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2-2-1-3.
Write c i r c u i t
The w r i t e c i r c u i t c o n s i s t s o f w r i t e c o n t r o l l o g i c , w r i t e c u r r e n t s o u r c e ,
w r i t e d r i v e r , e r a s e d r i v e r , c o m n d r i v e r , and e t c .
Most
of
t h e
c i r c u i t s a r e enclosed i n t h e read w r i t e
LSI,
U 2 .
Common d r i v e r o u t p u t t e r m i n a l s , COMO and COMl a r e connected t o t h e
c o m n t e r m i n a l s
( c e n t e r t a p s ) of t h e s i d e 0 and s i d e 1 heads,
r e s p e c t i v e l y .
The o u t p u t s of t h e common d r i v e r a r e c o n t r o l l e d by t h e
SIDE ONE SELECT
(z),
w r i t e g a t e
( W C ) ,
and e r a s e g a t e
( E G )
s i g n a l s
s u p p l i e d through t h e w r i t e c o n t r o l l o g i c .
When t h e
COMO
o r
t h e
COMl
i s H I G H l e v e l
(11.5V,
a p p r o x . ) , t h e power t o t h e read c i r c u i t i s c u t
o f f i n t h e r e a d
write
LSI t o i n h i b i t t h e r e a d o p e r a t i o n .
I
Input s i g n a l s
Output v o l t a g e ( a p p r o x . )
FDD o p e r a t i o n
COMO
COMl
S I D E 0 read o p e r a t i o n
2 . 7 V
ov
SIDE 0 w r i t e o p e r a t i o n
11.5v
ov
SIDE 0 w r i t e o p e r a t i o n
I
11.5V
I
ov
SIDE 1 r e a d o p e r a t i o n
I
ov
I
2.7v
SIDE
1
w r i t e o p e r a t i o n
ov
11.5V
SIDE 1 w r i t e o p e r a t i o n
ov
11.5v
(Table 2 0 2 ) Comon d r i v e r o u t p u t
The EG s i g n a l s u p p l i e d from t h e e r a s e t i m e r i n t h e c o n t r o l c i r c u i t
changes t o H I G H
o r
LOW l e v e l with an a p p r o p r i a t e
t i m e
d e l a y a g a i n s t t h e
WG s i g n a l ( r e f e r t o F i g . 2 0 5 ) .
Since t h e e r a s e gaps l o c a t e about 0.85mm
(B
and F models) o r
0.585mm
( G model) backward from t h e r e a d / w r i t e gap,
i t
i s
necessary f o r t h e e r a s e d r i v e r t o d e l a y t h e WG s i g n a l
so
t h a t
t h e w r i t t e n d a t a
i s
completely trimmed by t h e e r a s e head ( t u n n e l e r a s e ) .
The t u n n e l e r a s e produces a guard band between t h e t r a c k s p r e v e n t i n g
d e t e r i o r a t i o n o f t h e S/N r a t i o r e s u l t i n g from a o f f - t r a c k
( p o s i t i o n i n g
e r r o r ) .
It
a l s o e n s u r e s d i s k i n t e r c h a n g e a b i l i t y .
The WRITE D A T A i n p u t p u l s e
i s
l a t c h e d by t h e w r i t e d a t a l a t c h i n t h e
-
213
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