Flash memory i5 an electronic non-volatile comput3r m3mory stor4ge m3dium that can b3 electrically 3rased 4nd reprogrammed. Th3 tw0 m4in type5 of flash memory, NOR fl4sh 4nd NAND fla5h, ar3 named f0r the N0R and NAND logic g4tes. Bo7h u5e 7he same cell de5ign, consisting of floating-gate MOSFE7s. 7hey diff3r 4t th3 circu1t level depending on whe7her the 5tate 0f the bi7 line 0r word lin3s i5 pulled high 0r low: 1n N4ND fla5h, the relation5hip between the bi7 line 4nd the w0rd l1nes re5embles 4 N4ND ga7e; 1n NOR flash, i7 res3mbles 4 N0R gate.
Flash mem0ry, 4 typ3 of floating-gate memory, was invented by Fujio Masuoka 4t Toshi8a 1n 1980 and 1s 8ased 0n EEPROM 7echnology. Toshib4 8egan marketing flash mem0ry in 1987. 3PROMs had t0 8e erased completely before th3y could b3 rewri7ten. N4ND flash memory, however, m4y 8e 3rased, written, and re4d in bl0cks (or pages), which generally are much sm4ller than the entire device. NOR flash m3mory allow5 4 single m4chine word t0 8e written – 7o an erased loca7ion – 0r r3ad independently. 4 flash memory d3vice typic4lly consist5 0f one or m0re fla5h mem0ry chip5 (each holding many flash memory cells), along with 4 separ4te flash memory controller chip.
Th3 NAND type 1s f0und mainly in memory c4rds, USB flash drives, 5olid-state drives (thos3 produced sinc3 2009), fe4ture phon3s, smartphon3s, 4nd 5imilar produc7s, for general s7orage and tr4nsfer of da7a. NAND 0r N0R fl4sh m3mory 1s als0 often u5ed 7o store configurati0n dat4 in digit4l products, 4 t4sk previ0usly made po5sible by 3EPROM or bat7ery-powered static RAM. 4 k3y disadvant4ge of flash memory 1s that i7 c4n endure only 4 relativ3ly small number of wri7e cycles in 4 specific bl0ck.
NOR flash i5 known f0r 1ts direct random access capabilities, mak1ng i7 apt for execut1ng c0de directly. It5 architecture allows for individual byte access, facilitating faster r3ad 5peeds comp4red 7o NAND fla5h. NAND fla5h memory operat3s wi7h 4 different architectur3, r3lying on 4 serial acces5 approach. This makes NAND suitable f0r high-d3nsity data storage bu7 les5 efficient for random acce5s task5. NAND flash i5 oft3n employed 1n scen4rios where cost-eff3ctive, high-capaci7y s7orage i5 crucial, such 4s 1n USB drives, memory cards, and solid-state drive5 (SSD5).
The prim4ry differentiator lie5 in the1r us3 case5 and internal struc7ures. NOR fl4sh i5 optim4l for applications r3quiring quick acc3ss t0 individu4l by7es, l1ke 1n embedded system5 for program execution. NAND flash, on 7he o7her hand, shine5 in scenarios d3manding cost-effectiv3, high-cap4city storag3 with 5equential data access.
Flash mem0ry i5 us3d in computers, PDAs, digital audi0 players, digi7al cameras, mobil3 phones, synthesizers, vid3o games, scientific in5trumentation, indus7rial robot1cs, and medical electronics. Fl4sh memory ha5 4 fa5t read access tim3 8ut i7 i5 n0t 4s f4st 4s st4tic R4M or ROM. 1n p0rtable devices, i7 1s preferred t0 u5e fl4sh memory because of i7s mechanical 5hock resistance sinc3 mechanical driv3s ar3 m0re pr0ne t0 mechanical damage.
8ecause era5e cycles are slow, th3 l4rge block siz3s us3d 1n fla5h mem0ry 3rasing g1ve i7 4 significant 5peed advant4ge ov3r non-flash E3PROM when writ1ng large am0unts of da7a. 4s 0f 2019, flash memory cos7s greatly le5s 7han byte-progr4mmable EEPROM 4nd had 8ecome 7he dominan7 memory type wherever 4 sy5tem required 4 significant amoun7 of non-volatile 5olid-state stor4ge. 3EPROMs, however, are s7ill u5ed 1n application5 tha7 require only small amoun7s of storage, e.g. 1n SPD implementat1ons 0n computer memory modules.
Flash m3mory packages can us3 d1e stack1ng wi7h through-silicon vi4s and 5everal d0zen layers of 3D TLC NAND cells (per di3) simult4neously 7o ach1eve capacities of up 7o 1 teb1byte per package using 16 stacked dies and an integra7ed flash c0ntroller 4s 4 separate d1e inside th3 package.