Spectravideo MKI, Сервисное – Техническое руководство

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EXTV I D Ex t e rn a l v i d e o i np u t
C P U CLK
N T S C c o l o u r b u r s t f re qu e n c y c l o ck . Typ i ca l l y no t
use d .
I N T
CPU in t e r r up t o u t p u t . The V DP I N T ou t p u t p in i s
used
t o
g en e r a t e a n in t e r r u p t a t t h e e n d o f e a c h a c t i v e ­
d i s p l a y s c an , w h i c h i s a b o u t e v e r y
1/60
s e cond ( co l o u r
b u r s t f re qu e n c y/6 0 ,
1 92 ) .
The INT ou t p u t i s a c t i v e
wh e n t h e i n t e r r up t e n a b l e b i t ( I E ) in V D P r e g i s t e r 1
a ' 1 ' and t he
F
b i t o f t he s t a t us reg i s t er
i s
' 1 ' .
J n t e r r up t s a r e c l e a r e d whe n the s ta t u s reg i s t e r i s
r ea d .
COMV I D N T S C
c o m p o s
i
t
e
v i d e o ou t p u t . T h e compo s i t e v i d e o
ou t p u t s i g n a l f rom t he VDP d r i ve s o n NTSC c o l o u r
mon i t o r . Th i s s i gna l i n c o r p o r a t e s a l l ne c e s s a r y
h o r i z o n t a l
and
ve r t i c a l s y nc h r o n i z a t i on s
s igna l s a s
we l l a s
lum inance
a n d c hr o m i n a nc e
in f o rma t i on . I n
mon i t o r a p p l ic a t i o n s , t he re q u i reme n t s o f t h e
mon i tor
s h o u l d
be s t ud i e d
t o de t e rm in e
i f th
e VDP c a n be
c onnec t e d d i re c t ly t o i t .
In
some c a s e ,
i t may be
ne c e s s a r y
to
p rov i d e a s i mp l e i n t e r f a c e c i r c u i t
t o
ma t c h t
b
e VDP
o u t p u t v o l t a g e s w i th t he mon i to r
s p e c i f i ca t i ons . To d r i v e
a s t andard
TV
tha t
i s n o t
out f i t te d
w i th a c omp o s i te v i d e o
i npu t , the
s i gna l can be
run in t o
the
T V
ant enna te rm ina l s by
us ing an approp r i a t e RF modu l a t or on the VDP outpu t .
T h e
leas t - s ign i f icant a dd re s s
b i
t
, AD7 ,
i s
w i re d t o AO
of the dy nam ic
RAM s .
Likew i s e , A D 6
i s w i re d to
Al
of th e RAM s .
Ca r e
mus t be exe rc i s e d
in a s su r ing p roper or i e n t a t i on o f t he
TMS-99 1 8A
a dd re ss ou tputs t o the
dy nam ic RAM a dd re s s input s .
Wh en d r iven ex t e rna l ly , bo t h inputs must be d r i ven .
4 . 42