MensajePublicado:14 Abr 2007, 17:30
por draconiano
Aquí os pongo una cosilla que he encontrado por ahí, aunque creo que no nos sirve...
doc/protocol 100664 764 764 54352 7142623030 12406 0 ustar adrian adrian Clarion C-Bus protocol
======================
This describes part of the C-Bus protocol used to communicate between
a Clarion tuner/tape head unit and a remote CD changer. It's probably
considered by Clarion to be obsolete, since the latest units
(especially those with more advanced functions, like the AutoPC) use a
protocol called CE-Net. However, C-Bus is still used on low-end
devices sold to match factory-fitted head units : the best known of
these are the CDC-634 and CDC-635 changers (but note the comments
about the units I tested - I don't yet know whether the 634 and 635 use
the same protocol as the changer I examined).
The description of the command protocol was originally a set of notes
that I made and extended as I guessed functionality and extended test
software to cope with it. I've now added some more explanatory notes
describing the lower levels of the protocol and some summary
commments. As a result, there is some duplication of the content, and
may even be contradictions as a result of initial guesses that turned
out to be wrong. I'll develop this document further as I find out
more, and hope to clean it up and make it more readable as I go.
I haven't been able to find any public documentation on C-Bus, have
not agreed to any NDAs and have no knowledge of any private Clarion
documents. All the information presented was therefore guessed or
inferred by measuring the signals on connecting wires or by examining
the components inside parts of the system. Reverse-engineering for
interoperability in this guay is permitted under European and US law.
Note that I have only examined the interchange of messages between a
Clarion 3035 tuner/tape unit as fitted to a 1998 Peugeot 306, and a
Clarion-manufactured Rover-badged CD changer marked XQE 10009 of
uncertain age (possibly about 1990). Peugeot use the description
'Audio 3035' in the user's manual, but the radio itself is marked
'PU 1570C'.
The documented protocol may be completely wrong for any other
combination or even for any other specific unit. I'd welcome the
opportunity to test other combinations but don't currently intend to
make any commercial use of this information so I'm not about to buy
units specifically for the purpose. I'd particularly like to
investigate a pair of units that offer text labelling of CDs, as it
may give a clue to the commands for putting arbitrary text on the
radio display. At present, I've only been able to control numeric
fields in the track/time mode but the radio is capable of displaying
an 8-character alphanumeric (14-segment) message for some fixed
messages and for arbitrary text in RDS station idents.
The information is offered for any person to use without charge, and
without any guarantee that it is correct in any guay. Equipment
connected to a Clarion unit without Clarion's approval may void any
warranty for that unit and I can accept no responsibility for any
damage or loss that occurs as a result of the use of this information.
Software related to this documentation and published with it is also
offered without warranty of any kind, and may be used and distributed
in accordance with the conditions of the General Public License (known
as the GNU GPL) as described by the Free Software Foundation. The
conditions of this license are described more fully in the file
COPYING.
Clarion, C-Bus and CE-Net are presumably registered trademarks of
Clarion Car Audio Ltd. or associated companies.
Connections
===========
The connections between head and changer are via a multi-core cable
connected using 13-pin DIN connectors. Not all the pins were used
in the example I've looked at. Some of the descriptions are taken
from the silkscreen of the PCB used in the changer.
The DIN connector is numbered like this (looking at the holes in
a socket on either changer or head).
indent
______ ______
/ U \ (Despite this diagram, the
4 3 2 1 connector is actually circular
8 7 6 5
12 11 10 9 It's the same connector once
13 used for some Atari ST peripheral)
\_____________/
pin name description
1 SOI Data, Open-collector, 5V, driven by changer and head,
pulled up by head
2 SCK 5V, driven by head, clocks data on SDA. Data changes at
falling edge, may be sampled on rising edge.
3 REL Open-collector, 5V, driven by head, pulled up by changer.
No idea what this does - the head/changer combinaion I
tested works normally with it disconnected.
REL is pulled ow when the changer is inactive and
is pulled up when selected by the head unit.
