Tandy 1000 SL Technical Reference Manual page 312

2-2-2-5. -%tor-on g a t e
The c i r c u i t , r e c e i v i n g a s p i n d l e motor-on c o m a n d from t h e h c s t
c o n t r o l l e r , s u p p l y t h e
MC
(motor c o n t r o l ) s i g n a l t o t h e s p i n d l e motor
s e r v o c i r c u i t . The c i r c u i t c o n s i s t s o f OR-gate, 1 3 3 ~ s d e l a y c i r c u i t
a n d a u t o - t u r n 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.
A
motor-on command i n p u t t o t h e
3
o r
1 3 3 ~ 1 s d e l a y c i r c u i t v i a t h e OR-gate t o be d e l a y e d f o r 1 3 3
n d
2 6 7 ~ s .
The d e l a y c i r c u i t e l i m i n a t e s t h e n o i s e s mixed o n t o t h e i n t e r f a c e l i n e
a n d p r o t e c t s t h e c o n t r o l c i r c u i t from e r r o n e o u s o p e r a t i o n .
The
MC
s i g n a l g o e s t o TRUE i n t h e f o l l o w i n g c o n d i t i o n s .
t e r m i n a l i s s u p p l i e d t o
M C ( H ) = ( s ( L )
+
x ( L ) )
*
1 3 3 ~ s d e l a y
*
DISK(H)
N o t e s MC: Motor r o t a t i o n
a t
H I G H .
-
MONO: M O T O R ON i n p u t s i g n a l LOW.
MON1: DLED
i s low a t
MI,
s t r a p
i s
ON.
( F r o n t b e z e l i n d i c a t o r i s O N ) .
- -
DISK: F i x e d t o TRUE ( H I G H ) .
The a u t o - t u r n c i r c u i t makes t h e s p i n d l e motor r o t a t e a u t o m a t i c a l l y a t
a d i s k i n s e r t i o n t o improve t h e c h u c k i n g a c c u r a c y . The c i r c u i t i s s e t
by a n i n f o r m a t i o n o f d i s k i n s e r t i o n from t h e f i l e p r o t e c t s e n s o r , and
i s
r e s e t
by
a
d e t e c t i o n of r e a d y s t a t e o r by a d e t e c t i o n o f more t h a n
8 . 7 s e c o n d s , p a s s i n g a f t e r t h e i n p u t t e r m i n a l k e e p i n g TRUE (LOW)
.
Even t h o u g h t h e FDD g o e s t o t h e r e a d y
s t a t e
by a command from t h i s
c i r c u i t , t h e o u t p u t s i g n a l i n
i t e m
2-2-2-6 m a i n t a i n s FALSE ( H I G H
l e v e l )
.
-
233
-