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Co Nt Ro L S Y S T E M; C O M M A N D E X E C U T I O N - Siemens 100-8D Technical Manual

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C ON TRO L S Y S T E M
T h e c o n t r o l s y s t e m p r o v i d e s the i n t e r f a c e c i r c u i t r y b e t w e e n the d i s k c o n t r o l l e r and
the d i s k d r i v e .
T h e o p e r a t i o n a l s t a t u s Is m o n i t o r e d and r e p o r t e d to the d i s k c o n ­
t r o l l e r .
T h e d i s k c o n t r o l l e r a d d r e s s e s a d i s k d r i v e f o r o n - l i n e o p e r a t i o n by a c t i ­
vating a unique s e l e c t li ne .
s e l e c t e d d i s k d r i v e .
m o n i n t e r f a c e l i n e s , w h i le r e m a i n i n g i n d iv i d u a l ly s e l e c t a b l e .

C o m m a n d E x e c u t i o n

C o m m a n d s a r e r e c e i v e d by the d i s k d r i v e in the f o r m of a l o w - l e v e l i n t e r f a c e
s i g n a l w h i c h d e s i g n a t e s one of the f o l l o w i n g o p e r a t i o n s :
S E L E C T
w CTt?n
O X llj J T
S T E P IN
HEAD LOA D
(HDLD)
WR ITE
(WRT)
W R IT E DATA
(WRT DATA )
S E L E C T and H D L D c o m m a n d s m u s t p r e c e d e a re ad o r w r i t e o p e r a t i o n .
e n a b l e s a ll Input/output g a t e s , w h i l e HDLD p o s i t i o n s the r e a d / w r i t e head f o r w r i t ­
ing o r re a d i n g on the f lop py disk .
S T E P m o v e s the r e a d / w r i t e head to e i t h e r a h ig h e r o r l o w e r t r a c k p o s i t i o n d e p e n d ­
ing on the S T E P IN li n e .
t r o l l e r m a i n t a i n s c u r r e n t t r a c k p o s i t i o n and g e n e r a t e s the n u m b e r of p u l s e s n e c e s ­
s a r y to a c h i e v e a n e w t r a c k p o s it io n .
a re ad o r w r i t e o p e r a t i o n
In a W r i t e o p e r a t i o n , the d i s k d r i v e r e c o r d s the data in the s a m e e n c o d i n g m e t h o d
p r e s e n t e d by the d i s k c o n t r o l l e r .
C o m m a n d s a r e then r e c e i v e d and e x e c u t e d by the
T h is t e c h n i q u e a l l o w s m u l t i p l e d i s k d r i v e units to s h a r e c o m ­
P l a c e s d i s k d r i v e o n - l i n e with c o n t r o l l e r
E n a b l e s r e a d / w r i t e head p o s i t i o n i n g
D e t e r m i n e s r e a d / w r i t e head d i r e c t i o n
P l a c e s d i s k r e c o r d i n g s u r f a c e in c o n t a c t with
r e a d / w r i t e head
E n a b l e s w r i t e c u r r e n t to turn on and Inhibits
re ad output
E n a b l e s w r i t e data t r a n s f e r f r o m c o n t r o l l e r to
d i s k d r i v e
S i n c e r e l a t i v e t r a c k p o s i t i o n i n g is u s e d , the d i s k c o n ­
O n ce p o s i t i o n e d , the d i s k c o n t r o l l e r i n i t i a t e s
3 - 2
S E L E C T

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