Datasheet

User’s Manual U18698EJ1V0UD
485
CHAPTER 22 LOW-VOLTAGE DETECTOR
22.1 Functions of Low-Voltage Detector
The low-voltage detector (LVI) has the following functions.
• The LVI circuit compares the supply voltage (V
DD) with the detection voltage (VLVI) or the input voltage from an
external input pin (EXLVI) with the detection voltage (VEXLVI = 1.21 V (TYP.): fixed), and generates an internal
reset or internal interrupt signal.
• The supply voltage (V
DD) or input voltage from an external input pin (EXLVI) can be selected by software.
• Reset or interrupt function can be selected by software.
• Detection levels (16 levels) of supply voltage can be changed by software.
• Operable in STOP mode.
The reset and interrupt signals are generated as follows depending on selection by software.
Selection of Level Detection of Supply Voltage (VDD)
(LVISEL = 0)
Selection Level Detection of Input Voltage from
External Input Pin (EXLVI) (LVISEL = 1)
Selects reset (LVIMD = 1). Selects interrupt (LVIMD = 0). Selects reset (LVIMD = 1). Selects interrupt (LVIMD = 0).
Generates an internal reset
signal when V
DD < VLVI and
releases the reset signal when
V
DD ≥ VLVI.
Generates an internal interrupt
signal when V
DD drops lower
than V
LVI (VDD < VLVI) or when
V
DD becomes VLVI or higher
(V
DD ≥ VLVI).
Generates an internal reset
signal when EXLVI < V
EXLVI
and releases the reset signal
when EXLVI ≥ V
EXLVI.
Generates an internal interrupt
signal when EXLVI drops
lower than V
EXLVI (EXLVI <
V
EXLVI) or when EXLVI
becomes V
EXLVI or higher
(EXLVI ≥ V
EXLVI).
Remark LVISEL: Bit 2 of low-voltage detection register (LVIM)
LVIMD: Bit 1 of LVIM
While the low-voltage detector is operating, whether the supply voltage or the input voltage from an external input
pin is more than or less than the detection level can be checked by reading the low-voltage detection flag (LVIF: bit 0
of LVIM).
When the low-voltage detector is used to reset, bit 0 (LVIRF) of the reset control flag register (RESF) is set to 1 if
reset occurs. For details of RESF, see CHAPTER 20 RESET FUNCTION.