Intel
®
81341 and 81342—Interrupt Controller Unit
Intel
®
81341 and 81342 I/O Processors
Developer’s Manual
December 2007
746
Order Number: 315037-002US
11.4.2
Outbound Interrupts
When 81341 and 81342 is setup as an endpoint device with the PCI-X interface, the
XINT[3:0]#
pins act as output pins (
P_INT[D:A]#
)
respectively. The Messaging Unit
(MU) has the capability of generating interrupts on the PCI interrupt output pins. The
MU has four distinct messaging mechanisms. Each allows a host processor or external
PCI agent and the 81341 and 81342 to communicate through message passing and
interrupt generation. The four mechanisms are:
•
Message Registers
— allow the 81341 and 81342 and external PCI agents to
communicate by passing messages in one of four 32-bit Message Registers. In this
context, a message is any 32-bit data value. Message registers combine aspects of
mailbox registers and doorbell registers. Writes to the message registers may
optionally cause interrupts.
•
Doorbell Registers
— allow the 81341 and 81342 to assert the PCI interrupt
signals and allow external PCI agents to generate an interrupt to the Intel XScale
®
processor.
•
Circular Queues
— support a message passing scheme that uses four circular
queues.
•
Index Registers
— support a message passing scheme that uses a portion of the
81341 and 81342 local memory to implement a large set of message registers.
All four mechanisms can result in Outbound Interrupts to a host processor.
The external interrupt output interface for 81341 and 81342 consists of the pins shown
in
.
Table 453. Interrupt Output Pin Descriptions
Signal
Description
P_INTA#
Primary PCI Interrupt output of 81341 and 81342 source from the MU.
P_INTB#
Primary PCI Interrupt output of 81341 and 81342
source from the MU.
P_INTC#
Primary PCI Interrupt output of 81341 and 81342
source from the MU.
P_INTD#
Primary PCI Interrupt output of 81341 and 81342
source from the MU.