Signature analysis and Multiple Input Signature Registers (MISR): Signature analysis is the process of studying the behavior of a circuit or system under...
Signature analysis is the process of studying the behavior of a circuit or system under various stimulus conditions. This involves analyzing the output signals and determining how they relate to the input signals.
Multiple Input Signature Registers (MISR) are a special type of circuit that excels in this analysis. They consist of multiple inputs and a single output that reflects the combined effect of all input combinations.
How MISR works:
Each input pin of the MISR is connected to an input signal.
When a specific input is set to a certain value, it causes the output to change in a predictable way based on the other inputs.
The output changes are captured by the single output pin and fed back to the inputs.
By analyzing the output changes across different combinations of inputs, we can determine the relationship between the inputs and the output.
Testing and Testability of MISR:
Testing an MISR involves setting specific input values and observing the corresponding output behavior.
By analyzing the output changes, we can identify the relationships between the inputs and the output.
This information can be used to verify the theoretical model of the MISR and determine its performance characteristics.
Additionally, testing can help identify any design flaws or errors in the circuit.
Benefits of using MISR:
High degree of testability: MISR outputs a clear and predictable response based on the input combinations.
Ability to analyze complex relationships between multiple inputs and the output.
Can be used to test the functionality of other VLSI circuits.
Examples:
A 4-input MISR can be used to test the behavior of a digital circuit with 4 inputs and 1 output.
Analyzing the output of an MISR with 3 inputs can reveal the XOR logic between the 3 inputs.
A 4-input MISR can be used to implement a comparator circuit that is sensitive to the relative positions of the 4 inputs