1 TERMIOX(7I) Ioctl Requests TERMIOX(7I)
2
3 NAME
4 termiox - extended general terminal interface
5
6 DESCRIPTION
7 The extended general terminal interface supplements the termio(7I)
8 general terminal interface by adding support for asynchronous hardware
9 flow control, isochronous flow control and clock modes, and local
10 implementations of additional asynchronous features. Some systems may
11 not support all of these capabilities because of either hardware or
12 software limitations. Other systems may not permit certain functions to
13 be disabled. In these cases the appropriate bits will be ignored. See
14 <sys/termiox.h> for your system to find out which capabilities are
15 supported.
16
17 Hardware Flow Control Modes
18 Hardware flow control supplements the termio(7I) IXON, IXOFF, and IXANY
19 character flow control. Character flow control occurs when one device
20 controls the data transfer of another device by the insertion of control
21 characters in the data stream between devices. Hardware flow control
22 occurs when one device controls the data transfer of another device using
23 electrical control signals on wires (circuits) of the asynchronous
24 interface. Isochronous hardware flow control occurs when one device
25 controls the data transfer of another device by asserting or removing the
26 transmit clock signals of that device. Character flow control and
27 hardware flow control may be simultaneously set.
28
29 In asynchronous, full duplex applications, the use of the Electronic
30 Industries Association's EIA-232-D Request To Send (RTS) and Clear To
31 Send (CTS) circuits is the preferred method of hardware flow control. An
32 interface to other hardware flow control methods is included to provide a
33 standard interface to these existing methods.
34
35 The EIA-232-D standard specified only unidirectional hardware flow
36 control -- the Data Circuit-terminating Equipment or Data Communications
37 Equipment (DCE) indicates to the Data Terminal Equipment (DTE) to stop
38 transmitting data. The termiox interface allows both unidirectional and
39 bidirectional hardware flow control; when bidirectional flow control is
40 enabled, either the DCE or DTE can indicate to each other to stop
41 transmitting data across the interface. Note: It is assumed that the
42 asynchronous port is configured as a DTE. If the connected device is
43 also a DTE and not a DCE, then DTE to DTE (for example, terminal or
44 printer connected to computer) hardware flow control is possible by using
45 a null modem to interconnect the appropriate data and control circuits.
46
47 Clock Modes
48 Isochronous communication is a variation of asynchronous communication
49 whereby two communicating devices may provide transmit and/or receive
50 clock signals to one another. Incoming clock signals can be taken from
51 the baud rate generator on the local isochronous port controller, from
52 CCITT V.24 circuit 114, Transmitter Signal Element Timing - DCE source
53 (EIA-232-D pin 15), or from CITT V.24 circuit 115, Receiver Signal
54 Element Timing - DCE source (EIA-232-D pin 17). Outgoing clock signals
55 can be sent on CCITT V.24 circuit 113, Transmitter Signal Element Timing
56 - DTE source (EIA-232-D pin 24), on CCITT V.24 circuit 128, Receiver
57 Signal Element Timing - DTE source (no EIA-232-D pin), or not sent at
58 all.
59
60 In terms of clock modes, traditional asynchronous communication is
61 implemented simply by using the local baud rate generator as the incoming
62 transmit and receive clock source and not outputting any clock signals.
63
64 Terminal Parameters
65 The parameters that control the behavior of devices providing the termiox
66 interface are specified by the termiox structure defined in the
67 <sys/termiox.h> header. Several ioctl(2) system calls that fetch or
68 change these parameters use this structure:
69
70 #define NFF 5
71 struct termiox {
72 unsigned short x_hflag; /* hardware flow control modes */
73 unsigned short x_cflag; /* clock modes */
74 unsigned short x_rflag[NFF]; /* reserved modes */
75 unsigned short x_sflag; /* spare local modes */
76 };
77
78 The x_hflag field describes hardware flow control modes:
79
80 RTSXOFF 0000001 Enable RTS hardware flow control on input.
81 CTSXON 0000002 Enable CTS hardware flow control on output.
82 DTRXOFF 0000004 Enable DTR hardware flow control on input.
83 CDXON 0000010 Enable CD hardware flow control on output.
84 ISXOFF 0000020 Enable isochronous hardware flow control on input.
85
86 The EIA-232-D DTR and CD circuits are used to establish a connection
87 between two systems. The RTS circuit is also used to establish a
88 connection with a modem. Thus, both DTR and RTS are activated when an
89 asynchronous port is opened. If DTR is used for hardware flow control,
90 then RTS must be used for connectivity. If CD is used for hardware flow
91 control, then CTS must be used for connectivity. Thus, RTS and DTR (or
92 CTS and CD) cannot both be used for hardware flow control at the same
93 time. Other mutual exclusions may apply, such as the simultaneous
94 setting of the termio(7I) HUPCL and the termiox DTRXOFF bits, which use
95 the DTE ready line for different functions.
