HT68F016 Datasheet, PDF (35/116 Pages) Holtek Semiconductor Inc – Enhanced Flash Type 8-Bit MCU with EEPROM

HT66F016/HT66F017/HT68F016/HT68F017
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 the LIRC oscillator, to act as a temporary clock
to first drive the system until the original system oscilla-
tor 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 Fast
Wake-up function has no effect because the f_SUB clock
is stopped. The Fast Wake-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 en-
abled, then it will take one to two t_SUB clock cycles of the
LIRC oscillator for the system to wake-up. The system
will then initially run under the f_SUB clock source until 128
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 HIRC oscillators or LIRC oscillator is used as the
system oscillator then it will take 15~16 clock cycles of
the HIRC or 1~2 cycles of the LIRC to wake up the sys-
tem from the SLEEP or IDLE0 Mode. The Fast Wake-up
bit, FSTEN will have no effect in these cases.
System
Oscillator
HXT
HIRC
LIRC
FSTEN Wake-up Time
Bit (SLEEP0 Mode)
Wake-up Time
(SLEEP1 Mode)
Wake-up Time
(IDLE0 Mode)
Wake-up Time
(IDLE1 Mode)
0
128 HXT cycles
128 HXT cycles
1~2 HXT cycles
1~2 f_SUB cycles
1
128 HXT cycles (System runs with f_SUB first for 128 HXT cycles and 1~2 HXT cycles
then switches over to run with the HXT clock)
X 15~16 HIRC cycles
15~16 HIRC cycles
1~2 HIRC cycles
X
1~2 LIRC cycles
1~2 LIRC cycles
1~2 LIRC cycles
Wake-Up Times
Note that if the Watchdog Timer is disabled, which means that the LIRC is off, then there will be no Fast Wake-up func-
tion available when the device wakes-up from the SLEEP0 Mode.
Operating Mode Switching and Wake-up
²X²: don¢t care
NORM AL
fS Y S = fH ~ fH /6 4
fH o n
C P U ru n
fS Y S o n
fT B C o n
fS U B o n
SLEEP0
H A L T in s tr u c tio n is e x e c u te d
fS Y S o ff
C P U s to p
ID L E N = 0
fT B C o ff
fS U B o ff
W D T & L V D o ff
SLEEP1
H A L T in s tr u c tio n is e x e c u te d
fS Y S o ff
C P U s to p
ID L E N = 0
fT B C o ff
fS U B o n
W D T orLV D on
ID L E 1
H A L T in s tr u c tio n is e x e c u te d
C P U s to p
ID L E N = 1
FSYSO N =1
fS Y S o n
fT B C o n
fS U B o n
SLO W
fS Y S = fL
fL o n
C P U ru n
fS Y S o n
fT B C o n
fS U B o n
fH o ff
ID L E 0
H A L T in s tr u c tio n is e x e c u te d
C P U s to p
ID L E N = 1
FSYSO N =0
fS Y S o ff
fT B C o n
fS U B o n
Rev. 1.00
35
May 14, 2012