An interrupt must be initialized in the following order:

  1. 1.Configure the CPUINT if the default configuration is not adequate (optional):
    • Vector handling is configured by writing to the respective bits (IVSEL and CVT) in the Control A (CPUINT.CTRLA) register.
    • Vector prioritizing by round robin is enabled by writing a ‘1’ to the Round Robin Priority Enable (LVL0RR) bit in CPUINT.CTRLA.
    • Select the Priority Level 1 vector by writing the interrupt vector number to the Interrupt Vector with Priority Level 1 (CPUINT.LVL1VEC) register.
  2. 2.Configure the interrupt conditions within the peripheral and enable the peripheral’s interrupt.
  3. 3.Enable interrupts globally by writing a ‘1’ to the Global Interrupt Enable (I) bit in the CPU Status (CPU.SREG) register.