The DMA/Bridge Subsystem for PCI Express® ( PCIe® ) can be configured to be either a high-performance direct memory access (DMA) data mover or a bridge between the PCI Express and AXI memory spaces.
- DMA Data Mover
- As a DMA, the core can be configured with either an AXI (memory mapped) interface or with an AXI streaming interface to allow for direct connection to RTL logic. Either interface can be used for high performance block data movement between the PCIe address space and the AXI address space using the provided character driver. In addition to the basic DMA functionality, the DMA supports up to four upstream and downstream channels, the ability for PCIe traffic to bypass the DMA engine (Host DMA Bypass), and an optional descriptor bypass to manage descriptors from the FPGA fabric for applications that demand the highest performance and lowest latency.
- Bridge Between PCIe and AXI Memory
- When configured as a PCIe Bridge, received PCIe packets are converted to AXI traffic and received AXI traffic is converted to PCIe traffic. The bridge functionality is ideal for AXI peripherals needing a quick and easy way to access a PCI Express subsystem. The bridge functionality can be used as either an Endpoint or as a Root Port. PCIe Bridge functionality is only supported for AMD UltraScale+™ devices. For Bridge only option and for 7 series non-XT device, you should use AXI Memory Mapped to PCI Express (PCIe) Gen2. For details see, AXI Memory Mapped to PCI Express (PCIe) Gen2 LogiCORE IP Product Guide (PG055). For 7 series XT and UltraScale device, you should use AXI Bridge for PCI Express Gen3. For details, see AXI Bridge for PCI Express Gen3 Subsystem Product Guide (PG194).
This document covers DMA mode operation only.
Figure 1.
DMA/Bridge Subsystem for PCI Express® Overview
This diagram refers to the Requester Request (RQ)/Requester Completion (RC) interfaces, and the Completer Request (CQ)/Completer Completion (CC) interfaces. For more information about these, see the UltraScale+ Devices Integrated Block for PCI Express LogiCORE IP Product Guide (PG213).