Friedman's question: Detectability of bridging faults in irredundant computational logic networks

Abstract

Detection of bridging faults is very important in VLSI circuits. Friedman [2] in 1974 asked whether it is possible to have an undetectable AND bridging fault between input leads of an OR gate, or an OR bridging fault between input leads of an AND gate, in a combinational logic network irredundant with respect to single stuck-at type faults. An answer to Friedman's question was first provided by this author in 1981 [1]. In this paper, we prove that such a fault may exist and a theorem on the necessary conditions is proven. Some general theorems on the detectabihty of bridging faults are also presented.

Keywords:

• Boolean difference
• Boolean differential
• switching theory
• fault detection

C.R. Categories:

• B. Hardware B.6. LOGIC DESIGN
• B.6.2 Reliability and Testing
• B.7 INTEGRATED CIRCUITS
• B.7.3 Reliability and Testing.