P-tile Avalon® Memory-mapped Intel® FPGA IP for PCI Express* User Guide

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ID 683268
Date 7/14/2021
Public
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2.2.4.1. Endpoint Mode with Data Movers

When the Avalon® -MM Bridge is used in this mode, the following modules are enabled:
  • Read Data Mover (RDDM)
  • Write Data Mover (WRDM)
  • Bursting Master (BAM) in Non-Bursting Mode

The following figure shows how the DMA example design that you can generate using the Intel® Quartus® Prime software interfaces with the P-Tile Avalon® -MM IP to perform DMA operations. If you are not using the provided DMA example design, you need to implement your custom DMA Controller and BAR Interpreter in your application logic.

Figure 10. P-Tile Avalon® -MM IP in Endpoint Mode with Data Movers Enabled

In this DMA example design, the BAM is used in non-bursting mode by the host to program the Control and Status registers of the DMA controller in the user Avalon® -MM space. The DMA controller, after being programmed, sends descriptor-fetching instructions to the host via the RDDM. After the fetched descriptors are processed by the WRDM and RDDM, status and/or MSI-X messages are sent to the host via the WRDM in “Immediate” mode. In this mode, the data payload is embedded in bits [31:0] or [63:0] of the fetched descriptors that the WRDM receives (depending on whether a one- or two-dword immediate transfer is needed respectively). For more details on immediate transfers, refer to Write Data Mover Avalon -ST Descriptor Sinks.

The RDDM uses PCIe memory read TLPs and Avalon® -MM write transactions (which can be bursting transactions) to move large amounts of data from the host memory in PCIe space to the local FPGA memory in Avalon® -MM space. On the other hand, the WRDM uses PCIe memory write TLPs and Avalon® -MM read transactions to move large amounts of data from the FPGA memory in Avalon® -MM space to the host memory in PCIe space. The Data Movers' transfers are controlled by descriptors that are provided to the Data Movers through one of their Avalon® -ST sink interfaces. The Data Movers report the transfers’ status through their Avalon® -ST source interfaces.

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