Chip-8

A Chip-8 interpreter/emulator written in Go with terminal-based display.

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Features

• 35+ Chip-8 instructions implemented — draw, jump, subroutine, arithmetic, logic, keypad, timers
• Termbox-based 64×32 pixel display
• Hex keypad mapped to keyboard
• Delay and sound timer support
• Old/new behavior mode toggle (handles Chip-8 vs SUPER-CHIP quirks)
• ROM loading from disk
• Test ROMs included (IBM logo, Pong, Space Invaders, Connect 4, test suites)

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Quick Start

go run main.go

Edit main.go to switch between included ROMs:

n := "./pong.rom"       // Pong game
n := "./invaders.rom"   // Space Invaders
n := "./ibm_logo.ch8"   // IBM logo test
n := "./test_opcode.ch8" // Opcode test suite
n := "./connect4.rom"   // Connect 4

Controls

Chip-8 Keypad → Keyboard
  1 2 3 4     → 1 2 3 4
  q w e r     → q w e r
  a s d f     → a s d f
  z x c v     → z x c v

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Architecture

Package	Purpose
chip/	CPU core — fetch, decode, execute cycle, instruction set
display/	Termbox-go screen buffer with 64×32 pixel XOR drawing
keyboard/	Hex keypad state tracking and polling
memory/	4096-byte addressable memory
register/	16 general-purpose 8-bit Vx registers + 16-bit I register
stack/	16-level call stack for subroutines
timer/	60Hz delay and sound countdown timers
util/	Binary/decimal conversion utilities

Instruction Set

The emulator implements the standard Chip-8 instruction set including:

• Clear/Return: 00E0 (CLS), 00EE (RET)
• Jump/Call: 1NNN (JP), 2NNN (CALL), BNNN (JP V0+addr)
• Skip: 3XNN, 4XNN, 5XY0, 9XY0, EX9E, EXA1
• Arithmetic: 6XNN (LD Vx), 7XNN (ADD Vx), 8XY0–8XYE (LD/OR/AND/XOR/ADD/SUB/SHR/SUBN/SHL)
• Logic/Compare: CXNN (RND), FX07/FX15/FX18/FX1E/FX29/FX33/FX55/FX65
• Draw: DXYN (DRW) — XOR-based sprite rendering with collision detection
• Keypad: FX0A (wait for key), EX9E (skip if key), EXA1 (skip if not key)
• Timer/Sound: FX07 (get delay), FX15 (set delay), FX18 (set sound)

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Why This Matters

A Chip-8 emulator requires understanding:

• CPU fetch-decode-execute cycle
• Memory-mapped I/O and address spaces
• Bit-level sprite rendering with XOR collision
• Interrupt-driven timer systems
• Hexadecimal keypad polling

This is a foundational systems project that demonstrates low-level programming, architecture emulation, and Go concurrency.

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License

MIT