Adding serial terminals

Installing serial terminals

To install a terminal with the standard COM serial lines or with serial expansion cards:

  1. Unless you are adding a terminal directly to the COM1 port, run the Hardware/Kernel Manager and select Serial Port from the Drivers menu or run mkdev serial. See ``Adding and configuring serial cards'' for information on how to configure the serial ports for terminal connections.

  2. Make sure you are logged in as root in multiuser mode.

  3. Plug in your terminal and turn it on. Set its input and output speeds to 9600bps (or higher, see step 5 below), 8 data bits, 1 stop bit, no parity, full duplex, and XON/XOFF handshaking (software flow control). If your terminal does not work in this mode, look for advice on configuring your terminal in the gettydefs(F) and inittab(F) manual pages.

    Most terminals will be connected directly to the computer using a cable, although it is possible for terminals to connect to the system via a modem link. DTE-type terminals connected directly to a DTE-type serial port, or DCE-type terminals connected directly to a DCE-type serial port require a cable in which the Transmit Data (TD) pin on the serial port is connected to the Receive Data (RD) pin on the terminal, the RD pin on the serial port is connected to TD pin on the terminal, and the Signal Ground (SG) wire is connected straight through.

    DCE-type terminals connected to a DTE-type serial port, or DTE-type terminals connected to a DCE-type serial port require a cable in which these three wires are connected straight-through.

    It may also be necessary to link the Data Set Ready (DSR), Data Terminal Ready (DTR), and Carrier Detect (CD) pins in the connector at the computer-end of the cable if the serial port hardware requires this. If software flow control is used, the operating system requires only that pins 2, 3, and 7 are connected for DB25 connectors, and that pins 2, 3, and 5 are connected for DB9 connectors.

    For more information, see the serial(HW) manual page.

  4. Enable the terminal using the enable(C) command. For example:

    enable tty2a

    The enable command starts a getty process that displays the login: prompt on your terminal.

  5. Check that the entry for this serial port in the /etc/inittab file looks like the following example for /dev/tty2a:
       Se2a:234:respawn:/etc/getty tty2a m
    The /etc/inittab entry should appear as above. If the entry does not look like this example, edit the file to correct it. See inittab(F) for information on the /etc/inittab format.

    The last field in the /etc/inittab entry is a line-mode label from an entry in the /etc/gettydefs file. In the example above, ``m'' corresponds to the 9600bps entry in /etc/gettydefs. The maximum speeds that the serial driver supports depends on the characteristics of the underlying serial port hardware as shown in ``Serial port speeds, line-mode labels, and UART limitations''. For more information, see ``Changing default terminal line characteristics''.

    WARNING: To make permanent any changes to /etc/inittab, the same changes must also be applied to /etc/conf/init.d/sio. This is because each time the kernel is relinked (as when a driver is added or a tunable parameter is changed), /etc/inittab is reconstructed from the entries in /etc/conf/init.d/sio.

  6. If the port is enabled, press the <Enter> key a few times to see if a login: prompt appears. If so, you are ready to log in. If the prompt does not appear, see ``Testing a terminal connection''.

Next topic: Testing a terminal connection
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© 2003 Caldera International, Inc. All rights reserved.
SCO OpenServer Release 5.0.7 -- 11 February 2003