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30 CPCI-7806/CPCI-7806RC Pentium/Celeron M Universal CompactPCI Single Board Computer
Publication No. 500-657806-000 Rev. G
2.4 Interrupts
2.4.1 System Interrupts
In addition to an I/O port address, an I/O device has a separate hardware
interrupt line assignment. Assigned to each interrupt line is a corresponding
interrupt vector in the 256-vector interrupt table at $00000 to $003FF in memory.
The 16 maskable interrupts and the single Non-Maskable Interrupt (NMI) are
listed in
along with their functions.
details the
vectors in the interrupt vector table. The interrupt number in HEX and decimal
are also defined for real and protected mode in
The interrupt hardware implementation on the CPCI-7806/CPCI-7806RC is
standard for computers built around the PC architecture, which evolved from the
IBM PC/XT. In the IBM PC/XT computers, only eight interrupt request lines exist,
numbered from IRQ0 to IRQ7 at the PIC. The IBM PC/AT computer added eight
more IRQx lines, numbered IRQ8 to IRQ15, by cascading a second slave PIC into
the original master PIC. IRQ2 at the master PIC was committed as the cascade
input from the slave PIC. This architecture is represented in
To maintain backward compatibility with PC/XT systems, IBM chose to use the
new IRQ9 input on the slave PIC to operate as the old IRQ2 interrupt line on the
PC/XT Expansion Bus. Thus, in AT systems, the IRQ9 interrupt line connects to
the old IRQ2 pin (pin B4) on the AT Expansion Bus (or ISA bus).
NOTE
IPMI is no longer supported. Older boards may have IPMI.
Table 2-2 PC Hardware Interrupt Line Assignments
IRQ
AT FUNCTION
COMMENTS
NMI
Parity Errors (Must be enabled in BIOS Setup)
Used by CPCI-7806/CPCI-7806RC PCIbus
Interface
0
System Timer
Set by BIOS Setup
1
Keyboard
Set by BIOS Setup
2
Duplexed to IRQ9
3
COM2
4
COM1
5
IPMI
Reserved for IPMI Serial Port
6
Floppy Controller
7
Not Assigned
Determined by BIOS
8
Real-Time Clock
9
Old IRQ2
Determined by BIOS
10
Not Assigned
Determined by BIOS
11
Not Assigned
Determined by BIOS
12
Mouse
13
Math Coprocessor
14
AT Hard Drive
15
CompactFlash Drive