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125 wiersze
5.8 KiB
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<!-- received="Mon Sep 14 07:47:37 1998 PDT" -->
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<!-- sent="Tue, 8 Sep 1998 11:09:42 -0400 (EDT)" -->
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<!-- name="John M. Mills" -->
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<!-- email="jmills@jmills.gtri.gatech.edu" -->
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<!-- subject="Re: How to build a db25 terminator" -->
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<!-- id="" -->
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<!-- inreplyto="35F2EC92.42ACA35F@klub-kas.si" -->
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<title>sane-devel: Re: How to build a db25 terminator</title>
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<h1>Re: How to build a db25 terminator</h1>
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<b>John M. Mills</b> (<a href="mailto:jmills@jmills.gtri.gatech.edu"><i>jmills@jmills.gtri.gatech.edu</i></a>)<br>
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<i>Tue, 8 Sep 1998 11:09:42 -0400 (EDT)</i>
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<p>
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<ul>
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<li> <b>Messages sorted by:</b> <a href="date.html#87">[ date ]</a><a href="index.html#87">[ thread ]</a><a href="subject.html#87">[ subject ]</a><a href="author.html#87">[ author ]</a>
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<li> <b>Next message:</b> <a href="0088.html">Mariano Rinc\sn: "support for Mustek ScanMagic 9636P"</a>
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<li> <b>Previous message:</b> <a href="0086.html">Bill Trost: "network scanners"</a>
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</ul>
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<!-- body="start" -->
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I checked an old SCSI reference and found the following:<br>
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1) the given schematic is correct for single-ended SCSI termination, but<br>
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not for differential. For differential, they suggest:<br>
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<p>
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Vcc (+5.0 nominal)<br>
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<i> |</i><br>
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\<br>
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/ 330 ohm<br>
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/<br>
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\<br>
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<i> |</i><br>
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-Signal ---+<br>
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<i> |</i><br>
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\<br>
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/ 150 ohm<br>
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/<br>
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\<br>
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<i> |</i><br>
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+ Signal ---+<br>
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<i> |</i><br>
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\<br>
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/ 330 ohm<br>
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/<br>
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\<br>
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<i> |</i><br>
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GND (0.0 v. nominal)<br>
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<br>
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2. The signal table seems correct for differential 50-pin, but that was<br>
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not the same as single-ended 50 pin for at least some signals.<br>
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<p>
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3. My manual had no information on other configurations.<br>
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<p>
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I will look at the information which came with my SCSI card and my scanner<br>
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to see if they confirm and/or extend this. I have no reason to expect the<br>
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low-speed SCSI interface at my card or scanner are differential; my<br>
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aha1502e card uses the same DB-25 configuration as the Symbios P'n'P which<br>
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came with the HP 4p scanner, and the scanner uses a 50-pin configuration. <br>
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(My scanner includes a switch for internal termination, so I never worried<br>
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about this. Our Suns use submini DB-50 connectors and Sun provides a<br>
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terminator to plug in at the end of the chain. I have no descriptions of <br>
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these - sorry.)<br>
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<p>
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John M. Mills, Senior Research Engineer -- <a href="mailto:john.mills@gtri.gatech.edu">john.mills@gtri.gatech.edu</a><br>
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Georgia Tech Research Institute, Georgia Tech, Atlanta, GA 30332-0834<br>
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Phone contacts: 404.894.0151 (voice), 404.894.6285 (FAX)<br>
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"The cardinal virtues of a programmer are Laziness,<br>
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Impatience, and Hubris." -- attr. Larry Wall <br>
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<p>
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On Sun, 6 Sep 1998, Bostjan Lemut wrote:<br>
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<p>
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<i>> Rogier Wolff wrote:</i><br>
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<i>> </i><br>
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<i>> > Bostjan Lemut wrote:</i><br>
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<i>> > [Charset iso-8859-2 unsupported, filtering to ASCII...]</i><br>
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<i>> > > Hi!</i><br>
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<i>> > ></i><br>
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<i>> > > I've bought a second-hand UMAX Astra 600S scanner, but it came without</i><br>
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<i>> > > terminator (the scanner won't work without it). Since I can't buy it in</i><br>
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<i>> > > any computer shop in our country (it's very small one), I decided to</i><br>
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<i>> > > make one by myself. The problem is, i can't find a scheme on the WEB.</i><br>
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<i>> > ></i><br>
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<i>> > > I would be very greatful if anyone send me the scheme how to build the</i><br>
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<i>> > > damn terminator.</i><br>
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<i>> ></i><br>
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<i>> > +5V</i><br>
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<i>> > |</i><br>
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<i>> > |</i><br>
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<i>> > |-|</i><br>
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<i>> > | | 220 Ohm</i><br>
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<i>> > |_|</i><br>
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<i>> > |</i><br>
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<i>> > Signal ---------+</i><br>
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<i>> > |</i><br>
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<i>> > |-|</i><br>
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<i>> > | | 330 Ohm.</i><br>
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<i>> > |_|</i><br>
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<i>> > |</i><br>
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<i>> > |</i><br>
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<i>> > GND</i><br>
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<i>> ></i><br>
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<i>> </i><br>
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<i>> I've done some more detailed measurments, and I came up with next (see</i><br>
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<i>> attachments).</i><br>
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<i>> Can anybody confirm all this?</i><br>
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<i>> </i><br>
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<i>> Bostjan</i><br>
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<i>> </i><br>
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<p>
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<p>
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<pre>
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--
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Source code, list archive, and docs: <a href="http://www.mostang.com/sane/">http://www.mostang.com/sane/</a>
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To unsubscribe: echo unsubscribe sane-devel | mail <a href="mailto:majordomo@mostang.com">majordomo@mostang.com</a>
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</pre>
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<!-- body="end" -->
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<p>
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<ul>
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<!-- next="start" -->
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<li> <b>Next message:</b> <a href="0088.html">Mariano Rinc\sn: "support for Mustek ScanMagic 9636P"</a>
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<li> <b>Previous message:</b> <a href="0086.html">Bill Trost: "network scanners"</a>
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<!-- nextthread="start" -->
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</ul>
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