The Bandai RX-78 uses a proprietary joystick port with an 8 pin din. This din should be a 2-3-3 layout with all pins symmetrical. It also makes use of two ground connections, Ground 1 provides Fire, Left and Up when connected to the relevant pins and Ground 2 provides Right and Down.
Port as seen when looking at the machine
|2||Left / Right|
|6||Up / Down|