
CHAPTER 21 LOW-VOLTAGE DETECTOR
User’s Manual U17893EJ8V0UD
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21.5 Cautions for Low-Voltage Detector
(1) Measures method when supply voltage (VDD) frequently fluctuates in the vicinity of the LVI detection
voltage (VLVI)
In a system where the supply voltage (VDD) fluctuates for a certain period in the vicinity of the LVI detection
voltage (VLVI), the operation is as follows depending on how the low-voltage detector is used.
Operation example 1: When used as reset
The system may be repeatedly reset and released from the reset status.
The time from reset release through microcontroller operation start can be set arbitrarily by the following
action.
<Action>
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 21-11).
Remark
If bit 2 (LVISEL) of the low voltage detection register (LVIM) is set to “1”, the meanings of the above
words change as follows.
Supply voltage (VDD)
→ Input voltage from external input pin (EXLVI)
Detection voltage (VLVI) → Detection voltage (VEXLVI = 1.21 V)