Intel MultiProcessor manual 10.I/O Interrupt Entry Fields

MultiProcessor Specification

Table 4-10. I/O Interrupt Entry Fields

	Offset	Length
Field	(in bytes:bits)	(in bits)	Description
ENTRY TYPE	0	8	Entry type 3 identifies an I/O interrupt
			entry.
INTERRUPT TYPE	1	8	See Table 4-11 for values.
PO	2:0	2	Polarity of APIC I/O input signals:

			00 =	Conforms to
				specifications of bus (for
				example, EISA is active-
				low for level-triggered
				interrupts)
			01 =	Active high
			10 =	Reserved
			11 =	Active low
			Must be 00 if the 82489DX is used.
EL	2:2	2	Trigger mode of APIC I/O input signals:
			00 =	Conforms to
				specifications of bus (for
				example, ISA is edge-
				triggered)
			01 =	Edge-triggered
			10 =	Reserved
			11 =	Level-triggered
SOURCE BUS ID	4	8	Identifies the bus from which the interrupt
			signal comes.
SOURCE BUS IRQ	5	8	Identifies the interrupt signal from the
			source bus. Values are mapped onto
			source bus signals, starting from zero. A
			value of 0, for example, would indicate
			IRQ0 of an ISA bus. See Section D.3 for
			PCI bus semantics.
DESTINATION I/O APIC ID	6	8	Identifies the I/O APIC to which the signal
			is connected. If the ID is 0FFh, the signal
			is connected to all I/O APICs.
DESTINATION I/O APIC INTIN#	7	8	Identifies the INTINn pin to which the
			signal is connected.

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