CHIP-8 Emulator

This is a CHIP-8 emulator written in C++ using SDL3 for graphics. CHIP-8 is an interpreted programming language used on early home computers, notably the COSMAC VIP and Telmac 1800. The emulator allows you to run CHIP-8 games and programs, emulating the original hardware functionality on modern systems.

Features

• Emulates the full CHIP-8 instruction set.
• Loads and runs CHIP-8 ROM files.
• Simple graphics display with a 64x32 pixel resolution.
• Keyboard input mapping to simulate the CHIP-8 keypad.
• Sound has not yet been implemented

Architecture

The CHIP-8 architecture consists of the following components:

• Memory: 4KB of RAM, from 0x000 to 0xFFF, which stores the program, data, and stack.
• Registers: 16 general-purpose 8-bit registers (V0 to VF), used for arithmetic and logical operations.
• Stack: Used to store return addresses during subroutine calls. The stack can hold up to 16 return addresses.
• Timers: 2 8-bit timers (delay_timer and sound_timer) that decrease at 60Hz.
• Graphics: 64x32 pixel display for rendering the graphics. The display is monochrome (black/white).
• Keypad: 16 keys that simulate user input (mapped to your keyboard).

CHIP-8 Instruction Set

Here’s the complete CHIP-8 instruction set:

Opcode	Instruction	Description
00E0	CLS (Clear the screen)	Clears the screen.
00EE	RET (Return from subroutine)	Returns from a subroutine by popping the top of the stack into the program counter.
1NNN	JP NNN (Jump to address NNN)	Jumps to the address NNN.
2NNN	CALL NNN (Call subroutine at NNN)	Calls the subroutine at address NNN, pushing the return address onto the stack.
3XNN	SE VX, NN (Skip if VX == NN)	Skips the next instruction if register Vx is equal to NN.
4XNN	SNE VX, NN (Skip if VX != NN)	Skips the next instruction if register Vx is not equal to NN.
5XY0	SE VX, VY (Skip if VX == VY)	Skips the next instruction if register Vx equals register Vy.
6XNN	LD VX, NN (Set VX to NN)	Sets register Vx to the value NN.
7XNN	ADD VX, NN (Add NN to VX)	Adds the value NN to register Vx.
8XY0	LD VX, VY (Set VX to VY)	Sets register Vx to the value of register Vy.
8XY1	OR VX, VY (VX = VX OR VY)	Performs a bitwise OR on registers Vx and Vy, storing the result in Vx.
8XY2	AND VX, VY (VX = VX AND VY)	Performs a bitwise AND on registers Vx and Vy, storing the result in Vx.
8XY3	XOR VX, VY (VX = VX XOR VY)	Performs a bitwise XOR on registers Vx and Vy, storing the result in Vx.
8XY4	ADD VX, VY (VX = VX + VY, VF = carry)	Adds the value of Vy to Vx and sets the VF register to 1 if there is a carry, otherwise 0.
8XY5	SUB VX, VY (VX = VX - VY, VF = borrow)	Subtracts Vy from Vx and sets VF to 0 if there's a borrow, otherwise 1.
8XY6	SHR VX {, VY} (VX = VX >> 1)	Shifts Vx right by one bit, storing the result in Vx.
8XY7	SUBN VX, VY (VX = VY - VX, VF = borrow)	Subtracts Vx from Vy, and sets VF to 0 if there's a borrow, otherwise 1.
8XYE	SHL VX {, VY} (VX = VX << 1)	Shifts Vx left by one bit, storing the result in Vx.
9XY0	SNE VX, VY (Skip if VX != VY)	Skips the next instruction if Vx is not equal to Vy.
ANNN	LD I, NNN (Set I to address NNN)	Sets the I register to the address NNN.
BNNN	JP V0, NNN (Jump to NNN + V0)	Jumps to the address NNN plus the value in V0.
CXNN	RND VX, NN (VX = random AND NN)	Sets Vx to a random number AND NN.
DXYN	DRW VX, VY, N (Draw sprite)	Draws a sprite at position (Vx, Vy) with a width of N pixels, and stores the sprite in memory at I.
EX9E	SKP VX (Skip if key pressed)	Skips the next instruction if the key in register Vx is pressed.
EXA1	SKNP VX (Skip if key not pressed)	Skips the next instruction if the key in register Vx is not pressed.
FX07	LD VX, DT (Set VX to delay timer)	Sets Vx to the current value of the delay timer.
FX0A	LD VX, K (Wait for key press)	Waits for a key to be pressed and stores the value in Vx.
FX15	LD DT, VX (Set delay timer to VX)	Sets the delay timer to the value in register Vx.
FX18	LD ST, VX (Set sound timer to VX)	Sets the sound timer to the value in register Vx.
FX1E	ADD I, VX (I = I + VX)	Adds the value of register Vx to the I register.
FX29	LD F, VX (Set I to sprite location)	Sets I to the location of the sprite for the character in Vx.
FX33	LD B, VX (Store BCD of VX at I)	Stores the binary-coded decimal representation of Vx at memory locations I, I+1, and I+2.
FX55	LD [I], VX (Store registers in memory)	Stores the values of registers V0 through Vx at memory starting from address I.
FX65	LD VX, [I] (Read registers from memory)	Reads values into registers V0 through Vx from memory starting at address I.

Controls

• Use the following keys to simulate the CHIP-8 keypad:
  • 1, 2, 3, 4 for 1, 2, 3, C on the CHIP-8 keypad.
  • Q, W, E, R for 4, 5, 6, D.
  • A, S, D, F for 7, 8, 9, E.
  • Z, X, C, V for A, 0, B, F.

Prerequisites

• Make and g++ compiler for C++
• A CHIP-8 ROM file to test the emulator (you can find couple of ROMS in /roms folder).
  • if you download more roms, just put them in roms folder

Getting Started

To run the CHIP-8 emulator, do this:

make
./chip8 name_of_rom_from_roms_folder_without_ch8