Editing Flash memory (section)

{{Short description|Electronic non-volatile computer storage device}}
{{Redirect|FlashROM|programming utility|Flashrom (utility)}}
{{For|the neuropsychological concept related to human memory|Flashbulb memory}}
{{Use dmy dates|date=September 2020}}
[[File:USB flash drive.JPG|thumb|A disassembled [[USB flash drive]] in 2005. The chip on the left is flash memory. The [[flash memory controller|controller]] is on the right.]]
{{Memory types}}

'''Flash memory''' is an [[Integrated circuit|electronic]] [[Non-volatile memory|non-volatile]] [[computer memory]] [[storage medium]] that can be electrically erased and reprogrammed. The two main types of flash memory, '''NOR flash''' and '''NAND flash''', are named for the [[NOR gate|NOR]] and [[NAND gate|NAND]] [[logic gate]]s. Both use the same cell design, consisting of [[floating-gate MOSFET]]s. They differ at the circuit level, depending on whether the state of the bit line or word lines is pulled high or low; in NAND flash, the relationship between the bit line and the word lines resembles a NAND gate; in NOR flash, it resembles a NOR gate.

Flash memory, a type of [[floating-gate]] memory, was invented by [[Fujio Masuoka]] at [[Toshiba]] in 1980 and is based on [[EEPROM]] technology. Toshiba began marketing flash memory in 1987.<ref name=":0" /> [[EPROM]]s had to be erased completely before they could be rewritten. NAND flash memory, however, may be erased, written, and read in blocks (or pages), which generally are much smaller than the entire device. NOR flash memory allows a single [[machine word]] to be written{{snd}} to an erased location{{snd}} or read independently. A flash memory device typically consists of one or more flash [[memory chip]]s (each holding many flash memory cells), along with a separate [[flash memory controller]] chip.

The NAND type is found mainly in [[memory card]]s, [[USB flash drive]]s, [[solid-state drive]]s (those produced since 2009), [[feature phone]]s, [[smartphone]]s, and similar products, for general storage and transfer of data. NAND or NOR flash memory is also often used to store configuration data in digital products, a task previously made possible by EEPROM or battery-powered [[static RAM]]. A key disadvantage of flash memory is that it can endure only a relatively small number of write cycles in a specific block.<ref name="flashstorage-2015">{{Cite news |date=30 March 2015 |title=A Flash Storage Technical and Economic Primer |work=FlashStorage.com |url=http://www.flashstorage.com/flash-storage-technical-economic-primer/ |url-status=dead |archive-url=https://web.archive.org/web/20150720220844/http://www.flashstorage.com/flash-storage-technical-economic-primer/ |archive-date=20 July 2015 }}</ref>

NOR flash is known for its direct random access capabilities, making it apt for executing code directly. Its architecture allows for individual byte access, facilitating faster read speeds compared to NAND flash. NAND flash memory operates with a different architecture, relying on a serial access approach. This makes NAND suitable for high-density data storage, but less efficient for random access tasks. NAND flash is often employed in scenarios where cost-effective, high-capacity storage is crucial, such as in USB drives, memory cards, and solid-state drives ([[SSD]]s).

The primary differentiator lies in their use cases and internal structures. NOR flash is optimal for applications requiring quick access to individual bytes, as in embedded systems for program execution. NAND flash, on the other hand, shines in scenarios demanding cost-effective, high-capacity storage with sequential data access.

Flash memory<ref name="kingston-flash-ref">{{Cite web |year=2012 |title=Flash Memory Guide |url=https://media.kingston.com/pdfs/FlashMemGuide.pdf |url-status=live |archive-url=https://web.archive.org/web/20231019045415/https://media.kingston.com/pdfs/FlashMemGuide.pdf |archive-date=19 October 2023 |access-date=4 December 2023 |publisher=[[Kingston Technology]] |id=MKF-283US }}</ref> is used in [[computers]], [[Personal digital assistant|PDA]]s, [[digital audio players]], [[digital camera]]s, [[mobile phones]], [[synthesizers]], [[video games]], [[scientific instrument]]ation, [[industrial robotics]], and [[medical electronics]]. Flash memory has a fast read [[access time]] but is not as fast as static RAM or ROM. In portable devices, it is preferred to use flash memory because of its mechanical shock resistance, since mechanical drives are more prone to mechanical damage.<ref name="backblaze-20180306">{{Cite web |last=Bauer |first=Roderick |date=6 March 2018 |title=HDD vs SSD: What Does the Future for Storage Hold? |url=https://www.backblaze.com/blog/ssd-vs-hdd-future-of-storage/ |url-status=live |archive-url=https://web.archive.org/web/20221222025652/https://www.backblaze.com/blog/ssd-vs-hdd-future-of-storage/ |archive-date=22 December 2022 |publisher=[[Backblaze]] }}</ref>

