Altera IP Compiler for PCI Express - Manual (Page 195)

Chapter 10: Interrupts 10–5
PCI Express Interrupts for Root Ports
August 2014 Altera Corporation IP Compiler for PCI Express User Guide
■ When the AER option is enabled, the aer_msi_num[4:0] signal indicates which
MSI is being sent to the root complex when an error is logged in the AER
capability structure. This mechanism is an alternative to using the serr_out signal.
The aer_msi_num[4:0] is only used for root ports and you must set it to a constant
value. It cannot toggle during operation.
■ If the root port detects a power management event. The pex_msi_num[4:0] signal
is used by power management or hot plug to determine the offset between the
base message interrupt number and the message interrupt number to send
through MSI. The user must set pex_msi_num[4:0]to a fixed value.
The Root Error Status register reports the status of error messages. The root error
status
register is part of the PCI Express AER extended capability structure. It is
located at offset 0x830 of the configuration space registers.