AT32UC3C2512C Automotive Atmel Corporation, AT32UC3C2512C Automotive Datasheet - Page 188

• Manufacturer Part Number: AT32UC3C2512C Automotive
• Manufacturer: Atmel Corporation

12.6.2
9166C–AVR-08/11
Synchronization and Filtering of External Interrupts
Each external interrupt INTn can be configured to produce an interrupt on rising or falling edge,
or high or low level. External interrupts are configured by the MODE, EDGE, and LEVEL regis-
ters. Each interrupt has a bit INTn in each of these registers. Writing a zero to the INTn bit in the
MODE register enables edge triggered interrupts, while writing a one to the bit enables level trig-
gered interrupts.
If INTn is configured as an edge triggered interrupt, writing a zero to the INTn bit in the EDGE
register will cause the interrupt to be triggered on a falling edge on EXTINTn, while writing a one
to the bit will cause the interrupt to be triggered on a rising edge on EXTINTn.
If INTn is configured as a level triggered interrupt, writing a zero to the INTn bit in the LEVEL
register will cause the interrupt to be triggered on a low level on EXTINTn, while writing a one to
the bit will cause the interrupt to be triggered on a high level on EXTINTn.
Each interrupt has a corresponding bit in each of the interrupt control and status registers. Writ-
ing a one to the INTn bit in the Interrupt Enable Register (IER) enables the external interrupt
from pin EXTINTn to propagate from the EIC to the interrupt controller, while writing a one to
INTn bit in the Interrupt Disable Register (IDR) disables this propagation. The Interrupt Mask
Register (IMR) can be read to check which interrupts are enabled. When an interrupt triggers,
the corresponding bit in the Interrupt Status Register (ISR) will be set. This bit remains set until a
one is written to the corresponding bit in the Interrupt Clear Register (ICR) or the interrupt is
disabled.
Writing a one to the INTn bit in the Enable Register (EN) enables the external interrupt on pin
EXTINTn, while writing a one to INTn bit in the Disable Register (DIS) disables the external inter-
rupt. The Control Register (CTRL) can be read to check which interrupts are enabled. If a bit in
the CTRL register is set, but the corresponding bit in IMR is not set, an interrupt will not propa-
gate to the interrupt controller. However, the corresponding bit in ISR will be set, and
EIC_WAKE will be set. Note that an external interrupt should not be enabled before it has been
configured correctly.
If the CTRL.INTn bit is zero, the corresponding bit in ISR will always be zero. Disabling an exter-
nal interrupt by writing a one to the DIS.INTn bit will clear the corresponding bit in ISR.
Please refer to the Module Configuration section for the number of external interrupts.
In synchronous mode the pin value of the EXTINTn pin is synchronized to CLK_SYNC, so
spikes shorter than one CLK_SYNC cycle are not guaranteed to produce an interrupt. The syn-
chronization of the EXTINTn to CLK_SYNC will delay the propagation of the interrupt to the
interrupt controller by two cycles of CLK_SYNC, see
(FILTER off).
It is also possible to apply a filter on EXTINTn by writing a one to the INTn bit in the FILTER reg-
ister. This filter is a majority voter, if the condition for an interrupt is true for more than one of the
latest three cycles of CLK_SYNC the interrupt will be set. This will additionally delay the propa-
gation of the interrupt to the interrupt controller by one or two cycles of CLK_SYNC, see
12-2
and
Figure 12-3
for examples (FILTER on).
Figure 12-2
and
Figure 12-3
AT32UC3C
for examples
Figure
188