4 SRQ Open-collector, 5V, driven by changer, pulled up by
head. active-low requests the head to poll the changer
5 Ill Illumination. +12V enables panel light (this is a
logic signal only, the panel light is powered by
the main power line)
6 AGND Audio gnd
7 Left Audio left, looks about 0db level
8 Right Audio right, 0db
9 N/C
10 B/U 12V Power provided by head unit but unswitched
11 AC Changer power enable. Open-collector, 5V, driven by head,
pulled up by changer, active low turns changer on.
12 GND Power ground, keep separate from audio ground.
13 N/C
Note that pins shown unconnected (N/C) in this list may actually be
connected on other implementations, and may be connected in
the head unit : I only examined the changer.
Line protocol
=============
This section describes the bitwise protocol used for the lowest level
of data transfer. This could best be done with a clocked serial port,
but the timing doesn't seem too critical and I've been able to emulate
serial port hardware using a microcontroller capable of an interrupt
response in about 2us (and repeated every 7us).
Most of the action takes place on the SCK (clock) and SDA (data)
lines. The head unit is always the clock master, but the data line is
passively pulled up by the head unit and may be pulled down by an
open-collector driver in the changer. In the changer I looked at, this
open-collector driver is outside the microcontroller used for the
serial port, and the control of the output driver is handled via a
different pin to that used to read the state of the line. Although it
would normally be difficult to determine which end was controlling the
bidirectional data line (and hence which guay the data was flowing),
picking up these lines separately meant I could determine which end
was asserting zero data (clock the data from both lines into separate
receivers : when the values are equal, the changer is sending
data. When they're different, the head is sending). This is still
ambiguous when all-ones are sent, but this only occurs within the data
packets described later - no commands have the value FF as far as I
can tell. If they did, the context of surrounding commands would
probably indicate the direction but I think FF is specifically banned
as it would be impossible to determine whether the changer had
echoed it or was missing.
The clock and data lines both rest at 5V, and the data line normally
changes only on a falling edge of the clock (regardless of whether the
head or changer are driving it). However, when the head is trying to
re-establish communication with the changer (at power-up or after a
protocol error) it will hold the clock high while cycling the data
line. This is similar to part of a synchronous serial protocol
supported by the NEC microcontroller used in this changer, and
although that protocol doesn't seem to be used for the data handshake,
I think it's a deliberate violation used here to indicate that a bus
reset should be performed. In the NEC controller, the violation is
simply that the data line changes while the clock is low, but this is
sensitive to noise and poorly-propagated signals on the long cable
between head and boot-mounted changer. It's probably OK to implement
this reset more conveniently by detecting a relatively long period
during which the data line is low, and when no clock edges are seen.
Each byte referred to in later sections is transferred in a distinct
burst of clocks. This burst typically lasts about 2ms (though it could
vary widely) and there's usually a 2ms rest before another burst
occurs. Therefore, the bus only transfers about 1 byte every 4ms and
so is equivalent to about 2400 baud if no flowcontrol information
were required. The clocks themselves are very regular with a
duty cycle close to 50% and a period of just over 7us.
Data is transferred on the first 8 clocks of the burst, and I've
assumed most significant bit is sent first in the descriptions below
(this seems to be reasonable given that numeric values such as track
numbers tie up as expected .. not bit-reversed). The first edge of
the clock burst is obviously falling, so this can be used to shift the
most significant data bit onto SDA. It's value is then available in
time to be sampled by the receiver on the rising edge.
After the first 8 clocks, the data line stays high while several
hundred more clocks occur. This seems to hold the head off for as long
as the changer wants, though there may be a maximum permitted
time. Towards the end of the clock burst, the data line goes low,
again for a variable (but short) number of clocks - sometimes as few
as 1 - and finally goes high. The head stops clocking after receiving
that final 1, and the transfer is complete.
The actual number of clocks in high and low handshake states could be
significant, and is fairly repeatable on the measurements I made.
However, I hoped that it's irrelevant and indicated only how long the
changer took to process the command. This seems correct, as the
protocol seems to work correctly even in my implementation where the
number of clocks in the handshake are always the same.
