Atari ST series Technical Reference Manual page 402

1 0 7 4 - 1 0 7 7
A p o i n t e r t o t h e l o w e s t a v a i la b l e m e m o r y l o c a t i o n . T h e B I O S G e t m p b ( )
f u n c t i o n u s e s th is v a l u e a s t h e s t a r t o f t h e G E M D O S T r a n s i e n t P r o g r a m
A r e a ( T P A ) .
1 0 7 8 - 1 0 8 1
A p o i n t e r t o t h e h i g h e s t a v a i la b l e m e m o r y l o c a t i o n . T h e B I O S G e t m p b ( )
f u n c ti o n u s e s t h i s v a l u e a s t h e e n d o f t h e G E M D O S T r a n s i e n t P r o g r a m
A r e a ( T P A ) .
1 0 8 2 - 1 0 8 5
If th is l o c a t i o n c o n t a i n s t h e m a g i c n u m b e r $ 2 3 7 6 9 8 A A , a n d t h e m a g i c
n u m b e r in m e m v a l i d ( 1 0 5 6 , $ 4 2 0 ) is a l s o c o r r e c t , t h e n t h e c o l d s t a r t w a s
s u c c e s s f u l , a n d t h e m e m o r y c o n f i g u r a t i o n in m e m c n t l r ( b e lo w ) is c o r r e c t .
1 0 8 6 - 1 0 8 7
F l o p p y lo c k v a r ia b le . I f it c o n t a i n s a v a l u e o t h e r t h a n z e r o , t h e v e r t i c a l
b l a n k d i s k r o u t i n e is d i s a b l e d , w h i c h g u a r a n t e e s t h a t it d o e s n 't t o u c h t h e
D M A c h i p r e g i s t e r s . T h is v a r i a b l e m u s t b e n o n z e r o w h e n t h e D M A b u s is
b e i n g u s e d .
1 0 8 8 - 1 0 8 9
B its 0 a n d 1 o f th is w o r d c o n t a i n t h e d e f a u l t s e e k r a t e ( t h e ti m e it t a k e s f o r
t h e h e a d to m o v e t o t h e n e x t tr a c k ) f o r b o t h f l o p p y d r i v e s :
Value in
Bits 0 and 1 Seek Rate (in Milliseconds)
0 6
1 12
2 2
3 3 (d e f a u l t )
1 0 9 0 - 1 0 9 1
T h e t i m e b e t w e e n s y s t e m t i m e r tic k s in m il l i s e c o n d s . F o r c u r r e n t S T s , th is
v a l u e is 2 0 m i l l i s e c o n d s , w h i c h c o r r e s p o n d s to 5 0 t i m e r u p d a t e s p e r s e c ­
394
APPENDIX K
__membot
__memtop
memval2
flock
seekrate
__timr_ms
( $ 4 3 2 - $ 4 3 5 )
( $ 4 3 6 - $ 4 3 9 )
( $ 4 3 A - $ 4 3 D )
( $ 4 3 E - $ 4 3 F )
( $ 4 4 0 - $ 4 4 1 )
( $ 4 4 2 - $ 4 4 3 )