5.2.2. How Scan Chains Work

Try these first

1. 1.

   What is a scan chain?

   Hint

   Think about how flip-flops are connected.

2. 2.

   What does scan mode replace in a circuit?

   Hint

   Consider what testing replaces in a circuit.

3. 3.

   What happens during the test phase regarding data?

   • Data is ignored
   • Data is shifted into the scan chain
   • Data flows normally

   Hint

   Think about what the scan chain allows during testing.

4. 4.

   True or False: The scan chain can help detect stuck-at faults.

   • True
   • False

   Hint

   Recall what types of faults are indicated by test patterns.

5. 5.

   Design a small digital circuit that utilizes a scan chain. Explain how you would implement test vectors and what faults you would expect to catch.

   Hint

   Think about how each part of the circuit interacts with the test patterns.

6. 6.

   Consider a scenario where a scan chain fails to detect certain delayed signals in high-speed applications. How might you enhance fault coverage in this situation?

   Hint

   Reflect on the limitations of scan chains in complex systems and consider supplementary strategies.