CHAPTER 10 POWER MANAGEMENT UNIT (PMU)
User’s Manual U14272EJ3V0UM
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10.5 Power-on Control
The causes of CPU core activation (mode change from shutdown mode or Hibernate mode to Fullspeed mode)
are called activation factors. There are twenty activation factors: a power switch interrupt (POWER), sixteen types of
GPIO activation interrupts (GPIO(15:0)), a DCD interrupt (DCD#), a CompactFlash interrupt, and an ElapsedTime
interrupt.
Battery low detection (BATTINH/BATTINT# pin check) is a factor that prevents CPU core activation.
The period (power-on wait time) in which the POWERON pin is active at power-on can be specified by using
PMUWAITREG register. After RTCRST, by which the CPU core is initialized, the period is set as 343.75 ms. Power-
on wait time can be specified when activation is caused by sources other than RTCRST.
When MPOWER signal is at low level (Hibernate mode or during CPU core activation), to stop supplying voltage
to the 2.5 V power-supply systems is recommended to reduce leak current. This means that this power supply can be
0 V while the MPOWER signal is inactive. The following operation will not be affected by supplying voltage of 2.3 V or
more to this power supply within the period from when the MPOWER signal becomes active to when PLL starts
oscillation.
Caution
When the CPU core enters the Hibernate mode by executing the HIBERNATE instruction, if an
activation factor occurs simultaneously, the CPU core may be activated without asserting the
POWERON signal after the MPOWER signal is once de-asserted. Moreover, if RSTSW#, which is
not an activation factor of the Hibernate mode, is asserted at the same time a transition to the
Hibernate mode by executing the HIBERNATE instruction occurs, the CPU core may be activated
without asserting the POWERON signal after the MPOWER signal is de-asserted once.