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3.8.1. Link Descriptor
Offset | Byte Lanes | |||
3 | 2 | 1 | 0 | |
0x00 | DescrIDX | Control | FormatField[7:0] 0b00xx_xx01 |
|
0x04 | Reserved. Set to 0. | |||
0x08 | NextBlockAddress[31:0] | |||
0x0C | NextBlockAddress[63:32] | |||
0x10-0x1C | Reserved. Set to 0. |
Field | Description |
---|---|
DescrIDX | Unique Identifier for each descriptor. This value is updated to the following value:
Note: First descriptor DESC_IDX value is 1, not 0.
|
Control | The control field in the Link descriptor block. |
NextBlockAddress | The address of the next 4kB page/descriptor block in host memory containing the descriptors.
Note: If there is only one 4kB page/descriptor block is allocated, the NextBlockAddress values must be configured to the values as defined in Q_START_ADDR_L & Q_START_ADDR_H CSR registers.
For both DMA PCIe mode & DMA SoC mode: The NextBlockAddress[1:0] must be set to zero for DWord aligned addressing. This is also applicable to the Q_START_ADDR_L[1:0] as well. In addition, for DMA SoC mode: The NextBlockAddress and Q_START_ADDR_* from Device Port CSR configured by software must be aligned to the HOST_DWD boundary. For example, both NextBlockAddress and Q_START_ADDR_* must be aligned to 32 bytes boundary for HOST_DWD = 256. |
Bit | Field | Description |
---|---|---|
6:0 | Reserved | Set to 0. |
7 | DescValid | If set, indicate the current link descriptor content is valid. Notes: This bit must set to high always by software. |