82801DB Datasheet, PDF (335/587 Pages) Intel Corporation – Intel 82801DB I/O Controller Hub 4 (ICH4)

LPC Interface Bridge Registers (D31:F0)
9.5.10
Redirection Table
Index Offset:
Default Value:
10h–11h (vector 0) through
3E–3Fh (vector 23)
Bit 16=1, Bits[15:12]=0.
All other bits undefined
Attribute:
Size:
R/W, RO
64 bits each, (accessed as
two 32 bit quantities)
The Redirection Table has a dedicated entry for each interrupt input pin. The information in the
Redirection Table is used to translate the interrupt manifestation on the corresponding interrupt pin
into an APIC message.
The APIC will respond to an edge triggered interrupt as long as the interrupt is held until after the
acknowledge cycle has begun. Once the interrupt is detected, a delivery status bit internally to the
I/O APIC is set. The state machine will step ahead and wait for an acknowledgment from the APIC
bus unit that the interrupt message was sent over the APIC bus. Only then will the I/O APIC be
able to recognize a new edge on that interrupt pin. That new edge will only result in a new
invocation of the handler if its acceptance by the destination APIC causes the Interrupt Request
Register bit to go from 0 to 1. (In other words, if the interrupt was not already pending at the
destination.)
Bit
63:56
55:48
47:17
16
15
14
13
Description
Destination — R/W.
If bit 11 of this entry is 0 [Physical], then bits [59:56] specifies an APIC ID. In this case, bits 63:59
should be programmed by software to 0.
If bit 11 of this entry is 1 [Logical], then bits [63:56] specify the logical destination address of a set
of processors.
Extended Destination ID (EDID). These bits are only sent to a local APIC when in Processor
System Bus mode. They become bits [11:4] of the address.
Reserved
Mask — R/W.
0 = Not masked: An edge or level on this interrupt pin results in the delivery of the interrupt to the
destination.
1 = Masked: Interrupts are not delivered nor held pending. Setting this bit after the interrupt is
accepted by a local APIC has no effect on that interrupt. This behavior is identical to the
device withdrawing the interrupt before it is posted to the processor. It is software's
responsibility to deal with the case where the mask bit is set after the interrupt message has
been accepted by a local APIC unit but before the interrupt is dispensed to the processor.
Trigger Mode — R/W. This field indicates the type of signal on the interrupt pin that triggers an
interrupt.
0 = Edge triggered.
1 = Level triggered.
Remote IRR — R/W. This bit is used for level-triggered interrupts; its meaning is undefined for
edge-triggered interrupts.
0 = Reset when an EOI message is received from a local APIC.
1 = Set when Local APIC/s accept the level interrupt sent by the I/O APIC.
Interrupt Input Pin Polarity — R/W. This bit specifies the polarity of each interrupt signal
connected to the interrupt pins.
0 = Active high.
1 = Active low.
Intel^® 82801DB ICH4 Datasheet
335