termiox.7 (2010 09)

t
termiox(7) termiox(7)
(HP-PB Only)
NAME
termiox - extended general terminal interface
SYNOPSIS
#include <sys/termiox.h>
ioctl (int fildes, int request ,
struct termiox * arg)
DESCRIPTION
The extended general terminal interface supplements the termio(7) general terminal interface by adding
support for asynchronous hardware flow control and local implementations of additional asynchronous
features. Some systems may not support all of these capabilities because of hardware or software limita-
tions. Other systems may not permit certain functions to be disabled. In such cases, the appropriate bits
are ignored. If the capabilities can be supported, the interface described here must be used.
Hardware Flow Control Modes
Hardware flow control supplements the termio
IXON, IXOFF, and IXANY character flow control (see ter-
mio(7)). Character flow control occurs when one device controls the data transfer of another device by
inserting control characters in the data stream between devices. Hardware flow control occurs when one
device controls the data transfer of another device by using electrical control signals on wires (circuits) of
the asynchronous interface. Character flow control and hardware flow control can be simultaneously set.
In asynchronous, full duplex applications, the use of the Electronics Industries Association’s EIA-232-D
Request To Send (RTS) and Clear To Send (CTS) circuits is the preferred method of hardware flow con-
trol.
The EIA-232-D standard specified only unidirectional hardware flow control where the Data Circuit-
terminating Equipment or Data Communications Equipment (DCE) indicates to the Data Terminal
Equipment (DTE) to stop transmitting data. The termiox interface allows both unidirectional and
bidirectional hardware flow control; when bidirectional flow control is enabled, either the DCE or DTE
can indicate to each other to stop transmitting data across the interface.
Clock Modes
Isochronous flow control and clock mode communication are not supported.
Terminal Parameters
Parameters that control the behavior of devices providing the termiox interface are specified by the
ter-
miox structure, defined in the <sys/termiox.h>
header file. Several ioctl() system calls (see
ioctl (5)) that fetch or change these parameters use the
termiox structure which contains the following
members:
unsigned short x_hflag; /* hardware flow control modes */
unsigned short x_cflag; /* clock modes */
unsigned short x_rflag; /* reserved modes */
unsigned short x_sflag; /* spare local modes */
The x_hflag field describes hardware flow control modes:
RTSXOFF 0000001 Enable RTS hardware flow control on input.
CTSXON 0000002 Enable CTS hardware flow control on input.
The RTS and CTS circuits are involved in establishing CCITT modem connections. Since RTS and CTS
circuits are used both by CCITT modem connections and by hardware flow control, CCITT modem and
hardware flow control cannot be simultaneously enabled.
Variations of different hardware flow control methods can be selected by setting the appropriate bits. For
example, bidirectional RTS/CTS flow control is selected by setting both the
RTSXOFF and CTSXON bits.
Unidirectional CTS hardware flow control is selected by setting only the CTSXON bit.
If
RTSXOFF is set, the Request to Send (RTS) circuit (line) is raised, and if the asynchronous port needs
to have its input stopped, it lowers the Request to Send (RTS) line. If the RTS line is lowered, it is
assumed that the connected device will stop its output until RTS is raised.
If
CTSXON is set, output occurs only if the Clear To Send (CTS) circuit (line) is raised by the connected
device. If the CTS line is lowered by the connected device, output is suspended until CTS is raised.
HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1