CIS 103 — Applied Computer Technology

Last Edited: September 17, 2010by C.Herbert

Personal Computer Data Communications

CIS 103 Applied Computer Technology

Digital Data

Data in a computer is stored as a series of bits,

or binary digits.

Each bit is a one or a zero,

represented in a computer

by electrical, magnetic and

optical technology.

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CIS 103 Applied Computer Technology

Digital Data

Every object in a computer’s memory is stored as a series of bits.

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Numbers

CIS 103 Applied Computer Technology

Digital Data

Every object in a computer’s memory is stored as a series of bits.

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Text

CIS 103 Applied Computer Technology

Digital Data

Every object in a computer’s memory is stored as a series of bits.

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Pictures

CIS 103 Applied Computer Technology

Digital Data

Every object in a computer’s memory is stored as a series of bits.

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Sound

CIS 103 Applied Computer Technology

Digital Data

Every object in a computer’s memory is stored as a series of bits.

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Video

… every object is stored as a series of bits.

Digital Data

01000001 01000010 01000011 01000100 01000101 01000110 01000111 01001000

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Bits can be moved in groups over several parallel wires at the same time.

or one at a time over a single wire …

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0 1 0 0 0 0 0 1 0 1 0 0 0 0 1 0

0 1 0 0 0 0 1 00 1 0 0 0 0 0 1

Serial Communication

ParallelCommunication

Parallel and Serial Communication

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Parallel communication uses a set of wires called a data bus, so it is:

• faster• more expensive• often used for short distances (inside a computer)

0 1 0 0 0 0 1 00 1 0 0 0 0 0 1

Data Bus

The size of the data bus affects a computer’s

word length.

An 8-bit word

Serial and Parallel Communication

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Serial communication:• is not as fast • is less expensive

• is often used for long distances (between computers)• requires only one data wire• often uses two data wires– one in each direction

0 1 0 0 0 0 0 1 0 1 0 0 0 0 1 0

Serial Communication

Serial and Parallel Communication

CIS 103 Applied Computer Technology

Data Communication Standards

a communications protocol defines:

• the electronic signals to be used

• how fast the data should be sent

• error checking methods

• and other technical details

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CIS 103 Applied Computer Technology

Data Communication Standards

A data communication standard includes:

• a communications protocol

• the type of connectors to be used

• the type cables to be used

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CIS 103 Applied Computer Technology

Data Communication Standards

Several agencies and associations maintain data communications protocols and standards:

• International Telecommunications Union (ITU) – a technical committee sponsored by the United Nations

• Institute of Electrical and Electronics Engineers (IEEE) – a professional group

• Electronics Industries Association (EIA) – a trade association

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CIS 103 Applied Computer Technology

Data Communication Standards

Three commonly used serial communications standards are:

• RS-232c

• USB

• Firewire

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CIS 103 Applied Computer Technology

RS-232c

The RS-232c standard:• was created by the IEA in 1969 for terminals

connected to old mainframe computers

• Used with early personal computers and telephone modems

• not used as much today, but is still used with some printers and older equipment

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CIS 103 Applied Computer Technology

RS-232c

There are two types of RS232c connectors

• 9-pin

• 25-pin

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CIS 103 Applied Computer Technology

USB

In the 1990’s several computer companies formed a new trade association – the Universal Serial Bus Implementers Forum (USB-IF) – to develop a faster and less expensive data communication standard using newer technology. Their popular new standard is called USB (Universal Serial Bus).

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CIS 103 Applied Computer Technology

USB

USB is now the most widely used data communication standard for connecting devices to personal computers.

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CIS 103 Applied Computer Technology

USB

Three common versions of USB:

• USB USB 1.1 (1994)12 mbps (megabits per second), cables up to 3 meters

• Hi-Speed USB USB 2.0 (2001) 480 mbps, 5 meters

• SuperSpeed USB USB 3.0 (2008) 5 gbps (gigabits per second), 5 meters

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CIS 103 Applied Computer Technology

USB Connectors

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There are six different types of USB connectors.

… more about USB in the next lesson

CIS 103 Applied Computer Technology

Firewire

• first developed by Apple Computers • approved as standard IEEE 1394 in 1995• Sony’s version is iLInk, Texas Instruments’ is Lynx • is the High Definition Audio-Video Network Alliance

(HANA) standard for the audio visual industry • The automobile industry, the military, and the NASA

Space Shuttle all use Firewire

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CIS 103 Applied Computer Technology

Firewire

Two common versions of Firewire:

• Firewire 400 (IEEE 1394a) has a maximum data transfer rate of 400 Mbps

• Firewire 800 (IEEE 1394b) is capable of 800 Mbps over standard cables and up to 3,200 Mbps using fiber optic cables

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CIS 103 Applied Computer Technology

Firewire Connectors

Both 6-pin and 4-pin Firewire connectors are common

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CIS 103 Applied Computer Technology

Firewire vs. USB

• Firewire is faster and more sophisticated than USB

• Is capable of longer distances (up to 100 meters)

• the equipment is significantly more expensive

• It can be a little harder to use

• USB is far more common for connecting devices to personal computers.

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CIS 103 Applied Computer Technology

Next . . .

Connecting USB devices to a personal computer

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