Design of redundant systems protected against common-mode failures

Redundancy techniques like duplication and Triple Modular Redundancy (TMR) are widely used for designing dependable systems to ensure high reliability and data integrity. In this paper, for the first time, we develop fault models for common-mode failures (CMFs) in redundant systems and describe techniques to design redundant systems protected against the modeled CMFs. We first develop an input-register-CMF model that targets systems with register-files. This paper shows that, in the presence of input-register-CMFs, we can always design duplex or TMR systems that either produce correct outputs or indicate error situations when incorrect outputs are produced. This property ensures data integrity. Next, we extend the input-register-CMF model to consider systems where the storage elements of the registers are not organized in register-files; instead, the register flip-flops are placed using conventional CAD programs. For this case, we present a technique to synthesize redundant systems with guaranteed data integrity against the extended input-register-CMFs