asy(7)                           UNIX System V                           asy(7)


NAME
      asy - asynchronous serial port

DESCRIPTION
      The asy driver supports both the system board serial port and an
      additional serial adapter simultaneously.  Up to two serial ports are
      supported.  If an adapter for a port is not installed, an attempt to open
      it will fail.  The port can be programmed for speed (50-19200 baud),
      character length, and parity.  Output speed is always the same as input
      speed.  The port behaves as described in termio (7).

      The asynchronous port is a character-at-a-time device for both input and
      output.  This characteristic both limits the bandwidth which can be
      achieved over a line, and increases the interrupt loading on the central
      processor.  In particular, file transfer programs such as uucp(1) may not
      function well at speeds over 4800 baud.

      The baud rates of the serial adapter programmable baud-rate generator do
      not correspond exactly with system baud rates.  In particular, setting B0
      will cause a disconnect, setting EXTA will set 19200 baud, and setting
      EXTB will set 38400 baud.  It is not possible to directly set 2000, 3600,
      or 7200 baud.  The asynchronous ports driver supports line signal
      (hardware) flow control when the device node /dev/tty0?h is used.  The
      /dev/tty0? ports are software flow control nodes as are the /dev/tty0?
      nodes.

      Note:  when adding asy to the mdevice file [see mdevice(4)], the number
      in the Maximum Units field must be 1.

FILES
      /dev/tty* /dev/term/*

SEE ALSO
      signal(2), termio(7).




















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