Datasheet

78K0/Kx2-L CHAPTER 22 LOW-VOLTAGE DETECTOR
R01UH0028EJ0400 Rev.4.00 688
Sep 27, 2010
22.5 Cautions for Low-Voltage Detector
In a system where the supply voltage (V
DD) fluctuates for a certain period in the vicinity of the LVI detection voltage
(V
LVI), 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 (refer to Figure 22-11).
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 (V
DD) → Input voltage from external input pin (EXLVI)
• Detection voltage (VLVI) → Detection voltage (VEXLVI = 1.21 V)