L-Tile and H-Tile Avalon® Memory-mapped Intel® FPGA IP for PCI Express* User Guide
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8.4. Read DMA and Write DMA Descriptor Format
Read and write descriptors are stored in separate descriptor tables in PCIe* system memory. Each table can store up to 128 descriptors. Each descriptor is 8 DWORDs, or 32 bytes. The Read DMA and Write DMA descriptor tables start at a 0x200 byte offset from the addresses programmed into the Read Status and Descriptor Base and Write Status and Descriptor Base address registers.
Programming RD_DMA_LAST_PTR or WR_DMA_LAST_PTR registers triggers the Read or Write Descriptor Controller descriptor table fetch process. Consequently, writing these registers must be the last step in setting up DMA transfers.
Address Offset |
Register Name | Description |
---|---|---|
0x00 |
RD_LOW_SRC_ADDR | Lower DWORD of the read DMA source address. Specifies the address in PCIe* system memory from which the Read Data Mover fetches data. |
0x04 |
RD_HIGH_SRC_ADDR | Upper DWORD of the read DMA source address. Specifies the address in PCIe* system memory from which the Read Data Mover fetches data. |
0x08 |
RD_CTRL_LOW_DEST_ADDR | Lower DWORD of the read DMA destination address. Specifies the address in the Avalon-MM domain to which the Read Data Mover writes data. |
0x0C |
RD_CTRL_HIGH_DEST_ADDR | Upper DWORD of the read DMA destination address. Specifies the address in the Avalon-MM domain to which the Read Data Mover writes data. |
0x10 | CONTROL | Specifies the following information:
|
0x14 - 0x1C | Reserved | N/A |
Address Offset |
Register Name | Description |
---|---|---|
0x00 |
WR_LOW_SRC_ADDR | Lower DWORD of the write DMA source address. Specifies the address in the Avalon® MM domain from which the Write Data Mover fetches data. |
0x04 |
WR_HIGH_SRC_ADDR | Upper DWORD of the write DMA source address. Specifies the address in the Avalon® MM domain from which the Write Data Mover fetches data. |
0x08 |
WR_CTRL_LOW_DEST_ADDR | Lower DWORD of the Write Data Mover destination address. Specifies the address in PCIe* system memory to which the Write DMA writes data. |
0x0C |
WR_CTRL_HIGH_DEST_ADDR | Upper DWORD of the write DMA destination address. Specifies the address in PCIe* system memory to which the Write Data Mover writes data. |
0x10 | CONTROL | Specifies the following information:
|
0x14 - 0x1C | Reserved | N/A |