Getting/Monitoring Control Signal Non-Modem lines

[neal_...@hotmail.com]

How do you monitor or getting the status bit of a RS-232 line on a non-modem controlled line; as in TIOCMGET in ioctl () , I am looking to get a similar status of signal as in a modem line like TIOCM_DTR.

I’ve looked at the POSIX serial guide and other place on net , but they all speak of modem control line, and my lines are not modem controlled lines. ie

int fd;
int status;
ioctl(fd, TIOCMGET, &status);



Thanks
The Duke

[Scott Lurndal]

neal_...@hotmail.com writes:
>How do you monitor or getting the status bit of a RS-232 line on a non-mode=
>m controlled line; as in TIOCMGET in ioctl () , I am looking to get a simi=

>lar status of signal as in a modem line like TIOCM_DTR.
>

>I=92ve looked at the POSIX serial guide and other place on net , but they a=
>ll speak of modem control line, and my lines are not modem controlled lines=
>. ie=20
>

An RS-232 port on data terminal equipment has a defined set of signals. These
signals exist regardless of the type of data set equipment (either a modem or a
null-modem cable connectiong two DTEs).

Therefore, the signals that are presented via TIOCMGET are there regardless of
the type of equipment on the other end. Note that a null-modem cable may
effectively hardwire DSR/DTR and won't assert RI.

In other words, TIOCMGET will get signal state for any type of RS-232 port.

[neal_...@hotmail.com]

This make since, thank you.

Duke