Intel
®
81341 and 81342 I/O Processors
December 2007
Developer’s Manual
Order Number: 315037-002US
285
Address Translation Unit (PCI Express)—Intel
®
81341 and 81342
3.12
Message-Signaled Interrupts
The Messaging Unit is responsible for the generation of all of the Outbound Interrupts
from the 81341 and 81342. These interrupts can be delivered to the Host Processor via
the legacy Assert_INTx/Deassert_INTx messages or the Message Signaled Interrupt
(MSI) mechanism.
When a host processor enables Message-Signaled Interrupts (MSI) on the 81341 and
81342, an outbound interrupt is signaled to the host via a posted write instead of the
legacy Assert/Deassert messages.
In support of MSI, the 81341 and 81342 implements the MSI capability structure. The
capability structure includes the
Section 4.9.30, “MSI Capability Identifier Register -
Section 4.9.31, “MSI Next Item Pointer Register -
Section 4.9.33, “Message Address Register -
, the
Section 4.9.34, “Message Upper Address Register
- Message_Upper_Address” on page 454
and the
Register- Message_Data” on page 455
The Message Unit generates MSIs by writing to the MSI port via the internal bus. The
ATU generates a write transaction whenever the Message Unit writes to the MSI port,
using the address specified in the
Section 4.9.33, “Message Address Register -
Section 4.9.34, “Message Upper Address Register
- Message_Upper_Address” on page 454
and the data provided in the
“Message Data Register- Message_Data” on page 455
.
3.12.1
Legacy Interrupts
The ATU supports the generation of the legacy Assert_INTx/Deassert_INTx interrupt
messages.
3.12.2
Internal Interrupts
The ATU has 4 internal interrupts that connect to the internal Interrupt Controller Unit.
ATU Error Interrupt
ATU Inbound Message Interrupt
ATU Configuration Write Interrupt
ATU BIST Interrupt