Real-time clock (RTC)
RM0090
814/1731
DocID018909 Rev 11
Note:
This register can be written only when WUTWF is set to 1 in RTC_ISR.
This register is write protected. The write access procedure is described in
26.6.7 RTC
calibration
register (RTC_CALIBR)
Address offset: 0x18
Backup domain reset value: 0x0000 0000
System reset: not affected
Bits 31:16 Reserved
Bits 15:0
WUT[15:0]
: Wakeup auto-reload value bits
When the wakeup timer is enabled (WUTE set to 1), the WUTF flag is set every (WUT[15:0]
+ 1) ck_wut cycles. The ck_wut period is selected through WUCKSEL[2:0] bits of the
RTC_CR register
When WUCKSEL[2] = 1, the wakeup timer becomes 17-bits and WUCKSEL[1] effectively
becomes WUT[16] the most-significant bit to be reloaded into the timer.
Note: The first assertion of WUTF occurs (WUT+1) ck_wut cycles after WUTE is set. Setting
WUT[15:0] to 0x0000 with WUCKSEL[2:0] =011 (RTCCLK/2) is forbidden.
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
Reserved
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Reserved
DCS
Reserved
DC[4:0]
rw
rw
rw
rw
rw
rw
Bits 31:8 Reserved
Bit 7
DCS
: Digital calibration sign
0: Positive calibration: calendar update frequency is increased
1: Negative calibration: calendar update frequency is decreased
Bits 6:5 Reserved, must be kept at reset value.
Bits 4:0
DC[4:0]
: Digital calibration
DCS = 0 (positive calibration)
00000: + 0 ppm
00001: + 4 ppm (rounded value)
00010: + 8 ppm (rounded value)
..
11111: + 126 ppm (rounded value)
DCS = 1 (negative calibration)
00000:
−
0 ppm
00001:
−
2 ppm (rounded value)
00010:
−
4 ppm (rounded value)
..
11111:
−
63 ppm (rounded value)
Refer to
Case of RTCCLK=32.768 kHz and P1=128 on page 799
step value.