vcs

VCS Emulator

In its current form, it partially emulates a headless VCS which can only boot standard 4K ROMs and then simply output every instruction being fetched. Still no RIOT, TIA, illegal 6507 instructions or custom cartridges. In other words, it does not play any games yet.

Building

To build the emulator, you can use the provided build script:

./build.sh

Alternatively, you can run make directly. The final executable will be located in the dist/ directory.

Running

Run the emulator by providing a path to a standard 4K ROM file. You can use the provided run script:

./run.sh roms/adventure.a26

Alternatively, you can run the executable directly:

./dist/vcs roms/adventure.a26

Debugging

During execution, the emulator will log the CPU state for each instruction to the console. The output layout is as follows:

PC:1000 OP:4C A:00 X:00 Y:00 SP:FF ST:24

• PC: Program Counter (current instruction address)
• OP: Opcode (hexadecimal value of the instruction)
• A: Accumulator register
• X: X index register
• Y: Y index register
• SP: Stack Pointer
• ST: Status Flags (Processor Status register)

Press ESC to stop the emulator.

Notes

• Execution Speed: The emulator currently runs at the maximum speed allowed by your host CPU. There is no internal timing mechanism to match the original VCS clock speed.
• Logging Detail: The debug trace logs every single byte fetch. This means for a 3-byte instruction, you will see three lines of output (one for the opcode and two for the operand bytes).
• Compatibility: Only standard 4K ROMs are supported. Cartridges with bank-switching or special hardware will not work in the current implementation.

Project History

This project was originally developed using Borland Turbo C for DOS and has been ported to modern POSIX/Linux environments using standard termios for terminal handling.