Power Modes
426
SLAU356I – March 2015 – Revised June 2019
Copyright © 2015–2019, Texas Instruments Incorporated
Power Control Manager (PCM)
8.4.3 LPM3 and LPM4
Similar to LPM0, processor execution is halted during LPM3 and LPM4. LPM3 and LPM4 modes are
useful for relatively infrequent processor activity followed by long periods of low-frequency activity, better
known as low-duty-cycle applications. The wake-up time from LPM3 and LPM4 is longer than wake-up
times from LPM0, but the average power consumption is significantly lower. See the device-specific data
sheet for wake-up time from different low power modes. DC/DC regulator operation is not supported in
LPM3 and LPM4 modes. See
for all supported LPM3 and LPM4 transitions. LPM3 or LPM4 exit
always returns the device to the original active mode at the time of LPM3 or LPM4 entry. LPM3 and LPM4
modes are called Deep Sleep modes in Arm terminology.
MSP432P4xx family of devices have two different implementations for LPM3 and LPM4 depending on the
number of peripheral groups implemented in the devices.
8.4.3.1
LPM3 and LPM4 in MSP432P401R and MSP432P401M Devices
In MSP432P401R and MSP432P401M devices, LPM3 mode restricts maximum frequency of device
operation to 32.768 kHz. Only RTC and WDT modules are functional from the low-frequency clock
sources (LFXT, REFO, and VLO) while in LPM3. All other peripherals are disabled and high-frequency
clock sources are turned off in LPM3. LPM4 mode is entered when the device is programmed for LPM3
with RTC and WDT modules disabled. All clock sources are turned off in LPM4 mode and no peripheral
functionality is available.
All SRAM banks and blocks that are enabled for data retention during LPM3
or LPM4 and all peripheral registers retain the data through LPM3 and LPM4 modes. The device I/O
pin states are also latched and retained in LPM3 and LPM4 modes.
lists the different
LPM3 and LPM4 wake-up sources available on these devices.
8.4.3.2
LPM3 and LPM4 in All Other MSP432P4xx Devices
In all other MSP432P4xx devices, LPM3 mode restricts maximum frequency of device operation to
128 kHz. Most of the peripherals are functional from the low-frequency internal clock sources (LFXT,
REFO, and VLO) or low-frequency external clocks (maximum of 128 kHz) while in LPM3. In LPM4 most of
the peripherals can be operated from low-frequency external clock sources up to 128 kHz. All high-
frequency clock sources are turned off in LPM3 and LPM4. Peripherals are grouped into different
peripheral groups to provide flexibility to application optimize the system power. See device specific data
sheet for how peripherals are grouped into different power-groups.
All SRAM banks and blocks that are
enabled for data retention during LPM3 or LPM4 and all peripheral registers retain the data through
LPM3 and LPM4 modes. When no peripherals are used during LPM3 or LPM4 modes, the device
I/O pin states are also latched and retained.
lists the different LPM3 and LPM4 wake-up
sources available on these devices.
8.4.4 LPM3.5 and LPM4.5
LPM3.5 and LPM4.5 modes provide the lowest power consumption possible but at reduced functionality.
In LPM3.5 mode, all peripherals are disabled and powered down except for the RTC and WDT, which can
be optionally enabled by the application and clocked out of low-frequency clock sources (LFXT, REFO,
and VLO). Furthermore, the device is brought down to the core voltage level 0. Wake up is possible
through any of the wake-up events mentioned in
LPM3.5 mode does not retain any
peripheral register data.
In LPM3.5 mode however,
depending on the SRAM organization, Bank 0 or
Block 0 of SRAM is retained for application's use as a backup memory and also device I/O pin
states are latched and retained.
In LPM4.5 mode, all peripherals and clock sources are powered down and the internal voltage regulator is
switched off. Wake up is possible through any of the wake-up events mentioned in
.
LPM4.5
mode does not retain any SRAM or peripheral register data, but device I/O pin states are latched
and retained.
Any essential data must be stored to flash before entering LPM4.5 mode.
LPM3.5 and LPM4.5 modes are useful for complete power down or simple time keeping over long periods
of time with infrequent wake-up activity. See
for valid LPM3.5 and LPM4.5 transitions.
LPM3.5 and LPM4.5 modes are called Stop or Shut Down modes in Arm terminology.