Description Of Main Circuit Operation - Hitachi RAS-50FH5 Service Manual

DESCRIPTION OF MAIN CIRCUIT OPERATION

MODEL RAS-50FH5
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 ÒONÓ 5V voltage rises and reaches 4.4V,
microcomputer starts operation.
When power ÒOFFÓ voltage drops and reaches 4.2V, pin
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
pin 1 of IC521 is set to ÒHiÓ. At this time the
1 of IC521 is set to ÒLowÓ. This will RESET the
– 65 –
NORMAL : HI
RESET : LO
7
RES
Microcomputer
Reset enter at 4.2V