Read DMA and Write DMA Descriptor Table Format
Read and write descriptors are stored in separate descriptor tables in host 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
RC Read
Descriptor Base
and
RC Write Descriptor Base
address registers.
Table 7-17: Read Descriptor Table Format
Address
Offset
Register Name
Description
0x00
RD_RC_LOW_SRC_ADDR
Lower dword of the read DMA source address. Specifies
the address in Root Complex memory from which the
Read DMA fetches data.
0x04
RD_RC_HIGH_SRC_ADDR
Upper dword of the read DMA source address. Specifies
the address in Root Complex memory from which the
Read DMA fetches data.
0x08
RD_CTLR_LOW_DEST_ADDR
Lower dword of the read DMA destination address.
Specifies the address in the Avalon-MM domain to
which the Read DMA 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 DMA writes data.
0x10
CONTROL
Specifies the following information:
• [31:25] Reserved must be 0.
• [24:18]
ID
. Specifies the
Descriptor ID
.
Descriptor
ID
0 is at the beginning of the table.
Descriptor ID
is at the end of the table.
• [17:0]
SIZE
. The transfer size in dwords. Must be
non-zero. To enhance performance and reduce
internal buffers, the transfer size is limited to 8 KB.
0x14 -
0x1C
Reserved
N/A
Table 7-18: Write Descriptor Table Format
Address
Offset
Register Name
Description
0x00
WR_RC_LOW_SRC_ADDR
Lower dword of the write DMA source address.
Specifies the address in the Avalon-MM domain from
which the Write DMA fetches data.
7-22
Read DMA and Write DMA Descriptor Table Format
UG-01145_avmm_dma
2015.11.02
Altera Corporation
Registers
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