Hitachi RAS-E08H2A Service Manual page 56

6-3. Reset Circuit
HIC
12V
0V 0V 0V 0V
The reset circuit initializes the microcomputer program when Power is "ON" from "OFF" .
Low voltage at pin 7 resets the microcomputer, and HI activates the microcomputer.
Fig. 6-10 shows the reset circuit and Fig. 6-11 shows waveform at each point when power is turned on
and off.
When power is turned on, 12V line and 5V line voltages rise and 12V line voltage reaches 10.9V an
reset voltage input to pin 7 of microcomputer is set to Hi.
Reset voltage will be hold "Hi" until the 12V line voltage drops to 9.90V even though the power shuts
down.
12
6
0
12
6
0
5V
D208
R287
8
2
-
1
+
3
IC5(1/2)
R288
Fig. 6-10
10.9V
12V line
5V line
Reset voltage
– 54 –
0V
19
R252
7
C204
0V
12V line
5V line
Reset voltage
9.9V
Fig. 6-11
Microcomputer
RESET OUT.
RESET
Time
Time