Famicom 3D System

The Famicom 3D System (HVC-031) is a peripheral released for the Family Computer in 1987 by Nintendo. The system consists of a pair of special glasses with liquid crystals lenses, which plug into a special adapter utilizing 3.5mm jacks. There are two ports available on the adapter, allowing for two players to be able to utilize the 3D System for multiplayer games. Said adapter plugs into the expansion port to interface with the Famicom console.

Output ($4016 write)

7  bit  0
---- ----
xxxx xxFx
       |
       +--- 0: Next field of video is for left eye (left eye lens is transparent; right eye lens is opaque)
            1: Next field of video is for right eye

Because the Famicom only generated images at 60Hz, each resultant image will flicker at 30Hz.