
DocID024597 Rev 5
RM0351
Real-time clock (RTC)
1230
except if the TAMPxNOERASE bit is set, or if TAMPxMF is set in the RTC_TAMPCR
register.
Tamper detection initialization
Each input can be enabled by setting the corresponding TAMPxE bits to 1 in the
RTC_TAMPCR register.
Each RTC_TAMPx tamper detection input is associated with a flag TAMPxF in the RTC_ISR
register.
When TAMPxMF is cleared:
The TAMPxF flag is asserted after the tamper event on the pin, with the latency provided
below:
•
3 ck_apre cycles when TAMPFLT differs from 0x0 (Level detection with filtering)
•
3 ck_apre cycles when TAMPTS=1 (Timestamp on tamper event)
•
No latency when TAMPFLT=0x0 (Edge detection) and TAMPTS=0
A new tamper occurring on the same pin during this period and as long as TAMPxF is set
cannot be detected.
When TAMPxMF is set:
A new tamper occurring on the same pin cannot be detected during the latency described
above and 2.5 ck_rtc additional cycles.
By setting the TAMPIE bit in the RTC_TAMPCR register, an interrupt is generated when a
tamper detection event occurs (when TAMPxF is set). Setting TAMPIE is not allowed when
one or more TAMPxMF is set.
When TAMPIE is cleared, each tamper pin event interrupt can be individually enabled by
setting the corresponding TAMPxIE bit in the RTC_TAMPCR register. Setting TAMPxIE is
not allowed when the corresponding TAMPxMF is set.
Trigger output generation on tamper event
The tamper event detection can be used as trigger input by the low-power timers.
When TAMPxMF bit in cleared in RTC_TAMPCR register, the TAMPxF flag must be cleared
by software in order to allow a new tamper detection on the same pin.
When TAMPxMF bit is set, the TAMPxF flag is masked, and kept cleared in RTC_ISR
register. This configuration allows to trig automatically the low-power timers in Stop mode,
without requiring the system wakeup to perform the TAMPxF clearing. In this case, the
backup registers are not cleared.
Timestamp on tamper event
With TAMPTS set to ‘1’, any tamper event causes a timestamp to occur. In this case, either
the TSF bit or the TSOVF bit are set in RTC_ISR, in the same manner as if a normal
timestamp event occurs. The affected tamper flag register TAMPxF is set at the same time
that TSF or TSOVF is set.
Edge detection on tamper inputs
If the TAMPFLT bits are “00”, the RTC_TAMPx pins generate tamper detection events when
either a rising edge or a falling edge is observed depending on the corresponding