Design of Redundant Systems Protected Against Common-Mode Failures

Redundancy techniques like duplication and Triple Modular Redundancy (TMR) are widely used to design fault-tolerant systems. 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 and is called the fault-secure property. 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 modify our previous technique to synthesize redundant systems that are faultsecure against the extended input-register-CMFs. Our results show that redundant systems obtained using our technique require comparable or less area than conventional redundant systems that are not protected against CMFs.