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 unrecognised,
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.
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