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2.8
Interrupt Assignments
Interrupt
Two integral interrupt controllers of the type 82C59 handle the 16 hardware
Assignments
interrupts (IRQ 0 to IRQ 15).
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 9 is programmed for the
software interrupt vector 0A H (IRQ 2) by the ROM-BIOS.
Priority
The interrupts are priority-scheduled in reverse number order. 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 PC is
powered up.
I/O Addresses of
Interrupt
the Interrupt
SMI
Controllers
NMI
IRQ 0
IRQ 1
IRQ 2
IRQ 3
IRQ 4
IRQ 5
IRQ 6
IRQ 7
IRQ 8
IRQ 9
IRQ 10
IRQ 11
IRQ 12
IRQ 13
IRQ 14
IRQ 15
Do not use interrupts already assigned in the system.
*)
**)
RI 45 PIII, Manual
C79000-G7076-C817-01
Assignment
System management interrupt,
cannot be masked
Signal IO channel check 2
Timer output 0
Keyboard (keyboard buffer full)
Cascaded (slave interrupt controller)
Serial port 2
Serial port 1
Sound
FD controller
Parallel port 1
Real-time clock (RTC)
VGA (generally not used)
Onboard MPI / DP
Vacant
PS/2 mouse
Numeric processor
1st HD controller (primary)
2nd HD controller (secondary)
These components can be disabled via the BIOS SETUP. The
functions are then no longer available and the resources are released
for other components.
The on-board MPI/DP interface is plug&play-capable, the occupied
resources are managed by the BIOS.
Motherboard
Remark
Vector
-
-
Fixed
INT2H
Fixed
INT8H
Fixed
INT9H
Fixed
INTAH
Can be switched off *) INTBH
Can be switched off *) INTCH
P&P **)
INTDH
Can be switched off *) INTEH
Can be switched off *) INTFH
Fixed
INT70H
Vacant (AT 9 = XT 2)
INT71H
P&P **)
INT72H
Vacant
INT73H
Can be switched off *) INT74H
Fixed
INT75H
Fixed
INT76H
Can be switched off *) INT77H
2-23
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