ST STM32F446 Series User Manual

RM0390 Rev 4 167/1328
RM0390 Reset and clock control (RCC)
175
6.3.25 RCC Dedicated Clock Configuration Register (RCC_DCKCFGR)
Address offset: 0x8C
Reset value: 0x0000 0000
Access: no wait state, word, half-word and byte access.
This register allows to configure the timer clock prescalers and the PLLSAI and PLLI2S
output clock dividers for SAIs peripherals according to the following formula:
f
(PLLSAIDIVQ clock output)
= f
(PLLSAI_Q)
/ PLLSAIDIVQ
f(
PLLI2SDIVQ clock output)
= f
(PLLI2S_Q)
/ PLLI2SDIVQ
Bit 15 Reserved, must be kept at reset value.
Bits 14:6 PLLSAIN: PLLSAI division factor for VCO
Set and reset by software to control the multiplication factor of the VCO. These bits should be
written when the PLLSAI 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.
VCO output frequency = VCO input frequency x PLLSAIN with 50  PLLSAIN  432
000000000: PLLSAIN = 0, wrong configuration
000000001: PLLSAIN = 1, wrong configuration ...
001100010: PLLSAIN = 50
...
001100011: PLLSAIN = 99
001100100: PLLSAIN = 100
001100101: PLLSAIN = 101
001100110: PLLSAIN = 102
...
110110000: PLLSAIN = 432
110110000: PLLSAIN = 433, wrong configuration ...
111111111: PLLSAIN = 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 PLLSAIM: Division factor for audio PLLSAI input clock
Set and cleared by software to divide PLLSAI input clock before the VCO.
These bits can be written only when PLLSAI is 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 / PLLSAI with 2 <= PLLSAIM <= 63
000000: PLLSAIM = 0, wrong configuration
000001: PLLSAIM = 1, wrong configuration
000010: PLLSAIM = 2
000011: PLLSAIM = 3
000100: PLLSAIM = 4
...
111110: PLLSAIM = 62
111111: PLLSAIM = 63

ST STM32F446 Series Specifications

General

Brand	ST
Model	STM32F446 Series
Category	Microcontrollers
Language	English