EEPROM | DataRecoveryUnion.com

Flash memory is a form of non-volatile memory that can be electrically erased and rewrite, which means that it does not need power to maintain the data stored in the chip. In addition, flash memory offers fast read access times and better shock resistance than hard disks. These characteristics explain the popularity of flash memory for applications such as storage on battery-powered devices.

Flash memory is advance from of EEPROM (Electrically-Erasable Programmable Read-Only Memory) that allows multiple memory locations to be erased or written in one programming operation. Unlike an EPROM (Electrically Programmable Read-Only Memory) an EEPROM can be programmed and erased multiple times electrically. Normal EEPROM only allows one location at a time to be erased or written, meaning that flash can operate at higher effective speeds when the systems using; it read and write to different locations at the same time. Referring to the type of logic gate used in each storage cell, Flash memory is built in two varieties and named as, NOR flash and NAND flash.

Flash memory stores one bit of information in an array of transistors, called “cells”, however recent flash memory devices referred as multi-level cell devices, can store more than 1 bit per cell depending on amount of electrons placed on the Floating Gate of a cell. NOR flash cell looks similar to semiconductor device like transistors, but it has two gates. First one is the control gate (CG) and the second one is a floating gate (FG) that is shield or insulated all around by an oxide layer. Because the FG is secluded by its shield oxide layer, electrons placed on it get trapped and data is stored within. On the other hand NAND Flash uses tunnel injection for writing and tunnel release for erasing.

Although it can be read or write a byte at a time in a random access fashion, limitation of flash memory is, it must be erased a “block” at a time. Starting with a freshly erased block, any byte within that block can be programmed. However, once a byte has been programmed, it cannot be changed again until the entire block is erased. In other words, flash memory (specifically NOR flash) offers random-access read and programming operations, but cannot offer random-access rewrite or erase operations.

This effect is partially offset by some chip firmware or file system drivers by counting the writes and dynamically remapping the blocks in order to spread the write operations between the sectors, or by write verification and remapping to spare sectors in case of write failure.

Due to wear and tear on the insulating oxide layer around the charge storage mechanism, all types of flash memory erode after a certain number of erase functions ranging from 100,000 to 1,000,000, but it can be read an unlimited number of times.

Flash Card is easily rewritable memory and overwrites without warning with a high probability of data being overwritten and hence lost.

Data Storage

USB Flash Drives – Instant Storage

DATARECOVERYUNION.COM15 years ago11 years ago07 mins

What is the hottest back-to-school item this year? So red-hot that Mom and Dad will see it and want it too? It’s a tiny portable data storage device that plugs into the computer’s USB (Universal Serial Bus) port. Just a few of the brand names explain what it is. Here are some examples: TravelDrive™ from Memorex, Mini Cruzer™ from Sandisk, JumpDrive™ from Lexar. These small, pocket-sized storage devices are easy to work with, can plug in to any type of computer that is less than 8 years old or that has a USB port.

The great thing is that USB flash drives are really affordable now and for less than $100 you can get a 1GB USB storage device. Although flash drives have many uses, a common one is for transferring files from your work computer to your home computer, eliminating the need for lugging a laptop back and forth. (Although these devices go by many names, for purposes of this article, we will use the term flash drive.)

This article will take a look at this micro-technology, its history and future; you’ll be surprised to find out how prevalent this technology is and how long it has been around. As always, we will take a look at recovery options for these devices.

Flash Drives
In order to better understand the flash devices we have now, let’s take a moment and look at their history. Rudimentary flash memory began as integrated circuit chips that would come to be a standard in all electronic devices. These were known as CMOS (Complementary Metal-Oxide-Semiconductor, pronounced ‘see-moss’) circuits. These small, low power, high-density circuits could be designed to perform a variety of functions and operations. Initially designed in 1963 and first produced in 1968, these little chips were the beginning of the digital integrated circuit. Perhaps you had a computer 17 years ago and remember the importance of the CMOS chip; the CMOS chip controlled the basic system settings and is similar to the BIOS (Basic Input/Output System) on today’s computers.

CMOS integrated chips were a fantastic innovation; however, they were vulnerable to electro-static discharge, had to be handled carefully, and these chips always needed a constant power source to maintain the data. Did you ever have to replace the CMOS battery on your 8088 or 8086 computer? Then you remember that once the power was gone, you had to re-enter all of your computer’s settings.
A new style of chip called EEPROM (Electrically Erasable Programmable ROM or Read Only Memory) was the successor to the CMOS chip and had significant improvements. The major innovation was that the chips were designed to be written to and then to hold data without power. The on-board memory usually held 64k (65,536 bytes). However, the materials inside the chip would wear out over time due to the number of write operations, so the lifetime of these chips were 10,000 to 100,000 write cycles.

Flash memory was an improvement over the EEPROM circuits in that they provided faster access to the data. Originally designed by Intel in 1988 and followed up by Samsung and Toshiba in 1989, these chips started popping up everywhere as embedded memory on electronic devices. Most of the applications for this non-volatile memory storage were for devices where the chip was part of the internal electronics, for example mobile phones, VCRs, automotive electronics, and handheld devices. In fact, flash memory storage (NAND-type flash memory as it is known) could be used for any electronic application that required the storage of data without electrical current; even hard drives use flash memory chips!

After flash technology had proven its reliability, retail products were the next step. M-Systems (NasdaqNM:FLSH) lead the industry with the flash disk concept in 1989 and in 1995 started to offer retail products that were designed for cameras, PDAs, and removable memory sticks or cards. Quite a long history, wouldn’t you agree? As you read this, flash storage is replacing the floppy diskette for portable, temporary data storage. The beauty of the USB flash drive is that it is universal. Remember the Great Floppy Diskette Debate? Do we install 5¼” drives? 3½” drives? Both? The manufacturers have wisely stuck to a standard this time.

Flash Memory

USB Flash Drives – Instant Storage