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Chapter 4 System Support
Compaq iPAQ Series of Desktop Personal Computers
Second Edition – February 2001
4-8
8259 Mode
In 8259-Mode, interrupts IRQ0-IRQ15 are handled in the conventional (AT-system) method using
logic that is the equivalent of two 8259 interrupt controllers. Table 4-3 lists the standard source
configuration for maskable interrupts and their priorities in 8259 mode. If more than one interrupt
is pending, the highest priority (lowest number) is processed first.
Table 4-3.
Maskable Interrupt Priorities and Assignments
Table 4-3.
Maskable Interrupt Priorities and Assignments
Priority
Signal Label
Source (Typical)
1
IRQ0
Interval timer 1, counter 0
2
IRQ1
Keyboard
3
IRQ8-
Real-time clock
4
IRQ9
Unused
5
IRQ10
Unused
6
IRQ11
Unused
7
IRQ12
Mouse
8
IRQ13
Coprocessor (math)
9
IRQ14
IDE primary I/F
10
IRQ15
IDE secondary I/F
11
IRQ3
Serial port (COM2)
12
IRQ4
Serial port (COM1)
13
IRQ5
Unused
14
IRQ6
Diskette drive controller
15
IRQ7
Parallel port (LPT1)
--
IRQ2
NOT AVAILABLE (Cascade from interrupt controller 2)
APIC Mode
The Advanced Programmable Interrupt Controller (APIC) mode enhances interrupt-processing
performance with the following advantages:
♦
Eliminating the processor’s interrupt acknowledge cycle by using a separate APIC bus.
♦
Programmable interrupt priority.
♦
Additional interrupts (total of 24).
NOTE:
The APIC mode is supported by Windows NT/2000 operating systems. Systems
using the Windows 95 or 98 operating system will need to run in 8259 mode. The mode is
selectable through the Setup utility (access with F10 key during boot sequence).
Maskable Interrupt processing is controlled and monitored through standard AT-type I/O-mapped
registers. These registers are listed in Table 4-4.
Table 4-4.
Maskable Interrupt Control Registers
Table 4-4.
Maskable Interrupt Control Registers
I/O Port
Register
020h
Base Address, Int. Cntlr. 1
021h
Initialization Command Word 2-4, Int. Cntlr. 1
0A0h
Base Address, Int. Cntlr. 2
0A1h
Initialization Command Word 2-4, Int. Cntlr. 2
Содержание iPAQ 1.0
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