The Mouse is inserted into Joystick Port 0.
This port shares pin 9 with pin 6 of Joystick Port 1 (fire button).
| Pin | Color | Dir | Mouse | Joystick0 | Joystick1 |
|---|---|---|---|---|---|
| 1 | WHT | ![]() |
XB | Up | Up |
| 2 | BLU | ![]() |
XA | Down | Down |
| 3 | GRN | ![]() |
YA | Left | Left |
| 4 | BWN | ![]() |
YB | Right | Right |
| 5 | RED | n/c | n/c | n/c | |
| 6 | ORG | ![]() |
Left Button | Fire | Fire |
| 7 | ![]() |
VCC | VCC | VCC | |
| 8 | BLK | ![]() |
GND | GND | GND |
| 9 | YLW | ![]() |
Right Button | (Joy1 Fire) | n/c |
The ST-series joystick ports are compatible with Atari 2600 and Atari 7800
Paddles are not supported, though and unlike the XL/XE, the ST can not control the outputs of the first 4 port pins.





