UPD65 datasheet(27/64 Pages) NEC

27 / 64 page

µPD64A, 65

Data Sheet U14380EJ2V0DS00

7. POC CIRCUIT

The POC circuit monitors the power supply voltage and applies an internal reset in the microcontroller at the

time of battery replacement.

Cautions 1. There are cases in which the POC circuit cannot detect a low power supply voltage of less

than 1 ms. Therefore, if the power supply voltage has become low for a period of less than

1 ms, the POC circuit may malfunction because it does not generate an internal reset signal.

2. Clock oscillation is stopped by the resonator due to low power supply voltage before the

POC circuit generates the internal reset signal. In this case, malfunction may result, for

example when the power supply voltage is recovered after the oscillation is stopped. This

type of phenomenon takes place because the POC circuit does not generate an internal reset

signal (because the power supply voltage recovers before the low power supply voltage is

detected) even though the clock has stopped. If, by any chance, a malfunction has taken

place, remove the battery for a short time and put it back. In most cases, normal operation

will be resumed.

3. In order to prevent malfunction, be sure to input a low level to more than one of pins KI0 to

KI3 when POC is released due to supply voltage startup).

UPD65 Datasheet(PDF) 27 Page - NEC