Other P Ins - Spectravideo SVI 318 Service – Technical Manual

OTHER P INS

Cu r s o r
C l o c k ( CLK)
L i g h t P e n S t robe ( LPSTR )
.Yc..c. •
G
RES
Th i s TTL compa t i b l e ou t p u t i n d i c a t e s C u r so r
D i sp l a y t o e x t e r n a l V i d eo P ro c e s s i n g Log i c .
Ac t i v e h i gh s i g na l .
The TT L / MOS compa t i b l e inp u t i s u s e d to
CLK
s ync h r o n i z e a l l
e x t e rna l d o t co u n t e r is u s e d t o de r i ve t h i s
s i gna l wh i c h i s us u a l l y the c h a r a c t e r ra t �
in an a l p hanume r i c
s i t i o n i s h igh t o
T h i s h i gh i m p endan ce TTL /M OS compa t i b l e
inp u t la t c he s the cu rre n t Re f r e s h Add r e s s e s
i n the Reg i s t e r F i l e .
low t o h i gh edg e and i s s yn c h r o n i z e d
i n t e rna l l y t o cha r a c t e r c l ock
T he RES i np u t i s u s e d to R e s e t the CRTC .
An in p u t l o w l eve l on RES fo r c e s CRTC i n t o
fo l low ing s t a t u s :
( A ) A l l the count e r s in CRTC a r e c l ea r e d
a n d t he d e v i ce s t o p s t he d i s p l a y
op e r a t i on .
( B ) A l l the ou t p u t s go down to low l eve l .
( C ) Co n t r o l reg i s t e r s in CRTC a re no t
a f f ec t e d and rema i n unchange d .
Th i s s i g n a l i s d i f f e r ent f rom o t he r
f am i l y in the fo l l ow i ng func t ions :
( A) RES s i gna l has ca
func t i on o n l y when LPSTB i s a t l ow
l eve l .
( B ) A f t e r RES h a s gone down t o l ow l eve l ,
output s i g na l s o f
RA4 , s ynchron i z i n g w i t h CLK low l eve l ,
goes down to l ow l e ve l .
cy c l e CLK s i gna l is ne c e s sary for
r e s e t . )
4 . 76
co n t ro l s i gna l s .
CRT
The a c t i v e t ran­
CRT .
�
ow .
L a t c h ing i s o n the
•
p
a b i l i t y of re s e t
HAO-MA1 3
and RAO­
( At l e as t
An
6800
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