Technical data

SunOS 5.5 Devices mcpzsa(7D)

NAME mcpzsa − ALM-2 Zilog 8530 SCC serial communications driver

SYNOPSIS #include <fcntl.h>

#include <sys/termios.h>

open("/dev/term/n", mode);

open("/dev/cua/n", mode);

DESCRIPTION The ALM-2 board provides 16 serial input/output channelsthat are capable of supporting

a variety of communication protocols. A typical system uses these devices to implement

essential functions, including RS-423 ports (which also support most RS-232 equipment).

The mcpzsa module is a loadable STREAMS driver that provides basic support for the

8530 hardware, together with basic asynchronous communication support. The driver

supports those termio(7I) device control functions speciﬁed by ﬂags in the c_cﬂag word

of the termios structure and by theIGNBRK, IGNPAR, PARMRK, orINPCK 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/[0-15] are used to access the serial ports on the

ﬁrst ALM-2 board.

Subsequent instances of the ALM-2 board will use the next 16 numbers in sequence.

These term/n devices have minor device numbers in the range 0 − 127.

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

and have minor numbers 256 greater than their corresponding dial-in lines.

Once a /dev/cua/n line is opened, the corresponding term 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 /dev/term/n line has been opened successfully (usually only when carrier is recog-

nized by the modem) the corresponding /dev/cua/n line can not be opened. This allows a

modem to be attached to, for example, /dev/term/0 and used for dial-in (by enabling the

line for login in /etc/inittab) and also used for dial-out (by tip(1) or uucp(1C)) as

/dev/cua/0 when no one is logged in on the line.

modiﬁed 8 Mar 1993 7D-205