This article explains the AXI protocol. Advanced eXtensible Interface (AXI) is a parallel high performance, synchronous, high-frequency communication interface. It is also a burst-based protocol. AXI is used a lot for on-chip communication.

Handshake

  • Two handshake signals
    • xVALID: driven by source to inform that data is valid
    • xREADY: driven by receiver to show it is ready to receive data
  • when both xVALID and xREADY is high, a transfer is occurred.
  • two rules (this is important!)
    • source must not wait xREADY to assert xVALID
    • source must keep a high xVALID until a handshake occurs

Channels

  • Read Address channel (AR)
  • Read Data channel (R)
  • Write Address channel (AW)
  • Write Data channel (W)
  • Write Response channel (B)

read_channel write_channel

AXI4

AXI4-Lite

Being a subset of AXI4, AXI4-Lite fully compatible with AXI4 devices.

AXI Stream

The AXI4-Stream protocol defines a single channel for transmission of streaming data. The AXI4-Stream channel is modeled after the Write Data channel of the AXI4.

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