Sonic Alert msm83c154s User Manual
INPUT/OUTPUT PORTS
193
Q
D
MODIFY
READ
INTERNAL BUS
N
PORT 0
WPO
Figure 5-2 Port 0 input/Output port equivalent circuit in internal ROM mode
PC0~7
RA0~7
RA0~7
ACC0~7
READ
INTERNAL BUS
N
P
V
CC
PORT 0
Figure 5-3 Port 0 equivalent circuit during address and data input/output in external
ROM/RAM mode