Doc. No: Unex-QSG-21-003
23/30
A printed version of this document is an uncontrolled copy
© 2023 Unex Technology Corporation – Company Confidential
Figure 9: External 1PPS input pins
9.9.
BOOTSTRP
The BOOTSTRP pin (P46) will be sampled during the first 10ms upon power up. If the
BOOTSTRP is pulled HIGH (3.3V), the SOM-352 system will enter DFU (Device Firmware
Upgrade) mode and allows the host system to flash the entire NAND via USB0 at once;
otherwise, it will boot normally from NAND.
It is recommended to use a 0 Ohm resistor to pull-up the BOOTSTRP pin. The pull-up
resistor of BOOTSTRP should not exceed 5 KOhm.
9.10.
Tamper Detection (Optional)
The tamper detection function will be supported by project base. It is disabled by default.
The SOM-352 has to be powered up for the tamper detection function to work. The
design and implementation of a backup power source is not in the product scope and
should be considered by the user.
The tamper detection mechanism is part of the FIPS 140-2 Level 3 security
requirements. The tamper detection itself is carried out entirely in HW. On SW level, there
is only an API that allows enabling the tamper detection mechanism. Calling this API will
move tamper HW state from the testing mode to the production mode. Once called, it
1PPS (P49)
1
2
3
4
5
6
7
1PPS (P5)
