mirror of
https://github.com/cc65/cc65.git
synced 2024-12-25 02:29:52 +00:00
223 lines
6.6 KiB
Plaintext
223 lines
6.6 KiB
Plaintext
<!doctype linuxdoc system>
|
|
|
|
<article>
|
|
|
|
<title>Atari specific information for cc65
|
|
<author>Shawn Jefferson, <htmlurl url="mailto:shawnjefferson@24fightingchickens.com" name="shawnjefferson@24fightingchickens.com">
|
|
Christian Groessler, <htmlurl url="mailto:cpg@aladdin.de" name="cpg@aladdin.de">
|
|
<date>16-Oct-2003
|
|
|
|
<abstract>
|
|
An overview over the Atari runtime system as it is implemented for the cc65 C
|
|
compiler.
|
|
</abstract>
|
|
|
|
<!-- Table of contents -->
|
|
<toc>
|
|
|
|
<!-- Begin the document -->
|
|
|
|
<sect>Overview<p>
|
|
|
|
This file contains an overview of the Atari runtime system as it comes
|
|
with the cc65 C compiler. It describes the memory layout, Atari specific
|
|
header files, available drivers, and any pitfalls specific to that
|
|
platform.
|
|
|
|
Please note that Atari specific functions are just mentioned here, they are
|
|
described in detail in the separate <htmlurl url="funcref.html" name="function
|
|
reference">. Even functions marked as "platform dependent" may be available on
|
|
more than one platform. Please see the function reference for more
|
|
information.
|
|
|
|
|
|
<sect>Binary format<p>
|
|
|
|
The standard binary output format generated by the linker for the
|
|
Atari target is a machine language program with a standard executable
|
|
header (FF FF <start address> <end address>). These values are
|
|
calculated in the crt0.s file from the __CODE_LOAD__ and __BSS_LOAD__
|
|
values, so keep this in mind if you create a custom linker config file
|
|
and start moving segments around. You can override this behaviour by
|
|
creating your own crt0.s file and linking it into your program. A run
|
|
vector is added to the end of the file ($02E0 <run vector>)
|
|
and is calculated using __CODE_LOAD__ in crt0.s also.
|
|
|
|
|
|
<sect>Memory layout<p>
|
|
|
|
The default linker script assumes that the BASIC ROM is disabled (or
|
|
the BASIC cartridge unplugged). This gives a usable memory range from
|
|
$2E00 - $BC1F. The library startup code examines the
|
|
current memory configuration, which depends on the size of the
|
|
installed memory and cartridges present, by inspecting the value in
|
|
the MEMTOP ($2E5) variable. Then the initial stack pointer,
|
|
which indicates the upper bound of memory used, is adjusted. The load
|
|
address of $2E00 was chosen to accommodate having a DOS loaded
|
|
and a driver that resides in low memory such as the 850 R: handler.
|
|
You can override this behaviour by creating a custom linker config
|
|
file.
|
|
|
|
Special locations:
|
|
|
|
<descrip>
|
|
<tag/Text screen/
|
|
The text screen depends on the installed memory size and cartridges
|
|
and can be obtained from the SAVMSC variable ($58).
|
|
|
|
<tag/Stack/
|
|
The C runtime stack is located at MEMTOP and grows downwards,
|
|
regardless of how your linker config file is setup. This
|
|
accomodates the different memory configurations of the Atari
|
|
machines, as well as having a cartridge installed. You can override
|
|
this behaviour by writing your own crt0.s file and linking it to
|
|
your program.
|
|
|
|
<tag/Heap/
|
|
The C heap is located at the end of the program and grows towards the C
|
|
runtime stack.
|
|
|
|
</descrip><p>
|
|
|
|
|
|
|
|
<sect>Platform specific header files<p>
|
|
|
|
Programs containing Atari specific code may use the <tt/atari.h/
|
|
header file.
|
|
|
|
|
|
<sect1>Atari specific functions<p>
|
|
|
|
The functions listed below are special for the Atari. See the <htmlurl
|
|
url="funcref.html" name="function reference"> for declaration and usage.
