The following terms are used when describing serial devices and the TTY system:

Connect an appropriate cable from the ASCII terminal to the serial port on the computer I/O panel. See “Cabling the Serial Ports” for information about port cabling and pin signals.

This section tells you how to configure IRIX software to use an ASCII terminal with your computer system.

During configuration, you need to:

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Note: The utilities described in this section are distributed as part of the eoe2.sw.terminfo package. You must have installed this package on your system in order to use these utilities. See IRIX Admin: Software Installation and Licensing for information and specific instructions on installing this package.

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The /usr/lib/terminfo directory contains files that describe different terminal models, their capabilities, and how they operate. For most ASCII terminal models, you do not need to edit this database.

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Note: If your terminal is not in the database, or if it does not work properly after you have configured the software, you may need to write a terminal description. Refer to the optional Topics in IRIX Programming and the tset(1), stty(1), and terminfo(4) reference pages. Additionally, your terminal may support a compatible terminal mode (such as VT100). Check your terminal documentation for compatibility modes.

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The directory /usr/lib/terminfo is divided into numerical and alphabetical subdirectories. Each subdirectory contains entries for terminals whose names begin with that character. For example, /usr/lib/terminfo/v contains the entry for the Visual 50. The entry name listed in the subdirectory is v50am. Use the fgrep command to search for the terminal model name that corresponds to the entry name.

To find the entry name for your terminal and to configure software for an ASCII terminal, follow these steps:

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Note: If the default line speed set in /etc/inittab is incorrect, the prompt may be garbled or may not appear. You should choose another line speed.

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The TTY system described thus far establishes a basic style of communication between the user's terminal and the IRIX operating system. Once a user has successfully logged in, he or she may prefer terminal options other than the default set.

The stty command controls terminal options. Many users add an stty command to their .profile or .login file so the options they want are automatically set as part of the login process. Here is an example of a simple stty command:

stty cr0 nl0 echoe -tabs erase '^H'

The options in the example mean:

There are a few prerequisites you should be aware of before installing the modem. Review the following points before installing the modem.

To set up a modem, you must first make the following physical connections. With power to the modem off, connect the modem to:

The major tasks for setting up the modem software are fairly similar, despite how you choose to use your modem.

Table 1-2 provides an overview of the major tasks for each of the three usage modes. An “x” in the table cell denotes the task is performed.

The cu utility dials your modem. Before you attempt to dial out, make sure your local modem is connected to both your system and a working telephone line. Also, make sure the modem is turned on. The cu syntax to dial the number 1-800-555-1234 is:

cu 18005551234

Refer to the cu(1) reference page for complete information on cu. If everything is working, you should hear the modem dialing, and after a short time you should see the following message on your console:

Connected

The /etc/gettydefs file contains information used by the getty command to establish the speed and terminal settings for a line. The general format of the gettydefs file is:

label# initial-flags # final-flags #login-prompt #next-label

The following example shows a few lines from a gettydefs file:

dx_9600# B9600 # B9600 SANE TAB3 HUPCL #\r\n\n$HOSTNAME login: #dx_9600 
dx_4800# B4800 # B4800 SANE TAB3 HUPCL #\r\n\n$HOSTNAME login: #dx_4800 
dx_2400# B2400 # B2400 SANE TAB3 HUPCL #\r\n\n$HOSTNAME login: #dx_2400 
dx_1200# B1200 # B1200 SANE TAB3 HUPCL #\r\n\n$HOSTNAME login: #dx_1200 
du_1200# B1200 # B1200 SANE TAB3 HUPCL #\r\n\n$HOSTNAME login: #du_300 
du_300#  B300  # B300  SANE TAB3 HUPCL #\r\n\n$HOSTNAME login: #du_2400 
du_2400# B2400 # B2400 SANE TAB3 HUPCL #\r\n\n$HOSTNAME login: #du_1200 

The entries beginning with dx are typically used for terminals or modems; those beginning with du are typically for low-speed modems. See gettydefs(4) for more information on the fields of each entry.

These entries form a single, rotary hunt sequence; the last field on each line is the label of the next line. The next-label field for the last line shown points back to the first line in the sequence. The object of the hunt sequence is to link a range of line speeds. If you see garbage characters instead of a clear login prompt, press the <Esc> key to force getty to step to the next entry in the sequence. The hunt continues until the baud rate of the line matches the speed of the user's terminal.

The flag fields shown have the following meanings:

For a description of all getty flags, see termio(7).