96
97 Variations of different hardware flow control methods may be selected by
98 setting the appropriate bits. For example, bidirectional RTS/CTS flow
99 control is selected by setting both the RTSXOFF and CTSXON bits and
100 bidirectional DTR/CTS flow control is selected by setting both the
101 DTRXOFF and CTSXON. Modem control or unidirectional CTS hardware flow
102 control is selected by setting only the CTSXON bit.
103
104 As previously mentioned, it is assumed that the local asynchronous port
105 (for example, computer) is configured as a DTE. If the connected device
106 (for example, printer) is also a DTE, it is assumed that the device is
107 connected to the computer's asynchronous port using a null modem that
108 swaps control circuits (typically RTS and CTS). The connected DTE drives
109 RTS and the null modem swaps RTS and CTS so that the remote RTS is
110 received as CTS by the local DTE. In the case that CTSXON is set for
111 hardware flow control, printer's lowering of its RTS would cause CTS seen
112 by the computer to be lowered. Output to the printer is suspended until
113 the printer's raising of its RTS, which would cause CTS seen by the
114 computer to be raised.
115
116 If RTSXOFF is set, the Request To Send (RTS) circuit (line) will be
117 raised, and if the asynchronous port needs to have its input stopped, it
118 will lower the Request To Send (RTS) line. If the RTS line is lowered,
119 it is assumed that the connected device will stop its output until RTS is
120 raised.
121
122 If CTSXON is set, output will occur only if the Clear To Send (CTS)
123 circuit (line) is raised by the connected device. If the CTS line is
124 lowered by the connected device, output is suspended until CTS is raised.
125
126 If DTRXOFF is set, the DTE Ready (DTR) circuit (line) will be raised, and
127 if the asynchronous port needs to have its input stopped, it will lower
128 the DTE Ready (DTR) line. If the DTR line is lowered, it is assumed that
129 the connected device will stop its output until DTR is raised.
130
131 If CDXON is set, output will occur only if the Received Line Signal
132 Detector (CD) circuit (line) is raised by the connected device. If the
133 CD line is lowered by the connected device, output is suspended until CD
134 is raised.
135
136 If ISXOFF is set, and if the isochronous port needs to have its input
137 stopped, it will stop the outgoing clock signal. It is assumed that the
138 connected device is using this clock signal to create its output.
139 Transit and receive clock sources are programmed using the x_cflag
140 fields. If the port is not programmed for external clock generation,
141 ISXOFF is ignored. Output isochronous flow control is supported by
142 appropriate clock source programming using the x_cflag field and enabled
143 at the remote connected device.
144
145 The x_cflag field specifies the system treatment of clock modes.
146
147 XMTCLK 0000007 Transmit clock source:
148 XCIBRG 0000000 Get transmit clock from internal baud rate
149 generator.
150 XCTSET 0000001 Get transmit clock from transmitter signal
151 element timing (DCE source) lead, CCITT V.24
152 circuit 114, EIA-232-D pin 15.
153 XCRSET 0000002 Get transmit clock from receiver signal element
154 timing (DCE source) lead, CCITT V.4 circuit 115,
155 EIA-232-D pin 17."
156 RCVCLK 0000070 Receive clock source:
157 RCIBRG 0000000 Get receive clock from internal baud rate
158 generator.
159 RCTSET 0000010 Get receive clock from transmitter signal
160 element timing (DCE source) lead, CCITT V.24
161 circuit 114, EIA-232-D pin 15.
162 RCRSET 0000020 Get receive clock from receiver signal element
163 timing (DCE source) lead, CCITT V.24 circuit
164 115, EIA-232-D pin 17.
165 TSETCLK 0000700 Transmitter signal element timing (DTE source)
166 lead, CCITT V.24 circuit 113, EIA-232-D pin 24,
167 clock source:
168 TSETCOFF 0000000 TSET clock not provided.
169 TSETCRBRG 0000100 Output receive baud rate generator on circuit
170 113.
171 TSETCTBRG 0000200 Output transmit baud rate generator on circuit
172 113
173 TSETCTSET 0000300 Output transmitter signal element timing (DCE
174 source) on circuit 113.
175 TSETCRSET 0000400 Output receiver signal element timing (DCE
176 source) on circuit 113.
