Datasheet

Section 19 Power-On Reset and Low-Voltage Detection Circuits (Optional)
Rev. 4.00 Mar. 15, 2006 Page 404 of 556
REJ09B0026-0400
19.1 Features
• Power-on reset circuit
Uses an external capacitor to generate an internal reset signal when power is first supplied.
• Low-voltage detection circuit
LVDR: Monitors the power-supply voltage, and generates an internal reset signal when the
voltage falls below a specified value.
LVDI: Monitors the power-supply voltage, and generates an interrupt when the voltage falls
below or rises above respective specified values.
Two pairs of detection levels for reset generation voltage are available: when only the LVDR
circuit is used, or when the LVDI and LVDR circuits are both used.
PSS:
LVDCR:
LVDSR:
LVDRES:
LVDINT:
Vreset:
Vint:
Prescaler S
Low-voltage-detection control register
Low-voltage-detection status register
Low-voltage-detection reset signal
Low-voltage-detection interrupt signal
Reset detection voltage
Power-supply fall/rise detection voltage
[Legend]
RES
CK
R
PSS
R
S
Q
OVF
Vreset
Vcc
Vint
LVDRES
LVDCR
LVDSR
LVDINT
Reference
voltage
generator
Noise canceler
Noise canceler
Interrupt
control
circuit
Internal reset
signal
Power-on reset circuit
Low-voltage detection circuit
Internal data bus
Ladder
resistor
+
−
+
−
φ
Interrupt
request
C
RES
Figure 19.1 Block Diagram of Power-On Reset Circuit and Low-Voltage Detection Circuit