Create new lines for the gettydefs file by following the example shown in “Checking Line Settings Using IRIX Shell Commands.” Each entry in the file is followed by a blank line. After editing the file, run the command:

/etc/getty -c /etc/gettydefs 

This causes getty to scan the file and print the results on your terminal. Any unrecognized modes or improperly constructed entries are reported.

You can modify TTY line characteristics using an IRIX editor, such as vi, to edit /etc/inittab.

The /etc/inittab file contains configuration instructions for the /etc/init command. The general format of a line entry in the /etc/inittab file is as follows:

identification:level:action:process

The four colon-separated fields are as follows:

/etc/inittab contains several entries that spawn getty processes. The following example is a selection of such entries from a sample /etc/inittab:

t1:23:respawn:/etc/getty -s console ttyd1 co_9600 
t2:23:respawn:/etc/getty ttyd2 co_9600 

There are at least three things you might want to do to an inittab entry for a TTY line:

The workstation or server provides an RS-232 (or RS-423) or a DB-9 (9-pin) compatible serial interface. Additionally, some systems are equipped with the mini-DIN8 serial interface. These ports do not lay out the pins in a conventional pattern such as DB-9 or RS-232; instead, the plug is cylindrical. Adapter cables are available commercially or through Silicon Graphics to connect mini-DIN8 ports with DB-9 and RS-232 ports. Consult your system Owner's Guide for complete information on your system's serial ports. All serial data cables that you connect to the computer should be shielded. The computer can easily drive and receive signals on a 50-foot cable, and it typically drives and receives signals on a cable up to 200 feet long.

There are two types of serial interface equipment available: Data Terminal Equipment (DTE) and Data Communications Equipment (DCE). The primary difference between DTE and DCE is the use of several pins on the connector. For example, DTE devices output on pin 2 and input on pin 3. DCE devices output on pin 3 and input on pin 2. You can connect a DTE interface directly to a DCE interface.

To connect either a DCE to a DCE, or a DTE to a DTE, use a null modem cable. A null modem cable allows equipment interfaces of the same type to be connected by swapping the appropriate input and output pins.

The serial ports for workstations and servers are all configured as DTE devices. Most terminals are also configured as DTE devices. Therefore, to connect a terminal to a workstation that has RS-232 or DB-9 connectors, use a null modem cable (if this connection does not work correctly, consult the documentation for your terminal to determine its requirements). To connect a modem to the workstation, use a cable that connects each pin of the serial port to the corresponding pin of the modem. No signals need to be swapped. Ensure that your cable is a straight connection before using it with your system. Connect other peripheral devices according to the configuration data provided with the device.

Silicon Graphics provides three special files that determine the signals that are used on each port. The special files beginning with ttyd are used for devices such as terminals; the files ttymX are used for modems that do not use hardware flow control; and ttyfX files are used for devices that can use hardware flow control on the RTS and CTS pins.

This section describes the cables typically used to connect the computer to terminals and modems. The serial ports are designed to connect directly to Data Communications Equipment (DCE) devices such as modems through a serial cable. Each wire on this cable connects the same pin of the computer socket to the device, that is, it has a pin-to-pin correspondence. Connecting to Data Terminal Equipment (DTE) devices such as terminals requires a different cable arrangement: a null modem cable. A null modem cable has input and output signals swapped between the two connectors.

DB-9 Serial Connector Cabling

Table 1-5 lists the pin definitions for an example of a 9-pin (DB-9) null modem cable, as shown in Figure 1-1. Connect pins that are shown separated by commas in the Terminal column together with a wire or jumper at that end of the cable. Then connect these joined pins to the pin shown in the 9-pin column at the 9-pin end of the cable.

Figure 1-1. DB-9 Connector

Table 1-5. Pin Definitions for a Null Modem Cable

9-Pin	Signal	Terminal	Signal
2	Transmit Data	3	Receive Data
3	Receive Data	2	Transmit Data
4	Request To Send	5	Clear To Send
5	Clear To Send	4	Request To Send
7	Signal Ground	7	Signal Ground
8	Data Carrier Detect	6,8	Data Set Ready and Data Carrier Detect
9	Data Terminal Ready	20	Data Terminal Ready

Most terminals do not require the various handshaking lines such as Clear To Send or Data Set Ready and work with a three-wire null modem cable. To make one of these, you simply need to swap the signals for pins 2 and 3, and you need to connect pin 7 of the computer to pin 7 of the terminal. Table 1-6 lists the pin definitions for a three-wire null modem cable.

