67.4.2.1 Backup Mode

Backup mode achieves the lowest power consumption in the system with limited functionality.

In this mode, only the backup area is powered, maintaining the RTC, the back-up registers, the back-up SRAM and the security module running. This mode is entered by shutting down all the power rails except the VDDBU (refer to the section Shutdown Controller (SHDWC)). To exit Backup mode, the SHDN pin (connected to the enable of the external Power Management IC) must be driven high by an internal event (RTC) or by one of the external events listed below:

• WKUP0 to WKUP9 pins (level transition, configurable debouncing)
• Character received on a serial com receiver (RXLP)
• Analog comparison

Backup mode functionality has been extended with the possibility to keep the DDR memory in Self-refresh state.