A Software Anti-radiation Hardening Method Of Memory Device Based On NAND Flash

The data recorder is one of the key devices in the spacecraft for data recording and storage. NAND Flash, due to its versatile features such as high speed, low power consumption, is very fit for space applications. In order to work normally in the harsh radiation environment of space, the data stored in NAND Flash must be hardened.The paper analyses the characteristics of different error mode of NAND Flash caused by the single event effects and total dose effects in radiation environment. Considering the special controlling principles of NAND Flash, a software hardening method was designed based on error control coding. Use a systematic shortened RS (12,4) code based on GF(24) to guarantee the safety of the stored data in NAND Flash.The main work and contribution of the dissertation is as follows:⑴Combined with the special operating mode of NAND Flash, research a new parallel coding method based on look-up table. The new coding circuit reduces the critical path delay and greatly improving the efficiency of the encoder.⑵Comparing different RS decoding methods, the remainder decoding method was chosen and improved. The adoption of parallel remainder calculator and modified key equation accelerate decoding process. And the discovery of a new way reduces the iterations of the calculation of the error polynomial, which also contributes to cut down the expenditure of decoding time.⑶Combined the characteristics of RS (12,4) code with the pipeline managements of NAND Flash, store the information symbols and parity symbols in different chips. And it is possible to correct single event functional interrupt errors. Also the speed of the solid memory device will not fall by using pipeline technology.Finally, we realize the software hardening method and simulate different error patterns caused by radiation. The performance of the hardened solid storage device was tested by injecting single bit errors, multiple bit errors and function interrupt errors. The software hardening approach can reinforce the memory's anti-radiation performance 5-6 orders of magnitude.