Rd/Index G A T E - Tandy 1000 SL Technical Reference Manual

2-2-2-3.
RD/INDEX g a t e
READ D A T A
(G)
a n d I N D E X
(E)
p u l s e s a r e o u t p u t
to
t h e h o s t c o n t r o l l e r
t h r o u g h t h e RD/INDEX g a t e which i s e n c l o s e d i n t h e c o n t r o l LSI,
U1.
RD/INDEX g a t e c h a n g e s i t s f u n c t l o n a c c o r d i n g t o t h e M K E N i n p u t l e v e l .
I n t h i s FDD, t h e M K E N t e r m i n a l i s f i x e d t o LOW l e v e l a n d t h e g a t e
f u n c t i o n s
a s
f o l l o w s .
The
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Notes RDO: N e g a t i v e READ D A T A p u l s e o u t p u t t o t h e h o s t c o n t r o l l e r .
-
R D I : N e g a t i v e RD i n p u t from t h e r e a d i w r i t e LSI.
RDYO: RDYO o u t p u t s i g n a l LOW. FDD i s i n r e a d y s t a t e .
DSEL: DRIVE SELECT i n p u t s i g n a l LOW.
IDXO: N e g a t i v e INDEX p u l s e o u t p u t t o t h e h o s t c o n t r o l l e r .
IDXS: N e g a t i v e p u l s e i n p u t from t h e i n d e x s e n s o r .
- -
-
-
-
A l l
t h e INDEX ( = ) o u t p u t p u l s e s a r e v a l i d even i f t h e f i r s t o n e by
means o f i n d e x l a t c h
c i r c u i t
i n t h e LSI i n s p i t e o f t h e D R I V E SELECT
i n p u t t i m i n g . F o r example, i f t h e FDD i s s e l e c t e d i n t h e m i d s t o f a n
IDXS ( i n d e x s e n s o r o u t p u t ) p u l s e , t h e p u l s e w i l l n o t b e o u t p u t t o t h e
h o s t c o n t r o l l e r .
d i s k .
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The p u l s e w i l l b e o u t p u t a f t e r o n e r e v o l u t i o n o f a
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242
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