November 2012
Altera Corporation
Arria V GZ Hard IP for PCI Express
11. Interrupts
This chapter describes interrupts for the following configurations:
■
“Interrupts for Endpoints Using the Avalon-ST Application Interface” on
page 11–1
■
“Interrupts for Root Ports Using the Avalon-ST Interface to the Application Layer”
on page 11–5
■
“Interrupts for Endpoints Using the Avalon-MM Interface to the Application
Layer” on page 11–5
■
Refer to
“Interrupts for Endpoints” on page 6–32
“Interrupts for Root Ports Using
the Avalon-ST Interface to the Application Layer” on page 11–5
for a description of
the interrupt signals.
Interrupts for Endpoints Using the Avalon-ST Application Interface
The Arria V GZ Hard IP for PCI Express provides support for PCI Express legacy
interrupts, MSI, and MSI-X interrupts when configured in Endpoint mode. The MSI,
MSI-X, and legacy interrupts are
mutually exclusive.
After power up, the Hard IP block
starts in INTX mode, after which time software decides whether to switch to MSI
mode by programming the
msi_enable
bit of the
MSI message control
register
(bit[16] of 0x050) to 1 or to MSI-X mode if you turn on
Implement MSI-X
under the
PCI Express/PCI Capabilities
tab using the parameter editor. If you turn on the
Implement MSI-X
option, you should implement the MSI-X table structures at the
memory space pointed to by the BARs.
f
Refer to section 6.1 of
PCI Express 2.1 Base Specification
for a general description of PCI
Express interrupt support for Endpoints.
MSI Interrupts
MSI interrupts are signaled on the PCI Express link using a single dword memory
write TLPs generated internally by the Arria V GZ Hard IP for PCI Express. The
app_msi_req
input port controls MSI interrupt generation. When the input port
asserts
app_msi_req
, it causes a MSI posted write TLP to be generated based on the
MSI configuration register values and the
app_msi_tc
and
app_msi_num
input ports.
To enable MSI interrupts, software must first set the
MSI
enable
bit (
) and then disable legacy interrupts by setting the
Interrupt Disable
which is bit 10 of the
Command
register (
November 2012
UG-01097-1.4