Selection of partial scan flip-flops to break feedback cycles
First Claim
1. A method of determining an optimal quantity of scan flip-flops required to eliminate feedback loops in a sequential logic circuit, comprising the steps of:
- a) deriving an S-graph of the sequential logic circuit;
b) applying minimum feedback vertex set (MFVS) preserving transformations to the S-graph to reduce the S-graph to non-empty, compressed SCCs (strongly connected components);
c) performing a partitioned branch and bound method to solve the compressed SCCs of the graph;
d) applying integer linear programming (ILP) to obtain an optimal solution or lower bound for the MFVS of the S-graph, ande) if a lower bound is obtained in step (d), repeat steps (c) and (d) orf) if any optimal solution is obtained is step (d), incorporating the quantity of scan flip-flops obtained as the optimal solution into the sequential logic circuit for enabling partial scan testing of the sequential logic circuit.
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Abstract
In partial scan testing of a circuit the optimal quantity of scan flip-flops required to eliminate all feedback, except self-loops, in a circuit is determined. For determining a minimal feedback vertex set (MFVS) for the S-graph of a circuit to be tested, MFVS-preserving transformations, partitioned search strategy and integer linear program (ILP)-based lower bounding techniques are combined to obtain an exact algorithm for computing the MFVS. The result is used in the fabrication of the circuit with minimal overhead in terms of area and performance degradation as a result of providing the capability to perform partial scan testing of the fabricated circuit.
41 Citations
14 Claims
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1. A method of determining an optimal quantity of scan flip-flops required to eliminate feedback loops in a sequential logic circuit, comprising the steps of:
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a) deriving an S-graph of the sequential logic circuit; b) applying minimum feedback vertex set (MFVS) preserving transformations to the S-graph to reduce the S-graph to non-empty, compressed SCCs (strongly connected components); c) performing a partitioned branch and bound method to solve the compressed SCCs of the graph; d) applying integer linear programming (ILP) to obtain an optimal solution or lower bound for the MFVS of the S-graph, and e) if a lower bound is obtained in step (d), repeat steps (c) and (d) or f) if any optimal solution is obtained is step (d), incorporating the quantity of scan flip-flops obtained as the optimal solution into the sequential logic circuit for enabling partial scan testing of the sequential logic circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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Specification