CHIP-8/SUPER-CHIP Emulator

Another CHIP-8 and SUPER-CHIP emulator written in C++. Sound not implemented.

Table of Contents

• Usage
  • Dependencies
  • Build
  • Command line arguments
    • Quirk flags
  • Changing colors
  • Debugger
• Running tests
• Thanks

Usage

Dependencies

You will need,

• A C++ Compiler
• CMake Version 3.26+
• A CMake Build Generator
• SDL2

With CMake

git clone https://github.com/camelliya/schip8.git
cd schip8
cmake -S . -B build -G your_generator -DCMAKE_BUILD_TYPE=RELEASE -DCMAKE_PREFIX_PATH=path/to/SDL2install
cmake --build build
build/src/schip8.exe <ARGUMENTS>...

Important

The emulator won't run without being provided a rom.

Command line arguments

• -rom <path/to/rom> - This is the rom the emulator will play. Must be specified.
• -cycles_per_frame <number> - Controls the speed at which the emulator runs (default = 20). Changing it can help improve the "feel" of certain roms.
• --mode <type> - Allows either: superchip, xochip, or default (optional). This option will override all quirk flags except ioverflow
• -quirk <quirk_name=bool> - Used to toggle a specific quirk on or off.
• -debug - The emulator will start running immediately in debug mode.

Quirk flags

Quirk flags are used to toggle different implementation details from the various interpreters. Defaults are shown after the equal sign.

• vf_reset=true - set register Vf to 0 after vx |= vy, vx &= vy, and vx ^= vy.
• memory=true - opcodes that load from and store to memory will increment register i.
• shifting=false - opcodes using <<= and >>= will modify register Vx in place and ignore register Vy.
• jumping=false - jp_ with offset will use the value of register Vx instead of the 4 left-most bits of the target address.
• ioverflow=false - set register Vf to 0 on ioverflow of I = I + Vx (greater than 0x1000). Apparently used by at least one game: Spacefight 2091

Changing Colors

You can modify the colors of the emulator if you wish. The constants for them (colorOn and colorOff) are defined in the display header. Just append FF to whichever hex code you choose (e.g. the default on color is #9C5ECC + FF = 0x9C5ECCFF).

Debugger

The debugger outputs the current state of the registers, the opcode just executed and the current cycle number to the console. Using it is simple,

Press I to enter/exit_ debug mode.

Press O to step the interpreter forward once.

See command line arguments to enter the debugger immediately on launch of the emulator.

Running Tests

I used Google's GoogleTest framework to run unit tests during development. If you would like to use them, you will need to build the project with testing enabled.

cmake -S . -B build -G your_generator -DTESTING=ON -DCMAKE_BUILD_TYPE=RELEASE -DCMAKE_PREFIX_PATH=path/to/SDL2install
cmake --build build
cd build/tests/
ctest

For a more detailed report, the test logs are written to tests/Testing/Temporary/ or you can use the command,

cat Testing/Temporary/LastTestLog.txt

Thanks

• Timendus's CHIP-8 Test Suite was very helpful during development
• tobiasvl's CHIP-8 documentation
• John Earnest's Mastering SuperChip blog post