General-Purpose Inputs/Outputs (Gpios); Figure 2. Clock Tree - STMicroelectronics STM32F038C6 Manual

Functional overview
3.7

General-purpose inputs/outputs (GPIOs)

Each of the GPIO pins can be configured by software as output (push-pull or open-drain), as
input (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.
The I/O configuration can be locked if needed following a specific sequence in order to
avoid spurious writing to the I/Os registers.
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Figure 2. Clock tree

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STM32F038x6