DocID018909 Rev 11
825/1731
RM0090
Real-time clock (RTC)
828
Note:
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
26.6.19 RTC alarm B sub second register (RTC_ALRMBSSR)
Address offset: 0x48
Backup domain reset value: 0x0000 0000
System reset: not affected
Note:
This register can be written only when ALRBIE is reset in RTC_CR register, or in
initialization mode.
This register is write protected.The write access procedure is described in
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
Reserved
MASKSS[3:0]
Reserved
r
r
r
r
rw
rw
rw
rw
r
r
r
r
r
r
r
r
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Reserved
SS[14:0]
r
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
w
rw
rw
Bits 31:28 Reserved
Bits 27:24
MASKSS[3:0]
: Mask the most-significant bits starting at this bit
0x0: No comparison on sub seconds for Alarm B. The alarm is set when the seconds unit is
incremented (assuming that the rest of the fields match).
0x1: SS[14:1] are don’t care in Alarm B comparison. Only SS[0] is compared.
0x2: SS[14:2] are don’t care in Alarm B comparison. Only SS[1:0] are compared.
0x3: SS[14:3] are don’t care in Alarm B comparison. Only SS[2:0] are compared.
...
0xC: SS[14:12] are don’t care in Alarm B comparison. SS[11:0] are compared.
0xD: SS[14:13] are don’t care in Alarm B comparison. SS[12:0] are compared.
0xE: SS[14] is don’t care in Alarm B comparison. SS[13:0] are compared.
0xF: 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.
Bits 23:15 Reserved
Bits 14:0
SS[14:0]
: Sub seconds value
This value is compared with the contents of the synchronous prescaler’s counter to
determine if Alarm B is to be activated. Only bits 0 up to MASKSS-1 are compared.