Microchip Technology megaAVR 0 Series Manual page 107

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megaAVR 0-Series
CPU Interrupt Controller (CPUINT)
If the program never enables an interrupt source, the Interrupt Vectors are not used, and regular program
code can be placed at these locations.
12.3.2.3 Interrupt Response Time
The minimum interrupt response time for all enabled interrupts is three CPU clock cycles: one cycle to
(1)
finish the ongoing instruction, two cycles to store the Program Counter to the stack, and three cycles to
jump to the interrupt handler (JMP).
After the Program Counter is pushed on the stack, the program vector for the interrupt is executed. See
Figure 12-2, first diagram.
(1)
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 Figure 12-2, second
diagram.
If an interrupt occurs when the device is in sleep mode, the interrupt execution response time is
increased by five clock cycles. In addition, the response time is increased by the start-up time from the
selected sleep mode. See Figure 12-2, third diagram.
A return from an interrupt handling routine takes four to five clock cycles, depending on the size of the
Program Counter. During these clock cycles, the Program Counter is popped from the stack and the
Stack Pointer is incremented.
Datasheet Preliminary
DS40002015A-page 107
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