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Comparing AXI4-Lite to the Full AXI Protocol: Basics and Implementation

# Comparing AXI4-Lite to the Full AXI Protocol: Basics and Implementation

In the previous section of our tutorial series, we dived into understanding the fundamentals of the AXI protocol and delved into its various features. This article will compare AXI4-Lite to the full AXI protocol and implement a basic AXI4-Lite slave in Verilog. By the end of this discussion, you’ll clearly understand the differences between these protocols, and we’ll set the stage for the next article, where we’ll enhance the full AXI interface to handle complex burst transactions.

AXI4-Lite vs. Full AXI: The Basics

The full AXI (Advanced eXtensible Interface) protocol is a highly-flexible, high-performance interface that supports burst-based transactions, multiple outstanding transactions, and dynamic reordering of commands. It offers significant capabilities for modern, complex systems requiring high data throughput. On the other hand, AXI4-Lite is a simpler, lightweight subset of the AXI protocol designed for low-bandwidth, minimal-overhead communication. It supports only single-address, single-data transactions, lacks burst capabilities, and is much easier to implement and understand.

Think of AXI4 as a highway system with multiple lanes, allowing a large number of vehicles (transactions) to move through simultaneously with room for complex traffic patterns (bursts, out-of-order execution). In contrast, AXI4-Lite is like a simple single-lane road that can only handle one vehicle at a time, in a specific order, moving at a constant speed (single transaction with single write or read).

For this article, we’ll focus on implementing a basic AXI4-Lite slave module. This will serve as a lightweight model to handle basic read/write transactions, representing devices that do not require the complexity of the full AXI protocol. These kinds of devices can be seen in areas such as control systems or low-speed peripherals like GPIO.