
like Domain Nameservice, rely on the flexibility and free access to
many machines found on a network. If your font host, or name daemon,
are running on a host that is not your SLIP host, they will work
correctly if the physical connection to that host is present and
active. You should realize that transferring font files over the SLIP
serial lines will be slow, so most of these network processes (daemons
and servers) should typically be on an Ethernet connection host.
The selection of the physical port should consider that
CTS/RTS is the only flow control available, and this is only available
on Serial Port 2, the DB25 port. The XON/XOFF flow control can't be
used with CSLIP or SLIP. Note also that CSLIP and SLIP protocols must
run with 8 data bits and no parity.
Direct
Serial Connection to a Host
This page discusses a direct serial
connection to a host computer and the advantages of using one of the
ViewStation's local terminal emulators.
Making a TCP/IP Connection on a Serial Line with PPP
This page
discusses use of the serial connection for a TCP/IP connection to a host
computer with the PPP protocol or with the SLIP or CSLIP protocols.
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