== I/O ports ==
Port &F990 = Port A Actions bits
Port &F991 = Port B Actions bits
Port &F992 = Port A Mouse POS-X value
Port &F993 = Port A Mouse POS-Y value
Port &F994 = Port B Mouse POS-X value
Port &F995 = Port B Mouse POS-Y value
Ports &F996 and &F997 are unused