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Extended interrupt and event controller (EXTI) RM0367

294/1043 RM0367 Rev 7

13.3.3 Peripherals asynchronous interrupts

Some peripherals can generate events when the system is in Run mode or in Stop mode,

thus allowing to wake up the system from Stop mode.

To accomplish this, the peripheral generates both a synchronized (to the system clock, e.g.

APB clock) and an asynchronous version of the event. This asynchronous event is

connected to an EXTI direct line.

Note: Few peripherals with wakeup from Stop capability are connected to an EXTI configurable

line. In this case the EXTI configuration is required to allow the wakeup from Stop mode.

13.3.4 Hardware interrupt selection

To configure a line as an interrupt source, use the following procedure:

1. Configure the mask bits of the Interrupt lines (EXTI_IMR)

2. Configure the Trigger Selection bits of the Interrupt lines (EXTI_RTSR and

EXTI_FTSR)

3. Configure the enable and mask bits that control the NVIC IRQ channel mapped to the

extended interrupt controller (EXTI) so that an interrupt coming from any one of the

lines can be correctly acknowledged.

The direct lines do not require any EXTI configuration.

For code example, refer to A.7.2: Extended interrupt selection code example.

13.3.5 Hardware event selection

To configure a line as an event source, use the following procedure:

1. Configure the mask bits of the Event lines (EXTI_EMR)

2. Configure the Trigger Selection bits of the Event lines (EXTI_RTSR and EXTI_FTSR).

13.3.6 Software interrupt/event selection

Any of the configurable lines can be configured as software interrupt/event lines. The

procedure below must be followed to generate a software interrupt.

1. Configure the mask bits of the Interrupt/Event lines (EXTI_IMR, EXTI_EMR)

2. Set the required bit in the software interrupt register (EXTI_SWIER).

ST STM32L0x3 User Manual

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