The MCU enters the hibernation mode when the hibernation request bit in the control register is set. The device can also enter the hibernation mode when power is dynamically removed, while Vbat is connected and the registers are configured accordingly. When the MCU is in the hibernation mode, the HIB pin is asserted. This pin can be used to indicate to other external devices that the MCU is in hibernation mode and its core, along with other system peripherals, are powered off. The device will continue to stay in hibernation mode until one of the wake conditions occur. There are three wake conditions; assertion of the external wake signal, occurrence of an RTC match, or detection of low battery on the Vbat terminal. After the device wakes up, HIB pin is de-asserted and an internal power-on reset signal is issued so that the application code can begin to execute.