What Is Scan Chain Reordering?

What is Scan Chain Reordering?

What is Scan Chain Reordering?

Welcome to another installment of our “DEFINITIONS” series, where we dive deep into the world of technology and provide clear explanations of complex concepts. Today, we’ll be exploring the fascinating topic of Scan Chain Reordering.

Scan Chain Reordering is a technique used in VLSI (Very Large Scale Integration) design to optimize the scan chain architecture of a digital integrated circuit. But what does that mean exactly? Let’s break it down.

Key Takeaways:

  • Scan Chain Reordering improves the efficiency and effectiveness of testing digital integrated circuits.
  • It involves rearranging the order of the flip-flops within the scan chain to reduce the test application time and ensure maximum fault coverage.

Understanding Scan Chains

In order to grasp the concept of Scan Chain Reordering, it’s important to first understand what a scan chain is. A scan chain is a series of flip-flops connected in a chain-like structure within a digital circuit. This chain allows for easy shifting of data in and out of flip-flops, facilitating testing and diagnosis of potential faults in the circuit.

Scan chains play a crucial role in Built-In Self-Test (BIST) techniques, where the circuit is able to test itself without external equipment. By shifting test patterns through the scan chain, the circuit can observe the output responses, detect any potential faults, and improve its overall reliability.

The Need for Scan Chain Reordering

As digital circuits become more complex, the number of flip-flops within a scan chain increases, resulting in longer test application times. This can impact manufacturing costs and overall test efficiency. Additionally, certain fault types may remain undetected if the order of flip-flops in the chain is not optimized.

Scan Chain Reordering addresses these challenges by rearranging the order of flip-flops within the scan chain. By carefully considering the connections between the flip-flops and their proximity to other circuit components, engineers can optimize the test application time and improve fault coverage.

Imagine a scenario where a fault occurs deep within the circuit, far from the starting point of the scan chain. By strategically reordering the flip-flops, the fault can be reached more quickly during testing, reducing the overall test application time. This approach ensures that faults in different parts of the circuit are detected efficiently, improving the overall reliability of the digital integrated circuit.

Benefits of Scan Chain Reordering

Scan chain reordering offers several notable benefits, including:

  1. Reduced Test Application Time: By optimizing the order of flip-flops, the time required to apply test patterns can be significantly reduced, leading to faster testing processes and increased production efficiency.
  2. Improved Fault Coverage: By strategically rearranging the flip-flops, potential faults within the circuit can be targeted more efficiently, ensuring comprehensive fault coverage and higher quality products.

Implementing scan chain reordering may require sophisticated algorithms and simulation tools to analyze the circuit’s structure and evaluate different ordering options. However, the benefits of this technique in terms of cost savings, improved test efficiency, and enhanced circuit reliability make it a valuable practice in modern VLSI design.

So, next time you come across the term “Scan Chain Reordering,” you’ll have a solid understanding of what it means and why it’s important in the realm of digital integrated circuit testing.