An embedded system is a combination of computer hardware and software designed to perform a specific function. It has three main components - hardware, application software, and an optional real-time operating system. Embedded systems are used in devices like fire alarms, cruise control systems, and digital cameras where they perform specialized tasks in real-time. Common characteristics include being single-purpose, constrained by tight design requirements like size and power consumption, and reactive to changes in their environment.

1. An embedded system is a combination of computer hardware and software
designed for a specific function.
Embedded systems may also function within a larger system.
The systems can be programmable or have a fixed functionality.
An embedded system can be thought of as a computer hardware system having
software embedded in it.
An embedded system can be an independent system or it can be a part of a
large system.
An embedded system is a microcontroller or microprocessor-based system
which is designed to perform a specific task. For example, a fire alarm is an
embedded system; it will sense only smoke.
An embedded system has three components −
 It has hardware.
 It has application software.
 It has Real Time Operating system (RTOS) that supervises the
application software and provide mechanism to let the processor run a
process as per scheduling by following a plan to control the latencies.
RTOS defines the way the system works. It sets the rules during the
execution of application program. A small scale embedded system may
not have RTOS.
Characteristics of an Embedded System
 Single-functioned − An embedded system usually performs a specialized
operation and does the same repeatedly. For example: A pager always
functions as a pager.
 Tightly constrained − All computing systems have constraints on design
metrics, but those on an embedded system can be especially tight. Design
metrics is a measure of an implementation's features such as its cost, size,
power, and performance. It must be of a size to fit on a single chip, must
perform fast enough to process data in real time and consume minimum
power to extend battery life.
 Reactive and Real time − Many embedded systems must continually
react to changes in the system's environment and must compute certain

2. results in real time without any delay. Consider an example of a car cruise
controller; it continually monitors and reacts to speed and brake sensors.
It must compute acceleration or de-accelerations repeatedly within a
limited time; a delayed computation can result in failure to control of the
car.
 Microprocessors based − It must be microprocessor or microcontroller
based.
 Memory − It must have a memory, as its software usually embeds in
ROM. It does not need any secondary memories in the computer.
 Connected − It must have connected peripherals to connect input and
output devices.
 HW-SW systems − Software is used for more features and flexibility.
Hardware is used for performance and security
Advantages
 Easily Customizable
 Low power consumption
 Low cost
 Enhanced performance
Disadvantages
 High development effort
 Larger time to market
Basic Structure of an Embedded System
The following illustration shows the basic structure of an embedded system −

3.  Sensor − It measures the physical quantity and converts it to an electrical
signal which can be read by an observer or by any electronic instrument
like an A2D converter. A sensor stores the measured quantity to the
memory.
 A-D Converter − An analog-to-digital converter converts the analog
signal sent by the sensor into a digital signal.
 Processor & ASICs − Processors process the data to measure the output
and store it to the memory.
 D-A Converter − A digital-to-analog converter converts the digital data
fed by the processor to analog data
 Actuator − An actuator compares the output given by the D-A Converter
to the actual (expected) output stored in it and stores the approved output.
Why Use Microprocessors?
■ Microprocessors are a very efficient way to implement digital systems.
■Microprocessors make it easier to design families of products that can be built
to provide various feature sets at different price points and can be extended to
provide new features to keep up with rapidly changing markets.
■ Microprocessors execute programs very efficiently. Modern RISC processors
can execute one instruction per clock cycle most of the time, and high
performance processors can execute several instructions per cycle(MIPS).

4. ■Microprocessor manufacturers spend a great deal of money to make their
CPUs run very fast.
■ Microprocessors generally dominate new fabrication lines because they can
be manufactured in large volume and are guaranteed to command high prices.
■Microprocessors are very efficient utilizers of logic. The generality of a
microprocessor and the need for a separate memory may suggest that
microprocessor-based designs are inherently much larger than custom logic
designs.
Embedded system design process :--
An Embedded system is a controller, which controls many other electronic
devices.
It is a combination of embedded hardware and software.
There are two types of embedded systems microprocessors and micro-
controller.
Micro-processor is based on von Neumann model/architecture (where program
+ data resides in the same memory location), it is an important part of the
computer system, where external processors and peripherals are interfaced to it.
It occupies more area and has more power consumption. The application of the
microprocessor is personal computers.
What is an Embedded System Design?
A system designed with the embedding of hardware and software together for a
specific function with a larger area is embedded system design.
In embedded system design, a microcontroller plays a vital role. Micro-
controller is based on Harvard architecture, it is an important component of an
embedded system. External processor, internal memory and i/o components are
interfaced with the microcontroller. It occupies less area, less power
consumption. The application of microcontrollers is MP3, washing machines.

5. Elements of Embedded Systems
 Processor
 Microprocessor
 Microcontroller
 Digital signal processor.
Steps in the Embedded System Design Process
The different steps in the embedded system design flow/flow diagram include
the following.

6. Embedded design – process – steps
Abstraction
In this stage the problem related to the system is abstracted.
Hardware – Software Architecture
Proper knowledge of hardware and software to be known before starting any
design process.
Extra Functional Properties
Extra functions to be implemented are to be understood completely from the
main design.
System Related Family of Design
When designing a system, one should refer to a previous system-related family
of design.
Modular Design
Separate module designs must be made so that they can be used later on when
required.
Mapping
Based on software mapping is done. For example, data flow and program flow
are mapped into one.
User Interface Design
In user interface design it depends on user requirements, environment analysis
and function of the system. For example, on a mobile phone if we want to
reduce the power consumption of mobile phones we take care of other
parameters, so that power consumption can be reduced.
Refinement
Every component and module must be refined appropriately so that the software
team can understand.
Architectural description language is used to describe the software design.
 Control Hierarchy
 Partition of structure
 Data structure and hierarchy

7.  Software Procedure.
Embedded Software Development Process Activities
Embedded software development process activities mainly include the
following.
Specifications
Proper specifications are to be made so that the customer who uses the product
can go through the specification of the product and use it without any confusion.
Designers mainly focus on specifications like hardware, design constraints, life
cycle period, resultant system behavior.
Architecture
Hardware and Software architecture layers are specified.
Components
In this layer, components design is done. Components like single process
processor, memories- RAM/ROM, peripheral devices, buses etc.
System Integration
In this layer, all the components are integrated into the system and tested
whether its meeting designers, expectations.
Challenges in Embedded System Design
While designing any embedded system, designers face lots of challenges like as
follows,
 Environment adaptability
 Power consumption
 Area occupied
 Packaging and integration
 Updating in hardware and software
 Security
 There are various challenges the designers face while testing the design
like Embedded hardware testing, Verification stage, Validation
Maintainability.

8. Embedded System Design Examples
 Automatic chocolate vending machine (ACVM)
 Digital camera
 Smart card
 Mobile phone
 Mobile, computer, etc.