Hse32 Clock With Trimming; Figure 21. Clock Tree - STMicroelectronics STM32WLEx Reference Manual

Reset and clock control (RCC)
–
–
The functionality in Stop mode (including wakeup) is supported only when the clock is
LSI or LSE.
•
The IWDG clock is always the LSI clock.
The RCC feeds the CPU system timer (SysTick) external clock with the AHB clock (HCLK1)
divided by eight. The SysTick can work either with this clock or directly with the CPU clock
(HCLK1), configurable in the SysTick control and status register.
FCLK1 acts as CPU free-running clock. For more details, refer to the programming manual
STM32 Cortex
LSI RCC 32 kHz
LSCO
LSE OSC
OSC32_OUT
32.768 kHz
OSC32_IN
LSE CSS
MCO
/1 - 16
HSE32 OSC
OSC_OUT
32 MHz
OSC_IN
HSE CSS
HSI16 RC
16 MHz
MSI RC
100 kHz - 48 MHz
/M
PLL
x
N
1. For full details about the internal and external clock source characteristics, refer to the electrical characteristics section in
the device datasheet.
2. The ADC clock can additionally be derived from the AHB clock of the ADC bus interface, divided by a programmable factor
(1, 2 or 4). When the programmable factor is 1, the AHB prescaler must be equal to 1.
6.2.1

HSE32 clock with trimming

The HSE32 32 MHz external oscillator has the advantage of producing a very accurate rate
on the main clock. The HSE32 furthermore provides on-chip trimming capability.
234/1306
LSI clock
HSE32 clock divided by 32
®
-M4 MCUs and MPUs programming manual (PM0214).

Figure 21. Clock tree

LSIPRE
/1,128
LSI
/32
LSE
HSE32
SYSCLK
PLLRCLK
PLLQCLK
PLLPCLK
HSI16
PLLRCLK
MSI
HSEPRE
HSE32
/1,2
MSI
HSI16
SYSCLK
PLLPCLK
/P
PLLQCLK
/Q
PLLRCLK
/R
I2S_CKIN
LSI
LSE
CPU
HPRE
/1,2,...,512
SYS clock
source
control
MSI
SYSCLK
HSI16
AHB3
SHDHPRE
/1,2,...,512
PCLKn
HSI16
SYSCLK
to ADC
LSI
to SPI2S2
HSI16 LSE to RNG
MSI
RM0461 Rev 5
HCLK1 to CPU, AHB1, AHB2
to CPU system timer
/8
APB1
PCLK1
PPRE1
/1,2,4,8,16
x1 or
x2
APB2
PCLK2
PPRE2
/1,2,4,8,16
x1 or
x2
HCLK3 to AHB3, Flash, SRAM1, SRAM2
PCLK3
PCLKn
HSI16
to USART1
HSI16 to USART2 LSI
to LPUART1
LSE LSE
PCLKn
SYSCLK to I2C1
to I2C2
HSI16 to I2C3
LSI DAC
RM0461
to IWDG
to RTC
to CPU FCLK
to APB1
to APB1 TIMx
to APB2
to APB2 TIMx
to APB3
to RF
to LPTIM1
to LPTIM2
to LPTIM3
MSv62605V3