Date: Sat, 13 May 2000 01:14:17 -0400 (EDT) From: Mike Nowlin <mike@argos.org> To: andrew@ugh.net.au Cc: Kris Kirby <kris@hiwaay.net>, David Miller <dmiller@search.sparks.net>, freebsd-stable@FreeBSD.ORG Subject: Re: serial console buglet Message-ID: <Pine.LNX.4.05.10005130102440.23339-100000@jason.argos.org> In-Reply-To: <Pine.BSF.4.21.0005131435350.8910-100000@starbug.ugh.net.au>
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> 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
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