Embedded System basic and classifications

EMBEDDED SYSTEM BASICS
AND APPLICATION

What is a system?
A system is a way of working, organizing or doing
one or many tasks according to a fixed plan, program or
set of rules.
A system is also an arrangement in which all its
units assemble and work together according to the plan
or program.

EMBEDDED SYSTEM
Definition: An Embedded System is one that has
computer hardware with software embedded in it as
one of its important components.
SOFTWARE PROGRAM
#include <16f876a.h>
#use delay (clock=20000000)
#byte PORTB=6
main()
{
set_tris_b(0);
portb=255; //decimal
delay_ms(1000);
portb=0x55; //hexadecimal
delay_ms(1000);
portb=0b10101010; //binary
delay_ms(500);
}
Its software embeds in
ROM (Read Only
Memory). It does not need
secondary memories as in
a computer
HARDWARE

COMPUTER HARDWARE
A Microprocessor
A Large Memory
(Primary and Secondary)
(RAM, ROM and caches)
Input Units
(Keyboard, Mouse, Scanner, etc.)
Output Units
(Monitor, printer, etc.)
Networking Units
(Ethernet Card, Drivers, etc.)
I/O Units
(Modem, Fax cum Modem, etc.)

COMPONENTS OF EMBEDDED
SYSTEM
 It has Hardware
Processor, Timers, Interrupt controller, I/O Devices, Memories,
Ports, etc.
 It has main Application Software
Which may perform concurrently the series of tasks or multiple
tasks.
 It has Real Time Operating System (RTOS)
RTOS defines the way the system work. Which supervise the
application software. It sets the rules during the execution of the
application program. A small scale embedded system may not need
an RTOS.

EMBEDDED SYSTEM
CONSTRAINTS
An embedded system is software designed to keep in
view three constraints:
 Available system memory
 Available processor speed
 The need to limit the power dissipation

CLASSIFICATIONS OF EMBEDDED SYSTEM
1. Small Scale Embedded System
2. Medium Scale Embedded System
3. Sophisticated Embedded System

SMALL SCALE EMBEDDED SYSTEM
 Single 8 bit or 16bit Microcontroller.
 Little hardware and software complexity.
 They May even be battery operated.
 Usually “C” is used for developing these system.
 The need to limit power dissipation when system is running
continuously.
Programming tools:
Editor, Assembler and Cross Assembler

MEDIUM SCALE EMBEDDED SYSTEM
 Single or few 16 or 32 bit microcontrollers or
Digital Signal Processors (DSP) or Reduced
Instructions Set Computers (RISC).
 Both hardware and software complexity.
Programming tools:
RTOS, Source code Engineering Tool,
Simulator, Debugger and Integrated Development
Environment (IDE).

SOPHISTICATED EMBEDDED SYSTEM
 Enormous hardware and software complexity
 Which may need scalable processor or configurable processor
and programming logic arrays.
 Constrained by the processing speed available in their
hardware units.
Programming Tools:
For these systems may not be readily available at a
reasonable cost or may not be available at all. A compiler or
retargetable compiler might have to br developed for this.

PROCESSOR
 A Processor is the heart of the Embedded
System.
Two Essential Units: Operations
Control Unit (CU), Fetch
Execution Unit (EU) Execute
 General Purpose processor (GPP)
Microprocessor
Microcontroller
Embedded Processor
Digital signal Processor

MICROPROCESSOR
 A microprocessor is a single chip semi conductor
device also which is a computer on chip, but not a
complete computer.
 Its CPU contains an ALU, a program counter, a
stack pointer, some working register, a clock
timing circuit and interrupt circuit on a single
chip.
 To make complete micro computer, one must add
memory usually ROM and RAM, memory decoder,
an oscillator and a number of serial and parallel
ports.

HISTORY OF MICROPROCESSOR
1st Generation (4 bit processors)
4004 and 4040 4 bit in early 1970 by Intel (Integrated Electronics)
2nd Generation (8 bit processors)
8008 and 8080 8 bit in 1974 Intel with +5 V Input supply 8080  8085 8 bit
3rd Generation (16 bit processors)
8086 16 bit. Same as 8086, the 8088 introduced 8088 has only 8 bit data bus
(This made it easier to interface to the common 8 bit peripheral devices
available at the time)
Followed by:
The 80186 & 80286 (16 bit processor), the 80386 & 80486 (a 32 bit processor),
leading to the Pentium range of microprocessors (64 bit processors)
available today. The 80x86 and Pentium processors have all been designed
for use in personal computer type applications and have large memory maps.

MICROCONTROLLER
 A microcontroller is a functional computer system-on-a-chip. It
contains a processor, memory, and programmable input/output
peripherals.
 Microcontrollers include an integrated CPU, memory (a small
amount of RAM, program memory, or both) and peripherals
capable of input and output.
 Example
INTEL : 8031,8032,8051,8052,8751,8752
PIC : 8-bit PIC16, PIC18, 16-bit DSPIC33 / PIC24, PIC16C7x
Motorola :MC68HC11

MICROPROCESSOR Vs MICROCONTROLLER
MICROPROCESSOR MICROCONTROLLER
The functional blocks are ALU,
registers, timing & control units
It includes functional blocks of
microprocessors & in addition has
timer, parallel i/o, RAM, EPROM,
ADC & DAC
Bit handling instruction is less, One
or two type only
Many type of bit handling
instruction
Rapid movements of code and
data between external memory & MP
Rapid movements of code and
data within MC
It is used for designing general
purpose digital computers system
They are used for designing
application specific dedicated
systems

EMBEDDED PROCESSOR
 Special microprocessors & microcontrollers
often called, Embedded processors.
 An embedded processor is used when fast
processing fast context-switching & atomic
ALU operations are needed.
Examples : ARM 7, INTEL i960, AMD 29050.

DIGITAL SIGNAL PROCESSOR
 DSP as a GPP is a single chip VLSI unit.
 It includes the computational capabilities of
microprocessor and multiply & accumulate units (MAC).
 DSP has large number of applications such as image
processing, audio, video & telecommunication processing
systems.
 It is used when signal processing functions are to be
processed fast.
Examples : TMS320Cxx, SHARC, Motorola 5600xx

ARCHITECTURES
Processor arch.
CISC RISC
System arch.
Von Neumann Harvard

System architecture
 Von Neumann architecture
 Developed by John Von Neumann
 Most widely used architecture.
 Implemented in majority of the processors.
 All elements in the system are controlled
by single bunch of 3 busses.
 Address bus.
 Data bus.
 Control bus.
 Program instructions and data stored in
same memory area.

Harvard architecture
 Developed at Harvard university.
 Uses two different bus systems to transport
 Instruction codes from the program
memory
 Program memory has its own address, data and control bus.
 Data to CPU from peripherals or memory to CPU.
 Data bus has its own address, data and control bus.
 Program and data memories physically/logically separated (accessed
using different buses)
 Simultaneous fetch of instructions from program memory and data
from data memory.

Embedded System basic and classifications

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