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APPLICATION EXAMPLES
1/0
Expansion Techniques
The
following
are several examples
of
how
the basic
1/0
capability
of
the
MCS-48™
microcomputers can be easily expanded
externally using either the 8243
1/0
expander device
or
standard
logic
circuits.
These techniques can be used whenever
the combination
memoryllO
expanders
illustrated on the preceeding pages are
not
required.
+5V
GND
b~
20
Vee
VDD
Vss
2
---.r::--
XTAL 1
~
3
1
• XTAL 2
f----!
RESET
EA
8049
8048
-=
5
8748
Ne-
ss
8035
8039
1
{-
TO
39
INPUT
~
Tl
INT
ALE
PSEN
PROG
WR
1m
9
ADDING
AN
1/0 EXPANDER
Pl0
Pll
P12
P13
P14
P15
P16
P17
P20
P21
P22
P23
P24
P25
P26
P27
DBO
DBl
DB2
DB3
DB4
DBS
DB6
DB7
27
)
,m
28
29
30
31
32
33
34
+5V GND
8243
I/O
EXPANDER
P40 2
P41
3
P42 4
P43 5
~50
1
P51
23
P52 22
P53
21
P60 20
E
_____
--:'1'::1
1
P20
P61
19
E
_____
--'l~O
P21
P62
18
21
22
23
j.!;::
______
,9
P22 P63
17
~
______
=t8
P23
13
7 P70
14
r---I
PROG
P71
-
P72
15
~~C_S
_________________
P_7_3
16
-=
24
35
36
37
38
12
13
1/0
14
15
16
17
18
19
5-11
110