HT95AXXX
Rev. 1.20
15
May 26, 2004
Green mode to Normal mode:
Step 1: Set UPEN to 1
Step 2: Software delay 20ms
Step 3: Set MODE1 to 1
After Step 3, operation mode is changed to Normal
mode.
Sleep mode or Idle mode to Green mode:
Method 1: Any reset condition occurred
Method 2: Any interrupt is active
Method 3: Port A wake-up
Note: The timer 0, timer 1, RTC and dialer I/O inter-
rupt function will not work at the Idle mode be-
cause the 32768Hz crystal is stopped.
Theresetconditionsincludepoweronreset,externalre-
set, WDT time-out reset. By examining the processor
status flag, PDF and TO, the program can distinguish
between different reset conditions . Refer to the Reset
function for detailed description.
The port A wake-up and interrupt can be considered as
a continuation of normal execution. Each bit in port A
can be independently selected to wake-up the device by
mask option. Awakening from Port A stimulus, the pro-
gram will resume execution of the next instruction.
Any valid interrupts from Sleep mode or Idle mode may
cause two sequences. One is if the related interrupt is
disabled or the interrupt is enabled but the stack is full,
the program will resume execution at the next instruc-
tion. The other is if the interrupt is enabled and the stack
is not full, the regular interrupt response takes place. It is
necessary to mention that if an interrupt request flag is
set to 1 before entering the Sleep mode or Idle mode,
the wake-up function of the related interrupt will be dis-
abled.
Once a Sleep mode or Idle mode wake-up event occurs,
it will take SST delay time (1024 system clock period) to
resume to Green mode. In other words, a dummy period
is inserted after a wake-up. If the wake-up results from
an interrupt acknowledge signal, the actual interrupt
subroutine execution will be delayed by one or more cy-
cles. If the wake-up results in the next instruction execu-
tion, this will be executed immediately after the dummy
period is finished.
To minimize power consumption, all the I/O pins should
be carefully managed before entering the Sleep mode
or Idle mode.
The Sleep mode or Idle mode is initialized by the HALT
instruction and results in the following.
The system clock will be turned off.
The WDT function will be disabled if the WDT clock
source is the instruction clock.
The WDT function will be disabled if the WDT clock
source is the 32768Hz in Idle mode.
The WDT will still function if the WDT clock source is
the WDT OSC.
If the WDT function is still enabled, the WDT counter
and WDT prescaler will be cleared and recounted
again.
The contents of the on chip RAM and registers remain
unchanged.
All the I/O ports maintain their original status.
The flag PDF is set and the flag TO is cleared by hard-
ware.
Reset
There are three ways in which a reset can occur.
Power on reset.
A low pulse onto RES pin.
WDT time-out.
After these reset conditions, the Program Counter and
Stack Pointer will be cleared to 0.
To guarantee that the system oscillator is started and
stabilized, the SST (System Start-up Timer) provides an
extra-delay of 1024 system clock pulses when the sys-
tem is reset or awakes from the Sleep or Idle operation
mode.
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Reset Circuit
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Reset Configuration
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Reset Timing Chart