Clock Sources; Hse Clock (High-Speed External Clock) - STMicroelectronics STM32H7 User Manual

Hardware layout and configuration
6.5

Clock sources

6.5.1

HSE clock (high-speed external clock)

There are four ways to configure the pins corresponding to the external high-speed clock
(HSE):
•
MCO from STLINK-V3E (default): MCO output of ST-LINK is used as an input clock.
This frequency cannot be changed. It is fixed at 8 MHz and connected to the PF0/PH0-
OSC_IN of the STM32H7 series microcontroller. The configuration must be:
–
–
–
•
HSE on-board oscillator from X3 crystal (not provided): For its typical frequencies,
capacitors, and resistors, refer to the STM32H7 series microcontroller datasheet and
the application note Oscillator design guide for STM8AF/AL/S and STM32
microcontrollers (AN2867) for the oscillator design guide. The X3 crystal has the
following characteristics: 25 MHz, 6 pF, 20 ppm. The configuration must be:
–
–
–
–
• Oscillator from external PF0/PH0: from an external oscillator through pin 29 of the
CN11 connector. The configuration must be:
–
–
–
•
HSE not used: PF0/PH0 and PF1/PH1 are used as GPIOs instead of clocks. The
configuration must be:
–
–
–
24/49
SB44 and SB46 OFF
SB45 ON
SB3 and SB4 OFF
SB44 and SB46 OFF
SB3 and SB4 ON
C69 and C70 ON with 5.6 pF capacitors
SB45 OFF
SB46 ON
SB45 OFF
SB3 and SB4 OFF
SB44 and SB46 ON
SB45 OFF
SB3 and SB4 OFF
UM2407 Rev 3
UM2407