Documentation/networking/plip.rst

1 .. SPDX-License-Identifier: GPL-2.0
14 -----------------
17 This device interface allows a point-to-point connection between two
25 printer port.  PLIP is a non-standard, but [can use] uses the standard
26 LapLink null-printer cable [can also work in turbo mode, with a PLIP
27 cable]. [The protocol used to pack IP packages, is a simple one
35 The PLIP cable is all that's needed to connect two Linux boxes, and it
50 Doesn't work over a modem, like SLIP and PPP. Limited range, 15 m.
62 -------------------
72 PLIP driver is signaled whenever data is sent to it via the cable, such that
77 On these machines, the PLIP driver can be used in IRQ-less mode, where
82 indicate that there isn't a noticeable performance drop when using IRQ-less
92 When in IRQ-less mode, the PLIP driver polls the parallel port HZ times
99 10^6/HZ usecs. If both sides of a PLIP connection are used in IRQ-less mode,
108 of the net-tools package (its location can be found in the
114 -----------------------------
118 printer "null" cable to transfer data four bits at a time using
122 bi-directional parallel ports, rather than output-only ``printer``
123 ports.  This allows byte-wide transfers and avoids reconstructing
126 Parallel Transfer Mode 0 Cable
129 The cable for the first transfer mode is a standard
130 printer "null" cable which transfers data four bits at a time using
137 A cable that implements this protocol is available commercially as a
138 "Null Printer" or "Turbo Laplink" cable.  It can be constructed with
139 two DB-25 male connectors symmetrically connected as follows::
142     D0->ERROR	2 - 15		15 - 2
143     D1->SLCT	3 - 13		13 - 3
144     D2->PAPOUT	4 - 12		12 - 4
145     D3->ACK	5 - 10		10 - 5
146     D4->BUSY	6 - 11		11 - 6
150     SLCTIN	17 - 17
152     GROUND	25 - 25
156 If the cable you are using has a metallic shield it should be
157 connected to the metallic DB-25 shell at one end only.
163 bi-directional parallel ports, rather than output-only ``printer``
164 ports.  This allows byte-wide transfers, and avoids reconstructing
165 nibbles into bytes.  This cable should not be used on unidirectional
170 The cable for this transfer mode should be constructed as follows::
172     STROBE->BUSY 1 - 11
173     D0->D0	2 - 2
174     D1->D1	3 - 3
175     D2->D2	4 - 4
176     D3->D3	5 - 5
177     D4->D4	6 - 6
178     D5->D5	7 - 7
179     D6->D6	8 - 8
180     D7->D7	9 - 9
181     INIT -> ACK  16 - 10
182     AUTOFD->PAPOUT 14 - 12
183     SLCT->SLCTIN 13 - 17
184     GND->ERROR	18 - 15
186     GROUND	25 - 25
190 Once again, if the cable you are using has a metallic shield it should
191 be connected to the metallic DB-25 shell at one end only.
200    count-low octet
201    count-high octet
217   (OUT is bit 0-4, OUT.j is bit j from OUT. IN likewise)