The transmit AXI4-Stream interface uses two AXI4-Stream buses. The AXI4-Stream Data Bus is used for frame data only while the AXI4-Stream Control Bus contains control information. Similarly, the receive AXI4-Stream interface uses two AXI4-Stream buses. The AXI4-Stream Data Bus is used for frame data only, and the AXI4-Stream Status Bus provides status information. The control/status and data buses must have the same clock source but there is no synchronization between the two buses with regards to frame to frame data.
The transmit AXI4-Stream control bus can be configured to use one of two format types: Normal Transmit or Receive Status Transmit. This configuration is controlled by the first nibble (4 bits aligned left) of the first word transferred on the transmit control bus and the receive status bus. A value of 0xA identifies the transfer as a Normal Transmit control packet. A value of 0x5 identifies the transfer as a Receive Status packet. All other values are currently undefined and are ignored. These transfer types are defined in Normal Transmit AXI4-Stream Transfer – Flag=0xA and Receive Status Transmit AXI4-Stream Transfer – Flag=0x5. The receive AXI4-Stream interface only supports one format type.