Compaq iPAQ 1.0 User Manual

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

Compaq iPAQ 1.0 Specifications

General

Brand	Compaq
Model	iPAQ 1.0
Category	Desktop
Language	English