STM32W108CBU6 STMICROELECTRONICS [STMicroelectronics], STM32W108CBU6 Datasheet - Page 50

• Manufacturer Part Number: STM32W108CBU6
• Description: High-performance, IEEE 802.15.4 wireless system-on-chip
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

General-purpose input/outputs
Note:
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Input mode
Input mode is used both for general purpose input and for on-chip peripheral inputs. Input
floating mode disables the internal pull-up and pull-down resistors, leaving the pin in a high-
impedance state. Input pull-up or pull-down mode enables either an internal pull-up or pull-
down resistor based on the GPIO_PxOUT register. Setting a bit to 0 in GPIO_PxOUT
enables the pull-down and setting a bit to 1 enables the pull up.
When configured in input mode:
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Output mode
Output mode provides a general purpose output under direct software control. Regardless
of whether an output is configured as push-pull or open-drain, the GPIO's bit in the
GPIO_PxOUT register controls the output. The GPIO_PxSET and GPIO_PxCLR registers
can atomically set and clear bits within GPIO_PxOUT register. These set and clear registers
simplify software using the output port because they eliminate the need to disable interrupts
to perform an atomic read-modify-write operation of GPIO_PxOUT.
When configured in output mode:
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Depending on configuration and usage, GPIO_PxOUT and GPIO_PxIN may not have the
same value.
Alternate output mode
In this mode, the output is controlled by an on-chip peripheral instead of GPIO_PxOUT and
may be configured as either push-pull or open-drain. Most peripherals require a particular
output type - TWI requires an open-drain driver, for example - but since using a peripheral
does not by itself configure a pin, the GPIO_PxCFGH/L registers must be configured
properly for a peripheral's particular needs. As described in
page
addition to GPIO_PxCFGH/L determine which to use.
The output drivers are disabled.
An internal pull-up or pull-down resistor may be activated depending on
GPIO_PxCFGH/L and GPIO_PxOUT.
The Schmitt trigger input is connected to the pin.
Reading GPIO_PxIN returns the input at the pin.
The input is also available to on-chip peripherals.
The output drivers are enabled and are controlled by the value written to
GPIO_PxOUT:
In open-drain mode: 0 activates the N-MOS current sink; 1 tri-states the pin.
In push-pull mode: 0 activates the N-MOS current sink; 1 activates the P-MOS current
source.
The internal pull-up and pull-down resistors are disabled.
The Schmitt trigger input is connected to the pin.
Reading GPIO_PxIN returns the input at the pin.
Reading GPIO_PxOUT returns the last value written to the register.
47, when more than one peripheral can be the source of output data, registers in
Doc ID 16252 Rev 2
STM32W108CB, STM32W108HB
Section 6.1.2: Configuration on