Nations Technologies Inc.
Tel
:
+86-755-86309900
:
Address: Nations Tower, #109 Baoshen Road, Hi-tech Park North.
Nanshan District, Shenzhen, 518057, P.R.China
325
/
631
The calibration period is 8 seconds.
Using an accurate 8-second period to measure the 1Hz calibration output can ensure that the measurement error
is within 1.907ppm (0.5 RTCCLK cycles within 8 seconds).
Dynamic recalibration
When RTC_INITSTS.INITF=0, RTC_CALIB register can update by using following steps:
Wait RTC_INITSTS.RECPF=0.
A new value is written to the RTC_CALIB, then RTC_INITSTS.RECPF is automatically set to 1.
The new calibration settings will take effect within 3 ck_apre cycles after a data write to the RTC_CALIB.
RTC low power mode
Lower Power Mode
RTC Working State
Exit Low Power Mode
SLEEP
Normal work
RTC interrupt
LP RUN
Normal work when the clock source of RTC is LSE
or LSI
Alarm A, Alarm B, Periodic Wakeup, Tamper
event and Timestamp event
LP SLEEP
Normal work when the clock source of RTC is LSE
or LSI
Alarm A, Alarm B, Periodic Wakeup, Tamper
event and Timestamp event
STOP2
Normal work when the clock source of RTC is LSE
or LSI
Alarm A, Alarm B, Periodic Wakeup, Tamper
event and Timestamp event
STANDBY
Normal work when the clock source of RTC is LSE
or LSI
Alarm A, Alarm B, Periodic Wakeup, Tamper
event and Timestamp event
RTC Registers
RTC Register overview
Table 14-1 RTC register overview
Offset
Register
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
000h
RTC_TSH
Reserved
APM
HO
T
[1:0]
HOU[3:0]
R
es
er
ve
d
MIT[2:0]
MIU[3:0]
R
es
er
ve
d
SCT[2:0]
SCU[3:0]
Reset Value
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
004h
RTC_DATE
Reserved
YRT[3:0]
YRU[3:0]
WDU[2:0]
M
OT
MOU[3:0]
R
es
er
ve
d
DAT[1:0]
DAU[3:0]
Reset Value
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
1
0
0
0 0
0
1
008h
RTC_CTRL
Reserved
C
OE
N
OU
T
S
E
L
[1:0]
OPOL
C
AL
OSE
L
B
AK
P
S
U1H
AD
1H
T
S
IE
N
W
T
IE
N
AL
B
IE
N
AL
AI
E
N
T
S
E
N
W
T
E
N
AL
B
E
N
AL
AE
N
R
es
er
ve
d
HFM
T
B
YPS
R
E
F
C
L
KE
N
T
E
DG
E
W
KU
P
S
E
L
[2:0
]
Reset Value
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
00Ch
RTC_INITSTS
Reserved
R
E
C
P
F
T
AM
3F
T
AM
2F
T
AM
1F
T
IS
OV
F
T
IS
F
W
T
F
AL
B
F
AL
AF
INI
T
M
INI
T
F
R
S
YF
INI
T
S
F
S
HO
P
F
W
T
W
F
AL
B
W
F
AL
AW
F
Reset Value
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1