Description Of Main Circuit Operation - Hitachi RAD-50DH7A Service Manual

DESCRIPTION OF MAIN CIRCUIT OPERATION

MODEL RAD-50DH7A, RAD-60DH7A, RAD-70DH7A
1. Reset Circuit
Voltage supply to
pin of IC521
2
Voltage at pin
of microcomputer
The reset circuit initializes the microcomputer program when power is ON or OFF.
G
Low voltage at pin
G
When power "ON" 5V voltage rises and reaches 4.4V, pin 1 of IC521 is set to "Hi". At this time the
G
microcomputer starts operation.
When power "OFF" voltage drops and reaches 4.2V, pin 1 of IC521 is set to "Low". This will RESET the
G
microcomputer.
Voltage
5.0V
Reset release at 4.4V
voltage
5.0V
7
resets the microcomputer and Hi activates the microcomputer.
7
Fig. 1-1
Fig. 1-2
– 54 –
Reset enter at 4.2V