NAME

eia − serial communication control

SYNOPSIS

­bind -a ’#t’ /dev
 ­/dev/eia0
­/dev/eia0ctl
­/dev/eia0stat
­/dev/eia1
­/dev/eia1ctl
­/dev/eia1stat
...

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 corresponding 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 subsequent 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. 

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; otherwise 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; otherwise 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

Plan 9  —  June 07, 2000