It's possible that the handshake could be made faster by reducing the
number of busy clocks per byte. However, this might outrun the head
unit's ability to read response data and I haven't experimented with
this .. I've used about 148 high clocks or 1.3ms followed by 3 low
clocks.
Byte protocol
=============
The commands and responses in the next section are presented as
<Cmd> and a variable length response. Actually, it's a bit more
verbose - this syntax is summarised to make it easier to read.
All serial commands are initiated by the head unit and consist of a
command byte transmitted to the changer, a response byte from the
changer, and then some optional further data. In almost every case,
the initial response byte is an echo of the command byte and is
followed by a short message. This message is formatted as <length>
<data> <data> ... where <length> is the count of bytes following. A
zero length message is quite common, and consists only of the length
zero.
Each byte of the message (including the length) is actually sent
twice, the second occurrence being the complement of the first. Thus
the message in the example listed below as
<Cmd> <Rlen> 00 01 00
is actually transmitted as
09 command from head to changer
09 echo from changer to head
03 length from changer
FC complement of length from changer
00 first data byte from changer
FF complement of first data byte from changer
01 second data byte from changer
FE complement of second data byte from changer
00 third data byte from changer
FF complement of first data byte from changer
There are a couple of exceptions to this format, related to
an interrupt mechanism.
This mechanism uses an additional line in the cable for the changer to
request service by the head unit. The line (SRQ) is pulled to ground
and the head unit then issues a command 00. 00 is not echoed -
instead, the changer sends F7 on all occasions I've logged. Given the
line protocol it would be possible for multiple units to modify this
value, so it's possible that clearing a single bit in the response to
00 is really a response indicating a single station requesting service
(this would be similar to a parallel poll in the IEEE-488 protocol).
The head unit then sends F7. This command is echoed normally,
but there's no additional message : not even a 00 length byte.
The SRQ line is released at this time. So the sequence appears
to be that the changer requests service with SRQ, is polled
with 00 and has the service request acknowledged with F7.
After the SRQ handshake is complete, the head always sends
<Cmd>. This operates as a normal command (it results in the usual
length-and-data response) but the actual contents of the response vary
rather more widely than do most of the other responses logged, and
have a variety of effects on the head unit. Some change the track/time
display, one enables the audio from the changer, etc. <Cmd>
therefore appears to be a higher-level poll from the head (made in
response to a succesful SRQ) that permits the changer to send the head
an 'unsolicited' message. This is particularly noticeable in the
'10 xx yy' response mentioned below - every second, the changer performs
an SRQ and sends 10 xx yy in response to the <Cmd>. This results in
the head updating its display to show xx minutes and yy seconds on the
track progress display. The first byte of the response to <Cmd> can
probably be considered as a command to the head, rather than data
as in a normal response.
Thus the message listed later as
<SRQ> <Cmd> <Rlen> 32 01
is actually transmitted as
SRQ goes low
00 command from head to changer
F7 response from changer to head
F7 command from head to changer
SRQ rises
F7 echo from changer to head
11 command from head to changer
11 echo from changer to head
02 length from changer
FD complement of length from changer
32 first data byte from changer
CD complement of first data byte from changer
01 second data byte from changer
FE complement of second data byte from changer
F7 is also sent as part of the powerup / reset sequence and again
is only echoed, there's no command tail. In this case, no <Cmd>
follows F7.
If this protocol fails (a transfer times out, or a command is echoed
inaccurately, or true/complement data doesn't match) the head will
sometimes retry the command and if unsuccessful fall back to resetting
the bus using the F7 command. It then carries on with the command
sequence in progress. It doesn't normally start from scratch just to
repair a protocol failure, but if the changer doesn't respond to the
protocol reset the head will give up, reporting 'CONNECT' on the
display. Re-selecting the changer from the head unit front panel will
start the reset sequence up from scratch - it isn't necessary to power
cycle for the head unit to recognise that a changer is present.