|
|
|
|
<itemize>
|
|
<item>_gtia_mkcolor
|
|
<item>get_ostype
|
|
<item>get_tv
|
|
<item>getcolor
|
|
<item>getdefdev
|
|
<item>graphics
|
|
<item>rest_vecs
|
|
<item>save_vecs
|
|
<item>scroll
|
|
<item>setcolor
|
|
<item>setcolor_low
|
|
</itemize>
|
|
|
|
|
|
<sect1>Hardware access<p>
|
|
|
|
The following pseudo variables declared in the <tt/atari.h/ header
|
|
file do allow access to hardware located in the address space. Some
|
|
variables are structures, accessing the struct fields will access the
|
|
chip registers.
|
|
|
|
<descrip>
|
|
|
|
<tag><tt/GTIA_READ/ and <tt/GTIA_WRITE/</tag>
|
|
The <tt/GTIA_READ/ structure allows read access to the GTIA. The
|
|
<tt/GTIA_WRITE/ structure allows write access to the GTIA.
|
|
See the <tt/_gtia.h/ header file located in the include directory
|
|
for the declaration of the structure.
|
|
|
|
<tag><tt/POKEY_READ/ and <tt/POKEY_WRITE/</tag>
|
|
The <tt/POKEY_READ/ structure allows read access to the POKEY. The
|
|
<tt/POKEY_WRITE/ structure allows write access to the POKEY.
|
|
See the <tt/_pokey.h/ header file located in the include directory
|
|
for the declaration of the structure.
|
|
|
|
<tag><tt/ANTIC/</tag>
|
|
The <tt/ANTIC/ structure allows read access to the ANTIC.
|
|
See the <tt/_antic.h/ header file located in the include directory
|
|
for the declaration of the structure.
|
|
|
|
<tag><tt/PIA/</tag>
|
|
The <tt/PIA/ structure allows read access to the PIA 6520.
|
|
See the <tt/_pia.h/ header file located in the include directory
|
|
for the declaration of the structure.
|
|
|
|
</descrip><p>
|
|
|
|
|
|
|
|
<sect>Loadable drivers<p>
|
|
|
|
<sect1>Graphics drivers<p>
|
|
|
|
Currently there are no graphics drivers available for the Atari platform.
|
|
|
|
<sect1>Extended memory drivers<p>
|
|
|
|
Currently there are no extended memory drivers available for the Atari
|
|
platform.
|
|
|
|
<sect1>Joystick drivers<p>
|
|
|
|
<descrip>
|
|
|
|
<tag><tt/atari-stdjoy.joy/</tag>
|
|
Supports up to four standard joysticks connected to the joystick ports of
|
|
the Atari.
|
|
|
|
</descrip><p>
|
|
|
|
|
|
|
|
<sect1>Mouse drivers<p>
|
|
|
|
Currently no drivers available (in fact, the API for loadable mouse drivers
|
|
does not exist). There is a static driver you can use.
|
|
|
|
|
|
<sect1>RS232 device drivers<p>
|
|
|
|
Currently there are no RS232 loadable drivers available for the Atari
|
|
platform. There is a static driver you can use.
|
|
|
|
|
|
<sect>Limitations<p>
|
|
|
|
|
|
|
|
<sect>Other hints<p>
|
|
|
|
<sect1>Function keys<p>
|
|
|
|
These are defined to be Atari + number key.
|
|
|
|
|
|
|
|
<sect>Bugs/Feedback<p>
|
|
|
|
If you have problems using the library, if you find any bugs, or if you're
|
|
doing something interesting with it, I would be glad to hear from you. Feel
|
|
free to contact me by email (<htmlurl url="mailto:uz@cc65.org"
|
|
name="uz@cc65.org">).
|
|
|
|
|
|
|
|
<sect>License<p>
|
|
|
|
This software is provided 'as-is', without any expressed or implied
|
|
warranty. In no event will the authors be held liable for any damages
|
|
arising from the use of this software.
|
|
|
|
Permission is granted to anyone to use this software for any purpose,
|
|
including commercial applications, and to alter it and redistribute it
|
|
freely, subject to the following restrictions:
|
|
|
|
<enum>
|
|
<item> The origin of this software must not be misrepresented; you must not
|
|
claim that you wrote the original software. If you use this software
|
|
in a product, an acknowledgment in the product documentation would be
|
|
appreciated but is not required.
|
|
<item> Altered source versions must be plainly marked as such, and must not
|
|
be misrepresented as being the original software.
|
|
<item> This notice may not be removed or altered from any source
|
|
distribution.
|
|
</enum>
|
|
|
|
</article>
|