Description Of Main Circuit Operation; Reset Circuit - Hitachi RAK-25NH4 Service Manual

DESCRIPTION OF MAIN CIRCUIT OPERATION

MODEL RAK-25NH4, RAK-35NH4, RAK-50NH4

1. Reset Circuit

Voltage supply to
pin 2 of IC521
Voltage at pin
of microcomputer
The reset circuit initializes the microcomputer program when power is ON or OFF.
Low voltage at pin
When power "ON" 5V voltage rises and reaches 4.4V, pin 1 of IC521 is set to "Hi". At this time the
microcomputer starts operation.
When power "OFF" voltage drops and reaches 4.2V, pin 1 of IC521 is set to "Low". This will RESET the
microcomputer.
5V
2
1
5
3
IC521
Voltage
5.0V
Reset release at 4.4V
voltage
5.0V
7
resets the microcomputer and Hi activates the microcomputer.
7
R522
0V
Fig. 1-1
Fig. 1-2
– 62 –
NORMAL : HI
RESET : LO
7
RES
Microcomputer
Reset enter at 4.2V