Computer Architecture29x

Computer Architecture

Lecture 29

Fasih

ur

Rehman

Last Class

•
Memories

•
Virtual memory

–
Address Translation

•
Memory Management

Today’s Agenda

•
Computer Communication

Analog Vs. Digital


Data Communication

•
Transmission of data (voice, video or text) via
electrical, optical or wireless link between
computers or network processors is referred
to as Data Communication

–
In computer communication, the data is generally
digital.

•
Mostly, the data that is required to be communicated
is in analog form.

•
So an analog to digital converter ADC will be required
to convert the analog data into digital data.

–
The link can be

•
Free space

•
Wires (twisted pair, coaxial cable, parallel conductors)

•
Optical fiber

Why Digital

•
Easy to mix signals and data using digital
techniques

•
Less
noise prone

•
Good
processing techniques are available for
digital

•
signals, such as

–
Data
compression (or source
coding)

–
Error
Correction (or channel coding)

–
Equalization

–
Security

Components of a Communication System

•
Source (Transmitter)

•
Medium (Communication Line)

•
Sink (Receiver)

•
Communication networks

•
Communication rules (protocols
)

–
Both source and sink act as node


History

•
Telegraph

•
Telephone

•
Computer

•
Transistor

•
Integrated Circuits (LSI, VLSI)

•
Satellites

Transmission Direction

•
Simplex

–
One way communication e.g. TV transmission

•
Half Duplex

–
Two way communication but not simultaneously

–
e.g.
walkie

talkie

•
Full Duplex

–
Simultaneous two way communication

–
telephone


Codes

•
Human Codes

–
Morse Code

•
Dots and Dashes

•
Machine Codes

–
Binary codes

•
use binary states

•
use same number of bits

•
so transmitted in same time

•
perfectly formed

•
alphanumeric


Common Codes

•
Baudot

code

•
ASCII

•
EBCDIC

•
Unicode

Some Commonly used Terms

•
Throughput

–
The number bits transferred per second.

–
Also called bandwidth

•
Latency

–
The that is elapsed between initiation of
transmission and earliest possible reception of a
give piece of information.

–
Also called delay

•
Network Topology

–
The way hosts are connected to the network

•
Star, ring topologies etc.

•
Main goal of topology is to have minimum latency with
high throughput

•
Some commonly used topologies are described as

Mesh

•
All nodes are connected to each other.


Bus Topology

•
All nodes are connected to a common bus

Star Topology

•
All nodes are connected to common hub.

Ring Topology

•
All computers are connected in a way that
they form a loop.

Hybrid Topology

•
Mix of the above topologies

Protocols

•
Set of rules to be followed in order to
communicate among the network nodes

Summary

•
Data Communication

–
Signals

–
Analog and Digital