139 lines
5.4 KiB
HTML
139 lines
5.4 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
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<HTML>
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<HEAD>
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<META NAME="GENERATOR" CONTENT="SGML-Tools 1.0.9">
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<TITLE>Linux Networking-HOWTO (Previously the Net-3 Howto): Cables and Cabling</TITLE>
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<LINK HREF="NET3-4-HOWTO-10.html" REL=next>
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<LINK HREF="NET3-4-HOWTO-8.html" REL=previous>
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<LINK HREF="NET3-4-HOWTO.html#toc9" REL=contents>
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</HEAD>
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<BODY>
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<A HREF="NET3-4-HOWTO-10.html">Next</A>
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<A HREF="NET3-4-HOWTO-8.html">Previous</A>
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<A HREF="NET3-4-HOWTO.html#toc9">Contents</A>
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<HR>
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<H2><A NAME="s9">9. Cables and Cabling</A></H2>
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<P>Those of you handy with a soldering iron may want to build your own cables
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to interconnect two linux machines. The following cabling diagrams should
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assist you in this.
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<H2><A NAME="ss9.1">9.1 Serial NULL Modem cable</A>
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</H2>
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<P>Not all NULL modem cables are alike. Many null modem cables do little more
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than trick your computer into thinking all the appropriate signals are
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present and swap transmit and receive data. This is ok but means that you
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must use software flow control (XON/XOFF) which is less efficient than
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hardware flow control. The following cable provides the best possible signalling
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between machines and allows you to use hardware (RTS/CTS) flow control.
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<BLOCKQUOTE><CODE>
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<PRE>
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Pin Name Pin Pin
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Tx Data 2 ----------------------------- 3
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Rx Data 3 ----------------------------- 2
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RTS 4 ----------------------------- 5
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CTS 5 ----------------------------- 4
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Ground 7 ----------------------------- 7
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DTR 20 -\--------------------------- 8
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DSR 6 -/
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RLSD/DCD 8 ---------------------------/- 20
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\- 6
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</PRE>
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</CODE></BLOCKQUOTE>
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<H2><A NAME="ss9.2">9.2 Parallel port cable (PLIP cable)</A>
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</H2>
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<P>If you intend to use the PLIP protocol between two machines then this cable
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will work for you irrespective of what sort of parallel ports you have
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installed.
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<BLOCKQUOTE><CODE>
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<PRE>
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Pin Name pin pin
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STROBE 1*
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D0->ERROR 2 ----------- 15
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D1->SLCT 3 ----------- 13
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D2->PAPOUT 4 ----------- 12
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D3->ACK 5 ----------- 10
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D4->BUSY 6 ----------- 11
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D5 7*
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D6 8*
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D7 9*
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ACK->D3 10 ----------- 5
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BUSY->D4 11 ----------- 6
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PAPOUT->D2 12 ----------- 4
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SLCT->D1 13 ----------- 3
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FEED 14*
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ERROR->D0 15 ----------- 2
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INIT 16*
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SLCTIN 17*
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GROUND 25 ----------- 25
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</PRE>
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</CODE></BLOCKQUOTE>
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Notes:
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<UL>
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<LI>Do not connect the pins marked with an asterisk `*'.</LI>
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<LI>Extra grounds are 18,19,20,21,22,23 and 24.</LI>
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<LI>If the cable you are using has a metallic shield, it should be connected
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to the metallic DB-25 shell at <B>one end only</B>.</LI>
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</UL>
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<B>Warning: A miswired PLIP cable can destroy your controller card.</B> Be
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very careful and double check every connection to ensure you don't cause
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yourself any unnecessary work or heartache.
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<P>While you may be able to run PLIP cables for long distances, you should
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avoid it if you can. The specifications for the cable allow for a cable
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length of about 1 metre or so. Please be very careful when running long
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plip cables as sources of strong electromagnetic fields such as lightning,
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power lines and radio transmitters can interfere with and sometimes even
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damage your controller. If you really want to connect two of your computers
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over a large distance you really should be looking at obtaining a pair of
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thin-net ethernet cards and running some coaxial cable.
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<H2><A NAME="ss9.3">9.3 10base2 (thin coax) Ethernet Cabling</A>
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</H2>
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<P>10base2 is an ethernet cabling standard that specifies the use of 52 ohm
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coaxial cable with a diameter of about 5 millimeters. There are a couple of
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important rules to remember when interconnecting machines with 10base2 cabling.
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The first is that you must use terminators at <B>both ends</B> of the cabling.
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A terminator is a 52 ohm resistor that helps to ensure that the signal is
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absorbed and not reflected when it reaches the end of the cable. Without
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a terminator at each end of the cabling you may find that the ethernet is
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unreliable or doesn't work at all. Normally you'd use `T pieces' to
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interconnect the machines, so that you end up with something that looks like:
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<BLOCKQUOTE><CODE>
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<PRE>
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|==========T=============T=============T==========T==========|
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| | | |
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| | | |
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----- ----- ----- -----
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| | | | | | | |
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----- ----- ----- -----
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</PRE>
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</CODE></BLOCKQUOTE>
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where the `<CODE>|</CODE>' at either end represents a terminator, the
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`<CODE>======</CODE>' represents a length of coaxial cable with BNC plugs at either
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end and the `<CODE>T</CODE>' represents a `T piece' connector. You should keep the
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length of cable between the `T piece' and the actual ethernet card in the
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PC as short as possible, ideally the `T piece' will be plugged directly into
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the ethernet card.
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<H2><A NAME="ss9.4">9.4 Twisted Pair Ethernet Cable</A>
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</H2>
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<P>If you have only two twisted pair ethernet cards and you wish to connect
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them you do not require a hub. You can cable the two cards directly together.
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A diagram showing how to do this is included in the
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<A HREF="Ethernet-HOWTO.html">Ethernet-HOWTO</A>
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<HR>
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<A HREF="NET3-4-HOWTO-10.html">Next</A>
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<A HREF="NET3-4-HOWTO-8.html">Previous</A>
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<A HREF="NET3-4-HOWTO.html#toc9">Contents</A>
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</HTML>
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