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Why AXI Protocol Supports Multiple Outstanding Transactions and How to Verify It Using UVM?
Introduction
The AMBA AXI (Advanced eXtensible Interface) protocol, introduced by Arm as part of the AMBA 3 and 4 specifications, is a critical backbone for modern high-performance system-on-chip (SoC) designs. It offers several advanced features such as separate address and data channels, support for burst-based transfers, and perhaps most importantly, the ability to manage multiple outstanding transactions concurrently.
The support for multiple outstanding transactions is crucial for high-throughput, low-latency system designs. This feature allows AXI masters (such as processors, DMA controllers, or other initiators) to issue multiple read and write commands without waiting for previous transactions to complete. This pipelined approach improves bus utilization and avoids bottlenecks.
In this article, we will delve deep into the reasons behind this protocol feature, its architectural significance, and how to practically verify such behavior using Universal Verification Methodology (UVM). We will discuss how AXI channels manage these transactions, the challenges they introduce in verification, and how UVM provides a robust framework to validate them effectively.
