MirOS Manual: plip(4)

PLIP(4)                 BSD Programmer's Manual (i386)                 PLIP(4)


     plip - networking via the standard PC parallel port


     option    PLIP                # Ethernet over parallel port
     lpt0 at isa? port 0x378 irq 7 # standard PC parallel ports
     lpt1 at isa? port 0x278 irq 5
     lpt2 at isa? port 0x3bc irq 5 # Hercules cards don't have an IRQ


     The plip network interface shows up as plip0 when using lpt0, as plip1
     when using lpt1 and plip2 when using lpt2.

     A parallel port can not drive a plip interface when configured without an
     irq. The port can be used to drive other devices when the corresponding
     plip interface is configured down.

     The plip interface simulates Ethernet on a parallel cable with special
     wiring (see below), known as a parallel LapLink cable widely available
     from PC shops.

     Its acronym is derived from SLIP and means Parallel IP Protocol, which,
     in fact, is wrong: it can handle any protocol available on Ethernet, not
     just IP.

     Although a plip connection always is point-to-point, the interface is
     configured like every standard Ethernet interface and uses ARP to find
     its neighbor. This is inefficient, but provides interoperability with
     other operating systems.

     Set the link2 flag on the interface if it is not working. Please report
     back if it helps for you.


     plip uses the Crynwr protocol (CLPIP) defined by Russel Nelson
     <nelson@crynwr.com>. This makes it interoperable with the GPL licenced
     MS-DOS packet driver PLIP.COM available by anonymous ftp from
     ftp://ftp.crynwr.com/drivers/plip.zip and Linux 1.3.x (make sure to con-
     figure the interface to use ARP when connecting to a Linux system).


     The following describes the connection of two male 25 pin sub-D connec-
     tors which fit into standard PC parallel ports (no, PCs don't use Cen-
     tronics connectors).
           INIT(16)    INIT(16)
           SLCTIN(17)  SLCTIN(17)
           GROUND(25)  GROUND(25)
           D0(2)       ERROR(15)
           D1(3)       SLCT(13)
           D2(4)       PAPOUT(12)
           D3(5)       ACK(10)
           D4(6)       BUSY(11)

     Additional grounds are 18, 19, 20, 21, 22, 23 and 24. Do not connect
     D5(7), D6(8), D7(9), STROBE(1) and FEED(14).


     ifconfig(8), pppd(8), slip(8)


     Matthias Pfaller wrote the original NetBSD pc532 version.

     Martin Husemann ported it to the NetBSD i386 .

     Thorsten Glaser first ported the port of the NetBSD i386 version for
     OpenBSD by Pablo Ruiz Garcia to MirOS, then re-did the port using a newer
     NetBSD source version for MirOS #7.


     The plip driver has not yet been successfully tested on MirOS.

     The driver uses a hard-coded network soft interrupt, which is the only
     thing that makes it i386 architecture dependent. As soon as generic soft
     interrupt allocation is available, this should be changed, which would
     make the driver machine independent (but still dependent on the ISA
     parallel port architecture).

     The protocol is too much overhead, a bidirectional input/output routine
     switchable to a well-designed network line discipline with on-line
     compression would be far superior. FreeBSD does this, but it makes it im-
     possible to communicate with MS-DOS and Linux boxen.

     There are some parallel ports which can use all 8 data bits for input and
     output, you can make up a parallel handshake protocol and a cable with
     different wiring to get an 8 bit clean (instead of 4 bit now) data path
     out of this. This is currently not supported.

     There is apparently work on the way (the parbus) which will integrate
     this and other parallel-port devices (zip drives e.a.) more smoothly.

     The plip driver cannot currently drive a protocol other than IPv4.


     Go buy a pocket Ethernet adaptor or a PCMCIA Ethernet adaptor and write a
     driver for it. It has much better throughput, lower load and a less cou-
     pled system between client and server.

MirOS BSD #10-current          January 29, 2002                              1

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