I/O

I/O (input/output) refers to how a computer communicates with the outside world. In the Game Boy/Color's Z80-based processor, registers for the input/output range between 0xFF00 to 0xFF70.

The Game Boy/Color has included a huge amount of communication peripherals. One of the most commonly used is the Link Cable; which inspired the Pokémon concept as Satoshi Tajiri was a bug catcher during his childhood. Additionally, the Game Boy Color (but not the Game Boy Advance) included a built-in infrared port.

The Japanese version of Pokémon Crystal communicated over the Internet using a mobile phone and the Mobile GB Adapter, but the Mobile GB Adapter fell into relative obscurity and never left Japan.

DMG mode

• $FF00 - Joypad
• $FF01 - Serial transfer
• $FF04 $FF07 - Timer/divider
• $FF10 $FF26 - Audio
• $FF30 $FF3F - Wave pattern
• $FF40 $FF4B - LCD Control, Status, Position, Scrolling, Palettes
• $FF50 - Is boot ROM disabled? (non-zero if true)

CGB mode

• $FF4F - VRAM Bank Select
• $FF51 $FF55 - VRAM DMA
• $FF68 $FF69 - BG/OBJ Palettes
• $FF70 - WRAM Bank Select

External links

• Game Boy Memory Map - Pan Docs
• Dan Docs by Shonumi (obscure peripherals)

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