STM32W108CB datasheet(51/179 Pages) STMICROELECTRONICS

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STM32W108CB, STM32W108HB

General-purpose input/outputs

Doc ID 16252 Rev 2

51/179

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 GPIO_PxIN returns the input to the pin.

Note:

Depending on configuration and usage, GPIO_PxOUT and GPIO_PxIN 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.

6.1.7

Wake monitoring

The GPIO_PxWAKE registers specify which GPIOs are monitored to wake the processor. If

a GPIO's wake enable bit is set in GPIO_PxWAKE, then a change in the logic value of that

GPIO causes the STM32W108 to wake from deep sleep. The logic values of all GPIOs are

captured by hardware upon entering sleep. If any GPIO's logic value changes while in sleep

and that GPIO's GPIO_PxWAKE bit is set, then the STM32W108 will wake from deep sleep.

(There is no mechanism for selecting a specific rising-edge, falling-edge, or level on a GPIO:

any change in logic value triggers a wake event.) Hardware records the fact that GPIO

activity caused a wake event, but not which specific GPIO was responsible. Instead,

software should read the state of the GPIOs on waking to determine the cause of the event.

The register GPIO_WAKEFILT contains bits to enable digital filtering of the external wakeup

event sources: the GPIO pins, SC1 activity, SC2 activity, and IRQD. The digital filter

operates by taking samples based on the (nominal) 10 kHz RC oscillator. If three samples in

a row all have the same logic value, and this sampled logic value is different from the logic

value seen upon entering sleep, the filter outputs a wakeup event.

In order to use GPIO pins to wake the STM32W108 from deep sleep, the GPIO_WAKE bit in

the WAKE_SEL register must be set. Waking up from GPIO activity does not work with pins

configured for analog mode since the digital logic input is always set to 1 when in analog

mode. Refer to Section 5: System modules on page 33 for information on the STM32W108's

power management and sleep modes.

6.2

External interrupts

The STM32W108 can use up to four external interrupt sources (IRQA, IRQB, IRQC, and

IRQD), each with its own top level NVIC interrupt vector. Since these external interrupt

sources connect to the standard GPIO input path, an external interrupt pin may

simultaneously be used by a peripheral device or even configured as an output. Analog

mode is the only GPIO configuration that is not compatible with using a pin as an external

interrupt.

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