RM0090: Reference manual - STMicroelectronics

RM0090 Reset and clock control for (RCC)
6.3.29 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
Bits 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
Bit 29:28 Reserved, must be kept at reset value.
Bit 27:13 INCSTEP: Incrementation step
Set and cleared by software. To write before setting CR[24]=PLLON bit.
Configuration input for modulation profile amplitude.
Bit 12:0 MODPER: Modulation period
Set and cleared by software. To write before setting CR[24]=PLLON bit.
Configuration input for modulation profile period.
Doc ID 018909 Rev 3 178/1416