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Path: utzoo!utgpu!water!watmath!orchid!gamiddleton
From: gamiddleton@orchid.UUCP
Newsgroups: comp.unix.wizards,comp.bugs.4bsd
Subject: Re: lack of modem control on MVAX-II with DHV running 4.3bsd (solution)
Message-ID: <7788@orchid.UUCP>
Date: Tue, 26-May-87 03:44:57 EDT
Article-I.D.: orchid.7788
Posted: Tue May 26 03:44:57 1987
Date-Received: Tue, 26-May-87 06:36:56 EDT
References: <7597@orchid.UUCP>
Reply-To: gamiddleton@orchid.UUCP (Guy Middleton)
Organization: Network 42
Lines: 27
Xref: utgpu comp.unix.wizards:2254 comp.bugs.4bsd:341

In article <7597@orchid.UUCP> gamiddleton@orchid.UUCP (Guy Middleton) writes:
> We have a Microvax-II with a DHV11.  We're using the DHU driver from
> Berkeley, running 4.3BSD.  The DHV passes its hardware diagnostics perfectly.
> However, when the system is running, the DHV completely ignores modem
> controls (DTR, CTS, RTS and DCD).  Debug code in the driver shows that the
> board thinks it is asserting DTR at the right times (when in fact DTR is
> *never* raised).  Also the board never sees DCD.  Has anybody else seen
> this?  We're starting to get a bit annoyed here...

The problem turned out to be hardware.

There are two kinds of distribution panels for the DHV.  The standard one,
called an H3173, is a metal plate with 4 D-connectors.  It fits into the
back of the machine, and you need two of them for each DHV (which has eight
lines).  The other kind (an H3175) is a box with 8 D-connectors, and can be
mounted conveniently in a rack somewhere.  It is attached to the machine by
a ribbon cable.

We were persuaded (by our DEC salesman, I suppose) to get the H3175s,
because it's convenient to have all the wires connect to the same rack.
Unfortunately, it seems that these silly things completely lack modem
control.  The ribbon cable from the machine apparently does not carry any
signalling information; just data.

There was no bug at all, we just had the wrong kind of hardware.

 -Guy Middleton, University of Waterloo MFCF/ICR, gamiddleton@watmath