USER MANUAL
STM 550B / EMSIB - EASYFIT MULTISENSOR FOR IOT APPLICATIONS (2.4 GHZ BLE)
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F-710-017, V1.0
STM 550B / EMSIB User Manual | v1.3 | June 2020 | Page 65 / 115
9.5.14
SECURITY_CFG
The SECURITY_CFG register allows the configuration of the security parameters used by
STM 550B. Figure 46 below shows the structure of the SECURITY_CFG register.
SECURITY_CFG (Default Setting: 0x00)
Bit 7 Bit 6 Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
RFU
RPA
SECURITY_MODE
Figure 46
–
SECURITY_CFG register
The encoding for the SECURITY_MODE bit field is shown in Table 20 below.
STM 550B currently always uses authentication with a 32 bit sequence counter generating a
32 bit message integrity code (MIC) based on a 128 bit random device-unique security key.
Other security modes might be added in the future.
SECURITY_MODE Security Mode
0b0000 (Default)
Authentication with 32 bit sequence counter and 32 bit MIC
Others
Reserved (do not use)
Table 20
–
SECURITY_MODE bit field encoding
STM 550B uses by default a device-unique static source address (constant throughout the
lifetime of the device) starting with 0xE500 as described in chapter 5.4.5.
STM 550B can alternatively use a resolvable private address (RPA) to obfuscate the origin
of its data telegrams as described in chapter 5.4.6 and in Appendix C.
The selection between these two modes is done using the RPA bit field as shown in Table
21 below.
RPA
Address Mode
0b0 (Default)
Use Static Source Address
0b1
Use Resolvable Private Address (RPA)
Table 21
–
RPA bit field encoding
