Atari ST series Technical Reference Manual page 218

Produce Boot Sector Prototype
Protobt()
T h is f u n c t i o n is u s e d t o c r e a t e a b o o t s e c t o r in m e m o r y . T h is is a s p e c ia ll y
f o r m a t t e d b lo c k o f i n f o r m a t i o n t h a t m u s t b e s t o r e d o n t h e f ir s t s e c t o r o f
e a c h f l o p p y d i s k ( s i d e 0 , tr a c k 0 , s e c t o r 1 ) . T h e f in i s h e d b o o t s e c t o r s h o u l d
b e w r i t t e n to t h e f l o p p y d i s k , u s i n g t h e F l o p w r ( ) f u n c t i o n , n o t t h e B IO S
f u n c t i o n R w a b s ( ).
C macro format
i n t d i s k t y p e , e x e c f l a g ;
l o n g b u f f e r , s e r i a l n u m ;
P r o t o b t ( b u f f e r , s e r i a l n u m , d i s k t y p e , e x e c f l a g ) ;
Machine language format
m o v e . w e x e c f l a g , - (s p )
m o v e . w d i s k t y p e , - ( s p )
s e r i a l n u m , - (s p )
m o v e .l
m o v e .l b u f f e r , - (s p )
m o v e . w # 1 8 , - ( s p )
t r a p # 1 4
a d d .l # 1 4 , s p
Inputs
e x e c f l a g w o r d
w o r d
d i s k t y p e
s e r i a l n u m l o n g
b u f f e r l o n g
Results
N o n e
See also
Flopfmt(), Flopwr()
210
Protobt
A f la g t h a t i n d i c a t e s w h e t h e r to e x e c u t e
s o m e b o o t c o d e a t s t a r t u p ti m e . B o o t
c o d e is u p to 4 8 0 b y t e s o f m a c h i n e in ­
s t r u c t i o n , s t a r t i n g a t b y t e 3 0 o f t h e b o o t
s e c t o r .
0 = n o b o o t c o d e
1 = e x e c u t e b o o t c o d e
A c o d e w o r d t h a t s p e c i f i e s a d i s k 's s t o r ­
a g e c a p a c i t y a n d f o r m a t :
0 = 4 0 t r a c k s , s i n g l e s id e d ( 1 8 0 K )
1 = 4 0 t r a c k s , d o u b l e s id e d ( 3 6 0 K )
2 = 8 0 t r a c k s , s i n g l e s i d e d ( 3 6 0 K )
3 = 8 0 t r a c k s , d o u b l e s id e d ( 7 2 0 K )
A u n i q u e 2 4 - b i t i d e n ti f i e r c o d e u s e d b y
t h e file s y s t e m to te ll w h e t h e r d i s k s h a v e
b e e n c h a n g e d in a p a r t i c u l a r d r i v e . T o
g e n e r a t e a r a n d o m s e r i a l n u m b e r , p a s s a
v a l u e l a r g e r t h a n ( $ 1 0 0 0 0 0 0 ) .
T h e a d d r e s s o f a 5 1 2 - b y t e m e m o r y b u f f e r
w h e r e t h e b o o t b l o c k in f o r m a t i o n w ill b e
c r e a t e d .
Opcode = 18