AXI4/AXI3 of read channel

There are some differences between the AXI3 protocol and the AXI4 protocol for the read
channels:
• For the AXI4 protocol, the read address length signal ARLEN is wider. Therefore, AXI4 is able to
generate longer read bursts than AXI3.
• AXI4 reduces the ARLOCK signal to a single bit to only accommodate exclusive transfers
because locked transfers are not supported.
• As with the write channel signals, the concepts of quality of service and subordinate regions
apply to read transactions. These use the ARQOS and ARREGION signals in the AR channel.
• AXI4 adds user-defined signals to the two read channels.