Maxim Integrated MAX32660 - Table 4-5: Wake-Up Sources for each Low-Power Mode

MAX32660 User Guide
Maxim Integrated Page 28 of 195
their state (settings) during DEEPSLEEP mode. RAM retention is disabled by default. The application can explicitly enable
RAM retention for each RAM sector using the PWRSEQ_LP_CTRL.ramret_sel[3:0]. Set PWRSEQ_LP_CTRL.ramret_sel[3:0]
fields to 1 to enable data retention for each RAM sector respectively during DEEPSLEEP mode. GPIO also retain their
configuration during DEEPSLEEP mode.
Wakeup from DEEPSLEEP can occur from an external GPIO interrupt or from a RTC alarm, both of which must be enabled
separately. Refer to Table 4-5 for Wake-up sources for each low-power mode.
The High Frequency Oscillator, HFIO, must be powered off when entering DEEPSLEEP mode. Set GCR_PM.hfiopd = 1 to
enter DEEPSLEEP mode. The 8kHz and 32.768kHz oscillators are available. Additionally, the GCR_PM.mode field should be
set to 0 prior to entering DEEPSLEEP mode.
GCR_PMR.hfiopd = 1; // Set HFIO to automatic power down for DEEPSLEEP
GCR_PMR.mode = 0; // Set mode field to ACTIVE ensure DEEPSLEEP mode is entered
SCR.sleepdeep = 1; // DEEPSLEEP mode enabled
WFI; // Enter DEEPSLEEP mode, WFI can be replaced with WFE
4.5.4 BACKUP Low Power Mode
This is the lowest power operating mode. The HFIO is disabled in BACKUP mode. The 8kHz oscillator remains on. If the
32kHz oscillator is enabled, it remains enabled during BACKUP mode. The Arm Cortex-M4 with FPU state and all system and
peripheral registers do not retain state. The RTC and AoD registers do retain state during BACKUP mode.
RAM retention in BACKUP mode requires the Retention Regulator. If RAM retention is required, enable the RAM Retention
Regulator by setting the PWRSEQ_LP_CTRL.retreg_en field to 1. Enable each RAM sector individually for data retention
during BACKUP mode by setting the PWRSEQ_LP_CTRL.ramret_sel[3:0] fields to 1. By default, the RAM sectors do not retain
state during BACKUP mode.
Wakeup from BACKUP mode can occur from an external GPIO interrupt or from an RTC alarm, both of which must be
enabled separately. Refer to Table 4-5 for Wakeup sources for each low-power mode.
Set GCR_PM.mode = 4 to immediately enter BACKUP mode.
4.5.5 Wake-Up Sources
Table 4-5, below, lists the wake-up sources for each of the low-power modes supported by the MAX32660. Wake-up from a
GPIO interrupt and the RTC alarm must be enabled by the application to wake-up the device from SLEEP, DEEPSLEEP and
BACKUP mode.
Table 4-5: Wake-Up Sources for Each Low-Power Mode
Low Power Mode
Wake-Up Source
SLEEP
DEEPSLEEP
BACKUP
Internal Interrupt
Y
N
N
External Reset
Y
Y
Y
GPIO Interrupt
Y
Y
Y
RTC Alarm
Y
Y
Y
4.6 Shutdown State
Shutdown State is not a low-power mode. It is intended to wipe all volatile memory from the device. In the Shutdown State,
internal logic gates off all internal power. There is no data, register, or RAM retention in this mode. All wakeup sources,