Description Of Main Circuit Operation - Hitachi RAS-E10H2 Service Manual

DESCRIPTION OF MAIN CIRCUIT OPERATION

MODEL RAS-E10H2
1. Reset Circuit
Voltage supply to
pin 2 of IC521
Voltage at pin 7
of microcomputer
The reset circuit initializes the microcomputer program when power is ON or OFF.
Low voltage at pin 7 resets the microcomputer and Hi activates the microcomputer.
When power "ON" "ON" 5V voltage rises and reaches 4.4V, "ON"
starts operation.
When power "OFF" voltage drops and reaches 4.2V,
microcomputer.
5V
2
R552
1
5
3
IC521
0V
Voltage
5.0V
Reset release at 4.4V
Voltage
5.0V
4.4V pin 1 of IC521 is set to "Hi". At this time the microcomputer 4.4V,
4.2V pin 1 of IC521 is set to "Low". This will RESET the 4.2V,
Fig. 1-1
Power "ON"
Reset enter at 4.2V
Fig. 1-2
- 37 -
NORMAL : HI
RESET : LO
7
RES
Microcomputer
Power "OFF"