Casio PV-1000/Controller port pinout

The TJ-1 controllers used by Casio's PV-1000 and PV-2000 use a Mini-DIN-8.

The game expects the controllers to form a 4x4 button matrix, manually scanned by the software.

               GPI2
             ___|___
    GND ---8/-O O O-\6--- GPO52
           /         \
GPO55 ---5|-O   O   O-|3--- GPO53
           \    |    /
   GPI1 ---2]-O | O-[1--- n/c
             ---|---
                |
              GPO54

The actual mapping of which General Purpose Outputs and Inputs correspond to which button and thus which bits read from I/O port $FD has not yet been determined.