1asy(7D) Devices asy(7D)
2
6 asy - asynchronous serial port driver
7
9 #include <fcntl.h>
10 #include <sys/termios.h>
13 open("/dev/term/n", mode);
16 open("/dev/tty/n", mode);
19 open("/dev/cua/n", mode);
22
25 The asy module is a loadable STREAMS driver that provides basic support
26 for Intel-8250, National Semiconductor-16450, 16550, and some 16650 and
27 16750 and equivalent UARTs connected via the ISA-bus, in addition to
28 basic asynchronous communication support. The asy module supports those
29 termio(7I) device control functions specified by flags in the c_cflag
30 word of the termios structure, and by the IGNBRK, IGNPAR, PARMRK,
31 INPCK, IXON, IXANY, or IXOFF flags in the c_iflag word of the termios
32 structure. All other termio(7I) functions must be performed by STREAMS
33 modules pushed atop the driver. When a device is opened, the ldterm(7M)
34 and ttcompat(7M) STREAMS modules are automatically pushed on top of the
35 stream, providing the standard termio(7I) interface.
36 The character-special devices /dev/term/a, /dev/term/b, /dev/term/c and
39 /dev/term/d are used to access the four standard serial ports (COM1,
40 COM2, COM3 and COM4 at I/O addresses 3f8, 2f8, 3e8 and 2e8 respec‐
41 tively). Serial ports on non-standard ISA-bus I/O addresses are
42 accessed via the character-special devices /dev/term/0, /dev/term/1,
43 etc. Device names are typically used to provide a logical access point
44 for a dial-in line that is used with a modem.
45 To allow a single tty line to be connected to a modem and used for
48 incoming and outgoing calls, a special feature is available that is
49 controlled by the minor device number. By accessing character-special
50 devices with names of the form /dev/cua/n, it is possible to open a
51 port without the Carrier Detect signal being asserted, either through
52 hardware or an equivalent software mechanism. These devices are com‐
53 monly known as dial-out lines.
54 Note -
56 This module is affected by the setting of certain eeprom variables,
58 ttya-ignore-cd and ttya-rts-dtr-off (and similarly for ttyb-, ttyc-,
59 and ttyd- parameters). For information on these parameters, see the
60 eeprom(1M) man page.
61 Note -
63 For serial ports on the standard COM1 to COM4 I/O addresses above,
65 the default setting for ttya-ignore-cd and ttya-rts-dtr-off is true.
66 If any of these ports are connected to a modem, these settings should
67 be changed to false. For serial ports on non-standard I/O addresses,
68 the default setting for ttya-ignore-cd and ttya-rts-dtr-off is false.
69
71 Once a /dev/cua/n line is opened, the corresponding tty line cannot be
72 opened until the /dev/cua/n line is closed. A blocking open will wait
73 until the /dev/cua/n line is closed (which will drop Data Terminal
74 Ready, after which Carrier Detect will usually drop as well) and car‐
75 rier is detected again. A non-blocking open will return an error. If
76 the /dev/ttydn line has been opened successfully (usually only when
77 carrier is recognized on the modem), the corresponding /dev/cua/n line
78 cannot be opened. This allows a modem to be attached to /dev/term/[n]
79 (renamed from /dev/tty[n]) and used for dial-in (by enabling the line
80 for login in /etc/inittab) or dial-out (by tip(1) or uucp(1C)) as
81 /dev/cua/n when no one is logged in on the line.
82
84 The standard set of termio ioctl() calls are supported by asy.
85 Breaks can be generated by the TCSBRK, TIOCSBRK, and TIOCCBRK ioctl()
88 calls.
89 The input and output line speeds may be set to any speed that is sup‐
92 ported by termio. The speeds cannot be set independently; for example,
93 when the output speed is set, the input speed is automatically set to
94 the same speed.
95 When the asy module is used to service the serial console port, it sup‐
98 ports a BREAK condition that allows the system to enter the debugger or
99 the monitor. The BREAK condition is generated by hardware and it is
100 usually enabled by default.
101 A BREAK condition originating from erroneous electrical signals cannot
104 be distinguished from one deliberately sent by remote DCE. The Alter‐
105 nate Break sequence can be used as a remedy against this. Due to a risk
106 of incorrect sequence interpretation, SLIP and certain other binary
107 protocols should not be run over the serial console port when Alternate
108 Break sequence is in effect. Although PPP is a binary protocol, it is
109 able to avoid these sequences using the ACCM feature in RFC 1662. For
110 Solaris PPP 4.0, you do this by adding the following line to the
111 /etc/ppp/options file (or other configuration files used for the con‐
112 nection; see pppd(1M) for details):
113 asyncmap 0x00002000
115 By default, the Alternate Break sequence is a three character sequence:
119 carriage return, tilde and control-B (CR ~ CTRL-B), but may be changed
120 by the driver. For more information on breaking (entering the debugger
121 or monitor), see kbd(1) and kb(7M).
122
124 An open() will fail under the following conditions:
125 ENXIO The unit being opened does not exist.
127 EBUSY The dial-out device is being opened while the dial-in device
130 is already open, or the dial-in device is being opened with a
131 no-delay open and the dial-out device is already open.
132 EBUSY The unit has been marked as exclusive-use by another process
135 with a TIOCEXCL ioctl() call.
136 EINTR The open was interrupted by the delivery of a signal.
139
142 /dev/term/[a-d] dial-in tty lines
143 /dev/term/[012...]
144 /dev/cua/[a-d] dial-out tty lines
146 /dev/cua/[012...]
147 /kernel/drv/amd64/asy 64-bit kernel module for 64-bit x86 platform
149 /kernel/drv/asy.conf asy configuration file
152
155 See attributes(5) for descriptions of the following attributes:
156 ┌─────────────────────────────┬─────────────────────────────┐
161 │ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
162 ├─────────────────────────────┼─────────────────────────────┤
163 │Architecture │x86 │
164 └─────────────────────────────┴─────────────────────────────┘
165
167 tip(1), kbd(1), uucp(1C), eeprom(1M), pppd(1M), ioctl(2), open(2),
168 termios(3C), attributes(5), ldterm(7M), ttcompat(7M), kb(7M),
169 termio(7I)
170
172 asyn: silo overflow.
173 The hardware overrun occurred before the input character could be
175 serviced.
176 asyn: ring buffer overflow.
179 The driver's character input ring buffer overflowed before it could
181 be serviced.
182SunOS 5.11 9 Oct 2004 asy(7D)