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.
Page 1 Plan 9 (printed 12/22/24)
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
Page 2 Plan 9 (printed 12/22/24)