The constructor passes its arguments to the base class constructor for processing. It then sets up intrMethod as a SystemC method process, sensitive to the positive edge of each interrupt signal. There is no need to initialize this function.

  SC_METHOD( intrMethod );
  for( i = 0 ; i < NUM_INTR ; i++ ) {
    sensitive << intr[i].posedge_event();
  }
  dont_initialize();
	  

The interrupt method is triggered by a positive edge on one of the signals. It loops through to find which interrupt was triggered and generates a call to or1ksim_interrupt for that interrupt number. In principle more than one could be triggered in the same cycle, so all are checked.

  for( i = 0 ; i < NUM_INTR ; i++ ) {
    if( intr[i].event()) {
      or1ksim_interrupt( i );
    }
  }
	  

The implementation of the Or1ksim ISS wrapper module class with interrupts, Or1ksimIntrSC may be found in sys-models/intr-soc/Or1ksimIntrSC.cpp in the distribution.