The Universal Serial Bus

The Universal Serial Bus :

How it Works and What it Does

USB is a system for connecting a wide range of peripherals to a computer, including pointing devices, displays, and data storage and communications products. Although not a relatively new development in personal computing, it has only recently gained popularity due to increasing software support. This document discusses what the USB system does and how it is done. The technical detail covers the system's logical structure, rather than the electrical or software characteristics.

About this note

This was originally a first year uni assignment, so it is limited in depth and the content is rather dated. Things have changed a lot since then (e.g. USB2, and now 3). However, it should still serve as a useful background or introductory note.

Where new technical terms are introduced and defined in the text, they are printed in italics like this

Traditionally, computer hardware such as printers and mice were plugged into sockets on the back panel of a PC, with each connector being fairly specialised in its applications. For example, mice use one that is dedicated to transmitting serial data, while printers usually use a parallel data cable, and monitors have their own special plug. This system was quite suitable when it was implemented and has been used for many years. 

However, recent technological developments have created problems for many users of PCs with this system. Today there is a huge range of peripheral equipment including scanners, digital cameras, specialised pointing devices, high speed modems, all of which need their own connection to the PC. While the above mentioned parallel and serial sockets can indeed be used by many different devices, they cannot be shared by more than one device at once, and so we can quickly run out of space to attach this new equipment. 

Then why not just add more places to plug things into? This is quite possible, and has previously been the solution in many cases by installing more sockets, and even connecting devices internally to bypass the need for these plugs altogether. However, there is a practical limit to how much this can be done. To examine why, we need to investigate the structure of the PC. 

First of all, I would like to define a flash drive, and then tell you about its features before other storage devices.

USB-Flash Drive (flash drive, flash drive) - a device for storing and storing information. Data transferred to the device is located and stored in flash memory. For information, the USB flash drive must be connected to a TV (Smart), a computer, a tablet or any other reader.

Unfortunately not all USB storage devices work out their put time fairly. As a rule, the fault of this is the producers of little-known companies and companies with unknown origins that do not observe technological norms when creating a permanent storage device (ROM). Very often, our Chinese "friends" who like to make forgeries of eminent brands do not comply with technology (not quality parts) and create cheap storage devices that are out of order before the due time.

As I wrote above, that the USB-drive is based on a flash memory type NAND or NOR. In turn, the flash memory contains a silicon crystal on which the field-effect transistors with floating and controlling isolated gates are placed. It should be said that the field effect transistors have a drain and a source. So the floating gate of the transistor is able to hold the charge (electrons).

During data recording, a positive voltage is applied to the control gate and some of the electrons are directed (moving) from the drain to the source, deviating to the floating gate. Part of the electrons overcomes a thin layer of the insulator and penetrate the floating gate, where they remain for a long period of storage. The information storage time is measured by years, but in one way or another it is limited.

1.USB connector.

2. Microcontroller.

3.Control points.

4.Chip (chip) of flash memory.

5.Quartz resonator.

6.Light-emitting diode.

7.Switch (write-protect).

8.Space for the memory chip (additional space).

Disadvantages of USB-flash drives:

Limited number of cycles of recording and erasing before the failure.

Limited time of offline data storage.

The speed of writing and reading is limited by the bandwidth of the USB bus and the flash memory itself.

Sensitive to radiation and electrostatic discharge (usually observed in everyday life, most often in winter).

Адрес публикации: https://www.prodlenka.org/metodicheskie-razrabotki/325370-the-universal-serial-bus