Lvd Operation - Holtek HT68F Series Manual

HT68F20/HT68F30/HT68F40/HT68F50/HT68F60
HT68FU30/HT68FU40/HT68FU50/HT68FU60
Enhanced I/O Flash Type 8-Bit MCU with EEPROM

LVD Operation

The Low Voltage Detector function operates by comparing the power supply voltage, V
pre-specified voltage level stored in the LVDC register. This has a range of between 2.0V and 4.4V.
When the power supply voltage, V
set high indicating a low power supply voltage condition. The Low Voltage Detector function is
supplied by a reference voltage which will be automatically enabled. When the device is powered
down the low voltage detector will remain active if the LVDEN bit is high. After enabling the Low
Voltage Detector, a time delay t
LVDO bit. Note also that as the V
of V , there may be multiple bit LVDO transitions.
LVD
The Low Voltage Detector also has its own interrupt which is contained within one of the
Multi-function interrupts, providing an alternative means of low voltage detection, in addition to
polling the LVDO bit. The interrupt will only be generated after a delay of t
has been set high by a low voltage condition. When the device is powered down the Low Voltage
Detector will remain active if the LVDEN bit is high. In this case, the LVF interrupt request flag
will be set, causing an interrupt to be generated if V
cause the device to wake-up from the SLEEP or IDLE Mode, however if the Low Voltage Detector
wake up function is not required then the LVF flag should be first set high before the device enters
the SLEEP or IDLE Mode.
Rev. 2.10
, falls below this pre-determined value, the LVDO bit will be
DD
should be allowed for the circuitry to stabilise before reading the
LVDS
voltage may rise and fall rather slowly, at the voltage nears that
DD
V D D
V
L V D
L V D E N
L V D O
t
L V D S
LVD Operation
213
after the LVDO bit
LVD
falls below the preset LVD voltage. This will
DD
, with a
DD
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