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2-2-2-6.
Ready d e t e c t o r
Ready d e t e c t o r c o n s i s t s
of
80% s p e e d d e t e c t o r , i n t e r n a l r e a d y l a t c h , XON
d e l a y c i r c u i t which a r e e n c l o s e d i n t h e c o n t r o l LSI,
U1.
I n t h e b l o c k
d i a g r a m , t h e s e c i r c u i t s a r e shown
a s
o n e b l o c k o f r e a d y d e t e c t o r .
The
iclC
s i g n a l f o r c o n t r o l l i n g t h e s p i n d l e motor
i s
i n p u t t o t h e r e a d y
d e t e c t o r which e n a b l e s t h e o p e r a t i o n o f a l l t h e above t h r e e c i r c u i t s .
As t h e motor s p e e d i n c r e a s e d , t h e
8 0 %
s p e e d d e t e c t o r o p e r a t e s f i r s t , a n d
t n e n i n t e r n a l r e a d y l a t c h i s set when t h e i n d e x
(3)
p u l s e i n t e r v a l
becomes
l e s s
t h a n 250msec, a p p r o x .
( 1 . e . d i s k s p e e d r e a c h e s more t h a n
80%
of 300rpm).
On t h e o t h e r hand, t h e
MON
d e l a y c i r c u i t g e n e r a t e s
MON
d e l a y 1 s i g n a l
( 4 4 3
'L
461msec d e l a y ) a f t e r t h e l e v e l change
o f
t h e MC s i g n a l t o TRUE
( H I G H ) .
When t h e o u t p u t s of t h e MON d e l a y 1 a n d t h e i n t e r n a l r e a d y
l a t c h
a r e
c o i n c i d e n t w i t h e a c h o t h e r , FDD g o e s t o t h e p r e - r e a d y
s t a t e
and t h e n i t r e a c h e s t o t h e r e a d y s t a t e a f t e r f u r t h e r 49
5lmsec d e l a y
(MON
d e l a y 2 ) .
The sum o f t h e d e l a y t i m e
1 s
492
%
512ms.
I f
DSEL
i n p u t s i g n a l
i s
TRUE a f t e r t h e FDD r e a c h e s t o t h e r e a d y s t a t e ,
t h e
E
s i g n a l (which i n d i c a t e s t h a t t h e FDD
i s
i n r e a d / w r i t e r e a d y
s t a t e )
is
o u t p u t from t h e FDD.
F i g . 2 1 0 shows t h e t i m i n g c h a r t of t h e
r e a d y d e t e c t o r .
The
3
s i g n a l g o e s t o TRUE
(LOW)
i n t h e f o l l o w i n g
c o n d i t i o n .
=(L)
=
iMC(H)
*
80% s p e e d
*
MON d e l a y
11
*
MON d e l a y 2
*
E ( L )
I
1
I
P r e - r e a d y
-
Notes
RDYO: Ready
a t LOW.
MC:
Motor r o t a t e s a t HIGH.
80% s p e e d : Disk r o t a t i o n a l s p e e d
i s more
t h a n
80%,
a p p r o x .
of
300rpm.
MON d e l a y 1: I n t e r n a l s i g n a l o f
LSI.
443
461ms a f t e r a n i n p u t
of motor-on
command.
-
234
-
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