Holtek HT66F20-1 Manual page 176

LVD Interrupt
The Low Voltage Detector Interrupt is contained within the Multi-function Interrupt. An LVD
Interrupt request will take place when the LVD Interrupt request flag, LVF, is set, which occurs
when the Low Voltage Detector function detects a low power supply voltage. To allow the program
to branch to its respective interrupt vector address, the global interrupt enable bit, EMI, Low Voltage
Interrupt enable bit, LVE, and associated Multi-function interrupt enable bit, must first be set. When
the interrupt is enabled, the stack is not full and a low voltage condition occurs, a subroutine call to
the Multi-function Interrupt vector, will take place. When the Low Voltage Interrupt is serviced, the
EMI bit will be automatically cleared to disable other interrupts, however only the Multi-function
interrupt request flag will be also automatically cleared. As the LVF flag will not be automatically
cleared, it has to be cleared by the application program.
TM Interrupts
The Compact and Standard TM each has two interrupts, while the Enhanced Type TM has three
interrupts. All of the TM interrupts are contained within the Multi-function Interrupts. For the
Compact and Standard Type TM there are two interrupt request flags TnPF and TnAF and two
enable bits TnPE and TnAE. For the Enhanced Type TM there are three interrupt request flags TnPF,
TnAF and TnBF and three enable bits TnPE, TnAE and TnBE. A TM interrupt request will take
place when any of the TM request flags are set, a situation which occurs when a TM comparator P, A
or B match situation happens.
To allow the program to branch to its respective interrupt vector address, the global interrupt enable
bit, EMI, respective TM Interrupt enable bit, and relevant Multi-function Interrupt enable bit, MFnE,
must first be set. When the interrupt is enabled, the stack is not full and a TM comparator match
situation occurs, a subroutine call to the relevant Multi-function Interrupt vector locations, will take
place. When the TM interrupt is serviced, the EMI bit will be automatically cleared to disable other
interrupts, however only the related MFnF flag will be automatically cleared. As the TM interrupt
request flags will not be automatically cleared, they have to be cleared by the application program.
Interrupt Wake-up Function
Each of the interrupt functions has the capability of waking up the microcontroller when in the
SLEEP or IDLE Mode. A wake-up is generated when an interrupt request flag changes from low
to high and is independent of whether the interrupt is enabled or not. Therefore, even though these
devices are in the SLEEP or IDLE Mode and its system oscillator stopped, situations such as
external edge transitions on the external interrupt pins, a low power supply voltage or comparator
input change may cause their respective interrupt flag to be set high and consequently generate
an interrupt. Care must therefore be taken if spurious wake-up situations are to be avoided. If an
interrupt wake-up function is to be disabled then the corresponding interrupt request flag should be
set high before the device enters the SLEEP or IDLE Mode. The interrupt enable bits have no effect
on the interrupt wake-up function.
Rev. 1.40
HT66F20-1/HT66F30-1/HT68F20-1/HT68F30-1
Flash MCU with EEPROM
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