Datasheet

78K0/Ix2 CHAPTER 22 LOW-VOLTAGE DETECTOR
R01UH0010EJ0500 Rev.5.00 630
Feb 28, 2012
CHAPTER 22 LOW-VOLTAGE DETECTOR
22.1 Functions of Low-Voltage Detector
The low-voltage detector (LVI) is mounted onto all 78K0/Ix2 microcontroller products.
The low-voltage detector has the following functions.
 The LVI circuit compares the supply voltage (V
DD) with the LVI detection voltage (VLVI), and generates an internal
reset or internal interrupt signal.
 The low-voltage detector (LVI) can be set to ON by an option byte by default. If it is set to ON to raise the power
supply from the POC detection voltage (V
POR = 1.61 V (TYP.)) or lower, the internal reset signal is generated when
the supply voltage (V
DD) < the LVI detection voltage (VLVI = 1.91 V 0.1 V). After that, the internal reset signal is
generated when the supply voltage (V
DD) < the LVI detection voltage (VLVI = 1.91 V 0.1 V).
 A reset or an interrupt can be selected to be generated after detection by software.
 Detection levels (V
LVI,10 levels) of supply voltage can be changed by software.
 Operable in STOP mode.
Note This is a preliminary value and subject to change.
The reset and interrupt signals are generated as follows depending on selection by software.
Selection of Level Detection of Supply Voltage (VDD)
Selects reset (LVIMD = 1). Selects interrupt (LVIMD = 0).
Generates an internal reset signal when VDD < 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 VDD becomes VLVI or higher (VDD 
V
LVI).
Remark LVIMD: Bit 1 of low-voltage detection register (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, refer to CHAPTER 20 RESET FUNCTION.