IDT 89HPES12T3G2, Preliminary User'S Manual

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IDT Link Operation
PES12T3G2 User Manual 3 - 7 January 28, 2013
Notes
Downstream Port
A Set_Slot_Power_Limit message is sent by downstream switch ports when either of the following
events occur.
– A configuration write is performed to the corresponding PCIESCAP register when the link associ-
ated with the downstream port is up.
– A link associated with the downstream port transitions from a non-operational state to an opera-
tional (i.e., data link up) state.
Link States
The PES12T3G2 supports the following link states
– L0
• Fully operational link state
– L0s
• Automatically entered low power state with shortest exit latency
– L1
• Lower power state than L0s
• May be automatically entered or directed by software by placing the device in the D3
hot
state
– L2/L3 Ready
• The L2/L3 state is entered after the acknowledgement of a PM_Turn_Off Message.
• There is no TLP or DLLP communications over a link in this state.
– L3
• Link is completely unpowered and off
– Link Down
• A transitional link down pseudo-state prior to L0. This pseudo-state is associated with the
LTSSM Detect, Polling, Configuration, Disabled, Loopback and Hot-Reset states.
Figure 3.3 PES12T3G2 ASPM Link Sate Transitions
L0
L0s L1
L2/L3 Ready
L3
Link Down
Fundamental Reset
Hot Reset
Etc.