Panasonic KX-FB423CN Manual page 337

KX-FB423CN
7.3.2. RESET CIRCUIT
The output signal (reset) from pin 4 of the voltage detect IC (IC507) is input to the ASIC (IC501) 114 pin.
1. During a momentary power interruption, a positive reset pulse of 50~70 msec is generated and the system is reset completely.
2. The watch dog timer, built-in the ASIC (IC501), is initialized by the CPU about every 1.5 ms.
When a watch dog error occurs, pin 115 of the ASIC (IC501) becomes low level.
The terminal of the ´WDERR´ signal is connected to the reset line, so the ´WDERR´ signal works as the reset signal.
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