Technical data

termiox(7I) Ioctl Requests SunOS 5.5
NAME termiox − extended general terminal interface
DESCRIPTION The extended general terminal interface supplements the termio(7I) general terminal
interface by adding support for asynchronous hardware flow control, isochronous flow
control and clock modes, and local implementations of additional asynchronous features.
Some systems may not support all of these capabilities because of either hardware or
software limitations. Other systems may not permit certain functions to be disabled. In
these cases the appropriate bits will be ignored. See <sys/termiox.h> for your system to
find out which capabilities are supported.
Hardware Flow
Control Modes
Hardware flow control supplements the termio(7I) IXON, IXOFF, and IXANY character
flow control. Character flow control occurs when one device controls the data transfer of
another device by the insertion of control characters in the data stream between devices.
Hardware flow control occurs when one device controls the data transfer of another dev-
ice using electrical control signals on wires (circuits) of the asynchronous interface. Iso-
chronous hardware flow control occurs when one device controls the data transfer of
another device by assertingor removing the transmit clock signals of that device. Charac-
ter flow control and hardware flow control may be simultaneously set.
In asynchronous, full duplex applications, the use of the Electronic Industries
Association’s EIA-232-D Request To Send (RTS) and Clear To Send (CTS) circuits is the
preferred method of hardware flow control. An interface to other hardware flow control
methods is included to provide a standard interface to these existing methods.
The EIA-232-D standard specified only uni-directional hardware flow control - 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 uni-directional and bi-directional hardware flow control; when bi-directional
flow control is enabled, either theDCE or DTE can indicate to each other to stop transmit-
ting data across the interface. Note: It is assumed that the asynchronous port is
configured as a DTE. If the connected device is also a DTE and not aDCE, then DTE to DTE
(for example, terminal or printer connected to computer) hardware flow control is possi-
ble by using a null modem to interconnect the appropriate data and control circuits.
Clock Modes Isochronous communication is a variation of asynchronous communication whereby two
communicating devices may provide transmit and/or receive clock to each other. Incom-
ing clock signals can be taken from the baud rate generator on the local isochronous port
controller, from CCITT V.24 circuit 114, Transmitter Signal Element Timing - DCE source
(EIA-232-D pin 15), or from CCITT V.24 circuit 115, Receiver Signal Element Timing- DCE
source (EIA-232-D pin 17). Outgoing clock signals can be sent on CCITT V.24 circuit 113,
Transmitter Signal Element Timing - DTE source (EIA-232-D pin 24), on CCITT V.24 circuit
128, Receiver Signal Element Timing - DTE source (no EIA-232-D pin), or not sent at all.
In terms of clock modes, traditional asynchronous communication is implemented sim-
ply by using the local baud rate generator as the incoming transmit and receive clock
source and not outputting any clock signals.
7I-364 modified 3 Jul 1990