Data Link Feature Exchange

The PCIe Controller supports the data link feature exchange as per the PCI Express Base 4 specification. You enable/disable this feature by programming the DL Feature Exchange Enable bit in the dl_feature_capabilities_reg Configuration register. When enabled, the PCIe Controller's Data Link Control and Management State Machine enters the DL_Feature state from the DL_Inactive state after the LTSSM is in L0. In the DL_Feature state, the PCIe Controller transmits data link feature DLLPs continuously. It does not transmit any other TLPs or DLLPs in this state.

The PCIe Controller transitions from the DL_Feature state to the DL_Init state when a DL Feature DLLP is received with the feature Ack bit set. If the remote end device does not support DL Feature Exchange, the PCIe Controller transitions from the DL_Feature state to the DL_Init State when it receives a a InitFC1 DLLP.

The PCIe Controller supports the Scaled Flow Control Data Link features as described in the following topics.