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239 lines
6.4 KiB
Plaintext
239 lines
6.4 KiB
Plaintext
<!doctype linuxdoc system>
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<article>
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<title>Apple ][ specific information for cc65
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<author>Ullrich von Bassewitz, <htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">
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<date>2003-12-16
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<abstract>
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An overview over the Apple ][ runtime system as it is
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implemented for the 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 Apple ][ runtime system
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as it comes with the cc65 C compiler. It describes the memory layout,
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Apple ][ specific header files, available drivers, and any
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pitfalls specific to that platform.
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Please note that Apple ][ specific functions are just mentioned
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here, they are described in detail in the separate <htmlurl url="funcref.html"
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name="function reference">. Even functions marked as "platform dependent" may
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be available on more than one platform. Please see the function reference for
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more information.
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<sect>Binary format<p>
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The standard binary output format generated by the linker for the
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Apple ][ target is a machine language program with a 4 byte DOS
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3.3 header. The standard load address is $800.
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The DOS header is in it's own segment named <tt/EXEHDR/. If you don't want the
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header for some reason, you can change
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<verb>
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HEADER: start = $0000, size = $4, file = %O;
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</verb>
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to
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<verb>
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HEADER: start = $0000, size = $4, file = "";
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</verb>
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in the linker configuration to have the linker remove it.
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<sect>Memory layout<p>
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In the standard setup, cc65 generated programs use the memory from
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$800 to $8E00, so 33.5K of memory (including the stack) is
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available. ROM calls are possible without further precautions.
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Special locations:
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<descrip>
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<tag/Stack/
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The C runtime stack is located at $8DFF 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 Apple ][ specific code may use the
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<tt/apple2.h/ header file.
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<sect1>Apple ][ specific functions<p>
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The functions listed below are special for the Apple ][. See
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the <htmlurl url="funcref.html" name="function reference"> for declaration and
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usage.
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<itemize>
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<item>get_ostype
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</itemize>
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<sect1>Hardware access<p>
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There's currently no support for direct hardware access. This does not mean
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you cannot do it, it just means that there's no help.
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<sect>Loadable drivers<p>
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<em>Note:</em> Since the Apple ][ doesn't have working disk I/O
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(see <ref id="limitations" name="section "Limitations"">), the
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available drivers cannot be loaded at runtime (so the term "loadable drivers"
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is somewhat misleading). Instead, the drivers have to be converted using the
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<htmlurl url="co65.html" name="co65 utility"> and statically linked. While
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this may seem overhead, it has two advantages:
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<enum>
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<item>The interface is identical to the one used for other platforms
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and to the one for the Apple ][ once it has disk I/O.
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<item>Once disk I/O is available, existing code can be changed to load drivers
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at runtime with almost no effort.
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</enum>
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<sect1>Graphics drivers<p>
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<em>Note:</em> Since memory for the graphics has to be allocated, programs
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using graphics drivers will have to be linked using a special linker
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configuration. See the <tt/apple2-tgi.cfg/ file in the documentation
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directory, and the <htmlurl url="ld65.html" name="linker documentation"> on
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how to use it.
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<descrip>
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<tag><tt/a2-lo.tgi/</tag>
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This driver was written by Stefan Haubenthal. It features a resolution of
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40x40 with 16 colors. At the bottom of the screen, 4 additional text lines
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are available.
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<tag><tt/a2-hi.tgi/</tag>
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This driver was written by Stefan Haubenthal. It features a resolution of
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280x192 with 6 colors.
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</descrip><p>
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<sect1>Extended memory drivers<p>
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No extended memory drivers are currently available for the
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Apple ][.
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<sect1>Joystick drivers<p>
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<descrip>
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<tag><tt/a2-stdjoy.joy/</tag>
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Supports up to two standard joysticks connected to the joysticks port of
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the Apple ][.
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</descrip><p>
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<sect1>Mouse drivers<p>
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Currently no drivers available (in fact, the API for loadable mouse drivers
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does not exist).
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<sect1>RS232 device drivers<p>
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No serial drivers are currently available for the Apple ][.
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<sect>Limitations<label id="limitations"><p>
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<sect1>Disk I/O<p>
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The existing library for the Apple ][ doesn't implement C file
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I/O. There are two hacks for the <tt/read()/ and <tt/write()/ routines in
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place, which will make functions work that read from or write to <tt/stdout/
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(like <tt/printf()/). However, these functions have some shortcomings which
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won't be fixed, because they're going to be replaced anyway.
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To be more concrete, this limitation means that you cannot use any of the
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following functions (and a few others):
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<itemize>
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<item>fclose
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<item>fopen
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<item>fread
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<item>fprintf
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<item>fputc
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<item>fscanf
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<item>fwrite
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<item>...
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</itemize>
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<sect>Other hints<p>
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<sect1>Passing arguments to the program<p>
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Command line argument passing is currently not supported for the
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Apple ][.
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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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