HT46R068B/HT46R069B
Enhanced A/D Type 8-bit OTP MCU
Wake-up
After the system enters the Idle/Sleep Mode, it can be woken up from one of various sources listed
as follows:
An external reset
●
●
●
●
An external falling edge on PA0 to PA7
A system interrupt
A WDT overflow
If the system is woken up by an external reset, the device will experience a full system reset,
however, if the device is woken up by a WDT overflow, a Watchdog Timer reset will be initiated.
Although both of these wake-up methods will initiate a reset operation, the actual source of the
wake-up can be determined by examining the TO and PDF flags. The PDF flag is cleared by a
system power-up or executing the clear Watchdog Timer instructions and is set when executing the
"HALT" instruction. The TO flag is set if a WDT time-out occurs, and causes a wake-up that only
resets the Program Counter and Stack Pointer, the other flags remain in their original status.
Pins PA0 to PA7 can be setup via the PAWUK register to permit a negative transition on the pin to
wake-up the system. When a PA0 to PA7 pin wake-up occurs, the program will resume execution at
the instruction following the "HALT" 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 "HALT" 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 to "1" before entering
the Idle/Sleep Mode, then any future interrupt requests will not generate a wake-up function of the
related interrupt will be ignored.
No matter what the source of the wake-up event is, once a wake-up event occurs, there will be a
time delay before normal program execution resumes. Consult the table for the related time.
Oscillator Type
Wake-up
Source
ERC, IRC
RSDT + tSST1
Crystal
Exteꢁnal RES
PA Poꢁt
t
tRSDT + tSSTꢃ
Inteꢁꢁꢀpt
tSST1
tSSTꢃ
WDT Overflow
Note: 1. tRSTD (reset delay time), tSYS (system clock)
2. tRSTD is power-on delay, typical time=100ms
3. tSST1= 2 or 1024 tSYS
4. tSST2= 1024 tSYS
Wake-up Delay Time
Rev. 1.00
34
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HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
