Exiting LPM3.5 and LPM4.5 Modes
443
SLAU356I – March 2015 – Revised June 2019
Copyright © 2015–2019, Texas Instruments Incorporated
Power Control Manager (PCM)
8.21 Exiting LPM3.5 and LPM4.5 Modes
Exiting from LPM3.5 and LPM4.5 modes causes a POR event, which forces a complete reset of the
system. Therefore, it is the application responsibility to properly reconfigure the device upon exit from
LPM3.5 and LPM4.5 modes. The wake-up times from LPM3.5 and LPM4.5 modes are significantly longer
than the wake-up time from the other low-power modes (see the device-specific data sheet). Therefore,
the use of LPM3.5 and LPM4.5 modes should be restricted to very low duty cycle events. Any enabled
wake-up event causes an exit from LPM3.5 and LPM4.5 modes.
shows the different wake-up sources that are supported for the LPM3.5 and LPM4.5 exit.
The basic steps for exit from LPM3.5 and LPM4.5 modes follow. Details about the operation of RTC,
WDT, and Digital I/O during LPMx.5 modes can be found in the respective module chapters.
•
LPM3.5 and LPM4.5 wake-up events (for example, I/O wake-up interrupt or RTC event) cause a POR
event in the system, which reinitializes the complete system. All peripheral registers are set to their
default conditions.
•
The PCMCTL0 register is cleared.
•
The I/Os configured at entry into LPM3.5 and LPM4.5 modes retain their pin conditions due to
LOCKLPM5 = 1. Keeping the I/O pins locked ensures that all pin conditions remain stable upon
entering the active mode regardless of the default I/O register settings. All other port configuration
register settings such as PxDIR, PxREN, PxOUT, PxDS, PxIES, and PxIE contents are lost.
•
When in active mode, the I/O configuration and I/O interrupt configuration that was not retained during
LPM3.5 and LPM4.5 modes should be restored to the values before entering LPM3.5 and LPM4.5
modes.
•
If LPM3.5 was entered, the RTC interrupt configuration that was not retained in LPM3.5, should also
be restored to the values before entering LPM3.5.
•
At this point, the LOCKLPM5 and LOCKBKUP bits can be cleared. This releases the I/O pin
conditions, as well as, the port and RTC interrupt configurations.
•
NVIC interrupt enable register should be configured for port or RTC module if interrupt servicing is
desired.
•
To enter LPM3.5 or LPM4.5 mode again, the LOCKLPM5 and LOCKBKUP bits must be cleared before
re-entry, and the entry sequence to LPM3.5 and LPM4.5 should be followed.
NOTE:
Any enabled wake-up event causes the device to exit LPM3.5 or LPM4.5 mode, regardless
of priority. This differs from wake-up events during LPM0, LPM3, and LPM4 modes of
operation.
8.22 Supply Voltage Supervisor and Monitor and Power Modes
The high-side supply voltage supervisor and monitor (SVSMH) can be enabled as required by the
application. The SVSMH supports a full-performance mode and a low-power normal-performance mode.
The full-performance mode has faster response times at the cost of additional power. The SVSMHLP bit in
the PSS module selects the performance mode of SVSMH. See the Power Supply System (PSS) chapter
for details.
Specific power modes may require the full performance mode of SVSMH to ensure proper operation. The
PCM ensures that this is adhered to based on the power mode request. In these cases, the PCM
overrides the SVSMHLP setting. Note that the bit itself is not modified, only its effects on the system.
summarizes the SVSMH options with respect to each power mode.
(1)
Full performance mode is forced automatically by the PCM. SVSMHLP bit is do not care.
Table 8-9. SVSMH Performance and Power Modes
Mode
PSS Bandgap
SVSMH
SVSMH Mode
When Enabled
AM_LDO_VCORE0
Static
Optional
Full performance
(1)
AM_LDO_VCORE1
Static
Optional
Full performance
(1)
AM_DCDC_VCORE0
Static
Optional
Full performance
(1)