臺灣博碩士論文加值系統

由於快閃記憶體備具了許多記憶元件的優點於一身，使得快閃記憶體在大型儲存裝置上的應用逐漸展露頭腳。但是用在儲存裝置上的快閃記憶體仍有一些限制需要克服，而隨著快閃記憶體製成上的進步，用來當做攜帶儲存裝置的快閃記憶卡的密度、容量一直增加，因此負責管理記憶卡中資料擺放的控制器該如何克服快閃記憶體先天的不便，這樣的課題也就顯得更為重要。於是本人利用軟體程式去模擬快閃記憶體以及一些快閃記憶體的特性，基於這樣的軟體模組去開發和探討快閃記憶體控制器的設計。有鑑於之前的一些研究都只是針對如何選擇快閃記憶體内區塊來清除，以減少快閃記憶體的使用率，但並未考慮到輕便的記憶卡所擁有硬體資源上可能有限制，所以本篇論文將承現一個較為完整、較符合現實考量的快閃記憶體控制的設計。在設計的快閃記憶體控制器模擬程式模組裡頭包括了幾個部份：虛擬／實際位址轉換、揮發性記憶體的利用、使用者資料的結構資訊、結構資訊的快取、以及之前已有相當多討論的快閃記憶體管理。在建構完整個控制器之後，則有一連串的測試和數據結果，並依照數據的分析再進行設計上的改進。而本篇論文所承現的設計方式和數據結果，相信對於往後有關快閃記憶卡控制器的設計能有相當的參考價值或當為一個比較的對象。

This thesis is a research about the design of flash memory control. As capacity of flash memory card grows, the design of flash memory control, which governs data in flash memory, is getting more important. We divide the issue of flash memory control design into several parts: logical/physical address translation, utilization of limited local memory, manners of caching data from flash memory to local memory and flash memory management. About those topics, a complete flash memory control model is built in this paper. Besides, the design has improved the speed of seeking free space and the tradition update-algorithm.
In flash memory management, the emphasis of cycle-leveling enhances the flash memory performance dramatically. It shows that besides good clean policy and fine data classification, cycle-leveling is also essential for flash memory management.
Finally, there will be a series simulation result which is computed from a developed software model of our design. It will be a strong proof of this design.

Chapter 1 Introduction 1
1.1 Motivation 1
1.2 Thesis Organization 2
Chapter 2 Introduction of Flash Memory 3
2.1 Flash Memory Array Organization 4
2.2 Basic Operations of Flash Memory 5
2.3 Summary 8
Chapter 3 Flash Card System 10
3.1 System Architecture 12
3.2 Card Architecture 13
3.3 Translation Table Structure 16
3.4 Examples of Read and Write 18
3.5 Summary 22
Chapter 4 Flash Memory Management 23
4.1 Log-Like Structure 24
4.2 Cleanup Operation (Garbage Collection)26
4.3 Cycle Leveling 30
4.4 Data Classification 32
4.5 Summary 33
Chapter 5 Simulation Analysis and Crash Prevention 34
5.1 Improvement in Writing Speed 35
5.2 Advance Improvement in Writing Speed 39
5.3 Writing Speed Analysis with Consideration of Clean-Up 41
5.4 Flash Memory Management Analysis 44
5.5 The Prevention of Power Crash 47
5.6 Summary 49
Chapter 6 Conclusion and Discussion 50
REFERENCE 51

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[3] Samsung Electronics, “Flash/ SmartMediaTM File System,” February 17th 2000.
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[8] J. N. Matthews, D. Roselli, A. M. Costello, R. Y. Wang and T. E. Anderson, “Improving the Performance of Log-Structured File Systems with Adaptive Methods’,” Proceedings of the Sixteenth ACM Symposium on Operating System Principles, Saint Malo, France, October 5-8, 1997.
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[11] Mei-Ling Chiang and R. C. Chang, “Cleaning Policies in Mobile Computers Using Flash Memory,” Accepted by Journal of Systems and Software.
[12] SD Group “SD Memory Card Specifications,” March, 2000.