Universal Serial Bus (USB) is an industry standard that establishes specifications for connectors, cables and protocols for communication, connection and power supply between personal computers and their peripheral devices. There have been 3 generations of USB specifications:
1. USB 1.x 2. USB 2.0 3. USB 3.x
USB 2.0 have multiple updates and additions. The the USB Implementer Forum (USB IF) currently maintains the USB standard and it was released in 1996.
USB was designed to standardize the connection of peripherals like pointing devices, keyboards, digital still and video cameras. But soon devices such as printers, portable media players, disk drives and network adaptors to personal computers used USB to communicate and to supply electric power. It is a commonplace to many devices and has largely replaced interfaces such as serial ports and parallel ports. USB connectors have replaced other types for battery chargers of portable devices with itself.
Advantages of USB –
The Universal Serial Bus was designed to simplify and improve the interface between personal computers and peripheral devices, when compared with previously existing standard or ad-hoc proprietary interfaces.
- The USB interface is self-configuring. This means that the user need not adjust settings on the device and interface for speed or data format, or configure interrupts, input/output addresses, or direct memory access channels.
- USB connectors are standardized at the host, so any peripheral can use any available receptacle. USB takes full advantage of the additional processing power that can be economically put into peripheral devices so that they can manage themselves. USB devices mostly do not have user-adjustable interface settings.
- The USB interface is hot pluggable or plug and play, meaning devices can be exchanged without rebooting the host computer. Small devices can be powered directly from the USB interface thus removing extra power supply cables.
- The USB interface defines protocols for improving reliability over previous interfaces and recovery from common errors.
- Installation of a device relying on the USB standard minimal operator action is required.
Disadvantages of USB –
- USB cables are limited in length.
- USB has a strict “tree” topology and “master-slave” protocol for addressing peripheral devices. Peripheral devices cannot interact with one another except via the host, and two hosts cannot communicate over their USB ports directly.
- Some very high speed peripheral devices require sustained speeds not available in the USB standard.
- For a product developer, use of USB requires implementation of a complex protocol and implies an intelligent controller in the peripheral device.
- Use of the USB logos on the product require annual fees and membership in the organization.
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