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We propose a 256×8-bit ultra-low power asynchronous memory design with emphases on micropower, improved soft errors, and operation robustness (i.e. innately self-timed operation which can tolerate Process, Temperature, and Voltage variations) for sub-threshold operation (i.e. the supply voltage VDD is below the threshold voltage of transistors). The proposed memory, to the best of our knowledge, is the first asynchronous memory appropriate not only for bit-interleaving to reduce the impact of soft error, but also for robust full dynamic voltage range operation (from nominal to near-threshold to sub-threshold voltage operation). These attributes a re achieved in several ways. First, the 4-phase dual-rail a synchronous quasi-delay-insensitive (QDI) implementation is employed. Second, a Write Completion Detector and Read Completion Detector are proposed to respectively monitor the computation time required for a write and a read operation. Third, a novel 11-transitor memory cell embodying decoupled read buffers is proposed to improve read static-noise-margin (SNM) and applicable for bit-interleaving. The proposed memory is realized using a 130nm CMOS process, and we show that it can operate robustly from 0.2V to 1.2V, dissipates 96.7nW @ (0.2V, 2 kHz), and operate at average speed of 8.7μs @ 0.2V.