Hitachi RAS-50FH5 - Description of Main Circuit Operation

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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 ÒONÓ 5V voltage rises and reaches 4.4V, pin 1 of IC521 is set to ÒHiÓ. At this time the
microcomputer starts operation.
When power ÒOFFÓ voltage drops and reaches 4.2V, pin 1 of IC521 is set to ÒLowÓ. This will RESET the
microcomputer.
DESCRIPTION OF MAIN CIRCUIT OPERATION
MODEL RAS-50FH5
1. Reset Circuit
Fig. 1-1
Fig. 1-2
2
1
5
3
7
NORMAL : HI
RESET : LO
RES
Microcomputer
425C
125R
225C
125C
R522
5V
0V
IC521
Voltage
5.0V
Reset enter at 4.2V
Reset release at 4.4V
voltage
5.0V
Voltage at pin
7
of microcomputer
Voltage supply to
pin
2
of IC521