Message-Id: <199812081413.TAA16834@harrier.Uznet.NET>
From: Michael Sokolov <msokolov@harrier.Uznet.NET>
Date: 8 Dec 1998   14:13:08 GMT
To: pups@minnie.cs.adfa.edu.au
Subject: Re: 9-track tape interfaces
Sender: owner-pups@minnie.cs.adfa.edu.au
Precedence: bulk

   Dave Horsfall <dave@fgh.geac.com.au> wrote:
> From my TTL Data Book: Quadruple 2-input positive-NAND buffer (Y=AB bar).
> Outputs are 3, 6, 8, 11.  Corresponding inputs are 1/2, 4/5, 9/10, 12/13.
> Vcc is 14, GND is 7.
   
   Looks trivial, except that the author of the digital design textbook I'm
using has chosen to omit it. :-) Anyway, I have looked at the board again,
and all pins that go to the connector are outputs. This means that at least
in this form, with the U10 chip omitted, there are NO inputs on that
connector, only outputs.
   
   That missing chip could very well have to do with inputs, though. Hmm,
there are 4 lines going to that missing chip, and that sounds like the
number of input lines in some flavor of Centronics. On the output side, 8
pins go to the 74S241 and 3 pins go to the 7437, again suggesting 8-bit
output and some control signals.
   
   All this sounds very much like Centronics or some similar interface.
Figuring out what the host interface is and what do those myriads of
switches and jumpers mean would be harder, though.
   
   Sincerely,
   Michael Sokolov
   Cellular phone: 216-217-2579
   ARPA Internet SMTP mail: msokolov@harrier.Uznet.NET