Robert@sri-unix (06/30/82)
Date: 17 Jun 82 15:03:40-EDT (Thu) I am confused about two possibly related matters affecting my VADIC 3451P modem, which occaisionally does not go back on hook even after the remote carrier drops. But first: The normal behaviour my my modem and at least one other I know (MIT-MC) seems to be to keep the line off hook until the remote phone actually hangs up. I assume that this is the consequence of my dhdm driver which appears to keep DTR asserted until an interrupt occurs in which CD is found to be off. Since DTR on is the standard for staying off hook, it would seem that the remote modem is REQUIRED to drop the line first. Should simply doing a close (dhclose() ) cause DTR to drop? What is the remote phone has a log out but never hangs up? Do 2.8bsd and 4bsd behave this way? On two occaisions when a VADIC 3451 has CALLED my modem under ACU control, the remote user logged out normally, but my VADIC kept DSR and DTR on (hence the line off hook) even though CD dropped. Although this smells to me like a dropped dm interrupt, it appears that the intterrupt was serviced: in dmint() is code which resets the software image of CD, the CARRIER_ON bit in the tty_state word of the tty structure. Examining this bit in the kernel with adb finds it off, which I conclude could not happen unless the interrupt occured. Should I be looking for a problem with my (new) modem at the answering end?