Reset and clock control for STM32F405xx/07xx and STM32F415xx/17xx(RCC)
RM0090
264/1731
DocID018909 Rev 11
7.3.23
RCC spread spectrum clock generation register (RCC_SSCGR)
Address offset: 0x80
Reset value: 0x0000 0000
Access: no wait state, word, half-word and byte access.
The spread spectrum clock generation is available only for the main PLL.
The RCC_SSCGR register must be written either before the main PLL is enabled or after
the main PLL disabled.
Note:
For full details about PLL spread spectrum clock generation (SSCG) characteristics, refer to
the “Electrical characteristics” section in your device datasheet.
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
SSCG
EN
SPR
EAD
SEL
Reserved
INCSTEP
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
INCSTEP
MODPER
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
rw
Bit 31
SSCGEN:
Spread spectrum modulation enable
Set and cleared by software.
0: Spread spectrum modulation DISABLE. (To write after clearing CR[24]=PLLON bit)
1: Spread spectrum modulation ENABLE. (To write before setting CR[24]=PLLON bit)
Bit 30
SPREADSEL:
Spread Select
Set and cleared by software.
To write before to set CR[24]=PLLON bit.
0: Center spread
1: Down spread
Bits 29:28 Reserved, must be kept at reset value.
Bits 27:13
INCSTEP:
Incrementation step
Set and cleared by software. To write before setting CR[24]=PLLON bit.
Configuration input for modulation profile amplitude.
Bits 12:0
MODPER:
Modulation period
Set and cleared by software. To write before setting CR[24]=PLLON bit.
Configuration input for modulation profile period.