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Rev. 2.50
60
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Rev. 2.50
6�
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HT66F20/HT66F30/HT66F40/HT66F50/HT66F60
HT66FU30/HT66FU40/HT66FU50/HT66FU60
A/D Flash MCU with EEPROM
HT66F20/HT66F30/HT66F40/HT66F50/HT66F60
HT66FU30/HT66FU40/HT66FU50/HT66FU60
A/D Flash MCU with EEPROM
Fast Wake-up
To minimise power consumption the device can enter the SLEEP or IDLE0 Mode, where the system
clock source to the device will be stopped. However when the device is woken up again, it can take
a considerable time for the original system oscillator to restart, stabilise and allow normal operation
to resume. To ensure the device is up and running as fast as possible a Fast Wake-up function is
provided, which allows f
SUB
, namely either the LXT or LIRC oscillator, to act as a temporary clock
to first drive the system until the original system oscillator has stabilised. As the clock source for
the Fast Wake-up function is f
SUB
, the Fast Wake-up function is only available in the SLEEP1 and
IDLE0 modes. When the device is woken up from the SLEEP0 mode, the FastWake-up function has
no effect because the f
SUB
clock is stopped. The FastWake-up enable/disable function is controlled
using the FSTEN bit in the SMOD register.
If the HXT oscillator is selected as the NORMAL Mode system clock, and if the Fast Wake-up
function is enabled, then it will take one to two t
SUB
clock cycles of the LIRC or LXT oscillator for
the system to wake-up. The system will then initially run under the f
SUB
clock source until 1024
HXT clock cycles have elapsed, at which point the HTO flag will switch high and the system will
switch over to operating from the HXT oscillator.
If the ERC or HIRC oscillators or LIRC oscillator is used as the system oscillator then it will take
15~16 clock cycles of the ERC or HIRC or 1~2 cycles of the LIRC to wake up the system from the
SLEEP or IDLE0 Mode. The Fast Wake-up bit, FSTEN will have no effect in these cases.
System
Oscillator
FSTEN
Bit
Wake-up Time
(SLEEP0 Mode)
Wake-up Time
(SLEEP1 Mode)
Wake-up Time
(IDLE0 Mode)
Wake-up Time
(IDLE1 Mode)
HXT
0
�024 HXT cycles �024 HXT cycles
�~2 HXT cycles
�
�024 HXT cycles
�~2 f
SUB
cycles
(System r�ns with f
SUB
first for 1024 HXT cycles and
then switches over to r�n with the HXT clock )
�~2 HXT cycles
ERC
x
�5~�6 ERC cycles �5~�6 ERC cycles
�~2 ERC cycles
HIRC
x
�5~�6 HIRC cycles �5~�6 HIRC cycles
�~2 HIRC cycles
LIRC
x
�~2 LIRC cycles �~2 LIRC cycles
�~2 LIRC cycles
LXT
x
�024 LXT cycles �024 LXT cycles
�~2 LXT cycles
Wake-up Times
Note that if the Watchdog Timer is disabled, which means that the LXT and LIRC are all both off,
then there will be no Fast Wake-up function available when the device wakes-up from the SLEEP0
Mode.