Visible to Intel only — GUID: iga1401397406781
Ixiasoft
Visible to Intel only — GUID: iga1401397406781
Ixiasoft
32.6.4. DMA Descriptors
Byte Offset | Field Names | |||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
31 | 24 | 23 | 16 | 15 | 8 | 7 | 0 | |||||||||
base | source | |||||||||||||||
base + 4 | Reserved | |||||||||||||||
base + 8 | destination | |||||||||||||||
base + 12 | Reserved | |||||||||||||||
base + 16 | next_desc_ptr | |||||||||||||||
base + 20 | Reserved | |||||||||||||||
base + 24 | Reserved | bytes_to_transfer | ||||||||||||||
base + 28 | desc_control | desc_status | actual_bytes_transferred |
Field Name | Access | Description |
---|---|---|
source | R/W | Specifies the address of data to be read. This address is set to 0 if the input interface is an Avalon® -ST interface. |
destination | R/W | Specifies the address to which data should be written. This address is set to 0 if the output interface is an Avalon® -ST interface. |
next_desc_ptr | R/W | Specifies the address of the next descriptor in the linked list. |
bytes_to_transfer | R/W | Specifies the number of bytes to transfer. If this field is 0, the SG-DMA controller core continues transferring data until it encounters an EOP. |
actual_bytes_transferred | R | Specifies the number of bytes that are successfully transferred by the core. This field is updated after the core processes a descriptor. |
desc_status | R/W | This field is updated after the core processes a descriptor. See DESC_STATUS Bit Map for the bit map of this field. |
desc_control | R/W | Specifies the behavior of the core. This field is updated after the core processes a descriptor. See the DESC_CONTROL Bit Map table for descriptions of each bit. |
Bit (s) | Field Name | Access | Description |
---|---|---|---|
0 | GENERATE_EOP | W | When this bit is set to 1,the DMA read block asserts the EOP signal on the final word. |
1 | READ_FIXED_ADDRESS | R/W | This bit applies only to Avalon® -MM read host ports. When this bit is set to 1, the DMA read block does not increment the memory address. When this bit is set to 0, the read address increments after each read. |
2 | WRITE_FIXED_ADDRESS | R/W | This bit applies only to Avalon® -MM write host ports. When this bit is set to 1, the DMA write block does not increment the memory address. When this bit is set to 0, the write address increments after each write. In memory-to-stream configurations, the DMA read block generates a start-of-packet (SOP) on the first word when this bit is set to 1. |
[6:3] | Reserved | — | — |
3 .. 6 | AVALON-ST_CHANNEL_NUMBER | R/W | The DMA read block sets the channel signal to this value for each word in the transaction. The DMA write block replaces this value with the channel number on its sink port. |
7 | OWNED_BY_HW | R/W | This bit determines whether hardware or software has write access to the current register. When this bit is set to 1, the core can update the descriptor and software should not access the descriptor due to the possibility of race conditions. Otherwise, it is safe for software to update the descriptor. |
After completing a DMA transaction, the descriptor processor block updates the desc_status field to indicate how the transaction proceeded.
Bit | Bit Name | Access | Description |
---|---|---|---|
[7:0] | ERROR_0 .. ERROR_7 | R | Each bit represents an error that occurred on the Avalon® -ST interface. The context of each error is defined by the component connected to the Avalon® -ST interface. |