Storage and Multimedia Part III

1. Storage and Multimedia Part III Bayram Güzer

2. Flash Drive • A flash drive is a storage device that uses flash memory. • Flash memory is non-volatile(kalıcı). • It can be electrically erased and reprogrammed. • In this case it becomes Electrically Erasable, Programmable Read-Only Memory that is referred to as EEPROM.

3. Flash Drive • Flash memory is solid-state that is nothing in its is mechanical, everything is entirely electronic. • Flash memory has a grid of columns and rows and a cell having two transistors at each of the points of intersection of the grid. • Flash memory is used for the easy and speedy storage and transfer of information.

4. How does a flash drive work? • A flash drive has to be inserted in the USB port on the computer. • Latest operating systems detect the flash drive and install the necessary drivers on their own. • Once the device is detected, it can be used for storing the data. • The device needs to be ejected from the computer. The system prompts you when it is safe to remove the flash drive. It can be physically ejected then. • A flash drive consists of a PCB, a printed circuit board. It is covered in a plastic or rubber casing, making it strong.

5. How does a flash drive work? • During the early years of the evolution of flash drives, the devices used could not survive too many erase cycles. • The devices of modern times are made to survive a larger number of erases. • Flash drives especially find utility in running lightweight operating systems in order to turn personal computers into network appliances.

6. How does a flash drive work? • In such cases, flash drives contain the operating system and are used to boot the system. • Moreover, a flash drive is small in size and portable. • They enable a speedy transfer of data with less difficulty. • Mostly they are plug and play devices. • They demand no special training to be used. • Flash drives have a large memory store, larger than memory capacities that floppies or CDs have.

7. Types of Flash Drive • Flash drive can be investigated in three aspects. • USB flash drive • Solid-state drive • Memory cards that employ flash memory. • xD Picture Card • Compact Flash • Memory Stick • Secure Digital

8. Flash Memory • Flash memory is known as a solid state storage device, meaning there are no moving parts -- everything is electronic instead of mechanical. • Flash memory is a type of EEPROM chip, which stands for Electronically Erasable Programmable Read Only Memory.

9. Flash Memory • Flash memory works much faster than traditional EEPROMs because instead of erasing one byte at a time, it erases a block or the entire chip, and then rewrites it. • It has a grid of columns and rows with a cell that has two transistors at each intersection.

10. Flash Memory • Two types of flash memory is common. • NAND type. • NOR type. • The high density NAND type read in (smaller) blocks, or pages, while the NOR type allows a single machine word (byte) to be written and/or read independently.

11. Flash Memory • The NAND type is primarily used in memory cards, USB flash drives, solid-state drives, and similar products, for general storage and transfer of data. • The NOR type, which allows true random access and therefore direct code execution, is used as a replacement for the older EPROM and as an alternative to certain kinds of ROM applications.

12. Flash Memory • Example applications of both types of flash memory include • personal computers, PDAs, digital audio players, digital cameras, mobile phones,synthesizers, video games, scientific instrumentation, industrial robotics, medical electronics, and so on.

13. Flash Memory • In addition to being non-volatile, flash memory offers fast read access times. • It is highly durable that it is being able to withstand high pressure, temperature, immersion in water etc.

14. How Flash Memory Saves a File • Flash-based drives are thinner, faster and nearly permanent(kalıcı). • Like a traditional hard drive, a flash-based drive stores information in the computer-readable language of 0s and 1s. • But instead of writing data by flipping magnetic poles on a spinning disk, flash memory just shuttles electrons around on a stamp-size microchip.

15. How Flash Memory Saves a File • With no moving parts (except, the electrons), a flash drive requires less power and is more durable than an ordinary hard drive. • It can even survive if dropped fromthe top of a building but a hard drive can wipe out your data if its mechanical arm scratches its disk.

16. How Flash Memory Saves a File These scanning electron microscope images zoom 10,000x on a flash drive.

17. How Flash Memory Saves a File • Flash memory stores 0s and 1s in millions of miniature transistors, each 1,000 times as thin as a human hair. • If the transistor conducts current, the chip reads it as 1; if not, it’s 0. • The current flows just underneath the transistor along the chip’s base [A].

18. How Flash Memory Saves a File • When the chip is empty, all transistors are set to 1. • But when you hit “save,” the chip records data by blocking the current to some transistors, turning them into a 0. • To do so, the chip briefly applies 20 volts to a piece of silicon called a control gate [B].

19. How Flash Memory Saves a File • This pulls electrons onto another silicon bit called a floating gate [C], leaving a positively charged area directly below—and breaking up the usual path of electrical current.

20. How Flash Memory Saves a File • The only way to move the electrons and change the pattern of 1s and 0s—thereby changing your data—is by applying precise voltages to the transistors.

