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.
Page 1 Plan 9 (printed 12/27/24)
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 12/27/24)