Universal Serial Bus (USB) (Cambridge (CIE) O Level Computer Science)
Revision Note
Written by: Robert Hampton
Reviewed by: James Woodhouse
Universal Serial Bus (USB)
What is USB?
The Universal Serial Bus (USB) is an asynchronous and serial method of transmitting data between devices and has become an industry standard
Many devices use USB such as keyboards, mice, video cameras, printers, portable media players, mobile phones, disk drives, network adapters, etc
Different USB connectors exist for different devices:
USB-A (flash drives, mice, keyboards, external HDD, etc)
USB-B (printers, scanners, optical drives, floppy drives, etc)
USB-C (new standard of USB due to its small size and speed)
When a device is connected to a USB port the computer:
Automatically detects that the device has been connected
Automatically recognises and the appropriate device driver is loaded so that the device can communicate with the computer
If the device is new, the computer will look for a matching device driver
If one cannot be found then the user must download and install an appropriate driver manually
Advantages and disadvantages of USB
Advantages | Disadvantages |
|---|---|
Devices are automatically detected and drivers are automatically loaded for communication | The maximum cable length is roughly 5 metres meaning it cannot be used over long distances, limiting its use |
Cable connectors fit in only one way. This prevents incorrect connections and ensures compatible data transmission | Older versions of USB have limited transmission rates for example USB 2.0 has 480Mbps |
As USB usage is standardised, there is a lot of support available online and from retailers | Very old USB standards may not be supported in the near future (USB 1.1, USB 2.0, etc) |
Several different data transmission rates are supported. The newest transmission rate as of 2022 is USB4 2.0 with 80 Gbps (81,920 Mbps, 170x faster than USB 2.0) |
|
Newer USB standards are backwards compatible with older USB standards |
|
Worked Example
Julia uses a USB connection to transfer data onto her USB flash memory drive.
One benefit of using a USB connection is that it is a universal connection.
(i) State two other benefits of using a USB connection.
[2]
(ii) Identify the type of data transmission used in a USB connection.
[1]
Answers
(i) Any two of:
It cannot be inserted incorrectly [1]
Supports different transmission speeds [1]
High speed transmission [1]
Automatically detected [1]
Powers the device for data transfer [1]
(ii)
Serial [1]
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