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User Manual May 2019 | Page 15/28
USER MANUAL
Energy Harvesting Magnet Contact Transmitter Module
STM 320 / STM 329 / STM 320U
(Stepcode DE and later)
Remarks:
Calculation examples and values have tolerances of about +/- 20%.
Energy storage performance, power consumption and solar cell performance varies
over temperature.
Energy storage performance degrades over life time, especially if energy storage is
long time exposed to very high temperatures. High temperatures will accelerate ag-
ing, each 10 K increase from 25°C will half expected life time. Very low temperature
will temporary reduce capacity of energy store and this leads to considerable shorter
dark time operation.
Short wake-up cycles (e.g. 1 s) and transmit intervals (e.g. 1 s) significantly reduce
energy storage performance, for this use case an external power supply is recom-
mended
3.5.1
Consumption in secure mode
Enhanced security mode requires more energy due to encryption algorithm computing time
and extended telegram length because of CMAC. This added consumption is compensated
by reducing the subtelegram count to 2.
3.6
Storing the Rolling code counter
For the enhanced security features a RLC counter needs to be stored in non-volatile mem-
ory. For security reasons the RLC counter is incremented by every transmitted telegram.
Together with the CMAC the RLC ensures that messages cannot be reproduced or forged.
The RLC is stored in the Dolphin chip flash memory. To improve the endurance of the flash
memory and also the energy budget not every increment is saved to the non-volatile flash
memory. During deep sleep the RLC is stored in RAM0 memory.
