Technical data

SunOS 5.5 Devices zs(7D)
NAME zs − Zilog 8530 SCC serial communications driver
SYNOPSIS #include <fcntl.h>
#include <sys/termios.h>
open("/dev/term/n", mode);
open("/dev/ttyn", mode);
open("/dev/cua/n", mode);
AVAILABILITY SPARC
DESCRIPTION The Zilog 8530 provides two serial input/output channels that are capable of supporting
a variety of communication protocols. A typical system uses two or more of these dev-
ices to implement essential functions, including RS-423 ports (which also support most
RS-232 equipment), and the console keyboard and mouse devices.
The zs module is a loadable STREAMS driver that provides basic support for the 8530
hardware, together with basic asynchronous communication support. The driver sup-
ports those termio(7I) device control functions specified by flags in the c_cflag word of
the termios structure and by theIGNBRK, IGNPAR, PARMRK, or INPCK flags in the
c_iflag word of the termios structure. All other termio(7I) functions 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, pro-
viding the standard termio(7I) interface.
The character-special devices /dev/term/a and /dev/term/b are used to access the two
serial ports on the CPU board.
Note: /dev/cua/[a-z], /dev/term/[a-z] and /dev/tty[a-z] are valid name space entries. The
number of entries used in this name space are machine dependent.
The /dev/ttyn device names only exist if the binary compatibility package is installed. The
/dev/ttyn device names are created by the ucblinks command. This command is only
available via the binary compatibility package.
To allow a single tty line to be connected to a modem and used for both incoming and
outgoing calls, a special feature, controlled by the minor device number, is available. By
accessing character-special devices with names of the form /dev/cua/n it is possible to
open a port without the Carrier Detect signal being asserted, either through hardware or
an equivalent software mechanism. These devices are commonly known as dial-out
lines.
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, and a non-blockingopen will return an error. Also, if
the tty 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, for example, /dev/term/n (renamed from /dev/ttyn) and used for dial-in (by
enabling the line for login in /etc/inittab) and also used for dial-out (by tip(1) or
modified 2 Mar 1995 7D-413