DocID025202 Rev 7
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RM0365
Real-time clock (RTC)
764
27.6.18 RTC alarm B sub second register (RTC_ALRMBSSR)
This register can be written only when ALRBE is reset in RTC_CR register, or in initialization
mode.
This register is write protected.The write access procedure is described in
Address offset: 0x48
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
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, 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 B is to be activated. Only bits 0 up to MASKSS-1 are compared.