.TH UART 3 
.SH NAME
uart, eia - serial communication control
.SH SYNOPSIS
.nf
.B bind -a #t /dev

.B /dev/eia0
.B /dev/eia0ctl
.B /dev/eia0status
.B /dev/eia1
.B /dev/eia1ctl
.B /dev/eia1status
...
.fi
.SH DESCRIPTION
.PP
The serial line devices serve a one-level directory,
giving access to the serial ports.
Device
.I n
is accessed through
.B eia
.I n
(the data file),
.B eia
.I n
.I ctl
(the control file), and
.B eia
.I n
.I status
(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:
.TP
.B b n
Set the baud rate to
.IR n .
.TP
.B c n
Do hangup on DCD if
.I n
is non-zero; else clear it.
.TP
.B d n
Set DTR if
.I n
is non-zero;
else clear it.
.TP
.B e n
Do hangup on DSR if
.I n
is non-zero; else clear it.
.TP
.B f
Flush output queue.
.TP
.B h
Hangup input and output queue.
.TP
.B i n
Enable/disable the FIFOs.
If
.I n
is zero the FIFOs are disabled;
otherwise
.I 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
.I n
causes the maximum-supported trigger level to be set.
.TP
.B k n
Send a break lasting
.I n
milliseconds.
.TP
.B l n
Set number of bits per byte to
.IR n .
Legal values are 5, 6, 7, or 8.
.TP
.B m n
Obey modem CTS signal if
.I n
is non-zero;
else clear it.
.TP
.B n
Turn off blocking on read.
.TP
.B p c
Set parity to odd if
.I c
is
.BR o ,
to even if
.I c
is
.BR e ;
else set no parity.
.TP
.B q n
Set queue limit to
.IR n .
.TP
.B r n
Set RTS if
.I n
is non-zero;
else clear it.
.TP
.B s n
Set number of stop bits to
.IR n .
Legal values are 1 or 2.
.TP
.B w n
Set the uart clock timer to
n times 100us.
.IP
.PP
The status
files contain a textual representation of the status of the line, in the format of the
commands used on the
control
file.
.SH SOURCE
.B /sys/src/9/port/devuart.c
.br
.B /sys/src/9/*/uart*.c