Rtc Write Protection Register (Rtc_Wpr) - STMicroelectronics STM32F405 Reference Manual

RM0090
Note: This register can be written only when ALRBWF is set to 1 in RTC_ISR, or in initialization
mode.
This register is write protected. The write access procedure is described in
write protection on page
26.6.10

RTC write protection register (RTC_WPR)

Address offset: 0x24
Backup domain reset value: 0x0000 0000
31 30 29
15 14 13
Bits 31:8 Reserved, must be kept at reset value.
Bits 7:0 KEY: Write protection key
This byte is written by software.
Reading this byte always returns 0x00.
Refer to
protection.
26.6.11 RTC sub second register (RTC_SSR)
Address offset: 0x28
Backup domain reset value: 0x0000 0000
System reset: 0x0000 0000 when BYPSHAD = 0. Not affected when BYPSHAD = 1.
31 30 29
r r r
15 14 13
r r r
Bits 31:16 Reserved
Bits 15:0 SS: Sub second value
SS[15:0] is the value in the synchronous prescaler's counter. The fraction of a second is
given by the formula below:
Second fraction = ( PREDIV_S - SS ) / ( PREDIV_S + 1 )
Note: SS can be larger than PREDIV_S only after a shift operation. In that case, the correct
794.
28 27 26 25
12 11 10 9
Reserved
RTC register write protection
28 27 26 25
r r r r
12 11 10 9
r r r r
time/date is one second less than as indicated by RTC_TR/RTC_DR.
DocID018909 Rev 11
24 23 22 21
Reserved
8 7 6 5
w w w
for a description of how to unlock RTC register write
24 23 22 21
Reserved
r r r r
8 7 6 5
SS[15:0]
r r r r
Real-time clock (RTC)
RTC register
20 19 18 17
4 3 2 1
KEY
w w w w
20 19 18 17
r r r r
4 3 2 1
r r r r
16
0
w
16
r
0
r
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