UART(3)                                                   UART(3)

     NAME
          uart, 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 devices serve a one-level directory, giving
          access to the serial ports.  Device n is accessed through
          eian (the data file), eianctl (the control file), and
          eianstatus (the read-only status file).  Reads of the data
          file will block until at least one byte is available.  The
          control file configures the port.  It accepts the following
          commands:

          bn   Set the baud rate to n.

          cn   Set hangup on DCD if n is non-zero; else clear it.

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

          en   Set hangup on DSR if n is non-zero; else clear it.

          f    Flush output queue.

          h    Close input and output queues.

          in   Enable/disable the FIFOs.  If n is zero the FIFOs are
               disabled; otherwise n is taken as a trigger level for
               the FIFOs.  The trigger levels supported are device
               dependant, but usually include 1, 4 and 8.  An unrecog-
               nised, but non-zero, value of n causes the maximum-
               supported trigger level to be set.

          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; else clear it.

          n    Make writes non-blocking.

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     UART(3)                                                   UART(3)

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

          qn   Set input and output queue limits to n.

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

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

          wn   Set the uart clock timer to n times 100us.

          The status files contain a textual representation of the
          status of the line, in the format of the commands used on
          the control file.

     SOURCE
          /sys/src/9/port/devuart.c
          /sys/src/9/*/uart*.c

     Page 2                       Plan 9            (printed 10/29/25)