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    <META NAME="Author" CONTENT="Daniele Giacomini &nbsp;&nbsp; &nbsp;daniele&nbsp;@&nbsp;swlibero.org">
    <META NAME="Date" CONTENT="2001.08.18 ">
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<H1>Capitolo 369. &nbsp; <A NAME="title5302"></A><A NAME="anchor6483"></A> Porte parallele </H1>

<P>Il cavo parallelo incrociato, detto anche <A NAME="index26318"></A>Null-Printer o <A NAME="index26319"></A>Laplink o <A NAME="index26320"></A>Interlink, &egrave; utilizzabile in particolare per le connessioni PLIP. Permette il collegamento attraverso porte parallele normali. L'eventuale schermatura metallica pu&ograve; essere collegata alla massa del connettore, ma solo a uno dei due capi. Controllare la documentazione contenuta nel file <CODE>/usr/src/linux/drivers/net/README1.PLIP</CODE>.</P>

<TABLE ID="anchor6484" BORDER="3">

<THEAD>
<TR><TD>Connettore A </TD><TD> </TD><TD> </TD><TD>Connettore B </TD><TD> </TD></TR>
<TR><TD>DB-25 maschio </TD><TD> </TD><TD> </TD><TD>DB-25 maschio </TD><TD> </TD></TR>
<TR><TD>Nome </TD><TD>Contatto </TD><TD>Contatto </TD><TD>Nome </TD><TD> </TD></TR>
</THEAD>

<TBODY>
<TR><TD>Data Bit 0 </TD><TD>2 </TD><TD>15 </TD><TD>Error </TD><TD> </TD></TR>
<TR><TD>Data Bit 1 </TD><TD>3 </TD><TD>13 </TD><TD>Select </TD><TD> </TD></TR>
<TR><TD>Data Bit 2 </TD><TD>4 </TD><TD>12 </TD><TD>Paper Out </TD><TD> </TD></TR>
<TR><TD>Data Bit 3 </TD><TD>5 </TD><TD>10 </TD><TD>Acknowledge </TD><TD> </TD></TR>
<TR><TD>Data Bit 4 </TD><TD>6 </TD><TD>11 </TD><TD>Busy </TD><TD> </TD></TR>
<TR><TD>Acknowledge </TD><TD>10 </TD><TD>5 </TD><TD>Data Bit 3 </TD><TD> </TD></TR>
<TR><TD>Busy </TD><TD>11 </TD><TD>6 </TD><TD>Data Bit 4 </TD><TD> </TD></TR>
<TR><TD>Paper Out </TD><TD>12 </TD><TD>4 </TD><TD>Data Bit 2 </TD><TD> </TD></TR>
<TR><TD>Select </TD><TD>13 </TD><TD>3 </TD><TD>Data Bit 1 </TD><TD> </TD></TR>
<TR><TD>Error </TD><TD>15 </TD><TD>2 </TD><TD>Data Bit 0 </TD><TD> </TD></TR>
<TR><TD>Signal Ground </TD><TD>25 </TD><TD>25 </TD><TD>Signal Ground </TD><TD> </TD></TR>
</TBODY>
</TABLE>

<P><EM> Tabella <A HREF="a2472.html#anchor6484">369.1</A>. Cavo parallelo incrociato. </EM></P>

<P>Il cavo parallelo bidirezionale <STRONG>non &egrave; pi&ugrave; utilizzato</STRONG> con GNU/Linux: permetteva il collegamento attraverso porte parallele bidirezionali con velocit&agrave; di comunicazione maggiori rispetto a un cavo incrociato normale.</P>

<TABLE BORDER="3" WIDTH="100%">
<TR><TD>

<P>La connessione di un cavo bidirezionale su elaboratori accesi comporta qualche rischio in pi&ugrave; rispetto alla connessione di un cavo normale. Sotto questo aspetto, l'uso di un cavo del genere, anche se potrebbe fornire prestazioni doppie rispetto a un cavo incrociato normale, &egrave; <STRONG>generalmente sconsigliabile</STRONG>.</P>