At powerup, there's another possible variation. If the head fails to
get a sensible response from the changer (it has about 4 attempts to
send F7, and if the changer isn't present will receive FF in response
due to the lack of any active pulldown), it will try 7D instead (again
for 4 attempts). The safest response to this is FF, which looks like a
not-present. The head will then (perhaps on another occasion) send F7
and the protocol described can then be followed. My guess is that this
head unit is willing to talk to at least two distinct changer units
and attempts to find the right protocol by attempting a different reset
message. There's some need for experimentation here to see if this or
another changer will accept the 7D command, and what the head unit
will do if it's accepted.
Command protocol
================
This section describes the commands and responses sent during a
series of about 20 recorded operations, referred to as 'log xx'
where individual logs show specific behaviour.
Although I have very little understanding of the meaning of
some of these messages, simply copying their response seems to
work pretty well. A few are more critical - mostly those to
do with track selection and magazine status.
<Cmd>
Sent in response to SRQ. Always the same operation - SRQ goes active,
and 00 is sent. 00 is not echoed - the changer sends F7. The head then
sends the F7 command which is echoed and clears the SRQ. The head then
performs a command 11, which has many different contents. It appears
that the head is the bus master but the changer may want to initiate
an operation : it does this by performing the poll sequence and then
responding to a Cmd 11.
<Cmd>
Generally sent as last command of deselect, but also appears in
power-up-select sequence (log 19). Always gets zero-length response,
i.e. an echo of the command followed by a 00 tail - length byte.
<Cmd>
Sent as first command of select sequence. Always a 3-byte response,
with only the last byte apparently changing.
00 01 1A Always seen when magazine is empty, but also appears
when disc is present, not yet loaded (log 06). The
disc was then loaded and it ran, without another Cmd 09.
00 01 1B No magazine
00 01 00 Always the response when a disc is ready to go.
Log 19 has Cmd 09 sent twice.
<Cmd>
Sent only after an interrupt has been serviced (see Cmd 00). A wide
selection of responses may occur, all either 2 or 3 byte. Apparently
a poll for a changer-initiated command which are mostly display updates.
00 04 log 13, after failed attempt to change discs
00 01 01 Required before track (3x yy) and time (10 xx yy) will work
00 01 08 enables audio and causes head to issue cmd 5C
00 01 05 associated with disc change
00 01 0C only in log 13, as disc load failed
00 01 19
00 01 1B
10 xx yy is the most common. Appears to be sent every
second while playing, and updates the display
to read track timing xx minutes and yy seconds.
3x yy x matches disc number, yy matches track number, commonly
sent as play starts. yy value is AA at end of disc (i.e.
no more tracks), and causes a head-controlled change of
disc or restart of a single disc.
32 11 03 log 26
33 11 03 log 6, 27
42 03 01 log 26
43 03 01 log 6, 27
<Cmd>
00 01 05 associated with start play when CD is present
00 01 07 associated with start play when CD reloaded
<Cmd>
1A 55 55 55 no discs in magazine
1A 55 55 45 disc 2 in magazine
1A 55 51 11 discs 2, 3 and 4 in magzine
1A 55 55 51 disc 2 in drive, none in magazine
1A 55 55 05 disc 3 loaded, 4 in magazine
1A 55 50 00 disc 1 loaded, 2,3,4,5 and 6 in magazine
1A FF FF FF no magazine
It appears that 2 bits are assigned per disc
in the 6-disc changer. This only uses 12 out
of a possible 24 bits, and other bits may well be
significant in a 10 or 12-disc changer.
However, the head unit I have seems to only
handle 6 discs and ignores attempts to
enable more than 6 discs in the emulated changer.
<Cmd>
00 01 xx sent at deselection. xx is 00 if discs are present,
1B if magazine is empty. Similar to Cmd 09, but
deselect with no discs in magazine hasn't been logged.
<Cmd>
00 01 xx Same status as Cmd 09
<Cmd>
00 01 01 log 22, 27
<Cmd>
00 81 02 log 22, 27
<Cmd>
00 01 03 log 22
<Cmd>
00 01 02 log 22, 27
<Cmd>
00 00
<Cmd>
00 01 xx Same status as Cmd 09
<Cmd>
00 01 xx Same status as Cmd 09
<Cmd>
00 01 01 log 16 - repeat mode off
<Cmd>
00 11 01 log 16 - repeat mode on
<Cmd>
00 01 xx Same status as Cmd 09, except in failed change where
xx = 0C. This coincided with 00 01 0C in Cmd 11.
