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diff --git a/share/man/man4/lp.4 b/share/man/man4/lp.4 new file mode 100644 index 0000000..221b9c9 --- /dev/null +++ b/share/man/man4/lp.4 @@ -0,0 +1,241 @@ +.\" -*- nroff -*- +.\" +.\" Copyright (c) 1996 A.R.Gordon, andrew.gordon@net-tel.co.uk +.\" All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" 3. Neither the name of the University nor the names of its contributors +.\" may be used to endorse or promote products derived from this software +.\" without specific prior written permission. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND +.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE +.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS +.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) +.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY +.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +.\" SUCH DAMAGE. +.\" +.\" Id: man4.i386/lp.4,v 1.9 1999/02/14 12:06:16 nsouch Exp +.\" $FreeBSD$ +.\" +.Dd March 4, 1996 +.Dt LP 4 +.Os +.Sh NAME +.Nm lp +.Nd printer port Internet Protocol driver +.Sh SYNOPSIS +.Nm ifconfig +.Ar plip0 +.Ar myaddress hisaddress +.Op Fl link0 +.Pp +.Cd "device ppbus" +.Cd "device plip" +.Cd "device ppc" +.Sh DESCRIPTION +The +.Nm +driver allows a PC parallel printer port to be used as a +point-to-point network interface between two similarly configured systems. +Data is transferred 4 bits at a time, using the printer status lines for +input: hence there is no requirement for special bidirectional hardware +and any standard AT-compatible printer port with working interrupts may be used. +.Pp +During the boot process, for each +.Nm plip +device which is probed and has an interrupt assigned, a corresponding +.Nm network +device is created. +.Pp +Configuring an +.Nm +device with +.Xr ifconfig 8 +causes the corresponding +.Nm parallel port bus +to be reserved for PLIP until the network interface is configured 'down'. +.Pp +The communication protocol is selected by the +.Cm link0 +flag: +.Bl -tag -width Fl +.It Fl link0 +(default) Use +.Fx +mode (LPIP). +This is the simpler of the two modes +and therefore slightly more efficient. +.It Cm link0 +Use Crynwr/Linux compatible mode (CLPIP). +This mode has a simulated Ethernet +packet header, and is easier to interface to other types of equipment. +.El +.Pp +The interface MTU defaults to 1500, but may be set to any value. +Both ends +of the link must be configured with the same MTU. +.Ss Cable Connections +The cable connecting the two parallel ports should be wired as follows: +.Bd -literal + Pin Pin Description + 2 15 Data0 -> ERROR* + 3 13 Data1 -> SLCT + 4 12 Data2 -> PE + 5 10 Data3 -> ACK* + 6 11 Data4 -> BUSY + 15 2 ERROR* -> Data0 + 13 3 SLCT -> Data1 + 12 4 PE -> Data2 + 10 5 ACK* -> Data3 + 11 6 BUSY -> Data4 + 18-25 18-25 Ground +.Ed +.Pp +Cables with this wiring are widely available as 'Laplink' cables, and +are often coloured yellow. +.Pp +The connections are symmetric, and provide 5 lines in each direction (four +data plus one handshake). +The two modes use the same wiring, but make a +different choice of which line to use as handshake. +.Ss FreeBSD LPIP mode +The signal lines are used as follows: +.Bl -tag -width dataxxxx(Pinxx) +.It Em Data0 (Pin 2) +Data out, bit 0. +.It Em Data1 (Pin 3) +Data out, bit 1. +.It Em Data2 (Pin 4) +Data out, bit 2. +.It Em Data3 (Pin 5) +Handshake out. +.It Em Data4 (Pin 6) +Data out, bit 3. +.It Em ERROR* (pin 15) +Data in, bit 0. +.It Em SLCT (pin 13) +Data in, bit 1. +.It Em PE (pin 12) +Data in, bit 2. +.It Em BUSY (pin 11) +Data in, bit 3. +.It Em ACK* (pin 10) +Handshake in. +.El +.Pp +When idle, all data lines are at zero. +Each byte is signalled in four steps: +sender writes the 