CHAPTER 17 LOW-VOLTAGE DETECTOR
Preliminary User’s Manual U19014EJ1V0UD
444
17.5 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.
(1) When used as reset
The system may be repeatedly reset and released from the reset status.
In this case, the time from release of reset to the start of the operation of the microcontroller can be arbitrarily set
by taking action (1) below.
(2) When used as interrupt
Interrupt requests may be frequently generated. Take (b) of action (2) below.
In this system, take the following actions.
<Action>
(1) When used as reset
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 (see
Figure 17-9
).
(2) When used as interrupt
(a) Check that “supply voltage (V
DD
)
≥
detection voltage (V
LVI
)” in the servicing routine of the LVI interrupt by
using bit 0 (LVIF) of the low-voltage detection register (LVIM). Clear bit 0 (LVIIF) of interrupt request flag
register 0L (IF0L) to 0.
(b) In a system where the supply voltage fluctuation period is long in the vicinity of the LVI detection voltage, wait
for the supply voltage fluctuation period, check that “supply voltage (V
DD
)
≥
detection voltage (V
LVI
)” using the
LVIF flag, and clear the LVIIF flag to 0.
electronic components distributor
