SPRUI30H November 2015 – May 2024 DRA745 , DRA746 , DRA750 , DRA756
Most of the accesses (Memory-space) are typically flowing straight through the controller, from PCIe bus to L3_MAIN or the other way. However, some transactions are accesses to the PCIe device’s configuration registers:
Figure 24-161 also gives a simplified view of the accesses allowed by device PCIe controller.
On the right hand side of the diagram is the PCIe_PHY (PCS+PMA), itself connected to the PCIe wires. The same structure is expected in the link partner on the other side of the link. Each partner can initiate and complete transactions on the link, using a packet-based protocol. Each lane is a full-duplex serial channel, that is, packets can be exchanged in both directions simultaneously. When more than one lane is used, each packet is transmitted in parallel over all active lanes.
The bidirectional accesses, initiated from components on the PCIe bus (fabric) to/from the device local PCIe subsystem are identified as Inbound traffic, while the bidirectional accesses, initiated by device local PCIe system to/from the PCIe bus are identified as Outbound traffic.
Note that there are two ways to transmit data from the local PCIe system to a distant PCIe partner:
Likewise, there are two ways for the local PCIe system to receive data from a distant PCIe partner:
Inbound PCIe I/O transfers are supported by the PCIe controller only in EP mode (typically for legacy PCI - EPs).