Datasheet

DocID030538 Rev 3 23/226
STM32H743xI Functional overview
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3.7.1 Clock management
The devices embed four internal oscillators, two oscillators with external crystal or
resonator, two internal oscillators with fast startup time and three PLLs.
The RCC receives the following clock source inputs:
• Internal oscillators:
–
64 MHz HSI clock (1% accuracy)
– 48 MHz RC oscillator
– 4 MHz CSI clock
– 32 kHz LSI clock
• External oscillators:
– 4-48 MHz HSE clock
– 32.768 kHz LSE clock
The RCC provides three PLLs: one for system clock,
two for kernel clocks.
The system starts on the HSI clock. The user
application can then select the clock
configuration.
3.7.2 System reset sources
Power-on reset initializes all registers while system reset reinitializes the system except for
the debug, part of the RCC and power controller status registers, as well as the backup
power domain.
A system reset is generated in the following cases:
• Power
-on reset (pwr_por_rst)
• Brownout reset
• Low level on NRST pin (external reset)
• Window watchdog
• Independent watchdog
• Software reset
• Low-power mode security reset
• Exit from Standby
3.8 General-purpose input/outputs (GPIOs)
Each of the GPIO pins can be configured by software as output (push-pull or open-drain,
with or without pull-up or pull-down), as input (floating, with or without pull-up or pull-down)
or as peripheral alternate function. Most of the GPIO pins are shared with digital or analog
alternate functions. All GPIOs are high-current-capable and have speed selection to better
manage internal noise, power consumption and electromagnetic emission.
After reset, all GPIOs are in Analog mode to reduce power consumption.
The I/O configuration can be locked if needed by
following a specific sequence in order to
avoid spurious writing to the I/Os registers.
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