Atari ST series Technical Reference Manual page 355

Packet returned
Byte
Number Description
1 $ F 8 - $ F B ( m o u s e r e l a t i v e p o s i t i o n p a c k e t h e a d e r ) . B its 0 a n d 1
r e c o r d th e r i g h t a n d le f t m o u s e b u t t o n s t a t e :
$ F 8
$ F 9
$ F A
$ F B
2 C h a n g e in h o r i z o n t a l p o s i t i o n e x p r e s s e d a s s i g n e d i n t e g e r
3 C h a n g e in v e r t i c a l p o s i t i o n e x p r e s s e d a s s i g n e d in t e g e r
The Intelligent Keyboard Controller
= n e i t h e r b u t t o n p r e s s e d
= le f t b u t t o n o n l y p r e s s e d
= r i g h t b u t t o n o n l y p r e s s e d
= b o t h b u t t o n s p r e s s e d
347