Description Of Main Circuit Operation - Hitachi RAS-E08H2A Service Manual

DESCRIPTION OF MAIN CIRCUIT OPERATION

MODEL RAS-E08H2A, RAS-E10H2A
1. Reset Circuit
5
Voltage
Voltage supply to
pin 2 of IC521
Reset release at 4.4V
Voltage at pin 7
of microcomputer
The reset circuit initializes the microcomputer program when power is ON or OFF.
Low voltage at pin 7 7 7 7 7 resets the microcomputer and Hi activates the microcomputer.
When power "ON" 5V voltage rises and reaches 4.4V, pin 1 1 1 1 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 1 1 1 1 of IC521 is set to "Low". This will RESET the
microcomputer.
5V
2
R552
1
3
IC521
0V
Fig. 1-1
Power "ON"
5.0V
Voltage
5.0V
Fig. 1-2
NORMAL : HI
RESET
7
RES
Microcomputer
Power "OFF"
Reset enter at 4.2V
– 30 –
: LO