|Ⅱ Storage principle of USB flash drive|
|Ⅲ USB flash drive functional classification|
|Ⅳ How to use a USB flash drive?|
A USB flash drive is a miniature high-capacity mobile storage product that uses a USB interface without a physical drive, which is plug-and-play with a computer connected via a USB interface. After the USB interface of the USB flash drive is connected to the computer, the USB flash drive is exchanged with a computer. The biggest feature of the USB flash drive is: small and easy to carry, large storage capacity, and cheap. It is one of the mobile storage devices.
The composition of the USB flash drive is very simple, mainly composed of a shell + a PCB + USB main control chip + crystal oscillator + chip resistor, capacitor + USB interface + chip LED (not all USB flash drives have) + FLASH (flash memory). According to the material, the shell mainly includes ABS plastic, bamboo wood, metal, leather case, silicone, PVC software, etc.
The inside of the USB flash drive
Compared to other portable storage devices, the USB flash drive has many advantages: small space, fast speed (USB1, 2.0, 3.0 standard), big storage, and more reliability (due to not Mechanical equipment). This type of drive uses many USB storage device standards. Operating systems such as Linux, Mac OS X, Unix, and Windows have built-in support.
The USB flash drive typically uses the ABS plastic or metal housing, and there is a small printed circuit board inside. Only the USB connector protrudes outside the protective case and is usually covered by a small cover. Most USB flash drives use a standard Type-a USB connector, which allows them to directly insert into the USB port on your computer.
To access the USB flash drive, you must connect the USB flash drive to your computer, whether it is directly connected to the built-in USB controller or a USB hub. The flash drive is only started when the USB port is inserted, while the required power is also supplied by the USB connection.
The computer converts the binary digital signal to a composite binary digital signal (add assignment, check, stack, etc.), then reads and writes to the USB chip adapter interface. The corresponding address storage binary data is stored in the EEPROM memory chip through the chip processing signal to realize the storage of data. The control principle of EEPROM data memory is that the voltage control the voltage high and low value of the gate transistor, and the roll of the grid transistor can maintain the voltage value for a long time. The reason for preserving data after power off is mainly to add a floating gate and a selection gate on the original transistor. A floating gate of the storage electron is formed on the semiconductor in which the current and the drain are unidirectionally conducted. The floating gate is wrapped in a layer of silicon oxide film insulator. Its above is a selection/control gate that controls the transmission current between the source and drain. The data is 0 or 1 depends on whether there are electrons formed on the floating gate formed on the silicon bottom plate. There is an electron with 0, no electron is 1.
USB Flash Drive
The flash memory will remove the data before writing to initialize. Specifically, electrons are exported from all floating bales and the data will be "1". It is written only when it is 0. When 0 is written, a high voltage is applied to the gate electrode and the drain, increasing the electron energy conducted between the source and the drain. In this way, the electron will break through the oxide film insulator and enter the floating gate. When reading data, a certain voltage is applied to the gate electrode, the current is 1 when the current is large, and the current is 0 when the current is small.
When the floating gate has no electrons (data is 1), a voltage is applied to the drain when a voltage is applied to the gate electrode, and a current is generated between the source and the drain due to the movement of a large number of electrons. When there are electrons in the floating gate (the data is 0), the number of electrons conducted in the channel will decrease. Because the voltage applied to the gate electrode is absorbed by the floating gate electrons, it is difficult to affect the channel.
The main purpose of the USB flash drive is to store data. After the efforts of enthusiasts and merchants, we have developed more features: encrypt USB flash drive, launch USB flash drive, anti-Virus USB flash drive, temperature measurement USB flash drive, music USB flash drive, etc.
No drive type USB flash drive can be used in Windows 98 / ME / 2000 / XP and Linux, Mac OS, etc., which supports USB Mass Storage protocol, and uses only the driver installed under Windows 98, operating system over Windows ME. There is no need to install the driver to be properly identified and used by the system, and the convenience of "Plug and Play" is really reflected in the USB device. Most USB flash drive in the market are no-driven.
The encrypted type can be used as a normal type except that the stored content can be encrypted. There are two types: one is hardware encryption, such as fingerprint identification encryption USB flash drive, this type’s price is higher which is for users of special sectors. In general, the security of hardware encryption is better. Another type is software encryption. Software encryption can be specifically divided into a hidden partition (encrypted partition) in the USB flash drive to store files to encrypt, or you can only encrypt only a single file. Without a password, you cannot open the encrypted partition or encrypted single file.
The start-up USB flash drive joins the function of the boot system, which makes up for the defects of the encryption and no-driven USB flash drive. It is the emergence of this product, accelerating the process of being eliminated by the floppy drive. To perform system boot, the USB flash drive must simulate a USB peripheral implementation. The bootable USB flash drive on the market is mainly guided by the simulation USB_HDD mode. By the simulation USB_HDD mode boot system has a benefit: After the system is started, the USB flash drive is recognized as a hard drive, and the user can maximize the space of the USB flash drive. This USB flash drive with multiple boot functions can be widely applied to a laptop with an external USB floppy drive. In addition to the desktop, with this USB flash drive, the notebook can completely eliminate the floppy drive or even the optical drive.
The first time you use a USB flash drive on a computer (when you plug the USB flash drive into the USB port), the system will report "found new hardware". After a while, it will prompt: "The new hardware has been installed and can be used." (Sometimes it may need to restart). At this time, open "My Computer", you can see an extra icon called "Removable Disk". After this step, if you use the USB flash drive in the future, you can plug it in and open "My Computer" directly. At this time, notice that in the lower right corner of the screen, there will be a small icon, which means a USB device. (USB flash drive is one of the USB devices). Next, you can save and delete files on the USB flash drive as usual. However, it should be noted that after the USB flash drive is used, close all windows, especially the windows about the USB flash drive. Before removing the USB flash drive correctly, left-click the USB device icon in the lower right corner, and then left-click "Safely Remove Hardware". When the prompt: "You can safely remove the drive now" appears in the lower right corner, you can unplug the USB flash drive from the case. Another more convenient way to unplug is to directly left-click on the extra icon, and then click to stop the USB interface, and wait for the prompt that you can safely remove the drive now. Then left-click to confirm and the USB flash drive can be unplugged.