UPD78F1502AGK-GAK-AX Datasheet, PDF (820/1031 Pages) Renesas Technology Corp – 16-Bit Single-Chip Microcontrollers

78K0R/Lx3
CHAPTER 24 LOW-VOLTAGE DETECTOR
CHAPTER 24 LOW-VOLTAGE DETECTOR
24.1 Functions of Low-Voltage Detector
The low-voltage detector (LVI) is mounted onto all 78K0R/Lx3 microcontroller products.
The low-voltage detector has the following functions.
• The LVI circuit compares the supply voltage (VDD) with the detection voltage (VLVI) or the input voltage from an
external input pin (EXLVI) with the detection voltage (VEXLVI = 1.21 V ±0.1 V), 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 (VPOR = 1.61 V (TYP.)) or lower, the internal reset signal is generated when
the supply voltage (VDD) < detection voltage (VLVI = 2.07 V ±0.2 V). After that, the internal reset signal is generated
when the supply voltage (VDD) < detection voltage (VLVI = 2.07 V ±0.1 V).
• The supply voltage (VDD) or the input voltage from the external input pin (EXLVI) can be selected to be detected by
software.
• A reset or an interrupt can be selected to be generated after detection by software.
• Detection levels (VLVI,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 VDD < VLVI and
releases the reset signal when
VDD ≥ VLVI.
Generates an internal interrupt
signal when VDD drops lower
than VLVI (VDD < VLVI) or when
VDD becomes VLVI or higher
(VDD ≥ VLVI).
Generates an internal reset
signal when EXLVI < VEXLVI
and releases the reset signal
when EXLVI ≥ VEXLVI.
Generates an internal interrupt
signal when EXLVI drops
lower than VEXLVI (EXLVI <
VEXLVI) or when EXLVI
becomes VEXLVI or higher
(EXLVI ≥ VEXLVI).
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 22 RESET FUNCTION.
R01UH0004EJ0501 Rev.5.01
804
Jun 20, 2011