Spectravideo SVI 318 Service – Technical Manual page 11

PIN: NAME:
2 6 EXCSR
2 7
M l
28
EXCSW
29 W R
30 M REQ
31
IORQ
3 2
33-40 DO-D 7
4 1
CSOUND
4 2
INT
43
RAM DIS
4 4
ROMDIS
I/0:
Th i s is the ex te rn a l CPU - f rom-VDP READ se l ec t
I
s ignal , an d i s use d b y S pec t ravideo g ame adaptor
for cole c oyM games.
B uf fe re d MACHINE ONE CY CLE s i gna l .
0
in d i ca te s th a t O P co de fe tc h cyc l e is the c u rren t
mac h ine cy cle .
I Th i s i s the ex te rnal CPU- t oVDP WRITE se lect s i gnal ,
and i s u se d by S pe c t rav ideo game adap tor for
colec o
0 B uf fe re d WRITE s ignal .
the CPU da ta b us h ol d s val id d a ta for s t orage in
the a dd re s se d memory or I/0 devic e .
0 B u f fe r e d MEMORY REQU EST s ign a l .
in d i ca tes when t he a dd re s s b us is ho l d ing a va li d
memory a dd re s s .
0 B uf fe re d INPUT/OUTPUT REQUEST s igna l .
in d i ca te s the l owe r 8 b i t s o f the addre ss b us are
h ol d in g a val i d I/0 device addre s s , an d is a t h igh
s ta te ( i . e . in act i ve) du r in g the INTERRUPT cy c l e .
0 B u f fe re d READ s i gna l .
the Z80A CPU is wan t in g to rea d da ta f rom memory
or an I/0 device .
B u f fe re d b i d i re c t i onal DATA b us .
b id i re c t i ona l da t a b us for data exc hange betwe en
memory an d I/0 de v i ce s .
I
Aud i o in put s ignal f rom the S pec t ra v i deo game
a da p t or for c ole co
I
Gen e ra te d by I/0 dev i ce s to req ue s t in te r rupt to
Z80A CPU .
i
P ull ing th i s s ignal LOW d i s able s the SVI-3 1 8/
SVI-328 an d Mark II u se r
h igh by a 1K ohm re s i s t o r to + 5V .
I
Pull ing th i s s ignal LOW d i sable s the SVI-3 18/
SVI-328 an d Ma rk II BASIC ROM on b oa r d .
2.6
game s only .
Th i s s igna l in d ic a te s that
Th i s s igna l in dic a te s tha t
game s .
RAM
This s ign a l
This s i gnal
This s ign a l
T h i s is an 8 b it
.
Th i s l ine i s he l d