<Cmd>
00 01 04 Associated with Cmd 3E, and mutually exclusive with
5C (5C more common in logs).
<Cmd>
00 01 04
all these have zero-length response (single byte of 00)
<Cmd>
set disc number
<Cmd>
set track 0x (x is 0 to 9) - zero length response
<Cmd>
set track x1 (x is 0 to 9) - zero length response
<Cmd>
4x 03 01 x indicates current disc - possibly when selected
4x FF FF possibly not yet ready, eventually followed by 4x 03 01
This string also sent as one of the <Cmd> responses
<Cmd>
3x 11 03 x indicates current disc - possibly when selected
3x FF FF possibly not yet ready, eventually followed by 4x 03 01
This string also sent as one of the <Cmd> responses
Above responses where recorded with only a 3-track
CD present. If FF FF is returned, the head permits
track selection 1 - 99. If the other responses are
returned, the head selects only tracks 1 - 3.
It's not yet clear what the 01 / 11 part does,
nor which (or both) actually limits the selection.
<Cmd>
Sent at power-up and as part of SRQ response. Possibly clears interrupt.
Has no response tail - i.e. F7 is echoed but no count or data follows.
Example
=======
Select CD operation and run a disc already loaded from slot 2.
The head has already recognised the changer in a previous operation,
so there's no F7 command as an initial reset.
Unknown initial comamnds .. 00 01 00 seems a common response
<Cmd> <Rlen> 00 01 00
<Cmd> <Rlen> 00 00
Determine magazine loading
<Cmd> <Rlen> 1A 55 55 51
Several commands all appear to provoke the same response
from the changer.
<Cmd> <Rlen> 00 01 00
<Cmd> <Rlen> 00 01 00
<Cmd> <Rlen> 00 01 00
Start playing at disc 2, track 01
<Cmd> <Rlen>
<Cmd> <Rlen>
<Cmd> <Rlen>
<Cmd> <Rlen> 00 01 05
Changer responds with disc number
<SRQ> <Cmd> <Rlen> 32 01
Changer causes audio to turn on
<SRQ> <Cmd> <Rlen> 00 01 08
<Cmd> <Rlen> 00 01 04
Changer reports disc 2, track 1
<SRQ> <Cmd> <Rlen> 32 01
Changer starts displaying
<SRQ> <Cmd> <Rlen> 00 01 01
1 second updates to track time
<SRQ> <Cmd> <Rlen> 10 00 00
<SRQ> <Cmd> <Rlen> 10 00 01
<SRQ> <Cmd> <Rlen> 10 00 02
<SRQ> <Cmd> <Rlen> 10 00 03
<SRQ> <Cmd> <Rlen> 10 00 04
<SRQ> <Cmd> <Rlen> 10 00 05
<SRQ> <Cmd> <Rlen> 10 00 06
<SRQ> <Cmd> <Rlen> 10 00 07
<SRQ> <Cmd> <Rlen> 10 00 08
<SRQ> <Cmd> <Rlen> 10 00 09
Table of Contents
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Program (or any work based on the Program), you indicate your acceptance of
this License to do so, and all its terms and conditions for copying,
distributing or modifying the Program or works based on it.
6. Each time you redistribute the Program (or any work based on the
Program), the recipient automatically receives a license from the original
licensor to copy, distribute or modify the Program subject to these terms
and conditions. You may not impose any further restrictions on the
recipients' exercise of the rights granted herein. You are not responsible
for enforcing compliance by third parties to this License.
