Multiple input signature register

Definition

A multiple input signature register (MISR) is a digital circuit used in testing to compactly capture the outputs of a circuit under test and create a unique signature for its behavior. By feeding multiple inputs into the register, it can efficiently generate a single signature that represents the state of the circuit, helping to identify faults and verify functionality during testing processes. This technique enhances design for testability by simplifying the process of checking complex systems.

5 Must Know Facts For Your Next Test

1. MISR combines the outputs from multiple inputs into a single output signature, which can significantly reduce the amount of data needed for fault detection.
2. By using a polynomial function, MISRs can effectively compress information from multiple outputs, making it easier to compare against expected results.
3. Implementing a MISR can greatly decrease the time and complexity associated with testing large-scale integrated circuits.
4. MISRs are commonly used in conjunction with other testing techniques like scan chains to enhance overall test coverage and fault detection.
5. The efficiency of a MISR relies on its ability to generate unique signatures for different input conditions, allowing for effective differentiation between faulty and non-faulty states.

Review Questions

• How does a multiple input signature register improve the efficiency of fault detection in digital circuits?
  • A multiple input signature register improves fault detection efficiency by compressing the outputs of multiple inputs into a single output signature. This allows testers to analyze fewer data points when verifying circuit behavior, making it quicker to identify discrepancies between expected and actual outcomes. By streamlining this process, a MISR helps facilitate thorough testing without overwhelming engineers with excessive data.
• What role does the polynomial function play in the operation of a multiple input signature register during testing?
  • The polynomial function is crucial in the operation of a multiple input signature register as it determines how the inputs are combined to create the output signature. This mathematical approach ensures that different combinations of inputs yield distinct signatures, enhancing the accuracy of fault detection. The polynomial nature also allows for efficient data processing, enabling quicker comparisons against known good signatures.
• Evaluate how integrating a multiple input signature register with built-in self-test capabilities can enhance overall system reliability.
  • Integrating a multiple input signature register with built-in self-test capabilities greatly enhances system reliability by allowing devices to autonomously verify their functionality. This integration provides real-time diagnostics, enabling immediate detection of faults without external testing equipment. By combining these technologies, designers can achieve higher test coverage and ensure that any defects are identified and addressed before they impact system performance or reliability.

Related terms

Design for Testability: A set of techniques and methodologies aimed at improving the ease and effectiveness of testing digital circuits.

Test Pattern Generation: The process of creating specific input sequences that will exercise particular paths in a digital circuit during testing.

Built-In Self-Test: A mechanism that allows a device to test itself using its own circuitry and algorithms, often utilizing MISRs for result verification.