Chapter 11: Interrupts
11–3
Interrupts for Endpoints Using the Avalon-ST Application Interface
November 2012
Altera Corporation
Arria V GZ Hard IP for PCI Express
There are 32 possible MSI messages. The number of messages requested by a
particular component does not necessarily correspond to the number of messages
allocated. For example, in
, the Endpoint requests eight MSIs but is only
allocated two. In this case, you must design the Application Layer to use only two
allocated messages.
Table 11–1
describes 3 example implementations; 1 in which all 32 MSI messages are
allocated and 2 in which only 4 are allocated.
MSI interrupts generated for Hot Plug, Power Management Events, and System
Errors always use TC0. MSI interrupts generated by the Application Layer can use
any Traffic Class. For example, a DMA that generates an MSI at the end of a
transmission can use the same traffic control as was used to transfer data.
illustrates the interactions among MSI interrupt signals for the Root Port
. The minimum latency possible between
app_msi_req
and
app_msi_ack
is one clock cycle.
Figure 11–3. MSI Request Example
Table 11–1. MSI Messages Requested, Allocated, and Mapped
MSI
Allocated
32
4
4
System Error
31
3
3
Hot Plug and Power Management Event
30
2
3
Application Layer
29:0
1:0
2:0
Endpoint
8 Requested
2 Allocated
Root Complex
CPU
Interrupt Register
Root
Port
Interrupt
Block