
Connectivity line devices: reset and clock control (RCC)
RM0008
152/1096
Doc ID 13902 Rev 12
8.3.13
RCC register map
The following table gives the RCC register map and the reset values.
Bits 3:0
PREDIV1[3:0]
: PREDIV1 division factor
Set and cleared by software to select PREDIV1 division factor. These bits can be written only
when PLL is disabled.
Note: Bit(0) is the same as bit(17) in the RCC_CFGR register, so modifying bit(17) in the
RCC_CFGR register changes Bit(0) accordingly.
0000: PREDIV1 input clock not divided
0001: PREDIV1 input clock divided by 2
0010: PREDIV1 input clock divided by 3
0011: PREDIV1 input clock divided by 4
0100: PREDIV1 input clock divided by 5
0101: PREDIV1 input clock divided by 6
0110: PREDIV1 input clock divided by 7
0111: PREDIV1 input clock divided by 8
1000: PREDIV1 input clock divided by 9
1001: PREDIV1 input clock divided by 10
1010: PREDIV1 input clock divided by 11
1011: PREDIV1 input clock divided by 12
1100: PREDIV1 input clock divided by 13
1101: PREDIV1 input clock divided by 14
1110: PREDIV1 input clock divided by 15
1111: PREDIV1 input clock divided by 16
Table 19.
RCC register map and reset values
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
0x000
RCC_CR
Reser
ved
PL
L3 RD
Y
PLL
3
O
N
PL
L2 RD
Y
PLL
2
O
N
PLL
RD
Y
P
LLON
Reserved
CS
SON
H
S
EBY
P
HSERD
Y
HS
EON
HSICAL[7:0]
HSITRIM[4:0]
Reser
v
e
d
HSIRD
Y
HSION
Reset value
0
0
0
0
0
0
0
0
0
0
x
x
x
x
x
x
x
x
1
0
0
0
0
1
1
0x004
RCC_CFGR
Reserved
MCO [3:0]
Reser
v
ed
O
T
GFSPRE
PLLMUL [3:0]
P
LLXTP
RE
PL
LSRC
ADC
PRE
[1:0]
PPRE2
[2:0]
PPRE1
[2:0]
HPRE[3:0]
SWS
[1:0]
SW
[1:0]
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
0
0
0
0
0x008
RCC_CIR
Reserved
CS
SC
P
LL3RD
Y
C
P
LL2RD
Y
C
PL
LRD
Y
C
HSE
R
D
Y
C
HS
IR
D
Y
C
L
SERD
Y
C
LSI
R
D
Y
C
Reser
v
ed
P
LL3RD
Y
IE
P
LL2RD
Y
IE
PL
LRD
Y
IE
HSE
R
D
Y
IE
HS
IRD
Y
IE
L
SERD
Y
IE
LSI
R
D
Y
IE
CSS
F
PLL
3
RD
Y
F
PLL
2
RD
Y
F
PLLRD
Y
F
HSERD
Y
F
HSIRD
Y
F
LS
ERD
Y
F
LS
IR
D
Y
F
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
0x00C
RCC_APB2RSTR
Reserved
Reser
v
ed
USA
R
T1RST
Reser
v
ed
SP
I1
R
S
T
TI
M1
R
S
T
ADC2RST
ADC1RST
Reser
v
ed
IO
PE
RS
T
IOPDRST
IOPCRST
IO
PB
RS
T
IO
P
A
RS
T
Reser
v
ed
AFI
O
RST
Reset value
0
0
0
0
0
0
0
0
0
0
0
0x010
RCC_APB1RSTR
Reser
ved
D
A
CRST
P
W
RRST
BK
PRST
CAN2RST
CAN1RST
Re
se
rv
e
d
I2C2
RS
T
I2C1
RS
T
UA
R
T
5
R
S
T
UA
R
T
4
R
S
T
US
A
R
T
3
RS
T
US
A
R
T
2
RS
T
Re
se
rv
e
d
SPI
3RST
SPI
2RST
Re
se
rv
e
d
WWDGRST
Reserved
TM7RST
TM6RST
TM5RST
TIM4RST
TIM3RST
TIM2RST
Reset value
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0