Spectravideo MKI, Сервисное – Техническое руководство

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R e g i s t e r S e l ec t ( RS )
Re a d /W r i t e
( R/W )
CRT CONTROL
The RS
l i n e is a h ig h L m p
e
n
d a nc
e
TTL/MOS
compa t i b l e
i n p u t wh i c h s e l ec t s
e i t he r t h e
Add re s s Re g i s t e r ( RS
=
"0" ) o r o n e o f the
Da t a R e g i s t e r s
( RS
=
" 1 " )
o f
the i n t e r n a l
Re
g
i s
t
e r
F i
l
e
.
The R/W
l i ne i s a h i gh impe d a n c e TTL /MOS
compa t i b l e inp u t
1-1h i c h
d e t e rm i ne s whe t h e r
t h e i n t e r n a l
Re g i s t e r
F i l e g e t s w r i t r e n nr
re
a d
.
A
wr i t e
i s
ac t i ve l ow
( "0" ) .
The C RTC p rov i d e s ho r i z on t a l s ync ( HS ) ,
v
e r
t i
c a
l
s y nc
( VS ) ,
a n d D i sp l a y c · d
E n a b l e s i g na l s .
Ve r t i c a l s ync
( V
SYN C )
H o r i z on t a l S y nc
( H
SYN C )
D i s p l a y Ena b l e
Th i s TT L compa t i b l e ou t p u t i s a n ac r i ve
h i gh
s i g n a l 1-1h i c h d r i ve s a r e mo n i t o r
d i r e c t l y o r 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 . T h i s
s i gna l d e t e rm i n e s the ve r t i c a l p o s i t i
o n
n f
t he d i s p l a y e d t e x t .
Th i s TTL
c
o
m
p
a
t
i
b
l e
o u t p u t i s an ac t i v e
h i gh
s i g n a l
w
h i
c h
d r i v e s t h e mon i t o r
d i re c t l y o r
i s f e d to V i d e o
P roc e s s i n g
Lo
g i c f o r c omp o s i t e
g e n e r a t i on . Th i s
s i
g n
a
l d e t e rm i n e s t he
h
o
r
i
z
on t a l p o s i t i o n
o f
t he d i s p l a y e d
t ex t .
Th i s TT L compa t i b l e ou t p u t i s an ac t iv e
h i gh s i g n a l wh i c h i n d i c a t e s the CRTC i s
p rov i d i ng a
d d re s s i n g i n the a c t i ve D i sp l a y
A rea .
REFRESH MEMORY/ CHARACTER GENERATOR
ADDRESSING
The CRTC p rov i d e s Nemory Add r e s s e s
( HAO-�!A l 3 )
t o s
c
a
n t h e
Re f r e sh RAN . A l so
p ro v i d e d a r e Ra s t e r Add re s s e s
( RAO-RA4 )
f o
r
the
c h a ra c t e r
RON .
Re f re sh
Memory A dd r e s s e s
( 1!AO-MA 1 3 )
Ra s t e r A dd re s s e s
( RA0-RA4 )
The s e
1 4 o
• I
l
p u t s a r e u s e d
t o re f re s h t h e
CRT s c r e en w i th
p a g e s
o f d a t a l oc a t e d
w i t h i n a
1 6K
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 TTL load and 3 0p F .
A
h igh l eve l on NAO-HA 1 3 i s a lo g i c a l " 1 " .
T h e s e 5 o u t p u t s f rom the i n t e r na l R a s t e r
Coun t e r a dd re s s the Cha r a c t e r
ROM
f o r
th�
row of a c h a r a c t e r . T h e s e ou tpu t s d r i ve
a TTL l o a d and 3 0 p F . A h igh l eve l ( on
RAO-RA4 ) i s a l o g i c a l " 1 " .
4 . 75