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8331B–AVR–03/12
Atmel AVR XMEGA AU
13.7 Port Event
Port pins can generate an event when there is a change on the pin. The sense configurations
decide the conditions for each pin to generate events. Event generation requires the presence of
a peripheral clock, and asynchronous event generation is not possible. For edge sensing, the
changed pin value must be sampled once by the peripheral clock for an event to be generated.
For level sensing, a low-level pin value will not generate events, and a high-level pin value will
continuously generate events. For events to be generated on a low level, the pin configuration
must be set to inverted I/O.
13.8 Alternate Port Functions
Most port pins have alternate pin functions in addition to being a general purpose I/O pin. When
an alternate function is enabled, it might override the normal port pin function or pin value. This
happens when other peripherals that require pins are enabled or configured to use pins. If and
how a peripheral will override and use pins is described in the section for that peripheral.
The port override signals and related logic (grey) are shown in Figure 13-10 on page 151. These
signals are not accessible from software, but are internal signals between the overriding periph-
eral and the port pin.
Table 13-3. Limited asynchronous sense support.
Sense Settings Supported Interrupt Description
Rising edge No -
Falling edge No -
Any edge Yes Pin value must be kept unchanged during wake up
Low level Yes Pin level must be kept unchanged during wake up
Table 13-4. Event sense support.
Sense Settings Signal event Data event
Rising edge Rising edge Pin value
Falling edge Falling edge Pin value
Both edge Any edge Pin value
Low level Pin value Pin value
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