built-in logic block observer

Built-in Logic Block Observer (BILO): A Powerful Tool for Embedded System Testing

In the realm of embedded systems, ensuring the correct functionality and reliability of digital circuits is paramount. This is where the Built-in Logic Block Observer (BILO) comes into play. BILO is a sophisticated testing technique that blends the strengths of scan designs, pseudo-random test pattern generation, and test result signature analysis, providing a comprehensive approach to identify and diagnose faults within the circuit.

Understanding BILO's Components:

• Scan Designs: This technique introduces dedicated scan chains into the circuit. During test mode, these chains allow for controlled loading and observation of individual flip-flops, enhancing observability and controllability.
• Pseudo-random Test Pattern Generation: This method employs a pseudo-random pattern generator (PRPG) to generate a sequence of test patterns that effectively exercise the circuit's logic. The randomness helps cover a wide range of possible fault scenarios.
• Test Result Signature Analysis: Instead of storing and comparing the complete test response, the test results are compressed into a unique signature. This reduces the volume of data required for analysis and allows for efficient fault detection.

How BILO Works:

1. Test Pattern Generation: The BILO circuitry uses the PRPG to generate a set of pseudo-random test patterns. These patterns are applied to the circuit's inputs, effectively exercising the logic.
2. Data Compression: The circuit's outputs, after being processed by the logic, are compressed into a signature using a built-in compression circuit. This signature encapsulates the test results.
3. Signature Comparison: The generated signature is compared with a pre-defined "golden" signature, representing the expected behavior of a fault-free circuit. If any discrepancy is detected, it signals the presence of a fault.

Advantages of BILO:

• High Fault Coverage: The combination of scan designs and pseudo-random test patterns ensures extensive coverage of potential faults, minimizing the risk of undetected defects.
• Reduced Test Time: The test result signature analysis reduces the volume of data to be processed and stored, significantly decreasing the time needed for testing.
• Lower Hardware Overhead: While scan designs can introduce some hardware overhead, BILO cleverly integrates the observation and compression functionalities within the circuit, minimizing its impact.
• Enhanced Testability: BILO offers a more comprehensive and efficient approach to testing compared to traditional methods, improving the overall testability of the embedded system.

Applications of BILO:

• Microprocessors and microcontrollers: BILO helps ensure the reliability of these crucial components by enabling comprehensive testing of their internal logic.
• ASICs (Application-Specific Integrated Circuits): This technique is widely used in ASIC design to verify the functionality and identify potential faults within complex custom circuits.
• Memory chips: BILO's random pattern generation capabilities are particularly well-suited for testing memory components, ensuring data integrity and addressing potential read/write errors.

Conclusion:

The Built-in Logic Block Observer (BILO) is a highly effective testing technique that provides a robust solution for ensuring the reliability and functionality of complex digital circuits. By combining the strengths of scan designs, pseudo-random test patterns, and test result signature analysis, BILO offers a comprehensive and efficient approach to fault detection and diagnosis, making it an invaluable tool in the development of embedded systems.