
Reset and clock control (RCC)
RM0351
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DocID024597 Rev 5
6.4.29 Backup
domain
control register (RCC_BDCR)
Address offset: 0x90
Reset value: 0x0000 0000, reset by Backup domain Reset, except LSCOSEL, LSCOEN
and BDRST which are reset only by Backup domain power-on reset.
Access: 0
≤
wait state
≤
3, word, half-word and byte access
Wait states are inserted in case of successive accesses to this register.
Note:
The bits of the
Backup domain control register (RCC_BDCR)
are outside of the V
CORE
domain. As a result, after Reset, these bits are write-protected and the DBP bit in the
Section 5.4.1: Power control register 1 (PWR_CR1)
has to be set before these can be
Section 5.1.5: Battery backup domain on page 153
for further
information. These bits (except LSCOSEL, LSCOEN and BDRST) are only reset after a
Backup domain Reset (see
Section 6.1.3: Backup domain reset
). Any internal or external
Reset will not have any effect on these bits.
Bits 5:4
USART3SEL[1:0]
: USART3 clock source selection
This bit is set and cleared by software to select the USART3 clock source.
00: PCLK selected as USART3 clock
01: System clock (SYSCLK) selected as USART3 clock
10: HSI16 clock selected as USART3 clock
11: LSE clock selected as USART3 clock
Bits 3:2
USART2SEL[1:0]
: USART2 clock source selection
This bit is set and cleared by software to select the USART2 clock source.
00: PCLK selected as USART2 clock
01: System clock (SYSCLK) selected as USART2 clock
10: HSI16 clock selected as USART2 clock
11: LSE clock selected as USART2 clock
Bits 1:0
USART1SEL[1:0]
: USART1 clock source selection
This bit is set and cleared by software to select the USART1 clock source.
00: PCLK selected as USART1 clock
01: System clock (SYSCLK) selected as USART1 clock
10: HSI16 clock selected as USART1 clock
11: LSE clock selected as USART1 clock
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
Res.
Res.
Res.
Res.
Res.
Res.
LSCO
SEL
LSCO
EN
Res.
Res.
Res.
Res.
Res.
Res.
Res.
BDRST
rw
rw
rw
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RTC
EN
Res.
Res.
Res.
Res.
Res.
RTCSEL[1:0]
Res.
LSE
CSSD
LSE
CSSON
LSEDRV[1:0]
LSE
BYP
LSE
RDY
LSEON
rw
rw
rw
r
rw
rw
rw
rw
r
rw