Altera Stratix V Avalon-ST - Manual (Page 224)

Bit Field Description
[15:0] Write DMA EPLAS Indicates the number of the last descriptor completed by the write
DMA. For simultaneous DMA read and write transfers, EPLAST
is only supported for the final descriptor in the descriptor table.
The following table describes the fields in the DMA read status high register. All of these fields are read
only.
Table 17-6: Fields in the DMA Read Status High Register
Bit Field Description
[31:24] Reserved —
[23:21] Max Read Request Size The following encodings are defined:
• 001 128 bytes
• 001 256 bytes
• 010 512 bytes
• 011 1024 bytes
• 100 2048 bytes
[20:17] Negotiated Link Width The following encodings are defined:
• 4'b0001 ×1
• 4'b0010 ×2
• 4'b0100 ×4
• 4'b1000 ×8
16 Read DMA Descriptor
FIFO Empty
Indicates that there are no more descriptors pending in the read
DMA.
[15:0] Read DMA EPLAST Indicates the number of the last descriptor completed by the read
DMA. For simultaneous DMA read and write transfers, EPLAST
is only supported for the final descriptor in the descriptor table.
Chaining DMA Descriptor Tables
The following table describes the Chaining DMA descriptor table. This table is stored in the BFM shared
memory. It consists of a four-dword descriptor header and a contiguous list of four-dword descrip‐
tors. The Endpoint chaining DMA application accesses the Chaining DMA descriptor table for two
reasons:
• To iteratively retrieve four-dword descriptors to start a DMA
• To send update status to the RP, for example to record the number of descriptors completed to the
descriptor header
UG-01097_avst
2014.12.15
Chaining DMA Descriptor Tables 17-13
Testbench and Design Example Altera Corporation
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