How AXI4-Stream Works - 2021.2 English

Vitis High-Level Synthesis User Guide (UG1399)

Document ID
English (United States)
Release Date
2021.2 English

AXI4-Stream is a protocol designed for transporting arbitrary unidirectional data. In an AXI4-Stream, TDATA width of bits is transferred per clock cycle. The transfer is started once the producer sends the TVALID signal and the consumer responds by sending the TREADY signal (once it has consumed the initial TDATA). At this point, the producer will start sending TDATA and TLAST (TUSER if needed to carry additional user-defined sideband data). TLAST signals the last byte of the stream. So the consumer keeps consuming the incoming TDATA until TLAST is asserted.

Figure 1. AXI4-Stream Handshake

AXI4-Stream has additional optional features like sending positional data with TKEEP and TSTRB ports which makes it possible to multiplex both the data position and data itself on the TDATA signal. Using the TID and TDIST signals, you can route streams as these fields roughly corresponds to stream identifier and stream destination identifier. Refer to Vivado Design Suite: AXI Reference Guide (UG1037) or the AMBA AXI4-Stream Protocol Specification (ARM IHI 0051A) for more information.