STM32W108HB datasheet(92/278 Pages) STMICROELECTRONICS

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General-purpose input/output

STM32W108HB STM32W108CC STM32W108CB STM32W108CZ

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Doc ID 16252 Rev 14

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

GPIOx_ODR register controls the output. The GPIOx_BSR and GPIOx_BRR registers can

atomically set and clear bits within GPIOx_ODR 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 GPIOx_ODR.

When configured in output mode:

●

The output drivers are enabled and are controlled by the value written to GPIOx_ODR:

●

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 GPIOx_IDR returns the input at the pin.

●

Reading GPIOx_ODR returns the last value written to the register.

Note:

Depending on configuration and usage, GPIOx_ODR and GPIOx_IDR may not have the

same value.

Alternate output mode

In this mode, the output is controlled by an on-chip peripheral instead of GPIOx_ODR and

may be configured as either push-pull or open-drain. Most peripherals require a particular

output type - I2C requires an open-drain driver, for example - but since using a peripheral

does not by itself configure a pin, the GPIOx_CRH/L registers must be configured properly

for a peripheral's particular needs. As described in Section 8.1.2: Configuration on page 89,

when more than one peripheral can be the source of output data, registers in addition to

GPIOx_CRH/L determine which to use.

When configured in alternate output mode:

●

The output drivers are enabled and are controlled by the output of an on-chip

peripheral:

●

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 GPIOx_IDR returns the input to the pin.

Note:

Depending on configuration and usage, GPIOx_ODR and GPIOx_IDR may not have the

same value.

Alternate output SPI SCLK mode

SPI master mode SCLK outputs, PB3 (SC1SCLK) or PA2 (SC2SCLK), use a special output

push-pull mode reserved for those signals. Otherwise this mode is identical to alternate

output mode.

STM32W108HB Datasheet(PDF) 92 Page - STMicroelectronics

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