Cautions For Low-Voltage Detector - NEC 78K0S/KA1+ User Manual

16.5 Cautions for Low-Voltage Detector

In a system where the supply voltage (V
(V ), the operation is as follows depending on how the low-voltage detector is used.
LVI
<1> When used as reset
The system may be repeatedly reset and released from the reset status.
In this case, the time from release of reset to the start of the operation of the microcontroller can be arbitrarily
set by taking action (1) below.
<2> When used as interrupt
Interrupt requests may be frequently generated. Take (b) of action (2) below.
In this system, take the following actions.
<Action>
(1) When used as reset
After releasing the reset signal, wait for the supply voltage fluctuation period of each system by means of a
software counter that uses a timer, and then initialize the ports (see Figure 16-6).
(2) When used as interrupt
(a) Perform the processing
(V )" in the servicing routine of the LVI interrupt by using bit 0 (LVIF) of the low-voltage detection register
LVI
(LVIM). Clear bit 1 (LVIIF) of interrupt request flag register 0 (IF0) to 0.
(b) In a system where the supply voltage fluctuation period is long in the vicinity of the LVI detection voltage, wait
for the supply voltage fluctuation period, check that "supply voltage (V
LVIF flag and clear LVIIF flag to 0.
Note For low voltage detection processing, the CPU clock speed is switched to slow speed and the A/D
converter is stopped, etc.
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CHAPTER 16 LOW-VOLTAGE DETECTOR
) fluctuates for a certain period in the vicinity of the LVI detection voltage
DD
Note
for low voltage detection. Check that "supply voltage (V
User's Manual U16898EJ3V0UD
) ≥ detection voltage
DD
) ≥ detection voltage (V
DD LVI
)" using the