Intel® Stratix® 10 Hard Processor System Technical Reference Manual

ID 683222
Date 11/28/2022
Public

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17.6.2.2. Host Bus Burst Access

The DMA attempts to execute fixed-length burst transfers on the master interface if configured to do so through the FB bit of Register 0 (Bus Mode Register). The maximum burst length is indicated and limited by the PBL field (Bits [13:8]) Register 0 (Bus Mode Register). The receive and transmit descriptors are always accessed in the maximum possible (limited by packet burst length (PBL) or 16 * 8/bus width) burst size for the 16‑ bytes to be read.

The transmit DMA initiates a data transfer only when the MTL transmit FIFO has sufficient space to accommodate the configured burst or the number of bytes remaining in the frame (when it is less than the configured burst length). The DMA indicates the start address and the number of transfers required to the master interface. When the interface is configured for fixed-length burst, it transfers data using the best combination of INCR4, 8, or 16 and SINGLE transactions. When not configured for fixed-length burst, it transfers data using INCR (undefined length) and SINGLE transactions.

The receive DMA initiates a data transfer only when sufficient data to accommodate the configured burst is available in MTL receive FIFO buffer or when the end of frame (when it is less than the configured burst length) is detected in the receive FIFO buffer. The DMA indicates the start address and the number of transfers required to the master interface. When the interface is configured for fixed-length burst, it transfers data using the best combination of INCR4, 8, or 16 and SINGLE transactions. If the end-of-frame is reached before the fixed burst ends on the interface, then dummy transfers are performed in order to complete the fixed burst. If the FB bit of Register 0 (Bus Mode Register) is clear, it transfers data using INCR (undefined length) and SINGLE transactions.

When the interface is configured for address aligned words, both DMA engines ensure that the first burst transfer initiated is less than or equal to the size of the configured packet burst length. Thus, all subsequent beats start at an address that is aligned to the configured packet burst length. The DMA can only align the address for beats up to size 16 (for PBL > 16), because the interface does not support more than INCR16.