asy - asynchronous serial port driver
The asy module is a loadable STREAMS driver that provides
basic support for the standard UARTS that use Intel-8250,
National Semiconductor-16450 and 16550 hardware, in addition
to basic asynchronous communication support. The asy module
supports those termio(7I) device control functions specified
by flags in the c_cflag word of the termios structure, and
by the IGNBRK, IGNPAR, PARMRK, or INPCK flags in the c_iflag
word of the termios structure. All other termio(7I) func-
tions must be performed by STREAMS modules pushed atop the
driver. When a device is opened, the ldterm(7M) and
ttcompat(7M) STREAMS modules are automatically pushed on top
of the stream, providing the standard termio(7I) interface.
The character-special devices /dev/term/a and /dev/term/b
are used to access the two standard serial ports (COM1 and
COM2) on an x86 system. The asy module supports up to four
serial ports, including the standard ports. Device names are
typically used to provide a logical access point for a
dial-in line that is used with a modem.
To allow a single tty line to be connected to a modem and
used for incoming and outgoing calls, a special feature is
available that is controlled by the minor device number. By
accessing character-special devices with names of the form
/dev/cua/n, it is possible to open a port without the Car-
rier Detect signal being asserted, either through hardware
or an equivalent software mechanism. These devices are com-
monly known as dial-out lines.
This module is affected by the setting of certain
eeprom variables. For information on parameters that
are persistent across reboots, see the eeprom(1M) man
In Solaris 8 and later versions, the default setting
for ttya-ignore-cd and ttya-trs-dtr-off is true. To
avoid having their modems fail, users of Solaris 7 (and
earlier versions) should change the settings of ttya-
ignore-cd and ttya-trs-dtr-off to false.
APPLICATION PROGRAMMING INTERFACE
Once a /dev/cua/n line is opened, the corresponding tty line
cannot be opened until the /dev/cua/n line is closed. A
blocking open will wait until the /dev/cua/n line is closed
(which will drop Data Terminal Ready, after which Carrier
Detect will usually drop as well) and carrier is detected
again. A non-blocking open will return an error. If the
/dev/ttydn line has been opened successfully (usually only
when carrier is recognized on the modem), the corresponding
/dev/cua/n line cannot be opened. This allows a modem to be
attached to /dev/term/[n] (renamed from /dev/tty[n]) and
used for dial-in (by enabling the line for login in
/etc/inittab) or dial-out (by tip(1) or uucp(1C)) as
/dev/cua/n when no one is logged in on the line.
The standard set of termio ioctl() calls are supported by
Breaks can be generated by the TCSBRK, TIOCSBRK, and
TIOCCBRK ioctl() calls.
The input and output line speeds may be set to any speed
that is supported by termio. The speeds cannot be set
independently; for example, when the output speed is set,
the input speed is automatically set to the same speed.
When the asy module is used to service the serial console
port, it supports a BREAK condition that allows the system
to enter the debugger or the monitor. The BREAK condition is
generated by hardware and it is usually enabled by default.
A BREAK condition originating from erroneous electrical sig-
nals cannot be distinguished from one deliberately sent by
remote DCE. The Alternate Break sequence can be used as a
remedy against this. Due to a risk of incorrect sequence
interpretation, SLIP and certain other binary protocols
should not be run over the serial console port when Alter-
nate Break sequence is in effect. Although PPP is a binary
protocol, it is able to avoid these sequences using the ACCM
feature in RFC 1662. For Solaris PPP 4.0, you do this by
adding the following line to the /etc/ppp/options file (or
other configuration files used for the connection; see
pppd(1M) for details):
By default, the Alternate Break sequence is a three charac-
ter sequence: carriage return, tilde and control-B (CR ~
CTRL-B), but may be changed by the driver. For more informa-
tion on breaking (entering the debugger or monitor), see
kbd(1) and kb(7M).
An open() will fail under the following conditions:
ENXIO The unit being opened does not exist.
EBUSY The dial-out device is being opened while the
dial-in device is already open, or the dial-in
device is being opened with a no-delay open and
the dial-out device is already open.
EBUSY The unit has been marked as exclusive-use by
another process with a TIOCEXCL ioctl() call.
EINTR The open was interrupted by the delivery of a
dial-in tty lines
dial-out tty lines
asy configuration file
See attributes(5) for descriptions of the following attri-
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
| Architecture | x86 |
tip(1), kbd(1), uucp(1C), eeprom(1M), pppd(1M), ioctl(2),
open(2), termios(3C), attributes(5), ldterm(7M),
ttcompat(7M), kb(7M), termio(7I)
asyn : silo overflow.
The hardware overrun occurred before the input charac-
ter could be serviced.
asyn : ring buffer overflow.
The driver's character input ring buffer overflowed
before it could be serviced.
Man(1) output converted with