HT66F20_1006 Datasheet, PDF (179/250 Pages) Holtek Semiconductor Inc – Enhanced A/D Flash Type MCU 8-Bit MCU with EEPROM

HT66F20/HT66F30/HT66F40/HT66F50/HT66F60
HT66FU30/HT66FU40/HT66FU50/HT66FU60
Low Voltage Detector - LVD
Each device has a Low Voltage Detector function, also
known as LVD. This enabled the device to monitor the
power supply voltage, V_DD, and provide a warning signal
should it fall below a certain level. This function may be
especially useful in battery applications where the sup-
ply voltage will gradually reduce as the battery ages, as
it allows an early warning battery low signal to be gener-
ated. The Low Voltage Detector also has the capability
of generating an interrupt signal.
LVD Register
The Low Voltage Detector function is controlled using a
single register with the name LVDC. Three bits in this
register, VLVD2~VLVD0, are used to select one of eight
fixed voltages below which a low voltage condition will
be detemined. A low voltage condition is indicated when
the LVDO bit is set. If the LVDO bit is low, this indicates
that the V_DD voltage is above the preset low voltage
value. The LVDEN bit is used to control the overall
on/off function of the low voltage detector. Setting the bit
high will enable the low voltage detector. Clearing the bit
to zero will switch off the internal low voltage detector
circuits. As the low voltage detector will consume a cer-
tain amount of power, it may be desirable to switch off
the circuit when not in use, an important consideration in
power sensitive battery powered applications.
· LVDC Register
Bit
7
Name
¾
R/W
¾
POR
¾
6
5
4
3
2
1
0
¾
LVDO LVDEN
¾
VLVD2 VLVD1 VLVD0
¾
R
R/W
¾
R/W
R/W
R/W
¾
0
0
¾
0
0
0
Bit 7~6
Bit 5
Bit
Bit 3
Bit 2~0
unimplemented, read as ²0²
LVDO: LVD Output Flag
0: No Low Voltage Detect
1: Low Voltage Detect
LVDEN: Low Voltage Detector Control
0: Disable
1: Enable
unimplemented, read as ²0²
VLVD2 ~ VLVD0: Select LVD Voltage
000: 2.0V
001: 2.2V
010: 2.4V
011: 2.7V
100: 3.0V
101: 3.3V
110: 3.6V
111: 4.4V
Rev. 1.20
179
June 4, 2010