CIS 103 — Applied Computer Technology
Personal Computer Data Communications
Last Edited: September 17, 2010
by C.Herbert
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.
CIS 103 Applied Computer Technology
Data Communications
2
Digital Data
Every object in a computer’s memory is stored
as a series of bits.
Numbers
CIS 103 Applied Computer Technology
Data Communications
3
Digital Data
Every object in a computer’s memory is stored
as a series of bits.
Text
CIS 103 Applied Computer Technology
Data Communications
4
Digital Data
Every object in a computer’s memory is stored
as a series of bits.
Pictures
CIS 103 Applied Computer Technology
Data Communications
5
Digital Data
Every object in a computer’s memory is stored
as a series of bits.
Sound
CIS 103 Applied Computer Technology
Data Communications
6
Digital Data
Every object in a computer’s memory is stored
as a series of bits.
Video
CIS 103 Applied Computer Technology
Data Communications
7
Digital Data
… every object is stored as a series of bits.
01000001 01000010 01000011 01000100 01000101 01000110 01000111 01001000
Parallel and Serial Communication
Bits can be moved in groups over several parallel wires
at the same time.
01000010
01000001
Parallel
Communication
or one at a time over a single wire …
01000001
01000010
Serial Communication
CIS 103 Applied Computer Technology
Data Communications
9
Serial and Parallel Communication
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)
01000010
01000001
Data Bus
An 8-bit
word
The size of the data bus
affects a computer’s
word length.
Data Communications
10
Serial and Parallel Communication
01000001
01000010
Serial Communication
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
CIS 103 Applied Computer Technology
Data Communications
11
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
CIS 103 Applied Computer Technology
Data Communications
12
Data Communication Standards
A data communication standard includes:
• a communications protocol
• the type of connectors to be used
• the type cables to be used
CIS 103 Applied Computer Technology
Data Communications
13
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
CIS 103 Applied Computer Technology
Data Communications
14
Data Communication Standards
Three commonly used serial communications
standards are:
• RS-232c
• USB
• Firewire
CIS 103 Applied Computer Technology
Data Communications
15
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
CIS 103 Applied Computer Technology
Data Communications
16
RS-232c
There are two types of RS232c connectors
• 9-pin
• 25-pin
CIS 103 Applied Computer Technology
Data Communications
17
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).
CIS 103 Applied Computer Technology
Data Communications
18
USB
USB is now the most widely used data communication
standard for connecting devices to personal computers.
CIS 103 Applied Computer Technology
Data Communications
19
USB
Three common versions of USB:
• USB
USB 1.1
(1994)
12 mbps (megabits per second), cables up to 3 meters
• Hi-Speed USB
480 mbps, 5 meters
USB 2.0
• SuperSpeed USB
USB 3.0
5 gbps (gigabits per second), 5 meters
CIS 103 Applied Computer Technology
(2001)
(2008)
Data Communications
20
USB Connectors
There are six different types of USB connectors.
… more about USB
in the next lesson
CIS 103 Applied Computer Technology
Data Communications
21
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
CIS 103 Applied Computer Technology
Data Communications
22
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
CIS 103 Applied Computer Technology
Data Communications
23
Firewire Connectors
Both 6-pin and 4-pin Firewire connectors are common
CIS 103 Applied Computer Technology
Data Communications
24
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.
CIS 103 Applied Computer Technology
Data Communications
25
Next . . .
Connecting USB devices to a personal computer
CIS 103 Applied Computer Technology
Data Communications
26