Fast Wake-Up; Pe�Ating Mode Swit�Hing - Holtek TinyPower HT69F40A Manual

HT69F30A/HT69F40A/HT69F50A
TinyPower I/O Flash 8-Bit MCU with LCD & EEPROM
TM

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, stabilize 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
system until the original system oscillator has stabilised. As the clock source for the Fast Wake-up
function is f , the Fast Wake-up function is only available in the SLEEP1 and IDLE0 modes.
SUB
When the device is woken up from the SLEEP0 mode, the FastWake-up function has no effect
because the f
SUB
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
system to wake-up. The system will then initially run under the f
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/HIRC or EC/LIRC oscillator is used as the system oscillator, then it will take15~16 clock
cycles of the ERC/HIRC oscillator or 1~2 clock cycles of the LIRC osrillator respectively 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 FSTEN Wake-up Time
Oscillator Bit (SLEEP0 Mode)
0 1024 HXT �y�les
HXT
1 1024 HXT �y�les
ERC x 1�~16 ERC �y�les
HIRC x 1�~16 HIRC �y�les
EC x 1~2 EC �y�les
LIRC x 1~2 LIRC �y�les
LXT x 1024 LXT �y�les
Note that if the Watchdog Timer is disabled, which means that the f
or LIRC oscillator is off, then there will be no Fast Wake-up function available when the device
wakes-up from the SLEEP0 Mode.
Operating Mode Switching
The device can switch between operating modes dynamically allowing the user to select the best
performance/power ratio for the present task in hand. In this way microcontroller operations that
do not require high performance can be executed using slower clocks thus requiring less operating
current and prolonging battery life in portable applications.
In simple terms, Mode Switching between the NORMAL Mode and SLOW Mode is executed
using the HLCLK bit and CKS2~CKS0 bits in the SMOD register while Mode Switching from the
NORMAL/SLOW Modes to the SLEEP/IDLE Modes is executed via the HALT instruction. When
a HALT instruction is executed, whether the device enters the IDLE Mode or the SLEEP Mode is
determined by the condition of the IDLEN bit in the SMOD register and FSYSON in the SMOD1
register.
Rev. 1.20
, namely the LIRC oscillator, to act as a temporary clock to first drive the
SUB
clock is stopped. The FastWake-up enable/disable function is controlled using the
Wake-up Time
(SLEEP1 Mode)
1024 HXT �y�les
1~2 f �y�les
SUB
(System �uns with f
�y�les and then swit�hes ove� to �un with
the HXT �lo�k )
1�~16 ERC �y�les
1�~16 HIRC �y�les
1~2 EC �y�les
1~2 LIRC �y�les
1024 LXT �y�les
Wake-up Times
61
clock cycles of the LIRC oscillator for the
SUB
clock source until 1024 HXT
SUB
Wake-up Time Wake-up Time
(IDLE0 Mode) (IDLE1 Mode)
1~2 HXT �y�les
first for 1024 HXT
SUB
1~2 HXT �y�les
1~2 ERC �y�les
1~2 HIRC �y�les
1~2 EC �y�les
1~2 LIRC �y�les
1~2 LXT �y�les
clock drived from the LXT
SUB
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