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8331B–AVR–03/12
Atmel AVR XMEGA AU
12.4.1
NMI – Non-Maskable Interrupts
Which interrupts represent NMI and which represent regular interrupts cannot be selected. Non-
maskable interrupts must be enabled before they can be used. Refer to the device datasheet for
NMI present on each device.
An NMI will be executed regardless of the setting of the I bit, and it will never change the I bit. No
other interrupts can interrupt a NMI handler. If more than one NMI is requested at the same time,
priority is static according to the interrupt vector address, where the lowest address has highest
priority.
12.4.2
Interrupt Response Time
The interrupt response time for all the enabled interrupts is three CPU clock cycles, minimum;
one cycle to finish the ongoing instruction and two cycles to store the program counter to the
stack. After the program counter is pushed on the stack, the program vector for the interrupt is
executed. The jump to the interrupt handler takes three clock cycles.
If an interrupt occurs during execution of a multicycle instruction, this instruction is completed
before the interrupt is served. See