Retro Emulator Workshop

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1. What is CHIP-8?

CHIP-8 is an interpreted programming language developed in the mid-1970s by Joseph Weisbecker for the COSMAC VIP and Telmac 1800 microcomputers. It was designed to make game programming easier on those early systems. Today, CHIP-8 is the classic "first emulator project" — a rite of passage for anyone interested in emulation development. Its simplicity (only 35 opcodes!) makes it approachable, while still teaching all the fundamental concepts.

RAM:4 KB (4096 bytes)

Registers:16 general (V0-VF) + I, PC, SP

Display:64 x 32 pixels, monochrome

Input:16-key hexadecimal keypad

Timers:Delay Timer, Sound Timer (60 Hz)

Stack:16 levels of nesting

Clock:~500 Hz typical

Programs:Loaded at address 0x200

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2. Architecture Overview

Memory Map

0x000 - 0x1FFInterpreter / Font Data

0x200 - 0xE9FProgram / Data Space

0xEA0 - 0xEFFStack / Internal Use

0xF00 - 0xFFFDisplay Refresh (optional)

Registers

Register	Size	Description
V0-VF	8-bit	16 general purpose (VF = flag register)
I	16-bit	Index/Address register
PC	16-bit	Program Counter (starts at 0x200)
SP	8-bit	Stack Pointer
DT	8-bit	Delay Timer (decrements at 60Hz)
ST	8-bit	Sound Timer (beeps when > 0, decrements at 60Hz)

Display

64x32 monochrome pixels. Sprites are XOR'd onto the display — if any pixel is erased, VF is set to 1 (collision detection). Sprites are always 8 pixels wide and 1-15 pixels tall.

Keypad Layout

Original layout — typically mapped to keyboard: 1234/QWER/ASDF/ZXCV

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3. Opcode Table (35 Instructions)

Categories: ● math● display● flow● load● input● timer

Opcode	Mnemonic	Description	Cat
0NNN	SYS addr	Call machine code routine at NNN (ignored on modern)	flow
00E0	CLS	Clear the display	display
00EE	RET	Return from subroutine	flow
1NNN	JP addr	Jump to address NNN	flow
2NNN	CALL addr	Call subroutine at NNN	flow
3XKK	SE Vx, byte	Skip next instruction if Vx == KK	flow
4XKK	SNE Vx, byte	Skip next instruction if Vx != KK	flow
5XY0	SE Vx, Vy	Skip next instruction if Vx == Vy	flow
6XKK	LD Vx, byte	Set Vx = KK	load
7XKK	ADD Vx, byte	Set Vx = Vx + KK	math
8XY0	LD Vx, Vy	Set Vx = Vy	load
8XY1	OR Vx, Vy	Set Vx = Vx OR Vy	math
8XY2	AND Vx, Vy	Set Vx = Vx AND Vy	math
8XY3	XOR Vx, Vy	Set Vx = Vx XOR Vy	math
8XY4	ADD Vx, Vy	Set Vx = Vx + Vy, VF = carry	math
8XY5	SUB Vx, Vy	Set Vx = Vx - Vy, VF = NOT borrow	math
8XY6	SHR Vx	Set Vx = Vx >> 1, VF = bit 0	math
8XY7	SUBN Vx, Vy	Set Vx = Vy - Vx, VF = NOT borrow	math
8XYE	SHL Vx	Set Vx = Vx << 1, VF = bit 7	math
9XY0	SNE Vx, Vy	Skip next instruction if Vx != Vy	flow
ANNN	LD I, addr	Set I = NNN	load
BNNN	JP V0, addr	Jump to NNN + V0	flow
CXKK	RND Vx, byte	Set Vx = random byte AND KK	math
DXYN	DRW Vx, Vy, n	Draw N-byte sprite at (Vx,Vy), VF = collision	display
EX9E	SKP Vx	Skip if key with value Vx is pressed	input
EXA1	SKNP Vx	Skip if key with value Vx is NOT pressed	input
FX07	LD Vx, DT	Set Vx = delay timer value	timer
FX0A	LD Vx, K	Wait for key press, store in Vx	input
FX15	LD DT, Vx	Set delay timer = Vx	timer
FX18	LD ST, Vx	Set sound timer = Vx	timer
FX1E	ADD I, Vx	Set I = I + Vx	math
FX29	LD F, Vx	Set I = sprite addr for digit Vx	load
FX33	LD B, Vx	Store BCD of Vx at I, I+1, I+2	load
FX55	LD [I], Vx	Store V0..Vx in memory starting at I	load
FX65	LD Vx, [I]	Read V0..Vx from memory starting at I	load

35 of 35 opcodes shown

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4. Step-by-Step Implementation Guide

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5. Try It — Mini CHIP-8 Demo

A bouncing digit demo. The hex digit changes each time it bounces off a wall. Uses font sprites and basic collision logic.