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P o r t
2 0 0
-
207 RD
--
J o y s t i c k
Status
The d a t a
r e a d a t p o r t 20X, w h e r e X
= 0
t o
7 ,
w i l l b e t h e o u t p u t s
o f t h e
j o y s t i c k p o s i t i o n
c o m p a r a t o r s
a n d
t h e
s t a t e s
o f
t h e
j o y s t i c k p u s h b u t t o n s ,
i n t h e
same manner
a s t h e
c u r r e n t Tandy
1000 J o y s t i c k c i r c u i t r y .
P l a n a r C o n t r o l
P o r t
6 5
c o n t a i n s t h r e e
b i t s
which a r e u s e d t o e n a b l e t h e p r i n t e r
i n t e r f a c e ( b i t
l ) ,
t h e
p r i n t e r o u t p u t
( b i t
7 ) ,
a n d t h e s e r i a l
p o r t
( b i t
4 ) .
T h e s e b i t s
a r e a l l e n a b l e d ( s e t h i g h ) o n r e s e t ,
and must
be c l e a r e d
by
s o f t w a r e
t o
d i s a b l e
t h e
a p p r o p r i a t e
f u n c t i o n .
The p r i n t e r
o u t p u t e n a b l e f u n c t i o n i s l o g i c a l l y "or-
ed"
w i t h
t h e c u r r e n t
Tandy 1 0 0 0
p r i n t e r o u t p u t
e n a b l e
b i t ,
s o
t h a t e i t h e r o n e w i l l e n a b l e t h e p r i n t e r o u t p u t b u f f e r .
A d d i t i o n a l c o n t r o l
i s a v a i l a b l e
a t p o r t
FFEB.
B i t
DO
s e l e c t s
w h e t h e r t h e
s e r i a l c l o c k
i s d i v i d e d by 1 3 or
1.
B i t D 1
m u s t be
h i g h t o
e n a b l e t h e j o y s t i c k f u n c t i o n , a n d
b i t
D2 must
be
h i g h t o
e n a b l e t h e
sound c h i p f u n c t i o n s .
B i t s D 1
and D2 d e f a u l t t o h i g h
on power up.
11
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