Partial Scan

Definition

Partial scan is a design technique used in digital circuits to improve testability by selectively connecting a portion of a circuit to scan chains, allowing for easier observation and control of the internal states during testing. This method helps reduce the complexity and area overhead associated with full scan techniques, making it more efficient while still enhancing fault detection capabilities. By implementing partial scan, designers can maintain a balance between test coverage and design resources.

5 Must Know Facts For Your Next Test

1. Partial scan allows only selected flip-flops in a circuit to be included in the scan chain, reducing overhead compared to full scan techniques.
2. By focusing on critical sections of a design, partial scan can provide effective fault coverage without the need for complete visibility into all internal states.
3. This technique can significantly shorten test times since only a subset of flip-flops need to be scanned, making it more efficient for larger designs.
4. Partial scan can also help maintain performance levels in high-speed designs by minimizing the impact on timing and signal integrity.
5. Using partial scan can facilitate easier debugging since it allows designers to isolate and observe specific parts of the circuit without extensive modifications.

Review Questions

• How does partial scan enhance the testing process compared to full scan methods?
  • Partial scan enhances the testing process by allowing only selected parts of a digital circuit to be connected to scan chains. This reduces the complexity and resource overhead associated with full scan methods while still providing adequate fault coverage. By focusing on critical components, partial scan maintains performance and decreases testing time, making it an effective solution for large-scale designs.
• Discuss how partial scan fits into the broader strategy of Design for Testability (DFT).
  • Partial scan is an important aspect of Design for Testability (DFT) as it improves the ability to test and diagnose faults in digital circuits. By selectively connecting parts of the circuit to scan chains, partial scan supports comprehensive testing without overwhelming resource requirements or affecting performance significantly. This targeted approach aligns with DFT principles, which aim to make circuits more manageable during testing while ensuring that reliability and efficiency are not compromised.
• Evaluate the potential trade-offs that come with implementing partial scan in a digital design.
  • Implementing partial scan in a digital design involves weighing benefits against potential trade-offs. While it improves testability without incurring significant area or performance penalties compared to full scan, designers must carefully choose which flip-flops to include in the scan chain. This selection process can lead to inadequate coverage if not executed properly. Additionally, there might be increased complexity in the design phase as engineers strive to optimize test coverage while managing resources effectively, which can impact project timelines.

Related terms

Scan Chain: A series of flip-flops connected in a way that allows for serial input and output, facilitating easier testing by shifting test patterns through the circuit.

Design for Testability (DFT): A set of design practices that enhance the ability to test and diagnose faults in digital circuits, improving overall reliability and performance.

Boundary Scan: A testing method that allows for the testing of interconnections on printed circuit boards using special test access ports, enabling better diagnostics without physical access to all components.