Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!seismo!umcp-cs!chris From: chris@umcp-cs.UUCP (Chris Torek) Newsgroups: net.unix-wizards,net.unix Subject: Arcane modem configuration (was Re: Modems on Ultrix) Message-ID: <3030@umcp-cs.UUCP> Date: Wed, 20-Aug-86 12:31:40 EDT Article-I.D.: umcp-cs.3030 Posted: Wed Aug 20 12:31:40 1986 Date-Received: Thu, 21-Aug-86 01:47:08 EDT References: <282@cirl.UUCP> Reply-To: chris@umcp-cs.UUCP (Chris Torek) Distribution: net Organization: University of Maryland, Dept. of Computer Sci. Lines: 94 Xref: mnetor net.unix-wizards:7616 net.unix:5245 I have a few points to make. Overall, Dave's article is no doubt very useful to Ultrix 1.1 sites. In article <282@cirl.UUCP> das@cirl.UUCP (Dave Steffens) writes: >Ultrix as supplied does NOT support modem control on ANY terminal lines. A nit: it is not `does not support', but rather `ignores'. Ah well. >In order to enable modem control you **must** do a sysgen. Not so! You can use adb on the kernel image. It is possible to change either the running kernel, or the flags in the boot image, or both. The first is the easiest, as the boot-time flags are rather well buried. And in any case, after doing this, you should adjust your configuration file so that you need never do it again. Assuming that you wish to enable modem signals on DZ1, line 3: % adb -w /vmunix /dev/kmem dz_flags/x _dz_flags: _dz_flags: f3ff [N.B.: the above number may vary; but the idea is to clear bit eleven.] dz_flags/w 0ff3f _dz_flags: ffff = f3ff % I do not know the proper offsets for the boot-time flags---indeed, I cannot know them, as they are configuration-dependent as well as system dependent---but the procedure is similar: ubdinit+*+?x ...?w f3 The flags are stored separately for each DZ, thus the f3 above. In the DZ driver they are collected together into one array, thus the f3ff earlier. The value of can be found by looking at ioconf.c from a previous sysgen. Alternatively, it may be divined by certain Elvish arts, whose details are too complex to explain here. I daresay a reconfiguration and recompile is far easier for most. >Find the entry in the configuration file.... The bit in "flags" >corresponding to each line which has a modem on it must be zero >in order to get the driver to use the modem control signals. If >the bit is one, modem control is disabled (Ignored: though this distinction matters only in the driver itself.) >on the corresponding line. The "flags" are in HEX (base 16). Only because they are written as `0x...'. Be sure not to delete those first two characters! >NOTE: you cannot just set the all the bits to zero because once >a line is configured to use modem signals it will not be usable >with a directly-connected terminal! This is my real point of contention. This is not in fact the case! We run most of our terminal lines wired as follows: 1-----1 2-----3 3-----2 4-+ +-4 5-+ +-5 6-+--20 8-+ 7-----7 20--+-6 +-8 Some terminals demand different configurations; but typically, both the host and the terminal are properly configured to plug right into a modem. The above constitutes a `null modem' cable, crossing various signals around such that, while the terminal is on, the host sees a modem `carrier detect' signal. With this set-up, you need disable modem control on no lines--- that is, use `flags 0x0', or no `flags' word at all---and, more importantly, one can turn off a terminal to break its connexion. (Some people think this is a bad idea, but `naive users' tend to believe that turning terminals off is just as good as logging out. This seems intuitively correct to me, and it has not proven a problem at other times, as one can always use `stty mdmbuf'....) -- In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 1516) UUCP: seismo!umcp-cs!chris CSNet: chris@umcp-cs ARPA: chris@mimsy.umd.edu