Spectravideo SVI 318 Service – Technical Manual page 108

R e g i s t e r S e l ec t ( RS )
( R / W )
Re a d / W r i t e
CRT CONTROL
The C RTC p ro v i d e s h o r i z on t a l s ync ( HS ) ,
E n a b l e s i g n a l s .
( V
Ve r t i c a l s ync
( H
H o r i z on t a l S y nc
D i s p l a y E na b l e
REFRESH MEMORY/ CHARACTER GENERATOR
The CRTC p ro v i d e s N e m o r y A d d r e s s e s
p ro v i d e d a r e Ra s t e r Add re s s e s
Memory A dd r e s s e s
Re f r e sh
( 1 !AO-MA 1 3 )
Ra s t e r A dd re s s e s
SYN C )
SYN C )
( RAO-RA4 )
( RA0-RA4 )
4 . 7 5
The RS l i n e is a h i g h
compa t i b l e
i n p u t
Add re s s R e g i s t e r ( R S
e r
( R S
F i
D a t a R e g i s t e r s
Re i s l .
g t e
The R/W
l i n e i s a h i g h
compa t i b l e i np u t
Re g i s t e r
t h e i n t e r n a l
re A i s
a d w r i t e
.
e r
v
t i l
c a s y nc
T h i s TT L
c o m pa t i b l e o u t p u t
h i gh
s i g n a l 1-1h i c h d r i v e s a r e mo n i t o r
d i e t l o r
r c y i s f e d t o V i d e o P r o c e s s i ng
Log i c
f o r c omp o s i t e g e n e ra t i on .
s i gna l
d e t e rm i n e s t h e ve r t i c a l p
t he
d i s p l a y e d t e x t .
w
Th i s TT L o p t
c m a i
h i gh s i g n a l h i c h
d i re c t l y o r
i s f e d t o V i d e o
Lo
g i c f o r c om p o s i t e
s i a
g n l d e t e rm i n e s
o f
t he d i s p l a y e d
Th i s TT L compa t i b l e ou t p u t i s an ac t i v e
h i gh s i g n a l wh i c h i n d i c a t e s t he CRTC i s
p rov i d i n g a d re
d s
A r e a .
ADDRESS ING
( HAO-�!A l 3 )
t o s a
c
f o t h e
r c h a r a c t e r
• I
l
1 4 o
The s e p u t s a r e u s e d
CRT s c r e en w i th
1 6K
w i t h i n a
b l o c k o f re f re s h memo r y .
T he s e o u t p u t s d r i ve a TT L l o a d and 3 0p F .
A
h i g h l eve l on NAO -HA 1 3 i s a l o
5 o u t p u t s f rom t h e i n t e r na l R a s t e r
T h e s e
Cou n t e r a dd re s s t h e Cha r a c t e r
row o f a c h a r a c t e r .
a TTL l o a d a n d 3 0 p F .
RAO-RA4 ) i s a l o g i c a l " 1 " .
e
L p
w h i c h
m n d a nc e
e i t h e r t h e
s e l ec t s
" 0 " ) o r o n e o f t h e
=
" 1 " )
o f the i n t e r n a l
=
1-1h i c h
impe d a n c e TTL /MOS
d e t e rm i n e s whe t h e r
a c t i ve
t s
F i l e g e w
( "0 " ) .
l ow
( VS ) ,
a n d D i s p l a y c · d
i s a n
o
b o u t p u t i s an ac t i v e
l e
d r i v e s t h e mon i t o r
P roc e s s i n g
r z
g e n e r a t i on .
h on t a l p o s i t i o n
t he o i
t e x t .
s i g
the a c t i ve D i sp l a y
n i n
Re f r e s h RAN .
n t h e
RON .
t o re f re s h t h e
o f d a t a l oc a t e d
p a g e s
g
ROM
T h e s e ou t p u t s d r i ve
A h i g h l eve l ( o n
TTL /MOS
i t r n r
r n
e
i ve
a c r
o n
i t n f
T h i s
i
s
Th i s
A l s o
" 1 " .
i
c a l
f o r t h �