USER MANUAL
PTM 216B – BLUETOOTH
®
PUSHBUTTON TRANSMITTER MODULE
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F-710-017, V1.0
PTM 216B User Manual | v1.0 | February 2022 | Page 18/86
Whenever the receiver receives a data telegram with a resolvable private address (identi-
fied by the most significant bits of the address field being set to
0b10
), it will itself generate
a 24 bit
hash
from the 24 bit
prand
sequentially using each IRK known to it (i.e. the IRK of
each device that has been learned into it).
If an IRK matches (i.e. when
prand
is encoded with the IRK then the result matches
hash
),
then the receiver has established the IRK used by the transmitter and thereby the identity
of the transmitter.
So conceptually the IRK takes the role of the device address of the transmitter while
prand
and
hash
provide a mechanism for the receiver to select the correct IRK among the set of
IRK known to it.
This mechanism is illustrated in Figure 13 below.
Figure 13 – Resolving private addresses
Refer to Appendix B for an example of resolving a resolvable private address.
Note that commissioning telegrams (as described in chapter 5.3.2) always use static source
addresses (as described in chapter 4.4.1) since they establish the device identity and con-
tain the IRK in the payload.
Check Sum
The 3 byte BLE Check Sum is used to verify data integrity of received BLE radio telegrams.
It is calculated as CRC (cyclic redundancy check) of the BLE Header, Source Address and
Payload fields.
