ATXMEGA384C3_14 Datasheet, PDF (22/125 Pages) ATMEL Corporation – 8/16-bit Atmel XMEGA C3 Microcontroller

11.3.3 Power-save Mode
Power-save mode is identical to power down, with one exception. If the real-time counter (RTC) is enabled, it will keep
running during sleep, and the device can also wake up from either an RTC overflow or compare match interrupt.
11.3.4 Standby Mode
Standby mode is identical to power down, with the exception that the enabled system clock sources are kept running
while the CPU, peripheral, and RTC clocks are stopped. This reduces the wake-up time.
11.3.5 Extended Standby Mode
Extended standby mode is identical to power-save mode, with the exception that the enabled system clock sources are
kept running while the CPU and peripheral clocks are stopped. This reduces the wake-up time.
XMEGA C3 [DATASHEET]
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Atmel-8361F-AVR-ATxmega384C3-Datasheet–11/2014