PIN:
NAME:
2 6
EXCSR
2 7
M l
28
EXCSW
29
W R
30
MREQ
31
IORQ
32
33-40
DO-D7
41
CSOUND
4 2
INT
43
RAM DIS
44
ROMDIS
I/0:
I
0
I
0
0
0
0
I
I
i
I
Th i s is the ex te rn a l CPU-from-VDP READ se l ect
signal , an d i s use d by S pec t ravideo game adaptor
for colecoyM games.
B uf fere d MACHINE ONE CYCLE s igna l . This s ign a l
in d i ca tes that O P code fe tch cyc l e is the cu rren t
machine cy cle .
Th i s i s the ex te rnal CPU- toVDP WRITE se lect s i gnal ,
and i s use d by Spe c t ravideo game adap tor for
colec o
game s only .
B uf fe re d WRITE s ignal . Th is s igna l in d ic a te s that
the CPU da ta b us h olds val id data for storage in
the a dd re s se d memory or
I/0
device .
B u f fered MEMORY REQUEST s ign a l .
This s i gnal
in d i ca tes when t he a ddre s s b us is ho lding a va li d
memory a dd re s s .
B uf fe re d INPUT/OUTPUT REQUEST s igna l . This s igna l
in d i ca tes the lowe r
8
b i t s of the addre ss b us are
hol din g a val id
I/0
device addre s s , an d is at h igh
s ta te ( i . e . inact i ve) du r ing the INTERRUPT cy c l e .
B u f fe re d READ s i gna l .
Th i s s igna l in dic a te s tha t
the Z80A CPU is wan t ing to read da ta f rom memory
or an
I/0
device .
B u f fe red b id i re c t i onal DATA b us . This is an
8
b it
b id i re c t i ona l data b us for data exc hange between
memory and
I/0
dev i ce s .
Aud io input s ignal f rom the S pec t ravideo game
a da p t or for coleco
game s .
Gen e ra te d by I/0 dev i ce s to req ues t in te rrupt to
Z80A
CPU .
P ull ing th i s s ignal LOW d i s ables the
SVI-3 1 8/
SVI-328
an d Mark
II
u se r
RAM
.
Th is l ine i s he ld
h igh
by
a
1 K
ohm re s i s tor to +5V .
Pull ing th i s s ignal LOW d i sables the
SVI-3 18/
SVI-328
and Ma rk II BASIC ROM on b oa r d .
2.6
Содержание MKI
Страница 1: ...SERVICE TECHNICAL MANUAL VOL 1 l SVI318 328 MKI MKII COMPUTER SYSTEM SVI SPECTRAVIDEO ...
Страница 7: ...4 Remove the seven retaining screens 5 Remove the cover 2 2 ...
Страница 8: ...6 Remove the screens on the metal cover 7 Remove the metal cover 2 3 ...
Страница 9: ...To r e assemble u se the above procedures in the rever se order 2 4 ...
Страница 134: ...5 CIRCUIT SCHEMATIC AND COMPONENT LAYOUT 5 1 ...