February, 2007
INTx-Type Interrupt Message Remapping and Collapsing
6.2.1
INTx-Type Interrupt Message Remapping and Collapsing
INTx-type Interrupt messages from downstream devices are directly forwarded to the upstream port,
rather than being terminated and regenerated by the downstream port. The upstream port remaps and
collapses the INTx message type received at the downstream port, based upon the downstream port’s
Device Number and Received INTx message Requester ID Device Number, and generates a new
Interrupt message, according to the mapping defined in Table 6-1.
A downstream port transmits an Assert_INTA/Deassert_INTA message to the upstream port, due to
a device-specific error.
Internally generated INTx messages always originate as type INTA messages, because the PEX 8532 is
a single-function device. Internally generated Interrupt INTA messages from downstream ports are
remapped at the upstream port to INTA, INTB, INTC, or INTD messages, according to the mapping
defined in Table 6-1.
INTx messages from downstream devices and from internally generated Interrupt messages are ORed
together to generate INTA, INTB, INTC, or INTD level-sensitive signals, and edge-detection circuitry
in the upstream port generates the Assert_INTx and Deassert_INTx messages. The upstream port then
forwards the new messages upstream, by way of its link.
Table 6-1. Downstream/Upstream Port INTx Interrupt Message Mapping
Device Number
At Downstream Port
INTA
By Upstream Port
INTA
INTB
INTB
0, 8
INTC
INTC
INTD
INTD
INTA
INTB
INTB
INTC
1, 9
2, 10
3, 11
INTC
INTD
INTD
INTA
INTA
INTC
INTB
INTD
INTC
INTA
INTD
INTB
INTA
INTD
INTB
INTA
INTC
INTB
INTD
INTC
ExpressLane PEX 8532AA/BA/BB/BC 8-Port/32-Lane Versatile PCI Express Switch Data Book
Copyright © 2007 by PLX Technology, Inc. All Rights Reserved – Version 1.6
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