4 most significant bits and raises the handshake line; +receiver reads the 4 bits and raises its handshake to acknowledge; +sender places the 4 least significant bits on the data lines and lowers +the handshake; receiver reads the data and lowers its handshake. +.Pp +The packet format has a two-byte header, comprising the fixed values 0x08, +0x00, immediately followed by the IP header and data. +.Pp +The start of a packet is indicated by simply signalling the first byte +of the header. +The end of the packet is indicated by inverting +the data lines (i.e., writing the ones-complement of the previous nibble +to be transmitted) without changing the state of the handshake. +.Pp +Note that the end-of-packet marker assumes that the handshake signal and +the data-out bits can be written in a single instruction - otherwise +certain byte values in the packet data would falsely be interpreted +as end-of-packet. +This is not a problem for the PC printer port, +but requires care when implementing this protocol on other equipment. +.Ss Crynwr/Linux CLPIP mode +The signal lines are used as follows: +.Bl -tag -width dataxxxx(Pinxx) +.It Em Data0 (Pin 2) +Data out, bit 0. +.It Em Data1 (Pin 3) +Data out, bit 1. +.It Em Data2 (Pin 4) +Data out, bit 2. +.It Em Data3 (Pin 5) +Data out, bit 3. +.It Em Data4 (Pin 6) +Handshake out. +.It Em ERROR* (pin 15) +Data in, bit 0. +.It Em SLCT (pin 13) +Data in, bit 1. +.It Em PE (pin 12) +Data in, bit 2. +.It Em ACK* (pin 10) +Data in, bit 3. +.It Em BUSY (pin 11) +Handshake in. +.El +.Pp +When idle, all data lines are at zero. +Each byte is signalled in four steps: +sender writes the 4 least significant bits and raises the handshake line; +receiver reads the 4 bits and raises its handshake to acknowledge; +sender places the 4 most significant bits on the data lines and lowers +the handshake; receiver reads the data and lowers its handshake. +[Note that this is the opposite nibble order to LPIP mode]. +.Pp +Packet format is: +.Bd -literal +Length (least significant byte) +Length (most significant byte) +12 bytes of supposed MAC addresses (ignored by FreeBSD). +Fixed byte 0x08 +Fixed byte 0x00 +<IP datagram> +Checksum byte. +.Ed +.Pp +The length includes the 14 header bytes, but not the length bytes themselves +nor the checksum byte. +.Pp +The checksum is a simple arithmetic sum of all the bytes (again, including +the header but not checksum or length bytes). +.Fx +calculates +outgoing checksums, but does not validate incoming ones. +.Pp +The start of packet has to be signalled specially, since the line chosen +for handshake-in cannot be used to generate an interrupt. +The sender writes the value 0x08 to the data lines, and waits for the receiver +to respond by writing 0x01 to its data lines. +The sender then starts +signalling the first byte of the packet (the length byte). +.Pp +End of packet is deduced from the packet length and is not signalled +specially (although the data lines are restored to the zero, idle +state to avoid spuriously indicating the start of the next packet). +.Sh SEE ALSO +.Xr ppbus 4 , +.Xr ppc 4 , +.Xr ifconfig 8 +.Sh BUGS +Busy-waiting loops are used while handshaking bytes, (and worse still when +waiting for the receiving system to respond to an interrupt for the start +of a packet). +Hence a fast system talking to a slow one will consume +excessive amounts of CPU. +This is unavoidable in the case of CLPIP mode +due to the choice of handshake lines; it could theoretically be improved +in the case of LPIP mode. +.Pp +Polling timeouts are controlled by counting loop iterations rather than +timers, and so are dependent on CPU speed. +This is somewhat stabilised +by the need to perform (slow) ISA bus cycles to actually read the port. |
