User guide

Table Of Contents
5–8 Chapter 5: Parameter Settings for the Avalon-MM Cyclone V Hard IP for PCI Express
PCI Express/PCI Capabilities
Cyclone V Hard IP for PCI Express December 2013 Altera Corporation
User Guide
Power Management
Table 59 describes the Power Management parameters.
Table 5–9. Power Management Parameters
Parameter Value Description
Endpoint L0s
acceptable latency
< 64 ns – > No limit
This design parameter specifies the maximum acceptable latency that the
device can tolerate to exit the L0s state for any links between the device and
the root complex. It sets the read-only value of the Endpoint L0s acceptable
latency field of the
Device Capabilities
register (0x084).
The Cyclone V Hard IP for PCI Express does not support the L0s or L1
states. However, in a switched system there may be links connected to
switches that have L0s and L1 enabled. This parameter is set to allow
system configuration software to read the acceptable latencies for all
devices in the system and the exit latencies for each link to determine which
links can enable Active State Power Management (ASPM). This setting is
disabled for Root Ports.
The default value of this parameter is 64 ns. This is the safest setting for
most designs.
Endpoint L1
acceptable latency
< 1 µs to > No limit
This value indicates the acceptable latency that an Endpoint can withstand
in the transition from the L1 to L0 state. It is an indirect measure of the
Endpoint’s internal buffering. It sets the read-only value of the Endpoint L1
acceptable latency field of the
Device Capabilities
register.
The Cyclone V Hard IP for PCI Express does not support the L0s or L1
states. However, in a switched system there may be links connected to
switches that have L0s and L1 enabled. This parameter is set to allow
system configuration software to read the acceptable latencies for all
devices in the system and the exit latencies for each link to determine which
links can enable Active State Power Management (ASPM). This setting is
disabled for Root Ports.
The default value of this parameter is 1 µs. This is the safest setting for
most designs.