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275 lines
8.7 KiB
Plaintext
275 lines
8.7 KiB
Plaintext
<!doctype linuxdoc system>
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<article>
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<title>Atari Lynx specific information for cc65
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<author>Karri Kaksonen, <htmlurl url="mailto:karri@sipo.fi" name="karri@sipo.fi">
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Ullrich von Bassewitz, <htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">
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<date>2004-10-14
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<abstract>
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An overview over the Atari Lynx runtime system as it is implemented for the
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cc65 C compiler.
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</abstract>
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<!-- Table of contents -->
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<toc>
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<!-- Begin the document -->
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<sect>Overview<p>
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This file contains an overview of the Atari Lynx runtime system as it comes
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with the cc65 C compiler. It describes the memory layout, Lynx specific header
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files, available drivers, and any pitfalls specific to that platform.
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Please note that Lynx specific functions are just mentioned here, they are
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described in detail in the separate <htmlurl url="funcref.html" name="function
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reference">. Even functions marked as "platform dependent" may be available on
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more than one platform. Please see the function reference for more
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information.
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<sect>Binary format<p>
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The standard binary output format generated by the linker for the Lynx target
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is a machine language program with an executable header. It is of course
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possible to change this behaviour by using a modified startup file and linker
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config.
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You can also produce real carts with directory structures and encrypted
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headers by modifying the startup and linker config files. There is a simple
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example archive called <tt/lynx-cart-demo/ in the <htmlurl
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url="ftp://ftp.musoftware.de/pub/uz/cc65/contrib/" name="contrib directory">
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that shows how to create a complete bootable Lynx cart.
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<sect>Memory layout<p>
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cc65 generated programs with the default setup run with the I/O area and the
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kernal enabled, which gives a usable memory range of $400 - $C038.
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Special locations:
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<descrip>
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<tag/Text screen/
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No conio support is currently available for the Lynx.
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<tag/Keyboard/
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The Lynx "flabode" keys, Opt 1, Pause and Opt 2 are implemented using the
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conio interface. The only characters the keyboard is able to produce are
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'R' for Restart (Opt 1 + Pause), 'F' for flip (Opt 2 + Pause),
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'P' for pause, '1' for Opt 1, '2' for Opt 2, '3' for Opt 1 + Opt 2 and
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'?' for all keys down at the same time.
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<tag/Stack/
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The C runtime stack is located at $C037 and growing downwards.
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<tag/Heap/
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The C heap is located at the end of the program and grows towards the C
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runtime stack.
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</descrip><p>
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<sect>Platform specific header files<p>
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Programs containing Lynx specific code may use the <tt/lynx.h/ header file.
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<sect1>Lynx specific functions<p>
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<itemize>
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<item>lynx_eeprom_erase
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<item>lynx_eeprom_read
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<item>lynx_eeprom_write
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</itemize>
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<sect1>Hardware access<p>
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The following pseudo variables declared in the <tt/lynx.h/ header file do
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allow access to hardware located in the address space. Some variables are
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structures, accessing the struct fields will access the chip registers.
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<descrip>
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<tag><tt/MIKEY/</tag>
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The <tt/MIKEY/ structure allows access to MIKEY chip. See the <tt/_mikey.h/
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header file located in the include directory for the declaration of the
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structure.
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<tag><tt/SUZY/</tag>
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The <tt/SUZY/ structure allows access to SUZY chip. See the <tt/_suzy.h/
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header file located in the include directory for the declaration of the
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structure.
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</descrip><p>
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<sect>Loadable drivers<p>
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<sect1>Graphics drivers<p>
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A TGI driver for the standard graphics mode (160×102 in 16 colors) is
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available, but must be statically linked, because no file I/O is available.
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See the documentation for the <htmlurl url="co65.html" name="co65 utility">
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for information on how to do that.
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The TGI driver is implemented as an interrupt driven dual buffering device.
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To use it as a single-buffer device set draw page and view page to the same
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value 0 or 1;
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The TGI driver has a few Lynx-specific extensions.
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Calling tgi_sprite(spr) or tgi_ioctl(0, spr) will display a standard Lynx
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sprite on screen.
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Calling tgi_flip() or tgi_ioctl(1, 0) will do a flip screen.
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Calling tgi_setbgcolor(bgcolor) or tgi_ioctl(2, bgindex) will set the text
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background color to the index defined by bgindex. If bgindex is 0 then the
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background color is transparent.
