8-6
PG 720 P Programming Device
C79000-G7076-C721-02
8.2
Interrupt Assignments
The PG 720 uses the two integrated interrupt controllers of type 82C59 to handle
the 16 hardware 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 assigned to the software
interrupt vector 0A H (IRQ 2) by the ROM-BIOS.
The priority of the interrupts is in the reverse order of their numbering. This
means the following:
Interrupt IRQ 0 has the highest priority and interrupt IRQ 7 the lowest.
For triggering IRQ 2, interrupt IRQ 8 has the highest and IRQ 15 the lowest
priority. Interrupts IRQ 8 to IRQ 15 therefore have higher priority than
interrupts IRQ 3 to IRQ 7.
The interrupt vectors are initialized and masked when the PG 720 is powered
up.
Interrupt
Description
Assigned
Interrupt
Vector,
Memory
Address
SMI
System management interrupt, cannot be masked
–
NMI
Expansion slots signal I/O channel check 2
INT 2 H
IRQ 0
Internal timer (system clock)
INT 8 H
IRQ 1
Keyboard
INT 9 H
IRQ 2
Cascading from interrupt controller 2
INT A H
IRQ 3
Serial port 2 (COM2/IrDA) [can be enabled in setup]
INT B H
IRQ 4
Serial interface 1 (COM1/TTY) [can be enabled in
setup]
INT C H
IRQ 5
MPI port [can be enabled in setup]
INT D H
IRQ 6
Floppy controller
INT E H
IRQ 7
Parallel port 1 (printer port LPT 1/EPP/ECP)
[can be enabled in setup]
INT F H
IRQ 8
Battery-backed real-time clock (RTC)
INT 70 H
IRQ 9
VGA controller [generally not used]
INT 71 H
IRQ 10
Free or PCMCIA driver
INT 72 H
IRQ 11
Free or PCMCIA driver
INT 73 H
IRQ 12
PS/2 mouse or trackball in keyboard.
Can be enabled in setup if mouse/trackball function is
not required.
INT 74 H
IRQ 13
Math coprocessor error
INT 75 H
IRQ 14
IDE interface
INT 76 H
IRQ 15
Free or PCMCIA driver
INT 77 H
Note the interrupts which are already occupied in the system.
Interrupt
Assignment
Priority
I/O Addresses of
the Interrupt
Controllers
Hardware Information