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General-purpose I/Os (GPIO) RM0444

240/1390 RM0444 Rev 5

7.3.13 Using the HSE or LSE oscillator pins as GPIOs

When the HSE or LSE oscillator is switched OFF (default state after reset), the related

oscillator pins can be used as normal GPIOs.

When the HSE or LSE oscillator is switched ON (by setting the HSEON or LSEON bit in the

RCC_CSR register) the oscillator takes control of its associated pins and the GPIO

configuration of these pins has no effect.

When the oscillator is configured in a user external clock mode, only the OSC_IN or

OSC32_IN pin is reserved for clock input and the OSC_OUT or OSC32_OUT pin can still be

used as normal GPIO.

7.3.14 Using the GPIO pins in the RTC domain

The PC13/PC14/PC15 GPIO functionality is lost when the core supply domain is powered

off (when the device enters Standby mode). In this case, if their GPIO configuration is not

bypassed by the RTC configuration, these pins are set in an analog input mode.

For details about I/O control by the RTC, refer to Section 30.3: RTC functional description.

7.3.15 USB PD / Dead battery support

In the absence of V

supply, the device using the Dead battery capability of the USB

Type-C standard provides an internal pull-down resistor R

on CC lines if the input level on

DBCC pins is high. This is to signal VBUS supply request.

To enable this feature, it is necessary to connect UCPD_DBCC1 to UCPD_CC1 and

UCPD_DBCC2 to UCPD_CC2. To disable the feature, it is necessary to connect

UCPD_DBCC1 and UCPD_DBCC2 to ground. Refer to Section 38: USB Type-C™ / USB

Power Delivery interface (UCPD) for more detail.

Note: The DBCC pads (GPIOs of FT_d type) present more leakage than standard GPIOs. Refer

to product datasheet for values.

In applications that do not use the UCPD peripheral, disable the internal pull-down resistor

at startup through the strobe bits in SYSCFG registers.

In applications that use the UCPD peripheral, first configure the peripheral then load the

configuration to the UCPD_CCx GPIOs through the strobe bits in SYSCFG registers.

ST STM32G0 1 Series User Manual

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