412 Computer Architecture and Organization
So, what is an embedded system? An embedded system is primarily a combined hardware–software
placed within a system for some dedicated or specifi c application. Is our desktop or laptop an embedded
system? The answer is ‘no’. They are meant for executing user de ned software, whereas an embedded
system does not allow that.
14.2 TYPES AND CLASSIFICATIONS
Embedded systems may be classi ed in a variety of ways, only a part of which is presented in Figure 14.1.
As we can observe from Figure 14.1, different view-points would place various category-tags in
embedded systems. For example, embedded systems are being extensively adopted by the automobile
industries and also in consumer electronics, not indicated in Figure 14.1. We now discuss, very brie y,
about several types of embedded systems, which are well known to us but restricted to a narrower zone
of application.
14.2.1 Processing Power
In early days of embedded systems, only 8-bit microcontrollers were available to the designers. How-
ever, with the steady increase in demand and popularity, 16-bit, 32-bit and presently 64-bit (Intel Atom,
for example) microcontrollers are available in the market. This has increased the processing power
of the system by manifold and may be taken as the most important characteristics to distinguish one
embedded system from another. Example of a complex embedded system demanding enhanced pro-
cessing power may be our mobile handset, which is designed mostly around a 32-bit ARM controller.
On the other end of this spectrum, example may be cited from the keyboards of PCs, which need very
less processing power and use an 8-bit (Intel 8748/49) microcontroller.
14.2.2 Power Supply
From the power supply point of view, embedded systems may be classi ed as battery operated, battery
backed-up or normal A/C powered . Example of a battery operated embedded system may be a small
toy, battery backed-up system might be a digital clock and the billing machine of an STD booth may
be taken as an example of normal A/C powered embedded system. As most of the modern embedded
controllers have excellent power management features, battery-operated embedded systems consume
very less power and becoming increasingly popular day-by-day. In several situations, built-in recharg-
ing facilities for these batteries are offered by the manufactures to provide a maintenance-free system
with a longer life-span.
Finger-print reader or biometric reader and RFID based smart cards have invaded into industrial
security system. Days are not far off when every person would be carrying only one plastic
card using which cash may be collected from ATMs, daily attendance in work place may be
secured, petrol may be purchased, and vote may be cast and so on.
F
O
O
D
F
O
R
T
H
O
U
G
H
T
M14_GHOS1557_01_SE_C14.indd 412M14_GHOS1557_01_SE_C14.indd 412 4/29/11 5:27 PM4/29/11 5:27 PM
Embedded Systems 413
14.2.3 Life-span or Usage
Life-span or usage is another important criterion for classifying embedded systems. Usage-wise, embed-
ded systems may be classi ed as use and throw type and serviceable type. Our musical greetings card
belongs to the rst category, while a washing machine belongs to the second category. The reader may
note that with the present day technology, embedded controllers are becoming remarkably cheaper and
the embedded systems, like a tiny one placed within a greetings card operated by a small button-cell,
are meant for a very small life-span.
14.2.4 Wireless
Although mobile handsets are most popular examples, there are a whole lot of embedded systems which
have built-in wireless communication power. Another example may be the cluster robots , i.e., a group of
small autonomous robots, capable of communicating with each other and can accomplish a task sub-divided
to those. Embedded systems controlling these robots are capable of communicating through wireless. There-
fore, the embedded systems capable of communicating through wireless may be taken as a special category.
14.2.5 Instrumentation
Some embedded systems are fabricated around some special microcontrollers, which are speci cally
designed to be used for instrumentation. Analog Devices ADμc812 may be taken as an example case of
such a microcontroller belonging to this category. Instruments fabricated around this type of microcon-
trollers are very compact, accurate, generally battery operated, light weight and so on. Handheld decibel
meters may be taken as another example case of this.
14.2.6 Medical
Embedded systems are not only used in medical instrumentation like blood pressure or blood sugar
measuring devices, but also being utilized for medical equipments. These embedded systems are very
useful in ophthalmic and other elds of medical treatments. Equipments, like Humphrey Field Testing
machine by well-known manufacturer Carl Zeiss may be taken as one example of these equipments.
Figure 14.1 Classification of embedded systems (partial)
M14_GHOS1557_01_SE_C14.indd 413M14_GHOS1557_01_SE_C14.indd 413 4/29/11 5:28 PM4/29/11 5:28 PM
..................Content has been hidden....................
You can't read the all page of ebook, please click here login for view all page.