CHAPTER 4 CLOCK GENERATION FUNCTION
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User’s Manual U15109EJ3V0UD
4.5 Oscillation Stabilization Time
The following shows the methods for specifying the length of the oscillation stabilization time required to stabilize
the oscillator following cancellation of STOP mode.
(1) Cancellation by non-maskable interrupt or by unmasked maskable interrupt request
STOP mode is canceled by a non-maskable interrupt or an unmasked maskable interrupt request. When an
interrupt is input, the counter (watchdog timer) starts counting and the count time is the length of time that must
elapse until the oscillator’s clock output stabilizes.
The oscillation stabilization time is set by the oscillation stabilization time select register (OSTS).
Oscillation stabilization time
≅
WDT count time
After the specified amount of time has elapsed, system clock output starts and processing branches to the
interrupt handler address.
Figure 4-2. Oscillation Stabilization Time
STOP mode is set
Oscillator is stopped
Interrupt input
Oscillation wave
Main clock
STOP status
Oscillation stabilization time
count
(2) Use of RESET pin to allocate time (RESET pin input)
For allocating time with RESET pin, refer to
CHAPTER 14 RESET FUNCTION
.
The oscillation stabilization time is 2
18
/f
XX
, in accordance with the value of the OSTS register after reset.