SNES Game Pad Interface

I wanted to connect a game control pad to a microcontroller, so I started by finding an old Super Nintendo (SNES) controller. The controller is interfaced to the game console by a five-wire connection. The pad itself contains a 16-bit shift register, of which only 12 bits are used. The photo shows the scope trace when a single button is pressed on the game pad. The upper trace shows the data, and the lower trace shows the clock. The data signal goes low for one bit-time of the clock, corresponding to the button that has been pressed.