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Nand flash memory
This document discusses NAND flash memory, which is used in USB flash drives for portable storage. It describes how NAND flash works, including that it has a controller that sends commands serially to program and read the flash. Issues with NAND flash include bad blocks, long access times since it is not random access, and short lifetimes due to being programmable. Technologies like wear leveling aim to extend the lifetime by distributing writes across blocks.
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Nand flash memory
- 1. USB Flash driveProject Mohamed Fadel Buffon Storage Element NAND Flash Memory
- 2. Agenda What isNAND Flash? What does NAND Flash Controller do? What is ONFI? What are NAND Flash issues? What is wear leveling Technology?
- 3. What is NANDFlash? • Non Volatile Memory. • Programmable Memory. • Portable Storage.
- 4. Diff. between NANDFlash & Others • Serial Storage device. • Long Access Time. • Not RAM.
- 5. NAND Flash ||NOR Flash
- 6. What does NANDFlash Cont. Do? • Send Commands Serially (as packets). • Generate ECC Information.
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- 10. Storing 0 x x
- 11. Types of NANDFlash
- 12. Types of NANDFlash • MLC offers higher storage density. • But MLC is slower and less robust. • MLC 10,000 erase/program cycle. • SLC 100,000 erase/program cycle.
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- 14. What is ONFI? •Open Standard for device level NAND Flash interface. • Supported by new NAND Flash devices.
- 15. ECC • Is agood way to recover the wrong value. • Can be implemented by: – Hardware (Faster). – Software. • SLC 1-bit ECC correction per 512 bytes (which mean 24 ECC bits {Hamming Code}).
- 16. What are NANDFlash issues? • Bad Blocks. • Long Access Time. • No Random Access. • Short Life-time.
- 17. What is wearleveling? • Divide Data to Segments. • Distribute Segments on multi-pages. • Re-map the logical address to physical address. • Adv: – Extend the NAND Flash life-time.
- 18. What is RAMshadowing? • Like External Cache Memory. • Reasons: – Limit erase/program cycle. – Slow speed (compared to SDRAM).
- 19. Reference • “NAND FlashFAQ” from Eureka Technology.
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