82801CA Datasheet, PDF (106/521 Pages) Intel Corporation – I/O Controller Hub 3-S (ICH3-S)

Functional Description
5.7
Intel^® 8259 Interrupt Controllers (PIC) (D31:F0)
The ICH3 incorporates the functionality of two 8259 interrupt controllers that provide system
interrupts for the ISA compatible interrupts. These interrupts are: system timer, keyboard
controller, serial ports, parallel ports, floppy disk, IDE, mouse, and DMA channels. In addition,
this interrupt controller can support the PCI based interrupts, by mapping the PCI interrupt onto the
compatible ISA interrupt line. Each 8259 core supports 8 interrupts, numbered 0–7. Table 5-14
shows how the cores are connected.
.
Table 5-14. Interrupt Controller Core Connections
Intel^® 8259
Intel^® 8259
Input
Typical Interrupt
Source
Connected Pin / Function
Master
Slave
0
Internal
Internal Timer / Counter 0 output / MMT #0
1
Keyboard
IRQ1 via SERIRQ
2
Internal
Slave Controller INTR output
3
Serial Port A
IRQ3 via SERIRQ
4
Serial Port B
IRQ4 via SERIRQ
5
Parallel Port / Generic
IRQ5 via SERIRQ
6
Floppy Disk
IRQ6 via SERIRQ
7
Parallel Port / Generic
IRQ7 via SERIRQ
0
Internal Real Time Clock
Internal RTC / MMT #1
1
Generic
IRQ9 via SERIRQ
2
Generic
IRQ10 via SERIRQ
3
Generic
IRQ11 via SERIRQ
4
PS/2 Mouse
IRQ12 via SERIRQ
5
Internal
State Machine output based on processor FERR#
assertion.
6
Primary IDE cable
IRQ14 from input signal (primary IDE in legacy mode
only) or via SERIRQ
7
Secondary IDE Cable
IRQ15 from input signal (secondary IDE in legacy
mode only) or via SERIRQ
The ICH3 cascades the slave controller onto the master controller through master controller
interrupt input 2. This means there are only 15 possible interrupts for the ICH3 PIC.
Interrupts can individually be programmed to be edge or level, except for IRQ0, IRQ2, IRQ8#, and
IRQ13.
Note that previous PIIXn devices internally latched IRQ12 and IRQ1 and required a port 60h read
to clear the latch. The ICH3 can be programmed to latch IRQ12 or IRQ1 (see bit 11 and bit 12 in
the General Control Register, D31:F0, offset D0h).
106
Intel^® 82801CA ICH3-S Datasheet