Transcript Flash memory

Flash
Memory
Done By: Bashayer Al- Suroor
ID: 200800649
Outline:
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Introduction to How Flash Memory Works
A sample list of USB devices
USB Interface
Flash Memory: Tunneling and Erasing
How simple is the flash memory
Removable Flash Memory Cards
What is moseft and how its related to USB
What type of technology does USB work with
Advantages and disadvantages
what to do if you don’t have enough USB port?
Conclusion
Advice about this devise
Sources
Introduction :
 Flash
memory is used for easy and fast
information storage in computers. It is
used more like a hard drive than as RAM.
In fact, flash memory is known as a solid
state storage device, meaning there are
no moving parts -- everything is electronic
instead of mechanical.
Sample lists :
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Here are a few examples of flash memory:
Your computer's BIOS chip
CompactFlash (most often found in digital
cameras)
Smart Media (most often found in digital cameras)
Memory Stick (most often found in digital
cameras)
PCMCIA Type I and Type II memory cards (used as
solid-state disks in laptops)
Memory cards for video game consoles
* Printers
* Scanners
* Mice
* Keyboards
* Joysticks
* Digital cameras
* Webcams
* Speakers
* External hard drives
USB Interface
USB flash drive :
• plugged into a computer.
• connects into a USB port “tower”
 can easily be removed without damaging the
device. As a sign of the growing popularity of
USB flash drives
 both desktop and laptop computers have
numerous USB ports built into the hardware.
 The actual metal conductor that makes up the
USB interface is usually attached to a sliding
bar that makes the USB flash drive fit in your
pocket better
 not all models have this feature.
Flash memory is a type of EEPROM
chip, which stands for Electronically
Erasable Programmable Read Only
Memory. It has a grid of columns and
rows with a cell that has two
transistors at each intersection
Tunneling and Erasing
 Tunneling
is used to alter the placement
of electrons in the floating gate. An
electrical charge, usually 10 to 13 volts, is
applied to the floating gate. The charge
comes from the column, or bitline, enters
the floating gate and drains to a ground.
Removable Flash Memory
Cards
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There are a few reasons to use flash memory
instead of a hard disk:
It has no moving parts, so it's noiseless.
It allows faster access.
It's smaller in size and lighter.
So why don't we just use flash memory for
everything? Because the cost per megabyte
for a hard disk is drastically cheaper, and the
capacity is substantially more.
Removable Flash Memory
Cards
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The solid-state floppy-disk card (SSFDC), better
known as SmartMedia, was originally developed by
Toshiba. SmartMedia cards are available in
capacities ranging from 2 MB to 128 MB. The card
itself is quite small, approximately 45 mm long, 37 mm
wide and less than 1 mm thick.
As shown below, SmartMedia cards are extremely
simple. A plane electrode is connected to the flashmemory chip by bonding wires. The flash-memory
chip, plane electrode and bonding wires are
embedded in a resin using a technique called overmolded thin package (OMTP). This allows everything
to be integrated into a single package without the
need for soldering
MOSFET
 MOSFET, or Metal-Oxide-Semiconductor FieldEffect Transistor,
 is a small device that is capable of both
amplifying and switching an electronic signal.
 A MOSFET involves a metal “gate” that can
generate a conducting channel between the
two other contacts when a current is applied
to it
 MOSFETs are capable of handling 2000 watts of
electricity and are used in almost all analog
and digital circuits.
 important in USB flash drives :
• they use a very similar type of technology
called a floating-gate transistor.
Floating-gate Transistor
 very similar to MOSFET technology but instead of one
gate, it has two.
 The top gate is called the control gate while the
bottom is called the floating gate.
 completely insulated with an oxide layer. Each
memory cell of a USB flash drive is a floating-gate
transistor.
 When an electron is attached to the floating gate, it
is trapped within the oxide layer and causes a
difference in the voltage of the control gate. When
this is measured as a whole, each memory cell
makes up a 1 or 0 in binary code, depending on
whether it is storing an electron or not.
Advatages
 The main advantage of USB flash drives is that they are
extremely small and can fit in a pocket.
 USB flash drives do not contain any moving parts, unlike
hard drives, which make them very durable and longlasting. As technology has improved over recent years
 USB flash drives have steadily increased their storage
capacities while decreasing their price.
 USB flash drives also do not require any software to be
installed in order for them to work with a computer as all
computers that have a USB port have already been
programmed to recognize a USB flash drive.
 simplicity: even your grannie can plug and unplug her
webcam without studying for a PhD in computer science.
 you can't put them in the wrong way
round and cause any damage.
Unlike old-style connectors, they
don't have lots of fragile pins to get
bent up and damaged each time
you take them in and out.
 They're very robust—so you can plug
and unplug them zillions of times.
Disadvantages
 USB flash drives are far superior to other means of data
transportation
 but they do have a few drawbacks. For one, USB flash
drives are so small that they are often lost or forgotten.
 Also, USB flash drives often do not have any writeprotection software to keep viruses from infecting the USB
flash drive.
 Even these minor problems, however, have been met
and challenged in many recent models of USB flash
drives.
If you don't have enough USB ports on
your computer to accommodate all of
your devices:
Then you can buy a USB hub. Hubs can be
powered or unpowered. Hubs can be part of the
device such as a keyboard or monitor with USB
connections on it. The USB standard allows for
devices to draw their power from their USB
connection. A high power device like a printer
will have its own power supply, but low power
devices like mice and cameras can get their
power from USB bus so you don't need external
power. Individual USB cables can run as long as 5
meters.
USB port
 conclusion
<<Advice>>
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There is one thing to careful about:
USB sockets on computers are soldered directly to
the computer's main circuit board (often quite
weakly) and if you press them too hard you can
break the connections, which stops them from
working.
Be slow and gentle when you're taking plugs in
and out. Don't push them in hard or yank them
back out again.
http://www.explainthatstuff.com/usb.h
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http://www.tech-faq.com/how-a-usbflash-drive-works.html