I'm using ap_axiu from ap_axi_sdata.h in Vivado HLS like I saw in some example to stream data throught the AXI DMA.

I'm defining my value like this:

typedef ap_axiu<32,4,5,5> AXI_VALUE;

However, and even though I can see the following correspondence:

4  -->user
4  -->id
5  -->dest

I can't understand what the 4,4 and 5 are for. Can someone please explain me what's the difference between ap_axiu<32,1,1,1> and ap_axiu<32,4,4,5>?

Note: I think this is something that should be said on the header file ap_axi_sdata because it's somewhat important.

  • \$\begingroup\$ Found a solution here. \$\endgroup\$ Jun 22, 2015 at 16:01

1 Answer 1


I think that in most simple cases, where you don't need to route the stream chunks, you can safely use ap_axiu<32,1,1,1> V-italiano


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