Rev. 1.71
118
April 11, 2017
Rev. 1.71
119
April 11, 2017
HT66F002/HT66F0025/HT66F003/HT66F004
Cost-Effective A/D Flash MCU with EEPROM
HT66F002/HT66F0025/HT66F003/HT66F004
Cost-Effective A/D Flash MCU with EEPROM
EEPROM Interrupt
An EEPROM Interrupt request will take place when the EEPROM Interrupt request flag, DEF, is set,
which occurs when an EEPROM Write cycle ends. To allow the program to branch to its respective
interrupt vector address, the global interrupt enable bit, EMI, and EEPROM Interrupt enable bit,
DEE, must first be set. When the interrupt is enabled, the stack is not full and an EEPROM Write
cycle ends, a subroutine call to the respective EEPROM Interrupt vector, will take place. When the
EEPROM Interrupt is serviced, the EMI bit will be automatically cleared to disable other interrupts,
and the EEPROM interrupt request flag, DEF, will also be automatically cleared.
TM Interrupts
The TMs each has two interrupts. All of the TM interrupts are contained within the Multi-function
Interrupts. For each of the TMs there are two interrupt request flags xTMPnF and xTMAnF and
two enable bits xTMPnE and xTMAnE. 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 or comparator A match
situation happens.
To allow the program to branch to its respective interrupt vector address, the global interrupt enable
bit, EMI, and the respective TM Interrupt enable bit, and associated Multi-function interrupt enable
bit, MFnF, 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 TM 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 the device
is in the SLEEP or IDLE Mode and its system oscillator stopped, situations such as external edge
transitions on the external interrupt pin, 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.
Programming Considerations
By disabling the relevant interrupt enable bits, a requested interrupt can be prevented from being
serviced, however, once an interrupt request flag is set, it will remain in this condition in the
interrupt register until the corresponding interrupt is serviced or until the request flag is cleared by
the application program.
Where a certain interrupt is contained within a Multi-function interrupt, then when the interrupt
service routine is executed, as only the Multi-function interrupt request flags, MF0F~MF1F, will
be automatically cleared, the individual request flag for the function needs to be cleared by the
application program.
It is recommended that programs do not use the “CALL” instruction within the interrupt service
subroutine. Interrupts often occur in an unpredictable manner or need to be serviced immediately.
If only one stack is left and the interrupt is not well controlled, the original control sequence will be
damaged once a CALL subroutine is executed in the interrupt subroutine.