177 RSETCLK 0007000 Receiver signal element timing (DTE source)
178 lead, CCITT V.24 circuit 128, no EIA-232-D pin,
179 clock source:
180 RSETCOFF 0000000 RSET clock not provided.
181 RSETCRBRG 0001000 Output receive baud rate generator on circuit
182 128.
183 RSETCTBRG 0002000 Output transmit baud rate generator on circuit
184 128.
185 RSETCTSET 0003000 Output transmitter signal element timing (DCE
186 source) on circuit 128.
187 RSETCRSET 0004000 Output receiver signal element timing (DCE) on
188 circuit 128.
189
190 If the XMTCLK field has a value of XCIBRG the transmit clock is taken
191 from the hardware internal baud rate generator, as in normal asynchronous
192 transmission. If XMTCLK = XCTSET the transmit clock is taken from the
193 Transmitter Signal Element Timing (DCE source) circuit. If XMTCLK =
194 XCRSET the transmit clock is taken from the Receiver Signal Element
195 Timing (DCE source) circuit.
196
197 If the RCVCLK field has a value of RCIBRG, the receive clock is taken
198 from the hardware Internal Baud Rate Generator, as in normal asynchronous
199 transmission. If RCVCLK = RCTSET the receive clock is taken from the
200 Transmitter Signal Element Timing (DCE source) circuit. If RCVCLK =
201 RCRSET the receive clock is taken from the Receiver Signal Element Timing
202 (DCE source) circuit.
203
204 If the TSETCLK field has a value of TSETCOFF the Transmitter Signal
205 Element Timing (DTE source) circuit is not driven. If TSETCLK =
206 TSETCRBRG the Transmitter Signal Element Timing (DTE source) circuit is
207 driven by the Receive Baud Rate Generator. If TSETCLK = TSETCTBRG the
208 Transmitter Signal Element Timing (DTE source) circuit is driven by the
209 Transmit Baud Rate Generator. If TSETCLK = TSETCTSET the Transmitter
210 Signal Element Timing (DTE source) circuit is driven by the Transmitter
211 Signal Element Timing (DCE source). If TSETCLK = TSETCRBRG the
212 Transmitter Signal Element Timing (DTE source) circuit is driven by the
213 Receiver Signal Element Timing (DCE source).
214
215 If the RSETCLK field has a value of RSETCOFF the Receiver Signal Element
216 Timing (DTE source) circuit is not driven. If RSETCLK = RSETCRBRG the
217 Receiver Signal Element Timing (DTE source) circuit is driven by the
218 Receive Baud Rate Generator. If RSETCLK = RSETCTBRG the Receiver Signal
219 Element Timing (DTE source) circuit is driven by the Transmit Baud Rate
220 Generator. If RSETCLK = RSETCTSET the Receiver Signal Element Timing
221 (DTE source) circuit is driven by the Transmitter Signal Element Timing
222 (DCE source). If RSETCLK = RSETCRBRG the Receiver Signal Element Timing
223 (DTE source) circuit is driven by the Receiver Signal Element Timing (DCE
224 source).
225
226 The x_rflag is reserved for future interface definitions and should not
227 be used by any implementations. The x_sflag may be used by local
228 implementations wishing to customize their terminal interface using the
229 termiox ioctl system calls.
230
231 IOCTLS
232 The ioctl(2) system calls have the form:
233
234 struct termiox *arg;
235 ioctl(fildes, command, arg);
236
237 The commands using this form are:
238
239 TCGETX The argument is a pointer to a termiox structure. The current
240 terminal parameters are fetched and stored into that structure.
241
242 TCSETX The argument is a pointer to a termiox structure. The current
243 terminal parameters are set from the values stored in that
244 structure. The change is immediate.
245
246 TCSETXW The argument is a pointer to a termiox structure. The current
247 terminal parameters are set from the values stored in that
248 structure. The change occurs after all characters queued for
249 output have been transmitted. This form should be used when
250 changing parameters that will affect output.
251
252 TCSETXF The argument is a pointer to a termiox structure. The current
253 terminal parameters are set from the values stored in that
254 structure. The change occurs after all characters queued for
255 output have been transmitted; all characters queued for input
256 are discarded and then the change occurs.
257
258 FILES
259 /dev/*
260
261 SEE ALSO
262 stty(1), ioctl(2), termio(7I)
263
264 NOTES
265 The termiox(7I) system call is provided for compatibility with previous
266 releases and its use is discouraged. Instead, the termio(7I) system call
267 is recommended. See termio(7I) for usage information.
268
269 illumos October 29, 2017 illumos