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User Manual May 2019 | Page 29/49
USER MANUAL
Scavenger Transmitter Module
STM 330 / STM 331 STM 331U / STM 332U / STM 333U
(Stepcode DE and later)
VAES encryption
The security features are added to the communication by encapsulating the payload and
Teach-in telegram payload into a secured telegram. The payload itself is not changed and
corresponds to the standard mode payload like defined in chapter 3.10.1.
Please refer to the EnOcean Security Specification for details:
https://www.enocean.com/security-specification
3.11.2
Secure Teach-In
To process secure communication with a receiver STM 3xy has to send a secure teach-in
telegram to the receiver and so inform him about the used security profile, AES key and
initial RLC counter. The secure teach-in has to take place before any other communication
can be executed (profile teach-in included). Press the LRN button to trigger the transmis-
sion of the teach-in telegram. Take into account the information in chapter 3.1. The secure
teach-in and then the profile teach-in are transmitted. The profile teach-in telegram is al-
ready protected by advanced security features. Profile teach-in telegram corresponds to the
telegram defined in chapter 3.10.2.
The behaviour of the LRN button is the following:
1.
Button is pressed
2.
Secure teach-in is send.
3.
Profile teach-in is send.
For more information on the structure of the teach-in telegram please refer to chapter 4.2
of .
3.12
Transmit timing
The setup of the transmission timing allows avoiding possible collisions with data packages
of other EnOcean transmitters as well as disturbances from the environment. With each
default transmission cycle, 3 identical sub-telegrams are transmitted within 40 ms. Trans-
mission of a sub-telegram lasts approximately 1.2 ms. The delay between the three trans-
mission bursts is affected at random.
3.12.1
Secure transmission timing
In secure mode the transmission cycle includes 2 identical subtelegrams are transmitted
within 20 ms. This is required to compensate the additional energy requirement of en-
hanced security computing and additional payload. The transmission of a enhanced secure
subtelegram lasts approximately 1.6 ms.
