Concurrent Error Detection in Nonlinear Digital Circuits Using Time-Freeze Linearization

Concurrent error detection in digital circuits is very important in applications where error in processed data can have catastrophic effects. Typically, error detection is performed by a small amount of additional hardware called the checking circuit. In the past, researchers have developed techniques for concurrent error detection in linear digital state variable circuits. In this paper, we investigate concurrent error detection techniques for nonlinear digital circuits that compute polynomial functions of multiple variables. Such circuits have widespread use in the design of various classes of nonlinear digital filters. The proposed error detection schemes are possible due to the use of a new linearization method called time-freeze linearization. In this method, a nonlinear circuit is modeled as a linear circuit for each individual time frame corresponding to the time taken to process a given set of input data. The defining parameters of this linear model change from one time frame to another but are regarded as fixed or frozen in any given time frame. This allows the use of real number checksum codes for fault detection. As opposed to duplicating the entire nonlinear part of the circuit, our approach allows us to use the nonlinear functions to drive the check circuitry, while achieving full fault coverage at low hardware cost.