asy - asynchronous serial port driver


     #include <fcntl.h>

     #include <sys/termios.h>

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

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

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


     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.


     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):
     asyncmap  0x00002000

     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.

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