22. Limitations • Block erasure • One limitation of flash memory is that although it can be read or programmed a byte or a word at a time in a random access fashion, it can only be erased a "block" at a time. • Memory wear (eskime) • Another limitation is that flash memory has a finite number of program-erase cycles (P/E cycles). • Most commercially available flash products are guaranteed to withstand around 100,000 P/E cycles, before the wear begins to deteriorate the integrity of the storage. • Micron Technology and Sun Microsystems announced an SLC NAND flash memory chip rated for 1,000,000 P/E cycles on December 17, 2008.

23. Limitations • Read Disturb • The method used to read NAND flash memory can cause other cells near the cell being read to change over time if the surrounding cells of the block are not rewritten. This is generally in the hundreds of thousands of reads without a rewrite of those cells.

24. USB Mass-Storage Device Class • The USB mass storage device class, otherwise known as USB MSC or UMS, is a protocol that allows a Universal Serial Bus (USB) device to become accessible to a host computing device, to enable file transfers between the two. • To the host device, the USB device appears similar to an external hard drive, enabling drag-and-drop file transfers.

25. USB Mass-Storage Device Class • The USB mass storage device class comprises a set of computing communications protocols defined by the USB Implementers Forum that run on the Universal Serial Bus. The standard provides an interface to a variety of storage devices. • Devices which support this standard are referred to as MSC (Mass Storage Class) devices. While MSC is the official abbreviation, UMS (Universal Mass Storage) has become common in online jargon(argo).

26. USB Mass-Storage Device Class • Some of the devices that are connected to computers via this standard include: • external magnetic hard drives • external optical drives, including CD and DVD reader and writer drives • portable flash memory devices • adapters bridging between standard flash memory cards and USB connections • digital cameras • various digital audio players and portable media players • card readers • PDAs • mobile phones

27. USB Implementers Forum • The USB Implementers Forum (USB-IF) is a non-profit organisation to promote and support the Universal Serial Bus. • It was formed in 1995 by the group of companies that developed USB. • Notable members include Apple Computer, Hewlett-Packard, NEC, Microsoft, Intel, and Agere Systems.

28. SuperSpeed USB (USB 3.0) • SuperSpeed USB (USB 3.0) brings significant performance enhancements to the ubiquitous USB standard, while remaining compatible with the billions of USB enabled devices currently deployed in the market. • SuperSpeed USB (USB 3.0, 5 Gbit/s) will deliver 10x the data transfer rate of Hi-Speed USB (USB 2.0, 480 Mbit/s), as well as improved power efficiency.

29. USB Flash Drive • A USB flash drive is a data storage device that consists of NAND-type flash memory with an integrated Universal Serial Bus (USB) interface • USB flash drives are often used for the same purposes for which floppy disks or CD-ROMs were used. • They are smaller, faster, have thousands of times more capacity, and are more durable and reliable because of their lack of moving parts. • USB flash drives are typically removable and rewritable, and physically much smaller than a floppy disk. • Most weigh less than 30 g (1 oz).

30. USB flash drive • USB Flash drives use the USB mass storage standard, supported natively by modern operating systems such as Linux, Mac OS X, Windows, and other Unix-like systems. • USB drives with USB 2.0 support can store more data and transfer faster than a much larger optical disc drives like CD-RW or DVD-RW drives. • USB drives can be read by many other systems such as the Xbox 360, PlayStation 3, DVD players and in some upcoming mobile smartphones.

31. USB flash drive • Nothing moves mechanically in a flash drive and computers read and write flash-drive data using the same system commands as for a mechanical disk drive with the storage appearing to the computer operating system and user interface as just another drive.

32. USB flash drive • A flash drive consists of a small printed circuit board carrying the circuit elements and a USB connector, insulated electrically and protected inside a plastic, metal, or rubberized case which can be carried in a pocket or on a key chain, for example. • The USB connector may be protected by a removable cap or by retracting into the body of the drive, although it is not likely to be damaged if unprotected. • USB flash drives draw power from the computer via external USB connection.

33. USB flash drive – Essential Components 1 USB Standard-A plug provides a physical interface to the host computer. 2 USB mass storage controller device a small microcontroller with a small amount of on-chip ROM and RAM. 3 Test points for testing during the flash drive's manufacturing or loading code into the microprocessor. 4 Flash memory chip stores data (NAND flash is typically also used in digital cameras).

34. USB flash drive – Essential Components 5 Crystal oscillator produces the device's main 12 MHz clock signal and controls the device's data output through a phase-locked loop. 6 LED indicate data transfers or data reads and writes. 7 Write-protect switch (Optional) indicate data transfers or data reads and writes. 8 Space for second flash memory chip provides space to include a second memory chip. Having this second space allows the manufacturer to use a single printed circuit board for more than one storage size device.

