ASY(4,F)                    AIX Technical Reference                    ASY(4,F)



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asy



PURPOSE

Supports asynchronous serial ports.

DESCRIPTION

The asy driver supports asynchronous serial ports.  It is unique to AIX PS/2.
If a port is not installed, an attempt to open it fails.  Each port can be
individually programmed for speed (50-19.2K baud), character length, and
parity.  Output speed is always the same as input speed.  This driver supports
the PS/2 system board serial port, the IBM PS/2 Dual Async Adapter/A, and the
IBM PS/2 300/1200 Internal Modem/A.

The asynchronous port is a character-at-a-time device for both input and
output.  This characteristic limits the bandwidth, which can be achieved over a
line and increases the interrupt loading on the central processor.

If the port was opened with the modem control bit present in the minor device
(see the following text), modem control is enabled.  If enabled, the driver
waits in the open routine until data carrier detect is present.  Once opened,
if data carrier detect drops, the driver returns errors on any subsequent user
read or write attempts of the asynchronous port.  If the port was opened as a
controlling teletype, a SIGHUP signal is generated to the process that
performed the open.

If the port was opened with the printer control bit present in the minor device
number (see the following text), the port behaves as a serial printer port and
the driver interface is described by lp.  If the printer control bit is not
present, the port behaves as a terminal port and the driver interface is
described by termio.

Minor Device Numbers

The values of the low-order bits of the minor device number correspond to the
port addresses of the serial ports as configured by the IBM PS/2 Reference
Diskette.  These values are in the range of 0 through 7 and indicate serial
ports SERIAL_1 through SERIAL_8, respectively.  Bit 6 enables modem control on
the selected port.  Bit 7 indicates that the selected port is a serial printer
port.  Following are some examples of minor device numbers.

Minor device         Meaning
  0                  port SERIAL_1, no modem control, tty
  7                  port SERIAL_8, no modem control, tty
 64                  port SERIAL_1, modem control, tty
 65                  port SERIAL_2, modem control, tty
129                  port SERIAL_2, no modem control, lp
193                  port SERIAL_2, modem control, tty



Processed November 7, 1990         ASY(4,F)                                   1

ASY(4,F)                    AIX Technical Reference                    ASY(4,F)




FILES

/dev/tty*
        for terminal devices.

/dev/lp*
        for printer devices.

RELATED INFORMATION

In this book:  "sigaction, sigvec, signal," "lp," and "termio."

The devices command in AIX Operating System Commands Reference.









































Processed November 7, 1990         ASY(4,F)                                   2