Altera Arria V GZ Avalon-ST - Manual (Page 51)

Power Management
Table 4-10: Power Management Parameters
Parameter Value Description
Endpoint L0s
acceptable
latency
Maximum of 64 ns
Maximum of 128 ns
Maximum of 256 ns
Maximum of 512 ns
Maximum of 1 us
Maximum of 2 us
Maximum of 4 us
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).
This Endpoint 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
Maximum of 1 us
Maximum of 2 us
Maximum of 4 us
Maximum of 8 us
Maximum of 16 us
Maximum of 32 us
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
.
This Endpoint does not support the L0s or L1 states. However,
a switched system may include 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.
4-14 Power Management
UG-01127_avst
2014.08.18
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