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To: freebsd-questions@freebsd.org
Date: Thu, 03 Feb 2005 14:27:12 -0600
From: Martin McCormick <martin@dc.cis.okstate.edu>
Subject: /dev/ttyd0 as an Input Device Works on some Systems but not others.
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	I posted a question a few hours ago about the strange problems
I had been having with some FreeBSD systems and the use of /dev/ttyd0
as an input device for logging data.

	After searching the FreeBSD handbook, I found the discussion
of the "callout ports" cuaaN which do not use hardware RTS/CTS type
hand shakes.  I remember reading this one other time and thinking it
was for modems exclusively but it appears to be what I should have
been using all along.  What seems to happen is that older systems with
one serial port respond to both ttydN and cuaaN work properly.  The
newer platforms with at least two serial ports need cuaaN if there is
to be no hardware flow-control.  ttydN calls just hang forever and may
or may not unblock if they see DSR from the other system.

Martin McCormick