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To set the framerate of the display hardware call tgi_setframerate(rate) or
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tgi_ioctl(3, rate). The supported framerates are 50, 60 and 75 frames per
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second. Actually there is no real reason to use anything else than 75 frames
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per second.
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To check if the drawing engine is busy with the previous swap you can
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call tgi_busy or tgi_ioctl(4, 0). It returns 0 if idle and 1 if busy
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To update displays you can call tgi_updatedisplay() or tgi_ioctl(4, 1) it
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will wait for the next VBL interrupt and set the draw buffer to the
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view buffer. The draw buffer is also changed to (drawbuffer xor 1).
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<sect1>Extended memory drivers<p>
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No extended memory drivers are currently available for the Lynx.
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<sect1>Joystick drivers<p>
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A joystick driver for the standard buttons is available, but must be
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statically linked, because no file I/O is available. See the documentation for
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the <htmlurl url="co65.html" name="co65 utility"> for information on how to do
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that.
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The joystick will check to see if the screen is flipped or not in the install
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routine and adapt itself to the correct state.
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<sect1>Mouse drivers<p>
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No mouse drivers are currently available for the Lynx.
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<sect1>RS232 device drivers<p>
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<descrip>
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The ComLynx port has Tx and Rx wired together. Every byte is sent
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to all connected Lynxes. Only one Lynx can send at a time. There is no
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protocol created for communication. You are on your own.
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If the Lynx returns framing error then it is likely that another Lynx is
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sending data at the same time.
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The Lynx can also send a break and receive a break. The Lynx break is
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recognized if the bit is down for 24 bit cycles or more.
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To send a break you just set the break bit. The length of the break depends
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on how long this bit is down.
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The driver supports the baudrates:
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<itemize>
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<item>62500
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<item>31250
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<item>9600
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<item>7200
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<item>4800
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<item>3600
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<item>2400
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<item>1800
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<item>1200
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<item>600
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<item>300
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<item>150
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<item>134.5
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<item>110
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<item>75
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</itemize>
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The parity bit supports MARK and SPACE. It also supports EVEN and ODD parity
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but the parity bit is included in the calculation. Most of us don't want it
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this way. But there is nothing we can do about it.
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The Lynx hardware will always check parity on incoming traffic. Currently
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the driver cannot receive data from standard PC's due to this parity bug.
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For working with Lynx to Lynx communication use EVEN parity.
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To send data to standard PC's use MARK or SPACE as parity setting.
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There is always only one stop bit. And the data length is always 8 bits.
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We have no handshaking available. Even software handshake is impossible
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as ComLynx has only one wire for the data.
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Both transmit and receive are interrupt driven. The driver reserves a fixed
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area $200-$2ff for the transmit ring buffer and $300-$3ff for the receive
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ring buffer. This area can not be used at startup for anything as the Lynx
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ROM needs this area for decryption purposes.
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</descrip><p>
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<sect>Limitations<p>
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<sect>Other hints<p>
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At this point in time there is no support for the cart filesystem yet. I have
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a <tt/lynx-cart-demo/ example project that uses an interrupt driven display,
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has support for the cart filesystem and an abcmusic sound module.
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At some point in time we may find a way to rewrite these to fit the way the
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cc65 drivers require. But for the time being you can create less portable
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applications using these Lynx specific modules in <tt/lynx-cart-demo/.
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<sect>Bugs/Feedback<p>
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If you have problems using the library, if you find any bugs, or if you're
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doing something interesting with it, I would be glad to hear from you. Feel
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free to contact me by email (<htmlurl url="mailto:uz@cc65.org"
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name="uz@cc65.org">).
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<sect>License<p>
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This software is provided 'as-is', without any expressed or implied
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warranty. In no event will the authors be held liable for any damages
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arising from the use of this software.
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Permission is granted to anyone to use this software for any purpose,
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including commercial applications, and to alter it and redistribute it
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freely, subject to the following restrictions:
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<enum>
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<item> The origin of this software must not be misrepresented; you must not
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claim that you wrote the original software. If you use this software
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in a product, an acknowledgment in the product documentation would be
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appreciated but is not required.
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<item> Altered source versions must be plainly marked as such, and must not
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be misrepresented as being the original software.
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<item> This notice may not be removed or altered from any source
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distribution.
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</enum>
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</article>
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