Spectravideo MKI, Сервисное – Техническое руководство

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SVI-3 1 8 / SVI-3 28 AND MARK I I RAM/ROM DESCRIPTION
T he S V I - 3 1 8 / S V I - 3 2 8 and �la r k I I ba s i c un i t ha s 3 2 K ( S OK ) * b y t e s o f Random
Acce s s t·1 emo r y ( RAl-1) d i v i d e d i n t o two group .
You r i n s t r uc t i o n s or p ro g r amme to
comma n d the compu t e r i s s t o r e d in
1 6K
( 64K ) '"' o f RAM . Ano t h e r
1 6K
is s t r i c t l y
f or
u se b y t he V D P t o s t o re d i s p l a y i n f o rma t i on ( c a l l e d VRM-1 ) .
The me m o r y i s comp r i s e d
o f
e i gh t
4 1 1 6
( 4 1 6 4 ) * dy nam ic memo r y c h i p s . The c h i p s
a r e re f re sh e d ev e r y M l c y c l e . RAM ch ip enab l e by t h e RAM b l ock s e l ec t o r s .
The y go h i gh t o e n a b l e
a
b l o ck o f RAM ( 8 RAI'l ' s pe r b lo c k ) o r du r ing a
REFCLK
c y c l e t o re f re sh the RM1 ' s . Each
RAM
ch i p e n a b l e s i gna l goe s to the c h ip
e n a b l e i n p u t f o r t he r e s p e c t i ve b l ock o f RAM ' s .
RMl w r i t e f rom the R / W -
0
and MPX s i gna l . Whe n low the RAM ' s w i l l acc e p t d a t a
f rom t he b u s - t he RM1 ' s a re r ea d ing t he b u s ( R / W
=
0
i s h i gh , r e a d ) . When
h i gh the RAM ' s w i l l o u t p u t d a t a t o t h e b u s - t h e RAI-l ' s a re w r i t i n g t o t h e bus
( R / W
-
0
is l o w , w r i t e ) .
ROM
Th i s memo r y i s comp r i s e d o f two
1 6K
x
8 ma s k e d
ROM
c h ip s . I t con t a i n s t h e
BAS I C i n t e rp re t e r p ro g r amme as w e l l a s t he mon i t or prog ramme .
For
t h e SVI-3 18 / S V I -3 2 8 and M a r k I I
FCC
samp l e and e a r l y p ro duc t ion samp l e s ,
t he s e two
ROH
c h i p s w i l l be r e p l ace d b y f ou r 8K
x
8
EPROMS
c h i p s and a n
a dd i t i ona l sma l l
PCB
ca r ry ing t h e s e fou r c h i p s w i l l be u s e d t o p l ug int o the
o r i g i n a l
ROM
s ock e t .
ROM bank co n t ro l b y the Bank S w i t c h Add re s s Dec o d e r in the backpack . I t
e n a b l e s t he 3 2 K ROM B ank on t he CPU b o a r d ,
ROM
1 t h rough
ROM
8 . W i th no
b a c k p a c k on
ROM 1
t h ro ugh ROM 8 a r e a lw a y s e n a b l e d .
*
S V I - 3 2 8
4 .45