Atari ST series Technical Reference Manual page 217

Get Pseudo-Random Number
Random()
T h is f u n c ti o n r e t u r n s t h e n e x t 2 4 - b i t p s e u d o - r a n d o m n u m b e r in t h e s e r i e s
g e n e r a t e d b y t h e a l g o r i t h m :
SEED = (SEED * 3141592621) + 1
T h e v a l u e r e t u r n e d is t h e n e w s e e d v a l u e , s h if te d e i g h t b its t o t h e r i g h t .
S i n c e t h e in itia l s e e d v a l u e is t a k e n f r o m t h e s c r e e n 's v e r t i c a l b la n k f r a m e
c o u n t e r , th e s e q u e n c e s h o u l d b e d i f f e r e n t e a c h ti m e t h e m a c h i n e is t u r n e d
o n .
C macro format
lo n g m d n u m ;
m d n u m = R a n d o m ( )
Machine language format
m o v e . w # 1 7 , - ( s p )
t r a p # 1 4
a d d q .l # 2 , s p
Inputs
N o n e
Results
DO r n d n u m l o n g
Random
A 2 4 - b i t p s e u d o - r a n d o m n u m b e r (b its 2 4 - 3 1 a r e 0 )
Opcode = 17
209