termiox(7)termiox(7)NAMEtermiox - extended general terminal interface
SYNOPSIS
fildes, request, arg)
DESCRIPTION
The extended general terminal interface supplements the termio(7) gen‐
eral terminal interface by adding support for asynchronous hardware
flow control and local implementations of additional asynchronous fea‐
tures. Some systems may not support all of these capabilities because
of hardware or software limitations. Other systems may not permit cer‐
tain 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 and character flow control
(see termio(7)). Character flow control occurs when one device con‐
trols the data transfer of another device by inserting control charac‐
ters 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 control.
The EIA-232-D standard specified only unidirectional hardware flow con‐
trol where the Data Circuit-terminating Equipment or Data Communica‐
tions Equipment (DCE) indicates to the Data Terminal Equipment (DTE) to
stop transmitting data. The termiox interface allows both unidirec‐
tional 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 sup‐
ported.
Terminal Parameters
Parameters that control the behavior of devices providing the termiox
interface are specified by the structure, defined in the header file.
Several system calls (see ioctl(5)) that fetch or change these parame‐
ters use the structure which contains the following members:
The field describes hardware flow control modes:
Enable RTS hardware flow control on input.
Enable CTS hardware flow control on input.
The RTS and CTS circuits are involved in establishing CCITT modem con‐
nections. Since RTS and CTS circuits are used both by CCITT modem con‐
nections 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 and bits. Unidirectional
CTS hardware flow control is selected by setting only the bit.
If 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 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.
termiox Structure Related IOCTL Command
The system calls that reference the structure have the form:
Commands using this form are:
The argument is a pointer to a
structure. The current terminal parameters are
fetched and stored into that structure.
The argument is a pointer to a
structure. The current terminal parameters are
set from the values stored in that structure.
The change is immediate. Errors that can be
returned include:
The port does not support hardware flow control.
The file descriptor for this port is configured
for
CCITT mode access. Hardware flow
control is not allowed on CCITT mode
devices.
The argument is a pointer to a
structure. The current terminal parameters are
set from the values stored in that structure.
The change occurs after all characters queued for
output have been transmitted. This form should
be used when changing parameters that affect out‐
put. Errors that can be returned include:
The port does not support hardware flow control.
The file descriptor for this port is configured
for
CCITT mode access. Hardware flow
control is not allowed on CCITT mode
devices.
The argument is a pointer to a
structure. The current terminal parameters are
set from the values stored in that structure.
The change occurs after all characters queued for
output have been transmitted; all characters
queued for input are discarded, then the change
occurs. Errors that can be returned include:
The port does not support hardware flow control.
The file descriptor for this port is configured
for
CCITT mode access. Hardware flow
control is not allowed on CCITT mode
devices.
AUTHOR
was developed by HP and AT&T.
FILES
Files in or under
SEE ALSOioctl(2), termio(7), modem(7).
HP-PB Only termiox(7)
