From owner-freebsd-stable Fri May 12 22:15: 5 2000 Delivered-To: freebsd-stable@freebsd.org Received: from jason.argos.org (a1-3b058.neo.rr.com [24.93.181.58]) by hub.freebsd.org (Postfix) with ESMTP id 0F6DF37BBB4 for ; Fri, 12 May 2000 22:15:00 -0700 (PDT) (envelope-from mike@argos.org) Received: from localhost (mike@localhost) by jason.argos.org (8.9.1/8.9.1) with ESMTP id BAA23627; Sat, 13 May 2000 01:14:17 -0400 Date: Sat, 13 May 2000 01:14:17 -0400 (EDT) From: Mike Nowlin To: andrew@ugh.net.au Cc: Kris Kirby , David Miller , freebsd-stable@FreeBSD.ORG Subject: Re: serial console buglet In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-stable@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG > On Thu, 11 May 2000, Mike Nowlin wrote: > > > Wyse 150 & Wyse 60 terminals, they have the annoying habit of not > > rebooting if the serial console is turned off... Turn the console on or > > pull the serial cable, and the machine proceeds to boot. (3-wire > > Could this be related to bin/3862? The null modem cable in question was 3 > wire and the FreeBSD box would only boot if the mac was switched on... > I'm guessing it might be a similar problem caused by the same set of circumstances... It seems there might be some problems with whatever function in the kernel "waits for a break signal on a serial port to finish". Depending on the cheapness of the serial port in question (TTL<->RS232 driver chips, in particular), which these days includes 99.9% of all serial ports manufactured, the signals aren't terminated correctly -- this can cause the +/- 12V signal to float around wildly.... The kernel sees this floating value causing a false TRUE on the RX line, and mistakes this for someone sitting on the keyboard. Unfortunately, this problem can be caused at either end of the cable - both sides must be properly terminated. At least, that's my guess.... I'll stop myself from getting into a philosophical lecture about goof-proof circuit design. :) mike - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - "I was thinking of the immortal words of Socrates, who said, 'I drank what?'" -- Chris Knight (Val Kilmer), Real Genius Mike Nowlin, N8NVW mike@argos.org http://www.viewsnet.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message