CHAPTER 5 INITIALIZATION INTERFACE
User’s Manual U14272EJ3V0UM
102
5.2 Power-on Sequence
The factors that cause the V
R
4181 to switch from Hibernate mode or shutdown mode to Fullspeed mode are
called activation factors. There are five activation factors: assertion of the POWER pin, the DCD1# pin or the
GPIO(15:0) pins, or activation of the ElapsedTime or CompactFlash interrupt request. When an activation factor
occurs, the V
R
4181 asserts the POWERON pin to notify to external agents that the V
R
4181 is ready for power-on.
Three RTC clock cycles after the POWERON pin is asserted, the V
R
4181 checks the state of the
BATTINH/BATTINT# pin. If the BATTINH/BATTINT# pin’s state is low, the POWERON pin is deasserted one RTC
clock after the BATTINH/BATTINT# pin check is completed, then the V
R
4181 is not activated. If the
BATTINH/BATTINT# pin’s state is high, the POWERON pin is deasserted and the MPOWER pin is asserted three
RTC clocks after the BATTINH/BATTINT# pin check is completed, then the V
R
4181 is activated.
Figure 5-6 shows a timing chart of V
R
4181 activation and Figure 5-7 shows a timing chart of when activation fails
due to the BATTINH/BATTINT# pin’s “low” state.
Remark
While the MPOWER pin is inactive, 2.5 V power supply of the V
R
4181 (VDD_LOGIC, VDD_PLL) is not
needed. In order to reduce leak current, it is recommended to turn on/off the 2.5 V power supply of the
V
R
4181 according to MPOWER pin state.
Figure 5-6. V
R
4181 Activation Sequence (When Activation Is OK)
Reset# (Internal)
ColdReset# (Internal)
MPOW ER (Output)
BATTINH/BATTINT#
(Input)
RTC (Internal,
32.768 kHz)
Activation
of CPU
PLL (Internal)
Check
BATTINH/BATTINT#
pin
POWERON (Output)
Undefined
Stopped
Stable oscillation
Detection
of activation
factor