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An embedded system is a system which is going to do a predefined specified task is the
embedded system and is even defined as combination of both software and hardware. A
general-purpose definition of embedded systems is that they are devices used to control,
monitor or assist the operation of equipment, machinery or plant. "Embedded" reflects
the fact that they are an integral part of the system. At the other extreme a general-
purpose computer may be used to control the operation of a large complex processing
plant, and its presence will be obvious.
All embedded systems are including computers or microprocessors. Some of these
computers are however very simple systems as compared with a personal computer.
The very simplest embedded systems are capable of performing only a single function or
set of functions to meet a single predetermined purpose. In more complex systems an
application program that enables the embedded system to be used for a particular purpose
in a specific application determines the functioning of the embedded system. The ability
to have programs means that the same embedded system can be used for a variety of
different purposes. In some cases a microprocessor may be designed in such a way that
application software for a particular purpose can be added to the basic software in a
second process, after which it is not possible to make further changes. The applications
software on such processors is sometimes referred to as firmware.
The simplest devices consist of a single microprocessor (often called a "chip”), which
may itself be packaged with other chips in a hybrid system or Application Specific
Integrated Circuit (ASIC). Its input comes from a detector or sensor and its output goes to
a switch or activator which (for example) may start or stop the operation of a machine or,
by operating a valve, may control the flow of fuel to an engine.
As the embedded system is the combination of both software and hardware
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Figure: Block diagram of Embedded System
Software deals with the languages like ALP, C, and VB etc., and Hardware deals with
Processors, Peripherals, and Memory.
Memory: It is used to store data or address.
Peripherals: These are the external devices connected
Processor: It is an IC which is used to perform some task
Applications of embedded systems
Manufacturing and process control
Construction industry
Buildings and premises
Domestic service
Office systems and mobile equipment
Banking, finance and commercial
Medical diagnostics, monitoring and life support
Testing, monitoring and diagnostic systems
Processors are classified into four types like:
o C
o VB
o Processor
o Peripherals
o memory
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Micro Processor (µp)
Micro controller (µc)
Digital Signal Processor (DSP)
Application Specific Integrated Circuits (ASIC)
Micro Processor (µp):
A silicon chip that contains a CPU. In the world of personal computers, the terms
microprocessor and CPU are used interchangeably. At the heart of all personal computers
and most workstations sits a microprocessor. Microprocessors also control the logic of
almost all digital devices, from clock radios to fuel-injection systems for automobiles.
Three basic characteristics differentiate microprocessors:
Instruction set: The set of instructions that the microprocessor can execute.
Bandwidth : The number of bits processed in a single instruction.
Clock speed : Given in megahertz (MHz), the clock speed determines how many
instructions per second the processor can execute.
In both cases, the higher the value, the more powerful the CPU. For example, a 32-bit
microprocessor that runs at 50MHz is more powerful than a 16-bit microprocessor that
runs at 25MHz. In addition to bandwidth and clock speed, microprocessors are classified
as being either RISC (reduced instruction set computer) or CISC (complex instruction set
A microprocessor has three basic elements, as shown above. The ALU performs all
arithmetic computations, such as addition, subtraction and logic operations (AND, OR,
etc). It is controlled by the Control Unit and receives its data from the Register
Array. The Register Array is a set of registers used for storing data. These registers can
be accessed by the ALU very quickly. Some registers have specific functions - we will
deal with these later. The Control Unit controls the entire process. It provides the timing
and a control signal for getting data into and out of the registers and the ALU and it
synchronizes the execution of instructions (we will deal with instruction execution at a
later date).
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