mirror of
https://github.com/cc65/cc65.git
synced 2024-12-27 15:29:46 +00:00
193 lines
4.7 KiB
Plaintext
193 lines
4.7 KiB
Plaintext
<!doctype linuxdoc system>
|
|
|
|
<article>
|
|
<title>Nintendo Entertainment System specific information for cc65
|
|
<author>
|
|
<url url="mailto:uz@cc65.org" name="Ullrich von Bassewitz">,<newline>
|
|
<url url="mailto:polluks@sdf.lonestar.org" name="Stefan A. Haubenthal">
|
|
|
|
<abstract>
|
|
An overview over the NES 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 NES runtime system as it comes
|
|
with the cc65 C compiler. It describes the memory layout, NES specific header
|
|
files, available drivers, and any pitfalls specific to that platform.
|
|
|
|
Please note that NES specific functions are just mentioned here, they are
|
|
described in detail in the separate <url 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 NES target
|
|
is a machine language program with an INES cartridge header. It is of course
|
|
possible to change this behaviour by using a modified startup file and linker
|
|
config.
|
|
|
|
<sect>Memory layout<p>
|
|
|
|
cc65 generated programs with the default setup run with the I/O area and a
|
|
CHR bank enabled, which gives a usable memory range of $8000 - $FFF3.
|
|
All boot ROM entry points may be called directly without additional code.
|
|
|
|
Special locations:
|
|
|
|
<descrip>
|
|
<tag/Text screen/
|
|
The text screen is located at VRAM $2000.
|
|
|
|
<tag/Stack/
|
|
The C runtime stack is located at $7FFF and growing downwards.
|
|
|
|
<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 NES specific code may use the <tt/nes.h/ header file.
|
|
|
|
|
|
<sect1>NES specific functions<p>
|
|
|
|
<itemize>
|
|
<item>get_tv</item>
|
|
<item>waitvsync - wait until the start of the next frame</item>
|
|
</itemize>
|
|
|
|
|
|
|
|
<sect1>Hardware access<p>
|
|
|
|
The following pseudo variables declared in the <tt/nes.inc/ include file do
|
|
allow access to hardware located in the address space.
|
|
|
|
<descrip>
|
|
|
|
<tag><tt/PPU/</tag>
|
|
The <tt/PPU/ defines allow access to the PPU chip.
|
|
|
|
<tag><tt/APU/</tag>
|
|
The <tt/APU/ defines allow access to the APU chip.
|
|
|
|
</descrip><p>
|
|
|
|
|
|
|
|
<sect>Loadable drivers<p>
|
|
|
|
All drivers must be statically linked because no file I/O is available.
|
|
The names in the parentheses denote the symbols to be used for static linking of the drivers.
|
|
|
|
|
|
<sect1>Graphics drivers<p>
|
|
|
|
<descrip>
|
|
|
|
<tag><tt/nes-64-56-2.tgi (nes_64_56_2)/</tag>
|
|
This driver features a resolution of 64×56 with 2 colors using the
|
|
CHR bank.
|
|
|
|
</descrip><p>
|
|
|
|
|
|
<sect1>Extended memory drivers<p>
|
|
|
|
No extended memory drivers are currently available for the NES.
|
|
|
|
|
|
<sect1>Joystick drivers<p>
|
|
|
|
<descrip>
|
|
|
|
<tag><tt/nes-stdjoy.joy (nes_stdjoy)/</tag>
|
|
A joystick driver for the standard four buttons joypad is available.
|
|
|
|
</descrip><p>
|
|
|
|
The generic interface doesn't export the start and select buttons. To
|
|
test for those, use the defines in nes.h instead of the generic masks.
|
|
|
|
Example:
|
|
<tscreen><verb>
|
|
if (joy_read(0) & KEY_A)
|
|
</verb></tscreen>
|
|
|
|
|
|
<sect1>Mouse drivers<p>
|
|
|
|
No mouse drivers are currently available for the NES.
|
|
|
|
|
|
<sect1>RS232 device drivers<p>
|
|
|
|
No serial drivers are currently available for the NES.
|
|
|
|
|
|
|
|
<sect>Limitations<p>
|
|
|
|
<sect1>Disk I/O<p>
|
|
|
|
The existing library for the NES doesn't implement C file
|
|
I/O. There are no hacks for the <tt/read()/ and <tt/write()/ routines.
|
|
|
|
To be more concrete, this limitation means that you cannot use any of the
|
|
following functions (and a few others):
|
|
|
|
<itemize>
|
|
<item>fclose
|
|
<item>fopen
|
|
<item>fread
|
|
<item>fprintf
|
|
<item>fputc
|
|
<item>fscanf
|
|
<item>fwrite
|
|
<item>...
|
|
</itemize>
|
|
|
|
|
|
|
|
<sect>Other hints<p>
|
|
|
|
|
|
|
|
<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>
|