TAMPC supports an active shield to protect against physical access to the device and its connections on the PCB level.
- A TAMPC event is generated.
- A chip reset is triggered and the SECTAMPER value in the reset reason register indicates what happened, depending on the status of the register PROTECT.EXTRESETEN.CTRL.
A channel in the active shield detector consists of a signal propagating from an output pin to an input pin. The channels are enabled using the CH[i] fields in the register ACTIVESHIELD.CHEN. The GPIO pins reserved for the active shield detector channels must be configured before the channels are ready for use. Pin direction and CTRLSEL must be set according to the register interface in the GPIO peripheral. For more information about reserved active shield detector pins, see Pin assignments. Pins reserved for the active shield detector can be used as generic GPIO pins when the channel is unused.
The active shield detector contains a Pseudo-Random Bit Sequence (PRBS) generator. A PRBS signal is generated on an output pin at each rising edge of the 32 KHz clock. The signal is routed through an external shield to an input pin. The signal on the input pin is sampled on the falling edge of the 32KHz clock. If the sampled signal does not match the transmitted signal, a channel in the external shield is assumed broken and a tamper event is generated.