Exiting LPM3 or LPM4 Mode – Interrupt Based Wakeup
441
SLAU356I – March 2015 – Revised June 2019
Copyright © 2015–2019, Texas Instruments Incorporated
Power Control Manager (PCM)
clock requests and any new user POR [pin-based reset (RSTn/NMI) and debugger reset request
(DBGRSTREQ)] requests from entering the system.
5. The PCM then checks the current clock settings to determine if there are any outstanding clock
requests for clocks not supported during LPM3 mode. The clock invalid flag, LPM_INVALID_CLK_IFG,
is set when there are outstanding clock requests for clocks that are in violation of the LPM3 mode and
FORCE_LPM_ENTRY = 0. The PCM does not enter the LPM3 mode when this condition occurs. If the
clock settings are not in violation of the system clocks or when FORCE_LPM_ENTRY = 1, then the
PCM starts to initialize the transition to LPM3. In this case, LPM_INVALID_CLK_IFG is not set. In the
event of LPM_INVALID_CLK_IFG being set to 1, and LPM_INVALID_CLK_IE = 0, the system enters
the LPM0 mode corresponding to the active mode, until an interrupt event wakes it up.
6. LPM4 mode is entered by programming for LPM3 mode with disabled RTC and WDT modules. LPM4
mode cannot be entered when the clock requirements for LPM3 mode are not met.
7. The PCM then adjusts the power supply system for the LPM3 or LPM4 modes. When the power supply
system has been adjusted and is stable, the PCM unlocks the PCMCTL0 and CS registers and
enables clock requests. When the PCM completes its operations, the PMR busy flag is cleared
(PMR_BUSY = 0), and the PCMCTL0 and CS registers are unlocked.
NOTE:
Before LPM3 entry, the application must configure the watchdog timer in the interval timer
mode and not in the watchdog mode. Failure to do so might trigger a soft or hard reset
condition during the low-power mode transitions. This reset can result in the system being in
an indeterministic state.
NOTE:
Clocks brought out on device pins also cause clock requests to the respective clocks in the
device. The application should therefore treat these similar to other peripherals when
entering LPM3 or LPM4 modes.
NOTE:
MSP432P401R and MSP432P401M devices only: Application must ensure that the analog
modules (ADC14 or COMP_E) are disabled before entering LPM3 or LPM4 modes, if they
are configured to use the internal reference. This must be done regardless of the
FORCE_LPM_ENTRY bit setting.
8.17 Exiting LPM3 or LPM4 Mode – Interrupt Based Wakeup
Multiple interrupt sources of wakeup from LPM3 and LPM4 modes are available.
See
for wake-up sources from LPM3 or LPM4 mode for MSP432P401R and MSP432P401M
devices.
See
for wake-up sources from LPM3 or LPM4 modes for all other MSP432P4xx devices.
After wakeup, the device returns to the active mode from which LPM3 or LPM4 entry was initiated.
8.18 Exiting LPM3 or LPM4 Mode – Interrupt From Device Pins
In MSP432P401R and MSP432P401M devices, wakeup from LPM3 or LPM4 is possible when the port
pins are configured for GPIO function or digital peripheral function, by configuring the PxSELy and PxIE
registers of the port module. With this, it is possible to wake up from LPM3 or LPM4 modes on these
devices upon GPIO input events or upon input events of digital peripherals like UART RXD change from 1
to 0 or timer capture event. The device exits LPM3 or LPM4 modes at the input trigger event.
In all other MSP432P4xx devices, wakeup from LPM3 or LPM4 modes is possible only when the port pins
are configured for GPIO function (PxSEL0 = PxSEL1 = 0) together with proper configuration of PxIE
registers. Digital peripherals that need to be operational during LPM3 or LPM4 modes are configured by
software and the respective peripheral groups remain powered. The peripherals that are operational can
wake the device up from LPM3 or LPM4 modes through regular interrupts. For example, UART receive
complete interrupt or timer capture interrupt.