Memory cells have been protected from soft errors for more than a decade; due to the increase in soft error rate in logic circuits, the encoder and decoder circuitry around the memory blocks have become susceptible to soft errors as well and must also be protected. We introduce a new approach to design fault-secure encoder and decoder circuitry for memory designs.
The key novel contribution of this paper is identifying and defining a new class of error-correcting codes whose redundancy makes the design of fault-secure detectors (FSD) particularly simple.
We further quantify the importance of protecting encoder and decoder circuitry against transient errors, illustrating a scenario where the system failure rate (FIT) is dominated by the failure rate of the encoder and decoder.
We prove that Euclidean Geometry Low-Density Parity-Check (EG-LDPC) codes have the fault-secure detector capability. Using some of the smaller EG-LDPC codes, we can tolerate bit or nanowire defect rates of 10% and fault rates of 10 -18 psets/device/cycle, achieving a FIT rate at or below one for the entire memory system and a memory density of 10 11 bit/cm _ with nanowire pitch of 10 nm for memory blocks of 10 Mb or larger. Larger EG-LDPC codes can achieve even higher reliability and lower area overhead
In this paper, we introduce a fault-tolerant nano-scale memory architecture which tolerates transient faults both in the storage unit and in the supporting logic. The information bits are fed into the encoder to encode the information vector, and the fault secure detector of the encoder verifies the validity of the encoded vector. If the detector detects any error, the encoding operation must be redone to generate the correct codeword. The codeword is then stored in the memory.
Synthesis: Xilinx 9.1