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 function reference. Even functions marked as "platform dependent" may be available on more than one platform. Please see the function reference for more information.
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.
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:
The text screen is located at VRAM $2000.
The C runtime stack is located at $7FFF and growing downwards.
The C heap is located at the end of the program and grows towards the C runtime stack.
Programs containing NES specific code may use the nes.h header file.
The following pseudo variables declared in the nes.inc include file do
allow access to hardware located in the address space.
PPUThe PPU defines allow access to the PPU chip.
APUThe APU defines allow access to the APU chip.
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.
nes-64-56-2.tgi (nes_64_56_2)This driver features a resolution of 64×56 with 2 colors using the CHR bank.
No extended memory drivers are currently available for the NES.
nes-stdjoy.joy (nes_stdjoy)A joystick driver for the standard four buttons joypad is available.
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:
if (joy_read(0) & KEY_A)
No mouse drivers are currently available for the NES.
No serial drivers are currently available for the NES.
The existing library for the NES doesn't implement C file
I/O. There are no hacks for the read() and write() routines.
To be more concrete, this limitation means that you cannot use any of the following functions (and a few others):
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: