3. sub cpu and i/o port, Mz3500 – Sharp MZ-3500 User Manual
Page 15
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3-3. Sub CPU and I/O port
MZ3500
AS6
Y7
ASS
___2.
B
Y6
SUB
AS4 1
YS
CPU
AS7
“c
4G
G2A
Y4
Y3
3—
G2B
Y2
¥T
6
G1
Y1
YO
74LSI38
S07
S06
10 SOS
.11
S04
■ 12 S03
.15
S02
15 SOO
-►
gdc
-
i
Graphic option
-►cSP-1 .CSP-2
14 SOI
-►8251-CS
MAINCPU-INT
Shown
at the left is the circuit used by
the CPU to select the I/O ports The out
put address from the sub CPU is decoded
by the 74LS138to create the select signal.
Shown
below
Is
the
address
map
and
select signals.
->
Input
port
select
(LS244)
-►8255-‘cT
-►8253-CS
- 18 -
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