blagojeblagojevic/chip8

chip8 emulator (C, graphics.h)

CHIP8

About Chip-8

Chip-8 is a simple, interpreted, programming language which was first used on some do-it-yourself computer systems in the late 1970s and early 1980s. The COSMAC VIP, DREAM 6800, and ETI 660 computers are a few examples. These computers typically were designed to use a television as a display, had between 1 and 4K of RAM, and used a 16-key hexadecimal keypad for input. The interpreter took up only 512 bytes of memory, and programs, which were entered into the computer in hexadecimal, were even smaller.

Chip-8 Specifications

16 8-bit Registers

The CHIP-8 has sixteen 8-bit registers, labeled V0 to VF. Each register is able to hold any value from 0x00 to 0xFF.

4K Bytes of Memory

The address space is divided into three sections:

1. 0x000-0x1FF:

Originally reserved for the CHIP-8 interpreter, but in our modern emulator we will just never write to or read from that area.

2. 0x050-0x0A0:

Storage space for the 16 built-in characters (0 through F), which we will need to manually put into our memory because ROMs will be looking for those characters.

3. 0x200-0xFFF:

Instructions from the ROM will be stored starting at 0x200, and anything left after the ROM’s space is free to use.

16-bit Index Register

The Index Register is a special register used to store memory addresses for use in operations. It’s a 16-bit register because the maximum memory address (0xFFF) is too big for an 8-bit register

Other Registers

16-bit Program Counter

16-level Stack

8-bit Stack Pointer

8-bit Delay Timer

8-bit Sound Timer

The Instructions

The CHIP-8 has 34 instructions:

        00E0 - CLS
        00EE - RET
        0nnn - SYS addr
        1nnn - JP addr
        2nnn - CALL addr
        3xkk - SE Vx, byte
        4xkk - SNE Vx, byte
        5xy0 - SE Vx, Vy
        6xkk - LD Vx, byte
        7xkk - ADD Vx, byte
        8xy0 - LD Vx, Vy
        8xy1 - OR Vx, Vy
        8xy2 - AND Vx, Vy
        8xy3 - XOR Vx, Vy
        8xy4 - ADD Vx, Vy
        8xy5 - SUB Vx, Vy
        8xy6 - SHR Vx {, Vy}
        8xy7 - SUBN Vx, Vy
        8xyE - SHL Vx {, Vy}
        9xy0 - SNE Vx, Vy
        Annn - LD I, addr
        Bnnn - JP V0, addr
        Cxkk - RND Vx, byte
        Dxyn - DRW Vx, Vy, nibble
        Ex9E - SKP Vx
        ExA1 - SKNP Vx
        Fx07 - LD Vx, DT
        Fx0A - LD Vx, K
        Fx15 - LD DT, Vx
        Fx18 - LD ST, Vx
        Fx1E - ADD I, Vx
        Fx29 - LD F, Vx
        Fx33 - LD B, Vx
        Fx55 - LD [I], Vx
        Fx65 - LD Vx,