From owner-freebsd-hackers  Thu Dec  5 21:38:23 1996
Return-Path: <owner-hackers>
Received: (from root@localhost)
          by freefall.freebsd.org (8.8.4/8.8.4) id VAA29388
          for hackers-outgoing; Thu, 5 Dec 1996 21:38:23 -0800 (PST)
Received: from godzilla.zeta.org.au (godzilla.zeta.org.au [203.2.228.19])
          by freefall.freebsd.org (8.8.4/8.8.4) with ESMTP id VAA29381
          for <hackers@freebsd.org>; Thu, 5 Dec 1996 21:38:17 -0800 (PST)
Received: (from bde@localhost) by godzilla.zeta.org.au (8.8.3/8.6.9) id QAA12086; Fri, 6 Dec 1996 16:32:59 +1100
Date: Fri, 6 Dec 1996 16:32:59 +1100
From: Bruce Evans <bde@zeta.org.au>
Message-Id: <199612060532.QAA12086@godzilla.zeta.org.au>
To: bde@zeta.org.au, brandon@glacier.cold.org
Subject: RE: Help!  Turning off DTR on a serial device
Cc: hackers@freebsd.org
Sender: owner-hackers@freebsd.org
X-Loop: FreeBSD.org
Precedence: bulk

>> ioctls.  Set the output speed to B0 to turn DTR off.  Keep it as B0 to keep
>> DTR off.  Set it back to the actual speed to turn DTR on.
>
>So, uhh, what baud rate does it run at, when  you set it to zero?  Is the
>baud rate irrelevant over the serial cable to the device?

The same as before, or it wouldn't work.  Setting the speed to 0 is
impossible and is conventionally used to turn DTR off.

Bruce