7. If, as a consequence of a court judgment or allegation of patent
infringement or for any other reason (not limited to patent issues),
conditions are imposed on you (whether by court order, agreement or
otherwise) that contradict the conditions of this License, they do not
excuse you from the conditions of this License. If you cannot distribute so
as to satisfy simultaneously your obligations under this License and any
other pertinent obligations, then as a consequence you may not distribute
the Program at all. For example, if a patent license would not permit
royalty-free redistribution of the Program by all those who receive copies
directly or indirectly through you, then the only guay you could satisfy both
it and this License would be to refrain entirely from distribution of the
Program.
If any portion of this section is held invalid or unenforceable under any
particular circumstance, the balance of the section is intended to apply and
the section as a whole is intended to apply in other circumstances.
It is not the purpose of this section to induce you to infringe any patents
or other property right claims or to contest validity of any such claims;
this section has the sole purpose of protecting the integrity of the free
software distribution system, which is implemented by public license
practices. Many people have made generous contributions to the wide range of
software distributed through that system in reliance on consistent
application of that system; it is up to the author/donor to decide if he or
she is willing to distribute software through any other system and a
licensee cannot impose that choice.
This section is intended to make thoroughly clear what is believed to be a
consequence of the rest of this License.
8. If the distribution and/or use of the Program is restricted in certain
countries either by patents or by copyrighted interfaces, the original
copyright holder who places the Program under this License may add an
explicit geographical distribution limitation excluding those countries, so
that distribution is permitted only in or among countries not thus excluded.
In such case, this License incorporates the limitation as if written in the
body of this License.
9. The Free Software Foundation may publish revised and/or new versions of
the General Public License from time to time. Such new versions will be
similar in spirit to the present version, but may differ in detail to
address new problems or concerns.
Each version is given a distinguishing version number. If the Program
specifies a version number of this License which applies to it and "any
later version", you have the option of following the terms and conditions
either of that version or of any later version published by the Free
Software Foundation. If the Program does not specify a version number of
this License, you may choose any version ever published by the Free Software
Foundation.
10. If you wish to incorporate parts of the Program into other free programs
whose distribution conditions are different, write to the author to ask for
permission. For software which is copyrighted by the Free Software
Foundation, write to the Free Software Foundation; we sometimes make
exceptions for this. Our decision will be guided by the two goals of
preserving the free status of all derivatives of our free software and of
promoting the sharing and reuse of software generally.
NO WARRANTY
11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR
THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN
OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED
OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO
THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM
PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR
CORRECTION.
12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES,
INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING
OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO
LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR
THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER
PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGES.
END OF TERMS AND CONDITIONS
How to Apply These Terms to Your New Programs
If you develop a new program, and you want it to be of the greatest possible
use to the public, the best guay to achieve this is to make it free software
which everyone can redistribute and change under these terms.
To do so, attach the following notices to the program. It is safest to
attach them to the start of each source file to most effectively convey the
exclusion of warranty; and each file should have at least the "copyright"
line and a pointer to where the full notice is found.
one line to give the program's name and an idea of what it does.
Copyright (C) 19yy name of author
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
Also add information on how to contact you by electronic and paper mail.
If the program is interactive, make it output a short notice like this when
it starts in an interactive mode:
Gnomovision version 69, Copyright (C) 19yy name of author
Gnomovision comes with ABSOLUTELY NO WARRANTY; for details
type `show w'. This is free software, and you are welcome
to redistribute it under certain conditions; type `show c'
for details.
The hypothetical commands `show w' and `show c' should show the appropriate
parts of the General Public License. Of course, the commands you use may be
called something other than `show w' and `show c'; they could even be
mouse-clicks or menu items--whatever suits your program.
You should also get your employer (if you work as a programmer) or your
school, if any, to sign a "copyright disclaimer" for the program, if
necessary. Here is a sample; alter the names:
Yoyodyne, Inc., hereby disclaims all copyright
interest in the program `Gnomovision'
(which makes passes at compilers) written
by James Hacker.
signature of Ty Coon, 1 April 1989
Ty Coon, President of Vice
This General Public License does not permit incorporating your program into
proprietary programs. If your program is a subroutine library, you may
consider it more useful to permit linking proprietary applications with the
library. If this is what you want to do, use the GNU Library General Public
License instead of this License.
