All the logic of the controller is contained in a single chip (IC1) which is labled as follows:

+--------------+
| SEGA         |
| E2 MAPLE BUS |
| 315-6125-AB  |
| 841A2A20     |
+--------------+

Male connector pinout:

The plate on top of the connector is for the cable shield. It is internally connected to pin 3 (GND).

Internal connector inside controller pinout:

1 red serial data 2 blue +5V 3 black GND 4 green sense (connected to GND inside controller/keyboard) 5 white serial data

The current state of a gamepad is queried with the Get condition request. The condition stucture for the Controller function code ($001) is as follows:

int16 buttons       ; digital buttons bitfield (little endian)
int8 rtrigger       ; right analogue trigger (0-255)
int8 ltrigger       ; left analogue trigger (0-255)
int8 joyx           ; analogue joystick X (0-255)
int8 joyy           ; analogue joystick Y (0-255)
int8 joyx2          ; second analogue joystick X (0-255)
int8 joyy2          ; second analogue joystick Y (0-255)

Bit Button 0 C 1 B 2 A 3 START 4 5 6 7 8 Z 9 Y 10 X 11 D 12 2 13 2 14 2 15 2

The function_data for the Controller function code is a bitfield describing which controls are present on the particular device (zero = not present, one = present):

Bit Control 0 C 1 B 2 A 3 START 4 5 6 7 8 Z 9 Y 10 X 11 D 12 2 13 2 14 2 15 2 16 Analogue R trigger 17 Analogue L trigger 18 Analogue horizontal 19 Analogue vertical 20 Analogue horizontal 2 21 Analogue vertical 2