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Overview
The AxiStreamPacketizer takes incoming AxiStreams and breaks them into smaller sub-frames (packets). The AxiStreamDepacketizer does the reverse, reassembling a packetized stream into the original frames. The packetization protocol also takes AXI-Stream sideband data (TDEST, TID, TUSER) and inserts it in the data stream as part of the packetization format. Together these features are very useful for sending an AXI-Stream over an external transport such as UDP.
Details
Packet Header
The Packetizer breaks stream frames in to smaller frames called packets. Each packet contains an 8 byte header as follows:
...
| Byte | Bits | Name | Description |
|---|---|---|---|
| 0 | 6:0 | TUserLast | TUSER of of transaction of the AXI-Stream frame. Only valid if EOF=1 |
| 0 | 7 | EOF | Indicates that this is the last packet of a frame. |
Notes
- We steal the MSB of tUserLast to indicate EOF. EOF=0 indicates that there are more packets left in the frame.
- Having tUserLast/EOF in a tail allows the packetizer to function in streaming fashion and not have to buffer each packet worth of data in a FIFO.
- TDest, TId and TUserFirst are placed in the header of every packet, even though they don’t change after the first packet of the frame.
- TUserLast data is only valid if the EOF bit is 1
Contact
Ben Reese
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