</TD></TR>
</TABLE>

<TABLE ID="anchor6485" BORDER="3">

<THEAD>
<TR><TD>Connettore A </TD><TD> </TD><TD> </TD><TD>Connettore B </TD><TD> </TD></TR>
<TR><TD>DB-25 maschio </TD><TD> </TD><TD> </TD><TD>DB-25 maschio </TD><TD> </TD></TR>
<TR><TD>Nome </TD><TD>Contatto </TD><TD>Contatto </TD><TD>Nome </TD><TD> </TD></TR>
</THEAD>

<TBODY>
<TR><TD>Strobe </TD><TD>1 </TD><TD>11 </TD><TD>Busy </TD><TD> </TD></TR>
<TR><TD>Data Bit 0 </TD><TD>2 </TD><TD>2 </TD><TD>Data Bit 0 </TD><TD> </TD></TR>
<TR><TD>Data Bit 1 </TD><TD>3 </TD><TD>3 </TD><TD>Data Bit 1 </TD><TD> </TD></TR>
<TR><TD>Data Bit 2 </TD><TD>4 </TD><TD>4 </TD><TD>Data Bit 2 </TD><TD> </TD></TR>
<TR><TD>Data Bit 3 </TD><TD>5 </TD><TD>5 </TD><TD>Data Bit 3 </TD><TD> </TD></TR>
<TR><TD>Data Bit 4 </TD><TD>6 </TD><TD>6 </TD><TD>Data Bit 4 </TD><TD> </TD></TR>
<TR><TD>Data Bit 5 </TD><TD>7 </TD><TD>7 </TD><TD>Data Bit 5 </TD><TD> </TD></TR>
<TR><TD>Data Bit 6 </TD><TD>8 </TD><TD>8 </TD><TD>Data Bit 6 </TD><TD> </TD></TR>
<TR><TD>Data Bit 7 </TD><TD>9 </TD><TD>9 </TD><TD>Data Bit 7 </TD><TD> </TD></TR>
<TR><TD>Busy </TD><TD>11 </TD><TD>1 </TD><TD>Strobe </TD><TD> </TD></TR>
<TR><TD>Paper Out </TD><TD>12 </TD><TD>14 </TD><TD>Autofeed </TD><TD> </TD></TR>
<TR><TD>Select </TD><TD>13 </TD><TD>17 </TD><TD>Select </TD><TD> </TD></TR>
<TR><TD>Autofeed </TD><TD>14 </TD><TD>12 </TD><TD>Paper Out </TD><TD> </TD></TR>
<TR><TD>Error </TD><TD>15 </TD><TD>18 </TD><TD>Ground </TD><TD> </TD></TR>
<TR><TD>Reset </TD><TD>16 </TD><TD>10 </TD><TD>Acknowledge </TD><TD> </TD></TR>
<TR><TD>Ground </TD><TD>18 </TD><TD>15 </TD><TD>Error </TD><TD> </TD></TR>
<TR><TD>Signal Ground </TD><TD>25 </TD><TD>25 </TD><TD>Signal Ground </TD><TD> </TD></TR>
</TBODY>
</TABLE>

<P><EM> Tabella <A HREF="a2472.html#anchor6485">369.2</A>. Cavo parallelo bidirezionale <STRONG>non pi&ugrave; utilizzato</STRONG> con GNU/Linux. </EM></P>

<TABLE ID="anchor6486" BORDER="0" WIDTH="100%">
<TR><TD>
<HR>

<PRE>                         1                       13
                      .-----------------------------.
                       \ * * * * * * * * * * * * * /
                        \ * * * * * * * * * * * * /
                         `-----------------------'
                         14                     25</PRE>
<HR>

<P class="caption"> Figura <A HREF="a2472.html#anchor6486">369.1</A>. Disposizione dei contatti di un connettore BD-25 maschio. </P>

</TD></TR>
</TABLE>

<TABLE ID="anchor6487" BORDER="0" WIDTH="100%">
<TR><TD>
<HR>

<PRE>                  18                                 1
              .-------------------------------------------.
               \   # # # # # # # # # # # # # # # # # #   /
                \ ===================================== /
                 \ # # # # # # # # # # # # # # # # # # /
                  `-----------------------------------'
                  36                                 19</PRE>
<HR>

<P class="caption"> Figura <A HREF="a2472.html#anchor6487">369.2</A>. Disposizione dei contatti di un connettore Centronics a 36 poli (stampante). </P>

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