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Computer Systems. Nat 4/5 Computing Science Interfaces. Nat 4/5. Peripherals. How many of you have connected a device (peripheral) to your computer? USB Flash Drive Mobile Phone/ Ipod ? Printers/Scanners?
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Computer Systems Nat 4/5 Computing Science Interfaces
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
Nat 4/5 What is an 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 work differently. • It is the interface’s job to enable to devices to work together
Nat 4/5 Interface- Functions
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!
Nat 4/5 Function: Data Conversion (Analogue and Digital) • Computers use digital signals • 2 values 0 and 1 to represent on and off • A digital signal could look like:- • An analogue signal varies continuously between two limits • Sound, light, temperature are analogue
Examples of Data Conversion Interface carries out digital to analogue conversion Interface carries out analogue to digital
Nat 4/5 More Examples of Data Conversion Digital Analogue Digital Analogue
Function: Data Conversion (Serial and parallel) • Remember that data conversion means “change data from a peripheral so processor can understand it and vice versa” • E.g. change serial data to parallel and vice versa • Serial data transmission • 1 data line that bits go along 1 after another • efficient for long distances
Function: Data Conversion (Serial and parallel) • Parallel data transmission:- • Bits travel simultaneously along different lines • Fast • Suits short distances e.g. processor & peripherals or inside processor
Example of Data Conversion Interface carries out serial to parallel conversion
Nat 4/5 Function: Temporary Storage • The computer can send data to the printer more quickly than the printer can process it • The interface stores data temporarily to free up the processor • The interface sends more data to the printer when the printer is ready
Types of interface : USB 2 • USB = Universal Serial Bus - standardised the connection of devices – many devices use USB • Data transfer rate - 480 Megabits per second • 40 times faster than USB 1 • Used when connecting:- • mouse, keyboard, printer, etc • USB 2 can connect USB 1 devices – transfers data at USB 1 speed
Types of interface : USB 3 • 5 Gbit/s – called Superspeed • 10 times faster than USB 2 • Used when very fast access to data is required e.g • streaming HD movies • making a backing up of an internal hard drive to an external hard drive • USB 3 can connect USB 2 devices – transfers data at USB 2 speed
Types of interface : Firewire 800 • High speed connection • 800 Megabits per second • Similar uses to USB
Types of interface : Thunderbolt 7 SATA • Thunderbolt Version 2 – connects devices to the computer e.g. HD camera, keyboard, printer, etc • 20 GigaBits per second • SATA – connects motherboard to hard drive or optical drive • 6 Gigabits per second
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)
Infrared • Like tv remote control • Needs direct line of sight between transmitter an receiver • Short-range
Bluetooth • Uses radio waves that pass through walls so devices don’t need to point at each other • Temporary short-range link between personal devices e.g. • mobile phones and headsets • Palmtop • Laptop • Range 10m • Speed of data transfer 1 = Megabit per second
WiFi • Wireless Fidelity Alliance • Range 12 – 50 metres • Data transfer rate 5- 12 Megabits per second • Used by wireless networks in homes
Summary A device needs an interfaceto allow it to communicate with a system An interface has three main functions Nat 4/5
Summary - continued • There are many types of interface:- • USB 2, 3 • Firewire • Thunderbolt • SATA • Wireless:- • WiFi • Bluetooth • Infrared