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 77/86
C.1.2
Variable input parameters
The RFC3610 implementation in PTM 216B requires four variable input parameters:
Source address
The 6 byte source address used to identify the sender of an authenticated message.
The source address is required in little endian (least significant byte first) format.
Input
data
(Payload
to
be
authenticated)
The authenticated payload contains source address, sequence counter, switch status
and optional data (if present). See chapter 4.6.3 for a description of the authenti-
cated payload.
Input
length
(Size
of
the
payload
to
be
authenticated)
The length of the payload to be authenticated depends on the amount of optional
data used in the telegram. This is configured via the
Configuration
register, see
chapter
6.7.3.
By default, no optional data is present and the length of the authenticated payload
is 9 byte.
Sequence counter
Each PTM 216B contains a sequence counter which is initialized to zero during pro-
duction
and
increased
for
each
telegram
that
is
sent.
The sequence counter is transmitted as part of the input data.
The receiver of PTM 216B telegrams keeps track of this counter and will accept only
telegrams with counter values higher than the highest previously used value. This
eliminates the possibility of reusing previously transmitted telegrams.
Note that the individual (identical) advertising telegrams used to encode the same
data telegram use the same sequence counter value.
Security key
Each PTM 216B is programmed with a random 16 byte security key during manufac-
turing. This key can be modified using the NFC interface, see chapter 6.7.5.
Table 12 below summarizes these parameters.
Parameter
Comment / Description
Example
Source
Address
Unique source address of the
PTM 216B module (little endian)
B819000015E2 (little endian represen-
tation of E215000019B8)
Input Data Telegram data to be authenticated
0CFFDA035D04000011
Input
Length
Length of input data (in bytes, en-
coded using 2 bytes)
0x0009
(if optional data size = 0, default)
0x000A
(if optional data size = 1)
0x000B
(if optional data size = 2)
0x000D
(if optional data size = 4)
Sequence
Counter
Incrementing counter to avoid replay
Part of the input data (byte 4 … 7)
5D040000 (little endian representa-
tion of the counter value 0000045D)
Security
Key
128 bit random key that is known
both to sender and receiver
3DDA31AD44767AE3CE56DCE2B3CE2ABB
Table 12 – Variable input parameters
