USER MANUAL
TCM 410J
–
Transceiver Module
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TCM 410J User Manual | v2.3 | June 2022 | Page 21 / 46
3.2.3
Processing of received messages with implicit RLC
If a remote device does not transmit the Rolling Code (RLC) as part of the secure message
(implicit RLC, legacy feature that is not recommended for new designs), then TCM 410J has
to track the most recently received RLC.
Under special circumstances (for instance power-down or being outside of radio range), it is
possible that TCM 410J might not receive all messages from the remote device and there-
fore its tracked RLC is lower than the one that is used by the remote device.
TCM 410J provides the following functionality for this case:
◼
Temporary RLC window extension
TCM 410J will by default try up to 128 Rolling Code values to address this case. If
this is insufficient (for instance due to an extended power down), then the number
of Rolling Code (RLC) that will be tried can be extended for the next received tele-
gram from each device setup in the secure link table.
The extended Rolling Code search window can be enabled or disabled using the
ESP3 command CO_WR_TEMPORARY_RLC_WINDOW as described in Reference [2].
◼
Security RLC window counter (Amount of failed CMAC validation attempts)
This value defines the count of the wrong CMAC validation attempts, before TCM
410J sends the ESP3 Event CO_EVENT_SECUREDEVICES to the connected host to
signalize that the RLC might not be synchronized anymore.
Figure 2 shows the processing of received messages with implicit RLC.
