EIA(3)                                                     EIA(3)

     NAME
          eia - serial communication control

     SYNOPSIS
          bind -a '#t' /dev

          /dev/eia0
          /dev/eia0ctl
          /dev/eia0status
          /dev/eia1
          /dev/eia1ctl
          /dev/eia1status
          ...

     DESCRIPTION
          The serial line device serves a one-level directory that
          gives access to the serial ports.  Each file set eian ...
          represents one serial port and includes a data file (eg,
          eia0), a control file (eg, eia0ctl), and a status file (eg,
          eia0status).

          The data file can be read and written to access the corre-
          sponding serial port.  Reads will block until at least one
          character is available.

          The ctl file accepts textual commands, via write (see sys-
          read(2)), that control or condition the serial port for sub-
          sequent IO:

          bn   Set the baud rate to n.

          cn   If n is non-zero, cause a hangup if the remote drops
               DCD.

          dn   Set DTR if n is non-zero; otherwise clear it.

          en   If n is non-zero, cause a hangup if the remote drops
               DSR.

          f    Flush the output queue.

          h    Hangup both input and output queues.

          kn   Send a break lasting n milliseconds.

          ln   Set number of bits per byte to n. Legal values are 5,
               6, 7, or 8.

          mn   Obey modem CTS signal if n is non-zero; otherwise clear
               it.

     EIA(3)                                                     EIA(3)

          nn   Set the output queue to non-blocking, if n is non-zero;
               otherwise mark it as blocking (the default).  In non-
               blocking mode, if the output queue is full, new output
               is discarded rather than block the writer until the
               queue drains.

          pc   Set parity to odd if c is o, to even if c is e; other-
               wise set no parity.

          qn   Set the limit on input and output queues to n; both
               queues are initially set to 4k bytes.

          rn   Set RTS if n is non-zero; otherwise clear it.

          sn   Set number of stop bits to n. Legal values are 1 or 2.

          xn   Enable XON/XOFF flow control if n is non-zero; other-
               wise disable it (the default).

          Changes to port settings persist between a subsequent close
          and reopen.

          The status file can be read for a report of the serial port
          status.

     SOURCE
          /os/port/devns16552.c
          /os/*/devuart.c
          /os/*/devscc.c