139
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
Lowes t Priority
Highes t Priority
Lowes t Addres s
Highes t Addres s
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
IV EC x+1 las t ack now le dge d
inte r r upt
Low est Priority
IV EC x las t ack now le dge d
inte r r upt
