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<TITLE>The PLIP Driver</TITLE>
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<H1><A NAME="SECTION005500000">The PLIP Driver</A></H1>
<A NAME="hardwaredriversplip"></A>
PLIP stands for <em>Parallel Line IP</em> and is a cheap way to
network when you want to connect only two machines. It uses a
parallel port and a special cable, achieving speeds of 10kBps to
20kBps.
<P>
PLIP was originally developed by Crynwr, Inc. Its design is rather
ingenuous (or, if you prefer, hackish): for a long time, the parallel
ports on PCs used to be only uni-directional printer ports; that is,
the eight data lines could only be used to send from the PC to the
peripheral device, but not the other way round. PLIP works around
this by using the port's five status line for input, which limits it
to transferring all data as nibbles (half bytes) only. This mode of
operation is called mode zero PLIP. Today, these uni-directional
ports don't seem to be used much anymore. Therefore, there is also a
PLIP extension called mode 1 that uses the full 8-bit interface.
<P>
Currently, only supports mode 0. Unlike earlier versions of the
PLIP code, it now attempts to be compatible with the PLIP implementations
from Crynwr, as well as the PLIP driver in NCSA telnet.<A HREF="footnode.html#2220"><IMG ALIGN=BOTTOM ALT="gif" SRC="foot_motif.gif"></A> To connect two machines using PLIP, you need a special cable sold at
some shops as ``Null Printer'' or ``Turbo Laplink'' cable. You can,
however, make one yourself fairly easily. Appendix-<A HREF="node284.html#appendixplip"><IMG ALIGN=BOTTOM ALT="gif" SRC="cross_ref_motif.gif"></A>
shows you how.
<P>
The PLIP driver for is the work of almost countless persons.
It is currently maintained by Niibe Yutaka. If compiled into the
kernel, it sets up a network interface for each of the possible
printer ports, with plip0 corresponding to parallel port
lp0, plip1 corresponding to lp1, etc. The
mapping of interface to ports is currently this:
<pre>
--------------------------------
+-----------+-----------+------+
|Interface | I/O Port | IRQ |
+-----------+-----------+------+
|plip0 | 0x3BC | 7 |
|plip1 | 0x378 | 7 |
|plip2 | 0x278 | 5 |
+-----------+-----------+------+
+-----------+-----------+------+
</pre>
If you have configured your printer port in a different way, you
have to change these values in drivers/net/Space.c in
the kernel source, and build a new kernel.
<P>
This mapping does not mean, however, that you cannot use these
parallel ports as usual. They are accessed by the PLIP driver only
when the corresponding interface is configured up.
<P>
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<B> Next:</B> <A HREF="node52.html">The SLIP and PPP </A>
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<B> Previous:</B> <A HREF="node50.html">Ethernet Autoprobing</A>
<P><ADDRESS>
<I>Andrew Anderson <BR>
Thu Mar 7 23:22:06 EST 1996</I>
</ADDRESS>
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