UART(3)

NAME

duart, uart, eia, astar − serial communication control

SYNOPSIS

bind -a #t /dev
/dev/eia0
/dev/eia0ctl
/dev/eia1
/dev/eia1ctl
bind -a #G /dev
/dev/astar0ctl
/dev/astar0mem
/dev/eia000
/dev/eia000ctl
/dev/eia000stat
/dev/eia001
/dev/eia001ctl
/dev/eia001stat
...

DESCRIPTION

The serial line devices serve a one-level directory, giving access to the serial ports. There are several devices serving the same files; the particular one used depends on the machine involved. Eia0 is the data file. It can be read and written to use that port. Reads will block until at least one character is available. Eia0ctl is a control file associated with the port. Eia1 and eia1ctl are similar, but for a second serial line.

The ctl configures the port. It accepts the following commands:

bn Set the baud rate to n.

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

kn Send a break lasting n milliseconds.

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

mn Obey modem CTS signal if n is non-zero; else clear it.

in Enable input FIFO if n is non-zero; else disable.

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

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

ln Set number of bits per byte to n. Legal values are 5, 6, 7, or 8.

The Star Gate Avanstar intelligent serial board has a separate driver. The individual data and ctl files behave like regular UART files, but there are 16 per controller. The stat files contain a textual representation of the status of the line, in the format of the commands used on the ctl file. The astar0ctl and astar0mem files are used by the aux/astarld program to download the controller software for the boards.

FILES

/sys/lib/astar/∗ download files for the Avanstar

/bin/aux/astarld download program for the Avanstar

SOURCE

/sys/src/9/port/devns16552.c
/sys/src/9/ch/devz8530.c
/sys/src/9/pc/devastar.c