HT45F23/HT45F43
8-Bit Flash MCU with Op Amps & Comparators
Each pin on Port A can be setup using the PAWU register to permit a negative transition on the pin to
wake-up the system. When a Port A pin wake-up occurs, the program will resume execution at the
instruction following the ²HALT² instruction.
If the system is woken up by an interrupt, then two possible situations may occur. The first is where the
related interrupt is disabled or the interrupt is enabled but the stack is full, in which case the program
will resume execution at the instruction following the ²HALT² instruction. In this situation, the
interrupt which woke-up the device will not be immediately serviced, but will rather be serviced later
when the related interrupt is finally enabled or when a stack level becomes free. The other situation is
where the related interrupt is enabled and the stack is not full, in which case the regular interrupt
response takes place. If an interrupt request flag is set high before entering the SLEEP or IDLE Mode,
the wake-up function of the related interrupt will be disabled.
Low Voltage Detector - LVD
This device has a Low Voltage Detector function, also known as LVD. This enabled the device to
monitor the power supply voltage, VDD, and provide a warning signal should it fall below a certain
level. This function may be especially useful in battery applications where the supply voltage will
gradually reduce as the battery ages, as it allows an early warning battery low signal to be generated.
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. Alow voltage condition is indicated when the LVDO bit is set. If
the LVDO bit is low, this indicates that the VDD 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 certain 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.
Rev. 1.20
127
September 15, 2011
HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
