Espressif ESP32 Technical Reference Manual page 699

31 Low-Power Management (RTC_CNTL)
By default, ESP32-S2 first enters the Modem-sleep mode after a system reset and can be configured to Active
mode when transmitting or receiving packets. After the CPU stalls for a while, the chip can enter several low-
power modes. It is up to the user to select the mode that best balances power consumption, wake-up latency
and available wake-up sources. For details, please see Figure 31-10.
Please note that the predefined power mode could be further optimized and adapted to any application.
31.3.10 Wakeup Source
The ESP32 supports various wake-up sources, which could wake up the CPU in different sleep modes. The
wake-up source is determined by RTC_CNTL_WAKEUP_ENA, as shown in Table 31-2.
Espressif Systems 699 ESP32 TRM (Version 5.2)
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