35. USB flash drive – Essential Components USB connector cover or cap reduces the risk of damage, prevents the entry of dirt or other contaminants, and improves overall device appearance. Some flash drives use retractable (geri içeri çekilebilir) USB connectors instead. Others have a swivel arrangement so that the connector can be protected without removing anything.

36. USB flash drive – Essential Components Transport aid the cap or the body often contains a hole suitable for connection to a key chain or lanyard(kordon). Connecting the cap, rather than the body, can allow the drive itself to be lost.

37. USB Flash Drive • The storage part of an EEPROM cell acts like a permanently-open(ON)or closed(OFF) transistor. • Charging is accomplished by grounding the source and drain terminals and placing a voltage on the control gate. • When the “floating gate” is charged, it impedes the flow of electrons from the control gate to the silicon, and the 0 or 1 is determined by whether the voltage on the control gate is blocked or not. http://www.usbmemorysticks.net/flash-drive-technology

38. USB Flash Drive • Now, 0 means a transistor is off and 1 means it’s on because the gate is open and electricity can flow. • With a regular transistor the data would be lost once the power is turned off because that shuts down the whole thing and it stays in the 0 position even when power is back on. http://www.usbmemorysticks.net/flash-drive-technology

39. USB Flash Drive • A flash memory cell however saves the data because it’s basically in a permanent 1 position. That’s due to its second gate, the floating gate, which enables electricity to stay trapped between it and the first gate • The data can still be erased though by draining the electricity out, that’s what the drain to the right is for. http://www.usbmemorysticks.net/flash-drive-technology

40. USB flash drive - Advantages • Data stored on flash drives is impervious to scratches and dust, and flash drives are mechanically very robust making them suitable for transporting data from place to place and keeping it readily at hand. • Flash drives also store data densely compared to many removable media. In mid-2009, 256 GB drives became available, with the ability to hold many times more data than a DVD or even a Blu-ray disc.

41. USB flash drive - Advantages • Compared to hard drives, flash drives use little power, have no fragile moving parts, and for most capacities are small and light. • Flash drives implement the USB mass storage device class so that most modern operating systems can read and write to them without installing device drivers.

42. USB flash drive - Disadvantages • Like all flash memory devices, flash drives can sustain only a limited number of write and erase cycles before the drive fails(About 90.5 million writes). This should be a consideration when using a flash drive to run application software or an operating system. • Most USB flash drives do not include a write-protect mechanism, although some have a switch on the housing of the drive itself to keep the host computer from writing or modifying data on the drive. Write-protection makes a device suitable for repairing virus-contaminated host computers without risk of infecting the USB flash drive itself.

43. USB flash drive - Disadvantages • A drawback to the small size is that they are easily misplaced, left behind, or otherwise lost. This is a particular problem if the data they contain are sensitive. • As a consequence, some manufacturers have added encryption hardware to their drives—although software encryption systems which can be used in conjunction with any mass storage medium achieve the same thing.

44. USB flash drive - Disadvantages • Most drives can be attached to keychains, necklaces and lanyards. The USB plug is usually fitted with a removable and easily lost protective cap, or is retractable. • USB flash drives are more expensive per unit of storage than large hard drives, but are less expensive in capacities of a few tens of gigabytes as of 2011Maximum available capacity is increasing with time, but is less than larger hard drives. This balance is changing, but the rate of change is slowing.

45. Solid State Drives • The speed of hard drive technology is bound by physics and mechanics. • More data is being saved into smaller spaces, but the overall speed of the drive is still managed by the speed of the spinning platter. • In order to get more speed, manufacturers moved to different technology: flash memory.

46. Solid State Drives • The flash memory in an SSD is known as NAND-flash. • There are two types: • SLC (single-level cell): In SLC, each cell of memory stores one bit. • MLC (multi-level cell):In MLC, each cell of memory stores stores two bits.

47. Solid State Drives • The SLC cell will respond to a certain voltage: at one level, the cell is assumed to hold 0; at another level the cell is assumed to hold 1. • With MLC, the cell will respond to one of four different levels of voltage, which we can denote as 00, 01, 10, and 11. • With MLC memory, to read a cell you have four times the number of tests to make, which takes longer.

48. Solid State Drives • The issue is that setting a cell to hold a value involves two different voltages. • There’s the programming voltage, which essentially sets the cell to 0, and there’s the higher erasure voltage, which sets the cell to 1.

49. Solid State Drives • The following scenario, illustrates how these gates work: you have two jars of water connected by a pipe. • The pipe has a tap and one jar is lower than the other.

50. Solid State Drives • Fill the top jar. • When the top jar is full, the system is assumed to store 1.