The WKUP1 and WKUP2 functions are activated through the edge detection on all GPIO pins. Any one of these GPIO pins when configured as an input pin can be configured to wake up the device by setting GPIOn_SEL bit to select the WKUP1 or WKUP2 functions. In the example PFSM depicted in Figure 8-42, when a GPIO pin is configured as a WKUP1 pin, a rising or falling edge detected at the input of this pin (configurable by the GPIOn_FALL_MASK and the GPIOn_RISE_MASK bits) wakes up the device to the ACTIVE state. Likewise if a GPIO pin is configured as a WKUP2 pin, a detected edge wakes up the device to the MCU ONLY state. If multiple edge detections of WKUP signals occur simultaneous, the device goes to the state in the following priority order:

1. ACTIVE
2. MCU ONLY

When a valid edge is detected at a WKUP pin, the nINT pin generates an interrupt to signal the MCU of the wake-up event, and the GPIOx_INT interrupt bit is set. The wake request remains active until the GPIOx_INT bit is cleared by the MCU. While the wake request is executing, the device does not react to sleep requests to enter a lower power state until the corresponding GPIOx_INT interrupt bit is cleared to cancel the wake request. After the wake request is canceled, the device returns to the state indicated by the NSLEEP1 and NSLEEP2 signals as shown in Table 8-20.