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Hitachi MP-1802 Technical Manual page 48

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7 - 7
F D C W r i t e
C o m p e n s a t e C i r c u i t
( U p - 1 B 0 2 )
T h e F D C w r i t e
c o m p e n s a t e
c i r c u i t
i s
d i a g r a m e d
i n
F i g , 7 - 2 3
F o r a n e x p l a n a t i o n
o f
t h e
F D C ( n f o p p y D i s k
C o n t r o l - 1 e r )
M B -
8 8 6 6 ( r c 6 t a )
r e f e r
t o
t h e
M P - 3 6 3 0 / t l p - 1 B 0 6
S e r v i c e
M a n u a ] .
( W t r e n w r i t i n g
d a t a
w i t h
t h e
d o u b l e
d e n s i t y
r e c o r d . i n g
m e t h o d
( U p ' U r e c o r d i n g
) , t h e
w r i t e
c o n p e n s a t e d
d a t a
i s
w r i t t e n
b y
t h e
w r i t e
c o m p e n s a t e
c i r c u j - t .
H o w e v e r ,
w h e n t h e
s i n g l e
d e n s i t y
r e c o r d i n g
m e t h o d
( p t ' t r e c o r d i n g )
: - " u s e d ,
f f f f i - f D
o u t p u t f r o m I C 6 2 6 ( O p i n ,
a n d w h i c h i s n o t w r i t e
c o m p e n s a t e d ,
i s
w r i t t e n .
)
I C 6 2 8
d i v i d e s
t h e
l 6 t q C L K a n d g e n e r a t e s
/ + N I H z , l l l H z c l - o c k
s i g n a l s
( S e e F i g .
7 . 2 / o T i m e C h a r t . )
T h e w r i t e
c o m p e n s a t i o n
c i r c u i t
e o n s i s t s
o f
l C 6 1 / + , l C 6 1 g a n d
I C 6 2 1 .
W i t h
d o u b l e
d e n s i t y
r e c o r d i n g
( U n ' U r e c o r d i n g )
r " i t i n g ,
t o
r e d u c e
t h e
p e a k
s h i f t ,
t h e
t i m i r g
o f
t h e
p i n
o u t p u t
l d D
( W r i t e
D a t a )
i s
s h i f t e d
f a s t e r
o r
s l _ o w e r i n
a c c o r d a n c e
w i t h
t h e F D C ( r c 6 i e ) O p i n o u t p u t ( n a n r , v ) a n d G p i n o u t p u t ( l a t n ) .
T h e W R I T E D A T A s i g n a l
i s
c o m p e n s a t e d b y t h e w r i t e
c o m p e n s a t e
c i r c u i t
i n t h i s w a v .
( F i g . 7 . 2 5 s h o w s t h e t i m e c h a r t . )
7 - 8
M . o d e S e t e c t o r
( M p - 1 8 0 2 )
T h e m o d e s e l - e c t o r i s
s h o w n i n F i g . 7 - 2 6 .
w h e n r c 6 1 5 i s
a d d r e s s e d a s $ r n o 4 , , t h e d a t a i s
l a t c h e d
a t
t h e w r i t e
c y c l e .
( f n i s
d a t a i s
c l e a r e d
w h e n f f i
= r r ; r r , )
W h e n I C 6 2 5 i s
a d d r e s s e d a s $ f n O 4 , t h e d a t a i s
o u t p u t
a t
t h e w r i t e
c y c l e .
( D m a n d T E ' O a r e o u t p u t
a t D 7 a n d D 0
r e s p e c t i v e l y .
I C 6 2 7 m a s k s t h e N M T ( T m )
s i g n a l w h e n N M I M A S K = n H n ,
R 6 2 1
R 6 2 2 , C 6 3 l r a r e R C f i l t e r s
w h i c h r e m o v e n o i - s e f r o m o u t s i d e .
, . , / / 1 6

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