How does dual-slot mode *technically* work?

My goal is to reverse engineer the protocol, but I have no idea where to even start Specifically: How does the DS game know which GBA game is

It works with Game Boy, Game Boy Color and Game Boy Advance games through its cartridge slot, while games from the Sega Game Gear

ds with gameboy slot The DS Lite is unable to detect a game when the unit is on and a game is inserted You'll need to turn the device off, insert DS Lite andor GBA

ds lite gba slot I recommend it for those who mainly want to play PSP, Nintendo DS and Game Boy Advance, since its widescreen screen is ideal for this Good: - Price