Real-time Counter and Backup Supercap
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The real-time counter (RTC) of the EM1001 is a free-running 40-bit register that increments at a rate of 128Hz.
As a source of backup power, the EM1001 relies on a supercapacitor. Only EM1001-S devices carry this supercapacitor (see Specifications and Ordering Info).
The supercapacitor has many advantages -- it charges instantly and has a virtually unlimited lifespan. The disadvantage is that the supercapacitor is only able to sustain the RTC for several days (about 6 days for the 4F supercapacitor of the EM1001-S), which may appear insufficient. Remember, however, that the EM1001 is usually connected to the network and can always synchronize its clock* with an Internet time server or a master clock on the main server of your system. Therefore, the role of the supercapacitor is to provide the backup power during relatively short periods of power interruption, i.e. when the device is unplugged and moved to another location, or when the device is powered off over the weekend.
Your Tibbo BASIC/C application can access the RTC through the RTC (rtc.) object, which is documented in the "TIDE and Tibbo BASIC Manual".
*With the right application, that is.