DocID13902 Rev 15 84/1128
RM0008 Backup registers (BKP)
89
6.4.3 Backup control register (BKP_CR)
Address offset: 0x30
Reset value: 0x0000 0000
Note: Setting the TPAL and TPE bits at the same time is always safe, however resetting both at
the same time can generate a spurious Tamper event. For this reason it is recommended to
change the TPAL bit only when the TPE bit is reset.
6.4.4 Backup control/status register (BKP_CSR)
Address offset: 0x34
Reset value: 0x0000 0000
Bit 8 ASOE: Alarm or second output enable
Setting this bit outputs either the RTC Alarm pulse signal or the Second pulse signal on the
TAMPER pin depending on the ASOS bit.
The output pulse duration is one RTC clock period. The TAMPER pin must not be enabled
while the ASOE bit is set.
Note: This bit is reset only by a Backup domain reset.
Bit 7 CCO: Calibration clock output
0: No effect
1: Setting this bit outputs the RTC clock with a frequency divided by 64 on the TAMPER pin.
The TAMPER pin must not be enabled while the CCO bit is set in order to avoid unwanted
Tamper detection.
Note: This bit is reset when the V
DD
supply is powered off.
Bit 6:0 CAL[6:0]: Calibration value
This value indicates the number of clock pulses that will be ignored every 2^20 clock pulses.
This allows the calibration of the RTC, slowing down the clock by steps of 1000000/2^20
PPM.
The clock of the RTC can be slowed down from 0 to 121PPM.
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Reserved
TPAL TPE
rw rw
Bits 15:2 Reserved, must be kept at reset value.
Bit 1 TPAL: TAMPER pin active level
0: A high level on the TAMPER pin resets all data backup registers (if TPE bit is set).
1: A low level on the TAMPER pin resets all data backup registers (if TPE bit is set).
Bit 0 TPE: TAMPER pin enable
0: The TAMPER pin is free for general purpose I/O
1: Tamper alternate I/O function is activated.
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Reserved
TIF TEF
Reserved
TPIE CTI CTE
rr rwww
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