RM0090 Real-time clock (RTC)
Doc ID 018909 Rev 4 646/1422
Note: WUT = Wakeup unit counter value. WUT = (0x0000 to 0xFFFF) + 0x10000 added when
WUCKSEL[2:1 = 11].
Bits 7, 6 and 4 of this register can be written in initialization mode only (RTC_ISR/INITF = 1).
Bits 2 to 0 of this register can be written only when RTC_CR WUTE bit = 0 and RTC_ISR
WUTWF bit = 1.
It is recommended not to change the hour during the calendar hour increment as it could
mask the incrementation of the calendar hour.
ADD1H and SUB1H changes are effective in the next second.
This register is write protected. The write access procedure is described in RTC register
write protection on page 630.
23.6.4 RTC initialization and status register (RTC_ISR)
Address offset: 0x0C
Power-on reset value: 0x0000 0007
System reset value: Not affected except INIT, INITF and RSF which are cleared to 0.
Bit 3 TSEDGE: Timestamp event active edge
0: TIMESTAMP rising edge generates a timestamp event
1: TIMESTAMP falling edge generates a timestamp event
TSE must be reset when TSEDGE is changed to avoid unwanted TSF setting
Bits 2:0 WUCKSEL[2:0]: Wakeup clock selection
000: RTC/16 clock is selected
001: RTC/8 clock is selected
010: RTC/4 clock is selected
011: RTC/2 clock is selected
10x: ck_spre (usually 1 Hz) clock is selected
11x: ck_spre (usually 1 Hz) clock is selected and 2
16
is added to the WUT counter value
(see note below)
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
Reserved
RECAL
PF
r
1514131211109876543210
Res.
TA MP
2F
TA MP
1F
TSOVF TSF WUTF ALRBF ALRAF INIT INITF RSF INITS SHPF
WUT
WF
ALRB
WF
ALRA
WF
rc_w0 rc_w0 rc_w0 rc_w0 rc_w0 rc_w0 rc_w0 rw r rc_w0 r rc_w0 r r r
Bits 31:17 Reserved
Bit 16 RECALPF: Recalibration pending Flag
The RECALPF status flag is automatically set to ‘1’ when software writes to the RTC_CALR
register, indicating that the RTC_CALR register is blocked. When the new calibration
settings are taken into account, this bit returns to ‘0’. Refer to Section : Re-calibration on-the-
fly.
Bit 15 Reserved, must be kept at reset value.
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