Facts | How does flash drive?




Facts | How does flash drive?

Most often you store your pictures, songs and lyrics on the hard disk of a computer. But sometimes need a different drive, a mobile that you can carry around and open on any computer. Sometimes you need to make backup copies of important files. In such cases, the aid comes in flash memory . Special card of this type replace hard drives smart phones, tablets and digital cameras. The same memory is the basis of SSD-drives. It is called “solid-state» (solid state), because the drives are based on it, have no moving parts. learning how to overcome limitations of computer memory, our readers have expressed interest in SSD-drives. And now our story is dedicated to flash memory, which are based on these modern drives are becoming more and more common.

Some types of flash drives

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Before proceeding to a detailed examination of technology, we shall understand that what’s inside the chip flash memory. Here we can not do without the special terminology that will allow us to understand how the write and delete data from the memory cells of this type. It is important to understand that the flash drives occupy a well-known to our readers hierarchy of computer memory the same step as the hard drive. And, in fact, they play his role.

We begin our story with a brief list of drives, which use flash memory:

Your computer’s BIOS chip
Memory Cards CompactFlash (originally designed for digital cameras)
Memory Card SmartMedia (originally designed for digital cameras)
Memory cards Memory Stick (originally designed for digital cameras)
PCMCIA. Used in the SSD-drives for laptops
Memory cards for video game consoles

Flash memory is a type of electrically erasable programmable read-only memory (EEPROM, Electronically Erasable Programmable Read Only Memory, EEPROM). It has a kind of “grid” formed by rows and columns. Each grid cell is equipped with two transistors.

Transistors separated by a thin oxide layer. One transistor electronics engineers call the “floating gate» («floating gate»), and the second “control electrode» («control gate»). If the floating gate is connected to the cell, it takes the value “1”. To change the value to zero, the process is applied, which is known as tunneling, the FN.
Tunneling and erasing

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Tunneling is used to change the stacking order of the floating gate electrode. On the floating gate influences the current voltage is usually in the range of 10 to 13 volts. Current flows from the column or from the bit line.

This discharge compares the floating gate transistor “electron gun” that was used in the cathode ray tube of the old CRT monitors and televisions, the production of which was used a lot of lead. Excited electrons are on the way encountered obstacles in the form of the back side of a thin oxide layer, giving it a negative charge. These negatively charged electrons act as a barrier between the gate and the floating gate.

A special component monitors the charge passing through the floating gate. If the voltage of current flow exceeds fifty percent threshold, the value of the cell is equal to one. If the charge drops below this threshold, the value is reset to zero. The threshold voltage is calculated from the total charge. That is, if the voltage is equal to ten volts, if a floating gate passes current, voltage less than 5 volts, the cell value will be zero. The values ​​of all EEPROM cells are equal to one, and their control electrode and the floating gate is completely open.

The electrons in the cells of the chip flash memory can be returned to normal by exposure to an electric field of the same high voltage. Flash memory finest conductor network permeated material allowing an electric field to act both on the entire chip, and its individual segments. This allows you to erase the data in certain areas of flash memory, and then write back to the new information.

Flash memory is much faster than its ancient predecessor EEPROM. The fact that the EEPROM-memory simultaneously allows to erase only one byte of data. Flash memory allows you to simultaneously clear the information stored in it a block or the entire chip completely. Then, the memory cell can be filled with new data.
Not quite flash drive your car radio

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In the car radio (in addition to the drive), a special memory for storage of presets and program list. It may seem that this is too flash memory. But no, actually it’s a slightly different type of memory, called Flash-RAM (operational flash memory). It differs from the conventional flash memory is that the flash-RAM is volatile, it requires little power to retain the data.

Flash memory can store located in the information it without any external source of energy. But even when the radio is completely disconnected, it will still consume some power in order to avoid losing data from flash-RAM. If the battery is out of order, the receiver will lose all your settings. The same thing happens in the case of detaching the wires from it.

To be continued

According to the materials computer.howstuffworks.com
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