One of the major advantages of the tamper pins is the ability to monitor a switch in very low power conditions. Typically a pushbutton used to wake up a battery powered device would require an external pullup or pulldown resistor with a power source in order to generate an EXTI type GPIO interrupt.
The tamper internals eliminate this with an internal resistor and power source. The internal resistor is only powered at sampling intervals, reducing leakage current through the pin connection. There is also a debounce type sampling count to filter a short term contact, such as handling the package.
When micro-amps count the tamper power consumption makes a difference over GPIO/EXTI/WKUP configuration. Parasitic current leakage on external pins is always a headache with very low power devices when main power is cut.
The other advantage is the timestamp function. Assuming the RTC is running the date and time of the first tamper event is logged into the RTC and preserved as long as the VBAT supply is powered. This allows a very low power device that wakes at fixed intervals to log an external event without waking up. I've used this to track remote site cabinet open events which are expected but don't require device intervention (i.e. service techs , etc.).
Jack Peacock
