Figure 9. STM32G431KB Nucleo-32 board clock configuration
• HSI configuration (default): In that case, no external clock is used. The clock is coming from the
STLM32G4 microcontroller. The configuration is:
– SB9 and SB10 OFF
– SB11 and SB8 OFF
– SB13 OFF
• HSE bypass configuration (from ST-LINK): The input clock is the ST-LINK MCO output. The frequency is
fixed to 25 MHz, and connected to the PF0-OSC_IN of the STM32G4 microcontroller. The configuration
must be:
– SB9 and SB10 OFF
– SB11 and SB8 OFF
– SB13 ON
• HSE bypass configuration (from ARDUINO
®
D7): The clock is coming from an external oscillator through
the pin PF0 (ARDUINO
®
D7 pin 10 of the CN4 connector). The configuration must be:
– SB9 and SB10 OFF
– SB11 OFF and SB8 ON
– SB13 OFF
• HSE oscillator configuration: The clock is provided by an external crystal (X2) available in the PCB. The
X2 crystal has the following characteristics: 24 MHz, 6 pF load capacitance, 20 ppm. The recommendation is
to use NX2016SA-24MHz-EXS00A-CS10820 manufactured by NDK. For typical frequencies and its
capacitors and resistors, refer to the STM32 microcontroller datasheet and to the Oscillator design guide for
STM8S, STM8A and STM32 microcontrollers Application note (AN2867) for the oscillator design guide. The
configuration must be:
– SB9 and SB10 ON
– SB11 and SB8 OFF
– SB13 OFF
UM2397
Clock sources
UM2397 - Rev 2
page 15/30
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