25.6.10.4.2 Active Tamper Detection
The RTC provides a mean of detecting broken traces on the PCB , also known as Active Tamper Detection. In this mode, a generated internal RTC signal can be directly routed over critical components on the board using RTC OUT output pin to one RTC INn input pin. A tamper condition is detected if there is a mismatch on the generated RTC signal.
The Active Tamper Detection mode and the generation of the RTC signal is enabled by setting the RTCOUT bit in the Control B register (CTRLB.RTCOUT).
Enabling Active Tamper Detection requires the following steps:
- Enable the RTC prescaler output by writing a one to the RTC Out bit in the Control B register (CTRLB.RTCOUT). The I/O pins must also be configured to correctly route the signal to the external pins.
- Select the frequency of the
output signal by configuring the RTC Active Tamper Detection Frequency field in
the Control B register (CTRLB.ACTF)
- Enable the tamper input n (INn) in Active Tamper Detection by writing 3 to the corresponding Input Action field in the Tamper Control register (TAMPCTRL.INnACT).
- Select Active Tamper Detection Monitoring Source (TrustRAM or INn/OUTn tamper pins) using ALSIn bit of TAMPCTRLB register
- Enable Active Tamper Detection by setting the CTRLB.RTCOUT bit