Libelium Waspmote Technical Manual page 62

Hardware
As well as relative alarms, periodic alarms can be programmed by giving a time measurement, so that Waspmote
reprograms its alarm automatically each time one event is triggered.
The RTC chosen is the Maxim DS1337C, which operates at a frequency of 32.768 kHz (a second divisor value which
allows it to quantify and calculate time variations with high precision).
The RTC is powered by the battery. When the battery is connected, the RTC is powered on. However, the user must
keep in mind that if the battery is removed or out of load, then time data will be not maintained. This is the reason
we suggest to use RTC time as 'relative' and not 'absolute' (see Programming Guide for more info).
A coin or button battery is not needed. They have a limited life and therefore Waspmote can have a much longer
power life expectancy. This is so because the RTC is powered from the "main" battery which has a much bigger
charge.
The RTC is responsible for waking Waspmote up from sleep modes like Deep Sleep and Hibernate. This makes
possible to use its battery to just power the RTC in sleep modes. The RTC controls when the device has to wake
up and perform a particular action. This permits a consumption of 7 uA in the Hibernate mode. Please refer to
"Energy System" section for more information.
Related API libraries: WaspRTC.h, WaspRTC.cpp
All information about their programming and operation can be found in the RTC Programming Guide.
All the documentation is located in the Development section in the Libelium website.
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