In the SIMATIC Box PC 620, the 16 hardware interrupts (IRQ 0 to IRQ 15) are
processed by two integrated interrupt controllers of the type 82C59.
The INT output of the slave controller is connected to the IRQ 2 input of the master
controller. Interrupt 9 (IRQ 9) can be used on the bus for the assigned interrupt 2
(IRQ 2). In the initialization phase, IRQ is programmed for the software interrupt
vector 0A H (IRQ 2) by the ROM-BIOS.
The interrupts are priority-scheduled in the reverse order of their numbering.
Interrupt IRQ 0 has the highest priority and interrupt IRQ 7 the lowest. For
triggering IRQ 2, interrupt IRQ 8 has the highest priority and interrupt IRQ15 the
lowest. Interrupts IRQ 8 to IRQ 15 therefore have priority over interrupts IRQ 3 to
IRQ 7. The interrupt vectors are initialized and masked when the
SIMATIC Box PC 620 is powered up.
SIMATIC Box PC 620 Manual