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Computer Systems

Computer Systems. Nat 4/5 Computing Science Interfaces & Peripherals. Lesson Aims. By the end of this lesson: Pupils at Nat 5 level will be able to: Describe the need for and purpose of interfaces Identify the interface used on a specific device

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Computer Systems

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  1. Computer Systems Nat 4/5 Computing Science Interfaces & Peripherals

  2. Lesson Aims • By the end of this lesson: • Pupils at Nat 5 levelwill be able to: • Describe the need for and purpose of interfaces • Identify the interface used on a specific device • Identify the speed(transfer rate) of an interface • Describe the functions of an interface • Compensating for differences in speed between the CPU and peripherals • Data conversion from analogue to digital forms and • Temporary data storage

  3. Nat 4/5 Peripherals • How many of you have connected a device (peripheral) to your computer? • USB Flash Drive • Mobile Phone/Ipod? • Printers/Scanners? • You have either connected these using wires or wirelessly. But they have all connected using an interface

  4. Nat 4/5 Interface • An interface can be described as: • Boundary across which two systems communicate • This is the piece of equipment that allows your scanner to communicate with the PC or for the pc to send information to the printer. • The devices may speak different languages and work differently. • So the interface’ main role is to deal with this

  5. Nat 4/5 Interface- Functions

  6. Nat 4/5 Function: Compensation • Compensating for differences in speed between the CPU and peripherals • Compare the processor of a computer and an iPod? • Computer CPU Speed: 2.5Ghz • IPod CPU Speed: 800Mhz • If the computer tried to get the iPod to do instructions at the same rate as it could there would be a problem!

  7. Nat 4/5 Analogue and Digital • As we have previously discussed computers are digital machines. • This means that there are only 2 signals. A sample digital signal could look like • Analogue signals ( like our voice) are analogue – this means that they can be any value between a minimum and maximum. • Such as: -

  8. Nat 4/5 Function: Data Conversion • Data conversion from analogue to digital • Remember Computers are digital machines! • However it may deal with analogue data, such as an input from a microphone or a analogue stick movement from a game controller

  9. Nat 4/5 Examples of Data Conversion Digital Analogue Digital Analogue

  10. Nat 4/5 Function: Temporary Storage • Another function of an interface is temporary data storage • This would happen when a computer is trying to transfer data for example to a printer. • The computer is going to be able to send data to the printer far more quickly than the printer can process it.

  11. Nat 4/5 Function: Temporary Storage • So the printers interface would have to temporarily store the data • Then allow the printer to process it at a rate the printer could deal with. • This function is similar to using a funnel when filling a container with water.

  12. Nat 4/5 General Trends • Transfer Speeds • USB has improved up to USB 3 • 12 Mbs up to 4.8Gbps • SATA is now on revision 3 • 1.5 Gbit/s up to 6Gbit/s • Wireless • Wifi • Bluetooth • Infra Red (IR)

  13. Summary A device needs an interfaceto allow it to communicate with a system An interface has three main functions Nat 4/5

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