Power Management
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1.5.5 Power Configurations

The power-saving features described in the previous sections, such as peripheral clock gating, and

on-chip memory power down to name a few, can be combined to form a power configuration. Many

different power configurations can be created by enabling and disabling different power domains and clock

domains, however, this section defines some basic power configurations that may be useful. These are

shown and described in Table 1-31. Please note that there is no single instruction or register that can

place the device in these power configurations. Instead, these power configurations are achieved by

modifying multiple registers.

NOTE: Before you change the power configuration, make sure that there is a method for the device

to exit the power configuration. After exiting a power configuration, your software may have

to take additional steps to change the clock and power configuration for other domains.

NOTE: The on-chip Bootloader idles all peripherals and CPU ports at startup. It enables some

peripherals as it uses them. Your application code should check the idle configuration of

peripherals and CPU ports before using them to be sure these are not idle.

Table 1-31. Power Configurations

Stepsto Enter Clock AvailableMethods for
Power PowerDomain andPower Changing/ExitingClock and
Configuration State ClockDomain State Configuration PowerConfiguration
RTConly mode DVDDRTC,LDOI, OnlyRTC clock is SetLDO_PD and A.RTCinterrupt
andCVDDRTC running BG_PDbits in B.WAKEUP pin
poweredall others RTCPMGTregister
powered-down
IDLE3 All power domains RTC clock domain Idleperipheral domain A. WAKEUP pin
on enabled
Otherclock domains Idle CPU domain B.RTC interrupt
disabled.Clock
generatordomain
disabled(BYPASS
MODEand PLL
powerdown).
PLLin BYPASS MODE C.External hardware interrupt (INT0
PLLpowerdown or INT1).
Masterclock disable D.Hardware Reset
Executeidle instruction
IDLE2 All power domains RTC clock domain Idle peripheral domains A.WAKEUP pin
on enabled
Clockgenerator domain Idle CPU domain B. RTC interrupt
enabled(PLL_MODE)
Otherclock domains Execute idle instruction C.External hardware interrupt
disabled (INT0,INT1).
D.Any unmasked peripheral
interrupt.
E.Hardware Reset
Active All power domains Allclock domains Turn on all power
on enabled domains
Enableall clock
domains
50 SystemControl SPRUFX5A–October 2010 –Revised November 2010
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