Table 1-6. Pin Definitions for a Three-wire Null Modem Terminal Cable

Computer	Signal	Terminal	Signal
2	Transmit Data	3	Receive Data
3	Receive Data	2	Transmit Data
7	Signal Ground	7	Signal Ground

Note that the pinout of these DB-9 connectors is different from that of the DIN connectors that may be next to them. These DIN connectors also have different pinouts from the mini-DIN8 connectors used on some systems and documented in “Mini-DIN8 Serial Connector Cabling.” The DB-9 and DIN connectors are connected to the same internal port hardware.

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Caution: Do not use a cable designed for an IBM PC/AT™ compatible 9-pin connector. It does not work correctly with your Silicon Graphics workstation.

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For modem devices that use RTS/CTS hardware flow control, the following pinout allows “full flow control.” This cable is required to implement /dev/ttyf* devices. This cable also supports /dev/ttym* devices. (When using ttym devices, ensure that the connected device does not require flow control signals.) Figure 1-2 shows the DB-9 to DB-25 RTS/CTS cable and Table 1-7 lists the correct pin-out for hardware flow control devices.

Figure 1-2. DB-9 to DB-25 RTS/CTS Modem Control Cable

Table 1-7. Pin Definitions for a DB-9 to DB-25 RTS/CTS Modem Control Cable

DB-9-Male	Signal	DB-25-Male	Signal
1	not used	1	not used
2	Transmit Data	2	Transmit Data
3	Receive Data	3	Receive Data
4	Request to Send*	4	Request to Send*
5	Clear to Send*	5	Clear to Send
6	not used	6	not used
7	Signal Ground	7	Signal Ground
8	Data Carrier Detect	8	Data Carrier Detect
9	Data Terminal Ready	20	Data Terminal Ready

* RTS and CTS are ignored (optional) if using /dev/ttym* but required if using /dev/ttyf*.

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Note: This cable can be used with a null modem adapter for terminals and printers (see Table 1-5); however, it is recommended that you use this cable exclusively for modem connections. The IBM PC/AT to modem cable (“off the shelf cable”) does not work properly with your workstation. For additional information see the serial(7) reference page.

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Mini-DIN8 Serial Connector Cabling

There are three basic cable configurations for the mini-DIN8 serial ports. See your Owner's Guide to determine if you have a mini-DIN8 port on your workstation or server. Depending on the cables used, some functionality may be sacrificed. Note that the pinout of these mini-DIN8 connectors is different from that of the DIN connectors on larger systems. These larger systems also have DB-9 connectors that are connected to the same internal port hardware.

For most dumb terminals you should use a commercially available cable, Macintosh SE^® to ImageWriter1. This cable uses the normal three-wire connection and is used as a /dev/ttyd* device.

Figure 1-3 shows the mini-DIN8 to DB-25 Serial Terminal Cable and Table 1-8 lists the pin configuration.

Figure 1-3. Mini-DIN8 to DB-25 Serial Terminal Cable

Table 1-8. Pin Definitions for a Mini-DIN8 to DB-25 Serial Terminal Cable

Mini-DIN8- Male	Signal	DB-25-Male	Signal
1	not used	1	not used
2	not used	2	Transmit Data
3	Transmit Data	3	Receive Data
4	Signal Ground	4	Request to Send
5	Receive Data	5	Clear to Send
6	not used	8	Data Carrier Detect*
7	Data Carrier Detect*	20	Data Terminal Ready
8	Signal Ground

* /dev/ttym* devices should be used with this cable only if the system must notice when the terminal or printer is powered off.

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Note: A Macintosh SE cable has other pins connected but they can be ignored.

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For modem devices using RTS/CTS hardware flow control, the following pinout allows “full flow control.” This cable is required to implement /dev/ttyf* devices. It also supports /dev/ttym* devices. Table 1-9 shows the pinout:

Table 1-9. Pin Definitions for a Mini-DIN8 RTS/CTS Modem Cable

Mini-DIN8-Male	Signal	DB-25-Male	Signal
1	Data Terminal Ready	20	Data Terminal Ready
2	Clear to Send*	5	Clear to Send*
3	Transmit Data	2	Transmit Data
4	Signal Ground	7	Signal Ground
5	Receive Data	3	Receive Data
6	Request to Send*	4	Request to Send*
7	Data Carrier Detect	8	Data Carrier Detect
8	Signal Ground	7	Signal Ground

* RTS and CTS are ignored (optional) if using /dev/ttym* but required if using /dev/ttyf*

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Note: This cable is available from Silicon Graphics. Contact your sales representative. This cable can be used with a null modem adapter for terminals and printers (see Table 1-5); however, you should use this cable exclusively for modem connections. The commercially available cable that connects a Macintosh SE to a modem does not work properly with Silicon Graphics software.

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