12-05-2003
Please click on the rules link at the bottom of the page. I have deleted your other thread.
You're not going to be able to do what you want. Use the command "man termios" to see what is available from the terminal driver. Use our search function to searc this forum to see some examples of termios in use.
In you have the hardware, you can use modem control signals, but the driver does it on your behalf. For an incoming line, a open() call raises DTR which signals the modem that it may auto-answer a call. When it does, it will raise DSR which causes the open to complete. If DSR drops, a hup signal is generated. A very clever program might be able to use all of this to "read" the state of the DSR signal. But open() is an expensive system call and the bandwidth would be low.
Some unix systems (maybe most? or all?) you can use CTS for hardware flow control of output, and RTS for hardware flow control of input. There is no hope for RTS, but a clever program might be able to determine the state of CTS by seeing if a non-blocking write() succeeds. But DSR would need to be high.
You might be able to have a simple switch send a break character. Anyone who uses a Sun with a terminal console knows how easy that is. You can arrange for a break character to send an INT signal to the program.
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ace(7) Miscellaneous Information Manual ace(7)
NAME
ace - Serial communications interface
SYNOPSIS
controller ace0 at * slot ? vector aceintr
DESCRIPTION
The ace serial line controller provides a serial communications interface on DEC 2000, AlphaStation, and AlphaServer platforms. The serial
communications ports that are controlled by ace adhere to the RS-232 standard and can operate at rates from 50 to 115200 baud (see tty(7)).
These communications ports support serial-line printers, modems, and terminals.
In alternate console configurations (that is, no graphics head), the terminal to be the system console must be connected to the port that
is mapped to /dev/tty00. (See ports(7) for information about mapping AlphaStation and AlphaServer port labels to device pathnames.) Cur-
rently, some processors that use the ace driver limit the serial console port to 9600 baud, 8-bit, no parity and no modem support. However,
some processor consoles do support baud rates other than 9600 baud and allow the use of modems as console devices. Consult your hardware
documentation to determine the type of console support your system provides.
The driver for the ace interface supports hardware flow control using the Request to Send (RTS) and Clear to Send (CTS) signals. When
hardware flow control is enabled, the flow of input data is controlled by the RTS signal and the flow of output data is controlled by the
CTS signal. If the CTS signal is off, the driver suspends output to that line until the CTS lead is reasserted. Likewise the driver turns
off the RTS lead to tell the device connected to the line to stop sending data as a result of congestion on the host side. When the condi-
tion clears, the driver turns on the RTS lead to tell the device to resume sending data.
The DCD (carrier detect) timer value defaults to 2 seconds. This value may be changed if your modem hardware requires a different value.
the change can be made in the /etc/sysconfigtab file as follows:
ace: dcd_timer=n
where n is the time interval in seconds, and can be set to 0 (no timeout), 1, or 2 seconds. Alternatively, you can use the sysconfig com-
mand to set the same time interval option as follows:
# sysconfig -r ace dcd_timer=[n]
If you use the sysconfig command, the value will not be preserved when the system is rebooted. To preserve the setting, put the entry in
the /etc/sysconfigtab file
NOTES
If you are using the alternate system console to perform kernel debugging, you must change the kdebug entry in the /etc/remote file to use
/dev/tty01; when the kernel is running in debugging mode, no other application can use the port. See Kernel Debugging for information on
setting up your system for kernel debugging.
RESTRICTIONS
Unless alternative specifications are stated in your system hardware documentation, data communications equipment attached to the console
serial port in alternate console configurations must be set to 9600 baud, 8-bits, no parity. If a serial console is being used, /dev/tty00
cannot be opened by another process. The ace driver enforces this restriction.
Baud rates greater than 38400 are not supported on the two primary serial ports on the DEC 2000 system. However, if you use an ISA serial
or modem card that is capable of communicating at the higher rates, the higher rates are supported.
FILES
console terminal local terminal local terminal
RELATED INFORMATION
MAKEDEV(8), console(7), devio(7), modem(7), ports(7), tty(7)
Kernel Debugging
System Administration delim off
ace(7)