Because erase cycles are slow, the large block sizes used in flash memory erasing give it a significant speed advantage over non-flash EEPROM when writing large amounts of data. {{As of|2019|post=,}} flash memory costs greatly less than byte-programmable EEPROM and had become the dominant memory type wherever a system required a significant amount of non-volatile [[solid-state storage]]. EEPROMs, however, are still used in applications that require only small amounts of storage, e.g. in [[serial presence detect|SPD]] implementations on computer-memory modules.<ref name="micron-tn-04-42">{{Cite web |title=Memory Module Serial Presence-Detect Introduction |url=https://www.micron.com/-/media/client/global/documents/products/technical-note/dram-modules/tn_04_42.pdf?rev=e5a1537ce3214de5b695f17c340fd023 |url-status=live |archive-url=https://web.archive.org/web/20220726125258/https://www.micron.com/-/media/client/global/documents/products/technical-note/dram-modules/tn_04_42.pdf |archive-date=26 July 2022 |access-date=1 June 2022 |publisher=[[Micron Technology]] |id=TN-04-42 }}</ref><ref name="ti-spd-ref">{{Cite web |date=January 1998 |title=Serial Presence Detect - Technical Reference |url=https://www.ti.com/lit/ug/smmu001/smmu001.pdf |url-status=live |archive-url=https://web.archive.org/web/20231204093906/https://www.ti.com/lit/ug/smmu001/smmu001.pdf |archive-date=4 December 2023 |publisher=[[Texas Instruments]] |id=SMMU001 }}</ref>

Flash memory packages can use [[Three-dimensional integrated circuit|die stacking]] with [[through-silicon via]]s and several dozen layers of 3D TLC NAND cells (per die) simultaneously to achieve capacities of up to 1 [[tebibyte]] per package using 16 stacked dies and an integrated [[flash controller]] as a separate die inside the package.<ref name="anandtech-20190130">{{Cite news |last=Shilov |first=Anton |date=30 January 2019 |title=Samsung Starts Production of 1 TB eUFS 2.1 Storage for Smartphones |work=[[AnandTech]] |url=https://www.anandtech.com/show/13918/samsung-starts-production-of-1-tb-eufs-21-storage-for-smartphones |url-status=live |archive-url=https://web.archive.org/web/20231102131015/https://www.anandtech.com/show/13918/samsung-starts-production-of-1-tb-eufs-21-storage-for-smartphones |archive-date=2 November 2023 }}</ref><ref name="anandtech-20171205">{{Cite news |last=Shilov |first=Anton |date=5 December 2017 |title=Samsung Starts Production of 512 GB UFS NAND Flash Memory: 64-Layer V-NAND, 860 MB/s Reads |work=[[AnandTech]] |url=https://www.anandtech.com/show/12120/samsung-starts-production-of-512-gb-ufs-chips |url-status=live |archive-url=https://web.archive.org/web/20231103145651/https://www.anandtech.com/show/12120/samsung-starts-production-of-512-gb-ufs-chips |archive-date=3 November 2023 }}</ref><ref name="isscc-2017-3d-vnand">{{Cite conference |last1=Kim |first1=Chulbum |last2=Cho |first2=Ji-Ho |last3=Jeong |first3=Woopyo |last4=Park |first4=Il-han |last5=Park |first5=Hyun-Wook |last6=Kim |first6=Doo-Hyun |last7=Kang |first7=Daewoon |last8=Lee |first8=Sunghoon |last9=Lee |first9=Ji-Sang |last10=Kim |first10=Wontae |first11=Jiyoon |last11=Park |last12=Ahn |first12=Yang-lo |last13=Lee |first13=Jiyoung |last14=Lee |first14=Jong-Hoon |last15=Kim |first15=Seungbum |last16=Yoon |first16=Hyun-Jun |first17=Jaedoeg |last17=Yu |first18=Nayoung |last18=Choi |last19=Kwon |first19=Yelim |last20=Kim |first20=Nahyun |first21=Hwajun |last21=Jang |last22=Park |first22=Jonghoon |last23=Song |first23=Seunghwan |first24=Yongha |last24=Park |last25=Bang |first25=Jinbae |last26=Hong |first26=Sangki |last27=Jeong |first27=Byunghoon |last28=Kim |first28=Hyun-Jin |first29=Chunan |last29=Lee |first30=Young-Sun |last30=Min |display-authors=29 |year=2017 |title=11.4 a 512Gb 3b/Cell 64-stacked WL 3D V-NAND flash memory |conference=[[International Solid-State Circuits Conference]] |location=San Francisco |publisher=[[Institute of Electrical and Electronics Engineers|IEEE]] |pages=202–203 |doi=10.1109/ISSCC.2017.7870331 |isbn=978-1-5090-3758-2 |issn=2376-8606 |s2cid=206998691 }}</ref><ref name="hexus-20190131">{{Cite news |last=Tyson |first=Mark |title=Samsung enables 1TB eUFS 2.1 smartphones |work=Hexus |url=https://hexus.net/tech/news/storage/127010-samsung-enables-1tb-eufs-21-smartphones/ |url-status=live |archive-url=https://web.archive.org/web/20230423114928/https://hexus.net/tech/news/storage/127010-samsung-enables-1tb-eufs-21-smartphones/ |archive-date=23 April 2023 }}</ref>