info-vax@ucbvax.ARPA (08/08/85)
From: Kevin Carosso <engvax!KVC@cit-vax> > Does anyone know a way of cancelling CTRL/S on a terminal line other than > typing a CTRL/Q? > > Our students tend to hit CTRL/S unknowingly, wonder why the terminal > hangs, and leave. I can tell that this has happened because by evening > the process is still there and SHOW DEVICE indicates many errors on the > line, and sometimes a timeout as well. > ... > We are running VMS V4.1 on a 780, with DZ-11s and Able VMZ32Ns. What you are seeing may not be simply students getting themselves confused. There is a mode in the DMF-32 called "AUTOXON" or something like that, which appears to be some sort of hardware implementation of XON/XOFF flow control within the DMF's controller. The VMS terminal driver for the DMF-32 did not use the feature until VMS V4 came out. At that point, it became evident that many DMF emulators weren't. The symptoms are lines getting needing to be prodded with ^Q, especially when you try to login to a terminal, and high error counts on the lines. In VMS V4.1, the VMS people made the use of AUTOXON optional, under the control of a bit in a SYSGEN parameter that conveys information to the DMF port driver. Thus, setting TTY_DEFPORT (not DEFPROT) to 1 disables the feature and fixes the problem of some DMF emulators going into ^S mode without permission... I know that the Able VMZ-32 has this problem and I have heard that Emulexs might have the problem. By the way, ABLE has a firmware upgrade that they'll charge you $200 (or thereabouts) for as well that is supposed to fix it. /Kevin Carosso engvax!kvc @ CIT-VAX.ARPA Hughes Aircraft Co.