Atmel AVR XMEGA AU series - Page 139

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8331B–AVR–03/12
Atmel AVR XMEGA AU
Figure 12-3. Static priority.
12.6.2 Round-robin Scheduling
To avoid the possible starvation problem for low-level interrupts with static priority, where some
interrupts might never be served, the PMIC offers round-robin scheduling for low-level interrupts.
When round-robin scheduling is enabled, the interrupt vector address for the last acknowledged
low-level interrupt will have the lowest priority the next time one or more interrupts from the low
level is requested.
Figure 12-4. Round-robin scheduling.
IVEC 0
:
:
:
IVEC x
IVEC x+1
:
:
:
IVEC N Lowest Priority
Highest Priority
Lowest Address
Highest Address
Highest Priority
IV EC 0
:
:
:
IV EC x
IV EC x +1
:
:
:
IV EC N
IV EC 0
:
:
:
IV EC x
IV EC x +1
:
:
:
IV EC N
Highest Priority
Low est Priority
IV EC x +2
IVEC x+1 last acknow ledged
interrupt
Low est Priority
IVEC x last acknowledged
interrupt