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247 lines
6.9 KiB
Plaintext
247 lines
6.9 KiB
Plaintext
<!doctype linuxdoc system>
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<article>
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<title>PC-Engine (TurboGrafx 16) System-specific information for cc65
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<author><url url="mailto:groepaz@gmx.net" name="Groepaz">,<newline>
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<url url="mailto:greg.king5@verizon.net" name="Greg King">
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<abstract>
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An overview over the PCE 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 PCE runtime system as it comes
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with the cc65 C compiler. It describes the memory layout, PCE-specific header
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files, available drivers, and any pitfalls specific to that platform.
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Please note that PCE-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" might 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 binary output file generated by the linker, for the PCE target, is an
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image, with no header, that has 8K bytes in the wrong place. That file must be
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post-processed; the 8K at the end must be moved to the front of the image.
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On POSIX systems, the <tt/dd/ command and the shell give a convenient way to do
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it. Here is an example of their use:
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<tscreen><verb>
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dd if=conio.bin bs=8K skip=3 > conio.pce
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dd if=conio.bin bs=8K count=3 >> conio.pce
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</verb></tscreen>
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The first command grabs the last 8K of a 32K file, and writes it as the first
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part of a new file. The second command reads all but the last part of the old
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file, and appends it to the new file.
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<tscreen><verb>
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+--------+--------+--------+--------+
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| Bank 1 | Bank 2 | Bank 3 | Bank 0 | <-- "conio.bin"
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+--------+--------+--------+--------+
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+--------+--------+--------+--------+
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| Bank 0 | Bank 1 | Bank 2 | Bank 3 | <-- "conio.pce"
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+--------+--------+--------+--------+
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</verb></tscreen>
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<em/Note/: That <tt/.pce/ file shows the format of the ROM cartridge that is
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plugged into a PC-Engine. But, that <tt/.bin/ file shows what programs
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actually see when they execute the code in that cartridge.
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<sect>Memory layout<p>
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cc65-generated programs with the default setup run with the memory map that was
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used by many PC-Engine games:
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<itemize>
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<item>The first 8K bytes is the I/O area.
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<item>The second 8K bytes is RAM, which holds
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<itemize>
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<item>the redirected zero-page and the redirected hardware stack page,
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<item>and 7680 bytes of general memory ($2200 - $3FFF).
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</itemize>
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<item>The last 8K bytes in the usual 64K-byte range is the ROM that holds the
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program.
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</itemize>
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Special locations:
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<descrip>
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<tag/Text screen and Font/
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The text screen is located at Video RAM (VRAM) address $0000;
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the Font is located at VRAM address $2000.
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<tag/Stack/
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The C run-time stack is located in system RAM at $3FFF;
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and, grows downwards.
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<tag/Data and BSS/
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The Data (initialized variables) and BSS (uninitialized variables) sections are
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placed one after the other into system RAM at $2200.
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<tag/Heap/
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The C heap is located after the end of the BSS section;
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and, extends up to the C run-time stack.
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<tag/Code/
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In an 8K ROM cartridge, code and read-only data are located between
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$E000 and $FFF5 in the System bank.
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In a 16K cartridge, code and read-only data are located between $C000
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and $FFF5.
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In a 32K cartridge, code and read-only data are located between $8000
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and $FFF5.
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</descrip>
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<sect>Platform-specific header files<p>
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Programs containing PCE-specific code may use the <tt/pce.h/ header file.
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<sect1>PCE-specific functions<p>
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<itemize>
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<item>get_tv (since all PCE systems are NTSC, this always returns TV_NTSC)</item>
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<item>waitvsync</item>
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</itemize>
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<sect1>Hardware access<p>
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The following constants, defined in the <tt/pce.inc/ include file, do
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allow access to hardware that is located in the address space.
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<descrip>
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<tag><tt/PSG/</tag>
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The <tt/PSG/ defines allow access to the PSG (Programmable Sound Generator).
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<tag><tt/VCE/</tag>
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The <tt/VCE/ defines allow access to the VCE chip (Video Color Encoder).
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<tag><tt/VDC/</tag>
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The <tt/VDC/ defines allow access to the VDC chip (Video Display Controller).<newline>
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32K of 16-bit words of Video RAM can be accessed only through this chip.
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</descrip>
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<sect>Loadable drivers<p>
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All drivers must be statically linked because no file 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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No TGI graphics drivers are currently available for the PCE.
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<sect1>Extended memory drivers<p>
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No extended memory drivers are currently available for the PCE.
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<sect1>Joystick drivers<p>
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<descrip>
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<tag><tt/pce-stdjoy.joy (pce_stdjoy)/</tag>
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A joystick driver for the standard two-button joypad is available.
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Note that the Japanese 6-button pad currently is not supported.
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</descrip>
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<sect1>Mouse drivers<p>
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No mouse drivers are currently available for the PCE.
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<sect1>RS232 device drivers<p>
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No serial drivers are currently available for the PCE.
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<sect>Limitations<p>
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<sect1>Disk I/O<p>
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The existing library for the PCE doesn't implement C file
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I/O. There are no hacks for the <tt/read()/ and <tt/write()/ routines.
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To be more concrete, that 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>printf
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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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Some useful resources on PCE coding:
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<itemize>
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<item><url url="http://blog.blockos.org/?tag=pc-engine">
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<item><url url="http://pcedev.blockos.org/viewforum.php?f=5">
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<item><url url="http://www.romhacking.net/?page=documents&platform=4">
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<item><url url="http://archaicpixels.com/Main_Page">
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<item><url url="http://www.magicengine.com/mkit/doc.html">
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<item><url url="https://github.com/uli/huc">
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<item><url url="http://www.zeograd.com/parse.php?src=hucf">
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</itemize>
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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 marked plainly 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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