Spectravideo MKI, Service – Technical Manual

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9- 24
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SVI-318/SVI-328
a
n
d hark
II EXPANDER BUS SIGNAL DESCRITPION
*
NAME :
CNTR L 2
+12V
-12V
CNTRLl
WA IT
RST
CPUCLK
A15-AO
RFSH
I/0 :
0
I
0
0
I
I
I
0
0
DESC RI PTION :
+ 5V powe r supp l y . 300mA current i s av a i lab l e for
a l l pe r iphe ral cards.
Spec t rav i deo game adaptor fo r co l e co gam es CONTROL
s i gna l ( norma l l y he ld HIGH by a 3 . 3K ohm re s i s tor ) ,
Th i s s i gna l , when t h e game adap t o r i s i n use ,
con t ro l s the da ta tran s f e r be twe en the
CPU
and the
adap t o r du ring
the
ex t e r na l I / O a d d re s sing .
+1 2V power supp ly . Max imum current i s lOOmA for
a l l p e r iphe ral card s .
-1 2V power s upp ly . Maximum current
i s
SOmA for a l l
pe r i phe ra l cards .
Spec t rav ideo game a dapto r for co leco game s
CONTROL s i gna l ( norma l ly held HIGH by lK ohm
re s i s t or ) .
This
s i gna l , wh en pu l l e d LOW ( i. e .
Wh en t he adaptor i s i n u se ) , d i sab l e s a l l inte rna l
( i . e . SVI-3 1 8 / SVI-3 2 8 and M a rk II ) I /0 addre s s
decod ing , and inv e r s es A1 5 .
Ind i c a t e s to Z80A
CPU
tha t the addre s se d memo ry
or I / O dev ices a re no t ready for da ta t rans f e r .
Whe n th i s s igna l i s pu l l e d LOW the CPU beg ins a
RESET cyc l e.
Du r ing t h i s RESET c yc l e, the address
and data bus ent e r a high impendance s t a te and the
con t r o l s igna l s e n t e r th e i nac t ive s t a te .
Bu f f ered s y s tem c lock of f requency 3 .58MHz .
Bu f f e re d ADDRESS BU S . Th is i s a 1 6-b i t a dd res s
bus
p rov i d ing addre s ses for memory data exc hange
and
I / 0 dev ice da ta exchange .
Buf f e r e d REFRESH s i gna l for the dynam ic RAM
expand e rs on ly .
This
s i gna l indic a t es that the
lower
7
b i t s of the add res s bus con t a i n a refresh
a dd re s s for the dynam ic RAM.
2.5