Backup RAM (SRAM)
Enabling Backup RAM (SRAM)
Backup RAM is disabled by default, since it does require some maintenance power which may not be desired on some low-powered projects. Backup RAM consumes roughly 5uA or less on VIN and 9uA or less on VBAT.
Backup RAM is enabled with this code in setup():
void setup()
{
System.enableFeature(FEATURE_RETAINED_MEMORY));
}