HT67F30 Datasheet, PDF (68/242 Pages) Holtek Semiconductor Inc – TinyPowerTM A/D Flash Type 8-Bit MCU with LCD & EEPROM

HT67F30/HT67F40/HT67F50/HT67F60
TinyPower^TM A/D Flash Type 8-Bit MCU with LCD & EEPRO
Wake-up
After the system enters the SLEEP or IDLE Mode, it can be woken up from one of various sources
listed as follows:
●● An external reset
●● An external falling edge on Port A
●● 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.
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 "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 high before entering the SLEEP or IDLE Mode, the wake-up function of the related
interrupt will be disabled.
Programming Considerations
The HXT and LXT oscillators both use the same SST counter. For example, if the system is woken
up from the SLEEP0 Mode and both the HXT and LXT oscillators need to start-up from an off state.
The LXT oscillator uses the SST counter after HXT oscillator has finished its SST period.
●● If the device is woken up from the SLEEP0 Mode to the NORMAL Mode, the high speed system
oscillator needs an SST period. The device will execute first instruction after HTO is "1". At this
time, the LXT oscillator may not be stability if fSUB is from LXT oscillator. The same situation
occurs in the power-on state. The LXT oscillator is not ready yet when the first instruction is
executed.
●● If the device is woken up from the SLEEP1 Mode to NORMAL Mode, and the system clock
source is from HXT oscillator and FSTEN is "1" , the system clock can be switched to the LXT or
LIRC oscillator after wake up.
●● There are peripheral functions, such as WDT, TMs and SPIA, LCD driver and SIM, for which the
fSYS is used. If the system clock source is switched from fH to fL, the clock source to the peripheral
functions mentioned above will change accordingly.
●● The on/off condition of fSUB and fS depends upon whether the WDT is enabled or disabled as the
WDT clock source is selected from fSUB.
Rev. 1.50
68
March 06 , 2012