Figure 48. High Impedance Analog Configuration - STMicroelectronics STM32WL5 Series Reference Manual

General-purpose I/Os (GPIO)
10.3.12 Analog configuration
When the I/O port is programmed as analog configuration, the following occurs:
•
The output buffer is disabled.
•
The Schmitt trigger input is deactivated, providing zero consumption for every analog
value of the I/O pin. The output of the Schmitt trigger is forced to a constant value (0).
•
The weak pull-up and pull-down resistors are disabled by hardware.
•
Read access to the input data register gets the value 0.
The figure below shows the high-impedance, analog-input configuration of the I/O port bits.
To on-chip
peripheral
Read
Write
Read/write
From on-chip
peripheral
10.3.13 Using the LSE oscillator pins as GPIOs
When the LSE oscillator is switched off (default state after reset), the related oscillator pins
can be used as normal GPIOs.
When the LSE oscillator is switched on (by setting the LSEON bit in the RCC_CSR
register), the oscillator takes the 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 OSC32_IN pin is
reserved for clock input and the OSC32_OUT pin can still be used as normal GPIO.
Note: The HSE32 OSC_IN and OSC_OUT pins are dedicated oscillator pins and cannot be used
as GPIO.
10.3.14 Using the GPIO pins in the RTC supply domain
GPIO functionality of PC13, PC14 and PC15 is lost when the core supply domain is
powered off (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
408/1450

Figure 48. High impedance analog configuration

Analog
Input driver
Analog
RM0453 Rev 5
off
0
TTL Schmitt
trigger
Section 32: Real-time clock
RM0453
V
DDIOx
protection
diode
I/O pin
protection
diode
V
SS
MS31480V1
(RTC).