ST STM32F412 User Manual

Reset and clock control (RCC) for STM32F412xx RM0402
160/1163 RM0402 Rev 6
Bit 22 PLLI2SSRC: PLLI2S entry clock source
Set and cleared by software to select PLLI2S clock source. This bit can be written only when
PLLI2S is disabled.
0: HSE or HSI depending on PLLSRC of PLLCFGR
1: external AFI clock (CK_I2S_EXT) selected as PLL clock entry
Bits 21:15 Reserved, must be kept at reset value.
Bits 14:6 PLLI2SN[8:0]: PLLI2S multiplication factor for VCO
Set and cleared by software to control the multiplication factor of the VCO. These bits can be
written only when the PLLI2S is disabled. Only half-word and word accesses are allowed to
write these bits.
Caution: The software has to set these bits correctly to ensure that the VCO output frequency
is between 100 and 432 MHz. With VCO input frequency ranges from 1 to 2 MHz
(refer to Figure 14 and divider factor M of the RCC PLL configuration register
(RCC_PLLCFGR))
VCO output frequency = VCO input frequency × PLLI2SN with 50 ≤ PLLI2SN ≤ 432
000000000: PLLI2SN = 0, wrong configuration
000000001: PLLI2SN = 1, wrong configuration
...
001100010: PLLI2SN = 50
...
001100011: PLLI2SN = 99
001100100: PLLI2SN = 100
001100101: PLLI2SN = 101
001100110: PLLI2SN = 102
...
110110000: PLLI2SN = 432
110110000: PLLI2SN = 433, wrong configuration
...
111111111: PLLI2SN = 511, wrong configuration
Note: Between 50 and 99 multiplication factors are possible for VCO input frequency higher
than 1 MHz. However care must be taken to fulfill the minimum VCO output frequency
as specified above.
Bits 5:0 PLLI2SM[5:0]: Division factor for the main PLL (PLL) and audio PLL (PLLI2S) input clock
Set and cleared by software to divide the PLL and PLLI2S input clock before the VCO.
These bits can be written only when the PLL and PLLI2S are disabled.
Caution: The software has to set these bits correctly to ensure that the VCO input frequency
ranges from 1 to 2 MHz.It is recommended to select a frequency of 2 MHz to limit
PLL jitter.
VCO input frequency = PLL input clock frequency / PLLI2SM with 2 ≤ PLLI2SM ≤ 63
000000: PLLI2SM = 0, wrong configuration
000001: PLLI2SM = 1, wrong configuration...
000010: PLLI2SM = 2
000011: PLLI2SM = 3
000100: PLLI2SM = 4
.......
111110: PLLI2SM = 62
111111: PLLI2SM = 63

ST STM32F412 Specifications

General

Brand	ST
Model	STM32F412
Category	Microcontrollers
Language	English