Hitachi RAC-25NH5, Service Manual, Page: 79 / 112

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10. Reset Circuit
●
The reset circuit initializes the microcomputer program when Power is “ON” or “OFF”.
●
Low voltage at pin
48
resets the microcomputer, and HI activates the microcomputer.
●
Fig. 10-1 shows the reset circuit and Fig. 10-2 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 and
reset voltage input to pin
48
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.
Microcomputer
R252
R289
0V 0V
R288
0V
5V
12V
HIC
R284
JW10
IC5 (1/2)
C204
48
RESET
Main
P.W.B
Fig. 10-1
C215
R286
C225
C107
C226 R285
0V
1
3
2
62
8
–
+
+
0V
0V
R292
12V line
12V line
5V line
5V line
Fig. 10-2
Reset voltage
Reset voltage
12
6
0
Power is ON
V
oltage (V)
12
6
0
Power is OFF
V
oltage (V)
Time
Time