Real-time clock (RTC)
RM0365
761/1080
DocID025202 Rev 7
27.6.17 RTC alarm A sub second register (RTC_ALRMASSR)
This register can be written only when ALRAE is reset in RTC_CR register, or in initialization
mode.
This register is write protected. The write access procedure is described in
Address offset: 0x44
Backup domain reset value: 0x0000 0000
System reset: not affected
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
Res.
Res.
Res.
Res.
MASKSS[3:0]
Res.
Res.
Res.
Res.
Res.
Res.
Res.
Res.
rw
rw
rw
rw
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Res.
SS[14:0]
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
w
rw
rw
Bits 31:28 Reserved, must be kept at reset value.
Bits 27:24 MASKSS[3:0]: Mask the most-significant bits starting at this bit
0: No comparison on sub seconds for Alarm A. The alarm is set when the seconds unit is
incremented (assuming that the rest of the fields match).
1: SS[14:1] are don’t care in Alarm A comparison. Only SS[0] is compared.
2: SS[14:2] are don’t care in Alarm A comparison. Only SS[1:0] are compared.
3: SS[14:3] are don’t care in Alarm A comparison. Only SS[2:0] are compared.
...
12: SS[14:12] are don’t care in Alarm A comparison. SS[11:0] are compared.
13: SS[14:13] are don’t care in Alarm A comparison. SS[12:0] are compared.
14: SS[14] is don’t care in Alarm A comparison. SS[13:0] are compared.
15: All 15 SS bits are compared and must match to activate alarm.
The overflow bits of the synchronous counter (bits 15) is never compared. This bit can be
different from 0 only after a shift operation.
Bits23:15 Reserved, must be kept at reset value.
Bits 14:0 SS[14:0]: Sub seconds value
This value is compared with the contents of the synchronous prescaler counter to determine if
Alarm A is to be activated. Only bits 0 up MASKSS-1 are compared.