臺灣博碩士論文加值系統

現今的快閃記憶體(flash memory)，為了增加記憶體儲存密度 ，就會犧牲元件可靠度(reliability)。因此，維持元件可靠度的問題在多值快閃記憶體(multilevel flash memory, ML)上是非常重要的。在此篇論文中，我們提出一個格雷編碼(Gray coding)的架構，來減少多值快閃記憶體位移(shift level)所產生的位元錯誤，並且可以有效的提高多值快閃記憶體可靠度。
使用格雷編碼可以將位移錯誤的位元數控制在某一範圍，有效的降低錯誤更正碼(error correction codes, ECC)所需的檢查碼數 量，進而減少檢查碼(check code)所耗用的記憶體、面積(area pena-
lty)和峰值功率消耗(peak power dissipation)。最後我們使用C語言來驗証模擬，證明格雷編碼可以有效提高錯誤更正碼的更正成功機率。

In new-generation Flash memories, in order to economize the use of density of a cell that certainly will decrease the reliability of device. Thus, it is very important that how to maintain and improve the reliability of device in multilevel flash. In this work, we propose a new scheme of gray coding to reduce error bits caused by shift level in multilevel flash. Furthermore, the proposed scheme also can effectively enhance the reliability of multilevel flash. In our experiment results, gray coding method can limit the error bits caused by shift level in a scope, and validly reduce check bit number for error correction code. Moreover, it diminishes memory of error check code, area penalty and peak power dissipation.

第一章 簡介 ……………………………………………………1
1.1 研究動機與目標……………………………………………1
1.2 貢獻與成果簡述……………………………………………2
1.3 內容大綱……………………………………………………2
第二章 背景知識與相關研究………………………………………3
2.1 快閃記憶體的基本架構……………………………………3
2.2 多值邏輯快閃記憶體………………………………………5
2.3 多值快閃記憶體感測架構…………………………………6
2.4 相關研究 …………………………………………………10
2.4.1 錯誤更正碼……………………………………………… 14
第三章 多值快閃記憶體資料保存的問題………………………18
3.1 位移的探討 ………………………………………………18
3.2 多值快閃記憶體發生位移時的影響 ……………………20
3.3 位元分層 …………………………………………………22
第四章 格雷編碼Gray coding……………………………………25
4.1 格雷編碼與二進位編碼 …………………………………25
4.2 逆操作之格雷碼演算法 …………………………………27
4.3 格雷編碼的特性 …………………………………………30
第五章 模擬結果比較 ……………………………………………33
5.1 漢明距離HD比較圖 ……………………………………33
5.2 漢明碼更正機制下的比較 ………………………………37
5.3 檢查碼數量的比較 ………………………………………40
5.4 功率的比較 ………………………………………………44
第六章 結論與未來工作 …………………………………………48

參考文獻 ……………………………………………………………49

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