Sonic Alert msm83c154s User Manual

Page of 378
INPUT/OUTPUT PORTS
197
READ
N
OFF
P3
ON
R=100k
Ω
. .
P2
ON
R=10k
Ω
. .
P1
ON
R=500
Ω
. .
V
CC
INTERNAL
BUS
I
OH
(A) When accelerator circuit is activated
READ
N
OFF
P3
ON
R=100k
Ω
. .
P2
ON
R=10k
Ω
. .
P1
OFF
R=500
Ω
. .
V
CC
INTERNAL
BUS
I
OH
(B) When "1" data is held
OFF
READ
N
ON
P3
R=100k
Ω
. .
P2
R=10k
Ω
. .
P1
R=500
Ω
. .
V
CC
INTERNAL
BUS
I
OL
(C) When "0" data is held
OFF
OFF
Figure 5-5  Quasi-bidirectional port equivalent circuit