2014-05-16 00:26:20 +00:00
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<!doctype linuxdoc system>
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<article>
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<title>Atari 5200 specific information for cc65
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<author>
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<url url="mailto:chris@groessler.org" name="Christian Groessler"><newline>
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2014-05-27 00:44:59 +00:00
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<date>2014-05-27
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2014-05-16 00:26:20 +00:00
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<abstract>
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An overview over the Atari 5200 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 5200 runtime system as it comes
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with the cc65 C compiler. It describes the memory layout, Atari 5200 specific header
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files, available drivers, and any pitfalls specific to that platform.
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Please note that Atari 5200 specific functions are just mentioned here, they are
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described in detail in the separate <url 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 Atari 5200 target
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is a cartridge image. 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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<sect>Memory layout<p>
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2014-05-27 00:44:59 +00:00
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cc65 generated programs with the default setup use the RAM space from $021C to
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$3FFF. If you want to reserve memory for the display list and screen buffer
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you should define the __RESERVED_MEMORY__ linker variable. The number
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of bytes specified by __RESERVED_MEMORY__ are lowering the top of
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memory, therefore the available
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RAM memory for the program is $021C to $3FFF-__RESERVED_MEMORY__.
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The default linker config file sets __RESERVED_MEMORY__ to $1E0
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to reserve space for an optional CONIO text screen.
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2014-05-16 00:26:20 +00:00
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Special locations:
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<descrip>
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<tag/Text screen/
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2014-05-27 22:34:34 +00:00
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The text screen is only enabled if any of the CONIO output functions
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is used in the program. Its size is 20x24 characters (Antic mode 6,
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BASIC mode 1). The text screen is located at $3E00. The
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address of the screen memory is available at runtime in the variable
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SAVMSC ($001B).<p>
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If the program doesn't use any CONIO output functions it needs to setup its own
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display list.
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<tag/Stack/
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The C runtime stack is located at $3FFF-__RESERVED_MEMORY__ 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 Atari 5200 specific code may use the <tt/atari5200.h/ header file.
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<sect1>Atari 5200 specific functions<p>
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<itemize>
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<item>TBD.
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</itemize>
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<sect1>Hardware access<p>
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2014-05-27 00:44:59 +00:00
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The following pseudo variables declared in the <tt/atari5200.h/ header
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file do allow access to hardware located in the address space. Some
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variables are structures, accessing the struct fields will access the
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chip registers.
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<descrip>
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2014-05-27 00:44:59 +00:00
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<tag><tt/GTIA_READ/ and <tt/GTIA_WRITE/</tag>
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The <tt/GTIA_READ/ structure allows read access to the GTIA. The
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<tt/GTIA_WRITE/ structure allows write access to the GTIA.
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See the <tt/_gtia.h/ header file located in the include directory
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for the declaration of the structure.
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2014-05-27 00:44:59 +00:00
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<tag><tt/POKEY_READ/ and <tt/POKEY_WRITE/</tag>
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The <tt/POKEY_READ/ structure allows read access to the POKEY. The
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<tt/POKEY_WRITE/ structure allows write access to the POKEY.
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See the <tt/_pokey.h/ header file located in the include directory
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for the declaration of the structure.
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2014-05-27 00:44:59 +00:00
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<tag><tt/ANTIC/</tag>
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The <tt/ANTIC/ structure allows read access to the ANTIC.
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See the <tt/_antic.h/ header file located in the include directory
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for the declaration of the structure.
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2014-05-27 00:44:59 +00:00
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</descrip><p>
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2014-05-16 00:26:20 +00:00
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<sect>Loadable drivers<p>
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2014-05-27 00:44:59 +00:00
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All drivers must be statically linked because no disk I/O is available.
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The names in the parentheses denote the symbols to be used for static linking of the drivers.
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<sect1>Graphics drivers<p>
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<descrip>
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No graphics drivers are currently available for the Atari 5200.
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</descrip><p>
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<sect1>Extended memory drivers<p>
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No extended memory drivers are available for the Atari 5200.
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<sect1>Joystick drivers<p>
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<descrip>
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<tag><tt/atr5200std.joy (atr5200std_joy)/</tag>
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2014-05-27 22:34:34 +00:00
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A joystick driver for the standard Atari 5200 joystick is
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available. Depending on the version of the 5200 console, two or four joysticks can be attached.
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</descrip><p>
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<sect1>Mouse drivers<p>
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No mouse drivers are available for the Atari 5200.
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<sect1>RS232 device drivers<p>
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No serial drivers are available for the Atari 5200.
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<sect>Limitations<p>
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<sect1>Disk I/O<p>
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2014-05-27 00:44:59 +00:00
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Disk I/O is not supported by the <tt/atari5200/ target. This means that
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you cannot use any of the following functions (and a few others):
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2014-05-16 00:26:20 +00:00
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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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<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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