SPRUIL1D May 2019 – December 2024 DRA829J , DRA829J-Q1 , DRA829V , DRA829V-Q1 , TDA4VM , TDA4VM-Q1
The Transfer Request Descriptor contains the following information:
Transfer Request Packet Descriptors always contain 16 bytes of required information and a variable number of Transfer Request/Transfer Response Records (request and response counts match).
The Transfer Request descriptor layout is shown below.
Packet Info (16 bytes) |
Null (0-102 bytes to bring start of TR request array into natural alignment for memory fetch efficiency) |
Array of Transfer Request Records (M bytes) |
Array of Transfer Response Records (4 bytes per) |
Bits | Name | Description | Rx Overwrite |
---|---|---|---|
31:30 | 2’d3 | TR Packet Descriptor type. | Yes |
29 | RESERVED | Yes | |
28:20 | Reload Count | Specifies what to do when the last entry is processed in this
packet. This field specifies how many times to return to the Reload
Index upon reaching the Last Entry. When an internal count is
incremented to this value and the TR indicated by the Last Entry has
been processed, this packet will be considered complete and the
descriptor will be placed back on the return queue specified in Word
2. A value of 0x1FF indicates that a perpetual loop is desired. In this case, the loop count is considered infinite and the internal count will not be incremented. A teardown operation on the channel will cause the loop to be broken at the nearest iteration boundary. |
|
19:14 | Reload Index | Specifies the value to set the current processing index to when the last entry is processed and the Reload Enable is set to 1. This is basically an absolute index to jump to on the 2nd and following passes through the TR packet. | |
13:0 | Last Entry | Specifies the index of the last valid entry in this packet | Yes |
Bits | Name | Description | Rx Overwrite |
---|---|---|---|
31:28 | Error Flags | This field contains error flags that can be assigned based on the packet type | Yes |
27 | RESERVED | Yes | |
26:24 | Transfer Request Nominal Element Size | Specifies the stride between TR entries. The value in this field
must be set large enough that any TR in the buffer will fit within
the given dimension. TRs are expected to be placed on boundaries as
given in this dimension. This field is also used to calculate the
location where the Transfer Responses will be written back. This
field is encoded as follows: 0 = 16 byte Transfer Request record size 1 = 32-byte Transfer Request record size 2 = 64-byte Transfer Request record size 3 = 128-byte Transfer Request record size 4-7 = RESERVED |
Yes |
23:14 | Packet ID | Unique Packet ID for packet within FlowID | Yes |
13:0 | Flow ID | Flow ID within which this packet is being transported. The FlowID is used by downstream blocks to make decisions about packet steering and resource allocations. FlowIDs are also used to allow specific packets to be received into specific sets of buffers. | Yes |
Bits | Name | Description | Rx Overwrite |
---|---|---|---|
31:17 | RESERVED | No | |
16 | Return Push Policy | This field indicates how a Transmit DMA should return the
descriptor pointers to the free queues. This field is encoded as
follows: 0 = Descriptor must be returned to tail of queue 1 = Descriptor must be returned to head of queue This bit is only used when the Return Policy bit is set to 1. This field must be set to 0 for descriptors which will be placed on queues managed by the Ring Accelerator |
No |
15:0 | Packet Return Queue Num | This field indicates the queue number that the descriptor is to be returned to after transmission is complete. | No |
Bits | Name | Description | Rx Overwrite |
---|---|---|---|
31:24 | Source Tag – Hi | This field is application specific. During Packet reception, the DMA controller in the port will overwrite this field as specified in the rx_src_tag_hi_sel field in the flow configuration table entry. | Configurable |
23:16 | Source Tag – Lo | This field is application specific. During Packet reception, the DMA controller in the port will overwrite this field as specified in the rx_src_tag_lo_sel field in the flow configuration table entry. | Configurable |
15:8 | Dest Tag – Hi | This field is application specific. During Packet reception, the DMA controller in the port will overwrite this field as specified in the rx_dest_tag_hi_sel field in the flow configuration table entry. | Configurable |
15:0 | Dest Tag – Lo | This field is application specific. During Packet reception, the DMA controller in the port will overwrite this field as specified in the rx_dest_tag_lo_sel field in the flow configuration table entry. | Configurable |
Bits | Name | Description | Rx Overwrite |
---|---|---|---|
31:0 | Transfer Control Record Array | Transfer Control Records. This is an array of records which encapsulate the Transfer Request and Transfer Response messages which are used by the UTC | Yes (partial) |