Date: Mon, 29 Jan 1996 13:56:26 -0700 (MST) From: Terry Lambert <terry@lambert.org> To: msmith@atrad.adelaide.edu.au (Michael Smith) Cc: terry@lambert.org, hsu@clinet.fi, hm@altona.hamburg.com, freebsd-hackers@FreeBSD.ORG Subject: Re: Multi-Port Async Cards Message-ID: <199601292056.NAA04426@phaeton.artisoft.com> In-Reply-To: <199601290058.LAA08717@genesis.atrad.adelaide.edu.au> from "Michael Smith" at Jan 29, 96 11:28:35 am
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> > > mgetty would be useful as it can > > > actively reply calls instead of modems answering automatically, thus > > > avoiding callers getting modem answer when the terminal server has crashed > > > and won't be there. > > > > A properly configured modem and getty will do this as well. > > No, it won't. There is no hardware feature in the 8250-family UART that > deasserts DTR when the machine has crashed. In fact, I know of no UART > family that meets this criteria. There is a firmware feature. It's called BIOS POST initialization, and it is dependent on you buying good hardware. Your hardware should: 1) Do a hard reset, not a soft reset, on triple fault (this is the problem with not rebooting after shutdown on a machine with a buggered keyboard controller INT 19 interface). 2) POST initialize the UARTs to a known state as a result of a hard reset. This includes disabling FIFO's on UARTs that support them, something fully 90% of all BIOS' get wrong. If you are running a large site, invest $35 in a watchdog reset board. Do it, do it NOW. There are BSD drivers for several of this type of board. > > If the machine crashes, getty goes away (the POST state on a proper serial > > port is to not assert DTR), and so the modems are not answered. > > In my experience, very few system BIOSses reset DTR, and this isn't the > issue here anyway; if the system has rebooted there's a reasonably good > chance that it'll be back up and running properly shortly. Any BIOS that does PSOT initialization of UARTs will drop DTR. If you are worried about a hard hang requiring a human, invest in a watchdog reset board. If you have that many lines, you can afford it. As a matter of fact, if you have that many lines, you can't afford to *not* have such a board. This is really irrelevant. What is the use of not answering the phone vs. bogusly answering the phone and not talking? Long distance charges? Most US LD companies (not TelAmerica) start charging after 6 seconds, answered or not. Your customer is going to be pissed off by the fact that he did not get service, and won't really give a damn about the failure mode that caused him to not be serviced. Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers.
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